Methylation of softwood and hardwood kraft lignins with chloromethane

Methylation is a well-established means of enhancing the thermal stability, improving the compatibility in polymer blends, and lowering the glass-transition temperature of lignins. This process normally involves reagents that are costly, associated with poor atom economy and/or highly toxic. Herein, we report the methylation of softwood and hardwood kraft lignins using chloromethane in alkaline aqueous media. This reaction proceeds in high yields at 90-110 degrees C under moderate pressure (40 psi) while generating environmentally benign sodium chloride and water as by-products. A green methodology for the methylation of kraft lignins with chloromethane has been developed.