The Mechanism Of Inhibiting Plantfiber Performance Decay By Laccase Modification

The paper industry is an important industry which related to the national economy and social development.Due to the shortage of raw materials and the serious pollution,it has become the trend of the paper industry in China using wastepaper.However,the degradation of wastepaper fiber in the recycling process will lead to deterioration of the quality of paper.In this paper,it explores the effect on different pulp laccase/glutamic acid system catalytic,and discusses how the laccase catalyze lignin in ther raw fiber material to link glutamic acid improving the performance of paper strength,analyzes the effects on the structure and performance of OCC fibers,Result showed that laccase can oxidize lignin to phenoxy radicals which can transformed to benzoquinone structure through rearrangement reaction,radicals coupling reaction can occur between free radicals.Based on Michael addition reaction,glutamic acid was linked onto the position C5 of lignin radicals improving-COOH contents.The effect on the different Kappa number pulp by laccase/glutamic acid catalysis is different,the whiteness of paper decreases with the increase of Kappa number generally,compared to the control pulp after treated by laccase/glutamic acid,the Kappa number of no bleached eucalyptus kraft pulp,H2O2 bleached eucalyptus pulp increased 16.4%,26.5%,the whiteness of no bleached eucalyptus kraft pulp,Oxygen delignification of eucalyptus kraft pulp,H2O2 bleached eucalyptus pulp decreased 3.47%ISO,0.91%ISO,5.18%ISO.The laccase/glutamic acid system can cause irreversible closure of the cellulose pore and pore size transformed in the direction of smaller,increase BET specific surface area meanwhile the average pore width decreased.Because of the the micro-fibers exposed by laccase/glutamic acid system catalyzed oxidation of lignin on the surface of fiber,which led to form better bonding between fibers in handsheets.The results also showed that wet tensile strength,dry tensile strength,tear strength,the dry ring crush index increased103.6%,27.1%,43.4%,16.1% compared to the control pulp after treated by laccase/glutamic acid,respectively.Moreover,crystallinity,crystal size and micro-crystal cross area decreased 1.6%,4.1%,2.0%,intermolecularhydrogen bond O(2)H…O(6),O(3)H…O(5)decreased 19.6%,21.2%,respectively,and intramolecular hydrogen bond O(6)H … O(3′)increased 15.2%.