Production of and drying of copolymer fibers
View Patent ↗The present invention concerns processes for reducing water in never-dried fiber comprising copolymer derived from the copolymerization of para-phenylenediamine, 5(6) -amino-2-(p-aminophenyl)benzimidazole; and terephthaloyl dichloride, the process comprising the steps of: (a) heating the never-dried fiber to a temperature of at least 20° C. but less than 100 ° C. until the moisture content of the fiber is 20 weight percent or less of the fiber; and (b) further heating the fiber to a temperature of at least 350° C.
1. A process for reducing water in never-dried fiber comprising copolymer derived from the copolymerization of para-phenylenediamine, 5(6)-amino-2-(p-aminophenyl)benzimidazole, and terephthaloyl dichloride, said process comprising the steps of:
(a) heating said never-dried fiber to at least 20° C. but less than 100° C. until the moisture content of said fiber is 20 weight percent or less of said fiber; and
(b) further heating said fiber to a temperature of at least 350° C.
2. The process of claim 1 wherein the steps (a) and (b) are part of a continuous process.
3. The process of claim 1 wherein the sulfur content of said fiber is greater than 0.1 weight percent.
4. The process of claim 1 , wherein in step (a) said fiber is heated until the moisture content is 14 weight percent or less.
5. The process of claim 1 , wherein said fiber is heated at a temperature above 400° C. in step (b).
6. The process of claim 1 , wherein the ratio of moles of 5(6)-amino-2-(p-aminophenyl) benzimidazole to the moles of para-phenylenediamine is 30/70 to 85/15.
7. The process of claim 6 , wherein the ratio of moles of 5(6)-amino-2-(p-aminophenyl) benzimidazole to the moles of para-phenylenediamine is 45/55 to 85/15.
8. The process of claim 1 , wherein said fiber is heated in an oven in step (a).
9. The process of claim 1 , wherein said fibers are heated by contacting said fibers with a hot surface.
10. The process of claim 1 , wherein said fibers are heated in step (a) under a tension of at least 0.1 gpd.
11. The process of claim 1 , wherein said fiber is heated in step (b) under a tension of 1 gpd or less.
12. A process for producing filaments comprising a copolymer derived from the copolymerization of para-phenylenediamine, 5(6)-amino-2-(p-aminophenyl)benzimidazole, and terephthaloyl dichloride, the process having the following steps in a continuous process,
(a) a step of spinning filaments into a coagulation bath from a sulfuric acid solution of the copolymer;
(b) a step of contacting the filaments with one or more of (i) wash and (ii) neutralization fluid to form never-dried fiber; and
(c) a step of heating said never-dried fiber to at least 20° C. but less than 100° C. until the moisture content of said fiber is 20 weight percent or less of said fiber;
the fiber being further heated to a temperature of at least 350° C. in an additional continuous or separate step.
13. The process of claim 12 , wherein in step (c) said fiber is heated until the moisture content is 14 weight percent or less.
14. The process of claim 12 , wherein said fiber is heated in step (c) under a tension of at least 0.1 gpd.
15. The process of claim 12 , wherein said fiber is heated in the last step under a tension of 1 gpd or less.