FIELD

[0001] This application relates to a process for improving the color retention of textile materials, particularly to increase the crockfastness and/or the washfastness of the materials.

BACKGROUND

[0002] Crocking is a transfer of color from the surface of a colored fabric to an adjacent area of the same fabric or to another surface principally by rubbing action. Crockfastness is color fastness to rubbing (crocking). The improvement of crockfastness/colorfastness of dyed and printed textile fabrics has been an ongoing problem in the textile industry. Attempts to resolve the problem have entailed additives during the dyeing or printing process as well as post treatments. Washfastness is the ability of textile fabrics to retain the dyes and/or pigments used to color them when the fabrics are subjecting to washing.

[0003] For example, U.S. Patent No. 5,464,452 discloses a process for fixing a dye to a dyed fine-dimensional yarn fabric made from the group consisting of a polyamide-containing substrate, segmented polyester-polyurethane substrate, and combinations thereof, comprising contacting said fabric with an aqueous solution comprising a dye-fixative composition substantially free of phenol and formaldehyde residues, said dye-fixative composition being selected from the group consisting of (a) polymethacrylic acid, and (b) a copolymer of methacrylic acid and an ethylenically unsaturated comonomer selected from the group consisting of 2-acrylamido-2-methyl-propanesulfonic acid, sodium vinyl sulfonate, sodium styrene sulfonate, lower alkyl acrylates, and combinations thereof, said contacting step being for a time sufficient so that said dye-fixative composition is absorbed by said fabric.

[0004] In addition, U.S. Patent No. 5,525,125 discloses a process for fixing a dye to a dyed fine-dimensional yarn fabric made from the group consisting of a polyamide-containing substrate, segmented polyester-polyurethane substrate, and combinations thereof, comprising contacting said fabric with an aqueous solution comprising a dye-fixative composition substantially free of phenol and formaldehyde residues, said dye-fixative composition comprising a copolymer of: a) 1.0 to about 20 percent by weight of vinyl sulfonic acid residues; b) 5 to 20 percent by weight of nonpolar or hydrophobic (meth)acrylic monomer residues; and c) 60 to about 94 percent by weight of hydrophilic ethylenically unsaturated carboxylic acid residues, the copolymers having a weight average molecular weight of from about 1,500 to about 15,000, said contacting step being for a time sufficient so that said dye-fixative composition is absorbed by said fabric.

[0005] In U.S. Patent Application Publication No. 2013-0219635, we have described a method of dyeing and finishing cotton fibers, in which the fibers are initially treated with an emulsion copolymer and the copolymer is cured to chemically anchor the emulsion copolymer to the cotton. The copolymer-treated cotton fibers are then contacted with a dye material to affix at least a portion of the dye material to the copolymer component of the copolymer-treated cotton fibers. The dyed cotton fibers are subsequently treated with a surfactant- stabilized aqueous acrylic polymer dispersion, which partially removes the dye from the emulsion coated fibers to give the fibers a worn or vintage character. The acrylic polymer dispersion is then removed from the fibers, such as by rinsing.

[0006] According to the present invention, it has now been found that the crockfastness of colored textile materials can be improved by applying to the colored materials a coating of an aqueous dispersion of a specific (meth)acrylate ester polymer and drying the coating. In addition, it is found that the washfastness of the materials is also generally increased. Moreover, provided the weight of the dried coating is no more than 2 wt % of the material, the feel or "hand" of the material is substantially unchanged.

SUMMARY

[0007] In one aspect, the invention resides in a process for increasing the crockfastness and/or the washfastness of a textile material which has been colored by the application of a dye and/or pigment, the process comprising:

(a) depositing on the colored textile material an aqueous polymeric dispersion produced from a monomer composition comprising one or more alkyl acrylate or alkyl methacrylate monomers wherein the alkyl group has from 1 to 12 carbon atoms; and (b) drying the deposit to produce a color-retention composition on the colored textile material in an amount sufficient to improve crockfastness and/or the washfastness of the colored textile material.

