Drainage And Retention And Strengthening Effects Of Enzymes In Papermaking

Modification with enzymes consisting of cellulases and hemicellulases can promote fiber drainage and operating characteristic, so as that the qualities of pulp and sheet can be improved significantly. Enzymatic modification to natural fiber can be used to be one of the substitutions of chemical agents to some degrees, which can play an important role in drainage, retention and strengthening effects in paper making.The modification of enzymes to some kinds of HYPs was discussed and the optimum processes of enzymatic treatment were choosed in this paper with drainage improvement considered as the main target. Promotion of enzymatic modification to drainage, retenting and strengthening of pulp was discussed further. The Zeta potential tester FQA, XRD, and ESEM were used to analyze the effects of enzymatic modification on fiber qualities and surface properties.Firstly, the results of cellulase modification on APMP indicated that the best effects of drainage, retetion and strengthening turned out after enzymatic modifying for 60 min, with the dosage of 0.3U/g BD pulp, the consistency of 1.0%, the beginning pH value of 4.5, the temperature of 45℃. And after enzymatic treatment, the beating degree decreased by 6.5°SR, the dynamic drainage time reduced by 4.8 s, the retetion of fines increased by 71.61%, the effect of AKD sizing promoted a little, and the breaking length, the bursting index, and the tearing index increased by 6.15%, 9.52%, and 4.02% respectively. Analysis of fiber qualities and surface properties showed that the contents of fines declined, the fiber length and coarseness increased, the curl index and kink index decreased, the degree of crystallinity rosen, and the fiberillation deduced.Secondly, the results of xylanase modification on APMP indicated that the best effects of drainage, retetion and strengthening turned out after enzymatic modifying for 30 min, with the dosage of 1.5U/g BD pulp, the consistency of 0.5%, the beginning pH value of 7.0, the temperature of 45℃. And after enzymatic treatment, the beating degree decreased by 4.5°SR, the dynamic drainage time reduced by 2.8 s, the retetion of fines increased by 61.33%, the effect of AKD sizing promoted a little, and the breaking length, the bursting index, and the tearing index increased by 4.67%, 23.02%, and 12.95% respectively. Analysis of fiber qualities and surface properties showed that the contents of fines declined, the fiber length and coarseness increased, the curl index and kink index decreased, the degree of crystallinity rosen, and the fiberillation deduced.Thirdly, the results of pectase modification on BCTMP indicated that the best effects of drainage, retetion and strengthening turned out after enzymatic modifying for 60 min, with the dosage of 1000ppm/g BD pulp, the consistency of 1.0%, the beginning pH value of 4.5, the temperature of 45℃. And after enzymatic treatment, the beating degree decreased by 4.5°SR, the dynamic drainage time reduced by 2.3 s, the retetion of fines increased by 24.38%, the effect of AKD sizing promoted, and the breaking length, the bursting index, and the tearing index increased by 1.51%, 15.31%, and 26.01% respectively. Analysis of fiber qualities and surface properties showed that the contents of fines increased a little, the fiber length unchanged, the fiber coarseness increased, the curl index and kink index decreased, the degree of crystallinity rosen, and the floccule on and between fibers deduced.Finally, the results of complex cellulases modification on groundwood pulp indicated that the best effects of drainage, retetion and strengthening turned out after enzymatic modifying for 60 min, with the dosage of 600ppm/g BD pulp, the consistency of 1.0%, the beginning pH value of 7.0, the temperature of 45℃. And after enzymatic treatment, the beating degree decreased by 4.0°SR, the dynamic drainage time reduced by 1.9 s, the retetion of fines increased by 47.74%, and the breaking length, the bursting index, and the tearing index increased by 5.87%, 12.87%, and 6.09% respectively. Analysis of fiber qualities and surface properties showed that the contents of fines increased a little, the fiber length declined, the fiber coarseness increased, the curl index and kink index decreased, the degree of crystallinity rosen, the fiber abundle and fiber debris deduced, and some small dent and decortication appeared on fiber surface.