Method for producing surface-modified cellulose

Abstract

To provide a novel method that can readily modify the surface of nano cellulose.SOLUTION: The present invention provides a method for producing surface-modified nano cellulose by subjecting nano cellulose and carboxylic acid to mechanochemical treatment in the presence of ionic liquid. The mechanical treatment is performed by adding a specific reaction aid such as p-toluenesulfonyl chloride.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing surface-modified cellulose. [Background technology]

[0002] Cellulose is the most abundant renewable substance and has been used continuously from ancient times to modern technological society. Cellulose, a fiber derived from plants, has a small environmental impact and is a sustainable resource, and has excellent properties such as high elastic modulus, high strength, and low linear expansion coefficient. Therefore, it is used for a wide range of applications, such as materials for paper, films, sheets, etc., and resin composite materials (e.g., resin reinforcing agents). In particular, finely divided nanocellulose (nanofibers, etc.) is useful as a resin reinforcing agent, and many attempts have been made to compound it with resin.

[0003] Furthermore, cellulose has various characteristics not found in synthetic polymers such as polystyrene, including the following: (1) It is a biodegradable polymer and is considered to be harmless to the environment. (2) It is an amphiphilic polymer that has both water and oil absorbency. (3) It is relatively chemically stable and does not easily dissolve. (4) It is heat resistant and does not melt even at high temperatures. (5) It has many hydroxyl groups and can be easily chemically modified. (6) It has shapeability and molding properties. (7) It is derived from natural products and is considered to be harmless to the human body. (8) It is unlikely to interact with substances such as proteins and will not be adsorbed. (9) It burns easily and does not produce any harmful substances.

[0004] Making use of the above characteristics (1) to (9), cellulose powder and its dispersion liquid are adapted to various uses. For example, in addition to the above plastic extenders and plastic fillers, the uses are wide-ranging, including exterior paint modifiers, coating agents, fiber wall materials, dispersion stabilizers, column packing materials for various fractionations, enzyme supports, microbial culture carriers, cell culture carriers, filter media, adsorbents, pharmaceutical excipients, pharmaceutical disintegrants, pharmaceutical extenders, granulation base materials, food thickening regulators, thixotropy imparting agents, cosmetic foundation base materials, molding agents for the manufacture of baked catalysts, and compounding agents for pressure-sensitive copying paper.

[0005] It is also known that by forming a dispersion, it acts specifically on the dispersion medium and exerts a specific effect on the behavior of the dispersion. Furthermore, fine particles of cellulose derivatives obtained by chemically reacting the hydroxyl groups of cellulose are also used for various purposes.

[0006] In order to obtain high functionality in various applications, the morphology and surface state of cellulose are important. Regarding the morphology of cellulose, cellulose microparticles with various characteristics have been used so far depending on the above-mentioned applications. For example, those provided by physical or chemical micronization, those provided by preparing dissolved cellulose droplets and coagulating and regenerating them, etc. have been used.

[0007] Examples of the former type of cellulose fine particles include those described in Patent Documents 1 and 2. An example of the latter type of cellulose fine particles includes that described in Patent Document 3.

[0008] In addition, various approaches such as surface modification of nanocellulose have been made to facilitate the composite of nanocellulose and resin. For example, modified cellulose fibers obtained by reacting cellulose fibers activated with radicals in a solvent with a compound having a 9,9-bisarylfluorene skeleton have been proposed (see Patent Document 4). In addition, a method has been proposed in which a functional compound is coupled to cellulose after a polymer having a hydroxyl group is converted into a halogenated derivative (see Patent Document 5). In addition, a compound has been proposed in which an epoxy group is introduced into the cellulose skeleton using carboxymethylated cellulose converted into a sodium salt as a starting material (see Non-Patent Document 1).

