Dispersing agent applied to nanocellulose drying and application method thereof

Abstract

The invention relates to the field of drying of nano-crystalline cellulose, in particular to a dispersing agent for improving the redispersion efficiency of the dried nano-crystalline cellulose and a preparation method of the dispersing agent. The related drying agent is polyethylene glycol dialkyl ether, that is, two ends of polyethylene glycol are substituted by saturated alkyl chains, and the drying agent is prepared by carrying out nucleophilic substitution reaction on polyethylene glycol and alkyl halide. When the adding amount of the dispersing agent is 1%-50% of the dry weight of the nanocellulose, the redispersion performance of the dry nanocellulose can be remarkably improved. The dried nano cellulose not only can be re-dispersed in water, but also can be re-dispersed in polar aprotic solvents such as dimethyl sulfoxide, tetrahydrofuran and the like; and the re-dispersed nano-crystalline cellulose still keeps a nano-scale structure. The dispersing agent disclosed by the invention is easy to separate from the nanocellulose, is stable in property, does not participate in conventional chemical reaction, and is beneficial to chemical modification of the nanocellulose.

Description

[0001] The present invention relates to the field of drying of nanocellulose, and particularly to a dispersant for improving the redispersion efficiency of nanocellulose after drying and a preparation method thereof. Background Art

[0002] Nanocellulose is usually rod-shaped (CNC) or fibrillar (CNF) cellulose with a diameter less than 50 nm, and has received extensive attention in recent years as a green organic nanomaterial. Nanocellulose is mainly prepared from plant cellulose raw materials by physical, chemical or biological methods, and its application research involves many fields such as pulp and paper making, polymer reinforcement, electronic components, biomedicine, and tissue engineering scaffolds. The productivity and production efficiency of existing nanocellulose cannot meet the needs of large-scale applications. One of the main reasons is that nanocellulose is prone to irreversible aggregation during drying, and existing drying technologies cannot efficiently and economically prepare nanocellulose dry powder with good dispersibility. The produced nanocellulose needs to be dispersed in water, with an effective content of 2-8%, resulting in high transportation and storage costs, and its application is thus limited.

[0003] How to solve the problem of irreversible aggregation of nanocellulose during drying is a current challenge. Traditional nanocellulose dehydration methods mainly include: hot air drying, spray drying, freeze drying, and supercritical CO2 drying. Among them, spray drying is the most suitable for industrial-scale applications due to its low cost and high efficiency. However, the nanocellulose dry powder obtained by this method still has serious aggregation, and simply upgrading the drying equipment and optimizing the drying process parameters are difficult to completely solve the problem of irreversible aggregation of nanocellulose during drying. Adding a dispersant externally during the drying process is another strategy to inhibit the irreversible aggregation of nanocellulose during drying. The selected chemical substance should have the characteristics of inhibiting the hydrogen bonds between celluloses, being easily removed after redispersion, or having no negative impact on subsequent applications. The dispersants that have been studied mainly include sodium chloride, xanthan gum, sodium carboxymethyl cellulose, monosaccharides or oligosaccharides, etc. However, the use of these dispersants is not ideal. Sodium chloride is the most economical as a dispersant, but its anti-nanocellulose aggregation effect is relatively poor; anionic polymers such as sodium carboxymethyl cellulose (CMC) as dispersants for nanocellulose drying have good effects, but since these polymers all contain a large number of modifiable hydroxyl functional groups and are not easily separated and removed, they will interfere with the functional modification and application of nanocellulose.

[0004] In addition, to make nanocellulose suitable for different application scenarios, it is usually necessary to perform surface chemical modification on nanocellulose, such as introducing acrylate groups, epoxy groups, amino groups, silyl groups, etc. on the surface of nanocellulose. However, usually nanocellulose is dispersed in an aqueous environment, which is not convenient for its chemical modification. Usually, water needs to be replaced with other organic solvents. During this replacement process, it is necessary to use water-miscible solvents such as ethanol and acetone to replace it multiple times to completely remove water, and then use the required organic solvent to replace ethanol and acetone. The process is cumbersome and consumes a large amount of organic solvents, and it is not energy-saving and environmentally friendly. If nanocellulose is directly dried and then dispersed in the corresponding organic solvent, due to the irreversible aggregation of nanocellulose, the quality of the finally modified nanocellulose is seriously affected. Summary of the Invention

[0005] The object of the present invention is to provide a dispersant for improving the redispersion efficiency of nanocellulose after drying, so that nanocellulose can be redispersed into various solvents by simple mechanical action after drying, and has little influence on various performance indexes of nanocellulose, and can improve the modification efficiency of nanocellulose.

