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Abstract

A method is provided for producing a membrane from polycarbonate-polyether-blockcopolymers with about 5 to 35 weight percent of repeating alkyleneethercarbonate units and about 95 to 65 weight percent of repeating bisphenol A-carbonate units, wherein the polyethyleneoxide blocks have a molecular weight from about 1,000 to 20,000, wherein the intrinsic viscosity of the copolymer is from about 180 to 300 ml/g as measured in chloroform at 25.degree. C. and wherein the ultrafiltration rate is from about 4 to 200 ml/h.m.sup.2.mm Hg. In a first dissolving step a polycarbonate-polyether-copolymer is homogeneously mixed with a solvent at a temperature from about 80.degree. to 120.degree. C. and in a second dissolving step the temperature is brought to about 140.degree. to 180.degree. C. to produce a true solution. The filtered solution is cooled to from about 20.degree. to 50.degree. C. and is then extruded through a nozzle into a bath comprising a nonsolvent for the polymer for precipitating the polymer. The precipitated polymer is then washed and dried. The resulting membranes improve the processes of hemodialyzing and of homofiltration.

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