METHOD FOR TRANSFERRING A COLORANT TO A CELLULQSIC SUBSTRATE

[0001] Field of Invention

[0002] This invention relates to a method for transferring a colorant to a cellulosic substrate using solid particles. The method is especially useful for dyeing cotton which is typically in the form of a textile.

[0003] Background

[0004] PCT patent publication WO2006/040539 discloses a method for the application of at least one substance to a substrate using polymeric particles which are coated with said at least one substance. The substrate can be a textile and the substance can comprise a dye. That disclosure requires (as a mandatory or essential feature) that the polymeric particles are coated with the substance. Coating of the polymer particles is stated to be essential to the method of this invention.

[0005] Whilst the above method provides good colour leveling and colour intensity on the substrate the present inventors sought (among other things) to:

i. further improve the colour intensity of the coloured substrate for a given amount of colorant;

ii. further improve the efficiency of transferring the colorant to the substrate so as to reduce the amount of waste colorant;

iii. reduce the amount of un-fixed colorant at the end of the coloration method and thereby to reduce the amount of wasted colorant;

iv. provide a method wherein the particles can be utilized many times;

v. provide a method wherein the particles can be easily cleaned to remove any minor residues of colorant on the particles.

[0006] Summary of the Invention

[0007] The present inventors surprisingly found that, contrary to the teachings of WO2006/040539, excellent results can be obtained when a colorant (for example a dye) is dissolved and/or dispersed in the liquid medium rather than, for example, being coated on the particle.

[0008] According to a first aspect of the present invention there is provided a method for transferring a colorant to a substrate comprising agitating a composition comprising the substrate, solid particles, the colorant and a liquid medium

wherein:

the colorant is dissolved and/or dispersed in the liquid medium; the substrate is or comprises a cellulosic material;

the solid particles have a size of from 1 to 50mm.

[0009] Figures

[0010] Figure 1 a shows the visual appearance of an undyed cotton, Figures 1 b and 1 c show the visual appearance of cotton substrates after dyeing Comparative Examples 1 and 2 respectively.

[0011] Figure 2a shows the visual appearance of dyed cotton prepared by Example 1 , whilst Figure 2b shows the visual appearance of dyed cotton prepared by Comparative Example 3 where no solid particles were used.

[0012] Dissolved and/or dispersed

[0013] The colorant can be dissolved in the liquid medium. The colorant can be dispersed in the liquid medium. It is also possible that some of the colorant is dissolved and the remainder is dispersed in the liquid medium.

[0014] Preferably, the solid particles are uncoated with any colorant. It is possible for the solid particles to have small or trace amounts of colorant which are adsorbed onto the particle surface though this is not sufficient to form a coating. That is to say, any trace amounts of colorant which might tend to adsorb on the particle surface do not form a continuous layer surrounding or enveloping the particle.

[0015] It will therefore be appreciated that the method of the present invention suitably comprises no step or steps which have the effect of coating the solid particles with the colorant. In particular, it will be appreciated that the solid particles are not prior coated with the colorant before contact of the solid particles with the substrate. As an example, the method of the present invention preferably comprises no step in which the colorant and the particles are mixed without the presence of a liquid medium, in particular without the presence of a liquid medium suitable for effecting the transfer of colour to the substrate, and in particular without the presence of the liquid medium in which the transfer of colour to the substrate is effected.

[0016] Preferably, the colorant is dissolved and/or dispersed in the liquid medium in the absence of any solid particles. In this way a colorant solution and/or dispersion is prepared. Preferably, after the colorant solution and/or dispersion has been prepared, the solid particles are added.

[0017] Preferably, the colorant and the solid particles are not heated together in the absence of the substrate.

[0018] Preferably, the colorant is dissolved and/or dispersed in the liquid medium in the absence of the substrate.

[0019] Preferably, the colorant is dissolved and/or dispersed in the liquid medium in the absence of the substrate and in the absence of the solid particles. [0020] Thus, the first aspect of the present invention is preferably a method for transferring a colorant to a substrate as defined above and comprising the steps of:

dissolving and/or dispersing a colorant in a liquid medium in the absence of said solid particles; and

agitating said colorant dissolved and/or dispersed in the liquid medium with said substrate and said solid particles.

[0021] Preferably, if the solid particles are isolated from the liquid medium and the colorant prior to treating the substrate, the solid particles comprise less than 5wt%, more preferably less than 2.5wt%, especially less than 1wt%, more especially less than 0.5wt% and most especially less than 0.1wt% of the total amount of colorant which was present in the composition. Where such amounts of colorant are present in the solid particles they are not a coating. Instead, they can be internally absorbed into the particles or located in small regions (which do not form a coat) on the surface of the solid particles.

[0022] Solid particles

[0023] The solid particles can be or comprise a polymeric material, a non-polymeric material, or a mixture thereof.

[0024] Preferably the solid particles are or comprise a polymeric material.

[0025] Preferably, the polymeric material is a thermoplastic.

[0026] The polymeric particles can be polyamides, polyesters, polyalkylenes or polyurethanes.

[0027] Preferred polymeric materials include polyalkylenes, especially polyethylene, polypropylene and copolymers or physical blends thereof. Polypropylene is an especially preferred polymeric material. These preferred polymers show especially good results and the colorant tends not diffuse into their structure making them relatively inert and re-usable.

[0028] Preferably, the solid particles are hydrophobic.