[0006] The object of the present invention is achieved by the following technical solutions: A dispersant applied to the drying of nanocellulose, characterized in that the structure is as follows: Among them, R is a saturated alkyl chain with 1 to 12 carbon atoms. Preferably, R is a saturated alkyl chain with 1 to 6 carbon atoms; n represents the degree of polymerization, n = 4 to 500. Preferably, n = 15 to 150.

[0007] A preparation method of the dispersant for drying nanocellulose as described above, characterized in that the synthesis route is as follows: In the structural formula, R is a saturated alkyl chain with 1 to 18 carbon atoms. Preferably, R is a saturated alkyl chain with 1 to 6 carbon atoms; n represents the degree of polymerization, n = 4 to 500. Preferably, n = 15 to 150; The operation steps are as follows: Dissolve polyethylene glycol in a tetrahydrofuran solvent, then add an appropriate amount of strong base, stir at 15 to 35 °C for 10 to 30 minutes, add a monohaloalkane (R-X), and continue to stir at 15 to 35 °C for 5 to 12 hours. Evaporate the tetrahydrofuran, dilute the residue with water, then extract with dichloromethane, evaporate the dichloromethane, and then recrystallize with an appropriate amount of organic ether solvent to obtain polyethylene glycol dialkyl ether; Among them, the molar ratio of polyethylene glycol, strong base, and monohaloalkane is 1: (2.0 to 2.5): (2.1 to 3); the strong base is any one of sodium hydride, sodium amide, sodium acetylide, lithium diisopropylamide, and butyllithium; The described R-X is characterized in that X is any one of Cl, Br, and I; The described organic ether solvent is any one of diethyl ether and methyl tert-butyl ether; A method for applying a dispersant as described above in the drying of nanocellulose is characterized in that the application steps are as follows: Under the condition of 10°C to 35°C, add the above-mentioned dispersant to the nanocellulose suspension, stir with a mechanical stirrer for 1 h to 5 h, and then dry the nanocellulose suspension by physical drying means to obtain nanocellulose powder with a water content of 0.1% to 5%; The described physical drying means is any one of air drying, air atomization drying, pressure atomization drying, pulse combustion atomization drying, centrifugal atomization drying, freeze-vacuum drying, heat-vacuum drying, and freeze-vacuum atomization drying; The described nanocellulose suspension has a concentration of 0.5% to 10%, and preferably, the concentration of the nanocellulose suspension is 1% to 3%.

[0008] The addition amount of the described dispersant is 0.1% to 100% of the dry weight of the nanocellulose, and preferably, its addition amount is 1% to 50% of the dry weight of the nanocellulose.

[0009] Beneficial effects: After adding the dispersant of the present invention, the redispersion performance of the dried nanocellulose is significantly improved. The dried nanocellulose can not only be redispersed in water, but also in polar aprotic solvents such as dimethyl sulfoxide and tetrahydrofuran; the redispersed nanocellulose still maintains a nanoscale structure; the dispersant of the present invention is easily separated from the nanocellulose; the dispersant of the present invention is resistant to acids and bases in terms of structure and does not participate in conventional nucleophilic substitution reactions. Therefore, it has little influence on the chemical modification of nanocellulose. Description of the Drawings

[0010] Figure 1 It is a transmission electron micrograph measured after the nanocellulose dried in Example 4 of the present invention is redispersed in water.

[0011] Figure 2 It is a transmission electron micrograph measured after the nanocellulose dried in Example 5 of the present invention is redispersed in water.

