Methods for improving fibrillation or pill resistance of fabrics and fabrics with improved properties

FIELD OF THE INVENTION

[0002] This invention relates to methods for providing fabrics, particularly fabrics containing natural fibers such as cotton, rayon and the like, with improved fibrillation resistance and/or improved pill resistance, and, in further embodiments, in combination with good durable press properties and/or shrinkage resistance. This invention also relates to fabrics which have improved fibrillation resistance and/or improved pill resistance, and, in further embodiments, in combination with good durable press properties and/or shrinkage resistance.

BACKGROUND OF THE INVENTION

[0003] Many fabrics, particularly fabrics comprising natural fibers, do not possess durable press (or “wash and wear” or “smooth-dry”) performance or dimensional stability, i.e., shrinkage resistance. Cellulosic fabrics such as cotton have been treated with aminoplast resins, including N-methylol cross-linking resins such as dimethylol dihydroxyethyleneurea (DMDHEU) or dimethylol propylcarbamate (DMPC), to impart durable press properties, as disclosed, for example, in the Martin et al U.S. Pat. No. 4,521,176. Unfortunately, many reacted aminoplast resins break down during storage, thus releasing formaldehyde. The formaldehyde release may occur not only throughout the preparation of the fabric but also during garment-making. Further, garments or fabrics treated with aminoplast resins may release additional formaldehyde when stored under humid conditions. Aminoplast resins may also hydrolyze during washing procedures, resulting in a loss of the durable press performance. Additionally, aminoplast resins tend to give fabric a harsher handle, that is, make the fabric feel less soft. As the resins make the fabric feel less soft, the fabric must be treated with additional softeners. Unfortunately, both the aminoplast resins and the softeners tend to make fabric hydrophobic although it is often preferred that the fabric have hydrophilic properties.

[0004] Cellulosic fibers have also been cross-linked with formaldehyde to impart durable press properties. For example, the Payet U.S. Pat. Nos. 3,960,482, 3,960,483, 4,067,688 and 4,104,022 disclose durable press processes which comprise impregnating a cellulosic fiber-containing fabric with an aqueous solution comprising a catalyst, and, while the fabric has a moisture content of above 20% by weight, exposing the fabric to formaldehyde vapors and curing under conditions at which formaldehyde reacts with the cellulose. The Payet U.S. Pat. No. 4,108,598 discloses a process which comprises treating cellulosic fiber-containing fabrics with an aqueous solution of formaldehyde and a catalyst, heat curing the treated fabric by introducing the fabric into a heating zone, and gradually increasing the temperature of the heating zone, thereby increasing the temperature of the heated fabric to prevent the loss of an amount of formaldehyde which will reduce the overall extent of curing. The Payet U.S. Pat. No. 5,885,303 also discloses a durable press process for cellulosic fiber-containing fabrics. The process comprises treating the fabric with an aqueous solution of formaldehyde, a catalyst capable of catalyzing the cross-linking reaction between formaldehyde and cellulose, and an effective amount of a silicone elastomer to reduce loss in tear strength in the treated fabric. Formaldehyde is generally less expensive than aminoplast resins, and formaldehyde treatment of cellulosic fabrics typically results in durable press properties which are more durable than those obtained by aminoplast resins.

[0005] Rayon garments are desirable by consumers for a variety of reasons. However, many durable press treatment processes that have been provided for cotton cellulose fabrics have not been suitable for rayon fabrics. Although rayon and cotton are both cellulosic fibers, they react very differently from one another. Particularly, rayon-containing fabrics exhibit significant shrinkage when subjected to aqueous washing or laundering and therefore generally require dry cleaning as opposed to washing in an aqueous environment.

[0006] The copending Payet application Ser. No. 09/163,319 discloses processes for providing rayon fabrics with durable press properties and shrinkage resistance wherein a rayon fiber-containing fabric is treated with an aqueous mixture containing a high concentration of formaldehyde and a catalyst capable of catalyzing the cross-linking reaction between formaldehyde and the rayon, and the treated fabric is heat cured. Payet discloses that the fabric may be washed or laundered in an aqueous system and does not shrink substantially on aqueous washing. Additionally, a silicone elastomer may be employed to reduce loss in tear strength in the treated fabric.

[0007] On the other hand, while some fabrics exhibit some degree of durable press properties and/or shrinkage resistance, they exhibit noticeable fabric quality degradation upon aqueous washing. An example of such fabrics includes lyocell, a type of rayon available commercially as Lyocell by Lenzing and as Tencel by Acordis. While lyocell resists significant shrinkage and therefore is considered to be water washable, lyocell suffers from significant fibrillation when subjected to laundering. Furthermore, a fabric produced from rayon fibers such as the lyocell fibers loses much of its color intensity after being washed several times. Thus, although dimensionally stable, lyocell garments do not retain a new look upon aqueous washings, and after repeated washings, look unacceptably aged.

