Preparation method of surface modified chitin whisker

Abstract

The invention discloses a preparation method of a surface modified chitin whisker, which comprises the following steps: taking a proper amount of chitin to carry out acidolysis reaction, removing supernate through a centrifugation method after the reaction is finished, cleaning, then adding the acidolysis chitin into purified water, then adding sodium hydroxide or potassium hydroxide and chloroacetic acid according to a ratio, setting reaction conditions, and carrying out solid-liquid separation to obtain the surface modified chitin whisker. After the reaction is finished, diluting and standing, washing by adopting a centrifugal method to obtain a residual solid, adding water, dialyzing, carrying out ultrasonic treatment, freeze-drying and the like. On the basis of retaining the key structure of the chitin whisker, the surface-modified chitin whisker which is more excellent in dispersity and compatibility than the chitin whisker is simply and efficiently prepared, and meanwhile, a centrifugal-dialysis combined purification technology is matched, so that the reaction period is greatly shortened, the production cost is greatly reduced, and the method is suitable for industrial production. The application prospects of the chitin whiskers in the aspects of beauty makeup, daily chemicals and medicines are greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of biomaterials, and in particular relates to a method for preparing surface-modified chitin whiskers. Background Art

[0002] Chitin, also known as chitin, is abundant in nature and widely found in crustaceans. It has excellent biocompatibility and biodegradability, making it a biosafe material. However, chitin is insoluble in water and most organic solvents, which greatly limits its development and application. Chitin whiskers (CW) are chitin fibers obtained by removing the amorphous portion of chitin and retaining the highly ordered crystalline structure. This treatment method allows chitin to maintain its excellent biological characteristics and improve its purity, reaching the nanoscale microscopic size. Although chitin whiskers are as insoluble as chitin, they can form uniformly dispersed suspensions in water or water-oil systems, making them easier to process and handle. In addition, the orderly arrangement of atoms in chitin whiskers has the characteristics of high strength and high modulus. Chitosan whiskers are mainly prepared by acid hydrolysis, which removes the amorphous and disordered crystalline structure regions of chitosan, while the highly crystalline regions remain intact. The method includes acid hydrolysis, washing, dialysis, and ultrasonic or homogenization treatment. During the preparation process, the electrostatic repulsion caused by the protonation of the amine groups in chitosan, combined with ultrasonic or homogenization treatment, will form positively charged chitosan whiskers.

[0003] Chitosan whiskers, an important chitosan derivative, are widely used in various composite materials such as hydrogels, microspheres, and tissue engineering scaffolds. Their nanoscale size and high modulus make them excellent fillers that can improve the mechanical properties and shape stability of the matrix. They are also used in cosmetics, medicine, food, engineering materials, and other fields. However, if the concentration of chitosan whiskers in aqueous solution is high, or when mixed with other ingredients, the dispersed whiskers are still easily separated or precipitated, which limits the further application of chitosan whiskers.

[0004] Currently, research on chitin whiskers often involves mixing them with other polymer materials to form solid forms such as gels, microspheres, and scaffolds. For example, patent number CN 117304551A, entitled "A Method for Preparing a Modified Chitin Whiskers-Reinforced and Toughened PBAT Micro-Foamed Composite Material," uses chitin whiskers as an additive to enhance the strength and toughness of PBAT-based composite materials. However, research examining the structural properties of chitin whiskers as the primary component is limited. Other studies involve the modification of chitin whiskers, such as patent number CN 106868631A, entitled "A Chitin Nanowhisker, Chitin Nanofiber, and Preparation Method Thereof," which prepares whiskers with varying aspect ratios, focusing on improving whisker length and width. These methods are complex and lengthy, and significantly alter the structural properties of the chitin whiskers themselves. The present invention is based on the conventional chitin whisker preparation process, optimizes the traditional method, and introduces a method for surface modification of chitin whiskers, which solves the problems of long cycle, poor compatibility and stability of whisker finished products in the existing method. The method is simple and efficient, which is conducive to supporting the further in-depth application and industrial production of chitin whiskers in various fields. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention has made improvements and provides a method for preparing surface-modified chitin whiskers. Based on the characteristic structure of chitin whiskers, the present invention optimizes the conventional preparation and purification process while keeping its microstructure basically unchanged, and performs surface modification on it through a one-step method. Compared with other modification methods, the preparation is simple, the method cycle is short, and the production efficiency is high. At the same time, the compatibility of chitin whiskers in solution systems is significantly improved, and its application value in the fields of daily chemicals, medicine, and cosmetics is increased. The present invention is achieved through the following technical solutions:

