METHOD FOR REDUCING THE COLOUR INTENSITY OF A COLOURED TEXTILE

[0001] Field of the Invention

[0002] The present invention relates to a method for reducing the colour intensity of a coloured textile using a composition comprising, inter alia, solid particles and 2,2,6,6-tetramethylpiperidin- 1-oxyl or a derivative thereof (especially TEMPO and TEMPOL). The method is especially suitable for providing a faded or stonewashed appearance for denim.

[0003] Background to the Invention

[0004] Oxidation or bleaching of a colourant on the surface of coloured textiles is a widely used technique to achieve lighter hues, particularly within denim finishing. Typical oxidants used include percarbonates, perborates, hypochlorite or enzymes. That said, the techniques employing these oxidants suffer from a number of disadvantages. The prior art techniques suffer from one or more of the following technical problems: i. textile damage, ii. being costly iii. the techniques use large volumes of water and thereby generating large volumes of waste water; iv. the techniques require higher temperatures to be effective on a reasonable timescale; v. the techniques do not provide sufficient reduction in the colour intensity of the substrate, vi. the techniques are not readily or directly compatible with other important steps such as desizing and/or abrasion which leads to more complicated methods; vii. the techniques produce undesirable back-staining on for examples pockets in garments.

[0005] A number of techniques have been explored, one of which utilises an electrochemically generated oxidising agent to over-ride waste and reduce cost. US patent publication US2005/0028291 , discloses an electrochemical means to generate the oxidising/reducing agents for the surface treatment of denim. The electrochemical generation of oxidizing or reducing agents is mandatory and this document teaches the unsuitability of redox methods for industrial processes. An electrochemical cell, however, suffers from the inherent disadvantage of the use of electrical energy and requires a markedly more complex apparatus.

[0006] The present invention seeks to address, at least in part, one or more of the abovementioned disadvantages.

[0007] Summary of the Invention

[0008] According to a first aspect of the present invention there is provided a method of reducing the colour intensity of a coloured textile substrate comprising agitating said coloured textile substrate with a composition comprising solid particles, a liquid medium and a compound which is 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof, wherein:

the method does not comprise electrochemically generating one or more oxidizing agent(s); the coloured textile substrate is clean; and the solid particles have a size of from 1 to 50mm.

[0009] Thus, it will be appreciated that, the method is not and does not comprise cleaning. Thus, it will be appreciated that the method is not a laundering process.

[0010] 2,2,6,6-tetramethylpiperidine-1-oxyl and derivatives thereof

Preferably 2,2,6,6-tetramethylpiperidin-1-oxyl (also known as TEMPO) or a derivative thereof is an oxidant, more especially an oxidant capable of oxidizing a colourant (e.g. a dye) to a less coloured material. 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) or a derivative may be consumed in the method according to the first aspect of the present invention. Alternatively, 2, 2,6,6- tetramethylpiperidin-1-oxyl or a derivative thereof can be regenerated intermittently or continuously by the presence of a co-oxidant.

[0011] 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof can be in the form of a radical, which more specifically, can be in the form of a nitroxide radical.

[0012] 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof may be in the form of an N- oxoammonium ion or salt.

[0013] Preferred derivatives of 2,2,6,6-tetramethylpiperidin-1-oxyl are those substituted in the 4-position. Preferred optional substituents include hydroxy, amido (especially acetamido and maleimido), carboxy, amino, ester (especially benzoate), oxo, nitro, halide, cyano, sulfone (especially Ci-4alkyl-sulfone), alkyl (especially Ci-e alkyl) and thiol.

[0014] Examples of 2,2,6, 6-tetramethylpiperidin-1-oxyl (TEMPO) or a derivative thereof include: 4-acetamido-TEMPO (CAS 14691-89-5), 4-amino-TEMPO (CAS 14691-88-4), 2- azaadamantane-N-oxyl (CAS 57625-08-8), 9-azabicyclo[3.3.1]nonane /V-oxyl (CAS 31785-68-9), 4-carboxy-TEM PO (CAS 37149-18-1), 4-hydroxy-TEMPO (CAS 2226-96-2) (TEMPOL), 4- hydroxy-TEMPO benzoate (CAS 3225-26-1), 4-maleimido-TEMPO (CAS 15178-63-9), 4- methoxy-TEMPO (CAS 95407-69-5), 1-methyl-2-azaadamantane-N-oxyl (CAS 872598-44-2) and 4-oxo-TEMPO (CAS 2896-70-0).

[0015] Preferred examples of 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof include: 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL) and 4-acetamido-2,2,6,6-tetramethylpiperidin-1-oxyl (Acetamido-TEMPO). Of these the preferred compounds are TEMPO and TEMPOL, more preferably TEMPOL. [0016] The chemical structures of TEMPO - Formula (1), TEMPOL - Formula (2) and Acetamido-TEMPO - Formula (3) are as follows (shown in their radical form):

Formula (3)

[0017] As mentioned above any of these chemical structures can also be in the form of the N- oxoammonium ion or salt.

