WO1993010293A1

WO1993010293A1 - Improvements in polyester filaments, yarns and tows

Info

Publication number: WO1993010293A1
Application number: PCT/US1991/008381
Authority: WO
Inventors: John Paul Hendrix, Jr.; Benjamin Hughes Knox; 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

Air-jet texturing with 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 air-jet textured filaments and yarns of various denier. The resulting yarns have useful properties that are improved in certain respects.

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 textured yarns, 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; new polyester yarns, resulting from such processes, and downstream products from such

filaments and yarns.

According to the parent application

PCT/US91/XXXXX (DP-4040-B) 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.

The parent application is primarily concerned with the preparation of and improvement of flat yarns and filaments, as indicated. The present invention is concerned primarily with the air-jet texturing of such yarns to provide novel textured yarns.

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

A process for preparing a textured polyester yarn, wherein a feed yarn of spin-oriented polyester filaments is completely or partially drawn to a uniform yarn by hot-drawing or by cold-drawing, with or without heat-setting, and then said uniform yarn is air jet textured, said feed yarn being of

elongation-to-break (E3) 40 to 120%, tenacity at 7% elongation (T7) at least 0.7 grams/denier, boil-off shrinkage (S^) less than 10%, thermal stability as shown by an S2 value less than +1%, net shrinkage C^s12) l^ess 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 p - 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 combinations, as will become clear.

If desired, the feed yarn may be heat treated, without drawing, and then air jet textured. If desired, the process may be modified to provide a mixed-shrinkage air-jet .textured polyester yarn from such feed*yarns of spin-oriented flat polyester filaments. For instance, such a feed yarn (A) may be drawn to a uniform drawn yarn of high shrinkage by cold-drawing without any post heat treatment, and such a feed yarn (B) may be drawn to a uniform drawn yarn of lower shrinkage by hot or by cold-drawing with a post heat treatment to reduce shrinkage, and these uniform drawn yarns may be comingled and air-jet textured. If desired, however, such a feed yarn (B) may be drawn to a uniform drawn yarn of lower shrinkage by cold-drawing without any post heat treatment, wherein said draw ratios for drawing feed yarns (A) and (B) are selected to provide an elongation for the uniform drawn yarn of lower shrinkage from feed yarn (B) at least about 10% greater than the elongation of the uniform drawn yarn of higher shrinkage from feed yarn (A), and then the uniform drawn yarns may be co-mingled and air-j et textured.

Preferably, at least some difference in shrinkage of said mixed-shrinkage air-jet textured yarns is developed while said yarns are in the form of a weftless warp sheet prior to knitting or

weaving, by heat relaxing said warp sheet under tension not exceeding the shrinkage tension of the high shrinkage filaments.

The process of the invention is particularly useful in giving a capability of providing yarns desirably textured and with filaments of low denier, less than about 1, which are in great demand

commercially at this time.

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 σationic 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 Knox U. S. Patent No. 4,156,071, MaσLean 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). As will be understood, according to the present invention, the various embodiments and

variations disclosed in the parent application may be modified by including an air-jet texturing operation. Air-jet texturing is itself a known process, and commercial machines are available for practicing air-jet texturing.

Most of the drawing disclosure from our parent application (for instance in the Examples, including Tables 1-XV, which are specifically incorporated herein by reference) is applicable also to various texturing processes according to the present

invention. Air-jet texturing (AJT) may be carried out conventionally, using commercial equipment, such for example, as is available from Barmag, an example being referred to hereinafter, in relation to AJT Examples and Tables XVI and XVII (numbered

consecutively after Tables 1-XV). Indeed, the drawing and AJT stages may all conveniently be carried out on a commercial AJT machine, if desired. When post heat-set yarns are desired, the heat setting may precede or follow the AJT stage of the process.

EXAMPLES In the Examples, Tables XVI and XVII, with accompanying disclosure of AJT according to the present invention, 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 without any air-jet texturing). This is why the Tables herein are numbered XVI and XVII, as

Tables I-XV of the parent application are

incorporated herein, by reference. It will be understood that, in like manner, other disclosures according to the parent application may be modified by incorporating AJT according to the present

invention.

The term AJT is used herein variously to indicate air-jet texturing and air-jet textured, according to context.

