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OwnerYasuhiro Tada, Takeo Takahashi +1inventors
InventorsYasuhiro Tada, Takeo Takahashi, Toshiya Mizuno
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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%)/Pm4 of at least 7×105 (m/day·μm4), wherein the ratio F (L=200 mm, v=70%)/Pm4 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 Pm4 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.
A hollow-fiber porous membrane, having a whole shape of a hollow fiber, comprising a substantially single layer of stretched porous membrane of vinylidene fluoride resin having a crystallization temperature Tc of at least 143° C., having a micro-texture of gradient-network-texture membrane including a dense layer governing a filtration performance of an outer surface thereof, a sparse layer contributing to reinforcement of the membrane on a inner surface thereof and pores having pore sizes continuously increasing from the outer surface to the inner surface, and providing:
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Dependencies are inferred from the claim text.