Studies On Olefins Polymerization Catalyzed By Metallocene Complex Catalytic System

Group 4 metallocene-based catalysts have attracted extensive attention in the past decades, as homogeneous catalysts for olefin polymerization, since Kaminsky et al. discovered the highly active zirconocene dichloride/ methylaluminoxane (MAO) catalytic system for olefin polymerization in the early 1980's. Subsequently, research both academically and industrially has been focused on developing to develop new catalyst systems, which can provide high performance polyolefins, such as isotactic polypropylene, syndiotactic polypropylene, atactic polypropylene, high density polyethylene, linear low density polyethylene, syndiotactic polystyrene, and cyclo-olefin copolymer et al. Half-metallocene type catalysts have been widely studied in recent years, as one of the efficient catalyst precursors for olefin homopolymerization and copolymerization of ethylene withα-olefin. For example, this type of complex catalysts can be tuned by modification of cyclopentadienyl and/or ancillary anion aryloxide ligands with electronic and steric properties, thus displaying unique characteristics as the catalysts producing new polyolefins, including the copolymers of ethylene with cyclohexene, 2-methyl-1-pentene, and with vinylcyclohexane. In this dissertation, the preparation of a series of non-bridged titanocene complexes is described. And these titanium complexes are successfully used to catalyze the homopolymerization of ethylene/propylene and copolymerization of ethylene withα-olefin. Influences of the molecular structure of titanocene complexes and polymerization conditions on their catalytic performance were also studied.This paper studied the polymerization of a series of olefin under the metallocene catalyst. Norbornene polymerization ethylene/norbornene copolymerization ,α?olefin Oligomerization and polypropylene"alloy"in situ polymerization were studied using metallocene catalyst with AliBu3 and Ph3CB(C6F5)4 as cocatalysts.1,Study on Norbornene polymerization: High molecular weight norbornene polyer can be obtained by metallocene catalyst polymerization system, and the order of the catalytic activity is 1>2>3. The catalytic activity of these catalyst systems increases first with the increase in polymerization temperature, the catalytic activity increases with the increase in monomer concentration. The molecular weight of polymer decreased with increasing temperature but the polymer yield and the conversion rate of temperature increase with the increase temperature.2,Study on Ethylene/norbornene polymerization: Complexes 1-3 all can catalyze the copolymerization of norbornene with ethylene in the presence of AliBu3 and Ph3CB(C6F5)4 as cocatalysts. High molecular weight polyer can be obtained and the order of the catalytic activity is 1>2>3, which should mainly owe to the electronic effect of the substituent groups on the phenolate. Experimental results indicate that the catalytic activity is sensitive to the reaction temperature. The catalytic activity increases dramatically from 30 to 70℃and reaches the highest value at about 70℃. Further increase in the polymerization temperature results in a decrease in the catalytic activity. The molecular weight of the copolymers produced from these reactions also increases with the increase in polymerization temperature and reaches the highest point at about 50℃.The glass transition temperature of the copolymers increases with the polymerization temperature too since the incorporation of norbornene in the copolymer increases with the increase in polymerization temperature due to the decrease in concentration of ethylene. The catalytic activity increases first with the increase in the Al/Ti molar ratio and reaches the maximum with the Al/Ti ratio of about 120. Ethylene/norbornene copolymers with high norbornene incorporation (>50%) were easily obtained with these catalyst systems by increasing the norbornene feed concentration, glass transition temperature also changes in the range 37.5 to 133.3℃3,Study onα-olefin oligomerization under constrained geometry metallocene-based catalysts with a phenolate donor on the cyclopentadienyl ring in the presence of aluminum and boron-containing compounds as cocatalysts. Experimental results indicate that the metallocene catalyst system is desirable for the oligomerization ofα-olefin with good catalytic activity, and the oligomer obtained is a mixture consisting of di-, tri-, tetra- and pentamer. There is only few high molecular weight polyer. The oligomer is found suitable for lube base oil. A typical characteristic of the metallocene catalyst system used for catalystingα-olefin oligomerization is that it can be used directly with the olefin as solvent. The method has the advantage of reducing the use of solvent. It is a green pross for poly-α-olefin.