Patent ID: 7956095

Claim:
A process for preparing a membrane by extrusion of a thermoplastic polymer bearing acid ionic groups corresponding to the formula -A p− (H + ) p , in which A represents the anionic part of the ionic group and p represents the valency of the anionic group, comprising (a) preparing a mixture composed of a polymer having the acid ionic groups corresponding to the formula -A p− (H + ) p and of at least one plasticizer, (b) extruding the mixture obtained to form a film, and (c) washing the film obtained in aqueous medium to remove said plasticizer(s), wherein the plasticizer(s) is (are) chosen from non-volatile compounds which are stable with respect to the ionic groups of the polymer, which are soluble in water or in solvents that are miscible with water, said plasticizers being chosen from: compounds that react with the ionic group of the polymer via formation of a weak hydrogen bond, selected from the group consisting of sulfamide H 2 N—SO 2 —NH 2 , tetraalkylsulfamides, alkylsulfonamides, and arylsulfonamides R 3 —SO 2 —NH 2 in which R 3 is a phenyl group, a tolyl group or a naphthyl group; and compounds that react with the ionic group of the polymer by formation of a strong ionic bond, selected from the group consisting of : imidazole, N-alkylimidazole, N-vinylimidazole; ethylene oxide oligomers bearing a terminal primary amine group or a terminal secondary amine group; secondary amines; and tertiary amines bearing three ethylene oxide oligomer substituents.