[0018] Preferably, the amount of 2,2,6,6-tetramethylpiperidin-1-oxyl or derivative thereof used in the method is sufficient to provide a concentration thereof in the liquid medium at the start of the method of from about 0.01 mM to about 200 mM , preferably from about 0.1 mM to about 200 mM, more preferably from about 0.1 mM to about 100 mM, especially from about 0.1 mM to about 70mM and most especially from about 0.1 mM to about 50mM in the liquid medium. [0019] Coloured textile substrate

[0020] The coloured textile substrate is clean, that is to say that prior to the agitation of the composition the coloured textile substrate is clean. As described herein, the method of the present invention is not a laundry or cleaning method, and therefore it will be appreciated that the coloured textile substrate is not a soiled substrate. The substrate is not in need of cleaning. Thus, by“clean” it will be appreciated that the textile substrate is free or substantially free from at least dirt, sweat and stains.

[0021] Preferably, the textile substrate is or comprises a natural, a synthetic, or a semi synthetic fibre, or a mixture thereof.

[0022] Preferably, the textile substrate is or comprises cotton, polyester, or a mixture thereof.

[0023] Preferably, the textile substrate is or comprises a cellulosic fibre. Examples of suitable cellulosic fibres include hemp, linen, flax, jute, ramie, sisal and especially cotton.

[0024] Preferably, the textile substrate is or comprises denim.

[0025] In the present invention, reducing the colour intensity of the coloured textile preferably means lightening or whitening the shade of the coloured textile. The appearance, in essence, becomes more bleached, faded or aged.

[0026] Reducing the colour intensity preferably means reducing the chroma of the coloured textile, preferably as indicated by the chroma c* value from the L*, a*, b* CIE 1976 colourspace of the coloured textile. Here c* = (a* ² + b* ² ) ^1/2 .

[0027] Reducing colour can also optionally or additionally mean reducing the L* value.

[0028] Colour space measurements are preferably made by a spectrophotometer. A suitable apparatus is a Konica-Minolta CM-3600A spectrophotometer

[0029] The colourant present in the coloured textile substrate can be a pigment or dye, more preferably a dye, preferably wherein the dye is an azo compound, more preferably an indigo dye.

[0030] Denim may be dyed using an indigoid dye, or preferably with an indigo dye.

[0031] Before the method according to the first aspect of the present invention the textile is typically processed through a number of pre-conditioning steps. One optional step is known as scouring, wherein the surface wax of raw denim is removed. Another optional step is often termed desizing, this is generally an enzymatic process to remove the surface starch. A third optional step is abrasion, typically using cellulase to breakdown the cellulose fibres and expose the surface indigo in the denim for oxidation. Typically, prior to the method according to the first aspect of the present invention the scouring, desizing and abrasion steps are all performed and preferably in that order. [0032] Absorption

[0033] Optionally, the 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof is absorbed into or onto the solid particles. This absorption allows the 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof to be located at least partially inside or on the surface of a solid particle. Optionally, the 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof is located at least on the surface of a solid particle and preferably on the surface of a solid particle. TEMPO and TEMPOL, and more especially TEMPO tend to absorb readily into or onto solid particles.

[0034] Preferably, 2,2,6,6,-tetramethylpiperidin-1-oxyl or a derivative thereof is located on the surface of the solid particles and is attracted to the solid particles’ surfaces by means of H- bonding, dipole-dipole interaction, polar interaction, hydrophobic interactions, Van der Waals, London forces or a combination thereof

[0035] The absorption can be repeated multiple times. The absorption is suitably performed in the absence of the coloured textile substrate prior to the method according to the first aspect of the present invention.

[0036] The absorption of 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof is preferably performed by combining a liquid medium, the solid particles and the 2,2,6,6-tetramethylpiperidin- 1-oxyl or a derivative thereof. This combination is preferably mixed. In order of increasing preference, the mixing can be performed for at least 1 second, at least 5 seconds, at least 10 seconds, at least 15 seconds, at least 30 seconds, at least 40 seconds, at least 50 seconds, at least 60 seconds, at least 70 seconds, at least 80 seconds, at least 90 seconds, at least 100 seconds, at least 1 10 seconds or at least 120 seconds.

[0037] In order of increasing preference, the mixing can be performed for no more than 8 hours, no more than 1 hour, no more than 30 minutes, no more than 15 minutes, no more than 5 minutes, no more than 250 seconds, no more than 240 seconds, no more than 230 seconds, no more than 220 seconds, no more than 210 seconds or no more than 200 seconds.

[0038] Preferably, the 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof is not immobilised on the surfaces of the solid particles, for example the 2,2,6,6-tetramethylpiperidin-1- oxyl or a derivative thereof is not covalently bound to the surfaces of the solid particles.

[0039] Solid Particles

[0040] The solid particles can be or comprise a polymeric material, a non-polymeric material, or a combination thereof.

[0041] Preferably the solid particles are or comprise a polymeric material.

[0042] The polymeric material can be or comprise a poly(haloalkylene), a polyamide, a polyester, a polyalkylene, a polyurethane, or a copolymer or mixture thereof. [0043] Preferably, the polymeric material is or comprises a polyalkylene, more preferably a poly C2-4 alkylene and especially polypropylene. Solid particles which are or comprise polyalkylenes are especially reusable, cleanable and they can be readily used in multi-step variations of the present invention especially wherein desizing and/or abrasion has additionally been performed. A suitable poly(haloalkylene) is polytetrafluoroethylene (PTFE).

[0044] Preferably, the solid particles are hydrophobic.

[0045] 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.

[0046] By“hydrophobic”, it is preferably meant that the solid particles have a large contact angle with water.

