PURPOSE: To obtain a gas separation membrane excellent in heat resistance, chemical resistance and mechanical strength and having high transmission coefficient of hydrogen gas without damaging gas separation capacity, by setting the thickness of a dense layer comprising a polyparabanic acid type polymer to 20μm or less.
CONSTITUTION: A polyparabanic acid type polymer having a repeating unit shown by formula (wherein R is a divalent org. group) is used. Both of a homopolymer and a copolymer may be used but one with intrinsic viscosity (DMF 25°C) of 0.4W4 is pref. Further, one having diphenylether-4,4'-diyl is excellent in heat resistance. A membrane is formed from a dope solution so as to set the thickness of a dense layer substantially having no fine pore to 20μm or less. After the solvent of the dope solution is evaporated at ambient temp.W140°C, the membrane is heated to 150W200°C to further evaporate the residual solvent or the solvent is evaporated at 50°CWthe b.p. of the solvent or less and the resulting membrane is immersed in water at 0W40°C and gelled to obtain an anisotropic membrane.
IKEDA TADAO
IMAI CHIHIRO
