March 19, 1963 F. J. EVANS 3,081,516 ACRYLONITRILE POLYMER FABRICS Filed Dec

March 19, 1963 F. J. EVANS 3,081,516 ACRYLONITRILE POLYMER FABRICS Filed Dec. 5, 1958 , INVENTOR FRANKLIN JAMES EVANS BY ATTORNEY 1 1 assists? United States Patent 0 Patented Mar‘. 19, 1%53 1 2 improved resistance to pilling and greater aesthetic appeal 3,081,516 ACRYLONITRILE P?LYMER FABRICS along with greater softness and loftiness. These fabrics Franklin James Evans, Wilmington, Dek, assignor to are prepared from a yarn comprising a blend of high and E. 1. du Pont de Nemours and Company, Wilmington, low shrinkage acrylonitrile polymer ?bers, the weight Del., a corporation of Delaware ratio of low shrinkage ?bers to high shrinkage ?bers in Filed Dec. 5, 1958, Ser. No. 778,274 the yarn being about 1.85, the low shrinkage ?bers having 1 Claim. (£1. 28-78) a residual shrinkage of less than about 1% with less than 3 crimps per inch, and the high shrinkage ?bers having This invention is concerned with improved yarns and a residual shrinkage of about 18 to 25% and having a fabrics containing synthetic ?bers. 10 mechanical crimp level of about 20 crimps per inch as Synthetic ?bers have achieved notable acceptance for measured immediately after the mechanical crimping industrial and textile applications, but before they could process is completed and prior to fabric formation. be used widely for apparel fabrics, it was necessary that The drawing is a greatly enlarged plan view of fabric there be developed methods by which they could be han knitted as described except that an open structure is illus dled readily and uniformly on existing commercial textile 15 trated so that details are more readily visible. machinery. t was found, for example, that when syn In a preferred embodiment of this invention, fabrics thetic ?bers in staple length were used in applications are prepared from yarns having 11 turns per inch twist, where wool ?bers had previously been used, they could of blended high-shrinkage and low-shrinkage ?bers of not readily be made into yarns suitable for knitting or acrylonitrile polymers containing at least about 85% weaving. Because of the smooth surface and uniformity combined acrylonitrile. In these blended yarns the ?bers of synthetic staple ?bers, they lacked cohesiveness, and have a final size of 6 denier per ?lament or less. Prefer card sliver prepared from these ?bers tended to be fragile ably, the denier of the low shrinkage ?bers is from 1 to 33, and readily split so that processing a card sliver was di?i inclusive, and the high shrinkage ?bers are about 3 denier. cult. Moreover, woven and knitted fabrics made from Such yarns are particularly suited to the manufacture of synthetic ?ber staple yarns are not equivalent to similar 25 knitted sweaters with outstanding resistance to pilling and wool fabrics because the synthetic materials lacked the with particularly desirable aesthetic properties such as a bulky resilient handle characteristic of woolen materials. soft, warm, light handle comparable to cashmere. These two di?iculties were ameliorated simultaneously The crimp level at which these results are obtained is by the discovery that introduction of a reasonable degree unexpectedly critical. Improved aesthetic qualities have of crimp into synthetic ?ber staple provide inter?ber co~ 30 always been sought, but no particular degree of crimp of hesiveness leading to satisfactory ease of ?ber processing fibers has been deemed by the art to be important for and yarn preparation, and at the same time gives to the aesthetic values. The major value of crimped ?bers has ?nished fabric the desired loftiness, bulkiness and Warm been thought, heretofore, to lie in processing character handle generally associated with wool fabrics. The prep istics; that is, the ?ber should be crimped suf?ciently so aration of crimped acrylic ?bers is shown in U.S. Patent 35 that the ?bers hold together during the preparation of 2,747,233 to Hitt. yarn. It is now known that most existing process steps can It has now been found that the 8-12 crimps/inch be carried out with synthetic ?ber staple quite readily if which has been regarded heretofore as most satisfactory the ?bers are crimped. in general, staple ?bers containing for commercial operation is the level which is least sat from 4 to 50 crimps per inch have been utilized, and no 40 isfactory for the production of fabrics which have out preference has been noted for any particular crimp level standing aesthetic appeal and greatly improved resistance in this range. Currently accepted practice in the process to pilling. All ?bers in the yarns of this invention have ing of synthetic staple ?bers is to use ?bers having be a crimp level