METHOD OF POLYMERIC MULTILAYER PERVAPORATION MEMBRANE MAKING Russian patent published in 2001 - IPC

FIELD: organic chemistry, polymers. SUBSTANCE: invention describes method of making polymeric multilayer pervaporation membranes by successive preparing polymeric backing as microporous membrane of asymmetric structure followed by formation of diffusion layer on the surface of skin-layer made of polymer of other chemical structure and drying after each stage of membrane making. Backing is made by application of 10-14% solution of polyamidoimide in polar aprotonic solvent by layer (thickness is 100-500 mcm) on the surface of inert material followed by immersion in precipitator bath. Removed backing is washed out and dried and diffusion layer is formed by successive application of intermediate and covering layers. Intermediate layer is made by application of 0.02-0.1 wt.% aqueous solution of N,N,N,N-trimethylmethacry-loylhydroxyethylammonium methyl sulfate and covering layer is made by application of 0.5-2.0 wt.% solution of polyorgano-siloxane in organic solvent on the surface of intermediate layer in the presence of 0.5-5.0 wt.% of cross-linking agent as measured for polyorganosiloxane. The source of polyamidoimides is polymer with the formula of link (I) with molecular mass from 40 000 to 100 000 Da that corresponds to reduced viscosity value from 1.3 to 3.3 dl/g (for 0.5 wt.% solutions in N-methylpyrrolidone at 20 C) and where is polyamidoimide-1; (95 mole%) and (5 mole%) is copolyamidoimide-2; is polyamidoimide-3; is polyamidoimide-4; is polyamidoimide-5; is polyamidoimide-6 and is polyamidoimide-7. The source of poly-N,N,N,N- -trimethylmethacroylhydroxyethylammonium methyl sulfate is polymer with quaternization degree 98-100% and intrinsic viscosity from 5.6 to 9.0 dl/g. The source of polyorganosiloxane is copolymer with link structure of the formula (II) where m = 60-80; n = 100-200, molecular mass is 23 000-35 000 Da and γ-aminopropylethoxysiloxane is used as cross-linking agent. EFFECT: improved method of making, high efficiency and productivity of end membranes, especially in separation of polar and low-polar organic liquids. 10 tbl, 15 ex