PURPOSE: To obtain in high activity a rubbery propylene block copolymer high in molecular weight, with high rigidity and impact strength by two-step polymerization between propylene and an α-olefin using a specific carrying-type titanium catalytic system.
CONSTITUTION: Using a catalytic system composed of (A) a solid catalytic component essentially comprising Mg, Ti, halogen and electron donor, (B) an organoaluminum compound (pref. trialkylaluminum) and (C) a piperidine compound (pref. 2,2,6,6-tetramethylpiperidine), propylene (and a small amount of another α-olefin) is polymerized and further polymerization is then made between propylene and the rest of the other α-olefin, thus obtaining the objective copolymer 2 600000 in the weight-average molecular weight of the 20°C oylene solubles. The component A can pref. be prepared by the following process: aluminum trichloride is made to react with e.g. tetraethoxysilane followed by reaction with a Grignard reagent, and the resulting white solid is made to react with e.g. TiCl4 and an electrodonating o-phthalic diester.
TAMURA MASANORI
SUZUKI KAZUTAKA
YAMADA SHINICHIRO