[0009] Furthermore, a technology has been proposed for modified nanocellulose in which the surface of nanocellulose is modified using an esterification reaction, and for a resin composition containing nanocellulose (see Patent Document 6). In Patent Document 6, nanocellulose is chemically modified with an alicyclic hydrocarbon group or a group having an alicyclic hydrocarbon group, thereby improving dispersibility and adhesion with resins. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 3-163135 [Patent Document 2] Japanese Patent Application Publication No. 11-171901 [Patent Document 3] Japanese Patent Application Publication No. 11-181147 [Patent Document 4] JP 2017-222777 A [Patent Document 5] Japanese Patent Application Publication No. 4-76001 [Patent Document 6] Patent No. 6120590 [Non-patent literature]

[0011] [Non-Patent Document 1] Applied Catalysis A: General 519 (2016) 146‐154 Summary of the Invention [Problem to be solved by the invention]

[0012] The challenges for the widespread use of nanocellulose in industry are a significant reduction in the cost of nanocellulose itself, and diversification and cost reduction of composite materials using nanocellulose. Although various technologies have been proposed for surface modification of nanocellulose, a new method for more easily producing high-quality nanocellulose has been required.

[0013] The object of the present invention is to provide a novel method for easily modifying the surface of nanocellulose. [Means for solving the problem]

[0014] The present inventors have proposed a method for mechanochemically treating nanocellulose and carboxylic acid in the presence of an ionic liquid as a method for easily modifying the surface of nanocellulose (JP Patent Publication No. 2021-25055). However, although this method allows relatively easy introduction of a carboxylic acid containing an aromatic group, it is difficult to introduce a carboxylic acid containing a long-chain aliphatic group. As a result of further research into this proposed method, the inventors have found that by using a specific reaction aid in combination, it is possible to easily introduce carboxylic acids containing long-chain aliphatic groups, which was difficult to do using the above method, and have thus completed the present invention.

[0015] That is, the present invention is as follows. [1] A method for producing surface-modified nanocellulose comprising a mechanochemical process of mechanochemically treating nanocellulose and a carboxylic acid in the presence of an ionic liquid, A method for producing surface-modified nanocellulose, characterized in that the mechanical treatment in the mechanochemical process is carried out by adding a reaction aid capable of introducing p-toluenesulfonyl groups, methanesulfonyl groups, o-nitrobenzenesulfonyl groups, or trifluoromethanesulfonyl groups to the hydroxyl groups of the nanocellulose. [2] The method for producing surface-modified nanocellulose according to [1] above, characterized in that the reaction aid is p-toluenesulfonyl chloride. [3] The method for producing surface-modified nanocellulose according to [1] or [2] above, characterized in that the carboxylic acid is a carboxylic acid having 5 or more carbon atoms. [4] The method for producing surface-modified nanocellulose according to any one of [1] to [3] above, characterized in that the ionic liquid has Lewis acidity. [5] The method for producing surface-modified nanocellulose according to any one of [1] to [4] above, characterized in that the cation of the ionic liquid is an imidazolium cation. [6] The method for producing surface-modified nanocellulose according to any one of [1] to [5] above, characterized in that the anion of the ionic liquid is a hydrogen sulfate anion.

[0016] [7] The method for producing surface-modified nanocellulose according to any one of [1] to [6] above, characterized in that no organic solvent is used in the mechanical treatment in the mechanochemical process. [8] The method for producing surface-modified nanocellulose according to any one of [1] to [7] above, characterized in that the ionic liquid is added in an amount of 1 to 10 mol per 1 mol of carboxylic acid. [9] A method for producing surface-modified nanocellulose according to any one of [1] to [8] above, characterized in that the nanocellulose is defibrated in the mechanochemical process. Effect of the Invention

[0017] According to the present invention, surface-modified cellulose can be produced in a simple manner. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a conceptual diagram of a first embodiment. [Diagram 2] FIG. 1 is a conceptual diagram of a first embodiment. [Diagram 3] 1 is an IR spectrum of the surface-modified cellulose produced in Example 1. [Figure 4] 1 shows the thermogravimetric curve (TG curve) of the surface-modified cellulose produced in Example 1. [Diagram 5] FIG. 1 shows the XRD pattern of the surface-modified cellulose produced in Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The method for producing surface-modified nanocellulose of the present invention has a mechanochemical process in which nanocellulose and carboxylic acid are mechanochemically treated in the presence of an ionic liquid, and the mechanical treatment in the mechanochemical process is carried out by adding a reaction aid. As the reaction aid, a compound capable of introducing p-toluenesulfonyl, methanesulfonyl, o-nitrobenzenesulfonyl or trifluoromethanesulfonyl groups to the hydroxyl groups of nanocellulose is used.

