FIELD: medical engineering. SUBSTANCE: hydrophobic polymer mixture solution with water-soluble acrylonitrile and sodium metallylsulfonate copolymer in N-methyl-2-pyrrolidone containing non-solving hydrophobic polymer of the solvent is extruded through a draw plate and coagulated in partial or full contact with water or aqueous-organic coagulating bath. The so produced membrane is washed and dried. The component contents is selected to obtain thermodynamically instable homogeneous solution showing no stratification in visual inspection notwithstanding its turbidity and spontaneously changing its state for gel structure upon lowering temperature. Size fluctuations, when compared to a predefined norm, is not to exceed 3% when the membrane changes its dry state for moistened one at 40 C. The membrane has a bearing layer and a separating one having mesoporic compact structure. The latter one has more than 30% by mass of acrylonitrile copolymer which mean concentration in the membrane does not exceed 40% and yet the copolymer concentration in the separating layer is higher than its mean concentration in the whole membrane. EFFECT: enhanced effectiveness in separating blood or plasma to be injected into a human or animal organism. 13 cl, 4 dwg, 6 tbl
