WO1993010287A1

WO1993010287A1 - Improvements in polyester filaments, yarns and tows

Info

Publication number: WO1993010287A1
Application number: PCT/US1991/008379
Authority: WO
Inventors: John Paul Hendrix, Jr.; Benjamin Hughes Knox; Joe Forrest London, Jr.; James Bennett Noe
Original assignee: E.I. Du Pont De Nemours And Company
Priority date: 1991-11-18
Filing date: 1991-11-18
Publication date: 1993-05-27

Abstract

Drawing, especially cold-drawing, or hot-drawing or other heat-treatments of spin-oriented crystalline polyester filaments, and particularly polyester feed yarns, that have been prepared by spinning at speeds of, e.g. 4 km/min, and have low shrinkage and no natural draw ratio in the conventional sense, provides useful technique for obtaining uniform drawn filaments of desired denier and thereby provides improved flexibility to obtain filaments and yarns of various sub-deniers.

Description

TITLE

IMPROVEMENTS IN POLYESTER FILAMENTS, YARNS AND TOWS

This invention concerns improvements in and relating to polyester (continuous) filaments, especially in the form of sub-denier filaments, and yarns thereof, and more especially to a capability to provide from the same feed stock such polyester continuous filament yarns of various differing deniers, as desired, and of other useful properties, including improved processes; and new polyester flat yarns, as well as filaments, generally, including tows, resulting from such processes, and downstream products from such filaments and yarns.

According to the parent application

PCT/US91/XXXXX filed simultaneously herewith, and corresponding to USP 5,066,447, the disclosure of which is hereby incorporated herein by reference, processes are provided for improving the properties of feed yarns of undrawn polyester filaments. Such processes involve drawing with or without heat during the drawing and with or without post heat-treatment, and are most conveniently adapted for operation using a draw-warping machine, some such being sometimes referred to as draw-beaming or warp-drawing operations.

Preferred undrawn polyester feed yarns comprise spin-oriented polyester filaments of low shrinkage such as have been disclosed in Knox U.S. Pat. No. 4,156,071. Alternatively, spin-oriented feed yarns of low shrinkage may be prepared at speeds higher than are used in the Knox patent, including speeds and conditions such as are

disclosed by Frankfort & Knox in U.S. Patent Nos. 4,134,882 and 4,195,051.

Recently, much interest has been shown in making sub-denier filaments, both for continuous filament yarns and for conversion into sub-denier staple. By sub-denier herein we mean, for

convenience, any filaments having a denier (the weight in grams of a length of 9000 meters) per filament of about 1 or less. The manufacture of sub-denier filaments commercially is more costly than for most prior commercial filaments of regular denier, as is well known. Much of the prior commercial filament yarns of regular denier have been made by spinning continuously at high

withdrawal speeds. To make filaments of any

required lower denier by a like continuous process requires correspondingly lower throughputs of polymer. Also, as the filament denier is reduced, it becomes progressively more difficult to maintain uniformity, both along-end and between the various filaments. Lack of uniformity often shows up in the eventual dyed fabrics as dyeing defects, so is undesirable.

The present invention provides a technique by which sub-denier polyester filaments may be made efficiently, without some of the cost disadvantages referred to above.

According to the invention, there are provided the following processes:

A process for preparing a continuous filament yarn of deniers per filament up to about one, wherein a feed yarn of spin-oriented polyester filaments is completely or partially drawn to a uniform yarn of said deniers by hot-drawing or by cold-drawing, with or without heat-setting, said feed yarn being of elongation-to-break (E_B) 40 to

120%, tenacity at 7% elongation (T₇) at least 0.7 grams/denier, boil-off shrinkage (S₁) less than 10%, thermal stability as shown by an S₂ value less than +1%, net shrinkage (S₁₂) less than 8%, maximum shrinkage tension (ST) less than 0.3 grams/denier, density (p) 1.35 to 1.39 grams/cubic centimeter, and crystal size (CS) 55 to 90 Angstroms and also at least (250 ρ - 282.5) Angstroms. Partial drawing and/or cold-drawing are expected to be particularly important embodiments. Hot-drawing, with or without post heat-treatment, may also be very useful

embodiments, as will become clear.

If desired, a yarn (A) of a given denier per filament less than about one, and a different yarn (B) of a different denier per filament less than about one, are both produced by drawing the same such feed yarn of spin-oriented polyester filaments, and wherein the denier per filament of yarn (B) differs by at least 10% from the denier per filament of yarn (A).

If desired, a polyester filament yarn that is suitable for weaving or knitting may be prepared by heat-treating such a feed yarn of spin-oriented polyester filaments as it is advanced under a controlled tension.

