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Hangzhou, China

Wu J.,Zhcjiang University | Li W.,Zhcjiang University | Jiang B.,Zhcjiang University | Wang J.,Zhcjiang University | Yang Y.,Zhcjiang University
Acta Polymerica Sinica | Year: 2012

An organic/inorganic support of immobilizing catalysts for ethylene polymerization was devised. The composition of the hybrid catalyst is as following: styrene and acrylic copolymer (PSA) is the organic part for binding iron (M) acetylacetonate and bis (imino) pyridyl ligand catalyst, and SiO, (Davison 955 silical gel) is the inorganic part. The inorganic part is coated by the organic part (PSA) by sol-gel method. The catalyst could produce not only high crystallinity (72%) polyethylene,but also a-olefin. We considered the impact of different membrane materials and polymerization conditions (different cocatalyst, pressure, temperature, Al/Fe molar ratio) to the polymerization activity and properties of polymers and found that temperature had the greatest impact to the weight ratio of oligomer to PE. Because of the poor thermal stability of catalyst, the catalytic activity significantly attenuated with increasing temperature. When pressure increased, catalytic activity would increase too. The relationship of pressure and catalytic activity met the cossee catalytic reaction mechanism, which was widely accepted in Ziegler-Natta catalyst' s ethylene polymerization mechanism. Different membrane materials would affect the final polyethylene product performance, the pure PSA as organic part would increase the molecular weight significantly. Cocatalysts affect not only the catalytic performance, but also the property of the final product. The alkylaluminium as cocatalyst tended to decrease the molecular weight. The iron catalyst system binding on the PSA after the treatment of magnesium chloride could produce the polyethylene of lower molecular weight (Afw = 11.9 x 104) and higher crystallinity (72%). And the polyethylene' s melt index MI (2.35 g/lOmin) was higher than the iron catalyst binding on other membrane materials. The polyethylene can be used as the low molecular weight part of bimodal polyethylene.

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