Isocyanate-Free Moisture Cure Coatings

By J. Baghdachi, Dan Li, J. LaForest

Novel isocyanate-free moisture cure polyurethane coatings with excellent properties have been formulated and evaluated. These coatings utilize polyols derived from the renewable resource soybean oil and its simple derivatives. The coating is autocatalytic and does not require continuous exposure to moisture for the development of full properties. A series of soybean oil-based polyols were synthesized by treating either the raw oil or epoxidized soybean oil (ESO) by a variety of reagents including long chain fatty acids.

In a series of model reactions the above polyols were reacted with various diisocyanate compounds, at molar ratio of NCO/OH=1.5:1-3:1 to obtain prepolymers with residual NCO% of around 1.8. The isocyanate-free moisture curable resin was obtained by capping the prepolymer with of aminosilane followed by the addition of a small amount of methanol. Typical clearcoat formula-tions become tack-free in less than an hour, recoatable in about one hour, and reach a functional cure stage in 24 hr at 40% RH and 25°C.