The Synthesis And Research Of The New Kind Electron Donors And The Catalysts For The Polyolefin With Multi-Broad Molecular Weight Distribution

The high efficiency Ziegler-Natta catalysts supported by MgCl2 were prepared for the ethylene polymerization by the method of solution precipitation, and the new kind alkoxy silicon as the electron donor. The influences of the conditions for the dissolution of MgCl2, the structure and amount of electron donor, the dropping method and temperature of TiCl4 on the properties and particle morphology of the catalysts were discussed in detail. The particle morphology of the catalysts, the crystallization of MgCl2 before and after loading Ti and the amount of Ti of these catalysts were characterized by SEM, WAXD and ICP. The results show that the catalysts has the highest content(7.0 wt%)of Ti loading on the supporter and the particles are spherical and the processing is easy during the preparation of these catalysts when the added electron donor is 2-ethoxy-(isopropoxy)-tert-butoxy silane(Mg:ID=1:0.2/mol:mol)and the temperature of dropping the homogeneous solution of MgCl2 into TiCl4 is-20℃. The crystal properties of MgCl2 after loading Ti have changed obviously and no sharp peaks showed in WAXD.The effects of polymerization temperature, mole ratio of Al/Ti and the concentration of 1-hexene on ethylene polymerization were studies. The structure and properties of polymers were characterized by GPC, WAXD, FT-IR,13C NMR, DSC and other methods. The results show that cat.4 has the highest activity (8.1×106g PE/mol Ti h) when the polymerization temperature is 70℃and the mole ratio of Al/Ti is 90. The polyolefin obtained in the ethylene polymerization catalyzed by cat.4 has multi-broad molecular weight distribution. The SEM results show that the polymer particles are spherical and distributed uniformly. The 13C NMR result showed that the polyethylene was featured with linear structure. The WAXD and FT-IR results show that these catalysts obtained could catalyze the copolymerization of ethylene with 1-hexane. TG results showed that both polyethylene and copolymer of ethylene with 1-hexene had good thermal stability and low ash contents.