US3775961A - Yarn process - Google Patents

Abstract

A coherent continuous filament yarn substantially free of barre'' is produced at a high production rate by introducing true twist into an undrawn feed yarn free of twist and then drawing the yarn. The true twist can be introduced into the undrawn yarn by the utilization of a 2-for-1 twister. The use of a Godet roll as the feed roll minimizes filament breakage upon a start-up of the 2-for-1 twister. The Uster of the drawn yarn is minimized by wrapping the twisted yarn around the snubbing pin in the draw zone in the same direction as the direction of twist in the yarn. The drawn yarn can be simultaneously thermally stabilized and relaxed to provide the desired degree of residual shrinkage while maintaining the desired initial modulus of the yarn. The relaxed and stabilized yarn can be wound into a package without further twisting of the yarn.

Description

FOREIGN PATENTS OR APPLICATIONS 3/1952 Germany 57/157 R Umted States Patent 1 Womer Dec. 4, 1973 YARN PROCESS [75] Inventor: Walter D. Womer, Greenville, SC. Primary ExammerflDmiald watkms Att0meyY0ung & Quigg [73] Assignee: Phillips Fibers Corporation,

Greenville, S.C. [57] ABSTRACT [22] Filed: Nov. 22, 1971 A coherent continuous filament yarn substantially free [2]] Appl No: 201,053 of barre is produced at a high production rate by introducmg true twist Into an undraw'n feed yarn free of twist and then drawing the yarn. The true twist can be 1 57/157 57/36 introduced into the undrawn yarn by the utilization of CL .1 Dolh a 2-for-l twister. The use of u Godot roll as the feed [58] Field of Search 57/34 HS, 157 S, r 1] minimizes filament breakage upon a start-up of 5 0. 34 R the 2-for-1 twister. The Uster of the drawn yarn is minimized by wrapping the twisted yarn around the [56] References Cited snubbing pin in the draw zone in the same direction as UNITED STATES PATENTS the direction of twist in the yarn. The drawn yarn can 3,225,534 12/1965 Knospe 57/157 R X be si multaneu sly thermally Stabilized relaxed 3,413,797 12/1968 Chapman. 57/157 R X provide the desired degree of residual shrinkage while 3,159,964 9 4 KretSchm" 57 157 3 maintaining the desired initial modulus of the yarn. 3,616,635 11/1971 Petersen 57/157 R The relaxed and stabilized yam can be wound into a package without further twisting of the yarn.

11 Claims, 2 Drawing Figures strength and uniformity. The advent of manmade filament yarnsspun in'continuous lengths drastically reduced the need to twist the yarn bundle for strength. It was noted, however, that some twist was still required to impart sufficient yarn bundle cohesion in order to maintain good running properties on fabrimmaking equipment. Thus, continuous filament yarn intended for use as a warp yarn in weaving will generally have a twist level of from l'to 1.5 turns per inch (tpi) while a continuous filament weaving fill yarn will generally have a twist level of about 0.3 to about 0.5 tpi. Continuous filament yarn for tricot knitting most frequently has a twist level of about 0.5 toabout l tpi, while yarn intended for false twist texturizing will generally have around 0.3 tpi. However, the conventional processes for producing such yarns having true twist are expensive and have slower production rates than processes which do not require the introduction of true twist.

Processes employing a draw-twister generally require the utilization of a relatively high tension during winding, and this high tension results in greater variations in the characteristics of the yarn onthe wound package. Interlaced or randomly entangled yarn has achieved significant employment as asubstitute for true twist yarn because the interlacing operartion is generally less expensive than true twisting. However, the nature of interlaced yarn results in the appearance of flash, which can be defined as very short streaks in thin fabllCS produced from the randomly entangled yarn.

Accordingly, it is an object of the present invention 'to provide a new and improved system for providing low levels of true twist in continuous filament yarns. It is an object of the invention to produce a coherent yarn substantially free of the flash effect. Another object of the invention is to provide a high speed, low cost process for producing continuous filament yarn having true twist. Yet another object of the invention is to provide a process for producing an apparel denier weaving or knitting yarn having good cohesion and wound on a disposable support and which yields barre free dyed fabrics. A further obejct of the invention is to provide a more efficient and economical technique for introducing true twist into undrawn yarn for further processing. Another object of the invention is to minimize filament breakage upon start-up of a twist-draw machine. Yet another object of the invention is to provide a more uniform yarn in a twist-draw process. A further object of the invention is to achieve thermal stabilization and relaxation of a yarn with minimim equipment and at minimum operating costs.

