Production of depolymerized lignin resin material from lignocellulosic biomass using acetone–water binary solution

• Lignin was successfully separated from biomass and converted into resin material.
• The key for uniform curing was clarified to be a depolymerization of lignin.
• A half amount of fossil-derived resin material was able to be replaced by biomass derivatives.
• The proposed method was effective on some types of biomass.

The use of lignin, one of the main components of biomass, has only been for the recovery of energy through the combustion due to its complex structure. However, it needs to be used as more valuable material to make biorefinery feasible. In this study, the development of the lignin conversion method into resin materials was examined. Lignin was extracted from biomass with acetone/water binary solution at 220 °C. The extracted lignin solution was treated under the severer condition for the depolymerization using flow reaction system. Through these two-step treatment, the extracted lignin was depolymerized to Mw < 1000 fractions, which possessed many active sites for curing. More than 76.8% of lignin were recovered as depolymerized lignin through the whole treatment. The depolymerized lignin showed a fine activity of uniform curing with 10–15 per hundred resins (phr) of hexamine at 150 °C. This resinification method of lignin was confirmed to be adaptive to some types of biomass, despite the belonging groups such as a coniferous tree, a broadleaf tree, or herbaceous biomass. One of thus produced resins was confirmed to be the competitive resin with a conventional phenolic novolac resin.