Polyester polymers, used herein, may, if desired, be modified by incorporating ionic dye sites, such as ethylene-5-M-sulfo-isophthalate residues, where M is an alkali metal cation, for example in the range of about 1 to about 3 mole percent ethylene-5-sodium-sulfo-isophthalate

residues, to provide dyeability with cationic dyes, as disclosed by Griffing and Remington in U. S.

Patent No. 3,018,272. A suitable polymer of

relative viscosity (LRV) about 13 to about 18 is particularly useful. Representative copolyesters used herein to enhance dyeability with disperse dyes are described in part by Most U. S. Patent No.

4,444,710, Pacofsky U. S. Patent No. 3,748,844, Hancock U. S. Patent No. 4,639,347, and Frankfort and Knox U. S. Patent Nos. 4,134,882 and 4,195, 051, and representative chainbranching agents used herein to reduce shrinkage, especially of polyesters modified with ionic dye sites and/or copolyesters, are described in part in Kiiόx U. S. Patent No.

4,156,071, MacLean U. S. Patent No. 4,092,229, and Reese U. S. Patent Nos. 4,883,032, 4,996,740, and 5,034,174. To obtain spin-oriented feed yarns of low shrinkage from modified polyesters, it is generally advantageous to increase polymer viscosity by about +0.5 to about +1.0 LRV units and/or add minor amounts of chainbranching agents (e.g., about 0.1 mole percent).

Advantageously, according to the present invention, the spin-oriented polyester filaments may be provided in the feed yarn as filaments that are already sub-denier. However, the present invention provides an opportunity to reduce the denier of somewhat larger deniers into the sub-denier range.

According to an aspect of the invention, a soft bulky textured yarn may be provided by air-jet texturing the resulting sub-denier filament yarns.

According to an aspect of the present invention, an opportunity is .provided for making sub-denier staple, e.g. by mechanical crimping of the filaments and converting to staple, e.g., by cutting or stretch-breaking.

In the sub-denier Examples that follow. Tables XVI to XIX use feed yarns as disclosed in the Examples of the parent application, in Tables I-XV and the accompanying-disclosure of drawing of feed yarns. This is why the Tables herein are numbered consecutively, XVI-XIX, following Tables I-XV of the parent application, which are incorporated herein by reference. EXAMPLES

Eight sub-denier 91 denier, 100 filament, undrawn feed yarns, similar to feed yarns 1C, IV-1, V-3, and VI-3, were processed on a warp drawing (WD) machine cold at 600 mpm, using 1.0X, 1.1X, 1.2X, and

1.3X draw ratios (DR) under 2 sets of heat setting conditions to provide drawn flat textile yarns having properties as summarized in Table XVI, and with filament deniers between about 0.7 and 0.9 (before boil-off shrinkage, BBO) and filament deniers between about 0.74 and 0.94 (after boil-off shrinkage, ABO). Items XVI-1 to -4 were heat set by using the second heat-setting plate at a temperature of 190°C (without heating the first heat-setting plate) whereas XVI-5 to -8 were heat-set at the first heat-setting plate (at 190°C, and the second heat-setting plate was not heated). The warp drawn yarns of XVI-2,3 and -6,7 were uniformly partially cold drawn to residual elongations greater than 40% and were capable of being uniformly dyed without along-end dye variations (such as would result from nonuniform thick-thin drawing, characteristic of partially drawn conventional POY). Even at a residual elongation of about 30%, the boil-off and dry-heat shrinkages were less than 6% with a

differential shrinkage (DHS-BOS) less than +2%.

With hot drawing and/or heat setting using both plates 1 and 2, these shrinkages can be reduced to less than about 3%.

Co-cold drawing of undrawn flat textile yarns, wherein one yarn is heat-set to shrinkages less than about 3% and a second yarn is not heat-set, provides a simplified route to a mix-shrinkage warp sheet. This co-cold drawing can also be

extended to the co-drawing and subsequent

differential heat setting and co-mingling (plying) of single yarns to provide a simplified route to a mix-shrinkage yarn bundle. The high-shrinkage components of the mix-shrinkage warp sheet and of the single-end mix-shrinkage yarns of the invention differ from those made by drawing a conventional POY, in that the high shrinkage components of the invention have a differential shrinkage (DHS-BOS) typically less than about 2%; thus providing a very stable level of mix-shrinkage over a large end-use processing temperature range.

In a similar manner, eight 73 denier 68 filament undrawn feed yarns were uniformly cold warp-drawn, using various draw ratios to provide yarn properties summarized in Table XVII.

Three sub-denier 50 denier 68-filament undrawn feed yarns were similarly warp drawn (WD) cold at 1.42X draw ratio (DR) with heat-set

temperatures varying from 160°C to 180°C to provide drawn flat textile yarns as summarized in Table XVIII with filament deniers of about 0.51 before boil-off shrinkage, (BBO) and filament deniers of about 0.54 after boil-off shrinkage, (ABO). The boil-off shrinkages were all less than 5%. Cold drawing without heat setting would have provided shrinkages on the order of about 6 to 10%.

