Fusion free hydrolysis of polyphosphoric acid in spun multifilament yarns
View Patent ↗The invention concerns processes for hydrolyzing polyphosphoric acid in a never-dried spun multifilament yarn, comprising: a) removing surface liquid from filaments in a never-dried spun multifilament yarn; and b) contacting the yarn with a hot surface to hydrolyze polyphosphoric acid, wherein the filaments remain substantially unfused; wherein the hot surface has a surface temperature of at least about 150° C.
1. A process for hydrolyzing polyphosphoric acid in a never-dried spun multifilament yarn, comprising: a) removing surface liquid from filaments in a never-dried spun multifilament yarn; and b) contacting the yarn with a hot surface to hydrolyze polyphosphoric acid, wherein the filaments remain substantially unfused; wherein said hot surface has a surface temperature of at least about 150° C.
2. The process of claim 1 , further comprising the step of: c) removing hydrolyzed polyphosphoric acid from the yarn.
3. The process of claim 1 , wherein removing surface liquid from filaments in the never-dried yarn comprises drying.
4. The process of claim 3 , wherein the drying is performed at a temperature of less than about 140° C.
5. The process of claim 4 , wherein the drying is performed on heated rolls at a temperature of less than about 120° C.
6. The process of claim 1 , wherein the never-dried spun multifilament yarn is rinsed with aqueous fluid prior to removing surface liquid from filaments in the never-dried spun multifilament yarn.
7. The process of claim 1 , wherein the hot surface comprises heated rolls.
8. The process of claim 1 , wherein the hot surface has a surface temperature of at least about 180° C.
9. The process of claim 2 , wherein the removal of hydrolyzed polyphosphoric acid from the yarn includes washing with base.
10. The process of claim 9 , wherein the yarn is washed with water prior to and after washing with base.
11. The process of claim 9 , wherein the base comprises sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium bicarbonate, or any combination thereof.
12. The process of claim 10 , wherein the base comprises sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium bicarbonate, or any combination thereof.
13. The process of claim 9 , wherein the yarn is subsequently washed with a volatile acid.
14. The process of claim 1 , wherein the multifilament yarn comprises filaments of a polyareneazole polymer.
15. The process of claim 14 , wherein the polyareneazole is a polypyridazole.
16. The process of claim 15 , wherein the polypyridazole is a polypyridobisimidazole.
17. The process of claim 16 , wherein the polypyridobisimidazole is poly(1,4-(2,5-dihydroxy)phenylene-2,6-pyrido[2,3-d:5,6-d]bisimidazole.
18. The process of claim 14 , wherein the polyareneazole is a polybenzazole.
19. The process of claim 18 , wherein the polybenzazole is a polybenzobisoxazole.