[0008] One type of lyocell, A-100 Lyocell, is made from rayon fibers which have been treated with conventional aminoplast resins at the fiber stage. While the resin treatment may reduce fibrillation of resulting fabric, the resin treatment typically renders the fabrics stiff and unpleasant to the touch.

[0009] Various natural fiber fabrics are also susceptible to pilling, particularly as a result of wear and/or laundering. Pilling undesirably causes garments to appear aged and worn.

[0010] Accordingly, there is a continuing need to further improve individual characteristics of fabrics containing natural fibers, for example cotton and rayon, and to improve the overall combinations of properties exhibited by such fabrics.

SUMMARY OF THE INVENTION

[0011] Accordingly, it is an object of the present invention to obviate problems of the prior art. It is a further object of the present invention to provide methods for improving the fibrillation resistance and/or the pill resistance of fabrics and particularly to improve the fibrillation resistance and/or pill resistance of fabrics containing natural fibers. It is a related object to provide methods for preparing fabrics which exhibit improved fibrillation resistance and/or improved pill resistance and which are suitable for aqueous washing or laundering, and to provide fabrics which exhibit advantageous combinations of properties and which are suitable for aqueous washing or laundering.

[0012] These and additional objects are provided by the methods and fabrics of the invention. In one embodiment, the invention is directed to methods for providing fabric with improved fibrillation resistance and/or improved pill resistance, which methods comprise treating the fabric with a treatment composition comprising formaldehyde, catalyst for cross-linking the formaldehyde with natural fibers in the fabric, and silicone elastomer or a precursor thereof, and heating the treated fabric to effect cross-linking of the formaldehyde. In a further embodiment, the invention is directed to methods for providing fabric with improved fibrillation resistance and/or improved pill resistance, which methods comprise cross-linking natural fibers in the fabric with formaldehyde and providing the fabric with a silicone elastomer. In a further embodiment, the invention is directed to methods for providing fabric with improved fibrillation resistance and/or improved pill resistance, and with durable press properties, which methods comprise treating the fabric with a treatment composition comprising formaldehyde, catalyst for cross-linking the formaldehyde with natural fibers in the fabric, and silicone elastomer or a precursor thereof, and heating the treated fabric to effect cross-linking of the formaldehyde. In another embodiment, the invention is directed to methods for providing fabric with improved fibrillation resistance and/or improved pill resistance, and with shrinkage resistance, which methods comprise treating the fabric with a treatment composition comprising formaldehyde, catalyst for cross-linking the formaldehyde with natural fibers in the fabric, and silicone elastomer or a precursor thereof, and heating the treated fabric to effect cross-linking of the formaldehyde. In yet additional embodiments, the invention is directed to methods of providing lyocell fabric with improved fibrillation resistance and/or improved pill resistance, which methods comprise cross-linking cellulose in lyocell fibers of the fabric with formaldehyde and providing the fabric with a silicone elastomer.

[0013] The invention is also directed to fabric exhibiting improved fibrillation resistance and/or improved pill resistance, the fabric comprising natural fibers cross-linked with formaldehyde and the fabric being provided with a silicone elastomer thereon, wherein the fabric is not 100% cotton. In another embodiment, the invention is directed to lyocell fabric having a cross-linked formaldehyde treatment and exhibiting improved fibrillation resistance and/or improved pill resistance. In yet another embodiment, natural fibers, for example lyocell rayon fibers, are cross-linked with formaldehyde and provided with a silicone elastomer, and then formed into yarn to form a fabric, for example by weaving or knitting. The resulting fabric exhibits good fibrillation resistance and/or good pill resistance.

[0014] The methods of the invention are advantageous in providing fabrics which exhibit improved fibrillation resistance and/or improved pill resistance, and in providing fabrics exhibiting improved fibrillation resistance and/or improved pill resistance in combination with other desirable properties, for example durable press properties and/or shrinkage resistance.

[0015] These and additional aspects, objects and advantages of the invention are more fully described in the following detailed description.

DETAILED DESCRIPTION

[0016] The present invention is directed to methods for providing fabrics, particularly fabrics comprising natural fibers, with improved fibrillation resistance and/or improved pill resistance. The improved fibrillation resistance and/or improved pill resistance may be provided in combination with, inter alia, good durable press properties and/or shrinkage resistance. This invention also relates to fabrics which have improved fibrillation resistance and/or improved pill resistance, and to fabrics which exhibit improved fibrillation resistance and/or improved pill resistance in combination with durable press and/or shrinkage resistance and which can be subjected to aqueous laundering.

[0017] As is known in the art, the usefulness of some fabrics prepared from fibers is severely limited by the tendency of the fibers to fibrillate in the wet state. Fibrillation is understood as meaning the breaking up of the wet fiber in the longitudinal direction under mechanical stress up to the point of fibrils separating from one another along the fiber surface, giving the fabric a fuzzy or furry look. As employed in the present invention, improved fibrillation resistance indicates that the fabric exhibits less fibrillation than a fabric which is not subjected to the treatment methods described herein. Relative fibrillation can be measured by visual comparison of treated and nontreated fabrics, and can be evaluated numerically by trained fabric specialists.

