Polymerization of olefins

A method for preparing a catalyst composition comprising preparing a milled mixture of magnesium chloride and a titanium tetrachloride, and then gently milling the mixture with a magnesium alkoxide said gently milling being characterized by up to about 300 shaking, rocking or rotating movements per minute of a receptacle containing grinding elements, said magnesium alkoxide and said milled mixture.

A catalyst for the polymerization and copolymerization of olefins comprising two components A and B wherein:

• component A is obtained by gently milling magnesium alkoxide with a milled mixture of a magnesium chloride and a titanium tetrahalide said gently milling being characterized by up to about 300 shaking, rocking or rotating movements per minute of a receptacle containing grinding elements, said magnesium alkoxide and said milled mixture, and
• component B is a metallic hydride or organometallic compound wherein said metal is selected from an element of Groups IA, IIA and IIIA of the Periodic Table.

A method for the preparation of a catalyst which comprises:

• forming a component A by preparing an intimate mixture by milling a magnesium chloride and a titanium tetrahalide and then gently milling said mixture with a magnesium alkoxide said gently milling being characterized by up to about 300 shaking, rocking or rotating movements per minute of a receptacle containing grinding elements, said magnesium alkoxide and said milled mixture, and then
• combining component A with a component B which is a metallic hydride or organometallic compound wherein said metal is selected from an element of Groups IA, IIA and IIIA of the Periodic Table.

A catalyst composition obtained by milling a magnesium alkoxide with a milled mixture of a magnesium halide compound and a titanium tetrahalide, said milling of magnesium alkoxide with said milled mixture being carried out by rotating a milling vessel at speeds ranging from about 10 to 200 rpm.