Packaging Grade Kraft Pulp from Small-Diameter Softwood, 2000 Pulping / Process & Product Quality Conference Proceedings

A. Ahmed, G. Myers, S. AbuBakr--Many forests in the interior western region of the United States consist of densely stocked small-diameter trees of mixed softwood species. These forests have a potential for large-scale insect infestations, disease, and fire. Active management of these forests is costly and will probably generate a large volume of materials with very little commercial value. Using these materials to produce certain grades of paper might bring economic and environmental benefits. The principal wood species found in these forests are western larch, Douglas-fir, and lodgepole pine. The objective of this study was to establish the suitability of kraft pulping of interior western small- diameter matured softwoods for production of packaging grades of paper from high kappa number pulps. The kraft pulping process, suitable for all wood species, was used in the preparation of packaging grade handsheets. Pulps were prepared at around 70 kappa using the same liquor concentration and liquor to wood ratio but cooking to various H-factors. The pulp yield varied significantly even at similar kappa numbers for the various wood species. Mechanical properties of handsheets differed significantly for different raw materials when compared at similar CSF and sheet density levels. Adhesion-based properties, such as tensile strength and burst index values were highest forlodgepole pine and lowest for western larch and Douglas-fir/western larch mixture. However, tear values were highest for western larch and lowest for lodgepole pine. The vacuum compression apparatus (VCA) compression test was also performed to evaluate the suitability of the pulps for packaging grade paper.