Polymerization of vinylcyclohexane with TiCl 3 –Al(C 2 H 5 ) 3 catalysts

Abstract

The polymerization of vinylcyclohexane was followed dilatometrically in cyclohexane and n -heptane solvents with TiCl 3 –Al(C 2 H 5 ) 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 [TiCl 3 ] and [monomer] for concentrations >0.80 mole/l., and second order for monomer concentrations <0.80 mole/l. The rate was highest at [Al(C 2 H 5 ) 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(C 2 H 5 ) 3 ]. A kinetic model which can account for these observations involves the alkylation of the TiCl 3 surface by reaction with Al(C 2 H 5 ) 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 TiCl 3 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(C 2 H 5 ) 3 ] 0.005 mole/l. The rate of polymerization of vinylcyclohexane is compared with that of propylene, pentene-1, and stryrene on similar catalyst.