Nanodiamond dispersion composition

Abstract

Provided is a nanodiamond-dispersed composition in which nanodiamond particles are exceptionally well-dispersed in an organic dispersion medium. The nanodiamond-dispersed composition contains an organic dispersion medium, nanodiamond particles dispersed in the organic dispersion medium, and a fatty acid ester dispersant, the nanodiamond particles being surface-modified by an organic-group-containing surface-modifying group or compound. It is preferable that the fatty acid ester dispersant loses no more than 30% in mass when held in an air atmosphere at 200°C for 180 minutes.

Description

[Technical Field]

[0001] The present disclosure relates to a nanodiamond dispersion composition. More specifically, the present disclosure relates to a composition in which nanodiamond particles are dispersed in an organic dispersion medium. This application claims priority from Japanese Patent Application No. 2020-182785, filed on October 30, 2020, the contents of which are incorporated herein by reference. [Background technology]

[0002] It is known that nano-sized fine materials have new properties that cannot be expressed in a bulk state. For example, nanodiamond particles (=nano-sized diamond particles) have mechanical strength, high refractive index, thermal conductivity, insulating properties, antioxidant properties, and the ability to promote crystallization of resins, etc. Technology related to the production of such nanodiamonds is described, for example, in Patent Documents 1 and 2 listed below.

[0003] However, nanodiamond particles generally have a high proportion of surface atoms, which means that the sum of the 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, the Coulomb interaction between the crystal planes of adjacent crystallites can contribute to a phenomenon known as agglutination, in which the particles aggregate very tightly. For this reason, it has been very difficult to disperse nanodiamond particles in organic solvents in the form of primary particles.

[0004] Patent Documents 3 and 4 disclose lubricating oil compositions containing diamond nanoparticles and specific additives. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-001983 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-126669 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-241443 [Patent Document 4] Japanese Patent Application Laid-Open No. 2008-179738 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the lubricating oil compositions claimed to have excellent nanodiamond particle dispersibility in Patent Documents 3 and 4 all contain a small amount of nanodiamond particles. For example, in Patent Document 3, in order to disperse the nanodiamond particles in the composition, a dispersion solvent such as ethanol or DMSO is blended in an amount 10 times the amount of nanodiamond particles. Therefore, if a large amount of nanodiamond particles is to be blended in the lubricant composition of Patent Document 3, the amount of dispersion solvent used will also increase, making it difficult to use practically as a lubricating oil composition.

[0007] In addition, in Patent Document 4, in order to obtain a composition with good dispersibility, it is necessary to mix 200 times as much dispersant as the nanodiamond particles. Therefore, in Patent Document 4, if a large amount of nanodiamond particles is to be mixed, the amount of dispersant will also be large and will exceed the amount as an additive, so the dispersant cannot be mixed as an additive. For this reason, a dispersion composition with even better dispersibility of nanodiamond particles is required.

[0008] Therefore, an object of the present disclosure is to provide a nanodiamond dispersion composition that has excellent dispersibility of nanodiamond particles in an organic dispersion medium. [Means for solving the problem]

[0009] As a result of intensive research into achieving the above object, the inventors of the present disclosure have found that by using a specific dispersant, it is possible to obtain a nanodiamond dispersion composition that has excellent dispersibility of nanodiamond particles in an organic dispersion medium. The present disclosure relates to a product that has been completed based on these findings.

[0010] That is, the present disclosure provides a dispersion medium comprising an organic dispersion medium, nanodiamond particles dispersed in the organic dispersion medium, and a fatty acid ester-based dispersant, The nanodiamond particles provide a nanodiamond dispersion composition in which the nanodiamond particles are surface-modified with a surface-modifying group or compound containing an organic group.

[0011] The content of the nanodiamond particles may be more than 3.0% by mass.

[0012] The fatty acid ester-based dispersant preferably has a mass loss rate of 30% or less when maintained in an air atmosphere at a temperature of 200° C. for 180 minutes.

[0013] The acid value of the fatty acid ester dispersant is preferably 40 mgKOH / g or less.

[0014] The average dispersed particle size of the nanodiamond particles is preferably 2 to 240 nm.

[0015] The nanodiamond dispersion composition preferably has a haze value of 5 or less.

[0016] The SP value of the organic dispersion medium is 6.0 to 12.0 (cal / cm 3 ) 1 / 2 It is preferable that:

[0017] The nanodiamond dispersion composition preferably has a viscosity at 25°C of 0.2 to 120 mPa·s.

[0018] The fatty acid ester dispersant preferably has an average molecular weight Mp of 300 or more.

[0019] The nanodiamond particles preferably include surface-modified nanodiamonds in which the surface of the nanodiamond particles is modified with a group represented by the following formula (I): -XR (I) [In formula (I), X represents -Si-, -NH-, -O-, -OC(=O)-, -C(=O)-O-, -NH-C(=O)-, -C(=O)-NH-, or -S-, and the bond extending to the left from X is bonded to the nanodiamond particle. R represents a monovalent organic group, and the atom bonded to X is a carbon atom.]

[0020] In the above formula (I), X preferably represents -Si-, -NH-, -O-, or -OC(=O)-. [Effects of the Invention]

[0021] The nanodiamond dispersion composition of the present disclosure has excellent dispersibility of nanodiamond particles in an organic dispersion medium. In particular, even when the content of nanodiamond particles is large, the dispersibility of nanodiamond particles in an organic dispersion medium is excellent. In addition, fatty acid ester-based dispersants have high heat resistance, and the nanodiamond dispersion composition of the present disclosure also tends to have excellent dispersion stability in high-temperature environments. DETAILED DESCRIPTION OF THE INVENTION

[0022] A nanodiamond dispersion composition (ND dispersion composition) according to one embodiment of the present disclosure comprises at least an organic dispersion medium, nanodiamond particles (ND particles) dispersed in the organic dispersion medium, and a fatty acid ester-based dispersant.

[0023] The average dispersed particle diameter (D50, median diameter) of the ND particles in the ND dispersion composition is preferably 2 to 240 nm, more preferably 4 to 200 nm, more preferably 5 to 100 nm, even more preferably 10 to 70 nm, and particularly preferably 12 to 40 nm. The average dispersed particle diameter can be measured by dynamic light scattering. The ND dispersion composition has excellent dispersibility of ND particles, so that the ND particles can be dispersed in an organic dispersion medium with an average dispersed particle diameter within the above range.

[0024] The content of ND particles in the ND dispersion composition is, for example, 0.01 to 5.0% by mass, preferably 0.1 to 4.0% by mass, more preferably 0.25 to 3.0% by mass, and even more preferably 0.5 to 2.0% by mass. A content within the above range provides superior dispersibility of the ND particles. The content may be greater than 3.0% by mass, or even 3.5% by mass or greater. Because the ND dispersion composition provides superior dispersibility of ND particles, even if the content exceeds 3% by mass, the ND particles can be dispersed with a small dispersed particle size while reducing the amount of dispersant added. From the viewpoint of superior dispersibility of the ND particles, the content is preferably 10% by mass or less. The ND dispersion composition may be a concentrated solution that is diluted before use to reduce the ND particle content (for example, to 0.1 to 2,000 ppm by mass).

[0025] The content of the fatty acid ester-based dispersant in the ND dispersion composition is, for example, 10 to 10,000 parts by mass (or 10 parts by mass or more but less than 10,000 parts by mass), preferably 50 to 1,000 parts by mass, and more preferably 70 to 300 parts by mass, relative to 100 parts by mass of the total amount of ND particles in the ND dispersion composition. When the content of the fatty acid ester-based dispersant is within the above range, the dispersibility of the ND particles in the ND dispersion composition is even better.

[0026] The content of the solvent in the ND dispersion composition is, for example, 90 to 99.9999% by mass, or may be 90 to 96.999% by mass. The content of the organic dispersion medium in the total amount of solvent is, for example, 60% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0027] The ND dispersion composition preferably has a haze value of 5 or less, more preferably 3 or less, even more preferably 1 or less, even more preferably 0.5 or less, even more preferably 0.1 or less, and particularly preferably 0.05 or less. The ND dispersion composition has excellent dispersibility of ND particles, so an ND dispersion composition with the above haze value can be obtained. The haze value can be measured in accordance with JIS K 7136. Furthermore, the haze value of an ND dispersion composition having an ND concentration of 0.1% by mass may be within the above range.

[0028] The viscosity of the ND dispersion composition at 25°C is preferably 0.2 to 120 mPa·s, more preferably 10 to 100 mPa·s, and even more preferably 20 to 90 mPa·s. Because the ND dispersion composition has excellent dispersibility of ND particles, it also has excellent dispersibility in an organic dispersion medium even when the viscosity is within the above range. The rotor and the rotor rotation speed used in measuring the viscosity are appropriately selected depending on the measured value. The viscosity can be measured, for example, using an EMS viscometer (product name "EMS1000", manufactured by Kyoto Electronics Manufacturing Co., Ltd.).

[0029] The ND dispersion composition may consist solely of ND particles, a fatty acid ester-based dispersant, and an organic dispersion medium, or may contain other components. Examples of other components include dispersants other than fatty acid ester-based dispersants, surfactants, thickeners, coupling agents, rust inhibitors, corrosion inhibitors, freezing point depressants, antifoaming agents, anti-wear additives, preservatives, and colorants. The content of the fatty acid ester-based dispersant is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more, based on the total amount of dispersants in the ND dispersion composition. The content of the other components is, for example, 30% by mass or less, preferably 20% by mass or less, even more preferably 10% by mass or less, even more preferably 5% by mass or less, even more preferably 1% by mass or less, and particularly preferably less than 1% by mass, based on the total amount of the ND dispersion composition. Therefore, the total content of the ND particles, fatty acid ester-based dispersant, and organic 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, still more preferably 99% by mass or more, and particularly preferably more than 99% by mass, relative to the total amount of the ND dispersion composition. In particular, it is preferable that the content of the surfactant as the other component is within the range exemplified as the content of the other component.

[0030] (nanodiamond particles) The ND particles are not particularly limited, and known or conventional nanodiamond particles can be used. The ND particles may be surface-modified ND particles (surface-modified ND) or non-surface-modified ND particles. Non-surface-modified ND particles have hydroxyl groups (-OH) or carboxyl groups (-COOH) on the surface. Only one type of ND particle may be used, or two or more types may be used.

[0031] In the above-mentioned surface-modified NDs, examples of the compound or functional group that modifies the surface of the ND particles include a silane compound, a phosphonate ion or a phosphonic acid residue, a surface-modifying group having a vinyl group at the end, an amide group, a cation of a cationic surfactant, a group containing a polyglycerin chain, and a group containing a polyethylene glycol chain.

