WO2020095581A1 - Nanodiamond-dispersed composition - Google Patents

Abstract

Provided is a nanodiamond-dispersed composition, in which the dispersibility of nanodiamond particles in an organic dispersion medium is excellent.　A nanodiamond-dispersed composition comprising an organic dispersion medium, nanodiamond particles dispersed in the organic dispersion medium, and a dispersing agent having a mass average molecular weight of 500 or more and an amine value of 15 mgKOH/g or more. The average dispersion particle diameter of the nanodiamond particles is preferably 20 to 150 nm. The haze value of the nanodiamond composition is preferably 5 or less.

Description

Nano diamond dispersion composition

The present invention relates to a nanodiamond dispersion composition. More specifically, the present invention relates to compositions in which nanodiamond particles are dispersed in an organic dispersion medium. This application claims the priority of Japanese Patent Application No. 2018-208309 filed in Japan on November 5, 2018, and the content thereof is incorporated herein.

It is known that nano-sized fine substances have new properties that cannot be expressed in the bulk state. For example, nanodiamond particles (= nanosize diamond particles) have mechanical strength, high refractive index, thermal conductivity, insulating property, antioxidant property, action of promoting crystallization of resin and the like. Techniques relating to the production of such nanodiamonds are described in, for example, Patent Document 1 and Patent Document 2 below.

Japanese Patent Laid-Open No. 2005-001983 JP, 2010-126669, A

However, since nanodiamond particles generally have a large proportion of surface atoms, the total sum of van der Waals forces that can act between surface atoms of adjacent particles is large, and they are easily aggregated. In addition to this, in the case of nanodiamond particles, a phenomenon called agglutination in which Coulomb interaction between crystal faces of adjacent crystallites contributes to form a very strong aggregation may occur. Therefore, it was very difficult to disperse the nanodiamond particles in the organic solvent in the state of primary particles.

Therefore, an object of the present invention is to provide a nanodiamond dispersion composition having excellent dispersibility of nanodiamond particles in an organic dispersion medium.

The present inventors have conducted extensive studies to achieve the above object, and by using a specific dispersant, it is possible to obtain a nanodiamond dispersion composition having excellent dispersibility of nanodiamond particles in an organic dispersion medium. I found it. The present invention has been completed based on these findings.

That is, the present invention comprises an organic dispersion medium, nanodiamond particles dispersed in the organic dispersion medium, and a dispersant having a mass average molecular weight of 500 or more and an amine value of 15 mgKOH / g or more. A nanodiamond dispersion composition including the same is provided.

The average dispersed particle diameter of the nanodiamond particles is preferably 20 to 150 nm.

The haze value of the nanodiamond dispersion composition is preferably 5 or less.

The SP value of the organic dispersion medium is preferably 6.0 to 12.0 (cal / cm) ^1/2 .

The viscosity of the nanodiamond dispersion composition at 25 ° C. is preferably 20 to 90 mPa · s.

The dispersant preferably contains a compound having a structure derived from polyalkylene glycol monoalkyl ether.

The above dispersant preferably contains a compound having a carbamate structure.

The above dispersant preferably contains a compound having a structure derived from polycaprolactone.

The content ratio of the nanodiamond particles in the nanodiamond dispersion composition may be 0.01 to 5.0% by mass.

The nanodiamond particles are preferably surface-modified nanodiamonds having a silane compound bonded to the surface.

The nanodiamond dispersion composition of the present invention has excellent dispersibility of nanodiamond particles in an organic dispersion medium.

The nanodiamond dispersion composition (ND dispersion composition) of the present invention has an organic dispersion medium, nanodiamond particles (ND particles) dispersed in the organic dispersion medium, a mass average molecular weight of 500 or more, and And a dispersant having an amine value of 15 mgKOH / g or more. In the present specification, a dispersant having a mass average molecular weight of 500 or more and an amine value of 15 mgKOH / g or more may be referred to as a dispersant (A).

The average dispersed particle diameter (D50, median diameter) of the ND particles in the ND dispersion composition of the present invention is preferably 2 to 240 nm, more preferably 4 to 200 nm, more preferably 10 to 180 nm, further preferably 20 to 150 nm. Is. The average dispersed particle diameter can be measured by a dynamic light scattering method. Since the ND dispersion composition of the present invention has excellent dispersibility of ND particles, it can be dispersed in an organic dispersion medium with an average dispersed particle diameter within the above range.

