Process for the manufacture of pipes from a propylene-ethylene copolymer

摘要

A high molecular weight ethylene/propylene copolymer (I) has an ethylene content of 1-10 wt.%, a melt flow index (MFI 230/5) of less than 5 dg/min. and a molecular weight distribution (Mw/Mn) of 6-20. Also claimed is a 2-stage process for the production of (I) by copolymerisation of ethylene and propylene, optionally with another 4-20C 1-olefin, in suspension at 30-150 degrees C and 10-100 bar for 0.5-6 hr. in presence of a catalyst (A), an organoaluminium compound (B) and an organosilicon compound (C), in which stage 1 is carried out using the monomer itself as suspension medium to give polypropylene with a viscosity of 500-1400 ml/g and comprising 20-80% of the total polymer (I), and the product after stage 2 (i.e. polymer I) has a viscosity of 400-700 ml/g and Mw/Mn = 6-20.