High molecular weight poly(alpha-olefin) solutions and articles made therefrom

• US 20070231572A1
• Filed: 03/30/2006
• Published: 10/04/2007
• Est. Priority Date: 03/30/2006
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Tam, Thomas, Zhou, Qiang, Kavesh, Sheldon, Wagner, Lori, Young, John, Twomey, Conor, Arnett, Charles, Brodie, John
• Granted Patent: US 8,444,898 B2
• Time in Patent Office: Days
• US Class Current: 428/364
• CPC Class Codes: B29C 48/022 characterised by the choice of material
• CPC Class Codes: B29C 48/05 Filamentary, e.g. strands
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29C 48/405 Intermeshing co-rotating screws
• CPC Class Codes: B29C 48/41 Intermeshing counter-rotating screws
• CPC Class Codes: B29C 48/919 using a bath, e.g. extruding into an open bath to coagulate or cool the material
• CPC Class Codes: B29K 2023/0683 UHMWPE, i.e. ultra high molecular weight polyethylene
• CPC Class Codes: C08J 2323/02 not modified by chemical after treatment
• CPC Class Codes: C08J 3/091 characterised by the chemical constitution of the organic liquid
• CPC Class Codes: D01D 1/02 Preparation of spinning solutions
• CPC Class Codes: D01F 6/04 from polyolefins
• CPC Class Codes: Y10T 428/2913 Rod, strand, filament or fiber

Abstract

A robust process for the continuous preparation of solutions of high molecular weight UHMW PO that is capable of producing strong materials at high production capacity, is conservative of capital and energy requirements, and the articles made therefrom.

Claims

1. A process for the continuous preparation of solutions comprising up to 50 wt. % of an UHMW PO having an intrinsic viscosity from 5 to 45 dl/g measured in decalin at 135°

C. comprising the steps of;

a) forming a slurry of UHMW PO particles in a solvent for the UHMW PO at a first temperature which is below the temperature at which said UHMW PO particles will dissolve in said solvent;

b) processing said slurry through an extruder operating such that a mixture of said solvent and said UHMW PO is formed at a second temperature above the melting temperature of said UHMW PO, and the throughput rate of UHMW PO is at least the quantity 2.5 D² (2.5×

D×

D) grams per minute, where D represents the screw diameter of said extruder in centimeters;

c) optionally, discharging said mixture from the extruder through a positive displacement pump;

d) passing said mixture through a heated vessel at a temperature above the melting temperature of said UHMW PO in said solvent, said heated vessel having a volume such that the average residence time of the mixture in said vessel is from 2 to 120 minutes, whereby a solution of said UHMW PO is formed.

2. The process of claim 1, wherein said slurry is maintained at a temperature below the temperature at which the UHMW PO will dissolve in the solvent and for a time sufficient that the UHMW PO particles absorb at least 5 wt. % of the solvent prior to processing said slurry through an extruder.

3. The process of claim 1, wherein the average residence time of said mixture in said extruder is at most the quantity 0.6 D (0.6×

D) minutes where D represents the screw diameter of the extruder in centimeters.

4. The process of claim 1, wherein the throughput rate of UHMW PO is at least 4 D² grams/min where D represents the screw diameter of the extruder in centimeters.

5. The process of claim 1, wherein the throughput rate of UHMW PO is at least 6 D² grams/min where D represents the screw diameter of the extruder in centimeters.

6. The process of claim 1, wherein the throughput rate of UHMW PO is at least 10 D² grams/min, where D represents the screw diameter of the extruder in centimeters.

7. The process of claim 1 wherein the throughput rate of UHMW PO is from 2.5 D² to 40 D² grams/min where D represents the screw diameter of the extruder in centimeters.

8. The process of claim 1 wherein said extruder is an intermeshing co-rotating twin screw extruder.

9. The process of claim 8 where the screw elements of said extruder are forwarding conveying elements.

10. The process of claim 1 wherein the average residence time of the mixture in said heated vessel is from 2 to 90 minutes.

11. The process of claim 1 wherein the average residence time of the mixture in said heated vessel is from 4 to 60 minutes.

12. The process of claim 1 wherein the UHMW PO concentration in said solution is from 2 to 30 wt. %.

13. The process of claim 1, wherein the UHMW PO concentration in said solution is from 5 to 20 wt. %.

14. The process of claim 1 wherein the slurry is fed to the extruder under a pressure of greater than 20 kPa.

15. The process of claim 1 wherein said UHMW PO particles and said solvent are introduced into the extruder in separate feed streams and the slurry is formed within the extruder.

