US3143784A - Process of drawing for bulky yarn - Google Patents

Description

Aug. 11, 1964 P. T. SCOTT 3,143,784

PROCESS OF DRAWING FOR BULKY YARN I Filed July 5, 1962 INVENTOR PAUL T. SCOTT WZM ATTORNEY United States Patent 3,143,784 PROCESS OF DRAWING FOR EULKY YARN Paul T. Scott, Kinston, N11, assignor to E. i. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware Filed July 5, 1962, Ser. No. 207,654 5 Claims. (Cl. 2872) This invention relates to a process for drawing continuous filament yarn and, more particularly, to a process for drawing bulked crimped filament yarn from continuous synthetic linear polymer filaments.

Artificial fibers are normally produced most easily as continuous filaments. These continuous filament yarns are much more dense than yarns made from synthetic staple fibers and lack the bulk which provides lightness, covering power, and warmth-giving properties. Production of yarn from staple fibers, however, is time consuming and requires a complex series of operations. Recent developments in the textile industry have provided useful routes for improving the bulk and covering power of continuous filament yarns without resorting to conventional staple spinning systems.

As disclosed in Breen US. Patents No. 2,783,609, issued March 5, 1957, and No. 2,852,906, issued September 23, 1958, a textured yarn, such as that sold under the du Pont trademark Taslan, is produced by passing multifilament yarn through a jet where it is subjected to a turbulent stream of compressible fluid which temporarily separates the filaments and whips them into a multitude of loops and other convolutions. When operated with unheated compressed air, the filaments are recombined under a minimum of tension and twisted together to hold the convolutions in place in the yarn, since the convolutions are not set in the filaments. This textured continuous filament yarn has many of the desirable properties of spun staple yarn. However, the introduction of twist limits the bulk and limits the production rate to the relatively slow operating speeds of conventional yarn twisting apparatus, e.g., uptwisters or downtwisters. Although convolutions can be heat-set in the filaments by separate after-treatment, as by stearning, to provide a bulky, extensible yarn which does not require twist, this considerably increases the production cost.

Steam, hot air, or other heated compressible fluid can be used in the jet for bulking yarn and, under proper conditions, stable crimped yarn can be produced directly which does not require twist to hold the convolutions in place. This process can be operated at much higher speeds than when a twisting step is required, and produces a more desirable, much bulkier yarn. A highly desirable stable crimp having a random, three-dimensional, curvilinear, extensible configuration can be introduced in the filaments with apparatus and process conditions such as those disclosed in Breen et al. Canadian Patent No. 651,- 831 issued November 6, 1962. However, a difliculty encountered with low twist jet-crimped, continuous filament yarns is that the convolutions tend to snarl with those of adjacent yarns and to catch on parts of equipment, particularly during processing into fabric. In accordance with the present invention, a way has been found to overcome this difiiculty as part of the yarn treatment process. An object of the invention is to provide improvements in the process for jet crimping with heated compressible fluid. Other objects will become apparent from the specification and claims.

In the process of the present invention, bulky yarn, composed of continuous filaments of synthetic linear condensation polymer which have been drawn, crimped into 3,143,784 Patented Aug. 11, 1964 ice convolutions in a turbulent stream of heated compressible fluid and cooled to provide a crimp-set yarn having an elongation at break greater than 40% based on elongation occurring after the yarn has been extended to a length just sufficient to remove the convolutions, is redrawn at temperatures between about 0 C. and C. to about 1.10 to 1.50 times said extended length. After release of redrawing tension, this redrawn yarn has the appearance and mechanical processing properties of conventional uncrimped continuous filament yarn. However, the bulk is recovered when the yarn is hot-relaxed, as in conventional boil-off and heat-setting of woven or knitted fabric.

The elongation and the extent of redrawing referred to above and elsewhere in the specification and claims is in addition to, and distinct from, extension resulting solely from removal of crimp or other convolutions. Thus, to redraw crimped yarn 1.10 sufiicient tension is applied to straighten the filaments and the yarn is then stretched to increase the length an additional 10%.

The bulk yarn can be prepared as disclosed in more detail in Breen et al. Canadian Patent No. 651,831 by feeding drawn yarn through a jet supplied with steam or hot gas at a temperature of at least C. and forwarding the yarn against a screen which carries the yarn away from the jet and supports it until the crimp is set. The bulked yarn can pass directly from the screen to the redrawing step, or the bulked yarn can be collected and redrawn subsequently in a separate operation. This redrawing step may be accomplished with a yarn drawing apparatus comprising a means for supplying yarn at a uniform rate, a snubbing element, a means for applying drawing tension to the yarn, and means for winding up the drawn yarn.