[0020] The manufacturing method of the present invention has a wider range of substrates (carboxylic acids) to choose from than conventional surface modification methods for nanocellulose, and can produce various surface-modified nanocelluloses cheaply and safely from readily available commercially available compounds. In addition, since there is no need to use an organic solvent, large-scale exhaust equipment is not required, and the environmental impact is low. Furthermore, since it is a simple method such as mechanical mixing, surface-modified nanocellulose can be easily produced in large quantities. In addition, the produced surface-modified nanocellulose becomes smaller particles with a size that is smaller than that of the defibration. Conventionally, the defibration process and the surface modification process were separate unit operations, which complicated the process, leading to a decrease in yield and a factor in increasing costs, but in the manufacturing method of the present invention, disintegration and surface modification can be performed simultaneously, which can improve yield and reduce costs. In particular, the manufacturing method of the present invention using a reaction assistant makes it easy to introduce carboxylic acids containing long-chain aliphatic groups, and cellulose esterified with long-chain fatty acids can be easily obtained.

[0021] Each step will be described below. [Mechanochemical process] The mechanochemical process involves mechanochemically treating nanocellulose and carboxylic acids in the presence of an ionic liquid. Here, mechanochemical treatment is a method of mixing while applying mechanical energy such as shear force, collision force, or centrifugal force to the object to be treated. Such treatment can be performed using a grinding machine such as a ball mill, a bead mill, a jet mill, a vibration mill, a disk mill, a turbo mill, a homogenizer, or a mechanofusion. The mechanochemical treatment can disperse nanocellulose and promote the active reaction between the new active surface of nanocellulose and carboxylic acid, which causes an esterification reaction between the hydroxyl group of nanocellulose and the carboxyl group of carboxylic acid to obtain surface-modified nanocellulose. That is, depending on the polarity of the surface of nanocellulose, an electric double layer is formed by the positively charged component and the negatively charged component of the ionic liquid, and monodispersion progresses, and further, it is presumed that a new fracture surface is created by mechanical energy such as shear force, and surface modification progresses. This method does not require the use of an organic solvent, and the amount of ionic liquid added can be small, so that surface-modified cellulose can be mass-produced easily and environmentally.

[0022] In the production method of the present invention, a reaction aid is added in this mechanical step. As the reaction aid, as described above, a compound capable of introducing a p-toluenesulfonyl group, a methanesulfonyl group, an o-nitrobenzenesulfonyl group, or a trifluoromethanesulfonyl group to the hydroxyl group of nanocellulose is used. Among these, a compound capable of introducing a p-toluenesulfonyl group or a methanesulfonyl group is preferred.

[0023] Specific examples of the reaction aid include p-toluenesulfonyl chloride having a tosyl group, 1-tosylimidazole, p-toluenesulfonic anhydride, methanesulfonyl chloride having a mesyl group, o-nitrobenzenesulfonyl chloride having a nosyl group, and trifluoromethanesulfonyl chloride having a trifluoromethanesulfonyl group. These may be used alone or in combination.

[0024] The reaction aid may be added from the beginning of the reaction or during the reaction. The ratio of the reaction aid to the carboxylic acid is not particularly limited as long as the desired reaction proceeds, but is preferably 1 to 10 mol, more preferably 1 to 5 mol, and even more preferably 1 to 1.5 mol, per 1 mol of the carboxylic acid.

[0025] When dissolving nanocellulose, the viscosity of the resulting nanocellulose solution is preferably such that existing kneading equipment that provides a mechanochemical effect can be used. For example, the viscosity of the nanocellulose solution is preferably 30,000 centipoise (cP) or less, more preferably 25,000 centipoise or less, even more preferably 20,000 centipoise or less, and particularly preferably 15,000 centipoise or less. Furthermore, 10,000 centipoise or less, 8,000 centipoise or less, 6,000 centipoise or less, 4,000 centipoise or less, and 2,000 centipoise or less are more preferable.

[0026] The ratio of the ionic liquid to the carboxylic acid is not particularly limited as long as it is an amount that allows the desired reaction to proceed (an amount that functions as a catalyst), but is, for example, 1 to 15 mol per 1 mol of the carboxylic acid. In the present invention, the reaction proceeds even by adding a small amount of 1 to 10 mol, preferably 1 to 5 mol, and mixing (kneading).

