Process for the production of olefinic block copolymers

A process for the production of olefinic block copolymers comprising three consecutively blocks A, B and C, wherein

• block A is either
• an homopolyolefin block consisting of an olefin, or
• a random copolyolefin block consisting of ethylene and an olefin having less than 10 mol % of ethylene and more than 90 mol % of the olefin,
• block B is a random copolyolefin block consisting of ethylene and the same olefin having at least 10 mol % of ethylene and at most 90 mol % of the same olefin and
• block C is either
• a random copolyolefin block consisting of ethylene and the same olefin having less than 10 mol % of ethylene and more than 90 mol % of the same olefin, or
• a gradient copolyolefin block having less than 10 mol % of ethylene and more than 90 mol % of the same olefin,
• wherein the process comprises, within at least a reactor, the polymerization of ethylene and the olefin monomer in the presence of a catalyst system in which
• a catalyst is a ligand-metal complexes having a bridged bis-bi-aryl structure, the ligands are dianionic chelating ligands that can occupy up to four coordination sites of a metal precursor atom and, capable of undergoing reversible chain transfer to the chain transfer agent, showing negligible β-hydrogen transfer and able to be reactivated from its dormant state formed by 2,1-misinsertion by reacting with ethylene,
• a cocatalyst and,
• a metal chain transfer agent,
• and optionally a scavenger,
• wherein ethylene is added to the system to reactivate dormant sites of the catalyst, which have been formed after 2,1-misinsertion of the olefin monomer without terminating the growing polymer chain.