Other objects, aspects and advantages of the invention will be apparent from a study of the specification, the drawings and the appended claims to the invention.

In the drawings, FIG. 1 is a diagrammatic representation of a process for spinning a yarn and winding the spun yarn into a package free of twist, and FIG. 2 is a diagrammatic representation of a process for twisting and drawing the feed yarn embodying the features of the present invention; While the invention is generally applicable to any yarn of a plurality of continuous filaments, it is particularly advantageous with a yarn com-.

posed of a plurality of filaments of a melt spinnable synthetic organic thermoplastic polymer, for example, polyamides, polyesters, polyolefins such as polyethylene and polypropylene, polyurethanes, polyureas, vinyl polymers such as polyvinyl chloride; polyvinylidene chloride, and copolymers thereof, acrylic polymers such as polyacrylonitrile when sufiiciently plasticized to render it fusible, copolymers of acrylonitrile, halogenated hydrocarbons such as polychlorotrifluoroethylene, polyacetals, polyanhydrides, polyoxymethylenes, polyformals, polyethers, polythioethers, polysulfides, polythioesters, polysulfones, polythioureas, polythioamides, polysulfonamides, polyimides, and polytriazoles. The preferred group of polyamides comprises such polymers as poly( hexamethyleneadipamide, poly(hexamethylene sebacamide), poly(epsiloncaproamide), and the copolymers thereof. Among the polyesters that may be mentioned, besides poly(ethylene terephthalate), are the corresponding copolymers containing sebacic acid, adipic acid, or isophthalic acid aswell as the polyesters containing recurrent units derived frorn glycols with more than two carbons in the chain, e.g., diethylene glycol, butylene glycol, decamethylene glycoland trans-bis-l,4-(hydroxymethyl) cyclohexane.

Referring now to the drawing in detail, and to FIG. 1 in particular, ayarn 11 of a plurality of continuous filaments is extruded from spinneret 12, passed through converging ring 13 and transversing guide 14, and wound into a package 15 at least substantially free of twist. This package 15 is subsequently mounted in a conventional 2-for-1 twister 16 in FIG. 2. The yarn 11 is unwound from the exterior of package 15 by way of an adjustablepretension gate 17, and is then passed axially through the hollow core of the package 15 into spindle 18. The yarn thenexits spindle 18 in a radial direction and balloons outwardly from the twister 16 as the yarn moves to guide elements 19 .and 20.Spindle 18 is rotated by belt 2l driving shaft 22 mountedaxially on spindle 18. The unwinding of the yarn 11 from twister 16 results in the introductionof two turns of true twist into the yarn for each revolution of spindle 18. It is presently-=desirable that the amount of true twist so introduced be sufficient to provide from about one-fourth to two turns per inch in the final product yarn as subsequently drawn. The utilization of undrawn yarn free of twist as the feed yarn for the process of FIG. 2 eliminatesthe need for employing drawing and- /or twisting means in the spinning operation of FIG. 1, thereby permitting a significantly higher spinning production.

The twisted yarn makes several wraps around a Godet roll 23 and its associated separator roll: 24 and then passes to snubbingpin 25;In accordance with one aspect of the present invention, the twisted yarn is wrapped about snubbing pin 25 for at least one full wrap, the direction of the wrap being the same as the direction of true-twist in the yarn. The twisted yarn then passes several wraps around a Godet draw roll. 26 and its associated separator roll 27. The draw roll 26 is operated at a fasterperipheral surface speed than feed roll 23 to draw the yarn at least it percent and up to 1,200 percent, and preferably from at least 200 percent up to about SOOpercent, in length.

