Preparation Of Chitosan's Graft Copolymer And Its Application In Papermaking

Chitosan is a deacetylated derivative of chitin.a naturally occurring polymer. It has interesting functional groups ,presence of amino and hydroxyl groups.It has been received great attention on modifing it into various derivatives just due to its special properties, such as adsorption, film forming, fiber forming .hydroscopicity, moisture retention biodegradability and bacterinertness. It has been widely used in many fields-food service industry,medicament,printing&dyeing and papermaking.On the basis of the status of domestic making industry,a series of chitosan-DMDAAC graft copolymers(CSD) and chitosan-DMDAAC-starch graft copolymers (CSDS)used as papermaking additives agent were synthesized in this thesis.The conditions of synthesis,application and mechanism of action were discused in detail.As a result of study.it can be concluded:1.Two kinds of cationic graft copolymers which included chitosan-DMDAAC graft copolymers (CSD)and chitosan-DMDAAC-starch graft copolymers (CSDS)were synthesized that was initiated by using cerium ammonium nitrate(CAN) as initiator.2.The application results showed that the best synthesis condition of the CSDS graft copolymer was that reaction time at 95℃ was 2.5h, m(CS):m(DMDAAC):m(Starch) 1:1.2:4.concentration of CAN was[ Ce4+]0.1mmol·L^-13.Application of Chitosan graft copolymer in papermaking was studied. mainly described on viscosity and surface cationic charge of the graft copolymer,which affect the retention ,dewatering and strengthing performance.using collcid charge titration analyze the surface charge of graft copolymers and pulp suspension,calculate a certain dosage. The impact of additives both using in wheat straw pulp and NBKP ,the experiment results showed that the CSDS graft copolymers which paper strengthening effect was better than the CSD graft copolymers.4.The CSD graft copolymers and CSDS graft copolymers both have well retention aid.especially the CSD graft copolymers with higher surface cationic charge.5.The properties of CSDS graft copolymers were stable. When the dosage of the graft copolymer 10# was 0.6% in wheat straw pulp ,the breaking length increased 16.68%,tear index increased about 35.4%.burst index increased about 12.92%.The same dosage used in NBKP, the breaking length increased 20.36%,tear index increased about 15.27%.burst index increased about 12.14%.6.The X-ray diffraction and IR spectrao of chitosan and the graft copolymers(CSD and CSDS)indicated that the structure of a serial of CSD and CSDS graft copolymers synthesized in this thesis was in accord with the structure based on theory.The retention,dewatering ,strengthening mechanisms of CSD and CSDS graft copolymers synthesized in this thesis,studied by comparing the paper's physical property index the SEM photos of the surfaceof paper sheets treated by the graft copolymers or not.