TAED ACTIVATED HYDROGEN PEROXIDE BLEACHING OF HARDWOOD KRAFT PULP WITH ADSORBED BIRCH XYLAN AND ITS EFFECT ON PAPER PROPERTIES

摘要

The adsorption of xylan on pulp fibers improves the strength properties of paper. However, die brightness is decreased significantly. The objectives of our research were to bleach hardwood kraft pulp with adsorbed birch xylan by TAED (tetra acetyl ethylene diamine) activated hydrogen peroxide and also investigate the effect of bleaching parameters on paper properties. The bleaching parameters studied included molar ratio of TAED to H2O2, bleaching temperature, retention time as well as initial bleaching pH. The optical properties (brightness, post color number) and physical properties (tensile index, tearing index) of handsheets made from the bleached pulp with different bleaching variables were measured. Suitable molar ratio of TAED to H2O2 for bleaching the hardwood kraft pulp with adsorbed xylan was suggested as 0.1. Furthermore, the experimental results showed that bleaching with extended retention time, increased temperature, and an initial pH of 11 lead to higher brightness and less brightness reversion. On the other hand, better strength properties were obtained with shorter retention time, lower bleaching temperature and decreased alkalinity. Finally, through the comparison with conventional H2O2 bleaching, it is proved that TAED activated H2O2 bleaching system can accelerate the reaction rate and shorten bleaching time at relative low temperature and neutral pH, which has significant benefits in terms of retaining fiber quality, improving brightness, and reducing of production cost.