[0047] In order of increasing preference, the polymeric material of the solid particles preferably has a contact angle of at least 50, at least 55, at least 60, at least 65, at least 70, at least 75, at least 80, at least 85, at least 90, at least 95 and at least 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. Pure water is preferably distilled 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. A planar sample of the polymeric material of the solid particle is preferably used for the measurement. The droplet is preferably backlit.

[0048] The solid particles preferably have a contact angle with water of from 50° to 1 10°, more preferably from 60° to 105°.

[0049] 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 1.0wt% and especially less than 0.5wt% of water, relative to the weight of the dry solid particles. One preferred method for establishing the water absorption is to contact the dry 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 10Ox (Ww - Wd) / Wd.

[0050] Polyalkylenes, as mentioned herein before are especially suitable hydrophobic polymers for the solid particles.

[0051] In alternative embodiments, the polymeric material can by hydrophilic. For example the polymeric material can be a polyamide. Especially suitable polyamides are nylon 6 and 6,6.

[0052] The polymeric material can optionally be oxidized or hydrolysed so as to increase the hydrophilicity of a hydrophilic polymeric material even further. This oxidation or hydrolysis tends to promote the absorption of 2,2,6, 6-tetramethylpiperidin-1-oxyl or a derivative thereof into or onto the solid particles. Especially good absorption is obtained when a polyamide is hydrolysed, more especially when hydrolysed with an acid. TEMPO and TEMPOL, and especially TEMPO, tend to absorb especially well.

[0053] Optionally, the non-polymeric material can be or comprise ceramics, metals and alloys (for example steel) and glass.

[0054] Whilst the solid particles can be foamed or porous, they are preferably substantially non-porous. Non-porous particles have been found to be more robust and long lived in the method according to the first aspect of the present invention.

[0055] 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 or being oxidized. More preferably, the solid particles have few or no functional groups which are capable of reacting with or being oxidized by 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof.

[0056] 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.

[0057] Preferably, the solid particles have a size of from 1 to 10 mm.

[0058] In increasing preference, the solid particles preferably have a size of at least 2mm, at least 3mm or at least 4mm.

[0059] 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 .

[0060] The size is preferably a mean average size more preferably an arithmetic mean average size. The average is preferably taken from at least 100, at least 1000 or at least 10,000 solid particles. [0061] The size is preferably the longest linear dimension of the particles. 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.

[0062] 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 1.1g/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 .

[0063] In order of increasing preference, the solid particles preferably have a density of no more than 10.0 g/cm ³ , no more than 8.0 g/cm ³ , no more than 6.0 g/cm ³ , no more than 4.0 g/cm ³ , no more than 3.0 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 .

[0064] The density of the solid particles can be from 0.5 to 4.0 g/cm ³ , from 1.0 to 3.0 g/cm ³ or from 1.1 to 3.0 g/cm ³ .

[0065] Especially, where the cleanability of the solid particles is desired to be particularly easy 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.

[0066] Cleanability, as used herein preferably means the ability to suitably remove from the solid particles any fragments and components derived from the coloured textile substrate after the solid particles have been used in 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.

[0067] 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 any optional additives.

[0068] In the case of solid particles which are or comprise a polymeric material, a filler can be incorporated into the solid particles. Thus, the solid particles may be or comprise a polymeric material and a filler, which is preferably an inorganic filler. The presence of a filler can have several advantages including any one or more of: i. increased effectiveness at reducing the colour intensity of the coloured textile, ii. increased ease of separating the solid particles from the substrate after the agitation and iii. an increased ability for the solid particles to absorb 2, 2,6,6- tetramethylpiperidin-1-oxyl or a derivative thereof.

[0069] Preferably, the solid particles comprise or consist essentially of or consist of a polymeric material and a filler in a weight ratio of 90:10 to 20:80 and more preferably 70:30 to 30:70 (polymeric material : filler). Where good cleanability is desired, the solid particles suitably comprise no less than 50:50, more preferably no less than 70:30 and especially no less than 90: 10 of polymeric material to a filler on a weight ratio basis.

[0070] The solid particles can comprise at least 5wt%, at least 10wt%, at least 20wt%, at least 30wt%, at least 35wt%, at least 40wt%, at least 45wt% or at least 50wt% of filler, which is preferably an inorganic filler. Optionally, the solid particles comprise at least 20wt% filler, particularly where faster and/or more efficient separation of the solid particles from the substrate is desired. The remainder of the solid particles required to make 100wt% is preferably said polymeric material.

[0071] The solid particles can comprise no more than 90wt%, no more than 80wt%, and no more than 70wt% of filler, which is preferably an inorganic filler. The remainder of the solid particles required to make 100wt% is preferably said polymeric material.

[0072] Optionally, the solid particles can comprise a polymeric material and up to 30wt% of a filler. Optionally, the solid particles comprise a polymeric material and no filler (and in particular no inorganic filler). The solid particles can consist of polymeric material.

[0073] The solid particles can have a shape which is ellipsoidal, spherical, cylindrical or cuboid and any shape therebetween.

[0074] Preferably, the solid particles have a shape which is ellipsoidal or spherical as these shapes tend to be kinder to the substrate and they tend to separate well from the substrate after performing the methods described herein.

[0075] 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 a mean average, especially an arithmetic mean average. Preferably the average is of at least 100, more preferably at least 1000 and especially at least 10,000 solid particles.

[0076] Preferably the solid particles do not in any way become permanently attached, affixed, integrated or associated with the textile substrate. To put this another way, the solid particles may be readily separated from the textile substrate at the end of the method according to the first aspect of the present invention. Preferably, the solid particles are separated from the substrate after the agitation step described herein.

