Method for producing surface-modified nanodiamond and surface-modified nanocarbon particles

Abstract

To provide a surface-modified nano-diamond excellent in dispersibility in an organic solvent and a simple production method of surface-modified nano-carbon powders by which various surface-modification groups can be introduced while zirconia is less likely to be introduced.SOLUTION: A surface-modified nano-diamond comprises nano-diamond powders and a group expressed by formula (1) modifying the surface of the nano-diamond powders. -X-R1 (1) [In the formula (1), X represents -NH- or -O-, and the bond extending to the left from X bonds to the nano-diamond powders. R1 represents a monovalent organic group in which two hydrocarbon groups, which may have a substituent, are bonded through an ester bond, an ether bond, a carbonyl group, or an amide bond.]SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to methods for producing surface-modified nanodiamond and surface-modified nanocarbon particles. [Background technology]

[0002] Nano-sized fine materials such as nanocarbon particles are known to have new properties that cannot be expressed in the bulk state. For example, nanodiamond particles (= nano-sized diamond particles) have mechanical strength, high refractive index, thermal conductivity, insulation, oxidation resistance, and the ability to promote crystallization of resins, etc. However, nanodiamond particles generally have a large proportion of surface atoms, so the sum of van der Waals forces that can act between the surface atoms of adjacent particles is large, making them prone to aggregation. In addition, in the case of nanodiamond particles, a phenomenon called agglutination can occur in which the Coulomb interactions between the crystal faces of adjacent crystallites contribute to the formation of a very strong aggregate. For this reason, it has been very difficult to disperse nanodiamond particles in organic solvents or resins in the form of primary particles. Therefore, efforts have been made to modify the surface of nanodiamond particles to give them dispersibility and suppress their aggregation.

[0003] As examples of surface-modified nanodiamonds, surface-modified nanodiamonds are known in which a monovalent organic group having a hydroxyl group at the end is introduced to a nanodiamond particle via an ether bond (see Non-Patent Document 1). Also, surface-modified nanodiamonds are known in which a monovalent organic group having an amino group at the end is introduced to a nanodiamond particle via an amino bond (see Non-Patent Document 2).

[0004] In addition, methods for obtaining surface-modified nanodiamonds in which monovalent organic groups have been introduced onto the nanodiamond surface include, for example, a method in which a powder of nanodiamond particles is reacted with a reactant (see Non-Patent Documents 1 and 2), and a method in which zirconia beads or the like are used in a bead mill in an organic solvent to break down agglomerates of nanodiamond particles while reacting them with a reactant (see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-214244 A [Non-patent literature]

[0006] [Non-Patent Document 1] Journal of Materials Chemistry 19 (2009) 8432-8441 [Non-Patent Document 2] Chemistry of Materials 16 (2004) 3924-3930 Summary of the Invention [Problem to be solved by the invention]

[0007] However, nanodiamonds that have been surface-modified with monovalent organic groups having a hydroxyl group at the end, as described in Non-Patent Document 1, and nanodiamonds that have been surface-modified with monovalent organic groups having an amino group at the end, as described in Non-Patent Document 2, had poor dispersibility in organic solvents.

[0008] Therefore, a first object of the present disclosure is to provide a surface-modified nanodiamond that has excellent dispersibility in organic solvents.

[0009] In addition, the method of obtaining surface-modified nanocarbon particles such as surface-modified nanodiamonds by reacting nanodiamond particles with a reactant requires, from the viewpoint of the solubility of the reactant in the solvent, disintegrating the nanodiamond particles by bead milling or the like to obtain an aqueous dispersion, drying or desolvating the nanodiamond particles to obtain a powder, and dispersing the nanodiamond particles in a solvent that is excellent in the solubility of the reactant, which is troublesome. In addition, as disclosed in the above Patent Document 1, when disintegrating and reacting are performed simultaneously by bead milling, it is difficult to perform specific reactions such as heating and dehydration condensation, so the surface modification groups that can be introduced are limited, and there are problems such as contamination with zirconia derived from the zirconia beads used in the bead mill.

[0010] Therefore, a second object of the present disclosure is to provide a method for easily producing surface-modified nanocarbon particles that can introduce various surface-modifying groups and that has little zirconia contamination. [Means for solving the problem]

[0011] The inventors of the present disclosure have conducted extensive research to achieve the first object and have found that a specific surface-modified nanodiamond has excellent dispersibility in an organic solvent. The inventors of the present disclosure have conducted extensive research to achieve the second object and have found that various surface-modifying groups can be introduced by reacting nanocarbon particles having hydroxyl groups on the surface with a specific reactant in the presence of an acid catalyst in a nano-dispersed state in water, and that surface-modified nanocarbon particles can be easily produced with little zirconia contamination. The present disclosure relates to a product completed based on these findings.

[0012] The present disclosure provides a surface-modified nanodiamond comprising a nanodiamond particle and a group represented by the following formula (1) that surface-modifies the nanodiamond particle: -XR 1 (1) [In formula (1), X represents -NH- or -O-, and the bond extending to the left from X is bonded to the nanodiamond particle. R 1represents a monovalent organic group in which two optionally substituted hydrocarbon groups are bonded via an ester bond, an ether bond, a carbonyl group, or an amide bond.

[0013] In the above formula (1), X represents -NH-, and R 1 preferably represents a monovalent organic group in which two optionally substituted hydrocarbon groups are bonded via an ester bond, an ether bond, or an amide bond.

[0014] Above R 1 It is preferable that the monovalent organic group in the formula (I) has 5 to 30 carbon atoms, and the two hydrocarbon groups are linear or branched hydrocarbon groups.

[0015] The present disclosure also provides a nanodiamond dispersion composition comprising an organic dispersion medium and the surface-modified nanodiamond dispersed in the organic dispersion medium, the surface-modified nanodiamond having an average dispersed particle diameter D50 of 1 to 100 nm.

[0016] The SP value of the above organic dispersion medium is 6.0 to 23.0 (cal / cm 3 ) 1 / 2 It is preferable that:

[0017] The present disclosure also provides a method for producing surface-modified nanocarbon particles, comprising the step of reacting nanocarbon particles having hydroxy groups on the surface thereof in a nano-dispersed state in water with a compound represented by the following formula (2) in the presence of an acid catalyst to obtain surface-modified nanocarbon particles. R 1 -XH (2) [In formula (2), X represents -NH- or -O-. 1 represents a monovalent organic group in which two optionally substituted hydrocarbon groups are bonded via an ester bond, an ether bond, a carbonyl group, or an amide bond.

[0018] The nanocarbon particles are preferably nanodiamond particles. Effect of the Invention

[0019] The surface-modified nanodiamond of the present disclosure has excellent dispersibility in organic solvents. In addition, the method for producing surface-modified nanocarbon particles of the present disclosure can introduce various surface-modifying groups, and can easily produce surface-modified nanocarbon particles with little zirconia contamination. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 shows the FT-IR spectrum of the surface-modified nanodiamond obtained in Example 2. [Diagram 2] FIG. 1 shows the FT-IR spectrum of the surface-modified nanodiamond obtained in Example 4. [Diagram 3] FIG. 1 shows the FT-IR spectrum of the surface-modified nanodiamond obtained in Example 6. [Figure 4] FIG. 1 shows the FT-IR spectrum of the surface-modified nanodiamond obtained in Example 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] [Surface-modified nanodiamond] The surface-modified nanodiamond according to one embodiment of the present disclosure comprises a nanodiamond particle and a group represented by the following formula (1) which surface-modifies the nanodiamond particle. In this specification, the group represented by the above formula (1) may be referred to as a "surface-modifying group (L)". The surface-modified nanodiamond may have only one type of surface-modifying group (L), or may have two or more types. -XR 1 (1) [In formula (1), X represents -NH- or -O-, and the bond extending to the left from X is bonded to the nanodiamond particle. R 1 represents a monovalent organic group in which two optionally substituted hydrocarbon groups are bonded via an ester bond, an ether bond, a carbonyl group, or an amide bond.

