Patent ID: 8076379

Claim:
A proton-conducting polymer membrane which is based on sulfonated polymers based on polymers comprising recurring benzimidazole units and is made by a process comprising 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 a polyphosphoric acid/sulfonating agent mixture to form a solution and/or dispersion, the sulfonating agent is selected from the group consisting of i) concentrated sulfuric acid (>95%), ii) chlorosulfonic acid, iii) a complex of SO 3 with a Lewis base or other organic constituents, iv) an acyl or alkyl sulfate, and v) mixtures of i to iv, B) application of a layer using the mixture from step A) to a support or an electrode, C) heating of the sheet-like structure/layer made according to step B) under inert gas at temperatures of up to 350° C. to form the sulfonated polyazole polymer, D) treatment of the membrane formed in step C) in the presence of moisture at temperatures and for a time until the membrane is self-supporting and can be detached from the support without damage.