US3601972A

US3601972A - Drawing and bulking of synthetic filament yarns

Info

Publication number: US3601972A
Application number: US835714A
Authority: US
Inventors: Paul Rogers; Roy Spencer Holliss
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1968-07-12
Filing date: 1969-06-23
Publication date: 1971-08-31
Anticipated expiration: 1988-08-31
Also published as: GB1274854A; ZA694451B; DE1935389A1

Abstract

In a process for producing false twist crimped synthetic yarn from crimpless undrawn yarn comprising: partially drawing the crimpless undrawn yarn to less than full extent; imparting potential crimp by immediately and continuously imparting false twist to the partially-drawn yarn and heating the same under sufficient tension to complete the drawing; and releasing the tension.

Description

United States Patent inventors App]. No.

Filed Patented Assignee Priority DRAWING AND BULKING OF SYNTHETIC FILAMENT YARNS 7 Claims, 1 Drawing Fig.

US. Cl 57/157 Int. Cl D023 1/00, D02g i/02 Field 0| Search 57/34, 36,

Fabnb new! (more: per syua/eynm A x 3;

[56] References Cited UNITED STATES PATENTS 3,365,874 1/1968 Chidgey et a1. 57/157 3,404,525 10/1968 Tomkins 57/157 X 2,671,304 3/1954 Rowedder 57/51 2,890,568 6/1959 Willens 57/34 X 3,400,194 9/1968 Boone et al. 57/157 X 3,435,603 4/1969 Rice 57/34 3,457,338 7/1969 Lefevre 57/55.5 X 3,474,612 10/1969 Jenkins et al. 57/34 FOREIGN PATENTS 777,625 6/1957 Great Britain 57/34 815,202 6/1959 Great Britain 57/157 Primary Examiner-Donald E. Watkins Attorney-Cushman, Darby & Cushman .525 0 fiat/0 of draw l n /0 mfa/se DRAWING AND BULKING or SYNTHETIC FILAMENT 1 YARNS The invention concerns improvements in or relating to the drawing and bulking of synthetic filament yarns.

A widely employed method of bulking synthetic filament yarns is the method known as false twist crimping, in which a temporary, or false twist is continuously imparted to a running yarn the twist is set by heating means, and then the yarn is detwisted in a sense to remove the temporary twist. However, because the twist has been set, the final detwistingof the twistset yarn causes the filaments to crimp and cookie, and it is this operation which imparts bulk to the yarn, although the bulk may only be latent until some process to make it manifest has been performed on the yarn such as a heat treatment under conditions of controlled relaxation.

False twist crimping may be carried out on synthetic filament yarn supplied on packages in the fully drawn condition, i.e. the yarn has been packaged by the producer after the standard drawing process has been carried out, in which the undrawn yarn as spun from the spinning machines is extended by several times its undrawn length to orient the molecules.

Alternatively, it is known to combine the drawing and the false twist crimping stages on one machine, so that a package of undrawn yarn is first submitted to a standard drawing treatment and then the drawn yarn is immediately fed into the false twist crimping stage.

Yet another alternative is to submit undrawn yarn from a supply thereof to such conditions of tension in a false twist crimping process that the yarn is both drawn and crimped thereby.

This latter method has been found to be the better one of the two methods starting with an undrawn yarn supply from the point of view of the bulking effect at a given throughput. Nevertheless, there is some tendency for filaments to be broken; and also the bulked yarn seems to impart a glittery effect to fabric which may not be desirable. These potential defects are not present in yarn bulked by the former of the two methods starting with an undrawn yarn supply, i.e. the method in which the yarn is normally drawn before being fed into the false twist crimping stage; but, in order to attain a given level of bulk in yarn processed by this method, it is necessary to run the process at a lower throughput. Hence, the machines are not employed to their full capacity.

We have now discovered that the above mentioned potential defects found when undrawn yarn is directly false twist crimped and drawn can be ameliorated if the yarn is first predrawn to a less than full extent, and then the final amount of drawing, only, is performed coincidentally with the false twist crimping.

Accordingly, the invention comprises a process for false twist crimping a synthetic filament yarn, in which process the synthetic filament yarn in undrawn condition is firstly submitted to a predrawing stage in which the yarn is drawn by less than the full amount, and then the partially-drawn yarn is fed to a false twist crimping stage under such conditions of tension that drawing of the yarn is completed whilst the yarn is heated in said false twist crimping stage.

it is presently preferred to operate under conditions such that the total draw ratio achievable is not reduced much below that normally achieved when either of the two known methods are employed, i.e. when the yarn is either fully predrawn or is wholly drawn on the false twist crimping heater. This entails operating at either end of the scale, i.e. at the end where the yarn is nearly fully drawn during predrawing, or at the other end when only very slight predrawing is performed.