[0077] It will be appreciated that the solid particles are of such a size that does not permit them to enter inside the textile substrate structure.

[0078] Preferably the amount of solid particles used is from 1 to 3000kg, preferably from 1 to 2000kg, more preferably from 10 kg to 100 kg, even more preferably from 10 kg to 50 kg. [0079] Preferably the weight ratio of the solid particles to dry substrate is from 10: 1 to 1 : 10, more preferably from 10: 1 to 1 : 1.

[0080] Preferably, the solid particles are re-usable, especially re-usable in further methods according to the first aspect of the present invention. Re-usable solid particles are preferably not soluble or dissolvable (i.e. they are insoluble) in the liquid medium, more especially in aqueous liquid media and most especially in pure water. Preferably, less than 1 % by weight, preferably less than 0.1 % by weight, of the solid particles dissolves in water at 25°C over a period of 24 hours when 1g of solid particles are mixed with 99g of pure water.

[0081] Liquid Medium

[0082] Preferably, the liquid medium is aqueous. To put this another way, the liquid medium preferably is or comprises water. Where water is used in conjunction with other liquids, these liquids may be organic liquids such as alcohols, esters, ethers, amides and the like.

[0083] 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.

[0084] Preferably, the liquid medium is or comprises softened water, especially water containing less than 100mg of calcium per litre, more preferably less than 50mg of calcium per litre, especially less than 20mg of calcium per litre and most especially less than 10mg of calcium per litre.

[0085] Preferably, the liquid medium is or comprises water which contains less than 100mg of dissolved salts per litre, more preferably less than 50mg of dissolved salts per litre, especially less than 20 mg of dissolved salt per litre, more especially less than 10 mg of dissolved salt per litre.

[0086] In order of increasing preference, the pH of the liquid medium is at least 1.0, at least 2.0, at least 3.0 and at least 4.0.

[0087] In order of increasing preference, the pH of the liquid medium is no more than 13.0, no more than 12.0, no more than 1 1.0, no more than 10.0, no more than 9.0, no more than 8.0, no more than 7.0 and no more than 6.5.

[0088] Preferably the pH is from 3.0 to 1 1.0, more preferably from 4.0 to 8.0, especially from pH 4.0 to 6.5. More preferably the pH does not exceed pH 6.5.

[0089] In order of increasing preference, the liquid medium has a temperature at least 0°C, at least 2°C, at least 5°C, at least 10°C, at least 15°C or at least 20°C. [0090] In order of increasing preference, the liquid medium has a temperature of no more than 100°C, no more than 90°C, no more than 80°C, no more than 70°C, no more than 60°C, no more than 50°C or no more than 40°C

[0091] Preferably, the liquid medium has a temperature of from 5 to 70°C, more preferably from 5 to 40°C.

[0092] The pH of the liquid medium can be adjusted to suit the chemistry of the co-oxidant utilised.

[0093] The abovementioned preferred pH values and temperatures are those whilst the composition is being agitated.

[0094] Preferably, the weight ratio of liquid medium to dry substrate is at least 1 :1 , more preferably at least 2:1 and especially at least 4:1. Preferably, the weight ratio of liquid medium to dry substrate is no more than 100: 1 , more preferably no more than 70: 1 and especially no more than 50:1.

[0095] Optional Desizing

[0096] Optionally, the coloured textile substrate can be desized. Preferably the desizing is performed prior to reducing the colour intensity described hereinabove.

[0097] Optionally, the method according to the first aspect of the present invention comprises:

(i) desizing the coloured textile substrate by agitating said coloured textile substrate with a composition comprising solid particles, a liquid medium and an amylase;

(ii) reducing the colour intensity of the coloured textile substrate comprising agitating said coloured textile with a composition comprising solid particles, a liquid medium and a compound which is 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof;

wherein:

step (ii) does not comprise electrochemically generating one or more oxidizing agents;

the coloured textile substrate is clean; and

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

[0098] Steps (i) and (ii) may be performed simultaneously but preferably steps (i) and (ii) are performed separately. Preferably, step (i) precedes step (ii).

[0099] Preferably, steps (i) and (ii) are performed in the order of step (i) followed by step (ii).

[00100] Typically, in desizing, the coloured textile substrate initially has starch size on its surface. The desizing step removes the starch size. [00101] Preferably, desizing is performed at a temperature of at least 0°C, more preferably at least 5°C, even more preferably at least 10°C, especially at least 15°C and most especially at least 20°C.

[00102] Preferably, desizing is performed at a temperature of no more than 60°C, more preferably no more than 50°C and especially no more than 40°C.

[00103] Preferably, desizing is performed at a temperature of from 5 to 60°C, more preferably from 20 to 40°C.

[00104] Preferably, desizing is performed in a liquid medium having a pH of from 4.0 to 8.0, more preferably from 6.0 to 7.0.

[00105] Preferably, the solid particles used in step (ii) are the same as the solid particles of step (i). Preferably, the solid particles used in step (ii) are the same solid particles used in step (i) and recovered therefrom. In other words, it is preferred that the same batch of solid particles used for step (i) are used in step (ii).

