Chemical investigations of modified lignin and high-yield wood pulp

Today's market demands papers of increasingly high strength and long-lasting brightness, which severely limits the use of high-yield pulps. It has been the goal of many researchers to increase strength or inhibit yellowing of high-yield pulps, so that they may be substituted for chemical pulps for the production of higher quality papers.;This research investigated the simultaneous improvement of both the brightness stability and strength properties of high-yield wood pulp. The strategy herein involved a single, selective chemical modification of the free phenolic hydroxyl groups in the lignin component of high-yield wood pulp with a substituent designed to both inhibit photo-induced yellowing and increase hydrophilicity. The substituent utilized in this work was poly(ethylene glycol) methyl ether (or MPEG). The MPEG modification of high-yield wood pulp has been approached in a step-wise fashion. Appropriate reaction conditions have been developed by utilizing lignin model compounds. The methodology was then transferred to isolated lignin, and to the modification of wood pulp. The overall aim was to improve the quality of high-yield pulps so that they may be substituted for chemical pulps in some grades of paper.;The results indicate that lignin model compounds can be derivatized in yields of 60-80% at the phenolic hydroxyl position using MPEG. The structures of these derivatives have been confirmed by ;The reaction procedure developed for the model compounds also accomplished the derivatization of organosolv cottonwood lignin. This was confirmed by ;Modified high-yield pulps produced by this reaction procedure showed some enhancement of brightness stability relative to controls. No improvement in strength properties was achieved by this modification.