SLIGHTLY OXYGEN-DELIGNIFIED MASSON PINE KRAFT PULP AND ITS IMPACT ON PULP COLOURATION

The brown paper is growing fast due to a larger number of market demands in China. However, the colouration of paper sheet is usually hard to maintain stability if only by means of interior stock dyeing. So, in order to solve this problem, in this paper, slight medium consistency oxygen-delignified bleaching was used to improve the brightness and colouration of kraft pulp. Masson pine kraft pulps with similar to 55 Kappa number were slightly bleached through the orthogonal experiments, and the chromatic aberration principle was utilized to analyze the experimental results. The optimal parameters of the slight oxygen delignification for kraft paper were oxygen pressure 0.3MPa, temperature 85 degrees C, reaction time 20min, 3% of NaOH, and 0.5% of MgSO4; colour parameters were L* 67.58, a* 5.68, b* 21.89, and the brightness was 23.0%ISO, according to the target kraft paper. The slight oxygen delignification is hence a suitable bleaching for kraft paper.