[00106] Surprisingly, it was found that a significant advantage to the method described herein is that the same solid particles can be used in both steps (i) and (ii) without necessarily cleaning the particles, or if cleaning the particles is utilised then this can be readily effected. This advantage is more pronounced when the solid particles are inert or hydrophobic, and most especially wherein the solid particles are or comprise a polyalkylene. This allows the method to be performed with little or no cleaning of the solid particles between steps (i) and (ii), which means that the overall method is more efficient, quicker and more economic.

[00107] The amylase is preferably Beisol T 2090, commercially available for instance from CHT Group. Alternatives include Aquazyme R L from Novozymes, PrimaGreen ALL from Dow DuPont, or Stainzyme Plus L from Novozymes.

[00108] Optional Abrasion

[00109] Optionally, the coloured textile substrate can be abraded. Preferably the abrasion is performed prior to reducing the colour intensity described hereinabove.

[00110] Optionally, the method according to the first aspect of the present invention comprises:

(i) abrading the coloured textile substrate by agitating a composition comprising solid particles, a liquid medium, the coloured textile substrate and a cellulase;

(ii) reducing the colour intensity of the coloured textile substrate comprising agitating said coloured textile substrate with a composition comprising solid particles, a liquid medium and the compound which is 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof; wherein: step (ii) does not comprise electrochemically generating one or more oxidizing agents;

the coloured textile substrate is clean; and

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

[00111] Steps (i) and (ii) may be performed simultaneously but preferably, steps (i) and (ii) are performed separately. Preferably, step (i) precedes step (ii).

[00112] Preferably, steps (i) and (ii) are performed in the order step (i) followed by step (ii).

[00113] Advantageously, abrasion serves to improve the ability of the 2, 2,6,6- tetramethylpiperidin-1-oxyl or a derivative thereof to reduce the colour intensity of the coloured textile substrate.

[00114] The temperatures and/or pH values for the abrasion step are preferably the same as those for desizing.

[00115] Preferably, the solid particles used in step (ii) are the same as the solid particles of step (i). Preferably, the solid particles used in step (ii) are the same solid particles used in step (i) and recovered therefrom. In other words, it is preferred that the same batch of solid particles used for step (i) are used in step (ii).

[00116] Surprisingly, it was found that a significant advantage to the method described herein is that the same solid particles can be used in both steps (i) and (ii) without necessarily cleaning the particles, or if cleaning the particles is utilised then this can be readily effected. This advantage is more pronounced when the solid particles are inert or hydrophobic and most especially wherein the solid particles are or comprise a polyalkylene. This allows the method to be performed with little or no cleaning of the solid particles between steps i) and ii) which means that the overall method is more efficient, quicker and economic.

[00117] A preferred cellulase is cellulase LT, especially cellulase LT 19500 L commercially available from Novozymes. Alternatives include Ecostone LT from AB Enzymes, IndiAge Super L Dow DuPont, Beizym cellulases from CHT Group, Denimax CORE S from Novozymes.

[00118] Optional Desizing and Abrasion

[00119] The step of reducing the colour intensity described hereinabove can be preceded by desizing and abrasion.

[00120] Thus, the method according to the first aspect of the present invention optionally comprises:

(i) desizing the coloured textile substrate by agitating the coloured textile substrate with a composition comprising solid particles, a liquid medium and an amylase; (ii) abrading the coloured textile substrate by agitating the coloured textile substrate with a composition comprising solid particles, a liquid medium and a cellulase; and

(iii) reducing the colour intensity of the coloured textile substrate comprising agitating the coloured textile substrate with a composition comprising solid particles, a liquid medium and a compound which is 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof; wherein:

step (iii) does not comprise electrochemically generating one or more oxidizing agents;

the coloured textile substrate is clean; and

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

[00121] Steps (i) and (ii) may be performed separately or simultaneously. Preferably, step (i) precedes step (ii). Preferably, the order of the steps is (i), (ii) and then (iii), or (i) and (ii) together/simultaneously followed by (iii). In some instances, steps (i), (ii) and (iii) are performed simultaneously. Alternatively, steps (ii) and (iii) can be performed simultaneously optionally with step (i) being performed separately, preferably before steps (ii) and (iii) are performed. In a less preferred embodiment, steps (i) and (iii) can be performed simultaneously with step (ii) being performed separately, preferably before steps (i) and (iii) are performed.

[00122] Preferably, steps (i) and (ii) are performed without any rinsing of the coloured textile substrate during or between these steps. Preferably there is no rinsing of the coloured textile during or between steps (i), (ii) and (iii). Rinsing, if present is preferably employed on or after the completion of step iii).

[00123] Preferably, during or between steps (i) and (ii) no further liquid medium is added other than that present initially.

[00124] Preferably, steps (i), (ii) and optionally (iii) are performed in the same apparatus.

[00125] Preferably the coloured textile substrate is not isolated from the liquid medium until after the completion of step (ii), more preferably until after the completion of step (iii).

[00126] Preferably, the solid particles used in steps (i), (ii) and (iii) are the same solid particles, in the same way as described above. Thus, it is preferred that the same batch of solid particles used in step (i) is used in step (ii) and used in step (iii).

[00127] Re-use of the solid particles

[00128] Preferably the solid particles are re-used, more preferably they are re-used in further methods according to the first aspect of the present invention.

[00129] Preferably, the method according to the first aspect of the present invention is_a method for reducing the colour intensity of a coloured textile substrate comprising the steps: (a) agitating the coloured textile substrate with a composition comprising solid particles, a liquid medium and a compound which is 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof, wherein:

step (a) does not comprise electrochemically generating one or more oxidizing agents;

the coloured textile substrate is clean; and

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

(b) after the agitation in step (a) the solid particles are separated from the substrate;

(c) the solid particles are optionally cleaned;

(d) the solid particles are agitated with a liquid medium, a coloured textile substrate and_a compound which is 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof.

