PURPOSE: To improve adhesiveness of wax-coated surface of polypropylene support film so that thermal stripe seal can properly adhere thereon.

CONSTITUTION: Blocking of polymer film in storage is prevented and coating adhesiveness of thermal stripe seal is improved by reducing frictional resistance of polymer film surface by coating an adhesion promoter composition consisting of a wax emulsion, which is admixed with an ionomer of neutralized olefin- unsaturated carboxylic acid and a crosslinkable formaldehyde, and a binder on a polymer film support. A preferable ionomer is an ionomer composed of comonomers of ethylene and methacrylic acid, and a preferable crosslinkable resin is a melamine-formaldehyde resin.