水杉制浆性能的研究

Pulping of Metasequoia Glyptostroboides

本文研究了水杉(Metasequoia glyptostroboides)烧碱-蒽醌法和硫酸盐法的蒸煮性能,并取得了得率,卡伯值和平均聚合度与各种蒸煮参数的回归方程和最佳蒸煮条件。对最佳条件下的烧碱-蒽醌、硫酸盐法和烧碱法三个蒸煮过程的反应历程进行了对比研究。同时,对水杉材的漂白性能和浆的物理性能也作了一定的研究。

The fiber morphology and chemical composition of M. glyptostroboides were studied. Compared with fir and spruce wood, the fiber length of M. glyptostroboides was longer, the ratio of wall to cavity was smaller, and the content of α-cellulose needed for papermaking was higher. Soda-AQ and kraft pocess were employed for the digestion of M. glyptostroboides and results were compared. The relationship of pulp yield, Kappa number, averag degree of polymerization with the various cooking conditions, such as maximum temp., time at temp., charge of alkali andAQ, could be expressed by multinomial exponential equations. Optimum conditions for soda-AQ cooking of M. glyptostroboides were: maximumtemp.170℃ time at temp. 9Omin., charge of alkali (as Na_2O) 18% (based on OD wood), charge of AQ 0.30%, and liquor ratio 1∶4. Under these conditions, screened pulp yield of 48.01% and Kappa number 23.3 were claimed. Optimum conditions for kraft cooking were: max. temp.170℃, time at temp. 9Omin., charge of alkali (as Na_2O) 18% (based on OD wood), liquor ratio 1∶4, and sulfidity 25%. Under these conditions, screened pulp yield of 45.05% and Kappa number 24.6 were claimed. Therefore, cooking property of M. glyptostroboides in soda-AQ process, was superior to that in kraft process. The mechanisms of three pulping processes, soda-AQ, kraft, and soda, were also studied and compared. Delignification of soda-AQ and kraft was exercised in three phases: initial, bulk and residual delignification. The initial phase appeared from the beginning and ended when temp. reached 150℃, with a lignin removal of 20%. The bulk phase, from 150℃ to 170℃, lasted for 45 min. and the amout of lignin removed was 70%. The residual phase continued for the rest ofthe cooking period and only 8% of lignin was removed in this phase. The mechanism of delignification of soda-AQ was similar to that of kraft since the delignification curves of the two processess were very much alike. However, compared with kraft pulping, soda-AO pulping consumed Jess alkali, with less carbohydrate, being dissolved out. However, much similar pulp yield and α-cellulose content were reported. Bleaching of M. glyptostroboides pulps and their papermaking characteristics were also studied. The brightness of a CEHP bleached pulp from the soda-AQ process was 4% lower than that from the kraft process, chiefly due to the fact that unbleached soda-AQ pulp was at lower starting brightness. But the yield of bleached pulp from soda-AQ process was 3-4% higher, than that from kraft process, while tear strength of soda-AQ pulp was 22% lower than that of kraft, breaking length, folding endurance and bursting of soda-AQ (unbleached and bleached) were comparativly in a better position.