process and catalysts for the preparation of compositions of alpha olefin polymers or copolymers having a high index of isotatticita

摘要

A process for making crystalline polymers or copolymers of alpha-olefins containing 3 to 8 carbon atoms, such as polypropylene, by polymerization with a catalyst consisting of a combination of titanium chloride and an organic aluminum compound, in the presence of a stereospecificity additive. This stereospecificity additive is a cyclic polyether of the crown ether type, which may contain sulphur atoms and/or nitro radicals; this additive may be used together with an activator. The process produces polymers or copolymers with a high isotacticity index, while keeping catalyst activity sufficiently high.