POROUS WATER FILTRATION MEMBRANE OF VINYLIDENE FLUORIDE RESIN HOLLOW FIBER AND PROCESS FOR PRODUCTION THEREOF

摘要

A composition obtained by blending a vinylidene fluoride resin having improv ed crystallization characteristics such as Tm2 minus Tc of 32~C or below wherei n Tm2 is the melting point inherent in the resin having a relatively high molecular weight and Tc is the crystallization temperature inherent therein with a plasticizer for the vinylidene fluoride resin and a good solvent is melt-extruded into a hollow-fiber membrane and the membrane is introduced in to a cooling medium and thereby cooled from the outside surface and then subjected to solidification, extraction of the plasticizer, and stretching t o give a porous membrane of vinylidene fluoride resin hollow fiber wherein coexistence of oriented crystal portions and non-oriented crystal portions i s ascertained by X-ray diffraction. The obtained membrane has pores of suitabl e sizes and distribution and is excellent in mechanical strengths such as tensile strength and elongation at break, thus being useful as precision wat er filtration membrane.