[0012] Figure 3 It is a transmission electron micrograph measured after the nanocellulose dried in Comparative Example 1 of the present invention is redispersed in water. Detailed Embodiments

[0013] Example 1

[0014] Dissolve 100 g of polyethylene glycol with a molecular weight of 1000 Da in 400 mL of tetrahydrofuran, then add 8 g of a sodium hydride mineral oil mixture with a mass fraction of 60%. After stirring at 35 °C for 10 min, add 30 g of iodomethane and continue to stir at 35 °C for 5 h. Evaporate tetrahydrofuran to dryness, dilute the residue with 500 mL of water, then extract the aqueous phase three times with 2 L of dichloromethane. Combine the dichloromethane phases, distill off dichloromethane under reduced pressure, recrystallize with 400 mL of ether, filter and dry to obtain 92 g of polyethylene glycol dimethyl ether with a molecular weight of about 1000 Da, and the 1H-NMR is H 1 -NMR (400 MHz, CDCl3): 3.64 (m, 84H), 3.55 (m, 4H), 3.38 (s, 6H). Example 2

[0015] Dissolve 100 g of polyethylene glycol with a molecular weight of 6000 Da in 1 L of tetrahydrofuran, then add 20.8 mL of a tetrahydrofuran solution of lithium diisopropylamide with a concentration of 2 mol / L. After stirring at 15 °C for 30 min, introduce 15 g of chloromethane and continue to stir at 15 °C for 12 h. Then evaporate tetrahydrofuran to dryness, dilute the residue with 4 L of water, then extract the aqueous phase three times with 2 L of dichloromethane. Combine the dichloromethane phases, distill off dichloromethane under reduced pressure, recrystallize with 1 L of methyl tert-butyl ether, filter and dry to obtain 95 g of polyethylene glycol dimethyl ether with a molecular weight of about 6000 Da, and the 1H-NMR is H 1 -NMR(400 MHz, CDCl3): 3.64 (m, 544H), 3.55 (m, 4H), 3.38 (s, 6H). Example 3

[0016] Dissolve 100 g of polyethylene glycol with a molecular weight of 1000 Da in 400 mL of tetrahydrofuran solvent, then add 8 g of a sodium hydride mineral oil mixture with a mass fraction of 60%. After stirring at 15 °C for 10 min, add 41.1 g of 1-bromobutane, and then continue to stir at 15 °C for 12 h. Evaporate tetrahydrofuran to dryness, dilute the residue with water, then extract three times with 2 L of dichloromethane, distill off dichloromethane under reduced pressure, recrystallize with 400 mL of ether, filter and dry to obtain 88 g of polyethylene glycol dibutyl ether with a molecular weight of about 1000 Da, and the 1H-NMR is H 1 -NMR (400 MHz, CDCl3): 3.65 (m, 84H), 3.35 (t, J J = 6.4 Hz, 4H), 1.51 (m, 8H), 0.96 (t, J= 6.4 Hz, 6H). Example 4

[0017] 50 mg of the polyethylene glycol dimethyl ether prepared in Example 1 was added to 500 g of a 1% cellulose nanocrystal solution, stirred at 10 °C for 5 h, and then poured onto a tray with an area of about 800 cm 2 . The cellulose nanocrystal suspension was dried in a forced-air drying oven at 80 °C for about 8 h to obtain cellulose nanocrystal powder CNC-1 with a water content of 1.7%. Example 5

[0018] 500 mg of the polyethylene glycol dimethyl ether prepared in Example 1 was added to 100 g of a 1% cellulose nanocrystal solution, stirred at 35 °C for 1 h, and then poured onto a tray with an area of about 800 cm 2 . The cellulose nanocrystal suspension was dried in a forced-air drying oven at 80 °C for about 8 h to obtain cellulose nanocrystal powder CNC-2 with a water content of 2.3%. Example 6

[0019] 10 mg of the polyethylene glycol dimethyl ether prepared in Example 2 was added to 100 g of a 1% cellulose nanocrystal solution, stirred at 10 °C for 5 h, and then poured onto a tray with an area of about 800 cm 2 . The cellulose nanocrystal suspension was dried in a forced-air drying oven at 80 °C for about 8 h to obtain cellulose nanocrystal powder CNC-3 with a water content of 1.5%. Example 7

[0020] 30 mg of the polyethylene glycol dibutyl ether prepared in Example 3 was added to 100 g of a 3% cellulose nanocrystal solution, stirred at 35 °C for 1 h, and then poured onto a tray with an area of about 800 cm 2 . The cellulose nanocrystal suspension was dried in a forced-air drying oven at 80 °C for about 8 h to obtain cellulose nanocrystal powder CNC-4 with a water content of 2.0%. Example 8

