Preparation of a Polyhydric Aminated Lignin and Its Use in the Preparation of Polyurethane Film

In this paper, a polyhydric aminated lignin containing both amino and hydroxyl groups was prepared by hydroxylation and amination. The temperature, the reaction time, and the composition of the reaction mixture were found to have a significant influence on the extent and rate of the hydroxylation and amination reactions. Under the optimum reaction conditions, the content of aliphatic hydroxyls in lignin increased from 1.74 to 4.73%. The amine groups, mainly primary amine groups, were also introduced into the product, which lead to the nitrogen content increased from 0.64% to 4.58%. The performances of polyurethane film containing polyhydric aminated lignin (ALPU) were significantly improved compared with those of polyurethane film using soda lignin (LPU). The polyhydric aminated lignin replaced more polyol components in polyurethane (PU) film production. The maximum tensile strength of ALPU film was about 1.7 and 4.6 times of LPU film and PU film, respectively. The thermal stability of PU was also improved because of the addition of polyhydric aminated lignin, while the thermal stabilities of ALPU film and LPU film had similar performance.