PVA membrane and method for preparing the same

Abstract

A polyvinyl alcohol semi-permeable membrane is prepared which has micropores with an average diameter of 0.02 to 2 microns as defined by the interpore partition walls having thicknesses in the range of 50 to 5000 A and which is characterized by substantial cross-sectional uniformity. The membrane is prepared by extruding a PVA composition containing PAG with a molecular weight of 400 to 4,000 and a carbon-to-oxygen ratio of not more than 3 in a proportion of 2 to 200 parts by weight per 100 parts of PVA into a coagulation bath. In another embodiment of the invention, the membrane is formed from a PVA composition wherein the PAG has a molecular weight of 600 to 3,000 and a C/O ratio of not more than 3, the proportion of the PAG being 15 to 150 parts by weight per 100 parts of PVA and wherein the composition satisfies the relation: 0.65 .ltoreq. CBR (critical blending ratio) .ltoreq. 1.0. The membrane is useful in ultrafiltration, dialytic and osmotic separation applications.

Dependencies are inferred from the claim text.