[0022] The above-mentioned nanodiamond particles are not particularly limited, and known or conventional nanodiamond particles can be used. The nanodiamond particles have hydroxyl groups that are inherently generated during the manufacturing process. The nanodiamond particles may be used in one type or in two or more types.

[0023] As the above-mentioned nanodiamond particles, for example, detonation nanodiamond (i.e., nanodiamond produced by detonation method) or high-temperature high-pressure nanodiamond (i.e., nanodiamond produced by high-temperature high-pressure method) can be used. Among them, detonation nanodiamond is preferred because it has better dispersibility in the dispersion medium, that is, the particle size of the primary particle is one digit nanometer.

[0024] The detonation nanodiamond includes air-cooled detonation nanodiamond (i.e., nanodiamond produced by air-cooled detonation method) and water-cooled detonation nanodiamond (i.e., nanodiamond produced by water-cooled detonation method). Among them, air-cooled detonation nanodiamond is preferred because it has smaller primary particles than water-cooled detonation nanodiamond.

[0025] The detonation may be carried out in an air atmosphere or in an inert gas atmosphere such as nitrogen atmosphere, argon atmosphere, or carbon dioxide atmosphere.

[0026] In the above formula (1), X represents -NH- or -O-, and the bond extending to the left from X is bonded to the nanodiamond particle. In each of these listed bonds, the bond extending to the left is bonded to the nanodiamond particle, and the bond extending to the right is R 1 Bind to.

[0027] In the above formula (1), R 1 represents a monovalent organic group in which two optionally substituted hydrocarbon groups are bonded via an ester bond, an ether bond, a carbonyl group, or an amide bond, and the atom bonded to X is a carbon atom. That is, the group represented by the above formula (1) is a group represented by the following formula (1'). -XR 2 -YR 3 (1') [In formula (1'), X represents -NH- or -O-, and the bond extending to the left from X is bonded to the nanodiamond particle. R 2 and R 3 are the same or different and each represents a hydrocarbon group which may have a substituent, and Y represents an ester bond, an ether bond, a carbonyl group, or an amide bond.

[0028] The two hydrocarbon groups in the monovalent organic group (i.e., the R 2 and R 3 Examples of the hydrocarbon group in the above formula (1) include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and groups in which two or more of these are bonded together. The two hydrocarbon groups in the above monovalent organic group may be the same or different.

[0029] Examples of the aliphatic hydrocarbon group include an alkyl group, an alkenyl group, and an alkynyl group. Examples of the alkyl group include a C group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a hexyl group, an octyl group, an isooctyl group, a decyl group, and a dodecyl group. 1-22 Alkyl group (preferably C 2-20 Alkyl groups, more preferably C 3-18 Examples of the alkenyl group include C groups such as vinyl group, allyl group, methallyl group, 1-propenyl group, isopropenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, 1-pentenyl group, 2-pentenyl group, 3-pentenyl group, 4-pentenyl group, and 5-hexenyl group. 2-22 Alkenyl group (preferably C 4-20 Alkenyl groups, more preferably C 8-18 Examples of the alkynyl group include C alkynyl groups such as ethynyl and propynyl groups. 2-22 Alkynyl groups (preferably C 4-20 Alkynyl groups, more preferably C 8-18 alkynyl groups).

[0030] Examples of the alicyclic hydrocarbon group include C cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cyclododecyl groups. 3-12 Cycloalkyl groups; cyclohexenyl groups, etc. 3-12 Cycloalkenyl groups; bicycloheptanyl groups, bicycloheptenyl groups, etc. 4-15 A bridged cyclic hydrocarbon group is also included.

[0031] Examples of the aromatic hydrocarbon group include C phenyl groups, naphthyl groups, etc. 6-14 Aryl groups (especially C 6-10 Aryl groups).

[0032] Examples of the group in which an aliphatic hydrocarbon group and an alicyclic hydrocarbon group are bonded include a cyclohexylmethyl group and a methylcyclohexyl group. Examples of the group in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded include C groups such as a benzyl group and a phenethyl group. 7-18 Aralkyl groups (especially C 7-10 aralkyl group), cinnamyl group, etc. 6-10 Aryl-C 2-6 Alkenyl group, tolyl group, etc. 1-4 C such as alkyl-substituted aryl groups and styryl groups 2-4 Alkenyl-substituted aryl groups and the like.

[0033] Examples of the substituent that the above-mentioned hydrocarbon group may have include halogen atoms such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom; a cyano group; an isocyanate group; an isothiocyanate group; a substituted or unsubstituted silyl group; a thiol group; and an azide group.

[0034] Above R 2 As the R, a linear or branched hydrocarbon group is preferable, and an alkyl group is more preferable. 2 R is preferably a hydrocarbon group having 2 to 10 carbon atoms, and more preferably a hydrocarbon group having 3 to 7 carbon atoms. 2When is the above-mentioned hydrocarbon group, there is little steric hindrance between the nanodiamond and the raw material compound (the compound represented by formula (2) described below) during synthesis, and the reactivity is excellent.

[0035] Above R 3 As the R, a linear or branched hydrocarbon group or a group in which the linear or branched hydrocarbon group is bonded to an aromatic hydrocarbon group (particularly, a group in which the terminal is an aromatic hydrocarbon group) is preferable. 3 R is preferably a hydrocarbon group having 3 to 20 carbon atoms, and more preferably a hydrocarbon group having 4 to 18 carbon atoms. 3 When is the above-mentioned hydrocarbon group, the compound has high fat solubility and excellent dispersibility in various organic dispersion media.

[0036] Above R 1 The number of carbon atoms in the monovalent organic group in R is preferably 5 to 30, and more preferably 7 to 25. When the number of carbon atoms is 5 or more, the steric hindrance between the surface modifying groups is sufficient, and the surface modifying groups are easily dispersed in the dispersion medium. When the number of carbon atoms is 30 or less, the surface modifying groups are prevented from becoming entangled with each other, and the surface modifying groups are easily dispersed in the dispersion medium. 2 and R 3 It is preferable that the total number of carbon atoms is within the above range.

[0037] In the above formula (1'), Y represents an ester bond, an ether bond, a carbonyl group, or an amide bond. The ester bond may be either -C(=O)-O- or -OC(C=O)-. The amide bond may be either -C(=O)-NH- or -NH-C(=O)-.

[0038] In the above formula (1), when X is -NH-, R 1 is preferably a monovalent organic group in which two optionally substituted hydrocarbon groups are bonded via an ester bond, an ether bond, or an amide bond (preferably an ester bond or an ether bond) (i.e., Y in the above formula (1') is an ester bond, an ether bond, or an amide bond). In this case, the above R 1The number of carbon atoms in the monovalent organic group in R is preferably 5 to 30, and more preferably 5 to 25. 2 and R 3 In addition, when X is -NH-, the total number of carbon atoms in R in the above formula (1) is preferably within the above range. 1 Two hydrocarbon groups in the above formula (i.e., R 2 and R 3 ) is preferably a linear or branched hydrocarbon group.

[0039] In particular, R 1 is a monovalent organic group in which two optionally substituted hydrocarbon groups are bonded via an ester bond (i.e., Y in the above formula (1') is an ester bond), 1 The number of carbon atoms in the monovalent organic group in R is preferably 12 to 30, and more preferably 14 to 26. 2 and R 3 It is preferable that the total number of carbon atoms of R is within the above range. 2 The number of carbon atoms in R is preferably 3 to 7. 3 The number of carbon atoms is preferably 8 to 20.