[0006] The present invention discloses a method for preparing surface-modified chitin whiskers, which specifically comprises the following steps:

[0007] Step 1: Acid hydrolysis preparation of chitin: Chitosan powder is mixed with acid solution and heated and stirred to fully react. After the reaction stops, purified water is added and the supernatant is removed by high-speed centrifugation. The supernatant is then washed repeatedly by centrifugation 1-5 times. The solid remaining is the acid-hydrolyzed chitosan.

[0008] Step 2: Carboxymethylation modification: add acid-decomposed chitosan to purified water, the reaction temperature is 40°C-65°C, the mass ratio of chitosan to chloroacetic acid is 1:0.3-0.6, then add sodium hydroxide or potassium hydroxide to prepare a specific alkaline carboxylation reaction solution, and stir the reaction;

[0009] Step 3: After the reaction in step 2 is completed, purified water is added and the supernatant is removed by high-speed centrifugation, and then the centrifugation is repeated 1-5 times to obtain a washed solid;

[0010] Step 4: Add purified water to the solid obtained in step 3 and dialyze it. Then, perform ultrasound after dialysis to obtain an aqueous solution, which is a dispersion of surface-modified chitin whiskers. After freeze-drying, obtain a sponge sheet sample of surface-modified chitin whiskers.

[0011] As a further improvement, in step 1 of the present invention, the amount of purified water added is 1-5 times the total volume of the mixed solution, the speed of the high-speed centrifugation is 3000r / min-10000r / min, and the centrifugation time is 20min-60min. The repeated washing method is as follows: purified water is added and high-speed centrifugation is performed to remove the supernatant, and the centrifugation parameters are the same as above.

[0012] As a further improvement, in step 1 of the present invention, the acid solution is a sulfuric acid solution, the mass ratio of chitosan powder to sulfuric acid solute is 1:8-10, and the specific reaction conditions of chitosan powder and the sulfuric acid solution are: reaction temperature of 70°C-90°C, and reaction time of 9h-18h.

[0013] As a further improvement, in step 2 of the present invention, the pH of the alkaline carboxylation reaction solution is adjusted to 12-13 by sodium hydroxide or potassium hydroxide, and the reaction time is 1h-4h.

[0014] As a further improvement, in step three of the present invention, the amount of purified water added is 1-5 times the total volume of the mixed solution, the speed of the high-speed centrifugation is 3000r / min-10000r / min, and the centrifugation time is 20min-60min. The repeated washing method is as follows: purified water is added and high-speed centrifugation is performed to remove the supernatant, and the centrifugation parameters are the same as above.

[0015] As a further improvement, in step 4 of the present invention, the total dialysis time is 1-2 days, the time interval between each water change is 2h-4h, the ultrasonic parameters of the dialyzed solution are 150W-600W, 5min-30min, and the final aqueous solution obtained is a dispersion of surface-modified chitin whiskers. The dispersion is freeze-dried for 24h-48h to obtain a surface-modified chitin whisker sponge sample.