The drawn yarn passes from draw roll 26 into contact with the surface of heater 28. Idler rolls 29 and 30 can be provided in association with heater 28 so thatthe yarn canconta'ct the surfaces ofheater 28 more than i once. The yarn passes from heater 28 to a Godet roll 31 and its associated separator roll 32. The yarn then passes from roll 31 around stationary guide 33 through traversing guide 34 onto the package roll 35. The roll 35 is rotated by driving roll 36 which contacts the peripheral surface of the yarn package. In certain embodiments of the invention, Godet roll 31 and its separator roll 32 can be omitted. The amount of relaxation is then controlled by the ratio of the speeds of draw roll 26 and the take-up drive roll 36.

The utilization of the 2-for-l twister for the introduction of the true twist into the undrawn yarn is an important aspect of the present invention. With a standard uptwis'ter spindle, rotational speeds above about 10,000 rpmcan cause the undrawn yarn to distort sufficiently to severly unbalance the spindle, even at a package diameter as small as 4 inches. Another system involves the utilization of a rotatable can arrangement wherein the undrawn yarn is wound on a collapsible bobbin, the bobbin is collapsed, the hollow cheese package is placed in the can and the yarn is removed from the interior of the cheese package with twist being inserted as a function of the linear withdrawal rate and of the rotational speed. However, it is generally uneconomical to rotate large as-spun yarn packages at speeds high enough to produce acceptable twist levels. The 2- for-l twister does not suffer from these disadvantages because it does not require the yarn package to be rotated. The 2-for-1 twister also has the important advantage of producing at least two turns of twist per spindle revolution. The term 2-for-1 twister is generically employed to include the conventional modifications to introduce twist at a higher rate, for example the 4-for-l twister, as well as the simpler 2-for-1 twister. The 2-forl twister also has the advantage of the balloon configuration remaining constant despite variations in the diameter of the yarn package or variation in the position of the yarn in the package. The heavier nature of the undrawn yarn permits the formation of a larger balloon, thus enabling the use of a larger package than could be formed on a 2-for-b twister after the same yarn has been drawn.

Since the 2-for-l spindle requires that the yarn balloon around the feeder package, the design of the spindle will generally be dictated by the physical dimension of a spun bobbin which is practical from the standpoint of spinning economics. In general, the spindle can be operated at maximum rpm consistent with the mechanical limitations of the parts. More specifically, however, the spindle will normally be operated within an rpm range determined by the denier. The low end of the range is that speed which is just sufficient to cause the yarn to balloon around the pot without touching the pot at any point. For example, with a inch diameter pot, this minimum is about 5,000 rpm for 210 undrawn denier. The upper end of the range is determined by the acceptable level of pre-draw which is effected by the tension developed within the balloon. As the tension increases beyond the initial value required to initiate elongation of the yarn, the amount of elongation increases as a linear function of the tension until the tension exceeds the yield tension of the yarn. This yield tension is generally of the order of about 0.35-0.50 grams per undrawn denier and the elongation at the yield point is generally of the order of about 3-5 percent. Elongation up to this point is generally essentially totally recoverable. As the yarn passes through the yield tension, drawing begins to take place and the elongation introduced is only partially recoverable. More importantly, it is clear that, relatively speaking, large changes in tension up to the yield tension produce small changes in elongation whereas above the yield tension small changes in tension produce large changes in elongation. For this reason it is preferable to operate the 2-for-l spindle at speeds so that the yield tension is not exceeded.

It is possible, however, where sufficiently accurate spindle speed regulation is maintained, to exceed the yield tension without introducing severe nonuniformity merely by making an appropriate adjustment in the draw ratio between the Godet rolls 23 and 26.

This is in sharp contrast to the conventional draw twister wherein the higher the tension created by the traveler, the greater the degree of non-uniformity of the packaged yarn. In general, the spindle speed for the 2-for-l twister will be in the range of about 4,000 to about 16,000 rpm, and usually will be in the range of about 5,000 to about 12,000 rpm. The tension of the yarn in the balloon will generally be in the range of about 0.05 gram per denier of the undrawn yarn to about 0.35 gram per undrawn denier, and preferably will be in the range of about 0.1 gram per undrawn denier to about 0.3 gram per undrawn denier.

The feeder yarn pretension gate 17 serves to trap the twist formed in the package center and prevent this twist backing up onto the feed package 15 Failure to trap this twist can cause the yarn to collapse onto itself as it balloons away from the feed package and interrupt smooth let-off of yarn. A pretension setting which is too low can permit excess yarn to be pulled out by the outer balloon, resulting in the formation of wraps around the spindle disc, causing breakage. In general, pretension settings in the range of about 0.025 to about 0.050 gram per undrawn denier are sufficient to yield smooth and uniform operation.

