COMPOSITIONS AND METHODS FOR INDIGO DYEING

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 63/397,866, filed August 14, 2022, entitled “COMPOSITIONS AND METHODS FOR INDIGO DYEING” and U.S. Provisional Patent Application No. 63/525,730, filed July 10, 2023, entitled “COMPOSITIONS AND METHODS FOR INDIGO DYEING”. The contents of the above applications are all incorporated by reference as if fully set forth herein in their entirety.

FIELD OF THE INVENTION

[002] The invention relates generally to the field of indigo-dyed yarns and fabrics comprising thereof.

BACKGROUND

[003] During the conventional industrial indigo dyeing process indigo, which is insoluble in water, is first reduced into its water soluble leuco-indigo form, and subsequently applied to the substrate. Textile or yarn is dipped into the leuco-indigo solution and then the resulting substrate comprising leuco-indigo incorporated therewithin is subjected to oxidation process, so as to result in the formation of water-insoluble indigo on top of the textile/yarn substrate. Multiple applications of leuco-indigo are required to achieve dark shades significantly increasing the time period required for dyeing and further require complex dyeing systems composed of numerous dyeing bathes (6-12 cycles) and pre-/post-treatment bathes. For example, in order to improve the dyeing efficiency cotton textile/yarns need to undergo a pretreatment process (e.g., scouring, desizing and bleaching). Excessive use of toxic reducing agents and other toxic chemicals for indigo reduction and dye baths stabilization on air, as well as large amounts of water are required for this process. Instability of the reduced dyebath on air leads to the variations in color and color fastness.

[004] In the traditional process of yarn indigo dyeing, indigo must be converted into leuco-indigo (to be dissolved) by reduction and basification of the solution. The resulting solution is extremely sensitive to ambient conditions and therefore the usual concentration in the dyeing tanks varies from 0.2 % to 0.7% in slasher dyeing machine and can reach up to 5% in the rope dyeing machines. The solution degrades on air and requires addition of sodium dithionite and caustic soda for stabilization. Oxidation of sodium dithionite leads to the formation of the sodium sulfite and bisulfite, which accumulation makes further use of the solution impossible. The worked-out solution is discarded and requires extensive wastewater treatment. Due to the low concentration of the working solution the process utilizes large amount of water.

[005] In the traditional process leuco-indigo is deposited onto cotton yarns and then subjected to oxidation in air, giving rise to formation of the indigo pigment nanoparticles coating the yarns’ fibers. Due to the low affinity of indigo to the cotton and low concentration of the dyeing solution, only small number of nanoparticles is formed and adsorbed onto the substrate. Multiple cycles of dipping/ oxidation are done to achieve desirable depth of color.

[006] Many attempts have been made to establish an improved process for indigo dyeing. However, to this end, there is no viable alternative industrially applicable process for indigo dyeing of fabrics and yarns.

[007] Accordingly, there is a need for fast, efficient and environment-friendly process for indigo dyeing of various fabrics and yarns which doesn’t involve reagents toxic to the environment and provides an indigo dyed substrate preferably after a single dyeing cycle.

[008] The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the figures.

SUMMARY OF THE INVENTION

[009] The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope.

[0010] In one aspect of the invention, there is provided a composition comprising a plurality of indigo nanoparticles; and a dispersant; wherein the plurality of indigo nanoparticles is characterized by median particle size on an intensity basis of between 50 nm and 400 nm.

[0011] In one embodiment, a weight ratio between the plurality of indigo nanoparticles and the dispersant is between 0.01 : 1 and 2: 1.

[0012] In one embodiment, the dispersant is selected from: cationic acrylic block copolymers, anionic acrylic block copolymers, non-ionic acrylic block copolymers, polyacrylates, polyurethanes, alkylol ammonium salts of carboxylic acids, alkylol ammonium salts of acrylates, anionic phosphated alkoxylated polymers, non-ionic copolymers, styrene maleic acid copolymers, styrene maleic anhydride copolymers, polyglycols, carboxyl polyglycol copolymers, polyethers, oleo epoxide (alkylene oxide) block-copolymers, polyoxyethylene ethers of carboxylic acids, including any salt and any combination thereof.

[0013] In one embodiment, the composition is a solid composition, and wherein a weight content of the indigo nanoparticles within the solid composition is at between 30 and 95%.

[0014] In one embodiment, the composition further comprises an additional agent.

[0015] In one embodiment, a weight percentage of the additional agent within the composition is between 0.01 and 10%.

[0016] In one embodiment, the additional agent is selected from: a wetting agent, an antifoaming agent, a leveling agent, a cationization agent, a migration inhibitor, a fixing agent, binder, surfactant, gloss agent, blooming agent, pH modifier, conductivity modifier, rheology modifier, an antibacterial agent, and any combination thereof.

[0017] In one embodiment, the composition further comprises an aqueous carrier.

[0018] In one embodiment, is characterized by a surface tension of at least 28 din/cm-1 at 25 °C, or at least 40 dyn/cm-1 at 25 °C, or at least 55 dyn/cm-1 at 25 °C.

[0019] In one embodiment, the composition is characterized by viscosity between 2 cP and 50 cP at 25 °C, or between 3 cP and 10 cP at 25 °C.

[0020] In one embodiment, a w/w percentage of the plurality of indigo nanoparticles within the composition is between 0.1% and 30%. [0021] In one embodiment, the composition further comprises a co-solvent.

[0022] In one embodiment, the co-solvent is characterized by a flash point of at least 100 °C, at least 120 °C, at least 150 °C, or at least 170 °C.

[0023] In one embodiment, the composition is a textile dyeing composition.

[0024] In one embodiment, the indigo dyed substrate is substantially devoid of trace amounts of an indigo reducing agent.

[0025] In one embodiment, the indigo substrate fiber further comprises a surface active agent.

[0026] In one embodiment, a weight ratio between the surface active agent and the plurality of indigo particles is between 2: 1 and 0.001 : 1.

[0027] In one embodiment, the plurality of indigo particles further comprises indigo nanoparticles particles characterized by a median particle size on an intensity basis between 10 and 500 nm. In some embodiments, the plurality of indigo nanoparticles has a spheric geometry or shape. In some embodiments, the plurality of indigo nanoparticles has an inflated or deflated shape. In some embodiments, the plurality of indigo nanoparticles is devoid of any characteristic geometry or shape. In some embodiments, the plurality of indigo nanoparticles has a spherical shape, a quasi-spherical shape, a cubic shape, a semi-cubic shape, a quasi-elliptical sphere, a deflated shape, a concave shape, an irregular shape, or any combination thereof. One skilled in the art will appreciate that the exact shape of each of the plurality of particles may differ from one particle to another. Moreover, the exact shape of the plurality of indigo nanoparticles may be derived from any of the geometric forms listed above, so that the shape of the particle does not perfectly fit a specific geometrical form. One skilled in the art will appreciate that the exact shape of the nanoparticle may have substantial deviations (such as at least 5%, at least 10%, or at least 20% deviation) from a specific geometrical shape (e.g., a cube or a sphere).

[0028] In one embodiment, the indigo dyed substrate further comprises (i) a binder, (ii) a fixing agent, or both (i) and (ii). [0029] In one embodiment, the indigo dyed substrate maintains at least 50% of the initial loading of the plurality of indigo particles upon at least 10 successive laundry test cycles, wherein the laundry test is performed according to ISO 6330 laundry test.

[0030] In one embodiment, the indigo dyed substrate is compatible with a denim finishing process. In one embodiment, the denim finishing process includes but is not limited to: Desizing wash - high temperature wash, detergents wash, oxidative or hydrolytic desizing (such as alkali steeping or amylase wash); Stone wash with pumice stones; Enzyme wash (cellulase, peroxidase); Bleach: calcium or sodium hypochlorite, potassium permanganate wash, hydrogen peroxide wash, organic peroxides wash, inorganic salts wash (such as sodium perborate); Ozone treatment; Laser treatment; Sand blasting or abrasion.

[0031 ] Ring dyed yarns and textile made of them (including denim for denim apparel such as jeans) demonstrating ability to lose dyestuff and dyed fiber of outer portion of the yarns upon exposure to denim finishing, creates a finishing pattern on a surface of the garment (denim washes).

[0032] In one embodiment, the color strength of indigo dyed substrate is reduced upon subjecting thereof to a denim finishing. The changes are characterized by shift of the b value in CIELab color space to the toward the negative values. The changes are characterized by increase in chroma value C in CIELCh color space. The changes are characterized by increase of lightness (L value) in CIELab or CIELCh color spaces.

[0033] Wherein denim finishing being enzymatic, oxidative, acid or fermentative desizing wash, hot water wash, enzymatic wash with cellulase or peroxidase, stone wash with pumice stones, bleach wash with sodium or calcium hypochlorite, hydrogen peroxide wash, organic peroxides wash, inorganic salts wash (such as sodium perborate), potassium permanganate wash, exposure to sandblasting or abrasion, laser finishing, wet and dry ozone finishing.

[0034] In one embodiment, the textile fiber is selected from a natural fiber or a synthetic fiber.

[0035] In another aspect of the invention, there is provided a substrate comprising a plurality of the indigo dyed fibers of the invention.

[0036] In one embodiment, the plurality of indigo particles is in the form of a pattern. [0037] In one embodiment, the substrate is selected from a yarn, a fibrous substrate being in the form of a knitted, a woven or a non-woven textile substrate.

[0038] In one embodiment, the textile substrate comprises a material selected from a polyester, a polyamide, cotton, linen, wool, kapok, ramie, cellulose, acetylated cellulose, polyurethane, polyacrylate, rubber, rayon and silk or any combination thereof.

[0039] In another aspect, there is provided a method for manufacturing an indigo dyed substrate comprising: (i) contacting at least a portion of a substrate with a liquid composition comprising a plurality of indigo nanoparticles; and (ii) applying to the substrate in contact with the liquid composition ultrasonic waves and/or cavitation under appropriate conditions; thereby manufacturing the indigo dyed substrate; wherein the substrate is selected from a textile fiber, a yarn, and a textile substrate; and wherein the plurality of indigo nanoparticles is characterized by an average particle size between 10 and 500 nm.

[0040] In another aspect, there is provided a method for manufacturing an indigo dyed substrate comprising (i) contacting at least a portion of a substrate with the composition of the invention; and (ii) subjecting the substrate in contact with the composition to acoustic waves suitable for inducing cavitation under appropriate conditions; thereby manufacturing the indigo dyed substrate; wherein the substrate is selected from a textile fiber, a yarn, and a textile substrate.

[0041] In one embodiment, the substrate is a substrate substantially devoid of indigo; optionally wherein the substrate is an untreated substrate.

[0042] In one embodiment, the steps (i) and (ii) are performed simultaneously or subsequently.

[0043] In one embodiment, the composition of the invention is the dispersion disclosed herein.

[0044] In one embodiment, the contacting of the step (i) is performed under conditions appropriate for obtaining a moist substrate.

[0045] In one embodiment, the conditions comprise applying the liquid composition to the substrate by a method selected from dipping, spraying and coating, or any combination thereof. [0046] In one embodiment, the step (ii) is performed while the moist substrate is in operable communication with a solid vibrating element.

[0047] In one embodiment, the solid vibrating element comprises a source of ultrasonic waves, optionally further comprising at least one contact surface configured for being in contact with the moist substrate.

[0048] In one embodiment, the acoustic waves suitable for inducing cavitation are characterized by any one of: (i) a frequency between 15 KHz and 10 MHz; and (ii) input power between 30 and 2000 W.

[0049] In one embodiment, the liquid composition is a dispersion comprising an aqueous solvent, a surface active agent, and indigo nanoparticles, and optionally an additive selected from: a wetting agent, an antifoaming agent, a leveling agent, a cationization agent, a migration inhibitor, a fixing agent, binder, surfactant, gloss agent, blooming agent, pH modifier, conductivity modifier, rheology modifier, an antibacterial agent including any combination thereof.

[0050] In some embodiments, the surface active agent is devoid of polyethyleneglycol.

[0051] In some embodiments, the surface active agent is devoid of polyurethane.

[0052] In one embodiment, the indigo nanoparticles are characterized by an median particle size on an intensity basis between 10 and 500 nm, as determined by differential light scattering (DLS).

[0053] In some embodiments, the average particle size refers to median particle size on an intensity basis value, as determined by DLS.

[0054] In one embodiment, a weight ratio between the indigo nanoparticles and the surface active agent within the liquid composition is between 2: 1 and 0.01 :2.

[0055] In one embodiment, a w/w concentration of the indigo nanoparticles within the liquid composition is between 0.1% and 30%.

[0056] In one embodiment, the appropriate conditions are sufficient for embedding the indigo nanoparticles into at least a portion of the substrate. [0057] In one embodiment, the appropriate conditions comprise any one of: (i) a frequency of the ultrasonic waves between 15 KHz and 500 KHz; and (ii) input power between 30 and 2000 W.

[0058] In one embodiment, cavitation generates cavitation bubbles having an average size between 3 um and 150 um.

[0059] In one embodiment, indigo loading of the indigo dyed substrate after a single dyeing cycle is at least 0.5 %w/w.

[0060] In one embodiment, the appropriate conditions further comprise application time of at least 1 second.

[0061] In one embodiment, the method is characterized by an incorporation efficiency of the indigo nanoparticles ranging between 10 and 100%.

[0062] In one embodiment, the method further comprises a step (iii) of drying the indigo dyed substrate.

[0063] In one embodiment, the method further comprises a step (iv) of contacting the indigo dyed substrate with: a fixing agent, a sizing agent, or both.

[0064] In one embodiment, the indigo dyed substrate is characterized by a color difference in L*a*b or L*C*h color space of below 2 as calculated according to CIE76, CIE94, CIEDE2000 or CMC l:c (1984) formulas.

[0065] In one embodiment, the indigo dyed substrate is compatible with a denim finishing process.

[0066] In one embodiment, the denim finishing process comprises any one of: desizing wash, stone wash, enzyme wash, bleaching, ozone wash, laser wash, sand blasting, or any combination thereof.

[0067] In one embodiment, the method is for manufacturing the indigo dyed fibers of the invention, or the substrate of the invention.

[0068] In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the figures and by study of the following detailed description. [0069] In the proposed invention the indigo pigment particles are obtained by top-down approach prior to dyeing, providing stable dispersion of indigo particles. Those particles are further impregnated into textile substrate by the cavitation phenomena.

[0070] In some cases, process is devoid of scouring or mercerization. In those cases, textile substrate is devoid of trace amount of soda caustic used in scouring and mercerization processes.

[0071] In some cases, textile substrate is scoured or mercerized prior to dyeing.

[0072] Method can comprise pre-treatment of the yarns with hydrophobization or anti- wi eking agent to prevent dyestuff penetration into the yarn’s core.

[0073] Method further comprises treatment with fixing agent in the separate bath and subsequent drying of the substrate.

[0074] According to another aspect, there is provided a method for ring indigo dyeing of a substrate comprising contacting at least a portion of the substrate with the composition of the invention, wherein the composition is characterized by a surface tension above a critical surface tension of the substrate; and subjecting the substrate in contact with the composition to acoustic waves suitable for inducing a cavitation; thereby obtaining an indigo ring dyed substrate; wherein the substrate is selected from a yarn and a textile substrate; and; and wherein the cavitation is characterized by cavitation bubbles having an average size between 1 um and 200um.

[0075] In one embodiment, acoustic waves are characterized by a frequency between about 15 KHz and about 500 KHz.

[0076] In one embodiment, acoustic waves are characterized by an intensity equivalent to an input power of an acoustic waves source of between 30 and 2000 W.

[0077] In one embodiment, subjecting further comprises controlling cavitation parameters, to obtain a predetermined penetration depth of the indigo nanoparticles.

[0078] In one embodiment, predetermined penetration depth is between 1 and about 200 um. [0079] In one embodiment, controlling is by varying the frequency and/or the input power, thereby generating cavitation bubbles with a predetermined average size.

[0080] In one embodiment, the predetermined average size is substantially equivalent to the penetration depth.

[0081] In one embodiment, the method further comprises performing a preliminary prewetting step, wherein the preliminary pre-wetting step is performed prior to performing the step (i) or the step (ii).

[0082] In one embodiment, the indigo ring dyed substrate comprises a yarn having an indigo dyed outer portion, and an inner portion substantially devoid of indigo nanoparticles.

[0083] In one embodiment, the method further comprises a step (iii) of drying the indigo ring dyed substrate; and optionally comprises a step (iv) of contacting the indigo ring dyed substrate with: a fixing agent, a sizing agent, or both.

[0084] In one embodiment, indigo ring dyed substrate is characterized by a color difference in L*a*b or L*C*h color space of below 2 as calculated according to CIE76, CIE94, CIEDE2000 or CMC l:c (1984) formulas.

[0085] In one embodiment, indigo ring dyed substrate is compatible with a denim finishing process.

[0086] According to another aspect, there is provided a method for manufacturing a dyed substrate comprising: (i) contacting at least a portion of a substrate with a dyeing composition comprising a plurality of dye nanoparticles; and a dispersant; wherein the plurality of dye nanoparticles is characterized by median particle size on an intensity basis of between 10 nm and 500 nm; and (ii) subjecting the substrate in contact with the composition to acoustic waves suitable for inducing cavitation under appropriate conditions; thereby manufacturing the dyed substrate; wherein the substrate is selected from a textile fiber, a yarn, and a textile substrate; and wherein the dye nanoparticles are water-insoluble dye nanoparticles comprising a vat dye, a sulfur dye, or both.

[0087] In one embodiment, substrate is an untreated substrate.

[0088] In one embodiment, substrate is a substrate substantially undyed. [0089] In one embodiment, steps (i) and (ii) are performed simultaneously or subsequently.

[0090] In one embodiment, contacting is performed under conditions suitable for obtaining a moist substrate.

[0091] In one embodiment, suitable conditions comprise dipping; optionally wherein dipping further comprises applying acoustic waves suitable for inducing cavitation; and wherein the step (ii) is performed while the moist substrate is in operable communication with a source of acoustic waves.

[0092] In one embodiment, cavitation generates cavitation bubbles having an average size between 3 um and 150 um.

[0093] In one embodiment, method further comprises a step (iii) of drying the dyed substrate.

[0094] In one embodiment, method further comprises a step (iv) of contacting the dyed substrate with: a fixing agent, a sizing agent, or both.

[0095] In one embodiment, the method is for ring dyeing of the substrate.

[0096] In another aspect, there is provided a dyeing composition comprising a plurality of dye nanoparticles and a predetermined amount of a dispersant; wherein the plurality of dye nanoparticles is characterized by median particle size on an intensity basis of between 10 nm and 500 nm; wherein the dye nanoparticles comprise a water-insoluble dye selected from a vat dye, a sulfur dye, or both; and wherein the predetermined amount of the dispersant is sufficient to stabilize the plurality of dye nanoparticles in an aqueous dispersion.

[0097] In one embodiment, the predetermined amount of the dispersant is so that a weight ratio between the plurality of dye nanoparticles and the dispersant within the dyeing composition is between 0.01 : 1 and 2:1.

