Porous membrane separator for secondary battery, method for producing the same, and secondary battery

A method for producing a porous membrane separator for a secondary battery, the method comprising the steps of:

• applying a porous membrane slurry onto at least one surface of a separator substrate, the porous membrane slurry containing non-conductive particles and a water-soluble maleimide-maleic acid copolymer including a structural unit (a) represented by the following formula (I) and structural unit (b) represented by the following formula (II), followed by drying to form a porous membrane;
• wherein the maleimide-maleic acid copolymer includes the structural unit (b) at 30 mol % or more and 75 mol % or less, and
• applying an adhesive layer slurry onto the porous membrane, the adhesive layer slurry containing a particulate polymer having a glass transition temperature of 30° C. or higher and 100° C. or lower, followed by drying to form an adhesive layer,
• (in the formula (I), R1 represents at least one selected from the group consisting of a hydrogen atom, C1 to C6 alkyl groups, C3 to C12 cycloalkyl groups, a phenyl group, a phenyl group substituted by a C1 to C6 alkyl group, a phenyl group substituted by a C1 to C6 alkyloxy group, a phenyl group substituted by a halogen atom, and a hydroxyphenyl group),
• X (II)
• (in the formula (II), X represents a maleic acid unit, X may be partially neutralized by an ion other than a hydrogen ion, or may be partially dehydrated, or may be partially esterified), wherein
• the particulate polymer is a polymer including aromatic vinyl monomer units, and the ratio of the aromatic vinyl monomer units with respect to the total units of the particulate polymer is 70% by weight or more, and 95% by weight or less.