The content ratio of the ND particles in the ND dispersion composition of the present invention 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 more preferably 0.5 to 2.0 mass%. When the content ratio is within the above range, the dispersibility of the ND particles is more excellent.

The content of the dispersant (A) in the ND dispersion composition of the present invention is, for example, 10 to 10,000 parts by mass, preferably 50 to 100 parts by mass based on 100 parts by mass of the total amount of ND particles in the ND dispersion composition of the present invention. The amount is 1000 parts by mass, more preferably 70 to 300 parts by mass. When the content of the dispersant (A) is within the above range, the dispersibility of the ND particles in the ND dispersion composition of the present invention is further excellent. The ND dispersion composition of the present invention may be diluted at the time of use so that the content ratio of ND particles becomes low (for example, 0.1 to 2000 mass ppm), and the content of the dispersant (A) in this case is The amount of ND particles in the ND dispersion composition of the present invention is preferably 1,000 to 1,000,000 parts by mass, more preferably 2,000 to 100,000 parts by mass, and particularly preferably 3,000 to 50,000 parts by mass, based on 100 parts by mass.

The content ratio of the solvent in the ND dispersion composition of the present invention is, for example, 90 to 99.9999% by mass. 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.

The haze value of the ND dispersion composition of the present invention is preferably 5 or less, more preferably 3 or less, further preferably 1 or less, particularly preferably 0.5 or less. Since the ND dispersion composition of the present invention has excellent dispersibility of ND particles, the ND dispersion composition having the above haze value can be obtained. The haze value can be measured based on JIS K7136.

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

The ND dispersion composition of the present invention may consist of only ND particles, a dispersant (A), and an organic dispersion medium, or may contain other components. Other components include, for example, dispersants other than dispersant (A), surfactants, thickeners, coupling agents, rust inhibitors, corrosion inhibitors, freezing point depressants, antifoaming agents, antiwear additives. , Preservatives, coloring agents and the like. The content ratio of the dispersant (A) is preferably 90% by mass or more, more preferably 95% by mass or more, further preferably 99% by mass or more based on the total amount of the dispersant in the ND dispersion composition of the present invention. Is. The content ratio of the other components is, for example, 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, further preferably 5% by mass or less, based on the total amount of the ND dispersion composition of the present invention. It is particularly preferably 1% by mass or less. Therefore, the total content ratio of the ND particles, the dispersant (A), and the organic dispersion medium is, for example, 70% by mass or more, preferably 80% by mass or more, and more preferably based on the total amount of the ND dispersion composition of the present invention. 90 mass% or more, more preferably 95 mass% or more, and particularly preferably 99 mass% or more.

(Nano diamond particles)
The ND particles are not particularly limited, and known or commonly used nanodiamond particles can be used. The ND particles may be surface-modified ND (surface-modified ND) particles or may be non-surface-modified ND particles. The ND particles that are not surface-modified have hydroxyl groups (—OH) on the surface. The ND particles may be used alone or in combination of two or more.

Examples of the compound or functional group that surface-modifies the ND particles in the surface-modified ND include a silane compound, a carboxyl group (—COOH), a phosphonate ion or a phosphonic acid residue, a surface-modifying group having a vinyl group at the end, and an amide. Group, a cation of a cationic surfactant, a group containing a polyglycerin chain, a group containing a polyethylene glycol chain, and the like.

As the compound or functional group for surface-modifying the ND particles in the above-mentioned surface-modified ND, a silane compound is preferable from the viewpoint of being more excellent in dispersibility in an organic dispersion medium in combination with the dispersant (A). That is, it is preferable that the surface-modified ND is a surface-modified ND in which a silane compound is bonded to the surface.

The silane compound preferably has a hydrolyzable group and an aliphatic hydrocarbon group. The silane compound used for the surface modification of the ND particles may be only one kind or two or more kinds.

Among the above silane compounds, it is preferable to contain at least a compound represented by the following formula (1-1).

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

Examples of the aliphatic hydrocarbon group having 1 to 3 carbon atoms in R ¹ , R ² and R ³ include linear or branched alkyl groups such as methyl, ethyl, propyl and isopropyl groups; vinyl and allyl groups. And straight-chain or branched-chain alkenyl groups; and alkynyl groups such as ethynyl group and propynyl group. Of these, a linear or branched alkyl group is preferable.

