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  Elastic fabric including elastic fiber and hard yarn and methods for makingUSPTO Application #: 20070259583Title: Elastic fabric including elastic fiber and hard yarn and methods for making Abstract: Methods for making stretch fabric having stretch between 10% to 45% in the weft and/or warp direction are disclosed. A corespun composite elastomeric yarn is produced either (a) by low draft (2.7× or below) core-spinning of the elastomeric yarn, or (b) by pretreating the corespun composite yarn in steam or heated water at temperatures of at least 110° C. to reduce yarn power before dyeing or weaving. The fabric with such corespun composite elastomeric yarn in the weft meets end-use specifications without heat-setting. (end of abstract) Agent: Invista North America S.a.r.l. - Wilmington, DE, US Inventors: Graham H. Laycock, Raymond S.P. Leung, Tianyi Liao, Federica Maria Roberta Stoppa USPTO Applicaton #: 20070259583 - Class: 442184000 (USPTO) Related Patent Categories: Fabric (woven, Knitted, Or Nonwoven Textile Or Cloth, Etc.), Woven Fabric (i.e., Woven Strand Or Strip Material), Woven Fabric Has An Elastic Quality, Including Elastic Strand Or Strip The Patent Description & Claims data below is from USPTO Patent Application 20070259583. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This application is a continuation-in-part of U.S. application Ser. No. 11/268,112, filed on Nov. 7, 2005, which claims the benefit of U.S. Application No. 60/626,698 filed Nov. 10, 2004, both of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention relates to methods for making corespun composite elastic yarns and stretch woven fabrics from such yarns. [0004] 2. Summary of the Related Art [0005] Stretch woven fabrics have been produced for nearly 30 years. Those working in the textile industry, such as yarn spinners, weavers, dyers/finishers, cutters and designers, understand that consumers desire fabrics and garments made with quality standards. However, lightweight stretch woven shirting fabrics (weighing less than 175 g/m.sup.2) generally are more difficult to produce since normal elastane fibers such as spandex have too much stretch power, and thus too tightly contract, resulting in fabrics that are too tight and too heavy. The jammed fabric structure results in shirting fabrics with higher shrinkage, a harsher, non-cottony fabric hand, and thermal discomfort during wear. Heat-setting may be a necessary step in the process to making lightweight (less than 175 g/m.sup.2) spandex stretch shirting fabrics with high comfort. [0006] Even for heavy weight jeans, it is still difficult to produce denim with stretch in warp direction. There are some limited warp stretch denims in the market; however, these fabrics have undesirable properties including high shrinkage, high shrinkage variation, significant weft yarn distortion and excessive stretch. [0007] The warp yarns in denim are usually dyed into blue or black color with an indigo dye before weaving. The unique hue of clothes made from woven fabric dyed with indigo dye and the favorable change in that hue which occurs over time and after repeated washing by bleaching make it possible to design articles of clothing based on this sensitivity to hue change. [0008] Most stretch woven fabrics are made with elastomeric yarns in the direction in which the stretch will exist. For example, elastomeric yarns are used as warp yarn in order to make warp stretch fabrics. [0009] Typically, stretch denim can use composite yarn made with 70 denier (78 dtex) and 40 denier (44 dtex) spandex. The spandex (elastane) can be stretched to about 3.5.times. to about 4.0.times. machine draft during the yarn covering process. Such typical core spun yarn can have a high stretch. During the indigo yarn dyeing process under hot water, a stretched elastane fiber will recover causing the core spun combination yarn to shrink and subsequently coil and twist together. This shrinking and twisting makes it difficult to keep the yarn straight in further processing. After yarn dyeing, a non-uniform yarn sheet having a non-uniform tension amount the yarns is difficult to use in a warping and weaving operation. These difficulties may reduce the beaming and weaving efficiency or even make operation impossible, due to yarn end breaking, machine stopping and unacceptable fabric appearance. [0010] Moreover, the fabrics made from such yarns have poor quality. Specifically, these fabrics have high wash shrinkage, dimensional instability, poor recovery and high skew on the fabrics. [0011] For stretch woven fabric, most of the elastomeric yarns are used in combination with relatively inelastic fibers, such as polyester, cotton, nylon, rayon or wool. These relatively inelastic fibers sometimes are called "hard" fibers. [0012] Elastomeric fibers are commonly used to provide stretch and elastic recovery in woven fabrics and garments "Elastomeric 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 this