The In-Situ Copolymerization Of Ethylene Catalyzed Based On The Late Transition Catalyst

This thesis is composed in four parts: (1) the synthesis of branched polyethylene by in-situ copolymerization of ethylene catalyzed by bis(imino) pyridyl iron and bis(imino) pyridyl cobalt complexes; (2) the synthesis of long chain branched polyethylene by in-situ copolymerization of ethylene catalyzed by bis(imino) pyridyl iron complexes and supported metallocene; (3) the synthesis of long chain branched polyethylene by in-situ copolymerization of ethylene catalyzed by bis(imino) pyridyl iron or bis(imino) pyridyl cobalt complexes and BCH catalyst; (4)the relationship of the structure of the branched polyethylene and rheological behaviors of the copolymers.In part one, the performance of the cobalt-based catalyst 1, 2, 3 and 4 are estimated for preparing a-olefin. The results indicated that the catalysis activity and the carbon number distribution of the oligomers were effected on the loadings of methylaluminoxane(MAO), concentration of the catalyst and reaction temperature. The combination of the catalyst 7 and 6 was to adjust the distribution of the α-olefins. The DSC and 13C NMR results showed the low melting point and low crystallinity of the copolymer. It proved that the copolymer were the branched polyethylene and the degree of branches of 5C/1000C~10C/1000CIn part two, the long chain branched polyethylenes are synthesized by the combination of bis(imino) pyridyl iron complexe and supported metallocene. The performance of the catalytic systems for the copolymerization were investigated systematically The positive comonomer effect was observed. With the increasing the molar ratio of oligomerization catalyst to copolymerization catalyst from 0 to 4, the melting point decreased from 136.5℃to 112.3℃. The DSC and 13C NMR results showed the low melt point and low crystallinity of the copolymer. It proved that the copolymer were long chain branched polyethylene and the degree of branches polyethylene were 22C/1000C~40C/1000C.In part three, the long chain branched polyethylenes are synthesized by the combination of bis(imino) pyridyl iron or bis(imino) pyridyl cobalt complexes and the BCH catalyst, a conventional Ziegler-Natta catalyst. With the increasing the molar ratio of oligomerization catalyst to copolymerization catalyst from 0 to 0.25, the density and melting point of copolymer decreased from0.9600g/cm3 to 0.9387g/cm3. The properties of the polymers can be controlled to some extent by simply adjusting the ratio of oligomerization catalyst to copolymerization catalyst. The DSC and 13C NMR results showed that the copolymer was long chain branched polyethylene and the degree of branches polyethylene were 15 C/1000C~25C/1000C.The SEM of copolymer showed pretty good shape of the product.In part four, relationship of the structure of the copolymer and rheological behavior of the copolymer is investigated. The result proved that the structure of the branched polyethylene prepared by us had greatly effect on the rheological behavior of the copolymer. The copolymer had good fluidness than the industrial products at the same condition.