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Title:
ELASTIC FIBER, COMPOSITE YARNS AND FABRICS WITH ANTI-SLIPPAGE PERFORMANCE
Document Type and Number:
WIPO Patent Application WO/2021/183609
Kind Code:
A1
Abstract:
Elastic fiber with improved seam slippage resistance performance is provided. Also provided are elastic composite yarn, fabrics and articles of manufacture comprising the elastic fiber and methods for production of methods for making spandex fiber, composite yarn, fabric and articles of manufacture with improved elastane slippage resistance.

Inventors:
LIAO TIANYI (US)
KURLAND NICHOLAS E (US)
LIU HONG (US)
HUANG YUCHENG (US)
Application Number:
PCT/US2021/021646
Publication Date:
September 16, 2021
Filing Date:
March 10, 2021
Export Citation:
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Assignee:
THE LYCRA COMPANY LLC (US)
International Classes:
D01F1/10; D01F6/70; D01F6/94; D02G3/32; D03D15/56
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Claims:
What is Claimed is: 1. An elastomeric fiber with reduced elastane slippage, said fiber comprising an elastomer and at least one anti-slip polymeric additive having a glass transition temperature below 100 °C. 2. The elastomeric fiber of claim 1 wherein the elastomer is spandex. 3. The elastomeric fiber of claim 2 wherein the spandex a polyether-based spandex polymer. 4. The elastomeric fiber of claim 1 wherein the anti-slip polymeric additive is added at a concentration of about 1% to about 4% by weight of the fiber. 5. The elastomeric fiber of claim 1 wherein the anti-slip polymeric additive is added at a concentration of about 0.5% to about 10% by weight of the fiber. 6. The elastomeric fiber of claim 1 with a fiber denier of from 10d to 400d. 7. The elastomeric fiber of claim 1 with a fiber denier of from 15d to 180d. 8. The elastomeric fiber of claim 1, wherein the anti-slip polymeric additive is a polyurethane comprising bis(4-isocyanatocyclohexyl)methane and N-alkyldiethanolamine or a derivative thereof. 9. The elastomeric fiber of claim 1, wherein the anti-slip polymeric additive is a long side chain polymer. 10. The elastomeric fiber of claim 1 further comprising one or more additional additives. 11. The elastomeric fiber of claim 10 wherein the one or more additional additives are selected from delustrants, additional antioxidants, dyes, dye enhancers, UV stabilizers, pigments or combinations thereof. 12. An elastic composite yarn comprising the anti-slip elastomeric fiber of any of claims 1-11.

13. The elastic composite yarn of claim 12 comprising a core comprising the anti- slip elastomeric fiber. 14. The elastic composite yarn of claim 13 the core is surrounded by, twisted with, or intermingled with hard fiber. 15. The elastic composite yarn of claim 14 wherein the hard fiber is selected from staple fiber, cotton, wool, acrylic, polyamide or nylon, polyester, regenerated cellulose, bamboo, silk, soy or combinations thereof. 16. The elastic composite yarn of claim 13 wherein the core further comprises a control filament. 17. The elastic composite yarn of claim 16 wherein the control filament is selected from textured polyester, nylon, rayon filament, PPT filament, polyester bi-component filament, or PBT fiber or combinations thereof. 18. The elastic composite yarn of claim 13 wherein the composite yarn is a core spun yarn comprising anti-slip elastomeric fiber in the core. 19. The elastic composite yarn of claim 13 wherein the said composite yarn is an air covered yarn comprising anti-slip elastomeric fiber in the core. 20. A woven stretch fabric comprising the elastic composite yarn of any of claims 12-19. 21. An article of manufacture comprising the elastomeric fiber of any of claims 1- 11 or an elastic composite yarn of any of claims 12-19 or the fabric of claim 20. 22. The article of manufacture of claim 19 which is a garment.

Description:
ELASTIC FIBER, COMPOSITE YARNS AND FABRICS WITH ANTI-SLIPPAGE PERFORMANCE FIELD [0001] This disclosure relates to the manufacture of elastomeric fiber, composite yarns and fabrics with improved seam slippage resistance performance. More specifically, the disclosure relates to elastomeric fiber with anti-slip polymeric additives, as well as elastomeric composite yarns, fabrics and articles of manufacture comprising the elastomeric fiber. BACKGROUND [0002] Stretch fabrics with elastic composite yarn have been on the market for many years in many applications. Fabric and garment manufacturers generally know how to make fabrics with the right quality parameters to achieve fabrics acceptable to consumers. However, elastane fiber slippage often happens during garment manufacturing or consumer home laundry. This elastane fiber slippage has become one of the key quality complaints from consumers and one of the main reasons for garment return in department stores and brands. [0003] Elastic fiber, often referred to as spandex, when used in a woven fabric, is typically covered with a rigid yarn. Slippage of these yarns, oftentimes referred to as elastane yarns, occurs when the elastane yarn slips loose from a sewn seam, resulting in a loss of elasticity in the area where the elastane yarn has slipped. Sometimes, there is no visual indication that slippage has occurred. However, often, slippage can be observed as white whiskers of bare elastane yarn sticking up through the surface of the fabric. This slippage is therefore particularly noticeable on the dark fabrics. Slippage can also be observed as bubbles and/or puckers which appear between the areas of the fabric that still have elastane and those that do not. FIG.1 is a photograph of a defective garment with this seam slippage issue. [0004] In order to create fabric stretch and recovery, elastic fiber is processed under tension, i.e., in an extended state. During manufacture of composite stretch yarns for weaving, the elastane is stretched to approximately three times its original length while being covered with a companion fiber. [0005] Throughout the weaving, dyeing, and finishing processes the elastic fibers try to relax; however, even after finishing, the elastic fiber remains under slight tension. Sometimes this tension causes the elastic fibers to slip from the cut edge of the fabric past the sewing line. See FIG.2. This slippage is especially problematic in part of the garment where the fabric is under a lot of tension, such as the crotch or other tight-fitting areas. Slippage can also occur when a garment is wet processed at high temperature and high mechanical action. Even more problematic is when the elastane slippage does not occur during fabric and garment making, but instead occurs after several home laundering cycles. [0006] Seam slippage can be caused by a number of factors and while it can be reduced to some degree by following recommended procedures relating to fabric construction, cutting and sewing techniques, yarn draft and twist levels, heat-setting conditions; yarn selection, wet processing conditions, and use of softeners, elastane slippage still happens randomly, particularly for loose fabrics with high stretch levels and with polyester and rayon staple fibers. [0007] Composite elastic yarns are well known. For example, U.S. Patents 4,470,250; 4,998,403; 7,134,265; and 6,848,151 disclose elastomeric fibers, such as spandex, covered with relatively inelastic fibers in order to facilitate acceptable processing for knitting or weaving, and to provide elastic composite yarns with acceptable characteristics for various end-use fabrics. Published U.S. Patent Application No.2008/0268734A1 and Published U.S. Patent Application No.2008/0318485A1, disclosed a rigid filament used together with elastic filaments as the core inside a core spun yarn. [0008] WO 2010045637A2 disclose a fusible bi-component spandex used for slip prevention in knit fabrics. [0009] There is