New catalysts for poly(butylene terephthalate) synthesis. 2. Kinetic comparison using model compounds

A kinetic study of poly(butylene terephthalate) polymerization from dimethyl terephthalate and butanediol, using a catalyst mixture composed of titanium tetrabutoxide and hafnium acetylacetonate, in 1:3 molar ratio, was performed and compared to the standard titanium only catalyst. Arrhenius parameters were obtained from model reactions for both stages of polymerization. The mixed catalyst showed a consistently higher pre-exponential factor (A) and a higher activation energy (Ea) in the Arrhenius equation compared to the industrially used catalyst. For this reason the mixed catalyst, as observed in actual polymerizations, is more active at high temperature.