2001 Volume 13 Issue 1 Pages 32-38
The life time of growing polymer chain on the diester-type supported catalyst was investigated by the stopped-flow technique, as a part of our program to develop the novel olefin block copolymer, polypro-pylene-block-poly (ethylene-co-propylene) [PP-b-(PE-co-PP)], having well-defined structure and outstanding performance. The polymer yield and molecular weight of polypropylene obtained are proportional to time up to 1.2s when the pre-treatment of the catalyst was conducted with triethylaluminum (TEA). The efficiencies of various type of alkoxysilanes as an external donor to improve the productivity and molecular weight of PP-b (PE-co-PP) obtained were investigated in term of the commercial production. In all cases, an increase in the activity and weight-average molecular weight was observed on addition of the external donor at a Si/Ti mole ratio of ca. 1.0. Diisopropyldimethoxysilane (DIPDMS) was considered to be the most suitable donor for synthesis of the block copolymer, due to its higher initial activity and properties, giving a polymer having higher molecular weight. The improvement in molecular weight with considerable catalyst deactivation was apparently observed by increasing Si/Ti ratio and decreasing TEA concentration. The block copolymer having higher molecular weight (-MW=1, 400, 000) was achieved in the presence of excess DIPDMS (Si/Ti = 30) at law TEA concentration (Al/Ti=3).
