Novel polypropylene heat-shrinkable film

摘要

The heat-shrinkable film (1) for packaging and grouping products including bottles and cans, comprises three polymer layers including two outer layers (1a, 1b) that are identical and are made of polypropylene copolymer or a mixture of polypropylene copolymer and a middle layer (2) provided between the two outer layers. The middle layer is made of mixture of radical polyethylene (40-70 mass%) and linear polyethylene (30-60 mass%). The polypropylene copolymer is obtained by polymerization under metallocene catalysis, and has a tensile modulus of 500-1200 MPa and a grade of 1.5-3.5 or 1.7-2.5. The heat-shrinkable film (1) for packaging and grouping products including bottles and cans, comprises three polymer layers including two outer layers (1a, 1b) that are identical and are made of polypropylene copolymer or a mixture of polypropylene copolymer and a middle layer (2) provided between the two outer layers. The middle layer is made of a mixture of radical polyethylene (40-70 mass%) and linear polyethylene (30-60 mass%). The polypropylene copolymer is obtained by polymerization under metallocene catalysis, and has a tensile modulus of 500-1200 MPa and a grade of 1.5-3.5 or 1.7-2.5. Each of the outer layers has a thickness of 5-13 mu m. The film: is obtained by extrusion in given direction and by coextrusion-blowing; is heat-shrinkable in an extrusion direction and a transverse direction, where a longitudinal shrinkage rate of film in the extrusion direction is 60-80% and a transverse shrinkage rate of the film in the transverse direction to the extrusion direction is 20-30%; and has a thickness of = 40mu m and a stress of greater than 20 MPa at 10% of elongation in an extrusion direction and of greater than 17 MPa in the transverse direction to the extrusion direction. The packaged products are placed in a shrinking oven at a suitable temperature so that the film shrinks around the product so as to give the cohesiveness to the products. An independent claim is included for a process for fabricating a film.