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The invention relates to a preparation method of carboxymethyl chitosan

    Carboxymethyl chitosan is a kind of medical polymer polysaccharide with good biocompatibility, biodegradability and biological activity. It has clinical analgesic, hemostatic, bacteriostatic and promote wound healing.
    The traditional production process of carboxymethyl chitosan includes chitosan deacetylation from chitin and carboxymethyl chitosan from crude chitosan after washing and drying. The preparation process is complex and the reaction time is long. The patent application document with the publication number cn104292365 discloses a method of combining the preparation process of chitosan and carboxymethyl chitosan. The method provided is to directly add chloroacetic acid reaction after the completion of chitin deacetylation, and to precipitate carboxymethyl chitosan at low temperature. Due to the complex composition of the reaction liquid, the by-product of the reaction will precipitate together with carboxymethyl chitosan at low temperature, which is difficult to remove and the purity of the product obtained is low.
    The invention relates to a new preparation method of carboxymethyl chitosan. The preparation method can significantly shorten the reaction time, the carboxymethyl chitosan prepared has high purity, large molecular weight, and the solvent used can be recycled without pollution to the environment.
    To solve the above technical problems, the technical solution provided by the invention is:
    (1) Preparation of alkaline solution: weigh a certain amount of sodium hydroxide and add it to dimethyl sulfoxide, stir and dissolve, and heat up to 120℃ ~ 150℃;
    (2) deacetylation, carboxymethylation reaction: add chitin to the alkaline solution described in step (1), stirring reaction 10min ~ 40min; After the reaction, the temperature was lowered to 50℃ ~ 80℃, and chloroacetic acid ethanol solution was added for carboxymethylation.
    (3) Post-treatment: filter, add 65% ~ 100% ethanol solution, adjust ph to neutral with acidic solution, filter, ethanol washing, drying, packaging, sterilization.

    The carboxymethyl chitosan of the invention is sterilized by irradiation.
    The following is the description of the process and principle of the technical scheme of the invention:
    Chitin was added to sodium hydroxide dimethyl sulfoxide solution for deacetylation reaction. After the reaction was completed, chloroacetic acid ethanol solution was directly added to the reaction solution for carboxymethylation reaction. After the reaction was finished, carboxymethyl chitosan was obtained by washing and drying.
    According to the applicant’s research, the alkaline of sodium hydroxide in dimethyl sulfoxide solution is much stronger than that in aqueous solution, and the deacetylation of chitin in dimethyl sulfoxide solution with strong alkaline can be completed within 10min to 40min, and the amount of sodium hydroxide is significantly reduced. Due to the short reaction time, the molecular structure of chitosan is less damaged, and the obtained product has high molecular weight and correspondingly high viscosity.
    Chitosan and carboxymethyl chitosan do not dissolve in dimethyl sulfoxide solution, carboxymethyl chitosan prepared by chitosan carboxymethylation is still solid, the by-product generated by the reaction can be removed through filtration, washing and other processes, the product purity is high.
    The invention has the following beneficial effects:
    (1) The deacetylation reaction time of chitin is short, and the obtained products have high molecular weight and high viscosity.
    (2) Reaction solvent dimethyl sulfoxide, washing ethanol can be recycled through distillation or distillation, no waste water generation, do not pollute the environment.
    (3) The technical scheme provided by the invention is simple, easy to operate, and suitable for industrial scale-up production.

    Carboxymethyl chitosan was prepared by conventional two-step method:
    (1) Preparation of alkaline solution: weigh 450g sodium hydroxide and add it to 900ml purified water, stir to dissolve, and heat up to 120℃;
    (2) Deacetylation reaction: weigh 55g of chitin and add it to the above alkaline solution, stir and react for 60min; After the reaction, filter the purified water and wash it until neutral and dry.
    (3) carboxymethylation reaction: 40g of the dried chitosan was taken and added into 400ml isopropyl alcohol. Under stirring conditions, 80ml of sodium hydroxide solution with a concentration of 50% was slowly added. After continuous stirring for 2h, 88ml of ethanol solution with a concentration of 55% chloroacetic acid was added into the solution six times for carboxymethylation.
    (4) Post-treatment: filter to obtain carboxymethyl chitosan crude product, add 70% ethanol solution of 5 times the volume of the above crude product, adjust the reaction solution ph to 7.2 with 50% acetic acid solution, filter, wash with 70% ethanol 7 times, 95% ethanol 2 times, vacuum drying at 55℃ for 8h, packaging, sterilization, and obtain.
    From Embodiment 1 to Embodiment 3, carboxymethyl chitosan samples prepared proportionally were tested, and the test results of key indicators were as follows:
    .
    As can be seen from the test results, the technical scheme provided by the invention not only has short reaction time, the carboxymethyl chitosan prepared has large molecular weight and viscosity, and the carboxymethyl chitosan with high molecular weight and high viscosity has better anti-adhesion and lubrication effect, and can be used as a lubricant in bone joints to prevent and treat traumatic or degenerative osteoarthritis.
    The above embodiments are used only to illustrate the technical scheme of the invention and not to restrict it; Notwithstanding the detailed description of the invention by reference to the aforementioned embodiments, ordinary technical personnel in the field should understand that it may still modify the technical scheme recorded in the aforementioned embodiments, or make equivalent substitutions for some of the technical features thereof; Such modification or replacement shall not make the essence of the corresponding technical scheme depart from the spirit and scope of the technical scheme of the embodiment of the invention.

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