| abstract |
The invention relates to a method for producing integrally asymmetrical hydrophobic polyolefinic membranes with a separating layer, especially for the exchange of gases, 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 strong solvent and compound B is a weak non-solvent for the polymer. After leaving the nozzle, the shaped body is cooled using a solid or liquid cooling medium which will not dissolve the polymer and which will not chemically react with the polymer, until phase separation occurs and the polymer-rich phase hardens. The resulting integrally asymmetrical membrane has a porosity of more than 30 vol. % to 75 vol. %, a sponge-like, open-pored microporous support structure without macrovoids and with pores which are isotropic in the middle, a separating layer on at least one of its surfaces with pores <100 nm at most and a gas separation factor of alpha (CO2/N2) of at least 1. The membrane is preferably used for blood oxygenation. |