Proton-conducting membrane and its use

A process for manufacturing a polymer film which comprises the steps

• A) mixing of one or more aromatic tetramino compounds with one or more aromatic carboxylic acids or esters thereof which contain at least two acid groups per carboxylic acid monomer, or mixing of one or more aromatic and/or heteroaromatic diaminocarboxylic acids, in phosphoric acid to form a solution and/or dispersion wherein said phosphoric acid does not contain any polyphosphoric acid,
• B) heating of the solution and/or dispersion obtained in step A) to temperatures of up to 350° C. to form a polyazole polymer,
• C) applying a layer using the mixture from step B) to a support,
• D) treating the membrane formed in step C) until it is self-supporting,
• E) detaching of the membrane formed in step C) from the support,
• F) removing the phosphoric acid present and drying wherein the heating in step B) is done in such a manner that the phosphoric acid being present is not converted into polyphosphoric acid.