A composite membrane for use in gas separation.

摘要

There is disclosed a composite membrane comprising (A) a polysulfone type porous membrane capable of rejecting 90% or more of dextran molecules having a weight average molecular weight of 70,000 and (B) a specific styrene type resin coated on at least one side of the polysulfone type porous membrane in a thickness of 5 µm or less and in an amount of 1 x 10<Sup>-7</Sup> g/cm<Sup>2</Sup> of the polysulfone type porous membrane, the styrene type resin being selected from the group consisting of (I) a specific styrene type linear polymer having a weight average molecular weight of 1 x 10-<Sup>5</Sup> or more, (II) a specific blend polymer prepared by blending at least two different styrene type linear polymers each as defined above and (III) a specific crosslinked polymer selected from the group consisting of (i) one prepared by crosslinking a styrene type linear polymer having a weight average molecular weight of 1 x 10<Sub>.</Sub><Sup>3</Sup> or more and (ii) one prepared by blending at least two different styrene type linear polymers each having a weight average, molecular weight of 1 x 10<Sup>3</Sup>. Such a composite membrane has been found to be advantageously employed for gas separation because of its high gas permeability and high selective gas permeability.