Effects of loblolly pine tree age and wood properties on linerboard-grade pulp yield and sheet properties: Part 1 - Effects on pulp yield

Abstract

Results are reported on the relationships of loblolly pine tree age and wood characteristics and the yield of pulp obtained when the trees were chipped and pulped by the kraft process. Eighteen 13-year old and 18 22-year-old loblolly pine trees were selected to represent specified ranges of specific gravity and lignin content. The trees were further characterized by chemical analysis and near infrared spectroscopy before kraft pulping. The resulting pulps were characterized by measurements of yield and chemical analysis. Multiple regression analysis was used to identify wood characteristics that most influenced pulp yield and to derive equations relating pulp yield to tree age, specific gravity, and wood chemical composition. In addition, near-infrared spectroscopy calibrations were developed to allow prediction of pulp yield from analysis of wood. The results showed that wood specific gravity cannot be used to predict the yield of linerboard-grade pulp from trees of either age. The yield of pulp from 13-year-old trees can be predicted from the amounts of xylan and lignin present in the wood. The yield of pulp from 22-year-old trees decreased with increasing lignin content but was unrelated to xylan content. Thirteen-year-old trees had significantly higher xylan content and the excess xylan was lost during pulping. Regression equations were developed for estimating pulp yields from 13- and 22-year-old trees, given their xylan and lignin contents. Another equation derived from the combined data for trees of both age classes will be useful for predicting yields from trees of other ages, if it is assumed that the effect of tree age is linear.