PURPOSE: To obtain in high activity a high-molecular weight rubbery propylene block copolymer with high rigidity, excellent in impact strength by two-step polymerization between propylene and another α-olefin using each specific catalyst.
CONSTITUTION: Firstly, in the presence of a catalyst composed of (A) a solid catalytic component essentially comprising Mg, Ti, halogen and electron donor, (B) an organoaluminum compound (pref. trialkylaluminum) and (C) a silicate compound (pref. cyclohexylmethyldimethoxysilane), propylene (and a small amount of another α-olefin) is polymerized. Second, in the 2nd step, (D) a piperidine compound (pref. 2,2,6,6-tetramethylpiperidine) is added to the above reaction system without deactivating the above catalyst to conduct a polymerization between the propylene and the rest of the other α-olefin. The component A is pref. prepared by reaction of AlCl3 with e.g. tetraethoxysilane, a Grignard compound, o-phthalic diester and e.g. TiCl4, successively.
TAMURA MASANORI
SUZUKI KAZUTAKA
YAMADA SHINICHIRO
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