JPS6414019A - Heat-shrinkable polypropylene film - Google Patents

Abstract

PURPOSE:To obtain a film, superior in low-temperature shrinkage properties, does not generate shrink-back phenomenon at the time of cooling after shrink packaging and has a favorable fine appearance, by combining specific polypropylene resin composition and specific processing conditions. CONSTITUTION:The title film is of a stretched film comprised of by stretching unstretched film to be obtained by melting and extruding a compound of 98-50wt.% propylene copolymer and 2-50wt.% petroleum resin 1.5-7 times in a monoaxial direction at a stretching temperature of 70-110 deg.C and deformation rate of 500%/sec. or more. Then the stretched film is of a thermoshrinkable polypropylene film whose heat-shrinkable factors are respectively 20% or more in a stretching direction and 5% or less and S2/S1>=0.3, S2>=50g/mm<2> in a right angle direction (S1, S2 are residual shrinking stress respectively at 80 deg.C and 25 deg.C after they have been shrinked by 20% freely in the stretching direction at 80 deg.C.). A propylene-ethylene random copolymer or a propylene-ethylene-alpha olefin terpolymer is used as the propylene copolymer. A material having content of a 2-10wt.% ethylene ingredient is used for the former and that having content of a 0-5wt.% ethylene ingredient, 2-30wt.% alpha-olefin ingredient and 98-65wt.% propylene ingredient is used for the latter.