A presently preferred technique is to operate the 2- for-l twister spindle substantially at the maximum speed recommended by the spindle manufacturer and to utilize the pot size which best adapts to the balloon which is formed at this speed. The resulting balloon tension in grams per denier will be substantially constant at this speed throughout the textile denier range of 40 to 200 denier for the final drawn product yarn. For a spindle speed of 8,000 rpm, a pot size of approximately 10 inches has been found suitable for the undrawn yarns which are processed to produce drawn denier in the range of about 40 to about 100. For drawn deniers in the range of -200 a spindle rpm of about 6,000 and a pot size of about 12 inches in diameter has been found to be most satisfactory. In general the pot size will be in the range of about 6 to about 14 inches in diameter.

Another important aspect of the present invention is the utilization of a Godet roll as feed roll 23. Although the conventional cot roll system can be employed, I have found it to be disadvantageous in the present system. Employment of the cot roll requires that both the yarn speed and the spindle rpm be brought up to operating speeds very slowly and in synchronization to prevent yarn breakage. Such mode of operation eliminates the possibility of restringing broken ends and also prevents the use of random doffing, both of which can be readily accomplished with the Godet roll system. The difficulties with the cot roll system are believed to be the result of its inability to permit any slippage of the yarn in contrast to the more or less controlled slippage b which can occur in the initial wrap on a Godet roll. This employ either a separator roll or a grooved stationary pin instead of the associated separator roll to maintain the wraps separated.

Another important aspect of the present invention is i the wrapping of the yarn 11 around snubbing pin 25 in the same direction as the direction of true twist in the yarn, i.e., ,S wraps for S twist and Z wraps for Z twist. This correspondence in direction of wrapping is desirable in order to produce a high degree of uniformity in the yarn as measured by percent Uster. Another important aspect of the invention is the production. of a nylon yarnhaving a low value of residual shrinkage and a high value of initial modulus by simultaneously effecting thermal stabilization and relaxation of yarn 11 between rolls 26 and 31. The fabric defect known as pirn taper barre has been fairly well defined for years. The time delayed contraction of nylon filament yarns wound on a package such as a pim or tube occurs in a non-uniform fashion radially throughout the package. In the-pim package, the yarn in the tapered portion is held more firmly and cannot contract as readily. Hence this yarn has higher shrinkage, lower denier, etc., and dyes to a different depth of shade as compared to the yarn from the barrel. To solvethis problem, a process was developed in which, the freshly drawn yarn is relaxed in a controlled fashion at a very low tension under the accelerating influence of heat just prior to winding on a package. This process produces yarn which is more uniform in denier, shrinkage, etc., and results in fabrics essentially free from pim taper barre. At the same time it is possible to wind the yarn on a paper core since the high compressive forces have been largely removed.

While this controlled relaxation does permit preparation of fabrics free of pirn taper barre, the process, in addition to reducing yarn shrinkage, also reduces the initial modulus. This reduced modulus can introduce a different type of dye non-uniformity due to tension variations during textile processing. This defect most commonly arises from tension variations during quilling, hence the term quill taper barre. A process to overcome this problem of quill taper barre was subsequently developed in which the very low tension relaxation step is coupled with a separate high tension heat setting step at constant length. The heat setting can be carried outeither just prior to or subsequent to the relaxation step and prior to winding. However, this system requires additional rolls and heaters and associated control equipment, significantly increasing the capital cost of the equipment as well as the operating cost.

In accordance with an aspect of the present invention, the residual shrinkage of a yarn is reduced to the desired level while maintaining a high value of initial modulus without requiring any additional equipment.