[0032] In the surface-modified NDs, the compound or functional group that modifies the surface of the ND particles preferably contains an organic group. The organic group is more preferably an organic group having 4 or more carbon atoms (e.g., 4 to 25), even more preferably an organic group having 6 or more carbon atoms (e.g., 6 to 22), and particularly preferably an organic group having 8 or more carbon atoms (e.g., 8 to 20). When the surface-modifying compound or functional group contains an organic group (especially an organic group having 4 or more carbon atoms), the hydrophobic interaction between the organic group and the organic dispersion medium improves the dispersibility of the ND particles in the organic dispersion medium. Examples of the organic group include substituted or unsubstituted hydrocarbon groups, substituted or unsubstituted heterocyclic groups, and groups in which two or more of the above hydrocarbon groups and / or the above heterocyclic groups are bonded. Specific examples of the organic group include the organic groups in the monovalent organic groups exemplified and explained as R in formula (I) described below.

[0033] In the above surface-modified ND, the compound or functional group that modifies the surface of the ND particles is preferably a group represented by the following formula (I), from the viewpoint of achieving better dispersibility in an organic dispersion medium when combined with a fatty acid ester-based dispersant. That is, the above surface-modified ND is preferably a surface-modified ND in which the group represented by the following formula (I) modifies the surface of the nanodiamond particle. -XR (I) [In formula (I), X represents -Si-, -NH-, -O-, -OC(=O)-, -C(=O)-O-, -NH-C(=O)-, -C(=O)-NH-, or -S-, and the bond extending to the left from X is bonded to the nanodiamond particle. R represents a monovalent organic group, and the atom bonded to X is a carbon atom.]

[0034] Examples of the monovalent organic group in R include substituted or unsubstituted hydrocarbon groups (monovalent hydrocarbon groups), substituted or unsubstituted heterocyclic groups (monovalent heterocyclic groups), and groups in which two or more of the above monovalent hydrocarbon groups and / or monovalent heterocyclic groups are bonded together.The bonded groups may be bonded directly or via a linking group.Examples of the linking group include an amino group, an ether bond, an ester bond, a phosphinic acid group, a sulfide bond, a carbonyl group, an organic group-substituted amide group, an organic group-substituted urethane bond, an organic group-substituted imide bond, a thiocarbonyl group, a siloxane bond, and groups in which two or more of these are bonded together.

[0035] Examples of the hydrocarbon group in the monovalent organic group include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and groups in which two or more of these groups are bonded together.

[0036] Examples of the aliphatic hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, etc. 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, 5-hexenyl group, and oleyl group. 2-22 Alkenyl groups (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).

[0037] Examples of the alicyclic hydrocarbon group include C cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cyclododecyl groups. 3-12 Cycloalkyl groups; C such as cyclohexenyl groups 3-12 Cycloalkenyl group; C such as bicycloheptanyl group, bicycloheptenyl group 4-15 Examples include a bridged cyclic hydrocarbon group.

[0038] Examples of the aromatic hydrocarbon group include C groups such as phenyl and naphthyl groups. 6-14 Aryl groups (especially C 6-10 aryl groups).

[0039] Examples of heterocyclic rings constituting the heterocyclic group include aromatic heterocyclic rings and non-aromatic heterocyclic rings. Examples of such heterocyclic rings include 3- to 10-membered rings (preferably 4- to 6-membered rings) containing carbon atoms and at least one heteroatom (e.g., oxygen atom, sulfur atom, nitrogen atom, etc.) as ring-constituting atoms, and condensed rings thereof. Specific examples include heterocyclic rings containing an oxygen atom as a heteroatom (e.g., 3-membered rings such as oxirane ring; 4-membered rings such as oxetane ring; 5-membered rings such as furan ring, tetrahydrofuran ring, oxazole ring, isoxazole ring, γ-butyrolactone ring; 6-membered rings such as 4-oxo-4H-pyran ring, tetrahydropyran ring, morpholine ring; condensed rings such as benzofuran ring, isobenzofuran ring, 4-oxo-4H-chromene ring, chroman ring, isochroman ring); 3-oxatricyclo[4.3.1.1 4,8 ]undecan-2-one ring, 3-oxatricyclo[4.2.1.0 4,8]nonan-2-one ring and the like), heterocycles containing a sulfur atom as a heteroatom (for example, five-membered rings such as a thiophene ring, a thiazole ring, an isothiazole ring, and a thiadiazole ring; six-membered rings such as a 4-oxo-4H-thiopyran ring; fused rings such as a benzothiophene ring), heterocycles containing a nitrogen atom as a heteroatom (for example, five-membered rings such as a pyrrole ring, a pyrrolidine ring, a pyrazole ring, an imidazole ring, and a triazole ring; six-membered rings such as an isocyanuric ring, a pyridine ring, a pyridazine ring, a pyrimidine ring, a pyrazine ring, a piperidine ring, and a piperazine ring; and fused rings such as an indole ring, an indoline ring, a quinoline ring, an acridine ring, a naphthyridine ring, a quinazoline ring, and a purine ring).

[0040] 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 C such as alkenyl group, tolyl group 1-4 C such as alkyl-substituted aryl groups and styryl groups 2-4 Alkenyl-substituted aryl groups and the like are included.

[0041] Examples of the group in which two or more of the monovalent hydrocarbon groups and / or monovalent heterocyclic groups are bonded via a linking group include a group in which the monovalent hydrocarbon group and / or the monovalent heterocyclic group is bonded to an alkoxy group, an alkenyloxy group, an alkynyloxy group, an aryloxy group, an aralkyloxy group, an acyloxy group, an alkylthio group, an alkenylthio group, an arylthio group, an aralkylthio group, an acyl group, an alkenylcarbonyl group, an arylcarbonyl group, an aralkylcarbonyl group, an alkoxycarbonyl group, an alkenyloxycarbonyl group, an aryloxycarbonyl group, an aralkyloxycarbonyl group, a dialkylamino group, an acylamino group, an oxetanyl group-containing group, a carbamoyl group, or a group in which two or more of these are bonded.

[0042] The monovalent organic group may have a substituent. Examples of the substituent include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; a cyano group; an isocyanate group; or an isothiocyanate group. It is preferable that the monovalent organic group does not have a functional group containing active hydrogen (such as a hydroxy group, a carboxy group, an amino group, a mono-substituted amino group, a thiol group, or a phosphate group).

[0043] The number of carbon atoms in the monovalent organic group is preferably 4 to 25, more preferably 6 to 22, and even more preferably 8 to 20. When the number of carbon atoms is 4 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 25 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.

[0044] Among the above-mentioned monovalent organic groups, preferred are monovalent substituted or unsubstituted hydrocarbon groups, groups in which a monovalent substituted or unsubstituted hydrocarbon group is bonded to an alkoxy group, and groups in which a monovalent substituted or unsubstituted hydrocarbon group is bonded to a dialkylamino group.

[0045] Preferably, R contains a hydrocarbon group having four or more consecutive carbon atoms in a straight chain. Examples of such a hydrocarbon group include linear alkylene groups such as tetramethylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene, and decamethylene; branched alkylene groups such as 2-ethylhexamethylene; linear alkenylene groups such as 1-butenylene, 2-butenylene, 1-pentenylene, 2-pentenylene, and 3-pentenylene; branched alkenylene groups such as 2-methyl-2-butenylene; alicyclic hydrocarbon groups having four or more carbon atoms such as cyclohexyl; aromatic hydrocarbon groups having six or more carbon atoms such as phenyl; and heterocyclic groups having a structure with four or more consecutive carbon atoms such as a piperidine ring.

[0046] In formula (I), the molar ratio of carbon atoms to the total amount of heteroatoms selected from the group consisting of nitrogen atoms, oxygen atoms, sulfur atoms, and silicon atoms is preferably 4.5 or more, more preferably 5 or more, and even more preferably 5.5 or more. When the molar ratio is 4.5 or more, the dispersibility in organic solvents is more excellent. The molar ratio is not particularly limited, but may be, for example, 22 or less, or 20 or less.

[0047] In particular, in the above formula (I), X is preferably -Si-, -NH-, -O-, -OC(=O)-, or -C(=O)-O-, and more preferably -Si-, -NH-, -O-, or -OC(=O)-. In this case, a surface-modified ND having excellent dispersibility in an organic dispersion medium can be more easily prepared.

[0048] In the above formula (I), when X is -O-, -OC(=O)-, or -C(=O)-O-, R is preferably a monovalent substituted or unsubstituted hydrocarbon group, more preferably a linear or branched hydrocarbon group having 8 to 20 carbon atoms.

[0049] In the above formula (I), when X is -NH-, R is preferably a monovalent organic group containing 8 to 20 carbon atoms. The monovalent organic group is preferably a substituted or unsubstituted hydrocarbon group, more preferably a substituted or unsubstituted aliphatic hydrocarbon group, and even more preferably a substituted or unsubstituted unsaturated aliphatic hydrocarbon group. Furthermore, when X is -NH-, R is preferably a monovalent organic group containing a hydrocarbon group with four or more consecutive carbon atoms in a linear chain.

[0050] In the above formula (I), when X is -Si-, the silicon atom has two more bonds in addition to the bond bonded to the nanodiamond particle and the bond bonded to R in the above formula (I). The two bonds are the same or different and are bonded to a hydrogen atom, an aliphatic hydrocarbon group having 1 to 3 carbon atoms, a silicon atom in another group represented by the above formula (I), a silicon atom in a silane compound described below, or a nanodiamond particle via an oxygen atom. Specifically, the two bonds are the same or different and are bonded to the OR group described below. 1 , OR 2 , or bonded to nanodiamond particles.

[0051] In the above formula (I), when X is -Si-, the surface-modified ND is preferably a surface-modified ND having a silane compound bonded to the surface. The silane compound preferably has a hydrolyzable group and an aliphatic hydrocarbon group. The silane compound used for surface modification of the ND particles may be one type or two or more types.

[0052] The silane compound preferably contains at least a compound represented by the following formula (1-1).

[0053] [ka]

[0054] In the above formula (1-1), R 1 , R 2 , R 3 are the same or different and represent an aliphatic hydrocarbon group having 1 to 3 carbon atoms. 4 represents an aliphatic hydrocarbon group having one or more carbon atoms.

[0055] Above R 1 , R 2 , R 3Examples of the aliphatic hydrocarbon group having 1 to 3 carbon atoms in the formula include linear or branched alkyl groups such as methyl, ethyl, propyl, and isopropyl groups; linear or branched alkenyl groups such as vinyl and allyl groups; and alkynyl groups such as ethynyl and propynyl groups. Of these, linear or branched alkyl groups are preferred.