[0016] While retaining the key structure of chitin whiskers, the present invention simply and efficiently prepares a surface-modified chitin whisker with better dispersibility and compatibility than chitin whiskers. At the same time, combined with the centrifugation-dialysis purification technology, the reaction cycle and production cost are greatly reduced, greatly improving the application prospects of chitin whiskers in beauty, daily chemicals, and medicine.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] 1. The present application optimizes the preparation method based on the typical acidolysis reaction, sets the acid solution as sulfuric acid solution, the mass ratio of chitin powder to sulfuric acid solute is 1:8-10, and the specific reaction conditions of chitin powder and the sulfuric acid solution are that the reaction temperature is 70-90 DEG C, and the reaction time is 9-18 hours. On the other hand, the supernatant is removed by high-speed centrifugation, the speed of high-speed centrifugation is 3000-10000 r / min, the centrifugation time is 20-60 minutes, and the centrifugation method is used for repeated cleaning 1-5 times, so that impurities and reaction by-products are effectively removed, and the long-time standing step in the conventional method is replaced, thereby being beneficial to shortening the production cycle.

[0019] 2. On the basis of the optimized method of the present application, the acidolysis chitin obtained after centrifugation is directly subjected to surface carboxymethylation modification, the supernatant is removed from the obtained reaction product by high-speed centrifugation, the speed of high-speed centrifugation is 3000-10000 r / min, the centrifugation time is 20-60 minutes, and then the centrifugation method is used for repeated cleaning 1-5 times, and then after dialysis for 1-2 days, the solution is subjected to ultrasonic treatment, the parameters of ultrasonic treatment are 150-600 W, 5-30 minutes, and after ultrasonic treatment, the sample is freeze-dried for 24-48 hours to obtain a surface-modified chitin whisker sponge sample. The method omits the conventional standing step, greatly shortens the reaction cycle of dialysis and freeze-drying, and improves the reaction efficiency.

[0020] 3. The preparation of conventional chitin whiskers generally needs more than 10 days, and the preparation of different modified whiskers generally needs more than 7 days, and the method of the present application needs only about 7 days to prepare the surface-modified chitin whisker from chitin raw materials, saves more than 50% of time, greatly simplifies the reaction cycle and process, significantly improves the production efficiency and reduces the production cost.

[0021] 4. The present application avoids the great damage of chemical reaction to the molecular structure of chitin whiskers, and the reaction temperature is selected as 40-65 DEG C, the pH value of the solution is 12-13, the mass ratio of chitin to chloroacetic acid is 1:0.3-0.6, and the reaction time is 1-4 hours. The reaction conditions are mild, the surface-modified chitin whisker basically retains the key structural characteristics of chitin whisker, and therefore the various performances of chitin whisker are also continued, such as nanometer size and high crystallinity, so that the surface-modified chitin whisker can be used as a substitute filler of chitin whisker to improve the mechanical properties and shape stability of the matrix.

[0022] 5. The characteristic performance of chitin whiskers, namely dispersion performance, is greatly optimized using this method. The surface-modified whiskers prepared by the present invention have better dispersion performance than chitin whiskers. Under the same ultrasonic conditions, the ultrasonic treatment time is reduced from 30 minutes to 5-10 minutes, improving the dispersion efficiency by at least 200%. It also reduces equipment wear and facilitates continuous operation of the equipment. After dispersion, the whiskers can remain stable for a longer period of time.

[0023] 6. The surface-modified chitin whiskers prepared by this invention exhibit improved compatibility with a variety of commonly used active ingredients in solution systems, such as carboxymethyl chitosan, polyethylene glycol, and niacinamide, and can remain stable in solution for more than 14 days. Unmodified chitin whiskers often settle, precipitate, and precipitate within the same day, greatly enhancing the application prospects of chitin whiskers in cosmetics, daily chemicals, and medicine. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a flow chart of the method of the present invention;

[0025] Figure 2 This is the infrared spectrum of the surface-modified chitin whiskers prepared in the present invention;

[0026] Figure 3 This is the viscoelasticity graph of the surface-modified chitin whisker reinforced thermosensitive chitin gel prepared by the present invention;

[0027] Figure 4 This is a microscopic morphology of the surface-modified chitin whiskers prepared in the present invention;