[0029] Preferably, the polymeric material is hydrophobic. Preferred polymeric materials which are hydrophobic comprise few or more preferably no hydrophilic groups within their structure. Examples of hydrophilic groups which are preferably absent include ionic groups such as carboxylic acid, sulphonic acid, phosphonic acid, boronic acid as well as hydrophilic non-ionic groups such as -OH, -SH, - NH2, -NH-, -(OCH2CH2)- and the like. Preferably, the polymeric material comprises only carbon and hydrogen atoms.

[0030] By "hydrophobic", it is preferably meant that the solid particles have a large contact angle with water.

[0031] In order of increasing preference, the solid particles preferably have a contact angle of at least 70, 75, 80, 85, 90, 95 and 100 degrees with pure water. Preferably, the solid particle has a contact angle of no more than 120, more preferably no more than 1 15 degrees with pure water. Preferably, the measurement is recorded at a temperature of 20 or 25°C. Preferably, the relative humidity for measuring the contact angle is 65% RH. The contact angle can be measured as per international standard ISO 15989:2004. The contact angle can also be, and preferably is, measured using a contact angle telescope-goniometer (for instance using equipment available from Rame-Hart), in which the method comprises direct measurement of the tangent angle at the three-phase contact point on a sessile droplet profile. A static contact angle method is preferred. The droplet is preferably backlit.

[0032] Alternatively or additionally, by "hydrophobic" it is preferably meant that the solid particles absorb less than 5.0wt%, more preferably less than 2.5wt%, even more preferably less than 1wt% and especially less than 0.5wt% of water relative to the weight of the solid particles. One preferred method for establishing the water absorption is to contact the solid particles with water for a period of 24 hours, preferably at a temperature of 25°C. After this contact period, any water merely on the outside of the solid particles is removed, suitably by dabbing the solid particles on a filter paper. After dabbing, the wet weight (Ww) of the solid particles is recorded. The dry weight (Wd) of the solid particles is established, preferably by vacuum drying of the particles, preferably at a temperature of 30°C and preferably after at least 8 hours of drying. The weight% of water absorption is then given by 100x (WW - Wd) / Wd.

[0033] Optionally the non-polymeric material can be or comprise ceramics, metals and alloys (for example steel) and glass.

[0034] Whilst the solid particles can be hollow, foamed or porous, they are preferably substantially non-porous. Porosity is preferably measured by gas adsorption/desorption, preferably in a manner consistent with Brunauer-Emmett-Teller (BET) theory. The gas is preferably nitrogen and the adsorption/desorption is preferably performed at a temperature of about -195°C. A preferred apparatus for measuring the porosity is a Micromeritics TriStar II.

[0035] The solid particles are preferably inert. By "inert" it is preferably meant that the solid particles have few or no functional groups which are capable of reacting. More preferably the solid particles have few or no functional groups which are capable of reacting with the reactive groups of a reactive dye. Examples of reactive groups in reactive dyes include: halo triazines, halo pyrimidines, halo quinoxalines, vinyl sulfones and vinyl amides. Preferably, the solid particles comprise no ionic groups and no nucleophilic groups such as -OH, -SH, -NH- and -NH ₂ .

[0036] In increasing preference, the solid particles preferably have a size of no more than 40mm, no more than 30mm, no more than 25mm, no more than 20mm, no more than 15mm or no more than 10mm.

[0037] In increasing preference, the solid particles preferably have a size of at least 2mm, at least 3mm or at least 4mm. [0038] The surface area of the solid particles is preferably from 10mm ² to 400mm ² , more preferably from 40 to 200mm ² and especially from 50 to 190mm ² .

[0039] The size is preferably an average size more preferably a number average size. The average is preferably taken from at least 100, at least 1000 or at least 10,000 solid particles.

[0040] The size is preferably the longest linear dimension of the particle. The method of measuring the particle size is preferably performed by using calipers or a particle size measurement using image analysis, especially dynamic image analysis. A preferred apparatus for dynamic image analysis is a Camsizer as provided by Retsch.

[0041] In order of increasing preference, the solid particles preferably have a density of at least 0.5g/cm ³ , at least 0.75g/cm ³ , at least 0.9g/cm ³ , at least 1.0 g/cm ³ , at least 1.1 g/cm ³ , at least 1.2 g/cm ³ , at least 1.25 g/cm ³ , at least 1.30 g/cm ³ , at least 1.35 g/cm ³ , at least 1 .40 g/cm ³ , at least 1.45 g/cm ³ , at least 1.50 g/cm ³ , at least 1 .55 g/cm ³ , at least 1.60 g/cm ³ , at least 1.65 g/cm ³ , at least 1.70 g/cm ³ , at least 1.75 g/cm ³ , at least 1.80 g/cm ³ , at least 1 .85 g/cm ³ or at least 1.90 g/cm ³ .

[0042] In order of increasing preference, the solid particles preferably have a density of no more than 10 g/cm ³ , no more than 8 g/cm ³ , no more than 6 g/cm ³ , no more than 4 g/cm ³ , no more than 3 g/cm ³ , no more than 2.5 g/cm ³ , no more than 2.2 g/cm ³ and especially no more than 2.0 g/cm ³ .

[0043] The density of the solid particle can be from 0.5 to 2.5 g/cm ³ , from 1 to 2.2 g/cm ³ or from 1.1 to 2.0 g/cm ³ .

[0044] Especially, where the cleanability of the solid particles is desired to be particularly effective then lower densities are preferred. Thus, densities of no more than 1.8, 1.6, 1.5 and 1.4 g/cm ³ are also of value in the present invention. Cleanability, as used herein preferably means the ability to suitably remove the colorant residues from the solid particle after the method of the present invention. This is especially desirable where the solid particles are re-used in one or more subsequent methods according to the first aspect of the present invention.