a need for elastomeric fiber with good anti-slip performance which anchors well and prevents slipping away from garment seams. SUMMARY [00010] Provided by this disclosure are elastomeric fibers and composite yarns, fabrics and articles of manufacture comprising elastomeric fiber exhibiting improved elastane slippage resistance, easy stretch, easy processing, low shrinkage, facile garment making, excellent recovery power and low growth. [00011] An aspect of the present invention relates to an elastomeric fiber with improved seam-slippage performance comprising a polymeric additive with a glass transition below 100ºC. In one nonlimiting embodiment, the elastomer is spandex. In one nonlimiting embodiment, the polymeric additive is a polyurethane comprising bis(4- isocyanatocyclohexyl) methane and N-alkyldiethanolamine or a derivative thereof. In another nonlimiting embodiment, the polymeric additive is a long side chain copolymer comprising a reaction product of polystyrene and maleic anhydride. [00012] Another aspect of the present invention relates to an elastomeric composite yarn comprising the anti-slip elastomer fiber. In one nonlimiting embodiment, the elastomeric composite yarn comprises a core comprising the anti-slip elastomer fiber surrounded by, twisted with, or intermingled with hard fiber in the yarn surface which serves to protect the elastomeric fibers from abrasion during textile processes and helps to stabilize the elastic behavior of the elastomeric fiber. Composite yarns of this invention may include, but are not limited to single wrapping of the elastomer fibers with a hard yarn; double wrapping of the elastomer fibers with a hard yarn; continuously covering (i.e., core spun or core-spinning) an elastomer fiber with staple fibers, followed by twisting during winding; intermingling and entangling elastomer and hard yarns with an air jet; and twisting an elastomer fibers and hard yarns together. [00013] Another aspect of the present invention relates to a woven stretch fabric having warp and weft yarns and comprising a composite yarn comprising the anti-slip elastomer fiber. In one nonlimiting embodiment, the composite yarn comprises a sheath of at least one hard fiber and a core comprising the anti-slip fiber. [00014] Another aspect of the present invention relates to articles of manufacture comprising an elastomeric fiber with improved seam-slippage performance or a composite yarn or fabric comprising the elastomeric fiber. In one nonlimiting embodiment, the article of manufacture is a garment. [00015] Yet another aspect of the present invention relates to methods for making elastomeric fiber, composite yarn, fabric and articles of manufacture with improved elastane slippage resistance. In these methods, a polymeric additive with a glass transition below 100ºC is added to the elastomer fiber. In one nonlimiting embodiment, the elastomer is spandex. In one nonlimiting embodiment, the polymeric additive is a polyurethane comprising bis(4-isocyanatocyclohexyl) methane and N-alkyldiethanolamine or a derivative thereof. In another nonlimiting embodiment, the polymeric additive is a long side chain copolymer comprising a reaction product of polystyrene and maleic anhydride. BRIEF DESCRIPTION OF THE FIGURES [00016] FIG.1 is a photograph of a defective garment with seam slippage. [00017] FIG.2 is an illustration of elastic covered yarn with slippage. [00018] FIGs.3(A), 3(B), 3(C), 3(D) and 3(E) are schematics of various elastic composite yarns. [00019] FIGs.4A and 4B are chemical structures of nonlimiting embodiments of polymeric additives for use in the present invention. The structure of FIG.4A is a polyurethane comprising bis(4-isocyanatocyclohexyl)methane and N-alkyldiethanolamine, wherein R represents–CH 3 , -CH 2 CH 3 , -CH 2 CH 2 CH 3 , -CH 2 CH 2 CH 2 CH 3 , -C(CH 3 ) 3 3 or other alkyl groups with 18 carbons or less. In FIG.4B, R1 represents NH or O group; R2 represents alkyl or alkenyl, linear or branched C4-C22 group; and M represents a monomer which can copolymerize with maleic anhydride including, but not limited to, styrene, substituted styrene, ethylene, vinyl acetate, propene, butadiene, octadecene, acrylamide, acrylonitrile, acrylates, methacrylates, vinyl chloride [00020] FIG.5 is a schematic description of a core spinning apparatus. [00021] FIG.6 is a differential scanning calorimetry (DSC) curve of an additive PSC18. [00022] FIG.7 is a DSC curve of an additive 2PSC18. DETAILED DESCRIPTION [00023] The present invention relates to elastomeric fibers and composite yarns, fabrics and articles of manufacture comprising elastomeric fiber exhibiting improved elastane slippage resistance, easy stretch, easy processing, low shrinkage, facile garment making, excellent recovery power and low growth. [00024] More specifically, the present invention relates to anti-slip elastomer fiber comprising an elastomer and a polymeric additive with glass transition temperature below 100ºC. The invention also relates to elastic composite yarns which comprise the anti-slip elastomeric fiber. The invention is related to the stretch woven fabrics comprising such elastic composite yarns as well. The fabrics are substantially free of elastane slippage and have a desirable combination of stretch, a soft hand, excellent comfort when worn, dimensional stability, and natural fiber look and feel. The invention also relates to a process for making such fiber, yarn and fabrics, as well as garments comprising the fabric of the invention. [00025] As used herein, the term “seam slippage” or “elastane slippage” refers to when an elastomer fiber such as, but not limited to spandex, does not stay anchored and slips back in the cut end of the yarn in seam area. Thus, at one end of the yarn, there is no longer any elastane fiber as it has retracted axially inside of the yarn bundle and fabric. After the elastane fiber slips out of the seam, it creates a baggy/ wavy fabric appearance and/or non-elastic areas next to the seam line. [00026] As used herein, the terms “improved” and “reduced”, when referring to seam slippage or elastane slippage, mean a decrease in the length which the elastomeric fiber comprising an anti-slip additive in accordance with the present invention slips as compared to the same elastomeric fiber without the anti-slip additive. [00027] As used herein, the term “anti-slip” when used in reference to a fiber refers the elastane of the fiber exhibiting resistance to any slip-back from the cut edge of the yarn in seam area. [00028] As used herein, the term "rigid” or “hard” refers to a fiber or yarn which is substantially non-elastic. Examples of rigid or hard fiber include, but are not limited to, polyester, cotton, nylon, rayon and wool and any combinations thereof. [00029] Elastomeric or elastomer fibers are used interchangeably herein. An elastomer is a polymer with rubber-like elasticity. The term covers a wide range of materials. Elastomeric is an adjective for an elastomer. Elastomeric or elastomer fibers comprise an elastomer polymer. These fibers are commonly used by those skilled in the art to provide stretch and elastic recovery in fabrics and garments. “Elastomeric” or “elastomer” fibers are either a continuous filament (optionally a coalesced multifilament) or a plurality of filaments, free of diluents, which have a break elongation in excess of 100% independent of any crimp. An elastomeric fiber when (1) stretched to twice its length; (2) held for one minute; and (3) released, retracts to less than 1.5 times its original length within one minute of being released. As used in the text of this specification, “elastomeric fiber” or “elastomer fiber” means at least one elastomeric fiber or filament. Such elastomeric fibers include, but are not limited to rubber filament, biconstituent filament (which may be based on rubber, polyurethane, etc.), lastol, and