CHARACTERIZATION OF COLLOIDAL WOOD RESIN IN NEWSPRINT PULPS

The dispersed colloidal wood resin in newsprint pulps has been characterized in samples taken from mills both during periods of pitch difficulties and during periods of smooth operation. The chemical composition of the resin particles in pitch troublesome and nontroublesome pulps resembled those of the extractives in freshly cut and seasoned wood, respectively, which suggests that pitch problems were encountered when the mills were pulping relatively unseasoned wood. Electrophoretic mobilities of the resin particles, measured as functions of pH, and particle size distributions were the same, within experimental error, in troublesome and nontroublesome pulps. Much higher resin particle concentrations were observed in pitch troublesome samples, which has led to a previously published method for forecasting or diagnosing certain types of resin problems. The shelf life of colloidal wood resin suspensions in their native process liquids is considerable; particle concentration half-lives of the order of 5 months were observed. Stability was unaffected even by relatively high concentrations of Na+, Ca2+ and Al3+, which suggests that the stability of the particles is governed by more than surface charge effects and that steric stabilization plays a role. © 1979 Dr. Dietrich Steinkopff Verlag.