Evaluation of Kraft-PS Cooking for Eucalypt and Pine Wood Chip Mixtures

Abstract

The purpose of this study was evaluating polysulfides (PS) as additives in kraft cooking of wood mixtures eucalypt (E) and pine chips (P) wood mixtures, namely: 50E/50P, 70E/30P, and 90E/10P. Bleaching (O(D/A)(EP)D) and refining of pulps were also investigated. The PS addition (1.5 or 3.0%) to the kraft cooking preserved the hemicelluloses resulting increased pulp yield and reduced H-factor. The oxygen delignification was more efficient for chip mixtures containing higher proportion of pine chips, but was not largely affected by the addition of PS. The bleach chemical consumption was not significantly influenced by PS dosage or by the wood chip mixture. The burst and tear indexes were improved by increasing the proportion of pine chips to the mixture, but an opposite effect was observed for refinability, tensile index, and opacity. The kraft-PS pulps showed increased refinability, tensile, and burst strengths in relation the standard pulps, but lower opacities.