16. The process of claim 15 wherein said solvent has been preheated to a temperature above the melting temperature of said UHMW PO in said solvent.

17. The process of claim 1 wherein a concentrated slurry of said UHMW PO in said solvent is introduced at the feed section of the extruder and a separate solvent stream preheated to a temperature above the melting temperature of said UHMW PO, is introduced into the extruder downstream of the extruder feed section.

18. The process of claim 1 wherein said heated vessel is a pipe.

19. The process of claim 18 wherein the pipe contains one or more static mixers.

20. The process of claim 1 wherein the ultrahigh molecular weight UHMW PO is a linear polyethylene having an intrinsic viscosity measured in decalin at 135°

C. from 9 to 30 dl/g.

21. The process of claim 20 wherein the linear polyethylene has fewer than two substituent groups per 1000 carbon atoms.

22. The process of claim 20 wherein the linear polyethylene has fewer than one substituent group per 1000 carbon atoms.

23. The process of claim 1 wherein said solvent is selected from the group consisting of aliphatics, aromatics, cyclo-aliphatics, halogenated aliphatics, halogenated aromatics, halogenated cyclo-aliphatics and mixtures thereof.

24. The process of claim 1 where said solvent is selected from the group consisting of mineral oil and decalin.

25. A process for the continuous preparation of molded articles from slurries of ultrahigh molecular weight UHMW PO comprising the steps:

a) forming a slurry of ultrahigh molecular weight UHMW PO particles having an intrinsic viscosity measured in decalin at 135°

C. of from 5 to 45 dl/g in a solvent for the UHMW PO at a first temperature which is below the temperature which said UHMW PO will dissolve in said solvent;

b) processing said slurry through an extruder operating such that a mixture of said solvent and said UHMW PO is formed at a second temperature above the melting temperature of said UHMW PO, and the throughput rate of UHMW PO in said mixture is at least the quantity 2.5 D² (2.5×

D×

D) grams per minute wherein D represents the screw diameter of the extruder in centimeters;

c) optionally, discharging said mixture from the extruder through a positive displacement pump;

d) passing said mixture through a heated vessel at a temperature above the melting temperature of said UHMW PO, said vessel having a volume such that the average residence time of the mixture in said vessel is from 2 to 120 minutes, whereby a solution of said UHMW PO is formed;

e) passing the thus-formed solution out of said vessel through a positive displacement pump and through a shaping orifice, said solution being at a temperature below the atmospheric boiling point of said solvent to form a molded solution article;

f) optionally, stretching the molded solution article;

g) cooling the solution article obtain a molded gel article;

h) optionally stretching the molded gel article;

i) substantially removing the solvent from said molded gel article to form a molded solid article; and

j) optionally stretching the molded solid article in one or more steps at temperatures from 25°

C. to 165°

C.

26. The process of claim 25, wherein said slurry is maintained at a temperature below the temperature at which the UHMW PO will dissolve in the solvent and for a time sufficient that the UHMW PO particles absorb at least 5 wt. % of the solvent prior to processing said slurry through an extruder.

27. The process of claim 25, wherein the average residence time of said mixture in said extruder is less than the quantity 0.6 D (0.6×

D) minutes where D represents the screw diameter of the extruder in centimeters.

28. The process of claim 25, wherein the throughput rate of UHMW PO is from 2.5 D² to 40 D² grams/min where D represents the screw diameter of the extruder in centimeters.

29. The process of claim 25, wherein said molded gel article is a fiber, tape, film, sheet or tube.

30. The process of claim 25, wherein said molded solid article is a fiber, tape, film, sheet or tube.

31. A molded gel article comprising a member selected from the group consisting of a fiber, tape, film, sheet and tube prepared by the method of claim 25 steps a) through h).

32. A molded solid article comprising a member selected from the group consisting of a fiber, tape, film, sheet and tube prepared by the method of claim 25.

33. The article of claim 32 comprising a multi-filament UHMW PO fiber having a tenacity at least 27 g/d (23.8 cN/dtex).

34. The article of claim 32 comprising a multi-filament UHMW PO fiber having a tenacity at least 35 g/d (30.9 cN/dtex).

35. The article of claim 32 comprising a multi-filament UHMW PO fiber having a tenacity at least 40 g/d (35.3 cN/dtex).

36. The article of claim 32 comprising a multi-filament UHMW PO fiber having a tenacity at least 50 g/d (44.1 cN/dtex).