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. E. tion of sliver direct from tow. If a high level of crimp Stanley, Textile Research Journal, 26, 731-735 (1956). 20 is employed, it is also possible to form a conventional The testing process used in this article is the one em card sliver as in cotton or worsted systems and process ployed in obtaining the results .disclosed herein. Other the yarn into spun yarn without difficulty. methods for determining pilling tendency of fabrics are The residual shrinkage of all low-shrinkage ?bers in also available; for example, Technical Information Bul the examples is less than 1%, and the residual shrinkage letin No. X-46 issued December 1955, by the Technical of all high-shrinkage ?bers is 18-25%. The term “resid Service Section of the Textile Fibers Department of the ual shrinkage” is the loss in length which a fiber or yarn E. I. du Pont de Nemours and Company, Incorporated, will undergo when heated in a relaxed state with boiling describes a means of determining the pill tendency of water for 5 minutes. A yarn or ?ber with a residual woven fabrics employing a brush and sponge pilling shrinkage of 18% will retract to 82% of its original tester made by the Custom Scienti?c Instruments Com 30 length when heated under these conditions. pany, Incorporated, of Arlington, New Jersey. Examples 1-9 illustrate fabrics of this invention, and Aesthetic appeal, of course, is a subjective quality and Examples 10-14 illustrate fabrics outside of the invention. cannot be measured by instruments without reference to Examples 11-14 are commercial sweater fabrics. Wor individual preferences. However, it is possible to make sted count of all fabric yarns is 2/132. a statistically signi?cant estimate of aesthetic properties 35 The pill level rating indicated in the tables has the of two fabrics relative to one another by the use of a following signi?cance: large number of individual opinions. Such opinions are obtained by presenting to each person of a selected group, two fabrics of which he is to select one as preferable to (l)=very satisfactory-substantially no pills the other on aesthetic grounds. If such preferences are 40 (2)t=satisfactory-few pills made on a number of samples with proper regard to back (3)i=borderline satisfactory-several pills ehecking to determine consistency of choice, and if a (4)'=objectionable-considerable pilling large enough number of opinions are so gathered, it is (5) =very objectionable-heavy pilling found that the opinions of one group so determined will agree in a statistically signi?cant manner with the opin 45 ions of another different group who have evaluated the The pill level in Example 1 through 10 was measured same fabrics. Thus, it is possible to rate fabrics for after actual wear test for the indicated number of hours. aesthetic appeal relative to one another and to be sure The laboratory pill test indicated for Example 10‘ through that such ratings have a real degree of validity. 14 was carried out on the Random Tumble Pilling Tester In rating aesthetic appeal of fabrics, results may be 50 mentioned above. As shown in Example 10, wear test expressed in a number of different ways. One conven and laboratory test correlate very closely. ient method, that used in the description which follows Practice of the present invention is suitable over a below, consists of comparing the total number of choices wide range of fabric constructions to produce superior possible with the number of times any particular fabric fabrics so long as the primary requirements of crimp is selected as preferable over a comparison fabric. That level and yarn shrinkage characteristics are met. If a is, if a given fabric is compared with each of ?ve other crimp level outside of the range speci?ed in this inven fabrics, it could be graded as more preferable or less tion is employed, the aesthetic rating may be satisfactory, preferable ?ve times by each person making a choice. If but the pilling propensity is very high. If ?ber denier out twenty people participate in rating this group of fabrics, side of the preferred range is employed, the aesthetic be any one fabric can be selected 20x5 or 100 times. If a 60 havior of the fabric suffers accordingly. Examples 1 particular fabric is selected as preferable 75 times during through ‘8 show preferred sweater fabric constructions. this test, its aesthetic rating is 75%. Example 10 shows a sweater construction outside the The following examples illustrate speci?c embodiments limits of the present invention, and it can be seen the of the invention: All fabrics are sweaters prepared from results with this sweater are poor from an aesthetic ?bers of acryonitrile polymer containing about 94% 65 standpoint and in pilling performance. Examples 12 combined acrylonitrile and about 6% methylacrylate through 14 are commercial sweaters purchased in the spun into high bulk yarn; that is, a yarn containing both open market, laboratory tested and analyzed to deter high-shrinkage and low-shrinkage staple ?bers. The mine their construction. These sweaters are satisfac yarns are varied as the examples show to provide illus tory from an aesthetic standpoint, but are very poor in tration of the effect of various construction factors on 70 their pilling tendency. Only fabrics in which both crimp the aesthetic value and pilling tendency of the sweater level and shrinkage requirements are in accord with the fabrics. Sweaters are knit on a 24 gauge full-fashioned teachings of the present invention are superior in both machine using a jersey stitch. Some of the examples in factors. It is, of course, possible and within the scope of the table show a similar evaluation of commercial this invention to combine low crimp and high crimp ?bers sweaters. 75 in the same yarn and still achieve superior results. 3,081,516

