| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a vinylidene fluoride-based resin porous membrane having a good water penetration-sustaining performance and a large water penetration quantity, and to provide a method for producing the same. <P>SOLUTION: The vinylidene fluoride-based resin porous membrane which has a dense layer having small pore diameters on one side and has an asymmetric net-like inclined structure whose pore diameters are continuously expanded from one side to the opposite side is characterized by satisfying the following conditions (a) to (c): (a) the porosity of a 5 μm-thick portion continued from the surface of the thick layer is ≥60%; (b) the surface pore diameters of one side are ≤0.30 μm; (c) Q/P1<SP>4</SP>is ≥5×10<SP>4</SP>(m/day×μm<SP>4</SP>), wherein Q (m/day) is a value converted from a water penetration quantity into the whole layer porosity A2=80% in conditions of a pressure difference 100 kPa and a water temperature 25°C in a sample length L=200 mm, and P1<SP>4</SP>(μm<SP>4</SP>) is the fourth power value of the surface pore diameter P1 of one side. The method for producing the vinylidene fluoride-based resin porous membrane comprises melt-knead-extruding a vinylidene fluoride-based resin and a plasticizer having compatibility with the vinylidene fluoride-based resin, preferentially cooling the extruded film from one side, and then extracting the plasticizer. <P>COPYRIGHT: (C)2011,JPO&INPIT |