[0045] Preferably, the solid particles are more dense than the liquid medium, more preferably more dense than water and especially more dense than water comprising the relevant amounts of salts and optional additives.

[0046] In the case of solid particles which are or comprise a polymeric material, a filler can be incorporated into the solid particle. Thus, the solid particle may be or comprise a polymeric material and a filler, which is preferably an inorganic filler.

[0047] Preferably, a solid particle comprises or consists essentially of or consists of a polymeric material and an inorganic filler in a weight ratio of 90: 10 to 20:80 and more preferably 70:30 to 30:70 (polymenfiller). Where good cleanability is desired, the solid particle suitably comprises no less than 50:50, more preferably no less than 70:30 and especially no less than 90: 10 of polymeric material to an inorganic filler on a weight ratio basis. [0048] The solid particle can comprise at least 5, at least 10, at least 20, at least 30, at least 35, at least 40, at least 45 or at least 50wt% of filler, which is preferably an inorganic filler. In a preferred embodiment, the solid particle comprises at least 20wt% filler, particularly where faster and/or more efficient separation of the solid particles from the substrate is desirable. The remainder of the solid particle required to make 100wt% is preferably a polymeric material.

[0049] The solid particle can comprise no more than 90, no more than 80, and no more than 70wt% of filler, which is preferably an inorganic filler. The remainder of the solid particle required to make 100wt% is preferably a polymeric material.

[0050] Optionally, the solid particle can comprise a polymeric material and up to 30wt% of a filler. Optionally, the solid particle comprises a polymeric material and no filler (and in particular no inorganic filler). The solid particle can consist (exclusively) of polymeric material.

[0051] The solid particle can have a shape which is cubic, ellipsoidal, spherical and any shape therebetween.

[0052] Preferably, the solid particle has a shape which is ellipsoidal or spherical as these shapes tend to be kind to the substrate, they tend to provide good leveling of the colorant and they tend to separate from the substrate more readily.

[0053] Preferably, the solid particles have an aspect ratio of no more than 1.5, more preferably no more than 1.4, especially no more than 1.3 and most especially no more than 1.2. The aspect ratio is the ratio of the longest linear dimension to the shortest linear dimension for each particle. Preferably the aspect ratio is an average, especially a number average. Preferably the average is of at least 100, more preferably at least 1000 and especially at least 10,000 solid particles.

[0054] Preferably the solid particles do not in any way become permanently attached, affixed, integrated or associated with the substrate. To put this another way, the solid particles may be readily separated from the substrate at the end of the method according to the first aspect of the present invention.

[0055] Colorant

[0056] The colorant preferably is or comprises a dye. Preferably, the colorant is soluble in the liquid medium, more preferably the colorant is soluble in pure water at 25°C, even more preferably the colorant is soluble in pure water at 25°C to at least a solubility of 1 g/L.

[0057] The dye may be un-reactive but is preferably reactive, more preferably the dye carries one or more groups which are reactive towards the substrate which is or comprises a cellulosic material (e.g. cotton). Preferably, the reactive dye has from one to three, more preferably from one to two reactive groups. The reactive groups can be the same or different.

[0058] Other dyes which are suitable for use in the present invention include Cationic dyes, Direct dyes, Vat dyes and Disperse dyes. [0059] Preferably, the colorant is present in an amount of at least 0.1wt%, more preferably 0.5wt% relative to the dry weight of the substrate. Preferably, the colorant is present in an amount of no more than 20wt%, more preferably no more than 10wt% relative to the dry weight of the substrate.

[0060] A preferred reactive dye comprises one or more reactive groups selected from halo triazines, halo pyrimidines, halo quinoxalines, vinyl sulfones, aminonicotinotriazines quaternary groups and vinyl amides.

[0061] Halo groups in the abovementioned reactive groups are preferably chloro, fluoro or mixtures thereof.

[0062] Examples of preferred reactive groups include monochlorotriazine, mono fluorochlorotriazine, dichlorotriazine, difluorochloropyrimidine, dichloroquinoxaline, trichloropyrimidine, vinyl sulphone and vinyl amide groups.

[0063] The reactive dye can also be a homobifunctional or heterobifunctional reactive dye such as those sold under the tradename Sumifix™ Supra which are available from Sumika Chemtex Co Ltd. The reactive dye can be a Kayacelon React™ dye as supplied by Standard Dyes.

[0064] A single colorant can be used or two or more colorants can be used.

[0065] Preferably, when the colorant is a dye, the dye is dissolved in the liquid medium prior to adding the solid particles. Preferably, when the colorant is insoluble in the liquid medium the colorant is dispersed in the liquid medium prior to adding the solid particles.

[0066] Liquid medium

[0067] The liquid medium is preferably aqueous. To put it another way, the liquid medium preferably is or comprises water.

[0068] Where water is used in conjunction with other liquids, these liquids may be organic liquids such as alcohols, esters, ethers, amides and the like.

[0069] In order of increasing preference, the liquid medium comprises at least 50wt%, at least 60wt%, at least 70wt%, at least 80wt%, at least 90wt%, at least 95wt% or at least 99wt% of water. Most preferably the liquid medium consists of water and no other liquid components.

[0070] Preferably, the liquid medium has a pH which is at least 7, more preferably at least 10 and especially at least 1 1.

