Process for preparing narrow-distribution chitosan with controllable molecular weight through microwave-H2O2 combined degradation method

Abstract

The invention discloses a process for preparing narrow-distribution chitosan with controllable molecular weight through a microwave-H2O2 combined degradation method. The process comprises the following steps of: adding highly polymerized chitosan into a reactor, then stirring and dissolving by using an acetic acid solution, and standing for 10 minutes; adding 2-8 percent of H2O2 into the obtained solution; fixing the reactor in a microwave experimental instrument, simultaneously starting stirring, radiating for 3-8 minutes through a pulse mode to obtain a pale yellow solution; and regulating a pH value to be 7-8 by using an alkaline liquor, filtering, collecting the precipitation, performing vacuum drying to obtain water-soluble oligochitosan. Due to the adoption of the microwave-H2O2 combined degradation method, the narrow-distribution water-soluble oligochitosan is prepared under homogeneous-phase condition, According to the method, the operation is easy, environmental protection is realized, and secondary pollution is avoided; and moreover, the reaction is rapid during synergism of microwave and H2O2, a large quantity of energies and resources are saved, the molecular weight and distribution of the oligochitosan can be effectively controlled, and the repeatability is good.

Description

technical field [0001] The present invention relates to the preparation of water-soluble chitosan, specifically utilizes microwave and H 2 o 2 The chitosan is degraded by synergistic action to obtain oligomeric chitosan products with controllable molecular weight and narrow molecular weight distribution. technical background [0002] Chitosan is the only cationic alkaline polysaccharide that exists in nature. It is a product of high deacetylation of chitin and has good biocompatibility. It is widely used in biomedicine, agriculture, forestry, chemical industry and other fields. As a high polymer, chitosan is composed of glucosamine units linked numerous times, with molecular weights ranging from hundreds of thousands to millions. As the molecular weight increases, the strength, modulus, and toughness of chitosan slow down, and finally tend to a certain limit value. When the molecular weight is very high, that is to say, when the molecular chain is very long, the flow is di...

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Problems solved by technology

However, the degradation process of this method is difficult to control, the molecular weight range of the resulting degradation product is very wide, the stability and repeatability of the reaction are poor, the yield of the product is low, and the environmental pollution caused is more serious; the physical degradation method obeys the dynamics of random degradation Science, simple operation, fast response, low energy consumption, no pollution

However, this method is easy to cause some crosslinking and branching reactions, the post-treatment is complicated, and the yield is too low, resulting in high production costs. It is difficult to apply to industrial production as the main method, but can only be used as an auxiliary means to accelerate the reaction. ;The enzymatic degradation method is carried out under milder conditions, does not require a large amount of reaction reagents, and the molecular weight of the degradation product is easy to control

However, this degradation method has strict requirements for raw enzymes, and different enzymes have different degrees of degradation of chitosan. At the same time, it is difficult to obtain enzymes, purify enzymes, and immobilize enzymes, and the cost is also very high.

There are also combined use of different degradation methods, but it still cannot solve the problems of long operation process, high energy consumption, low yield and complicated process. It is difficult to achieve standardized control of the molecular weight of the final product, and the repeatability is poor.

There are individual methods that can partially achieve molecular weight-controlled degradation, but the product is water-insoluble chitosan with a high molecular weight, and there is no mention of the molecular weight distribution characteristics of the degradation

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