TABLE I

Fiber Description Yarn Description Results

Example Denier Turns Aesthetic Ratio 3 Crimps/ Per Fabric 4 Pill Level Rating, in. Inch 5 C x W Percent Gore 1 Surf.2

4. 5 2. 0 1. s5 20 9. 7 350 { _ i 70 4.5 2.0 4.0 20 9.7 350 $231k"; } 74 3- ° 2- 0 2~ 7 2° 9~ 7 35° {588 252322211331: } 78 a. 0 2. 0 1. s5 20 11.1 450 { 7s a 0 2. 0 2. 7 20 11.1 450 87 4. 5 2. 0 1. s5 0 s. a 450 71 6.0 2. 0 1. s5 0 8.3 350 { 71 e. 0 2. 0 2. 7 0 s. 3 450 7, a. 0 2. 0 1. s5 20 9. 7 350 10.0 2.0 1. s5 10 9. 7 400 { 1s 2. 0 2. 0 1. 27 10 i 9. 7 470 2. 0 2. 0 1. 27 10 1 9. 7 390 80-90 2. 0 2. 0 1. 27 10 6 9. 7 504 3. 0 2. 0 1. 27 10 6 9. 7 368 70-80

1 Denier oi high~shrinkage ?ber. 2 Denier of low-shrinkage ?ber. _ a Weight ratio of low-shrinkage ?ber to high-shrinkage ?ber. 4 Courses per inch x wales per inch. 6 As spun. 6 Yarns removed from ?nal fabric.

