Medium-density ethylene polymers, method of obtaining them and application of carbonyl group containing, chain transferring agents

摘要

The present invention relates to an ethylene homo or copolymer having a density of between 0.923 and 0.935 g/cm³, having a molecular weight distribution M_w/M_n of between 3 and 10, and comprising from 0.10 to 0.50 wt.% of units derived from a carbonyl group containing compound, based on the total weight of the homo or copolymer. In addition, the invention relates to a free radical initiation polymerization process for the preparation of medium density ethylene polymers or copolymers, comprising reacting ethylene and optionally one or more comonomers at a high pressure, conveniently between 1600 and 4000 kg/cm², and at temperatures of about 150-330°C in a reactor system consisting of at least one autoclave reactor or of a combination of autoclave and tubular reactors, in the presence of free radical initiators and a carbonyl group containing compound, characterized in that such amounts of the carbonyl group containing compound are used so as to provide an ethylene polymer or copolymer comprising 0.15-0.50 wt.% of carbonyl group containing compound derived units based on the weight of the total polymer and having a density of between 0.923 and 0.935 g/cm³. Finally, the invention relates to carbonyl group containing chain tranfer agents to obtain improved polymer processing and performance properties in flat die extrusion processes and applications.