The invention will be more easily understood by referring to the accompanying drawing, which is a schematic perspective view of apparatus suitable for carrying out the steps of drawing, bulking and redrawing in accordance with the principles of this invention.

In the drawing, undrawn yarn 1 is shown passing continuously between feed rolls 2 and 3 around pin 4 to draw roll 5. Several wraps are placed about the draw roll and idler roll 6. The drawn yarn is then passed continuously through guide 7 to jet 8 and crimp set on the screen surface of screen disk 9. The disk is rotated to carry the bulked yarn away from the jet stream, and the bulked yarn is withdrawn from the disk through guide 10 at a subsequent position in its rotation by take-off rolls 1?. and 12. From the take-off rolls, the bulky yarn is passed around pin 13 to redraw roll 14. If desired, the pin 13 may be omitted with no deleterious etiects. \Vhen it is des red to heat the yarn, this can be done by use of a heated pin at 13. It is preferred that a pin be used and that an unheated pin be used, i.e., that redrawing be carried out at room temperature. Several wraps are taken around redraw roll 14 and idler roll 15, the redrawn yarn is then passed continuously over guide roll 36 and through traversing guide 17 to package 13 driven by roll 19.

Normally, draw ratios of 1.1 and higher are necessary in order to remove the bulk from the yarn. At draw ratios of up to 1.03, some bu k remains; while at draw ratios of 1.1 and higher, the yarn becomes filament-like in appearance. At draw ratios in excess of 1.5, the yarns begin to exhibit loss of bulk on subsequent boil-off. Draw ratios between 1.1 and 1.2 are preferred since the lower draw ratios are attended by lower shrinkage levels.

During drawing, the yarn should not be heated above 130 C. and preferably not above 115 C. Useful bulk and/ or crimp can be obtained from yarns drawn at temperatures as high as 130 C. However, maximum bulk is realized when the yarn is drawn at temperatures below 115 C., and drawing temperatures, therefore, will normally range from room temperature to approximately 115 C.

During the production of bulked yarns as described above, a most surprising shrinkage of the filaments and relaxation of the molecules making up the filaments occur. The dynamic relaxation which occurs in the hot turbulent fluid of the bulking jet eliminates most of the non'uniformities from the yarn filaments and, thus, the treated yarns have much more uniform dyeability; and, in addition, there is a large increase in dye receptivity.

The dynamic relaxation is responsible for a considerable amount of deorientation of the molecules. In drawing these yarns during the practice of this invention, the molecules of the fibers are reoriented and, as would be expected, there is a corresponding increase in the shrinkage. However, when these redrawn yarns are boiled off, the resulting fibers possess the same high degree of dyeability possessed by the original bulk yarn, and there is no discernible difference in their dyeing uniformity.

The crimp of the bulked yarns is described in the Canadian Patent No. 651,831 as a random curvilinear configuration, the useful products having a crimp level in excess of crimps per inch. In redrawing the bulked yarns, the crimps are removed in order to improve processability of the subsequent product which has the physical appearance of a conventional filament yarn. Most surprisingly, however, when the redrawn yarns are again subjected to shrinkage conditions, the filaments assume their original curvilinear configuration with no apparent change in crimp frequency and, most preferably, have a crimp frequency of to crimps per inch.

The term synthetic linear condensation polymer used above refers to fiber-forming linear polyesters and polyamides.

By polyesters is meant crystallizable linear condensation polymers containing in the polymer chain carbonyloxy linking radicals Polymers containing oxycarbonyloxy radicals are comprehended within this group. The polymers should be of fiber-forming molecular weight. Copolyesters, terpolyesters, and the like, are intended to be comprehended within the term polyesters.

Examples of crystallizable, linear condensation polymers include polyethylene terephthalate, polyethylene terephthalate/isophthalate (85/15), polyethylene terephthalate/S-(sodium sulfo) isophthalate (97/3), poly(phexahydroxylene terephthalate), poly(diphenylolpropane isophthalate), poly(diphenylolpropane carbonate), the polyethylene naphthalene dicarboxylates (especially those derived from the 2,6- and 2,7-isomers) and poly(mphenylene isophthalate) as Well as many others.

