An important suitability parameter of pulps produced from industrial hemp is their bleachability. The research outlined
here enables a comparison to be made of the bleachability of pulps produced from semi-manufactured hemp products and that of birch- and pine kraft pulp. In this study, oxygen-delignified hemp- and birch pulps of kappa number 10 - 12 and pine pulp of kappa number 13 were used. Pulp samples were bleached with chlo- rine dioxide (the elemental chlorine free (ECF) bleaching) and hydrogen peroxide (the total chlorine free (TCF) bleaching) as the main bleaching agents. In the ECF bleaching (D stages), a ratio of 3% ClO2 to oven-dried pulp was used.
The results of pulp bleaching, i.e. their R457 brightness levels, are presented in Figure 3 compared with their initial (unbleached) brightness values