spandex. [00030] “Spandex” is a manufactured fiber in which the fiber-forming substance is a long chain synthetic polymer comprised of at least 85% by weight of segmented polyurethane. Since spandex fibers are based on segmented polyurethane elastomers, spandex fiber is a sub-category of the elastomeric fibers. [00031] “Elastoester” is a manufactured fiber in which the fiber forming substance is a long chain synthetic polymer composed of at least 50% by weight of aliphatic polyether and at least 35% by weight of polyester. Although not elastomeric, elastoester may be included in some fabrics herein. [00032] “Polyester bi-component fiber” means a continuous filament comprising a pair of polyesters intimately adhered to each other along the length of the fiber, so that the fiber cross section is, for example, a side-by-side, eccentric sheath-core or other suitable cross- section from which useful crimp can be developed. The polyester bicomponent filament comprises poly(trimethylene terephthalate) and at least one polymer selected from the group consisting of poly(ethylene terephthalate), poly(trimethylene terephthalate), and poly(tetramethylene terephthalate) or a combination of such members, having an after heat- set crimp contraction value of from about 10% to about 80%. [00033] The term “elastic fiber” refers to any fiber that can provide elasticity and recovery to a stretch fabric. Elastic fibers include “elastomeric fiber”, “elastoester fiber”, spandex, “polyester bi-component filament” and others throughout the specification. [00034] A “composite yarn” is one comprising both elastic fiber surrounded by, twisted with, or intermingled with rigid fiber. The rigid fiber serves to protect the elastic fibers from abrasion during textile processes. Such abrasion can result in breaks in the elastic fiber with consequential process interruptions and undesired fabric non-uniformities. Further, the covering helps to stabilize the elastic fiber elastic behavior, so that the elongation of composite yarn can be more uniformly controlled during textile processes than would be possible with bare elastic fibers. The composite yarn also can increase the tensile modulus of the yarn and fabric, which is helpful to improve the fabric recovery power and dimensional stabilities. Multiple nonlimiting examples of composite yarns are shown in FIGs.3(A)-3(E), including FIG.3(A) continuously covering (i.e., core spinning) an anti-slip spandex with staple fibers, followed by twisting during winding; FIG.3(B) intermingling and entangling anti-slip spandex and hard yarns with an air jet; FIG.3(C) single wrapping of the anti-slip spandex with a hard yarn; FIG.3(D) double wrapping of the anti-slip spandex with a hard yarn; and FIG.3(E) twisting anti-slip spandex and hard yarns together. [00035] One nonlimiting example of a composite yarn is a “core spun yarn” (CSY), which consists of a separable core surrounded by a spun fiber sheath. For example, in a cotton/anti-slip spandex core spun yarn, the core comprises an anti-slip spandex and is covered by staple cotton fibers. [00036] As used herein, the term "fabric" refers to a knitted or woven material. The knitted fabric may be flat knit, circular knit, warp knit, narrow elastic, and lace. The woven fabric may be of any construction, for example sateen, twill, plain weave, oxford weave, basket weave, and narrow elastic and the like. [00037] As used herein, “pick-and-pick” means a weaving method and a woven construction in which one weft yarn containing an anti-slip elastomeric fiber and another weft yarn containing regular textile filament or staple fibers are woven in alternating picks. [00038] “Co-insertion” means a weaving method and a woven construction in which the low-melt fiber and a regular spun staple or filament weft yarn are woven as one, in the same pick. [00039] “Grin-through” is a term used to describe the exposure, in a fabric, of bare anti-slip spandex filaments. The term can also be applied to composite yarn, in which case grin-through refers to the exposure of the core anti-slip spandex through the covered yarn. Grin-through can manifest itself visibly as an undesirable glitter or to the touch as a synthetic feeling or hand. Low grin-through on the face side of the fabric is preferable to low grin- through on the back side of the fabric. [00040] The inventors herein have surprisingly found that upon addition of a polymeric additives with glass transition temperature below 100ºC to an elastomer such as spandex, elastane slippage is decreased. Without being bound to any theory, it is believed that this decrease in elastane slippage occurs due to migration of the polymer onto the elastomer surface during spinning and storage period. It is believed that the additives increase the adhesive and friction force between the elastomer and any sheath staple fibers, thus preventing the elastic fiber slippage during, for example, garment making, garment wet processing and home laundry. [00041] Thus, one aspect of this invention relates to an anti-slip elastomeric fiber comprising an elastomer and an effective amount of a polymeric additive with glass transition temperature below 100ºC. [00042] In accordance with this invention, the amount of the polymeric additive with glass transition temperature below 100ºC effective in producing an anti-slip fiber can vary over a fairly broad range. Improvements in the resistance of elastomeric fiber to slippage are obtained when a concentration of the polymeric additive as low as one-half percent by weight of the fiber is used in combination with conventional finishers in the fiber. However, a larger improvement is obtained when the polymeric additive is at least 1%. Although large concentrations of the polymeric additive can sometimes be used (e.g.10%), a concentration of less 5% is usually used and the preferred concentration is in the range of 1 to 3%. [00043] In one nonlimiting embodiment, the polymer additive incorporated for anti- slip characteristics is comprised of the reaction product between an aliphatic diisocyanate, and a polyol or aliphatic diol (glycol). [00044] Bifunctional aliphatic isocyanates are preferred in order to maximize efficacy of the additive by way of enhanced phase separability from the polymer, a family which includes bis(4-isocyanato-cyclohexyl)methane and 1,6-diisocyanatohexane. However, other examples of bifunctional isocyanates which may be useful in the present invention include 4,4’-methylene bis(phenyl isocyanate) (also referred to as 4,4-diphenylmethane diisocyanate (MDI)), 2,4’- methylene bis(phenyl isocyanate, 4,4’-methylenebis(cyclohexyl isocyanate), 1,4-xylenediisocyanate, 1,4-bis(isocyanatomethyl)cyclohexane, 2,6-toluenediisocyanate, 2,4- toluenediisocyanate, and mixtures thereof. Examples of specific diisocyanates include Takenate® 500 and FORTIMO® 1,4-H6XDI (Mitsui Chemicals), Mondur® MB (Bayer), Lupranate® M (BASF), and lsonate® 125 MDR (Dow Chemical), and combinations thereof. [00045] Aminodiols and other amino-functionalized polyols are the preferred polyol source, in order to impart a dye-site and improved environmental durability. Such aminodiols may include, but are not limited to, N-tert-butyldiethanolamine, N-emethyldiethanolamine, N-ethyldiethanolamine, and mixtures thereof. Other polyols may be used including, but not limited to, poly(tetramethylene ether) glycols (PTMEG), copolyether glycols such as poly(tetramethyleneether-co-ethyleneether) glycol and poly(tetramethylene ether-co-2- methyltetramethylene ether) glycol, polyester and copolyester glycols such as polycaprolactone diol and those produced by condensation polymerization of aliphatic dicarboxylic acids and diols, or their mixtures, of low molecular weights with no-more than 12 carbon atoms in each molecule, and polycarbonate glycols produced by condensation