| abstract |
A hollow-fiber porous membrane, comprising a hollow fiber-form porous membrane of vinylidene fluoride resin providing: a ratio F (L=200 mm, v=70%)/Pm 4 of at least 7×10 5 (m/day·μm 4 ), wherein the ratio F (L=200 mm, v=70%)/Pm 4 denotes a ratio between F (L=200 mm, v=70%) which is a value normalized to a porosity v=70% of a water permeation rate F (100 kPa, L=200 mm) measured at a test length L=200 mm under the conditions of a pressure difference of 100 kPa and a water temperature of 25° C. and a 4-th order value Pm 4 of an average pore size Pm. The hollow-fiber porous membrane has an average pore size smaller than before leading to an improved ability of removing fine particles, while suppressing the lowering in water permeability. The hollow-fiber porous membrane is produced by melt-extrusion and low-temperature cooling of a starting composition including a resin material containing an ultra-high molecular weight resin component in a larger amount than before, and increased amounts of plasticizer and good solvent. |