R ⁴ is an aliphatic hydrocarbon group having 1 or more carbon atoms, 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, isobehenyl group, and other linear or branched alkyl groups; vinyl Straight-chain or branched-chain alkenyl groups such as allyl, 1-butenyl, 7-octenyl, 8-nonenyl, 9-decenyl, 11-dodecenyl and oleyl groups; direct groups such as ethynyl, propynyl, decynyl, pentadecynyl and octadecynyl groups. Chain or branched alkynyl group, etc. And the like.

Among them, R ⁴ is higher in lipophilicity and can be a larger steric hindrance, so that it has an excellent effect of suppressing aggregation and can impart a higher degree of dispersibility, and thus R ⁴ is an aliphatic carbon atom having 4 or more carbon atoms. A hydrogen group is preferable, and an aliphatic hydrocarbon group having 6 or more carbon atoms is particularly preferable. In addition, the upper limit of the carbon number of the aliphatic hydrocarbon group is, for example, 25, preferably 20, and more preferably 12. As the aliphatic hydrocarbon group, a linear or branched alkyl group or alkenyl group is preferable, and a linear or branched alkyl group is particularly preferable.

When R ⁴ is an aliphatic hydrocarbon group having 4 or more carbon atoms, it exhibits affinity for an organic dispersion medium, and since it may cause larger steric hindrance, it is excellent in the aggregation suppressing effect, and further contains a group containing an oxygen atom. (OR ¹ 'group and OR ² ' group in the formula (1)) show an affinity for the organic dispersion medium, so that the affinity for the organic dispersion medium is excellent and the dispersibility is further enhanced in the organic dispersion medium. can do.

Therefore, examples of the 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).

In the above formula (1), R ⁴ represents an aliphatic hydrocarbon group having 1 or more carbon atoms. R ¹ 'and R ² ' are the same or different and each is a hydrogen atom, an aliphatic hydrocarbon group having 1 to 3 carbon atoms, or a group represented by the following formula (a). The bond with a wavy line in the formula bonds to the surface of the nanodiamond particle.

In the above formula (a), R ⁴ represents an aliphatic hydrocarbon group having 1 or more carbon atoms. R ³ and R ⁵ are the same or different and each represents a hydrogen atom or an aliphatic hydrocarbon group having 1 to 3 carbon atoms. m and n are the same or different and each represents an integer of 0 or more. The bond extending from the silicon atom to the left bonds to the oxygen atom. In addition, the bond with a wavy line is bonded to the surface of the nanodiamond particle. R ⁴ in the formula (1) correspond to R ⁴ in the formula (1-1).

The aliphatic hydrocarbon group having 1 to 3 carbon atoms in R ¹ ′, R ² ′, R ³ and R ⁵ in the above formula (1) is, for example, a straight chain such as methyl, ethyl, propyl or isopropyl group. Or a branched alkyl group; a linear or branched alkenyl group such as vinyl or allyl group; an alkynyl group such as ethynyl group or propynyl group. Of these, a linear or branched alkyl group is preferable.

ㆍ m and n are the numbers of structural units shown in parentheses, and are the same or different and represent an integer of 0 or more. When m and n are 2 or more, the method of bonding the 2 or more structural units may be random, alternating, or block.

In addition to the group represented by the formula (1), the silane compound surface-modified ND particles include, for example, a group represented by the following formula (1 ′) and other surface functional groups (eg, amino group, hydroxyl group, carboxyl group). It may have other functional groups such as groups). The other functional groups may be only one kind or two or more kinds.

In the above formula (1 ′), R ¹ ′ and R ⁴ are the same as above. The bond with a wavy line in the formula bonds to the surface of the nanodiamond particle.

When a silane compound (particularly, a compound represented by the above formula (1-1)) is used as the compound to be surface-treated, the compound may be, for example, an OR ¹ group or an OR ² group in the above formula (1-1). , OR ³ groups and other hydrolyzable alkoxysilyl groups are easily hydrolyzed to form silanol groups. For example, one of the silanol groups is dehydrated and condensed with a hydroxyl group present on the surface of the ND particles to form a covalent bond. And the remaining two silanol groups can be condensed with silanol groups of other silane compounds to form a siloxane bond (Si-O-Si), and the ND particles have an affinity for an organic dispersion medium. Can be imparted, and even more excellent dispersibility can be exhibited in the organic dispersion medium.

