CA1123280A - Continuous filament yarn with wool-like hand - Google Patents

Abstract

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

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CONTINUOUS FIL~ENT YARN WITH WOOL-LIKE H~ND
SPECIFICATION
The invention relates to the art of melt-spun synthetic yarns and processes for their production, and more particularly to such yarns which combine high bulk with a wool-like hand.
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. This may be done by spinning the filaments from different polymers, as in Reese U.S. patent 3,444,681, or by spinning from different filament cross-sections from a common polymer, as typified by several patents. Such known yarns ordinarily do not have hi~h bulk, nor do fabrics made therefrom ordinarily provide a hand similar to that of wool, combining an initial crispness on light touch with softness on more firm compression.
These and other difficulties of the prior art are avoided by the present invention~ whichprovides novel and ~seful 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 irst 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 diff~rent velocities; converging the individual streams side-by-side to form a combined stream;
and quenchlng the combined stream to form a combined filament;

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-2- C-14-54-0~30 spinning the second type of filaments by e~trudîng a third stream of molten polym~r of fi~er-forming molecular weight from an or;fice selected to give a filament with lower shrinkage than said com~ined filament~ 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 2200 meters per minute; and combining the filaments into a yarn.
According to another aspect, each of the streams is 10 of polyester polymer.
According to another aspect, the spinning speed is selected such that the yarn has a shrinkage below 20%.
According to another aspect, the spinning speed is selected such that the yarn has a shrinka~e below 8%.
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 filaments having a periodic variation in denier of greater than + 15% about 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 of 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 mult.ifilamen~ 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;
3Q each of the filaments of the second class being longer than the filaments of the first class whereby the filaments 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 following detailed description taken in connection with the accompanying drawings wherein:

-3- C-14-54-0~30 FIGU~E 1 is a vertical sectional view of a spinneret orlfice;
FIGURE 2 is a bottom plan view of the FIGUR~ 1 orifice looking up;
FIGURE 3 is a graph of s~rlnkage versus spinning speed used in explaining the principles upon which certain aspects of the ~nvent;on are based;
FIGURE 4 is a cross-sectional view of a filament according to certain aspects of the invention;
ln FIGURE 5 is a side elevation view of the molten streams issuing from the FIGUP~ 1 s~inneret 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 învention; and FIGURE 7 is a graph illustrating the distribution of the fluctuations illustrated in FIGURE 5 for a representa-tive multiple oriice spinneret according to certain aspects of the invention.
The invention will be specifically exemplified using polyester polymer, it being understood that certain aspects of the invention are applicable to the class of melt-spinnable polymers generall~. "Polyester" as used herein means fiber-forming polymers 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 far obtaining the first type of filaments accordinc to the invention. The spinneret includes a large counterbore 20 for~ed 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 25 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 degre~s from the vertical, and thus have an included angle of eight degrees Counterbore 20 has a diameter of 0.113 inch (2.87 mm.), while counterbore 24 has a diameter of 0.~52 lnch (1.32 mm.). Capillary 26 has a dlameter 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 capillaries 26 and 30 as they emerge at surface 28, and ~as 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 with counterbores 20 and 24 constitute a combined orifice for spinning various noveI and useful filaments according to the invention, as will be more particularly described hereinafter.
FIGURE 3 is a graph showing how polyester filament shrinkage varies with spinning speed for two illustrative cases of jet stretch. The curve in dotted lines shows that the shrinkage falls from about 65% at 3400 ypm (about 3100 mpm) to about 5% at 5000 ypm (about 4500 mpm) when using s~inneret capillaries having diameters of 0.063 inch (1.6 mm.) and when simultaneously spinning 34 such filaments to be false-twist draw-textured to yield a textured yarn having 150 denier. The solid curve shows that the shrinkage drops off 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 lS0 denier. Using different capillary diameters produces a family of curves between, to the left, and to the right o those illustrated.
The curves also can be shifted ~for a given capillary diameter) by varying the polymer throughput. In other words, the curves 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 is thus 35 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 shrlnkage than the other side.
This is done by selecting the individual capillaries to give different jet stretches, and also selecting the spinning . . .

