Method for preparing dissolved nano cellulose by using aqueous solvent
The preparation of soluble nanocellulose by means of phosphoric acid-water system and high-speed shearing technology solves the problems of high cost and low yield of existing cellulose dissolution, and realizes low cost and environmentally friendly preparation of nanocellulose with stable product performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-10
- Publication Date
- 2026-04-07
AI Technical Summary
Existing cellulose dissolution processes are costly, polluting, and prone to damaging the cellulose structure, resulting in low yields. Existing alternative solvent systems, such as NMMO, suffer from high production costs, sensitivity to moisture, and difficulties in solvent recovery.
Soluble cellulose nanoparticles were prepared by using a phosphoric acid-water system as a solvent, combined with high-speed shearing, ultrasonic treatment and homogenization technology, through a nanoscale dispersion and washing process. Water and ethanol were used as antisolvents, the dissolution conditions were controlled at -30~60℃, and the cellulose nanoparticle dispersion was obtained by centrifugation and washing.
It achieves low-cost and environmentally friendly preparation of nanocellulose, with stable product performance, solving the problems of severe cellulose structure damage and low yield in existing technologies, and is compatible with a variety of cellulose raw materials with strong process adaptability.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of nanocellulose material, and particularly relates to a method for preparing dissolved nanocellulose by using an aqueous solvent. BACKGROUND
[0002] Commercial production of regenerated cellulose materials still largely relies on the NaOH-SC2 cellulose-based dissolution process (viscose process). The environmental problems of this time-consuming and highly polluting process (e.g., emission of toxic gases) have prompted extensive research activities aimed at developing alternative, more environmentally friendly, and preferably non-derivatizing cellulose dissolution / regeneration solvent systems. However, most of the solvent systems developed so far have limitations, including the Lyocell process of N-methylmorpholine-N-oxide (NMMO). The dissolution of cellulose in aqueous NMMO is highly demanding in terms of water content of the system, dissolution temperature, and DP (degree of polymerization) distribution of cellulose. It is also prone to form explosive, colored, and even carcinogenic degradation products (nitromorpholine).
[0003] To solve the above problems, the strategy of dissolving cellulose by using low co-solvent, ionic liquid is generally adopted. However, due to high production cost (solvent cost is 10-20 times that of NMMO), sensitivity to water content, and insufficient development of solvent recovery and purification process, the large-scale application of these solvent systems is still limited.
[0004] Therefore, it is necessary to provide an efficient, non-derivatizing and non-destructive dissolution, low-cost and environmentally friendly method for preparing nanocellulose. SUMMARY
[0005] In order to solve the problems of high cost of cellulose dissolution, destruction of the structure of the dissolution process, and low yield, the purpose of the present application is to provide a method for preparing dissolved nanocellulose by using an aqueous solvent.
[0006] The purpose of the present application is achieved by the following technical solutions: A method for preparing dissolved nanocellulose by using an aqueous solvent, comprising the following steps: 1) dissolving cellulose raw material by using a solvent to obtain a cellulose solution; the solvent is a phosphoric acid-water system; 2) mixing the cellulose solution with an anti-solvent, and then performing nanoscale dispersion to obtain a nanocellulose dispersion; the anti-solvent is one or more of water and ethanol; the nanoscale dispersion is performed by one or more of high-speed shearing (25000-15000 rpm, 10-20 min), ultrasonic treatment (1000-600 W, 5-15 min), and homogenization (8000-4000 rpm, 5-20 min); 3) washing the nanocellulose dispersion to obtain the dissolved nanocellulose; the washing refers to washing with water.
[0007] The cellulose raw material is kapok, microcrystalline cellulose, hemp, sulfite bleached wood pulp, coconut fiber, pomegranate peel, bamboo pulp, cotton, cotton linters, straw pulp, reed pulp, etc., which can be sieved, dried or crushed for pretreatment to control the particle size to be less than 500 um if necessary.
[0008] The amount of the cellulose raw material is 0.5%-10% of the mass of the solvent.
[0009] The dissolving is carried out at a speed of 100-800 rpm under stirring at-30~60℃ for 1-24 h to form a uniform transparent cellulose solution.
[0010] The mass ratio of the cellulose solution to the anti-solvent is 1:1-10; the anti-solvent is water, ethanol or a mixture of ethanol and water; the mass ratio of water to ethanol in the anti-solvent is 100:0~0:100; the temperature during mixing is 0-60℃. The mass ratio of water to ethanol in the anti-solvent is preferably 100:0~60:40, preferably 100:0~80:20, more preferably 95:5~80:20.