(Organic dispersion medium)
As the organic dispersion medium, a known or common organic solvent can be used. Among them, the SP value [solubility parameter (δ) by Hildebrandt, unit: (cal / cm) ^{1/2 at} 25 ° C.] is 6.0 to 12.0 (from the viewpoint of more excellent dispersibility of ND particles). Particularly, in the ND dispersion composition of the present invention, even when an organic solvent having a low dispersibility of ND particles is used by blending the dispersant (A), the dispersibility of the ND particles is Since it is excellent, the SP value is preferably 8.2 or less (eg 6.0 to 8.2) or 9.0 or more (eg 9.0 to 12.0), more preferably 8.0 or less (eg The organic dispersion medium is preferably 6.5 to 8.0) or 9.2 or more (for example, 9.2 to 12.0). More than one kind may be used, and when two or more kinds of organic dispersion media are used, The SP value of the mixture of at least one organic dispersion medium is preferably within the above range, and the SP value of each organic dispersion medium may be outside the above range.

Examples of the organic dispersion medium include alkanes such as hexane (SP: 7.0); acetone (SP: 10.0), methyl ethyl ketone (MEK, SP: 9.3), methyl isobutyl ketone (MIBK, SP: 8). .4) and other ketones; dioxane (SP: 9.8), tetrahydrofuran (SP: 9.1) and other ethers; n-propanol (SP: 11.9), isopropanol (IPA, SP: 11.5), Alcohols such as 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 (SP: 7.6) and other aromatic compounds; chloroform (SP: 9.3), methylene chloride (SP: 9.7), ethyl dichloride. Halogenated hydrocarbons such as ethylene carbonate (SP: 9.8); ethylene carbonate / diethyl carbonate (EC / DEC = 1/1: volume ratio) mixed solvent (SP: 11.75), ethylene carbonate / diethyl carbonate / methyl ethyl Carbonate (1/1/1: volume ratio) mixed solvent (SP: 10.97) and other carbonate compounds; poly-α-olefin (SP: about 6.0 to 8.0) and other polyolefins; mineral oil (SP: 6) 0.0 to 8.0), acetic acid (SP: 12.4), acetonitrile (SP: 11.8) and the like.

(Dispersant (A))
The dispersant (A) has a mass average molecular weight of 500 or more and an amine value of 15 mgKOH / g or more. By using such a dispersant, the dispersibility of the ND particles in the organic dispersion medium is particularly excellent. As the dispersant (A), only one kind may be used, or two or more kinds may be used.

The mass average molecular weight of the dispersant (A) is 500 or more, preferably 650 or more, more preferably 950 or more. The mass average molecular weight is preferably 20,000 or less, more preferably 10,000 or less. In the present specification, the mass average molecular weight is a standard polystyrene-equivalent molecular weight measured by gel permeation chromatography (GPC).

The amine value of the dispersant (A) is 15 mgKOH / g or more, preferably 18 mgKOH / g or more, more preferably 20 mgKOH / g or more, further preferably 30 mgKOH / g or more. The amine value is preferably 100 mgKOH / g or less, more preferably 90 mgKOH / g or less, still more preferably 60 mgKOH / g or less.

As the dispersant (A), among others, a compound having a structure derived from polyalkylene glycol monoalkyl ether (particularly a structure derived from polyethylene glycol monoalkyl ether or a structure derived from polypropylene glycol monoalkyl ether), a compound having a carbamate structure A compound having a structure derived from polycaprolactone is preferable. The above compounds may each contain only one kind or may contain two or more kinds. Further, one compound may have one kind or two kinds or more of the above structures.

A commercially available product may be used as the dispersant (A). Examples of commercially available dispersants (A) include, for example, trade name “DISPERBYK-2008”, trade name “BYK-9076”, trade name “BYK-9077”, trade name “ANTI-TERRA-U” (above, BIC -Chemie) and the like.