In a similar manner sub-denier 100 filament undrawn textile flat yarns were uniformly cold warp drawn to various draw ratios with yarn properties summarized in Table XIX.

Advantageously, if desired, fine denier drawn filament yarns may be prepared according to the invention from undrawn feed yarns that have been treated with caustic in the spin finish (as taught by Grindstaff and Reese in copending allowed Patent Application Serial No. 07/420,459, filed October 12, 1989) to enhance their hydrophilicity and provide improved moisture-transport and comfort.

Incorporating filaments of different deniers and/or cross-sections may also be used to reduce

filament-to-filament packing and thereby improve tactile aesthetics and comfort. Unique dyeability effects may be obtained by co-mingling drawn

filaments of differing polymer modifications, such as homopolymer dyeable with disperse dyes and ionic copolymers dyeable with cationic dyes.

To provide drawn polyester filament yarns capable of being dyed with cationic dyestuffs and being easier to nap and brush or cut into staple and flock, polyester polymer of relative viscosity (LRV) about 13 to about 18 and containing about 1 to about 3 mole percent of ethylene-5-sodium-sulfo

isophthalate is preferred. Undrawn feed yarns capable of being partially drawn and of being cold drawn to provide uniform drawn filament yarns were prepared by spinning 15.3 LRV copolymer at about 285°C and quenched using laminar cross-flow quench apparatus with a 5.6 cm delay, essentially as described in U. S. Patent No. 4,529,638, and

converging the filament bundle at about 109 cm with metered finish tip guides, and with drawn at spin speeds of 2468 and 2743 mpm, respectively, to provide 100 filament undrawn yarns of nominal 0.75 denier per filament and elongations about 113% and 102%, respectively. The undrawn yarns can be drawn up to 1.77X and 1.68X, respectively, to provide drawn filament yarns of at least about 20%

elongation and said drawn filament yarns may be air-jet textured yarns. The undrawn yarns may also be drawn with or without heat treatment and combined with homopolymer drawn filament yarns to provide mixed dyeability yarns.

The relative viscosity (LRV) of the polyester is as defined according to Broaddus U. S. Patent No.4,712,998.

TABLE XVI 1 2 3 4 5 6 7 8

WD Process

Draw Ratio (DR) 1.0 1.1 1.2 1.3 1.0 1.1 1.2 1.3

Drawn Yarn Properties

Denier 91.1 83.7 77.0 71.2 91.4 83.8 77.2 71.5 Modulus, gpd 45.1 58.5 70.5 80.0 47.2 58.0 69.0 77.7 Tenacity, gpd 2.66 2.90 3.20 3.52 2.75 2.90 3.14 3.47 Elongation, % 72.7 56.8 42.9 31.7 74.1 57.1 41.3 30.2 RDR 1.73 1.57 1.43 1.32 1.74 1.57 1.41 1.30 BOS, % 3.0 4.8 4.8 4.7 3.1 5.1 5.2 4.3 DHS, % 3.1 5.1 5.3 5.5 3.7 5.7 5.8 5.2 (DHS-BOS), % 0.1 0.3 0.5 1.2 0.6 0.6 0.6 0.9 Uster, % 2.0 3.1 2.6 2.3 2.3 3.2 3.5 2.6

TABLE XVIII

WD ProcessExample XVIII 1 2 3

W. D. Process

T_{set 2,}C 160 170 180

Drawn Yam Properties

Denier 35.9 36.1 36.1

T_{7 %}, _gpd 3.54 3.54 3.49 Tenacity, gpd 4.56 4.5 4.5 Elongation, % 26.7 27.2 28.6 RDR 1.27 1.27 1.29

BOS, % 4.0 4.0 4.9

Uster, % 2.1 2.1 2.4

TABLE XIX

SPUN DRAWN DRAW GOAL

DEN. DEN. TEMP D.R % E TEN. T7 MOD BOS % U D.S.

