Diels‐Alder adduct of sorbic acid and methyl ester of soyabean oil as substitute to conventional dimer acids

Abstract

Purpose

The purpose of this paper is to synthesise new fatty dicarboxylic acid half ester (NFAHE) C25, which can be used as substitute to dimer/trimer acids commonly used (C36, 54) as basic raw materials for manufacture of polyamides for printing inks or as curing agents for epoxy paints and adhesives. This could be an economically viable synthesis by which the user could manufacture the finished products from relatively low cost raw materials.

Design/methodology/approach

Vegetable oils have several double bonds that undergo large number of reactions. Diels‐Alder addition is one of them. Dimer acids have been produced by using these double bonds by reaction of two fatty acid molecules. Maleic acid, acrylic acid has also been used for this purpose. Sorbic acid is a derivative of alcohol and hence a renewable raw material. It is relatively less used by the coating chemists due to its relatively limited availability due to restricted uses.

Findings

It was found that sorbic acid reacts easily with unsaturated fatty acids. Its solubility in fatty acids and esters is limited. A common solvent that can be removed easily after the reaction was necessary. Cyclohexanone was found to meet this requirement. The resultant half ester of dicarboxylic acid could be easily converted to polyamides for curing epoxies.

Practical implications

The user can manufacture his own dibasic/tribasic acid as a first step. As a source of methyl esters of fatty acids with iodine value about 110 to 130, vegetable oils such as soyabean oil can be used. Low value acid oils obtained from vegetable oil refining are also suitable. Bio diesel could be used directly. To account for large saturated fatty acids in bio diesel, corresponding trimer may be produced by appropriate addition of sorbic acid to fatty acid.

Originality/value

The process allows a manufacturer to develop low cost formulations for bulk products using simple chemistry that can be integrated in the existing process.

Citation

Malshe, V.C., Phadke, J.P. and Jadhav, M.A. (2013), "Diels‐Alder adduct of sorbic acid and methyl ester of soyabean oil as substitute to conventional dimer acids", Pigment & Resin Technology, Vol. 42 No. 1, pp. 15-23. https://doi.org/10.1108/03699421311288724