4,4 '- Bis (methylene) Biphenyl Bridge Even Dual-core Titanium, Zirconium Metallocene Catalyzed Polymerization Characteristics

Metallocene catalysts have been established as excellent catalysts for the polymerization after the Ziegler-Natta catalyst. The produced polyolefins have narrow molecular weight distributions due to identical active sites of the catalyst. However, this can be disadvantageous for industrial processing. The dinuclear complexes, which has two different active sites in one molecule, should be able to produce polymer with bimodal or broader molecular weight distributions. Recently a variety of dinuclear metallocene compounds have been prepared to examine their catalytic properties.Three novel bridged homodinuclear transitionmetal metallocene compounds [(C₅H₅)₂TiCl₂] [CH₂C₆H₄-p-C₆H₄CH₂][(C₅H₅)₂TiCl₂](A) and [(C₅H₅)2ZrCl₂][CH₂C₆H₄-p-C₆H₄CH₂][(C₅H₅)₂ZrCL₂ (B) phenylenedimethylene bis(r|5-cyclopentadienyl) titanium (C) were synthesized for the first time. In order to investigate the catalytic behaviors of the prepared dinuclear catalysts, many of polymerization are conducted as follows: (1) A/MAO and B/MAO systems for ethylene polymerization. (2) A/Al(i-Bu)3 system for methyl methacrylate (MMA) polymerization.Catalyst A and catalyst B have been used for the polymerization of ethylene activated by MAO. Some special behaviors were found. The dinuclear metallocenes of titanium (A) and zirconium (B) are expected to be efficient catalysts for ethylene polymerization, because of some similarities in structure compared to those of the mononuclear analogs Cp₂MCl₂ (M=Ti, Zr). Under the same polymerization condition, the activity of A/MAO system is lower than that of B/MAO system. The catalytic activity of dinuclear catalysts is higher than the corresponding mononuclear metallocene of Ti or Zr. The influences of reaction conditions, such as temperature, time, catalyst concentration and molar ratio of [Al]/ [Cat.] on ethylene polymerization were investigated in detail. For the system A/MAO, the catalytic activity increases with rise of the molar ratio of MAO/Cat and the concentration of catalyst, but the molecular weight of polyethylene dropped clearly. The activity and molecular weight of polyethylene dropped quickly with the elevation of the temperature. The melting point of the polymer were about 134.02℃. For the system B/MAO, with the concentration of catalyst rise, the catalytic activity and the molecular weight declined. The optimal temperature for polymerization was 60 ℃. The molecular weight of polyethylene dropped quickly with the elevation of the temperature. The melting point of the polymer were about 131.85℃, somewhat higher than the Cp₂ZrCl₂/MAO.Polymerization of MMA was catalyzed by A/Al(i-Bu)₃, produced polymer with high molecular weight ( M₅x10⁵). Cocatalyst Al(i-Bu)3 was suitable for the polymerization. The monomer conversion was rised as the MMA/Cat molar ratio decreased. The polymerization rate increased with the elevation of the temperature and Al/Cat molar ratio. Some polymer sample obtained by this catalyst system was not good dissolve in CHC13. PMMA produced under the temperature (40℃) showed a bimodal distribution (Mw/Mn=8.04, Al/Cat=l0; Mw/Mn=7.84, Al/Cat=20).