Abstract: A cation-exchange membrane for electrolysis which comprises a fluoropolymer having ion-exchange groups and a porous base. It is characterized by having, on the anode-side surface of the membrane, protrusions comprising a polymer having ion-exchange groups. It is further characterized in that: when the average value of the heights of the tops of the protrusions from the anode-side surface of the membrane is expressed as h (?m), then 20?h?150; when the density of the protrusions distributed is expressed as P (protrusions per cm2), then 50?P?1,200; when the average proportion of the areas of those bottom parts of the protrusions which are on the same level as the anode-side surface of the membrane to the area of the anode-side surface of the membrane is expressed as S (cm2/cm2), then 0.001?S?0.6; and when the average proportion of the areas of the top parts of the protrusions to the area of the anode-side surface of the membrane is expressed as T (cm2/cm2), then T?0.05.

Abstract: A cation-exchange membrane for electrolysis which comprises a fluoropolymer having ion-exchange groups and a porous base. It is characterized by having, on the anode-side surface of the membrane, protrusions comprising a polymer having ion-exchange groups. It is further characterized in that: when the average value of the heights of the tops of the protrusions from the anode-side surface of the membrane is expressed as h (?m), then 20?h?150; when the density of the protrusions distributed is expressed as P (protrusions per cm2), then 50?P?1,200; when the average proportion of the areas of those bottom parts of the protrusions which are on the same level as the anode-side surface of the membrane to the area of the anode-side surface of the membrane is expressed as S (cm2/cm2), then 0.001?S?0.6; and when the average proportion of the areas of the top parts of the protrusions to the area of the anode-side surface of the membrane is expressed as T (cm2/cm2), then T?0.05.

Abstract: A method for the electrolysis of an alkali metal chloride in an electrolytic cell is disclosed, in which use is made of a cation exchange membrane comprising a carboxylate-containing fluorocarbon polymer layer disposed on a cathode compartment side and provided on its surface with an inorganic coating, and a sulfonate and/or carboxylate-containing fluorocarbon polymer layer disposed on an anode compartment side and having a water content of from 3 to 10% by weight. By this method, an alkali metal hydroxide, e.g., sodium hydroxide, can be directly produced in a concentration as high as 45-55 % by weight from a saline solution having an alkali metal chloride concentration as low as from 3.0 to 3.5N with reduced energy consumption, stably for a prolonged period of time.

Abstract: A highly stable cation exhange membrane for use in the electrolysis of an alkali metal chloride is disclosed, which comprises a reinforced base membrane comprised of at least one layer of a fluorocarbon polymer and a reinforcing woven fabric encapsulated therein and a coating disposed on at least one surface of the reinforced base membrane, the coating comprising particles of at least one inorganic material selected from the group consisting of oxides, nitrides and carbides of elements belonging to group IV of the periodic table, which particles have an average primary particle diameter as small as from 0.01 to 0.2 .mu.m, and a binder polymer. In the cation exchange membrane, the coating containing particles of an inorganic material, uniformly and strongly adheres to the surface of the reinforced base membrane, so that the inorganic material can remain in the coating for a prolonged period of time.

Abstract: In cation exchange membranes having a multi-layer structure consisting of two or three layers or more each having different equivalent weight and/or different kind of ion exchange group used for the electrolysis of alkali metal chloride according to an ion exchange membrane process, a homogeneous cation exchange membrane which comprises that at least one outer layer having a lower water content of both outer layers of said membrane has a roughened surface so that the amount of hydrogen gas bubbles generated from the cathode and attached to the membrane surface is the least whereby the electrolysis voltage is the lowest and the process for the production thereof.

Abstract: A homogeneous cation exchange membrane having at least one roughened surface, which is assembled in an electrolytic cell with the roughened surface facing toward the cathode side of the cell, is employed in the electrolysis of an alkali chloride in an electrolytic cell divided by a cation exchange membrane into an anode compartment and a cathode compartment to produce an alkali hydroxide. The electrolysis voltage can be considerably reduced at a high current efficiency to provide a great economical advantage.