Fluid separation membranes prepared from blends of polyimide polymers

In a method of forming a hollow fiber membrane by extruding a polymer solution in the form of a hollow fiber into a gaseous atmosphere maintained at a subatmospheric pressure and solidifying the membrane in a liquid medium, the improvement consisting essentially of employing as said polymer solution a polyimide reaction product of a polyimide reaction product of (1) a benzophenone tetracarboxylic dianhydride with toluene diisocyanate and methylene di p-phenyl diisocyanate and/or (2) benzophenone tetracarboxylic dianhydride with pyromellitic dianhydride, toluene diisocyanate and methyl di p-phenyl diisocyanate, and said second polymer being a phenylindane--containing polyimide in a ratio of from about 1:0.1 to 1:0.3.

In a fluid separation process in which a fluid feed stream is contacted with a fluid separation membrane capable of selectively permeating one component of said fluid feed stream, with the more selectively permeable component being withdrawn as permeate fluid, and the less selectively permeable component being withdrawn as retentate fluid, the improvement consisting essentially of contacting said fluid feed stream with an anisotropic fluid separation membrane having an integral discriminating layer formed of a blend of first and second polymers, said first polymer being a polyimide reaction product of (1) a benzophenone tetracarboxylic dianhydride with toluene diisocyanate and methylene di p-phenyl diisocyanate and/or (2) benzophenone tetracarboxylic dianhydride with pyromellitic dianhydride, toluene diisocyanate and methyl di p-phenyl diisocyanate, and the second polymer being a phenylindane--containing polyimide in a ratio of about 1:0.01 to 1:1.