Chain termination reactions in the polymerization of ethylene over TiCl4-AIR2Cl

Abstract

1. In the steady polymerization of ethylene in the presence of TiCl4-AlEt2Cl, the molecular weight of the polyethylene is independent of polymerization time. 2. Under these conditions, the length of the polymer chain with ethylene concentrations of the order of 10−2 mole/liter is determined by the ratio of the constants of polymer chain growth and termination by the monomer. The rate of chain termination by the catalyst components becomes commensurate with the rate of termination by the monomer only at lower ethylene concentrations. Spontaneous chain termination is practically absent. 3. A sharp increase in the molecular weight of the polyethylene with an increase in the molar ratios of the catalyst components results from a change in the kinetic properties of the catalytic complex (chain propagation constants and constants of chain termination and transfer on the monomer) and not from a fall in the rate of chain termination by TiCl4, as has been proposed in the papers of a number of investigators.