Olefin copolymerization and olefin/diene terpolymerization with a zirconocenium catalyst system

Abstract

The kinetics of ethylene (E)/propene (P) copolymerization by heterogeneous Ziegler-Natta catalysts have characteristic rE * rp (product of monomer reactivity ratios) and p (persistence ratio) both greater than unity. The resulting E/P copolymers tend to contain short blocks of E. Therefore, uniform E/P copolymers and terpolymers are manufactured with homogeneous vanadium catalysts. The vanadium catalysts, however, have low productivity, require halogen-containing modifiers, and the high catalyst residue needs to be removed. The new zirconocene/MAO (methylaluminoxane) catalyst is superior'-9) to the above catalyst in most respects. It exhibits very high activity (> lo7 g E/P (mol Zr * h * bar)-') for random copolymerization of E and P (rE * rp < 1; p < 1). By proper choice of the hapto ligand, catalysts can be prepared which have rE and rp values different by orders of magnitudel9). At one time the zirconocene/MAO catalyst suffered an economical handicap because it requires MA0 in amount as high 0,l M. It also had apparent limitation for fluidized bed application because MA0 is essentially nonvolatile. Recently, the zirconocenium ion, produced by the reaction between rac-ethylenebis(indeny1)diethylzirconium (1) with triphenylcarbenium tetrakis(pentafluoropheny1)borate (2), has been found to be an exceedingly active and stereoselective propene polymerization catalyst 'O), especially at low polymerization temperatures ( T J . We now report that this system is a very efficient catalyst for E/P copolymerization and terpolymerizations.The metallocenium species (tetravalent, group 4, 3d O, 14 electrons) is commmonly prepared by the following method: Metallocene dichloride was converted to the dimethyl derivative, then a methyl anion is removed by a variety of reagents discussed in Jordan's review 'I). However, metallocene alkyls are unstable to heat, light, moisture and air and have short storage lives. We have developed an economical and efficient synthesis of zirconocenium species from stable precursors, such as rac-ethylenebis(in-deny1)dichlorozirconium (Et [Ind],ZrCI,, 3). The Zr compound is alkylated by triethylaluminium (TEA) which in turn reacts with 2 12) to produce the corresponding ruc-ethylenebis(indeny1)ethylzirconocenium species (Et[Ind],Zr + (C,H,), 4).

Reaction of AlR3 with [CPh3][B(C6F5)4]: Facile Degradation of [B(C6F5)4]- by Transient “[AlR2]+”

“…Because of the high sensitivity of these catalyst systems toward trace impurities the addition of aluminum alkyls is usually beneficial. For example, we have shown previously that the addition of 1 equiv of AlMe 3 stabilizes the 14-electron cation [Cp 2 ZrMe] + by formation of a heterobinuclear complex, [Cp 2 Zr(μ-Me) 2 AlMe 2 ] + , and Chien et al have developed highly active catalysts based on mixtures of metallocene dichlorides and [CPh 3 ][B(C 6 F 5 ) 4 ] in the presence of an excess of AlMe 3 or AlEt 3 …”

Low Molecular Weight Ethylene/Propylene Copolymers. Effect of Process Parameters on Copolymerization with Homogeneous Cp2ZrCl2 Catalyst

“…The temperature dependence of the catalyst activity was nevertheless stronger in our study than it was in that of Chien and Xu. 32 The viscosity average molecular weight was low for all the copolymers studied. The activity of the catalyst was 19 kg of polymer/(g of catalyst bar h) for the copolymer having viscosity average molecular weight 2500 g/mol.…”

Metallocene Complexes of Group 4 Elements in the Polymerization of Monoolefins

“…The zirconocenium ion, produced by the reaction between rac-ethylene bis(indeny1) diethyl zirconium with triphenyl carbenium tetrakis @entafluorophenyl)borate, has been found [282] to be an efficient catalyst for ethylene-propylene random copolymerization and ethylenepropylene-ethylidenenorbomene terpolymerization.…”