POLYOLEFIN MEMBRANE WITH AN INTEGRALLY ASYMMETRIC STRUCTURE AND METHOD FOR THE PRODUCTION THEREOF

摘要

The invention relates to a method for the production of an integrally asymmetric hydrophobic polyolefinic membrane with a spongy, open-pored microporous support structure and a separating layer having a thicker structure by means of a thermally induced liquid-liquid-phase separation process. A solution of at least one polyolefin is extruded to form a shaped body. The solvent used is such that the separation temperature of a 25 wt. % solution of the polyolefin in said solvent is between 10 - 70 ~C above the setting temperature. After de-moulding, the shaped body is cooled by a liquid cooling medium which does not dissolve the polymer at temperatures up to the tool temperature, up to the phase separation and setting of the polymer rich phase. The thus produced integrally asymmetric membrane has a porosity which is greater than 30 vol. % - 75 vol. %, a spongy, open-pored microporous support structure devoid of macrovoids and has isotropic pores in the centre thereof and at least one separating layer having a maximum number of pores < 100 arranged on at least one surface thereof. The membrane is preferably used for gas separation or gas transfer processes and especially for blood oxygenation.