Patent ID: 7189346

Claim:
A process for removing polyphosphoric acid from a polybenzazole dope filament, comprising: (a) during or immediately after the dope filament is coagulated, contacting the coagulated dope filament with a washing solution containing water, or a mixture of water and polyphosphoric acid, under conditions sufficient to hydrolyze the polyphosphoric acid; and then (b) contacting the coagulated dope filament with a neutralizing solution containing water and an effective amount of a base under conditions sufficient to neutralize polyphosphoric acid in the filament to a salt of the base and the acid, such that the resulting filament has an average degree of polymerization of the polyphosphoric acid content in the filament less than or equal to 1.5, wherein in step (a) a catalyst is present during said contacting for increasing the rate of hydrolysis of the polyphosphoric acid.