双组分水性聚氨酯涂料的分散和成膜

Dispersion and Film Formation of Two component Waterborne Polyurethane Coatings

研究了异氰酸酯低聚物在羟基组分中的分散、透明涂料和加颜填料涂料的成膜．由于异氰酸酯低聚物粘度高，必须有较高的剪切力才能保证其在羟基组分中的分散．透明涂料在混合后的反应是以异氰酸基与羟基的反应为主，而加颜填料涂料混合后的反应是以异氰酸基与水的反应为主．双组分水性聚氨酯涂料的成膜与溶剂型聚氨酯涂料及聚合物乳液涂料成膜机理不同。

Two component waterborne polyurethane system for wood can be formulated with hydrophilically modified HDI based polyisocyanate and hydroxyl contained polyacrylate. Due to high tension and viscosity relative to the polyol dispersion high shear is needed to disperse the polyisocyanate into the polyol. Investigation was made to compare mixing methods for dispersing. Film formation mechanism of waterborne polyurethane coating is different from solvent based polyurethane coating and polymer emulsion coating system. Pot life of waterborne polyurethane system should be determined by its hardness or gloss change with time instead of viscosity change. It is found that in clear coating of waterborne polyurethane the reaction between isocyanate and hydroxyl dominates and in pigmented coating the reaction between isocyanate and water dominates.