[0071] Cellulosic material

[0072] The cellulosic material may be or comprise any of the natural cellulosic materials including wood pulp, flax, hemp, jute ramie and especially cotton.

[0073] The cellulosic material can be or comprise regenerated cellulose. The regenerated cellulosic material can be or comprise rayon for example viscose, modal and lyocell (also known as tencel). [0074] The cellulosic material can be modified, for example nitrocellulose, cellulose esters or cellulose ethers.

[0075] The substrate can comprise other materials in addition to the cellulosic material. The substrate may optionally also comprise a polyamide (e.g. Nylon), a polyester, a polyacrylic, wool, silk, Lycra (sometimes called spandex) or mixtures of one or more of these materials.

[0076] Preferably, the cellulosic material has one or more nucleophilic groups within its chemical structure. Preferred examples of nucleophilic groups are -NH ₂ , -NH-, -SH and especially -OH.

[0077] Substrate

[0078] Preferably, the substrate is in the form of a filament, a fibre, a yarn, a fabric, a textile or a garment.

[0079] The substrate may comprise at least 10wt%, more preferably at least 50wt% of cellulosic material.

[0080] The substrate may be cotton, which can be denim.

[0081] Preferably the substrate has no pre-treatment which is designed to aid colorant pick-up and/or colorant fixation.

[0082] Transfer Efficiency

[0083] In order of increasing preference, at least 10wt%, at least 20wt%, at least 30wt%, at least 40wt%, at least 50wt%, at least 60wt%, at least 70wt%, at least 80wt, at least 90wt%, at least 95wt%, at least 97%, at least 98wt%, or at least 99wt% of the initial amount of colorant is transferred to the substrate. The transfer efficiency is preferably established using the amount of colorant which is present in the liquid medium after the method has been performed and which has not successfully transferred to the substrate. The percentage amounts of colorant in the liquid medium after the method has been performed are thus suitably equal to 100 minus the abovementioned preferred transfer percentages.

[0084] Conditions for the method

[0085] In order of increasing preference, the method according to the first aspect of the present invention is performed at a temperature of no more than 100°C, no more than 95°C, no more than 90°C, no more than 80°C, no more than 70°C or no more than 60°C.

[0086] In order of increasing preference, the method according to the first aspect of the present invention is performed at a temperature of no less than 0°C, no less than 5°C, no less than 10°C or no less than 15°C.

[0087] A particularly preferred temperature range is from 5°C to 95°C.

[0088] The agitation may be performed for a period of at least 1 second, at least 15 seconds, at least 30 seconds or at least 1 minute. [0089] The agitation may be performed for a period of no more than 48 hours, no more than 24 hours, no more than 16 hours, no more than 8 hours, no more than 5 hours, no more than 4 hours, no more than 3 hours or no more than 2 hours.

[0090] The agitation is preferably performed for a period of from 1 minute to 2 hours.

[0091] In order of increasing preference, the weight ratio of the dry solid particles to the dry substrate is at least 0.01 :1 , at least 0.1 : 1 ; at least 0.3: 1 , at least 0.5: 1 ; at least 1 :1 and at least 2: 1.

[0092] In order of increasing preference the weight ratio of the dry solid particles to the dry substrate is no more than 100: 1 , no more than 50: 1 , no more than 30: 1 , no more than 20:1 , no more than 10:1 and no more than 5: 1 .

[0093] In order of increasing preference, the weight ratio of the dry solid particles to the dry substrate is from 0.01 : 1 to 100: 1 , from 0.1 : 1 to 50:1 , from 0.1 : 1 to 20: 1 , from 0.1 : 1 to 10: 1 , from 1 : 1 to 20: 1 , from 1 : 1 to 10: 1 and from 2: 1 to 10: 1.

[0094] Agitation

[0095] The agitation may be performed by shaking, oscillating, stirring, fluidizing, pulsing or more preferably by rotating (the composition).

[0096] Apparatus

[0097] Preferably, the agitation is performed within an apparatus comprising a treatment chamber. The treatment chamber may be shaken, oscillated, pulsed or more preferably rotated. The rotation may be at any suitable G force, however the preferred G force is from 0.05G to 2G, more preferably from 0.05G to 1.5G and especially from 0.05 to 0.95G. The G force is preferably calculated at the inner surface of the treatment chamber. The treatment chamber is preferably in the form of a cylinder. The G force can be calculated by G=1.1 18x R x (RPM/1000) ² wherein R is the radius in millimeters and RPM is the rotation speed expressed in revolutions per minute.

[0098] The apparatus may alternatively or additionally comprise one or more stirrers, fluidizing beds or jets configured so as to agitate the composition.

[0099] Optional composition components

[00100] The composition may additionally optionally comprise one or more of the following: sequesterants, lubricants, anti-crease agents, pre-treatment agents, levelling agents, dispersants, antifoaming agents, desizing agents, mercerizing agents, optical brighteners, salts, buffers, biocides, acids, bases, surfactants, organic solvents, fixing catalysts, enzymes or anti- redeposition agents.

[00101] Salts [00102] The liquid medium may comprise salts which are dissolved therein. Preferably, the liquid medium contains no more than 150g/l, more preferably no more than 10Og/l of salts. Optionally the liquid medium comprises no more than 90g/l, no more than 80g/l, no more than 70g/l, no more than 60g/l, no more than 50g/l, no more than 40g/l, no more than 30 g/l, no more than 20g/l, no more than 10g/I, no more than 5g/l, no more than 2.5g/l, no more than 1 g/l, no more than 0.5g/l, or no more than 0.1 g/l of salts. Optionally, the liquid medium is entirely free of salts.