More specifically, this aspect of the invention can be utilized to produce a nylon 6,6 yarn which has a residual shrinkage in the range of about 2 to about 9 percent, preferably in the range of about 4 to about 6 percent, and an initial modulus of at least 30, preferably at least 35. This is accomplished by heating the yarn on heater 28 to a temperature greater than that required for maximum relaxation at zero tension while operating roll 31 at a peripheral speed which is lower than the peripheral speed of roll 26 by the desired degree of relaxation. The desired degree of relaxation is the difference between the residual shrinkage of the drawn but unrelaxed yarn and the desired residual shrinkage for the product yarn, and will usually be in the range of about 4 to about 11 percent, preferably in the range of about 5' to about 8 percent.The attainment of a temperature greater than that required, for maximum relaxation at zero tension will generally resultin a tension on the yarn between rolls 26 and 31 of at least 0.1 gram per denier, and preferably in the range of about 0.25 gram per denier to about 0;50gram per denier. The temperature for heater 28 will generally be in the range of about 120 to about 300 CsThe tension on the yarn between roll 31 and package35 will usually be in the range of about 0.05 to about 0.35 gram'per denier. For fully relaxed yarn (having a residual shrinkage of 5 percent or less), acceptable packages can be formed at winding tensions of from 0. 2 to 0.35 gram per denier without crushing a one-fourth inch wallpaper tube, and packages of 8 pounds can be formed without any evidence of sloughing.

Although the speed of the running yarn can be critical in obtaining these conditions, ithas beenfound that t the key to optimizing speeds lies in improving heat transfer from the platen or heater 28 to the yarnl It has also been shown that the length of the platen has insignificanteffect on the results. For example, no difference in'propertiescould be detected between an ,8 inch long platen compared to a 16 inch long. platen when both were runatthe same temperature. Also, runs on a double sided heater showedno improvement in properties by increasing thenumber of wraps around the heater from one-half to 10. The most significant improvement in properties was obtained simply by running the yarn from the top toward the bottom of a vertically mounted heater as compared to a bottom to top direction. It can be theorized that the heat rising by convection warms the air immediately above the heater which in turn preheats the envelope of air which is en trained by the moving filament bundle. This preheated air envelope markedly improves heat transfer to the yarn. A similareffect can be realized on the bottom toward top thread line configuration by introducing heated air from aseparate source just prior to initial yarn contact at the platensurface. Additional improvements when needed for higher speed operation (above about 600-700 m/mican be obtained on the vertically downward'mode of operation by encasing the platen using a hinged cover thus creating a chimney effect. It is also important to insure that the heating of the air is accomplished with relatively little air movement since moving large masses of heated air can still produce a coolingeffecton the platen and cancel or reverse the improvement in properties.

The simultaneous heat setting/relaxation system meets the requirements of a stabilized yarn for weaving and tricot knitting. A yarn for texturizing, however, frequently requires a higher level of shrinkage in order to perform properly in the texturizing zone. A modification which fulfills this requirement while still providing The indicated speed is yarn takeup speed on package 35. The percent relax is the percent of the peripheral speed of roll 26 at which roll 31 is operating slower than roll 26. The relax tension is the tension,

enough stabilization to permit winding on paper tubes comprises heating the draw roll 26 to a temperature sufficient to set the yarn at a given yarn speed prior to in grams, winding but which can be overcome by the conditions n the yarn between rolls 26 and 31. M and percent U of texturizing. A roll temperature of l25-150C. works r th initial dulus nd percent Uster of the prodwell at yarn speeds up to about 1,200 m/m- Boiling uct yarn on package 35. Similarly, the indicated denier, Water shrinkage is Slightly reduced but texturlzlng P tenacity, and percent elongation are for the product formance is not Significantly changed- Th6 winding yarn. The relatively high percent Uster values for the sion for this type of yarn will usually be about 0.1 gram 10 product yams f these runs are the result f per denier or less, decreasing to about two-thirds of the initial value at full diameter since the yarn can still sponding values of percent Uster for the undrawn feed yarn. These data establish the suitability of the present process for producing a yarn having a desired residual shrinkage while maintaining a high value of ini under these conditions, but such difference does not hm affect dyeability.

relax to some degree on the tube. There can be a difference in properties between inside yarn and outside yarn tial mod- The following examples are presented in further illustration of the invention and should not be considered to unduly limit the invention.

