US3552679A - Yarn package - Google Patents

Abstract

A yarn package comprising freshly drawn polyamide yarn in which the yarn on withdrawal possesses substantially constant shrinkage tension throughout its wound length by arranging for the yarn to be wound onto the package at different balloon (wind-on) tensions.

Description

United States Patent 72] Inventors Christopher John Rollason Pontypool; Gerald Henry Sutclilt Tinsley, Doncaster,

- England [21] AppLNo. 775,511

[22] Filed Nov. I3, 1968 [45] Patented Jan. 5, 1971 [73] Assignee Imperial Chemical Industries Limited London, England a corporation of Great Britain [32] Priority Nov. 17, 1967 I3 3] Great Britain [54] YARN PACKAGE 2 Claims, No Drawings [52] U.S.Cl. 242/159, 57/156 [51] lnt.Cl B6Sh 55/00; DOlh l/26 [50] Field olSearch 57/106T. 94, 93, 92, 96, 156; 242/18, 18T, 26.1, 46.2. 45, 147, 159

[56] References Cited UNITED STATES PATENTS 1,965,163 7/1934 Truslow Y 5'7/93 1,985,851 12/1934 Brooks et a1. 57/94 3,315,904 4/1967 Hardee 242/18 3,329,360 7/1967 Schippers.. 242/45X 3,357,655 12/1967 lwnicki et al. 57/94X 3,450,371 6/1969 Phillips 57/93X Primary ExaminerDonald E. Watkins Attorney-Cushman, Darby & Cushman ABSTRACT: A yarn package comprising freshly drawn polyamide yarn in which the yarn on withdrawal possesses substantially constant shrinkage tension throughout its wound length by arranging for the yarn to be wound onto the package at different balloon (wind-0n) tensions.

1 YARN PACKAGE The present invention relates to thermoplastic polyamide filaments, yarns and the like. More particularly, the invention relates to an improvement in the properties of such structures.

For the sake of convenience that expression yarn will be used hereinafter to describe single and multifilament continuous strands.

When a process or treatment is to be either continuously or batchwise applied to a yam so as to modify or otherwise alter the properties or characteristics of that yarn, it is often particularly important that such a process or treatment be applied uniformly, thus ensuring a constancy of new yarn properties from one portion or section of the yarn to another.

Unfortunately, such a consideration frequently suffers from the serious limitation that however meticulous the technical attention given to the process or 'treatmentinquestion, its resultant effect can be no better than that which the chemical and physical uniformity of the yarnpermits, which in turn will depend, iutcr alia, upon those processes and treatments which the yarn may have already undergone.

In any yarn process ortreatment, therefore, the ultimate desired result will depend in the first instance upon the constancy, uniformity and levelness of the properties and character of the yarn prior to that process or treatment. In other words, the success of each processing step will depend, inter alia, upon those preceding it.

Before a polyamide yarn is woven, knitted or otherwise made up into a fabric or other structure it may undergo a succession of operations that may at the same time undesirably influence its properties. i

In particular, a molecularly oriented or drawn polyamide yarn, after it has been wound onto a bobbin or like container following drawing, is frequently found to possess varying properties along its length on unwinding which are sufficient to adversely influence the behavior of the yam both chemically and physically when it is subjected to further treatments, often to such an extent that in some instances'the final use to which the yarn is put may be significantly affected.

Very often such variation in yar'n properties may be attributed to the variable extent of lengthwise shrinkage of yarn that arises throughout the yarn package during and after its formation following the drawing process,which in turn may be ascribed to the manner in which such a package is built.

The extent of polyamide yarn shrinkage usually changes gradually throughout a wound package, i.e. from the inside or core of the package tothe outside, or vice versa, and although in some instances the gradual variation in yarn character which results may be insufficient to lead'to visible defects or other detrimental changes in yarn taken from a single package, there is, regardless of the manner in which yarn properties may vary across the diameterof a package, usually a substantial difference between the character of the yarn on the inside of the package and that in the outer layers of the package. Under these circumstances, the jump" in properties when the transfer-tail of one package is joined to the leading end of another as in magazine creelirig is sufficient to cause a significant imperfection in a product derived from such joined yarns. I

In particular, when drawn polyamide yarn is wound onto a bobbin the yarn is still tending to shrink after drawing. The innermost package layers are held firmly against the container barrel and are unable to shrink any further, while the outer package layers are able to shrink to some extent onto the layers beneath. The middle package layers are less free to shrink but are also subjected to crushing due to shrinkage of the outer layers. Thus, when yarn is taken from the package, the residual tendency to shrink is lowest in yarn from the middle of the package and greatest in yarn from the inside.

In the case of a 3-pound polyamide yarn package, the lowest shrinkage tension values occur in yarn taken from approximately the l to 2 pound region of'the package.

Thus, it is an object of the present-invention to provide a package of polyamide yarn that'is substantially free from such variation of shrinkage tension on unwinding as is likely to lead to an unsatisfactory final product.

it is a further object of the presentinvention to provide a process whereby the aforementioned object may be successfully achieved. I

Accordingly, the present invention provides a yarn package comprising freshly drawn polyamide yarn in which the yarn on withdrawal possesses substantially constant shrinkage tension throughout its wound length.

