US3851457A - Core yarns and methods for their manufacture - Google Patents

Abstract

A core yarn having a decitex of 120 to 400 comprising a set false twisted core and a wrapper of filaments formed in reversing helices, the core having a decitex between 25 and 40 percent of the decitex of the core yarn. The core yarn is made by simultaneously drawing and false-twist crimping two as-spun components having different extensibility under a given stress.

Description

11111100 States Patent 11 1 1111 3,851,457 Waters Dec. 3, 1974 CORE YARNS AND METHODS FOR THEIR MANUFACTURE [56] References Cited [75] Inventor: Graham Thomas Waters, NITED STATES PATENTS Pontypool, England 3,079,746 3/1963 Field 57/77.33 X 3,120,095 2/1964 Guthrie 57/140 BY X [7.3] Assgnee' 'f f lndusmes 3,416,302 12/1968 Knospe 57/140 BY London, England 3,439,490 4/1969 Tarkington et a1 57/140 BY 22 Filed: Apr. 9 197 3,608,295 9/1971 Kitazawa 57/140 BY 3,691,750 9/1972 Waters 57/140 BY X [21] Appl. No.: 349,164

Related U.S. Applicati0n Data 5 i P" fi l J [60] Continuation-impart of Ser. No, 260,934, June 8, q or "m.- er en 1972, Pat. No. 3,780,515, which is a division of Ser.

No. 125,683, March 18, 1971, Pat. N0. 3,691,750, TRA T which is a colilinuation-in-pafl 1 A core yarn having a decitex of 120 to 400 comprising March 1969' 3557373 a set false twisted core and a wrapper of filaments formed in reversing helices, the core having a decitex [52] Cl 57/144 57/140 57/157 between and percent of the decitex of the core 7 yarn. The core yarn is made by simultaneously draw- [51] 1t. Cl. D028 3/38, D02] 1/12 g and false twist p g two as spun components [58] Field 011 Search 57/77.3, 144, R, 139,

57/140 BY, 157 R, 157 TS, 157 MS, 157 F, 160

having different extensibility under a given stress.

9 Claims, 3 Drawing Figures.

CORE YARNS AND METHODS FOR THEIR MANUFACTURE This is a continuation-in-part of Ser. No. 260,934 filed June 8, 1972, now US. Letters Pat. No. 3,780,515, which is division of Ser. No. 125,683 filed Mar. 18, 1971, now US. Letters Pat. No. 3,691,750, which is a continuation-in-part of Ser. No. 805,598 filed Mar. 10, 1969, now US Letters Pat. No. 3,557,873.

The present invention concerns core yarns and methods for their manufacture.

British Pat. specification No. 1,258,905 describes a core yarn comprising a core component of set false twisted synthetic continuous filaments and at least one wrapping component of synthetic continuous filaments which are formed in helices, the directions of which helices reverse at intervals along the yarn.

We have now found a range of core yarns which, when in the form of fabric, possess the handle, staple appearance and warmth of wool combined with the easy care properties, e.g., dry crease shedding and washability, of synthetic continuous filaments.

Accordingly we provide a well integrated core yarn comprising a core component of set false twisted synthetic continuous filaments and at least one wrapping component of synthetic continuous filaments which are formed in helices, the directions of which helices reverse at intervals along the yarn, said core yarn having a decitex as defined herein within the range 120 to 400 inclusive and said core component having a decitex as ces may be only intermittently wrapped around the core com'ponenLSuch yarns have been designated as core yarns of low order.

The nature and thickness of the synthetic filaments of the wrapping component or components are such as to cause the helices of that component(s) to stand out proud of the core component, and to provide the surface texture which, after fabrication, simulates that of a wool yarn. It is preferred that the wrapping component has a decitex per filament within the range 2.5 to 7.5 inclusive. 1

The low order core yarns are fluffier than the high order ones, and, despite the intermittency of the wrapping, the yarns are a well-integrated filamentary body, i.e., the wrapper and core components do not become separated during textile processing such as weaving and knitting.

