Nanodiamond dispersion composition

Abstract

To provide a nanodiamond dispersion composition excellent in dispersibility of nanodiamond particles in an organic dispersion medium and containing a small amount of zirconia.SOLUTION: A nanodiamond dispersion composition comprises an organic dispersion medium, nanodiamond particles dispersed in the organic dispersion medium, and a dispersant, wherein the nanodiamond particles are nanodiamond particles not surface-modified by a surface modification group or compound other than the dispersant, and the dispersant has a mass reduction rate of 25% or less when maintained at 200°C in an air atmosphere for 180 minutes.SELECTED DRAWING: None

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.

Background Art

[0002] It is known that nano-sized fine substances have new properties that cannot be exhibited in the bulk state. For example, nanodiamond particles (= nano-sized diamond particles) have mechanical strength, a high refractive index, thermal conductivity, insulation, antioxidant properties, and an action of promoting crystallization of resins and the like.

[0003] However, since nanodiamond particles generally have a large proportion of surface atoms, the sum of the van der Waals forces that can act between the surface atoms of adjacent particles is large, and they tend to aggregate. In addition, in the case of nanodiamond particles, a phenomenon called agglutination occurs in which the Coulomb interaction between the crystal planes of adjacent crystallites contributes and they aggregate very strongly. Therefore, it has been very difficult to disperse nanodiamond particles in an organic solvent in the state of primary particles.

[0004] For example, Patent Document 1 describes that by adding a fatty acid ester-based dispersant, the dispersibility of nanodiamond particles in an organic dispersion medium is excellent. Further, Patent Document 2 describes that a lubricant composition using surface-modified nanodiamond particles having a silane compound bonded to the surface as nanodiamond particles and containing zirconia is excellent in the dispersibility of nanodiamond particles. Further, Patent Document 3 discloses a refrigerant oil composition containing a dispersant and excellent in the dispersibility of nanodiamond particles.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] Generally, in order to improve the dispersibility of nanodiamond particles in an organic dispersion medium, it has been effective to introduce a surface modification group into the nanodiamond particles. The introduction of the surface modification group is carried out, for example, by mixing a compound for introducing the surface modification group and the nanodiamond particles in a bead mill while stirring. However, since the reaction for introducing the surface modification group requires a long-time treatment, zirconia, which is a constituent component of the bead mill, may be mixed into the nanodiamond dispersion composition.

[0007] Therefore, an object of the present disclosure is to provide a nanodiamond dispersion composition that is excellent in the dispersibility of nanodiamond particles in an organic dispersion medium and has a small amount of zirconia mixed therein.

Means for Solving the Problems

[0008] As a result of intensive studies to achieve the above object, the inventors of the present disclosure have found that by using a specific dispersant for non-surface-modified nanodiamond particles, a nanodiamond dispersion composition with a small amount of zirconia mixed therein and excellent dispersibility of nanodiamond particles in an organic dispersion medium can be obtained. The present disclosure is based on these findings.

[0009] That is, the present disclosure includes an organic dispersion medium, nanodiamond particles dispersed in the organic dispersion medium, and a dispersant, wherein the nanodiamond particles are nanodiamond particles that are not surface-modified by a surface modification group or compound other than the dispersant, The above dispersant provides a nanodiamond dispersion composition having a mass reduction rate of 25% or less when maintained in an air atmosphere at a temperature of 200 °C for 180 minutes.

[0010] The above dispersant may be a fluorine-based compound.

[0011] The above dispersant may have an amine value of 10 mgKOH / g or more.

[0012] The above dispersant is preferably a polymer dispersant.

[0013] The mass reduction rate of the above dispersant when maintained in an air atmosphere at a temperature of 200 °C for 180 minutes is preferably 15% or less.

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

[0015] In the above nanodiamond dispersion composition, the content of zirconia is preferably 50 parts by mass or less with respect to 100 parts by mass of the total amount of the above nanodiamond particles.

Advantages of the Invention

[0016] The nanodiamond dispersion composition of the present disclosure has excellent dispersibility of nanodiamond particles in an organic dispersion medium and a small amount of zirconia mixed therein.

Modes for Carrying Out the Invention

[0017] The nanodiamond dispersion composition (ND dispersion composition) according to an embodiment of the present disclosure includes at least an organic dispersion medium, nanodiamond particles (ND particles) dispersed in the organic dispersion medium, and a dispersant.

