POLYMERIZATION PROCESS TO PREPARE A POLYOLEFIN FROM STERICALLY HINDERED, METHYL BRANCHED, ALPHA-OLEFINS

A process comprising contacting under polymerization conditions: at least one trialkylaluminum cocatalyst; at least one alpha-olefin which has a methyl branch at the 3-position and which has at least five carbon atoms; with a catalyst prepared by the process comprising comminuting, at least one aluminum halide, at least one electron donor, at least one metal compound wherein the metal is selected from the group consisting of chromium, hafnium, molybdenum, niobium, tantalum, titanium, tungsten, vanadium, zirconium, and mixtures thereof, a salt compound wherein at least one component of said salt compound is selected from the group consisting of barium, beryllium, calcium, magnesium, strontium, zinc, and mixtures thereof, to produce a comminuted solid then subjecting said comminuted solid to a double activation-extraction step; to produce a polymer at a productivity level of at least 700 grams of polymer per gram of catalyst utilized.