The kinetics of polyesterification. III. A mathematical model for quantitative prediction of the apparent rate constants

Abstract

Abstract A mathematical model for the apparent constants k 1 and k 2 which presents a quantitative explanation of the observed kinetic behavior in both uncatalyzed and acid‐catalyzed polyesterification between ethylene glycol and a dibasic acid in different initial molar ratios was developed. This model consists of two types of similar semiempirical equations, one of which applies to the uncatalyzed reaction and the other to the acid‐catalyzed reaction. They are both based on the same apparent dissociation coefficient, k h , of a dibasic acid in ethylene glycol, which can be expressed as k h = K e ar at constant temperature. The symbol a in the equation represents the sensitivity constant to change in the initial molar ratio r = [OH] 0 /[COOH] 0 . The value of the true rate constant for polyesterification between succinic acid and ethylene glycol at 195°C was estimated to be 3.02 × 10 −3 [in kg 2 /(equiv. moles) 2 ·min] based on this model.