To provide a production method whereby an ion exchange membrane for alkali chloride electrolysis can be obtained which has high current efficiency, little variation in current efficiency and high alkaline resistance. This is a method for producing an ion exchange membrane 1 having a layer (C) 12 containing a fluorinated polymer (A) having carboxylic acid type functional groups, by immersing an ion exchange membrane precursor film having a precursor layer (C) containing a fluorinated polymer (A) having groups convertible to carboxylic acid type functional groups, in an aqueous alkaline solution comprising an alkali metal hydroxide, a water-soluble organic solvent and water, and converting the groups convertible to carboxylic acid type functional groups to carboxylic acid functional groups, wherein the concentration of the water-soluble organic solvent is from 1 to 60 mass % in the aqueous alkaline solution (100 mass %); the temperature of the aqueous alkaline solution is at least 40 C. and less than 80 C.; and the proportion of structural units having carboxylic acid type functional groups in the fluorinated polymer (A) is from 13.0 to 14.50 mol % in all structural units (100 mol %) in the fluorinated polymer (A).

To provide a method whereby it is possible to efficiently produce an ion exchange membrane for alkali chloride electrolysis, which has high current efficiency and high alkali resistance at the time of electrolyzing an alkali chloride. This is a method for producing an ion exchange membrane 1 for alkali chloride electrolysis, having a layer (C) 12 containing a fluorinated polymer (A) having carboxylic acid type functional groups, by immersing an ion exchange membrane precursor film having a precursor layer (C) containing a fluorinated polymer (A) having groups convertible to carboxylic acid type functional groups, in an aqueous alkaline solution comprising an alkali metal hydroxide, a water-soluble organic solvent and water, and subjecting the groups convertible to carboxylic acid type functional groups to hydrolysis treatment to convert them to carboxylic acid type functional groups, wherein the concentration of the water-soluble organic solvent is from 1 to 60 mass % in the alkaline aqueous solution (100 mass %); the proportion of structural units having carboxylic acid type functional groups in the fluorinated polymer (A) is from 14.00 to 14.50 mol %; and the resistivity in the layer (C) 12 is from 3.010.sup.3 to 25.010.sup.3 .Math.cm.

An ion exchange membrane has multiple layers of ionic polymers which each contain substantially different chemical compositions. i.e. varying side chain lengths, varying backbone chemistries or varying ionic functionality. Utilizing completely different chemistries has utility in many applications such as fuel cells where for example, one layer can help reduce fuel crossover through the membrane. Or one layer can impart substantial hydrophobicity to the electrode formulation. Or one layer can selectively diffuse a reactant while excluding others. Also, one chemistry may allow for impartation of significant mechanical properties or chemical resistance to another more ionically conductive ionomer. The ion exchange membrane may include at least two layers with substantially different chemical properties.

A composite membrane includes an ion-conductive polymer layer; and a plurality of gas blocking inorganic particles non-continuously aligned on the ion-conductive polymer layer, wherein the composite membrane has a radius of curvature of about 10 millimeters or less.

An ion exchange membrane has multiple layers of ionic polymers which each contain substantially different chemical compositions. i.e. varying side chain lengths, varying backbone chemistries or varying ionic functionality. Utilizing completely different chemistries has utility in many applications such as fuel cells where for example, one layer can help reduce fuel crossover through the membrane. Or one layer can impart substantial hydrophobicity to the electrode formulation. Or one layer can selectively diffuse a reactant while excluding others. Also, one chemistry may allow for impartation of significant mechanical properties or chemical resistance to another more ionically conductive ionomer. The ion exchange membrane may include at least two layers with substantially different chemical properties.

Improved additives can be used to prepare polymer electrolyte for membrane electrode assemblies in polymer electrolyte fuel cells. Use of these improved additives can not only improve durability and performance, but can also provide a marked performance improvement during initial conditioning of the fuel cells. The additives are chemical complexes comprising certain metal and organic ligand components.