| 摘要 |
1284184 Ion exchange membranes; vinyl alcohol copolymers RHONE-POULENC SA 16 Oct 1970 [17 Oct 1969] 49330/70 Heading C3P [Also in Division C2] Ion exchange membranes comprise a crosslinked polymeric material consisting essentially of recurring units of the formula and and optionally in which R is H or lower alkyl, R<SP>1</SP> is H or an acyl group, and Z is a radical containing an ion exchange group, the oxygen atoms of units (i) being attached to polyvalent organic crosslinking groups, for example, of formula and/or where n is greater than or equal to 2. Ion exchange groups specified are carboxylic acid, phosphonic acid and sulphonic acid groups or salts thereof and quaternary ammonium groups such as: or in which R 1 , R 2 and R 3 may be the same or different lower alkyl group and A# is an organic or inorganic anion. Units (1) are vinyl alcohol units which may be derived by saponification of a vinyl ester copolymer. Units (ii) are polymerized units of, for example, 2-vinyl pyridine, 4-vinyl pyridine, a 3-vinyl picoline, a 3-vinyl lutidine or a para-dialkylaminostyrene, and vinyl sulphonic acids such as sodium vinyl sulphonate. Agents which may be used to crosslink the vinyl alcohol copolymers via their hydroxyl groups are polycarboxylic acids, or chlorides or anhydrides thereof, polyisocyanates and α-chlorinated polyethers. The membranes may be prepared by polymerizing the monomers, e.g. vinyl acetate and the "ion exchange" comonomer, saponifying to produce the vinyl alcohol copolymer, casting a solution of the resulting non-cross-linked polymer and a crosslinking agent on to a surface such as glass, heating to cross-link the polymer and simultaneously or subsequently evaporating the solvent and removing the resulting film from the surface. The membranes preferably have a theoretical exchange capacity of between 1 and 2À5 milliequivs. per gram. |
