Study On The Preparation Of High Melt Index Polyethylene By The Supported Ziegler-Natta Catalyst Based On Novel P Electron Donor

As an important part of Ziegler-Natta catalyst, electron donor plays an crucial role on the influence of the performance of catalyst. Study on the electron donor has become one of the important fields of the polyolefin industry. We prepared high performance Ziegler-Natta catalyst with anhydrous magnesium chloride as support and four types novel P materials as electron donor(ED1、ED2、ED3、ED4).The influence of the structure and amount of electron donor and the dropping temperature and amount of TiCl4 were discussed. The amount of titanium loading、the morphology of catalyst、the oxidation state of titanium were characterized by ICP、WAXD、SEM and XPS. Compared with the catalysts without electron donor and Si(OEt)4 as electron donor, the catalysts we prepared exhibit higher activity and the polyethylene obtained showed high melt index. The melt flow rate is 533 g/10min、485 g/10min、557 g/10min、 521g/10min respectively. When the n(ED)/n(MgCl2) was 0.25 and the TiCl4 dropping temperature was -10℃, we get the optimum preparation of catalyst. SEM result showed that the catalyst particles are spherical and have uniform particle size.The effects of mole ratio of Al/、Ti polymerization temperature and H2 partial on the ethylene polymerization were discussed. The results show that the obtained polyethylene has the best comprehensive performance when the mole ratio of Al/Ti is 90:1 and the polymerization temperature is 80℃, when the pressure ratio of hydrogen and ethylene was 28:45, the catalyst exhibits the highest activity which was 25300 g PE/g cat. SEM show that the morphology of polyethylene is spherical and the polyethylene particle size is 100 μ m～300 μm. WAXD show that the crystallinity of polyethylene is high which is 78.1%, TG analysis results show the decomposition temperature of obtained polyethylene is high which demonstrate its good heat resistance.