| 摘要 |
PURPOSE: To obtain an opaque film excellent in air permeability by stretching a crystalline propylene homopolymer characterized by that a melt flow rate is a specific value, a ratio of a wt. average mol.wt. and a number average mol.wt. is a specific value or more and the isotactic pentad rate of a polypropylene crystal part of a boiling n-heptane insoluble component is a specific value or more. CONSTITUTION: A crystalline propylene homopolymer characterized by that a melt flow rate (MFR: 10min molten resin emitting amt. at 230 deg.C when load of 2.16 kg is applied) is 0.03-2.0g/10min, a ratio of a wt. average mol.wt.(Mw) and a number average mol.wt. (Mn) is 6 or more and the isotactic pentad rate of a polypropylene crystal part of a boiling n-heptane insoluble component is 0.96 or more is stretched to produce an opaque stretched film. When the MFR of the propylene homopolymer is 0.03/10min or less, extrusion processability at the time of the formation of a film is bad and, when the MFR is 2.0 or more, uniform stretching is hardly performed and an obtained film is easy to tear and an opaque film becomes hard to obtain. |