[0018] As is also known in the art, the usefulness of some fabrics prepared from fibers is severely limited by the tendency of the fibers or yarns to pill. Pilling is understood as meaning the formation of groups of fibers into tiny balls, i.e., pills, at the fabric surface. While some fabrics may exhibit pilling, if the fibers which hold the pills to the surface are weak and the pills easily fall off, whereby pills do not appear on the fabric surface, such fabrics, within the scope of this invention, are considered pill resistant. Pilling may be the result of fibrillation, wear, home laundering or the like. As employed in the present invention, improved pill resistance indicates the fabric exhibits less pilling than a fabric which is not subjected to the treatment methods described herein. Pilling may be evaluated by various techniques. For example, pilling may be evaluated by visual inspection by a trained technician, in which a scale of, for example, 1 to 5 is employed to rate a fabric's pilling, with 1 representing severe pilling and 5 representing no pilling. Another technique for evaluating a fabric's pilling is according to ASTM D3512: Resistance to Random Tumble Pilling, which also employs a scale of 1 to 5, with 1 representing poor resistance to pilling and 5 representing excellent resistance to pilling.

[0019] The fabrics employed in the present invention preferably comprise natural fibers. As used herein, “individual fiber” refers to a short and/or thin filament, such as short filaments of cotton as obtained from the cotton boll, short filaments of wool as sheared from the sheep, filaments of cellulose or rayon, or the thin filaments of silk obtained from a silkworm cocoon. As used herein, “fibers” is intended to include filaments in any form, including individual filaments, and the filaments present in formed yarns, fabrics and garments.

[0020] As used herein, “yarn” refers to a product obtained when fibers are aligned. Yams are products of substantial length and relatively small cross-section. Yarns may be single ply yarns, that is having one yarn strand, or multiple ply yarns, such as 2-ply yarn which comprises two single yarns twisted together or 3-ply yarn which comprises three yarn strands twisted together. As used herein, “fabrics” generally refer to knitted fabrics, woven fabrics, or non-woven fabrics prepared from yarns or individual fibers, while “garments” generally refer to wearable articles comprising fabrics, including, but not limited to, shirts, blouses, dresses, pants, sweaters and coats. Non-woven fabrics include fabrics such as felt and are composed of a web or batt of fibers bonded by the application of heat and/or pressure and/or entanglement. “Textiles” includes fabrics, yarns, and articles comprising fabrics and/or yarns, such as garments, home goods, including, but not limited to, bed and table linens, draperies and curtains, and upholsteries, and the like.

[0021] As used herein, “natural fibers” refer to fibers which are obtained from natural sources, such as cellulosic fibers and protein fibers, or which are formed by the regeneration of or processing of natural occurring fibers and/or products. Natural fibers are not intended to include fibers formed from petroleum products. Natural fibers include fibers formed from cellulose, such as cotton fiber and regenerated cellulose fiber, commonly referred to as rayon, or acetate fiber derived by reacting cellulose with acetic acid and acetic anhydride in the presence of sulfuric acid. As used herein, “natural fibers” are intended to include natural fibers in any form, including individual filaments, and fibers present in yarns, fabrics and other textiles, while “individual natural fibers” is intended to refer to individual natural filaments.

[0022] As used herein, “cellulosic fibers” are intended to refer to fibers comprising cellulose, and include, but are not limited to, cotton, linen, flax, rayon, cellulose acetate, cellulose triacetate, hemp and ramie fibers. As used herein, “rayon fibers” is intended to include, but is not limited to, fibers comprising viscose rayon, high wet modulus rayon, cuprammonium rayon, saponified rayon, modal rayon and lyocell rayon. Lyocell fibers are fibers which are obtained by a process in which cellulose is dissolved in an organic solvent, in a combination of an organic solvent with an inorganic salt, or in aqueous salt solutions, and the fibers are then spun from the solution. “Protein fibers” are intended to refer to fibers comprising proteins, and include, but are not limited to, wools, such as sheep wool, alpaca, vicuna, mohair, cashmere, guanaco, camel and llama, as well as furs, suedes, and silks.

[0023] As used herein, “synthetic fibers” refer to those fibers which are not prepared from naturally occurring filaments and include, but are not limited to, fibers formed of synthetic materials such as polyesters, polyamides such as nylons, polyacrylics, and polyurethanes such as spandex. Synthetic fibers include fibers formed from petroleum products.

[0024] Fabrics for use in the present invention preferably comprise natural fibers, which natural fibers may be included in any form, including, but not limited to, in the form of individual fibers (for example in nonwoven fabrics), or in the form of yarns comprising natural fibers, woven or knitted to provide the fabrics. Additionally, the fabrics may be in the form of garments or other textiles comprising natural fibers. The fabrics may further comprise synthetic fibers. Preferably, the fabrics comprise at least about 20% natural fibers. In one embodiment, the fabrics comprise at least about 50% natural fibers such as cotton fibers, rayon fibers or the like. In another embodiment, the fabrics comprise at least about 80% natural fibers such as cotton fibers, rayon fibers or the like, and in a further embodiment, the fibers comprise 100% natural fibers. Fabrics comprising cellulose fibers such as cotton and/or rayon are preferred for use in the present invention. Fabrics comprising lyocell rayon fibers are also preferred for use in the present invention.