EXAMPLE II EXAMPLE I The apparatus of FIG. 2 was utilized to process nylon 6,6 yarn having 34 filaments and an undrawn denier of The apparatus of FIG. 2 was utilized to process nylon 6,6 yarn having 34 filaments and an undrawn denier of 210. The indle 18 w t d t 8 000 rpm, h 210. The spindle 18 was operated at various rpm as inmanufacturers maximum recommended speed, to indica ed in Ta e II. The roll 6 was Operated at a pctroduce into the undrawn yarn 16,000 turns per minute n'pheral speed which was 2.948 times the peripheral of true twist in the S direction. The pot size was 10-% speed of roll 23. The roll 31 was operated at a peripheral speed of 7.5 percent less than the peripheral speed of roll 26. The tension of the yarn between rolls 26 and 30 31 was maintained at 18 grams, and the yarn was inches in diameter. The yarn was wrapped about snubbing pin 25 in the S direction. Other operating conditions and resulting product yarn characteristics are set forth in the following table: wound onto package 35 at a rate of 325 meters per TABLE I Percent el0ugn Percent residual Heater Speed, 28, M /m l 11.

tion

temp. Percent Relax shrink- M., Percent Tenaci- C. relax tension age g.p. l. U Denier ty,g.p.d.

Run

characteristics are set forth in Table II:

TABLE I1 Balloon Tenac- Spindle, tension, ity, Elng., Perg. g.p.d. percent Denier cent U TP[ 1 Dye level is measured as a percentage of a standard.

These data indicate that a uniform yarn product can be achieved at various spindle speeds and balloon tensions.

EXAMPLE III The apparatus of FIG. 2 was modified as follows: (1) an induction coil heating system was added to roll 23 to permit heating of the undrawn yarn tofacilitate processing of polyester, (2) snubbing pin 25 was replaced by a heated platen similar in configuration to heater 28 and idler rolls 29 and 30, (3) heated platen 28 and idler rolls 29 and 30 and Godet rolls 31 and 32 were omitted. The thus modified apparatus was utilized to process polyethylene terephthalate yarn having 34 filaments and an undrawn denier of 556. The spindle 18 was operated at 5,600 rpm to produce 11,200 turns/min. Z twist, the roll 26 was operated at a peripheral speed which was 3.78 times the peripheral speed of roll 23 and the yarn was wound onto package 35 at a rate of 1,210 meters/min. Roll 23 was operated at a surface temperature of 110 C and the heated platen (pin 25) was operated at a surface temperature of 125 C. The spindle pot size was 12.5 inches in diameter and balloon tension was 175 g. Two positions were operated simultaneously to produce a number of full 8 lb. net wt. packages which were fully commercially acceptable with regard to both package formation and yarn physical properties. The resulting yarn characteristics are set forth in Table III.

TABLE III Tenac- Pesi- Perit Elontp, Mi, 1) ye Run tion Denier cent. U gpd. percent g.p.d. BWS 1 level 2 150. 5 1. 01 4. 4 26 117 8. 2 105. 5 151. 7 0. J0 4. 7 27 134 7. 7 107. 3 150. 5 0. 80 4. 0 20 121i 8. 4 102. 3 150. 5 1. 28 4. 0 24 134 8. 2 105. 2 151. 3 1. 02 4. 6 25 122 7. 0 102. 5 150. 1 1. 08 4. 4 23 144 7. 9 100. 7 150. 0 1. 10 4. 5 28 125 7. J 105.5 150. 9 1. 20 4. 3 24 120 7. 9 106. 3 148. 8 1. 30 4. 4 20 126 8. 8 101. 3 150. 1 1. 05 4. 3 22 132 7. 9 105. 3 150. 5 0. 93 4. 6 26 127 7. 7 106. 0 150. 5 1. 05 4. 5 25 128 8. 0 102. 4 150. 5 1. 05 4. 5 26 129 7. 9 107. 5 149. 7 1. 25 4. 4 23 137 7. 9 103. 6 150. 9 1. 25 4. 5 28 132 7. 7 104. 9

1 Boiling water shrinkage.

Reasonable variations and modifications are possible within the scope of the foregoing disclosure, the drawing and the appended claims to the invention.

What is claimed is:

1. In a process for producing at a high production rate, a coherent, at leastgbsta ntially streak-free, con

tinuous filament yarn, which comprises, in a continuous sequence, the steps of utilizing a 2-for-l twister to withdraw from a source thereof an at least substantially twist free, at least substantially undrawn yarn contain- 5 ing a plurality of continuous filaments, and to introduce true twist into the thus withdrawn yarn, passing the thus twisted yarn into contact with a feed roll, then around a snubbing device, and then into contact with a draw roll, while rotating said draw roll at a higher surface 10 speed than said feed roll to draw said yam at least 120 percent; the improvement comprising utilizing a Godet roll as said feed roll.

