EFFECT OF ETHOXYSILANE AND METHOXYSILANE DONORS IN PROPENE 1-HEXENE COPOLYMERIZATION WITH HIGH-YIELD SUPPORTED ZIEGLER-NATTA CATALYSTS

The effects of two alkoxysilane donors, triethoxyphenylsilane (PTES) a nd dimethoxyditert-butylsilane (DTBDMS), on the propene/1-hexene copol ymerization with MgCl2/DIBP/TiCl4 (DIBP: diisobutyl phthalate) are com pared. Two series of copolymers of different compositions were produce d and the copolymers with the lowest hexene content, were fractionated . An analogous series, produced with the same catalyst without the use of an external donor, is the point of reference. All the fractions we re characterized by C-13 NMR. The data reported show that there is a n oticeable difference in the behaviour of ethoxy- and methoxysilanes in the copolymerization. The copolymers prepared with ethoxysilanes can be separated into fractions characterized by increasing isotacticity a nd decreasing comonomer content as long as the fractionation temperatu re increases. The copolymer obtained with DTBDMS is nearly completely isospecific while the comonomer content distribution is even wider tha n with ethoxysilanes. The sum of these data provides a deeper insight into the alkoxysilane activation mechanism.