HOLLOW-FIBER POROUS WATER FILTRATION MEMBRANE OF VINYLIDENE FLUORIDE RESIN AND PROCESS FOR PRODUCING THE SAME

摘要

A hollow fiber-form porous membrane of vinylidene fluoride resin having a high crystallinity as represented by a crystal melting enthalpy of at least 58 J/g is produced by forming a composition of a vinylidene fluoride resin having a relatively high weight-average molecular weight of at least 3 × 10⁵ blended with a plasticizer and a good solvent for vinylidene fluoride resin, melt-extruding the composition into a hollow fiber-form film, and solidifying the film by cooling it from an outside thereof by contact with a cooling liquid inert to vinylidene fluoride resin while crystallizing the vinylidene fluoride resin at an appropriately moderate speed. The resultant hollow fiber-form porous membrane is excellent in mechanical strength represented by tensile strength and elongation at break, and also excellent in chemical resistance, thus being effectively used as a water micro-filtration membrane.