[0021] 100 mg of the polyethylene glycol dimethyl ether prepared in Example 1 was added to 1000 g of a 1% cellulose nanocrystal solution, and then stirred at 10 °C for 5 h. Then, spray drying was carried out using an air flow spray dryer (model: QFN-8000S). The instrument parameters were as follows: the inlet air temperature was 150 °C, the peristaltic pump speed was 20 revolutions / min, and the inlet air pressure was 0.2 MPa. Finally, cellulose nanocrystal powder CNC-5 was obtained. The average particle size of the powder was measured to be 25 μm by a laser particle size analyzer, and the water content was 1.1%. Example 9

[0022] 10 mg of the polyethylene glycol dimethyl ether prepared in Example 2 was added to 100 g of a 1% cellulose nanocrystal solution, stirred at 10 °C for 5 h, then frozen at -70 °C for 5 h, and then freeze-dried using a freeze dryer. Finally, cellulose nanocrystal powder CNC-6 was obtained, and the water content was 1.4%. Example 10

[0023] 10 mg of the polyethylene glycol dibutyl ether prepared in Example 3 was added to 100 g of a 1% cellulose nanocrystal solution, stirred at 25 °C for 2 h, then frozen at -70 °C for 5 h, and then freeze-dried using a freeze dryer. Finally, cellulose nanocrystal powder CNC-7 was obtained, and the water content was 1.3%. Example 11

[0024] 10 mg of the polyethylene glycol dimethyl ether prepared in Example 1 was added to 100 g of a 1% cellulose nanofiber solution, stirred at 10 °C for 5 h, and then poured onto a tray with an area of about 800 cm 2 . The cellulose nanocrystal suspension was dried using a forced air drying oven at 80 °C for about 10 h to obtain cellulose nanofiber powder CNF-1, with a water content of 2.0%. Example 12

[0025] 100 mg of the polyethylene glycol dimethyl ether prepared in Example 2 was added to 1000 g of a 1% cellulose nanofiber solution, and then stirred at 10 °C for 5 h. Then, spray drying was carried out using an air flow spray dryer (model: QFN-8000S). The instrument parameters were as follows: the inlet air temperature was 150 °C, the peristaltic pump speed was 20 revolutions / min, and the inlet air pressure was 0.2 MPa. Finally, cellulose nanofiber powder CNF-2 was obtained. The average particle size of the powder was measured to be 30 μm by a laser particle size analyzer, and the water content was 1.2%. Comparative Example 1

[0026] Pour 100 g of a cellulose nanocrystal solution with a content of 1% onto a tray with an area of approximately 800 cm 2 Dry the cellulose nanocrystal suspension in a forced-air drying oven at 80 °C for approximately 8 h to obtain cellulose nanocrystal film fragments CNC-h with a water content of 1.9%. Comparative Example 2

[0027] Spray-dry 1000 g of a cellulose nanocrystal solution with a content of 1% using an air-flow spray dryer (model: QFN-8000S). Instrument parameters: inlet air temperature is 150 °C, peristaltic pump speed is 20 revolutions / min, and inlet air pressure is 0.2 MPa. Finally, obtain cellulose nanocrystal powder CNC-p. The average particle size of the powder measured using a laser particle size analyzer is 50 μm, and the water content is 1.3%. Comparative Example 3

[0028] Freeze 100 g of a cellulose nanocrystal solution with a content of 1% at -70 °C for 5 h, and then freeze-dry it using a freeze dryer to finally obtain cellulose nanocrystal powder CNC-d with a water content of 1.8%. Comparative Example 4

[0029] Pour 100 g of a cellulose nanofibril solution with a content of 1% onto a tray with an area of approximately 800 cm 2 Dry the cellulose nanofibril suspension in a forced-air drying oven at 80 °C for approximately 10 h to obtain cellulose nanofibril film fragments CNF-h with a water content of 2.1%. Comparative Example 5

[0030] Spray-dry 1000 g of a cellulose nanofibril solution with a content of 1% using an air-flow spray dryer (model: QFN-8000S). Instrument parameters: inlet air temperature is 150 °C, peristaltic pump speed is 20 revolutions / min, and inlet air pressure is 0.2 MPa. Finally, obtain cellulose nanofibril powder CNF-p. The average particle size of the powder measured using a laser particle size analyzer is 65 μm, and the water content is 1.6%. Comparative Example 6

[0031] Freeze 100 g of a cellulose nanofibril solution with a content of 1% at -70 °C for 5 h, and then freeze-dry it using a freeze dryer to finally obtain cellulose nanofibril aerogel CNF-d with a water content of 1.8%. Comparative Example 7