[0027] The ratio of carboxylic acid added to nanocellulose is, for example, 1 to 100 mol, and preferably 1 to 10 mol, per 1 mol of nanocellulose.

[0028] The mixing temperature depends on the type of ionic liquid used, and is, for example, about 0° C. to 200° C., and preferably about 30 to 100° C. The mixing time is, for example, about 1 to 96 hours, preferably about 2 to 72 hours, and more preferably about 3 to 48 hours.

[0029] (Ionic Liquid) The ionic liquid in the present invention is a salt having an ion conductivity and a low melting point, for example, a liquid in which an organic onium ion as a cation and an organic or inorganic anion as an anion are combined. The ionic liquid is usually a salt that becomes liquid at 100° C. or lower (for example, room temperature 25° C. or lower).

[0030] Examples of the cation of the ionic liquid include organic nitrogen-based cations, organic phosphorus-based cations, and organic sulfur-based cations. In the present invention, among these, organic nitrogen-based cations are preferred, and organic nitrogen-based cations having one or more nitrogen atoms in a part of the ring structure are particularly preferred. Examples of such organic nitrogen-based cations include imidazolium cations, pyridinium cations, pyridazinium cations, pyrimidinium cations, pyrazinium cations, pyrazolium cations, and pyrrolidinium cations. In the present invention, among these, imidazolium cations are preferred, and specific examples include 1-ethyl-3-methylimidazolium, 1,3-dimethylimidazolium, 1-methyl-3-propylimidazolium, 1-methyl-3-isopropylimidazolium, 1,3-diethylimidazolium, 1,3-dipropylimidazolium, 1-ethyl-3-propylimidazolium, and 1-butyl-3-methylimidazolium cation [BMIM].

[0031] The anion is not particularly limited as long as it can be combined with the above cation, and may be, for example, HSO 4 - , NO 2 - , NO 3 - , I - , B.F. 4 - , P.F. 6 - , AsF 6 - , SbF 6 - , NbF 6 - , TaF 6 - , F(HF)2.3 - , P-CH 3 PhSO 3 - , C.H. 3 CO 2 - , C.F. 3 CO 2 - , C.H. 3 SO 3 - , C.F. 3 SO 3 - , C 4 F 9 SO 3 - , (CF 3 SO 2 ) 3 C - , C 3 F 7 CO 2 - , (C 2 F 5 SO 2 ) 2 N - , (CF 3 SO 2 ) 2 N - , (CF 3 SO 2 )(CF 3 CO)N - , (CN) 2 N - , AlCl 4 - Among these, HSO 4 - is preferred.

[0032] The ionic liquid in the present invention can be appropriately combined with the cations and anions exemplified above, but preferably has Lewis acidity.Specific examples of such preferred ionic liquids include 1,3-dimethylimidazolium hydrogen sulfate, 1-methyl-3-propylimidazolium hydrogen sulfate, 1-methyl-3-isopropylimidazolium hydrogen sulfate, 1,3-diethylimidazolium hydrogen sulfate, 1,3-dipropylimidazolium hydrogen sulfate, 1-ethyl-3-propylimidazolium hydrogen sulfate, 1-butyl-3-methylimidazolium hydrogen sulfate, and 1-ethyl-3-methylimidazolium hydrogen sulfate.These may be used alone or in combination of two or more.

[0033] (Nanocellulose) The nanocellulose in the present invention can be prepared by micronizing natural cellulose or synthetic cellulose. Examples of natural cellulose include cellulose derived from plants, specifically, broadleaf pulp, coniferous pulp, bamboo, oil palm, etc.

[0034] Methods for micronizing natural cellulose and the like to produce nanocellulose include various known methods, such as a high-pressure homogenizer method, a ball mill pulverization method, a grinder grinding method, a high shear force kneading method, and a freeze-pulverization method.

[0035] Here, examples of nanocellulose include cellulose nanofibers, cellulose nanocrystals, cellulose microcrystals, cellulose nanowhiskers, etc., and cellulose nanofibers and cellulose microcrystals are preferred. In the present invention, a mixture of nanocellulose such as lignocellulose and other substances may be used.

