The Study On The Preparation Of Modified Nano Polysaccharide And Its Application

Nowadays, with the shortage of the non-renewable resources, such as oil, naturalgas and coal, researchers pay more and more attention on the renewable naturalpolysaccharine resources, such as starch, cellulose and guar gum. The modified naturalsaccharine particles with nano size have a wide range of applications in many differentfields, especially in pulp and paper industry.Firstly, starch was mechanically activated and grinded by a stirring-type ball mill.Using H2O2as oxidant and CuSO4as catalyst, the nano oxidized starch was preparedby semi-dry method. The effect of reaction condition on the nano oxidized starch wasdiscussed. On the condition that the mircowave treat time is3min，oxidant amount was10%, catalyst amount was0.03%, reaction temperature was65℃, and reaction timewas6h, the size of the preparated nano starch is79nm.The nano starch was modified by using the3-chloro-2-hydroxypropyl trimethylammonium chloride as etherifying agent by three different methods--semi-drymethod, microwave method and slurry method. The optimum microwave methodreaction conditions were as follows: the mircowave treat time is2.5min, the dosage ofetherifying agent55%, sodium hydroxide12%, temperature65℃and reaction time3.5hours, and the DS of the nano cationic starch is0.28. The comparison of modifiedstarch with nanometer size and micrometer size was discussed. The result shows thatthe nano starch was modified more easier than the starch with micrometer size.The AKD neutral sizing agent was prepared by using the nano cationic starch asemulsifier. The optimal emulsification condition is as follows: temperature is75℃, theshear speed is9000r/m, emulsification time was10min. Particle size of emulsifiedAKD emulsion by using the nano cationic starch is1884nm, and the charge density is14.8mV.Secondly, microcrystalline cellulose was mechanically activated and grinded by astirring-type ball mill, then the cellulose power was dissolute in sodium hydroxide-urea aqueous solutions, and cationic modified with the3-chloro-2-hydroxypropyl trimethyl ammonium chloride. The optimum reactionconditions were as follows: the ritio of etherifying agent to cellulose is12:1, thetemperature was25℃and reaction time was10hours, and the DS of the nano cationiccellulose is0.091, the cationic charge density is1.03meq·g-1. The viscosity of1%aqueous solution of the nano cationic cellulose was1.24mPa s. the application of thenano cationic cellulose as strengthen and AKD sizing promoter was discussed.Thirdly, low viscosity guar gum was prepared by oxidative method. The effect ofoxidative reaction condition was discussed. The optimal reaction conditions was asfollows, the dosage of hydrogen dosage is8.6%, the reaction temperature is65℃, thereaction time was4h. the viscosity of the modified guar gum was dropped from2390mPa·s to3.47mPa·s. the optimal surface sizing conditions of the modified guar gumon the filter paper is50-60℃，6-8%concentration.