[0098] In one embodiment, the dispersant is selected from: cationic acrylic block copolymers, anionic acrylic block copolymers, non-ionic acrylic block copolymers, polyacrylates, polyurethanes, alkylol ammonium salts of carboxylic acids, alkylol ammonium salts of acrylates, anionic phosphated alkoxylated polymers, non-ionic copolymers, styrene maleic acid copolymers, styrene maleic anhydride copolymers, polyglycols, carboxyl polyglycol copolymers, polyethers, oleo epoxide (alkylene oxide) block-copolymers, polyoxyethylene ethers of carboxylic acids.

[0099] In one embodiment, (i) the dyeing composition is a solid composition, and wherein a weight content of the indigo nanoparticles within the solid composition is between 30 and 95%; or (ii) the dyeing composition is an aqueous composition, and wherein a weight content of the indigo nanoparticles within the aqueous composition is between 0.1% and 30%.

[00100] In one embodiment, the dyeing composition further comprises an additional agent; optionally wherein a weight percentage of the additional agent within the dyeing composition is between 0.01 and 10%; further optionally wherein the additional agent is selected from a wetting agent, an antifoaming agent, a leveling agent, a cationization agent, a migration inhibitor, a fixing agent, binder, surfactant, gloss agent, blooming agent, pH modifier, conductivity modifier, rheology modifier, an antibacterial agent, and any combination thereof.

[00101] In one embodiment, the sulfur dye is sulfur black.

[00102] In another aspect, there is provided a method for manufacturing a dyed substrate comprising: (i) contacting at least a portion of a substrate with the dyeing composition of the invention; and (ii) subjecting the substrate in contact with the dyeing composition to acoustic waves suitable for inducing cavitation under appropriate conditions; thereby manufacturing the dyed substrate; wherein the substrate is selected from a textile fiber, a yarn, and a textile substrate; and wherein the dye nanoparticles are water-insoluble dye nanoparticles comprising a vat dye, a sulfur dye, or both.

[00103] In one embodiment, the substrate is an untreated substrate.

[00104] In one embodiment, the substrate is substantially undyed.

[00105] In one embodiment, steps (i) and (ii) are performed simultaneously or subsequently.

[00106] In one embodiment, contacting is performed under conditions suitable for obtaining a moist substrate.

[00107] In one embodiment, the conditions comprise dipping; optionally wherein the dipping further comprises applying acoustic waves suitable for inducing cavitation; and wherein the step (ii) is performed while the moist substrate is in operable communication with a source of acoustic waves.

[00108] In one embodiment, cavitation generates cavitation bubbles having an average size between 3 um and 150 um.

[00109] In one embodiment, the method further comprises a step (iii) of drying the dyed substrate.

[00110] In one embodiment, the method further comprises a step (iv) of contacting the dyed substrate with: a fixing agent, a sizing agent, or both.

[00111] In one embodiment, the composition is characterized by a surface tension above a critical surface tension of the substrate; and wherein the method is for ring dyeing of the substrate with the vat dye, the sulfur dye, or both.

[00112] In one embodiment, the untreated substrate is (i) a textile substrate characterized by a critical surface tension of at least 28 dyn - cm- 1 ; or (ii) a yarn characterized by a diffusion coefficient (D) below 0.1.

BRIEF DESCRIPTION OF THE DRAWINGS

[00113] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

[00114] Fig.l. Intensity-based size distribution of hydrodynamic size of the indigo nanoparticles prepared by indigo milling in presence of dispersing agent.

[00115] Fig. 2 SEM image of nanoparticles of indigo obtained by milling in presence of dispersing agent.

[00116] Fig. 3. Fabrics, dyed with indigo nanoparticles with and without application of a fixing agent after 0, 1, 3 and 10 cycles of home laundry/drying.

[00117] Fig. 4. Cotton fabric, dyed with formulation containing 1 wt.% of indigo nanoparticles without (left) and with ultrasonication applied (right). [00118] Figs. 5A-5B Sonication (center) and dipping dyeing (5A). Sonication (center) and dipping dyeing after 10 cycles of home laundry and drying (5B).

[00119] Fig. 6. Cotton fabric, dyed with formulation containing 1 wt.% of indigo nanoparticles without (left) and with ultrasonication applied (right).

[00120] Figs. 7A-7H SEM images of indigo dyed substrates. Figs. 7A-C are SEM images of the indigo nanoparticles on the conventionally dyed fabric. Figs. 7D-E are SEM images of the indigo nanoparticles on the fabric pad-dyed with milled indigo nanoparticles. Figs. 7F-7H are SEM images of the indigo nanoparticles on the fabric dyed with milled indigo nanoparticles under ultrasonication.

[00121] Figs. 8A-8C are TEM images. Fig. 8A is a TEM image of the cross-section of conventionally dyed denim. Fig. 8B is a TEM image of the cross-section of the fabric pad- dyed with milled indigo nanoparticles. Fig. 8C TEM image of the cross-section of the fabric dyed with milled indigo nanoparticles under ultrasonication.

[00122] Figs. 9A-9B present images of cotton fabric dyed with indigo particles characterized by an average particle size of Fig. 9A 500nm and Fig 9B 150nm.

[00123] Figs. 10A-10D present images of ring dyeing of yarn at different ultrasound wave frequencies. Fig. 10A 25kHz, Fig. 10B 40 kHz, Fig. 10C 80 kHz and Fig. 10D 100 kHz.

[00124] Fig. 11 presents a flow chart of the dyeing method of the invention.

[00125] Figs 12A-12B presents illustrations of: dyeing method of the invention (Fig. 12A) and traditional indigo dying process (Fig. 12B).

[00126] Fig. 13 presents images of pre- wetted raw cotton yarns without (left) and with (right) sonication applied.

[00127] Fig. 14 presents images of denim fabrics woven from the yarns dyed following an exemplary dyeing method of the invention (right). The fabric was subjected to enzyme (middle) and bleach (left) washes.

[00128] Fig.15 is a graph presenting intensity-based size distribution of hydrodynamic size of the milled Sulfur Black 1 nanoparticles. [00129] Figs. 16A-C are illustrations of wet sonication systems which can be applied along with the method of the invention.

DETAILED DESCRIPTION

[00130] The present invention in some embodiments thereof, is based on a surprising finding that indigo nanoparticles can be utilized in an ultrasound/cavitation assisted dyeing process, resulting in improved dyeing efficiency without using toxic reducing agents. Furthermore, the process of the invention requires a single dyeing step, whereas the standard industrial indigo dyeing requires a multi-step process, as described in the background section.

[00131] Moreover, the inventor surprisingly found that the indigo nanoparticle size affects the dyeing efficiency, particles characterized by an average particle size of about 500 nm resulted in reduced dyeing efficiency.

[00132] As used herein, the term average particle size refers to the median particle size on an intensity basis value obtained by laser diffraction particle size analyzers such as DLS.

[00133] As used herein, the term “indigo” solely refers to: . Furthermore, the term “indigo nanoparticles”, as used herein consist essentially of indigo (e.g. between 90-100%, between 95-100% by dry weight of the nanoparticles consist of indigo). In some embodiments, the indigo nanoparticles are devoid of indigo derivatives (such as leucoindigo, indigo-disulfonate, etc.)

[00134] According to one aspect of the invention, there is provided a composition comprising a plurality of indigo nanoparticles and a dispersant; wherein the plurality of indigo nanoparticles is characterized by an average particle size of below 500 nm, such as between lOnm and 480nm, between 50 and 480, between 50 and 450, between 50 and 400, between 55 and 450nm, between 55 and 400, between 55 and 300, between 55 and 250, between 60 and 250, or between 60 and 300, including any range between. [00135] In some embodiments, a weight content of the plurality of indigo nanoparticles within the composition is between 0.1% and 99%, between 0.1% and 30%, between 0.1% and 10%, between 1% and 30%, between 1% and 10%, between 1% and 20%, between 30% and 40%, between 30% and 50%, between 30% and 60%, between 30% and 70%, between 30% and 80%, or between 30% and 90%, including any range in between.

[00136] In some embodiments, the plurality of indigo nanoparticles is characterized by an average particle size between about 50 and about 450 nm, between 50 and 400 nm, between 50 and 350 nm, between 50 and 300 nm, between 60 and 300 nm, between 60 and 250 nm, between 60 and 220 nm, between 50 and 300 nm, between 50 and 250 nm, between 50 and 220 nm, between 80 and 300 nm, between 80 and 250 nm, between 80 and 200 nm, between 80 and 150 nm, between 90 and 300 nm, between 90 and 250 nm, between 90 and 200 nm, between 90 and 150 nm, between 100 and 150 nm, or between 100 and 250 nm, including any range between, as determined by DLS. In some embodiments, the plurality of indigo nanoparticles is characterized by a polydispersity index between about 0.2 and about 0.35, between about 0.1 and about 0.35, between about 0.22 and 0.3, or between about 0.2 and 0.3, including any range between, as determined by DLS.

[00137] In some embodiments, the plurality of indigo nanoparticles is characterized by a D90 below 500 nm, below 400, or below 350 nm, as determined by DLS.

[00138] Without being bound to any particular theory, it is postulated that indigo particles with an average particle size above 500 nm, are inferior in terms of indigo dyeing of the substrate, according to the method of the invention. More details are provided in Example 3.

[00139] In some embodiments, the plurality of indigo nanoparticles has a spheric geometry or shape. In some embodiments, the plurality of indigo nanoparticles has an inflated or deflated shape. In some embodiments, the plurality of indigo nanoparticles is devoid of any characteristic geometry or shape. In some embodiments, the plurality of indigo nanoparticles has a spherical shape, a quasi-spherical shape, a cubic shape, a semi-cubic shape, a quasielliptical sphere, a deflated shape, a concave shape, an irregular shape, or any combination thereof. One skilled in the art will appreciate that the exact shape of each of the plurality of particles may differ from one particle to another. Moreover, the exact shape of the plurality of indigo nanoparticles may be derived from any of the geometric forms listed above, so that the shape of the particle does not perfectly fit a specific geometrical form. One skilled in the art will appreciate that the exact shape of the nanoparticle may have substantial deviations (such as at least 5%, at least 10%, or at least 20% deviation) from a specific geometrical shape (e.g., a cube or a sphere).

[00140] In some embodiments, the plurality of indigo nanoparticles comprises or consist essentially of indigo in a crystalline state. In some embodiments, the plurality of indigo nanoparticles consists essentially of indigo in an amorphous state.

[00141 ] In some embodiments, the indigo nanoparticles are obtained by milling or grinding a bulk indigo material. In some embodiments, prior to milling or grinding, the bulk indigo material is mixed with the dispersant, wherein the dispersant is as described herein.

[00142] In some embodiments, the dispersant is a water-soluble polymeric dispersant. In some embodiments, water-soluble dispersant, is selected from: a cationic dispersant, anionic dispersant, or non-ionic dispersant, including any combination thereof. In some embodiments, the dispersant includes a single dispersant specie. In some embodiments, the dispersant includes a plurality of chemically distinct dispersant species.

[00143] The dispersant may be a polymeric dispersant or a non-polymeric dispersant (i.e. a small molecule-based dispersant). Non-limiting examples of polymeric dispersants include but are not limited to: acrylate-based block copolymers (e.g., polyacrylamides, polyacrylates, alkylol ammonium salts of acrylates, etc.), polyurethanes, styrene-based copolymers (e.g., styrene maleic acid copolymers, styrene maleic anhydride copolymers, etc.), glycol-based polymers (e.g., polyglycols, carboxyl polyglycol copolymers, etc.), polyethers, phosphated alkoxylated polymers, oleo epoxide (alkylene oxide) blockcopolymers, alkyol ammonium salts of carboxylic acids, salts of carboxylic acids, polyoxyethylene ethers of carboxylic acids, alkylphenol alkoxylates, alkoxylated acetylene polyols, acetylene diol surfactants, fluorinated surfactants, sulfosuccinates, alkoxylated alcohols, siloxane gemini surfactants; alkylphenol alkoxylates, alkoxylated acetylene polyols, acetylene diol surfactants, fluorinated surfactants, sulfosuccinates, alkoxylated alcohols, siloxane gemini surfactantor any combination thereof. In some embodiments, the dispersant is devoid of polyethyleneglycol. In some embodiments, the polymeric dispersant is devoid of polyurethanes.

[00144] In some embodiments, the polymeric dispersant is, selected from: Tego® series of Evonik (such as Tego® 655), Dispex® and Efka® series of BASF (such as Dispex® Ultra 4575, Dispex® Ultra 4290, Efka® 4585, Efka® FA4671), Triton® series of DOW, Edaplan® series of Munzig, DISPERBYK® and BYKJET® series of Altana (such DISPERBYK® 2015, BYKJET® 9151, Solsperse® series of Lubrizol (such as Solsperse® 1700, Solsperse® 20000)

[00145] Additional examples of dispersants include but are not limited to limited to: cationic, anionic, and/or non-ionic surfactant such as alkoxy lated fatty acid, glucosyl dialkyl ether, polysorbate, span, tween, triton, triton X-100, quaternary ammonium salts such as benzalkonium chloride, benzethonium chloride, and cetylpyridinium chloride, pyridinium salts, ethoxylated castor oil, alkyl benzene sulfonate, alcohol ether sulfate, secondary alkane sulfonates and alkyl sulfates, a salt of a fatty acid or a substituted fatty acid including any combination thereof including any mixture or a copolymer thereof.

[00146] In some embodiments, the composition of the invention consists essentially of the plurality of indigo nanoparticles and the polymeric dispersant, and optionally of one or more additive(s) disclosed herein.

[00147] In some embodiments, the composition is in a form of a solid (or solid composition). Non-limiting examples of solid compositions include but are not limited to powder, capsules, granules, or flakes. In some embodiments, the composition is a powder. In some embodiments, the solid composition is dispersible. In some embodiments, by adding a predetermined amount of an aqueous carrier to the solid composition a dispersion is obtained, wherein the predetermined amount is so as to obtain a stable dispersion, as disclosed hereinbelow. In some embodiments, weight ratio between the plurality of indigo nanoparticles and the polymeric dispersant is so that upon addition of the predetermined amount of an aqueous carrier to the solid composition a dispersion is obtained, and wherein the dispersion is characterized by a predetermined surface tension above the surface tension of the substrate (for example: a surface tension of at least 28 dyn cm' ¹ , at least 30 dyn cm' ¹ , at least 35 dyn cm' ¹ , at least 40 dyn cm' ¹ , including any range or value in between). A skilled artisan will appreciate that the predetermined surface tension of the dispersion may vary, based on the surface tension of the substrate to be dyed with the composition of the invention. Accordingly, the weight ratio between the plurality of indigo nanoparticles and the polymeric dispersant in the solid composition may be selected so as to obtain the predetermined surface tension of the dispersion.

[00148] In some embodiments, a weight ratio between the dispersant and the plurality of indigo nanoparticles within the composition is between 2: 1 and 0.001:1, between 2: 1 and 0.01: 1, between 2: 1 and 0.1 :1, between 2:1 and 1: 1, between 1: 1 and 0.001 : 1, between 0.1 :1 and 0.001: 1, between 0.5: 1 and 0.001 :1, between 0.01 :1 and 0.001 :1, including any range between. In some embodiments, a weight ratio between the plurality of indigo nanoparticles and the dispersant within the composition is between 0.5: 1 and 0.05: 1.

[00149] In some embodiments, the composition further comprises an aqueous carrier. In some embodiments, the composition comprising the aqueous carrier (also referred to herein as “dispersion”) is in a form of a dispersion.

[00150] In some embodiments, a weight percentage of the aqueous carrier within the dispersion is sufficient to form a stable dispersion. In some embodiments, a weight percentage of the aqueous carrier within the dispersion is the predetermined amount required to form a stable dispersion. In some embodiments, the weight percentage of the aqueous carrier within the dispersion is between 85% and 99%, between 85% and 95%, between 85% and 90%, or between 90% and 99%, including any range between.

[00151] In some embodiments, the dispersion is characterized by a surface tension of at least 28 dyncm' ¹ , at least 30 dyncm' ¹ , at least 35 dyncm' ¹ , at least 40 dyncm' ¹ , including any range or value in between.

[00152] In some embodiments, the dispersion is characterized by viscosity between 2 cP and 50 cP, between 3 cP and 10 cP, between 3 cP and 20 cP, between 3 cP and 30 cP, between 3 cP and 40 cP at 25 °C.

[00153] In some embodiments, the weight percentage of the dispersant within the dispersion of the invention is between about 1 and about 30%, between about 1 and about 20%, between about 1.5 and about 20%, including any range in between. [00154] In some embodiments, a weight percentage of the plurality of indigo nanoparticles within the dispersion is between 0.1% and 30%, between 0.1% and 10%, between 1% and 30%, between 1% and 10%, between 1% and 20%, between 1% and 5%, between 1% and 8%, between 2% and 30%, between 5% and 20%, between 5% and 30%, including any range in between. In some embodiments, a weight percentage of the plurality of indigo nanoparticles within the dispersion is between 0.1% and 10%, between 0.1% and 1%, between 0.1% and 5%, between 1% and 10%, between 2% and 10%, between 4% and 10%, between 5% and 10% including any range in between. Based on extensive experiments the inventors have arrived at the above-mentioned weight concentration of indigo nanoparticles in the dispersion as being suitable for efficient dyeing of various substrates. A skilled artisan will appreciate that the exact concentration of indigo nanoparticles may vary based on: (i) the amount of repetitive dyeing cycles using in the dyeing process; and (ii) on the desired shade (predetermined by the indigo loading) of the dyed substrate.

[00155] In some embodiments, the dispersion of the invention is stable for at least 1 h, at least 5 h, at least 10 h, at least 24 h, at least 1 d, at least 5 d, at least 10 d, at least 30 d, or at least 2 months, including any range between.

[00156] The term “stable” refers to the composition of the invention that encompasses dispersion stability. In some embodiments, a stable dispersion is substantially devoid of precipitation. Precipitation may be determined visually or by DLS. Furthermore, the dispersion stability is determined under ambient conditions, such as a temperature (i.e., between 5 and 40°C), and exposure to the ambient atmosphere. In some embodiments, dispersion stability is characterized by an average size distribution that is essentially similar to the average size distribution of the composition of the invention. As used here the term “essentially similar” refers to having at most 5%, at most 10%, at most 15%, including any range or value in between, difference in the value of the average particle size.

[00157] In some embodiments, the composition (i.e., solid composition or dispersion) further comprises an additional agent (also used herein as “additive”). In some embodiments, the additional agent affects the mechanical and physical properties of the composition of the invention. [00158] In some embodiments, the dry weight concentration of the additional agent within the composition is between 0.01 and 10%, between 0.01% and 0.1%, between 0.01% and 1%, between 0.1% and 1%, between 0.1% and 5%, between 0.2% and 5%, between 0.5% and 10%, or between 0.1% and 10%, including any range in between.

