Polymerization of vinylcyclohexane with TiCl3–Al(C2H5)3 catalysts

Abstract

AbstractThe polymerization of vinylcyclohexane was followed dilatometrically in cyclohexane and n‐heptane solvents with TiCl3–Al(C2H5)3 as catalyst. In n‐heptane constant rates were obtained, while in cyclohexane a slow change of the initial rate to a lower steady‐state value was found. Polymerization rates were first order to [TiCl3] and [monomer] for concentrations >0.80 mole/l., and second order for monomer concentrations <0.80 mole/l. The rate was highest at [Al(C2H5)3] 0.005 mole/l. (Al/Ti = 0.28). Polymer intrinsic viscosity increased with time, with increasing monomer concentration, and with decreasing temperature. It was independent of [Al(C2H5)3]. A kinetic model which can account for these observations involves the alkylation of the TiCl3 surface by reaction with Al(C2H5)3 as the site‐generating step. It is also suggested that monomer molecules partake in the site‐generating step by reaction with the partially reduced TiCl3 surface. This possibility demands a rate of polymerization dependent upon the monomer concentration to a power between 1 and 2. The lower the liquid phase monomer concentration the higher the exponent of the monomer concentration in the rate expression. The melting point of the polymer was 280–285°C. The solubility of polyvinylcyclohexane was investigated for fifteen paraffinic and aromatic hydrocarbons. Only two polymer fractions exhibited amorphous x‐ray spectra, and both of these occurred at [Al(C2H5)3] 0.005 mole/l. The rate of polymerization of vinylcyclohexane is compared with that of propylene, pentene‐1, and stryrene on similar catalyst.