TOTALLY CHLORINE-FREE BLEACHING OF SODA.AQ PULP WITH LOW KAPPA NUMBER MADE FROM TRIPLOID OF POPULUS TOMENTOS

摘要

An OqpQP totally chlorine-free (TCF) bleaching sequence was investigated on a soda-AQ pulp with low kappa number made from triploid of Populus Tomentos. The results showed that the optimal conditions of OqpQP bleaching sequence were as follows: for the first OQP stage, pulp consistency 10%, DTPA 0.3%, NaOH 2.5%, H2O2 3.0%, MgSO4 0.5%, oxygen pressure 0.6MPa, temperature 100°C and time 100 min;for the second Q stage, pulp consistency 8%, DTPA 0.3%, pH value 4.0-7.0, temperature 70°C and time 60min;and for the last P stage, pulp consistency 10%, H2O2 1.52%, MgSO4 0.5%, Na2SiO3 0.7%, temperature 70°C, time 90~120min and pH value 12. A pulp with brightness 82% ISO, viscosity 716mL/g and bleaching yield 91.78% was obtained through the OqpQP bleaching sequence. Compared with the unbleached pulp, brightness of the bleached pulp was improved significantly, and viscosity decreased only slightly. The bleached pulp with such high brightness and viscosity may be used to make high quality paper.