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CN-122011218-A - Preparation method of nanocellulose with uniform size

CN122011218ACN 122011218 ACN122011218 ACN 122011218ACN-122011218-A

Abstract

The invention relates to a preparation method of nanocellulose, which comprises the steps of grinding and screening microcrystalline cellulose, collecting and screening microcrystalline cellulose, then adding the microcrystalline cellulose into an acetic acid-sodium acetate buffer solution for sterilization, adding endo-cellulase for enzymolysis after sterilization, inactivating the endo-cellulase after enzymolysis is finished, centrifugally washing the inactivated endo-cellulase to obtain the enzymolysis cellulose, then carrying out 2, 6-tetramethylpiperidine-1-oxygen free radical oxidation modification on the enzymolysis cellulose to obtain oxidized cellulose, carrying out high-speed shearing emulsification on the oxidized cellulose to obtain emulsified cellulose, then adding the emulsified cellulose into an aqueous solution of a eutectic solvent DES formed by choline chloride and urea for swelling, carrying out high-pressure homogenization, and carrying out freeze drying after the high-pressure homogenization is finished to obtain nanocellulose. The invention can obviously improve the size uniformity and the dispersity of the nanoscale cellulose and reduce the size of the cellulose.

Inventors

  • SHEN XINYI
  • Fu Zhizhu
  • ZHANG YIXUAN
  • YANG ZHONGWEI
  • SHEN JIAYUAN
  • MEI JIAYU
  • JIN JIALE
  • SHI ZHENGNAN

Assignees

  • 湖州市菱湖新望化学有限公司

Dates

Publication Date
20260512
Application Date
20260108

Claims (10)

  1. 1. A method for preparing nanocellulose with uniform size, which is characterized by comprising the following steps: (1) Grinding microcrystalline cellulose, sieving by a filter sieve, and collecting and sieving microcrystalline cellulose; (2) Adding screened microcrystalline cellulose into acetic acid-sodium acetate buffer solution, then sterilizing, adding endo-type cellulase for enzymolysis after sterilization, inactivating endo-type cellulase after enzymolysis is finished, and centrifugally washing after inactivation to obtain enzymatic hydrolysis cellulose; (3) Adding enzymolysis cellulose, 2, 6-tetramethyl piperidine-1-oxygen free radical and sodium bromide into water, performing ultrasonic dispersion under ice bath condition to obtain reaction liquid, dripping sodium hypochlorite aqueous solution into the reaction liquid, dripping sodium hydroxide aqueous solution, continuously stirring for oxidation reaction, adding ethanol to terminate the reaction after the oxidation reaction is completed, and performing centrifugal washing to obtain oxidized cellulose; (4) Adding oxidized cellulose into water for ultrasonic dispersion, and performing high-speed shearing emulsification after ultrasonic dispersion is completed to obtain emulsified cellulose; (5) Adding emulsified cellulose into an aqueous solution of a eutectic solvent DES formed by choline chloride and urea, swelling the emulsified cellulose, performing centrifugal washing after the swelling is sufficient, then adding the emulsified cellulose into water for ultrasonic dispersion, performing high-pressure homogenization after the ultrasonic dispersion, and performing freeze drying after the high-pressure homogenization is completed to obtain the nanocellulose.
  2. 2. The method according to claim 1, wherein in the step (1), the mesh number of the filter screen is 200 to 300 mesh.
  3. 3. The preparation method according to claim 1, wherein in the step (2), the screened microcrystalline cellulose is added into an acetic acid-sodium acetate buffer solution, and the pH is adjusted to 4.8-5.0; The sterilization condition is that the sterilization is carried out for 10-30 min at 110-130 ℃.
  4. 4. The preparation method according to claim 1, wherein in the step (2), the weight ratio of the screened microcrystalline cellulose to the endo-type cellulase is 100 (0.5-1.5); the enzymolysis temperature is 48-52 ℃, the time is 2.5-3 h, and the stirring speed of enzymolysis is 100-200 rpm; The inactivation temperature is 90-100 ℃ and the time is 5-15 min.
  5. 5. The preparation method of claim 1, wherein in the step (3), the weight ratio of the enzymatic hydrolysis cellulose, 2, 6-tetramethylpiperidine-1-oxyl, sodium bromide and water is (0.5-1.5): 0.01-0.02): 0.05-0.15): 100; The volume ratio of the reaction solution to the 10% sodium hypochlorite aqueous solution is 100 (3-4); The concentration of the sodium hydroxide aqueous solution is 0.1-0.2M, and the sodium hydroxide aqueous solution is dropwise added until the pH is adjusted to 10-10.5.
  6. 6. The method according to claim 1, wherein in the step (3), the time of the oxidation reaction is 2.5 to 3 hours.
  7. 7. The method according to claim 1, wherein in the step (3), the ice bath condition is 2 to 4 ℃.
  8. 8. The preparation method of claim 1, wherein in the step (4), the rotation speed of high-speed shearing emulsification is 10000-15000 rpm, the control temperature of a cooling circulation system is set to be 4-15 ℃, and shearing emulsification is carried out for 10-15 min; After shearing emulsification, the mixture was filtered through a 100 μm sieve to obtain emulsified cellulose.
  9. 9. The method according to claim 1, wherein in the step (5), the volume concentration of the aqueous solution of the eutectic solvent DES is 20 to 40%.
  10. 10. The preparation method according to claim 1, wherein in the step (5), high-pressure homogenization is performed in a high-pressure homogenizer, a cooling circulation system of the high-pressure homogenizer is set to control the temperature to be 4-15 ℃, the initial pressure is 50-80 mpa, the homogenization is circulated for 1-3 times, then the pressure is gradually increased, the pressure is increased for 20-30 mpa each time, and sampling detection is performed after the circulation is performed for several times; wherein the end pressure of the pressurization is not more than 150MPa.

