A method for preparing self-assembled nanocellulose
The preparation of nanocellulose by self-assembly method solves the problem of difficult control of structure and function in the existing technology, realizes green and efficient preparation of nanocellulose and recycling of waste resources, and broadens the application scenarios.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING INST OF TECH
- Filing Date
- 2024-02-02
- Publication Date
- 2026-07-21
Smart Images
Figure CN118047881B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing self-assembled nanofibers, belonging to the field of nanocellulose preparation technology. Background Technology
[0002] With the continuous depletion of global energy and resources, and the increasing severity of environmental problems due to the depletion of non-renewable resources, the search for and development of renewable and environmentally friendly resources has become an urgent issue. The resource utilization and high-value transformation of biomass materials, such as trees, plants, and agricultural waste, into green, renewable, and sustainable materials, has become a hot topic of research. Cellulose is the most widely distributed and abundant natural organic compound, found in plants, algae, and microorganisms. Nanocellulose is a cellulose material with high application value and advantages such as large specific surface area, high aspect ratio, ease of surface modification, and good biocompatibility.
[0003] The preparation of nanocellulose can be categorized into two methods: "top-down" and "bottom-up." The common "top-down" method primarily involves disrupting the amorphous regions or interchain interactions of large cellulose units. However, the resulting nanocellulose structure and function are difficult to control precisely, limiting its applications. Existing techniques for preparing nanocellulose include acid hydrolysis, which uses strong or weak acids or acid-buffered solutions to hydrolyze cellulose nanofibers (e.g., patent CN110760009 A). However, this method has a low reaction rate, and the resulting nanocellulose is mostly needle-shaped. Furthermore, the treatment of acidic wastewater must be considered. Another method is carboxymethylation or oxidation, such as CN111533924A and CN111206449A, which introduces hydrophilic groups onto the cellulose surface to prepare cellulose nanofibers. Nanocellulose prepared by either method does not contain hydrophobic groups and is suitable for hydrophilic systems. Further hydrophobic modification is required for its application in organic resin systems.
[0004] With the development of polymer chemical preparation technology, artificially synthesized polymers can obtain multi-level structures through self-assembly mechanisms. Self-assembly has gradually become a common means of constructing novel structures, providing a new approach for the "bottom-up" preparation of nanocellulose materials. This is conducive to the controllable adjustment of the structure and function of nanocellulose and broadens the application scenarios of nanocellulose in organic polymer systems. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing self-assembled cellulose nanoparticles. This method uses nitrocellulose as a raw material and prepares cellulose nanoparticles through self-assembly. The process is simple, the reaction time is short, it is easy to control, and the energy consumption is low. The product obtained is a nanosphere with small particle size, controllable structure, and contains hydrophobic groups.
[0006] The technical solution adopted in this invention is as follows:
[0007] A method for preparing self-assembled cellulose nanoparticles includes the following steps:
[0008] (1) Mix nitrocellulose and sodium sulfide solution evenly and stir under constant temperature conditions to carry out the reaction; the reaction temperature is 40-60℃ and the reaction time is 0.5-1.5h.
[0009] (2) Take out the hydrolysis product dispersion after the reaction in step (1), centrifuge it quickly at room temperature, and then ultrasonically disperse it in deionized water. Repeat the process multiple times until the supernatant is neutral. Add an appropriate amount of deionized water to the precipitate and ultrasonically disperse it. The resulting product is a nanocellulose dispersion.
[0010] In the above preparation method, the sodium sulfide solution mentioned in step (1) can be replaced by sodium hydrogen sulfide solution.
[0011] In step (1), the mass ratio of nitrocellulose to sodium sulfide ranges from 0.5 to 2.5: 0.78 to 5.85, preferably 1 to 1.5: 2 to 4; the mass ratio of nitrocellulose to sodium sulfide ranges from 1 to 2: 1.4 to 5.6, preferably 2: 1.4 to 3.5.