The ND dispersion composition of the present invention can be preferably used, for example, as an additive that imparts the characteristics of fine ND particles to a resin or the like (for example, a heat or photocurable resin or a thermoplastic resin). The properties of the ND particles include, for example, mechanical strength, high refractive index, thermal conductivity, insulating property, antioxidant property, crystallization promoting action, and dendrite suppressing action. The composition obtained by adding the ND dispersion composition of the present invention to a resin is, for example, a functional hybrid material, a thermal function (heat resistance, heat storage, heat conduction, heat insulation, etc.) material, photonics (organic EL element, LED, liquid crystal display, optical disk, etc.) material, bio / biocompatible material, coating material, film (hard coat film such as touch panel and various displays, heat shield film, etc.) material, sheet material, screen (transparent transparent screen, etc.) It can be preferably used as a material, a filler (heat radiation filler, mechanical property improving filler, etc.) material, a heat-resistant plastic substrate (flexible display substrate, etc.) material, a lithium ion battery material, etc. In addition, the ND dispersion composition of the present invention is preferably used as a lubricant or lubricant (initial familiarization application, main lubrication application, etc.) applied to sliding parts of machine parts (eg, automobiles, aircrafts, etc.). it can.

(Method for producing nanodiamond dispersion composition)
The ND dispersion composition of the present invention can be produced, for example, by mixing the organic dispersion medium with ND particles, the dispersant (A), and, if necessary, other components. For example, a dispersion composition using surface-modified ND particles can be produced through a step (modification step) of reacting a compound to be surface-treated with ND particles in an organic dispersion medium. In this case, the solvent used in the modification step may be used as it is as the organic dispersion medium in the ND dispersion composition, or the solvent may be exchanged after the modification step.

In the modification step, when the ND particles include an ND particle aggregate in which the ND particles are aggregated to form secondary particles, the reaction between the compound for surface modification and the ND particles is performed. It is preferable to carry out while crushing or dispersing. Thereby, the ND particle aggregate can be crushed into primary particles, the surface of the ND primary particles can be modified, and the dispersibility of the nanodiamond particles in the ND dispersion composition can be improved. Because it will be.

The mass ratio (former: latter) of the ND particles to be subjected to the reaction in the modification step and the compound to be surface-treated (particularly, the silane compound) is, for example, 2: 1 to 1:20. The concentration of the ND particles in the organic dispersion medium when the surface treatment is performed is, for example, 0.5 to 10% by mass, and the concentration of the compound is, for example, 5 to 40% by mass.

The reaction time for surface treatment is, for example, 4 to 20 hours. Further, the above reaction is preferably performed while cooling the generated heat with ice water or the like.

Examples of the method of crushing or dispersing the ND particles include a method of treating with a high shear mixer, high shear mixer, homomixer, ball mill, bead mill, high pressure homogenizer, ultrasonic homogenizer, colloid mill, jet mill and the like. .. Above all, it is preferable to perform the ultrasonic treatment in the presence of a crushing medium (for example, zirconia beads or the like).

The diameter of the 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.

Further, when obtaining an ND dispersion composition using an organic dispersion medium in which the dispersibility of ND particles is relatively low, a dispersant is added to an ND dispersion liquid in which the dispersibility of ND particles is relatively high, and the mixture is stirred, and then ND is used with an evaporator or the like. It can also be produced by distilling off the organic dispersion medium in the dispersion liquid, then newly mixing and stirring the organic dispersion medium, that is, by exchanging the organic dispersion medium. After obtaining the dispersion liquid in which the ND particles are nano-dispersed once, the method of exchanging the organic dispersion medium without making the ND particles into a dry powder is adopted, and the wettability between the organic dispersion medium before and after the exchange and By appropriately selecting both organic dispersion media in consideration of solubility, ND particles are easily nano-dispersed in the organic dispersion media having relatively low dispersibility.

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

The above ND particles can be manufactured, for example, by the detonation method. Examples of the detonation method include an air-cooled detonation method and a water-cooled detonation method. Above all, the air-cooled detonation method is preferable in that ND particles having smaller primary particles than the water-cooled detonation method can be obtained.

Detonation may be performed in the atmosphere, or in an inert gas atmosphere such as a nitrogen atmosphere, an argon atmosphere, or a carbon dioxide atmosphere.

An example of a method for producing ND particles will be described below, but the ND particles used in the present invention are not limited to those obtained by the following production method.

(Generation process)
A molded explosive equipped with an electric detonator is installed inside a pressure-resistant container for detonation, and the container is hermetically sealed in the container in which the atmospheric gas of atmospheric composition and the explosive used coexist. .. The container is made of, for example, iron, and the volume of the container is, for example, 0.5 to 40 m ³ . As explosive, it is possible to use a mixture of trinitrotoluene (TNT) and cyclotrimethylenetrinitroamine or hexogen (RDX). The mass ratio of TNT and RDX (TNT / RDX) is, for example, in the range of 40/60 to 60/40.

