Electrolytic production of high purity alkali metal hydroxide

Claim 1

An electrolytic cell for the production of aqueous alkali metal hydroxide solution substantially free of alkali metal halide and other impurities comprising (1) a first hollow cell section having disposed therein a dimensionally stable anode, an electrolyte inlet, a spent electrolyte outlet, a halogen gas outlet and electrical connection means for supplying current to said anode; (2) a second hollow cell section having disposed therein a metal cathode, an outlet for the aqueous solution of alkali metal hydroxide product, an outlet for hydrogen gas and electrical connection means for conducting current from said cathode; and (3) a hydrated fluorinated copolymer cationic exchange resin film membrane having pendant sulfonic acid groups or derivatives thereof arranged between said hollow cell sections closely spaced between a surface of each said anode and said cathode and held in fixed juxtaposed position by said hollow cell sections, said film membrane having the structural formula: ##STR3## and --CXX'--CF.sub.2 -- (2) wherein R represents the group --CF--CF.sub.2 --O--CFY--CF.sub.2 O).sub.m in which R' is fluorine or perfluoralkyl of 1 to 10 carbon atoms, Y is fluorine or trifluoromethyl, and m is 1, 2 or 3, n is 0 or 1; X is fluorine, chlorine, hydrogen or trifluoromethyl; and X' is X or CF 3 --CF 2 ) z wherein z is 0 or an integer from 1 to 50; the units of formula (1) being present in an amount from 3 to 20 mole percent.