Wood Adhesives from Phenolysis Lignin

The lignin extracted from steam exploded pulp was phenolated in the presence of sulfuric acid. The degree of phenolation was calculated to be in excess of one mole/lignin (C9) unit on the basis of 13C NMR measurements. The phenolated lignin was methylolated in order to prepare adhesive resins. The cure behavior of the adhesive resins was examined by Torsional Braid Analysis (TBA). Results revealed that the phenolated steam explosion lignin-based resins had intrinsic retardation in cure as compared to a commercial phenolic resin. This defect, however, was partly overcome by increasing their pH values. The adhesives from these resins generally provide excellent bond strength comparable to phenolic resin.