polymerization of aliphatic diols with phosgene, dialkylcarbonates or diarylcarbonates. Examples of specific commercially available glycols are Terathane® glycols (INVISTA of Wichita, Kansas, USA), PTG-L glycols (Hodogaya Chemical Co., Ltd., Tokyo, Japan), ETERNACOLL® diols (Ube Industries, Ltd., Tokyo, Japan) and STEPANPOL® polyols (Stepan, Illinois, USA). [00046] One nonlimiting example of an effective polymeric additive is a polyurethane comprising bis(4-isocyanatocyclohexyl)methane and N-alkyldiethanolamine or a derivative thereof. See, for example FIG.4A wherein the R represents a –CH 3 , -CH 2 CH 3 , - CH 2 CH 2 CH 3 , -CH 2 CH 2 CH 2 CH 3 , -C(CH 3 ) 3 or other alkyl groups with 18 carbons or less. This type of additive has adhesive functions. It is a polymeric basic amine with tertiary amine repeat units along the polymer chains, which can be used as an acid dye assist agent. It also provides some benefits in whiteness retention, when used at very high levels. It can provide substantial benefit in acid dyeability plus improvements in performance following fume gas and NOx emissions. [00047] Another nonlimiting example of an effective polymeric additive is a copolymer with long alkyl or alkenyl, linear or branched side chain. See for example FIG. 4B, wherein R1 represents NH or O group; R2 represents alkyl or alkenyl, linear or branched C4-C22 group; and M represents the monomer which can copolymerize with maleic anhydride including, but not limited to, styrene, substituted styrene, ethylene, vinyl acetate, propene, butadiene, octadecene, acrylamide, acrylonitrile, acrylates, methacrylates, vinyl chloride. This polymer additive is prepared by reacting amine or alcohol with a copolymer containing maleic anhydride. This chemical allows the elastomer to which it is added to be tackier and sticky. The additive contains -COOH, long alkyl or alkenyl, linear or branched side chain and exhibits a softening temperature below 75ºC, which may result in interaction with cotton and increase friction with staple fibers. [00048] While spandex was used as the elastomer by the inventors herein, as will be understood by the skilled artisan, other elastomeric polymers with rubber-like elasticity can be routinely used in the fiber as well as yarn, fabric and articles of manufactures comprising and are included with the scope of the present invention. [00049] When using spandex, the fibers are made from segmented polyurethane polymers, such as those based on polyethers, polyesters, polyetheresters and the like. Such polymers and preparation of the fibers from such polymers are well-known methods and described, for example, in U.S. Patent Nos.2,929,804, 3,097,192, 3,428,711, 3,553,290 and 3,555,115, the contents of which are incorporated herein by reference in their entireties. With regard to the present invention, while any segmented polyurethane polymer can be used, it has been found that spandex fibers made from polyether-based polyurethanes benefit more than others from the inclusion of the additive in accordance with this invention. For this reason, embodiments of the invention that include polyether-based polyurethanes are preferred. [00050] In making anti-slip spandex fibers according to the present invention, a solution of long alkyl or alkenyl, linear or branched side chain synthetic polymer comprising at least 85% segmented polyurethane is prepared and then dry spun through orifices into filaments. An effective amount of the polymeric additive with glass transition temperature lower than 100ºC and any other desired additives are usually dissolved or dispersed in the solvent and then added to the polymer solution at any of several points in the solution- handling system upstream of the orifices. [00051] In addition to the polymeric additive with glass transition temperature lower than 100ºC mentioned above, the anti-slip elastomeric fibers of the invention may also comprise one or more additional additives with a different purposes including, but not limited to, delustrants, additional antioxidants, dyes, dye enhancers, UV stabilizers, pigments and other function-enhancing materials. [00052] In one nonlimiting embodiment of this invention, the anti-slip elastomeric fiber is used in an elastic composite yarn comprising the anti-slip elastomeric fiber covered with sheath hard fibers. Nonlimiting examples of such composite yarns are depicted in in FIGs 3(A)-3(E). An anti-slip spandex is surrounded by, twisted with, or intermingled with at least one hard fiber or yarn. The composite yarn that comprises anti-slip elastomeric fiber and hard yarn is also termed a “covered yarn” in the text of this specification. The hard yarn sheath covers the synthetic luster, glare, and bright appearance of elastomeric fibers of spandex. The hard yarn covering also serves to protect the elastomer from abrasion during the weaving processes which can result in break in the elastomeric fiber with consequential process interruptions and undesired fabric non-uniformities. Further, the covering helps to stabilize the fiber’s elastic behavior, so that the composite yarn elongation can be more uniformly controlled during weaving processes than would be possible with bare elastomeric fiber. [00053] In one nonlimiting embodiment, the composite yarn is a core spun yarn produced by introducing an anti-slip elastomeric fiber of the present invention to the front drafting roller of a spinning frame where it is covered by staple fibers. A nonlimiting embodiment of a representative core spinning apparatus 40 is shown in FIG.5. [00054] During core spinning processing, an anti-slip fiber of the present invention is combined with a hard yarn to form a composite core spun yarn. As shown in FIG.5, the anti- slip fiber from tube 48 is unwound in the direction of arrow 50 by the action of positively- driven feed rollers 46. The feed rollers 46 serve as a cradle for the tube 48 and deliver the anti-slip fiber 52 at a pre-determined speed. [00055] The hard fiber or yarn 44 is unwound from tube 54 to meet the anti-slip fiber 52 at the set of front rollers 42. The combined anti-slip fiber 52 and hard fiber 44 are core spun together at spinning device 56. [00056] The anti-slip fiber 52 is stretched (drafted) before it enters the front rollers 42. The anti-slip fiber is stretched through the speed difference between feed rollers 46 and front rollers 42. The delivery speed of the front rollers 42 is greater than the speed of the feed rollers 46. Adjusting the speed of feed rollers 46 gives the desired draft or stretch ratio. [00057] This stretch ratio is normally 1.01 times to 5.0 times (1.01X to 5.0X) compared to the unstretched fiber. Too low a stretch ratio will result in low quality yarns having grin-through and an uncentered anti-slip fiber. Too high a stretch ratio will result in breakage of the anti-slip fiber and core void. [00058] In one nonlimiting embodiment, the core spun yarn of the present invention comprises anti-slip fiber having linear density in the range from about 10 denier to about 180 denier, for example from about 20 denier to about 140 denier. The linear density of the hard yarn can range from about 5 English cotton count (Ne) to about 60 English cotton count, for example from 6 English cotton count to about 40 English cotton count. [00059] The anti-slip fibers of the present invention can also be used in core spun yarn with two core filaments, core filament I and core filament II. Within the core spun yarn, core filament I is anti-slip elastomeric fiber, preferably anti-slip spandex and core II is control filament. These two core filaments are covered by rigid staples fibers on the surface as a sheath. In one nonlimiting embodiment, the control filament of core filament II is textured polyester, nylon, rayon filament, PPT filament, bi-component fiber, or PBT stretch fiber. The inventors