[0040] Also, R 1 is a monovalent organic group in which two optionally substituted hydrocarbon groups are bonded via an ether bond (i.e., Y in the above formula (1') is an ether bond), 1 The number of carbon atoms in the monovalent organic group in R is preferably 4 to 10, and more preferably 5 to 8. 2 and R 3 It is preferable that the total number of carbon atoms of R is within the above range. 2 The number of carbon atoms in R is preferably 2 to 5. 3 The number of carbon atoms is preferably 3 to 8.

[0041] In the above formula (1), when X is -O-, R 1is preferably a monovalent organic group in which two optionally substituted hydrocarbon groups are bonded via an ester bond, an ether bond, or an amide bond (preferably an ester bond or an ether bond) (i.e., Y in the above formula (1') is an ester bond, an ether bond, or an amide bond). In this case, the above R 1 The number of carbon atoms in the monovalent organic group in R is preferably 5 to 30, and more preferably 5 to 25. 2 and R 3 It is preferable that the total number of carbon atoms in the above formula (1) is within the above range. 1 Two hydrocarbon groups in the above formula (i.e., R 2 and R 3 ) is preferably a linear or branched hydrocarbon group.

[0042] The nanodiamond particles constituting the surface-modified nanodiamond preferably contain primary particles of nanodiamond. In addition, secondary particles formed by aggregation (adhesion) of the primary particles may also be included. In addition, the surface of the surface-modified nanodiamond may have one or more types of other surface functional groups (e.g., amino groups, hydroxyl groups, carboxyl groups, etc.) in addition to the surface-modifying group (L).

[0043] The mass ratio of nanodiamond to surface modification group (L) in the surface-modified nanodiamond [nanodiamond / surface modification group (L)] is not particularly limited, but is preferably 0.5 or more, more preferably 2.5 or more. The mass ratio is preferably 17.0 or less, more preferably 15.0 or less, even more preferably 10.0 or less, and particularly preferably 5.0 or less. When the mass ratio is 0.5 or more, the properties as a nanodiamond material are not easily impaired. When the mass ratio is 17.0 or less, the degree of modification of the surface modification group (L) is sufficient, and the dispersibility in an organic solvent is superior. The mass ratio is calculated based on the weight loss rate from 200°C to 450°C measured by thermogravimetric analysis, and the reduced weight is taken as the mass of the surface modification group (L).

[0044] The surface-modified nanodiamond has excellent dispersibility in organic solvents, and the X and R in the group represented by the above formula (1) 1 and Y and R in the group represented by the above formula (1'). 2 , and R 3 By controlling the structure of nanodiamond particles through adjustments, etc., it is possible to achieve dispersibility in various organic solvents and affinity for resins. For this reason, they can be used in engineering applications such as polishing agents and dresser materials for CMP, corrosion-resistant electrode plating materials for fuel cells, high-hardness surface coating layer forming materials for cutting tools, and high-heat resistance and high-thermal conductivity materials.

[0045] The particle size (D50) of the surface-modified nanodiamond is, for example, 400 nm or less, preferably 300 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less. The lower limit of the particle size (D50) of the surface-modified nanodiamond is, for example, 5 nm. The particle size (D90) is, for example, 500 nm or less, preferably 400 nm or less, and more preferably 150 nm or less. The lower limit of the particle size (D90) of the surface-modified nanodiamond is, for example, 50 nm. The smaller the particle size of the surface-modified nanodiamond, the more preferable it is in terms of obtaining high transparency in the composite material described below. The (average) particle size of the surface-modified nanodiamond can be measured by dynamic light scattering.

[0046] The above surface-modified nanodiamond can be produced by the method for producing surface-modified nanocarbon particles described below.

[0047] [Method of manufacturing surface-modified nanocarbon particles] A method for producing surface-modified nanocarbon particles according to one embodiment of the present disclosure includes at least a step (sometimes referred to as a "reaction step") of reacting nanocarbon particles having hydroxy groups on the surface thereof, in a nano-dispersed state in water, with a compound represented by the following formula (2) in the presence of an acid catalyst to obtain surface-modified nanocarbon particles. R 1 -XH (2) [In formula (2), X represents -NH- or -O-. 1 represents a monovalent organic group in which two optionally substituted hydrocarbon groups are bonded via an ester bond, an ether bond, a carbonyl group, or an amide bond.

[0048] (Reaction process) In the above reaction process, nanocarbon particles having hydroxyl groups on their surfaces are nano-dispersed in water and then reacted with the compound represented by formula (2) above, and the hydroxyl groups in the nanocarbon particles and -H in the compound represented by formula (2) are dehydrated and condensed to obtain surface-modified nanocarbon particles.

[0049] The nanocarbon particles are not particularly limited, and particles of known or commonly used nano-order carbon materials (nanocarbon materials) can be used. Examples of the nanocarbon materials in the nanocarbon particles include nanodiamond, fullerene, graphene oxide, nanographite, carbon nanotubes, carbon nanofilaments, onion-like carbon, diamond-like carbon, amorphous carbon, carbon black, carbon nanohorns, and carbon nanocoils. As the nanocarbon particles, nanodiamond particles are preferred. The nanocarbon particles may be used in combination of one type or two or more types.

[0050] In the above formula (2), X and R 1 respectively represent X and R in the above formula (1). 1 That is, the compound represented by the above formula (2) is a compound represented by the following formula (2'). R 3 -YR 2 -XH(2') [In formula (2'), X represents -NH- or -O-. 2 and R 3 are the same or different and each represents a hydrocarbon group which may have a substituent, and Y represents an ester bond, an ether bond, a carbonyl group, or an amide bond.

[0051] The compound represented by the above formula (2) is appropriately selected depending on the group represented by the above formula (1). The compound represented by the above formula (2) can be prepared by a known or conventional method. For example, when the compound represented by the above formula (2) has a structure in which two hydrocarbon groups, which may have a substituent, are bonded via an ester bond and X is -NH-, it can be prepared by esterification of an amino alcohol with an acid halide or esterification of an amino acid with an alcohol.

[0052] The reaction step is carried out in a state where the nanocarbon particles are nano-dispersed in water, i.e., in an aqueous dispersion composition of nanocarbon particles. The median diameter (D50) of the nanocarbon particles in the aqueous dispersion composition is preferably 1 to 100 nm, more preferably 1 to 50 nm, and even more preferably 1 to 10 nm. When the median diameter is within the above range, the amount of hydroxyl groups on the surface of the nanocarbon particles is large, and the reaction with the compound represented by formula (2) proceeds more. In addition, the dispersibility of the obtained amino group-modified nanocarbon particles is excellent.

[0053] The compound represented by the formula (2) is preferably one that has excellent solubility or dispersibility in water in the presence of the acid catalyst. When the compound represented by the formula (2) has poor solubility or dispersibility in water, the compound represented by the formula (2) can be dissolved or dispersed in an organic solvent and the reaction can be carried out in a mixed solvent system of water and an organic solvent.

[0054] Examples of the organic solvent include aliphatic hydrocarbons such as hexane, heptane, and octane (particularly, linear saturated aliphatic hydrocarbons); aromatic hydrocarbons such as benzene, toluene, and xylene; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; aprotic polar solvents such as dimethylformamide (DMF), dimethylacetamide, N-methylpyrrolidone, and dimethylsulfoxide; alcohols such as methanol; halogenated hydrocarbons such as chloroform, dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene, and trifluoromethylbenzene; chain or cyclic ethers such as diethyl ether, diisopropyl ether, dimethoxyethane, tetrahydrofuran, and dioxane; esters such as ethyl acetate and butyl acetate; chain ketones such as methyl ethyl ketone (MEK) and methyl isobutyl ketone; and nitriles such as acetonitrile. Only one type of the organic solvent may be used, or two or more types may be used.

