Succinylation of three different lignins by reactive extrusion

Succinate esters of three lignin materials were prepared by reactive extrusion. Reactive extrusion was developed as a facile route to chemically modify lignin with the benefits of being a scalable, solvent‐free, and economic process. Kraft lignin and crude and purified enzyme saccharification lignins were reactively extruded with varying amounts of succinic anhydride. The resulting products were characterized chemically and thermally. Succinylation occurred preferentially at the aliphatic hydroxyl groups of kraft lignin, with phenolic substitution occurring at higher amounts of succinic anhydride addition. The degree of substitution was dependent on the relative amounts of succinic anhydride and lignin substrate. Thermal stability of the products decreased with increasing levels of substitution, primarily due to the loss of succinate groups on heating. The degree of substitution influenced the glass transition temperature, which reflected the melt flow and solubility of the products. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013