[00103] When the amount of salt of less than 20g/l in the liquid medium, it is preferable that the liquid medium has a neutral to acidic pH, more preferably a pH of from 4 to 7, even more preferably from 5 to 7. These preferred pH values can be achieved using citric acid/citrate buffers.

[00104] Examples of salts include sodium salts, especially sodium chloride and/or sodium sulfate.

[00105] Preferably, the weight ratio of the liquid medium to the dry substrate is greater than 2: 1 , more preferably greater than 3: 1 .

[00106] Preferably, the weight ratio of the liquid medium to the dry substrate is no more than 100: 1 , more preferably no more than 50: 1 , especially no more than 20: 1 , more especially no more than 15: 1 and most especially no more than 10: 1.

[00107] Fixation

[00108] It is often advantageous to raise the temperature of the composition to a temperature of at least 40°C, more preferably at least 50°C and especially at least 60°C, more especially at least 70°C and most especially at least 80°C. This can assist in fixing the colorant to the substrate. Such fixation is especially of assistance with colorants which are dyes, especially reactive dyes.

[00109] Re-use

[00110] The solid particles are preferably re-used, preferably in one or more methods according to the first aspect of the present invention.

[0011 1] Accordingly, the method of the first aspect of the present invention preferably additionally comprises the steps:

i. separating the substrate from the solid particles;

ii. re-using the solid particles in the colorant transferring method according to the first aspect of the present invention.

[00112] Preferably, step ii. as mentioned above comprises transferring a colorant to a substrate in a method comprising agitating a composition comprising a substrate, the separated solid particles, a colorant, a liquid medium;

wherein:

the colorant is dissolved and/or dispersed in the liquid medium;

the substrate is or comprises a cellulosic material; the separated solid particles have a size of from 1 to 50mm.

[00113] Typically, the colorant in step ii. is fresh or unused and/or the liquid medium is fresh or un-used and/or the substrate is fresh or unused.

[00114] It may be desirable to clean the solid particles between the steps i. and ii. This can be effected by washing the solid particles with liquid medium, especially water. The water may optionally comprise one or more surfactants and/or organic liquids. It has been surprisingly found that hydrophobic and especially polyalkylene solid particles are cleaned particularly well. Solid particles with lower densities and/or lower levels of filler, as described hereinabove, are also preferred as they tend to clean better between steps i. and ii.

[00115] Steps i. and ii. May be repeated any number of times, preferably steps i. and ii. are repeated at least 5, at least 10, at least 20, at least 50 and at least 100 times.

[00116] Preferably, after the method of the present invention, the solid particles comprise no more than 5wt%, more preferably no more than 1wt%, even more preferably no more than 0.5wt% and yet more preferably no more than 0.1 wt% of the initial amount of colorant after the transfer of the colorant to the substrate. Preferably, these preferences are also achieved even after the solid particles have been re-used for at least 5 times, at least 10 times, at least 25 times, at least 50 times or at least 100 times in the method of the first aspect of the present invention.

[00117] Optional Method steps

[00118] The method according to the first aspect of the present invention may additionally comprise one or more of the following steps:

a) bleaching the substrate;

b) scouring the substrate;

c) rinsing the substrate (for example so as to remove unfixed colorant);

d) fixing the colorant to the substrate;

e) extracting the liquid medium;

f) separating the substrate from the solid particles;

g) drying the substrate;

h) ironing or pressing the substrate;

i) stitching, gluing, shape-forming and/or cutting the substrate especially wherein the substrate is a textile;

j) surface treating the substrate.

[00119] Preferably steps (a) and (b) are performed before agitating the composition comprising the solid particles, the colorant and the liquid medium. [00120] Preferably steps (c) to (j) are performed after agitating the composition comprising the solid particles, the colorant and the liquid medium.

[00121] Substrate

[00122] According to a second aspect of the present invention there is provided a cellulosic substrate obtained or obtainable by the method of according to the first aspect of the present invention.

[00123] General

[00124] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. Thus, by example a colorant means one or more colorants and a substrate means one or more substrates.

[00125] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[00126] The present invention will now be illustrated by reference to the following examples, without in any way limiting its scope.

[00127] Examples

[00128] Comparative Example 1 - using Solid Particles prepared according to WO2006/040539

[00129] Step 1 - Preparation of Solid Particles

[00130] Solid particles consisting of polypropylene, having a density of 0.9g/cm ³ , having a size (longest linear dimension) of 3 to 4 mm and having an ellipsoidal shape were prepared by hot melt extrusion. [00131] Step 2 - Preparation of a Colorant solution

[00132] A colorant solution was prepared by dissolving 4g of Reactive Red 120 (Procion Red HE- SB as supplied by Dystar) in 96gms of deionized water. Reactive Red 120 is a reactive dye having two monochlorotriazine reactive groups.

[00133] Step 3 - Attempt to Coat the Solid Particles

[00134] So as to attempt to coat the solid particles prepared in Step 1 with the colorant, the colorant solution prepared in Step 2 was added to 50g of the polypropylene solid particles and the resulting mixture was heated to 50°C at pH 7 for a period of 30 minutes. This coating method is substantially as disclosed in WO2006/040539 at page 8, lines 16 to 26.

[00135] Step 4 - Isolation of "Coated" Solid Particles

[00136] The polypropylene solid particles prepared in Step 3 were then removed from the colorant solution by filtration, the polypropylene particles were washed with 50g of deionized water to remove any uncoated colorant and air dried at ambient temperature.

