Patent ID: 8394182

Claim:
A hollow fiber polymer membrane comprising: a polyimide polymer membrane material made from a crosslinkable polymide polymer having an average molecular weight of at least 20,000 and including the monomers A+B+C; where A is a dianhydride of the formula; where X 1 and X 2 are the same or different halogenated alkyl group, phenyl or halogen; where R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are H, alkyl, or halogen; where B is a diamino cyclic compound without a carboxylic acid functionality; where C is a diamino cyclic compound with a carboxylic acid functionality; and wherein the ratio of B to C is between 1:4 and 8:1; and wherein the hollow fiber polymer membrane material further comprises at least some covalent ester crosslinks.