[0056] Above R 4 corresponds to R in the above formula (I) and represents a monovalent organic group. The monovalent organic group is preferably an aliphatic hydrocarbon group having one or more carbon atoms, and examples thereof include linear or branched alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl, pentyl, hexyl, n-octyl, 2-ethylhexyl, nonyl, isononyl, decyl, isodecyl, lauryl, myristyl, isomyristyl, butyloctyl, isocetyl, hexyldecyl, stearyl, isostearyl, octyldecyl, octyldodecyl, and isobehenyl; linear or branched alkenyl groups such as vinyl, allyl, 1-butenyl, 7-octenyl, 8-nonenyl, 9-decenyl, 11-dodecenyl, and oleyl; and linear or branched alkynyl groups such as ethynyl, propynyl, decynyl, pentadecynyl, and octadecynyl.

[0057] R 4 Among these, aliphatic hydrocarbon groups having 4 or more carbon atoms are preferred, and particularly preferred are aliphatic hydrocarbon groups having 6 or more carbon atoms, because they have higher lipophilicity and can cause greater steric hindrance, resulting in an excellent aggregation-inhibiting effect and being able to impart a higher degree of dispersibility. The upper limit of the number of carbon atoms in the aliphatic hydrocarbon group is, for example, 25, preferably 20, and more preferably 12. Furthermore, as the aliphatic hydrocarbon group, linear or branched alkyl or alkenyl groups are preferred, and linear or branched alkyl groups are particularly preferred.

[0058] R 4When is an aliphatic hydrocarbon group having 4 or more carbon atoms, it exhibits affinity to the organic dispersion medium and can become a large steric hindrance, so it has an excellent aggregation suppression effect. Furthermore, when is a group containing an oxygen atom (OR 1 ' OR group 2 Since the (a) group exhibits affinity for the organic dispersion medium, the compound has excellent affinity for the organic dispersion medium and can exhibit even better dispersibility in the organic dispersion medium.

[0059] Therefore, examples of ND particles surface-modified with a silane compound (silane compound surface-modified ND particles) include ND particles having a structure surface-modified with a group represented by the following formula (1).

[0060] [ka]

[0061] In the above formula (1), R 4 corresponds to R in the group represented by the above formula (1) and represents a monovalent organic group. 1 ', R 2 ' may be the same or different and are a hydrogen atom, an aliphatic hydrocarbon group having 1 to 3 carbon atoms, or a group represented by the following formula (a): The bond marked with a wavy line in the formula bonds to the surface of the nanodiamond particle.

[0062] [ka]

[0063] In the above formula (a), R 4 corresponds to R in the group represented by the above formula (1) and represents a monovalent organic group. 3 , R 5 are the same or different and represent a hydrogen atom or an aliphatic hydrocarbon group having 1 to 3 carbon atoms. m and n are the same or different and represent an integer of 0 or more. The bond extending to the left from the silicon atom is bonded to the oxygen atom. The bond marked with a wavy line is bonded to the surface of the nanodiamond particle. R in the above formula (1) 4 is R in formula (1-1)4 Corresponds to.

[0064] R in the above formula (1) 1 ', R 2 ', R 3 , R 5 Examples of the aliphatic hydrocarbon group having 1 to 3 carbon atoms in the formula include linear or branched alkyl groups such as methyl, ethyl, propyl, and isopropyl groups; linear or branched alkenyl groups such as vinyl and allyl groups; and alkynyl groups such as ethynyl and propynyl groups. Of these, linear or branched alkyl groups are preferred.

[0065] m and n are the numbers of structural units shown in parentheses, and may be the same or different and represent integers of 0 or greater. When m and n are 2 or greater, the two or more structural units may be bonded randomly, alternately, or in blocks.

[0066] The silane compound surface-modified ND particles may have other functional groups in addition to the group represented by formula (1), such as a group represented by formula (1') below, or other surface functional groups (e.g., amino groups, hydroxyl groups, carboxyl groups, etc.). The number of such other functional groups may be one or more.

[0067] [ka]

[0068] In the above formula (1'), R 1 ', R 4 The bond marked with a wavy line in the formula is bonded to the surface of the nanodiamond particle.

[0069] When a silane compound (particularly, a compound represented by the above formula (1-1)) is used as the compound for surface treatment, the compound may be, for example, OR 1 Group, OR 2 Group, OR 3Hydrolyzable alkoxysilyl groups such as groups are easily hydrolyzed to form silanol groups, and for example, one of the silanol groups undergoes dehydration condensation with a hydroxyl group present on the surface of the ND particle to form a covalent bond, and the remaining two silanol groups can condense with silanol groups of other silane compounds to form siloxane bonds (Si-O-Si), which can impart affinity to the ND particles for organic dispersion media and enable them to exhibit even better dispersibility in the organic dispersion media.

[0070] The ND particles constituting the surface-modified ND preferably contain primary particles of nanodiamond. They may also contain secondary particles formed by aggregation (adhesion) of multiple primary particles. Furthermore, the surface of the surface-modified ND may have one or more types of other surface functional groups (e.g., amino groups, hydroxy groups, carboxy groups, etc.) in addition to the surface-modifying groups.

[0071] The mass ratio of ND to the surface-modifying group in the surface-modified ND [ND / surface-modifying group] is not particularly limited, but is preferably 0.5 or more, more preferably 2.5 or more. Furthermore, the mass ratio is preferably 15.0 or less, more preferably 10.0 or less, even more preferably 7.0 or less, and particularly preferably 5.0 or less. When the mass ratio is 0.5 or more, the properties of the nanodiamond material are less likely to be impaired. When the mass ratio is 15.0 or less (particularly 7.0 or less), the degree of modification with the surface-modifying group is sufficient, resulting in superior dispersibility in organic dispersion media. The mass ratio is determined based on the mass loss rate between 200°C and 450°C measured by thermogravimetric analysis, with the weight loss being the mass of the surface-modifying group.

[0072] (Organic dispersion medium) As the organic dispersion medium, known or commonly used organic solvents can be used. Among them, from the viewpoint of excellent dispersibility of ND particles in organic dispersion media with a lower SP value, it is preferable to use an organic dispersion medium with a lower SP value [Hildebrand solubility parameter (δ), at 25°C, unit: (cal / cm)]. 3 ) 1 / 2

[0043] is preferably 6.0 to 12.0, more preferably 6.0 or more and less than 11.0. In particular, since the ND dispersion composition has excellent ND particle dispersibility even when an organic solvent with low ND particle dispersibility is used by blending a fatty acid ester-based dispersant, the organic dispersion medium preferably has an SP value of 8.2 or less (e.g., 6.0 to 8.2) or 9.0 or more (e.g., 9.0 to 12.0), more preferably 8.0 or less (e.g., 6.5 to 8.0) or 9.2 or more (e.g., 9.2 to 12.0, preferably 9.2 or more and less than 11.0). One or more of the organic dispersion media may be used. 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.

[0073] 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 (SP: 9.1); alcohols such as 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); toluene (SP: 8.8), alkylbenzene (S Examples of suitable solvents include aromatic compounds such as chloroform (SP: 9.3), methylene chloride (SP: 9.7), and ethylene dichloride (SP: 9.8); halogenated hydrocarbons such as ethylene carbonate / diethyl carbonate (EC / DEC = 1 / 1:volume ratio) mixed solvent (SP: 11.75) and ethylene carbonate / diethyl carbonate / methyl ethyl carbonate (1 / 1 / 1:volume ratio) mixed solvent (SP: 10.97); polyolefins such as poly-α-olefins (SP: approximately 6.0 to 8.0); and mineral oil (SP: approximately 6.0 to 8.0), acetic acid (SP: 12.4), and acetonitrile (SP: 11.8).

[0074] Furthermore, when the ND dispersion composition is used as a lubricant (described later), the organic dispersion medium may be a lubricant base. Examples of the lubricant base include known or commonly used organic solvents, such as polyphenyl ether, alkyl benzene, alkyl naphthalene, ester oil, glycol-based synthetic oil, polyolefin-based synthetic oil, and mineral oil. More specifically, examples include polyα-olefin, ethylene-α-olefin copolymer, polybutene, alkyl benzene, alkyl naphthalene, polyalkylene glycol, polyphenyl ether, alkyl-substituted diphenyl ether, polyol ester, dibasic acid ester, carbonate ester, phosphate ester, silicone oil, fluorinated oil, GTL (Gas to Liquids), and mineral oil. Among these, polyol ester, polyα-olefin, mineral oil, alkyl benzene, and polyalkylene glycol are preferred from the viewpoint of their excellent effect of reducing the wear of sliding members.

[0075] Furthermore, when the lubricating base is used as the organic dispersion medium, the ND dispersion composition has excellent dispersibility of ND particles in the lubricating base, so there is no need to add a dispersion solvent (ethanol, DMSO, etc.) other than the lubricating base to improve dispersibility. Therefore, the content of the solvent (particularly the dispersion solvent) other than the lubricating base is preferably less than 1000 parts by mass, more preferably 100 parts by mass or less, even more preferably 50 parts by mass or less, relative to 100 parts by mass of the total amount of ND particles, and particularly preferably is not substantially contained (i.e., is not actively added except for those that are unavoidably present).

[0076] (fatty acid ester dispersant) The ND dispersion composition uses a fatty acid ester-based dispersant, which provides particularly excellent dispersibility of ND particles in an organic dispersion medium. Furthermore, fatty acid ester-based dispersants have high heat resistance and are therefore less susceptible to thermal decomposition. Therefore, even when the temperature of the ND dispersion composition increases during use or when used in a high-temperature environment, the ND dispersion composition has excellent dispersion stability in high-temperature environments and is less susceptible to discoloration. Furthermore, since fatty acid ester-based dispersants are commercially available and easily available, there is no need to produce them through complicated production processes, resulting in excellent ease of production. Only one type of fatty acid ester-based dispersant may be used, or two or more types may be used.

[0077] The acid value of the fatty acid ester-based dispersant is preferably 40 mgKOH / g or less, more preferably 35 mgKOH / g or less, even more preferably 30 mgKOH / g or less, even more preferably 20 mgKOH / g or less, and particularly preferably 6 mgKOH / g or less. The acid value may be, for example, 0.1 mgKOH / g or more, 0.3 mgKOH / g or more, or 0.5 mgKOH / g or more. When the acid value is 40 mgKOH / g or less (particularly 30 mgKOH / g or less), the dispersibility in organic dispersion media with low SP values ​​tends to be better.

