Olefin polymerization process in the presence of a ziegler-natta type catalyst modified with tributyl phosphite

Claim 1

IN THE PROCESS OF POLYMERIZING PROPYLENE WHICH COMPRISES CONTACTING PROPYLENE WITH A CATALYST PREPARED BY THE SEQUENCE OF STEPS COMPRISING (1) REACTING HYDROCARBON SOLUTIONS OF ALUMINUM TRIETHYL AND TITANIUM TETRACHLORIDE IN A MOLE RATIO RANGING FROM ABOUT 0.1:1 TO LESS THAN 0.4:1 AT ELEVATED TEMPERATURES UNTIL THE ALUMINUM TRIETHYL IS COMPLETELY OXIDIZED AND (2) THEREAFTER REACTING THE TOTAL PRODUCT OF (1) WITH A HYDROCARBON SOLUTION OF ALUMINUM TRIETHYL OR ALUMINUM DIETHYL CHLORIDE, IN AN AMOUNT TO GIVE A TOTAL ALUMINUM TO TITANIUM MOLE RATIO OF AT LEAST 1:1; THE IMPROVEMENT WHICH COMPRISES CARRYING OUT SAID CONTACT IN THE PRESENCE OF AN EFFECTIVE AMOUNT IN THE RANGE FROM 2 TO 10 MOLE PERCENT, BASED ON THE COMBINED ATOMIC PROPORTIONS OF METAL IN THE CATALYST OF TRIBUTYL PHOSPHITE.