herein have surprisingly found that the addition of the control filament as core filament II helps to hold the anti-slip fiber of core filament I in place and prevents its pull- back. Fabrics prepared from this dual core spun yarn have high stretch and high recovery power. In one nonlimiting embodiment, the linear density of the control filament core II ranges from about 15 denier (16.5 dtex) to about 450 denier (495 dtex), including from about 30 denier to 150 denier (33dtex to 165 dtex). Use of higher linear denier control filament may result in fabric with substantial grin through. [00060] In one nonlimiting embodiment of the present invention, the composite yarn is synthetic filament/elastic fiber air covered yarn such as shown in FIG.3(B). The term "entangling", "intermingling", "interlacing" and “covering”, (also referred to as “entangled”, ”intermingled”, ”interlaced” or “covered”), as used herein, refers to a process and product in which a jet or jets of air are directed against the yarn or yarns, usually at a 90° angle to the yarn path. For this embodiment, as depicted in FIG.3(B), during production, the speed or tension on the yarn is substantially the same at the entrance and exit of the intermingle and the resultant product has a high degree of intermingling or entangling of the filaments with anti-slip spandex. During processing, anti-slip fiber is fed to an intermingling jet together with covering rigid filament. By intermingling the rigid filament, the components are bonded together. This method is characterized by high processing speeds. Twist deadening is not required. [00061] In one nonlimiting embodiment of the present invention, the covered yarn is single covered yarn, also called single wrapping, where anti-slip fiber is wrapped with a rigid hard filament fiber such as depicted in FIG.3(C). In this nonlimiting embodiment, the anti- slip fiber is precisely elongated through a hollow spindle, covered by the rigid covering yarn, and wound on cross wound bobbins. The anti-slip fiber is only covered in one direction, either S-turn or Z-turn. These single covered yarns have a tendency to twist which can complicate further processing. However, the twisting effect can be reduced by thermal treatment streaming which reduces the extensibility. Further, this twisting effect can be reversed nearly 100% by shrinking during the finishing process. [00062] In one nonlimiting embodiment of the present invention, the covered yarn is double covered yarn, also called double wrapping, where anti-slip fiber is wrapped with two rigid hard filament fibers, such as shown in FIG.3(D). In this nonlimiting embodiment, the anti-slip spandex is precisely elongated through a hollow spindle covered by two rigid covering yarns and wound on cross wound bobbins. The doubled covered yarn is covered crosswise, i.e. in the S and the Z direction. The inner covering regulates the stretch and the outer covering compensates for the twist tendency of the yarn. The additional coverage of the anti-slip fiber by this composite yarn makes these yarns well-suited for articles that must be extremely durable. [00063] In one nonlimiting embodiment of the present invention, the composite yarn is a twisted covered yarn. In this embodiment, the spun yarns are first twisted or plied together from staple fibers. Then, anti-slip fiber is added and twisted together. Nonlimiting examples of these types of yarns include two-for-one twisted yarns and Hamel twisted yarns. In two- for-one twisted yarns, the anti-slip fiber is assembled with a rigid spun yarn on a high-speed assembly winder. The subsequent twisting is performed on two-for-one twisting frames. In this nonlimiting embodiment, the anti-slip fiber is well-covered in twists. Finished articles made of such yarns have a very high service performance and good anti-slippage. Elastic two-for-one composite yarn may also be produced using a bare anti-slip fiber. The covering operation is replaced by an assembling and drafting operation. This is done on an assembly winding machine fitted with feeder rollers to adjust the anti-slip fiber draft. During this operation, the anti-slip fiber is stretched and simultaneously assembled with the rigid fiber components. The twisting of this yarn is performed on two-for-one frames. [00064] In one nonlimiting embodiment of the present invention, the covered yarn is a hollow spindle twisted composite yarn (Hamel yarn), wherein, anti-slip fiber is covered by a spun yarn or filament. The anti-slip fiber is led through the hollow spindle, as shown in FIG. 3(E). The hard yarn is wound on a pre-twisted flanged bobbin (HD bobbin) that is subsequently put into the tube spindle. During the twisting process the HD bobbin rotates with the spindle which is fitted with a cover which hermetically seals the bobbin interior in order to avoid dirt depositions. The anti-slip spandex remains free from twists and is completely covered by the hard fiber yarn. In one nonlimiting embodiment of the present invention, the covered yarn is a Siro-spun® composite yarn. In this nonlimiting embodiment, two separate roving yarns are fed to the drafting system of a spinning frame. The anti-slip fiber is guided between the two rovings. These component yarns are combined after the last cylinder of the draft field and scrambled by a certain twist. Within the Siro-spun technique, it is possible to produce a yarn with twist characteristics in one step. Thus, the technique results in a double covered yarn consisting of individual twisted threads. The anti-slip fiber is combined with the two roving via a second feed roller whereby the anti-slip fiber has a defined draft. After the spinning process, the Siro-spun yarn can be optionally steamed optionally, and wound on tubes with the help of auto cones. As compared with core spun yarn, Siro-spun yarn have better covering and good hand feel. [00065] Stretch woven fabric comprising the anti-slip fiber the invention can be made by the following process. anti-slip fiber is combined with the hard fibers, such as filament or staple roving yarn, i.e. cotton, wool, linen, polyester, nylon, and rayon or a combination of these, to make an anti-slip fiber composite yarn. The anti-slip fiber is drafted from about 1.01× to about 5.0× of its original length during formation of the composite yarn with anti- slip fiber core. The composite yarn is then woven with at least one staple spun yarn or filament to form a fabric, which is then dyed and finished by piece dyeing or continuous dyeing methods. The anti-slip fiber composite yarn may be used in either warp or weft direction to produce warp or weft stretch fabric. The available fabric stretch (elongation) in the direction of the core spun yarn can be at least about 10% and no more than about 110%. This range of available fabric stretch provides sufficient comfort to the wearer while avoiding poor fabric appearance and too much fabric growth. The anti-slip fiber composite yarn may also be used in both the warp and weft direction of a fabric to obtain a bi-stretch fabric, one which has stretch in both the warp and the weft directions. In this case, the available fabric stretch can be at least about 10% and no more than about 110% in each direction. [00066] When anti-slip elastic composite yarn is used in one direction, for example in the weft direction, there are no particular restrictions on the fibers in the other direction of the fabric, provided the benefits of the present invention are not compromised. Spun staple fibers of cotton, polycaprolactam, poly(hexamethylene adipamide), poly(ethylene terephthalate), poly(trimethylene terephthalate), poly(tetramethylene terephthalate), wool, linen, and blends thereof can be used, as can filaments of polycaprolactam, poly(hexamethylene adipamide), poly(ethylene terephthalate), poly(trimethylene