[0055] The acid catalyst may be a known or conventional acid catalyst used in the esterification of carboxylic acid and alcohol, the dehydration condensation reaction of alcohol and amine, the dehydration condensation reaction of alcohol and thiol, etc. Examples of the acid catalyst include a sulfonic acid group-containing compound, hydrochloric acid, nitric acid, sulfuric acid, sulfuric anhydride, phosphoric acid, boric acid, trihaloacetic acid (trichloroacetic acid, trifluoroacetic acid, etc.), their salts (ammonium salts, etc.), inorganic solid acids, etc. The acid catalyst may be used alone or in combination of two or more.

[0056] The acid catalyst may be in the form of either a homogeneous catalyst that can be dissolved in a solvent or a substrate during the reaction, or a heterogeneous catalyst that cannot be dissolved during the reaction. Examples of heterogeneous catalysts include supported catalysts in which an acid component is supported on a carrier.

[0057] Examples of the sulfonic acid group-containing compound include aliphatic sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, dodecanesulfonic acid, hexadecanesulfonic acid, trifluoromethanesulfonic acid, and heptadecafluorooctanesulfonic acid; alicyclic sulfonic acids such as 10-camphorsulfonic acid; benzenesulfonic acid, p-toluenesulfonic acid, 2,4,6-trimethylbenzenesulfonic acid, hexylbenzenesulfonic acid, and octylbenzenesulfonic acid. aromatic sulfonic acids such as sulfonic acid, decylbenzenesulfonic acid, dodecylbenzenesulfonic acid (DBSA), octadecylbenzenesulfonic acid, 1-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, and butyl-2-naphthalenesulfonic acid; sulfonic acid-type ion exchange resins, 3-[trioctylammonio]propane-1-sulfonic acid-triflimide, 4-[trioctylammonio]butane-1-sulfonic acid-triflimide, and compounds represented by the following formula (A).

[0058] [ka]

[0059] Examples of the inorganic solid acid include silica, silica alumina, alumina, zeolites, activated clay, and montmorillonite.

[0060] Examples of the ammonium salt as the acid catalyst include an ammonium ion salt represented by the following formula (B-1), an ammonium ion salt represented by the following formula (B-2), an ammonium ion salt represented by the following formula (B-3), and an ammonium ion salt represented by the following formula (B-4). [ka]

[0061] In the above formula (B-1), R I ~R IIIare the same or different and each represents a group containing a hydrogen atom, an aliphatic hydrocarbon group, or an aromatic hydrocarbon group. The aliphatic hydrocarbon group is a linear or branched C 1-22 Hydrocarbon groups are preferred. Examples of the group containing an aromatic hydrocarbon group include aromatic hydrocarbon groups such as a phenyl group; and groups in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded, such as a 4-t-butylphenyl group and a mesityl group. Among these, the above R I ~R III It is preferable that two or more of the above groups contain an aromatic hydrocarbon group.

[0062] The acid anion serving as a counter anion to the ammonium ions represented by the above formulas (B-1) to (B-3) is preferably a sulfonate ion, more preferably an aromatic sulfonate ion, and particularly preferably a p-dodecylbenzenesulfonate ion.

[0063] In the above formula (B-4), R i and R ii are the same or different and each represents a group containing a hydrogen atom, an aliphatic hydrocarbon group, or an aromatic hydrocarbon group. The aliphatic hydrocarbon group is a linear or branched C 1-4 Hydrocarbon groups are preferred. Examples of the group containing an aromatic hydrocarbon group include aromatic hydrocarbon groups such as a phenyl group, and groups in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded. Among these, a hydrogen atom, a methyl group, an isopropyl group, and a phenyl group are preferred.

[0064] The acid anion serving as a counter anion to the ammonium ion represented by the above formula (B-4) is preferably a sulfonate ion or a sulfate ion, and particularly preferably a trifluoromethanesulfonate ion, a 10-camphorsulfonate ion, a benzenesulfonate ion, or a sulfate ion.

[0065] The acid anion serving as the counter anion of the ammonium ion represented by the above formulae (B-1) to (B-4) may form a complex salt by forming a hydrogen bond between an oxygen atom forming an acid group and a hydrogen atom on a nitrogen atom in the above formulae (B-1) to (B-4). The above complex salt may form one salt with one ammonium cation and one acid anion, or may form one salt with two ammonium cations and two acid anions, and the number of ammonium cations and acid anions forming one salt is not particularly limited. In one salt, the acid anion may form a polymer. For example, sulfuric acid forming a sulfate ion is [H2SO4(SO3) X An example of the complex salt formed between the acid anion and the above formula (B-4) is a compound represented by the following formula (C). [ka]

[0066] In the above formula (C), R i and R ii is the same as in the above formula (B-4).

[0067] As the acid catalyst, from the viewpoint of further accelerating the reaction in the condensation step, a sulfonic acid group-containing compound or an ammonium salt of a sulfonic acid group-containing compound is preferred.

[0068] The ratio (former:latter, mass ratio) of the nanocarbon particles to the compound represented by formula (2) to be reacted is, for example, 1:1 to 1:25. The concentration of the nanocarbon particles in the aqueous dispersion composition is, for example, 1 to 10 mass%, and the concentration of the compound represented by formula (2) in the aqueous dispersion composition is, for example, 1 to 60 mass%.

[0069] The reaction conditions for the nanocarbon particles and the compound represented by formula (2) can be appropriately selected within the ranges of, for example, a temperature of 0 to 100° C., a reaction time of 1 to 48 hours, and a pressure of 1 to 5 atm.

[0070] The above-mentioned production method may have other steps other than the above-mentioned reaction step. It is preferable to purify the product obtained after the above-mentioned reaction step by, for example, filtration, centrifugation, extraction, water washing, neutralization, or a combination of these. In addition, for example, a crushing step may be performed before the above-mentioned condensation step in order to obtain a water-dispersed composition in which the above-mentioned nanocarbon particles are nano-dispersed in water.

[0071] As described above, the manufacturing method including at least the reaction step can produce surface-modified nanocarbon particles that include nanocarbon particles and groups represented by formula (1) that surface-modify the nanocarbon particles.

[0072] According to the above manufacturing method, since there is no need to use nanocarbon particle powder, there is no need to obtain a water dispersion by crushing by bead milling or the like, and then dry or remove the solvent to obtain a nanodiamond particle powder, and surface-modified nanocarbon particles can be easily manufactured. In addition, since crushing and reaction are not performed simultaneously by bead milling, and the nanocarbon particles are dispersed in water and reacted with a reactant, the surface modification group that can be introduced is not limited compared to the conventional method, and various surface modification groups can be introduced. Furthermore, since crushing and reaction are not performed simultaneously by bead milling, the crushing processing time can be minimized, so that the contamination of zirconia is reduced, and side reactions due to the generation of radicals can be suppressed.

[0073] [Nanocarbon particle dispersion composition] By dispersing the surface-modified nanodiamond or the surface-modified nanocarbon particles obtained by the above-mentioned manufacturing method in a dispersion medium, a nanocarbon particle dispersion composition containing the dispersion medium and the surface-modified nanocarbon particles dispersed in the dispersion medium can be obtained. If the nanocarbon particle aggregate remains after the above-mentioned reaction process, the liquid after the reaction process can be left to stand and the supernatant liquid can be collected and used as the nanocarbon particle dispersion composition. In addition, after obtaining the aqueous dispersion composition obtained by the above-mentioned manufacturing method, before or after distilling off the water in the dispersion composition with an evaporator, the nanocarbon particle dispersion composition can also be produced by mixing and stirring a new dispersion medium, i.e., by exchanging the solvent.