[0025] While not being bound by theory, it is believed that when natural fibers are treated with a composition comprising formaldehyde and a catalyst capable of cross-linking formaldehyde with a natural fiber, a chemical modification of the natural fibers occurs. It is believed that the formaldehyde reacts chemically with the natural fibers to cross-link the individual polymer chains of the natural fibers. In accordance with the present methods, a silicone elastomer or precursor thereof is included in the formaldehyde treatment. The fabrics surprisingly exhibit improved fibrillation resistance and/or improved pill resistance, preferably in combination with durable press properties and/or dimensional stability, i.e., reduced shrinkage. The fabrics preferably also exhibit good strength, for example good tear strength.

[0026] To provide the cross-linked formaldehyde treatment, the fabric is typically treated with a treatment composition comprising formaldehyde, a catalyst and a silicone elastomer or precursor thereof, followed by drying and/or curing of the treated fabric. Formaldehyde is generally available in an aqueous solution, referred to as formalin, comprising water, about 37% by weight formaldehyde, and generally about 10% to 15% by weight methanol.

[0027] The amount of formaldehyde in the treatment composition is preferably sufficient to impart improved fibrillation resistance and/or pill resistance. The amount of formaldehyde is preferably sufficient to further provide a durable press property and/or shrinkage resistance to the fabric. Generally the fabric is treated with at least about 3% by weight formalin, and preferably with from about 3% to about 35% by weight formalin, based on the weight of the fabric. In one embodiment, for example wherein the fabric comprises cotton fibers, the fabric is treated with about 3% to about 8% formalin, based on the weight of the fabric. In another embodiment, for example wherein the fabric comprises rayon fibers, including lyocell fibers, the fabric is treated with from about 10% to about 20% by weight formalin, based on the weight of the fabric. In yet another embodiment, for example wherein the fabric comprises a 50/50 rayon/polyester blend, the fabric is treated with from about 5% to about 10%, more specifically, about 8%, by weight formalin, based on the weight of the fabric. As used herein, “formalin” refers to an aqueous solution comprising 37%, by weight, formaldehyde. As will be apparent to one of skill in the art, formaldehyde solutions comprising levels of formaldehyde other than 37%, by weight, may also be used. Using the above ranges of formalin, the fabric is treated with actual formaldehyde, as opposed to formalin, at a level of from about 1% to about 13%, preferably from about 1% to about 12%, based on the weight of the fabric. Thus, in one embodiment, for example wherein the fabric comprises cotton fibers, the fabric is treated with about 1% to about 3% formaldehyde, as opposed to formalin, based on the weight of the fabric. In another embodiment, for example wherein the fabric comprises rayon fibers, the fabric is treated with from about 4% to about 8% by weight formaldehyde, as opposed to formalin, based on the weight of the fabric. In yet another embodiment, for example wherein the fabric comprises a 50/50 rayon/polyester blend, the fabric is treated with about 2% to about 4% formaldehyde, as opposed to formalin, based on the weight of the fabric.

[0028] Suitable catalysts are those capable of catalyzing a cross-linking reaction between formaldehyde and a natural fiber, and preferably are catalysts capable of catalyzing the cross-linking of formaldehyde with a natural fiber comprising hydroxy groups, such as cellulosic fibers. Catalysts which may be used include mineral acids, organic acids, salts of strong acids, ammonium salts, alkylamine salts, metallic salts and combinations thereof. In one embodiment the catalyst is other than a mineral acid.

[0029] Suitable mineral acid catalysts include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and boric acid. Suitable organic acids include oxalic acid, tartaric acid, citric acid, malic acid, glycolic acid, methoxyacetic acid, chloroacetic acid, lactic acid, 3-hydroxybutyric acid, methane sulfonic acid, ethane sulfonic acid, hydroxymethane sulfonic acid, benzene sulfonic acid, p-toluene sulfonic acid, cyclopentane tetracarboxylic acid, butane tetracarboxylic acid, tetrahydrofuran-tetracarboxylic acid, nitrilotriacetic acid, and ethylenediaminetetraacetic acid. Suitable salts of strong acids include sodium bisulfate, sodium dihydrogen phosphate and disodium hydrogen phosphate. Suitable ammonium salts include ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium bisulfate, ammonium dihydrogen phosphate and diammonium hydrogen phosphate. Suitable alkanolamine salts include the hydrochloride, nitrate, sulfate, phosphate and sulfamate salts of 2-amino-2-methyl-1-propanol, tris (hydroxymethyl) aminomethane and 2-amino-2-ethyl-1-3-propanediol. Suitable metal salts include aluminum chlorohydroxide, aluminum chloride, aluminum nitrate, aluminum sulfate, magnesium chloride, magnesium nitrate, magnesium sulfate, zinc chloride, zinc nitrate and zinc sulfate, and mixtures thereof.

