Badania kopolimeryzacji propylenu z etylenem

Abstract

Propylene/ethylene copolymers (EPR) containing up to 4 molar % of ethylene were prepared in the presence of supported titanium-magnesium catalyst TiCl 4 /MgCl 2 activated with dibutyl phthalate as internal donor, AlEt 3 ascocatalyst and dicyclopentylodimethoxysilane as external donor. The process of one-stage suspension copolymerization has been carried out. The effects of copolymerization time, initial ethylene content in the reaction mixture (c E t ), temperature and pressure on the catalytic system activity and copolymerization rate (R p ) were studied (Figs. 1 and 2, Table 1). Ethylene content in EPR and its weight average molecular weight (M w ) as time functions were also analyzed (Figs. 3 and 4). The results show that using of highly active titanium catalyst let obtain higher yield of copolymers containing up to 4 molar % of ethylene, in comparison with the yield of propylene homopolymer. However, an increase in ethylene content in EPR causes increase in atactic propylene fraction content and decrease in isotacticity index (II) as well as in bulk density (Table 1). Tensile properties and freeze resistance (impact strength at low temperature) of selected EPR samples have been determined and compared with respective properties of propylene homopolymer and of copolymer prepared earlier in two-stage process (Table 2). Copolymers, especially those produced in two-stage process, show improved strength properties, particularly better freeze resistance.