[0074] The surface-modified nanocarbon particles obtained by the above production method and the surface-modified nanodiamond having the above surface-modifying group (L) may be collectively referred to as "surface-modified nanocarbon particles (P)".

[0075] When obtaining the nanocarbon particle dispersion composition by exchanging the solvent, it is preferable to add a new dispersion medium, wash with water and / or saline, and then remove the water by extraction and / or distillation.

[0076] The dispersion medium is a medium for dispersing the surface-modified nanocarbon particles, and examples thereof include water, an organic dispersion medium (organic solvent), and an ionic liquid. Among these, an organic dispersion medium is preferable from the viewpoint of excellent dispersibility of the surface-modified nanocarbon particles (P) in an organic solvent. The dispersion medium may be used alone or in combination of two or more.

[0077] As the organic dispersion medium, known or commonly used organic solvents can be used. Among them, from the viewpoint of excellent dispersibility of the surface-modified nanocarbon particles (P) in various organic dispersion media, the SP value [Hildebrand solubility parameter (δ), at 25° C., unit: (cal / cm 3 ) 1 / 2

[0033] is preferably 6.0 to 23.0, more preferably 7.0 to 23.0. The organic dispersion medium may be used alone or in combination of two or more. When two or more organic dispersion media are used, the SP value of the mixture of the two or more organic dispersion media is preferably within the above range, and the SP value of each organic dispersion medium may be outside the above range.

[0078] Examples of the organic dispersion medium include alkanes such as hexane (SP: 7.0); ketones such as acetone (SP: 10.0), methyl ethyl ketone (MEK, SP: 9.3), and methyl isobutyl ketone (MIBK, SP: 8.4); ethers such as dioxane (SP: 9.8) and tetrahydrofuran (THF, SP: 9.1); alcohols such as methanol (SP: 14.5), n-propanol (SP: 11.9), isopropanol (IPA, SP: 11.5), hexanol (SP: 10.7), and cyclohexanol (SP: 11.4); esters such as ethyl acetate (SP: 9.1) and polyol ester (SP: 9.6); amines such as ethanolamine (SP: 15.4); aromatic compounds such as toluene (SP: 8.8) and alkylbenzene (SP: 7.6); N-methylpyrrolidone (NMP, SP: dimethylacetamide (DMAc, SP: 10.8); ethylene glycol (SP: 16.1), diethylene glycol (SP: 14.6), and other polyhydric alcohols; chloroform (SP: 9.3), methylene chloride (SP: 9.7), ethylene dichloride (SP: 9.8), and other halogenated hydrocarbons; ethylene carbonate / diethyl carbonate (EC / DEC = 1 / 1: volume ratio) mixed solvent (SP: 11.75), ethylene carbonate / diethyl carbonate / methyl ethyl carbonate (1 / 1 / 1: volume ratio) mixed solvent (SP: 10.97), and other carbonate compounds; polyolefins such as poly-α-olefins (SP: about 6.0 to 8.0); mineral oil (SP: about 6.0 to 8.0), acetic acid (SP: 12.4), acetonitrile (SP: 11.8), and the like.

[0079] The content of the nanocarbon particles in the nanocarbon particle dispersion composition is not particularly limited, but is, for example, 0.1 ppm by mass to 10% by mass.

[0080] The content of the nanocarbon particles can be calculated from the absorbance at 350 nm. When the content of the surface-modified nanocarbon particles is low (e.g., 2000 mass ppm or less), the content can be determined based on the amount of the compound that has surface-modified the nanocarbon particles detected by inductively coupled plasma atomic emission spectrometry (ICP atomic emission spectrometry).

[0081] The content of the dispersion medium in the nanocarbon particle dispersion composition is, for example, 90 to 99.9999% by mass, with the upper limit being 100% by mass.

[0082] The nanocarbon particle dispersion composition may consist of only the surface-modified nanocarbon particles (P) and the dispersion medium, or may contain other components. Examples of other components include surfactants, thickeners, coupling agents, dispersants, rust inhibitors, corrosion inhibitors, freezing point depressants, antifoaming agents, anti-wear additives, preservatives, and colorants. The content ratio of the other components is, for example, 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 1% by mass or less, based on the total amount of the nanocarbon particle dispersion composition. Therefore, the total content ratio of the surface-modified nanocarbon particles (P) and the dispersion medium is, for example, 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more, based on the total amount of the nanocarbon particle dispersion composition.

[0083] The nanocarbon particle dispersion composition contains surface-modified nanocarbon particles (P) in a highly dispersed state. The average dispersed particle size (D50) of the nanocarbon particles in the nanocarbon particle dispersion composition is, for example, 100 nm or less, preferably 60 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. The lower limit of the average dispersed particle size of the nanocarbon particles is, for example, 1 nm.

[0084] The nanocarbon particle dispersion composition preferably has a haze value of 5 or less, more preferably 3 or less, and even more preferably 1 or less. The nanocarbon particle dispersion composition has excellent dispersibility of the surface-modified nanocarbon particles (P), so that a nanocarbon particle dispersion composition having the above haze value can be obtained. The haze value can be measured based on JIS K 7136.

[0085] The nanocarbon particle dispersion composition can be preferably used as an additive for a composite material that imparts the properties of fine nanocarbon particles (for example, mechanical strength, high refractive index, thermal conductivity, insulating properties, antioxidant properties, crystallization promotion action, dendrite suppression action, etc.) to a resin or the like (for example, a heat- or light-curable resin or a thermoplastic resin, etc.). The composition obtained by adding the nanocarbon particle dispersion composition to a resin can be preferably used as, for example, a functional hybrid material, a thermal function (heat resistance, heat storage, thermal conduction, insulation, etc.) material, a photonics (organic EL element, LED, liquid crystal display, optical disk, etc.) material, a biocompatible material, a heat shielding film, etc.) material, a sheet material, a screen (transparent screen, etc.) material, a filler (heat dissipation filler, mechanical property improvement filler, etc.) material, a heat-resistant plastic substrate (substrate for flexible display, etc.) material, a lithium ion battery material, etc. The nanocarbon particle dispersion composition can also be used for other medical purposes.

[0086] Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Each configuration in each embodiment and their combinations are merely examples, and addition, omission, substitution, and other modifications of the configuration are possible as appropriate within the scope of the present disclosure. In addition, each invention according to this disclosure is not limited by the embodiments or the following examples, but is limited only by the claims. EXAMPLES

[0087] Hereinafter, one embodiment of the present disclosure will be described in more detail based on examples.

[0088] Example 1 Surface-modified nanodiamond particles and a dispersion composition were produced through the following steps.

[0089] (Preparation of amines) To 3 mmol of 3-amino-1-propanol, 3.6 mmol of 1M aqueous hydrochloric acid was added at 0°C, and the mixture was stirred at room temperature for 2 hours. After the reaction was completed, methanol was added and the mixture was azeotropically dehydrated under reduced pressure. To the resulting compound, 3 mL of toluene and 3 mmol of stearic acid halide were added, and the mixture was stirred at 70°C for 2 hours. After the reaction was completed, the mixture was concentrated under reduced pressure to obtain the corresponding amine hydrochloride (3-(stearoyloxy)propylamine hydrochloride).

[0090] (Surface modification process) 81 mg (0.25 mmol) of dodecylbenzenesulfonic acid as an acid catalyst, 1 mL of water, 500 mg of detonation nanodiamond aqueous dispersion (solid content concentration about 6% by mass), and 1 mmol of the amine hydrochloride prepared above were added in sequence, and the mixture was stirred at 90 ° C for about 16 hours to react. After the reaction was completed, 3 mL of water and 3 mL of toluene were added, and the aqueous phase was removed. The resulting toluene phase was centrifuged (20000 G, 10 minutes) to obtain a toluene dispersion of nanodiamond particles surface-modified with amino groups (3-(stearoyloxy)propylamino groups). 3 mL of isopropanol was added to the resulting dispersion, and centrifuged (20000 G, 5 minutes) to obtain a solid of surface-modified nanodiamond. 3 mL each of toluene, THF, NMP, and DMAc were added to this solid to obtain each dispersion.