The core yarn of the invention can be homogeneous in the sense of the core and wrapping components being made of filaments of the same synthetic fibres, as for instance, polyhexamethylene adipamide (nylon 66) or polyethylene terephthalate. However, this is not essential; and dye variations and other effects may be better obtained if the components or filaments differ in respect of chemical character, or at least the wrapping components differ when there are more than one of them. The filaments may be pigmented differently. F i1- aments may be all of circular cross-section; or some, at least may be of .non-circular cross-section, e.g., trilobal.

Although possessing a set false twisted, and hence extensible, core component, the core yarn of the invention exhibits no sharply defined yield point under load at a constant rate of extension, i.e., the core yarn exhibits load/extension characteristics similar to those of a conventional flat yarn and can be regarded as being sufficiently tension-stable for weaving or knitting into fabric in which the textured effect of the helical wrapping component or components is adequately maintained.

The core yarn of the invention, owing to its false- I twisted components, may possess torque; and hence it may be desirable for two such yarns of opposite torque to be doubled to balance the torques, or for a single such yarn to be submitted to a subsequent heat treatment to cause the decay of the torque, in order that the yarn may be readily usable for knitting or weaving.

According to the invention we also provide a process for making a core yarn having a decitex as defined herein within the range 120 to 400 inclusive comprising supplying at least two synthetic continuous filamentary components to in sequence a feed means, a heating zone, a cooling zone and a false twisting element and withdrawing said filamentary components from said sequence under a higher tension than that under which the said components were supplied to said sequence such that the filaments are drawn one and one-half to six times their feed length, the filamentary components differing as to their extensibility under the stresses on entering the yarn section of increasing twist gradient, the ratio of the decitex of the component of greater extensibility to the decitex of the component of lesser extensibility being within the range 1.5 2 1 to 3 2 l inclusive.

The draw ratio is more preferably between 2.0 and 3.5 for most yarns, but can vary within the noted larger range depending on the particular core yarn being produced.

The purpose of the heating zone followed by the cooling zone is to set the yarn in its twisted configuration. The cooling zone may comprise natural cooling or forced cooling. The latter may be achieved by directing a stream of cool air on to the yarn.

The degree of order of the core yarn may be controlled in several ways, particularly by selection of decitex per filament differences between the core and wrapper. The order may also be controlled by the degree of set and by extensibility differences which are produced by different spun birefringence, shrinkage, intrinsic viscosities and the like. As the wrapper decitex per filament decreases with respect to the core decitex When a feed yarn composed of two as-spun filamentary components having differing values of extension under a given stress is submitted to a combined drawing and false twist crimping process, then, in the false twisting zone, that is, upstream of the twisting element, the component of greater extensibility forms a unidirectional helix of substantially constant radius around the other component which is a twisted yarn in which filament migration occurs. Downstream of the draw roll, the wrapping is of alternating helix direction.

Most practically, such method involves the employment of as-spun filaments having differing birefringence values, e.g., differing by 3 to 5 X units as measured, for instance, by a Berek compensator with a polarized microscope. Details of a method for so measuring birefringence are given in our British Pat. Specification No. 762,190.

It is possible to prepare the as-spun filamentary components with differing extensibilities under a given stress either by spinning them from differing polymer feed stocks, or by using a common polymer feed stock and varying spinning parameters such as the wind-up speed on the spinning machine.

Such varying extensibility of filaments can be usefully achieved by varying the spun birefringence of the filaments that are combined to form the feed yarn, such filaments being of homogeneous feedstock. For instance, polymeric material for extrusion into filaments by melt-spinning can be split into two or more fractions prior to or immediately after extrusion, and the required differential potential can be provided for by treating the fractions differently in regard to their extrusion conditions. One such method involves the injection of a modifying agent for the polymer into one or more of the stream fractions within the spinning pack. Another method involves variable quenching of the filaments through the use of water or other fluids. A further method involves applying an intermediate forwarding force to one fraction of filaments between their fluid and solidified regions and not to the other fraction.

It is also within the scope of the invention that certain of the filaments shall themselves be of the conjugate type, say those of two constituents, in sheath-and-core or side-by-side arrangement.

According to the invention, it is possible to have a feed yarn in which the filaments are of only two different types having differing values of extension under the drawing stress. Equally, however, it is possible to employ a feed yarn having filaments of more than two such types, whereby a wider spectrum of effects may be obtained.