[0030] In one embodiment of the invention, the catalyst is a halide or nitrate salt of zinc or magnesium, and preferably the catalyst is magnesium chloride. An organic acid, such as citric acid, may be used in combination with the halide or nitrate salt of zinc or magnesium. Generally the molar ratio of metal salt to organic acid is from about 5:1 to about 20:1. In one embodiment, the catalyst comprises magnesium chloride and citric acid, while in another embodiment the catalyst comprises magnesium chloride and aluminum chloride.

[0031] The fabric is typically treated with an amount of catalyst sufficient to catalyze cross-linking of the natural fibers by the formaldehyde to provide improved fibrillation resistance and/or improved pill resistance, and in more specific embodiments, to further provide a durable press treatment and/or reduced shrinkage, for example reduced shrinkage upon aqueous laundering. In one embodiment, the catalyst may be employed in an amount sufficient to provide a formaldehyde:catalyst weight ratio of from about 10:1 to about 1:10, and preferably from about 5:1 to about 1:5.

[0032] The formaldehyde treatment composition may comprise, by weight, up to about 12% of a catalyst solution, and preferably from about 1% to about 9% of a catalyst solution. Generally, the catalyst solution comprises from about 20% to about 50%, by weight catalyst. In one embodiment, for example wherein the fabric comprises cotton fibers, the treatment solution comprises from about 2 to about 4% by weight of a catalyst solution comprising about 30% by weight catalyst, and in another embodiment, for example wherein the fabric comprises rayon fibers, including lyocell fibers, the treatment solution comprises from about 6% to about 8% by weight of a catalyst solution comprising about 30% by weight catalyst. In yet a further embodiment, the catalyst solution comprises about 40%, by weight, magnesium chloride, for a final magnesium chloride level of up to about 5%, by weight of the treatment solution. Suitable catalyst solutions include FREECAT® LF (magnesium chloride and citric acid) and FREECAT® No. 9 (aluminum chloride and magnesium chloride), commercially available from B. F. Goodrich.

[0033] The formaldehyde treatment composition typically comprises a liquid carrier, preferably water, although, as noted above, the formalin used to prepare the treatment composition may comprise small amounts of organic solvents such as methanol or the like. In one embodiment, the treatment composition is free of any organic solvents other than that present in the formalin or the catalyst solution. In another embodiment, the carrier may comprise pentamethylcyclosiloxane.

[0034] According to the present methods, a silicone elastomer or precursor thereof is included in the formaldehyde-containing treatment composition with which the fabric is treated. Thus, the formaldehyde treatment composition comprises formaldehyde, catalyst and silicone elastomer or a precursor thereof. It has been surprisingly discovered that the resulting treated fabric exhibits improved fibrillation resistance and/or improved pill resistance. In further embodiments of the invention, the combination of the silicone elastomer or precursor thereof and the formaldehyde-containing treatment composition provides the fabric with improved fibrillation resistance and/or improved pill resistance while also providing good durable press, shrinkage resistance properties, good fabric hand or feel and/or good strength. This is surprising in that conventional durable press and/or shrinkage resistance processing can render fabrics more susceptible to stiff fabric hand and/or can result in reduced fabric strength, rather than providing improvement in these various other properties. The silicone elastomer is particularly effective to reduce the loss in tear strength that typically occurs during formaldehyde cross-linking of fibers. In another embodiment, the fabrics treated according to the invention exhibit good water absorbency, for example as measured according to AATCC Method 79-1995 wherein the fabric absorbs a drop of water placed thereon in less than about 100 seconds, specifically less than about 80 seconds.

[0035] Various silicone elastomers are known in the art and are suitable for use in the methods and fabrics of the invention. In one embodiment, the silicone elastomer is a polysiloxane. Similarly, the silicone elastomer precursor which forms an elastomer upon curing, typically by self curing, may be a polysiloxane. Elastomers are polymers which are capable of being stretched with relatively little applied force, and which return to the unstretched length when the force is released. Silicone elastomers have a backbone made of silicon and oxygen with organic substituents attached to silicon atoms, with a number n of repeating units of the general formula:

[0036] The groups R and Rÿ are each independently selected from lower alkyls, preferably C1-C3 alkyls, phenyl, or lower alkyls or phenyls comprising a group reactive to cellulose, such as hydroxy groups, halogen atoms, for example, fluoride, or amino groups. Suitable elastomers include those disclosed in U.S. Pat. No. 5,885,303, incorporated herein by reference.

