Process for producing polyethylene

The Ziegler-Natta catalyst according to claim 14, wherein the solid Ziegler-Natta catalyst component comprises a solid MgCl2 supported component which is prepared by a method comprising the steps:

• a) providing solid carrier particles of MgCl2*mROH adduct, wherein R is a linear or branched alkyl group with 1 to 12 C atoms, and m is 0 to 6,
• b) pre-treating the solid carrier particles of step a) with a compound of Group 13 metal;
• c) treating the pre-treated solid carried particles of step b) with a transition metal compound of Group 4 to 6, and
• d) recovering the solid catalyst component;
• wherein the solid carrier particles are contacted with an internal organic compound of formula (II) or isomers or mixtures therefrom before treating the solid carrier particles in step c)
• wherein in the formula (II) or isomers or mixtures therefrom
• R1 to R5 are the same or different and can be hydrogen, a linear or branched C1 to C8-alkyl group, or a C3-C8-alkylene group, or two or more of R1 to R5 can form a ring, and
• the two oxygen-containing rings are individually saturated or partially unsaturated or unsaturated.

A Ziegler-Natta catalyst comprising:

• a cocatalyst of an organometal compound of Group 13 metal;
• an external additive of formula (I)
• R1nSi(OR2)4-n (I)
• wherein, in formula (I),
• n is an integer 0 to 3,
• each R1 are equal or different and are selected among H, halogen, alkyl groups of 1 to 6 carbon atoms optionally substituted with one or more halogen atoms, alkenyl groups of 2 to 6 carbon atoms optionally substituted with one or more halogen atoms, and aryl groups of 6 to 12 carbon atoms optionally substituted with one or more halogen atoms, or the R1 groups can form with the Si atom they are linked to a ring of 3 to 8 ring atoms, provided that all R1 are not hydrogen,
• R2 are equal or different and are selected among alkyl groups of 1 to 6 carbon atoms optionally substituted with one or more halogen atoms, alkenyl groups of 2 to 6 carbon atoms optionally substituted with one or more halogen atoms, and aryl groups of 6 to 12 carbon atoms optionally substituted with one or more halogen atoms, or the OR2 groups can form with the Si atom they are linked to a ring of 3 to 8 ring atoms, and
• halogen is Br, Cl or F;
• and
• a solid Ziegler-Natta catalyst component supported on a magnesium dichloride support, the solid Ziegler-Natta catalyst component comprising a compound of Group 4 to 6 metal, an aluminum compound, and an internal organic compound of formula (II)
• wherein, in formula (II),
• R1 to R5 are the same or different and are selected from the group consisting of hydrogen, linear or branched C1 to C8-alkyl groups, and C3-C8-alkylene groups, or wherein two or more of R1 to R5 form a ring;
• and
• the two oxygen-containing rings are individually saturated, partially unsaturated, or unsaturated.