Electrolysis of aqueous solution of sodium chloride

Claim 2

In a method of subjecting an aqueous sodium chloride solution to electrolysis to produce chlorine and sodium hydroxide in an electrolysis cell which is partitioned by a diaphragm into an anolyte compartment and catholyte compartment, the improvement which comprises a diaphragm which is a fluorinated polymeric cation exchange membrane having a water permeability under electrolysis conditions of from 2 to 3.5 moles/Faraday; and containing carboxylic acid groups as the ion exchange groups.

Claim 3

The method of claim 1, wherein said fluorinated cation exchange membrane is a fluorinated polymer having an ion-exchange capacity of 0.5 to 4.0 milliequivalent/gram dried polymer and a glass transition temperature at least 20° C. lower than the temperature of electrolysis.

Claim 4

The method of claim 1 wherein said fluorinated polymer has a volumetric melt flow rate of 100 mm 3 /second at 150° to 300° C.

Claim 5

The method of claim 1, wherein said fluorinated cation exchange membrane has an electric resistance of less than 10 Ω-cm 2 under the electrolysis conditions.

Claim 6

The method of claim 1, wherein said fluorinated polymer is a copolymer produced by copolymerizing a fluorinated olefin monomer and a monomer containing carboxylic acid groups or functional groups which can be converted to carboxylic acid groups.

Claim 7

The method of claim 5, wherein the fluorinated copolymer comprises repeating units of the formula: ##STR3## wherein X represents --F, --Cl, --H or --CF 3 ; X' and X" respectively represent --F, --Cl, --H, --CF 3 or --(CF 2 ) m CF 3 ; m is 1 to 5; Y represents --A, --φ--A, --P--A, --O--(CF 2 ) n (P,Q,R)A and P represents (CF 2 ) a (CXX') b (CF 2 ) c ; Q represents (CF 2 --O--CXX') d ; R represents (CXX'--O--CF 2 ) e and (P, Q, R) represents an arrangement of at least one P, Q and R in desired order; φ represents a phenylene group; X and X' are defined above; n is 0 or 1; a, b, c, d, and e respectively 0 to 6; A represents --COOH or a functional group which can be converted to --COOH selected from the group consisting of --CN, --COF, --COOR 1 , --COOM, and --CONR 2 R 3 ; R 1 represents a C 1-10 alkyl group; M represents an alkali metal or a quaternary ammonium group and R 2 and R 3 respectively represent hydrogen atom or a C 1-10 alkyl group.

Claim 8

The method of claim 6 wherein Y is selected from the group consisting of ##STR4## wherein x, y and z respectively 1 to 10; Z and R f respectively represent --F and a C 1-10 perfluoroalkyl group, A is as defined in claim 6.

Claim 9

The method of claim 6 wherein repeating unit (b) comprises from 1 to 40 mole % of the total polymer.

Claim 10

The method of claim 6, wherein repeating unit (b) comprises from 3 to 20 mole % of the total copolymer.