| 摘要 |
A cation exchange membrane of a fluorocarbon polymer containing pendant carboxylic acid and/or carboxylate groups, preferably having, at a predetermined ratio, pendant carboxylic acid and/or carboxylate groups and pendant sulfonic acid and/or sulfonate groups uniformly distributed therein, is produced by contacting with a reducing agent a fluorocarbon polymer containing pendant groups of the formula: -O(CF2)mSO2X wherein X is a fluorine atom, a chlorine atom, a hydrogen atom, M or OM in which M represents a hydrogen atom, a metal atom or an ammonium group, and m is as defined above, and transforming the resultant to a film. An excellent double-layer type composite cation exchange membrane can be produced by laminating the above-mentioned membrane having pendant carboxylic acid and/or carboxylate groups and pendant sulfonic acid and/or sulfonate groups on a membrane of a fluorocarbon polymer containing pendant sulfonic acid and/or sulfonate groups. In such a type of double-layer cation exchange membrane, both the two membranes are based on the same kind of polymer and, hence, peeling-off at the interface of the two layers can be well prevented while exhibiting high current efficiency and low electrolytic voltage. |
