Pre-extraction of hemicelluloses from bagasse fibers: Effects of dry-strength additives on paper properties

The aim of this study was to further evaluate the viability of the integrated pulp mill biorefinery concept. On one side the properties of hot-water pre-extractions were studied, in order to determine the effect of extraction on soda pulping and bleachability. On the other side, the performance of two dry-strength agents on the paper properties obtained from extracted and un-extracted (control) samples were investigated. It was found that hemicelluloses removal of the depithed bagasse chips was 24.6% at 140 degrees C for 10 min with a solid to liquor ratio (S:L) of 1:8 (w/w), and that mass removal increased with extraction time and temperature. The hemicelluloses removal reached 65.5% at 170 degrees C for 30 min. The residual extracted bagasse were subjected to soda pulping at 160 degrees C for 1 h with 11, 14 and 17% active alkali charge and a S:L of 1:5 (w/w). Conventional elemental chlorine free bleaching (D0ED1) sequence was also used to compare the results with the un-extracted ones. Compared with the control sample, the overall pulp yield for extracted bagasse increased considerably while Kappa number and rejects decreased moderately. In addition, yield and Kappa number of the pulps improved with increasing alkali charge from 11% to 17%. After pre-extraction, better brightness compared with the control pulp was also shown. However, hot-water extraction was found to negatively impact some pulp properties including decreases in burst and tensile indices while addition of chitosan and cationic starch could improve the strength properties. Overall, papers treated with chitosan gave superior mechanical properties compared to the papers treated with cationic starch. (C) 2012 Elsevier B.V. All rights reserved.