[0078] The amine value of the fatty acid ester-based dispersant is preferably 5 mgKOH / g or less, more preferably 1 mgKOH / g or less, even more preferably 0.5 mgKOH / g or less, still more preferably 0.1 mgKOH / g or less, and particularly preferably 0 mgKOH / g.

[0079] The fatty acid ester dispersant preferably has an average molecular weight Mp of 300 or more, more preferably 1000 or more (e.g., 1000 to 100,000), and even more preferably 3000 or more (e.g., 3000 to 10,000). When the average molecular weight Mp is 300 or more, the dispersibility in organic dispersion media with low SP values ​​tends to be superior. The average molecular weight Mp is the molecular weight measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0080] The fatty acid ester-based dispersant preferably has a mass loss rate of 30% or less when maintained in an air atmosphere at 200°C for 180 minutes (sometimes referred to as "200°C 180-minute mass loss rate"), more preferably 25% or less, even more preferably 20% or less, and particularly preferably 15% or less. When the mass loss rate is 30% or less, the ND dispersion composition has excellent heat resistance and dispersion stability in high-temperature environments. The mass loss rate can be measured by simultaneous thermogravimetry and differential thermal analysis (TG-DTA).

[0081] The fatty acid ester dispersant may have an acidic functional group, such as a carboxylic acid, a sulfonic acid, or a salt thereof.

[0082] Examples of fatty acids constituting fatty acid ester-based dispersants include carboxylic acids, sulfonic acids, and salts thereof. Examples of the carboxylic acids include aliphatic monocarboxylic acids such as acetic acid, propionic acid, caprylic acid, nonanoic acid, capric acid, octylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, isononanoic acid, and arachic acid; and aromatic monocarboxylic acids such as benzoic acid and p-(t-butylbutyl)benzoic acid. Examples of the sulfonic acids include naphthalenesulfonic acid. The fatty acids are preferably higher fatty acids. In other words, the fatty acid ester-based dispersants are preferably higher fatty acid ester dispersants. Only one type of fatty acid may be used, or two or more types may be used.

[0083] Examples of compounds constituting the ester component of fatty acid ester-based dispersants include cyclic ester compounds such as propiolactone, valerolactone, and caprolactone; condensates of glycols and dibasic acids; and glycerin. Furthermore, the polyester in the fatty acid ester-based dispersant preferably has a molecular weight of approximately 300 to 9,000, more preferably 400 to 6,000. Specific examples of fatty acid ester-based dispersants include glycerol monooleate.

[0084] The fatty acid ester-based dispersant may be a commercially available product, such as "Ajisper PA111" or "Ajisper PN411" (both manufactured by Ajinomoto Fine-Techno Co., Ltd.), or "Rheodor MO-60" (manufactured by Kao Corporation).

[0085] The ND dispersion composition may or may not contain zirconia. When zirconia is contained, the zirconia may be attached to the ND particles, or may be dispersed in the ND dispersion composition without being attached. The state of attachment of zirconia may be physical attachment (fixation, adhesion, etc.), chemical attachment (covalent bond with the ND particles or the surface modifying group, bond due to intermolecular force, hydrogen bond, ionic bond, etc.), or both.

[0086] The zirconia content in the ND dispersion composition is preferably less than 100 ppm by mass, more preferably 20 ppm by mass or less, and even more preferably 2 ppm by mass or less. When the zirconia content is less than 100 ppm by mass, the ND dispersion composition, when used as a lubricant (particularly an initial break-in lubricant), exhibits excellent break-in surface formation properties, making it easy to form a break-in surface on a sliding member. Furthermore, the incorporation of zirconium into the break-in surface is suppressed, and even a thin film exhibits excellent wear suppression and friction reduction effects. The lower limit of the zirconia content may be, for example, 0.02 ppm by mass or 0.1 ppm by mass.

[0087] The zirconia content in the ND dispersion composition may be 0.01 to 7.5 mass%, 0.1 to 6.0 mass%, 0.25 to 4.5 mass%, or 0.5 to 3.0 mass%. The zirconia content in the lubricant composition may be, for example, 0.1 to 3,000 mass ppm, 0.2 to 1,500 mass ppm, 0.5 to 750 mass ppm, or 1 to 150 mass ppm. Because the ND dispersion composition exhibits excellent dispersibility of ND particles, even with such two-stage content ratios, it exhibits excellent dispersibility in organic dispersion media (particularly lubricant bases). Therefore, the zirconia content in the ND dispersion composition may be different during distribution and use, for example, 0.01 to 7.5 mass% during distribution and 0.1 to 3,000 mass ppm during use.

[0088] The zirconia content can be determined by detecting Zr using inductively coupled plasma atomic emission spectroscopy (ICP atomic emission spectroscopy) and using a dispersion with a known content as a reference, based on the amount of Zr detected. Zirconia is often mixed into the ND dispersion composition due to the zirconia beads contained in a bead mill used to break down ND particle aggregates and nano-disperse the ND particles. For this reason, an ND dispersion composition with a low zirconia content can be obtained by not performing bead milling using zirconia beads or by minimizing the time spent on bead milling.

[0089] The ND dispersion composition can be preferably used, for example, as an additive that imparts the properties of the fine ND particles to resins (e.g., heat- or photo-curable resins, thermoplastic resins, etc.). Examples of the properties of the ND particles include mechanical strength, a high refractive index, thermal conductivity, insulating properties, antioxidant properties, crystallization-promoting properties, and dendrite-suppressing properties. Furthermore, compositions obtained by adding the ND dispersion composition to resins can be preferably used, for example, as functional hybrid materials, thermally functional (heat resistance, heat storage, thermal conduction, insulation, etc.) materials, photonics (organic electroluminescence (EL) elements, LEDs, liquid crystal displays, optical disks, etc.) materials, biocompatible and biocompatible materials, coating materials, film (hard coat films for touch panels and various displays, heat-shielding films, etc.) materials, sheet materials, screen (transparent screen, etc.) materials, filler (heat dissipation filler, mechanical property-improving filler, etc.) materials, heat-resistant plastic substrate (substrate for flexible displays, etc.) materials, and materials for lithium-ion batteries. The ND dispersion composition can also be preferably used as an antifriction agent or lubricant (for initial break-in, main lubrication, etc.) for application to sliding parts of machine parts (for example, automobiles, aircraft, etc.).

[0090] The lubricant for initial break-in (initial break-in lubricant) is used to form a low-friction surface (break-in surface) in the initial stage of a machine having sliding members. The initial break-in lubricant can be used to smooth out irregularities on the surface of the sliding member or to form a modified surface. After the break-in surface is formed, the initial break-in lubricant is removed by washing or the like, and sliding is performed using a lubricant that provides main lubrication. Here, the lubricant that provides main lubrication generally refers to a lubricant that remains present in the sliding part during operation of the sliding member (during machine use). The initial break-in lubricant can also be used as the lubricant that provides main lubrication after the formation of the break-in surface, either without being removed or by being temporarily removed and then resupplied to the sliding part.

[0091] (Method of manufacturing nanodiamond dispersion composition) The ND dispersion composition can be produced, for example, by mixing ND particles, a fatty acid ester-based dispersant, and, if necessary, other components into the organic dispersion medium. For example, a dispersion composition using surface-modified ND particles can be produced through a step (modification step) in which a compound to be surface-treated is reacted with the ND particles in the organic dispersion medium. In this case, the solvent used in the modification step may be used as the organic dispersion medium in the ND dispersion composition, or solvent exchange may be performed after the modification step.

[0092] In the modification step, when the ND particles contain ND particle aggregates formed by the aggregation of ND particles to form secondary particles, the reaction between the surface-modifying compound and the ND particles may be carried out while the ND particles are being crushed or dispersed. This allows the ND particle aggregates to be crushed down to primary particles, the surfaces of the ND primary particles to be modified, and the dispersibility of the nanodiamond particles in the ND dispersion composition to be improved.

[0093] (1) Modification / dispersion process First, the modification step will be described in the case where the reaction between the surface-modifying compound and the ND particles is carried out while the ND particles are being crushed or dispersed (modification / dispersion step). The mass ratio (former:latter) of the ND particles subjected to the reaction in the modification step to the surface-treating compound (particularly, a silane compound) is, for example, 2:1 to 1:20. Furthermore, the concentration of the ND particles in the organic dispersion medium when the surface treatment is carried out is, for example, 0.5 to 10 mass %, and the concentration of the compound is, for example, 5 to 40 mass %.

[0094] The reaction time for the surface treatment is, for example, 4 to 20 hours. It is preferable to carry out the reaction while cooling the generated heat with ice water or the like.

[0095] Examples of methods for crushing or dispersing ND particles include methods using a high-shear mixer, a high-shear mixer, a homomixer, a ball mill, a bead mill, a high-pressure homogenizer, an ultrasonic homogenizer, a colloid mill, a jet mill, etc. Among these, ultrasonic treatment in the presence of crushing media (e.g., zirconia beads) is preferred.

[0096] The diameter of the above-mentioned crushing media (for example, zirconia beads) is, for example, 15 to 500 μm, preferably 15 to 300 μm, and particularly preferably 15 to 100 μm.

[0097] (2) Modification process The modification step for preparing surface-modified NDs containing groups represented by the above formula (I) can be carried out separately from the crushing or dispersing of ND particles in order to minimize the contamination of zirconia in the ND dispersion composition. The surface-modified NDs can be produced by a production method including a step (sometimes referred to as a "reaction step") of reacting ND particles having hydroxyl or carboxyl groups on their surfaces, in a nano-dispersed state in water, with a compound represented by the following formula (II) in the presence of an acid catalyst to obtain the surface-modified ND particles. RXH (II) [In formula (II), X and R correspond to R and X in formula (I), respectively.]

[0098] In the reaction step, ND particles having hydroxy groups and / or carboxy groups on the surface are nano-dispersed in water and reacted with the compound represented by formula (II) above, and the hydroxy groups and / or carboxy groups in the ND particles and -H in the compound represented by formula (II) undergo dehydration condensation to obtain surface-modified ND particles.

[0099] The reaction step is carried out in a state where the ND particles are nano-dispersed in water, i.e., in an aqueous dispersion composition of ND particles. The median diameter (D50) of the ND 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 hydroxy groups and / or carboxy groups on the ND particle surface is large, and the reaction with the compound represented by formula (II) proceeds more efficiently. In addition, the dispersibility of the resulting surface-modified ND particles is excellent.

