Effect of high polymerization temperature on the microstructure of isotactic polypropylene prepared using heterogeneous TiCl4/MgCl2 catalysts

摘要

The effects of alkylaluminum and polymerization temperature on propylene polymerization without an external donor in the use of a TiCl4-MgCl2-diether(BMMF) catalyst were investigated. The results indicated that with increasing polymerization temperature the concentrations of [mmmm] of heptane-insoluble poly(propylene) (PP) fraction increased. Crystallization analysis fractionation (CRYSTAF) results showed the fractions of different crystallization temperatures were changed according to various polymerization temperatures. The activity with Et3Al as cocatalyst at 100degreesC was much lower than that at 70degreesC. However, the activity with i-Bu3Al at 100degreesC was as high as that at 70degreesC. The fraction of high-crystallization temperature of PPs obtained with i-Bu3Al increased with increasing polymerization temperature, which was opposite to that with Et3Al, thus implying that the copolymerization of propylene with the monomer arising from Et3Al led to the lower crystallization ability of PPs obtained with Et3Al. The terminal groups of PP suggested that the chain-transfer reaction by beta-H abstraction was the main chain-transfer reaction at 120degreesC. (C) 2003 Wiley Periodicals, Inc. [References: 14]