Patent ID: 7820281
Filing Date: 2010-10-26
Classification: B01D,B29C,B29D,B29K,B29L,Y10T

Abstract:
1. A porous film having a number of continuous micropores, wherein the film has a thickness of 5 to 200 μm, has an average surface pore size A of 0.01 to 10 μm and an average surface porosity C and has an average inside pore size B and an average inside porosity D, wherein the ratio A/B of A to B is in the range of 0.3 to 3, wherein a maximum surface pore size is 15 μm or less; the ratio A wherein a polymer component forming the film comprises at least one selected from a group of amide-imide polymers, imide polymers, polyethersulfones, polysulfones, acrylic polymers or cellulose acetate, wherein a Gurley permeability of the porous film is from 0.2 to 29 seconds per 100 cc, and wherein the porous film is produced in a method comprising the steps of casting a polymer solution comprising a polymer onto a substrate to form a film; and subjecting the film to phase conversion to thereby form the porous film, wherein the polymer constituting the porous film has a surface tension Sa [mN/m], wherein the substrate has a surface tension Sb [mN/m], and wherein Sa and Sb satisfy the following condition: Sa−Sb≧−10.