A polymer electrolyte membrane having an ionic bond between a sulfonate anion and a bismuth cation, an electrochemical battery and a flow battery including the same, a composition for a polymer electrolyte membrane, and a method for preparing a polymer electrolyte membrane.

To provide a liquid composition capable of forming a membrane excellent in durability against hydrogen peroxide or peroxide radicals and excellent in hydrogen gas barrier property; a polymer electrolyte membrane; a membrane electrode assembly; and a polymer electrolyte fuel cell. Liquid composition comprising a liquid medium, an acid-type sulfonic acid group-containing fluorocarbon polymer of which the hydrogen gas permeation coefficient under the conditions of a temperature of 80 C. and a relative humidity of 10% is at most 2.510.sup.9 cm.sup.3.Math.cm/(s.Math.cm.sup.2.Math.cmHg), and cerium atoms; a polymer electrolyte membrane 15 comprising the acid-type sulfonic acid group-containing fluorocarbon polymer, and cerium atoms; and a membrane electrode assembly 10 comprising an anode 13 having a catalyst layer, a cathode 14 having a catalyst layer, and the polymer electrolyte membrane 15 disposed between the anode 13 and the cathode 14.

Multi-acid polymers are produced having the formula RSO.sub.2NH(SO.sub.3.sup.H.sup.+).sub.n or RSO.sub.2NH(PO.sub.3.sup.H.sup.2+).sub.n and made from a polymer precursor in sulfonyl fluoride form or sulfonyl chloride form The R is one or more units of the polymer precursor without sulfonyl fluoride or sulfonyl chloride, n is one or more, and the multi-acid polymer has two or more proton conducting groups. A method of making the multi-acid polymers includes reacting an amino acid having multiple sulfonic acids or phosphonic acids with a polymer precursor in sulfonyl fluoride form or sulfonyl chloride form in a mild base condition to produce the multi-acid polymer having two or more proton conducting groups.

A process for producing a liquid composition, which includes holding a fluorinated polymer having SO.sub.2F groups at from 140 to 160 C. for at least 45 minutes, cooling it to less than 110 C. at a rate of at least 50 C./min, converting the SO.sub.2F groups in the fluorinated polymer to ion exchange groups to obtain a fluorinated polymer having ion exchange groups, and mixing the fluorinated polymer having ion exchange groups and a liquid medium.

A process for producing a liquid composition, which includes holding a fluorinated polymer having SO.sub.2F groups at from 110 to 130 C. for at least 45 minutes, cooling it to less than 110 C., converting the SO.sub.2F groups in the fluorinated polymer to ion exchange groups to obtain a fluorinated polymer having ion exchange groups, and mixing the fluorinated polymer having ion exchange groups and a liquid medium.

To provide a method capable of efficiently producing an ion exchange membrane for alkali chloride electrolysis 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, wherein 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 the layer (C) 12, the value of resistivity is from 4.010.sup.3 to 25.010.sup.3 .Math.cm, and the variation in resistivity is at most 4.010.sup.3 .Math.cm, and the concentration of the water-soluble organic solvent is from 1 to 60 mass % in the alkaline aqueous solution.

Provided are a membrane electrode assembly for polymer electrolyte membrane water electrolysis and a water electrolyzer which can achieve a low electrolysis voltage with low hydrogen crossover. The membrane electrode assembly for polymer electrolyte membrane water electrolysis of the present invention comprises a polymer electrolyte membrane, an anode having a catalyst layer provided on one side of the polymer electrolyte membrane, a cathode having a catalyst layer provided on the other side of the polymer electrolyte membrane, and the polymer electrolyte membrane comprises a fluorinated polymer having ion exchange groups and an ion exchange capacity of from 1.25 to 2.00 meg/g dry resin and a platinum-containing substance.

To provide a method for producing a fluorinated polymer, in which it is possible to efficiently and easily control the molecular weight to be proper when polymerizing a perfluoromonomer having a dioxolane ring containing a polymerizable double bond in the ring skeleton, and in which the obtainable fluorinated polymer is less susceptible to a decrease in molecular weight even when contacted with a base. A method for producing a fluorinated polymer, comprising polymerizing a raw-material mixture which contains at least one of a monomer composition M11 which comprises a perfluoromonomer represented by the formula m11 and a fluorinated monomer m11H having at least some of fluorine atoms of said perfluoromonomer substituted by hydrogen atoms, and a monomer composition M12 which comprises a perfluoromonomer represented by formula m12 and a fluorinated monomer m12H having at least some of fluorine atoms of said perfluoromonomer substituted by hydrogen atoms, wherein the total amount of the fluorinated monomer mil H and the fluorinated monomer m12H is from 10 to 1,100 ppm to the total amount of the monomer composition M11 and the monomer composition M12. ##STR00001##

An ion permeable membrane includes ion conductor particles and a fiber base material, in which each of the ion conductor particles has a first portion embedded inside the fiber base material, and a second portion exposed on outside surfaces of the fiber base material, and the second portions are continuous between an upper surface and a lower surface in a thickness direction of the ion permeable membrane.

The present invention pertains to a membrane for an electrochemical device, to a process for manufacturing said membrane and to use of said membrane in a process for manufacturing an electrochemical device.