Studies on the formation of poly(ethylene terephthalate): 6. Catalytic activity of metal compounds in polycondensation of bis(2-hydroxyethyl) terephthalate

The rate parameters (p and d values) associated with the rate constants of propagation and thermal degradation reactions in the polycondensation process of bis(2-hydroxyethyl) terephthalate (BHET) in the presence of various metal compounds as catalysts at 283°C, calculated from the time dependence of the molecular weight of the formed polymer, were used to evaluate each metal compound in its catalytic activity. These logarithms of the p and d values were correlated by linear relationships (mountain-shaped) with the stability constants (log β1) of dibenzoyl methane (DBM) complexes of the corresponding metal species. Consequently, the stability constant of DBM complex of each metal species was found to be very useful in forecasting the catalytic activity of the metal compound. The compound of metal species with values of log β1 about 12 was most active as the catalyst on the propagation reaction and that of values about 11 was most active on the thermal degradation reaction.