| abstract |
A process for the polymerization of an alpha monoolefin in the presence of certain supported coordination catalysts systems which comprise (a) a procatalyst, (b) a cocatalyst and, (c) a selectivity control agent, whereinn (a) is a solid composition comprising magnesium chloride, titanium tetrachloride, and an electron donor;n (b) is an aluminium trialkyl; andn (c) is a combination of a strong selectivity control agent and a weak selectivity control agent. |