[00159] In some embodiments, the additional agent is selected from a wetting agent, an antifoaming agent, a leveling agent, a cationization agent, a migration inhibitor, a fixing agent, binder, surfactant, gloss agent, blooming agent, pH modifier, conductivity modifier, rheology modifier, an antibacterial agent including any combination thereof or any combination thereof.

[00160] In some embodiments, the composition of the invention consists essentially of the indigo nanoparticles, the polymeric dispersant and the surfactant (and optionally further comprises the additive), wherein the weight ratio between the dispersant and the surfactant within the composition of the invention is so as to obtain the predetermined surface tension, as disclosed above. In some embodiments, the chemical nature and/or concentration of the dispersant is selected to obtain the predetermined surface tension of the dispersion. In some embodiments, the fixing agent enhances the adhesion between the plurality of indigo particles and a textile substrate/fiber by non-covalent bonding of the fixing agent to the substrate, such as by electrostatic interactions. In some embodiments the fixing agent forms a film on the surface of the substrate comprising the nanoparticles embedded therewithin. In some embodiments, the dry weight concentration of the fixing agent within the dispersion is between 0.1% and 10%, between 0.5% and 3%, between 0.5% and 5%, between 0.5% and 10%, between 1% and 5%, between 1% and 10%, including any range in between.

[00161] Non-limiting examples of the fixing agent include but are not limited to, poly cations (cationic oligomers/polymers), polyamines, polysaccharides (e.g., alginic acid, alginate, cellulose, gum, etc.), proteins (e.g. soy protein), amine compounds (e.g., trialkyl amine, diethylenetriamine, epichlorohydrin, dimethyl diallyl ammonium chloride, diallylamine etc.), phosphonium cations, epoxy, formaldehyde and tertiary sulphonium groups including any combination thereof. [00162] In some embodiments, the composition of the invention consists essentially of the indigo nanoparticles, the polymeric dispersant, and the fixing agent.

[00163] In some embodiments, the binder enhances the adhesion between the plurality of indigo particles and the substrate by forming a polymer film on top of the dyed substrate, thereby embedding the indigo nanoparticles and enhancing the affinity of indigo particles to the substrate.

[00164] In some embodiments, the dry weight percentage of the binder within the composition is between 0.1% to 10%, including any range in between.

[00165] In some embodiments, the binder comprises a resin, such as acrylate resin, urethane resin, acrylonitrile resin, epoxy resin including any mixture thereof.

[00166] In some embodiments, the composition of the invention further comprises a cosolvent. In some embodiments, the co-solvent is characterized by a flash point of at least 170 °C. The following co-solvents may be used without any limitation to these: glycerol, polyethylene glycol, mono-, di- and tri-propylene glycol, wherein the PEG has a molecular weight that ranges from 200 Dalton to 1000 Dalton.

[00167] In some embodiments, the composition of the invention is a textile substrate (fibers, yarn, textile) dyeing composition. In some embodiments, dyeing is by embedment of the plurality of indigo nanoparticles on or within a substrate (e.g., textile substrate, textile fiber, yarn, etc.) in need of dyeing. In some embodiments, embedment is by non-covalent interaction (e.g., physical interactions, electrostatic interaction, etc.). In some embodiments, dyeing is by ultrasonication and/or cavitation process, such as disclosed hereinbelow. In some embodiments, the composition of the invention is a sonication textile substrate indigo dyeing composition. In some embodiments, the composition of the invention is a cavitation textile substrate indigo dyeing composition.

[00168] The terms “plurality of indigo nanoparticles” and “indigo nanoparticle(s)” are used herein interchangeably and refer to indigo nanoparticles in a solid composition or dispersion of the invention. In contrast, the term “indigo particles” refer to indigo on or with the dyed substrate (e.g. embedded into the substrate, as disclosed herein). 1 [00169] In another aspect, there is provided a dyeing composition comprising a plurality of dye nanoparticles and a predetermined amount of a dispersant; wherein each of the plurality of dye nanoparticles comprises a water-insoluble dye selected from a vat dye, a sulfur dye, or both; and wherein the predetermined amount of the dispersant is sufficient to stabilize the plurality of dye nanoparticles in an aqueous dispersion. In some embodiments, the plurality of dye nanoparticles is characterized by median particle size on an intensity basis of between about 10 and about 500 nm, between about 10 and about 200 nm, between about 10 and about 300 nm, between about 10 and about 400 nm, between about 50 and about 500 nm, between about 50 and about 400 nm, between about 50 and about 300 nm, between about 50 and about 200 nm, between about 10 and about 100 nm, between about 10 and about 150 nm, between about 50 and about 200 nm, between about 100 and about 200 nm, between about 10 and about 90nm, below 100 nm, between about 20 and about 100 nm, between about 20 and about 90 nm, between about 30 and about 100 nm, between about 30 and about 90 nm, between about 20 and about 50 nm, including any range between. The median particle size is determined by DLS.

[00170] In some embodiments, each of the plurality of dye nanoparticles consists essentially of the water-insoluble dye. In some embodiments, at least 90%, at least 95%, at least 97%, between 90 and 99%, between 80 and 95%, between 90 and 97%, between 90 and 95%, between 90 and 99.9, between 80 and 99%, between 80 and 95% by weight of the plurality of dye nanoparticles consist of the water-insoluble dye, including any salt or hydrate thereof.

[00171] In some embodiments, the dye nanoparticles are spherical particles. In some embodiments, the dye nanoparticles are non-spherical particles, or are substantially devoid of a defined shape. In some embodiments, the spherical dye nanoparticles are substantially characterized by a shape selected from a sphere, hemi-sphere, and ellipse, including any combination thereof.

[00172] In some embodiments, a weight content of the plurality of dye nanoparticles within the dyeing composition is between 0.1% and 99%, between 0.1% and 30%, between 0.1% and 10%, between 1% and 30%, between 1% and 10%, between 1% and 20%, between 30% and 40%, between 30% and 50%, between 30% and 60%, between 30% and 70%, between 30% and 80%, or between 30% and 90%, including any range in between.

[00173] In some embodiments, the dispersant is a water soluble dispersant, such as a polymeric dispersant or a non-polymeric dispersant (i.e. a small molecule-based dispersant), as described above. In some embodiments, a weight ratio between the dispersant and the plurality of dye nanoparticles within the dyeing composition is between 2:1 and 0.001: 1, between 2: 1 and 0.01: 1, between 2: 1 and 0.1: 1, between 2:1 and 1: 1, between 1 :1 and 0.001: 1, between 0.1: 1 and 0.001: 1, between 0.5: 1 and 0.001: 1, between 0.01: 1 and 0.001: 1, including any range between.

[00174] In some embodiments, the dyeing composition is as described above for indigobased composition of the invention (including a powderous composition, aqueous dispersion, and optionally further comprising one or more additives, as disclosed above).

[00175] In another aspect, there is provided a dyeing kit comprising (i) the composition of the invention (e.g. consisting essentially of the water insoluble dye nanoparticles, such as indigo nanoparticles/vat-, sulfur-dye and the dispersant), and optionally further comprising (ii) one or more additive, and/or a sizing agent. In some embodiments, the constituents of the kit are stored in a single container, or in separate containers. In some embodiments, the constituents are packaged unit dosage forms, wherein each unit dosage is sufficient for dyeing a predefined amount of the substrate. In some embodiments, the constituents of the kit are in a form of solids (dispersible solids), and the kit further comprises an aqueous carrier along with instructions for mixing a predetermined amount of the liquid carrier with a predetermined amount of the solid constituents of the kit, to obtain the dispersion of the invention. In some embodiments, at least some of the constituents of the kit are in a form of liquid compositions (solution or dispersion).

Dyed substrate

[00176] According to one aspect, there is provided an indigo dyed fiber comprising a textile fiber in contact with a plurality of indigo particles (also referred to herein as “indigo particles”) embedded on or within the textile fiber wherein the plurality of indigo particles comprises a plurality of elongated indigo particles (also referred to herein as “elongated indigo particles”) characterized by an average length dimension in a range between 300 nm and 20 um and a plurality of spherical indigo particles (also referred to herein as “spherical indigo particles”) characterized by an average particle size of between 10 nm and 500 nm.

[00177] The terms “indigo particles” refers to indigo micro/nano-particles embedded in or on a textile fiber/substrate. The terms “textile substrate” and “substrate” are used herein interchangeably.

[00178] Furthermore, the inventors surprisingly found that indigo dyed yarns and fabrics of the invention exhibited characteristic needle-shaped and/or rod-shaped indigo particles, optionally along with substantially spherically-shaped indigo particles embedded on or within the surface of the dyed yarns or fabrics. As visualized by SEM, the surface of the yarns and fabrics dyed according to the method of the invention is characterized by the presence of elongated (e.g., needle-shaped and/or rod-shaped) indigo particles with an average size (i.e., average length) ranging between several hundreds of nanometers and tens of microns. In contrast, exemplary yarns and/or fabrics dyed according to the conventional leuco-indigo based process (without application of ultrasonic waves) resulted in the formation of substantially spherical nanoparticles.

[00179] In another aspect of the invention, there is provided an indigo dyed substrate comprising a substrate in contact with indigo particles (i.e., elongated indigo particles and spherical indigo particles) embedded on or within the outer surface of the substrate, wherein the indigo particles comprise elongated particles characterized by an average length dimension in a range between 300 nm and 20 um. In some embodiments, the substrate is bound to the indigo particles, wherein bound is via a non-covalent bond or a non-covalent interaction. In some embodiments, the substrate is bound to the indigo particles, wherein bound is via physical interactions, including inter aha physisorption.

[00180] In some embodiments, the indigo particles comprise or consist essentially of the elongated indigo particles and the spherical indigo nanoparticles. In some embodiments, the elongated indigo particles comprise indigo particles characterized by a length dimension in a range between 300 nm and 20 um, between 300 nm and 20 um, between 500 nm and 20 um, between 700 nm and 20 um, between 300 nm and 15 um, between 300 nm and 10 um, between 700 nm and 10 um, between 700 nm and 15 um, between 500 nm and 10 um, between 500 nm and 20 um, between 300 nm and 1 um, between 500 nm and 1 um, between 700 nm and 5 um, between 700 nm and 5 um, between 1 and 20 um, between 1 and 15 um, between 1 and 10 um, between 1 and 5 um, between 5 and 20 um, between 5 and 15 um, between 5 and 10 um, above 300 nm, above 500 nm, above 700 nm, including any range between.

[00181] In some embodiments, the spherical indigo particles have a spheric geometry or shape. In some embodiments, the spherical indigo particles have an inflated or deflated shape. In some embodiments, the spherical indigo particles are devoid of any characteristic geometry or shape. In some embodiments, the spherical indigo particles have a spherical shape, a quasi-spherical shape, a cubic shape, a semi-cubic shape, a quasi-elliptical sphere, a deflated shape, a concave shape, an irregular shape, or any combination thereof. One skilled in the art will appreciate that the exact shape of each spherical indigo particle may differ from one particle to another. Moreover, the exact shape of spherical indigo particles may be derived from any of the geometric forms listed above, so that the shape of the particle does not perfectly fit a specific geometrical form.

[00182] In some embodiments, the elongated indigo particles comprise indigo particles characterized by a length dimension, as described hereinabove, and further characterized by a width dimension between 50 and 800 nm, between 50 and 100 nm, between 50 and 200 nm, between 50 and 300 nm, between 50 and 500 nm, between 50 and 600 nm, between 10 and 200 nm, between 200 and 800 nm, between 200 and 500 nm, between 100 and 500 nm, between 200 and 600 nm, between 200 and 400 nm, between 400 and 600 nm, between 600 and 800 nm, including any range between.

[00183] In some embodiments, the elongated indigo particles are characterized by an aspect ratio between about 5 and about 100, between about 5 and about 10, between about 5 and about 20, between about 5 and about 30, between about 5 and about 50, between about 10 and about 100, between about 10 and about 50, between about 10 and about 20, between about 10 and about 30, including any range between. In some embodiments, the elongated indigo particles are characterized by a length dimension and by an aspect ratio, as described herein.

[00184] In some embodiments, the elongated indigo particles are substantially characterized by a rod shape, a bar shape, a needle shape, cylindrical shape, elliptical shape, etc. a skilled artisan will appreciate that the shape of each of the elongated indigo particles may slightly or substantially vary from a specific geometrical shape. Accordingly, the elongated particles may have a rod-like shape, a bar-like shape, a needle-like shape, a cylinder-like shape, or ellipse-like shape, meaning that the actual shape of the particle has some deviations (e.g., at least 10%, at least 50%, or more deviation) from a perfect geometrical shape.

[00185] In some embodiments, the elongated indigo particles are uniformly shaped particles, wherein at least 70%, at least 80%, at least 90%, at least 95%, at least 97%, at least 99% of the elongated particles on or within the surface of the dyed substrate have the same shape, including any range between. In some embodiments, the elongated particles are non- uniformly shaped particles, or particles being devoid of a defined shape. In some embodiments, at least 10%, at least 20%, at least 50%, at least 70% of the elongated indigo particles on or within the surface of the dyed substrate are non-uniformly shaped particles, or particles being devoid of a defined shape, including any range between.

[00186] The terms “length dimension” and “width dimension” as used herein, each independently refers to the average value (e.g., number average), as determined by SEM. Methods for determining average length or average width of the elongated particles in a given sample are well-known in the art. In an exemplary embodiment, the average length or average width of the elongated particles can be determined by SEM, using an appropriate SEM image processing software.

[00187] In some embodiments, the indigo particles disclosed herein comprise or consist essentially of indigo in a crystalline state. In some embodiments, the indigo particles disclosed herein comprise or consist essentially of indigo in an amorphous state.

[00188] In some embodiments, the spherical indigo particles are substantially characterized by a shape selected from a sphere, hemi-sphere, and ellipse, including any combination thereof. In some embodiments, the spherical indigo particles are characterized by an average particle size between about 10 and about 200 nm, between about 10 and about 100 nm, between about 10 and about 150 nm, between about 50 and about 200 nm, between about 100 and about 200 nm, between about 10 and about 90nm, below 100 nm, between about 20 and about 100 nm, between about 20 and about 90 nm, between about 30 and about 100 nm, between about 30 and about 90 nm, between about 20 and about 50 nm, including any range between.

[00189] In some embodiments, the indigo particles disclosed herein are substantially devoid of particles (e.g., indigo particles) characterized by a particle size about 100 nm, about 90 nm, or about 90 nm. In some embodiments, the indigo particles disclosed herein are substantially devoid of elongated particles (e.g., elongated indigo particles) characterized by a length dimension below about 300 nm, below about 400 nm, below about 500nm, below about 600 nm, below about 700 nm, including any range between.

[00190] Methods for determining average particle size of the spherical indigo particles in a given sample are well-known in the art. In an exemplary embodiment, the average particle size of the spherical indigo particles can be determined by SEM, using an appropriate SEM image processing software.

[00191] In some embodiments, between 10 and 90%, between 10 and 20%, between 10 and 30%, between 10 and 50%, between 10 and 60%, between 60 and 90% of the entire indigo particles on or within the surface of the indigo dyed substrate are elongated particles, including any range between.

[00192] In some embodiments, the substrate is or comprises a fibrous substrate. In some embodiments, the substrate comprises any one of: a textile fiber, a yarn, a textile substrate, or any combination thereof. In some embodiments, the substrate disclosed herein encompasses a textile fiber, a yarn, a textile substrate, or any combination thereof further in contact with an additional pigment and/or a dye, and/or a nanoparticle, other than indigo. In some embodiments, the substrate disclosed herein is solely in contact with the indigo particles. In some embodiments, the substrate disclosed herein is in contact with a plurality of indigo particles, wherein the plurality of indigo particles is composed essentially of the elongated indigo particles and the spherical indigo nanoparticles, wherein the elongated indigo particle and spherical indigo nanoparticles are as disclosed herein. In some embodiments, the substrate disclosed herein is substantially devoid of a nano- and/or microparticle other than indigo particle.

[00193] In some embodiments, the textile substrate comprises a plurality of fibers or a plurality of yarns. In some embodiments, the fibers or yarns are in contact with each other. In some embodiments, the fibers or yarns are in a form of a mat. In some embodiments, the textile substrate is a fibrous substrate. In some embodiments, the textile substrate is a woven or a non-woven textile substrate. In some embodiments, each yarn comprises a plurality of fibers. As used herein, the terms “fiber” and “textile fiber” are used herein interchangeably.

[00194] In some embodiments, each of the plurality of fibers or yarns comprises a synthetic or a natural material. In some embodiments, each of the plurality of fibers or yarns comprises material selected from a polyester, a polyamide, cotton, linen, cellulose, cellulose derivative, or any combination thereof.

[00195] The material of the fibers or yarns is not particularly limited, and examples include natural fibers such as cotton, linen, silk, and sheep wool; semi-synthetic fibers such as rayon and acetate; synthetic fibers such as nylon, polyester, polyurethane, and polypropylene; composite fibers thereof; and blend fibers. The form of fibers may be any form of thread, fabric, non-woven fabric, paper, and the like.

[00196] In some embodiments, the textile fiber comprises a natural textile fiber, a synthetic textile fiber, or a mixture thereof. In some embodiments, the textile fiber comprises a material selected from a polyester, a polyamide (e.g., Nylon), cotton, linen, wool, kapok, ramie, cellulose, acetylated cellulose, polyurethane, polyacrylate, rubber, modacryl, polypropylene, a polyolefin (e.g., polyethylene, polypropylene, etc.), a nanofiber, hemp, bamboo, viscose, modal, rayon, and silk or any combination thereof.

[00197] In some embodiments, the textile substrate of the invention is selected from a knitted textile substrate, a woven textile substrate, and a non-woven textile substrate, including any combination thereof.

[00198] In some embodiments, the textile substrate of the invention is a textile fabric, the textile fabric is a woven fabric, a knitted fabric, or a uniaxial or multiaxial composite. If the textile substrate is a woven textile substrate, the term woven refers to any type of weave, such as plain weave, satin weave, panama weave, twill weave, and the like.

[00199] In some embodiments, the substrate (such as a textile substrate) has an outer surface and an inner surface, wherein the outer surface is configured to face an ambient and/or is referred to an exterior layer. In some embodiments, the outer surface and the inner surface are the same or different. In some embodiments, the outer surface is an indigo dyed surface. In some embodiments, the outer surface is in contact with the indigo particles. In some embodiments, the inner surface is an undyed surface. In some embodiments, the inner surface of the textile substrate is substantially devoid of indigo particles, or any other particles such as a dye, a pigment, etc., in contact therewith.

[00200] In some embodiments, the textile substrate is a single-layer substrate. In some embodiments, the textile substrate comprises a plurality of layers.

[00201] In some embodiments, the substrate is an untreated substrate (e.g., devoid of postmanufacturing processing such as bleaching, scouring, etc.). In some embodiments, the substrate is a pre-treated substrate, wherein pre-treatment refers to any treatment process performed on the substrate prior to dyeing thereof (such as bleaching, desizing, scouring, mercerization, bottoming dyeing, hydrophobization etc.). In some embodiments, the untreated substrate is a hydrophobic substrate (i.e. unscoured substrate). In some embodiments, the untreated substrate is a hydrophobic substrate comprising natural yarns (e.g. cotton, wool, silk, linen, etc.).

