Cation exchange membrane of fluoro polymer - with sulphonyl gps. modified by amination, for electrolysis of alkali chlorides

摘要

A cation exchange membrane comprising a fluoro polymer with sulphonyl gps. in the side chains, has one surface which has been treated with a polyamine to convert most of the sulphonyl gps. to a depth of >10u to gps. of formula SO2NRR'NRR" (where R is H, Na or K. R' is 3-6C alkylene, Z2N(R") gp. or ZN(R")Z2N(R") gp. Z is 2-6C alkylene and R" is R or -SO2). The pref. polymer is a copolymer of tetrafluoroethylene and a monomer of formula CF2=CFYfSO2F (where Yf is a 2-8C bifunctional aliphatic gp) and it has a mol. wt. of 1100-1200 per proton equiv. Also claimed is an electrolytic cell using the above membrane between anode and cathode. Used for electrolysis of alkali chlorides for prodn. of Cl and alkali metal hydroxides, the amine modified side of the membrane facing the cathode. Migration of OH ions back intot the anode compartment is prevented resulting in reduced formation of chlorate and oxygen and increased current yield.