PROCESS FOR PRODUCING POROUS MEMBRANES

摘要

The present invention provides a process for producing porous membranes which comprises the steps of dissolving a film-forming polymer in a good solvent for said polymer, forming a film of the resulting polymer solution, and forcibly contacting saturated steam or mist-containing steam with at least one surface of said film. The resulting porous membranes have pores having a narrow pore diameter distribution and extending in a direction substantially perpendicular to the membrane surface at a high surface pore density on at least one surface thereof. In another embodiment, the resulting porous membranes, although having no straight pores, are devoid of a nonporous layer.