[0018] (Nanodiamond Particles) The above-mentioned ND particles are ND particles without surface modification. The above-mentioned ND particles without surface modification refer to ND particles that are not surface-modified by a surface modification group or compound other than the above-mentioned dispersant. Note that the ND particles without surface modification may have groups existing since the generation of ND particles such as by the detonation method, and for example, may have hydroxy groups (-OH) or carboxy groups (-COOH) on the surface. Also, the above-mentioned ND particles without surface modification may be modified by the above-mentioned dispersant in the above-mentioned ND dispersion composition. Note that in this specification, the above-mentioned ND particles without surface modification may be referred to as "unmodified ND particles". Only one type or two or more types of the above-mentioned unmodified ND particles may be used.

[0019] Examples of the above-mentioned surface modification group or compound include silane compounds, phosphonate ions or phosphonate residues, surface modification groups having a vinyl group at the terminal, amide groups, cations of cationic surfactants, groups containing a polyglycerol chain, groups containing a polyethylene glycol chain, and the like. The above-mentioned surface modification group or compound or functional group includes those containing an organic group.

[0020] The above-mentioned ND particles preferably contain primary particles of nanodiamond. In addition, they may contain secondary particles in which a plurality of the above-mentioned primary particles are aggregated.

[0021] As the above-mentioned ND particles, for example, detonation method nanodiamond (that is, nanodiamond produced by the detonation method) or high temperature and high pressure method nanodiamond (that is, nanodiamond produced by the high temperature and high pressure method) can be used. Among them, detonation method nanodiamond is preferable in that the dispersibility in the dispersion composition is more excellent, that is, the particle diameter of the primary particles is in the single-digit nanometer range.

[0022] The above-mentioned detonation method nano-diamond includes air-cooled detonation method nano-diamond (i.e., nano-diamond produced by the air-cooled detonation method) and water-cooled detonation method nano-diamond (i.e., nano-diamond produced by the water-cooled detonation method). Among them, the air-cooled detonation method nano-diamond is preferable in that the primary particles are smaller than those of the water-cooled detonation method nano-diamond.

[0023] From the viewpoint of making the mixing amount of zirconia lower, the content of unmodified ND particles in the above ND dispersion composition is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 96% by mass or more, and particularly preferably 99% by mass or more based on 100% by mass of the total amount of ND particles.

[0024] (Organic dispersion medium) As the above organic dispersion medium, known or commonly used organic solvents can be used. Examples of the above organic dispersion medium include aliphatic hydrocarbons such as hexane, heptane, and octane (particularly linear saturated aliphatic hydrocarbons); aromatic hydrocarbons such as benzene, toluene, and xylene; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; aprotic polar solvents such as dimethylformamide (DMF), dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide; alcohols such as methanol; halogenated hydrocarbons such as chloroform, dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene, and trifluoromethylbenzene; chain or cyclic ethers such as diethyl ether, diisopropyl ether, dimethoxyethane, tetrahydrofuran (THF), and dioxane; esters such as ethyl acetate and butyl acetate; chain ketones such as methyl ethyl ketone (MEK) and methyl isobutyl ketone; nitriles such as acetonitrile, etc. The above organic dispersion medium may be used alone or in combination of two or more.

[0025] Also, when the above-mentioned ND dispersion composition is used as a lubricant described below, the above-mentioned organic dispersion medium may be a lubricating base. As the above-mentioned lubricating base, known or conventional organic solvents used as lubricating bases can be used. For example, polyphenyl ether, alkylbenzene, alkylnaphthalene, ester oil, glycol-based synthetic oil, polyolefin-based synthetic oil, mineral oil, etc. can be mentioned. More specifically, poly-α-olefin, ethylene-α-olefin copolymer, polybutene, alkylbenzene (AB), alkylnaphthalene, polyalkylene glycol (PAG) types, polyphenyl ether, alkyl-substituted diphenyl ether, polyol ester (POE) types, dibasic acid ester, carbonate ester, phosphate ester, silicone oil, fluorinated oil, GTL (Gas to Liquids), mineral oil, etc. can be mentioned. Among them, from the viewpoint of excellent wear reduction effect of the sliding member, polyol ester, poly-α-olefin, mineral oil, alkylbenzene, and polyalkylene glycol are preferable.

