PRODUCTION OF ALPHA-OLEFIN BLOCK COPOLYMER

PURPOSE:To obtain a block copolymer excellent in heat resistance without encountering a problem of loosing fluidity and consequent adhesion among polymer particles, by adding a hydrocarbon together with an aluminum alkoxide to a polymerization mixture and copolymerizing the polymer with an alpha-olefin in vapor phase. CONSTITUTION:Propylene is polymerized in the presence of a catalyst (e.g., a catalyst comprising TiCl3 and diethylaluminum chloride). Without deactivating this catalyst, an aluminum alkoxide of the formula (wherein R is an alkyl, an aryl or a halogen, R' is an alkyl or an aryl and n is 0, 1 or 2), e.g., ethylaluminum dethoxide, and an ethylenically unsaturated bond-free hydrocarbon (e.g., heptane) in at least an amount sufficient to establish its saturated vapor pressure are added to the polymerization mixture and then the polymer is copolymerized with an alpha-olefin in vapor phase. The latter vapor phase block copolymerization can be effected without a problem of adhesion among polymer particles and a problem of loosing fluidity, so that it is possible to obtain a block copolymer excellent in impact resistance in extremely high activity.