[0037] A preferred silicone elastomer or precursor composition comprises up to about 60%, by weight, silicone solids. In one embodiment, the silicone elastomer or precursor composition comprises from about 20% to about 60%, preferably from about 30% to about 60%, by weight of silicone solids, while in another embodiment the silicone elastomer or precursor composition comprises from about 20% to about 30% by weight of silicone solids. Suitable silicone elastomer precursors include a dimethyl silicone emulsion containing from about 30% to about 60%, by weight, silicone solids, commercially available as SM2112 from General Electric. Another suitable commercially available elastomer precursor is Sedgesoft ELS from Sedgefield Specialties, containing from about 24% to about 26%, by weight, silicone solids.

[0038] When the silicone elastomer or precursor thereof is applied to the fabric with a liquid formaldehyde treatment composition, the liquid treatment composition may comprise up to about 10%, preferably from about 1% to about 5%, more preferably from about 1% to about 3%, by weight of the elastomer or precursor solids. In one embodiment, the treatment composition comprises from about 1% to about 3%, preferably from about 1.5% to 3%, by weight silicone solids, while in another embodiment, the composition comprises from about 1% to about 1.5% by weight silicone solids.

[0039] The formaldehyde treatment composition may be applied to the fabric in accordance with any of the conventional techniques known in the art. In one embodiment, the treatment composition may be applied to the fabric by saturating the fabric in a trough and squeezing the saturated fabric through pressure rollers to achieve a uniform application (padding process). As used herein “wet pick-up” refers to the amount of treatment composition applied to and/or absorbed into the fabric based on the original weight of the fabric. “Original weight of the fabric” refers to the weight of the fabric prior to its contact with the treatment composition. For example, 50% pick-up means that the fabric picks up an amount of treatment solution equal to 50% of the fabric's original weight. Preferably the wet pick-up is at least 20%, preferably from about 50% to 100%, more preferably from about 65% to about 80%, by weight of the fabric.

[0040] Other application techniques which may be employed include kiss roll application, engraved roll application, printing, foam finishing, vacuum extraction, spray application or any process known in the art. Generally theses techniques provide lower wet pick-up than the padding process. The concentration of the chemicals in the solution may be adjusted to provide the desired amount of chemicals on the weight of the fabric (OWF).

[0041] In a preferred embodiment, the formaldehyde treatment composition is applied in an amount to insure a moisture content of more than 20% by weight, preferably more than 30% by weight, on the fabric before curing. Optionally, a wetting agent may be included in the treatment composition to facilitate obtaining the desired moisture content. Nonionic wetting agents are preferred.

[0042] Once the treatment composition has been applied to the fabric, the fabric is typically heated for a time and at a temperature sufficient for the cross-linking of the natural fibers with the formaldehyde. For example, the fabric may be heated at a temperature greater than about 250 ÿF, preferably from about 250 ÿF to about 350 ÿF, in an oven for a period of from about 15 seconds to about 15 minutes, preferably from about 45 seconds to about 3 minutes, to react the formaldehyde with the natural fibers in the fabric and affect cross-linking of the formaldehyde and natural fibers to provide durable press and/or shrinkage resistance effects. Generally, there is an inverse relationship between curing temperature and curing time, that is, the higher the temperature of curing, the shorter the dwell time in the oven; conversely, the lower the curing temperature, the longer the dwell time in the oven.

[0043] In another embodiment, the present invention comprises methods for improving the fibrillation resistance and/or the pill resistance of fabric, wherein the silicone elastomer may be included in the treated fabric by means of a separate treatment step before or after the formaldehyde cross-linking treatment. Additionally, if the silicone elastomer or precursor thereof is applied to the fabric subsequent to treatment with the formaldehyde cross-linking composition, the silicone elastomer precursor thereof may be applied prior to or subsequent to the heating step which is employed to affect curing of the formaldehyde with the natural fibers of the fabric, although application prior to heating is preferred. The applied silicone elastomer or precursor thereof may be dried, with self curing of the precursor being affected thereby.

[0044] In yet a further embodiment of the invention, individual fibers are treated with the described formaldehyde cross-linking treatment composition containing a silicone elastomer or a precursor thereof, heated to effect cross-linking of the formaldehyde with cellulose in the fibers and then used to form fabric, for example by forming into yarns which are woven or knitted. The resulting fabric exhibits improved resistance to fibrillation, particularly upon washing of the fabric. This embodiment is particularly suitable for treatment of rayon fibers, and more particularly for lyocell fibers.

[0045] In one embodiment, the fabrics according to the present invention exhibit improved fibrillation resistance and/or improved pill resistance. As noted above, improved fibrillation resistance indicates that the fabric exhibits less fibrillation than a fabric which is not subjected to the treatment methods described herein. Relative fibrillation can be measured by visual comparison of treated and nontreated fabrics, and can be evaluated numerically by trained fabric specialists. The improved fibrillation resistance is evident after one washing, but is more clearly evident after two or more and after a number of repeated washings, of the fabrics. The improved fibrillation resistance is particularly advantageous when the fabric is used in garment manufacture, as garments which resist fibrillation maintain a new appearance and therefore are preferred by consumers over garments which exhibit noticeable and significant fibrillation after one or several washings. Alternatively or additionally, the fabrics according to the invention exhibit improved pill resistance. As noted above, improved pill resistance indicates the fabric exhibits less pilling than a fabric which is not subjected to a treatment method according to the invention as described herein. The improved pill resistance is particularly advantageous when the fabric is used in garment manufacture, as garments which resist pilling maintain a new appearance and are preferred by consumers over garments which exhibit noticeable and significant pilling.