[0100] The acid catalyst may be a known or conventional acid catalyst used in the esterification of a carboxylic acid and an alcohol, the dehydration condensation reaction of an alcohol and an amine, the dehydration condensation reaction of an alcohol and a thiol, etc. Examples of the acid catalyst include sulfonic acid group-containing compounds, hydrochloric acid, nitric acid, sulfuric acid, sulfuric anhydride, phosphoric acid, boric acid, trihaloacetic acids (trichloroacetic acid, trifluoroacetic acid, etc.), salts thereof (ammonium salts, etc.), inorganic solid acids, etc. One or more of the acid catalysts may be used.

[0101] 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.

[0102] 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):

[0103] [ka]

[0104] Examples of the inorganic solid acid include silica, silica alumina, alumina, zeolites, activated clay, and montmorillonite.

[0105] Examples of the ammonium salt as the acid catalyst include a salt of an ammonium ion represented by the following formula (B-1), a salt of an ammonium ion represented by the following formula (B-2), a salt of an ammonium ion represented by the following formula (B-3), and a salt of an ammonium ion represented by the following formula (B-4). [ka]

[0106] In the above formula (B-1), R I ~R IIIare the same or different and represent 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 R I ~R III It is preferred that two or more of the above groups contain an aromatic hydrocarbon group.

[0107] The acid anion that serves as the counter anion of the ammonium ion 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.

[0108] In the above formula (B-4), R i and R ii are the same or different and represent 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 A hydrocarbon group is 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.

[0109] The acid anion serving as a counter anion of 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.

[0110] The acid anion serving as the counter anion of the ammonium ion represented by the above formulas (B-1) to (B-4) may form a complex salt by forming a hydrogen bond between the oxygen atom forming the acid group and the hydrogen atom on the nitrogen atom in the above formulas (B-1) to (B-4). The 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. The number of ammonium cations and acid anions forming one salt is not particularly limited. Furthermore, the acid anion may form a polymer in one salt. For example, sulfuric acid forming a sulfate ion is [H2SO4(SO3) X The complex salt formed between the acid anion and the above formula (B-4) may include, for example, a compound represented by the following formula (C). [ka]

[0111] In the above formula (C), R i and R ii is the same as in the above formula (B-4).

[0112] As the acid catalyst, from the viewpoint of further accelerating the reaction in the reaction step, sulfonic acid group-containing compounds and ammonium salts of sulfonic acid group-containing compounds are preferred.

[0113] The ratio (former:latter, mass ratio) of the ND particles to be reacted to the compound represented by formula (II) is, for example, 1:1 to 1:25. The concentration of the ND particles in the water-dispersed composition is, for example, 1 to 10 mass%, and the concentration of the compound represented by formula (II) in the water-dispersed composition is, for example, 1 to 60 mass%.

[0114] The reaction conditions for the ND particles and the compound represented by formula (II) 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.

[0115] In this manner, a water-dispersed composition of surface-modified ND containing a group represented by the above formula (I) is obtained.

[0116] When an ND dispersion composition is obtained using an organic dispersion medium in which ND particles have a relatively low dispersibility, or when the ND dispersion composition is obtained as an aqueous dispersion composition, the dispersion medium in the ND dispersion composition may be replaced. For example, a dispersant may be added to an ND dispersion composition in which ND particles have a relatively high dispersibility, followed by stirring. The organic dispersion medium in the ND dispersion composition may then be removed using an evaporator or other device, and a new organic dispersion medium may then be added and stirred. After obtaining a dispersion composition in which ND particles are nano-dispersed, replacing the organic dispersion medium without drying the ND particles may be performed. By appropriately selecting both organic dispersion media in consideration of the wettability and solubility of the organic dispersion media before and after the replacement, ND particles can be easily nano-dispersed in an organic dispersion medium with a relatively low dispersibility. The addition and stirring of the dispersant may be performed either before or after the replacement of the dispersion medium. If the dispersion medium is not replaced, the dispersant may be added to the resulting ND dispersion composition and stirred.

[0117] In this manner, an ND dispersion composition in which ND particles are dispersed in an organic solvent is obtained.

[0118] The ND particles can be produced by, for example, a detonation method. Examples of the detonation method include an air-cooled detonation method and a water-cooled detonation method. Among these, the air-cooled detonation method is preferred because it can produce ND particles with smaller primary particles than the water-cooled detonation method.

[0119] 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.

[0120] An example of a method for producing ND particles will be described below, but the ND particles are not limited to those obtained by the following production method.

[0121] (generation process) The formed explosive with an electric detonator attached is placed inside a pressure-resistant container for detonation, and the container is sealed in a state where atmospheric gas and the explosive coexist. The container is made of, for example, iron, and has a volume of, for example, 0.5 to 40 m 3 As the explosive, a mixture of trinitrotoluene (TNT) and cyclotrimethylenetrinitramine, i.e., hexogen (RDX), can be used. The mass ratio of TNT to RDX (TNT / RDX) is, for example, in the range of 40 / 60 to 60 / 40.

[0122] In the production process, an electric detonator is then detonated to detonate the explosive inside the container. Detonation refers to an explosion caused by a chemical reaction in which the flame front of the reaction moves at a speed exceeding the speed of sound. During detonation, the explosive used undergoes partial incomplete combustion, liberating carbon as raw material, and ND particles are generated by the action of the pressure and energy of the shock wave generated by the explosion. The generated ND particles aggregate very firmly between adjacent primary particles or crystallites due to the action of van der Waals forces and the Coulomb interaction between crystal planes, forming an aggregate.

[0123] In the production process, the container is then left to cool at room temperature for about 24 hours, allowing the temperature of the container and its interior to drop. After this cooling process, the ND particle crude product (including the ND particle aggregates and soot produced as described above) adhering to the inner wall of the container is scraped off with a spatula, and the ND particle crude product is recovered. By the above method, the ND particle crude product can be obtained. Furthermore, by performing the above nanodiamond production process as many times as necessary, it is possible to obtain the desired amount of nanodiamond crude product.

[0124] (Acid treatment process) In the acid treatment process, a strong acid is applied to the raw nanodiamond crude product in, for example, an aqueous solvent to remove metal oxides. The nanodiamond crude product obtained by the detonation method is likely to contain metal oxides, such as Fe, Co, and Ni, which originate from the container used in the detonation method. For example, by applying a strong acid in an aqueous solvent, metal oxides can be dissolved and removed from the nanodiamond crude product (acid treatment). Mineral acids are preferred as the strong acid used in this acid treatment, and examples include hydrochloric acid, hydrofluoric acid, sulfuric acid, nitric acid, and aqua regia. One or more of the above strong acids may be used. The concentration of the strong acid used in the acid treatment is, for example, 1 to 50% by mass. The acid treatment temperature is, for example, 70 to 150°C. The acid treatment time is, for example, 0.1 to 24 hours. The acid treatment can be performed under reduced pressure, normal pressure, or increased pressure. After this acid treatment, the solids (including nanodiamond aggregates) are washed with water, for example, by decantation. It is preferable to repeatedly wash the solid matter with water by decantation until the pH of the precipitation liquid reaches, for example, 2 to 3. If the content of metal oxides in the crude nanodiamond product obtained by the detonation method is low, the acid treatment described above may be omitted.

[0125] (Oxidation treatment process) The oxidation treatment process is a process in which graphite is removed from the ND particle crude product using an oxidizing agent. The ND particle crude product obtained by the detonation method contains graphite, which is derived from the carbon liberated by the partial incomplete combustion of the explosive used and which did not form ND particle crystals. Graphite can be removed from the ND particle crude product by applying an oxidizing agent to the ND particle crude product in an aqueous solvent. Furthermore, applying an oxidizing agent can introduce oxygen-containing groups such as carboxyl groups and hydroxyl groups onto the ND particle surface.

[0126] Examples of oxidizing agents used in this oxidation treatment include chromic acid, chromic anhydride, dichromic acid, permanganic acid, perchloric acid, nitric acid, mixtures thereof, mixed acids of at least one acid selected from these with another acid (such as sulfuric acid), and salts thereof. Among these, the use of mixed acids (particularly mixed acids of sulfuric acid and nitric acid) is preferred because it is environmentally friendly and has an excellent effect of oxidizing and removing graphite.

[0127] The mixing ratio of sulfuric acid to nitric acid (former / latter; mass ratio) in the mixed acid is preferably, for example, 60 / 40 to 95 / 5, since graphite can be efficiently oxidized and removed at temperatures of, for example, 130°C or higher (particularly preferably 150°C or higher; the upper limit is, for example, 200°C) even under pressures near atmospheric pressures (for example, 0.5 to 2 atm). The lower limit is preferably 65 / 35, more preferably 70 / 30. The upper limit is preferably 90 / 10, more preferably 85 / 15, and even more preferably 80 / 20. When the mixing ratio is 60 / 40 or higher, the content of sulfuric acid, which has a high boiling point, is high, so that the reaction temperature is, for example, 120°C or higher under pressures near atmospheric pressures, and graphite removal efficiency tends to be improved. When the mixing ratio is 95 / 5 or less, the content of nitric acid, which significantly contributes to graphite oxidation, is high, so that graphite removal efficiency tends to be improved.

[0128] The amount of oxidizing agent (particularly the mixed acid) used is, for example, 10 to 50 parts by mass, preferably 15 to 40 parts by mass, and more preferably 20 to 40 parts by mass per part by mass of the crude nanodiamond product. The amount of sulfuric acid used in the mixed acid is, for example, 5 to 48 parts by mass, preferably 10 to 35 parts by mass, and more preferably 15 to 30 parts by mass per part by mass of the crude nanodiamond product. The amount of nitric acid used in the mixed acid is, for example, 2 to 20 parts by mass, preferably 4 to 10 parts by mass, and more preferably 5 to 8 parts by mass per part by mass of the crude nanodiamond product.

[0129] When the mixed acid is used as an oxidizing agent, a catalyst may be used together with the mixed acid. The use of a catalyst can further improve the efficiency of graphite removal. Examples of the catalyst include copper (II) carbonate. The amount of catalyst used is, for example, about 0.01 to 10 parts by mass per 100 parts by mass of the crude nanodiamond product.

[0130] The oxidation treatment temperature is, for example, 100 to 200° C. The oxidation treatment time is, for example, 1 to 24 hours. The oxidation treatment can be carried out under reduced pressure, normal pressure, or increased pressure.

[0131] After the oxidation treatment step, it is preferable to remove the supernatant liquid, for example, by decantation. Furthermore, during decantation, it is preferable to wash the solids with water. Although the supernatant liquid is colored at the beginning of washing, it is preferable to repeatedly wash the solids with water until the supernatant liquid becomes transparent to the naked eye.

