Liquid Pool Copolymerization of Propylene/1-Butene with a MgCl_2-Supported Ziegler-Natta Catalyst

摘要

Liquid pool propylene/1-butene copolymeriza-tions were carried out in a batch reactor with a high activity Ziegler-Natta catalyst system.Experimental runs were performed to evaluate the effect of the 1-butene content on the crystallinity and melt temperature of the polymer resins.According to the results,1-butene can be significantly incorporated into the polymer chain at high polymerization rates over the whole range of copolymer compositions,leading to a decrease in the melting temperature (Tm)of the polymer,when compared to the poly(propylene)homopolymer,allowing for reduction of the sealing initiation temperature.It was observed by GPC and MFI measurements that the average molecular weights and the polydispersity index of the copolymer significantly decreased when compared to the ones obtained from poly(propylene).Despite high polymerization rates,polymer particles with good morphological features were produced in all cases.It was also observed that the absence of an external electron donor led to low crystallinity values for both the poly(propylene)homopolymer and for copolymers with different fractions of 1-butene,when compared to literature values frequently reported for polymer resins based on 1-butene and propylene.The obtained results indicate that a family of bulk propylene/1-butene copolymer grades can be successfully developed for packaging and film applications.