| abstract |
The invention relates to a method for producing an integrally asymmetrical hydrophobic polyolefinic membrane with a sponge-like, open-pored microporous support structure and an separating layer with a structure which is denser than the support structure, by means of a thermally induced liquid-liquid phase separation process. A solution of at least one polyolefin in a solvent system consisting of a compound A and a compound B, is extruded to obtain a shaped body. Compound A is a weak solvent and compound B is a non-solvent for the polymer. After leaving the moulding tool, the shaped body is cooled using a solid or liquid cooling medium which will not dissolve the polymer at temperatures up to the temperature of the tool and which will not chemically react with the polymer, until phase separation occurs and the polymer-rich phase hardens. |