Suitable polyamides are those melt-spinnable synthetic linear polyamides which are prepared from polymerizable monoamino monocarboxylic acids or their amideforming derivatives, or from suitable diamines and suitable dicarboxylic acids or from amide-forming derivatives of these compounds. Typical of such polyamides are those formed from an aliphatic diamine and an aliphatic acid containing the repeating unit linkage. Especially useful polyamides are those in which -X and Y are (CH where n is an integer of 4 from 0 to 12 inclusive; X and Y may be the same or different. Polyhexamethylene adipamide, polycaproamide (i.e., 66 and 6 nylons) and polyundecanoamide are typical. Other suitable polyamides are those having the repeating structure wherein -A is a divalent aromatic radical and X and Z are as previously defined. Polyhexamethylene isophthalamide is illustrative of such polymers. Additionally polyamides having repeating units such as Where B is divalent flkaryl (such as xylene) may be used provided that only the melt spinnable polymers and copolymers are intended. Another class of suitable polyamides containing other than aromatic intracarbonamide repeating units are those prepared from piperazine, such as those from piperazine and adipic acid, and the like. Melt-spinnable copolymers wherein the amide linkage is the predominant linkage and polyamide mixtures are also useful.

The process of this invention produces a yarn that will show a gross increase in bulk on subsequent boil-ofi'. A comparison of the boil-01f denier to the redrawn denier is a crude indication of the bulk increase. However, a better measure of bulk can be obtained by determining the volume of a definite weight of fabric while under pressure. For the purpose of this invention, bulk is, therefore, measured under a pressure of 3.4 lbs/sq. in. Before testing, the fabric is preconditioned at 55i5 C. for a minimum of two hours and is then conditioned for 16 hours at relative humidity at 21 C. Fabric samples of known area are then weighed. The thickness of the sample under a pressure of 3.4 pounds per square inch is then determined. The volume in cubic centimeters is then calculated, and this value divided by the weight of the sample in grams is the specific volume (cc./g.).

EXAMPLE I A polyethylene terephthalate/S-(sodium sulfo)-isophthalate (98/2) yarn having a trilobal cross-section is drawn to denier and bulked according to Canadian Patent No. 651,831 at a steam temperature of 500 F. and pressure of 50 p.s.i.g. to give a denier of 117 and a break elongation of The bulked yarn is forwarded by feed rolls to an unheated draw pin 13 and around redraw rolls 14 and 15 as illustrated in the figure of the accompanying drawing. Three wraps are taken around the redraw rolls to prevent slippage. The yarn is redrawn 1.123 and wound up at a speed of 454 y.p.m. The redrawn yarn has a denier of 105, a tenacity of 2.0 g./d., an elongation of 64%, a yield point of 0.82 g./d., an initial modulus of 47 g./d., and a boil-off shrinkage of 10.0%. The redrawn yarn is downtwisted to 3 t.p.i. twist and woven into a plain fabric. The woven fabric has a loom count of 64 by 64 ends/inch, a fabric weight of 1.85 0unces/yd. and a fabric bulk before finishing of 1.5 cc./ g. The fabric is boiled off at C. for 15 minutes and heat set at C. After boil-off and heat setting, the fabric has a loom count of '72 by 74 ends/inch, a fabric weight of 2.25 ounces/yd. and a fabric bulk of 2.75 cc./ g. The aesthetics of the finished fabric are excellent.

Specimens of the drawn, the bulked, and the redrawn yarn are dyed in a 0.016% Latyl Yellow 3G bath at 100 C. for 25 minutes. Dye absorption is found to be 0.4% for the initial drawn yarn, 1.0% for the bulked yarn, and 1.0% for the redrawn yarn, showing that there is no change in the dyeability as a result of the redrawing. Dyeing uniformity of the bulked and of the redrawn yarn is equivalent and both have dyeing uniformity superior to the drawn yarn.

EXAMPLE II Apparatus for processing yarn is set up as shown in the drawing. A 40-denier drawn yarn of polyethylene terephthalate having 27 filaments is delivered from rolls 5 and 6 at 100 yds./min. to the bulking jet 8, whence it is deposited on screen 9. The steam temperature in the jet is 293 C. and the pressure is 50 psig. The yarn is carried along on the screen at 50 y.p.m. until it is cooled and the crimp is set. The bulked yarn, having a denier of 67 and a break elongation of 95%, continues around pin 13 and over rolls 14 and 15 for redrawing. The yarn is drawn at a draw ratio of 1.12 at room temperature and wound up at 589 yds./min. The redrawn yarn has a denier of 60, a tenacity of 2.7 g./d., an elongation of 64%, a yield point of 0.80 g./d., an initial modulus of 47 g./d., and a boil-ofi shrinkage of 10.0%.

Specimens of the drawn, the bulked and the redrawn yarn are dyed at 100 C. in a 0.016% Latyl Yellow 36 bath. Dye absorption is found to be 0.2% for the drawn yarn, 0.4% for the bulked yarn, and 0.4% for the redrawn yarn, showing that there has been no change in the dyeability as a result of the redrawing process.