[0008] In one embodiment, the monomer composition comprises one or more alkyl acrylate or alkyl methacrylate monomers selected from butyl acrylate, methyl methacrylate, ethyl acrylate and mixtures thereof. Generally, the monomer composition further comprises up to 20 % by weight, such as from 5 to 10 % by weight, for example from 6 to 12 , of acrylonitrile based on the total weight of monomers in said monomer composition.

[0009] Conveniently, the aqueous polymer dispersion is deposited on the colored textile material by spraying.

[0010] Generally, the aqueous polymer dispersion has a solids content of less than 20 wt .

[0011] Typically, the drying (b) is conducted at a temperature of 80 to 150 °C, such as 80 to 110 °C.

[0012] Generally, wherein the color retention composition produced in (b) is present in amount no more than 2 wt , such as from 0.5 to 2 wt , for example from 0.75 to 1.5 wt , of the colored textile material.

[0013] In one embodiment, the treated textile material produced in (b) has a wet crockfastness as determined according to AATCC Test Method 8 at least 2 points higher than that of the colored textile material prior to the depositing (a). AATCC is an abbreviation for American Association of Textile Chemists and Colorists and AATCC Test Method 8 is described as follows:

• AATCC Test Method 8 - Colorfastness to Crocking: Crockmeter Method - developed in 1936, partly equivalent to ISO 105-X12. Crocking is defined as a transfer of colorant from the surface of a colored yarn or fabric to another surface or to an adjacent area of the same fabric primarily by rubbing.

[0014] In a further aspect, the invention resides in a textile material which has been colored by the application of a dye and/or pigment and which has a wet crockfastness as determined according to AATCC Test Method 8 of at least 4, wherein the colored textile material has a color retention composition deposited on the surface of the material and formed of a dried aqueous polymeric dispersion produced by emulsion polymerization of a monomer composition comprising one or more alkyl acrylate or alkyl methacrylate monomers wherein the alkyl group has from 1 to 12 carbon atoms.

[0015] In yet a further aspect, the invention resides in a textile material which contains at least 25 wt cotton and which has been colored by the application of a dye and/or pigment to a K/S level of at least 20, wherein the colored textile material has a wet crockfastness as determined according to AATCC Test Method 8 of at least 4.

DETAILED DESCRIPTION

[0016] The crockfastness of a textile material which has been colored with a dye and/or a pigment is improved by an after-treatment process in which an aqueous polymeric dispersion produced from a monomer composition comprising one or more alkyl acrylate or alkyl methacrylate monomers, wherein the alkyl group has from 1 to 12 carbon atoms, is deposited on the colored textile material and the polymeric dispersion is then dried. The process is also generally found to improve the washfastness of the material. Moreover, by limiting the amount of the polymeric dispersion that is deposited on the textile material, it is possible to produce an after-treated product which has an improved crockfastness, but similar feel or hand, as compared with the original colored material.

[0017] Any textile material can be employed in the present process including fibers, before and after spinning into yarn, fabrics and garments. The textile material can be formed of natural fibers, such as cotton, silk, linen, wool, angora and mohair, or of synthetic fibers, such as polyester fibers, aramid fibers, polyamide (nylon) fibers, acrylic (acrylonitrile) fibers, spandexes, rayons, Tencel and cellulose acetate fibers. Combinations of natural and synthetic fibers can also be used. The color retention of materials containing significant amounts of cotton (at least 25 wt , such as at least 50 wt , even up to 100 wt%) is particularly improved by the present process.

[0018] Any dye or pigment conventionally used to color textile materials can be used in the present process and can be applied by both batch and continuous processes. In this respect, the term "dye" is used in its commonly accepted sense to mean a colorant which either is itself a liquid or is soluble in its vehicle (resulting in a solution), while the term "pigment" refers to colorants which are insoluble in the vehicle (resulting in a suspension). In addition, dyed goods have a wide variety of dye classes that each use different dye-fiber fixation methods; such as Van der Waal forces, covalent bonding, ionic bonds, physical entrapment; whereas in a pigment dyed garment attachment of the pigment to the garment is by physical entrapment.