terephthalate), poly(tetramethylene terephthalate), spandex, and blends thereof. Similarly, when anti-slip composite yarn is used in the warp direction, there are no particular restrictions on the weft fibers of the fabric, provided the benefits of the present invention are not compromised. Many types of spun staple fibers and filaments, as exemplified for warp yarns, may be used in the weft direction. [00067] A variety of different fibers and yarns may be used with the fabrics and garments of some embodiments. These include cotton, wool, acrylic, polyamide (nylon), polyester, spandex, regenerated cellulose, rubber (natural or synthetic), bamboo, silk, soy or combinations thereof. [00068] In one nonlimiting embodiment of the present invention, if anti-slip fiber composite yarn is used in one direction, for example in the weft direction, a filament of yarn having stretch-and-recovery properties (for example spandex, polyester bicomponent fibers, and the like) may be used in the other direction, for example in the warp direction. In this case, the fabric can have warp stretch as well as weft-stretch characteristics. [00069] The woven fabric of the invention can be a plain woven, twill, weft rib, or satin fabric. Examples of twill fabric include 2/1, 3/1, 2/2, 1/2, 1/3, herringbone, and pointed twills. Examples of weft rib fabrics include 2/3 and 2/2 weft ribs. The fabric of the invention is suitable for use in various garments for which stretch is desirable, such as pants, jeans, shirts, and sportswear. [00070] Loom types that can be used to make the woven fabrics of the invention include airjet looms, shuttle looms, waterjet looms, rapier looms, and gripper (projectile) looms. [00071] Piece dyeing or continuous dyeing processes can be used for dyeing and finishing the fabrics of the invention. Denim fabric is an important application area for the anti-slip fiber and composite yarn of the present invention. [00072] Fabrics of the present invention have a very good, cottony hand. The fabrics feel soft, smooth, and are comfortable to wear. No anti-slip fiber exposure occurs on the fabric surface; anti-slip fiber cannot be seen or felt. The fabrics feel more natural and have better drape than conventional elastic wovens, which are usually too stretchy and have a synthetic, hot hand. ANALYTICAL METHODS [00073] The following analytical methods were used. Fabric Load and Unload Force [00074] Elongation and tenacity properties were measured on fabrics using a dynamic tensile tester Instron. The sample size was 1 x 3 inches (1.5 cm x 7.6 cm) measured along the long dimension. The sample was placed in clamps and extended at a strain rate of 200% elongation per minute until a maximum elongation was reached. The denim samples are extended from 0 to 30% elongation for three cycles. The load forces and unload forces at 12% or 30% extension were measured after the third cycle. Elastic Fiber Seam Slippage [00075] Fabric specimens are tested under standardized conditions of temperature, time and mechanical action to recreate the elastic fiber slippage that occurs in industrial garment washing and home laundering. Subsequently, elastic fiber slippage is measured according to the standard procedure shown. Two representative 50 x 50 cm fabric specimens cut parallel to the fabric length and width are prepared. Each specimen should contain different groups of warp and weft yarns. The specimen should be marked to indicate the warp direction. [00076] Each specimen is over locked stitched using the following conditions to prevent raw edges from unravelling during washing: Sewing needle: 100 –110 SUK systems; Sewing thread: 30 Nm/3 piles for both needle and bobbin thread; Stitch density: 3 – 4 stitch per cm. [00077] The fabric samples are washed and dried in following conditions: Wash machine: similar to a Tupesa TSP-15, 1 vertical machine with a single 75 cm diameter compartment; Bath temperature: 98°C; Process time: 90 munities; Liquor ratio: 1/8; Machine speed: 25-28rp; PH:10; Salt:20 gr/1; Drying temperature: 90 0 C. [00078] After finishing washing and tumble drying, the specimens are conditioned for at least 16 hours by laying each specimen as a single layer. The sample is lightly steam ironed in order to facilitate measuring. [00079] The elastic fiber seam slippage is measured as follows: along both sides of the specimen warp and/or weft direction, two spots are selected and marked. In each marked spot, the fabric is cut 5 cm in fabric width and/or length direction and the over locked stitch threads are carefully removed. Under the fabric inspection light, the weft yarns and/or warp yarn are removed one after another from the 5.0 cm area and observed for warp/weft elastic fiber. Sometime de-twisting the covered yarn is needed to find the elastic fiber. As soon as the elastic fiber is found, removal of the weft/warp yarn ceases. The distance between the fabric edge to the position of the elastic thread is measured. The average of this distance in two specimens is considered as elastic fiber slippage in millimeters. EXAMPLES [00080] The following examples demonstrate the present invention and its capability for use in manufacturing a variety of fabrics. The invention is capable of other and different embodiments, and its several details are capable of modifications in various apparent respects, without departing from the scope and spirit of the present invention. Accordingly, the examples are to be regarded as illustrative in nature and not as restrictive. Example 1: Preparation of an additive from polyurethane comprising bis(4- isocyanatocyclohexyl)methane and N-alkyldiethanolamine [00081] A polyurethane additive was prepared by reacting bis(4- isocyanatocyclohexyl)methane with N-alkyldiethanolamine. See FIG.4A. As an example, N-tert-butyldiethanolamine (1600.0g) and bis(4-isocyanatocyclohexyl)methane (2290.0g, Desmodur® W from Covestro) was added into 3287.0g dimethylacetamide (DMAC). The solution was heated to 70°C-120°C for 4-12 hours before cooling to room temperature. The molecular weight Mn = 5300 and dispersity Đ = 2.14 were measured by gel permeation chromatograph (GPC) with a refractive index detector. DMAc with 0.1% LiCl was used as eluent for GPC at 60°C and a flow rate of 1.0 mL/min. GPC was calibrated with polystryrene (PS) standards.” [00082] An example for MDEA-105: Bis(4-isocyanatocyclohexyl)methane (152.0g) was added into 300.0g DMAC in a reaction kettle. N-methyldiethanolamine (80.0g) with 100.0g DMAC was slowly added into the kettle. The solution was heated to 85°C for 6 hours before cooling to room temperature. The polymer was analyzed by GPC with molecular weight Mn = 3500 and dispersity Đ = 2.19. [00083] An example for BDEA-105: Bis(4-isocyanatocyclohexyl)methane (158.4g) was added into 360.0g DMAC in a reaction kettle. N-butyldiethanolamine (113.3g) with 120.0g DMAC was slowly added into the kettle. The solution was heated to 85°C for 6 hours before cooling to room temperature. The polymer was analyzed by GPC with molecular weight Mn = 3400 and dispersity Đ = 2.01. Example 2: Preparation of an additive from polyurethane comprising bis(4- isocyanatocyclohexyl)methane and N-methyldiethanolamine [00084] A polyurethane additive was prepared by reacting bis(4- isocyanatocyclohexyl)methane with N-methyldiethanolamine. Bis(4- isocyanatocyclohexyl)methane (152.0g) was added into 300.0g DMAC in a reaction kettle. N-methyldiethanolamine (80.0g) with 100.0g DMAC was slowly added into the kettle. The solution was heated to 85°C for 6 hours before cooling to room temperature. The polymer was analyzed by GPC with molecular weight Mn = 3500 and dispersity Đ = 2.19. Example 3: Preparation of an additive from polyurethane comprising bis(4- isocyanatocyclohexyl)methane and a diol [00085] Polyurethane additives were prepared by reacting bis(4- isocyanatocyclohexyl)methane with 