SEMIPERMEABLE COMPOSITE MEMBRANES COMPRISING MODIFIED POLYVINYL ALCOHOL, PROCESS FOR THEIR PREPARATION AND THEIR USE

摘要

Semipermeable composite membranes containing on one surface of a porous support a superficial thin film having semipermeable properties. The film contains polyvinyl alcohol (PVA)/polyvinyl alcohol-copolymers (PVA-copolymers) modified by at least radicals containing ionizable groups are provided. The modification steps comprise e.g. reacting PVA/PVA-copolymer films with (a) a monomeric organic compound containing at least two functional groups, (b) a linear or branched polyfunctional oligomer or polymer, and (c) a compound containing cross-linking and ionizable groups. The novel membranes show good mechanical, temperature and pH-stabilities and are suitable, for example, for separating monovalent ions of low ionic weight from polyvalent ions of low or high ionic weight or for separating ionic compounds from non-ionic compounds or from ionic compounds which have a different molecular weight or opposite charge. They can be used for example for separating salts from organic compounds (dyes) or in waste-water treatment.