[0132] (Crushing process) The ND particles may be subjected to a crushing treatment as necessary. For the crushing treatment, for example, a high-shear mixer, a high-shear mixer, a homomixer, a ball mill, a bead mill, a high-pressure homogenizer, an ultrasonic homogenizer, a colloid mill, or the like can be used. The crushing treatment may be carried out wet (for example, crushing treatment in a state of being suspended in water, etc.) or dry. When carried out dry, it is preferable to provide a drying step before the crushing treatment.

[0133] (drying process) After the oxidation treatment, it is preferable to provide a drying step. For example, the liquid content of the ND particle-containing solution obtained through the alkaline hydrogen peroxide treatment step is evaporated using a spray dryer or evaporator, and the resulting residual solid content is then dried by heating in a drying oven. The heating and drying temperature is, for example, 40 to 150°C. ND particles are obtained through this drying step.

[0134] Furthermore, the ND particles may be subjected to an oxidation treatment (e.g., oxygen oxidation) or a reduction treatment (e.g., hydrogenation) in the gas phase, as needed. By performing an oxidation treatment in the gas phase, ND particles having many C=O groups on the surface can be obtained. By performing a reduction treatment in the gas phase, ND particles having many CH groups on the surface can be obtained.

[0135] Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Each configuration and combination thereof in each embodiment is an example, and addition, omission, substitution, and other modifications of configurations are possible as appropriate within the scope of the present disclosure. Furthermore, each invention according to this disclosure is not limited by the embodiments or the following examples, but is limited only by the scope of the claims. [Example]

[0136] Hereinafter, one embodiment of the present disclosure will be described in more detail based on examples.

[0137] Manufacturing Example 1 (Preparation of silane compound surface-modified ND particles (1)) First, the nanodiamond production process was carried out by detonation. In this process, the formed explosive with an electric detonator attached was placed inside a pressure-resistant container for detonation and the container was sealed. The container was made of iron and had a volume of 15 m. 3 The explosive used was a mixture of 0.50 kg of TNT and RDX. The mass ratio of TNT to RDX in this explosive (TNT / RDX) was 50 / 50. Next, an electric detonator was detonated to detonate the explosive inside the container (production of nanodiamonds by detonation method). The container and its interior were then allowed to cool for 24 hours at room temperature. After cooling, the crude nanodiamond product (including the aggregates of nanodiamond particles and soot produced by the detonation method) adhering to the inner wall of the container was scraped off with a spatula, and the crude nanodiamond product was recovered.

[0138] The crude nanodiamond product obtained by repeating the above-described production process multiple times was then subjected to an acid treatment process. Specifically, 200 g of the crude nanodiamond product was added to 6 L of 10% by mass hydrochloric acid to obtain a slurry, which was then heated under reflux at atmospheric pressure for 1 hour. The heating temperature in this acid treatment was 85 to 100°C. Next, after cooling, the solid matter (including nanodiamond aggregates and soot) was washed with water by decantation. The solid matter was repeatedly washed with water by decantation until the pH of the precipitated liquid reached 2 from the low pH side.

[0139] Next, an oxidation treatment step was carried out. Specifically, 6 L of 98% by mass sulfuric acid and 1 L of 69% by mass nitric acid were added to the precipitate liquid (containing nanodiamond aggregates) obtained through decantation after the acid treatment to form a slurry, and this slurry was then heat-treated for 48 hours under reflux at atmospheric pressure. The heating temperature in this oxidation treatment was 140 to 160°C. Next, after cooling, the solid content (including nanodiamond aggregates) was washed with water by decantation. The supernatant liquid was colored at the beginning of the washing, so the solid content was repeatedly washed with water by decantation until the supernatant liquid became visually transparent.

[0140] Next, 1000 mL of the nanodiamond-containing liquid obtained after the above-mentioned water washing process was spray-dried using a spray dryer (trade name "Spray Dryer B-290", manufactured by Nippon Buchi Co., Ltd.) (drying step). As a result, 50 g of nanodiamond powder was obtained.

[0141] 0.3 g of nanodiamond particles obtained in the drying process above was weighed into a reaction vessel, and 13.5 g of MIBK and 1.2 g of hexyltrimethoxysilane as a silane compound were added and stirred for 10 minutes.

[0142] After stirring, 36 g of zirconia beads (Tosoh Corporation, registered trademark "YTZ," diameter 30 μm) were added. After the addition, the mixture was cooled in ice water and sonicated for 20 hours using an ultrasonic disperser (model "UP-400s," Hielscher) with the tip of the ultrasonic disperser's transducer immersed in the solution in the reaction vessel. This allowed the ND particles and the silane compound to react with each other. Initially, the color of the solution was gray, but the particle size gradually decreased and the dispersion improved, eventually becoming a uniform, black liquid. This is thought to be due to the ND particles gradually being disintegrated (disintegrated) from the ND particle aggregates, the silane compound acting on the dissociated ND particles to bond them, and the ND particles surface-modified by the silane compound becoming dispersed and stabilized in MIBK. In this way, a silane compound surface-modified ND dispersion (MIBK dispersion) was obtained.

[0143] Manufacturing Example 2 (Preparation of ND particles surface-modified with oleylamino groups) The crude nanodiamond product obtained by the detonation method in the same manner as in Production Example 1 was subjected to the acid treatment and oxidation treatment processes in the same manner as in Production Example 1, and then the solids (including nanodiamond aggregates) were washed with water by decantation. The supernatant liquid was initially colored, so the solids were repeatedly washed with water by decantation until the supernatant liquid became visually transparent. The solids were then dried to obtain ND aggregates as powder. The product was then heated at 400°C for 6 hours in a rotary kiln into which a gas of approximately 8% by volume of oxygen and approximately 92% by volume of nitrogen was blown at a flow rate of 20 L / min.

[0144] Next, about 30 ml of the slurry containing the ND aggregates was adjusted to pH 10 using ammonia water, and then bead milling was carried out using a bead milling device (trade name "Parallel Four-Cylinder Sand Grinder LSG-4U-2L Type", manufactured by Aimex Co., Ltd.). Specifically, 30 ml of the ultrasonically irradiated slurry and zirconia beads with a diameter of 30 μm were charged into a 100 ml mill vessel (manufactured by Aimex Co., Ltd.) and sealed therein, and the device was operated to carry out bead milling. In this bead milling, the amount of zirconia beads charged was, for example, 33% by volume relative to the volume of the mill vessel, the mill vessel rotation speed was 2570 rpm, and the milling time was 3 hours.

[0145] Next, the slurry that had undergone the above-mentioned disintegration process was centrifuged using a centrifugal separator (classification operation). The centrifugal force in this centrifugation process was 20,000 × g, and the centrifugation time was 30 minutes. Next, 10 ml of the supernatant of the ND-containing solution that had undergone the centrifugal separation process was collected. In this way, an ND aqueous dispersion in which nanodiamonds were dispersed in pure water was obtained. The solid content of this ND aqueous dispersion was 6.0 mass % and the pH was 9.0. The median diameter (particle size D50) of the ND aqueous dispersion obtained as described above was 6.0 nm.

[0146] Next, 1.5 mmol of dodecylbenzenesulfonic acid as an acid catalyst and 3 mmol of oleylamine were added to 3.33 g of the ND aqueous dispersion obtained through the above-mentioned disintegration step, and the mixture was reacted for 8 hours with stirring at 80° C. After the reaction was completed, 10 g of toluene was added, and the mixture was cooled to room temperature, followed by washing with water and saturated saline to obtain a toluene dispersion composition of ND particles surface-modified with oleylamino groups.

[0147] Manufacturing Example 3 (Preparation of ND particles surface-modified with oleyloxy groups) In the same manner as in Production Example 2, 0.5 mmol of dodecylbenzenesulfonic acid as an acid catalyst and 2 mmol of oleyl alcohol were added to 1 g of the ND aqueous dispersion obtained through the crushing step, and the mixture was reacted for 24 hours at 80° C. while stirring. After the reaction was completed, 10 mL of toluene was added, and the mixture was cooled to room temperature, followed by washing with water and saturated saline to obtain a toluene dispersion composition of ND particles surface-modified with oleyloxy groups.

[0148] Manufacturing Example 4 (Preparation of ND particles surface-modified with oleate groups) In the same manner as in Production Example 2, 0.5 mmol of dodecylbenzenesulfonic acid as an acid catalyst and 2 mmol of oleic acid were added to 1 g of the ND aqueous dispersion obtained through the crushing step, and the mixture was reacted for 24 hours at 100°C while stirring. After the reaction was completed, 10 mL of toluene was added, and the mixture was cooled to room temperature, followed by washing with water and saturated saline to obtain a toluene dispersion composition of ND particles whose surfaces were modified with oleate groups.

[0149] Production Example 5 (Preparation of silane compound surface-modified ND particles (2)) 0.3 g of nanodiamond particles obtained through the drying process in the same manner as in Production Example 1 was weighed into a reaction vessel, and 13.5 g of toluene and 1.2 g of hexyltrimethoxysilane as a silane compound were added and stirred for 10 minutes.

[0150] After stirring, 36 g of zirconia beads (Tosoh Corporation, registered trademark "YTZ," diameter 30 μm) were added. After the addition, the mixture was cooled in ice water and ultrasonicated for 7 hours using an ultrasonic disperser (model "UP-400s," Hielscher) with the tip of the ultrasonic disperser's transducer immersed in the solution in the reaction vessel, resulting in a reaction between the ND particles and the silane compound. Initially, the mixture was gray, but the particle size gradually decreased and the dispersion improved, eventually becoming a uniform, black liquid. This is thought to be due to the ND particles gradually being disintegrated (disintegrated) from the ND particle aggregates, the silane compound acting on the dissociated ND particles to bond them, and the ND particles surface-modified by the silane compound becoming dispersed and stabilized in toluene. In this way, a silane compound surface-modified ND dispersion (toluene dispersion) was obtained.

