PURPOSE: To obtain a porous polyethylene body having stable heat resistance, ion exchange characteristic, and hydrophilic property by supporting a crosslinked polymer having ion exchange groups consisting of a specific polymerizble monomer and divinyl benzene on the surface of pores of a porous polyethylene membrane.
CONSTITUTION: A polymerizble monomer consisting of styrene or chloromethyl styrene, divinyl benzene, and a radical initiator are dissolved in a solvent. A polyethylene porous membrane obtd. by drawing the resin after melt-casting is immersed in the soln., then the solvent is evaporated, and a crosslinked polymer is supported on the surface of pores of the porous membrane by carrying out heat polymn. in N2. When, for example, sulfonic acid groups are to be introduced, the membrane is dipped succeedingly in H2SO4, etc., and sulfonated, and washed thereafter. Thus, a heat resistant porous membrane having 5W40% unboiled xylene-insoluble fraction and 0.01W2meq/g ion exchange capacity, and ≥30% breaking elongation, as well as ≤10% contraction coefft. when heat-treated for 30min in steam at 121°C, is obtd.
OHORI YASUSHI
MITANI KAZUTAMI