[0011] The washing is carried out by centrifugal washing. The centrifugal washing is carried out at 5000~7000 rpm for 5~15 min.
[0012] The nanocellulose in the application is prepared by a dissolving-regenerating process to realize the preparation of the dissolved nanocellulose.
[0013] The application is compatible with various cellulose raw materials and various aqueous cellulose solvents, has strong process adaptability and mild operating conditions.
[0014] Compared with the prior art, the application has the following advantages and beneficial effects: The application prepares the dissolved nanocellulose, and the prepared product has stable performance and uniform size. The method of the application is simple, energy-saving and low-consumption, and has certain production advantages. The application prepares the dissolved nanocellulose, realizes the bottom-up dissolution and regeneration of fibers, and solves the problems of serious structure damage and low yield in the preparation of the existing nanocellulose. BRIEF DESCRIPTION OF DRAWINGS
[0015] Figure 1 AFM image of the nanocellulose prepared in Example 1; Figure 2 AFM image of the nanocellulose prepared in Example 2; Figure 3 SEM image of the nanocellulose prepared in Example 5. DETAILED DESCRIPTION
[0016] The present application will be described in further detail by the following specific examples, but the embodiments of the present application are not limited thereto.
[0017] Example 1 A method for preparing a dissolved nanocellulose, comprising the following steps: 1) mixing cotton and phosphoric acid-water system (phosphoric acid concentration 85wt%) at a mass ratio of 4%, then stirring at a speed of 200 rpm and cooling to -10℃, dissolving for 2h to obtain a cellulose solution; 2) cooling water to 0℃ to obtain an anti-solvent; 3) slowly adding the anti-solvent to the cellulose solution at a mass ratio of 1:6 to perform homogenization (5000 rpm, 10 min); 4) washing and concentrating the nanocellulose dispersion by centrifugation (6000 rpm, 5 min) to obtain nanocellulose with a yield of 90%.
[0018] Figure 1 AFM image of the nanocellulose prepared in Example 1 after dispersion in water (concentration 0.005%).
[0019] Example 2 A method for preparing a dissolved nanocellulose, comprising the following steps: 1) mixing microcrystalline cellulose and phosphoric acid-water system (phosphoric acid concentration 85wt%) at a mass ratio of 8%, then stirring at a speed of 200 rpm and cooling to -10℃, dissolving for 2h to obtain a cellulose solution; 2) mixing water and ethanol at a mass ratio of 90:10, cooling to 0℃ to obtain an anti-solvent; 3) slowly adding the anti-solvent to the cellulose solution at a mass ratio of 1:6 to perform homogenization (5000 rpm, 10 min); 4) washing and concentrating the nanocellulose dispersion by centrifugation (6000 rpm, 5 min) to obtain nanocellulose with a yield of 93%.
[0020] Figure 2 AFM image of the nanocellulose prepared in Example 2 after dispersion in water (concentration 0.005%).
[0021] Example 3 A method for preparing a dissolved nanocellulose, comprising the following steps: 1) Microcrystalline cellulose and phosphoric acid-water system (phosphoric acid concentration 85 wt%) were mixed at a mass ratio of 8%, then stirred at a speed of 200 rpm and cooled to -10°C, and dissolved for 2h to obtain a cellulose solution; 2) Water and ethanol were mixed at a mass ratio of 60:40, and cooled to 0°C to obtain an anti-solvent; 3) The anti-solvent was slowly added to the cellulose solution at a mass ratio of 1:6 to perform homogenization (5000 rpm, 10 min); 4) The nanocellulose dispersion was washed and concentrated by centrifugation (6000 rpm, 5 min) to obtain nanocellulose with a yield of 90%.
[0022] Example 4 A method for preparing a dissolved nanocellulose, comprising the following steps: 1) Microcrystalline cellulose and phosphoric acid-water system (phosphoric acid concentration 85 wt%) were mixed at a mass ratio of 8:100, then stirred at a speed of 200 rpm and cooled to -10°C, and dissolved for 2h to obtain a cellulose solution; 2) Water and ethanol were mixed at a mass ratio of 50:50, and cooled to 0°C to obtain an anti-solvent; 3) The anti-solvent was slowly added to the cellulose solution at a mass ratio of 1:6 to perform homogenization (5000 rpm, 10 min); 4) The nanocellulose dispersion was washed and concentrated by centrifugation (6000 rpm, 5 min) to obtain nanocellulose with a yield of 88%.