In the context of this invention the'expression substantially constant shrinkage tension meansa variation about a mean of not more than 10 percent. i

The invention further provides a process for building a package of drawn polyamide yarn in which the yarn on withdrawal possesses substantially constant shrinkage tension throughout its wound length, by arranging for yarn to be wound onto the package at different balloon (wind-on) tensions so as to counteract the forces which develop in the package after it has been built.

Preferably, the necessary changes in balloon tension are brought about by arranging for an appropriate change in the speed of the spindle driving the package.

Generally, such a program consists of commencing to build a package of drawn yarn at a low balloon tension (without deteriorating drawing performance), increasing to a maximum at some specific package weight, and thenfinally decreasing to a low balloon tension. Such variation in balloon tension may be achieved by-arranging for an initial continuous increase in the speed of the spindle driving the package followed by a continuous decrease in the spindle speed.

This program, which is applicable to packages wound in' parallel layers, e.g. the so called long to short packages, winds yarn onto the package at a sequence of balloon tensions that are designed to counteract the internal forces which develop in a package after it has been built and which are caused by the differential shrinkage of yarn within the package.

in order to achieve the minimum variation in shrinkage tension throughout the full package, it has'been found desirable to continuously increase the balloon tension until about one third of the full package has been built.

When yarn is subsequently taken from the package it ex-- hibits a substantially constant shrinkage tension of the lowest level.

Thus, the effect of differential shrinkage of drawn polyamide yarn within a package which may give rise to tension fluctuations in the running yarn during subsequent treatments, such as false-twist bulking, with commensurate stripiness and variation in dye uptake in a resulting fabric, may be met by an appropriate variation in the speed of the spindle driving that package. 7

Normally, programming will be applied by a suitable profiled cam which will cause the spindle to be rotated at an appropriately varying rotational "speed during the winding of the full package. Equipment for programming spindle speeds is available from a number of sources and is readily accessible to those familiar with the art. A

By shrinkage tension is meant, that tension which occurs -when the polyamide yarn is held to substantially constant length and heated to a temperature of li5 C. Alternatively, a closer simulation of tensions developed during false-twist bulking processes can be achieved bymeasuring the tension required to stretch the polyamide yarn'by 3 percent while passing it over a heater plate at a yarn temperature of l90i5C.

The effect of shrinkage tension is important in any process in which polyamide yarn is relaxed by heat or steam and where uniformity of properties and character is important. Thus, e.g., in finishing fabrics comprising in part'or in whole polyamide yarns, heat-setting is likely .to be far more effective if the fabric comprises polyamide yarns prepared according to the present invention. y

The invention is applicable to any polyamide yarn that has a tendency to shrink after being held under tension, especially after drawing, and in particular there may be mentioned polyamide (which expression is to be taken as including copolyamide) yarns such as those derived from polyhexamethylene adipamide, polyhexamethylene sebacamide and polyepsilon caprolactam.

In the following illustrative examples, there are particularly described processes whereby the beneficial effects of the present invention may be realized.

In the examples a 70 denier, 34 filament polyhexamethylene adipamide yarn was drawn at 3,300 feet/minute before it was wound-up using a ring and traveller system to form a 3 pound package, the yarn being wound on the package in parallel layers of decreasing traverse length.

Example 1 In conventional prior art systems, the spindle speed might well be adjusted to give a constant balloon tension of about 3 grams throughout the package build. Under the characteristics of the present system this was achieved with an initial spindle speed of the order of 9,600 r.p.m. decreasing to about 6,800 rpm. by the time the package was complete. I

After unwinding the package about two weeks later, the shrinkage tension i.e., the tension required .to stretch the yarn by 3 percent while passing it over a heater plate at a yarn temperature of 1905C. varied from 32 grams to 48 grams, with the lowest level being at about one-third of the full package and the highest at the barrel of the container.

Woven and weft knitted fabrics prepared from yarns subsequently bulked by false-twisting. and dyed in the usual manner clearly showed a variation in dye-uptake.

EXAMPLE 2 In the process of the present invention, the spindle speed was programmed to give balloon tensions starting at about I gram, increasing to about 8 grams at approximately one-third of the full package and then decreasing to about l'grarh again at the full package. In this case initial spindle speed was of the order of 8,500 r.p.m. increasing to approximately 9,200 r.p.m. and then decreasing to about 5,700 r'.p.m.

After unwinding the package about two weeks later, the shrinkage tension varied only between4'0 and 45 grams and the dyeing differences in bulkedyarn fabrics were greatly. reduced with the largest differences beingb'eing barely visible.

We claim: I 1

l. A process for winding a package of freshly drawn polyamide yarn on a bobbin with a ring-and-traveller system in order that the yarn on unwinding possesses substantially constant shrinkage tension along its wound length, being the'tension required to stretch the yarn by 3 percent while passing ,it over a heater plate at a yarn temperature of '190i-5C., by programming the speed of the spindle carryingthe bobbin to give a gradually increasing yarn balloon tension until approximate,-

ly one-third of the full package has been-wound, and then a gradually reducing yarn balloon tension over the remainder of the winding period.

2. A yarn package of freshly drawn. polyamide yarn when wound according to the process as claimed in claim I.

Claims (1)

1. 2. A yarn package of freshly drawn polyamide yarn when wound according to the process as claimed in claim 1.