PURPOSE: To prepare a composite membrane suitable as an electrolytic membrane capable of keeping high current efficiency for a long period, by applying fine powder of a polylmer compound and a vinyl monomer to the surface of a fluorine-containing cation exchange membrane, etc., and polymerizing the monomer thereby bonding the polymer to the membrane.
CONSTITUTION: Fine powder of a polymer compound (e.g. ethylene, ethylene oxide, etc.) having a particle diameter of preferably 0.01W10μ is dispersed in a vinyl monomer (e.g. styrene) to obtain a dispersion composed of 0.5W50wt% of the polymer compound and 5W80wt% of the vinyl monomer. The dispersion is applied to the surface of a polymer membrane having fluorine atom and cation exchange group (e.g. sulfonic acid group) or a functional group (e.g. acid ester group) to which a cation exchange group can be introduced easily, by impregnation or coating. The vinyl compound is polymerized on the surface of the membrane, and if necessary, ion exchange group is introduced to the product to obtain the objective composite membrane.
MOYA KENSUKE
NAKAHARA AKIHIKO
MURATA YASUO
