Process for producing aromatic polyimide composite separating membrane

Abstract From the Canadian patent

An aromatic polyimide composite membrane having an excellent gas-separating property is produced by a process comprising the steps of:, coating at least one surface of a substrate consisting of an aromatic polyimide porous membrane with a solution of 0.05% to 10% by weights of an aromatic polyamic acid in an polar organic solvent, which is not capable of dissolving the polyimide porous membrane at a temperature, not exceeding 140°C; after a during drying the resultant thin coating layer of the polyamic acid solution, heating the resultant polyamic acid layer at a temperature of 150°C or more so as to convert the polyamic acid layer to the corresponding polyimide layer.