N, N'-di-n-alkanoyl substituted terephthalic acid dihydrazides with from 2 to 19 alkanoyl carbons were added to polypropylene (PP). Their crystal nucleating activity for PP was evaluated by the rise in crystallization temperature of PP, and their metal deactivation activity was evaluated by the lifetime of PP when in contact with copper. The crystallization temperature and lifetime thus obtained were plotted against the number of carbons of the alkanoyl substituents. It was found that both plots exhibit a group of characteristic and periodic peaks, the positions of which are coincident in both plots. These results suggest that the hydrazides stabilize PP against copper-catalyzed oxidation, not only by deactivating copper, but also by promoting the crystallization of PP.
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).