Polypropylene membranes with porous surface - are used for filters, microfilters, membrane supports and as oxygenation agents

摘要

Mfr. of membranes of a thermoplastic polymer contg. 10-90 vol. % pores in connection with each other comprises (A) extruding a homogeneous liq. mixt. consisting of at least 10-90 wt.% of a fusible polymer (I) and 90-10 wt.% of a pore-forming liq. (II) which is inert w.r.t. (I); (B) choosing the type and amt. of the inert liq. (II) such that (II) forms a binary system with (I) which in the liq. state has a region of complete miscibility and a region of incomplete miscibility of the components and which demixes into two phases at a temp. (the demixing temp.) below the extrusion temp.; (C) leading the extruded mass into a bath in which the bath liquor is below the demixing temp. and cooling such that the (II) and (I) demix into two co-existing liq. phases before the polymer (I) solidifies and (D) opt. washing (II) out of the solidified membrane with a solvent, such that the bath contains the same inert solvent, e.g. N,N-bis-(2-hydroxyethyl)hexadecylamine, as the extruded mixt. and the membrane, esp. formed from polypropylene and extruded in the form of flat film, tubular film or a hollow fibre, has a smooth surface with open pores occupying 10-90 % of the surface area.