In addition to the fabrics indicated in Table 1, Exam through 8, which illustrate the best combinations of some ples 1 through 14, other superior sweater fabrics have known key variables which contribute to desirable fabric been prepared as described in Table II, Examples 15 aesthetics and greatest pill resistance, including crirnps through 25. These latter fabric illustrate three speci?c 35 per inch, denier of core ?ber and surface ?ber, weight embodiments of the present invention, one being par ratio of core ?ber to surface ?ber, yarn denier, twist ticular combinations of ?ne (below 6 denier) ?bers, a multiplier and fabric tightness, as measured in the product second being the use of both high and low crimp in the of C x W (courses per inch x wales per inch) of the knit same blended yarn, and the third being the use of low material. shrinkage ?bers of greater denier than the high-shrinkage While the above examples show the practice of the ?bers. Evaluation of the fabrics of Table II was com present invention in reference to knitted sweaters from pleted in a manner similar to that described of the fabrics blended yarns of high- and low-shrinkage ?bers, it has of Table I. All of the fabrics of Table ‘II had an aesthetic also been found that woven fabrics from acrylic yarns of rating of 70% or higher in paired comparison evalua blended high-shrinkage and low-shrinkage ?bers show tions with control fabrics and other experimental fabrics. 45 the same behavior; that is, woven fabrics of superior The results of pilling tests on the fabrics of Table 11 aesthetic level and much improved resistance to pilling indicate that all of these fabrics would have a pill rat are obtained when the proper crimp level is chosen. In ing of less than 3 and frequently less than 2. addition, the principles and practice of the present inven TABLE II tion are not limited to acrylic ?bers, but are also applic 50 able to fabrics made from other synthetic fibers such as Fiber Description poly—(ethylene terephthalate). Pilling of fabrics from poly-(ethylene terephthalate) is reduced when either high Yarn, Fabric,‘ Example Core Surface Ratio 2 Turns] 0 x W or low crimp level is employed in tight fabric (e.g., inch 3 product of C x W is 350 or higher) and when other vari Denier c.p.i.1 Denier c.p.i.1 55 ables are also controlled in accordance with the teach ing of the present invention. The same is true of fabrics 2 0 1 0 1. 35 11.2 450 made from polyamide [?bers and other synthetic ?bers 2 0 1 0 1.35 11.2 500 of like characteristics in which the amount of crimp can 1 O 1 0 1. 35 11.2 450 6 2O 1 20 2.63 9. 7 400 be controlled. 6 0 3 0 1. 85 11. 2 450 This application is a continuation-in-part of applica 3 0 2 20 1. 85 11.2 450 3 20 2 0 1. 85 11. 2 450 tion Serial No. 704,333, ?led December 23, 1957, now 2 22 3 22 1. 85 11.2 450 abandoned. 2 0 3 0 1. 85 11.2 450 3 0 3 0 1. 85 9. 7 450 The claimed invention: 1 22 4. 5 22 1. 40 11.2 450 For providing improved resistance to pilling of tight 65 fabric composed of high bulk, acrylonitrile polymer, 1 Crimps per inch. staple ?ber yarn, a fabric knitted in a courses per inch 2 Weight ratio of l0w»shrinkage ?ber to high-shrinkage ?ber. 3 As spun. times wales per inch count of at least about 350 with 11 4 Courses per inch x wales per inch. turns per inch yarn consisting of a blend of acrylonitrile While the ?ber characteristics already de?ned are neces polymer staple ?bers of (1) low shrinkage 2 denier ? sary to the practice of the present invention, it is neces 70 bers having a residual shrinkage of less than 1% and sary, in order to obtain the highest quality fabrics, to less than 3 crimps per inch, and (2) high shrinkage 3 take into account as well the interaction of all of the denier mechanically crimped ?bers having a residual variables involved in fabric preparation. Outstanding shrinkage of 18 to 25% and about 20 crimps per inch in sweater constructions, and the most preferable embodi a weight ratio of low shrinkage ?bers to high shrinkage ment of the present invention, are shown in Examples 1 75 ?bers of about 1.85 in the yarn, the fabric having a high 3,081,516 8 : aesthetic rating, and exhibiting no more than ‘a few pills 2,764,468 Hare ______Sept. 25, 1956 when tested by the random tumble pilling tester method, 2,789,340 Cresswell ______Apr. 23, 1957 after heat relaxation in boiling Water. 2,805,464 Bolrneyer' et a1 ______Sept. 10, 1957 2,810,281 Appleton et a1. ______Oct. 22, 1957 References Cited in the ?le of this patent 2,878,548 Lohr et a1. ______Mar. 24, 1959 UNITED STATES PATENTS 2,920,934 Schaefer et a1. ______Jan. 12, 1960 2,948,133 Schwartz ______Aug. 9, 1960 2,155,519 Whitehead ______Apr. 25, 1939 2,401,389‘ Truitt ______June 4, 1946 OTHER REFERENCES ‘2,558,732 Cresswell ______July 3, 1951 1 “Suggestions for Knitting Sweaters of New HighdBulk 2,575,839 Rainard ______Nov. 20, 1951 ‘Orion Yarns,” by Charles Reichman, Ed., Knitted Outer 2,623,266‘ Hernrni ______Dec. 30, 1952 wear Times, April 19, 1954, pgs. 3 and 18. Q ~ 2,686,339 Holt ______Aug. 17, 1954 “Du Pont Textile Fibers Technical Information,” Pre 2,701,406 Bloch ______Feb. 8, 1955 liminary Bulletin OR-42, December 1954, 7 pp.