[0036] (Carboxylic Acid) The carboxylic acid in the present invention is a molecule having a carboxyl group in its composition and is a compound represented by R'-COOH (where R' represents an organic group). Examples of the organic group represented by R' include an aliphatic group which may be substituted with a functional group, an aromatic group which may be substituted with a functional group, and a group in which an aliphatic group which may be substituted with a functional group and an aromatic group are combined. The aliphatic group may be a saturated aliphatic group or an unsaturated aliphatic group, and the number of unsaturated bonds may be 1 or 2 or more. Examples of the functional group include, for example, an amino group, a hydroxyl group, a carboxyl group, a halogen group, a nitro group, an aryl group, an epoxy group, an azide group, etc., and an amino group, a hydroxyl group, and a carboxyl group are preferable.

[0037] In the production method of the present invention, even a carboxylic acid (fatty acid) containing a long-chain aliphatic group can easily proceed with the reaction, and cellulose esterified with a long-chain fatty acid can be easily obtained. Examples of the carboxylic acid containing a long-chain aliphatic group include carboxylic acids having 5 or more carbon atoms containing a long-chain aliphatic group having 4 or more carbon atoms, and may be carboxylic acids having 7 or more carbon atoms containing a long-chain aliphatic group having 6 or more carbon atoms, and may be carboxylic acids having 9 or more carbon atoms containing a long-chain aliphatic group having 8 or more carbon atoms, and may be carboxylic acids having 15 or more carbon atoms containing a long-chain aliphatic group having 14 or more carbon atoms. Further, for example, it may be a polymer or oligomer having a carboxylic acid at the terminal such as polylactic acid, polycaprolactone, and polyglycolic acid.

[0038] Incidentally, the production method of the present invention is also useful in the case of a carboxylic acid having 4 or less carbon atoms containing a short-chain aliphatic group having 3 or less carbon atoms, and can introduce a carboxylic acid more efficiently as compared with the case where no reaction assistant is used.

[0039] Preferable examples of the carboxylic acid containing a long-chain aliphatic group include caproic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, oleic acid, elaidic acid, erucic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, arachidonic acid, EPA, DHA, etc. These may be used in combination of two or more.

[0040] [Removal process] The production method of the present invention preferably includes a removal step of removing the ionic liquid and the reaction aid from the treated product obtained in the mechanochemical step. Note that other steps may be included before or after the mechanochemical step and / or before or after the removal step.

[0041] The treatment for removing the ionic liquid and the reaction aid in the removal step of the present invention is not particularly limited as long as it is a treatment that can remove the ionic liquid and the reaction aid from the treated product obtained in the mechanochemical step, and examples of such treatments include heating treatment, treatment using an acid or alkali, washing treatment, ultrasonic treatment, treatment by electron beam irradiation, and centrifugation treatment. These removal treatments may be used alone or in combination. In addition, in the removal step, it is preferable to simultaneously remove unreacted carboxylic acids and by-products contained in the ionic liquid. EXAMPLES

[0042] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0043] [Example 1] <Synthesis of surface-modified cellulose using p-toluenesulfonyl chloride (TsCl) as a reaction aid>

[0044] 1 and 2 are conceptual diagrams of Example 1. The specific operation is as follows.

[0045] (Synthesis Example 1) 0.5 g of microcrystalline cellulose (MCC), 5 g of oleic acid (OA) and 3.6 g of [BMIM][OAc] were placed in a magnetic pestle apparatus (MMPS-T1, AS-ONE, Japan) and kneaded at 80°C for 1 hour, after which 3.5 g of p-toluenesulfonyl chloride (TsCl) was added and kneaded for another 11 hours. After the treatment, the kneaded product was washed with acetone and subjected to Soxhlet extraction with methanol for 6 hours. The obtained extract was washed with ethanol and dried in vacuum to obtain a cellulose derivative modified with oleic acid (surface-modified cellulose of the present invention).

[0046] (Synthesis Example 2) A cellulose derivative modified with crotonic acid (surface-modified cellulose of the present invention) was obtained in the same manner as in Synthesis Example 1, except that 1.55 g of crotonic acid (CA) was used instead of 5 g of oleic acid.

[0047] (Synthesis Example 3) A cellulose derivative modified with succinic acid (surface-modified cellulose of the present invention) was obtained in the same manner as in Synthesis Example 1, except that 2.13 g of succinic acid (SA) was used instead of 5 g of oleic acid.