[0032] Add 10 mg of sodium chloride to 100 g of a cellulose nanocrystal solution with a content of 1%, then stir it at 10 °C for 5 h, and then pour it onto a tray with an area of approximately 800 cm 2On the tray, the cellulose nanocrystal suspension was dried in a forced air drying oven at 80 °C for about 8 h to obtain cellulose nanocrystal film fragments CNC-NaCl with a water content of 18%. Redispersion performance test

[0033] The nanocellulose powders obtained in Examples 1-12 and Comparative Examples 1-7 above were dispersed in a solvent. The mass ratio of the powder to the solvent was 1:100. The solvent included any one of water, dimethyl sulfoxide (DMSO), and tetrahydrofuran (THF). Then, a magnetic stirrer was used for stirring and dispersion for 3 h. Then, an ultrasonic instrument was used for ultrasonic treatment for 10 min (power 60 W, model JP-020S). Then, the dispersion stability of the nanocellulose in the solvent was observed, and the particle size distribution of the nanocellulose in the solvent was measured using a laser particle size analyzer and compared with the nanocellulose before drying. The cellulose nanocrystal suspension before drying was CNC-0 with a content of 1%, and the cellulose nanofibril before drying was CNF-0 with a content of 1%.

[0034] Table 1 Particle size distribution of nanocellulose measured by laser particle size analyzer (unit: nm) Serial number Sample Water DMSO THF 1 CNC-1 532~785 755~963 957~1266 2 CNC-2 416~635 512~796 762~1132 3 CNC-3 435~706 627~962 904~1365 4 CNC-4 468~692 654~915 819~1538 5 CNC-5 337~585 583~862 769~1274 6 CNC-6 313~572 517~913 812~1423 17 CNC-7 306~592 577~854 847~1295 8 CNF-1 1855~3120 2535~4570 2535~4570 9 CNF-2 1325~2140 1795~3350 1795~3350 10 CNC-h 1130~3765 1696~4381 1696~4381 11 CNC-p 975~2664 1575~3197 1575~3197 12 CNC-d 672~1813 1277~1963 1277~1963 13 CNF-h >4570 >5755 >5755 14 CNF-p >3650 >4959 >4959 15 CNF-d 2475~5426 3245~7271 3245~7271 16 CNC-NaCl 685~1447 1205~2438 1205~2438 17 CNC-0 300~450 / / 18 CNF-0 925~1500 / / The experimental results show that cellulose nanocrystals or cellulose nanofibrils added with dimethyl ether of polyethylene glycol or dibutyl ether of polyethylene glycol can be stably redispersed in solvents such as water, DMSO, and THF after drying. They are more stable in water and DMSO and do not show stratification after standing for 30 days. However, in THF, stratification occurs after standing for 2 days, and the upper clear water layer accounts for about 20% of the total suspension volume. After standing for another 30 days, there is no obvious change. In contrast, cellulose nanocrystals and cellulose nanofibrils without a dispersant mostly show aggregated flakes after drying and are difficult to disperse. Obvious sedimentation occurs after standing in solvents such as water, DMSO, and THF for 30 minutes, and the supernatant accounts for more than 80% of the total suspension volume.

[0035] The test data results of the laser particle size analyzer show that the particle sizes of the nanocellulose added with a dispersant in solvents such as water, DMSO, and THF (Table 1, serial numbers 1-9) are close to those of the nanocellulose before drying (Table 1, serial numbers 17 and 18). The order of particle size in these three solvents is: r 水 < r DMSO < r THF, while the dried and redispersed nanocellulose without added dispersant (Table 1, serial numbers 10 - 15) has a particle size several times larger than that of the nanocellulose before drying. Compared with sodium chloride as the dispersant (Table 1, serial number 16), the dispersant of the present invention has significantly superior drying and redispersion effects on nanocellulose. Characterization by transmission electron microscopy:

[0036] The CNCs in Example 4, Example 5, and Comparative Example 1 were redispersed in water by magnetic stirring, and then the morphology of the samples was characterized using a transmission electron microscope.