[00137] Step 5 - Preparation of the Cotton Substrate

[00138] A white cotton textile substrate which had previously been double scoured, bleached and which comprised no optical brightening agent was prepared.

[00139] Step 6 - Dyeing of the Cotton Substrate

[00140] The cotton substrate as prepared in Step 5 was dyed in a Roaches Pyrotec 3 dyeing machine.

[00141] Dyeing Step 6 was as follows:

The amount of cotton substrate used was 10g and the amount of polypropylene particles as prepared in Step 4 was 50g.

The cotton substrate was loaded into the dyeing machine, the substrate was wetted with the water (20g) and the polypropylene particles prepared in Step 4 were added. Excess water was removed from the cotton substrate by squeezing the cloth with approximately 10g of water remaining on the substrate

The temperature inside the dyeing machine was raised from ambient at a rate of 1.5°C per minute and then held at 95°C for a period of 45 minutes and after this the temperature was allowed to cool to 65°C.

The pH of the water used was 7;

The drum of the dyeing machine was rotated at 25rpm throughout the dyeing step which equates to a G force of 0.14G at the internal wall of the drum; The dyed cotton substrate was removed from the dyeing machine, washed with water, namely twice with 200g of cold water and once with 200g of water at a temperature of 70°C. After washing, the cotton substrate was then air dried.

[00142] Measurement method

[00143] The amount of dye successfully transferred to the cotton substrate was quantified spectrophotometrically using a Konica Minolta CM-3600A spectrophotometer fitted with a D65 light source and using SpectraMagic NX Colour Data Software CM-S100w, Professional/Lite Ver2.2. The L*, a* and b* CIE colour space values were recorded at four different points on the dyed cotton substrate and the values recorded were the average of those four measurements. The delta E* values were calculated using Equation 1 :

[00144] Delta E*= [ (L* ₂ -L*i) ² + (a* ₂ -a*i) ² + (b* ₂ -b*i) ² ] ^1/2 Equation 1

[00145] wherein L*i, a*i and b*i values are taken from the average colour space measurements of the un-dyed cotton textile substrate and L* ₂ , a* ₂ and b* ₂ are taken from the average colour space measurements of the dyed substrates prepared in Comparative Examples 1.

[00146] Comparative Example 2 - Conventional Dyeing without any solid particles

[00147] Step 1 - Preparation of a Colorant solution

[00148] A colorant solution was prepared by dissolving 4g of Reactive Red 120 (Procion Red HE- SB as supplied by Dystar) in 96gms of deionized water.

[00149] Step 2 - Preparation of the Cotton Substrate

[00150] A white cotton textile substrate which had previously been double scoured, bleached and which comprised no optical brightening agent was prepared.

[00151] Step 3 - Dyeing of the Cotton Substrate

[00152] The cotton substrate as prepared in Step 2 was dyed in a Roaches Pyrotec 3 dyeing machine.

[00153] Dyeing Step 3 was as follows:

The amount of cotton substrate used was 10g; the amount of Colorant solution as prepared in Step 1 was 3.3g.

The cotton substrate was loaded into the dyeing machine and the substrate was wetted with the colorant solution.

The temperature inside the dyeing machine was raised from ambient at a rate of 1.5°C per minute and then held at 95°C for a period of 45 minutes; after this the temperature was allowed to cool to 65°C before the cotton substrate was removed.

The pH of the water used was 7; The drum of the dyeing machine was rotated at 25rpm throughout the dyeing step which equates to a G force of 0.14G at the internal wall of the drum;

[00154] The dyed cotton substrate was removed from the dyeing machine, washed with water, namely twice with 200g of cold water and once with 200g of water at a temperature of 70°C. After washing, the cotton substrate was then air dried.

[00155] The amount of dye successfully transferred to the cotton substrate was quantified spectrophotometrically using the same method as described in Comparative Example 1.

[00156] Results

[00157] The results of the dyeing Comparative Example 1 and Comparative Example 2 were as tabulated in table 1 below.

[00158] Table 1 - Dyeing results

[00159] Larger delta E* values correspond to a darker and more intense shade and therefore to more dye having been successfully transferred.

[00160] Both the quantitative spectrophotometric results and the visual appearances in Figures 1 a, 1 b and 1 c confirm that the coating method of WO2006/040539 did not provide superior results as compared to the Conventional Dyeing method (wherein no solid particles were present). This was the observation even though the coating method used in Comparative Example 1 exposed the particles to a much larger total amount of colorant than was present in Comparative Example 2. Whilst not wishing to be limited by any particular theory it is hypothesized that especially when the solid particles are hydrophobic (as is the case with polypropylene) then the coating method used in WO2006/040539 is particularly ineffective. Thus, the solid particles are substantially not coated and so very little if any colorant is transferred to the substrate.

[00161] Example 1 - Uncoated solid particles [00162] Step 1 - Preparation of Solid Particles

[00163] Solid particles comprising polypropylene and an inorganic filler, having a density of 1.76g/cm ³ , a surface area of about 60mm ² , a size (longest linear dimension) of about 4mm and an ellipsoidal/spherical shape were prepared by hot melt extrusion.

[00164] Step 2 - Preparation of a Colorant solution

[00165] A colorant solution was prepared by dissolving 4g of Reactive Red 120 (Procion Red HE- SB as supplied by Dystar) in 96gms of deionized water.