[0048] (Synthesis Example 4) A cellulose derivative modified with malic acid (surface-modified cellulose of the present invention) was obtained in the same manner as in Synthesis Example 1, except that 2.41 g of malic acid (MA) was used instead of 5 g of oleic acid.

[0049] (Synthesis Example 5) A cellulose derivative modified with lauric acid (surface-modified cellulose of the present invention) was obtained in the same manner as in Synthesis Example 1, except that 3.61 g of lauric acid (LA) was used instead of 5 g of oleic acid.

[0050] (Synthesis Example 6) A cellulose derivative modified with stearic acid (surface-modified cellulose of the present invention) was obtained in the same manner as in Synthesis Example 1, except that 5.12 g of stearic acid (STA) was used instead of 5 g of oleic acid.

[0051] (Synthesis Example 7) A cellulose derivative modified with dicarboxylic acid (surface-modified cellulose of the present invention) was obtained in the same manner as in Synthesis Example 1, except that 6.13 g of 9-octadecenedioic acid (dicarboxylic acid (DA)) was used instead of 5 g of oleic acid.

[0052] The materials used in Synthesis Examples 1 to 7 are shown in Table 1.

[0053] [Table 1]

[0054] The introduction of carboxylic acid into cellulose was confirmed by Fourier transform infrared spectroscopy (FT-IR). Figure 3 shows the IR spectrum obtained by Fourier transform infrared spectroscopy.

[0055] As shown in Figure 3, the spectra obtained are compared, and the peak at 1745 cm -1 The nearby carbonyl (C=O) peak clearly confirmed that esterification had occurred.

[0056] Thermogravimetric analysis (TG) and powder X-ray diffraction (XRD) were also performed. Figure 4 shows the thermogravimetric curve (TG curve), and Figure 5 shows the XRD pattern. For comparison, MCC is also shown. The substitution rate (DS) of cellulose was determined by titration. The results are shown in Table 2. Titration (quantitative determination of carboxylic acid) was performed using phenolphthalein indicator after hydrolysis of the side chains with KOH.

[0057] [Table 2]

[0058] As shown in Figure 4 and Table 2, the thermal stability changed due to surface modification by introducing carboxylic acid. The degradation temperature decreased from 260.4°C for unmodified cellulose (MCC) to 250-200°C. Furthermore, Figure 5 and Table 2 confirmed that the esterified cellulose prepared by the mechanochemical method retained the untreated cellulose I structure.

[0059] In the above Synthesis Example 1 (introduction of oleic acid), the reaction was carried out at various temperatures (50°C, 80°C, 100°C) and reaction times (4 hours, 12 hours, 24 hours), and in all cases, the introduction of oleic acid was confirmed. [Industrial Applicability]

[0060] The present invention is industrially useful because it can produce surface-modified nanocellulose.

Claims

1. A method for producing surface-modified nanocellulose, comprising a mechanochemical process of mechanochemically treating nanocellulose (excluding silyl ether cellulose) and a carboxylic acid having 7 or more carbon atoms and a long-chain aliphatic group having 6 or more carbon atoms in the presence of an ionic liquid, A method for producing surface-modified nanocellulose, characterized in that the mechanical treatment in the mechanochemical process is carried out by adding p-toluenesulfonyl chloride.

2. The method for producing surface-modified nanocellulose according to claim 1, characterized in that the ionic liquid has Lewis acidity.

3. The method for producing surface-modified nanocellulose according to claim 1 or 2, characterized in that the cation of the ionic liquid is an imidazolium cation.

4. The method for producing surface-modified nanocellulose according to any one of claims 1 to 3, characterized in that the anion of the ionic liquid is a hydrogen sulfate anion.

5. The method for producing surface-modified nanocellulose according to any one of claims 1 to 4, characterized in that no organic solvent is used in the mechanical treatment in the mechanochemical process.

6. The method for producing surface-modified nanocellulose according to any one of claims 1 to 5, characterized in that the ionic liquid is added in an amount of 1 to 10 mol per 1 mol of carboxylic acid.

7. The method for producing surface-modified nanocellulose according to any one of claims 1 to 6, characterized in that the nanocellulose is defibrated in the mechanochemical process.

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