[00202] In some embodiments, the substrate is a hydrophobized substrate. Hydrophobization treatment is known in the art and includes for example water repellency treatment, moisture anti-wicking treatment, etc.

[00203] In some embodiments, the substrate is a hydrophobic substrate. In some embodiments, the hydrophobic substrate is characterized by a water contact angle above 90°, above 90°, above 100°, above 120°, above 130°, or between 90 and 170°, between 100 and 170°, between 100 and 160°, between 90 and 150°, including any range between.

[00204] In some embodiments, the substrate is a hydrophilic substrate characterized by a water contact angle below 90°. In some embodiments, the hydrophilic substrate is a pretreated substrate (e.g. a scoured substrate).

[00205] In some embodiments, the indigo particles are embedded on or within the outer surface of the fiber, of the yarn, of the textile substrate, or any combination thereof. In some embodiments, the indigo particles are embedded between the adjacent fibers or yarns within the textile substrate. In some embodiments, the indigo particles are embedded on top of the fibers or yarns within the textile substrate. In some embodiments, the indigo particles are embedded on top of the fibers or yarns, and between the adjacent fibers or yarns within the textile substrate. In some embodiments, the textile substrate is stably bound to the indigo particles, wherein stable is described herein. In some embodiments, the substrate is fully or partially coated by the indigo particles.

[00206] In some embodiments, between 30 and 99.9%, between 30 and 40%, between 30 and 50%, between 30 and 80%, between 30 and 90%, between 50 and 99.9%, between 50 and 90%, between 50 and 80%, between 30 and 70%, between 30 and 60%, between 60 and 99.9%, between 60 and 90%, between 70 and 99.9%, between 70 and 90%, between 50 and 70%, between 70 and 80%, between 80 and 99.9%, between 80 and 90%, between 90 and 95%, between 95 and 97%, between 97 and 99.9%, of the substrate surface is in contact with the indigo particles, including any range between. In some embodiments, the entire surface of the substrate is in contact with the indigo particles.

[00207] In some embodiments, the indigo particles are distributed in a form of a coating layer on top of the substrate. In some embodiments, the coating layer has a substantially homogenous thickness ranging between about 40 nm and about 1000 nm, about 40 nm and about 800 nm, about 100 nm and about 1000 nm, about 100 nm and about 500 nm, including any range between. In some embodiments, the term “layer”, refers to a substantially homogeneous substance of substantially uniform-thickness. In some embodiments, the term “layer”, refers to a layer of indigo particles of substantially uniform-thickness.

[00208] In some embodiments, the indigo particles form a plurality of agglomerates or clusters on top of the outer surface of the substrate. In some embodiments, the indigo particles are distributed in a form of a homogenous coating on top of the substrate. In some embodiments, the outer surface of the substrate is in contact with the indigo particles. In some embodiments, the outer surface of the textile substrate is bound to the indigo particles.

[00209] In another aspect of the invention, there is provided an indigo dyed substrate comprising a substrate in contact with indigo particles embedded on or within the outer surface of the substrate, wherein the indigo particles comprise spherical indigo particles, as disclosed herein, wherein the spherical indigo particles are in a form of a homogenous layer characterized by a substantially uniform thickness ranging between about 40 nm and about 1000 nm, about 40 nm, and about 800 nm, about 100 nm and about 1000 nm, about 100 nm and about 500 nm, including any range between. In some embodiments, the indigo dyed substrate is substantially devoid of elongated indigo particles. In some embodiments, the spherical indigo particles are embedded on and/or within the surface of the substrate. In some embodiments, the above disclosed indigo dyed substrate (e.g., comprising a uniform layer of spherical particles) is obtained by contacting the composition of the invention with the substrate (e.g., by dipping or spraying, etc.), subjected to cavitation (without applying ultrasonic waves). In some embodiments, it is further postulated that the application of ultrasonic waves subsequently or during the coating process induces formation of elongated particles (or increases a length dimension thereof).

[00210] In some embodiments, the indigo particles are in contact with or embedded into substrate. In some embodiments, the indigo particles are in contact with the textile fiber. In some embodiments, the indigo dyed yarns of the invention are ring-dyed yarns.

[00211] Ring dyeing is known in the art and refers to a dyeing technique in which dyes partially penetrate into the yarn (e.g., occupy only between 5-50% of the yarn cross-section). In ring dyeing the outer portion of the yarn is dyed, whereas the core remains undyed. Ring dyed yarns are characterized by a ring-like dyeing pattern in the cross-sectional view.

[00212] In some embodiments, the penetration depth of the indigo nanoparticles into the ring-dyed yarn (i.e. the thickness of the ring-like pattern) is between 1 and about 200 um, between 3 and about 200 um, between 3 and about 150 um, including any range between. In some embodiments, the penetration depth is predetermined by the average size of the cavitation bubbles generated during the dyeing process. In some embodiments, a predetermined penetration depth (i.e. between 1 and about 200 um) is modified/controlled by varying the cavitation/ultrasonication conditions (e.g. intensity and/or frequency of the acoustic waves) required for generation of the cavitation bubbles with predetermined average size. In some embodiments, the core of the ring-dyed yarn is substantially devoid of indigo particles (e.g. retains the color of the undyed yarn).

[00213] Ring dyed yarn may comprise indigo nanoparticles adjacent to the external portion of the yarn. Ring dyed yarns may comprise indigo nanoparticles and surface active agent. The article of the invention (e.g. ring dyed fabric) may comprise or consists essentially of, comprising weft and warp yarns, at least portion of which (warp only, weft only, or both) comprised of ring dyed yarns. The thickness of the outer ring may range from about 5 percent to 100% of a total thickness of the yarn.

[00214] The inventors have surprisingly observed that it is essential to maintain the surface tension (e.g., by varying the amount/type of the dispersant, or by adding an appropriate amount of a surfactant) of the dispersion of the invention above the predetermined surface tension value as disclosed above, to obtain ring dyeing. When the surface tension was below the predetermined surface tension value, an almost uniform penetration of the indigo nanoparticles inside the dyed fiber has been observed (so that no ring dyeing has been obtained).

[00215] In some embodiments, the indigo particles are in contact with or embedded into at least a portion of the plurality of yarns composing the textile substrate.

[00216] In some embodiments, the indigo particles are embedded or impregnated into the fiber, into the yarn and/or into the textile substrate. In some embodiments, the indigo dyed substrate comprises indigo particles embedded or impregnated into the fiber, into the yarn, and/or into the textile substrate by applying ultrasonic waves (e.g., having a suitable frequency and/or input power of the ultrasonic source, and being applied for a sufficient time) for embedding the indigo particles into at least a portion of the substrate (i.e., fiber, yarn, or textile substrate). In some embodiments, the indigo dyed substrate of the invention comprises the indigo particles embedded or impregnated into the fiber, the yarn, and/or into the textile substrate.

[00217] In some embodiments, a weight ratio between the indigo particles and the substrate (pristine fiber, pristine yarn or pristine textile substrate) within the indigo dyed substrate of the invention is between 0.2: 1 and 0.001 : 1 , between 0.1: 1 and 0.001 : 1 , between 0.15: 1 and 0.001: 1, between 0.05:1 and 0.001: 1, between 0.01: 1 and 0.001: 1, including any range between.

[00218] In some embodiments, the indigo dyed substrate of the invention further comprises the dispersant and optionally the surfactant. In some embodiments, the dispersant and optionally the surfactant is in contact with the indigo particle and/or with the substrate. In some embodiments, a weight ratio between the dispersant and the indigo particles within the indigo dyed substrate is between 2: 1 and 0.001 : 1, between 2: 1 and 0.01 : 1, between 2: 1 and 0.1 :1, between 2:1 and 1: 1, between 1:1 and 0.001: 1, between 0.1 :1 and 0.001: 1, between 0.5:1 and 0.001 : 1, between 0.01 : 1 and 0.001 : 1, including any range between.

[00219] In some embodiments, the surfactant and/or dispersant are as disclosed herein.

[00220] In some embodiments, the indigo dyed substrate of the invention further comprises an additive, wherein the additive is as described hereinabove. In some embodiments, the additive is selected from (i) a binder, (ii) a fixing agent, or both (i) and (ii). In some embodiments, the indigo dyed substrate of the invention consists essentially of indigo particles, a binder and optionally of at least one of a fixing agent, a surface active agent, or any combination thereof. In some embodiments, the binder and the fixing agent are as disclosed herein. In some embodiments, the additive further comprises a sizing agent.

[00221] In some embodiments, a weight ratio between the additive and the substrate (pristine substrate or indigo dyed substrate) is between 0.0001 : 1 and 0.2: 1, between 0.0001 : 1 and 0.01: 1, between 0.0001 :1 and 0.1: 1, between 0.001 :1 and 0.2: 1, between 0.01: 1 and 0.2:1, including any range between.

[00222] In some embodiments, the indigo dyed substrate comprises indigo particles stably bound to the substrate (pristine textile fiber, pristine yarn, pristine textile substrate). In some embodiments, the indigo particles are stably bound to the substrate by non-covalent interaction and/or covalent interaction.

[00223] In some embodiments, the term “stably bound” refers to the capability of the indigo dyed substrate of the invention to maintain at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, between 50 and 99%, between 50 and 95%, between 50 and 90%, between 60 and 99%, between 70 and 99%, between 50 and 70%, between 80 and 99%, between 80 and 95% of the initial loading of the indigo particles upon at least 5, at least 10, at least 20, at least 30, at least 50, at least 100 successive laundry test cycles, including any range between. In some embodiments, the laundry test is performed according to ISO 6330 laundry test. In some embodiments, the term “stably bound” refers to bleaching and/or abrasion stability of the indigo dyed substrate, as determined by conventional tests known in the textile industry. [00224] In some embodiments, the indigo particles content can be determined spectrophotometrically (e.g. by color difference in L*a*b and L*C*h color space, as disclosed below), as compared to the initial loading, which refers to the weight percentage of indigo particles relative to the pristine substrate. The term “initial loading” refers to the indigo particles loading immediately after the dying process (or upon a washing cycle after the dying).

[00225] In some embodiments, the indigo dyed substrate has a uniform color intensity/color distribution. In some embodiments, the indigo dyed substrate is characterized by a color difference AE below 2, below 1, below 0.9, below 0.8, below 0.6, below 0.5, below 0.3, between 0.3 and 1, between 0.5 and 1, including any value in between, wherein AE is in L*a*b or L*C*h color space as calculated according to CIE76, CIE94, CIEDE2000 or CMC l:c (1984) formulas. In some embodiments, the above disclosed color difference of the indigo dyed substrate is upon at least 10 successive laundry test cycles, wherein the laundry test is performed according to ISO 6330 laundry test.

[00226] In some embodiments, the dyed substrate is substantially devoid of a reducing agent trace amounts. The term “reducing agent” encompasses any sulfur-based indigo reducing agents and derivatives thereof, such as sulfite, sulfide, sulfate, bisulfite, metabisulfite, dithionite, thiosulfate, including any combination thereof. In some embodiments, the term “trace amounts” refers to a weight content of the reducing agent in the dyed substrate of between 1 ppm and 0.5%, between 1 ppm and 0.1%, between 1 ppm and lOOOppm, including any range between. In some embodiments, the term “trace amounts” refers to a weight content of the reducing agent above the weight concentration of the same reducing agent in the pristine (non-dyed) substrate. In some embodiments, the article of the invention is substantially devoid of a reducing agent, such as an indigo reducing agent (e.g., dithionite, including any salt thereof). In some embodiments, the article of the invention is devoid of trace amounts of indigo reducing agent (e.g., dithionite, including any salt thereof).

[00227] In some embodiments, the dyed substrate of the invention is characterized by a sodium, potassium, and/or calcium weight content (including salts thereof, such as hydroxides) that is similar (i.e., not more than 10% greater Na-, K-, and/or Ca-content) to the undyed substrate. In some embodiments, the Na-content of the dyed substrate of the invention is between 0.07 and 0.1%, in contrast, indigo dyed substrates obtained by traditional indigo dyeing methods have a significantly greater sodium content (such as between 0.3 and l%w/w, which is almost 10 times greater than the Na-content of the substrate of the invention).

Article

[00228] In another aspect, there is provided an indigo dyed textile substrate comprising or consisting essentially of (i) the indigo dyed fibers disclosed herein, (ii) indigo dyed yarns disclosed herein, or of both (i) and (ii).

[00229] In another aspect, there is provided an article comprising the indigo dyed textile substrate, wherein the indigo dyed textile substrate comprises or consists essentially of (i) the indigo dyed fibers disclosed herein, (ii) indigo dyed yarns disclosed herein, or of both (i) and (ii). In some embodiments, the indigo dyed textile substrate is an ultrasonically dyed textile substrate. In some embodiments, the indigo dyed textile substrate is a cavitation dyed textile substrate.

[00230] In some embodiments, a weight ratio between the indigo particles and the textile substrate within the article of the invention is between 1: 10.000 and 1 :5, between 1: 1.000 and 1 :5, between 1: 100 and 1 :5, between 1: 10.000 and 1: 10, between 1:1.000 and 1 :10, between 1:10.000 and 1 : 100, between 1:10.000 and 1: 1000, including any range between.

[00231 ] In some embodiments, the article of the invention is characterized by a loading of the indigo particles relative to the surface area of the textile substrate ranging between 0.1 and 20 g/m ² , between 0.1 and 0.2 g/m ² , between 0.1 and 2 g/m ² , between 0.1 and 5 g/m ² , between 0.1 and 10 g/m ² , between 0.2 and 0.5 g/m ² , between 0.5 and 0.8 g/m ² , between 0.8 and 1 g/m ² , between 1 and 1.5 g/m ² , between 1.5 and 2 g/m ² , between 1 and 20 g/m ² , between 1 and 10 g/m ² , between 10 and 20 g/m ² , including any range therebetween.

[00232] In some embodiments, the article of the invention is characterized by indigo loading (relative to the dry weight of the dyed substrate) of between 0.5 and 10%, between about 0.5 and about 5%, between 0.5 and 1%, between 0.5 and 3%, between 1 and 5%, between 1 and 8%, between 2 and 10%, between 2 and 8%, between 5 and 10%, between 3 and 6%, including any range in between.

[00233] In some embodiments, the article of the invention is at least partially dyed by indigo particles. In some embodiments, between 10 and 99.9%, between 10 and 50%, between 50 and 99.9%, between 10 and 30%, between 30 and 99.9%, between 50 and 99.9%, between 70 and 99.9% of the outer surface of the substrate or of the article comprising thereof, is in contact with the indigo particles, as disclosed herein.

[00234] In some embodiments, the article of the invention (e.g., in a form of a garment) comprising the indigo dyed substrate (e.g., a yarn or a textile substrate), is characterized by indigo particles stably bound to the substrate.

[00235] In some embodiments, the article of the invention (e.g. the indigo dyed textile substrate, the indigo dyed textile fiber, or the indigo dyed yarn) is stable at a temperature up to 200°C, including any range or value therebetween, wherein “stable” refers to a stable bonding of the indigo particle to the substrate, as disclosed herein.

[00236] In some embodiments, the article of the invention is stable upon successive washings cycles. In some embodiments, the article of the invention is stable upon successive washings and drying cycles. In some embodiments, the washings and drying cycles are performed under regular conditions (e.g., a temperature of up to 60°C, or up to 90°C, and/or application of standard laundry detergents).

[00237] In some embodiments, the article of the invention is stable upon at least 3, at least 5, at least 7, at least 10, at least 15, at least 20, at least 30, at least 50 laundry test cycles, including any range between. In some embodiments, the laundry test stability is assessed via a standard ISO 6330 laundry test.

[00238] In some embodiments, the article of the invention maintains at least 50%, at least 55%, at least 60%, at least 70%, of the initial loading of the plurality of indigo particles, upon at least 10 successive laundry test cycles, wherein the laundry test is performed according to ISO 6330 laundry test, including any range or value in between.

[00239] In some embodiments, the article of the invention is characterized by a substantially homogenous dyeing on the outer surface of the article. In some embodiments, the outer surface of the article is characterized by a substantially uniform color intensity and/or uniform color distribution across the indigo dyed substrate. In some embodiments, the outer surface of the article (or an indigo dyed portion thereof) is characterized by a uniform color intensity/color distribution. In some embodiments, the outer surface of the article is characterized by a color difference AE below 2, below 1, below 0.9, below 0.8, below 0.6, below 0.5, below 0.3, between 0.3 and 1, between 0.5 and 1, including any value in between, wherein AE is in L*a*b or L*C*h color space as calculated according to CIE76, CIE94, CIEDE2000 or CMC l:c (1984) formulas.

[00240] In one embodiment, the indigo dyed article is compatible with a denim finishing process. Ring dyed yarns and textile made of them (including denim for denim apparel such as jeans) demonstrating ability to lose dyestuff and dyed fiber of outer portion of the yarns upon exposure to denim finishing, creates a finishing pattern on a surface of the garment (denim washes).

[00241] In one embodiment, the denim finishing process includes but is not limited to: Desizing wash - high temperature, detergents, can be with amylase; Stone wash with pumice stones; Enzyme wash (cellulase, peroxidase); Bleach: calcium or sodium hypochlorite, PP; Ozone, laser washes; Sand blasting.

[00242] In some embodiments, the article is substantially devoid of trace amounts of a reducing agent. In some embodiments, the article of the invention is devoid of trace amounts of indigo reducing agent (e.g., dithionite, including any salt thereof).

[00243] In some embodiments, the article of the invention is characterized by a sodium, potassium, and/or calcium weight content that is similar (i.e., not more than 10% greater Na- , K-, and/or Ca-content) to the undyed article. In some embodiments, the Na-content of the article is between 0.07 and 0.1%, in contrast, indigo dyed articles obtained by traditional indigo dyeing methods have a significantly greater sodium content (such as between 0.3 and l%w/w, which is almost 10 times greater than the Na-content of the substrate of the invention).

[00244] In some embodiments, the indigo particles are in a form of a layer or agglomerates on top of the outer surface of the indigo dyed substrate, or of the article of the invention. In some embodiments, the indigo particles are homogenously distributed on the outer surface of the indigo dyed substrate, or of the article of the invention. In some embodiments, the indigo particles are in a form of a pattern on the outer surface of the indigo dyed substrate, or of the article of the invention.

[00245] In some embodiments, the article of the invention is manufactured according to a method disclosed herein.

[00246] In some embodiments, the article of the invention is stable for at least 12 months, for at least 15 months, for at least 18 months, for at least 20 months, at least 24 months at a temperature range as disclosed hereinabove, and upon exposure thereof to the ambient conditions (comprising inter alia ambient atmosphere, UV radiation, etc.).

[00247] As used herein the term “stable” refers to the capability of the article of the invention to substantially maintain its structural and/or mechanical integrity, and to substantially maintain its initial loading of the indigo particles, as described hereinabove.

