| 摘要 |
PROBLEM TO BE SOLVED: To provide a crystalline polymer microporous membrane which can effectively catch fine particles and reduce a number of exchanging a cartridge due to a long filtration life, to provide its production method, and to provide a filter for filtration using it. SOLUTION: The production method of the crystalline polymer microporous membrane has an asymmetric swelling step which makes one surface of a film consisting of a crystalline polymer contact with a swelling solvent to form a semi-swelling film having a crystallinity index gradient formed in the depth direction of the film, and a drawing step for drawing the semi-swelling film. The crystalline polymer microporous membrane has a mean pore diameter of the one surface which is larger than the mean pore diameter of the other surface and continuously changes from the one surface toward the other surface, wherein an amount of the swelling solvent remaining in the crystalline polymer microporous membrane is 1 ppb-10,000 ppb. COPYRIGHT: (C)2009,JPO&INPIT
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