| abstract |
Improved 1-olefin polymerization catalyst system, and process employing same, comprising a reaction product of alumina and an organometallic compound of the formula (RCH 2 ) 4 M wherein M is Ti, Zr or Hf and R is a group which is such that there is no hydrogen atom attached to an atom which is in the β-position to M, the improvement characterized in that the preformed catalyst system is controlled in its mode of action and is protected from impurities by mixing with it an oxide, hydroxide, or carbonate of magnesium, calcium, strontium, or barium. |