Composition useful in process for preparing powadir membranes from tetrahalobisphenol a polycarbonates

Claim 1

A composition useful for preparing a membrane comprising a tetrahalogenated bisphenol polycarbonate which comprises: (A) a bisphenol polycarbonate wherein at least 25 percent by weight of the bisphenol moieties are tetrahalogenated wherein the halogen is chlorine or bromine which polycarbonate is polymerized to the extent that the polycarbonate will form a membrane with sufficient mechanical strength to withstand use conditions; (B) a solvent for the polycarbonate which dissolves at least about 5 weight percent of the polycarbonate present at the membrane extrusion temperature and which comprises at least one compound selected from the group consisting of a glycol ether which corresponds to the formula R 3 O-(CH 2 CH 2 O) r -R 3 wherein R 3 is methyl or ethyl, and r is an integer of between about 1 and 20; morpholine substituted on the nitrogen atom with an alkyl, formyl, or alkanoyl moiety; an unsubstituted or N-C 1-4 alkyl, N-C 5-6 cycloalkyl, or N-C 6-10 aryl or alkaryl substituted pyrrolidinone; C 1-4 alkoxycarbonyl, formyl, nitro, or halo substituted benzene; dimethylformamide, cyclohexanone; N,N-dimethyl acetamide; acetophenone; sulfolane; cyclohexyl acetate; 1,1,3,3-tetramethylurea; isophorone; caprolactone; 1-formylpiperidine; methyl salicylate; hexamethylphosphoramide; phenyl ether; and bromonaphthalene; and (C) a non-solvent for the polycarbonate which dissolves less than about 5 weight percent of the polycarbonate present at the membrane extrusion temperature, which is soluble in the solvent for the polycarbonate, and which aids in the formation of pores, and which comprises at least one compound selected from the group consisting of a glycol or glycol ether which corresponds to the formula R 4 O-(CH 2 CH 2 O) q -R 4 wherein R 4 is separately in each occurrence hydrogen or C 1-4 alkyl, and q is an integer of about 1 to about 250; an ester corresponding to the formula R 5 COOR 6 wherein R 5 is hydrogen or C 1-19 alkyl, and R 6 is C 1-10 alkyl; a C 1-10 alkanol; cyclohexane, unsubstituted or substituted with an alkyl, cycloalkyl, or perfluoralkyl moiety; a C 5-20 alkane; a dialkyl ketone wherein at least one of the alkyl moieties is C 3 or greater; an amide corresponding to the formula R 7 CONHR 8 wherein R 7 is hydrogen or C 1-10 alkyl and R 8 is C 1-10 alkyl; an acetyl or C 1-10 alkyl nitrile; acetone; a C 1-10 alkyl aldehyde; a trialkyl amine; nitromethane; trialkyl ortho-formate; diacetone alcohol; dimethyl malonate; decahydronaphthalene; tetrahydronaphthalene; malononitrile; ethylene carbonate; sulfolane; alkyl or cycloalkyl substituted benzene; and water; wherein the composition is useful for the preparation by a wet extrusion process of a membrane which has one or more porous regions and one or more discriminating regions capable of separating one or more gases from one or more other gases.