Process for the manufacture of a composition comprising ethylene polymers

Process for the manufacture of a composition comprising ethylene polymers, in at least two polymerization reactors connected in series, according to which:

• in a first reactor, ethylene is polymerized in suspension in a first mixture comprising a diluent, hydrogen, a catalyst based on a transition metal and a non-halogenated organoaluminum cocatalyst having the formula AlR3, wherein R represents a C1-8 alkyl group, so as to form from 30 to 70% by weight with respect to the total weight of the composition of an ethylene homopolymer (A) having a melt flow index MI2 of 5 to 1000 g/10 min, to form a second mixture comprising hydrogen and said homopolymer (A),
• said second mixture is withdrawn from said reactor and is subjected to a reduction in pressure, so as to degas at least a portion of the hydrogen to form an at least partially degassed mixture, then
• said at least partially degassed mixture, together with ethylene and 1-hexene and, optionally, at least one other α-olefin, are introduced into a subsequent reactor and the suspension polymerization is carried out therein in order to form from 30 to 70% by weight, with respect to the total weight of the composition, of a copolymer of ethylene and of hexene (B) having a melt flow index MI5 of 0.01 to 2 g/10 min.