[0091] Example 2 Surface-modified nanodiamond particles and a dispersion composition were produced through the following steps.

[0092] (Preparation of amines) An amine hydrochloride (5-(stearoyloxy)pentylamine hydrochloride) was obtained in the same manner as in Example 1, except that 5-amino-1-pentanol was used instead of 5-amino-1-propanol.

[0093] (Surface modification process) A solid nanodiamond surface-modified with an amino group (5-(stearoyloxy)pentylamino group) was obtained in the same manner as in Example 1, except that the 5-(stearoyloxy)pentylamine hydrochloride obtained above was used as the amine hydrochloride. 3 mL each of toluene, THF, NMP, and DMAc were added to this solid, and a dispersion was obtained. The average dispersion particle diameter D50 of the surface-modified nanodiamond particles in the obtained dispersion was about 19 nm in toluene, about 22 nm in THF, about 14 nm in NMP, and about 21 nm in DMAc. In addition, the mass ratio [nanodiamond / surface modification group] determined by thermogravimetric analysis was 3.2.

[0094] Example 3 Surface-modified nanodiamond particles and a dispersion composition were produced through the following steps.

[0095] (Preparation of amines) To 3 mmol of γ-aminobutyric acid, 3.6 mmol of 1M aqueous hydrochloric acid was added at 0°C, and the mixture was stirred at room temperature for 2 hours. After the reaction was completed, methanol was added and the mixture was azeotropically dehydrated under reduced pressure. To the resulting compound, 3 mL of toluene and 3.6 mmol of thionyl chloride were added, and the mixture was stirred at 60°C for 2 hours. After the reaction was completed, 3 mL of toluene and 3 mmol of dodecyl alcohol were added again, and the mixture was stirred at 70°C for 2 hours. After the reaction was completed, the mixture was concentrated under reduced pressure to obtain the corresponding amine hydrochloride (γ-aminobutyric acid dodecyl ester hydrochloride).

[0096] (Surface modification process) A solid nanodiamond surface-modified with an amino group (3-(dodecyloxycarbonyl)propylamino group) was obtained in the same manner as in Example 1, except that the γ-aminobutyric acid dodecyl ester hydrochloride obtained above was used as the amine hydrochloride. When 3 mL each of toluene, THF, NMP, and DMAc was added to this solid, a dispersion was obtained.

[0097] Example 4 Surface-modified nanodiamond particles and a dispersion composition were produced through the following steps.

[0098] (Preparation of amines) An amine hydrochloride (6-aminohexanoic acid dodecyl ester hydrochloride) was obtained in the same manner as in Example 3, except that 6-aminohexanoic acid was used instead of γ-aminobutyric acid.

[0099] (Surface modification process) A solid nanodiamond surface-modified with an amino group (5-(dodecyloxycarbonyl)pentylamino group) was obtained in the same manner as in Example 3, except that the 6-aminohexanoic acid dodecyl ester hydrochloride obtained above was used as the amine hydrochloride. 3 mL each of toluene, THF, NMP, and DMAc were added to this solid, and a dispersion was obtained. The average dispersion particle diameter D50 of the surface-modified nanodiamond particles in the obtained dispersion was about 27 nm in toluene, about 31 nm in THF, about 20 nm in NMP, and about 43 nm in DMAc. In addition, the mass ratio [nanodiamond / surface modification group] determined by thermogravimetric analysis was 13.5.

[0100] Example 5 Surface-modified nanodiamond particles and a dispersion composition were produced through the following steps.

[0101] (Preparation of amines) An amine hydrochloride (8-aminooctanoic acid dodecyl ester hydrochloride) was obtained in the same manner as in Example 3, except that 8-aminooctanoic acid was used instead of γ-aminobutyric acid.

[0102] (Surface modification process) A nanodiamond solid surface-modified with an amino group (7-(dodecyloxycarbonyl)heptylamino group) was obtained in the same manner as in Example 3, except that the 8-aminooctanoic acid dodecyl ester hydrochloride obtained above was used as the amine hydrochloride. When 3 mL each of toluene, THF, NMP, and DMAc was added to this solid, a dispersion was obtained.

[0103] Example 6 Surface-modified nanodiamond particles and a dispersion composition were produced through the following steps.

[0104] (Preparation of amines) An amine hydrochloride (6-aminohexanoic acid cinnamyl ester hydrochloride) was obtained in the same manner as in Example 3, except that 6-aminohexanoic acid was used instead of γ-aminobutyric acid and cinnamyl alcohol was used instead of dodecyl alcohol.

[0105] (Surface modification process) A nanodiamond solid surface-modified with an amino group (5-(cinnamyloxycarbonyl)pentylamino group) was obtained in the same manner as in Example 3, except that the 6-aminohexanoic acid cinnamyl ester hydrochloride obtained above was used as the amine hydrochloride. To this solid, 3 mL each of toluene, THF, NMP, and DMAc was added to obtain a dispersion. The average dispersion particle diameter D50 of the surface-modified nanodiamond particles in the obtained dispersion was about 24 nm in toluene, about 30 nm in THF, about 21 nm in NMP, and about 28 nm in DMAc. In addition, the mass ratio [nanodiamond / surface modification group] determined by thermogravimetric analysis was 12.5.

[0106] Example 7 A nanodiamond solid surface-modified with an amino group (3-butoxypropylamino group) was obtained in the same manner as in Example 1, except that 3-butoxypropylamine was used instead of amine hydrochloride. To this solid, 3 mL each of toluene, NMP, and DMAc were added to obtain a dispersion. The average dispersion particle diameter D50 of the surface-modified nanodiamond particles in the obtained dispersion was about 30 nm in toluene, about 22 nm in NMP, and about 19 nm in DMAc. In addition, the mass ratio [nanodiamond / surface modification group] determined by thermogravimetric analysis was 15.6.

[0107] <Particle size D50> The median diameter (particle size D50) of the nano-diamond particles in the nano-diamond dispersion of the example obtained as described above is a volume-based value measured from the particle size distribution of the nano-diamond obtained by the dynamic light scattering method. Specifically, the above particle size distribution was measured by the dynamic light scattering method (non-contact backscattering method) using an apparatus manufactured by Malvern (trade name "Zetasizer Nano ZS") to measure the particle size distribution of the nano-diamond.

[0108] <Thermogravimetric analysis> Using a TG / DTA (thermogravimetric measurement / differential thermal analysis) apparatus (trade name "EXSTAR6300", manufactured by SII NanoTechnology Inc.), a sample (about 3 mg) was heated at a heating rate of 20 °C / min in an air atmosphere to measure the weight loss. Alumina was used as the reference substance.

[0109] <FT-IR analysis> Regarding the surface-modified nano-diamond obtained in the example, FT-IR measurement was performed using an apparatus equipped with a Fourier transform infrared spectrophotometer "IRTracer" (manufactured by Shimadzu Corporation) and a heating vacuum stirring reflection "Heat Chamber Type-1000 °C" (manufactured by S.T. Japan Co., Ltd.). In order to remove the adsorbed water of the nano-diamond particles, after heating at 150 °C for 10 minutes under a vacuum of 2×10 -3 Pa, FT-IR measurement was carried out.