2. In a process in accordance with claim 1 the further improvement comprising wrapping the yarn about said l5 snubbing device for at least one fullwrap, the direction of said wrap being the same as the direction of said true twist introduced into said yarn.

3. In a process in accordance with claim 2 the further improvement comprising simultaneously thermally sta- 20 bilizing and relaxing the thus twisted and drawn yarn by passing said twisted and drawn yarn from said draw roll to a third roll, the surface rotational speed of which is less than that of said draw roll, while heating the yarn between said draw roll and said third roll to a tempera- 2 ture required to maintain a tension on the yarn between said draw roll and said third roll of at least 0.1 gram per denier.

4. In a process for producing at a high production rate, a coherent, at least substantially streak-free, con- 30 tinuous filament yarn, which comprises, in a continuous sequence, the steps of withdrawing'from a source thereof an at least substantially twist free, at least substantially undrawn yarn containing a plurality of continuous filaments, introducing true twist into the thus 35 withdrawn yarn, passing the thus twisted yarn into contact with a feed roll, then around a snubbing device, and then into contact with a draw roll, while rotating said draw roll at a higher surface speed than said feed roll to draw said yam at least 120 percent; the improvement comprising utilizing a Godetroll as said feed roll.

thereof an at least substantially twist free, at least substantially undrawn yarn containing a plurality of continuous filaments, introducing true twist into the thus withdrawn yarn, passing the thus twisted yarninto contact with a feed roll, then around a snubbing device, and then into contact with a draw roll, while rotating said draw roll at a higher surface speed than saidfeed roll to draw said yarn at least 120 percent; the improvement comprising simultaneously thermally stabilizing and relaxing the thus twisted and drawn yarn by passing said twisted and drawn yarn from said draw rollto a third roll, the surface rotational speed of which is less than that of said draw roll, while heating the yarn between said draw roll and said third roll to a temperature required to maintain a tension on the yarn betweensaid drawroll and said third roll of at least 0.1 gram per demer.

6. A process for drawing a yarn having turns of twist therein, which comprises feeding said twisted yarn from a feed roll at a first rate, snubbing the thus fed yarn away from said snubbing device at a sec o r rcl rate V greater than said frist rate, the direction of said at least one full wrap about said snubbing device being the same as the direction of said turns of twist in said yarn.

7. A process in accordance with claim 6 wherein said snubbing device is a draw pin and wherein said fed yarn A -is passed for at least three full wraps about said draw 8. A process in accordance with claim 6 wherein said turns of twist are true twist and wherein said yarn is formed of continuous filaments.

9. A process comprising passing a drawn yarn of continuous filaments from a first roll to a second roll, operating the second roll at a slower surface rotational speed than that of said first roll, and heating said yarn as it passes from said first roll to said second roll to a temperature required to maintain a tension on the yarn between said first roll and said second roll of at least 0.1 gram per denier.

10. A process in accordance with claim 9 wherein said yarn is composed of polyamide filaments, wherein said first surface rotational speed of said second roll is at least 4 percent less than the surface rotational speed of said first roll, and wherein said yarn is heated as it passes between said first roll and said second roll to a 5 temperature in the range of about 150 C. to about 300 C. to maintain a tension on said yarn between said first roll and said second roll of at least 0.25 gram per denier to thereby produce a product yarn having a residual shrinkage in the range of about 2 to about 7 per-, cent and an initial modulus of at least 30 grams per demer.

11. A process in accordance with claim 10 wherein said drawn yarn has a residual shrinkage of at least 10 percent and an initial modulus of at least 35 grams per denier wherein said product yarn has a residual shrinkage in the range of about 4 to about 6 percent and an initial modulus of at least 35 grams per denier.

