Research On Preparation Technology Of Low Molecular Weight Chitosan With High Degree Deacetylation

Objective:In this dissertation, chitosan degradation with hydrogen peroxide in the homogeneous system, preparation of chitosan with high degree of deacetylation and preparation of chitosan lactate with high degree of deacetylation and low molecular weight were studied.Methods:1. The process of producing chitosan with high degree of deacetylation with phase transfer catalyst was developed,to inspect influencing factor of the react with react time,temperature,density of NaOH,density of phase transfer catalysis and addition technique of interval etc.2. The mechanism and influencing factors of chitosan degradation by hydrogen peroxide in the homogeneous system were presented,to inspect influencing factor of the react with degradation time,temperature,dosage of hydrogen peroxide,density of HC1 and so on.3. Use chitosan with high degree of deacetylation and low molecular weight to prepare chitosan lactate with high degree of deacetylation and low molecular weight.Results:1. The results indicated that the high degree of deacetylation of chitosan could be obtained under the following optimized conditions:tempetraute 121℃,amount of phase transfer catalyst 3%(catalyst(m)/chitosan(m)), reaction time 3h, concentration of alkali 40% NaOH.Using intermittent addition of NaOH,the deacetylation degree of chitosan could be increased significantly.The FT-IR spectrum proved that chitosan was almost completely deacelyated.2. The results indicated that low molecular weight of chitosan could be obtained under the following optimized conditions:the high degree of deacetylation of chitosan 10g, dissolve in HC11% 180mL,amount hydrogen peroxide 36% 20mL,60℃water bath reaction time 4.5h, abtain chitosan that hydrogen peroxide in about 6000-7000,good of solution,blonde.3. The results indicated that chitosan lactate could be obtained under the following optimized conditions:the high degree of deacetylation and low molecular weight chitosan 10g, dissolve in deionized water 500mL,amount lactic acid 20mL,60℃water bath reaction time 1h,dialyse(3500),concentrate,freeze-dry.Conclusion:The method is simple in synthesizing technology for production of chitosan lactate, its process is easy to control, the cost of operation is low and it is easy for in-dustrializing production.The chitosan lactate granules prepared has strong power of solubility and is hopeful to be used as raw material in production of artificial tears.