Conversion of this yarn to fabric and subsequent boiloff as in Example I shows a bulk of 2.9 cc./ g. vs. a bulk before boil-off of 1.8 cc./ g.

A second run at a draw ratio of 1.42 gives equivalent results.

EXAMPLE III A 10-filament polyhexamethylene adipamide yarn is drawn and steam bulked as in Example I to a denier of 105 and a break elongation of 64%, and is then redrawn with the arrangement of pin and draw rolls described. The yarn is drawn 1.16 at 26 C. and wound up at 454 y.p.m. The redrawn yarn has a denier of 91, a tenacity of 3.5 g./d., and an elongation of 43%, and a boil-off shrinkage of 16%. Conversion of this yarn to fabric and subsequent boil-off shows a bulk of 2.8 cc./g. versus a bulk before boil-oft of 1.6 cc./ g.

Repeating the above experiment, except that the yarn is drawn 1.38 gives a yarn having a bulk of 2.8 cc./g. after being boiled-off.

EXAMPLE 1V Yarn is prepared as in Example 1 except that the draw pin 13 is heated. In this example, 6 runs, A through F, are made at temperatures ranging from 43 C. to 160 C. Specimens prepared at each temperature are woven into a satin ribbon construction. Fabric samples are finished as described above and the efiect of the redrawing temperature on bulk development is determined. The results, tabulated in Table 1, show that very little bulk is obtained by redrawing at 160 C. and that, while useable bulk is obtained at temperatures as high as 130 C., optimum bulk is obtained at temperatures below 112 C.

Table 1 Specific Volume (cc.lg.) Draw pin Run Temp.

C 0.) Before After Boilofi Boil-0E Since many difierent embodiments of the invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited by the specific illustrations except to the extent defined in the following claims.

I claim:

1. In the production of bulky yarn from continuous filaments of synthetic linear condensation polymer by drawing the filaments, crimping the filaments in a turbulent stream of heated compressible fluid to impart a random, three-dimensional, curvilinear, extensible configuration, and cooling the filaments to set the crimp, the improvement of conducting said process to provide bulky, crimped yarn having an elongation at break greater than 40%, based on elongation occurring after the yarn has been extended to a length just sufficient to remove the crimp, and redrawing the yarn at temperatures between 0 C. and 130 C. to 1.10 to 1.50 times said extended length to provide a yarn having the appearance and mechanical processing properties of uncn'mped yarn but which recovers the crimp when hot-relaxed.

2. A process as defined in claim 1 wherein said bulky yarn is redrawn to 1.1 to 1.2 times said extended length.

3. A process as defined in claim 1 wherein said bulky yarn is redrawn at temperatures between room temperature and C.

4. A process as defined in claim 1 wherein said yarn is composed of polyethylene terephthalate and is redrawn to 1.1 to 1.2 times said extended length While at a temperature of 20 to 112 C.

5. A process as defined in claim 1 wherein said yarn is composed of polyhexamethylene adipamide and is redrawn to 1.1 to 1.2 times said extended length while substantially unheated.

References Cited in the file of this patent UNITED STATES PATENTS 3,017,685 I-Ieberlein Jan. 23, 1962 3,055,080 Claussen et al Sept. 25, 1962 FOREIGN PATENTS 636,054 Canada Feb. 6, 1962 1,225,587 France Feb. 15, 1960

Claims (1)

1. IN THE PRODUCTION OF BULKY YARN FROM CONTINUOUS FILAMENTS OF SYNTHETIC LINEAR CONDENSATION POLYMER BY DRAWING THE FILAMENTS, CRIMPING THE FILAMENTS IN A TURBULENT STREAM OF HEATED COMPRESSIBLE FLUID TO IMPART A RANDOM, THREE-DIMENSIONAL, CURVILINEAR, EXTENSIBLE CONFIGURATION, AND COOLING THE FILAMENTS TO SET THE CRIMP, THE IMPROVEMENT OF CONDUCTING SAID PROCESS TO PROVIDE BULKY, CRIMPED YARN HAVING AN ELONGATION AT BREAK GREATER THAN 40%, BASED ON ELONGATION OCCURRING AFTER THE YARN HAS BEEN EXTENDED TO A LENGTH JUST SUFFICIENT TO REMOVE THE CRIMP, AND REDRAWING THE YARN AT TEMPERATURES BETWEEN 0* C. AND 130* C. TO 1.10 TO 1.50 TIMES SAID EXTENDED LENGTH TO PROVIDE A YARN HAVING THE APPEARANCE AND ME-

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