Rendering polybenzimidazole solid materials more resistant to darkening upon exposure to light

An improved process for the formation of a poly-2,2'-(m-phenylene)-5,5'-bibenzimidazole fibrous material having an enhanced resistance to undergo the usual darkening upon exposure to light comprising:

• a. forming a spinning solution comprising (1) a solvent selected from the group consisting essentially of N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, and N-methyl-2-pyrrolidone, (2) about 10 to 45 percent by weight based upon the total weight of the solution of dissolved poly-2,2'-(m-phenylene)-5,5'-bibenzimidazole, and (3) about 0.1 to 8 percent by weight based upon the weight of said poly-2,2'-(m-phenylene)-5,5'-bibenzimidazole of dispersed finely divided pigment selected from the group consisting essentially of arsenic thioarsenate, copper phthalocyanine, anatase titanium dioxide, and mixtures of the foregoing, and
• b. extruding said solution through a shaped orifice into an evaporative atmosphere to form a poly-2,2'-(m-phenylene)-5,5'-bibenzimidazole fibrous material having said finely divided pigment substantially uniformly distributed therein in a concentration of about 0.1 to 8 percent by weight based upon the weight of said poly-2,2'-(m-phenylene)-5,5'-bibenzimidazole.

A polybenzimidazole fibrous material exhibiting an enhanced resistance to undergo the usual darkening upon exposure to light comprising about 0.1 to 8 percent by weight based upon the weight of said polybenzimidazole of a finely divided pigment substantially uniformly dispersed therein selected from the group consisting essentially of arsenic thioarsenate, copper phthalocyanine, anatase titanium dioxide, and mixtures of the foregoing.

An improved solution suitable for the formation of shaped polybenzimidazole articles comprising:

• a. a solvent capable of dissolving the polybenzimidazole which is selected from the group consisting essentially of N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, and N-methyl-2-pyrrolidone,
• b. dissolved polybenzimidazole, and
• c. a minor concentration sufficient to stabilize the color of the resulting shaped polybenzimidazole article of a finely divided pigment which is dispersed in said solution selected from the group consisting essentially of arsenic thioarsenate, copper phthalocyanine, anatase titanium dioxide, and mixtures of the foregoing.