[0012] The molar concentration range of the sodium sulfide solution is 0.2–1.5 mol / L, and the molar concentration range of the sodium hydrogen sulfide solution is 0.5–2.0 mol / L.
[0013] The preferred reaction temperature is 60°C, and the reaction time is 1 hour.
[0014] The centrifugation speed in step (2) is 8500-10000 rpm, the centrifugation time is 10-15 min, and the cycle is preferably 6-8 times.
[0015] The nanocellulose prepared by the above method is preferably nanocellulose with a spherical structure with a particle size of 15-160 nm, and more preferably nanocellulose with a particle size of 15-75 nm, wherein the nanocellulose contains hydrophobic groups.
[0016] The beneficial effects of this invention are:
[0017] (1) The raw materials prepared by this invention are reacted with sodium sulfide solution or sodium hydrogen sulfide solution. It does not contain acid and does not require additional acid treatment. The reaction is controllable and the product has a small particle size. Industrial nitrocellulose or its waste can be used as raw materials to realize the reuse of waste resources. In addition, some hydrophobic groups are retained in the product structure, which gives nanocellulose a certain degree of hydrophobicity and broadens its application scenarios.
[0018] (2) This invention can realize the hydrolysis and self-assembly of nitrocellulose in one pot. The preparation process is carried out in an aqueous environment without the need for any organic solvents. It is simple to operate, has low temperature requirements, fast reaction, green and efficient, and easy to industrialize.
[0019] (3) The nanocellulose prepared by this invention contains hydrophobic groups that can be dispersed in organic solvents, especially some weakly polar organic solvents, which greatly improves its applicability. Attached Figure Description
[0020] Figure 1 These are scanning electron microscope (SEM) images and particle size distribution diagrams of the nanocellulose prepared in Example 1 of this invention: a. Scanning electron microscope image, b. Particle size distribution diagram;
[0021] Figure 2 Here are scanning electron microscope (SEM) images and particle size distribution diagrams of the nanocellulose prepared in Example 2 of this invention: a. Scanning electron microscope image, b. Particle size distribution diagram;
[0022] Figure 3 Here are scanning electron microscope (SEM) images and particle size distribution diagrams of the nanocellulose prepared in Example 3 of this invention: a. Scanning electron microscope image, b. Particle size distribution diagram;
[0023] Figure 4 These are scanning electron microscope (SEM) images and particle size distribution diagrams of the nanocellulose prepared in Example 4 of this invention: a. SEM image, b. Particle size distribution diagram.
[0024] Figure 5 These are scanning electron microscope (SEM) images and particle size distribution diagrams of the nanocellulose prepared in Example 5 of this invention: a. SEM image, b. particle size distribution diagram.
[0025] Figure 6 These are scanning electron microscope (SEM) images and particle size distribution diagrams of the nanocellulose prepared in Example 6 of this invention: a. SEM image, b. particle size distribution diagram.
[0026] Figure 7 The above diagrams show the dispersion of the nanocellulose prepared in this invention in ethyl acetate (a), acetone (b), N,N-dimethylformamide (c), and water (d). The top diagram shows the dispersion immediately after addition, and the bottom diagram shows the dispersion after 3 hours. Detailed Implementation
[0027] The present invention will be further described below with reference to specific typical embodiments.
[0028] Nitrocellulose products typically contain a certain amount of water or ethanol as a wetting agent to prevent spontaneous combustion. In this embodiment of the invention, nitrocellulose containing a wetting agent is used directly, and the measurement is based on dry nitrocellulose.
[0029] Example 1
[0030] A method for preparing self-assembled cellulose nanoparticles, comprising the following steps:
[0031] (1) Nitrocellulose containing wetting agent and sodium sulfide solution are mixed evenly at a ratio of 1.5:50 (g:ml, the ratio of dry nitrocellulose mass to sodium sulfide solution volume), wherein the sodium sulfide solution concentration is 0.5mol / L, and the mixture is placed in a 60℃ constant temperature water bath and reacted for 1h under stirring to obtain a suspension.
