Patent ID: 8277897

Claim:
A method of producing a reactive polymer-supporting porous film for use as a battery separator comprising a porous substrate film and a reactive polymer partially crosslinked and supported on the porous substrate film, the reactive polymer being obtained by the reaction of a crosslinkable polymer having at least one reactive group selected from the group consisting of 3-oxetanyl group and epoxy group in the molecule with a polycarboxylic acid, the method comprising: supporting the crosslinkable polymer having at least one reactive group selected from the group consisting of 3-oxetanyl group and epoxy group in the molecule and a polycarboxylic acid on the porous substrate film; and reacting a part of the at least one reactive group with the polycarboxylic acid, thereby partially crosslinking the crosslinkable polymer and forming the reactive polymer on the porous substrate film, wherein the crosslinkable polymer is a radical copolymer of at least one radical polymerizable monomer selected from the group consisting of 3-oxetanyl group-containing radical polymerizable monomers and epoxy group-containing radical polymerizable monomers with another radical polymerizable monomer, wherein the 3-oxetanyl group-containing radical polymerizable monomer is 3-oxetanyl group-containing (meth)acrylate represented by the general formula (I) wherein R 1 is a hydrogen atom or a methyl and R 2 is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, wherein the epoxy group-containing radical polymerizable monomer is an epoxy group-containing (meth)acrylate represented by the general formula (II): wherein R 3 is a hydrogen atom or a methyl group and R 4 is an epoxy group-containing group represented by the formula (I): wherein said another radical polymerizable monomer is at least one selected from the group consisting of (meth)acrylates represented by the following general formula (III): wherein R 5 is a hydrogen atom or a methyl group; A is an oxyalkylene group having 2 or 3 carbon atoms; R 6 is an alkyl group having 1 to 6 carbon atoms or a fluorinated alkyl group having 1 to 6 carbon atoms; and n is an integer of 0 to 3; and vinyl esters represented by the general formula (IV): wherein R 7 is a methyl or an ethyl group and R 8 is a hydrogen atom or a methyl group.