Stopping and restarting polymerisation of alpha:mono:olefin cpds. - in presence of Ziegler-Natta catalyst, by introducing carbon mon:oxide and/or di:oxide as stopper

摘要

The process involves stopping and restarting the homo- or co-polymerisation 2-6C alpha-monoolefins at 40-120 degrees C. and 1-100 bar using a Ziegler-Natta catalyst of (a) a TiCl3 cocrystallisate of the formula TiCl3.nAlCl3 (in which n = 0.31-0.35), opt. modified with an electron donor, and (b) an Al cpd. of the formula R2AlX (in which R is 1-6C alkyl; X is Cl or R) in an (a):(b) molar ratio of 1:1-100. Polymerisation is stopped by introducing CO and/or CO2 to a concn. of min. 0.5 mmole/l. reactor vol. under 2 min. and restarted by replacing the CO/CO2 with fresh monomer. Overheating and the danger of explosion can be avoided easily and economically. Introduction of the stopper can be controlled automatically by a safety system.