[0110] The FT-IR spectra of the surface-modified nano-diamond obtained in Example 2 are shown in Figure 1, the FT-IR spectra of the surface-modified nano-diamond obtained in Example 4 are shown in Figure 2, the FT-IR spectra of the surface-modified nano-diamond obtained in Example 6 are shown in Figure 3, and the FT-IR spectra of the surface-modified nano-diamond obtained in Example 7 are shown in Figure 4, respectively.

[0111] In the surface-modified nano-diamond of Example 2, around 2918 cm -1 nearby, around 2851 cm -1 nearby, and around 1456 cm -1A peak derived from the alkyl group was confirmed around 2928 cm for the surface-modified nanodiamond of Example 4. -1 Near, 2857cm -1 Near, and 1456 cm -1 A peak derived from the alkyl group was confirmed around 2961 cm for the surface-modified nanodiamond of Example 6. -1 Near, 2928cm -1 Near, 2857cm -1 Near, and 1456 cm -1 A peak due to alkyl groups is observed around 746 cm -1 Near and 698cm -1 In the surface-modified nanodiamond of Example 7, a peak derived from the benzene ring was observed at 2961 cm -1 Near, 2930cm -1 Near, 2866cm -1 Near, and 1458 cm -1 A peak due to alkyl groups is observed near 1265 cm -1 Peaks derived from ether bonds were observed in the vicinity.

[0112] Variations of the invention according to the present disclosure are described below. [Appendix 1] A surface-modified nanodiamond comprising a nanodiamond particle and a group represented by the following formula (1) that surface-modifies the nanodiamond particle. -XR 1 (1) [In formula (1), X represents -NH- or -O-, and the bond extending to the left from X is bonded to the nanodiamond particle. R 1 represents a monovalent organic group in which two optionally substituted hydrocarbon groups are bonded via an ester bond, an ether bond, a carbonyl group, or an amide bond. [Appendix 2] In the formula (1), the R 1 The surface-modified nanodiamond according to claim 1, wherein the monovalent organic group has 5 to 30 (or 7 to 25) carbon atoms. [Appendix 3] The surface-modified nanodiamond according to appendix 1 or 2, wherein the two hydrocarbon groups are the same or different and are an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, a group in which an aliphatic hydrocarbon group and an alicyclic hydrocarbon group are bonded together, or a group in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded together. [Note 4] In the formula (1), X represents -NH-, and R 1 The surface-modified nanodiamond according to any one of claims 1 to 3, wherein represents a monovalent organic group in which two optionally substituted hydrocarbon groups are bonded via an ester bond, an ether bond, or an amide bond. [Appendix 5] R 1 5. The surface-modified nanodiamond according to any one of claims 1 to 4, wherein the monovalent organic group has 5 to 30 (preferably 5 to 25) carbon atoms.

[0113] [Appendix 6] A surface-modified nanodiamond according to any one of Appendices 1 to 5, wherein the group represented by the formula (1) is a group represented by the following formula (1'): -XR 2 -YR 3 (1') [In formula (1'), X represents -NH- or -O-, and the bond extending to the left from X is bonded to the nanodiamond particle. R 2 and R 3 are the same or different and each represents a hydrocarbon group which may have a substituent, and Y represents an ester bond, an ether bond, a carbonyl group, or an amide bond. [Note 7] In the formula (1'), X represents -NH-, Y represents an ester bond, an ether bond, or an amide bond (preferably an ester bond or an ether bond), and R 2 and R 3 The surface-modified nanodiamond according to claim 6, wherein the total number of carbon atoms is 5 to 30 (preferably 5 to 25). [Additional Note 8] R in the above formula (1') 2 and R 3 and are the same or different and are linear or branched hydrocarbon groups.

[0114] [Appendix 9] In the formula (1'), Y represents an ester bond, and R 1 The surface-modified nanodiamond according to any one of Appendices 6 to 8, wherein the monovalent organic group has 12 to 30 (preferably 14 to 26) carbon atoms. [Appendix 10] In the formula (1'), R 2 and R 3 The surface-modified nanodiamond according to appended claim 9, wherein the total number of carbon atoms is 12 to 30 (preferably 14 to 26). [Appendix 11] In the formula (1'), R 2 11. The surface-modified nanodiamond according to claim 9 or 10, wherein the number of carbon atoms is 3 to 7. [Appendix 12] In the above formula (1'), R 3 12. The surface-modified nanodiamond according to any one of claims 9 to 11, wherein the number of carbon atoms is 8 to 20.

[0115] [Appendix 13] In the formula (1'), Y represents an ether bond, and R 1 The surface-modified nanodiamond according to any one of Appendices 6 to 8, wherein the monovalent organic group has 4 to 10 (preferably 5 to 8) carbon atoms. [Appendix 14] In the formula (1'), R 2 and R 3 The surface-modified nanodiamond according to claim 13, wherein the total number of carbon atoms is 4 to 10 (preferably 5 to 8). [Appendix 15] In the formula (1'), R 2 15. The surface-modified nanodiamond according to claim 13 or 14, wherein the number of carbon atoms is 2 to 5. [Appendix 16] In the formula (1'), R 3 16. The surface-modified nanodiamond according to any one of claims 13 to 15, wherein the number of carbon atoms is 3 to 8.

[0116] [Appendix 17] In the formula (1'), X represents -O-, Y represents an ester bond, an ether bond, or an amide bond (preferably an ester bond or an ether bond), and R 2 and R 3The surface-modified nanodiamond according to claim 6, wherein the total number of carbon atoms is 5 to 30 (preferably 5 to 25). [Appendix 18] R in the above formula (1') 2 and R 3 and are the same or different and are linear or branched hydrocarbon groups.

[0117] [Appendix 19] R 2 19. The surface-modified nanodiamond according to any one of claims 6 to 18, wherein is a linear or branched hydrocarbon group (preferably an alkyl group). [Appendix 20] R 2 20. The surface-modified nanodiamond according to any one of claims 6 to 19, wherein is a hydrocarbon group having 2 to 10 carbon atoms (preferably 3 to 7). [Appendix 21] R 3 is a linear or branched hydrocarbon group, or a group in which the linear or branched hydrocarbon group is bonded to an aromatic hydrocarbon group (particularly, a group whose terminal is an aromatic hydrocarbon group). [Appendix 22] R 3 22. The surface-modified nanodiamond according to any one of claims 6 to 21, wherein is a hydrocarbon group having 3 to 20 carbon atoms (preferably 4 to 18).

[0118] [Appendix 23] A surface-modified nanodiamond described in any one of Appendices 1 to 22, wherein the mass ratio of nanodiamond to group represented by formula (1) [nanodiamond / group represented by formula (1)] is 0.5 or more (preferably 2.5 or more). [Appendix 24] A surface-modified nanodiamond described in any one of Appendices 1 to 23, in which the mass ratio of nanodiamond to group represented by formula (1) [nanodiamond / group represented by formula (1)] is 17.0 or less (preferably 15.0 or less, more preferably 10.0 or less, and even more preferably 5.0 or less). [Appendix 25] A surface-modified nanodiamond according to any one of Appendices 1 to 24, having a particle diameter (D50) of 400 nm or less (preferably 300 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less). [Appendix 26] The surface-modified nanodiamond according to any one of Appendices 1 to 25, having a particle diameter (D90) of 500 nm or less (preferably 400 nm or less, more preferably 150 nm or less).

