Cation exchange membranes having carboxylic acid groups

In preparing cation exchange membranes having carboxylic acid groups, acrylic acid, methacrylic acid and their esters, etc., are copolymerized with divinylbenzene and, optionally, other vinyl monomers. The copolymer membranes are then immersed in hydroxide solution, or the ester groups of the membranes are hydrolyzed. 

One of the technically and commercially most important cation-exchange membranes developed in recent years is based on perfluorocarbon polymers. Membranes of this type have extreme chemical and thermal stability and they are the key component in the chlorine-alkaline electrolysis as well as in most of today s fuel cells. They are prepared by copolymerization of tetrafluoroethylene with perfluorovinylether having a carboxylic or sulfonic acid group at the end of a side chain. There are several variations of a general basic structure commercially available today [11]. The various preparation techniques are described in detail in the patent literature. 

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