[0151] Examples 1 to 4 (Preparation of ND dispersion composition) 0.2 g of dispersant was added to 10 g of the surface-modified ND dispersion obtained in Production Example 1 above and stirred, after which the MIBK was removed using a rotary evaporator and a dispersion medium was added to bring the total weight to 10 g. In this way, an ND dispersion composition was prepared. The nanodiamond concentration in the ND dispersion composition was 2 mass %. The nanodiamond concentration was determined from the absorbance at 350 nm. The dispersants and dispersion mediums used in Examples 1 to 4 are as follows. Example 1 Dispersant: Higher fatty acid ester dispersant (acid value 35 mg KOH / g, amine value 0 mg KOH / g, average molecular weight Mp 5200, mass loss rate at 200°C for 180 minutes: 17.8%) Dispersion medium: POE (polyol ester) Example 2 Dispersant: Higher fatty acid ester dispersant (acid value 35 mg KOH / g, amine value 0 mg KOH / g, average molecular weight Mp 5200, mass loss rate at 200°C for 180 minutes: 17.8%) Dispersion medium: hexane Example 3 Dispersant: Higher fatty acid ester dispersant (acid value 0.5 mg KOH / g, amine value 0 mg KOH / g, average molecular weight Mp 8100, mass loss rate 12.1% at 200°C for 180 minutes) Dispersion medium: POE Example 4 Dispersant: Higher fatty acid ester dispersant (acid value 0.5 mg KOH / g, amine value 0 mg KOH / g, average molecular weight Mp 8100, mass loss rate 12.1% at 200°C for 180 minutes), Dispersion medium: Hexane

[0152] Examples 5 to 10 (Preparation of ND dispersion composition) 0.06 g of dispersant was added to 3 g of each of the surface-modified ND dispersions obtained in Production Examples 2 to 4 above, and the mixture was stirred. The toluene was then removed using a rotary evaporator, and a dispersion medium was added to bring the total weight to 3 g. In this way, an ND dispersion composition was prepared. The nanodiamond concentration in the ND dispersion composition was 2% by mass. The nanodiamond concentration was determined from the absorbance at 350 nm. The surface-modified NDs, dispersants, and dispersion mediums used in Examples 5 to 10 are as follows: Example 5 Surface-modified ND: oleylamino group surface-modified ND obtained in Production Example 2 Dispersant: Higher fatty acid ester dispersant (acid value 0.5 mg KOH / g, amine value 0 mg KOH / g, average molecular weight Mp 8100, mass loss rate 12.1% at 200°C for 180 minutes) Dispersion medium: POE Example 6 Surface-modified ND: oleylamino group surface-modified ND obtained in Production Example 2 Dispersant: Higher fatty acid ester dispersant (acid value 0.5 mg KOH / g, amine value 0 mg KOH / g, average molecular weight Mp 8100, mass loss rate 12.1% at 200°C for 180 minutes) Dispersion medium: hexane Example 7 Surface-modified ND: oleyloxy group surface-modified ND obtained in Production Example 3 Dispersant: Higher fatty acid ester dispersant (acid value 0.5 mg KOH / g, amine value 0 mg KOH / g, average molecular weight Mp 8100, mass loss rate 12.1% at 200°C for 180 minutes) Dispersion medium: POE Example 8 Surface-modified ND: oleyloxy group surface-modified ND obtained in Production Example 3 Dispersant: Higher fatty acid ester dispersant (acid value 0.5 mg KOH / g, amine value 0 mg KOH / g, average molecular weight Mp 8100, mass loss rate 12.1% at 200°C for 180 minutes) Dispersion medium: hexane Example 9 Surface-modified ND: Oleate group surface-modified ND obtained in Production Example 4 Dispersant: Higher fatty acid ester dispersant (acid value 0.5 mg KOH / g, amine value 0 mg KOH / g, average molecular weight Mp 8100, mass loss rate 12.1% at 200°C for 180 minutes) Dispersion medium: POE Example 10 Surface-modified ND: Oleate group surface-modified ND obtained in Production Example 4 Dispersant: Higher fatty acid ester dispersant (acid value 0.5 mg KOH / g, amine value 0 mg KOH / g, average molecular weight Mp 8100, mass loss rate 12.1% at 200°C for 180 minutes) Dispersion medium: hexane

[0153] Comparative Examples 1 to 5 An ND dispersion composition was prepared in the same manner as in Example 1, except that the following dispersants and dispersion media were used: In Comparative Examples 1 and 2, no dispersant was used. Comparative Example 1 Dispersion medium: hexane Comparative Example 2 Dispersion medium: POE Comparative Example 3 Dispersant: Trade name "SOLSPERSE 20000" (manufactured by Lubrizol Corporation, polyether-based dispersant, mass loss rate at 200°C for 180 minutes: 49.2%) Dispersion medium: POE Comparative Example 4 Dispersant: Product name "SN Sparce 70" (manufactured by San Nopco Ltd., unsaturated hydrocarbon / saturated fatty acid dispersant, mass loss rate at 200°C for 180 minutes: 32.3%) Dispersion medium: POE Comparative Example 5 Dispersant: Product name "SN Sparce 70" (manufactured by San Nopco Ltd., unsaturated hydrocarbon / saturated fatty acid dispersant, mass loss rate at 200°C for 180 minutes: 32.3%) Dispersion medium: hexane

[0154] Examples 11 and 12 (Preparation of ND dispersion composition) 0.1 g of dispersant was added to 10 g of the various surface-modified ND dispersions (ND concentration: 2% by mass) obtained in Production Examples 2 and 5 above, and the mixture was stirred. The toluene was then removed using a rotary evaporator, and a dispersion medium was added to a nanodiamond concentration of 4% by weight, followed by slow stirring and mixing. In this way, a black, transparent ND dispersion composition was prepared. The nanodiamond concentration was determined from the absorbance at 350 nm. The surface-modified NDs, dispersants, and dispersion mediums used in Examples 11 and 12 are as follows: Example 11 Surface-modified ND: Silane compound surface-modified ND particles obtained in Production Example 5 Dispersant: Fatty acid ester dispersant (acid value 2 mg KOH / g or less, amine value 0 mg KOH / g, average molecular weight Mp 360, mass loss rate 25.0% at 200°C for 180 minutes) Dispersion medium: PAO (poly alpha-olefin) Example 12 Surface-modified ND: oleylamino group surface-modified ND obtained in Production Example 2 Dispersant: Fatty acid ester dispersant (acid value 2 mg KOH / g or less, amine value 0 mg KOH / g, average molecular weight Mp 360, mass loss rate 25.0% at 200°C for 180 minutes) Dispersion medium: PAO

[0155] Comparative Example 6 0.4 g of nanodiamond powder obtained through the drying process in the same manner as in Production Example 1, 0.2 g of fatty acid ester dispersant (acid value 2 mg KOH / g or less, amine value 0 mg KOH / g, average molecular weight Mp 360, 200 ° C 180 min mass loss rate 25.0%), and 9.4 g of PAO were added and vigorously stirred using a shaker. Some became gray and cloudy, and most settled, and it did not become a black and transparent ND dispersion composition like Examples 11 and 12.

[0156] (evaluation) The ND dispersion compositions obtained in the examples and comparative examples and the dispersants used were evaluated as follows, and the evaluation results are shown in the table below.

[0157] (1) Haze value The ND dispersion compositions obtained in the examples and comparative examples were measured using a haze measuring device (trade name "Haze Meter 300A", manufactured by Nippon Denshoku Industries Co., Ltd.). Each sample solution used for measurement was subjected to ultrasonic cleaning for 10 minutes using an ultrasonic cleaner. The thickness (internal dimensions) of the measurement glass cell filled with the sample solution and used for measurement was 1 mm, and the optical path length within the sample for measurement was 1 mm. Note that "-" in the table indicates that no measurement was performed. Note that for Examples 11 and 12, measurements were taken on samples diluted with a dispersion medium so that the nanodiamond concentration was 0.1% by mass.

[0158] (2) D50 The ND dispersion compositions obtained in the examples and comparative examples were diluted to 0.1% by mass by adding a dispersion medium, and the particle size distribution of the ND particles was measured by dynamic light scattering (non-contact backscattering method) using an apparatus manufactured by Malvern (trade name "Zetasizer Nano ZS").

[0159] (3) Dispersibility The ND dispersion compositions obtained in the examples and comparative examples were diluted to 0.1% by mass by adding a dispersion medium, and the dispersibility was evaluated visually based on the following evaluation criteria. ○: Transparent and no aggregation observed. △: Slightly cloudy, but no aggregation was observed. ×: Cloudy, and obvious aggregation was observed.

[0160] (4) Viscosity The ND dispersion compositions obtained in the examples and comparative examples were measured using an EMS viscometer (product name "EMS1000", manufactured by Kyoto Electronics Manufacturing Co., Ltd.) 500 μL of the sample and a φ2 mm aluminum ball were placed in a test tube, and the measurement was performed at a temperature of 25°C and a rotation speed of 1000 rpm.

[0161] (5) Mass loss rate at 200℃ for 180 minutes The mass loss rate of the dispersants used in the examples and comparative examples was measured at 200°C for 180 minutes under the following conditions using a thermogravimetric and differential thermal analyzer (product name "TG-DTA 6200", manufactured by Hitachi High-Tech Science Corporation). Atmosphere: Air Temperature: From 30°C, increase the temperature to 200°C at a rate of 20°C / min, and hold for 180 minutes after reaching 200°C Sample pan: Quartz

[0162] [Table 1]

[0163] As can be seen from Table 1, the ND dispersion compositions (Examples) using fatty acid ester-based dispersants had excellent dispersibility in hexane, POE, and PAO, which have low SP values. On the other hand, when no dispersant was used (Comparative Examples 1 and 2), and when a polyether-based dispersant (Comparative Example 3) or an unsaturated hydrocarbon / saturated fatty acid-based dispersant (Comparative Examples 4 and 5) was used, the dispersibility was poor in hexane and POE, which have low SP values.

[0164] Furthermore, 40 g of the ND dispersion composition obtained in Example 3 was placed in an air-filled three-neck flask equipped with a stirrer and a thermometer and stirred for 17 hours at a heating temperature of 230°C (liquid temperature 190 to 200°C). After heating, the degree of discoloration and acid value were evaluated visually. The acid value was 0.43 mg KOH / g, and no discoloration was observed. A similar test was also performed on Comparative Example 2, in which no dispersant was used. The acid value was 0.42 mg KOH / g, and no discoloration was observed. Therefore, the ND dispersion composition obtained in Example 3 is evaluated to have heat resistance comparable to that of a composition not using a dispersant. The same dispersant as in Example 3 was used in Examples 4 to 10. Furthermore, the mass loss rate at 200°C for 180 minutes of the dispersant used in Examples 1 and 2 was comparable to that of the dispersant used in Example 3. Therefore, it is presumed that Examples 1, 2, and 4 to 10 also have heat resistance comparable to that of Example 3.