83.2 58.4 COLD 1.45 33.7 4.9 3.2 82.7 4.8 .52 1.78

" 56.2 " 1.50 28.8 5.1 3.7 89.4 4.7 .50 1.71

" 54.7 " 1.55 25.7 5.3 4.1 93.9 5.3 .53 1.90

" 58,6 155C 1.45 35.3 4.9 3.2 86.7 5.9 .58 1.96

" 56.7 " 1.50 31.2 5.1 3.7 90.4 5,5 .56 1.94

55.0 " 1.55 25.8 5.2 4,1 95.2 5.7 .63 1.95

75.9 53.2 COLD 1.45 34.0 5.0 3.4 91.0 4.6 .49 1.83

" 51.4 " 1.50 26.5 5.1 3.9 96.1 4,6 .57 1.90

50.3 " 1.55 22.6 5.3 4.3 100.5 4.5 .50 1.76

" 53.5 155C 1.45 32.6 4.8 3.4 89.9 5.6 .59 2.02

" 51.8 " 1.50 28.2 5.1 3.9 93.5 5,2 .65 2.74

49.8 " 1.55 24.0 5.3 4.4 99.2 5.5 .67 2.11

69.0 48.3 COLD 1.45 30.8 5.0 3.6 94.7 4.7 0.62 2.08 " 46.7 " 1.50 27.0 5.2 4.0 37.4 4.3 0.62 2.18 " 45.5 " 1.55 22.8 5.3 4.4 99.3 4.5 0.56 2.19 " 48.6 155C 1.45 30.8 4.9 3.6 90.5 5.0 0.63 2.20

"

" 47.1 1.50 25.5 5.0 4.0 96.8 5.2 0.64 2.19 " 46.1 " 1.55 22.5 5.2 4.4 99.4 5.3 0.71 2.29

Claims

CLAIMS :

1. A process for preparing a continuous filament yarn of deniers per filament up to about one, wherein a feed yarn of spin-oriented polyester filaments is completely or partially drawn to a uniform yarn of said deniers by hot-drawing or by cold-drawing, with or without heat-setting, said feed yarn being of elongation-to-break (E_B) 40 to

120%, tenacity at 7% elongation (T₇) at least 0.7 grams/denier, boil-off shrinkage (S₁) less than 10%, thermal stability as shown by an S₂ value less than

+1%, net shrinkage (S₁₂) less than 8%, maximum shrinkage tension (ST) less than 0.3 grams/denier, density (p) 1.35 to 1.39 grams/cubic centimeter, and crystal size (CS) 55 to 90 Angstroms and also at least (250 ρ - 282.5) Angstroms.

2. A process according to Claim 1, wherein the feed yarn is drawn to a uniform yarn by partial drawing.

3. A process according to Claim 1 or 2, wherein the feed yarn is drawn to a uniform yarn by cold-drawing.

4. A process wherein a yarn (A) of a given denier per filament up to about one, and a different yarn

(B) of a different denier per filament up to about one, are both produced by drawing the same feed yarn of spin-oriented polyester filaments, and wherein the denier per filament of yarn (B) differs by at least 10% from the denier per filament of yarn, (A), and wherein said feed yarn is of elongation-to-break (E_B) 40 to 120%, tenacity at 7% elongation (T₇) at least 0.7 grams/denier, boil-off shrinkage (S₁) less than 10%, thermal stability as shown by an S₂ value less than +1%, net shrinkage (S₁₂) less than 8%, maximum shrinkage tension (ST) less than 0.3 grams/denier, density (p) 1.35 to 1.39 grams/cubic centimeter, and crystal size (CS) 55 to 90 Angstroms and also at least (250ρ - 282.5) Angstroms.

5. A process according to any one of Claims 1 to 5, wherein a plurality of said feed yarns of spin- oriented polyester filaments are drawn, to provide a plurality of uniform yarns of filament deniers up to about one, by draw-warping and the resulting drawn yarns are wound onto a beam suitable for weaving or knitting.

6. A process for preparing a polyester filament yarn that is suitable for weaving or knitting, by heat-treating a feed yarn of spin-oriented polyester filaments as it is advanced under a controlled tension, said feed yarn being of elongation-to-break (E_B) 40 to 120%, tenacity at 7% elongation (T₇) at least 0.7 grams/denier, boil-off shrinkage (S₁) less than 10%, thermal stability as shown by an S₂ value less than +1%, net shrinkage (S₁₂) less than 8%, maximum shrinkage tension (ST) less than 0.3

grams/denier, density (p) 1.35 to 1.39 grams/cubic centimeter, and crystal size (CS) 55 to 90 Angstroms and also at least (250 ρ - 282.5) Angstroms, said heat-treating optionally being performed on a draw- warping machine and the resulting yarns being wound onto a beam suitable for weaving or knitting.

7. A process according to any one of Claims 1 to 6, characterized in that said feed yarn is comprised of filaments of denier less than one.

8. A process for making staple fiber, wherein polyester filaments are prepared by a process according to any one of Claims 1 to 4, 6 or 7, and the resulting filaments are mechanically crimped and cut or stretch-broken into staple fibers that are of denier less than one.

9. A process according to any one of Claims 1 to 8, characterized in that the polyester is of

relative viscosity (LRV) 13 to 18 and contains 1 to 3 mole percent of

ethylene-5-sodium-sulfo-isophthalate.

10. A process according to any one of Claims 1, 2 or 4, wherein the drawn filament yarns are heat-set and are air jet-textured to provide a bulky soft textured yarn, and wherein the air jet-texturing takes place before or after heat-setting.