2-methyl-1,3-propanediol. [00086] An example for MPD-105: Bis(4-isocyanatocyclohexyl)methane (150.8g), 2- methyl-1,3-propanediol (60.0g), K-KAT XK640 (0.04g, King Industries, Inc.), and DMAC (370.0g) were added into a reaction kettle. The solution was heated to 90°C for 6 hours before cooling to room temperature. The polymer was analyzed by GPC with molecular weight Mn = 4100 and dispersity Đ = 2.07. [00087] An example for MPenD-105: Bis(4-isocyanatocyclohexyl)methane (150.8g), 3-methyl-1,5-pentanediol (79.5g), K-KAT XK640 (0.04g, King Industries, Inc.), and DMAC (400.0g) were added into a reaction kettle. The solution was heated to 90°C for 6 hours before cooling to room temperature. The polymer was analyzed by GPC with molecular weight Mn = 4500 and dispersity Đ = 2.10. [00088] An example for PD-105: Bis(4-isocyanatocyclohexyl)methane (150.8g), 1,5- pentanediol (70.8g), K-KAT XK640 (0.04g, King Industries, Inc.), and DMAC (385.0g) were added into a reaction kettle. The solution was heated to 90°C for 6 hours before cooling to room temperature. The polymer was analyzed by GPC with molecular weight Mn = 4500 and dispersity Đ = 2.14. Example 4: Preparation of long side chain copolymer [00089] A long side chain copolymer was prepared by reacting alkyl or alkenyl, linear or branched amine or alcohol with anhydride group in poly (M-co-maleic anhydride) copolymer. See FIG.4B. In a typical experiment, poly(M-co-maleic anhydride) was dissolved in dimethylacetamide (DMAC) solution, which was followed by adding alcohol or amine. The mixture was heated to 50-120°C for 1-10 hours. The reaction was fully converted by the disappearance of 1854 cm -1 and 1772 cm -1 peaks from FT-IR (vibration of anhydride group). [00090] A poly(styrene-co-maleic anhydride) is commercially available as XIRAN® from Polyscope company. A stearamine is commercially available as Armeen 18D from Nouryon company.41.70g poly(styrene-co-maleic anhydride) (XIRAN® 1000, 474 mg/KOH acid value) was added into 250.0g dimethylacetamide (DMAC) in a reaction kettle. After the solid was dissolved, 44.10g stearamine (Armeen 18D) was added into the solution and heated to 85°C for 4 hours. The long side chain copolymer PS-C18 solution was formed by cooling to room temperature. The polymer was recovered by removing DMAC solvent under vacuum. The glass transition temperature (Tg) of PS-C18 polymer was 55.85°C, as measured by differential scanning calorimetry (DSC) (FIG.6). [00091] The 2PS-C18 polymer was prepared similarly by reacting XIRAN® 2000 (370 mg/KOH acid value) with Armeen 18D. The Tg of 2PS-C18 was 41.37°C, as measured by DSC (FIG.7). Example 5: Fiber Spinning Process [00092] For all examples, 100.00 parts of Terathane® 1800 was reacted with 23.46 parts of Isonate® 125MDR to produce an isocyanate-terminated prepolymer. The concentration of the isocyanate terminal groups in the formed prepolymer was at 2.60% by weight of the prepolymer. This prepolymer was mixed with and dissolved into N,N-dimethylacetamide (DMAc) to give a solution with about 45% solids by weight, and then further reacted with a DMAc solution containing a mixture of ethylenediamine (EDA) and 2-methylpentanediamine with a molar ratio of 90 to 10 and diethylamine (DEA) to form a viscous poly(urethane urea) solution with 35% polymer solids. [00093] This polymer solution was mixed with additives in a slurry form, at a level producing approximately 1.35% of LOWINOX® GP45 antioxidant, 0.54% silicone-oil based spinning aid, 1.50% huntite/hydromagnesite, and 0.17% titanium oxide powder based on the total weight of the solids. The resulting polymer solution including the mixed additives was spun into a 44 dtex 5 filament spandex fiber using a dry-spinning process at a wound-up speed of 869 meters per minute. For different examples, various levels of polyurethane-based anti-slip additive are blended into the polymer in slurry form. All examples are spun under similar conditions in terms of decitex (44dtex) and spinning speed. Example 6: Elastic Composite Yarn and Fabric Making [00094] For each of the following denim fabric examples, 100 % cotton open end spun yarn or ring spun was used as warp yarn. Denim fabrics included two count yarns: 7.0 Ne OE yarn and 8.5 Ne OE yarn with irregular arrangement pattern. The yarns were indigo dyed in rope form before beaming. Then, they were sized and wound onto the weaving beam. [00095] Several composite yarns with elastic fibers and low-melt fibers were used as weft yarn, including core spun, air jet covering, and dual core spun. Table 1 lists the materials and processes that were used to make the composite yarns for each example. Lycra® spandex are available from The LYCRA Company, Wilmington, Delaware. [00096] Stretch woven fabrics were subsequently made, using the composite yarn of each example. Table 1 summarizes the yarns used in the fabrics, and the seam slippage length of the fabrics. Unless otherwise noted, the fabrics were woven on a Donier air-jet or rapier loom. Loom speed was 500 picks/minute. The fabric was 3/1 twill. The widths of the fabric were about 76 and about 72 inches in the loom and greige state respectively. The loom has double weaving beam capacity. [00097] Each greige fabric in the examples was finished by a jiggle dye machine. Each woven fabric was pre-scoured with 3.0 weight % Lubit ^64 (Sybron Inc.) at 49°C for 10 minutes. Afterwards it was de-sized with 6.0 weight % Synthazyme ^ (Dooley Chemicals. LLC Inc.) and 2.0 weight % Merpol ^ LFH (E. I. DuPont Co.) for 30 minutes at 71°C and then scoured with 3.0 weight % Lubit ^ 64, 0.5 weight % Merpol ^ LFH and 0.5 weight % trisodium phosphate at 82°C for 30 minutes. Example A: 44dtex Anti-slip spandex fibers and core spun yarns [00098] Example A includes a group of spandex fibers and cotton core spun yarn and fabrics. The spandex fibers are made various finishes, ingredients and with or without anti- slip polymeric additives. The bis(4-isocyanatocyclohexyl)methane with N- alkyldiethanolamine are used as anti-slip polymeric additives.14s cotton core spun yarns with these spandex fibers are made under draft 3.5X.1/3 twill denim fabrics are woven with 40 picks per inch and finished. The spandex slippage length was then tested. [00099] Sample 1 is a Comparative Example as no anti-slip polymeric additive is added. The fabric has very high seam slippage, 28.7 mm. Such fabric has high risk for producing a defective garment related to slippage after laundering. The fabric load force at 30% elongation is 1616.6 grams and unload force (recovery force) at 12% elongation is 156.2 grams. [000100] In Sample 2, 2% of anti-slip polymeric additive is added during the fiber spinning process. The test data shows the fabric slippage to be reduced dramatically to 9.4% (see Table1). Such fabric has very low risk for slippage related defects after garment wash processes. [000101] In Sample 3, 3% of anti-slip polymeric additive is added into the fiber. The fabric slippage length is also at a very low level (9.5 mm). [000102] In Sample 4, high content level of mineral chloride resist is added while keeping anti-slip polymeric additive as 3%. The fabric still maintains slippage length at a low level (11.1%). [000103] Sample 5 demonstrates that even after adding an anti-tack additive, spandex with anti-slip polymeric additive still performs well at anti-slippage. The fabric anti-slippage length is 11.7 mm. The fabric load force at 30% elongation is 1880 grams and the unload force (recovery force) at 12% elongation is 191.5 grams. As compared with Sample 1, this fabric of Sample 5 continues to provide comfort and move freedom while maintaining excellent recovery. [000104] Sample 6, which is 44 dtex anti-slippage spandex with 3 filaments also has a very low slippage level after adding anti-slip polymeric additive. The slippage length is 12.2 mm, which is similar