VINYLIDENE FLUORIDE RESIN POROUS MEMBRANE, MANUFACTURING METHOD THEREFOR, AND METHOD FOR MANUFACTURING FILTRATE WATER

摘要

Provided is a vinylidene fluoride porous membrane characterized in that in a continuous area of thickness 10 µm from one surface, as measured by a focused ion beam/scanning electron microscope, the mean diameter of netlike resin fibers is at most 100 nm and the porosity (A1) is at least 60%; also, the surface pore diameter (P1) at the aforementioned surface is at most 0.3 µm. In addition to having a small surface pore diameter suitable for water filtration, the provided porous membrane comprises extremely thin netlike resin fibers and has a treated-water-side surface layer with extremely high porosity, thereby excelling at preventing particulate penetration and also being extremely reusable and resistant to contamination. The provided porous membrane is manufactured through a method wherein a melt-extruded membrane is obtained by adding a comparatively large amount of a polyester plasticizer which is compatible with a high-molecular-weight vinylidene fluoride resin and which, when kneaded together with the vinylidene fluoride resin, causes the crystallization temperature to be nearly equal to that of the vinylidene fluoride resin alone. After the melt-extruded membrane is preferentially cooled from one side and solidified, the plasticizer is extracted, the surface is partially wetted, and the membrane is stretched.