[0023] Example 5 A method for preparing a dissolved nanocellulose, comprising the following steps: 1) Sulfate bleached wood pulp (hardwood pulp) and phosphoric acid-water system (phosphoric acid concentration 85 wt%) were mixed at a mass ratio of 8%, then stirred at a speed of 200 rpm and cooled to -10°C, and dissolved for 2h to obtain a cellulose solution; 2) Water and ethanol were mixed at a mass ratio of 90:10, and cooled to 0°C to obtain an anti-solvent; 3) The anti-solvent was slowly added to the cellulose solution at a mass ratio of 1:6 to perform homogenization (5000 rpm, 10 min); 4) The nanocellulose dispersion was washed and concentrated by centrifugation (6000 rpm, 5 min) to obtain nanocellulose with a yield of 91%.
[0024] Figure 3SEM image of nanocellulose prepared for Example 5.
[0025] Comparative Example 1 A method for preparing a dissolved nanocellulose, comprising the steps of: 1) mixing sulphate bleached wood pulp and zinc chloride-water system at a mass ratio of 8%, then stirring at a speed of 150 rpm and heating to 80°C, dissolving for 2 h to obtain a cellulose solution; 2) dissolving water and ethanol in a ratio of 80:20 to obtain an anti-solvent, and heating to 80°C; 3) slowly adding the anti-solvent to the cellulose solution and performing ultrasonic treatment (800 W, 10 min); 4) washing the nanocellulose dispersion by centrifugation (6000 rpm, 10 min) to obtain nanocellulose with a yield of 85%.
[0026] Comparative Example 2 A method for preparing a dissolved nanocellulose, comprising the steps of: 1) mixing cotton linter pulp and zinc chloride-water system at a mass ratio of 4%, then stirring at a speed of 150 rpm and heating to 80°C, dissolving for 2 h to obtain a cellulose solution; 2) dissolving water and ethanol in a ratio of 50:50 to obtain an anti-solvent, and heating to 80°C; 3) slowly adding the anti-solvent to the cellulose solution and performing ultrasonic treatment (800 W, 10 min); 4) washing the nanocellulose dispersion by centrifugation (6000 rpm, 10 min) to obtain nanocellulose with a yield of 82%.
Claims
1. A method for preparing soluble nanocellulose using an aqueous solvent, characterized in that: Includes the following steps: 1) The cellulose raw material is dissolved in a solvent to obtain a cellulose solution; the solvent is a phosphoric acid-water system; 2) The cellulose solution is mixed with an antisolvent and then dispersed at the nanoscale to obtain a nanocellulose dispersion; the antisolvent is one or more of water and ethanol, and the mass ratio of water to ethanol in the antisolvent is 100:0~60:40; the nanoscale dispersion method is one or more of high-speed shearing, ultrasonic treatment, and homogenization; the conditions for high-speed shearing are: 25000~15000 rpm, 10-20 min; the conditions for ultrasonic treatment are: 1000~600 W, 5-15 min; the conditions for homogenization are: 8000~4000 rpm, 5-20 min. 3) The nanocellulose dispersion is washed to obtain soluble nanocellulose; the washing refers to washing with water.
2. The method for preparing soluble nanocellulose using an aqueous solvent according to claim 1, characterized in that: The cellulose raw material is one or more of the following: kapok, microcrystalline cellulose, hemp, sulfate bleached wood pulp, coconut fiber, pomegranate peel, bamboo pulp, cotton, cotton linters, rice straw pulp, and reed pulp. The mass ratio of water to ethanol in the antisolvent is 100:0 to 80:20; The concentration of the phosphoric acid is 80-85 wt%.
3. The method for preparing soluble nanocellulose using an aqueous solvent according to claim 1, characterized in that: The dissolution is carried out at -30~50℃ with stirring at 100-800 rpm for 1-24 hours to form a homogeneous and transparent cellulose solution; The mass ratio of the cellulose solution to the antisolvent is 1:1-10.
4. The method for preparing soluble nanocellulose using an aqueous solvent according to claim 1, characterized in that: The temperature at which the antisolvent is mixed with the cellulose solution is 0-60℃; The particle size of the cellulose raw material is less than 500 μm; The amount of the cellulose raw material used is 0.5%-10% of the solvent mass.
5. The method for preparing soluble nanocellulose using an aqueous solvent according to claim 1, characterized in that: The washing process is performed by centrifugal washing.
6. The method for preparing soluble nanocellulose using an aqueous solvent according to claim 5, characterized in that: The conditions for centrifugal washing are 5000~7000 rpm and centrifugation for 5~15 min.