Composite membrane for gas separation

摘要

A composite membrane for gas separation having a three-layered structure comprising: (A) a porous polymer supporting membrane layer having a cross-sectional oxygen permeation flux of at least 5 m3/m2.hr.atm (STP) and having an asymmetric porous structure such that the average pore diameter at one surface is from 5 to 500 ANGSTROM and the average pore diameter at the other surface is greater than that at said one surface; (B) a polyorganosiloxane layer having a thickness of from 300 ANGSTROM to 5 mu m; and (C) a thin layer having a thickness of from 100 to 5000 ANGSTROM and made of a polymer containing monomer units of at least one monomer selected from the group consisting of fluoroolefin monomers and pivalate group-containing monomers, being soluble in an organic solvent and having an O2/N2 permeability coefficient ratio of at least 3.5; said layer B contacting said one surface with the smaller pore diameter of the layer A, said layer C contacting the surface of the layer B, and the composite membrane having an oxygen permeation flux of at least 0.1 m3/m2.hr.atm (STP) and an O2/N2 permeation flux ratio of at least 2.5.