Process for producing atactic polyolefin polymers

摘要

The invention relates to a process for the controlled polymerization of alpha-olefins selected from the group consisting of propylene and butylene in order to form a polymer containing by weight about 10% to 30% isotactic polyolefin, 25% to 70% atactic polyolefin and 0% to 65% by weight of an amorphous ethylene/olefin copolymer which process comprises combinations of the steps of: (a) homopolymerizing the alpha-olefin at a temperature of from about 0 DEG C. to about 90 DEG C. (preferably from about 20 DEG C. to about 60 DEG C.) in the presence of a high yield catalyst comprising a titanium compound supported on activated MgCl2 and metal alkyl compound wherein the metal is selected from the group consisting of the metals of groups II and III of the Periodic Table for a first period of time; (b) adding a comonomer such as ethylene to the system; and (c) copolymerizing the alpha-olefin and the comonomer with stirring in order to assure a more uniform composition of the reacting phase at a temperature of from about 0 DEG C. to about 90 DEG C. in the presence of the same catalyst as used in step (a), for a second period of time, wherein said first period of time exceeds said second period of time. The mole fraction of comonomer in the reacting phase is from about 1% to about 300% of the mole fraction of alpha-olefin.