Chitosan with high deacetylation degree and high molecular weight and preparation method thereof

Abstract

The invention relates to chitosan with high deacetylation degree and high molecular weight and a preparation method thereof. The preparation method comprises the following steps: dissolving chitin ina strong alkali solution to obtain a chitin-strong alkali solution; then, increasing the strong alkali content in the chitin-strong alkali solution to 35 to 45wt% in a manner of supplementing a strongalkali solution under the condition that the temperature is 0 to 10 DEG C; wherein the strong base is KOH or NaOH, and the deacetylation reaction is specifically carried out in an oil bath heater ora microwave reactor; the deacetylation degree of the prepared chitosan is 80-95%, and the viscosity-average molecular weight of the prepared chitosan is 7.9 * 10 < 5 >-9.0 * 10 < 5 > g/mol. Accordingto the preparation method disclosed by the invention, deacetylation is carried out under homogeneous conditions, so that the concentration of strong base and the temperature of deacetylation reactionare reduced, the process is simple, the conditions are mild, and the molecular weight of chitosan is remarkably improved; the prepared chitosan is high in deacetylation degree and high in molecular weight and has a great application prospect.

Description

technical field [0001] The invention belongs to the technical field of chitosan preparation, and relates to chitosan with high deacetylation degree and high molecular weight and a preparation method thereof. Background technique [0002] Chitosan, also known as deacetylated chitin, is obtained through deacetylation of chitin, which exists widely in nature. Since chitosan was first discovered by the Frenchman Rouget in 1859, this natural polymer has become more and more It has received widespread attention from all walks of life and has been widely used in many fields such as medicine, food, chemical industry, cosmetics, water treatment, metal extraction and recovery, biochemical and biomedical engineering. [0003] At present, chitosan is mainly obtained by deacetylation of chitin under concentrated NaOH and high temperature. The deacetylation reaction of chitin is essentially the hydrolysis reaction of amide bonds under alkaline conditions, but the intramolecular and molec...

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Problems solved by technology

However, chitin powder reacts directly under high-concentration alkali and high temperature conditions. Because the alkali concentration is too high and the reaction temperature is too high, although it promotes the deacetylation of chitin, it also promotes the destruction of the carbon chain skeleton of chitosan. The molecular chain is broken, which leads to a decrease in the molecular weight of chitosan. It is difficult to find chitosan with a higher molecular weight, and it is impossible to take into account the high degree of deacetylation and high molecular weight of chitosan at the same time.

For example, patent CN200710168573.5 discloses a method for preparing chitosan with high degree of deacetylation and high viscosity by using shrimp shells, which is to carry out microwave under the conditions of heterogeneous phase, alkali concentration of 40-50wt% and temperature of 100°C. Deacetylation reaction, after the reaction, the obtained chitosan and the ethanol solution of NaOH will continue to undergo deacetylation reaction. Although it can produce chitosan with a high degree of deacetylation, its operation is cumbersome, and the alkali concentration and reaction temperature are high. The obtained chitosan has a low molecular weight; patent CN201310676454.6 discloses a method for preparing chitosan with an ultra-high deacetylation degree using Antarctic krill as raw material. After removing mineral proteins and lipids, the mass fraction It is deacetylated at 110°C in 50% sodium hydroxide solution. Although it can produce chitosan with a high degree of deacetylation, high temperature and high alkali concentration will seriously affect the molecular weight of chitosan

[0004] The molecular weight of chitosan will directly affect its mechanical properties. The current low molecular weight of chitosan has seriously affected the application of chitosan in various fields.

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