Patent ID: 9095824
Filing Date: 2015-08-04
Classification: B01D,B29C,C02F,D01D,D01F

Abstract:
1. A porous membrane of vinylidene fluoride resin, having two major surfaces sandwiching a certain thickness, including a dense layer which governs filtration performance on one major surface side and a sparse layer which contributes to reinforcement on an other opposite major surface side, and having an asymmetrical gradient network texture including pore sizes which increase continuously from the one major surface to the other opposite major surface, wherein the dense layer includes a 7 μm-thick portion contiguous to the one major surface showing a porosity A 1 of at least 50%, the one major surface shows a pore size of at most 0.30 μm, and the vinylidene fluoride resin shows a difference Tm 2 −Tc of at most 32° C. between an inherent melting point Tm 2 (° C.) of the resin and a crystallization temperature Tc (° C.) according to DSC measurement.