In the generation process, next, detonate the electric detonator and detonate explosives in the container. Detonation refers to an explosion caused by a chemical reaction, in which the flame surface in which the reaction occurs moves at a high speed exceeding the speed of sound. At the time of detonation, the explosive used causes partially incomplete combustion to release carbon as a 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 are extremely strongly assembled between adjacent primary particles or crystallites due to Coulomb interaction between crystal faces in addition to the action of Van der Waals force, and form an aggregate.

In the production process, next, let stand for 24 hours at room temperature to allow it to cool and lower the temperature of the container and its inside. After this cooling, the ND particle coarse product (including the agglomerates and soot of the ND particles produced as described above) adhering to the inner wall of the container was scraped off with a spatula to remove the ND particle coarse particles. Collect the product. A crude product of ND particles can be obtained by the method described above. In addition, it is possible to obtain a desired amount of the crude nanodiamond product by performing the above-mentioned nanodiamond production process a necessary number of times.

(Acid treatment step)
In the acid treatment step, the raw material nanodiamond product is treated with a strong acid in, for example, a water solvent to remove the metal oxide. The crude nanodiamond product obtained by the detonation method is likely to contain a metal oxide, and the metal oxide is an oxide such as Fe, Co, or Ni derived from the container or the like used in the detonation method. .. For example, the metal oxide can be dissolved and removed from the crude nanodiamond product by applying a strong acid in an aqueous solvent (acid treatment). The strong acid used for this acid treatment is preferably a mineral acid, and examples thereof include hydrochloric acid, hydrofluoric acid, sulfuric acid, nitric acid, and aqua regia. The strong acids may be used alone or in combination of two or more. 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 carried out under reduced pressure, normal pressure, or increased pressure. After such acid treatment, the solid content (including the nanodiamond aggregate) is washed with water, for example, by decantation. It is preferable to repeatedly wash the solid content with water by decantation until the pH of the precipitation liquid reaches, for example, 2 to 3. When the content of metal oxide in the nanodiamond crude product obtained by the detonation method is small, the above acid treatment may be omitted.

(Oxidation process)
The oxidation treatment step is a step of removing graphite from the ND particle crude product using an oxidizing agent. The ND particle crude product obtained by the detonation method contains graphite (graphite), but this graphite does not form ND particle crystals out of the carbon released by the incomplete combustion of the explosive used. Derived from carbon. Graphite can be removed from the ND particle crude product by reacting the ND particle crude product with an oxidizing agent in a water solvent. In addition, an oxygen-containing group such as a carboxyl group or a hydroxyl group can be introduced on the surface of the ND particles by causing the oxidizing agent to act.

Examples of the oxidizing agent used in this oxidation treatment include chromic acid, chromic anhydride, dichromic acid, permanganic acid, perchloric acid, nitric acid, mixtures thereof, and at least one acid selected from these. The mixed acid with other acid (for example, sulfuric acid etc.), these salts are mentioned. Above all, it is preferable to use a mixed acid (particularly, a mixed acid of sulfuric acid and nitric acid) because it is environmentally friendly and has an excellent effect of oxidizing and removing graphite.

The mixing ratio (former / latter; mass ratio) of sulfuric acid and nitric acid in the above mixed acid is, for example, 60/40 to 95/5, but even under a pressure near normal pressure (eg, 0.5 to 2 atm). For example, at a temperature of 130 ° C. or higher (particularly preferably 150 ° C. or higher, the upper limit is, for example, 200 ° C.), graphite can be efficiently oxidized and removed, which is preferable. The lower limit is preferably 65/35, more preferably 70/30. Further, the upper limit is preferably 90/10, more preferably 85/15, further preferably 80/20. When the mixing ratio is 60/40 or more, the content of sulfuric acid having a high boiling point is high, so that the reaction temperature becomes 120 ° C. or more under a pressure near normal pressure, and the graphite removal efficiency tends to improve. is there. When the mixing ratio is 95/5 or less, the content of nitric acid, which greatly contributes to the oxidation of graphite, increases, so that the graphite removal efficiency tends to improve.

