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

A kinetic study of poly(butylene terephthalate) polymerization from dimethy l terephthalate and butanediol, using a catalyst mixture composed of titani um tetrabutoxide and hafnium acetylacetonate, in 1:3 molar ratio, was perfo rmed and compared to the standard titanium only catalyst. Arrhenius paramet ers were obtained from model reactions for both stages of polymerization. T he mixed catalyst showed a consistently higher pre-exponential factor (A) a nd a higher activation energy (E-a) in the Arrhenius equation compared to t he industrially used catalyst. For this reason the mixed catalyst, as obser ved in actual polymerizations, is more active at high temperature. (C) 2001 Elsevier Science Ltd. Ah rights reserved.