Hydrophilic polymeric membranes, process for their preparation, their use as ultrafiltration membranes, and precursor membranes adapted to be converted thereto

摘要

The invention provides a hydrophilic microporous polymeric membrane comprising an intimate blend of a vinylidene fluoride polymer and from 20 to 75% by weight, based on total polymer, of a vinyl alcohol polymer. This membrane may be prepared by casting a thin film of a casting solution comprising a solution of a vinylidene fluoride polymer and from 35 to 85 weight percent, based on total polymer, of a vinyl acetate polymer in a solvent on a support base, partially evaporating the solvent from the cast film, contacting the partially evaporated cast film with a leaching liquid to render the film microporous, and hydrolyzing the vinyl acetate polymer in the leached membrane to convert the acetate groups to hydroxyl groups and provide a membrane having good mechanical strength and hydrophilic properties.;The membrane is useful as an ultrafiltration membrane, particularly in the treatment of oil-in-water emulsions or whey.;By first forming a film of the vinylidene fluoride polymer and the vinyl acetate polymer, the difficulty previously associated with incorporating a hydrophilic polymer, such as a vinyl alcohol polymer, in a hydrophobic polymer, such as a vinylidene fluoride polymer is obviated.