Soybean Oil Based Polyurethane Coatings

Epoxidized soybean oil is a commonly known plasticizer. We have reacted it with diisocyanates to obtain isocyanate-terminated prepolymers, which can be utilized as raw materials for a number of polyurethane products. An epoxy ring in epoxidized oils is not very reactive, and fairly drastic conditions and specific catalysts are required to produce prepolymers suitable for coatings. The prepolymers from epoxidized soybean oil prepared in our laboratory showed good shelf stability and were used as a base for developing a new class of polyurethane coatings. The coating samples were prepared by reacting the prepolymers with crosslinkers, such as water, glycerin, PPO 240, PPO 168, Curene 185, Thanol LS, Thanol R-310, Versalink 250 and TMP. Soypolyol 206, Soypolyol 180, Soypolyol 160 (the numbers refer to the OH number), which were original products developed in our institute, were used as crosslinkers. The samples based on water, glycerin, Curene 185, Thanol R-310 and trimethylol propane, possessed good hardness and scratch resistance but they were brittle. The coatings of the superior properties were obtained by using soybean oil based polyol as the crosslinker. They displayed very good adhesion and excellent elasticity, hardness and scratch resistance. The soybean oil content in the coatings was about 60%.