Cationic, thermally cured coatings using epoxidized soybean oil

Cycloaliphatic epoxy resins are used in coatings and inks because of their exceptionally low viscosity and reactivity with a variety of co-reactants, thus permitting high-solids and zero VOC coatings. The low viscosity of epoxidized soybean oil (ESBO), its reactivity, and relatively low cost make it an inexpensive candidate co-resin in cationic thermally cured coatings and inks using blocked acid catalysts. Formulations with up to 40% ESBO in the epoxy resin blend were investigated. Blending of cycloaliphatic resin with 10% ESBO gave a bake coating with the same results as the standard formulation except pencil hardness was one unit lower when cured for 12 mm at 120 deg C with a heat de-blocked catalyst. The hardness of coatings with ESBO is adjustable by changing the epoxy/polyol ratio, using harder polyols and harder epoxy resins. Substrates: steel panels.