[0019] In either case, the colorant can be applied to the entire textile material, for example by spraying or immersion in a bath, or to selected parts of the material, for example by printing. Suitable dye materials include disperse, reactive, direct, sulfur, vat, indigo and mordant dyes, whereas suitable pigments include minerals, such as titanium dioxide, biological materials and synthetic materials, such as azo and diazo compounds. Combinations of dyes and pigments, such as a dyed background and a pattern formed of a pigment printed on the colored background, can also be employed.

[0020] The dye or pigment can be applied directly to the textile material or through the intermediary of a surface bonding layer. In one embodiment, as disclosed in US Published Patent Application No. 2012-0246842, the entire contents of which are incorporated herein by reference, the bonding layer is a dried and cross-linked emulsion copolymer selected from vinyl ester-based, acrylic -based, styrene/acrylic-based and styrene/butadiene-based emulsion copolymers.

[0021] After application of the dye or pigment to the textile material, the colored textile material is subjected to an after-treatment process to enhance the color retention or crockfastness of the material. The after-treatment process involves initially applying a specific aqueous polymeric dispersion to the colored textile material so produce a deposit of the dispersion on at least the surface of the textile material. The treated material is then heated to remove water from the surface deposit of the polymeric dispersion and produce a polymeric color retention layer on the surface of the colored textile material. The color retention composition is preferably homogeneously dispersed over the surface of the colored textile material but is not necessarily sufficient to produce a continuous coating over the surface.

[0022] The aqueous polymeric dispersion employed in the after-treatment process is produced, generally by emulsion polymerization, from a monomer composition comprising one or more alkyl acrylate or methacrylate monomers monomers wherein the alkyl group has from 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms. Suitable include alkyl acrylates and alkyl methacrylates include butyl acrylate, methyl methacrylate, ethyl acrylate and mixtures thereof. In addition to the alkyl (meth)acrylates, which generally comprises at least 80 weight , or even at least 85 weight % of the total monomers, the monomer composition may comprise up to 20 % by weight, such as from 5 to 10 % by weight, for example from 6 to 12 , of non-acrylic monomers such as styrene and substituted styrenes, acrylonitrile, vinylchloride, and generally any compatible monomer the homopolymer of which has a Tg above 50° C.

[0023] In addition to the main monomers described above, the monomer composition can comprise from 0.1 wt to 10 wt , based on total monomers in the copolymer, of one or more ethylenically unsaturated cross-linking co-monomers having, for example, at least one amide, epoxy, or alkoxysilane group. Examples of such suitable self cross-linking co-monomers include N-methylol (meth)acrylamide and esters therof, N-vinylpyrrolidinone, dimethylaminoethyl acrylate, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, vinyl glycidyl ether, acryloxy-propyltri(alkoxy)silanes, methacryloxypropyltri(alkoxy)silanes, vinyltrialkoxysilanes, vinylmethyldialkoxysilanes and combinations of these cross -linkable co-monomers.

[0024] Suitable aqueous polymeric dispersions for use in the present after-treatment process can frequently be selected from commercially available acrylic emulsions. Alternatively, suitable polymeric dispersions can be prepared in conventional manner using known free-radical emulsion polymerization techniques and raw materials. In general, such emulsion copolymers can be prepared by polymerizing appropriate co-monomers in appropriate amounts in an aqueous reaction mixture using conventional polymerization initiators and catalysts and conventional polymerization conditions. The polymer dispersions so prepared can be stabilized with suitable emulsifiers (surfactants) and/or protective colloids. Prior to use in the present process, the polymeric dispersions are normally diluted with water to a polymeric solids content of less than 20 wt , such as from about 2.0 wt to about 10 wt , more preferably from about 3 wt to about 6 wt . Generally, the pH of the aqueous polymeric dispersions used in the present after- treatment process are adjusted to a value from about 3 to about 7, more preferably from about 5 to about 7.

