Method for removing sulfur from fiber using halide salt 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 aqueous salt solution comprising halide anions to displace at least a portion of the sulfate anions with halide anions; and b) rinsing the fiber to remove displaced sulfate anions.
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 salt solution comprising halide anions 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-chloride.
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 aqueous salt solution comprises halide anions comprising one or more of sodium chloride, sodium bromide, potassium chloride, potassium bromide, lithium chloride, lithium bromide, calcium chloride, calcium bromide, magnesium chloride, magnesium bromide, ammonium chloride, ammonium bromide, ferrous chloride, ferrous bromide, ferric chloride, ferric bromide, zinc chloride, zinc bromide, or mixtures of two or more of these.
10. The method of claim 9 , wherein said aqueous salt solution comprising halide anions comprises sodium chloride.
11. The method of claim 1 , wherein in step b), at least a portion of residual halide anions is removed.
12. 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.
13. The method of claim 12 , wherein after step b), the fiber has less than 2.5 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 1.0 weight percent sulfur based on the weight of the fiber.