| abstract |
The present invention describes a composition comprising at least one chromium compound; at least one aryloxy compound of the element M, the element M being selected from the group consisting of magnesium, calcium, strontium and barium having the general formula [M (RO)2-nXn]y, wherein RO is an aryloxy group having 6 to 80 carbon atoms of the derivative ROH, X is a halogen or a hydrocarbon group having 1 to 30 carbon atoms, and n is a value of 0 or 1 An integer and y is an integer in the range of 1 to 10; and at least one additive selected from the group consisting of ether compounds, which may or may not be cyclic, is introduced in an amount close to the stoichiometric amount of the element M. |