[00248] In some embodiments, the article according to some embodiments of the present invention can be used for the preparation of clothing, bedding, and the like such as side fabric for down, coats, blousons, windbreakers, blouses, dress shirts, skirts, slacks, gloves, hats, mattress sheets, mattress covers, curtains, or tents.

[00249] In some embodiments, the article of the invention is or comprises a textile product. Non-limiting examples of textile products include but are not limited to: apparel, carpets, rugs, towels, curtains, sheets, twine, clothing, bedding, and the like such as side fabric for down, coats, blousons, windbreakers, blouses, dress shirts, skirts, slacks, gloves, hats, mattress sheets, mattress covers, curtains, or tents, furniture upholstery and automotive upholstery, or any combination thereof.

[00250] In some embodiments, the substrate is textile fiber, yarn, woven or non-woven or knitted fabric, or garment.

[00251] In some embodiments, the substrate is textile yarn. In some embodiments, the yarn is a warp yarn for denim. The term textile yarn includes, but not limited to the ring spun or open-end yarns consisting of cotton, lycra bamboo, Tencel, modal, viscose, polyester, a polyamide (e.g. Nylon), linen, wool, kapok, ramie, cellulose, acetylated cellulose, polyurethane, polyacrylate, rubber, modacryl, polypropylene, a polyolefin (e.g. polyethylene, polypropylene, etc.), a nanofiber, hemp, rayon and silk or any combination thereof. Yarns count is Ne (Number English) is from 4.0 to 30.0, from 5.5 to 12.5.

Manufacturing process

[00252] Denim is an extremely popular textile material due to its unique ability to fade, creating “used” look desired in fashion industry. This fabric consists of dyed warp and white weft, which give the denim its characteristic “salt and pepper” pattern. A faded look can be achieved due to the ring dyeing of warp yarns - meaning that only the external part of the yarn is dyed, whereas the core stays white. Various washing techniques are used to remove the dyed layers of the yarn revealing its white core.

[00253] Vat dyes and sulfur dyes are traditionally used for denim dyeing. Indigo dye is the most popular dye of vat dyes. Vat and sulfur dyes are not soluble in water and to be dissolved for dyeing they need to be reduced by reduction agent (such as sodium dithionite or glucose) in basic condition (usually achieved by addition of soda caustic). The dyebaths (vats) are unstable on air due to the oxidation by atmospheric oxygen and requires addition of the reducing agent to maintain dye in its soluble reduced form.

[00254] Textile substrate is immersed into solution of the reduced dye, absorbs that solution, and subsequently removed from the solution and exposed to air and/or hot steam for oxidation of the dyestuff into its insoluble form. The insoluble form of dye forms particles on the surface of the textile. Process is repeated a few times to achieve desired depth of shade.

[00255] The particles do not form chemical bonds with the substrate. Lack of affinity of those particles to the substrate leads to the poor resistance to washes and abrasion, which, being a defect for other dyes, is a unique feature of textile dyed by sulfur and vat dyes. Poor resistance to washes and abrasion in combination with ring dyeing allows to create faded, vintage look of the garments made of such textile.

[00256] Destuff inevitably degrades due to exposure to air, whilst accumulating salts deteriorate quality of dyeing. Due to the limited affinity of indigo to cellulose, dyestuff instability on air and a need for the ring dyeing effect, the dyeing is carried out by multiple dipping (8-12 baths) in diluted solutions. Large amount of dyebaths and washing bath before and after dyeing results in massive, energy-demanding production lines.

[00257] Dyeing with vat and sulfur dyes results in, essentially, pigmentation of the textile (since dye particles cover textile substrate without chemical bonding to it). The inventors were surprised to find that those dyes can be dispersed into stable liquid ink without chemical transformation of the dye. Specifically, indigo can be dispersed to the dispersion containing particles of the same size as ones found on the surface of denim dyed by traditional technology. The dispersing method does not require any post-treatment of the dispersion (such as filtration or size-selective precipitation) to remove larger particles.

[00258] Since pigment do not form chemical bonds with textile, binder (resins) are required to fix pigment on the substrate. Comparing to the traditional pigments dyeing, our method does not require thermal curing. Fixing agents can be used to improve rubbing or washing fastness, if needed. Binders, however, can also be used if the dyestuff should be fixed to level constraining further wash down, for creation of various effect on the garment (such as jeans crease), or if pigments dyeing is done on the same substrate (for example, in so called pigment wash of denim).

[00259] In one aspect, the method of the invention comprises the following steps:

[00260] Step 1. Immersing textile substrate into liquid dyestuff, containing indigo nanoparticles, surface active agent and, optionally, wetting agent, an antifoaming agent, a leveling agent, a migration inhibitor, and a cationization agent, fixing agent, binder, emulsifier, including any combination thereof; applying acoustic waves sufficient for inducing cavitation to that liquid dyestuff; removing textile substrate from the liquid dyestuff.

[00261] Step 2. Drying.

[00262] Steps 1-2 can be repeated 1-3 times.

[00263] Step 3. Treatment with the fixing agent with subsequent drying. Such treatment can be repeated multiple times using different fixing agents.

[00264] Step 4. Sizing with sizing agent and subsequent drying.

[00265] Steps 3 and 4 can be combined. [00266] The inventors have observed that this method allows to obtain shade of 5-6 weight % of indigo loading in single pass of the textile substrate through the sonication-assisted dyebath.

[00267] Cavitation is a phenomena formation of vapor bubbles (also used herein as “cavitation bubbles”, or “bubbles”) within a liquid at low-pressure regions that occur in places where the liquid has been accelerated to high velocities. Subsequent implosions of the bubbles create areas of high temperature and pressure. Cavitation allows to incorporate water-based dyestuff into relatively hydrophobic substrate. Ultrasonication is a convenient way to induce cavitation in liquid. It is also known to the skilled in art how sonication parameters affect the cavitation bubbles. So, size of the bubbles depends on the frequency of the acoustic waves, and amount of the appearing bubbles depends on the intensity of the acoustic waves (e.g. sonication power).

[00268] The inventors surprisingly found that depth of penetration of the liquid into substrate can be tuned by the frequency of the acoustic waves (the higher, the less penetration) and, to much less extent, amplitude of the acoustic waves (the lower, the less penetration). The observed phenomena apparently is caused by different pressure generated by implosion of the bubbles of different size.

[00269] The inventors surprisingly found that sonication-induced cavitation significantly improves wettability of the unscoured textile substrate (specifically, raw cotton) without any pre-treatment, and allows direct dyeing of the dry, unscoured textile.

[00270] According to another aspect of some embodiments of the present invention there is provided a method of manufacturing a dyed substrate, the method comprises (i) contacting at least a portion of a substrate with dyeing composition of the invention (e.g. an aqueous dispersion comprising water- insoluble dye nanoparticles having a particle size between 10 and 500nm and a dispersant); and (ii) subjecting the substrate in contact with the dispersion to acoustic waves suitable for inducing cavitation under appropriate conditions; thereby manufacturing the dyed substrate; wherein the substrate comprises at least one of: a textile fiber, a yarn, and a textile substrate and wherein the dye is a water insoluble dye selected from vat dyes and sulfur dyes. In some embodiments, depth of penetration of dyeing liquid, and/or dye nanoparticles into the yarns of the substrate is controlled by means of cavitation. Cavitation is controlled by sonication parameters. In some embodiments, step (i) and/or step (ii) are as disclosed hereinbelow. In some embodiments, the process further comprises performing any one of steps (iii)-(v), as disclosed hereinbelow (for indigo dyeing process). In some embodiments, the aqueous dispersion is characterized by a surface tension above the critical surface tension of the substrate, as disclosed herein below.

[00271] Exemplary vat dyes include but are not limited to: indigo, indigo derivatives, such as thio-indigo, brom-indigo; anthraquinone derivatives (e.g. Indanthrene, Marione, Algol dyes, Helindone), carbazol derivatives (e.g. Hydron Blue), and any combinations thereof.

[00272] Exemplary sulfur dyes include but are not limited to: Sulphur Black (e.g. Sulphur Black 1), Sulphur Blue, Sulphur Green, Sulphur Brown, Sulphur Yellow, sulphurized vat dyes (e.g. Novatic Yellow 5G) and any combinations thereof. Additional vat/sulfur dyes are well known in the art.

[00273] The dyed substrate (i.e. a substrate dyed by dye nanoparticles performed according to the method disclosed herein) comprises the dye nanoparticles stably bound to at least one surface of the dyed substrate. In some embodiments, the dyed substrate (i.e. a substrate dyed by dye nanoparticles performed according to the method disclosed herein) is characterized by any one of: (i) bleaching and/or abrasion stability; (ii) laundry stability; (iii) color uniformity (i.e. uniform color intensity and/or uniform color distribution), as disclosed herein for indigo dyed substrate.

[00274] According to another aspect of some embodiments of the present invention there is provided a method of manufacturing an indigo dyed substrate, the method comprises (i) contacting at least a portion of a substrate with or applying the dispersion of the invention on top of a substrate; and (ii) subjecting the substrate in contact with the dispersion to acoustic waves suitable for inducing cavitation under appropriate conditions; thereby manufacturing the indigo dyed substrate; and wherein the substrate comprises at least one of: a textile fiber, a yarn, and a textile substrate. In some embodiments, depth of penetration of dyeing liquid into the yarns is controlled by means of cavitation. Cavitation is controlled by sonication parameters.

[00275] In some embodiments, step (i) and step (ii) of the method are performed simultaneously or subsequently. In some embodiments, step (ii) is performed after step (i). [00276] In some embodiments, the substrate is an untreated substrate, wherein “untreated substrate” is as described above (i.e., devoid of a pretreatment process. Such as desizing, bleaching or scouring, etc.) In some embodiments, the substrate is an pre-treated substrate, as disclosed hereinabove. The inventors have surprisingly observed that the dyeing process of the invention can be performed by utilizing either untreated or treated substrate (especially relevant for substrate comprising natural fibers which requires a hydrophilization pretreatment during conventional indigo dyeing processes).

[00277] In some embodiments, the untreated substrate is an unscoured substrate characterized by a critical surface tension of at least 28 dyn cm' ¹ , at least 30 dyn cm' ¹ , at least 35 dyn cm' ¹ , at least 40 dyn cm' ¹ , including any range or value in between. For textile fabric substrates the critical surface tension can be measured according to a method described in C. Kim, Y.-L. Hsieh; “Wetting and absorbency of non-ionic surfactant solutions on cotton fabrics”; Colloids and Surfaces A: Physicochem. Eng. Aspects, 187-188 (2001), pp: 385-397.

[00278] For the case when the substrate is a yarn, the untreated substrate can be defined using capillary diffusion coefficient of the yarns (D). The inventors have determined the D value of the untreated substrate to be below 0.1, or below 0.01 measured upon contacting the yarn with an aqueous composition (e.g. an indigo-based composition of the invention). A value of D for a specific yarn and a specific aqueous composition can be determined based on a wicking curve, such as disclosed in Ferrero, F., Periolatto, M. (2015). Modification of surface energy and wetting of textile fibers. Wetting and wettability, 139-168.

[00279] In some embodiments, the untreated substrate is a yarn characterized by D value below 0.1, below about 0.08, below about 0.05, below about 0.03, below about 0.01, below about 0.008, below about 0.005, including any range between. In some embodiments, the untreated substrate is a yarn characterized by absorption height (h) above 1mm, when measured 100 second upon immersion of the yarn into the aqueous composition. Absorption height (h) of a yarn can be determined as described in Ferrero et. al.

[00280] In some embodiments, the method of the invention is for manufacturing the indigo dyed substrate of the invention, and/or the article of the invention. [00281] In some embodiments, the method of the invention comprises (i) contacting the substrate with the dispersion disclosed herein, thereby manufacturing a substrate in contact with the dispersion. In some embodiments, the substrate in contact with the dispersion is a moist substrate. In some embodiments, the dispersion is applied on or contacted with the substrate in an amount sufficient for obtaining a moist substrate. In some embodiments, the dispersion is applied on or contacted with the substrate in an amount sufficient for obtaining a moist substrate in contact with an effective amount of the indigo nanoparticles.

[00282] In some embodiments, contacting (step (i)) is performed under conditions suitable for obtaining a moist substrate. In some embodiments, suitable conditions comprise applying the dispersion of the invention to the substrate by a method selected from, spray coating (warm or cold), flow coating, dip coating, extrusion coating, transfer coating, electrospinning, printing, and spin coating or any combination thereof. Additional methods are well-known in the art.

[00283] In some embodiments, the method further comprises a preliminary step of prewetting the substrate, wherein the preliminary step is performed prior to performing the step (i). In some embodiments, the pre- wetting step is applied to a hydrophobic substrate (e.g. non-pretreated or non-scoured substrate). In some embodiments, the hydrophobic substrate is not easily water wettable (e.g. the wetting rate of the hydrophobic substrate is to slow for implementation thereof in a wet-dyeing industrial process).

[00284] Indigo and leuco-indigo have low affinity to textile substrate. Besides that, the textile substrate (such as the most common substrate for the indigo dyeing - cotton), is naturally covered by waxes, pectines and other organic materials, which constrain its wettability with water-based dyestuff. Therefore, cleaning pretreatment of the substrate is required to assure dyeability of the substrate. Such pretreatment (scouring or mercerization) is made by mixture of caustic soda, detergent and wetting agent.

[00285] In the proposed invention no scouring is needed for dyeing process. Cavitation provides wetting of the substrate and adhesion of the indigo nanoparticles on fiber of the substrate in the sonication affected areas. Yarns can be subjected to the additional pretreatment with hydrophobic or anti-wicking (blocking capillary movement) materials, constraining dyeing in areas not subjected to sonication and improving ring dyeing effect (i.e. decreasing dyestuff penetration depth).

[00286] This approach allows to use high concentration of dyestuff (up to 30%), and dye only external part of the yarns (ring dyeing effect), since yarn’s core is not wetted and stays unaffected by process.

[00287] Nevertheless, scoured or mercerized yarns can be dyed with the proposed method. That can be beneficial for the multistep processes requiring scoured or mercerized textile for the steps preceding or following to dyeing (such as topping or bottoming in denim dyeing, mercerized textile production).

[00288] In some embodiments, the preliminary step is performed under conditions suitable for obtaining a moist substrate (e.g. a partially prewetted substrate, such that only a portion of the yarn is pre-wetted, wherein the core of the yarn remains dry). In some embodiments, suitable conditions comprise applying cavitation field on the substrate in contact with or immersed into a pre-wetting bath, or into a dyeing bath. In some embodiments, the prewetting bath comprises an aqueous solution. In some embodiments, the pre-wetting bath/pre- wetting step is as described in PCT/IL2023/050570, which is incorporated herein in its entirety.

[00289] In some embodiments, suitable conditions comprise controlling cavitation parameters (such as frequency, and/or intensity of the acoustic waves). In some embodiments, suitable conditions comprise controlling the time period of subjecting the substrate to cavitation field.

[00290] In some embodiments, the frequency is between 15 KHz and 10 MHz, between 10 KHz and 1000 KHz, between 10 KHz and 2000 KHz, including any range between. In some embodiments, the intensity of the acoustic waves refers to an input power of the source of between 30 and 2000 W. In some embodiments, the frequency and/or intensity of the acoustic waves is selected based on the predetermined wetting depth. In some embodiments, the predetermined wetting depth is controlled by selecting cavitations parameters suitable for obtaining cavitation bubbles with a predetermined average size. In some embodiments, the predetermined wetting depth is substantially equivalent to the predetermined average size of the cavitation bubbles. [00291] In some embodiments, the predetermined average size of the cavitation bubbles is between 3 um and 150 um, between 3 um and 100 um, between 3 um and 50 um, between 5 um and 150 um, between 7 um and 150 um, between 10 um and 150 um, including any range in between. The inventors have observed that the frequency between 20 and 1000 KHz generates cavitation bubbles with an average size between 3 um and 150 um.

[00292] The wetting of the yarn by the water-born indigo nanoparticles is dependent on its hydrophobic or hydrophilic nature. This might not be consistent along the same yarn or might be variable between yarn to yarn. This can influence the depth of particle penetration (color ring), and its control. To improve this, a primary surface wetting can be applied using a pigment less wetting material (water in most of the cases) and an additional separate cavitation field. The control of the travel-period of the yarn in this liquid, and the intensity and frequency of the ultrasound field there, can provide non colored wet ring on the yarn. Now, when the yarn will enter the bath contains water and indigo particles, the wetting capabilities of the yarn itself are not relevant and the penetration of the indigo particles to the yarn using the controlled cavitation field will be more consistent.

[00293] Yarn passing through the pigment containing dyebath, or through the prewetting bath, releases the air contained in it in the more efficient manner, if the yarns moves through the liquid with inclination comparing to the vertical movement. That is due to the absence of reverse capture of the air bubbles released from the yarn (and replaced with the wetting liquid) by upper portion of the yarn.

[00294] In some embodiments, the amount of the dispersion of the invention applied to the substrate is sufficient for obtaining a predefined loading of the indigo (optionally in a form of plurality of indigo particles disclosed herein) within the indigo dyed substrate. In some embodiments, the amount of the dispersion of the invention applied to the substrate is sufficient for indigo dying the substrate. In some embodiments, the amount of the dispersion of the invention applied to the substrate is sufficient for providing one or more predefined color to the substrate.

[00295] In some embodiments, the effective amount of the dispersion of the invention is predetermined by a moisture content of the moist substrate. In some embodiments, the moisture content enables or increases the embedment of the indigo within the moist substrate.

[00296] In some embodiments, the moisture content is sufficient for guiding the ultrasonic waves and/or cavitation to the plurality of fibers or yarns in contact with indigo particles on or within the moist substrate. In some embodiments, the moisture content is sufficient for impregnation of the moist substrate with indigo particles. In some embodiments, the moisture content is sufficient for embedding an effective amount of indigo on or within the substrate.

[00297] In some embodiments, the moisture content of the moist substrate is greater than a moisture content of a dry substrate. In some embodiments, the term “dry substrate” refers to a substrate which has been stored at ambient conditions and has not been wetted by a liquid. In some embodiments, the moisture content of the dry substrate substantially originates from the moisture absorbed during the manufacturing process, and/or during storage. One skilled artisan will appreciate that a moisture content of dry substrates may vary, depending on the physico-chemical characteristic of the substrate (e.g., chemical composition of the fibers/or yarns) and/or on the storage conditions. Usually, a moisture content of the substrate (e.g., fabrics) is less than 10%w/w.

[00298] In some embodiments, the moisture content of the moist substrate is greater by at least 10%, at least 30%, at least 50%, at least 100%, at least 150%, at least 200%, than a moisture content of the dry substrate. In some embodiments, the moisture content of the moist substrate is at least 1%, at least 5%, at least 7%, at least 10%, at least 15%, at least 17%, at least 18%, at least 19%, at least 20%w/w, including any range between.

