Cellulose acetate membranes modified by organosilicon polymers

The surface of reverse-osmosis, cellulose acetate membranes was modified by the products of hydrolytic polycondensation of oligo(organosiloxanes) with the formula EtO[SiMe2O](n)[(EtO)(H2NCH2CH2CH2)SiO](m)Et. The as-modified membranes were studied in the pervaporation separation of a water-isopropanol mixture, It was shown that, at a given length of a dimethylsiloxane chain between the network junctions (the Win ratio), the selective properties of composite membranes are strongly affected by the method of applying a siloxane layer, as well as its thickness. An increase in Win from 4 to 8 enhances the sorption properties of the membrane with respect to water. Membranes coated by an organosilicon polymer with n/m = 4 from a 2% aqueous dispersion were found to be optimal for separating water-isopropanol mixtures of various compositions. It was demonstrated that cellulose acetate membranes can be modified directly in the modulus of a roll filtering element.