to 44 dtex spandex with 5 filament fiber (Sample 5). The fabric load force at 30% elongation is 1686.2 grams and unload force (recovery force) at 12% elongation is 145.2 grams. [000105] Sample 7 utilizes an anti-slip additive based on bis(4-isocyanatohexyl)methane with N-methyldiethanolamine, and was spun as a 44 dtex anti-slippage spandex with 5 filaments. The fiber slippage length is 9.4 mm, which is similar to 44 dtex spandex with 5 filament fiber (Sample 5). The fabric load force at 30% elongation is 2377.2 grams and unload force (recovery force) at 12% elongation is 259.1 grams. [000106] Sample 8 utilizes an anti-slip additive based on bis(4-isocyanatohexyl)methane with 3-methyl-1,5-pentanediol, and was spun as a 44 dtex anti-slippage spandex with 5 filaments. The fiber slippage length is 14.9 mm, which also yields improved performance relative to the control (Sample 1). The fabric load force at 30% elongation is 2398.0 grams and unload force (recovery force) at 12% elongation is 250.0 grams. Example B: 78dtex Anti-slip spandex fibers and core spun yarns [000107] Example B include two types of anti-slip 77 dtex spandex fiber and cotton core spun yarn and fabrics. The spandex fibers have 5 filaments. [000108] The spandex in Sample 7 is a Comparative Example of spandex without anti- slip additive. The fabric made from this fiber has very high seam slippage, 20.2 mm, as shown in Table 1. The fabric load force at 30% elongation is 1639.5 grams and unload force (recovery force) at 12% elongation is 232.1 grams. [000109] In Sample 8, 2% anti-slip polymeric additive of bis(4- isocyanatocyclohexyl)methane with N-alkyldiethanolamine was added to the spandex during fiber making. The fabric seam slippage length reduced to 13.5 mm, which indicates the fabric has low risk for producing defective garments related to spandex slippage after garment wash. The fabric load force at 30% elongation is 1599.7 grams and unload force (recovery force) at 12% elongation is 284.9 grams. Thus, as compared with Sample 7, adding anti-slip additives does not affect fabric load force and unload force which are related to fabric comfort and shape retention. Example C: Anti-slip spandex fibers with long side chain additive [000110] Example C includes three spandex fibers and cotton core spun yarns and fabrics. The spandex fibers are made with or without anti-slip polymeric additives. The long side chain polymer is used as the anti-slip polymeric additive.14s cotton core spun yarns with these spandex fibers were made under draft 3.5X.1/3 twill denim fabrics were woven with 40 picks per inch and finished. [000111] Sample 9 is a Comparative Example of 50 dtex spandex with no anti-slip polymeric additive added. The fabric has a high seam slippage of 20.4 mm. This fabric has a high risk for producing defective garments related to slippage after laundering. [000112] In Sample 10, 2% of the anti-slip polymeric additive PS-C18 was added during the fiber spinning process. The fabric slippage reduced to 17.1 mm (see Table1). [000113] In Sample 11, 2% of another type anti-slip polymeric additive, 2PS-C18, was added into the fiber. The fabric slippage length reduced even lower in this Sample to 15.4 mm. Example D: Two Step covered composite yarns [000114] Example D includes four pieces of core spun composite yarns and fabrics comprising double filaments as core and covered by cotton staple fiber as sheath. The composite yarn is made with three types of yarns: a first type 1 of sheath fiber, a second type 2 of spandex fiber, and a third type yarn 3 of anchor filament, wherein, the elastic fiber and anchor fiber adhere together in discontinuous bonding knots. The yarns are made through a two-step process. [000115] In the first step, the spandex fiber and anchor filament are interlaced together through an air jet covering process. After the air covering process, spandex fiber and anchor filament form the pre-bounded composite core. Then, in the second step, the pre-bounded composite core is covered by cotton on the yarn surface in a core spun machine. The sheath fiber cotton covers the yarn surface to provide authentic appearance and soft touch. The pre- bonded composite core can provide a bonding force to help preventing the spandex slippage during garment making, garment wet process and home laundry. [000116] Sample 12 is a Comparative Example wherein the spandex fiber is 44/5 dtex without anti-slip polymeric additive. The anchor filament is 75d/144f polyester textured filament. These two filaments are pre-bonded together at an air jet covering machine. Then this pre-bonded filament is covered by cotton in core spun yarn to form 14S cotton core spun yarn. Finally, this core spun is woven into denim fabric with 40 picks per inch. The slippage of this fabric is 14.3 mm. [000117] Sample 13 has the same yarn and fabric structure as Sample 12. The only difference is the spandex contains 2% of anti-slip polymeric additive of bis(4- isocyanatocyclohexyl)methane with N-alkyldiethanolamine. As shown in Table 1, the fabric slippage is 4.5 mm. [000118] Sample 14 is also a Comparative Example having the same spandex fiber, yarn structure and fabric structure as Sample 12. The only difference is the anchor filament: 75D/34f polyester bi-component LYCRA® T400® Fiber made by The LYCRA® Company. The fabric slippage is 4.9 mm. [000119] Sample 15 has the sample yarn and fabric structure as Sample 14. The only difference is the spandex contains 2% of anti-slip polymeric additive of bis(4- isocyanatocyclohexyl)methane with N-alkyldiethanolamine. As shown in Table 1, the fabric slippage is 2.8 mm. Example E: Double Core composite yarns [000120] Example E includes four pieces of core spun composite yarns and fabrics comprising double filaments as the core and covered by cotton staple fiber as the sheath. The composite yarn is made with three types of yarns: a first type 1 of sheath fiber, a second type 2 of spandex fiber, and a third type yarn 3 of anchor filament, wherein, the elastic fiber and anchor fiber are directly fed into the core spun yarn machine without any pre-bound processing such as performed in Example D. [000121] Sample 16 is a Comparative Example with 44/5 dtex spandex fiber without any anti-slip polymeric additive. The anchor filament is 75d/144f polyester textured filament. These two filaments are directly fed into the core spun yarn machine and covered by cotton to form 14S cotton core spun yarn. This yarn is then woven into denim fabric with 40 picks per inch. The slippage of this fabric is 20.8 mm. [000122] Sample 17 has the sample yarn and fabric structure as Sample 16. The only difference is the spandex contains 2% of anti-slip polymeric additive bis(4- isocyanatocyclohexyl)methane with N-alkyldiethanolamine. As shown in Table 1, the fabric slippage is 8.5 mm. [000123] Sample 18 is a Comparative Example having the same spandex fiber, yarn structure and fabric structure as Sample 16. The only difference is the anchor filament: 75D/34f polyester bi-component LYCRA® T400® Fiber made by The LYCRA® Company. The fabric slippage is 8.0 mm. [000124] Sample 19 has the sample yarn and fabric structure as Sample 18. The only difference is the spandex contains 2% of anti-slip polymeric additive of bis(4- isocyanatocyclohexyl)methane with N-alkyldiethanolamine. As shown in Table 1, the fabric slippage is 5.9 mm. Example F: Air Jet covered composite yarns [000125] Example F includes two pieces of air covered composite yarns and the fabrics. 225D polyester textured filament are interlaced with 44 dtex spandex. [000126] Sample 20 is a Comparative Example with no anti-slip additive added. The fabric slippage length is 15.4 mm. [000127] In sample 21, the spandex added contains anti-slip polymeric additive bis(4- isocyanatocyclohexyl)methane with N-alkyldiethanolamine. The fabric slippage is 10.0 mm. Table 1