The polymerization of conjugated dialkenes with transition metal catalysts began in 1954, soon after the first results on the polymerization of propylene had been obtained. The first stereoregular dialkene polymer obtained was a polyisoprene with a structure similar to that of natural rubber.1 An isoprene polymer with a structure identical to that of natural gutta percha was obtained soon after,2 along with stereoregular polymers of butadiene and pentadiene.2–4

Conjugated Diene Polymerization

A mathematical model which describes conversion and molecular weight development in the homogeneous polymerization of butadiene has been developed. The reaction scheme and derivation of the model equations are included. It was found that a catalyst formation efficiency must be estimated for each polymerization. The correct trends were predicted, although weight-average molecular weight was often underestimated. The model could not fully account for the effect of water concentration.

A mathematical model for the Ziegler-Natta polymerization of butadiene

High activity TiCl4/MgCl2/ethyl benzoate (EB)/triethyl aluminum (TEA) catalysts for the polymerization of propylene were synthesized and characterized for particle size distribution and crystallinity. Polymerization was carried out in a semibatch, constant pressure slurry reactor. A correction for interfacial mass transfer was found to be necessary to relate the monomer feed rate to the instantaneous rate of polymerization. Without such a correction serious misinterpretation of rate data could result. Optimum productivity was observed with respect to the Al/Ti ratio. Similar behavior was observed with polymerization temperature. Isotacticity increased with polymerization tamperature and decreased with Al/Ti ratio. The addition of a small amount of 2,2,6,6-tetramethylpiperidine increased the percentage of isotactic polypropylene to 98% without significantly affecting productivity.

Propylene polymerization in a semibatch slurry reactor over supported TiCl4/MgCl2/ethyl benzoate/triethyl aluminum catalyst. I. Catalytic behavior

Two-level fractional factorial designs were employed to study the solution polymerization of butadiene in a batch reactor using cobalt octoate/DEAC/water as catalyst. Conversion and molecular weight data obtained as functions of time were used to develop a kinetic model, and the estimated kinetic parameters were correlated empirically with four operating variables: temperature and concentrations of cobalt octoate, DEAC, and water. The experimental data indicate that at high water concentration a significant amount of oligomers is formed during early stages of polymerization, and the molecular weight of polymer increases with time. Analysis of the data suggests instantaneous initiation, first order propagation with cobalt and monomer, and transfer to monomer. Models which do not take account of the branching are shown to be incapable of fitting data for both Mn and Mw. The catalyst decay seems to follow a first-order mechanism, but the evidence is somewhat inconclusive.

Modeling of butadiene polymerization using cobalt octoate/DEAC/water catalyst

A kinetic modeling study was conducted for the Ziegler–Natta polymerization of butadiene with cobalt octoate/DEAC/water catalyst. The model equations for the single and dual active site models were analytically solved, and the closed-form expressions for conversion and both number and weight average molecular weights were obtained. The expressions for conversion and number average molecular weight are identical for both models. Also, the expressions of weight average molecular weight are similar for both models, but the expression for the dual active site model includes an additional scalar parameter. The parameter can be regarded as a “correction factor of weight average molecular weight,” which reflects the effect of dual active sites on the polydispersity. Using the expressions, a simple and noniterative kinetic modeling algorithm was established, and the parameter estimates were obtained. The estimated value of the correction factor ranges from 1.2 to 1.5 depending on the experimental data. The modeling results indicate the validity of the dual active site model. © 1994 John Wiley & Sons, Inc.

An analytic approach in kinetic modeling of Ziegler–Natta polymerization of butadiene

The polymerization of butadiene in toluene using Co(acac)3–(i-Bu)3Al–H2O catalyst system was studied. Presented are the effects of the addition order, aging time, and composition of catalysts on rates, polymer microstructure, and molecular weights. The polymerization was found to be initiated by the Co(acac)3-hydrolized aluminum alkyl complex. The chain propagation proceeds according to a first-order reaction with respect to monomer and active species and is a strong function of Al/H2O with an optimum ratio of 1.0, but independent of Al/Co. The nature of polymerization seems to change as Al/H2O increases from less than 1 to greater than 1. Transfer reaction is significant. From the kinetic data it was found that the termination reaction is most likely to be by combination.

Polymerization of butadiene with Co(acac)3–(i-Bu)3Al–H2O catalyst

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Polymerization of butadiene with Co(acac)3–(i-Bu)3Al–H2O catalyst