[0028] Figure 5 This is a crystallinity curve of the surface-modified chitin whiskers prepared in the present invention;

[0029] Figure 6 This is a graph showing the nanoparticle size distribution of the surface-modified chitin whiskers prepared in the present invention;

[0030] Figure 7 This is a diagram showing the dispersion state of the surface-modified chitin whiskers prepared in the present invention after ultrasonic treatment;

[0031] Figure 8 This is a diagram of the state of the surface-modified chitosan whiskers prepared in the present invention mixed with active ingredients. DETAILED DESCRIPTION

[0032] The present application is based on the conventional chitin whisker acidolysis preparation method, a large number of method optimization is carried out, and the chitin whisker is surface carboxymethyl modified. In the reaction process, the method of high-speed centrifugation is reasonably applied to the preparation process of chitin whisker and surface modified chitin whisker, which plays a role in separation and purification, greatly shortens the period of dialysis and freeze-drying steps, and further improves the overall production efficiency and reduces the production cost.

[0033] The modification method of the present application can be directly continued on the basis of acidolysis chitin, which simplifies the modification method, and selects a relatively mild reaction step, only needs to add materials in appropriate proportion in a low-temperature aqueous solution, and reacts for a short time, so that the surface carboxymethyl modified chitin whisker can be obtained. The surface modified chitin whisker basically maintains the key structure of chitin whisker, that is, nanometer size and high crystallinity, and can be used as a substitute filler for chitin whisker to improve the mechanical properties and shape stability of the matrix. Furthermore, it also has better dispersion performance and compatibility than chitin whisker.

[0034] In order to further understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0035] Embodiment one:

[0036] Preparation of surface modified chitin whisker: 0.5g of chitin powder was weighed, and 15ml of 3mol / L sulfuric acid solution was added at a temperature of 90℃ for acidolysis reaction. After 9h of reaction, the reaction product was washed by high-speed centrifugation, and the solid part was left. The washing was repeated once, and acidolysis chitin solid was obtained. The acidolysis chitin solid was added to 200ml of purified water, and sodium hydroxide was added to adjust the pH of the alkaline carboxylation reaction solution to 12. 0.15g of chloroacetic acid was added, and the solution was stirred in a 65℃ water bath for 1h. After the reaction was completed, 800ml of purified water was added and separated by high-speed centrifugation. The speed of high-speed centrifugation was 10000r / min, and the centrifugation time was 20 minutes. The washing was repeated once, and the supernatant was poured out each time, and the precipitate was left. The precipitate obtained by the last centrifugation was dialyzed for 1 day, and the water was changed every 2-4h. The dialyzed solution was ultrasonicated (150W, 30min), and the nanoscale dispersion of the surface modified chitin whisker was obtained. The dispersion obtained by ultrasonication was freeze-dried for 24h, and 0.25g of surface modified chitin whisker sponge-like sample was obtained. The preparation method of surface modified chitin whisker of the present application is shown in the following figure: Figure 1The main steps include acid hydrolysis from chitin raw material, centrifugal purification, hydroxymethylation modification, centrifugal-dialysis purification, ultrasonic and freeze-drying, as shown in the figure.

[0037] Take 0.05 g of the freeze-dried surface-modified chitin whiskers prepared by the above method, and use a Fourier transform infrared spectrometer to perform infrared spectrum analysis, with the scanning range set to 4000 cm -1 ~ 600 cm -1 , the resolution is 4 cm -1 , and the scanning is 10 times. The results are shown in Figure 2 , there is a clear infrared absorption peak near 1600 cm -1 , which is related to the C=O stretching vibration of carboxyl, indicating that the carboxymethyl-modified chitin whiskers have been successfully prepared.