Core yarns according to the invention may be processed from such heterogeneous filament bundles concurrently with their production, or as a separate step following on after the preparation of the heterogeneous filament bundles in the form, for instance, of wound packages of as-spun filaments.

In yet another method by which the said core yarns may be made, we employ as-spun filamentary components of the same or differing extension under a given stress, and positively feed them at the same or differing speeds to a false twisting device and withdraw them fering heat treatments can be imparted by contacting the filamentary components with a heated surface or surfaces having portions at different temperatures, as for instance with a heated feed roll having portions of its peripheral surface heated from internally, e.g., by electric resistance heaters, at different temperatures.

This method of making the said core yarns is especially adapted to the invention when to be carried out with filamentary components of polyester material, as for instance polyethylene terephthalate filaments. In this latter method, the temperature of portions of a heated feed roll, or of a plurality of heated feed rolls, can differ in the range between, say and C.

The synthetic filaments of the wrapping components may, or may not, be completely drawn, although it is preferred that they should be. The filaments of the core component will, however, be preferably at least substantially fully drawn.

It is possible, however, to produce useful core yarns from filamentary components wherein at least some of the filaments are already in a drawn state, or in a partially drawn state, provided that they nevertheless differ as to their extensibility under the stress to which they will be submitted in the false twisting process.

It is within the scope of this invention to provide for additional differences between the filaments than that of extension under a given stress. For example, the filaments may also be of different decitex.

Preferably, owing mainly to the higher throughput which it allows, the false twist crimping machine has twisting elements of the friction type, by which the false twist is inserted by the direct action of rotating annular friction means on the yarn. Alternatively a spindle false twisting machine may be used with correspondingly good results.

It is usually desired to decay the torque necessarily induced in the false twisting process; and such may be achieved by imparting a limited degree of heating to the composite, core yarn on the way to the wind-up, or after having been wound on the wind-up package. The decaying of the torque under tension contributes to the lesser bulk of the core components compared to the wrapper component.

Such limited degree of heating on the run" may be provided by contact with a heated surface, e.g., a roll or a curved plate. In certain circumstances, if desired, the draw roll may be heated to serve for this purpose.

Alternatively, the limited degree of heating on the run may be provided by passage of the composite, core yarn through a heated fluid, such as hot air or steam in a steaming tube or a jet.

Heating on the wind-up package may likewise be in steam, in a dry heat atmosphere or in a heated dyebath.

In either case of limited heating, the composite, core yarn may be heat treated while under a controlled tension and temperature depending on the nature of the bulkiness desired.

The invention will now be described with reference to the drawings filed with the provisional specification, in which:

FIG. 1 is a schematic representation of a core yarn of high order according to the present invention.

FIG. 2 is a schematic representation of a core yarn of low order according to the present invention.

FIG. 3 is a diagrammatic representation of one embodiment of the process of the invention.

Referring now to FIG. ll, there is shown a core yarn of high order having a core component 1 and a wrapping component 3 composed of individual filaments 5 formed in helices and continuously wrapped around said core component. The direction of the helix of a filament around the core reverses at points 7 and 9.

Referring to FIG. 2, there is shown a core yarn of low order having a core component 1 and a wrapping component 3 composed of individual filaments 5 formed in helices and intermittently wrapped around said core component.

Referring to FIG. 3, one embodiment of the process of the invention will now be described. As-spun yarns l5 and 17, of differing birefringence values, are withdrawn from supply packages 16 and 18 by feed roll assembly 21, comprising a feed roll 23, a separator roll 25, and a nip roll 26, the undrawn yarns having been brought together at thread guide 19. From the feed roll assembly the yarns pass to a false twisting and drawing stage comprising a heater plate 27, a natural cooling zone 28, a friction twisting element 29 and a draw roll assembly 31 comprising a draw roll 33 and a separator roll 35. On'leaving the feed roll assembly 21, the yarns enter a section of increasing twist gradient 30 due to the insertion of twist into the yarns by friction twisting element 29. The twist gradient reaches a maximum value on the heater plate 27. The draw roll is rotated at a given higher speed compared with the feed roll and drawing takes place on the heater plate 27. The yarns are subjected to stresses on entering the yarn section of increasing twist gradient 30 due to the higher speed of the draw roll 33 compared with the feed roll 23 and the insertion of twist by friction twisting element 29. Since the yarns have differing birefringence values they differ as to their extensibilities under the stresses on entering the yarn section of increasing twist gradient. In this section, that is, upstream of twisting element 29, the component of greater extensibility forms a unidirectional helix of substantially constant radius around the other component which is a twisted yarn in which filament migration occurs. Downstream of twist element 29, the core yarn produced has a set false twisted core and a wrapping component of alternating helix direction; From the draw roll assembly the core yarn passes to a heater plate 37 and thence to a relax roll assembly 39 comprising a relax roll 41 and a separator roll 43.

