Oblon, Spivak McClelland, Maier & Neustadt
Four layer cation exchange fluoropolymer membrane
 A cation exchange fluoropolymer membrane comprising at least three integrally laminated layers including a main layer made of a perfluorocarbon polymer having carboxylic acid groups as its ion exchange groups with an ion exchange capacity of from 1.4 to 2.0 meq/g dry resin and having a thickness of from 50 to 250 .mu.m, a sulfonic acid film surface layer formed on one side of said main layer, made of a perfluorocarbon polymer having sulfonic acid groups as its ion exchange groups with an ion exchange capacity of from 0.5 to 1.5 meq/g dry resin and having a thickness of from 5 to 50 m, and a carboxylic acid film surface layer formed on the other side of said main layer, made of a perfluorcarbon polymer having carboxylic acid groups as its ion exchange groups with an ion exchange capacity of from 0.5 to 1.3 meq/g dry resin and having a thickness of from 5 to 50 .mu.m, said sulfonic acid film surface layer and carboxylic acid film surface layer constituting the outer-most layers, respectively. 
Asahi Glass Company Ltd.
C C C
C25B C08J C08J
inventional additional inventional
Haruhisa Ryoji Hiroaki Koji
Miyake Yamada Ito Suzuki