[0025] The aqueous polymeric dispersion can be applied to the colored textile material by any known method of applying liquids, such as dyes, to textiles. For example, the dispersion can be applied by exhaustion processing; that is, batchwise, with the textile material being immersed in a dilute aqueous treatment bath containing the polymeric dispersion. In another embodiment, textile materials can be treated on a continuous apparatus for immersion treating textiles, as is disclosed, for example, in U.S. Patent No. 4,920,621, the entire disclosure of which is incorporated herein by reference. An alternative application method, particularly suitable for woven and knit textile fabrics, is continuous padding. It is also possible to apply the polymeric dispersion to a textile yarn for example in a continuous slasher type machine to allow, for example, the production of a crockfast denim fabric with the warp yarn, but not the weft yarn, having a polymeric color retention layer as described herein. A preferred method of applying the polymeric dispersion is by spraying since this allows a limited and controlled amount of polymeric dispersion to be applied to surface of the textile material.

[0026] After treatment of the colored textile material with the aqueous polymeric dispersion, the treated material is heated to remove water from the polymeric dispersion deposited on the material. Generally, the heating is conducted at a temperature from 80 to 150 °C, such as 80 to 110 °C, for example 85 to 100 °C. While such a heating step may be insufficient to effect substantial curing or cross-linking of the polymeric material, it is believed that, where present, the cross-linking co-monomer results in the molecular weight of the polymer deposit increasing during the drying step.

[0027] After the drying step, a polymeric color retention composition remains on the surface of the colored textile material. Typically, the color retention composition is present in amount no more than 2 wt , such as from 0.5 to 2 wt , for example from 0.75 to 1.5 wt , of the colored textile material. By maintaining the amount of the color retention composition within this narrow range it is found that the crockfastness of the material is enhanced, while the feel or hand of the material remains substantially unaffected. Using AATCC Test Method 8 to determine crockfastness, it is found that the present after-treatment process typically produces an increase in the wet crockfastness of a colored textile material by at least 2 points. In addition, treated colored textile materials can be produced with a wet crockfastness of at least 4, again as determined according to AATCC Test Method 8. In general, the washfastness of the material is also improved. Washfastness is conveniently measured by AATCC Test Method 61 (IIA).

[0028] In one embodiment, where the textile material contains at least 25 wt , such as at least 50 wt , for example at least 60 wt of cotton fibers, and is treated with colorant to produce a K/S value of at least 20 (where K is the adsorption and S is the scattering of incident light on the colored material at a particular wavelength and the K/S value is determined from the % reflectance according to the Kubelka-Monk equation), then the after-treatment process described herein is found to produce colored textile materials with uniquely high wet crockfastness values of 4 and above, again as determined according to AATCC Test Method 8. Such results are obtained even with indigo dyed denim fabric.

[0029] The invention will now be more particularly described with reference to the following non-limiting Examples, in which all parts are by weight unless otherwise indicated.

[0030] In the Examples, a commercially available aqueous acrylic dispersion is employed. The dispersion is produced by emulsion polymerization of monomer composition comprising 91.5 parts of ethyl acrylate, 8.5 parts of acrylonitrile and 3 parts of N-methylolacrylamide (NMA). The dispersion is stabilized with 1.8 parts of a non-ionic surfactant and 1.1 parts of an anionic surfactant. The as-supplied dispersion has a solids content of 45-55 % by weight and is diluted with water to a solids content of 1-1.5 % by weight before being used in the Examples.

Example 1

[0031] The diluted acrylic dispersion described above is sprayed directly onto a dyed garment and the garment is then dried at 90 °C for 30-40 seconds to produce a treated garment, in which the add-on level of the acrylic polymer is between 0.75% and 1.5% by weight of the garment. The resultant treated garment is found to exhibit a wet crockfastness as determined according to AATCC Test Method 8 of 3 points higher than the untreated material.

Example 2

[0032] The diluted acrylic dispersion described above is continuously padded onto a dyed woven or knit fabric and the fabric is then dried at 90 °C for 30-40 seconds to produce a treated fabric, in which the add-on level of the acrylic polymer is between 0.75% and 1.5% by weight of the fabric.