[00299] In some embodiments, the moisture content of the moist substrate is between 5 and 300%, between 5 and 10%, between 10 and 300%, between 15 and 300%, between 20 and 300%, between 20 and 30%, between 25 and 300%, between 30 and 50%, between 50 and 100%, between 100 and 150%, between 150 and 200%, between 250 and 300%w/w, including any range between. In some embodiments, the moisture content of the moist substrate of the invention is greater than 300%w/w.

[00300] In some embodiments, the method of the invention comprises step (ii) subjecting the moist substrate in contact with the dispersion to cavitation or ultrasonic waves under appropriate conditions. In some embodiments, the step (ii) is performed subsequently to the step (i). In some embodiments, the step (ii) and the step (i) are performed simultaneously.

[00301] In some embodiments, the step (ii) comprises subjecting the moist substrate to acoustic waves suitable for inducing cavitation under appropriate conditions, wherein at least a portion of the moist substrate faces the ambient atmosphere.

[00302] In some embodiments, the step (ii) comprises subjecting the moist substrate to acoustic waves suitable for inducing under appropriate conditions, wherein at least a portion of the moist substrate is immersed within the dispersion of the invention (e.g., an ultrasonic bath comprising the dispersion of the invention). In some embodiments, the step (ii) comprises subjecting the moist substrate to acoustic waves suitable for inducing cavitation under appropriate conditions, wherein the entire portion of the moist substrate in operable communication with the source of ultrasonic waves or cavitation is immersed within the dispersion.

[00303] In some embodiments, the step (ii) comprises subjecting the moist substrate to acoustic waves suitable for inducing cavitation, wherein the moist substrate is not immersed within the dispersion. In some embodiments, the step (ii) comprises subjecting the moist substrate to acoustic waves suitable for inducing cavitation under appropriate conditions, wherein the entire moist substrate is immersed within the dispersion.

[00304] In some embodiments, step (ii) is performed while the moist substrate is in operable communication (e.g., in close proximity or in contact) with a solid vibrating element or with the source of acoustic waves suitable for inducing cavitation.

[00305] In some embodiments, the solid vibrating element is composed essentially of a source of ultrasonic waves, or a source of acoustic waves suitable for inducing cavitation. In some embodiments, the solid vibrating element comprises a source of acoustic waves and at least one contact surface for being in contact with the substrate. The terms “solid vibrating element” and “source of acoustic waves suitable for inducing cavitation” are used herein interchangeably. The terms “acoustic waves suitable for inducing cavitation” and “acoustic waves” are used herein interchangeably and encompass any acoustic waves in wavelength range suitable for inducing cavitation in an aqueous composition (e.g. water, the aqueous composition of the invention, or any other aqueous solution or dispersion, optionally wherein the aqueous composition is devoid of an organic solvent). In some embodiments, the acoustic waves encompass any sonic/ultrasonic waves at a frequency between 10 KHz and 1 MHz, between 15 KHz and 1000 KHz, between 10 KHz and 500 KHz, between 15 KHz and 500 KHz, between 15 KHz and 400 KHz, between 15 KHz and 450 KHz, between 15 KHz and 350 KHz, between 15 KHz and 300 KHz, between 15 KHz and 250 KHz, between about 15 KHz and about 300 KHz, between about 15 KHz and about 250 KHz, including any range between. In some embodiments, the acoustic waves suitable for inducing cavitation are waves at a frequency ranging between 15 KHz and 300 KHz, between 15 KHz and 250 KHz, between about 15 KHz and about 300 KHz, between about 15 KHz and about 250 KHz, including any range between.

[00306] In some embodiments, the source of acoustic/ultrasonic waves (also referred to herein as “the source”) refers to any apparatus or system configured for generating ultrasonic and/or acoustic waves. Various sources are known in the art (e.g. acoustic transducer). Optionally, the can provide between 30 to 150 W of acoustic waves per 100 cm ² of a treated substrate.

[00307] In some embodiments, the contact surface is in operable communication with the source. In some embodiments, the contact surface is configured to receive the acoustic waves from the source. In some embodiments, the contact surface is configured to transmit or transfer the acoustic waves. In some embodiments, the contact surface is configured to transmit or transfer the acoustic waves to the moist substrate in contact therewith. In some embodiments, the contact surface is permeable to acoustic waves.

[00308] In some embodiments, the contact surface is located in close proximity to the source. In some embodiments, the contact surface is in contact with the source. In some embodiments, the contact surface is operably coupled to the source, such as via a medium (e.g., a liquid) capable of transferring ultrasonic waves from the source to the contact surface. In some embodiments, the substrate is located in close proximity to the solid vibrating element. In some embodiments, at least a portion of the substrate is in contact with the contact surface. In some embodiments, the term “close proximity” encompasses a predetermined distance is as disclosed below. [00309] In some embodiments, step (ii) is performed while the substrate is immersed into the dispersion within the sonication unit (also referred to herein as “sonobox”, as disclosed in further details in PCT/IL2023/050570, which is incorporated herein in its entirety). In some embodiments, the sonobox comprises a sonication unit comprising at least one first source of acoustic/ultrasonic waves (also termed herein as “the first source”); a sonication bath; and optionally at least one second source of acoustic/ultrasonic wave s(also termed herein as “the second source”) and a delivery system configured to continuously deliver the substrate into and throughout the sonication bath such that a predetermined distance is formed between the substrate and the first source and optionally the second source, wherein the predetermined distance is as disclosed below (i.e. a distance of between about 0.1 and about 1.0 times of acoustic wavelength emitted by the source).

[00310] In some embodiments, the sonication bath is a container configured to hold a liquid volume of a dyeing composition sufficient for immersion of the substrate therewithin. In some embodiments, the first source and optionally the second source is in operable communication with the substrate. In some embodiments, the first source and optionally the second source is in contact with the dyeing composition. In some embodiments, the first source and optionally the second source is located within the sonication bath. In some embodiments, the first source and optionally the second source is within the sonication bath so that upon filling the sonication bath with the dyeing composition the first source and optionally the second source are in liquid communication with each other and with the substrate (i.e. immersed within the liquid volume of the dyeing composition). In some embodiments, the first source and the second source face the opposite surfaces of the substrate.

[00311] In some embodiments, the sonobox further comprises a pre- wetting bath located upstream to the sonication bath and is configured to contain a pre-wetting solution. In some embodiments, the pre-wetting bath is adopted for immersion of the substrate. In some embodiments, the pre- wetting solution is an aqueous composition (i.e. a solution or dispersion). In some embodiments, the aqueous composition in the pre-wetting bath may be the same or may be different form the aqueous solution in the sonication bath. [00312] In some embodiments, the delivery system is configured to continuously deliver the substrate into a pre-wetting bath (prior to delivering thereof into the sonication bath), and continuously deliver the substrate from the pre-wetting bath to the sonication bath. In some embodiments, the delivery system may include a conveyor configured to continuously convey a textile fabric, for example, using a plurality of rollers configured to deliver textile fabric inside sonication bath such that a predetermined distance is formed between the fabric and first sonotrode, and/or between the fabric and any one of the plurality of sonotrodes.

[00313] Reference is now made to Figs. 16A, 16B, and 16C which are illustrations of exemplary wet sonication systems (or sonoboxes). A wet sonication system 100 may include a sonication unit 20 that may include at least one first sonotrode 22 and a sonication bath 21. In some embodiments, sonication unit 20 may further include at least one of: at least one second sonotrode 24 (illustrated in Figs 16A and 16B) and optionally at least one reflector 26 (illustrated in Fig. 16C). In some embodiments, the sonication unit 20 is devoid of a reflector. In some embodiments, the wet sonication systems comprises a plurality of sonotrodes. In some embodiments, the sonotrodes are located within the sonication bath 21. In some embodiments, the sonotrodes are fully or partially immersed within the aqueous composition.

[00314] In some embodiments, the system comprises a plurality of sonotrodes, wherein the plurality of sonotrodes or sources (e.g. the first source 22 and the second source 24) are located at opposed sides of the fabric, as illustrated in Figs 16A and 16B.

[00315] In some embodiments, sonication bath 21 is configured to hold a liquid volume. In some embodiments, the liquid volume is sufficient for sonicating the fabric. In some embodiments, the dimensions of the sonication bath 21 and or the pre-wetting bath (length, width, height dimensions) and/or the volume thereof are sufficient for immersing at least a portion of the fabric within the liquid volume included within the sonication bath 21.

[00316] In some embodiments, sonication bath 21 may include an aqueous composition comprising dye nanoparticles (i.e. water-insoluble dyes, such as indigo, vat-, or sulfur-dyes). In some embodiments, the aqueous composition may include a dispersion of dye nanoparticles. In some embodiments, the aqueous composition may include the dye nanoparticle dispersion and at least one of: a wetting agent and a wicking agent. [00317] In some embodiments, sources 22 and 24 may be similar or different. In the nonlimiting example illustrated in Figs. 16A-16C sonotrodes 22 and 24 are rectangular plates. In some embodiments, sources 22 and 24 can provide between 30 to 150 W per 100 cm ² of a treated substrate 5 (e.g. textile fabric).

[00318] In some embodiments, reflector 26 includes any material (e.g., metal) that can reflect back US waves inside a sonication bath.

[00319] System 100 may further include a delivery system 30 configured to deliver substrate 5 to and from sonication bath 21. Delivery system 30 may include a conveyor configured to continuously convey substrate 5, for example, using a plurality of rollers 35 configured to deliver substrate 5 inside sonication bath 21 such that a predetermined distance is formed between the fabric and first sonotrode 22, and/or between the fabric and any one of the plurality of sonotrodes, wherein the predetermined distance is as disclosed herein.

[00320] In some embodiments, the first source 22 faces a first surface of the fabric, and the second source 24 faces a second surface of the fabric. In some embodiments, the delivery system 30 is configured to deliver fabric between the first source 22 and the second source 24. In some embodiments, the plurality of sources located at both sides of fabric delivered by the delivery system 30, induce uniform impregnation or embedding of the dye nanoparticles into the first surface and into the second surface of the fabric. In some embodiments, the delivery system 30, is configured to deliver fabric between the first source 22 and the second source 24 so that the predetermined distance is formed between the fabric and first source 22 and between the fabric and second source 24. In some embodiments, the first source 22 and the second source 24 are opposed to each other. In some embodiments, the first source 22 and the second source 24 are distant from each other along the propagation direction of the fabric.

[00321] In some embodiments, reflector 26 is optionally located at the predetermined distance 6 from first source 22, and delivery system 30 directs substrate 5 between reflector 26 and source 22, as illustrated in Fig. 16B. The system may be operated without the reflector. It is postulated that the fabric reflects almost the entire ultrasound waves applied thereto. [00322] In some embodiments, second source 24 is located at the predetermined distance from the fabric, and delivery system 30 directs substrate 5 between first and second sources 22 and 24, as illustrated in Figs. 16A and 16C.

[00323] In some embodiments, delivery system 30 may further be configured to deliver substrate 5 into a prewetting step, that may be performed in sonication bath 21, as illustrated in Figs. 16B and 16C or into the pre-wetting bath 10, illustrated in Fig. 16A. In such case, system 100 may further include pre- wetting bath 10 and delivery system 30 may continuously deliver substrate 5 from the pre- wetting bath to the sonication bath 21.

[00324] In some embodiments, pre-wetting bath 10 is in operable communication with the sonication bath 21. In some embodiments, pre-wetting bath 10 is in fluid communication with the sonication bath 21.

[00325] In some embodiments, pre-wetting bath 10 is configured to hold a liquid volume. In some embodiments, the liquid volume is sufficient for sonicating the fabric. In some embodiments, the dimensions of pre- wetting bath 10 (length, width, height dimensions) and/or the volume thereof are sufficient for immersing at least a portion of the fabric within the liquid volume included within the pre- wetting bath 10. In some embodiments, prewetting bath 10 is adopted for immersion of the fabric. In some embodiments, pre- wetting bath 10 contains first and/or second source(s) 22 and 24.

[00326] In some embodiments, the step (ii) comprises applying to the moist substrate acoustic waves under appropriate conditions, while the moist substrate is in operable communication with the source of acoustic waves. In some embodiments, operable communication comprises the moist substrate (or a portion thereof) located in close proximity to the source. In some embodiments, operable communication comprises the moist substrate (or a portion thereof) in contact with the source of acoustic waves or with the contact surface.

[00327] In some embodiments, operable communication comprises bonding the moist substrate (or a portion thereof) to the contact surface. In some embodiments, bonding comprises fixating the moist substrate at a predefined location on the contact surface. In some embodiments, bonding is by applying a pressure to the moist substrate, thereby contacting the moist substrate (or a portion thereof) with the source of ultrasonic waves or with the contact surface. In some embodiments, bonding is by providing a fixating device to the moist substrate. In some embodiments, bonding comprises delivering the substrate via the delivery system at the predetermined distance from the source.

[00328] In some embodiments, the substrate is in contact with a plurality of contact surfaces. In some embodiments, at least two surfaces of the substrate are independently in contact with the contact surface (wherein the contact surface is the same or different). In some embodiments, at least two surfaces of the substrate are independently in contact with a contact surface, wherein each contact surface is independently in operable communication with a source of ultrasonic waves.

[00329] In some embodiments, the contact surface is substantially dry. In some embodiments, the contact surface is not immersed within a liquid (e.g., the dispersion, as disclosed herein).

[00330] In some embodiments, the contact surface is attached to the source (i.e. a source of acoustic waves such as acoustic transducer). In some embodiments, the contact surface is at a predetermined distance from the source (i.e. acoustic transducer). In some embodiments, the predetermined distance is between the distal end of the source and the contact surface. In some embodiments, the predetermined distance is from 0.1 mm to 10 cm, from 0.1 to 1 mm, from 1 to 10 mm, from 1 to 10 cm, including any range between. In some embodiments, predetermined distance is equivalent to a distance of between about 0.1 and about 1.0 times (such as 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, or between about 0.4 and about 0.6 times, between about 0.1 and about 0.6 times, between about 0.2 and about 1 times, between about 0.3 and about 0.8 times, between 0.3 and 0.7, between 0.4 and 0.8 times) of acoustic wavelength emitted by the source, including any range between.

[00331] The acoustic wavelength may be calculated from the corresponding frequency of acoustic waves emitted by the source, taking into account the velocity of sound in an aqueous solution. In some embodiments, the predetermined distance is 5-40 mm, between 5 and 35mm, between about 5 and about 40mm, between about 5 and about 30mm, for example, 5, 10 mm, 15 mm, 20 mm, 30mm, 40mm including any value in between.

[00332] In some embodiments, the contact surface is an inner surface of a container. In some embodiments, the container comprises at least one wall defining a lumen. In some embodiments, the wall comprises an outer surface facing an ambient and an inner surface. In some embodiments, the inner surface faces the lumen.

[00333] In some embodiments, the moist substrate is located within the lumen, and at least a portion of the moist substrate is in contact with the inner surface of the container. In some embodiments, the container is immersed within a liquid. In some embodiments, the container is immersed within an ultrasonic bath.

[00334] In some embodiments, the appropriate conditions comprise applying ultrasonic waves for a time period sufficient for stably binding or embedding indigo on or within the textile substrate. In some embodiments, the method of the invention comprises applying an ultrasonic waves for a time period of at least 1 second (s), at least 3s, at least 10s, at least 30s, at least 60s, at least 2 minutes (m), at least 3m, at least 10m, at least 30m, including any range or value therebetween. It should be appreciated that exact application time depends on the input power of the source, and/or on the frequency and/or intensity of the ultrasonic waves applied to the moist substrate.

[00335] In some embodiments, appropriate conditions comprise applying the ultrasonic waves, while the moist substrate is at least partially immersed within the dispersion disclosed herein.

[00336] In some embodiments, appropriate conditions further comprise providing the moist substrate to a temperature of at least 10°C, at least 20°C, at least 30°C, at least 40°C, at least 50°C, at least 60°C, at least 70°C, including any range or value therebetween. In some embodiments, the temperature is above the melting point of the solvent. In some embodiments, the temperature is below the boiling point of the solvent.

[00337] In some embodiments, the temperature is less than the boiling point of the solvent of the dispersion (e.g., water and/or a polar organic solvent).

[00338] In some embodiments, appropriate conditions comprise a frequency of the ultrasonic waves of between 15 KHz and 10 MHz, between 10 KHz and 1000 KHz, between 10 KHz and 2000 KHz, between 15KHz and 400KHz, between 20KHz and 3 OKHz, between 30KHz and 40KHz, between 40KHz and 60KHz, between 60KHz and lOOKHz, between 1 OOKHz and 400KHz, including any range or value therebetween. [00339] In some embodiments, appropriate conditions comprise an input power of the source between 30 and 2000 W, between 50 and 2000 W, between 30 and 200 W, between 50 and 100 W, between 50 and 500 W, between 50 and 1000 W, between 100 and 2000 W, between 100 and 1000 W, including any range or value therebetween.

[00340] In some embodiments, appropriate conditions comprise at least one of: (i) a time period of at least 2 seconds, (ii) a frequency of between 15 KHz and 1000 KHz, (iii) an input power of the source between 30 and 2000 W, and (iv) a temperature of at least 20°C, or a combination of i-iv.

[00341] In some embodiments, appropriate conditions comprise a power of the ultrasonic waves of at least 10 W/m ² , at least 20 W/m ² , at least 50 W/m ² , at least 100 W/m ² , at least 500 W/m ² , at least 1000 W/m ² , at least 10.000 W/m ² , at least 100.000 W/m ² , at least 1 MW/m ² , including any range or value therebetween. In some embodiments, the step (ii) comprises subjecting the moist substrate to cavitation under appropriate conditions, wherein at least a portion of the moist substrate (or the entire moist substrate) is immersed within the dispersion.

[00342] In some embodiments, step (ii) is performed while the moist substrate is subjected to cavitation. In some embodiments, the appropriate conditions for cavitation comprises conditions sufficient for generating the cavitation bubbles within a predetermined range suitable for indigo embedding into the substrate. In some embodiments, the predetermined range of the cavitation bubbles comprises an average bubble size of between 3 um and 150 um, between 3 um and 100 um, between 3 um and 50 um, between 5 um and 150 um, between 7 um and 150 um, between 10 um and 150 um, including any range in between.

[00343] Non-limiting examples of methods for inducing cavitation include but are not limited to: vibration, acoustic cavitation, liquid jetting, etc.

[00344] Acoustic cavitation occurs whenever a liquid is subjected to sufficiently intense sound or ultrasound (that is, sound with frequencies of roughly 20 kHz to 10 MHz). When sound passes through a liquid, it consists of expansion (negative-pressure) waves and compression (positive-pressure) waves. If the intensity of the sound field is high enough, it can cause the formation, growth, and rapid recompression of vapor bubbles in the liquid. The implosive bubble collapse generates localized heating, a pressure pulse, and associated localized high-energy transfer. Increasing the ultrasound frequency decreases the sound wavelength and increases the density of the vapor bubbles. Increasing the ultrasound intensity causes faster growth of the vapor bubbles and increases the intensity of the pressure pulses. Thus, the use of higher ultrasound frequency while keeping the same accumulative intensity can cause smaller vapor bubbles with lower distance between them. Their collapse will enable a more uniform pressure pulses field. The intensity variation controls the vapor bubble growth rate and changes the pressure pulses field, as well. As the pressure pulses field controls the depth of penetration of the nano indigo particles to the yarn, changing the ultrasound frequency and intensity controls this penetration and obviously controls the generation of the colored ring.

