Patent ID: 7973089

Claim:
A process for preparing a membrane by extrusion of a thermoplastic polymer bearing alkaline ionic groups, comprising (a) preparing a mixture composed of a polymer having alkaline ionic groups corresponding to the formula -A p− (M + ) p in which A represents the anionic part of the ionic group, p represents the valency of the anionic part and M represents an alkali metal 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, and is (are) selected from the group consisting of: i) oligoethers which optionally have terminal CH 3 , OH or NH 2 groups; ii) carboxylic amides corresponding to the formula HCONR 6 R 7 in which R 6 and R 7 represent alkyl groups having from 1 to 4 carbon atoms or hydrogen atoms; iii) sulfonic amides which bear alkyl groups or hydrogen atoms on the nitrogen atom; iv) plasticizers having protic functional groups selected from the group consisting of alcohol, thiol, phenol, primary amine and secondary amine; v) alkanols having at least 2 carbon atoms, polyols derived from alkanes by replacing at least two hydrogen atoms with an OH group, and compounds having ether groups; vi) monoamine, diamine or triamine oligomers and in which the nitrogen atom bears from 1 to 3 oligo(oxyethylene) groups; vii) the sulfamide H 2 N—SO 2 —NH 2 , the sulfonamides R 8 —SO 2 NH 2 in which R 8 is an alkyl group which has from 1 to 5 carbon atoms, or an aryl group comprising one or more fused or unfused aromatic rings; and viii) primary or secondary amides.