A model study on fatty acid methyl esters as reactive diluents in thermally cured coil coating systems

A model study on the transesterification reaction between fatty acid methyl ester (FAME), e.g. methyl oleate, methyl linoleate, rape seed methyl ester and different alcohols in thin films have been performed. The purpose was to evaluate the possibility to use fatty acid methyl ester (FAME) as reactive diluent in thermally cured coil coating paints. A reactive diluent must be compatible, act as a diluent, react into the film without affecting the end properties. The transesterification between the methyl ester and hydroxyl functional model compounds was monitored by 1H NMR and real time IR. The effects addressed in the present study were compatibility, temperature, catalyst, alcohol structure, and fatty acid methyl ester (FAME) structure. Competing factors with the transesterification reaction were shown to be evaporation and side reactions, i.e. oxidation. The structure of the fatty acid methyl ester (FAME) affects the conversion as a higher amount of unsaturations triggers the competing side reaction oxidation. The reaction time and temperature affects both the degree of transesterification conversion, degree of side reactions and the catalyst choice. The present study has shown that a fatty acid methyl ester (FAME) fulfils the reactivity part for a reactive diluent in a thermally cured coating system.