[0026] Also, when the above-mentioned lubricating base is used as the above-mentioned organic dispersion medium, the above-mentioned ND dispersion composition has excellent dispersibility of ND particles with respect to the above-mentioned lubricating base. Therefore, it is not necessary to blend a dispersion solvent (such as ethanol, DMSO, etc.) other than the lubricating base for improving dispersibility. Therefore, the content of the solvent other than the above-mentioned lubricating base (especially the dispersion solvent) is preferably less than 1000 parts by mass, more preferably 100 parts by mass or less, still more preferably 50 parts by mass or less, and particularly preferably substantially not contained (that is, not actively blended except for those inevitably present) with respect to 100 parts by mass of the total amount of ND particles.

[0027] (Dispersant) The above-mentioned ND dispersion composition contains a dispersant. By using the dispersant with a mass reduction rate of 25% or less when maintained in an air atmosphere at a temperature of 200°C for 180 minutes, the dispersibility of unmodified ND particles in the organic dispersion medium is particularly excellent. In particular, since the dispersant with a mass reduction rate of 25% or less has high heat resistance, thermal decomposition is less likely to occur. Therefore, even when the above-mentioned ND dispersion composition is heated during use or used in a high-temperature environment, the above-mentioned ND dispersion composition is also excellent in dispersion stability in a high-temperature environment and is less likely to discolor. The above-mentioned dispersant may be any of cationic, anionic, and nonionic. The above-mentioned dispersant may be used alone or in combination of two or more.

[0028] The above-mentioned dispersant has a mass reduction rate (which may be referred to as the "mass reduction rate at 200°C for 180 minutes") of 25% or less when maintained in an air atmosphere at a temperature of 200°C for 180 minutes, preferably 20% or less, more preferably 15% or less. When the above-mentioned mass reduction rate is 25% or less, the above-mentioned ND dispersion composition is more excellent in heat resistance and excellent in dispersion stability in a high-temperature environment. The above-mentioned mass reduction rate can be measured by simultaneous differential thermal and thermogravimetric measurement (TG-DTA). Further, the above-mentioned mass reduction rate refers to the mass reduction rate of the dispersant itself. For example, for a dispersant dissolved and dispersed in a solvent, it refers to the mass reduction rate of its active ingredient.

[0029] The amine value of the above-mentioned dispersant is preferably 10 mgKOH / g or more, more preferably 20 mgKOH / g or more, and may be 400 mgKOH / g or more, 500 mgKOH / g or more. Further, the above-mentioned amine value is preferably 1000 mgKOH / g or less, more preferably 900 mgKOH / g or less, still more preferably 800 mgKOH / g or less.

[0030] As the above-mentioned amine value, the value described in the catalog provided by the manufacturer, supplier, etc. may be adopted, or the actually measured value may be adopted. For example, the above-mentioned amine value can be measured in accordance with JIS K 7237.

[0031] The above dispersant may be a fluorine-based compound. Examples of the above fluorine-based compound include low-molecular compounds or high-molecular compounds (fluorine-based polymers) containing fluorine atoms in the molecule. The above fluorine-based compound preferably contains an alkyl fluoride group, and more preferably contains a perfluoroalkyl group. The above alkyl fluoride group (especially perfluoroalkyl group) preferably has 1 to 10 carbon atoms, and more preferably 4 to 8 carbon atoms.

[0032] The above dispersant is preferably a high-molecular dispersant. Examples of the above high-molecular dispersant include fluorine-based polymers, polyvinyl alcohol, polyvinyl pyrrolidone, maleic acid copolymers (ethyl vinyl ether-maleic acid copolymer, styrene-maleic acid copolymer, etc.) and their various metal salts and ammonium salts, acrylic acid polymers (polyacrylic acid, copolymers of acrylic acid, etc.) and their various metal salts and ammonium salts, maleic acid monoester copolymers, acryloylmethylpropanesulfonic acid copolymers, polyester-based, CMC (carboxymethyl cellulose), HEC (hydroxyethyl cellulose), hydroxypropyl cellulose, hydroxypropylmethyl cellulose, carboxymethyl starch, alginic acid, pectic acid, etc.

[0033] The above high-molecular dispersant preferably has a weight-average molecular weight Mw of 300 or more, more preferably 1000 or more (for example, 1000 to 100000), and even more preferably 3000 or more (for example, 3000 to 10000). The above weight-average molecular weight Mw is the molecular weight in terms of standard polystyrene measured by gel permeation chromatography (GPC).

