PURPOSE: To obtain a gas-permeable membrane excellent in permeability, separating ability and stability, by forming on a porous support a composite membrane consisting of a polymeric thin membrane of an organopolysiloxane having no film-forming ability and a vitreous polymer thin membrane having a glass transition temperature above a specific value.
CONSTITUTION: A thin membrane of either an organopolysiloxane or an organopolysiloxane copolymer which have no film-forming ability, such as methylhydrogen polysiloxane, is allowed to adhere to the surface of a porous support. Then, a solution of poly-1-(trimethylsilyl)propyne in n-hexane etc. is dropped on the surface of water to form a thin membrane of the polymer. This water surface-cast membrane is bonded with the surface of the porous support to which the methylhydrogen polysiloxane has adhered. Thus, a composite membrane having selective permeability to gases is obtained, said membrane being composed of the porous support, the polymeric thin membrane of organopolysiloxane, which is formed on the support and has no film-forming ability, and the membrane of vitreous polymer which is formed on the thin membrane and has a glass transition temperature, Tg, of 180°C or higher.
SEKI MIDORI
ASAKAWA SHIRO
