It is intended to provide a
reactive polymer-supported
porous film that is capable of achieving sufficient adhesion between the
electrode and the separator; reduced in
internal resistance; and excellent in
high rate characteristics, the
porous film being useful as a battery separator which, after production of the battery, is not melted or broken under a high temperature and functions as a separator having a small heat shrinkage ratio as well as to provide a process for producing batteries using the
reactive polymer-supported
porous film. According to this invention, there is provided a
reactive polymer-supported porous film for a battery separator, characterized in that the reactive
polymer-supported porous film has: a substrate porous film of a porous film, the porous film has a temperature, at which a thickness of the porous film is reduced to 1 / 2 of a thickness when a prove is placed on the porous film in the case that the thickness of the porous film is measured by placing the probe having a
diameter of 1 mm on the porous film under a load of 70 g and heating the porous film from a
room temperature at a temperature-increase rate of 2 DEG C / minute, of 200 DEG C or more; and a reactive
polymer supported on the substrate porous film, the reactive
polymer is obtainable by reacting: a crosslinkable polymer obtainable by copolymerizing: a crosslinkable
monomer having in a molecule at least one reactive group selected from a 3-oxetanyl group and an
epoxy group; and a crosslinkable
monomer having a reactive group capable of reacting with an
isocyanate group; and a polyfunctional
isocyanate to be partially crosslinked.