[0034] The above dispersant can also be a commercially available product. Examples of commercially available products of the dispersant include product name "TEGO Dispers 1010" (manufactured by Evonik Industries AG), product name "HYPERMER KD3-SO-(JP)", product name "HYPERMER KD11-LQ-(JP)" (both manufactured by Croda International Plc), product name "Hexafor 636" (manufactured by Maflon S.p.a.), product name "Newcol-3-80", product name "Newcol-80", product name "Newcol-20" (all manufactured by Nippon Emulsion Co., Ltd.), product name "Leodol SP-O10V" (manufactured by Kao Corporation), product name "Floren DOPA-15BHFS", product name "Floren DOPA-17HF" (both manufactured by Kyoeisha Chemical Co., Ltd.), product name "Ionet S-80" (manufactured by Sanyo Chemical Industries, Ltd.), product name "Surflon S-CFJ" (manufactured by AGC Seimi Chemical Co., Ltd.), product name "DISPERBYK-2008" (manufactured by BYK), product name "Adeka Estol S-80" (manufactured by Adeka Corporation), and the like.

[0035] The content of the dispersant in the above ND dispersion composition is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 96% by mass or more, and particularly preferably 99% by mass or more, based on 100% by mass of the total amount of the dispersant.

[0036] (ND dispersion composition) The average dispersed particle diameter (D50, median diameter) of the ND particles in the above ND dispersion composition is preferably 2 to 240 nm, more preferably 4 to 200 nm, still more preferably 5 to 100 nm, further preferably 10 to 70 nm, and particularly preferably 12 to 40 nm. The above average dispersed particle diameter can be measured by the dynamic light scattering method. Since the above ND dispersion composition has excellent dispersibility of ND particles, it can be dispersed in the organic dispersion medium with an average dispersed particle diameter within the above range.

[0037] The content ratio of the ND particles in the above 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 still more preferably 0.5 to 2.0% by mass. When the content ratio is within the above range, the dispersibility of the ND particles is more excellent. Also, the above content ratio may exceed 3.0% by mass, and may be 3.5% by mass or more. Since the above ND dispersion composition is excellent in the dispersibility of ND particles, even if the content ratio exceeds 3.0% by mass, the ND particles can be dispersed with a small dispersed particle diameter while suppressing the addition amount of the dispersant. From the viewpoint of more excellent dispersibility of the ND particles, the above content ratio is preferably 10% by mass or less. Incidentally, the above ND dispersion composition may be a concentrated liquid that is diluted during use so that the content ratio of the ND particles is low (for example, 0.1 to 2000 mass ppm).

[0038] The content of the dispersant in the above ND dispersion composition is, for example, 10 to 10000 parts by mass, preferably 50 to 5000 parts by mass, and more preferably 100 to 1000 parts by mass with respect to 100 parts by mass of the total amount of the ND particles in the above ND dispersion composition. When the content of the dispersant is within the above range, the dispersibility of the ND particles in the above ND dispersion composition is even more excellent.

[0039] The content ratio of the solvent in the above ND dispersion composition is, for example, 90 to 99.9999% by mass, and may be 90 to 96.999% by mass. And the content ratio of the organic dispersion medium in the total amount of the 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.

[0040] The above ND dispersion composition preferably has a haze value of 5 or less, more preferably 3 or less, still more preferably 1 or less, still more preferably 0.5 or less, still more preferably 0.1 or less, and particularly preferably 0.05 or less. Since the above ND dispersion composition is excellent in the dispersibility of ND particles, the ND dispersion composition having the above haze value can be obtained. The above haze value can be measured based on JIS K 7136. Also, the haze value of the ND dispersion composition having an ND concentration of 0.1% by mass may be within the above range.

[0041] The viscosity of the above-mentioned ND dispersion composition at 25°C is preferably 0.2 to 200 mPa·s, more preferably 0.3 to 180 mPa·s, and even more preferably 0.5 to 150 mPa·s. Since the above-mentioned ND dispersion composition is excellent in the dispersibility of ND particles, even when the viscosity is within the above range, it is excellent in the dispersibility in the organic dispersion medium. The rotor and the rotation speed of the rotor during the measurement of the above viscosity are appropriately selected according to the measured value. The above viscosity can be measured, for example, using an EMS viscometer (trade name "EMS1000", manufactured by Kyoto Electronics Industry Co., Ltd.).