of from 0 to about- 3 crimps per inch, or tween 8 and 12 crimps per inch. greater than about 17 crimps per inch. Fabrics of synthetic ?ber staple yarns are extremely 45 The high-shrinkage and low-shrinkage acrylic ?bers of easy to care for. They do not shrink in washing, and this invention can be obtained in any one of several they dry rapidly. However, along with these advantages ways; for example, the high-shrinkage and the low there are certain disadvantages, such as the tendency to shrinkage yarns may have slightly varying chemical com pill. Pilling is a well-known phenomenon which may be position or may have been treated by different drawing described as the tendency to form small balls of inter 50 processes or by different thermal processes at any of sev entangled ?ber ends on the surface of a fabric. eral stages in their preparation. One suitable Way of Fabrics prepared from continuous ?lament yarns do obtaining blends of high-shrinkage and low-shrinkage not pill to any notable extent because there are very few yarns is to start with a heavy denier tow of acrylic ?ber loose ?ber ends in any small surface area. Fabrics pre which already has a moderate degree of crimp. The pre pared from wool ?bers pill just as readily as fabrics from 55 synthetic ?bers, but because of the lower tenacity of wool cise level of crimp is‘ not important at this stage. This ?bers, the pills break off rapidly as they are formed and tow is subjected to an additional drawing step and then there is little or no degradation of the fabric appearance. is broken into staple ?bers by the action of breaker bars With synthetic ?bers, however, when a pill forms, it is (serrated or gear-like intermeshing opposed rollers with roughened surfaces which break the continuous ?la attached to the fabric surface by a few single ?ber strands 60 which, because of their high tenacity, are not readily ments into random staple-length ?bers). During the re broken, and, therefore, the pill remains. It is possible drawing and breaking operations, all crimp initially pres to brush or to clip such fabrics and remove such pills, but ent in the tow is removed. Then, the broken sliver is it would be desirable to provide fabrics with better pill crimped to any .desired degree in a mechanical crimping resistance and with improved aesthetic properties. process such as that already referred to above in US. According to this invention there are provided fabrics Patent 2,747,233. of acrylic staple ?ber yarn, knitted with a courses per Following the crimping, a portion of the sliver is sub inch x wales per inch count of at least about 350, having jected, in a relaxed state, to a heat-treatment which 3 4 shrinks the ?bers, leaving less than 5% residual shrink The acrylic ?ber tow from which the yarns are made age in the sliver. Preferably, the sliver, after the heat possessed about 8 crimps per inch, but this crimp is re treatment, retains less than 1% residual shrinkage. A moved in the staple-forming process which redraws the portion of the sliver ?bers which have not thus been yarn to give a tow free-of-crimp. Following breakage relaxed and heat-set retains at least 15% residual shrink to form staple ?ber sliver, the sliver is crimped at the age and preferably more than 18% residual shrinkage level indicated and also subjected to a di?'erential shrink which will be activated by contacting with hot water. age treatment in which part of the sliver is heat-set and The two portions of sliver are then combined and drafted part of the sliver is not heat-set so as to set up the indi into a yarn and this yarn becomes a high bulk yarn when cated shrinkage differential. Other means of introducing it is treated with hot water as, for example, in a dyeing 10 differential shrinkage are also satisfactory and any such process when the yarn is either in skeins or in the form technique is suited to the practice of the present of a ?nished fabric. invention. Pilling propensity can be measured by actual wearing It should be noted that crimp is needed in preparation or subjecting standard fabrics to precisely controlled lab— of yarns only to permit easy formation of a staple sliver oratory treatments suited to develop the maximum level 15 from loose staple. If the present invention is practiced of pills on the surface. A number of laboratory treat employing very low crimp yarn, then it is advisable to ments are available for the testing of pilling propensity. use a yarn-spinning process which does not require for One is described in an article entitled “Random Tumble mation of a card sliver, but rather permits the prepara . Pilling Tester” by E. M. Baird, L. C. Legere, and H.

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