JPH05287083

PURPOSE:To improve the heat sealability and heat resistance of a plastic film or tube. CONSTITUTION:A film laminate of a film layer 1 consisting of a plastic alone with a film layer 2 consisting of a plastic contg. a radiation energy absorbent is prepd. by simultaneous extrusion. The laminate is irradiated with a radiation, e. g. an electron beam, at such a dose that the gel fraction of the film layer 1 is 70% or higher and that of the film layer 2 is 30% or lower. Thus, the film layer 1 turns into a highly crosslinked layer 3, and the film layer 2 into a lowly crosslinked layer 4 due to the effect of the absorbent contained. The highly crosslinked layer improves the heat resistance, and the lowly crosslinked one is heat-sealable.