Table XVI shows the properties resulting from AJT according to the invention of undrawn feed yarns that were similar to feed yarns IC, IV-1, V-3 and VI- 3, but of 91 denier and 100 filaments. All four yarns were processed similarly by cold drawing, then (sequentially) AJT on a Barmag FK6T-80 machine, using a conventional air-jet at 125 psi (8.8 kg/cm²), and heat set at 105°C at speeds of 300 mpm, but the cold draw ratios were varied, as indicated, to provide bulky (looped) textile yarns with filament deniers between about 0.7 and 0.9 before boil-off shrinkage (BBO) and filament deniers between about 0.77 and 0.94 after boil-off shrinkage (ABO). The deniers shown in Table XVI are for drawn yarns. (Denier) D&JT is the denier of the yarn measured after AJT.

(Denier) D is an estimated value for the drawn yarn before AJT, calculated from the draw ratio (DR) used and the denier of the undrawn feed yarn, which is referred to hereinafter as (Denier)_Flat

(Denier)_D = (Denier)_Flat/DR

The denier of AJT yarn XVI-1 (wherein no draw was taken) showed an increase in yarn denier of about 10% due to the formation of filament loops (i.e., the ratio (Denier) DAJT/(Denier) piat was greater than about 1.1); however, as expected, the denier of the actual filaments remained the same.

The "Bulk" of an AJT yarn is herein defined by the ratio of yarn deniers; that is, the Bulk is calculated by subtracting the calculated value of the denier of the drawn yarn before AJT (Denier)_D from the denier of the yarn measured after AJT

(Denier)_DAJT and given as a percentage of the denier of the drawn yarn before AJT (Denier) _Q; that is,

Preferred AJT yarns have Bulk values at least about 10%.

As expected, AJT yarn strengths (Tenacity, T and Tenacity-at-break, T_B, herein defined as the product of Tenacity × RDR), were lower than those of the drawn flat yarns, owing to the filament loop structure; but our AJT yarn strengths were adequate for bulky fabric end uses.

AJT yarns XVI-2 and XVI-3 were uniformly partially cold drawn to provide residual elongations greater that 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 27%, AJT yarn XVI-4 had boil-off and dry-heat shrinkages (BOS and DHS) of 12.7 and 11.0%, respectively, with a differential shrinkage (DHS-BOS) less than +2%. With mild heat setting, these BOS and DHS shrinkages can be reduced to less than about 3%.

Co-mingling (plying) 2 or more cold drawn AJT textile yarns, wherein at least one AJT yarn has been heat set to shrinkages less than about 3%, and a second AJT yarn has not been heat set, so has

significantly higher shrinkage, provides a simplified route to a mixed shrinkage AJT yarn. Similar mixed shrinkage AJT yarns may be provided with the lower shrinkage component provided by alternative

techniques, for instance by hot drawing, with or without heat setting. Alternatively, mixed shrinkage AJT yarns may be provided by co-mingling 2 or more drawn filament bundles wherein both bundles are drawn by cold drawing without post heat treatment, but the bundles are cold drawn to different elongations, preferably differing by about 10% or more (compare EX. XVI-2 to XVI-4, for example) . The resulting mixed shrinkage drawn yarn may then be AJT to provide a mixed shrinkage textured yarn.

The higher-shrinkage components of our mixed shrinkage yarns of the invention differ from yarns made by drawing a conventional POY, in that our higher shrinkage yarns have a differential shrinkage (DHS-BOS) typically less than about 2%, this low differential shrinkage for a higher shrinkage

component provides a very stable level of mixed shrinkage over a large end-use processing temperature range. The level of the "feed" yarn interlace is optimized for desired mixed shrinkage and AJT yarn aesthetics.

Preferred AJT filament yarns are prepared from undrawn feed yarns that have been treated with caustic in the spin finish (as taught by Grindstaff and Reese, in allowed copending Application Serial No. 07/420,459, filed October 12, 1989) to enhance their hydrophilicity and provide improved moisture-wicking properties, 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.

A mixed shrinkage flat yarn can be formed in a similar manner, wherein the yarns by-pass the air- jet.

In a similar manner a 73 denier 68 filament undrawn textile flat yarn was uniformly cold AJT to various draw ratios with AJT yarn properties

summarized in Table XVII.