[0042] The above-mentioned ND dispersion composition may consist only of ND particles, a dispersant, and an organic dispersion medium, or may contain other components. Examples of other components include surfactants, thickeners, coupling agents, rust inhibitors, corrosion inhibitors, freezing point depressants, defoamers, anti-wear additives, preservatives, colorants, and the like. The content ratio of the above other components is, for example, 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, even more preferably 1% by mass or less, particularly preferably less than 1% by mass, based on the total amount (100% by mass) of the above-mentioned ND dispersion composition. Therefore, the total content ratio of ND particles, a dispersant, and an 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, even more preferably 99% by mass or more, particularly preferably more than 99% by mass, based on the total amount of the above-mentioned ND dispersion composition. In particular, it is preferable that the content ratio of the surfactant as the above other component is within the range exemplified as the content ratio of the above other components.

[0043] The above-mentioned ND dispersion composition may or may not contain zirconia. When zirconia is contained, the zirconia may be attached to the above-mentioned ND particles or may be dispersed in the ND dispersion composition without attachment. The state of attachment of zirconia may be physical attachment (such as sticking or adhesion), chemical attachment (such as covalent bond with ND particles or the above-mentioned surface modification groups, bonding by intermolecular forces, hydrogen bond, ionic bond, etc.), or both of these.

[0044] The content of zirconia in the above-mentioned ND dispersion composition is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 15 parts by mass or less with respect to 100 parts by mass of the total amount of ND particles. When the content of the above-mentioned zirconia is 15 parts by mass or less, for example, when the above-mentioned ND dispersion composition is used as a lubricant (especially a lubricant for initial break-in), it is excellent in the formability of the break-in surface, and an easily break-in surface can be formed on the sliding member. Further, the incorporation of zirconium into the break-in surface is suppressed, and even a thin film exhibits excellent wear suppression effect and friction reduction effect. The lower limit of the content of the above-mentioned zirconia may be, for example, 0.1 part by mass or 0.3 part by mass.

[0045] The content of zirconia can be determined based on the detected amount of Zr with reference to a dispersion liquid in which Zr is detected by high-frequency inductively coupled plasma optical emission spectrometry (ICP optical emission spectrometry) and the content ratio is known. Further, the content of the above-mentioned zirconia can also be calculated as the amount of non-combustible matter by TG / DTA on the premise that the ND dispersion composition does not contain non-combustible matter other than zirconia. Specifically, a poor solvent is added to the ND dispersion composition to precipitate ND particles and zirconia to obtain a solid, and the obtained solid is subjected to TG / DTA to obtain the mass of Zr with respect to the ND particles. Zirconia often enters the ND dispersion composition from zirconia beads contained in a bead mill used for crushing aggregates of ND particles to nano-disperse the ND particles. Therefore, a ND dispersion composition with a low content of zirconia can be obtained by not performing bead milling using zirconia beads or minimizing the time for performing the bead milling.

[0046] The above-mentioned ND dispersion composition can be preferably used, for example, as an additive that imparts the properties of fine ND particles to resins (such as thermosetting or photocurable resins and thermoplastic resins). Examples of the properties of the above-mentioned ND particles include mechanical strength, high refractive index, thermal conductivity, insulation, antioxidant property, crystallization promotion effect, dendrite suppression effect, etc. And the composition obtained by adding the above-mentioned ND dispersion composition to a resin can be preferably used, for example, as a functional hybrid material, a material with thermal functions (heat resistance, heat storage, thermoelectric conduction, heat insulation, etc.), a photonics (organic EL element, LED, liquid crystal display, optical disk, etc.) material, a bio-bio compatibility material, a coating material, a film (hard coat film for touch panels and various displays, heat shielding film, etc.) material, a sheet material, a screen (transmission type transparent screen, etc.) material, a filler (heat dissipation filler, filler for improving mechanical properties, etc.) material, a heat-resistant plastic substrate (substrate for flexible displays, etc.) material, a material for lithium ion batteries, etc. Further, the above-mentioned ND dispersion composition can be preferably used as an antifriction agent or a lubricant (for initial running-in use, normal lubrication use, etc.) applied to the sliding parts of mechanical parts (such as automobiles and airplanes).

