Process for hydrolyzing polyphosphoric acid in a spun yarn

1. A process for removing polyphosphoric acid from a fiber, comprising the steps of:

a) heating a fiber comprising polymer and polyphosphoric acid to at least 120° C. for a time effective to hydrolyze polyphosphoric acid; and

b) in a separate step, removing hydrolyzed polyphosphoric acid from the fiber by washing said fiber with an aqueous liquid at a temperature of 100° C. or less.

2. The process of claim 1 , wherein the time effective to hydrolyze polyphosphoric acid is up to about 120 seconds.

3. The process of claim 1 wherein the heating includes convective heating, radiant heating, radiation heating, RF heating, conductive heating, steam heating, or any combination thereof.

4. The process of claim 1 wherein the polymer comprise a polyareneazole.

5. The process of claim 4 wherein the polyareneazole is poly(2,6-diimidazo[4,5-b:4′,5′-e]pyridinylene-1,4-(2,5-dihydroxy)phenylene).

6. The process of claim 1 wherein removing hydrolyzed polyphosphoric acid includes washing the fiber with a base.

7. The process of claim 6 wherein the fiber is washed with water prior to and after washing with the base.

8. The process of claim 6 wherein the base includes sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium bicarbonate, or any combination thereof.

9. The process of claim 7 wherein the base includes sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium bicarbonate, or any combination thereof.

10. The process of claim 6 wherein the fiber is subsequently washed with an acid.

11. A process for hydrolyzing polyphosphoric acid in a fiber, comprising

heating a fiber comprising polymer and polyphosphoric acid in an acidic medium having a pH less than 4.0 to a temperature above 100° C. for a time effective to hydrolyze polyphosphoric acid; and

in a separate step, removing hydrolyzed polyphosphoric acid from the fiber in a process comprising contacting the fiber containing hydrolyzed polyphosphoric acid with an aqueous liquid.

12. The process of claim 11 , wherein the acidic medium comprises up to about 80% phosphoric acid by weight.

13. The process of claim 11 , wherein the time effective to hydrolyze polyphosphoric acid is up to about 120 seconds.

14. The process of claim 11 wherein the acid medium has a pH less than 2.0.

15. The process of claim 12 , wherein the acidic medium comprises boiling phosphoric acid have a temperature less than 140° C.

16. The process of claim 11 , wherein the polymer remains substantially non-hydrolyzed.

17. A process for hydrolyzing polyphosphoric acid in a polyareneazole polymeric material, comprising the steps of:

a) providing a polymeric material comprising polyareneazole and polyphosphoric acid, wherein at least 50 mole percent of the polyareneazole repeating unit structure comprise 2,5-dihydroxy-p-phenylene moieties;

b) heating the polymeric material to more than 100° C. to hydrolyze at least a portion of polyphosphoric acid; and

c) removing hydrolyzed polyphosphoric acid from the polymeric material by contacting the polymeric material with an aqueous liquid at temperature of 100° C. or less.

18. The process of claim 1 , wherein the fluid has a temperature of about 60° C. or less.