Study On Producing Microparticles Of Supported Metallocene Catalyst (Cp₂TiCl₂/PMMA) By Co-Precipitation Of RESS

Metallocene catalysts have many advantages, such us high catalytic activity, narrow molecular-weight distribution of polymerization products, and excellent catalytic capacity of copolymerization. Nevertheless, before the metallocene catalysts are widely used in industry, some important problems are needed to be solved. These contain the poor morphology of polymerization products, the inability to be used in continuous slurry and gas-phase polymerization process, and a very large supply of the precious MAO needed to achieve the maximum catalytic activity. As far, the most effect way to solve these problems is producing the supported metallocene catalyst as the supported Ziegler-Natta catalyst. Generally, the supporters are the inorganic compounds, such as SiCh, AI203 and MgCI2. However, the catalytic activity of metallocene catalyst is always decreased by the acidness of the surface of these inorganic supporters, and lots of inorganic residues are adulterated in the polymerization products. Recently, the polymer-supported metallocene catalyst is paid more and more attentions because it doesn't damage the catalytic activity of metallocene catalysts and the quality of polymerization products.The rapid expansion of supercritical solutions (RESS) is a novel process preparing microparticles, which has been developed in the recent decade. It causes the supercritical solutions saturated with solute depressurizedly to expand through a capillary nozzle (25-60um) within an extremely short time (10"8-10~5s). And because of the very high supersaturation (about 106) and homogeneous nucleation condition engendered by the mechanical perturbations, the RESS process produces microparticles which range from nanometer to micron and have narrow particle size distribution and goodmorphology. This process has been fully used to prepare polymeric microparticles and fibers, the pharmaceutical microparticles, organic materials, inorganic materials and microparticles of the ceramic precursor. It not only produces microparticles and fibers of the single solute, but also produces the compound microparticles of two solutes. So the RESS process is extremely potential method to prepare the microparticles of polymer-supported metallocene catalysts.The main purpose of the thesis is to prepare polymethyl methacrylate [PMMA]-supported metallocene catalyst [Cp2TiCI2] by the RESS process. The solubility of PMMA in the supercritical propane [CaHs] (binary system) is measured. These data are correlated by a solution model and an empirical model respectively. Satisfying agreements are obtained. Meanwhile, the solubility data in the ternary systems (PMMA- Cp2TiCl2-C3H8) are measured. These data are compared with those of the binary system (PMMA-CsHs and CpzTiCb-CsHs) respectively. Based on these works, the microparticles of the pure PMMA, the pure Cp2TiCl2, and the microparticles of the PMMA-supported Cp2TiCI2 are prepared by the RESS process respectively. The effects of process parameters on the microparticles size and morphology are investigated systematically.Through the investigations of different process parameters and the characterizations of the transmission electronic microscope (TEM), scanning electronic microscope (SEM), and the electron diffraction analysis, we find that the compound microparticles of PMMA/Cp2TiCI2 are not coated particles, but agglomerating particles of several micron size, which are agglomerated by the smaller microparticles of the PMMA and the Cp2TiCI2.