Porous hollow-yarn membrane of vinylidene fluoride resin

Abstract

A hollow-fiber porous membrane comprising a hollow fiber-form porous membrane of vinylidene fluoride resin and having an average pore size Pm of 0.05-0.20 μm, a maximum pore size Pmax giving a ratio Pmax/Pm of at most 2.0 between the maximum pore size Pmax and the average pore size Pm and a standard deviation of pore size distribution of at most 0.20 μm based on a pore size distribution according to the half dry/bubble point method (ASTM•F316 and ASTM•E1294) is provided, as a hollow-fiber porous membrane of vinylidene fluoride resin having minute pores with a size (average pore diameter) and a further uniform pore size distribution suitable for water (filtration) treatment. The hollow-fiber porous membrane is produced through a process of producing a hollow-fiber porous membrane by melt-extruding a mixture of a vinylidene fluoride resin, a plasticizer and a good solvent for vinylidene fluoride resin into a hollow fiber-form, followed by cooling and extraction of the plasticizer, wherein the proportion of the good solvent in the total amount of the plasticizer and the good solvent contained in the mixture is increased to 20-35 wt. %.

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