[0047] The above-mentioned lubricant for initial running-in (lubricant for initial running-in) is used to form a low-friction surface (running-in surface) at the initial stage of a machine having a sliding member. By using the lubricant for initial running-in, for example, the unevenness on the surface of the sliding member is leveled and smoothed, or a modified surface is formed. After the formation of the running-in surface, the lubricant for initial running-in is removed by washing or the like, and sliding is performed using the lubricant for normal lubrication. Here, the lubricant for normal lubrication refers to a lubricant that is not removed during the operation of the sliding member (during the use of the machine) and continues to exist in the sliding part. In addition, the above-mentioned lubricant for initial running-in can also be used as the lubricant for normal lubrication without being removed after the formation of the running-in surface, or after being removed once and then supplied again to the sliding part.

[0048] (Method for manufacturing nanodiamond dispersion composition) The above-mentioned ND dispersion composition can be produced, for example, by mixing ND particles, the above-mentioned dispersant, and, if necessary, other components in the above-mentioned organic dispersion medium. For example, a dispersion composition using unmodified ND particles can be produced by mixing cluster nanodiamonds and the above-mentioned dispersant, and, if necessary, other components in the organic dispersion medium, and then crushing or dispersing the cluster nanodiamonds in the organic dispersion medium.

[0049] Examples of methods for crushing or dispersing ND particles such as cluster nanodiamonds include methods of treating with 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 them, it is preferable to perform ultrasonic treatment in the presence of a crushing medium (for example, zirconia beads, etc.).

[0050] The diameter of the above-mentioned crushing medium (for example, zirconia beads, etc.) is, for example, 15 to 500 μm, preferably 15 to 300 μm, and particularly preferably 15 to 100 μm. The conditions for crushing or dispersing can be appropriately selected from, for example, the range of temperature 0 to 40 °C, reaction time 0.5 to 10 hours, and pressure 0.5 to 3 atm.

[0051] As described above, an ND dispersion composition in which ND particles are dispersed in an organic solvent is obtained.

[0052] The above-mentioned ND particles can be produced, for example, by the detonation method. Examples of the detonation method include an air-cooled detonation method and a water-cooled detonation method. Among them, the air-cooled detonation method is preferable in that ND particles with smaller primary particles can be obtained compared to the water-cooled detonation method.

[0053] The detonation may be carried out in an air atmosphere, or may be carried out in an inert gas atmosphere such as a nitrogen atmosphere, an argon atmosphere, or a carbon dioxide atmosphere.

[0054] Each aspect disclosed in this specification can be combined with any other features disclosed in this specification. Each configuration and their combinations in each embodiment are examples, and within the scope not departing from the gist of the present disclosure, additions, omissions, substitutions, and other changes to the configuration can be made as appropriate. Also, each invention according to the present disclosure is not limited by the embodiments and the following examples, but is limited only by the claims.

Examples

[0055] Hereinafter, an embodiment of the present disclosure will be described in more detail based on examples.

[0056] Examples and Comparative Examples (Preparation of ND Dispersion Composition) 0.6 g of cluster nanodiamond (trade name "DINNOVARE", manufactured by Daicel Corporation) and the dispersant shown in Table 1 were added to 30 g of toluene to obtain a slurry, and bead milling was performed using a bead milling device (trade name "Parallel Four-Cylinder Sand Grinder LSG-4U-2L Type", manufactured by Aimax Co., Ltd.). Specifically, 30 ml of the slurry after ultrasonic irradiation and zirconia beads with a diameter of 30 μm were put into a vessel (manufactured by Aimax Co., Ltd.) which is a 100 ml mill container, sealed, and the device was driven to perform bead milling. In this bead milling, the input amount of zirconia beads is, for example, 33% by volume with respect to the volume of the mill container, the rotational speed of the mill container is 2570 rpm, the temperature is 30 °C, the atmospheric pressure is 1 atm, and the milling time is 1 hour.

[0057] (Evaluation) The ND dispersion compositions obtained in the examples and comparative examples and the dispersants used were evaluated as follows. The evaluation results are shown in the table.

[0058] (1) 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 visually evaluated based on the following evaluation criteria. ◎: Black and transparent. 〇: Black but slightly lacking in clarity. △: Black but turbid. ×: Remains gray or separation is confirmed.