application, "elastomeric fibers" should be interpreted to mean at least one elastomeric fiber or filament Such elastomeric fibers include, but are not limited to, rubber filament, biconstituent filament and elastoester, lastol, and spandex [0013] "Spandex" is a manufactured filament in which the filament-forming substance is a long chain synthetic polymer comprised of at least 85% by weight of segmented polyurethane. [0014] "Elastoester" is a manufactured filament 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. [0015] "Biconstituent filament" is a continuous filament comprising at least two polymers adhered to each other along the length of the filament, each polymer being in a different generic class, for example, an elastomeric polyetheramide core and a polyamide sheath with lobes or wings. [0016] "Lastol" is a fiber of cross-linked synthetic polymer, with low but significant crystallinity, composed of at least 95% by weight of ethylene and at least one other olefin unit. This fiber is elastic and substantially heat resistant. [0017] A "covered" elastomeric fiber is one surrounded by, twisted with, or intermingled with hard yarn. The covered yarn that comprises elastomeric fibers and hard yarns is also termed a "composite yarn" in this application. The hard-yarn covering serves to protect the elastomeric fibers from abrasion during weaving processes. Such abrasion can result in breaks in the elastomeric fiber with consequential process interruptions and undesired fabric non-uniformities. Further, the covering helps to stabilize the elastomeric fiber elastic behavior, so that the composite yarn elongation can be more uniformly controlled during weaving processes than would be possible with bare elastomeric fibers. [0018] There are multiple types of composite yarns, including: (a) single wrapping of the elastomer fibers with a hard yarn; (b) double wrapping of the elastomer fibers with a hard yarn; (c) continuously covering (i.e., core spinning) an elastomer fiber with staple fibers, followed by twisting during winding; (d) intermingling and entangling elastomer and hard yarns with an air jet, and (e) twisting an elastomer fibers and hard yarns together. The most widely used composite yarn is a cotton/spandex corespun yarn. A "corespun yarn" consists of a separable core surrounded by a spun fiber sheath. Elastomeric corespun yarns are produced by introducing a spandex filament to the front drafting roller of a spinning frame where it is covered by staple fibers. [0019] A representative core-spinning apparatus 40 is shown in FIG. 1. During core-spin processing, an elastomeric fiber, such as spandex, is combined with a hard fiber to form a composite corespun yarn. The spandex from tube 48 is unwound in the direction of arrow 50 by the action of positively-driven rollers 46. The rollers 46 serve as a cradle for the tube 48 and deliver the spandex filament or yarn 52 at a pre-determined speed. [0020] The hard fiber or yarn 44 is unwound from tube 54 to meet the spandex filament 52 at the set of front rollers 42. The combined spandex filament 52 and hard fiber 44 are core-spun together at spinning device 56. [0021] The spandex filament 52 is stretched (drafted) before it enters the front rollers 42. The spandex 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 the feed rollers 42 gives the desired draft, which is known as the machine draft. Normally, the machine draft for corespun elastomeric composite yarns is from about 3.0.times. to about 4.0.times. including from about 3.0.times. to about 3.8.times.. This corresponds to a spandex elongation of 200% to 300%, or more. The stretching of the spandex imparts elasticity to the final corespun yarn because the spandex core will retract when stress is removed, thus compacting and bulking the spun yarn cover. The resulting composite yarn can then be extended to the point where the non-elastic cover yarn is stretched to its limit [0022] Referring to FIG. 2, a representative method for making a core-spun elastomeric yarn and weaving that yarn to form a stretch fabric is disclosed. The elastomeric fiber and hard yarn, denoted as cotton in FIG. 2, are combined by core-spinning such as by the apparatus of FIG. 1, to form a composite corespun yarn 10. In the example processing method set out in FIG. 2, this composite corespun yarn is twist set 12 (i.e., treated with steam at temperatures of about 70.degree. C. to about 80.degree. C., sometimes up to 110.degree. C.), wound 14, scoured, and/or bleached and dyed 16, rewound 18, woven into a shirting fabric 20, singed 21, de-sized 22, scoured, and/or bleached and dyed 24 and heat set at temperatures of 190.degree. C. or greater 26, and sanforized 28. [0023] For shirting, the yarn preparation processes may include scouring and/or bleaching, and dyeing including package dyeing. For denim, the yarn preparation processes may include yarn rope dyeing, slasher dyeing, and beam dyeing. Continue reading... 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