[00130] In step (d) the coloured textile substrate is preferably not the same substrate as that used in step (a) Preferably, step (d) does not comprise electrochemically generating one or more oxidizing agents. Preferably, in step (d) the coloured textile substrate is clean. Preferably no part of the method electrochemically generates one or more oxidizing agents.

[00131] In order of increasing preference, the solid particles are re-used at least 1 time, at least 3 times, at least 5 times, at least 10 times, at least 50 times, at least 100 times, at least 250 times, at least 500 times, at least 1 ,000 times and at least 2,000 times.

[00132] Agitating

[00133] Agitation in the method according to the first aspect of the present invention can be performed by stirring, rotating, shaking, vibrating and sonicating the composition. Agitation is preferably performed by rotating, especially by rotating a treatment chamber in which is contained the coloured textile substrate and said composition.

[00134] Apparatus

[00135] Preferably, the agitation is performed in a treatment chamber.

[00136] Preferably, the treatment chamber is a cylinder, more preferably a rotatable cylinder.

[00137] Preferably, the composition comprising the solid particles, the liquid medium and the compound which is 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof is present in the treatment chamber.

[00138] Preferably, the agitation is performed by rotating a cylindrical treatment chamber such that the centrifugal G force experienced at the inner walls of the chamber is from 0.05 to 2G, more preferably from 0.05 to 1 G and especially from 0.1 to 0.9G. [00139] Apparatus suitable for performing the method according to the first aspect of the present invention preferably include those described in PCT patent publications: WO2011/098815, WO2014/147389, WO2015/049544 and WO2016/193703.

[00140] Preferably, the agitation is performed within an apparatus comprising a treatment chamber (especially a rotatable cylinder) and optionally a particle storage tank

[00141] Preferably, the apparatus for performing the method is capable of automatically separating the solid particles from the substrate after the agitation. This can be achieved by holes in the treatment chamber which are larger than the solid particles but smaller than the substrate.

[00142] Optionally, agitation is performed by means of an apparatus which comprises one or more nozzles which are configured so as to direct a liquid medium which can impinge upon the composition and coloured textile substrate.

[00143] Optionally, the apparatus may comprise a pump. The pump is preferably configured so as to be able to transfer liquid medium and solid particles from the particle storage tank to the treatment chamber. Preferably, the pump is activated during at least some, more preferably all of the method such that solid particles and liquid medium are recirculated over the coloured textile substrate.

[00144] Premixing

[00145] Preferably, the 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof is premixed with the solid particles. Premixing is preferably performed in the absence of the coloured textile substrate. Premixing is preferably performed in a liquid medium. This premixing allows for the 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof to be absorbed onto or into the solid particles (as mentioned above).

[00146] The product of the premixing step can then be transferred from the particle storage tank to the treatment chamber. The coloured textile substrate, and optionally further liquid medium, can then be added to the treatment chamber.

[00147] In order of increasing preference, premixing is performed for at least 1 second, at least 5 seconds, at least 10 seconds, at least 20 seconds and at least 30 seconds. In order of increasing preference, premixing is performed for no more than 1 hour, no more than 30 minutes, no more than 20 minutes, no more than 10 minutes and no more than 5 minutes.

[00148] Premixing can be performed by stirring, vibration, rotation, sonication or more preferably by pumping the liquid medium in the premixture comprising the liquid medium, the solid particles and the 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof.

[00149] Premixing can be performed before, during or after the agitation. It is desirable to perform at least some, more preferably all, of the premixing whilst also agitating. In this way, the solid particles are premixed with 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof and are ready for the next re-use of the solid particles in a speedy fashion.

[00150] Preferably, the concentration of 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof used in a premixing step is from about 0.1 mM to about 200 mM, preferably from about 1 mM to about 200 mM, more preferably from about 1 mM to about 100 mM, especially from about 1 mM to about 70mM and most especially from about 1 mM to about 50mM in the liquid medium.

[00151] In order of increasing preference, premixing is performed at a temperature of at least 5°C, at least 10°C, at least 20°C, at least 30°C and at least 40°C. In order of increasing preference, the premixing is performed at a temperature of no more than 80°C, no more than 70°C and no more than 60°C.

[00152] Preferably, premixing is performed at a temperature of from 40 °C to 60 °C.

[00153] Whilst this premixing can be performed in a treatment chamber suitable for contacting the solid particles with the coloured textile substrate, it is more preferably performed in a particle storage tank.

[00154] Regeneration of 2,2,6,6-tetramethylpiperidine-1-oxyl or a derivative thereof

[00155] In the absence of special measures, the 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof is deactivated in the method of the first aspect of the present invention. Accordingly, it is possible to add fresh 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof as required.

[00156] More preferably, however, the 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof is regenerated chemically, more especially by the addition of a co-oxidant. Regeneration is preferably performed at least once.

[00157] Preferably, the composition comprising solid particles, a liquid medium and a compound which is 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof described hereinabove in respect of the first aspect of the invention comprises a co-oxidant. The co-oxidant can be added to the composition before, during or after the agitation. The co-oxidant can be added to solid particles and the 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof in the presence, or more preferably in the absence, of the coloured textile substrate.

