Production of modified polypropylenes

Claim 1

A process for producing a heteroblock copolymer of polypropylene which sequentially comprises two stages: Stage I. catalytically polymerizing propylene at a polymerization temperature of 0* to 100* C and a polymerization pressure of not higher than 30 atmospheres and a catalyst comprising a titanium halogen compound and an organoaluminum compound to produce isotactic polypropylene which amounts to 40 to 70 percent by weight of the modified polypropylene to be finally produced, Stage II. subjecting the resulting product of the Stage I to successive polymerization under the above temperatures and pressures with a feed of a mixture of propylene and ethylene thereby to continue the polymerization of the Stage I, which successive polymerization comprises further polymerizing under the same reaction conditions with a feed of a mixture of propylene and ethylene, the quantity of the ethylene being 35 to 60 mole percent of the propylene in the feed to produce an ethylene-propylene copolymer which amounts to 5 to 15 percent by weight of the modified polypropylene to be finally produced, and still further polymerizing under the same reaction conditions with a feed of a mixture of propylene and ethylene, the quantity of ethylene being 2.0 to 4.5 mole percent of the propylene in the feed to produce a second ethylene-propylene copolymer which amounts to 25 to 40 percent by weight of the modified polypropylene to be finally produced, the total quantity of polymerized ethylene being 1.5 to 8 percent by weight of the modified polypropylene to be finally produced.