Abstract: Process for polymerization of ethylene using a catalyst system including (i) a solid catalyst of Ti, Mg and halogen, (ii) a first activator which is at least one trialkylaluminium compound of the formula AlR3, where each R is independently a C2 to C20 alkyl radical, and (iii) a second activator which is at least one alkylaluminium chloride of the formula AlR?2Cl, where each R? is independently a C2 to C20 alkyl radical. The second activator is introduced directly into the polymerization reactor, without precontact with the solid catalyst, continuously or semi-continuously, and at a maximum rate of introduction at any time corresponding to less than 10 ppm by weight of chlorine relative to the rate of polyethylene production.

Abstract: The present invention relates to a process for polymerisation of ethylene, in particular a process which comprises using a catalyst system comprising comprising a catalyst system comprising: i) a solid catalyst comprising Ti, Mg and halogen, ii) a first activator which is at least one trialkylaluminium compound of the formula AIR3, where each R is independently a C2 to C20 alkyl radical, and iii) a second activator which is at least one alkylaluminium chloride of the formula AlR?2Cl, where each R? is independently a C2 to C20 alkyl radical, characterised in that the second activator is introduced directly in the polymerisation reactor, without precontact with the solid catalyst, continuously or semi-continuously and at a maximum rate of introduction at any time corresponding to less than 10 ppm by weight of chlorine relative to the rate of polyethylene production.