Process for preparing aramid copolymer yarn using a halide acid wash
The present invention concerns methods for removing sulfur from yarn comprising the steps of: a) contacting never-dried polymeric yarn with an aqueous base, the polymer comprising imidazole groups and said polymer comprising sulfur atoms characterized as being in the form of sulfate anions; b) contacting the yarn with an aqueous acid comprising a halide; and c) rinsing the yarn.
1. A process for removing sulfur from yarn comprising the steps of:
a) contacting never-dried polymeric yarn with an aqueous base, said polymeric yarn made from polymer comprising imidazole groups and said polymer comprising sulfur atoms in the form of sulfate anions; and subsequently
b) contacting the yarn with an aqueous acid comprising a halide; and
c) rinsing the yarn.
2. The process of claim 1 , further comprising rinsing the yarn after step a) but prior to step b).
3. The process of claim 2 , wherein the rinsing of the yarn in claim 2 is an aqueous rinse.
4. The process of claim 1 , wherein said polymer comprises residues of 5(6)-amino-2-(p-aminophenyl)benzimidazole, aromatic diamine, and aromatic diacid-chloride.
5. The process of claim 4 , wherein said aromatic diacid-chloride is terephthaloyl dichloride.
6. The process of claim 4 , wherein said aromatic diamine is para-phenylenediamine.
7. The process of claim 4 , 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.
8. The process of claim 4 wherein the molar ratio of 5(6)-amino-2-(p-aminophenyl)benzimidazole to aromatic diamine is 45/55 to 85/15.
9. The process of claim 1 , wherein the acid comprising a halide is one or more of hydrofluoric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, or mixtures thereof.
10. The process of claim 9 , wherein said acid comprising a halide is hydrochloric acid.
11. The process 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 process of claim 1 , wherein in step (c) the yarn is rinsed with water.
13. The process of claim 1 , wherein at least a portion of residual halide anions is removed from the fiber in step c).
14. The process of claim 1 , wherein after step c), the yarn has 3.0 weight percent sulfur or less, based on the weight of the yarn.
15. The process of claim 14 , wherein after step c), the yarn has 2.5 weight percent sulfur or less, based on the weight of the yarn.
16. The process of claim 15 , wherein after step c), the yarn has 1.0 weight percent sulfur or less, based on the weight of the yarn.