CA1129732A - Continuous filament yarn with wool-like hand - Google Patents

Abstract

C-14-54-0430 CONTINUOUS FILAMENT YARN WITH WOOL-LIKE HAND ABSTRACT OF THE DISCLOSURE A yarn for producing fabrics with a wool-like hand, by combining textured filaments with longer filaments preferably of larger average denier. The longer filaments thus protrude in loops from the yarn bundle.

Description

The i.nvention relates to the art of melt-spun s~nthetic yarns and processes for their production, and more particularly to such yarns wh;ch combine high bulk with a wool-like hand.
This application is a divisional of copending application Serial Number 336,733, filed October 1, 1979.
It is known to produce somewhat bulky yarns by combining filaments with different shrinkages into a yarn, then shrinking so that the resulting longer filaments protrude in loops from the yarn. I'his may be done by spinning the filaments from different polymers, as in Reese U.S. patent 3,~44,681, or by spinn.ing from di:Eferent fi1.ament cross-sec-tions from a common polymer, as typified by several patents. Such known yarns ordinarily do not have high bulk, nor do fabrics made therefrom ordinarily provide a hand simi.lar to that of wool, combining an initial crispness on ligh.t toueh with softness on more firm compression.
: These and other difficulties of the prior art are avoided by the present invention, which provides novel and useful processes and improved yarn products.
According to a first major aspect of the invention, there is provided a process for producing a self-crimping yarn comprising fi.rst and second types of filaments, the process comprising spinning the first type of filaments by generating first and second individual streams of molten polymer of fiber-forming molecular weight, the individual streams travelling at different velocities; converging the indi.vidual streams side-by-side to form a combined stream;
and quenchi:ng the com~ined stream to form a combined filament;

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-2- C-1~-5~-0430 spinning the second ~ype of filaments by ex-truding a third stream of molten polymer of fi~er-forming molecular weIght from an orifice selected to give a filament wi~ lower shrinkage than said com~ine~ fllament, at a given common spinning speed; and quenching the third stream into a fila-ment; withdrawing the filaments from the streams at the given common spinning speed in excess of 220Q meters per minute; and combining the filaments into a yarn.
According to another aspect, each of the streams is of polyester polymer.
According to another aspect, the spinning speed is selec~ed such that the yarn has a shrinkage below ~0/O.
According to another aspect, the spinning speed is selected such that the yarn has a shrinkage below 8~/o.
According to another major aspect of the invention, there is provided a multifilament yarn comprising first and second classes of filaments, each of the first class of ilaments having a periodic variation in denier of greater than ~ 15% a~out a mean value and possessing latent crimp;
each of the second class of filaments having lower shrinkage than the shrinkage of the filaments of the first class.
According to another aspect, each o the second class of filaments has a denier larger than the average denier of the first class of filaments.
According to another major aspect of the invention, there is provided a multifilament yarn comprising first and second classes of filaments; each of the filaments of the first class having a periodic variation in denier of greater than ~ 15% about a mean value and possessing developed crimp;
each of the filaments o~ the second class being longer than the filaments of the first class whereby the fila~ents of the second class protrude from the yarn in loops.
According to another aspect, each of the second class of filaments has a denier larger than the average denier of the first class of filaments.
These and other aspects of the invention will in part appear hereinafter and will in part appear hereinafter in the follow;ng detailed description taken in connection with the accompanying drawings wherein:

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FIGURE 1 is a vertical sectional view of a spinneret orifice;
FIGURE 2 is a bottom plan view of the FI~UR~ 1 orifice, looking up;
FIGU~E 3 is a grap~ of shrinkage versus spinning speed used in explainin~ the prlnciples upon which certain aspects of t~e invention are based;
FIGURE 4 is a cross-sectional view o:f a filament accordîng to certaîn aspects of the invention;
FIGURE 5 is a side elevation view of the molten streams issuing from the FIGUP~ 1 spinneret according to certain aspects of -the invention;
FIGURE 6 is a graph illustrating the variation in denier along a representative filament according to certain aspects of the invention; and FIGURE 7 is a graph illustrating the distribution of the fluctuations illustrated in FIGUR~. 5 for a representa-tive multiple orifice spinneret according to certain aspects of the invention.
The invention will be specifically exemDlified using polyester polymer, it being un~erstood that certain aspects of the invention are applicable to the class of melt-spinnable ~olymers generally. "Polyester" as used herein means fiber-forming pol~mers at least 85% by weight of which is formable by reacting a dihydric alcohol with terephthalic acid.
Polyester typically is formed either by direct esterification of ethylene glycol with terephthalic acid, or by ester inter-change between ethylene glycol and dimethylterephthalate.
FIGURES 1 and 2 illustrate the preferred embodiment of a spinneret design which can be employed for obtaining ~he first type of filaments according to the invention The spinneret includes a large counterbore 20 formed in the upper surface 21 of spinneret plate 22. Small counterbore 24 is - formed in the bottom of and at one side of large counterbore 20. A large capillary 26 extends from the bottom of large counterbore 20 at the side opposite small counterbore 24, and connects the bottom of large counterbore 20 with -the lower surface 28 of plate 22. Small capillary 30 connects the bottom of counterbore 24 with surface 28. Capillaries 26 and ~,:

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30 are each inclined four degrees from the vertical, and thus have an included angle of eight degrees. Counterbore 20 has a diam2ter of 0.113 inch (2.87 mm.), while coun.erbore 24 has a diameter of 0.052 Inc~ Cl.3~ mm.). Capillary 26 has a S diameter of 0.016 inch ~0.406 mm.) and a length of 0.146 inch (3.71 mm.), while capillary 30 haa a diameter of 0.009 inch (O.229 mm.~ and a length of 0.032 inch (0.813 mm.). Land 32 separates caplllaries 26 and 30 as they emerge at surface 28 and has a width of 0.0043 inch (0.109 mm.). Plate 22 has a thickness of 0.554 inch (14.07 mm.~. Capillaries 26 and 30 together wi~h counterbores 20 and 24 constitute a combined orifice for spinnlng various novel and useful filaments according to the invention, as will be more particularly described hereinafter.
FIGU~E 3 is a graph showing how polyester filament shrinkage varies with spinning speed for two illustrative cases of jet stretch. The curve in dotted llnes shows that the shrinka~e falls from about 65% at 3400 ypm (about 3100 mpm) to about SaZ at 5000 ypm (about 4500 rnpm) when using sDinneret capillaries having diameters of 0.063 i.nch (1.6 mm.) and when simultaneously spinning 3~ such filaments to be alse-twist draw-textured to yield a textured yarn having 150 denier. The solid curve shows that the shrinkage drops of at higher speeds when using spinneret capillaries having diameters of 0.015 inch (0.38 mm.) when similarly simul-taneously spinning 34 such filaments to be false-twist draw-textured to yield a textured yarn having 150 denier. Using different capillary diameters produces a family of curves between, to the left, and to the right of those illustrated.
The curves also can be shifted (for a given capillary diameter) by varylng the polymer throughput. In other words, the cu-rves can be shifted by varying the jet stretch, which is the ratio of yarn speed just after solidification to average speed of molten polymer in the capillary. It ls thus possible to provide a combined orifice for spinning a com-posite filament of a single polymer wherein one side of the filament has a much higher shrinkage than the other side.
This is done by selecting the indlvidual capillaries to give different jet stretches, and also selecting the spinning ~Z~3~

-5- C-14-54-0430 speed within ~he range wherein an individual filarnent quencned from one of the individual streams would have a shrinkage at least ten percentage points higher than that of an individual fil~ment quenched from the other of the individual streams. Under t~.e spinning conditions illustra-ted in FIGURE 3, at a spinning speed of 5000 yards per minute the individual streams would have shrinkages differing by about 25 percentage points. Co~bining these molten streams into a ~ide-by-side configuration results in a highly crimped filament in its as-spun form, without the necessity of draw-ing the yarn to develop the crimp. Such combining may be done using a spinneret design similar to that disclosed in FIGURE 1, or the spinneret may merge the two streams at or just prior to emergence of the streams from surface 28. In any event, the two streams merge substantially coinc`ident with the face of the spinneret according to this aspect of the invention.
Advantageously, the spinneret is so designed that one of the individuaL streams has a velocity in i.ts capillary between 2,0 and 7 times (preferably between 3.5 and 5.5 times) the velocity of the other of the streams in its capillary.
Further advantages are obtained when the faster of the two streams has a smaller cross-sectional area than the slower of the streams7 particularly in degree of crimp and spinning stability. Productivity is increased when the spinning speed is selected such that the combined filament has a shrinkage less than 30%, and is maximized when the shrinkage is less than 10%.
Further aspects of the invention, applicable to melt-spinnable polymers as a class, are achievable by use of spinnerets wherein the streams intersect outside the spinneret.
As a specific example, molten polyester polymer of normal textile molecular weight is metered at a temperature of 290C.
through a spinneret having 34 combined orifices as above specifically disclosed. The polymer throughput is adjusted to produce filaments of 4 average denier per filament at a spinning speed of 5200 yards per minute, the molten streams being conventionally quenched into filaments by transversely directed quenching air.