The extent of relaxation achieved is governed by the temperature of heater plate 37 and the speed at which relax roll M is operated compared with draw roll 33.

From the relax roll assembly 39, the core yarn is passed to a conventional wind-up assembly (not shown) for orderly collection.

The following example illustrates but does notlimit our invention.

EXAMPLE 1 The core component comprised 207 decitex/lS filament as-spun poly(ethylene terephthalate) yarn of spun birefringence value 8 X The wrapping component. comprised 414 decitex/30 filament as-spun poly(ethylene terephthalate) yarn of spun birefringence value 5 X l0'.

The two as-spun yarn components were fed together by the feed roll of a positive feed spindle false twisting machine,.the draw roll of which was rotated at a given higher speed compared with the feed roll such as to simultaneously draw the yarn components whilst they were being false twisted, drawing occurring an inch or two along the length of a 40 inch long contact heater plate, maintained at 210C and positioned between the feed roll and the false twisting spindle.

The linear speed of the composite yarn at the draw roll was 183 m/min and the draw ratio 2.82 to l. The false twisting spindle was rotated at 335,000 rpm.

The yarn was then fed at an overfeed of 14 percent through a 40 inch long convection tube heater, maintained at 200C, to a relax roll. The yarn was finally wound on a package at an underfeed of 2.7 percent.

The yarn so produced was a 250 decitex/45 filament core yarn of high order.

A double pique fabric was made from the yarn by knitting as slackly as possible. The knitted fabric was scoured for 30 minutes at 60C and then dyed for 2 hours at 999C. After a reduction clearing treatment and a softening treatment, the fabric was heat set on a stenter for 30 seconds at 170C.

The fabric so produced possessed a handle and staple appearance similar to a wool fabric. Further, these properties were retained in garments made from the fabric even after repeated wearing and washing.

EXAMPLE 2 A yarn and knitted fabric were produced as in Example 1 except that the core component comprised 153 decitex/ l 0 filament as-spun polyethylene terephthalate yarn, the wrapping component comprised 465 deci- ,tex/30 filament as-spun polyethylene terephthalate yarn and the false twisting spindle was rotated at 346,700 rpm.

The yarn produced was a 250 decitex/40 filament core yarn.

The knitted fabric had a wool-like handle similar to the fabric of Example 1.

EXAMPLE 3 A yarn and knitted fabric were produced as in Exam- EXAMPLE 4 A fabric and knitted yarn were produced as in Example l exceptthat the core component comprised decitex/l5 filament as-spun trilobal polyethylene terephthalate yarn, the wrapping component comprised 300 decitex/30 filament as-spun trilobal polyethylene terephthalate yarn, the false twisting spindle was rotated at 269,000 rpm, the linear speed of the composite yarn at the draw roll was 133 m/min, the draw ratio was 2.60 to 1 and the secondary heater was maintained at 220C.

The yarn produced was a 150 decitex/45 filament core yarn. A yarn suitable for knitting was obtained by plying to three turns per inch two core yarns produced under S and Z twisting conditions respectively.

The knitted fabric possessed a handle similar to a wool fabric.

EXAMPLE A yarn and knitted fabric were produced as in Example 1 except that the core component comprised 109 decitex/30 filament as-spun pigmented trilobal polyhexamethylene adipamide yarn and 88 decitex/five filament as-spun black polyethylene terephthalate yarn of spun bi-refringence value 8 X 10 the wrapping component comprised 300 decitex/30 filament as-spun trilobal polyethylene terephthalate yarn of spun birefringence value 5 X 10', the contact heater plate was maintained at 200C, the linear speed of the composite yarn at the draw roll was 152 m/min, the false twisting spindle was rotated at 320,000 rpm and the secondary heater was maintained at 190C.

