SUMMARY Propene polymerizations were performed using the two ansa-zirconocene catalyst systems dimethylsilylbis( 1 -indenyl)zirconium dichloride/methylaluminoxane and dimethylsilylbis(2-methyl-1 -indeny1)zirconium dichloride/methylaluminoxane. The polymerization rate was observed by continuously monitoring the monomer consumption. Reaction rate profiles were obtained in the temperature range from 40 "C to 130°C at pressures between 1 and 2.5 bar and catalyst concentrations from 4.6-10" M to 4.2. lCr5 M. Isotacticity, as measured by NMR, melting point and molecular weight decreases markedly at higher temperatures. Small amounts of 1,3-inserted monomer (el mol-%) was observed at polymerization temperatures above 80 "C. No 2,1-inserted monomer was detected. A kinetic model was developed that describes the polymerization rate for Me2Si(Ind)2ZrC12 as the catalyst over the entire observed temperature range, and the polymerization rate for Me&Si(2-Me-Ind)&C12 in a limited temperature range. The model includes an activation reaction, latent sites that may revert to active sites and a permanent deactivation that is second order with respect to the active sites. The activation energy for the propagation reaction was found to be 37 kT/mol for Me2Si(Ind)2ZrC12 and 32 kJ/mol for Me2Si(2-Me-Ind)2ZrClJMAO. Several kinetic models are compared and discussed.
The effects of injecting ethene, propene, 1-hexene, 2-methylpropene, 3,3-dimethyl-Ibutene, cis-2-butene, trans-2-butene, 2,3-dimethyl-2-butene, cyclopentene, styrene, 1,3butadiene and 1,4-pentadiene during polymerizations of ethene and propene have been investigated. Catalysts used were a supported MgC12/EB/TiC14 ballmilled catalyst and precipitated MgCl2/2-EH/TiCl4/DIBP catalysts activated with triethylaluminium in presence of EB. (EB = ethyl benzoate, 2-EH = 2-ethylhexanol, DIBP = diisobutyl phthalate).The polymerizations were performed at 50°C, in a heptane slurry at 1 atm (1.00 -lo5 Pa) total pressure.The instantaneous polymerization rate was observed by continuous monitoring of the monomer consumption, the time resolution of the measurements being less than one second. Two different kinetic effects can be observed after injection of the comonomer. First there is an immediate rate change, usually a rate reduction. Then a secondary effect may follow, which is a slow, and sometimes significant and persistent, activation. The two effects obviously have different causes, and for none of these we found single causes that can explain all the observations. The strongest immediate effect was observed after addition of dienes and indicates a direct association of the comonomer to the active center. A marked nonlinearity in the response may hint to inhomogeneity in the structural environment of the active centers. Addition of a-olefins during ethene polymerization gave the strongest secondary effect. In general the immediate effects were stronger during propene polymerization than during the polymerization of ethene. A significant difference in the effects of cis-2-butene and trans-2-butene in the polymerization of propene indicates that steric effects may be important.
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