[0032] (2) The nanocellulose suspension obtained in step (1) is first centrifuged at 8500 rpm for 10 min at room temperature, then ultrasonically dispersed in deionized water, and then centrifuged to remove the supernatant. This process is repeated 6 to 8 times until the pH of the supernatant is neutral. The precipitate is then added to an appropriate amount of deionized water and ultrasonically dispersed to obtain a self-assembled nanocellulose aqueous dispersion.
[0033] The obtained nanocellulose (e.g.) Figure 1 Particle size: 26.99±6.30nm.
[0034] Example 2
[0035] A method for preparing self-assembled cellulose nanoparticles, comprising the following steps:
[0036] (1) Nitrocellulose containing wetting agent and sodium sulfide solution are mixed evenly at a ratio of 1:50 (g:ml, the ratio of dry nitrocellulose mass to sodium sulfide solution volume), wherein the sodium sulfide solution concentration is 0.7mol / L, and the mixture is placed in a constant temperature water bath at 60℃ and reacted for 1h under stirring to obtain a suspension.
[0037] (2) The nanocellulose suspension obtained in step (1) is first centrifuged at 8500 rpm for 10 min at room temperature, then ultrasonically dispersed in deionized water, and then centrifuged to remove the supernatant. This process is repeated 6 to 8 times until the pH of the supernatant is neutral. The precipitate is then added to an appropriate amount of deionized water and ultrasonically dispersed to obtain a self-assembled nanocellulose aqueous dispersion.
[0038] The obtained nanocellulose (e.g.) Figure 2 Particle size: 43.03±8.55nm.
[0039] Example 3
[0040] A method for preparing self-assembled cellulose nanoparticles, comprising the following steps:
[0041] (1) Nitrocellulose containing wetting agent and sodium sulfide solution are mixed evenly at a ratio of 1:50 (g:ml, the ratio of dry nitrocellulose mass to sodium sulfide solution volume), wherein the sodium sulfide solution concentration is 1.0mol / L, and the mixture is placed in a 60℃ constant temperature water bath and reacted for 1h under stirring to obtain a suspension.
[0042] (2) The nanocellulose suspension obtained in step (1) is first centrifuged at 10,000 rpm for 10 min at room temperature, then ultrasonically dispersed in deionized water, and then centrifuged to remove the supernatant. This process is repeated 6 to 8 times until the pH of the supernatant is neutral. The precipitate is then added to an appropriate amount of deionized water and ultrasonically dispersed to obtain a self-assembled nanocellulose aqueous dispersion.
[0043] The obtained nanocellulose (e.g.) Figure 3 Particle size: 54.46±15.43nm.
[0044] Example 4
[0045] (1) Nitrocellulose containing wetting agent and sodium sulfide solution are mixed evenly at a ratio of 2:50 (g:ml, the ratio of dry nitrocellulose mass to sodium sulfide solution volume), wherein the molar concentration of sodium sulfide solution is 0.8mol / L, and the mixture is placed in a constant temperature water bath at 60℃ and reacted for 1h under stirring to obtain a suspension.
[0046] (2) The nanocellulose suspension obtained in step (1) is first centrifuged at 10,000 rpm for 10 min at room temperature, then ultrasonically dispersed in deionized water, and then centrifuged to remove the supernatant. This process is repeated 6 to 8 times until the pH of the supernatant is neutral. The precipitate is then added to an appropriate amount of deionized water and ultrasonically dispersed to obtain a self-assembled nanocellulose aqueous dispersion.
[0047] The obtained nanocellulose (e.g.) Figure 4 Particle size: 38.47±8.46nm.
[0048] Example 5
[0049] (1) Nitrocellulose containing wetting agent and sodium sulfide solution are mixed evenly at a ratio of 2:50 (g:ml, the ratio of dry nitrocellulose mass to sodium sulfide solution volume), wherein the molar concentration of sodium sulfide solution is 0.5mol / L, and the mixture is placed in a constant temperature water bath at 60℃ and reacted for 1h under stirring to obtain a suspension.