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~ 2~ ~?~_6_ C-14-5~-0430 Under these spinning conditlons a remarkable phenomenon occurs, as il]us~rated in FIGURE 5. Due to the geometry of the splnneret construction, the polymer flowing through the smaller capillaries 30 has a higher velocity than that flowing through the larger capillaries. The speeds and momenta of the paired streams issuing from each combined orifice and the angle at ~hic~ the streams converge outside the spinneret are such that the slower streams 3~ travel in substantially straight lines after the points at which the paired streams first touch and attach, while each of the smaller and faster of the streams 36 forms sinuous loops back and forth between successive points of attac~ent 38 with its associated larger streams. This action can be readily observed using a stroboscopic light directed onto the stream immediately below the spinneret face 28. As the molten streams accelerate away from the spinneret, the slower stream attenuates between the points of attachmen~ 38 and the loops of the faster stream become straightened until the Easter stream is brought into continuous contact with the slower stream. The s].o~er stream attenuates more between than at the points of first attachment, so that the resulting combined stream has a cross-section which is larger at the points of first attachment than in the regions between these points. The resulting combined stream is then further attenuated somewhat until it is solidified into a filament 40 by the transverse quench air.
Each solidified filament 40 has non-round cross-sectional areas which vary repetitively along its length, and, after being heated while under low tension, has variable 3Q pitch S-twisted and Z-twisted helically coiled sections, the sections being less tightly coiled in regions of large cross-sectional area than in regions of small cross-sectional area.
As illustrated qualitatively in FI5UR~ 6, when using the above spinning conditions, the filament cross-sectional area repeti-tively varies at a repetition rate of about one per meter,although this can be varied by modifying the spinning conditions and the geometry of the spinneret passages.
Due to minor differences between combined orifices, temperature gradations across the spinneret, and other like fZ~73~
_7_ C-14-54-0430 deviations fr~m e~Yactly the same treatment for each pair of streams, a multiple orifice s-pinneret will typically provide somewhat different repetition rates among the several result-ing streams and filaments. An example of t~is is quali-tatively shown in FIGURE 7, ~herein is shown that variousorifices produce somewhat different repetition rates 2S deter-mined ~y stro~oscopic examination of the com~ined streams just below the spinneret face. In the result;ng multifilament yarn, the f,laments have non-round cross-sections which vary by more than + 10~/o along the length of the filaments, and alternating S-twisted and Z-twisted helically crimped sections, the variations in cross-sectional areas being out of phase rrom filament to filament and the helically crimped sections being out of phase from filament to filament.
For certain effects, it is advantageous that the filaments vary repetitively along their lengths by more than + 25% (preferably more than + 30%) inAcross-sectional area.
The effects are particularly pronounced when ~he yarn has a Uster unevenness of at Least 2 5% U. The Uster measurement is.made using the Uster ~venness Tester, Model C) together with integrator ITG-101 for this instrument. The yarn speed is 182.8 meters per minute (200 ypm), the service selector is set on normal, and the sensitivity selector is set to 12.5%.
The % U is read from the integrator after a sample run time of 5 minutes.
Shrinkage is determined by the method disclosed in ~hls paragraph. Generally speaking, a sample yarn~s initial length Lo is determined while the yarn is under a tension of 0.1 grams per denier. The yarn is then subjected to a tension 30 of 0.0025 grams per denier and placed in an oven at 120C.
for five minutes. The yarn is then removed ~rom the oven) again subjected to a tension of 0.1 grams per denier and its - length L2 determined. Shrinkage percentage equals Lo-L2 - X 100.
Lo ~1297~

The ~econd class of fila~ents may be spun from spinneret orifices selected suc~ t~at, at the gi~en coT~mon spi`nning speed, the filaments of the first class will have a hi`g~er s~rinkage than those of the second class.
As a specific e~ample, molten polyet~ylene tereph-thalate polymer of normal molecular weight for textile apparel yarns is extruded simultaneously through two spinnerets, one of w~Ich contains 34 combined orifices as above descrïbed and the other o which contains 34 round orifices having diameters of 0.009 inch (0.229 mm.). The extrusion rates are selected such that each resulting class of 34 filaments has a denier of 77 at a winding or spinning speed of 5600 ypm (about 5100 meters per minute). I'he 68 molten streams are quenched into filaments by transversely directed movlng air, and the 68 fîlaments are converged into a common yarn bundle and wound on a bobbin at 5600 ypm as a yarn having a denier of 154..
The yarn is heated to 150C. while under low tension to develop the latent crimp in those filaments of the first class and to develop the shrinkage differences between the two classes of filaments. Those filaments of the first class, collected separately, have a shrinkage of 1~.6%, while those of the second class, collected separatelyj have a shrinkage of 4.5%. The combined yarn has a shrinkage of

6.3%. Each filament of the first class has a periodic variation in denier from approximately one denier to approxi-matel~ four denier, while the filaments of the second class protrude in relatively large loops from the yarn bundle.
To produce a more wool-like hand, the denier per filament o the filaments of the second class can be increased~ the ran~e of about 5-9 dpf bein~ particularly suitable.

Claims (3)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A multifilament yarn comprising first and second classes of filaments characterized by:
a. each of the filaments of said first class having a periodic variation in denier of greater than ? 15% about a mean value and possessing a developed crimp;
b. each of the filaments of said second class being longer than said filaments of said first class whereby said filaments of said second class protrude from said yarn in loops.

2. The yarn of claim 1 characterized in that each of said second class of filaments has a denier larger than the average denier of said first class of filaments.

3. The yarn of claim 1 characterized in that said first class of filaments are polyester.