[00345] In some embodiments, controlling the cavitation bubbles within a predetermined range is by operating the cavitation source under suitable conditions, wherein the suitable conditions comprise controlling cavitations parameters (such as frequency, and/or intensity of the acoustic waves). In some embodiments, suitable conditions comprise controlling the time period of subjecting the substrate to cavitation field.

[00346] In some embodiments, suitable conditions comprise a frequency of acoustic waves between 15 KHz and 10 MHz, between 15 KHz and 500 KHz, between 15 KHz and 1000 KHz, between 15 KHz and 300 KHz, between 15 KHz and 250 KHz, including any range between. In some embodiments, the intensity of the acoustic waves refers to an input power of the source of between 30 and 2000 W. In some embodiments, the frequency and/or intensity of the acoustic waves is selected based on the predetermined wetting depth. In some embodiments, the predetermined wetting depth is controlled by selecting cavitations parameters suitable for obtaining cavitation bubbles with a predetermined average size. In some embodiments, the predetermined wetting depth is substantially equivalent to the predetermined average size of the cavitation bubbles.

[00347] In some embodiments, the predetermined average size of the cavitation bubbles is between 3 um and 150 um, between 3 um and 100 um, between 3 um and 50 um, between 5 um and 150 um, between 7 um and 150 um, between 10 um and 150 um, including any range in between. The inventors have observed that the frequency between 20 and about 200 KHz generates cavitation bubbles with an average size between 3 um and 150 um. [00348] In some embodiments, the steps (i) and (ii) of the method are performed once (i.e. the method of the invention includes a single dyeing cycle).

[00349] In some embodiments, the method of the invention is characterized by an indigo particle loading within the indigo dyed substrate after a single dyeing cycle of at least 0.5%, at least 1%, at least 1.5%, at least 2%, at least 2.5%, and between 0.5 and 10%, between 0.5 and 5%, between 1 and 10%, between 1 and 8%, between 3 between 8%, between 4 and 8%, and between 4 and 10%, including any range or value in between.

[00350] In some embodiments, the method of the invention is characterized by an indigo particle loading relative to the surface area of the indigo dyed substrate after a single dyeing cycle ranging between 0.1 and 20 g/m ² , between 0.1 and 0.2 g/m ² , between 0.1 and 2 g/m ² , between 0.1 and 5 g/m ² , between 0.1 and 10 g/m ² , between 0.2 and 0.5 g/m ² , between 0.5 and 0.8 g/m ² , between 0.8 and 1 g/m ² , between 1 and 1.5 g/m ² , between 1.5 and 2 g/m ² , between 1 and 20 g/m ² , between 1 and 10 g/m ² , between 10 and 20 g/m ² , including any range therebetween.

[00351] In some embodiments, the method of the invention is characterized by an indigo particle loading within the indigo dyed substrate after a single dyeing cycle of at least 0.5%, at least 1%, at least 1.5%, at least 2%, at least 2.5%, and between 0.5 and 10%, between 0.5 and 5%, between 1 and 10%, between 1 and 8%, between 3 between 8%, between 4 and 8%, and between 4 and 10%, including any range or value in between.

[00352] In some embodiments, the method of the invention is characterized by an indigo particle loading relative to the surface area of the indigo dyed substrate after a single dyeing cycle ranging between 0.1 and 20 g/m ² , between 0.1 and 0.2 g/m ² , between 0.1 and 2 g/m ² , between 0.1 and 5 g/m ² , between 0.1 and 10 g/m ² , between 0.2 and 0.5 g/m ² , between 0.5 and 0.8 g/m ² , between 0.8 and 1 g/m ² , between 1 and 1.5 g/m ² , between 1.5 and 2 g/m ² , between 1 and 20 g/m ² , between 1 and 10 g/m ² , between 10 and 20 g/m ² , including any range therebetween.

[00353]

[00354] In some embodiments, the method comprises sequentially or simultaneously repeating the step (i) and/or step (ii). In some embodiments, the method comprises performing the step (i) and/or the step (ii) for at least 2 times, at least 3 times, at least 5 times, at least 10 times, at least 20 times, or more, including any value therebetween.

[00355] In some embodiments, the method of the invention further comprises a step (iii) of drying the indigo dyed substrate. In some embodiments, drying comprises exposing the indigo dyed substrate to a thermal radiation, thereby providing the indigo dyed substrate to a temperature of between 40 and 200°C, between 80 and 100°C, between 100 and 150°C, between 150 and 200°C, including any range or value therebetween.

[00356] In some embodiments, drying is performed by convection drying, such as by applying a hot gas stream to a coated surface. In some embodiments, drying is performed by cold drying, such as by applying a de-humidified gas stream to the surface. In some embodiments, drying is performed by infrared (IR) drying. In some embodiments, drying is performed by microwave drying. Generally, the drying method and exact drying conditions selected will depend upon, among other things, chemical and physical properties of the substrate material.

[00357] In some embodiments, the drying optionally comprises vacuum drying of the impregnated substrate. In some embodiments, the method comprises a partial drying of the impregnated substrate.

[00358] As opposed to the traditional vat dyeing (e.g. indigo dyeing), no oxidation treatment is necessary. Fixing agent can be used to improve rubbing or washing fastness, if needed.

[00359] In some embodiments, step (ii) and step (iii) are performed sequentially. In some embodiments, the step (iii) is performed after step (ii).

[00360] In some embodiments, the method further comprises a step (iv) of contacting the indigo dyed substrate and/or moist substrate with a composition comprising fixing agent, wherein contacting is as described hereinabove. In some embodiments, step (iv) is performed after step (ii) and before step (iii). In some embodiments, step (iv) is performed after step (iii). In some embodiments, step (iv) is performed simultaneously with step (i) and/or (ii) (e.g. wherein the fixing agent is a prat of the dispersion). [00361] In some embodiments, the method further comprises a step (v) of contacting the indigo dyed substrate with a composition comprising a sizing agent, wherein contacting is as described hereinabove. In some embodiments, step (v) is performed on a dried dyed substrate. In some embodiments, step (v) is performed after step (iii), or after step (ii) and before step (iii).

[00362] Non-limiting examples of sizing agents include but are not limited to: chitosan, pectin, polyvinyl alcohol, polyacrylates carbomethylcellulose, starch, wax, gelatine, or any combination thereof.

[00363] In some embodiments, wherein the method of the invention is characterized by an incorporation efficiency of indigo ranging between 10 and 100%, between 10 and 20%, between 20 and 30%, between 30 and 50%, between 50 and 60%, between 60 and 70%, between 70 and 90%, between 80 and 95%, between 90 and 93%, between 93 and 95%, between 95 and 97%, between 97 and 99%, between 99 and 99.9%, between 99.9 and 100%, including any range between. In some embodiments, the term “incorporation efficiency” refers to a weight portion of indigo embedded into the substrate, relative to the total amount (e.g., dry weight) of indigo applied to the substrate. In some embodiments, the term “incorporation efficiency” refers to a ratio between a loading (or w/w concentration) of indigo within the indigo dyed substrate, and a concentration of indigo within the dispersion disclosed herein (or in the immersion bath). In some embodiments, the method is for embedding an effective amount of indigo on or within the substrate. In some embodiments, the method is for obtaining the impregnated substrate having a predefined loading of indigo, wherein loading refers to a w/w amount of indigo relative to the pristine substrate. In some embodiments, the effective amount of indigo is sufficient for at least partially dying the surface of the substrate.

[00364] In some embodiments, the terms “predefined loading”, “loading”, and “effective amount” are used herein interchangeably, and refer to a specific w/w concentration, or a concentration range of indigo within the indigo dyed substrate, wherein the w/w concentration or the concentration range is it least sufficient for providing any one of: a predetermined color, a predetermined color intensity, a predetermined color strength, a predetermined light fastness, including any combination thereof. [00365] In some embodiments, the method of the invention is substantially devoid of the application of a reducing agent. The method of the invention enables achieving the desired indigo loading (as reflected by a desired L*a*b value) in a single dyeing cycle, whereas traditional indigo dyeing methods require a plurality of repetitive leuco-indigo dyeing and reduction cycles. In some embodiments, the method of the invention is devoid of washing during the dyeing process (except washing after substrate pre-treatment). In some embodiments, the method of the invention is devoid of post-dyeing washing step. In contrast, traditional indigo dyeing methods requires at least one step of washing before the dyeing process (a wash step between scouring and dyeing, then multiple dyeing steps, then 1-3 washes after last dyeing).

[00366] In some embodiments, the method of the invention further comprises subjecting the indigo dyed substrate to a denim finishing process, wherein the denim finishing process is as disclosed hereinabove.

[00367] In some embodiments, the method of the invention is for obtaining the substrate impregnated with indigo. In some embodiments, the method of the invention is for impregnating the indigo on or within at least one surface of the substrate. In some embodiments, the method of the invention is for coating the substrate with indigo. In some embodiments, the method of the invention is for coating at least a portion of the substrate with indigo, wherein the substrate is as described herein.

[00368] In some embodiments, the method of the invention is for manufacturing the indigo dyed substrate of the invention, and/or the article of the invention.

[00369] Reference is now made to Fig 11 which is a flowchart representing an exemplary a method of dyeing a substrate according to some embodiments of the invention. First, the method comprises contacting a substrate (i.e., treated, or untreated substrate) with the composition of the invention to obtain a wet substrate, and subjecting the wet substrate to ultrasound waves or cavitation (step 130), thereby obtaining a dyed substrate.

[00370] The method may further comprise an optional step of drying the dyed substrate (step 140), thereby obtaining a dried substrate. The method may further comprise a step of contacting the dried substrate with an additional agent (e.g. a wetting agent, an antifoaming agent, a leveling agent, a cationization agent, a migration inhibitor, a fixing agent, binder, surfactant, gloss agent, blooming agent, pH modifier, conductivity modifier, rheology modifier, an antibacterial agent including any combination thereof) and drying (step 150), thereby obtaining the substrate of the invention.

[00371 ] Optionally, the method may comprise a preliminary step performed prior to dyeing step. The preliminary step may comprise pretreating an untreated (pristine) substrate by any of: scouring, desizing, bleaching, mercerizing, bottoming dyeing, hydrophobization and subsequently may comprise a washing step (step 120), thereby obtaining a treated substrate.

[00372] Reference is now made to Fig 12B which is an illustration of traditional indigo dyeing process. The traditional indigo dyeing process 11 comprises: a beam creel unit 100, wherein the substrate (e.g., yarn) is loaded; a scouring unit, which includes a scouring bath 200, a washing bath(s) 230. The scouring bath 200 and washing bath(s) 230 correspond to step 120 of the flowchart. The traditional indigo dyeing process 11 further includes a steamer 220; a dyeing unit 300, which comprises five leuco-indigo dyeing baths 340, 342, 344, 346 and 348 containing a leuco-indigo solution along with toxic reducing agents (dyeing step), and a steamer 350. Subsequently, traditional indigo dyeing process 11 includes a washing bath 380 for performing a post-dyeing wash; an accumulator unit 400; a drying unit 500 (drying step); a sizing unit 600; an additional drying unit 700 (additional drying step), a separation unit 800, which separates the substrate from one another; and a beam winder unit 900.

[00373] Traditional dyeing comprises numerous dyeing baths (usually 6-12), and requires numerous sequential dyeing cycles. In addition, traditional dyeing requires a washing step (before dyeing, after pre-treatment, especially for cotton substrate), and furthermore an additional washing step after dyeing before drying the dyed substrate. Traditional dyeing further requires a step of post-dyeing oxidation of the leuco-indigo, which is tedious, time consuming and in addition the shade of the dyed substrate may vary from one cycle to another.

[00374] Reference is now made to Fig 12B which is an illustration of the indigo dyeing process according to some embodiments of the invention. The dyeing method of the invention optionally comprises: a beam creel unit 10, wherein the substrate is loaded; optionally a scouring unit, which includes a scouring bath 20, a washing bath 28, and optionally a steamer 24 (corresponding to optional preliminary step 120 of the flow chart); a dyeing unit 30, which comprises a single dyeing bath comprising the aqueous dispersion of the invention and a source of ultrasonic waves/cavitation (corresponding to step 130 of the flow chart). Subsequently, the dyeing method comprises a drying unit 35, to perform drying step after the dyeing step. Further, the dyeing method comprises an accumulator unit 40; a drying unit 50 (corresponding to step 140 of the flow chart); a sizing unit 60 and an additional drying unit 70 (corresponding to step 150 of the flow chart), a separation unit 80, which separates the substrate from one another; and a beam winder unit 90.

[00375] Thus the method/system of the invention doesn’t require a pre-treatment and a post-dyeing wash step, and operates only a single dyeing bath (so that the substrate dyeing can be accomplished in a single dyeing cycle).

Ring dyeing

[00376] Denim yarns are characterized by ring dyeing effect, i.e. only external fibers of the yarns are intensively dyed and fiber of the inner core are almost not dyed. That makes a cross-section of the yarn look like dyed “ring” (peripheral portion of the yarn) around almost white core (weakly dyed or undyed center). The creation of the desired worn denim looks is based on this phenomenon and low affinity of the used dye (such as indigo or sulfur dyes) to textile, which allows to remove the dye from the peripheral portion of yarn, exposing white core.

[00377] Traditionally, ring dyeing effect is achieved by use of very diluted dyestuff, short immersion of the yarns to the dyebath, multiple dipping (for dyestuff, such as leuco-indigo, uptake) and skyeing (for dyestuff oxidation and fixation) steps, and, in case of indigo dyeing, pH control which has a great effect on diffusion speed of leuco-indigo.

[00378] Cotton fibers are naturally covered by oils, waxes, pectines and other hydrophobic organic materials, which make quality dyeing impossible. Traditional dyeing requires scouring (cleaning with NaOH, wetting and detergent agent) of the yarns prior to dyeing, making the yarn hydrophilic and wettable by water-based dyestuff. However, hydrophilicity of the yarns leads to easy diffusion of the dyestuff into the yarn’s core, deteriorating ring dyeing effect. [00379] Attempts on optimization of the scouring process have been made to improve the ring dyeing by performing gentle scouring to avoid thorough cleaning of the yarn’s core. However, scouring or mercerization prior to dyeing remains necessary in traditional indigo dyeing.

[00380] Multiple attempts to adopt pigments dyeing to denim yarns have been made so far. However, they do not provide ring dyeing effect. Ring dyeing effect can be achieved by shock drying of the yarns to induce dyestuff migration towards external portion of the yarn. These methods require use of polymeric binders (polyacrylates or polyurethanes) and high temperature curing (above 130°C, usually above 150°C) for the pigment fixation in the polymer matrix.

[00381] Cavitation is a phenomena formation of vapor bubbles within a liquid at low- pressure regions that occur in places where the liquid has been accelerated to high velocities. Subsequent implosions of the bubbles create areas of high temperature and pressure. Cavitation allows to incorporate water-based dyestuff into relatively hydrophobic substrate. Ultrasonication is a convenient way to induce cavitation in liquid. It is also known to the skilled in art how sonication parameters affect the cavitation bubbles. So, size of the bubbles depends on sonication frequency and amount of the appearing bubbles depends on sonication power.

[00382] The inventors were surprised to find that depth of penetration of the liquid into substrate can be tuned by sonication frequency (the higher, the less penetration) and, to much less extent, amplitude (the lower, the less penetration). The observed phenomena apparently is caused by different pressure generated by implosion of the bubbles of different size.

[00383] The inventors have found that sonication-induced cavitation significantly improves wettability of the unscoured textile substrate (specifically, raw cotton) without any pretreatment, and allows direct dyeing of the dry, unscoured textile.

[00384] Ultrasonication-induced cavitation bubbles’ size depends primarily on sonication frequency. Number of bubbles’ per volume of liquid depends both on frequency and acoustic power of sonication. The higher the sonication frequency is, the smaller cavitation bubbles it induces. Thus, if the same sonication power is maintained, higher frequency sonication will induce higher amount of smaller cavitation bubbles. The energy needed to induce cavitation bubbles equals to energy released in bubble’s implosion and depends on its size. Implosion of the smaller bubbles releases less energy than implosion of large ones.

[00385] The more powerful implosions and higher their amount of them lead to the deeper penetration of the liquid into the textile substrate. Thus, tuning of the sonication frequency, power and exposure time allows to control depth of dyestuff penetration into the yarns, providing control over ring dyeing effect.

[00386] In another aspect, there is provided a method for ring dyeing of a substrate comprising: (i) contacting at least a portion of the substrate with the dispersion of the invention, wherein the dispersion is characterized by a surface tension above a critical surface tension of the substrate; and (ii) subjecting the substrate in contact with the dispersion to acoustic waves suitable for inducing a cavitation; thereby obtaining an indigo ring dyed substrate; and wherein the cavitation is characterized cavitation bubbles having an average size between 1 um and 200 um, or between 3 and 150 um. In some embodiments, the substrate is as described herein. In some embodiments, the steps (i) and (ii) are performed simultaneously, or subsequently. In some embodiments, the step (ii) is performed while the substrate is at least partially immersed in the dyeing bath.

[00387] In some embodiments, acoustic waves suitable for inducing cavitation are characterized by a frequency between 15 KHz and about 1.5 MHz; between 15 KHz and about 500 KHz, between 15 KHz and about 300KHz, between 10 KHz and 2000 KHz, between about 20 KHz and about 1000 KHz, including any range between.

[00388] In some embodiments, acoustic waves suitable for inducing cavitation are generated via an acoustic source, wherein the input power of the acoustic source is between 30 and 2000 W. In some embodiments, acoustic waves suitable for inducing cavitation w are characterized by (i) a frequency between about 15 KHz and about 500 KHz, and (ii) intensity corresponding to input power of the source of between 30 and 2000 W.

[00389] In some embodiments, step (ii) comprises controlling the penetration depth of the indigo nanoparticles (i.e. the thickness of the ring-like pattern) within a predetermined range. In some embodiments, the predetermined range of the penetration depth is between 1 and about 200 um, between 3 and about 200 um, between 3 and about 150 um, between 3 and about 50 um, between 3 and about 10 um, between 5 and about 100 um, between 5 and about 50 um, including any range between.

[00390] In some embodiments, the penetration depth is predetermined by the average size of the cavitation bubbles. In some embodiments, the average size of the cavitation bubbles is between 3 um and 150 um, between 3 um and 100 um, between 3 um and 50 um, between 5 um and 150 um, between 7 um and 150 um, between 10 um and 150 um, including any range in between. The inventors have observed that the frequency between 20 and about 200 KHz generates cavitation bubbles with an average size between 3 um and 150 um.