The knitted fabric possessed a handle and staple appearance similar to a wool fabric together with a pleasing three-colour marl effect.

What l claim is:

l. A well integrated core yarn comprising a core component of set false twisted synthetic continuous filaments and at least one wrapping component of synthetic continuous filaments which are formed in helices, the directions of which helices reverse at intervals along the yarn, said core yarn having a decitex as defined hereinbefore within the range 120 to 400 inclusive and said core component having a decitex as defined hereinbefore between 25 and 40 percent of the decitex of said core yarn.

2. A core yarn according to claim I in which the filaments of the wrapping component are intermittently wrapped around the core component.

3. A core yarn according to claim 1 in which the wrapping component has a decitex per filament within the range 2.5 7.5 inclusive.

4. A core yarn according to claim 1 in which at least some of the synthetic continuous filaments are conjugate filaments.

5. A core yarn according to claim 1 in which at least some of the synthetic continuous filaments are of noncircular cross-section.

6. A core yarn according to claim 1 which has been stabilised to decay torque.

7. A process for making a core yarn having a decitex as defined hereinbefore within the range to 400 inclusive comprising supplying at least two synthetic continuous filamentary components to in sequence a feed means, a heating zone, a cooling zone and a false twisting element and withdrawing said filamentary components from said sequence under a higher tension than that under which the said components were supplied to said sequence such that the filaments are drawn 1.5 to 6.0 times their feed length, the filamentary components differing as to their extensibility under the stresses on entering the yarn section of increasing twist gradient, the ratio of the decitex of the component of greater extensibility to the decitex of the component of lesser extensibility being within the range 1.5 l to 3 l inclusive.

8. A process according to claim 7 in which the filaments are drawn 2.0 to 3.5 times their feed length.

9. A process according to claim 7 in which the filamentary components are withdrawn and subsequently heat treated while under a controlled tension and temperature.

Claims (9)

1. A WELL INTEGRATED CORE YARN COMPRISING A CORE COMPONENT OF SET FLASE TWOSTED SYNTHETIC CONTINUOUS FILAMENTS AND AT LEAST ONE WRAPPING COMPONENT OF SYNTHETIC CONTINUOUS FILAMENTS WHICH ARE FORMED IN HELICES, THE DIRECTIONS OF WHICH HELICES REVERSE AT INTERVALS ALONG THE YARN, SAID CORE HAVING A DECITEX AS DEFINED HEREINBEFORE WITHIN THE RANGE 120 TO 400 INCLUSIVE AND SAID CORE COMPONENT HAVING A DECITEX AS DEFINED

2. A core yarn according to claim 1 in which the filaments of the wrapping component are intermittently wrapped around the core component.

3. A core yarn according to claim 1 in which the wrapping component has a decitex per filament within the range 2.5 - 7.5 inclusive.

4. A core yarn according to claim 1 in which at least some of the synthetic continuous filaments are conjugate filaments.

5. A core yarn according to claim 1 in which at least some of the synthetic continuous filaments are of non-circular cross-section.

6. A core yarn according to claim 1 which has been stabilised to decay torque.

7. A process for making a core yarn having a decitex as defined hereinbefore within the range 120 to 400 inclusive comprising supplying at least two synthetic continuous filamentary components to in sequence a feed means, a heating zone, a cooling zone and a false twisting element and withdrawing said filamentary components from said sequence under a higher tension than that under which the said components were supplied to said sequence such that the filaments are drawn 1.5 to 6.0 times their feed lenGth, the filamentary components differing as to their extensibility under the stresses on entering the yarn section of increasing twist gradient, the ratio of the decitex of the component of greater extensibility to the decitex of the component of lesser extensibility being within the range 1.5 : 1 to 3 : 1 inclusive.

8. A process according to claim 7 in which the filaments are drawn 2.0 to 3.5 times their feed length.

9. A process according to claim 7 in which the filamentary components are withdrawn and subsequently heat treated while under a controlled tension and temperature.

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