High solids primer composition based on epoxy ring opening curing reaction

摘要

This invention relates to a primer composition having a low VOC content useful in the manufacture of automobiles and trucks in which the film forming binder contains: a) a cycloaliphatic or polycycloaliphatic epoxy compound; b) an alkoxy silane or silicate reactive diluent; and, c) a curing catalyst to catalyze the reaction between (a) and (b). These primers are characterized in that the curing or crosslinking reaction is presumably based, at least in part, on a ring opening polymerization reaction between the epoxy structures of (a) and silanol groups formed on (b) in the presence of atmospheric moisture and acid. Curing chiefly utilizing a ring opening reaction of the forgoing epoxy structures with the forgoing reactive diluents not only avoids volatile compounds from being generated and released into the atmosphere during the curing process, but also keeps the viscosity low enough for practical application such as by spraying. These primers are especially useful in reducing emissions, while also meeting today's performance requirements, such as ease of application and excellent physical properties such as corrosion resistance, a high level of adhesion to primed and unprimed substrates, and provide a surface to which conventional automotive topcoats will adhere.