[0046] In further embodiments, the fabrics according to the invention also exhibit good durable press properties and/or good shrink resistance. In one embodiment, it is preferred that the fabric exhibit good durable press, for example a DP (durable press) rating of at least about 3.0, preferably at least about 3.25, and more preferably at least about 3.5, as measured according to AATCC Test Method 124-1996, after one aqueous washing, and preferably after five washings, and/or good shrinkage resistance, for example a length shrinkage and a width shrinkage of less than about 10% each, preferably less than about 5% each, more preferably less than about 4% each, and even more preferably less than about 2% each, and in specific embodiments less than about 1%, as measured according to AATCC Test Method 135-1995, after one washing, preferably after five washings. Shrinkage resistance may also be measured according to AATCC Test Method 150-1995. In further preferred embodiments, the fabrics exhibit good filling tensile and tear strengths, for example of at least about 25 pounds and at least about 24 ounces, respectively, as measured according to ASTM D-5035-95 for tensile strength, and ASTM D-2261-96 for tear strength.

[0047] In another embodiment, fabric comprising natural fibers cross-linked with formaldehyde and provided with silicone elastomer thereon exhibits improved fibrillation resistance and/or improved pill resistance, provided that the fabric does not comprise 100% cotton. These fabrics may, for example, comprise greater than about 20% cotton fibers, greater than about 50% cotton fibers, greater than about 80% cotton fibers, greater than about 20% rayon fibers, greater than about 50% rayon fibers, greater than about 80% rayon fibers, or about 100% rayon fibers. In one embodiment, the rayon fibers comprise lyocell. In further embodiments, the fabric exhibits a length shrinkage and a width shrinkage of less than about 5% each after the fabric has been aqueous laundered at least one time. In another embodiment, the fabric exhibits a durable press value of at least about 3 after the fabric has been aqueous laundered at least one time.

[0048] In yet a further embodiment, the invention is directed to lyocell fabric having a cross-linked formaldehyde treatment and exhibiting improved fibrillation resistance and/or improved pill resistance. Preferably, the fabric is provided with a silicone elastomer, for example in accordance with the methods described above.

[0049] In processes in accordance with the present invention, unreacted formaldehyde remaining on the fabric is removed during subsequent processing of the fabric. Generally, the final substrate will comprise less than about 300 ppm formaldehyde, preferably less than about 200 ppm formaldehyde, more preferably less than about 100 ppm formaldehyde, and even more preferably less than about 50 ppm formaldehyde, as measured according to AATCC Test Method 112-1993.

[0050] Some polysiloxanes, generally referred to as silicone oils, have a liquid form, are not elastomeric and do not self-cross-link. Silicone oils include, for example, non-reactive linear polydimethyl siloxanes, that is, siloxanes which are not capable of further reaction with other silicones and are not capable of a self curing reaction. Silicone oils have a tendency to produce non-removable spots on fabrics. In contrast, the silicone elastomers used in the present invention generally do not produce such spots. Although the fabrics or treatment compositions may comprise silicone oil, in one embodiment, the fabrics and treatment compositions are substantially free of, and preferably are free of, silicone oil. As used herein, substantially free of silicone oils means the treatment compositions and fabrics comprise less than 1%, by weight, silicone oil.

[0051] Thermosetting resins which have been used conventionally to impart durable press properties to fabrics are generally aminoplast resins. Aminoplast resins are the products of the reaction of formaldehyde with compounds such as urea, thiourea, ethylene urea, dihydroxyethylene urea and melamines. As used herein “aminoplast resins” is intended to include resins formed with N-methylolamide cross-linking agents such as dimethylol dihydroxyethylene urea, dimethylol urea, dimethylolethylene urea, dimethylol propylene urea, dimethylol methyl carbamate, dimethylol n-propylcarbamate, dimethylol isopropylcarbamate trimethylolated melamine, and tris(methoxymethol) melamine. Preferably, the fabrics, methods and formaldehyde treatment compositions of the invention are substantially free of, and more preferably are free of, aminoplast resins, and particularly, are free of resins formed with N-methylol cross-linking agents. As used herein, “substantially free” of aminoplast resins is intended to mean the fabrics and treatment solutions comprise less than about 0.5%, by weight, aminoplast resin, including resins formed with methylol cross-linking agent.

