| E.ucalyptus as an important fast-growing hardwood timber species, with an excellent performance of pulp and paper, with its pine pulp and paper thickness, and the paper is soft, flexible, and sheet-forming Well, the advantage of transparency. Compare with other timber species, eucalyptus pulp fiber content less wee fiber, have good drainability and drying properties, particularly suitable for the production of printing paper, writing paper and thin pages. Vigorously develop eucalyptus pulp, to alleviate China's Paper Industry irrational structure of the material contradictions is of great significance.The research use the E.urophylla×grandis as rawmertarial, study the pulpability and bleaching ability by different bleaching process, at the same time study the biobleaching mechanism. Conclusions were as follows:(1) E.urophylla×grandis from Leizhou contains 77.33% holcellulose, 47.89% cellulose, 26% lignin and 1.48% bezene-ethanol extraction. The length of fiber is 1.05mm, the width of fiber is 13.40μm, and L/W is 78.36. The KP-AQ cooking condition is: dosage of alkali (based on Na2O)15%~17%, sulfidity (based on Na2O)20%~22%, dosage of disperse AQ 0.05%, up-time 110min, hold on 90min, maximum temperature 165~170℃, liquor to wood ratio 5:1.(2) General D1-E-D2-P bleaching result is: brightness is 81.1%ISO, viscosity is 972ml/g. Using Mg (OH) 2 instead of Na (OH) D1-E-D2-P bleaching result is: brightness is 81.0%ISO, viscosity is 931ml/g. Brightness of Oxygen delignification Lignin is 58.4%ISO, viscosity is 914ml/g, Kappa is 7.76. O-D1-E-D2 bleaching result is: brihtness is 86.0%ISO, viscosity is 872ml/g; O-D-E-P bleaching result is: brightness is 85.4%ISO, viscosity is 883ml/g.(3) An optimum process of biobleaching treatment could be the dosage of xylanse 10U/g, treating time of 90min, treating temperature of 60℃, pH 6.0, pulp consistency of 10%. E.urophylla×grandis KP-AQ pulp was bleached in this condition with the enzyme. The brightness of biobleached pulp is55.2%ISO, Kappa value is 8.38, and the viscosity was increased to 990ml/g. The biobleaching by xylanse can impove the pulp bleaching ability in some degree. The burst index, tear index, tensile index and breaking length are increase.(4) In O-X-Mn-P bleaching process, dosage of KMnO4 0.6%, the brightness of pulp is 80%ISO, and viscosity can above 800ml/g. In light or super light ECF bleaching process, O-X-A-D1-Ep-D2 is better than other method, when dosage of chlorine 0.95%, the brightness of pulp can above 85%ISO. In the same brightness, O-X-A-D1-Ep-D2 can save 60% ClO2 than O-D1-E-D2, and 40% ClO2 than O-D1-Ep-D2.(5) Compared to the contrast pulp, the content of pentosan reduced 3.51%, the content of Klason lignin reduced 0.12%, and the crystallinity of the biobleached pulp don not have changed with unbiobleaching pulp.According to SEM, the surface of the unbiobleaching fiber is smooth, and the surface of the biobleaching fiber is not smooth and has some holes. According to IR and UV, biobleach can increase free hydroxide radical, and increase hydrogen bond. At the same time, biobleach can also degradation the pentosan, and dissolve out some lignin.
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