To provide drawn polyester filament yarns that are capable of being dyed with cationic dyestuffs, and are easier to nap and brush or cut into staple and flock, polyester co 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. Accordingly, undrawn feed yarns that were capable of being partially and cold drawn to provide uniform drawn filament yarns were prepared by spinning 15.3 LRV copolymer at about

285°C, and quenching, 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 withdrawing 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) that may be air-jet textured to provide bulky, soft cationic-dyeable 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. TABLE XVI

Example XVI - 1 2 3 4

Process

Draw Ratio (DR) 1.0 1.1 1.2 1.32

Drawn Yam Properties

(Denier) DAJT 101.4 95.0 85.8 77.3 (Denier) D 91 85 77 69

Bulk,% 11.4 11.8 11.4 12.0

E_B , % 61.1 57.1 41.3 27.2

RDR 1.61 1.57 1.41 1.27

T. gpd 1.96 2.22 2.42 2.64 τ_{B '} gpd 3.16 3.49 3.42 3.34

BOS, % 3.5 4.3 8.2 12.7

DHS, % 2.8 4.1 7.6 11.0

(DHS-BOS), % -0.7 -0.2 -0.6 -1.7

TABLE XVII

Example XVI - 1 2 3 4 Process

Draw Ratio (DR) 1.0 1.1 1.2 1.32 Drawn Yam Properties

(Denier) DAJT 81.8 75.1 70.4 64.7

(Denier) D 73.0 66.4 60.8 55.3

Bulk,% 12.1 13.1 15.7 17.0

E_B , % 64.4 60.9 43.3 29.6

RDR 1.64 1.61 1.43 1.30

T,gpd 2.12 2.46 2.58 2.78 T_B, gpd 3.48 3.96 3.69 3.61

BOS, % 3.4 4.9 8.2 11.8 DHS, % 3.2 4.4 7.1 10.4 (DHS-BOS), % -0.2 -0.5 -1.1 -1.4

Claims

We Claim:

1. A process for preparing a textured polyester yarn, wherein a feed yarn of spin-oriented polyester filaments is completely or partially drawn to a uniform yarn by hot-drawing or by cold-drawing, with or without heat-setting, and .then said uniform yarn is air jet textured, 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 for preparing a textured polyester yarn, wherein a feed yarn of spin-oriented polyester filaments is heat treated, without drawing, and then said heat treated yarn is air jet textured, 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 p - 282.5) Angstroms.

5. A process for providing a mixed-shrinkage air-jet textured polyester yarn from feed yarns of spin-oriented flat polyester filaments, characterized in that a feed yarn (A) is drawn to a uniform drawn yarn of high shrinkage by cold-drawing without any post heat treatment, and in that a feed yarn (B) is drawn to a uniform drawn yarn of lower shrinkage by hot or by cold-drawing with a post heat treatment to reduce shrinkage, and said uniform drawn yarns are co-mingled and air-jet textured, said feed yarns (A) and (B) 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 p - 282.5) Angstroms.

6. A process for providing a mixed-shrinkage air-jet textured polyester yarn from feed yarns of spin-oriented flat polyester filaments, characterized in that a feed yarn (A) is drawn to a uniform drawn yarn of high shrinkage by cold-drawing without any post heat treatment, and in that a feed yarn (B) is drawn to a uniform drawn yarn of lower shrinkage by cold-drawing without any post heat treatment, wherein said draw ratios for drawing feed yarns (A) and (B) are selected to provide an elongation for the uniform drawn yarn of lower shrinkage (B) at least 10%

greater than the elongation of the uniform drawn yarn of higher shrinkage from feed yarn (A), and said uniform drawn yarns are co-mingled and air-jet textured, said feed yarns (A) and (B) being of elongation-to-break (Eg) 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 p - 282.5)

Angstroms.

7. A process according to Claim 5 or 6, wherein difference in shrinkage of said mixed-shrinkage air-jet textured yarns is developed while said yarns are in the form of a weftless warp sheet prior to knitting or weaving, by heat relaxing said warp sheet under tension not exceeding the shrinkage tension of the high shrinkage filaments.

8. A process according to any one of Claims 1 to 8, wherein the filaments of the drawn yarns are of denier less than 1.0.

9. A process according to any one of Claims 1 to 7, wherein the polyester polymer contains 1 to 3 mole percent of ethylene-5-sodium-sulfo isophthalate.