A New Soybean Oil-baseo Reactive Diluent for Low VOC Solvent-borne Wood Stains

摘要

Solventborne coatings are facing increasingly strict volatile organic compounds (VOC) regulations. It is a challenge to reduce their VOC content while maintaining their low cost and high performance. In this study, we have developed a low-cost, soybean oil-based reactive diluent that can significantly reduce the VOC contents of solvent-borne air-drying alkyd wood stains. The reactive diluent was synthesized by a two-step process. A soy intermediate composed of a mixture of mono-hydroxyl functional soy derivatives was first prepared by reacting soybean oil with mono-hydroxyl functional amines such as ethanolamine. The structure and composition of the soy intermediate were characterized with FTIR and NMR. A star-branched reactive diluent was then obtained by reacting a multifunctional core molecule with the soy intermediate and a polyol. The reactive diluent was formulated into 250 g/liter VOC wood stains in combination with a fast-drying alkyd resin to evaluate its effect on the drying performance of the stains. A 550 g/liter VOC wood stain formula based on the same fast-drying alkyd resin and a 250 g/liter VOC wood stain formula based on a 100% solid alkyd resin were used as the controls. The results revealed that the reactive diluent-based, low-VOC stains have comparable or better drying performance over the controls. In addition, it was observed that the reactive diluent not only improves the stability of the pigments in the stains but also enhances stain penetration into wood substrates. The reactive diluent is also an effective grinding and dispersing medium for inorganic pigments in preparing zero VOC tinting paste.