[0050] (2) The nanocellulose suspension obtained in step (1) is first centrifuged at 10,000 rpm for 10 min at room temperature, then ultrasonically dispersed in deionized water, and then centrifuged to remove the supernatant. This process is repeated 6 to 8 times until the pH of the supernatant is neutral. The precipitate is then added to an appropriate amount of deionized water and ultrasonically dispersed to obtain a self-assembled nanocellulose aqueous dispersion.
[0051] The obtained nanocellulose (e.g.) Figure 5 Particle size: 155.56±57.49nm.
[0052] Example 6
[0053] (1) Nitrocellulose containing wetting agent and sodium sulfide solution are mixed evenly at a ratio of 2:50 (g:ml, the ratio of dry nitrocellulose mass to sodium sulfide solution volume), wherein the molar concentration of sodium sulfide solution is 1.2mol / L, and the mixture is placed in a constant temperature water bath at 60℃ and reacted for 1h under stirring to obtain a suspension.
[0054] (2) The nanocellulose suspension obtained in step (1) is first centrifuged at 10,000 rpm for 10 min at room temperature, then ultrasonically dispersed in deionized water, and then centrifuged to remove the supernatant. This process is repeated 6 to 8 times until the pH of the supernatant is neutral. The precipitate is then added to an appropriate amount of deionized water and ultrasonically dispersed to obtain a self-assembled nanocellulose aqueous dispersion.
[0055] The obtained nanocellulose (e.g.) Figure 6 Particle size: 143.65±34.90nm.
[0056] Dispersed comparative experiment:
[0057] The nanocellulose prepared in Example 1 of this invention was added to ethyl acetate, acetone, N,N-dimethylformamide, and water, respectively, and ultrasonically vibrated and allowed to stand for 3 hours. Figure 7 The results showed that the nanocellulose prepared by this invention still had good dispersion in ethyl acetate and N,N-dimethylformamide solutions due to the presence of hydrophobic groups.
[0058] The above-described embodiments are further illustrations of the technical solutions of the present invention. It should be understood that the above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications or improvements made within the scope of the principles of the present invention should be included within the scope of the present invention.
Claims
1. A method for preparing self-assembled cellulose nanoparticles, characterized in that, The steps include the following: (1) Mix nitrocellulose and sodium sulfide solution evenly and stir under constant temperature conditions to carry out the reaction; the reaction temperature is 40~60℃, the reaction time is 0.5~1.5h; the mass ratio of nitrocellulose to sodium sulfide is 0.5~2.5 : 0.78~5.85; the molar concentration of sodium sulfide solution is 0.2~1.5mol / L; (2) Take out the hydrolysis product dispersion after the reaction in step (1), centrifuge it quickly at room temperature, and then ultrasonically disperse it in deionized water. Repeat the process multiple times until the supernatant is neutral. Add an appropriate amount of deionized water to the precipitate and ultrasonically disperse it to obtain the nanocellulose dispersion.
2. The method for preparing self-assembled cellulose nanoparticles according to claim 1, characterized in that, The sodium sulfide solution mentioned in step (1) is replaced by sodium hydrogen sulfide solution; the mass ratio of nitrocellulose to sodium hydrogen sulfide is in the range of 1~2 : 1.4~5.6; the molar concentration of sodium hydrogen sulfide solution is in the range of 0.5~2.0 mol / L.
3. The method for preparing self-assembled nanocellulose according to claim 1, characterized in that, In step (1), the mass ratio of nitrocellulose to sodium sulfide is in the range of 1~1.5 : 2~4.
4. The method for preparing self-assembled cellulose nanoparticles according to claim 1, characterized in that, The centrifugation speed in step (2) is 8500~10000 rpm, the centrifugation time is 10~15 min, and the cycle is 6~8 times.