(DE3615649-C)      An integral asymmetric membrane is produced by (A) as known a) mixing polyetherimide membrane former, a halohydrocarbon solvent and/or swelling agents, (b) spreading the mixt out sheetlike and contacting it with a precipitating agent and (B) applying an organic liq. having a swelling or solvent effect on the polyetherimide to the selective layer of the membrane by immersion, spraying or brushing and evaporating the organic liq.    The organic liq is e.g. Et Me ketone, Me formate, xylene, CHCl3 and esp contains polyetherimide or polyvinyl fluoride. The solvent for the polyetherimide is toluene or cyclohexane. The treated membrane is additionally coated with a styrene/ethene/ butene/styrene block polymer.    USE/ADVANTAGE -   In the form of tubing, sheets, hollow fibres for the sepn of gases; the selectivity of the membrane is increased compared with known ones with only a slight loss of permeability of the faster permeates. (8pp)p    (US5007944-A)      A method for producing integral, asymmetric membranes for sepg. gases in mixt. comprises (1) mixing together a polyether imide membrane forming polymer which forms membranes that are permeable to at least one gas in a mixt. of gases, a volatile solvent for polymer having a lower b.pt. than any other component in the mixt., and an organic liq. swelling agent in which polymer is not soluble and which does not react with either polymer of solvent, to form pourable liq. mixt.; (2) spreading liq. mixt. to form a thin film; (3) exposing thin film to air or an inert gas to form a surface skin by evapn.; (4) contacting thin film with pptn. agent to form an integral, asymmetric polyetherimide membrane; (5) treating membrane with an organic cluid which a solvent for polyether imide, or a swelling agent in which membrane is not soluble, and a selective polymer dissolved in organic fluid selected from gp. consisting of polyether imide and polyvinyl fluoride, and (b) removing organic fluid.    ADVANTAGE -   Improved method for sepg. gases. (7pp)