Ethylene/propylene copolymers titanium-based catalysts

IV to VIII metals and base metal alkyls of Group II or III metals (Penczek and Premia, 2012 Boor, 1979 Ciardelli, 1992). It arose from the spectacular discovery of Ziegler et al. (1955) that mixtures of titanium tetrachloride and aluminum alkyls polymerize ethylene at low pressures and temperatures and from the equally spectacular discovery by Natta (1955) that the Ziegler catalysts can stereospecifically polymerize monoolefins to produce tactic, crystalline polymers. As can be imagined, these systems can involve many combinations of catalyst components, not all of which are catalytically active or stereospecific. However, we shall be concerned here only with polymerizations involving the commercial elastomers, principally polyisoprene, polybutadiene (Duck and Locke, 1977 Zohuri et al., 2012 Teyssie et al., 1988), and the ethylene-propylene copolymers (Schobel et al., 2012 Ver Strate, 1986 Davis et al., 1996 Noordermeer, 2003 Baldwin and Strate, 1972). 

Elastomeric copolymers are made by either solution or suspension process using a vanadium based catalyst along with alkyl aluminum compound as cocatalyst. In the suspension process propylene is used as a diluent, whereas in the solution process hexane is used as diluent. Superior catalysts based on supported titanium compounds have further improved the suspension process in recent years. In the conventional suspension process, ethylene, propylene and catalysts are fed continuously to a stirred reactor at 20 °C and 12 kg cm total pressure. Diethylzinc is used to control molecular weight. 

The copolymerizations between monoolefins and dienes have been considered to be of practical and theoretical importance. As reported in the literatures ethylene-butadiene and propylene-butadiene copolymers can be prepared with conventional Ziegler-Natta titanium-based or vanadium-based catalysts. The copolymer composition and monomer sequence distribution strongly depend on the catalyst system and polymerization conditions. Alternating copolymers were synthesized when the catalyst components were mixed at the... 

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