Electrolytic cation exchange membrane

Claim 2

An electrolytic cation exchange membrane which comprises a first film made of a fluorinated polymer having the following repeating units (a) and (b): (a) --(CF 2 --CXX')-- ##STR6## wherein: X and X' is --F, --Cl, --H or --CH 3 ; A is --COOM or --PO 3 M 2 , wherein M is hydrogen, an alkali metal or a group hydrolyzable to such a group; and Y is selected from the group consisting of --(CF 2 ) x --, --O--(CF 2 ) x --, ##STR7## wherein Z is --F or a perfluoroalkyl group having from 1 to 10 carbon atoms; and each of x and y is an integer of from 1 to 10, and containing a fibrillated tetrafluoroethylene polymer, and a second film laminated thereon, made of a fluorinated polymer having carboxylic acid groups as its ion exchange groups; said first film having a greater thickness and smaller specific electric resistance than said second film.

Claim 3

The electrolytic cation exchange membrane according to claim 1, wherein the first film has a thickness of from 50 to 500 μm, the second film has a thickness of from 5 to 50 μm and the ratio of the thickness of the first film to the thickness of the second film is within a range of from 2 to 50.

Claim 4

The electrolytic cation exchange membrane according to claim 1, wherein the first film has a thickness of at least 50 μm and contains from 3 to 15% by weight of the fibrillated tetrafluoroethylene polymer.

Claim 5

The electrolytic cation exchange membrane according to claim 1, wherein the fibrillated tetrafluoroethylene polymer is fibrils of emulsion-polymerized tetrafluoroethylene having a specific surface area of from 3 to 30 m 2 /g.

Claim 6

The electrolytic cation exchange membrane according to claim 1, wherein the fibrillated tetrafluoroethylene polymer is fibrils of a tetrafluoroethylene copolymer containing at most 5 molar % of a monomer represented by the formula: ##STR8## where R f is a perfluoroalkyl group having from 1 to 10 carbon atoms, as the comonomer unit.

Claim 7

The electrolytic cation exchange membrane according to claim 1, wherein the first film contains a reinforcing material composed of a woven or non-woven fabric of a fluorinated polymer.

Claim 8

The electrolytic cation exchange membrane according to claim 6, wherein the woven or non-woven fabric has a thickness of from 50 to 500 μm and a mesh size of from 15 to 50 mesh.

Claim 9

The electrolytic cation exchange membrane according to claim 1, wherein the cation exchange groups of the first film are carboxylic acid groups, and the first film has a greater ion exchange capacity than the second film.

Claim 10

The electrolytic cation exchange membrane according to claim 1, wherein a gas and liquid permeable porous layer composed of catalytically active particles is provided on one side or both sides of the membrane.

Claim 11

The electrolytic cation exchange membrane according to claim 1, wherein a gas and liquid permeable porous layer composed of catalytically inactive particles is provided on one side or both sides of the membrane.

Claim 12

The electrolytic cation exchange membrane according to claim 1, wherein at least one side of the membrane has a roughened surface.

Claim 13

An electrolytic cell which comprises anode and cathode compartments partitioned by an electrolytic cation exchange membrane as defined in claim 1.

Claim 14

The electrolytic cell according to claim 12, wherein the electrolytic cation exchange membrane is disposed so that the first film faces the anode side and the second film faces the cathode side.

Claim 15

The electrolytic cell according to claim 12, wherein an aqueous alkali metal chloride solution is electrolyzed to obtain an alkali metal hydroxide and chlorine.

Claim 16

An electrolytic process which comprises electrolyzing an aqueous alkali metal chloride solution in the electrolytic cell as defined in claim 14, at a temperature of from 80° to 120° C. and at a current density of from 10 to 100 A/dm 2 while supplying a 2.5-5.0N alkali metal chloride aqueous solution to the anode compartment and water or a dilute alkali metal hydroxide aqueous solution to the cathode compartment.

Claim 17

An electrolytic cation exchange membrane which consists of a first film made of a fluorinated polymer having the following repeating units (a) and (b): (a) --(CF 2 --(CXX')-- ##STR9## wherein: X and X' independently represent --F, --Cl, --H or CH 3 ; A is --COOM or --PO 3 M 2 , wherein M is hydrogen, an alkali metal ion, or a group hydrolyzable to an alkali metal ion; and Y is selected from the group consisting of --(CF 2 ) x --, --O--(CF 2 ) x --, ##STR10## wherein Z is --F or a perfluoroalkyl group having from 1 to 10 carbon atoms; and each of x and y is an integer of from 1 to 10, wherein said first film contains a fibrillated tetrafluoroethylene polymer, and a second film laminated thereon, made of a fluorinated polymer having carboxylic acid groups as its ion exchange groups; said first film having a greater thickness and smaller specific electric resistance than said second film wherein said first film has a thickness of from 50 to 500 μm, said second film has a thickness of from 5 to 50 μm, and the ratio of the thickness of said first film to the thickness of said second film is within a range of from 2 to 50.

Claim 18

An electrolytic cation exchange membrane which consists of a first film made of a fluorinated polymer having the following repeating units (a) and (b): (a) --(CF 2 --(CXX')-- ##STR9## wherein: X and X' independently represent --F, --Cl, --H or CH 3 ; A is --COOM or --PO 3 M 2 , wherein M is hydrogen, an alkali metal ion, or a group hydrolyzable to an alkali metal ion; and Y is selected from the group consisting of --(CF 2 ) x --, --O--(CF 2 ) x --, ##STR10## wherein Z is --F or a perfluoroalkyl group having from 1 to 10 carbon atoms; and each of x and y is an integer of from 1 to 10, wherein said first film contains a fibrillated tetrafluoroethylene polymer, and a second film laminated thereon, made of a fluorinated polymer having carboxylic acid groups as its ion exchange groups; said first film having a greater thickness and smaller specific electric resistance than said second film wherein said first film has a thickness of from 50 to 500 μm, said second film has a thickness of from 5 to 50 μm, and the ratio of the thickness of said first film to the thickness of said second film is within a range of from 2 to 50.