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-5- C-14-54-0430 speed ~ithin th~ range ~h.erein an individual filament quenched from one of the individual streams would have a shrinkage at least ten percentage points higher than that of an individual filament quenched from the other o -the individual streams. ~nder the spinning conditions illustra-ted in FIGURE 3, at a spinning speed of 5000 yards per minute the indlvidual streams would have shrinkages differing by a~out 25 percentage points. Combining these molten streams into a side-by-side configuration results in a highly crimped filament in its as-spun form, without the necessity of draw-ing the yarn to deveIop 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 coincident 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 its 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 streams, particularly in degree of crimp and spinning stability. Productlvity is increased when the spinning speed is selected such that the combined ~ilament has a shrinkage less than 30%, and is maximized when the shrinkage is less than lQ%.
Further aspects of the invention, applicable to melt-spinnable polymers as a class, are achievable by use o spinnerets wherein the streams intersect outside the spinneret.
As a specific example, molten polyester polymer of normal te~tile molecular weight is metered at a temperature o 29~C.
through a spinneret having 34 combined orifices as above specifically disclosed. The polymer throughput is adjusted to produce fllaments 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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Under these spinning conditions a remarkable phenomenon occurs, as illustrated in FIGURE 5. Due to the geometry of the spinneret construction, the polymer flowing through the smaller capillaries 30 has a higher veloci~y than that flowing through the larger capillaries. The speeds and momenta of the paired streams issuing rom each combined orifice and the angl~ at ~ic~ the strea~s con~erge outside the spinneret are such that the slower streams 34 travel in substantially straight lines after the points at which the paired streams ~irst touch and attach, while each of the smaller and faster of the streams 36 forms sinuous loops back and orth between successive points o attachment 38 with its associated larger streams. This action can be readily observe.d 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 attachment 38 and the loops of the faster stream become straightened until the faster stream is brought into continuous contact with the slower stream. The slower 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 urther attenuated somewhat until it is solidified into a filament 40 by the transverse quench air.
Each solidified ilament 40 has non-round cross-sectional areas ~hich vary repetitively along its length, and, ater being heated while under low tension, has variable 3a 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 o~ small cross-sectional area.
As illustrated qualitatively in FIGURE 6, when using the above spinning conditions, the ilament cross-sectional area repeti-tively varies at a repetition rate of about one per meter,although this can be varied by modi~ying the spinning conditions and the geometry of the spinneret passages.
Due to minor differences ~etween combined orifices, temperature gradations across t~e spinneret, and other like ~, . , . - , - : , - - : ; :
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-7- C-14-54-0430 deviations from exactly the same treatment for each pair of streams, a multiple orifice spinneret wLll typically provide somewhat di~ferent repetition rates among the several result-ing strea~s and filaments, An example of t~is is quaLi-tativeI~ shown in FIGURE 7, wherein is shown that varlousorifices produce somewhat different repetition rates as deter-mined ~y stroboscopic examination of the combined streams just below the spinneret face. In the resulting multifilament yarn, the fîlaments have non-round cross-sections which vary by more than + 10% along the length of the filamen~s, and al~ernating S-twisted and Z-twisted helically crimped sections, the variations in cross-sectional areas being out of phase from filament to ~ilament 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 + 30V/~) in cross-sectional area.
The effects are particulariy pronounced when the yarn has a Uster unevenness of at least 2.5% U. The Uster measurement is made using the Uster Evenness Tester, Model C, together ~ith integrator ITG-101 for this instrument. The yarr. speed is 182.8 meters per minute (200 ypm), the service selector is set on normal, and the sensitivity selec~or i9 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 this paragraph. Generally speaking, a sample yarn's initial length Lo is determined while the yarn is u~der a tension of 0.1 grams per denier. The yarn is then subjected to a tension of 0.0025 grams per denier and placed in an oven at 120C.
for five minutes. The yarn is then removed from the o~en, again subjected to a tension of 0.1 grams per denier and its length L2 determined. Shrinkage percentage equals Lo-L2 Lo X 100.

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The second class of ~ilam~nts may be spun from spinneret orifices selected such that, at the given common spi-nning speed, the filaments of the. first class will have a higher s~rinkaOe 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 sLmultaneously through two spinnerets, one of w~ich contains 34 combined orifices as above descrï.bed and the other of w~ich contains 34 round orifices having diameters of 0.009 inch (0.22g 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 Cabout 5100 meters per minute). The 68 molten streams are quenched into filaments by transversely directed moving air, and the 68 filaments 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 10.6%, while those of the second class, collected separately, 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~
mately 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 of the filaments of the second class can be increased, the range of about 5-9 dpf being particularly suitable.

Claims (8)

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

1. A process for producing a self-crimping yarn comprising first and second types of filaments, character-ized by:
a. spinning said first type of filaments by (1) generating first and second individual streams of molten polymer of fiber-forming molecular weight, said in-dividual streams travelling at dif-ferent velocities;
(2) converging said individual streams side-by-side to form a combined stream;
and (3) quenching said combined stream to form a combined filament;
b. spinning said second type of filaments by (1) extruding a third stream of molten polymer of fiber-forming molecular weight from an orifice selected to give a filament with lower shrinkage than said combined filament at a given com-mon spinning speed; and (2) quenching said third stream into a fila-ment;
c. withdrawing said filaments from said streams at said given common spinning speed in ex-cess of 2200 meters per minute; and d. combining said filaments into a yarn.

2. The process of claim 1, characterized in that each of said streams is of polyester polymer.

3. The process of claim 2, characterized in that said spinning speed is selected such that said yarn has a shrinkage below 20%.

4. The process of claim 3, characterized in that said spinning speed is selected such that said yarn has a shrinkage below 8%.

5. The process of claim 1, characterized in that said spinning speed is between 5000 and 6000 yards per minute, and wherein each of said first type of filaments is polyester.

6. A multifilament yarn comprising first and second classes of filaments characterized by:
a. each of said first class of filaments having a periodic variation in denier greater than ? 15% about a mean value and possessing latent crimp;
b. each of said second class of filaments having lower shrinkage than the shrinkage of said filaments of said first class.

7. The yarn of claim 6 characterized in that each of said second class of filaments has a denier larger than the average denier of said first class of filaments.

8. The yarn of claim 6 characterized in that said first class of filaments are polyester.