| 摘要 |
PROBLEM TO BE SOLVED: To develop a polypropylene based biaxially stretched film having improved transparency, heat shrinkage property, linear tear resistance in a flow direction of film, and unsealing property. SOLUTION: There is provided a propylene based block copolymer comprising 1-70wt.% of propylene based random copolymer component containing 90 mole % or more of propylene component or monomer unit based on propylene, 10-40 mole % of monomer unit based on ethylene, and 30-99wt.% of propylene-ethylene random copolymer component containing 90-60 mole % of monomer unit based on propylene, and ultrasonic wave transmission time in a flow direction of film/ultrasonic wave transmission time in a direction normal to a flow direction of film is 0.85-1.3. |
