Pulping properties of tropical acacias.

Abstract

Bleached kraft (sulfate) and unbleached neutral sulfite semi-chemical (NSSC) pulps were prepared from Queensland-grown 12-year-old Acacia aulacocarpa, 10-year-old A. cincinnata and A. crassicarpa of unknown age. The basic densities were 598 kg/m³ for A. aulacocarpa, 580 kg/m³ for A. cincinnata and 638 kg/m³ for A. crassicarpa. The screened yields from the kraft process were 55.4% for A. aulacocarpa, followed by 53.1% for A. cincinnata and 47.2% for A. crassicarpa. The pulp yields from the NSSC process followed the same ranking. The A. aulacocarpa kraft pulp could be bleached to 84.6% ISO brightness with moderate chemical consumptions, compared with only 76.7 and 72.2% ISO, respectively for the A. cincinnata and A. crassicarpa pulps. The bleached kraft pulp from A. aulacocarpa was the strongest, followed by A. crassicarpa and then A. cincinnata. It is suggested that all three acacias would be suitable for a wide range of end products. The NSSC pulps would be strong enough to supplement kraft pulps in unbleached packaging products. A. aulacocarpa compares favourably with A. mangium and A. auriculiformis, especially in terms of pulp yield per cubic metre of wood. A. cincinnata is also acceptable, but further samples of A. crassicarpa of known age are needed to verify the suitability of this species as pulpwood.