| 摘要 |
A copolymer composition comprises isotactic polypropylene and contains polymer units of a second a -olefin, the homopolymer of which melts above 180 DEG C., the composition containing at least 70% of propylene monomer units by weight of the polymer. Polymerization is effected sequentially in the presence of a stereospecific catalyst and a hydrocarbon diluent, e.g. heptane. Either the second a -olefin is polymerized initially followed by the polymerization of propylene, or propylene is polymerized initially followed by the polymerization of the second a -olefin and thereafter propylene is further polymerized. In one example, the further polymerization of propylene is followed by the polymerization of ethylene. Second a -olefins exemplified are 3-methyl butene-1, 3-methyl pentene-1, and 4,41-dimethyl pentene-1. Catalysts exemplified are mixtures of titanium trichloride with ethyl aluminium dichloride or diethyl aluminium chloride. After polymerization of the second a -olefin the resultant dispersion catalyst and polymer may be washed free of hydrocarbon-soluble materials, stored, and subsequently used with added organo-metallic activator to polymerize propylene. Polymerization may be effected in the presence of hydrogen. |
