PURPOSE: To impart permanent hydrophilicity by using a hydrophilic copolymer X consisting essentially of a long-chain alkyl mono(meth)acrylate unit A shown by a specified formula and a specified hydrophilic monomer unit B and a polyolefin Y.
CONSTITUTION: A hydrophilic copolymer X consisting essentially of a long-chain alkyl mono(meth)acrylate unit A shown by formula I (R1 is hydrogen or methyl, and R2 is a ≥8C alkyl) and at least one kind of hydrophilic monomer unit B selected from hydroxyethyl (meth)acrylate, (meth)acryloyl-2,3-dihydroxypropyl, (meth)acryloyloxyethylsuccinic acid, (meth)acryloyloxyethylphthalic acid and N-vinylpyrrolidone and a polyolefin Y are mixed, and the mixture is melted and shaped. The shaped material is heat-treated in vacuum or in an inert gas medium below the m.p. of the polyolefin Y and then stretched to produce a porous membrane.
MATSUMOTO SHIRUYOSHI
TAKAHASHI HIROSHI
TAKEHATA KOJI
HAYASHIDA KAZUAKI