[0038] Example 2:

[0039] Preparation of surface-modified chitin whiskers: take 2.5 g of chitin powder, add 85 ml of 3 mol / L sulfuric acid solution at a temperature of 70°C for acid hydrolysis reaction, and after 18 h of reaction, use high-speed centrifugation to clean the reaction product, leaving the solid part, and repeat the cleaning 5 times to obtain acid-hydrolyzed chitin solid. Add the acid-hydrolyzed chitin solid to 400 ml of purified water, adjust the pH of the alkaline carboxylation reaction solution to 13 with potassium hydroxide, then add 1.5 g of chloroacetic acid, and place it in a 40°C water bath for stirring for 4 h. After the reaction is completed, 400 ml of purified water is added and separated by high-speed centrifugation at a speed of 3000 r / min for 60 minutes, and the cleaning is repeated 5 times. The precipitate obtained by the last centrifugation is dialyzed for 2 days, with a 2 h-4 h interval between each water change. The solution after dialysis is subjected to ultrasonic treatment (600 W, 10 min), and the resulting solution is a nanoscale dispersion of surface-modified chitin whiskers. The dispersion obtained by ultrasonic treatment is subjected to freeze-drying treatment for 48 h, and 1.1 g of a surface-modified chitin whisker sponge-like sample is obtained.

[0040] The above surface-modified chitin whiskers are added to a temperature-sensitive chitin gel, and the viscoelasticity of the formed composite hydrogel is measured at a shear frequency of 1 Hz, as shown in Figure 3 , the elastic modulus of the composite hydrogel is increased from 150 Pa-350 Pa to 400 Pa-600 Pa, and the viscous modulus is increased from 5 Pa-50 Pa to 10 Pa-100 Pa. This reflects that the surface-modified chitin whiskers basically retain the key structure of chitin whiskers, and also have the same mechanical properties and shape stability as chitin whiskers, and can be used as a reinforcing filler for composite materials.

[0041] Comparative Example 1:

[0042] The unmodified chitin whiskers were prepared by the conventional method as follows: after the acidolysis reaction was completed, the solution was diluted to 1000 ml with purified water, and then stirred magnetically for 10 minutes, and then left to stand for 3 hours. The supernatant was discarded, and the operation was repeated 5 times. After the above operation was completed, the solution was dialyzed for 4 days. After dialysis, the solution was ultrasonically treated at 600 W for 30 minutes. The nanoscale dispersion of the chitin whiskers was obtained, and then freeze-dried for 72 hours to obtain the unmodified chitin whisker sponge sample 1.2 g.

[0043] The surface modified chitin whiskers were prepared from chitin raw material by the method of the present application, and the yield of the product was similar to that of the chitin whiskers prepared by the conventional method. The time spent on the standing, dialysis and freeze-drying steps in the production was effectively shortened, the production cost and equipment wear were reduced, the production efficiency was greatly improved, the key structural parameters of the unmodified chitin whiskers were basically retained, and the dispersing performance was greatly improved. The specific statistics are shown in the following table:

[0044]

[0045] 0.1 g of the freeze-dried surface modified chitin whiskers prepared in Example 2 was added to 100 ml of purified water and ultrasonically dispersed (600 W, 30 min). In addition, 0.1 g of the freeze-dried unmodified chitin whiskers prepared by the conventional method in the above Comparative Example 1 was also added to 100 ml of purified water and ultrasonically dispersed (600 W, 30 min). The microstructure of the dispersed whisker samples was studied by transmission electron microscopy, and the results are shown in Figure 4 The surface modified chitin whiskers and the chitin whiskers both showed needle-like nanostructure, and the size and shape of the microstructure were basically the same, with no obvious difference.