[00158] The co-oxidant can be or comprise an enzyme. Preferably, the enzyme is a phenol- oxidising enzyme. Preferred phenol-oxidising enzymes can be selected from tyrosinase, peroxidase and laccase (CAS 80498-15-3, enzyme classification 420-150-4), and more preferably the phenol-oxidizing enzyme is a laccase. The laccase is preferably obtained from the organism Cerrena unicolor. [00159] Preferably the amount of co-oxidant enzyme (preferably laccase) is of from 10 g to 300 g of enzyme for each 50kg of solid particles.

[00160] Preferably the amount of co-oxidant enzyme is at least 10 g, more preferably at least 25 g, and especially at least 100 g of enzyme for each 50kg of solid particles.

[00161] Preferably, the enzyme contains a metal, more preferably a transition metal and most preferably copper.

[00162] The co-oxidant can be or comprise a hypohalite.

[00163] The hypohalites are preferably used in stoichiometric amounts to regenerate 2, 2,6,6- tetramethylpiperidin-1-oxyl or a derivative thereof.

[00164] Preferred hypohalites include hypoiodite (IO ), hypofluorite (FO ), more preferably hypobromite (BrO ) and especially hypochlorite (CIO ).

[00165] In some preferred embodiments, the co-oxidant can be or comprise a peroxide.

[00166] Examples of peroxides include organic peroxides, organic peroxy acids, hydrogen peroxide, percarbonates and perborates.

[00167] The co-oxidant may also be violuric acid.

[00168] Preferably, the 2,2,6,6-tetramethylpiperidine-1-oxyl or a derivative thereof is

regenerated in the absence of the coloured textile substrate.

[00169] Optionally, the 2,2,6,6-tetramethylpiperidine-1-oxyl or a derivative thereof is

regenerated outside a treatment chamber such as that described hereinabove, for example in a particle storage tank. Thus, the co-oxidant is suitably added to the 2,2,6,6-tetramethylpiperidin- 1-oxyl or a derivative thereof in a particle storage tank.

[00170] Preferably, the co-oxidant is added to the 2,2,6,6-tetramethylpiperidin-1-oxyl or a derivative thereof is done in the presence of a liquid medium, more preferably in the presence of the solid particles.

[00171] Regeneration can be done whilst premixing as described above.

[00172] The regeneration may be performed for the same duration and under the same conditions as agitation.

[00173] The regeneration may be performed for the same duration and under the same conditions as premixing.

[00174] Regeneration may be effected during both the premixing and agitation steps.

[00175] Textiles resulting from the method [00176] There is also provided a textile substrate obtained or obtainable by the method according to the first aspect of the present invention.

[00177] It was surprisingly found that textiles prepared by the method according to the first aspect of the present invention have good or improved reduction in colour intensity whilst maintaining the mechanical strength of the textile. It will be appreciated that many denim bleaching processes can obtain colour reduction but often at the undesirable expense of mechanical properties. The textiles prepared by the method of the invention also exhibit reduced back-staining (as a result of less re-deposition of the dye onto the textile during the colour reduction process). Preferably, the textiles prepared by the method also exhibit good softness.

[00178] The invention is further illustrated by reference to the following examples. The examples are not intended to limit the scope of the invention as described above.

[00179] EXAMPLES

[00180] Materials

[00181] Solid Particles

[00182] Solid particles comprising polypropylene (PP) (38wt%) and barium sulfate filler (62wt%) having a density of 1.63 g/cm ³ and diameter of 3.75 to 4.5 mm were prepared by hot melt extrusion.

[00183] Denim

[00184] Two types of denim samples were used in the Examples, namely, Swissatest (E-277) swatch available from Swissatest Testmaterialien AG and Thai FK denim jeans (supplied by ThaiMid, Thailand).

[00185] Enzymes

(i) Desizing enzyme: Amylase, Beisol T 2090, which was obtained from CHT Group.

(ii) Abrasion enzyme: Cellulase LT 19500 L, which was obtained from Novozymes.

(iii) Co-oxidant enzyme: Laccase (CAS 80498-15-3), Nearbleach Eco LT, which was obtained from Nearchimica S.p.A. This was used as a laccase powder mixture comprising 0.5-1wt% laccase and 10-12.5wt% adipic acid.

(iv) Oxidant enzyme: Peroxidase, Denilite Cold, which was obtained from Novozymes. This was used as a peroxidase mixture comprising of 5wt% peroxidase, 5-10 wt% violuric acid, and 30 to 50wt% sodium percarbonate in water.

[00186] Apparatus

[00187] The apparatus used was similar to that described in WO 201 1/098815. The apparatus comprised a treatment chamber in the form of a rotatable cylinder and a particle storage tank. The apparatus also comprised a pump to transfer the solid particles from the particle storage tank to the treatment chamber and an electric motor to rotate the treatment chamber. The apparatus had a nominal load capacity of 25Kg of dry coloured textile substrate.

[00188] Simultaneous Desizing and Abrasion

[00189] The following components were loaded into the particle storage tank of the apparatus as described directly above: 50 kg of the PP solid particles, 52 litres of softened buffered water (Calcium < 5 ppm), 1 % on weight of fibre (owf) of Amylase and 0.3% (owf) Cellulase. This formed a mixture in the particle storage tank. The softened buffered water was buffered using 14 mM sodium citrate and citric acid to achieve and maintain a pH of from 6 to 7. The water was heated to and maintained at a temperature of 40°C throughout the simultaneous desizing / abrasion steps.