[00391 ] In some embodiments, controlling the penetration depth is by varying the intensity and/or frequency of the acoustic waves, so as to obtain cavitation bubbles with a predetermined average size, wherein the penetration depth is almost equal (e.g. the penetration depth varies from the predetermined average size by up to 30%, up to 20%, up to 10%, including any rang between).

[00392] In some embodiments, the frequency and/or intensity of the acoustic waves is selected based on the predetermined wetting depth. In some embodiments, the predetermined wetting depth is controlled by selecting cavitations parameters suitable for obtaining cavitation bubbles with a predetermined average size. In some embodiments, the predetermined wetting depth is substantially equivalent to the predetermined average size of the cavitation bubbles.

[00393] In some embodiments, the method for ring dyeing of a substrate further comprises a preliminary pre-wetting step, as disclosed hereinabove. In some embodiments, the prewetting step is performed under conditions suitable for inducing a ring-patterned wetting of the yarn. In some embodiments, the ring-patterned wetting is obtained by controlling the cavitation parameters, so as to generate cavitation bubbles with a predetermined average size, as disclosed herein. In some embodiments, the pre-wetting step is performed in the dyeing bath, or in the pre- wetting bath (e.g. comprising an aqueous solution, and being substantially devoid of indigo nanoparticles), as disclosed above.

[00394] In some embodiments, the wetting depth obtained during the pre- wetting step predetermines the penetration depth of indigo nanoparticles during the step (ii). In some embodiments, the method for ring dyeing of the substrate comprises the preliminary step of pre-wetting, and subsequently comprises performing the step (i), thereby obtaining the indigo dyed substrate. ). In some embodiments, the method for ring dyeing of the substrate comprises the preliminary step of pre-wetting, and subsequently comprises performing the step (i), thereby obtaining the indigo dyed substrate; wherein step (i) is solely performed by contacting (e.g. by immersing, coating, spraying, etc.) the pre- wetted substrate into the dispersion of the invention without applying acoustic waves suitable for inducing a cavitation. Inventors have successfully performed indigo-dyeing of substrates by using a pre- wetting step, followed by dip dyeing step without application of ultrasound/cavitation.

[00395] In some embodiments, the method for ring dyeing of the substrate further comprises performing the steps (iii)-(v), as disclosed herein.

General

[00396] As used herein the term “about” refers to ± 10 %.

[00397] The terms “comprises”, “comprising”, “includes”, “including”, “having” and their conjugates mean “including but not limited to”.

[00398] The term “consisting of means “including and limited to”.

[00399] The term “consisting essentially of’ means that the composition, method or structure may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure. Specifically, the term “consisting essentially of’ means that at least 90 %, at least 95 %, at least 97 %, at least 99 %, at least 99.9 % of the composition or of the article is composed of the ingredients listed herein, including any range or value therebetween.

[00400] The word “exemplary” is used herein to mean “serving as an example, instance or illustration”. Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments.

[00401] The word “optionally” is used herein to mean “is provided in some embodiments and not provided in other embodiments”. Any particular embodiment of the invention may include a plurality of “optional” features unless such features conflict. [00402] The term “enhancing” is by at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 80%, at least 100%, at least 150%, at least 200%, at least 250%, at least 300%, including any range or value therebetween.

[00403] As used herein, the singular form “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “a compound” or “at least one compound” may include a plurality of compounds, including mixtures thereof.

[00404] Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[00405] Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases “ranging/ranges between” a first indicate number and a second indicate number and “ranging/ranges from” a first indicate number “to” a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

[00406] As used herein the term “substantially” refers at least 60 %, at least 70 %, at least 80 %, at least 85 %, at least 90 %, at least 95 %, at least 97 %, at least 99 %, at least 99.9 %, including any rage or value therebetween. In some embodiments, the terms “substantially” and the term “consisting essentially of’ are used herein interchangeably.

[00407] As used herein the term “method” refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, pharmacological, biological, biochemical and medical arts.

[00408] It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

[00409] Various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below find experimental support in the following examples. Reference is now made to the following examples, which together with the above descriptions illustrate some embodiments of the invention in a non-limiting fashion.

EXAMPLES

EXAMPLE 1

Nanoparticles preparation.

[00410] Indigo nanoparticles were obtained by milling in the presence of different dispersant, exemplary procedure is presented: indigo nanoparticles were obtained by milling 100 g indigo pigment in the bead mill with 0.3 mm beads in presence of the 125 g BASF Dispex 4575 dispersing agent (40% active material), 0.3 g of Agitan 701 anti-foaming agent and 775 g of water. Obtained dispersion contains aggregates with intensity-weighted average hydrodynamic size of 202 nm (PDI 0.36, see Fig.l). SEM image reveals that aggregates consist of 25±7 nm nanoparticles (Fig. 2). Additional dispersants that were successfully implemented during the milling process and/or for stabilization of the dispersion are as follows:

Indigo pad dyeing [00411] 100% cotton fabrics were pad-dyed by the dispersion described above, dried at 65°C and temperature-cured at 180°C, rinsed with water and dried at 65°C. Some of the dyed fabrics were padded in chitosan solution in acetic acid (1 wt.% chitosan and 1 wt.% of acetic acid), dried at 65°C, cured at 150°C, rinsed with water and dried at 65°C. Fig. 3 shows dyed fabrics with and without fixing agent post-treatment after 0, 1, 3 and 10 cycles of home laundry/drying.

Ultrasonication dyeing.

1. Plate transducer as a source of the ultrasonic energy.

[00412] Dyeing was performed in the sonobox - dyeing bath with two ultrasonic plate transducers in two opposite walls of the bath (such as disclosed in greater details in US 63/348,109, which is incorporated herein by reference in its entirety). Sonobox was filled with the formulation containing 1, 2, 5 or 10 wt.% of indigo nanoparticles for different final shades.

[00413] 100% cotton fabrics were placed into the sonobox at the equal distance between the transducers, fabric surface parallel to the plates and sonication immediately has been applied by one or both transducers for 2 and 5 s. Frequency of the ultrasonic generator was 25 kHz. Alternatively, samples without ultrasonication applied were prepared for comparison.

[00414] In another example, fabric was first prewetted in the dyeing bath for 2 or 5 s without ultrasonication applied and then subjected to the ultrasonication. Prewetting of the dry fabric allows to increase overall dye uptake and remove entrapped air from the fabric.

[00415] In another example, 100% cotton fabric was first scoured, washed with water, padded to uptake of 70 or 100% and then subjected to dyeing, with or without prewetting step. In some examples fabrics were padded to 70 or 100% dye uptake after sonication. In some examples yarns were used for dyeing, being fixed on the holder parallel to the transducers plates with a distance of 0.5-2 mm between yarns. In some examples dyeing formulations contained additive of 0.1% of acetic acid and 0.1% of chitosan as leveling and thickening agent. After dyeing fabrics or yarns were thermally cured at 180°C, washed with water and dried at 150, 65 or 25°C. [00416] Fig. 4 shows fabrics, dyed with dyed with formulation containing 1 wt.% of indigo nanoparticles without and with ultrasonication applied. Sample, dyed with ultrasonication has significantly darker shade and less dyeing defects.

2. Probe sonicator as a source of the ultrasonic energy.

[00417] Ultrasonication dyeing can also be performed with use of the probe sonicator as ultrasonic energy source. Probe sonicator allows fast buildup of the dark shades due to the high power density of the ultrasonication but is limited dimensionally (exemplary system and methods are described in US 63/302,164, which is incorporated herein by reference).

[00418] 100% cotton fabrics were wetted by the dispersion containing 10 wt.% of indigo nanoparticles up to 300% dye uptake and subjected to the sonication in contact with 3, 19 or 40 mm diameter probe of sonicator at amplitude of 80, 60 or 17 pm for 2, 5 or 10 seconds. Frequency of the ultrasonic generator was 20 kHz.

[00419] Fabric was then washed by water, dried at 65°C and temperature-cured at 180°C, rinsed with water and dried at 65°C.

[00420] Fig. 5a shows the sample after dyeing (dark dot in the center is sonication-affected area) using 3 mm probe at 80 pm amplitude for 2 second. Fig. 5b shows the dyed sample after 10 cycles of home laundry/drying. Area, subjected to the sonication, demonstrated much darker color shade and superior laundry fastness than surrounding area.

3. 40 kHz - ultrasonic bath

[00421] Ultrasonication dyeing can also be performed with use of the 40 kHz ultrasonic generator. Glass container was placed at 1 cm distance from bottom transducer of the ultrasonic bath and filled with the dispersion containing 1 wt.% of indigo nanoparticles. 100% cotton fabrics were placed into the container for 5 s for prewetting and then were subjected to ultrasonication for 5 s. Fabrics were fixed in the container by metal ring weight. Alternatively, fabric was submerged into the container without sonication for 10 s. Fabrics were dried and thermally cured at 180°C, washed with water and dried at 150°C. Fig. 6 demonstrates fabrics dyed without and with sonication applied.

EXAMPLE 2 Microstructure of the dyed fabrics

[00422] The inventors surprisingly observed that the indigo dyed fabrics exhibit a ‘fingerprint” being specific for the indigo dyed substrates of the invention. SEM images (Fig. 7) of sonication-treated area of fabric was compared with conventional leuco-indigo dyed fabric and the sample pad-dyed by the same indigo nanoparticles dispersion. For preparation of leuco-indigo dyed sample 100% cotton fabric was dyed by the immersion into solution of 0.5 wt.% leuco-indigo for 10s, removed from the solution, allowed to be oxidized in air flow and dried at 150°C. Sample, pad-dyed with indigo nanoparticles, was prepared as described above.

[00423] Conventionally dyed fabric (Fig. 7 a, b, c) contains indigo pigment in form of irregular-shaped small crystals, elongated needles, and irregular shaped flakes. Dark shade denim has a dense, film-like indigo coating of the fibers. Fabric, pad-dyed with indigo nanoparticles (Fig. 7 d, e), contains aggregates of these spheric particles from the dispersion. Fabric, dyed with indigo nanoparticles under sonication (Fig. 7 f, g, h) demonstrates presence of both small particles and long needles, having 2 types of nanocrystals as conventionally- dyed sample, but superior length of the crystals and even particles distribution on the fiber. At proper conditions dense, film-like indigo coating of the fibers is achieved.

[00424] Fig. 8 shows TEM images of the cross-section of conventionally dyed denim (Fig. 8a), fabric dyed with milled indigo nanoparticles by padding (Fig. 8b) and with ultrasonication (Fig. 8c). Both conventionally dyed sample and the sample dyed with ultrasonication contain indigo agglomerates both inside the fiber and on its surface.

EXAMPLE 3

[00425] The inventors tested dispersions containing indigo nanoparticles with different average particle size. Exemplary dispersions containing indigo nanoparticles with an average particle size of 500 nm and 150 nm, respectively were prepared and further utilized for ultrasonication assisted dyeing of cotton pads, as described above.

[00426] Indigo particles with an average size of 500 nm were highly inferior to smaller particles, and resulted in an undesired brownish color of the dyed pad (Fig. 9A) (which is attributed to a significantly lower indigo loading).

1 [00427] Cotton pad presented in Fig. 9A is characterized by an L*a*b values of L 66.2, a - 3.8, b -9.8. In contrast, cotton pads presented in Fig. 9B dyed with indigo particles having an average size of 150 nm, show a uniform blue indigo color with L*a*b values of L 27.7, a 2.3, b -10.9.

[00428] Furthermore, various concentrations of the indigo nanoparticles (i.e. between 0.1 and 20%w/w) have been successfully implemented for ultrasound/cavitation assisted dyeing process of the invention. For example, a concentration of at least l%w/w is required for an efficient dyeing after a single cycle. A skilled artisan will appreciate that the actual concentration may vary, depending on the desired shade of the dyed substate. Furthermore, even by using dispersions with low nanoparticles concentration (between 0.1 and 0.5%) may result in an efficient dyeing when implementing repetitive dyeing cycles.

[00429] Furthermore, the inventors prepared various dispersions of indigo nanoparticles with an average particle size ranging between 60 nm and 500 nm using different dispersants. Stable dispersions were obtained using the following dispersants: BASF Dispex 4290, BASF Dispex 4575, Triton X-100, Tween 80, DISPERBYK 2015, BYKJET 9151, Evomk Tego 655.

[00430] Surprisingly, the inventors obtained high indigo loading of up to 5-6%w/w after a single dyeing cycle.

[00431 ] In addition, different compositions of the invention were formulated based on some embodiments of the invention comprising various additives, such as binders, surfactant, and/or fixing agents. Exemplary compositions are summarized below.

Wetting agents: Biolite RW-150 of Avco, Metolat 364 of Munzig.

Binders: Denimcol Binder-RE NEU of CHT, Impranil DL 2077 of Covestro.

[00432] Exemplary ultrasonication conditions for yarn dyeing are as follows:

Sonication of 25, 28, 40, 80, 100, 200 kHz and power of 20, 350, 540, 700 and 1000 W was used for the textile substrate/yarn dyeing experiments.

[00433] Exemplary cavitation parameters implemented for textile dyeing are as follows: Cavitation with the resonance size of the cavitation bubble between 150 um and 15 um was utilized for the textile dyeing experiments. [00434] The inventors additionally examined the weight percentage of sodium cations on a dyed substrate. Interestingly, the amount of sodium in dyed substrates according to the invention are at most 0.099% (which is even lower than the original Na content of the pristine substrate). In contrast, dyed substrates obtained by traditional indigo dyeing exhibited significantly higher Na content (up to 9 times higher Na content). The results are summarized in Table 1.

Table 1.

EXAMPLE 4

[00436] The inventors surprisingly observed that cotton yarn can be dyed without scouring pretreatment when the sonication is applied. 100% raw cotton yarns were placed into the sonobox filled by dispersion of 150 nm indigo nanoparticles at the equal distance between the transducers, fabric surface parallel to the plates and sonication immediately has been applied by one or both transducers plates for 5 s. Frequency of the ultrasonic generator was 40 kHz. Alternatively, samples were pad-dyed by the same indigo nanoparticles dispersion for comparison. Fig. 13 presents image of yarns dyed with or without sonication. The samples dyed without sonication applied demonstrated very poor dye uptake and ununiform coating. The samples dyed with sonication applied demonstrated uniform coating without undyed spots. Color strength at 610 nm of the yarns dyed with the sonication was significantly higher than of those dyed by padding (23 and 11, respectively).

EXAMPLE 5

[00437] The inventors surprisingly observed that penetration depth of the indigo nanoparticles into the yarns substrate depends on the cavitation parameters. 100% raw cotton 10 Ne yarns were placed into the sonobox filled by dispersion of 150 nm indigo nanoparticles at the equal distance between the transducers and sonication immediately has been applied by one of the transducers plates. Yarns were subjected to sonication of 25, 40, 80 and 100 kHz for 5 s. Penetration depth of the dyestuff was 17±3 um in the yarns when treated with 100 kHz, 48±6 um when treated with 80 kHz, 89±8 um when treated with 40 kHz and 150±18 um when treated with 25 kHz (Fig. 10).

EXAMPLE 6

[00438] 100% raw cotton yarns were dyed in the slasher machine by the indigo dispersion containing indigo nanoparticles of the medium size of 150 nm wherein the dyeing process consisted of steps 130, 140 and 150 of the flowchart at the Fig. 11. After the exposure to the sonication in the dyebath yarns were dried at 110 °C. In some examples yarns were dried at 80°C. Yarns were sized after the dyeing and drying. 3/1 twill fabric was woven from the sized yarns. The resulting fabric was consequently subjected to desizing wash (amylase, 55°C, 15 min), enzyme wash (cellulase 0.9%, 55°C, 60 min), and bleach wash (sodium hypochlorite 0.2%, 55°C, 15 min), Fig. 13. The washes resulted in increase of L (lightness) and C (chroma) values of the colors of the fabrics in CIELCH color space. The L value was 20.8, 21.4, 22.3 and 32, correspondingly. The C value was 7.3, 8.6, 10.8 and 13.2, correspondingly.

EXAMPLE 7

Sulfur black dyeing process

[00439] The inventors have successfully implemented the process of the invention for dyeing a textile substrate (e.g. cotton fabrics) with an additional water insoluble dye (a sulfur dye, Sulfur black 1).

[00440] First, the inventors prepared Sulfur black 1 nanoparticles, according to the milling method disclosed hereinabove. Subsequently, an aqueous dispersion of the Sulfur black 1 nanoparticles has been used for easy and efficient cavitation/sonication-based dyeing of cotton fabrics (without the need for applying tedious steps of dye reduction and oxidation, as performed during the convenient commercial sulfur dyeing process) according to the procedure disclosed above for indigo dyeing. The inventors strongly presume that the process described hereinbelow can be applied for additional water-insoluble dyes (sulfur-, and vat-dyes). Furthermore, it is presumed that similar to indigo dyeing, any kind of substrate (including yarns and textiles, as disclosed above) can be dyed with water-insoluble dyes sulfur-, and vat-dyes according to the procedure disclosed herein.

Nanoparticles preparation.

[00441] Sulfur Black 1 nanoparticles were obtained by milling in the presence of a dispersing agent. In brief, sulfur black nanoparticles were obtained by milling 100 g of Sulfur Black grains in the bead mill with 0.1 mm beads in presence of the 500 g Munzig Edaplan 490 dispersing agent (40% active material), water and an anti-foaming agent. Obtained particles (aggregates) were characterized by intensity-weighted average hydrodynamic size of 115 nm (PDI 0.34, see Fig.15).

Sulfur Black dyeing

[00442] Dyeing was performed in the sonobox - dyeing bath with two ultrasonic plate transducers (sonotrodes) in two opposite walls of the bath and further including a delivery system configured to continuously deliver a fabric into and throughout the sonication bath such that a predetermined distance is formed between the fabric and the first sonotrode; wherein the predetermined distance between the fabric and any one of the two sonotrodes is between about 0.1 to about 1 time of ultrasound wavelength emitted by any one of the two sonotrodes, respectively (or between about 5 and about 40 mm). Sonobox is disclosed above and is further disclosed in greater details in PCT/IL2023/050570, which is incorporated herein by reference in its entirety.

[00443] Sonobox was filled with a dyeing composition comprising 10 wt.% of Sulfur Black 1 nanoparticles (SBNP) and a dispersant (Munzig Edaplan 490) at a dispersant: SBNP weight ratio of about 2: 1.

[00444] 100% raw cotton fabrics were placed into the sonobox at the equal distance between the transducers, fabric surface parallel to the plates and sonication immediately has been applied by one or both transducers for 5 s. Frequency of the ultrasonic generator was 25 kHz.

[00445] Fabrics were padded to 70 % dye uptake after sonication and dried at 110°C.

[00446] The dyed fabrics were subjected to 0, 1, 3 and 10 cycles of home laundry/drying. Fabrics after the washes demonstrate good washing fastness and are characterized by the following color in CIELab color spaced 18.7, a 0.8, b -0.6; L 17.8, a 0.9, b -0.7; L 18.6, a 0.9, b -0.6; L 17.5, a 0.9, b -0.6 for 0, 1, 3 and 10 cycles, respectively.