[0046] The surface modified chitin whiskers prepared in Example 2 and the unmodified chitin whiskers prepared by the conventional method were analyzed for crystallinity by XRD. The peaks at 2θ = 12.7°, 19.3°, 20.8°, 23.4°, 26.4°, 32.0° in the XRD pattern belong to the (021), (110), (120), (101), (130) and (104) crystal planes of chitin macromolecules, respectively. The crystallinity of the ordinary chitin raw material is mostly about 50%. The test results are shown in Figure 5 The crystallinity of the surface modified chitin whiskers was 87.5%, and the crystallinity of the unmodified chitin whiskers was 92.9%. The crystallinity of the surface modified chitin whiskers was only 5.8% lower than that of the unmodified chitin whiskers, and 75% higher than that of the chitin raw material. This indicates that the internal structure of the surface modified chitin whiskers is basically the same as that of the unmodified chitin whiskers, and has an ultra-high crystallinity close to that of the unmodified chitin whiskers.

[0047] The surface modified chitin whiskers prepared in Example 2 and the unmodified chitin whiskers prepared by conventional methods were taken and the particle size distribution was tested using a nanoparticle size distribution instrument. Before the test, the two were prepared into 1 mg / ml dispersions, and then the samples were transferred to a quartz cuvette for testing. The test results are shown in Figure 2. Figure 6 As shown in Figure 2, the surface modified chitin whiskers not only have a more concentrated particle size distribution, but also have an average particle size of about 2*10 3 The average particle size of unmodified chitin whiskers prepared by conventional methods is about 2*10 4 The average particle size of the surface-modified chitin whiskers is only 10% of that of the unmodified chitin whiskers, which shows that the aggregation of the surface-modified chitin whiskers in the solution is greatly reduced by 90% compared with the unmodified chitin whiskers.

[0048] like Figure 7 As shown, the surface modified chitin whiskers of Example 2 were prepared into a 1 mg / ml solution and subjected to ultrasound at 600W for 5 minutes, and then the unmodified chitin whiskers of Comparative Example 1 were prepared into a 1 mg / ml solution and subjected to ultrasound at 600W for 5 minutes. Figure 7 As shown in the figure, the dispersion effect of unmodified chitin whiskers is significantly worse than that of surface-modified chitin whiskers, with noticeable turbidity. This indicates that surface-modified chitin whiskers have much better ultrasonic dispersion performance than unmodified chitin whiskers. In practice, unmodified chitin whiskers require ultrasonication at a power of 600W for 30 minutes, while surface-modified chitin whiskers have a higher ultrasonic efficiency, saving over 80% of this time.

[0049] Comparative Example 2:

[0050] Different from Example 1, the chitosan powder was subjected to acid hydrolysis at a temperature of 60°C.

[0051] Comparative Example 3:

[0052] The difference from Example 1 is that the pH of the alkaline carboxylation reaction solution is adjusted to 14.

[0053] Comparative Example 4:

[0054] The difference from Example 1 is that a total of 0.5 g of chloroacetic acid is added.

[0055] Comparative Example 5:

[0056] The difference from Example 1 is that the reaction temperature is adjusted to 30°C.

[0057] Comparative Example 6:

[0058] The difference from the first embodiment is that the rotation speed of the high-speed centrifuge is adjusted to 2000 r / min.

[0059] Comparative Example 7:

[0060] The charging ratio, reaction temperature, reaction time, acidity and alkalinity and centrifugal speed in the surface modification method of the present invention all affect the dispersion performance of the final surface-modified chitin whiskers. The ultrasonic parameters of 600W and 5min were fixed, and the surface-modified chitin whiskers in the above-mentioned Examples 1 and 2 and Comparative Examples 3, 4, 5, 6 and 7 were mixed into 1mg / ml and subjected to ultrasonic treatment. By observing whether the final ultrasonic dispersion solution had visible insoluble matter and whether it had Tyndall effect when irradiated with infrared light, it was judged whether the solution achieved nano-scale dispersion effect, and then the parameter range in the technical solution of the present invention was determined, as shown in the following table:

[0061]

[0062]

[0063] Comparative Example 8:

[0064] The samples in Example 1 and Comparative Example 1 were weighed, and 1 mg / ml of surface-modified chitin whisker dispersion and 1 mg / ml of unmodified chitin whisker dispersion were prepared respectively and subjected to ultrasonic treatment at 600W for 5 min. Then, active ingredients of different concentrations, such as 1% propylene glycol, 4% glycerol, 1% PEG, 0.1% chitosan, 0.25% arginine, 0.5% nicotinamide, 0.5% carboxymethyl chitosan, 0.2% disodium EDTA, and 0.5% p-hydroxyacetophenone, were mixed. Except for the alcohol component, the chitosan whisker solution quickly precipitated, settled, or produced floccules when it came into contact with other ingredients, while the mixed solution of surface-modified chitin whiskers and multiple active ingredients remained stable for two weeks. Some of the mixed results are shown in FIG. Figure 8 As shown in the table below, no obvious floccules or precipitation were observed during the experiment. The specific results are shown in the table below, which shows that the surface-modified chitosan whiskers have better stability and compatibility than chitosan whiskers.

[0065]

[0066]

[0067] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing surface-modified chitin whiskers, characterized in that: The steps include: Step 1: Acid hydrolysis preparation of chitin: Chitosan powder is mixed with acid solution and heated and stirred to fully react. After the reaction stops, purified water is added and the supernatant is removed by high-speed centrifugation. The supernatant is then washed repeatedly by centrifugation 1-5 times. The solid remaining is the acid-hydrolyzed chitosan. Step 2: Carboxymethylation modification: add acid-decomposed chitosan to purified water, the reaction temperature is 40°C-65°C, the mass ratio of chitosan to chloroacetic acid is 1:0.3-0.6, then add sodium hydroxide or potassium hydroxide to prepare a specific alkaline carboxylation reaction solution, and stir the reaction; Step 3: After the reaction in step 2 is completed, purified water is added and the supernatant is removed by high-speed centrifugation, and then the centrifugation is repeated 1-5 times to obtain a washed solid; Step 4: Add purified water to the solid obtained in step 3 and dialyze it. Then, perform ultrasound after dialysis to obtain an aqueous solution, which is a dispersion of surface-modified chitin whiskers. After freeze-drying, obtain a sponge sheet sample of surface-modified chitin whiskers.

2. The method for preparing surface-modified chitin whiskers according to claim 1, wherein: In the step 1, the amount of purified water added is 1-5 times the total volume of the mixed solution, the speed of the high-speed centrifugation is 3000r / min-10000r / min, and the centrifugation time is 20min-60min. The repeated washing method is as follows: purified water is added and high-speed centrifugation is performed to remove the supernatant. The centrifugation parameters are the same as above.

3. The method for preparing surface-modified chitin whiskers according to claim 2, wherein: In the step 1, the acid solution is a sulfuric acid solution, the mass ratio of chitosan powder to sulfuric acid solute is 1:8-10, and the specific reaction conditions of chitosan powder and the sulfuric acid solution are: reaction temperature of 70°C-90°C, and reaction time of 9h-18h.

4. The method for preparing surface-modified chitin whiskers according to claim 1, 2 or 3, wherein: In the step 2, the pH of the alkaline carboxylation reaction solution is adjusted to 12-13 by sodium hydroxide or potassium hydroxide, and the reaction time is 1h-4h.

5. The method for preparing surface-modified chitin whiskers according to claim 4, wherein: In step three, the amount of purified water added is 1-5 times the total volume of the mixed solution, the speed of the high-speed centrifugation is 3000r / min-10000r / min, and the centrifugation time is 20min-60min. The repeated washing method is as follows: adding purified water and high-speed centrifugation to remove the supernatant, and the centrifugation parameters are the same as above.

6. The method for preparing the surface-modified chitin whiskers according to claim 1, 2, 3 or 5, wherein: In the step 4, the total dialysis time is 1-2 days, the time interval between each water change is 2h-4h, the ultrasonic parameters of the dialyzed solution are 150W-600W, 5min-30min, and the final aqueous solution obtained is a dispersion of surface-modified chitin whiskers. The dispersion is freeze-dried for 24h-48h to obtain a surface-modified chitin whisker sponge sample.

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