[00190] Ballast comprising 96 g of denim swatches and 10 kg of denim jeans was loaded into the treatment chamber of the same apparatus. The mixture was then pumped into the treatment chamber so as to form the composition as defined in the first aspect of the present invention within the treatment chamber. The solid particles and the liquid medium were continuously recirculated between the treatment chamber and the particle storage tank during the desizing / abrasion steps. The agitation was continued for a period of 30 minutes. Agitation was effected by rotating the treatment chamber.

[00191] After agitating the composition, the liquid medium and any chemicals therein were extracted by means of a high spin speed extraction.

[00192] Following the extraction, a wash-off step was performed using 45 litres of hot water containing a non-ionic detergent, and a 10 minutes separation cycle was performed to remove the PP solid particles from the denim swatches/jeans. In the separation cycle the PP solid particles fall through holes in the rotatable cylinder into the particle storage tank and they are not recirculated to the rotatable cylinder.

[00193] The desized and abraded denim swatches and jeans were then unloaded from the apparatus and dried in a conventional clothes drier at temperature of from 50 °C to 80 °C.

[00194] Measurement method

[00195] The reduction in the colour intensity of the denim swatches and jeans were measured by the L* (lightness, CIE 1976 colour space) value using a Konica Minolta CM-3600A spectrophotometer.

[00196] Example 1

[00197] In Example 1 TEMPOL was used to reduce the colour intensity of Indigo coloured denim.

[00198] 1.1 Pre mixing [00199] In a 25 kg load capacity apparatus as described above, 52g of TEMPOL and 150 g of the laccase mixture were mixed with 50 kg of the PP solid particles in 51 litres of softened water (calcium < 5 ppm) within the particle storage tank.

[00200] The premixing was effected by means of a pump which circulated the resulting premixture from the front of the particle storage tank to the back of the particle storage tank for a period of 1 minute. Premixing was performed at a temperature of about 20°C.

[00201] 12 Agitating a composition

[00202] 7.5 kg of polyester ballast sheets and 2.5 kg of the desized and abraded denim jeans and 24 g of the Swissatest swatches as prepared above, were loaded into the rotatable cylinder of same the apparatus to which the premix was added in 1.1. The premixture was pumped from the particle storage tank into the rotatable cylinder and so the contents of the rotatable cylinder then contained all of the components of the composition as described in the first aspect of the present invention.

[00203] The water was buffered to a pH of from 6.3 to 6.6 using 14 mM sodium citrate and citric acid.

[00204] The composition was heated to and maintained at a temperature of 40°C.

[00205] The composition was agitated by rotating the rotatable cylinder for a period of 30 minutes.

[00206] After agitating the composition, the liquid medium was extracted by means of a high spin speed extraction.

[00207] Following the extraction, a wash-off step was performed using two lots of 30 litres of cold water, and a 10 minutes separation cycle was performed to remove the PP solid particles from the denim swatches/jeans. In the separation cycle the PP solid particles fall through holes in the rotatable cylinder into the particle storage tank.

[00208] The treated denim swatches and jeans were then dried in a conventional clothes drier at temperature ranges of from 50 °C to 80 °C.

[00209] Comparative Example 1 - No Solid Particles

[00210] Comparative Example 1 was performed exactly as described in Example 1 except that no solid particles were used.

[00211] Comparative Example 2 - Peroxidase/violuric acid/sodium percarbonate mixture

[00212] Comparative Example 2 was performed exactly as described in Example 1 except that the TEMPOL and laccase were replaced with 15 g of the peroxidase mixture. [00213] Comparative Example 2a - Peroxidase/violuric acid/sodium percarbonate mixture and no solid particles.

[00214] Comparative Example 2a was performed exactly as described in Comparative Example 2, except that, no PP solid particles were used.

[00215] Back-staining

[00216] Prior to and following treatment of the substrates the colour intensity (L*) of the front, back, warp and weft fibres of the treated Swissatest denim and the Thai FK denim jeans was measured using the same measurement technique as described above.

[00217] Results

[00218] Table 1 shows the results of the L* value measured on denim samples;

[00219] Table 1 : L* values for the denim samples

[00220] In Table 1 a larger L* value corresponds to a lighter colour and so to a more successful reduction in colour intensity (oxidising/bleaching). The desized and abraded L* values were measured after drying the denim from the desizing and abrasion steps described above. The desized and abraded L* values represent the starting point. Table 1 shows that the method according to the first aspect of the present invention was very effective in reducing the colour intensity of indigo coloured denim. Thus, the experiments demonstrate that the colour-reducing effect of the TEMPOL and laccase mixture was surprisingly enhanced when combined with the solid particles. The experiments further demonstrate that the present invention was more effective than the peroxidase/violuric acid/sodium percarbonate mixture. [00221] Table 2: Back-staining L* values for the denim samples

[00222] In Table 2 a larger L* corresponds to a lighter colour of the white weft fibres (reverse side of the denim treated substrates) indicating that there has been a reduction in the back-staining during treatment and thus less re-deposition of the indigo dye onto the substrate. The results show that the undesirable back-staining effect was reduced when the TEMPOL and laccase mixture was combined with the solid particles. The results also show that the combination of solid particles and TEMPOL/laccase mixture was superior to the violuric acid/peroxidase/sodium percarbonate combination.