The Application Of Enzyme Treatment On The Papermaking Of Secondary Fiber Induced Wrapping Tissue Paper And Its Mechanism

The most familiar drawback of using waste paper as raw material of tissuewrapping paper is its high production cost and pollution load deinking process,though it could protect forest resources effectively. Modern enzymatic deinkingtechnology could not only overcome those shortcomings but also has other advantagesas chemical dosage saving, low waste water pollution and pulp property improvement.Hence, In this thesis, the enzyme was applied in deinking and beating processes withthe aim of producing secondary fiber blended bleached kraft softwood based tissuewrapping paper pulp which is suitable for high speed paper machine.Firstly, the lipase and cellulase deinking processes were optimized. In addition,the enzyme deinking mechanism was exploited by using XPS, ESEM, fiber qualityanalyzer and so on. Secondly, the enzymatic beating process was optimized, theprediction empirical model for pulp beating degree was established based on beatingrevolution and enzyme dosage. Then the enzyme beating mechanism was analyzed bythe fiber quality analyzer, ESEM and the X-ray diffractometer. The influence of ratioof deinking pulp and bleached kraft pulp of softwood on the properties of paper wasalso studied eventually.The effect of lipase and cellulase on the mixed office waste paper deinkingefficiency were studied. The optimized condition of office wastepaper lipase deinkingprocess: Enzyme dosage30U·g^-1, Enzyme treatment time15min, Enzyme treatmentconcentration9%, Pulping time8min, pH7⁷.5, Enzyme treatment temperature50⁵5oC, Emulsifier dosage0.05%, the dust of deinking pulp could achieve12.33mm2·m^-2. The optimized condition of office wastepaper cellulase deinking process:Enzyme dosage1.2U·g^-1, Enzyme treatment time15min, Enzyme treatmentconcentration9%, Pulping time8min, pH4.5⁵, Enzyme treatment temperature55⁶0oC, Emulsifier dosage0.05%, the dust of deinking pulp could achieve10.40mm2·m^-2. After hydrogen peroxide bleaching, lipase deinking pulp and cellulasedeinking pulp’s whiteness were85.60%ISO and83.95%ISO respectively.Through the comparison of the ink particle size on pulp before and after enzymatic treatment, the quantity and area of the ink particles of lipase and cellulasedeinking were found lower and smaller than the control pulp. According to the resultfrom ESEM, pulp fiber’s surface became smooth and clean after cellulase and lipasedeinking processing. Meantime, the micro fiber filaments were also observed incellulase deinking pulp. The test result of deinking pulp fiber analysis showed thatcompared with the control pulp, the lipase deinking pulp fiber length of numberaverage length and weight average length basically remained unchanged, the widthwas slightly lower. However, both number average length and weight average lengthof cellulase deinking pulp fiber were slightly lower and also the width was reduced.Informed by XPS analysis, After cellulase and lipase deinking, the pulp’s O/C becomelarger. It confirms that the size of ink （mainly composed of C element） decreasedsignificantly.Through the single factor analysis, the effects of beating enzyme to promote thebleached kraft pulp of softwood beating efficiency were studied: Enzyme dosage0.06U·g-1, Enzymatic pretreatment temperature60oC, Enzyme processing time30min,Beating revolution7500r, Beating concentration10%. the pulp beating degree is57.0°SR under the optimal conditions. After beating pulp, the tensile index and tear indexof paper were85.13N·m·g-1and9.41mN·m2·g-1. For without and after enzymetreatment pulp, under different beating degree, Paper’s physical strength was foundonly related to the beating degree, It is independent of the pretreatment method andcondition variables. It confirmed that the essence of the enzymatic beating was notimproved the physical strength properties of the paper, but reduced energyconsumption in the same strength beating performance of paper. To analysis thequantitative mathematical relations between enzyme treatment process and reductionof energy consumption of beating, In this paper, firstly, we fixed other factors, andthen analysised corresponding relation of both beating revolutions with beating degreeand enzyme dosage with beating degree. The pulp beating degree experienceprediction model could be established as:y （x）（y AeR0x210）; Aftertransformation we could get the relation of beating revolutions and beating degree under different pretreatment conditions: Based on the equation, we could obviously find that enzyme treatment could significantly reduce the beating revolution,when it achieved the same beating degree. For example, When dosage of enzyme was0.10U-g-1and beating degree was at45°SR, beating revolutions could reduce about10%. In addition, with ESEM observing the surface’s microscopic characteristics before and after beating pulp, we could find that the fiber surface had some fragments and small components, and meantime, it also had some holes and cracks after enzyme treatment, It indicated that the beating enzyme can slightly cut off or improve performance of the fiber surface. Under the same beating conditions, After the enzyme treatment, the value of Zeta increased, and the water retention value increased by6.4%. The results of fiber quality analysis proved that if the pulp has been treated by beating enzyme, the number average length, weight average length both increased, fiber width and fines content decreased and the kink on average rate of fiber increased. According to the analysis results of the XRD, the crystallinity of cellulose not changed significantly.When the ratio of bleached kraft pulp of softwood and deinking pulp was80:20, The tightness, tear index and breaking length of paper were0.65g-cm-3,7.4mN·m2·g-1and5.5km. performance index of the paper could reach the national standard of tissue paper. The whiteness was85.80%ISO. In the paper, The number of ink which size in the range of0.3mm2-1.0mm2was zero。...