| abstract |
(57) [Summary] [Purpose] To obtain a polypropylene block copolymer for a film which does not cause fish eyes and the like, has a good appearance, and has excellent impact resistance and blocking resistance at low temperatures. [Structure] Using a Ziegler-Natta type catalyst, in the first step, 60-80% by weight of the total polymerization amount of a polymer portion (component A) mainly composed of propylene is produced in the substantially absence of an inert solvent. Then, in the second step, a block copolymer obtained by polymerizing 20 to 40% by weight of the total amount of the ethylene-propylene copolymerized portion (component B) having an ethylene content of 20 to 50% by weight in the gas phase. And the intrinsic viscosity ([η] B) of the B component is 2.0 dl / g or more, the ratio of the intrinsic viscosity ([η] B) of the B component and the intrinsic viscosity ([η] A) of the A component. A polypropylene block copolymer obtained by melt-kneading a block copolymer having a ([η] B / [η] A) of 1.8 or less, and a film thereof. |