[0037] The experimental results show that the nanocellulose without added dispersant aggregates severely, while the nanocellulose with added dispersant has good dispersibility, maintains a whisker-like nanostructure, and the dispersing effect is enhanced with the increase in the amount of dispersant added. Example 13

[0038] 1 g of the dried nanocellulose in Example 4 was dispersed in 10 mL of water, magnetically stirred for 15 minutes, then centrifuged. The solid was then soaked in 10 mL of water under magnetic stirring for 15 minutes and centrifuged again. The supernatants from the two times were combined and then evaporated to dryness to obtain 9.8 mg of a waxy solid, which was characterized by nuclear magnetic resonance. The nuclear magnetic resonance hydrogen spectrum data proved that the obtained waxy solid was polyethylene glycol dimethyl ether. Example 14

[0039] 1 g of the dried nanocellulose in Example 7 was dispersed in 10 mL of water, magnetically stirred for 15 minutes, then centrifuged. The solid was then soaked in 10 mL of water under magnetic stirring for 15 minutes and centrifuged again. The supernatants from the two times were combined and then evaporated to dryness to obtain 9.6 mg of a waxy solid, which was characterized by nuclear magnetic resonance. The nuclear magnetic resonance hydrogen spectrum data proved that the obtained waxy solid was polyethylene glycol dibutyl ether.

[0040] The experimental results of Example 13 and Example 14 show that the dispersant of the present invention is easily separated from nanocellulose, which facilitates the removal of the dispersant during application.

Claims

1. A dispersant applied to the drying of nanocellulose, characterized in that, The structure is as follows: Among them, R is a saturated alkyl chain of C1-C12. Preferably, R is a saturated alkyl chain of C1-C6; n represents the degree of polymerization, n = 4-500. Preferably, n = 15-150.

2. The preparation method of the dispersant for drying nanocellulose according to claim 1, characterized in that, The synthesis route is as follows: In the structural formula, R is a saturated alkyl chain with 1 to 18 carbon atoms. Preferably, R is a saturated alkyl chain with 1 to 6 carbon atoms; n represents the degree of polymerization, where n = 4 to 500. Preferably, n = 15 to 150; The operation steps are as follows: Dissolve polyethylene glycol in a tetrahydrofuran solvent, then add an appropriate amount of strong base, stir at 15 - 35 °C for 10 - 30 min, add a monohaloalkane, continue to stir at 15 - 35 °C for 5 - 12 h, evaporate the tetrahydrofuran to dryness, dilute the residue with water, then extract with dichloromethane, evaporate the dichloromethane to dryness, and then recrystallize with an appropriate amount of organic ether solvent to obtain polyethylene glycol dialkyl ether.

3. The preparation method of the dispersant for drying nanocellulose according to claim 2, wherein, The molar ratio of polyethylene glycol, strong base, and monohaloalkane is 1:(2.0 - 2.5):(2.1 - 3).

4. The preparation method of the dispersant for drying nanocellulose according to claim 2, characterized in that, The strong base is any one of sodium hydride, sodium amide, sodium acetylide, lithium diisopropylamide, and butyllithium.

5. The preparation method of the dispersant for drying nanocellulose according to claim 2, characterized in that, The organic ether solvent is any one of diethyl ether and methyl tert-butyl ether.

6. The application of the dispersant according to claim 1 in the drying of nanocellulose.

7. The application method of the dispersant in the drying of nanocellulose according to claim 1, characterized in that, The application steps are as follows: At 10 °C - 35 °C, add the dispersant to the nanocellulose suspension, stir with a mechanical stirrer for 1 h - 5 h, and then dry the nanocellulose suspension by physical drying to obtain nanocellulose powder with a water content of 0.1% - 5%.

8. The method for applying the dispersant in the drying of nanocellulose according to claim 7, characterized in that, The physical drying methods include any one of air drying, pneumatic spray drying, pressure spray drying, pulsating combustion spray drying, centrifugal spray drying, freeze-vacuum drying, heat-vacuum drying, and freeze-vacuum spray drying.

9. The method for applying the dispersant in the drying of nanocellulose according to claim 7, characterized in that, The concentration of the nanocellulose suspension is 0.5% - 10%, preferably, the concentration of the nanocellulose suspension is 1% - 3%.

10. The method for applying the dispersant in the drying of nanocellulose according to claim 7, characterized in that, The addition amount of the dispersant is 0.1% - 100% of the dry weight of the nanocellulose, preferably, the addition amount is 1% - 50% of the dry weight of the nanocellulose.

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