[0059] (2) Mass loss rate at 200°C for 180 minutes For the dispersants used in the examples and comparative examples, the mass loss rate at 200°C for 180 minutes was measured under the following conditions using a differential thermal thermogravimetric simultaneous measurement device (trade name "TG-DTA 6200", manufactured by Hitachi High-Tech Science Corporation). Atmosphere: Air Temperature: Starting from 30°C, the temperature was raised to 200°C at a heating rate of 20°C / min and held at 200°C for 180 minutes after reaching 200°C. Sample pan: Quartz

[0060] (3) Zirconia content Methanol was added as a poor solvent to the ND dispersion composition obtained in Example 4 to agglomerate the solid matter. Then, the liquid phase and the solid matter were separated by centrifugation, and the solid matter was recovered and dried to obtain a solid sample. The above solid sample was subjected to TG / DTA analysis to determine the mass ratio of [volatile component / dispersant / ND / Zr], calculate the ratio of Zr to ND100, and use that value as the zirconia content. As a result, the zirconia content was approximately 10 parts by mass per 100 parts by mass of ND. Since the bead milling conditions were the same in all examples, it was judged that the zirconia content in the ND dispersion compositions of the other examples was also approximately 10 parts by mass.

[0061]

Table 1

[0062] As can be seen from Table 1, when using a dispersant (Examples 1 to 15) with a mass reduction rate of 25% or less when maintained in an air atmosphere at 200 °C for 180 minutes, even when using unmodified ND particles under mild bead milling conditions, the dispersibility in an organic dispersion medium was excellent. And it was confirmed that the content of zirconia was small. Further, since the dispersibility of the unmodified ND particles was excellent, it was not necessary to perform surface modification of the ND particles, and the time required for crushing and dispersing the ND particles could be shortened. As a result, the amount of zirconia mixed in could be made small. On the other hand, the ND dispersion composition of the comparative example had poor dispersibility of the unmodified ND particles, and surface modification of the ND particles was required to improve the dispersibility. In this case, it was judged that the amount of zirconia mixed in would increase.

[0063] Hereinafter, variations of the invention according to the present disclosure will be described. [Appendix 1] An organic dispersion medium, nanodiamond particles dispersed in the organic dispersion medium, and a dispersant, The nanodiamond particles are nanodiamond particles not surface-modified by a surface modification group or compound other than the dispersant, The dispersant is a nanodiamond dispersion composition having a mass reduction rate of 25% or less when maintained in an air atmosphere at 200 °C for 180 minutes. [Appendix 2] The nanodiamond dispersion composition according to Appendix 1, wherein the dispersant is a fluorine-based compound. [Appendix 3] The nanodiamond dispersion composition according to Appendix 1 or 2, wherein the dispersant has an amine value of 10 mgKOH / g or more. [Appendix 4] The nanodiamond dispersion composition according to any one of Appendices 1 to 3, wherein the dispersant is a polymer dispersant. [Appendix 5] The nanodiamond dispersion composition according to any one of Appendices 1 to 4, wherein the mass reduction rate of the dispersant when maintained in an air atmosphere at 200 °C for 180 minutes is 15% or less. [Appendix 6] The nanodiamond dispersion composition according to any one of Appendices 1 to 5, wherein the average dispersed particle diameter of the nanodiamond particles is 2 to 240 nm. [Supplementary Note 7] The nanodiamond dispersion composition according to any one of Supplementary Notes 1 to 6, wherein the zirconia content is 50 parts by mass or less with respect to 100 parts by mass of the total amount of the nanodiamond particles.

Claims

1. The method includes: an organic dispersion medium; nanodiamond particles dispersed in the organic dispersion medium; and a dispersant; The nanodiamond particles are not surface-modified with a surface-modifying group or compound other than the dispersant, The dispersant is a nanodiamond dispersion composition having a mass loss rate of 25% or less when maintained in an air atmosphere at a temperature of 200°C for 180 minutes.

2. The nanodiamond dispersion composition according to claim 1, wherein the dispersant is a fluorine-based compound.

3. The nanodiamond dispersion composition according to claim 1 or 2, wherein the dispersant has an amine value of 10 mg KOH / g or more.

4. The nanodiamond dispersion composition according to claim 1 or 2, wherein the dispersant is a polymeric dispersant.

5. A nanodiamond dispersion composition as described in claim 1 or 2, wherein the mass loss rate of the dispersant when maintained in an air atmosphere at a temperature of 200°C for 180 minutes is 15% or less.

6. A nanodiamond dispersion composition according to claim 1 or 2, wherein the average dispersed particle size of the nanodiamond particles is 2 to 240 nm.

7. 3. A nanodiamond dispersion composition as described in claim 1 or 2, wherein the zirconia content is 50 parts by mass or less per 100 parts by mass of the total amount of the nanodiamond particles.

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