Semipermeable asymmetric membrane for reverse osmosis - contg. hydrophilic gelling or thixotropic agent added to membrane casting soln.

摘要

Membranes are prepd. from a brushable casting soln. contg. water-swellable polymer, solvent and swelling agents, with the addn. to casting soln., of a hydrophilic gelling- or thixotropic agent. Additive is a commercially available thickener and dispersant auxiliary of clay mineral origin, as used for aq. systems, e.g. in disperse dye industry. Membranes are used for water desalination by reverse osmosis. Additive (i) increases prim. water content of membrane matrix; (ii) homogenises and improves brushability of casting solns. Inan example, casting soln. contg. 25% cellulose acetate, 45% acetone and 30% formamide, was modified to contain 25 parts cellulose acetate, 53 parts acetone, 30 parts formamide, 0.1 parts "Bentone WS" (RTM). Water content of resulting membrane was increased, e.g. from 67.1 to 69% before heating.