Novel polyesters for hotmelts and adhesives from black liquor

One major side stream in paper industry is the black liquor from kraft pulp process. Black liquor consists of numerous degradation products of polysaccharides among which up to 29 wt% of black liquor dry content consists of a broad range of different, mainly hydroxy acids. These acids include glycolic acid (GA), racemic lactic acid (LA), and racemic 2-hydroxybutyric acid (2HBA). The possibility to utilize the three components in interpolymers eg. hotmelts with varying compositions without further separation reduce the need of challenging fractionation technologies in future biorefineries.

Copolymerization of three smallest a-hydroxy acids, GA, LA and 2HB, can be performed with similar polymerization procedure as copolymerization of GA and LA. These results give basis for the further studies regarding the utilization of sustainable black liquor based hydroxy acids as monomers. After the copolymerization these novel polyesters may be used as hotmelts and adhesives.