Description

Preparation method of nanocellulose with uniform size Technical Field The invention belongs to the technical field of nano materials, and particularly relates to a preparation method of nano cellulose with uniform size. Background The natural polymer material, especially cellulose, is an ideal material for replacing petroleum-based plastics due to rich sources, strong reproducibility and biodegradability, and the nanocellulose, which is a novel bio-based nanomaterial, has great potential in the fields of material science, biomedicine, energy storage, food industry and the like due to high specific surface area, high strength, degradability and functionalization characteristics. The existing preparation method of nanocellulose mainly depends on a mechanical method and a chemical method. The mechanical method physically cuts the cellulose raw material into nano-scale fibers by means of high-pressure homogenization, ultrasonic treatment and ball milling, the method is simple to operate, but high in energy consumption, and the prepared nano-cellulose has wide particle size distribution. The common chemical methods comprise a chloric acid method, a nitric acid method and a hydrogen peroxide method, and have the advantages that the uniform particle size can be obtained, but the particle size is still larger, a large amount of acid wastewater can be generated, and the post-treatment is complex. Disclosure of Invention Based on the above-mentioned drawbacks and deficiencies of the prior art, it is an object of the present invention to at least solve one or more of the above-mentioned problems of the prior art, in other words, to provide a method for preparing nanocellulose of uniform size which meets one or more of the aforementioned needs. In order to achieve the aim of the invention, the invention adopts the following technical scheme: A method for preparing nanocellulose with uniform size, comprising the following steps: (1) Grinding microcrystalline cellulose, sieving by a filter sieve, and collecting and sieving microcrystalline cellulose; (2) Adding screened microcrystalline cellulose into acetic acid-sodium acetate buffer solution, then sterilizing, adding endo-type cellulase for enzymolysis after sterilization, inactivating endo-type cellulase after enzymolysis is finished, and centrifugally washing after inactivation to obtain enzymatic hydrolysis cellulose; (3) Adding enzymolysis cellulose, 2, 6-tetramethyl piperidine-1-oxygen free radical and sodium bromide into water, performing ultrasonic dispersion under ice bath condition to obtain reaction liquid, dripping sodium hypochlorite aqueous solution into the reaction liquid, dripping sodium hydroxide aqueous solution, continuously stirring for oxidation reaction, adding ethanol to terminate the reaction after the oxidation reaction is completed, and performing centrifugal washing to obtain oxidized cellulose; (4) Adding oxidized cellulose into water for ultrasonic dispersion, and performing high-speed shearing emulsification after ultrasonic dispersion is completed to obtain emulsified cellulose; (5) Adding emulsified cellulose into an aqueous solution of a eutectic solvent DES formed by choline chloride and urea, swelling the emulsified cellulose, performing centrifugal washing after the swelling is sufficient, then adding the emulsified cellulose into water for ultrasonic dispersion, performing high-pressure homogenization after the ultrasonic dispersion, and performing freeze drying after the high-pressure homogenization is completed to obtain the nanocellulose. Preferably, in the step (1), the mesh number of the filter screen is 200 mesh. In the step (2), the screened microcrystalline cellulose is added into an acetic acid-sodium acetate buffer solution, and the pH is adjusted to 4.8-5.0; The sterilization condition is that the sterilization is carried out for 10-30 min at 110-130 ℃. In the step (2), the weight ratio of the screened microcrystalline cellulose to the endo-type cellulase is 100 (0.5-1.5); the enzymolysis temperature is 48-52 ℃, the time is 2.5-3 h, and the stirring speed of enzymolysis is 100-200 rpm; The inactivation temperature is 90-100 ℃ and the time is 5-15 min. In the step (3), the weight ratio of the enzymatic hydrolysis cellulose, the 2, 6-tetramethylpiperidine-1-oxygen radical, sodium bromide and water is (0.5-1.5): 0.01-0.02): 0.05-0.15): 100; The volume ratio of the reaction solution to the 10% sodium hypochlorite aqueous solution is 100 (3-4); The concentration of the sodium hydroxide aqueous solution is 0.1-0.2M, and the sodium hydroxide aqueous solution is dropwise added until the pH is adjusted to 10-10.5. Preferably, in the step (3), the time of the oxidation reaction is 2.5-3 hours. In the preferred embodiment, in the step (3), the ice bath condition is 2 to 4 ℃. In the step (4), the rotation speed of high-speed shearing emulsification is 10000-15000 rpm, the control temperature of a cooling circulation system is set to