Patent ID: 7276561

Claim:
A process for producing a polymer ion-exchange membrane comprising the steps of: irradiating a polymer film substrate with high-energy heavy ions to form irradiation damage; etching the irradiation damage chemically or thermally to form fine cylindrical through-holes in the film substrate such that they have an average diameter of at least 10 nm and range in number from 10 4 to 10 14 per square centimeter on the substrate surface; adding to the resulting perforated film substrate at least one monomer selected from the group consisting of monomers having a sulfonyl halide group, namely, CF 2 ═CF(SO 2 X 1 ) (where X 1 is the halide group fluorine or chlorine as applicable hereinafter), CH 2 ═CF(SO 2 X 1 ), CF 2 ═CF(O(CF 2 ) 1-4 SO 2 X 1 and CF 2 ═CF(OCH 2 (CF 2 ) 1-4 SO 2 X 1 ); degassing the added monomer or monomers; applying γ-rays, X-rays or electron beams as an ionizing radiation, thereby graft polymerizing the monomer or monomers on a surface of the film substrate or within the holes; and converting the [—SO 2 X 1 ] group in the grafted molecular chains to the sulfonate group [—SO 3 M] (where M is the alkali metal Na or K), and then to the sulfonic acid group [—SO 3 H].