Technologies For Improving The Reactivity Of Dissolving Pulp And Its Fundamentals

Cellulose is the most abundant renewable resource in the world and playing an important part in human’s life.Dissolving pulp contained high purity of cellulose and has been applied in viscose rayon,cellulose ester,and cellulose ether.With the rapid development of textile production,the demanding of dissolving pulp would keep increasing in a high speed.For dissolving pulp,the Fock reactivity was one of essential parameter,which was determined the processiblity of dissolving pulp in downstream production.Therefore,the improvement of Fock reactivity was focused in this thesis.The PFI refining,ultrasonic and xylanase pretreatment was employed and combined with cellulase treatment,respectively.What’s more,the ionic liquid was also included here to explore the effect on Fock reactivity.The results were present as followed.PFI refining enchanced cellulase efficiency in improving Fock reactivity of dissolving.The refiner could enhance the fibrillation of fibers,thus improving the adsorption of cellulase onto fibers.Results showed that when increasing beating degree from 19 ~oSR to 50 ~oSR,the Fock reactivity was increased from 54.8%to 78%,and the cellulase adsorption ratio was increased to 35.8%from 61.3%.When combined PFI refining with cellulase treatment,the cellulase efficiency was greatly enhanced in comparison with the controls.The optimal condition was beating degree of 50 ~oSR,cellulase dosage of 0.5 mg/g,time 4 h.Under such condition,the Fock reactivity and intrinsic viscosity was 89.2%and 448 m L/g,respectively.The characteristic of treated fiber showed that the specific surface area(SSA)and water retention value(WRV)were all increased due to the fibrillation,fiber length was reducted slightly,and the fines was increased.Ultrasonic treatment enhanced cellulase efficiency in improving Fock reactivity of dissolving.The cavitation effect of ultrasonic could deconstruct the compact structure of fibers,thus increasing the cellulase reaction sites.Results showed that the Fock reactivity was improved after ultrasonic treatment.The optimal ultrasonic treatment condition was 1000 W and 2 min,which increase Fock reactivity from 54.8%to 59.7%,while intrinsic viscosity was decreased to 637 m L/g.Once combined ultrasonic with cellulase treatment,the cellulase efficiency was increased greatly,the Fock reactivity was increased to 95.8%and intrinsic viscosity was decreased to 548m L/g when using 1 mg/g cellulase and 4 h.Other results were as,alkaline solubitliy was kept constant,SSA was increased,and Cr I was decreased.Xylanase treatment enhancing cellulase efficieny in improving Fock reactivity of dissolving.The residual xylose would binded cellulose fiber tightly,which hindered the reaction site of cellulase.The synergy of xylanase and cellulase was explored to upgrade the dissolving pulp.Results showed that the synergy treatment could further remove hemicellulose and increase the cellulase efficieny in improving Fock reactivity.The Fock reactivity could increased to 88%after xylanase and cellulase treatment,and the intrinsic viscosity andα-cellulose was 94.6%,respectively.The xylanase treatment could increase cellulase efficiency through cutting the bonding between hemicellulose and cellulose,thus increasing the cellulase catalyzed sites.Ionic liquid(IL)treatment was employed to improve the Fock reactivity of dissolving pulp.IL was recognized as green solvent and used widely in biorefinery.The swellon effect of IL was expored in dissolving pulp,thus opening up the compact structure of cellulose.Results showed that the Fock reactivity of dissolving pulp was increased to 87.3%and intrinsic viscosity was decreased to 492 m L/g after IL treatment under condition of IL dosge of 5 wt%,60 ~oC and 3 h.The IL could be recovery by filtration and vacuum evaporation,thus could be reused in dissolving pulp treatment.