Process for drawing gel-spun polyethylene yarns

• US 20050093200A1
• Filed: 10/31/2003
• Published: 05/05/2005
• Est. Priority Date: 10/31/2003
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Arnett, Charles R., Wagner, Lori L., Tam, Thomas Y-T., Tan, Chok Bin
• Granted Patent: US 7,344,668 B2
• Time in Patent Office: Days
• US Class Current: 264/211.14
• CPC Class Codes: B29C 48/0018 combined with shaping by orienting, stretching or shrinking, e.g. film blowing B29C48/0017 takes precedence
• CPC Class Codes: B29C 48/05 Filamentary, e.g. strands
• CPC Class Codes: B29C 48/91 Heating, e.g. for cross linking
• CPC Class Codes: B29K 2023/0683 UHMWPE, i.e. ultra high molecular weight polyethylene
• CPC Class Codes: B29L 2031/707 Cables, i.e. two or more filaments combined together, e.g. ropes, cords, strings, yarns filamentary material B29L2031/731, electric cables B29L2031/3462, optical cables B29L2011/0075
• CPC Class Codes: B29L 2031/731 Filamentary material, i.e. comprised of a single element, e.g. filaments, strands, threads, fibres cables B29L2031/707
• CPC Class Codes: D01F 6/04 from polyolefins
• CPC Class Codes: D02J 1/22 Stretching or tensioning, shrinking or relaxing, e.g. by use of overfeed and underfeed apparatus, or preventing stretch stretch spinning D01D5/12

Abstract

A process for drawing essentially diluent-free gel-spun polyethylene multi-filament yarns in a forced convection air oven and the drawn yarns produced thereby, The process conditions of draw ratio, stretch rate, residence time, oven length and feed speed are selected in specific relation to one another so as to achieve enhanced efficiency and productivity. The drawn yarns are useful in armor, composites, fishing line, ropes, sutures, fabrics and other applications.

Claims

1. A process for drawing a gel-spun multi-filament yarn comprising the steps of:

a) forming a gel-spun polyethylene multi-filament feed yarn comprising a polyethylene having an intrinsic viscosity in decalin at 135°

C. of from 5 dl/g to 35 dl/g, fewer than two methyl groups per thousand carbon atoms, and less than 2 wt. % of other constituents;

b) passing said feed yarn at a speed of V₁ meters/minute into a forced convection air oven having a yarn path length of L meters, wherein one or more zones are present along the yarn path having zone temperatures from 130°

C. to 160°

C.;

c) passing said feed yarn continuously through said oven and out of said oven at an exit speed of V₂ meters/minute wherein the following equations are satisfied

0.25≦

L/V₁≦

20, min
1.5≦

V₂/V₁≦

20
1≦

(V₂−

V₁)/L≦

60, min<sup>−

1</sup>
0.55≦

2L/(V₁+V₂)≦

10, min.

2. The process of claim 1 additionally satisfying the condition that the mass throughput of yarn passing through the oven is at least 0.25 grams/minute per yarn end.

3. The process of claim 1 wherein the yarn is drawn at constant tension throughout the oven neglecting the effect of air drag.

4. The process of claim 1 wherein the yarn is drawn at increasing tension through the oven.

5. The process of claim 1 wherein the feed yarn comprises a polyethylene having an intrinsic viscosity in decalin at 135°

C. of from 8 dl/g to 30 dl/g, fewer than one methyl groups per thousand carbon atoms, and less than 1 wt. % of other constituents, said feed yarn having a tenacity from 6 to 76 g/d as measured by ASTM D2256-97.

6. The process of claim 5 wherein the feed yarn has a tenacity from 11 to 66 g/d.

7. The process of claim 5 wherein the feed yarn has a tenacity from 16 to 56 g/d.

8. The process of claim 5 wherein the feed yarn has a tenacity from 21 g/d to 51 g/d.

9. The process of claim 5 wherein the feed yarn has a tenacity from 26 g/d to 46 g/d.

10. The process of claim 5 wherein the feed yarn comprises a polyethylene having an intrinsic viscosity in decalin at 135°

C. of from 10 dl/g to 25 dl/g.

11. The process of claim 5 wherein the feed yarn comprises a polyethylene having an intrinsic viscosity in decalin at 135°

C. of from 12 dl/g to 20 dl/g, fewer than 0.5 methyl groups per thousand carbon atoms, and less than 0.5 wt. % of other constituents, said feed yarn having a tenacity from 21 to 51 g/d.

23. A gel-spun polyethylene multifilament yarn drawn by the process of claim 1.

12. A process for drawing a gel-spun multi-filament yarn comprising the steps of:

a) forming a gel-spun polyethylene multi-filament feed yarn comprising a polyethylene having an intrinsic viscosity in decalin at 135°

C. of from 5 dl/g to 35 dl/g, fewer than two methyl groups per thousand carbon atoms, and less than 2 wt. % of other constituents;

b) passing said feed yarn at a speed of V₁ meters/minute into a forced convection air oven having a yarn path length of L meters, wherein one or more zones are present along the yarn path having zone temperatures from 130°

C. to160°

C.;

c) passing said feed yarn continuously through said oven and out of said oven at an exit speed of V₂ meters/minute wherein the following equations are satisfied

1≦

L/V₁≦

20, min
1.5≦

V₂/V₁≦

20
0.01≦

(V₂−

V₁)/L≦

1, min<sup>−

1</sup>
1.1≦

2L/(V₁+V₂)≦

10, min.

13. The process of claim 12 additionally satisfying the condition that the mass throughput of yarn passing through the oven is at least 0.25 grams/minute per yarn end.

14. The process of claim 12 wherein the yarn is drawn at constant tension throughout the oven neglecting the effect of air drag.

15. The process of claim 12 wherein the yarn is drawn at increasing tension through the oven.

16. The process of claim 12 wherein the feed yarn comprises a polyethylene having an intrinsic viscosity in decalin at 135°

C. of from 8 dl/g to 30 dl/g, fewer than one methyl groups per thousand carbon atoms, and comprising less than 1 wt. % of other constituents, said feed yarn having a tenacity from 5 to 76 g/d as measured by ASTM D2256-97.

17. The process of claim 12 wherein the feed yarn has a tenacity from 11 to 66 g/d.

18. The process of claim 12 wherein the feed yarn has a tenacity from 16 to 56 g/d.

19. The process of claim 12 wherein the feed yarn has a tenacity from 21 to 51 g/d.

20. The process of claim 12 wherein the feed yarn has a tenacity from 26 to 46 g/d.

21. The process of claim 12 wherein the feed yarn comprises a polyethylene having an intrinsic viscosity in decalin at 135°

C. of from 10 dl/g to 25 dl/g.

22. The process of claim 12 wherein the feed yarn comprises a polyethylene having an intrinsic viscosity in decalin at 135°

C. of from 12 dl/g to 20 dl/g, fewer than 0.5 methyl groups per thousand carbon atoms, and less than 0.5 wt. % of other constituents, said feed yarn having a tenacity from 21 to 51 g/d.

24. A gel-spun polyethylene multifilament yarn drawn by the process of claim 12.