Investigations of the kinetics of maleate–fumarate isomerization during the polyesterification of maleic anhydride with different glycols

Abstract

SynopsisThe rate of isomerization during the polyesterification of maleic acid or maleic anhydride depends on the structure of the glycol used: the longer the chain of the glycol, the lower the isomerization rate. The rate constants differ greatly from one case to another. Thus, the difference in the reaction rate constants depends mainly on the steric effects caused by the different types of glycols used in the polycondensation. The isomerization approaches a constant value, ;which after a certain time depends on the structure of the glycol and the temperature of the condensation. The activation energies calculated from the rate constants would fall at about 20 f 4 kcal./mole. This value for the activation energy corresponds to that reported in the literature for the transformation of maleic acid into fumaric acid. The reaction apparently follows secondorder kinetics due to the catalytic effect of the maleic acid on the isomerization.

Effect of composition and polyesterification catalysts on the optical properties of cured polyesters

“…Prolonged heating of maleic acid at 150 °C converts it into fumaric acid 4. It has also been reported20 that maleic anhydride is converted in low degree isomerization to fumaric acid during esterification at 120 °C. The degree of this isomerization depends on the maximum temperature and the duration of polymerization in the high temperature range.…”

Unsaturated Polyesters and Vinyl Esters

“…Secondary glycols like propylene glycol favor high isomerization of maleate to fumarate (isomerization degree at a reaction temperature of 180°C % 96%), whereas isomerization will be less with primary glycols like ethylene glycol, diethylene glycol, or 1,6-hexamethylene glycol, which lead to isomerization degrees of 64, 53, and 36%, respectively [11]. Isomerization also depends on reaction temperature and time, higher temperatures and longer times generally favoring greater isomerization.…”

Porous polymer oil sorbents based on PET fibers with crosslinked copolymer coatings

“…The isomerization of maleic anhydride to the fumarate was not obtained in the present reaction, while it has long been known that the isomerization of maleic anhydride to fumarate in polycondensation reactions depends on the temperature and the glycol chemical structures. 20 On the other hand, the isomerization to the fumarate can be carried out at high temperature in the presence of catalysts such as mineral acid or thiourea and under applied pressure, which further prevents the esterication reaction. 21…”