Method for removing sulfur from fiber using halide acid ion exchange
View Patent ↗The present invention concerns methods for removing sulfur from a fiber made from a polymer comprising imidazole groups, said method comprising: a) contacting never-dried sulfate anion-containing polymeric-fiber with an halide-containing acid to displace at least a portion of the sulfate ions with halide anions; and b) rinsing the fiber to remove the displaced sulfate ions.
1. A method for removing sulfur from a fiber made from a polymer comprising imidazole groups, said method comprising:
a) contacting never-dried sulfate anion-containing polymeric-fiber with an aqueous acid comprising a halide to displace at least a portion of the sulfate anions with halide anions; and
b) rinsing the fiber to remove displaced sulfate anions.
2. The method of claim 1 , wherein said polymer comprises derivatives of 5(6)-amino-2-(p-aminophenyl)benzimidazole, aromatic diamine, and aromatic diacid-hloride.
3. The method of claim 2 , wherein said aromatic diacid-chloride is terephthaloyl dichloride.
4. The method of claim 2 , wherein said aromatic diamine is para-phenylenediamine.
5. The method of claim 2 , wherein the molar ratio of 5(6)-amino-2-(p-aminophenyl)benzimidazole to aromatic diamine is in the range of from 30/70 to 85/15.
6. The method of claim 5 , wherein the molar ratio of 5(6)-amino-2-(p-aminophenyl)benzimidazole to aromatic diamine is in the range of from 45/55 to 85/15.
7. The method of claim 1 , wherein said halide anions comprise one or more of F—, Cl—, Br—, and I—.
8. The method of claim 7 , wherein said halide anions comprise one or more of Cl— and Br—.
9. The method of claim 1 , wherein said acid comprising a halide is one or more of hydrofluoric acid, hydrochloric acid, hydroiodic acid , or hydrobromic acid.
10. The method of claim 9 , wherein said acid comprising a halide is hydrochloric acid.
11. The method of claim 1 , wherein the halide acid is formed from a material that forms a halide-containing acid when in contact with water.
12. The method of claim 1 , wherein in step b), at least a portion of residual halide anions is removed.
13. The method of claim 1 , wherein after step b), the fiber has less than 3.0 weight percent sulfur based on the weight of the fiber.
14. The method of claim 13 , wherein after step b), the fiber has less than 2.5 weight percent sulfur based on the weight of the fiber.
15. The method of claim 14 , wherein after step b), the fiber has less than 1.0 weight percent sulfur based on the weight of the fiber.