[0119] [Appendix 27] A nanodiamond dispersion composition comprising a dispersion medium and the surface-modified nanodiamond of any one of Appendices 1 to 26 dispersed in the dispersion medium. [Appendix 28] A nanodiamond dispersion composition according to Appendix 27, wherein the dispersion medium is an organic dispersion medium. [Appendix 29] A nanodiamond dispersion composition according to appendix 27 or 28, wherein the average dispersed particle diameter D50 of the surface-modified nanodiamond is 1 to 100 nm (preferably 1 to 60 nm, more preferably 1 to 50 nm, and even more preferably 1 to 30 nm). [Appendix 30] The SP value of the organic dispersion medium is 6.0 to 23.0 (cal / cm 3 ) 1 / 2 (Preferably 7.0 to 23.0 (cal / cm 3 ) 1 / 2 30. A nanodiamond dispersion composition according to any one of claims 27 to 29, wherein [Appendix 31] A nanodiamond dispersion composition according to any one of Appendices 27 to 31, having a haze value of 5 or less (preferably 3 or less, more preferably 1 or less).

[0120] [Appendix 32] A method for producing surface-modified nanocarbon particles, comprising the step of reacting nanocarbon particles having hydroxy groups on the surface thereof, in a nano-dispersed state in water, with a compound represented by the following formula (2) in the presence of an acid catalyst to obtain surface-modified nanocarbon particles: R 1 -XH (2) [In formula (2), X represents -NH- or -O-. 1represents a monovalent organic group in which two optionally substituted hydrocarbon groups are bonded via an ester bond, an ether bond, a carbonyl group, or an amide bond. [Appendix 33] A method for producing surface-modified nanocarbon particles according to Appendices 32, wherein the nanocarbon particles are nanodiamond particles. [Appendix 34] In the formula (2), the R 1 The method for producing surface-modified nanocarbon particles according to claim 32 or 33, wherein the monovalent organic group has 5 to 30 (or 7 to 25) carbon atoms. [Appendix 35] A method for producing surface-modified nanocarbon particles according to any one of Appendices 32 to 34, wherein the two hydrocarbon groups are the same or different and are an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, a group in which an aliphatic hydrocarbon group and an alicyclic hydrocarbon group are bonded together, or a group in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded together. [Note 36] In the formula (2), X represents -NH-, and R 1 The surface-modified nanodiamond according to any one of Appendices 32 to 35, wherein represents a monovalent organic group in which two optionally substituted hydrocarbon groups are bonded via an ester bond, an ether bond, or an amide bond. [Appendix 37] R 1 37. The method for producing surface-modified nanocarbon particles according to any one of claims 32 to 36, wherein the monovalent organic group has 5 to 30 (preferably 5 to 25) carbon atoms.

[0121] [Appendix 38] A method for producing surface-modified nanocarbon particles according to any one of Appendices 32 to 37, wherein the group represented by formula (2) is a group represented by the following formula (2'): -XR 2 -YR 3 (2') [In formula (2'), X represents -NH- or -O-, and the bond extending to the left from X is bonded to the nanodiamond particle. R 2 and R 3 are the same or different and each represents a hydrocarbon group which may have a substituent, and Y represents an ester bond, an ether bond, a carbonyl group, or an amide bond. [Additional Note 39] In the formula (2'), X represents -NH-, Y represents an ester bond, an ether bond, or an amide bond (preferably an ester bond or an ether bond), and R 2 and R 3 The method for producing surface-modified nanocarbon particles according to claim 38, wherein the total number of carbon atoms is 5 to 30 (preferably 5 to 25). [Appendix 40] R in the above formula (2') 2 and R 3 and are the same or different and are linear or branched hydrocarbon groups.

[0122] [Additional Note 41] In the above formula (2'), Y represents an ester bond, and R 1 41. The method for producing surface-modified nanocarbon particles according to any one of claims 38 to 40, wherein the monovalent organic group has 12 to 30 (preferably 14 to 26) carbon atoms. [Appendix 42] In the above formula (2'), R 2 and R 3 42. The method for producing surface-modified nanocarbon particles according to claim 41, wherein the total number of carbon atoms is 12 to 30 (preferably 14 to 26). [Appendix 43] In the formula (2'), R 2 43. The method for producing surface-modified nanocarbon particles according to claim 41 or 42, wherein the number of carbon atoms is 3 to 7. [Additional Note 44] In the above formula (2'), R 3 44. The method for producing surface-modified nanocarbon particles according to any one of claims 41 to 43, wherein the number of carbon atoms is 8 to 20.

[0123] [Additional Note 45] In the above formula (2'), Y represents an ether bond, and R 1 41. The method for producing surface-modified nanocarbon particles according to any one of claims 38 to 40, wherein the monovalent organic group has 4 to 10 (preferably 5 to 8) carbon atoms. [Additional Note 46] In the formula (2'), R 2 and R 3 The method for producing surface-modified nanocarbon particles according to Appendix 45, wherein the total number of carbon atoms is 4 to 10 (preferably 5 to 8). [Appendix 47] In the formula (2'), R 2 47. The method for producing surface-modified nanocarbon particles according to claim 45 or 46, wherein the number of carbon atoms is 2 to 5. [Appendix 48] In the formula (2'), R 3 48. The method for producing surface-modified nanocarbon particles according to any one of claims 45 to 47, wherein the number of carbon atoms is 3 to 8.

[0124] [Additional Note 49] In the formula (2'), X represents -O-, Y represents an ester bond, an ether bond, or an amide bond (preferably an ester bond or an ether bond), and R 2 and R 3 The method for producing surface-modified nanocarbon particles according to claim 38, wherein the total number of carbon atoms is 5 to 30 (preferably 5 to 25). [Additional Note 50] R in the above formula (2') 2 and R 3 and are the same or different and are linear or branched hydrocarbon groups.

[0125] [Appendix 51] R 2 51. The method for producing surface-modified nanocarbon particles according to any one of claims 38 to 50, wherein is a linear or branched hydrocarbon group (preferably an alkyl group). [Appendix 52] R 2 52. The method for producing surface-modified nanocarbon particles according to any one of Appendices 38 to 51, wherein is a hydrocarbon group having 2 to 10 (preferably 3 to 7) carbon atoms. [Appendix 53] R 3 is a linear or branched hydrocarbon group, or a group in which the linear or branched hydrocarbon group is bonded to an aromatic hydrocarbon group (particularly, a group whose terminal is an aromatic hydrocarbon group). [Appendix 54] R 3 The method for producing surface-modified nanocarbon particles according to any one of Appendices 38 to 53, wherein is a hydrocarbon group having 3 to 20 (preferably 4 to 18) carbon atoms.

Claims

1. A surface-modified nanodiamond comprising a nanodiamond particle and a group represented by the following formula (1) that surface-modifies the nanodiamond particle. -X-R １ (1) [In formula (1), X represents -NH-, and the bond extending to the left from X is bonded to the nanodiamond particle. R １ represents a monovalent organic group in which two optionally substituted hydrocarbon groups are bonded via an ester bond, an ether bond, or an amide bond.

2. The R １ The surface-modified nanodiamond of claim 1, wherein the monovalent organic group has 5 to 30 carbon atoms, and the two hydrocarbon groups are linear or branched hydrocarbon groups.

3. A nanodiamond dispersion composition comprising an organic dispersion medium and the surface-modified nanodiamond according to claim 1 or 2 dispersed in the organic dispersion medium, wherein the average dispersed particle diameter D50 of the surface-modified nanodiamond is 1 to 100 nm.

4. The SP value of the organic dispersion medium is 6.0 to 23.0 (cal / cm ３ ) １／２ The nanodiamond dispersion composition according to claim 3,

5. The method includes a step of reacting nanocarbon particles having hydroxy groups on the surface thereof, in a nano-dispersed state in water, with a compound represented by the following formula (2) in the presence of an acid catalyst to obtain surface-modified nanocarbon particles, A method for producing surface-modified nanocarbon particles, wherein the nanocarbon particles are nanodiamond particles. R １ -X-H (2) [In formula (2), X represents -NH-. １ represents a monovalent organic group in which two optionally substituted hydrocarbon groups are bonded via an ester bond, an ether bond, or an amide bond.

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