[00166] Step 3 - Preparation of the Cotton Substrate

[00167] A white cotton textile substrate which had previously been double scoured, bleached and which comprised no optical brightening agent was prepared.

[00168] Step 4 - Dyeing of the Cotton Substrate

[00169] The cotton substrate as prepared in Step 3 was dyed in a Roaches Pyrotec 3 dyeing machine.

[00170] Dyeing Step 4 was as follows:

The amount of cotton substrate used was 10g; the amount of polypropylene particles used was 100g, as prepared in Step 1 ; and the amount of colorant solution used was 70g as prepared in step 2.

The cotton substrate was loaded into the dyeing machine, the substrate was wetted with water (20g). Excess water was removed from the cotton substrate by squeezing the cloth with approximately 10g of water remaining on the substrate.

The polypropylene particles were added and then the colorant solution was added.

The temperature inside the dyeing machine was raised from ambient at a rate of 1.5°C per minute and then held at 95°C for a period of 15 minutes; after this the temperature was allowed to cool and once at 65°C then 0.3g of a solution of a soda ash solution in water (15g/L) was added, the temperature was then raised to 95°C and held at that temperature for a period of 30 minutes, after this the temperature was allowed to cool to 65°C.

The pH of the water used was 7 before the addition of soda and 11.5 after the addition of soda;

The drum of the dyeing machine was rotated at 25rpm throughout the dyeing step which equates to a G force of 0.14G at the internal wall of the drum. [00171] The dyed cotton substrate was removed from the dyeing machine, washed with water, namely twice with 200g of cold water and once with 200g of water at a temperature of 70°C. After washing, the cotton substrate was then air dried. This produced Substrate 1.

[00172] Comparative Example 3 - Conventional Process without solid particles

[00173] Example 1 was repeated with the exception that no solid particles were present in the Dyeing step 4. Thus, this Comparative Example represents the conventional process without any solid particles. This produced Comparative Substrate 3.

[00174] Measurement method

[00175] The amount of dye successfully transferred to the cotton substrate was quantified spectrophotometrically using a Konica Minolta CM-3600A spectrophotometer fitted with a D65 light source and using SpectraMagic NX Colour Data Software CM-S100w, Professional/Lite Ver2.2. The L*, a* and b* CIE colour space values were recorded at four different points on the dyed cotton substrate as prepared in Step 4 and the values recorded were the average of those four measurements. The delta E* values were calculated using Equation 1

[00176] Delta E*= [ (L* ₂ -L*i) ² + (a* ₂ -a*i) ² + (b* ₂ -b*i) ² ] ^{1 2} Equation 1

[00177] wherein L ^* i, a ^* ^ and b ^* i values are taken from the average colour space measurements of the un-dyed cotton textile substrate and L ^* ₂ , a ^* ₂ and b ^* ₂ are taken from the average colour space measurements of the dyed substrate obtained from Example 1 or Comparative Example 3.

[00178] Results

[00179] The results of the dyeing Example 1 and Comparative Example 3 were as tabulated in table 2 below.

[00180] Table 2 - Dyeing results

Sample Comment Figure Delta E*

Solid particles and

wherein the

colorant is Fig 2a

Example 1 dissolved in the 79.5

water but not

coated on the

particles

Conventional

Comparative Example 3 Dyeing without any Fig 2b 73.8

solid particles [00181] Higher delta E* values correspond to a more intense shade and to a more successful transfer of colorant to the substrate.

[00182] It was clearly demonstrated that contrary to the teaching of WO2006/040539 excellent transfer of the colorant to a substrate was obtained when the colorant was not coated on the solid particles. The results were superior to the conventional process wherein no solid particles are used.

[00183] Whilst not wishing to be limited by any particular theory it is hypothesized that especially when the solid particles are hydrophobic (as is the case with polypropylene) then solid particles are substantially not coated with the colorant. Surprisingly, however, this coating is not essential to the transfer of the colorant and superior results as compared to a conventional method using no solid particles were obtained. It is hypothesized that the mechanical action imparted to the cellulose substrate by the solid particles assists the colorant in the transfer.

[00184] Wash-off Examples

The dyed substrate as prepared in each of Example 1 and Comparative Example 3 were each separately washed using the following method. The dyed cotton substrate was washed 5 times, each time with (fresh) deionized water. In each wash, the ratio of wash water to substrate was 20: 1 by weight. The temperature of the wash water was 75°C. Each wash was performed over a period of 10 minutes allowing any unfixed or hydrolysed dye time to wash off from the substrate. The washing was performed in a 500ml beaker on a hot-plate using a stirrer. The final washed substrate was air dried at ambient temperature.

[00185] The delta E* value of the dyed substrate and the delta E* value after washing were recorded using the previously described method.

[00186] The change in the delta E* (Dyed - Washed) was calculated and was as tabulated in Table 3 below:

[00187] Table 3 - Change in Delta E* after washing

Sample Comment Change in Delta E*

Solid particles and wherein the

Example 1 colorant is dissolved in the water but 4.8

not coated on the particles

Comparative Conventional Dyeing without any

9.9

Example 3 solid particles [00188] A smaller change in Delta E* corresponds to more dye having been fixed to the substrate during the dyeing process.

[00189] The results in Table 3 show that (as well as being more intensely coloured) the substrate prepared by the method of the present invention also shows an increased level of fixation as compared to the conventional method where no solid particles where used.

[00190] Thus, surprisingly, it was found that the method of the present invention provides coloured substrates with a more intense shade and wherein more of the colorant is successfully fixed to the substrate.

