PROBLEM TO BE SOLVED: To provide a microporous poly(vinylidene difluoride) membrane having high asymmetricity and a high flow rate.;SOLUTION: The poly(vinylidene difluoride) membrane is internally hydrophilic, and has a first surface including a minimum pore, a second surface including a maximum pore and a thickness part between the surfaces, wherein the minimum pore has a first average diameter, the maximum pore has a second average diameter and the thickness part includes filamentous webs of a polymer material containing poly(vinylidene difluoride), the polymer material has an integrally arranged hydrophilic polymer sufficient for making the membrane essentially wetted with water, and the hydrophilic polymer contains a polyvinylpyrrolidone including a kind having a Dalton average molecular weight of 150,000-360,000.;COPYRIGHT: (C)2009,JPO&INPIT
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