Synthesis and properties of self-matte polyurethane emulsions with high bio-based content

To solve the problem of poor film flatness of matte waterborne polyurethane (WPU) prepared with additional matting agent and the shortcomings of poor water and heat resistance of vegetable oil-based WPU, the bio-based emulsifier monotrihydroxyethyl isocyanurate succinate (SATH) was prepared by using succinic anhydride and trihydroxyethyl isocyanurate and used together with sodium salt of 2-(2-aminoethyl)aminoethanesulfonate (SAAS) to prepare castor oil-based self-matting WPU. Compared with the WPU prepared using dimethylolpropionic acid, the WPU prepared using SATH showed better water and heat resistance, with a reduction in water absorption from 34.31% to 15.23%, an increase in the initial decomposition temperature of the films from 181.33 degrees C to 224.61 degrees C, and a reduction in gloss from 6.5% to 6.0%. With the increase in R-value (molar ratio of NCO/OH), the emulsion particle size decreased and gloss increased; however, too high R-value easily led to too many side reactions in the emulsification stage, which was not conducive to obtaining a flat film; with the increase in SATH additive amount, the emulsion particle size increased and then decreased, and the film gloss decreased and then increased. Finally, a bio-based self-matting WPU with a high bio-based content of 60% and a low gloss of 6.0% was obtained.