Study On Effects And Mechanism Of Enzymatic Pretreatment On The Properties And Refining Energy Of Masson Pine TMP

Thermo-mechanical pulp (TMP) of Masson Pine is a kind of high yieldpulping that comes with the comprehensive utilization of wood. TMP has lots ofbenefits, such as simple process, low pollution, good bulkiness, fine printability,higher opaqueness and light-scattering coefficient and so on. However, thedisadvantages of TMP including higher refining energy and pulping cost, lowerdegree of external fibrillation and fiber bonding strength, and the fiber is stiffbecause of the insufficiency soften action. It can increase the degree offibrillation and improve the quality of TMP using enzymes to pretreat the rawmaterials before refining, and also can reduce the energy consumption.In this paper, cellulase and acid xylanase were used to pretreat the TMP ofMasson Pine before refining. The effects of enzymes pretreatment on the TMPproperties and pulping energy consumption were studied. The change of pulpproperties and fiber characteristics during the refining in the TMP process wascontrastively analyzed. And the wet-end chemistry characteristics of enzymespretreated TMP were studied. Through the test and analysis of zero span tensilestrength, internal bond strength, cellulose crystallity, contact angle, AFM(atomicforce microscope), SEM(scanning electron microscope), infrared spectroscopyand TGA(thermal gravimetric analysis), the acting mechanism of cellulase andxylanase pretreatment on the TMP of Masson Pine was studied.The optimum applications of cellulase were: dosage75IU/g，temprature50℃, pH5.5, time150min. After the pretreatment of cellulase, the paperstrength, bulk and longer fiber yield increased. It is not suitable for the dosage ofcellulase exceed75IU/g，otherwise the tensile strength of paper would decreased.The pretreatment of cellulase on Masson Pine TMP decreased the refining energy. And the descent rate of refining energy increased with the increase ofcellulase dosage and pretreatment time. The quantities relationship betweencellulase dosage, pretreatment time and the refining energy were established byCurve fitting analysis and Logistic monadic regressive analysis.The optimum applications of xylanase were as follows: dosage90IU/g，temperature50℃, pH5.0, time150min. After the pretreatment of cellulase, thepaper strength, bulk and longer fiber yield increased. It is not suitable for thedosage of cellulase exceed90IU/g，otherwise the tensile strength of paper woulddecreased.The pretreatment of xylanase on Masson Pine TMP decreased the refiningenergy. And the descent rate of refining energy increased with the increase ofxylanase dosage and pretreatment time. The quantities relationship betweenxylanase dosage, pretreatment time and the refining energy were established byCurve fitting analysis and Logistic monadic regressive analysis.The shives of TMP decreased after the pretreatment of cellulase andxylanase. And xylanase had better effect on the decrease of shives. When thedosage of xylanase was120IU/g，the shives decreased1.76%when pretreatbefore the first refining, and2.39%when pretreat before the second refining.The screening results showed that the total yield of R100increased with theincrease of cellulase and xylanase dosage. And the fine fiber of P200decreasedobviously. Pulping process of enzyme pretreatment before first refining, fiberquantity of R50and R200were significantly higher, while R100and P200werelower. Pulping process of enzyme pretreatment before second refining, thequantity of middle and shorter length components were higher.The fiber quality analysis showed that the fiber was longer when pretreatedbefore first refining. Modest cellulase pretreatment could increase the fiberlength, decrease fines and increase curl and kink index. Cellulase pretreatmentbefore first refining, the length weighted length of fiber increased0.22mm, thedosage of xylanase was very key for the fiber length.The optimum dosage of enzyme was higher when pretreatment before thefirst refining. Enzyme pretreatment before the first refining, the optimumdosages were: cellulase75IU/g, xylanase90IU/g; pretreatment before the secondrefining, the optimum dosages were: cellulase50IU/g, xylanase60IU/g. Refining proceeded after cellulase or xylanase pretreatment, the freeness ofmasson pine TMP increased slightly, cationic demand decreased obviously, andthe Zeta potential decreased.Zero span tensile strength had a higher growing rate after pretreated byxylanase. When the dosage of xylanase was60IU/g, zero span tensile strengthwas51.8N/cm, increased by15.0N/cm than the untreated pulp. When thedosage of cellulase was75IU/g, zero span tensile strength was45.1N/cm,increased by8.3N/cm, and the internal bond strength was0.031N/cm, increasedby0.016N/cm than the untreated pulp. When the dosage of xylanase was90IU/g, the internal bond strength was0.028N/cm, increased by0.012N/cm thanthe untreated pulp.The XRD and TGA analysis showed that the crystallinity of Masson PineTMP cellulose decreased after cellulase pretreatment, while increased afterxylanase pretreatment. And the pretreatment of xylanase and cellulase improvedthe thermo stability of Masson TMP fiber.The contact angle of the paper surface decreased after cellulase pretreatment,demonstrated that the wettability of fiber improved. When the dosage ofcellulase was50IU/g, at the time of0.2s, contact angle was33o, decreased by9o.When the dosage of xylanase was90IU/g, the wettability of fiber improved, andat the time of0.2s, contact angle was38o, decreased by4o.SEM showed that after cellulase pretreatment, fiber crushing collapse andlongitudinal rip obviously, internal fine fibrosis increased, produced filamentousfines and fragments of fiber. While after xylanase pretreatment, fragmentsbreakaway obviously, assumed that fragments fiber adhere to fiber surface, partof the cell wall thinking.AFM showed that after cellulase pretreatment, the surface roughness ofTMP fiber decreased, while after xylanase pretreatment, the surface roughness ofTMP fiber increased...