Reaction of Methyl Esters of Fatty Acids of Linseed Oil on Autoxidation and Heating

Abstract

The object of this experiment is to reveal the chemical changes of fatty acids of oil on its' casting use. As linseed oil is a typical casting oil, the authors employed the fatty acids of this oil as the sample in the form of methyl esters. The experimental treatments of the sample were carried under the conditions similar to the industrial operating conditions. As the catalysts, both lead- and cobalt-naphthenate were added to the sample ester. Autoxidation was made at 40°C by bubbling air into the sample. The reaction proceeded rapidly and the content of ethylene linkage decreased with the lapse of time and the cis-double bonds transformed into trans-isolated double bonds and conjugated double bonds, and most of the peroxides produced were hydro-peroxide-type. When autoxidized sample were heated at 200°C for 1hr, the hydroperoxides decomposed vigorously, and polymerization proceeded partly, and yet the conjugated double bonds and the trans-isolated double bonds were contained considerably. When the sample, treated at 200°C was heated at 300°C, the content of -OH decreased and polymerization proceeded and yet the conjugated double bonds remained a little and the content of the trans-isolated double bonds increased. After 400°C- or 500°C- treatment, the cleavaged products of low molecular weight increased and the content of -OH decreased and polymerization proceeded much more and most of the conjugated double bonds disappeared, but yet the trans-isolated double bonds remained cosiderably. And the reaction mechanisms of each treatment were discussed.