[0052] Prior to treatment with the formaldehyde composition and silicone elastomer or precursor thereof, the fabric may optionally be prepared using any fiber, yarn, or textile pre-treatment preparation techniques known in the art. Suitable preparation techniques include brushing, singeing, desizing, scouring, mercerizing, and bleaching. For example, fabric may be treated by brushing which refers to the use of mechanical means for raising surface fibers which will be removed during singeing. The fabric may be then be singed using a flame to burn away fibers and fuzz protruding from the fabric surface. Textiles may be desized, which refers to the removal of sizing chemicals such as starch and/or polyvinyl alcohol, that are put on yarns prior to weaving to protect individual yarns. The fabrics may be scoured, which refers to the process of removing natural impurities such as oils, fats and waxes and synthetic impurities such as mill grease from fabrics. Mercerization refers to the application of high concentrations of sodium hydroxide to a fabric to alter the morphology of fibers, particularly cotton fibers. Fabrics may be mercerized to improve fabric stability and luster. Finally, bleaching refers to the process of destroying any natural color bodies within the natural fiber. A typical bleaching agent is hydrogen peroxide.

[0053] The various preparation techniques are optional and dependent upon the desired final product. For example, when the final fabric is to be dyed a dark color, there may be no need to bleach the substrate. Similarly, there may be no need to desize a knit which was prepared without using any sizing agents, and no need to separately scour knits and woven textiles as the scouring may be done during bleaching.

[0054] The following example is set forth to demonstrate the methods of the present invention and the improved fibrillation resistance which is obtained in fabrics by the methods of the present invention. Throughout the examples and the present specification, parts and percentages are by weight unless otherwise specified. The following example is illustrative only and is not intended to limit the scope of the methods and fabrics of the invention as defined by the claims.

EXAMPLE 1

[0055] In this example, a lyocell fabric comprising 100% lyocell fibers is treated in accordance with the methods of the invention to provide a cross-linked formaldehyde silicone elastomer treatment thereon. Specifically, the lyocell is treated with an aqueous solution comprising about 10% to about 20% formalin, a weight ratio of formalin to catalyst of about 18:5 and about 3% (solids) silicone elastomer precursor, based on the weight of the fabric. The aqueous solution is padded on the fabric to provide a moisture content of greater than about 30% and the treated fabric is heated at a temperature greater than about 300 ÿF for a period of time sufficient to effect cross-linking of the formaldehyde with the cellulose in the rayon fabric.

[0056] The treated lyocell fabric and an untreated lyocell fabric are subjected to machine washing, after which the fabrics are compared to evaluate the relative fibrillation of the fabrics. The untreated lyocell fabric exhibits severe fibrillation, evident by visual inspection of the fabric and evaluation by a technically trained grader. In contrast, the fabric treated according to the present methods (formaldehyde-silicone elastomer treated) maintains a new appearance and exhibits no significant or noticeable fibrillation. The treated fabric is also advantageous in that it exhibits good durable press properties, good shrinkage resistance and good strength.

EXAMPLE 2

[0057] In this example, several different types of fabric as described in Table 1 are treated in accordance with the methods of the invention to provide a cross-linked formaldehyde-silicone elastomer treatment thereon. Specifically, the fabrics are treated with an aqueous solution comprising formalin, catalyst and silicone elastomer precursor. The amount of formalin which is employed is set forth in Table 1 as weight percent based on the weight of the fabric. The aqueous solution is padded on the fabric to provide a moisture content of greater than about 30% and the treated fabric is heated at a temperature greater than about 300 ÿF for a period of time sufficient to effect cross-linking of the formaldehyde with the cellulose in the respective fabrics.

[0058] The treated fabrics and untreated control fabrics are evaluated according to ASTM D3512: Resistance to Random Tumble Pilling, after 30 minutes. The fabrics are evaluated on a scale of 1 to 5, with 1 representing fabrics exhibiting poor resistance to pilling and 5 representing fabrics exhibiting excellent resistance to pilling. The results of the evaluation are also set forth in Table 1.

1TABLE 1ASTM D3512: Resistance to Random Tumble PillingMeasured at 30 minutesScale = 1(poor) to 5(best)% FormalinSam-Fabric Wton WtPillingpleFabric(oz/yd2)of FabricResistance150/50 polycotton woven4.2554.5265/35 polycotton woven4.25Untreated3.0control350/50 polycotton woven7.2595.0450/50 polycotton woven7.25Untreated3.5control5100% cotton knit jersey5.555.06100% cotton knit jersey5.5Mechanically3.0finishedcontrol7100% cotton knit jersey5.5Untreated2.5control

[0059] A comparison of fabric samples 1 and 2, a comparison of fabric samples 3 and 4, and a comparison of fabric samples 5, 6 and 7 demonstrate that the fabrics treated according to the methods of the present invention exhibited improved pilling resistance as compared with the untreated fabrics.

[0060] The examples and specific embodiments set forth herein are for illustrative purposes only and are not intended to limit the scope of the methods and fabrics of the invention. Additional methods and fabrics within the scope of the claimed invention will be apparent to one of ordinary skill in the art in view of the teachings set forth herein.

Methods for improving fibrillation or pill resistance of fabrics and fabrics with improved properties

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