| 摘要 |
PROBLEM TO BE SOLVED: To provide a filter membrane capable of effectively removing small particles from a liquid, exhibiting minimum adsorbing property and being subjected to the test to examine its completeness prior to practical use and to provide a method of producing the same. SOLUTION: The filter membrane is an isotropic, skinless porous polyvinylidene fluoride membrane which exhibits KUF of at least about 15 psi (103 kPa) when the membrane is subjected to the test using a liquid couple having an interfacial tension of about 4 dyne/cm (4 mN/m). The filter membrane is obtained by preparing a casting solution containing a polyvinylidene fluoride and a solvent for the polyvinylidene fluoride, then heating the casting solution to a uniform temperature of about 57 to 60 deg.C, expanding the casting solution on a supporter to form a film, rapidly cooling the film in a rapid cooling bath to form a porous membrane, cleaning and drying the porous membrane.
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