Description:
AbstractThe influence of cobalt driers on the initial stages of the drying of polyunsaturated esters has been studied. Cobalt (II) appears to from an unstable complex of variable composition with the polyunsaturated ester. This complex catalyzes the uptake of oxygen and increases the rate of oxygen absorption by the ester. The energy of activation for oxygen uptake by the ester in the presence of cobalt is only 1.3 kcal/mole, while in the absence of cobalt, the activation energy is 10.8 kcal/mole. The absorption of oxygen by the ester is followed by the formation of hydroxy and/or hydroperoxy groups, the loss of alkene groups, an increase in conjugation and conversion from the cis to the trans isomer. Polymerization occurs during these latter changes.