Patent ID: 6110369
Filing Date: 2000-08-29
Classification: B01D,B32B,C12H,G01N

Abstract:
A method for preparing a polymer membrane having a first and second surface and having a relatively large pore size in the first surface, a substantially asymmetric structure, and an enhanced flow rate, comprising:preparing a homogeneous casting solution comprising a polymer, a solvent for the polymer, and a non-solvent for the polymer at a selected casting temperature;casting the dispersion into a thin layer at the casting temperature;contacting the cast layer with a pore forming atmosphere for a period of time sufficient to form surface pores greater than 1.2 microns; andquenching the cast layer with a non-solvent quench liquid in which the solvent is miscible and in which the polymer is substantially insoluble to precipitate the polymer as an integral membrane;recovering the membrane from the quench liquid, wherein the membrane has a region of substantial asymmetry through at least fifty percent of the membrane, and wherein the membrane further has a substantially isotropic region extending from the first surface to the region of substantial asymmetry.