The invention may be illustrated with reference to the attached drawing which shows diagrammatically the relationship for poly(hexamethylene adipamide) between fabric weight and the ratio of the draw ratio in the false twist crimping stage to the draw ratio in the predrawing stage. This relationship was obtained by processing a filament supply yarn of poly(hexamethylene adipamide) at a throughput speed of 1700 feet/minute, the undrawn denier being 211 to be drawn to a nominal 70 denier. The weight of fabric per square yard, which is a measure of bulk, was determined for twofold 70 denier yarns knitted in an 18 gauge interlock fabric with a stitch length of 0. 144 inches.

As illustrated in the FIGURE high bulk may be obtained when the ratio of the two draw ratios is. selected in the range 0.3 to 0.8 or when the ratio is above. 1.3. The upper limit for the ratio is determined by the desirability of avoiding the glittery effect imparted to fabric when undrawn yarn is both drawn and crimped in a false twist crimping process. Hence, it is essential that some drawing takes place in a predrawing stage. We have found that values for the ratio of the two draw ratios up to about 2.8 are particularly useful.

The invention is applicable to all synthetic filament yarns capable of being heat-set and is particularly applicable to polyamide yarns such as poly(hexamethylene adipamide) yarns.

The polyamide yarn may be derived from a polyamide polymer of a kind which has been nucleated with calcium fluoride in such manner that the mean maximum nucleant separation distance is given by the expression where- G is the linear rate of crystallization at a temperature T S is the mean maximum nucleant separation distance and KC is the distance of the solidification point from the spinneret for unnucleated polymer when :spun into filaments.

The use of a yarn derived from such a nucleated polymer enables higher throughput speeds to be used in the present invention as compared with the use of a yam derived from an unnucleated polymer.

The invention is not limited by the means adopted for drawing and for false twist crimping. Nevertheless, it is preferred to predraw the yarn between a feed roll and a faster rotating draw roll whilst localizing the point of draw at a ceramic snubbing-pin; and it is preferred to fed the predrawn yarn directly into the false twist crimping zone by and from said draw roll, with the false twist being imparted directly to the yarn by a rotary friction device. The yarn is then withdrawn from the friction device at a speed greater than that at which it was fed thereto by the draw roll. The false twist is set, and the final drawing is carried out, while the yarn is passing through or over the heater of the false twist crimping zone.

It is, of course, possible to carry out bulk-development or other post-treatments on the false twist crimped yarn either concurrently or at some later stage in yarn or fabric production. Thus, bulk may be developed by heat treating the false twist crimped yarn under a controlled tension and temperature.

What we claim is:

1. In a process for producing a false twist crimped synthetic filament yarn the improvement consisting in firstly submitting the synthetic filament yarn in undrawn condition to a predrawing stage in which the yarn is drawn by less than the full amount and then feeding the partially-drawn yarn to a false twist crimping stage under such conditions of tension that drawing of the yarn is completed, whilst the yarn is heated in said false twist crimping stage.

2. A process according to claim 1 in which the synthetic filament yarn is a polyamide yarn.

3. A process according to claim 2 in which the synthetic filament yarn is poly(hexamthylene adipamide) yarn.

4. A process for developing bulk in a false twist crimped synthetic filament yarn made by a process according to claim l in which process the false twist crimped yarn is heat treated under a controlled tension and temperature.

5. A process according to claim 3 in which the ratio of the draw ratio in the false twist crimping stage to the draw ratio in the predrawing stage lies in the range 0.3 to 0.8.

6. A procels as in claim 3 in which the draw ratio in the false twisting crimping stage at the draw ratio in the predrawing stage is above 1.3. I

7 In a process for producing false twist crimped synthetic yarn from crimpless undrawn yarn comprising: partially drawing the crimpless undrawn yarn to less than full extent; impart-

Claims

2. A process according to claim 1 in which the synthetic filament yarn is a polyamide yarn.
3. A process according to claim 2 in which the synthetic filament yarn is poly(hexamthylene adipamide) yarn.
4. A process for developing bulk in a false twist crimped synthetic filament yarn made by a process according to claim 1 in which process the false twist crimped yarn is heat treated under a controlled tension and temperature.
5. A process according to claim 3 in which the ratio of the draw ratio in the false twist crimping stage to the draw ratio in the predrawing stage lies in the range 0.3 to 0.8.
6. A process as in claim 3 in which the draw ratio in the false twisting crimping stage at the draw ratio in the predrawing stage is above 1.3.
7. In a process for producing false twist crimped synthetic yarn from crimpless undrawn yarn comprising: partially drawing the crimpless undrawn yarn to less than full extent; imparting potential crimp by immediately and continuously imparting false twist to the partially-drawn yarn and heating the same under sufficient tension to complete the drawing; and releasing the tension.