| 摘要 |
A porous membrane of vinylidene fluoride resin, having two major surfaces, including a dense layer which governs filtration performance on one major surface side and a sparse layer which contributes to reinforcement on the 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 A1 of at least 50%, and the one major surface shows a pore size of at most 0.30 μm. The vinylidene-fluoride-resin porous membrane is useful as a porous membrane for separation and particularly exhibits good water-permeation-rate retentivity even in continuous filtration of cloudy water. |
