US3436904A - Method of producing bulked yarns - Google Patents

Description

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US. Cl. 57-157 9 Claims ABSTRACT OF THE DISCLOSURE A method of making a bulky or structured yarn by drafting a sliver of fibers which are in substantially relaxed condition and are of varying length while using a reach for such drafting that is less than the length of a substantial number of such fibers, so that such number of fibers are stretched to varying amounts, assembling the drafted sliver into yarn, and treating the yarn to develop the latent shrinkage characteristic imparted by the variable stretch. The sliver is made from a tow of man-made filaments adapted to stretch under tension. The initial sliver can be obtained in different ways, eg by cutting into staple composed of fibers of dilfering length a tow of substantially uniformly highly stretched filaments and then relaxing this sliver, or \by cutting into staple composed of fibers of uniform length a tow lof variably stretched filaments and then relaxing such staple to variably shrink the fibers.

This invention concerns staple yarns the final structure of which is determined by causing the constituent fibres to have differing ability to shrink on the yarn being subjected to a uniform shrinkage treatment, and then subjecting the yarn to such treatment. Such yarns and processes for making them are the subject of co-p'ending application Ser. No. 176,455, filed Feb. 12, 1962, now abandoned; application Ser. No. 219,048, filed Aug. 23, 1962, now US. Patent No. 3,302,385; and application Ser. No. 346,870, filed Feb. 24, 1964, filed by inventors Ruddell and Todd. For most desired yarn structures it is necessary for the shrinkages involved not to exceed a given percentage, and naturally the effect of the necessary steps involved in spinning the yarn after variable shrinkage characteristics have been induced in the yarn material must not be such as to destroy the effectiveness of those characteristics. With certain yarn materials this has given rise to diificulties and the principal object of the present invention is to enable these difficulties to be overcome. These difficulties exist with certain yarn materials such as those consisting of or including vinyl chloride polymer, which have very low tenacities and therefore are readily stretched by substantial amounts even under very light loads. As a result, when processing such materials according to the process of US. specification No. 3,302,- 385 the desired result was not accomplished because the high stretch which occurred during the conversion of the staple fibre to yarn induced correspondingly high shrinkage potential in addition to the variable shrink-age previously induced in the tow, with the result that the variable component, so far as yarn modification was concerned, was largely masked, and that in any event the general level of shrinkage was so high as to preclude the desired effect. The object of the present invention is to overcome these difficulties.

According to the present invention a method of producing a staple yarn from a tow of man-made filaments includes the steps of converting said tow to a substantially States Patent fully relaxed sliver of staple fibres of varying lengths, and passing said sliver through a drafting system having a reach which is less than the lengths of at least a sub-stantial number of said staple fibres. In one useful embodiment of the invention a tow of p.v.c. filaments is stretched and then cut to produce bias staple, whereafter it is passed through the usual spinning processes until in sliver form, heat relaxed and then passed through the drafting zone. The amount of initial stretch is such that the fibres are not stretched [by any substantial amount during the conversion from tow to sliver. In another useful embodiment an unstretched p.v.c. tow is processed according to the invention described in the earlier patent applications mentioned aforesaid to give variable shrinkage characteristics to the filament, cut to give staple fibres of the same length, converted from tow to sliver, heat relaxed in sliver form, whereupon the fibres assume differing lengths because of their varying shrinkage characteristics, and then passed through the drafting zone.

The invention will be described further, by way of example only, with reference to the processing of undyed and also tow-dyed p.v.c. filaments (the latter needed to be relaxed prior to processing because of strains occurring during dyeing (about 6% shrinkage was recovered) and refinished.

Both samples were first subjected, in tow form, to variable stretching in order to give a shrinkage characteristic which varied cyclically from 0% to 28% and back to 0% over a length of 20 yards. The tow was then cut into staple of length 5.9 inches, carded on a fiat card and then prepared by three passages over intersectors to finisher sliver.

The finisher sliver was relaxed in an autoclave and the resulting fibre lengths extended over a range the limits of which lay above and below 4.5 inches. A 2-roller drawing system was set up having a reach of 4.5 inches and a draft of 1.62. The relaxed finisher sliver was drawn on this system in order that fibres below 4 /2 inches would pass through without drawing while fibres over 4.5 inches would be drawn by amounts varying with fibre length according to the formula:

SL is the actual stretch imlposed by rollers on a fibre of length L, when L is greater than R (i.e., SN is the nominal stretch imparted by the rollers) L is the fibre length R is the reach V is the surface speed of the drafting rollers V is the surface speed of the feed rollers In the examples quoted above the theoretical range of the differential stretch would be, according to the formula, 048%, but because of crimp regeneration during the relaxation of the finisher sliver, which effected the fibre length in the drawing reach, this range was not fully achieved.

The drawn sliver was spun on an apron drafting frame to l0s worsted count with 4 t.p.i. Z twistca.re being taken to keep the tension in the reach (controlled by carrier rollers) to a minimum consistent with fairly good spinning. This yarn was 4 folded with 2 t.p.i. S twist, hanked and relaxed. The resulting hank shrinkage was of the order of 30% of which a substantial amount was true fibre shrinkage the remainder being due to crimp regeneration.

The yarn so produced is a structured yarn a substantial part of the bulk of which is caused by the range of differential shrinkage in the fibre.

What we claim is:

1. A method of processing a tow of man-made filaments made from material adapted to be stretched to modify the shrinkage characteristics thereof which ineludes the steps of producing from said tow a fully relaxed sliver of staple fiber of varying lengths by-steps in which said tow is stretched, cut to predetermined lengths, formed into sliver and substantially completely relaxed to shrink said sliver, and passing said sliver through a drafting system having a reach which is less than the lengths of at least a substantial number of said staple fibres.

2. A method as set forth in claim 1 comprising the further step of converting said drafted sliver into yarn.

3. A method as set forth in claim 2 comprising the further step of subjecting said yarn to a uniform shrinkage treatment.

4. A method of processing a tow of man-made filaments made from material adapted to be stretched to modify the shrinkage characteristics thereof which includes the steps of highly stretching said tow, cutting said tow into staple fibre of varying lengths, converting said staple fibre to sliver, substantially completely relaxing to shrink said sliver, and passing said sliver through a drafting system having a reach which is less than the lengths of at least a substantial number of said staple fibres.

5. A method as set forth in claim 4 comprising the further step of converting said drafted sliver into yarn.

6. A method as set forth in claim 5 comprising the further step of subjecting said yarn to a uniform shrinkage treatment,

7. A method of processing a tow of man-made filaments made from material adapted to be stretched to modify the shrinkage characteristics thereof which includes the steps of stretching to induce variable shrinkage characteristics in said tow, cutting said tow into staple fibre of uniform length, converting said staple (fibre to sliver, substantially completely relaxing said sliver where by to shrink said staple fibres variably, and passing said sliver through a drafting system having a reach which is less than the lengths of at least a substantial number of said staple fibres.

8. A method as set forth in claim 7 comprising the further step of converting said drafted sliver into yarn.

9. A method as set forth in claim 8 comprising the further step of subjecting said yarn to a uniform shrinkage treatment.

References Cited UNITED STATES PATENTS 3,302,385 2/1967 Ruddell et a1. 57--l57 JOHN PETRAKES, Primary Examiner.

US, Cl. X.R.