Ethylene@ (co)polymer(s) with wide mol. wt. distribution - by radical-initiated polymerisation in 2-zone tubular reactor, with ratio of polymer concns. in zones 1 and adjusted to given valve

摘要

A process is claimed for the prod. of ethylene homo and copolymers with a wide mol. wt. distribution (I), in 2-zone, tubular reactor systems with length/dia. (L/D) ratio 4000-20,000, at 150-250 MPa and 413-598 K in the presence of radical initiators and opt. mol. wt. regulators and comonomers; the ratio of polymer concns. in the 1st and 2nd reaction zones is set at (0.65-0.85):1. The above ratio is specifically adjusted by adding to zone 1 and/or 2 another peroxide with 1-min. half-life temp. = 383-403 K (II) at a point in the zone(s) when the temp. of the reaction mixt. has fallen from its peak value to 533-543 K; (II) can also be bifunctional peroxide with the same of different substits. on the -O-O- gp., esp. pref. 2,2-bis-(tert.-butyl-peroxy)-butane (IIA) or 2,5-dimethylhexane- 2-tert.-butylperoxy-5 -perpivalate (IIB). USE/ADVANTAGE - Modified tubular-reactor polymerisation is used for prodn. of ethylene (co)polymers with a wide mol. wt. distribution, suitable for use esp. in extrusion coating processes with large coating widths and high take-off speeds; the modification enables increased monomer conversion, to give polymers with good barrier properties and no processing de