Claims
- 1. A process comprising the steps:
- (a) forming a solution of a substantially linear polyacrylonitrile having a weight average molecular weight at least about 500,000 in a first solvent at a first concentration of about 2 to about 15 weight percent polyacrylonitrile,
- (b) extruding said solution through an aperture, said solution being at a temperature no less than a first temperature upstream of the aperture and being substantially at the first concentration both upstream and downstream of said aperture,
- (c) cooling the solution adjacent to and downstream of the aperture to a second temperature below the temperature at which a rubbery gel is formed, forming a gel containing first solvent of substantially indefinite length,
- (d) extracting the gel containing first solvent with a second, volatile solvent for a sufficient contact time to form a fibrous structure containing second solvent, which gel is substantially free of first solvent and is of substantially indefinite length;
- (e) drying the fibrous structure containing second solvent to form a xerogel of substantially indefinite length free of first and second solvent; and
- (f) stretching at least one of:
- (i) the gel containing the first solvent,
- (ii) the fibrous structure containing the second solvent and,
- (iii) the xerogel, at a total stretch ratio sufficient to achieve a tenacity of at least about 5 g/denier and a secant modulus of at least about 100 g/denier.
- 2. The process of claim 1 wherein said aperture has an essentially circular cross-section; said gel containing first solvent is a gel fiber; and said xerogel is a xerogel fiber.
- 3. The process of claim 2 wherein said first temperature is between about 130.degree. C. and about 250.degree. C.; said second temperature is between about 0.degree. C. and about 50.degree. C.; and the cooling rate between said first temperature and said second temperature is at least about 50.degree. C./min.
- 4. The process of claim 3 wherein said first solvent is dimethylsulfoxide, said first temperature is about 130.degree. C. to about 200.degree. C. and said first concentration is about 5 to about 8 weight percent.
- 5. The process of claim 4 wherein said first temperature is about 140.degree. C. to about 180.degree. C.
- 6. The process of claim 3 wherein said first solvent has a vapor pressure less than 80 KPa at said first temperature.
- 7. The process of claim 3 wherein said first solvent is selected from the group consisting of dimethylsulfoxide, dimethylformamide, dimethylacetamide, gamma-butyrolactone and ethylene carbonate.
- 8. The process of claim 7 wherein said first solvent is dimethylsulfoxide.
- 9. The process of claim 2 wherein said first solvent is selected from the group consisting of dimethylsulfoxide, dimethylformamide, dimethylacetamide, gamma-butyrolactone and ethylene carbonate.
- 10. The process of claim 9 wherein the said first solvent is dimethylsulfoxide.
- 11. The process of claim 2 wherein the total stretch ratio is about 5 to about 15.
- 12. The process of claim 2 wherein said stretching step (f) is conducted in at least two stages.
- 13. The process of claim 12 wherein a first stretching stage is of the gel containing the first solvent.
- 14. The process of claim 13 wherein a second stretching stage is of the gel containing the first solvent.
- 15. The process of claim 13 wherein a second stretching stage is of the xerogel.
- 16. The process of claim 12 wherein at least two stretching stages are performed on the xerogel.
- 17. The process of claim 2 wherein the stretching is primarily performed on the xerogel.
- 18. The process of claim 2 wherein at least a portion of stretching is performed at a temperature between about 130.degree. C. and about 230.degree. C.
- 19. The process of claim 18 wherein the stretching is performed in at least two stages with the latest stage performed at a temperature of between about 130.degree. C. and about 230.degree. C.
- 20. The process of claim 19 wherein said latest stage is performed on the xerogel.
- 21. The process of claim 2 wherein said polyacrylonitrile has a weight average molecular weight of at least about 750,000.
- 22. The process of claim 21 wherein said linear polyacrylonitrile has a weight average molecular weight of about 1,000,000 to about 4,000,000.
- 23. The process of claim 22 wherein said linear polyacrylonitrile has a weight average molecular weight of about 1,500,000 to about 2,500,000.
- 24. The process of claim 2 wherein said cooling step (c) includes immersing the solution in a quench bath containing a mixture of first solvent and water at a temperature of about 0.degree. C. to about 50.degree. C.
- 25. The process of claim 24 wherein said first solvent is dimethylsulfoxide.
Parent Case Info
This application is a continuation of application Ser. No. 557,984 filed December 5, 1983, now abandoned.
US Referenced Citations (20)
Foreign Referenced Citations (7)
Number |
Date |
Country |
45-1650 |
Jan 1970 |
JPX |
45-16246 |
Jun 1970 |
JPX |
45-40700 |
Dec 1970 |
JPX |
48-534 |
Jan 1973 |
JPX |
49-126923 |
Dec 1974 |
JPX |
50-62258 |
May 1975 |
JPX |
1100497 |
Jan 1968 |
GBX |
Continuations (1)
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Number |
Date |
Country |
Parent |
557984 |
Dec 1983 |
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