| In this work, effects of modification of secondary-fiber pulp with cellulases on pulp drainage and paper sheets were studied, the optimal process was worked out, and on the base of the optimal process, effects of sequences of refining, different secondary-fiber pulps and different enzyme systems on modification of secondary fiber were researched. The main conclusions are as follows:With studying effects of factors named pulp concentration, pH, temperature, dosages of enzyme and time on modification of secondary fiber, the concluded optimal process is 3-5% pulp concentration, pH5.0-6.0, 50-60℃, 0.3IU/g oven-dried pulp and 1.0-1.5h.After modification under the optimal conditions,Schopper-Riegler is decreased by 5.5゜SR, break length nearly have no change but tear index is dramatically damaged.Sequences of refining affect drainage of cellulase-modified pulp. After modification, refining of 1000 and 3000 revolutions improved drainage of pulp. Respectively, Schopper-Riegler were decreased by 7.0゜SR and 6.8゜SR , break length 2.29% and 7.75%,tear index 26.16 and 7.51%. Respectively, compared with unrefined pulp, Schopper-Riegler are decreased by 4.5゜SR and 4.3゜SR , break length were increased by 7.35% and 12.5%,but tear index decreased by22.39% and 23.90%.With refining of 6000 revolutions after modification and refinings before modification, drainage and strength properties were destroyed.Types of waste paper is one important factor affecting cellulase modification of secondary pulp. Under the same conditions, Schopper-Riegler of ONP was decreased by 11.3%, break length 3.31%,and tear index 20.88%; Schopper-Riegler of MOW was decreased by 15.97%, break length 6.93%,and tear index 12.63%; but drainage and tensile strength of OCC had no change, only tear index was decreased by 31.74%. |