[00191] Additionally, it was found that the present method wherein the colorant is dissolved or dispersed in the liquid medium results in solid particles which are less contaminated with traces of colorant and/or which are more readily cleaned so as to remove any minor traces of colorant, in comparison to the coated particles of WO2006/040539. Cleaner solid particles are useful when the shade of the colorant is changed such that there is no colour to colour contamination. Also, cleaner solid particles mean that the solid particles can be re-used more times.

[00192] Reactive Black 5

[00193] Example 1 and Comparative Example 3 were repeated except that the colorant used was Reactive Black 5. Reactive Black 5 is a reactive dye having two vinyl sulphone reactive groups. The results of this comparison again showed a more intense and effective coloration of the substrate along with better fixation to the substrate (versus the conventional method where no solid particles were present).

[00194] Example 2 - standard reactive dyeing with solid particles and without salt

[00195] A 2.5 kg load of garments was wetted out in a 14 kg rotatory drum machine with a liquor ratio (liquid medium to dry substrate) of 7: 1. For the experiments with solid particles, the particles were polypropylene particles as described for Example 1 , and these particles were added to the wetted garments in the rotatory drum. The amount of Reactive Blue 19 dye added to the garments was 25 grams (1 % of weight of garments). The garments were then mixed with the dye at a temperature of 60°C for 20 minutes at 10 rpm. After this, 169 grams of sodium carbonate was added to the dyed garments over a period of 20 minutes which was then further tumbled for 45 minutes at 60°C. The dyed garments were then washed at a temperature of 30°C for 5 minutes and the pH was checked to ensure it was between 6 and 7, before draining and refilling the drum again with water at 30°C. 203 grams of 40 % formic acid (for neutralisation) was then added to the dyed garments and run for 10 minutes. The pH of the solution was adjusted to 5.5 - 6.5. Subsequently, a series of wash-offs were undertaken at a liquor ratio of 7: 1 , at temperatures of 95°C, 40°C, 60°C and 35°C and each wash-off step was run for 10 minutes to ensure no more colour was removed from the garment. Additional wash-off steps were continued at 40°C until the wash-off liquor was clear to ensure all the hydrolysed dye was removed from the garments. The dye process as stated above was repeated using the solid particles at 3: 1 and 5: 1 ratio. The results are presented in table 4 below. High ΔΕ values indicate high dye fixation onto the cotton substrates.

[00196] Table 4: Average ΔΕ values for the Reactive Blue 19, without salt, and with or without solid particles

[00197] The results in table 4 show better dye fixation in the presence of the solid particles compared to no solid particles.

[00198] Example 3 - standard reactive dyeing with salt and with and without solid particles

[00199] Example 2 was repeated at a lower liquor ratio of 4: 1 and in the presence of salt (50 g/L) as recommended by the dye industry, in a rotatory drum. The results are presented in table 5.

[00200] Table 5 - Average ΔΕ values for Reactive Blue 19 with salt, with or without solid particles

[00201] Example 4 - Ambient/low temperature reactive dyeing with or without solid particles and without salt

[00202] The above experiment was repeated as follows. The cotton substrate (10 g) was dyed in a tumbler. The cotton substrate was loaded into the tumbler and the substrate was wetted with water at a liquor ratio of 5:1. The pH of the water was adjusted to 7. The excess amount of liquor left in the drum was used to dissolve 0.2 grams of Procion Red PX-8B dye (printing dye; DyStar, Singapore). The reactive dye was mixed well with the cotton swatches in the tumbler for 20 minutes at room temperature. Sodium carbonate (0.75 grams; Sigma Aldrich, UK) was then added to increase the pH to 12 and to enable fixation of the dye on to the cotton substrate for 45 minutes. The dyed cotton substrate was then washed with 200g of soft water (pH 7) at 30°C followed by 200g of water at a temperature of 60°C. A further 3 wash steps were undertaken with the dyed cotton swatches at 40°C to remove any unfixed dye with solid particles and 6 wash-offs without solid particles to achieve the same level of coloured effluent. The cotton substrates were then air-dried and the amount of dye successfully transferred to the cotton substrate was quantified spectrophotometrically using the same method as noted above. An average ΔΙ_* was then calculated for each experiment, and the results presented in table 6 below.

[00203] Table 6 - Average ΔΙ_* values for Procion Red PX-8B dye with or without solid particles, and without salt

[00204] The above procedure was repeated using the Remazol Navy RGB dye (DyStar, Singapore). The results are presented in table 7 below.

[00205] Table 7 - Average AL* values for Remazol Navy RGB with or without solid particles

[00206] Analysis of particles using the spectrophotometer (as described above) before and after 20 dye treatment cycles indicated minimal colour change (ΔΕ*) on the surface of the particles. No blue dye adsorption could be visually observed on the surface of the particles. These results are presented in table 8 below.

[00207] Table 8 - Average ΔΕ for new solid particles and after 20 treatment cycles

Sample Average L* ΔΕ

New solid particles 68.7 -

Solid particles used 20 times 66.1 2.6 [00208] A comparison was made between polypropylene particles and nylon particles before and after 20 dye treatment cycles as described above. In contrast to the polypropylene particles, the nylon particles exhibited significant colour uptake. Table 8 below shows the colour change (AL*) measured using the spectrophotometer as described above.

[00209] Table 8: Average AL* for PP and nylon particles and after multiple dye treatment cycles

Particle Type Dye Concentration AL*

Polypropylene

4.0% 2.6

Nylon 4.0% 39.5