[0165] Variations of the invention according to the present disclosure are described below. [Appendix 1] A nanodiamond dispersion composition comprising an organic dispersion medium, nanodiamond particles dispersed in the organic dispersion medium, and a fatty acid ester-based dispersant. [Appendix 2] A nanodiamond dispersion composition as described in Appendix 1, in which the mass loss rate of the fatty acid ester-based dispersant when maintained in an air atmosphere at a temperature of 200°C for 180 minutes is 30% or less (preferably 20% or less, more preferably 15% or less). [Appendix 3] A nanodiamond dispersion composition according to Appendix 1 or 2, wherein the acid value of the fatty acid ester-based dispersant is 40 mgKOH / g or less (preferably 35 mgKOH / g or less, more preferably 30 mgKOH / g or less, even more preferably 20 mgKOH / g or less, and particularly preferably 6 mgKOH / g or less). [Appendix 4] A nanodiamond dispersion composition described in any one of Appendices 1 to 3, wherein the acid value of the fatty acid ester-based dispersant is 0.1 mg KOH / g or more (preferably 0.3 mg KOH / g or more, more preferably 0.5 mg KOH / g or more). [Appendix 5] A nanodiamond dispersion composition according to any one of Appendices 1 to 4, wherein the average dispersed particle diameter of the nanodiamond particles is 2 to 240 nm (preferably 4 to 200 nm, more preferably 5 to 100 nm, even more preferably 10 to 70 nm, and particularly preferably 12 to 40 nm). [Appendix 6] A nanodiamond dispersion composition according to any one of Appendices 1 to 5, having a haze value of 5 or less (preferably 3 or less, more preferably 1 or less, and even more preferably 0.5 or less). [Appendix 7] The SP value of the organic dispersion medium is 6.0 to 12.0 (cal / cm 3 ) 1 / 2 A nanodiamond dispersion composition according to any one of Appendices 1 to 6, wherein the .DELTA..times ... [Appendix 8] A nanodiamond dispersion composition according to any one of Appendices 1 to 7, having a viscosity at 25°C of 0.2 to 120 mPa·s (preferably 10 to 100 mPa·s, more preferably 20 to 90 mPa·s). [Appendix 9] A nanodiamond dispersion composition according to any one of Appendices 1 to 8, wherein the average molecular weight Mp of the fatty acid ester-based dispersant is 300 or more (preferably 1000 or more (e.g., 1000 to 100,000), more preferably 3000 or more (e.g., 3000 to 10,000)). [Appendix 10] A nanodiamond dispersion composition described in any one of Appendices 1 to 9, wherein the amine value of the fatty acid ester-based dispersant is 5 mgKOH / g or less (preferably 1 mgKOH / g or less, more preferably 0.5 mgKOH / g or less, even more preferably 0.1 mgKOH / g or less, and particularly preferably 0 mgKOH / g). [Appendix 11] A nanodiamond dispersion composition according to any one of Appendices 1 to 10, having a nanodiamond particle content of 0.01 to 5.0 mass% (preferably 0.1 to 4.0 mass%, more preferably 0.25 to 3.0 mass%, and even more preferably 0.5 to 2.0 mass%). [Appendix 12] A nanodiamond dispersion composition according to any one of Appendices 1 to 10, in which the content of nanodiamond particles is greater than 3.0% by mass (preferably 3.5% by mass or more). [Appendix 13] A nanodiamond dispersion composition described in any one of Appendices 1 to 12, wherein the content of the fatty acid ester-based dispersant is 10 to 10,000 parts by mass (preferably 50 to 1,000 parts by mass, more preferably 70 to 300 parts by mass) per 100 parts by mass of the total amount of nanodiamond particles in the nanodiamond dispersion composition. [Appendix 14] A nanodiamond dispersion composition described in any one of Appendices 1 to 13, wherein the content of fatty acid ester-based dispersant is 90 mass% or more (preferably 95 mass% or more, more preferably 99 mass% or more) relative to the total amount of dispersant in the nanodiamond dispersion composition. [Appendix 15] A nanodiamond dispersion composition according to any one of Appendices 1 to 14, wherein the total content of nanodiamond particles, fatty acid ester-based dispersant, and organic dispersion medium is 70 mass% or more (preferably 80 mass% or more, more preferably 90 mass% or more, even more preferably 95 mass% or more, and particularly preferably 99 mass% or more) relative to the total amount of the nanodiamond dispersion composition. [Appendix 16] A nanodiamond dispersion composition described in any one of Appendices 1 to 15, wherein the content of surfactants other than the fatty acid ester-based dispersant is 30 mass% or less (preferably 20 mass% or less, more preferably 10 mass% or less, even more preferably 5 mass% or less, even more preferably 1 mass% or less, and particularly preferably less than 1 mass%) relative to the total amount of the nanodiamond dispersion composition.

[0166] [Appendix 17] A nanodiamond dispersion composition described in any one of Appendices 1 to 16, wherein the nanodiamond particles include surface-modified nanodiamond particles that have been surface-modified with a compound containing an organic group or a functional group. [Appendix 18] A nanodiamond dispersion composition according to Appendix 17, wherein the organic group is an organic group having 4 or more carbon atoms (e.g., 4 to 25) (preferably 6 or more (e.g., 6 to 22), more preferably 8 or more carbon atoms (e.g., 8 to 20)). [Appendix 19] A nanodiamond dispersion composition described in any one of Appendices 1 to 18, wherein the nanodiamond particles comprise surface-modified nanodiamonds in which the nanodiamond particle surface is modified with a group represented by the following formula (I): -XR (I) [In formula (I), X represents -Si-, -NH-, -O-, -OC(=O)-, -C(=O)-O-, -NH-C(=O)-, -C(=O)-NH-, or -S-, and the bond extending to the left from X is bonded to the nanodiamond particle. R represents a monovalent organic group, and the atom bonded to X is a carbon atom.] [Appendix 20] A nanodiamond dispersion composition according to Appendix 19, wherein the monovalent organic group is a monovalent substituted or unsubstituted hydrocarbon group, a group in which a monovalent substituted or unsubstituted hydrocarbon group is bonded to an alkoxy group, or a group in which a monovalent substituted or unsubstituted hydrocarbon group is bonded to a dialkylamino group. [Appendix 21] A nanodiamond dispersion composition according to appendix 19 or 20, wherein the number of carbon atoms in the monovalent organic group is 4 to 25 (preferably 6 to 22, more preferably 8 to 20). [Appendix 22] A nanodiamond dispersion composition according to any one of Appendices 19 to 21, wherein in the formula (I), X represents -Si-, -NH-, -O-, -OC(=O)-, or -C(=O)-O- (preferably -Si-, -NH-, -O-, or -OC(=O)-). [Appendix 23] In the formula (I), X is -O-, -OC(=O)-, or -C(=O)-O-, and R is a monovalent substituted or unsubstituted hydrocarbon group (preferably a linear or branched hydrocarbon group having 8 to 20 carbon atoms), a nanodiamond dispersion composition described in any one of Appendices 19 to 22. [Appendix 24] A nanodiamond dispersion composition according to any one of Appendices 19 to 23, wherein in the formula (I), X is -NH- and R is a monovalent organic group containing 8 to 20 carbon atoms. [Appendix 25] A nanodiamond dispersion composition according to any one of Appendices 19 to 24, wherein in the formula (I), X is -NH- and R is a monovalent organic group containing a hydrocarbon group having four or more consecutive carbon atoms in a linear chain. [Appendix 26] A nanodiamond dispersion composition according to any one of Appendices 19 to 25, wherein in the formula (I), R contains a hydrocarbon group having four or more consecutive carbon atoms in a linear chain. [Appendix 27] A nanodiamond dispersion composition according to any one of Appendices 19 to 26, wherein in the formula (I), the molar ratio of carbon atoms to the total amount of heteroatoms selected from the group consisting of nitrogen atoms, oxygen atoms, sulfur atoms, and silicon atoms is 4.5 or more (preferably 5 or more, more preferably 5.5 or more). [Appendix 28] A nanodiamond dispersion composition described in any one of Appendices 1 to 27, wherein the organic dispersion medium contains a lubricating base and the content of solvents other than the lubricating base is less than 1,000 parts by mass (preferably 100 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably substantially none) per 100 parts by mass of the total amount of the nanodiamond particles. [Industrial Applicability]

[0167] The nanodiamond dispersion composition disclosed herein has mechanical strength, a high refractive index, thermal conductivity, insulation, antioxidant properties, and the ability to promote crystallization of resins, etc., and can be used in products that have these characteristics.

Claims

1. The present invention comprises an organic dispersion medium, nanodiamond particles dispersed in the organic dispersion medium, and a fatty acid ester-based dispersant; The nanodiamond particles are surface-modified with a surface-modifying group or compound containing an organic group; A nanodiamond dispersion composition in which the content of the fatty acid ester-based dispersant is 10 to 300 parts by mass per 100 parts by mass of the total amount of the nanodiamond particles.

2. The nanodiamond dispersion composition according to claim 1, wherein the content of the nanodiamond particles is more than 3.0 mass%.

3. A nanodiamond dispersion composition as described in claim 1 or 2, wherein the mass loss rate of the fatty acid ester-based dispersant when maintained in an air atmosphere at a temperature of 200°C for 180 minutes is 30% or less.

4. A nanodiamond dispersion composition according to any one of claims 1 to 3, wherein the acid value of the fatty acid ester-based dispersant is 40 mg KOH / g or less.

5. A nanodiamond dispersion composition according to any one of claims 1 to 4, wherein the average dispersed particle size of the nanodiamond particles is 2 to 240 nm.

6. A nanodiamond dispersion composition according to any one of claims 1 to 5, having a haze value of 5 or less.

7. The SP value of the organic dispersion medium is 6.0 to 12.0 (cal / cm ３ ) １／２ The nanodiamond dispersion composition according to any one of claims 1 to 6,

8. A nanodiamond dispersion composition according to any one of claims 1 to 7, having a viscosity at 25°C of 0.2 to 120 mPa·s.

9. A nanodiamond dispersion composition according to any one of claims 1 to 8, wherein the fatty acid ester-based dispersant has an average molecular weight Mp of 300 or more.

10. A nanodiamond dispersion composition according to any one of claims 1 to 9, wherein the nanodiamond particles comprise surface-modified nanodiamonds in which the nanodiamond particle surface is modified with a group represented by the following formula (I): -X-R (I) [In formula (I), X represents -Si-, -NH-, -O-, -O-C(=O)-, -C(=O)-O-, -NH-C(=O)-, -C(=O)-NH-, or -S-, and the bond extending to the left from X is bonded to the nanodiamond particle. R represents a monovalent organic group, and the atom bonded to X is a carbon atom.]

11. 11. The nanodiamond dispersion composition according to claim 10, wherein in formula (I), X represents -Si-, -NH-, -O-, or -O-C(=O)-.

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