Claims (11)

1. In a process for producing at a high production rate, a coherent, at least substantially streak-free, continuous filament yarn, which comprises, in a continuous sequence, the steps of utilizing a 2-for-1 twister to withdraw from a source thereof an at least substantially twist free, at least substantially undrawn yarn containing a plurality of continuous filaments, and to introduce true twist into the thus withdrawn yarn, passing the thus twisted yarn into contact with a feed roll, then around a snubbing device, and then into contact with a draw roll, while rotating said draw roll at a higher surface speed than said feed roll to draw said yarn at least 120 percent; the improvement comprising utilizing a Godet roll as said feed roll.

2. In a process in accordance with claim 1 the further improvement comprising wrapping the yarn about said snubbing device for at least one full wrap, the direction of said wrap being the same as the direction of said true twist introduced into said yarn.

3. In a process in accordance with claim 2 the further improvement comprising simultaneously thermally stabilizing and relaxing the thus twisted and drawn yarn by passing said twisted and drawn yarn from said draw roll to a third roll, the surface rotational speed of which is less than that of said draw roll, while heating the yarn between said draw roll and said third roll to a temperature required to maintain a tension on the yarn between said draw roll and said third roll of at least 0.1 gram per denier.

4. In a process for producing at a high production rate, a coherent, at least substantially streak-free, continuous filament yarn, which comprises, in a continuous sequence, the steps of withdrawing from a source thereof an at least substantially twist free, at least substantially undrawn yarn containing a plurality of continuous filaments, introducing true twist into the thus withdrawn yarn, passing the thus twisted yarn into contact with a feed roll, then around a snubbing device, and then into contact with a draw roll, while rotating said draw roll at a higher surface speed than said feed roll to draw said yarn at least 120 percent; the improvement comprising utilizing a Godet roll as said feed roll.

5. In a process for producing at a high production rate, a coherent, at least substantially streak-free, continuous filament yarn, which comprises, in a continuous sequence, the steps of withdrawing from a source thereof an at least substantially twist free, at least substantially undrawn yarn containing a plurality of continuous filaments, introducing true twist into the thus withdrawn yarn, passing the thus twisted yarn into contact with a feed roll, then around a snubbing device, and then into contact with a draw roll, while rotating said draw roll at a higher surface speed than said feed roll to draw said yarn at least 120 percent; the improvement comprising simultaneously thermally stabilizing and relaxing the thus twisted and drawn yarn by passing said twisted and drawn yarn from said draw roll to a third roll, the surface rotational speed of which is less than that of said draw roll, while heating the yarn between said draw roll and said third roll to a temperature required to maintain a tension on the yarn between said draw roll and said third roll of at least 0.1 gram per denier.

6. A process for drawing a yarn having turns of twist therein, which comprises feeding said twisted yarn from a feed roll at a first rate, snubbing the thus fed yarn by passing said fed yarn at least one full wrap about a snubbing device, and drawing the thus snubbed yarn away from said snubbing device at a second rate greater than said frist rate, the direction of said at least one full wrap about said snubbing device being the same as the direction of Said turns of twist in said yarn.

7. A process in accordance with claim 6 wherein said snubbing device is a draw pin and wherein said fed yarn is passed for at least three full wraps about said draw pin.

8. A process in accordance with claim 6 wherein said turns of twist are true twist and wherein said yarn is formed of continuous filaments.

9. A process comprising passing a drawn yarn of continuous filaments from a first roll to a second roll, operating the second roll at a slower surface rotational speed than that of said first roll, and heating said yarn as it passes from said first roll to said second roll to a temperature required to maintain a tension on the yarn between said first roll and said second roll of at least 0.1 gram per denier.

10. A process in accordance with claim 9 wherein said yarn is composed of polyamide filaments, wherein said first surface rotational speed of said second roll is at least 4 percent less than the surface rotational speed of said first roll, and wherein said yarn is heated as it passes between said first roll and said second roll to a temperature in the range of about 150* C. to about 300* C. to maintain a tension on said yarn between said first roll and said second roll of at least 0.25 gram per denier to thereby produce a product yarn having a residual shrinkage in the range of about 2 to about 7 percent and an initial modulus of at least 30 grams per denier.

11. A process in accordance with claim 10 wherein said drawn yarn has a residual shrinkage of at least 10 percent and an initial modulus of at least 35 grams per denier wherein said product yarn has a residual shrinkage in the range of about 4 to about 6 percent and an initial modulus of at least 35 grams per denier.

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