The amount of the oxidizing agent (particularly the above-mentioned 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 with respect to 1 part by mass of the nanodiamond crude 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 with respect to 1 part by mass of the nanodiamond crude 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 with respect to 1 part by mass of the nanodiamond crude product.

Also, when the above mixed acid is used as an oxidizing agent, a catalyst may be used together with the mixed acid. By using the catalyst, the efficiency of removing graphite can be further improved. Examples of the catalyst include copper (II) carbonate and the like. The amount of the catalyst used is, for example, about 0.01 to 10 parts by mass with respect to 100 parts by mass of the nanodiamond crude product.

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

(Alkaline water treatment process)
Even after passing through the acid treatment step, if the metal oxide that cannot be completely removed remains in the ND particles, the coagulates (secondary particles) that are aggregated due to the extremely strong interaction between the primary particles (secondary particles) Particles). In such a case, alkali and hydrogen peroxide may be allowed to act on the ND particles in a water solvent. As a result, the metal oxide remaining on the ND particles can be removed, and the separation of the primary particles from the agglomerate can be promoted. Examples of the alkali used for this treatment include sodium hydroxide, ammonia, potassium hydroxide and the like. In the alkaline hydrogen peroxide treatment, the concentration of alkali is, for example, 0.1 to 10 mass%, the concentration of hydrogen peroxide is, for example, 1 to 15 mass%, the treatment temperature is, for example, 40 to 100 ° C., and the treatment time is For example, it is 0.5 to 5 hours. The alkaline hydrogen peroxide treatment can be performed under reduced pressure, normal pressure, or increased pressure.

After the oxidation treatment step or the alkaline hydrogen peroxide treatment step, it is preferable to remove the supernatant by, for example, decantation. Moreover, it is preferable to wash the solid content with water during decantation. Although the supernatant liquid at the beginning of washing with water is colored, it is preferable to repeatedly wash the solid content with water until the supernatant liquid becomes transparent visually.

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

(Drying process)
It is preferable to provide a drying step after the above alkaline hydrogen peroxide treatment step. For example, after the liquid content is evaporated from the ND particle-containing solution obtained through the above alkaline hydrogen peroxide treatment step by using a spray dryer or an evaporator, the residual solid content generated by this is heated in a drying oven. Dry by drying. The heating and drying temperature is, for example, 40 to 150 ° C. ND particles are obtained through such a drying process.

Further, the ND particles may be subjected to oxidation treatment (for example, oxygen oxidation) or reduction treatment (for example, hydrogenation treatment) in a gas phase, if necessary. By performing the oxidation treatment in the gas phase, ND particles having many C = O groups on the surface can be obtained. Further, by performing the reduction treatment in the gas phase, ND particles having many C—H groups on the surface can be obtained.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Examples 1-5
The surface-modified ND particles and the ND dispersion composition were manufactured through the following steps.

(Preparation of surface modified ND particles)
First, a nanodiamond generation process by the detonation method was performed. In this step, first, a molded explosive with an electric detonator attached was placed inside a pressure-resistant container for detonation, and the container was sealed. The container is made of iron and has a volume of 15 m ³ . As the explosive, 0.50 kg of a mixture of TNT and RDX was used. The mass ratio of TNT and RDX (TNT / RDX) in this explosive is 50/50. Next, the electric detonator was detonated and the explosive was detonated in the container (generation of nanodiamond by detonation method). Next, the temperature of the container and its inside was lowered by leaving it to stand at room temperature for 24 hours. After this cooling, the crude nanodiamond product (including the agglomerates and soot of the nanodiamond particles produced by the above detonation method) adhering to the inner wall of the container is scraped off with a spatula, The crude product was collected.

Next, an acid treatment step was performed on the crude nanodiamond product obtained by performing the above-described production steps multiple times. Specifically, a slurry obtained by adding 6 L of 10 mass% hydrochloric acid to 200 g of the crude nanodiamond product was subjected to a heat treatment for 1 hour under reflux under normal pressure conditions. The heating temperature in this acid treatment is 85 to 100 ° C. Next, after cooling, the solid content (including the nanodiamond aggregate and soot) was washed with water by decantation. The solid content was repeatedly washed with water by decantation until the pH of the precipitation liquid reached 2 from the low pH side.

Next, an oxidation process was performed. Specifically, after adding 6 L of 98% by mass sulfuric acid and 1 L of 69% by mass nitric acid to a precipitation liquid (including a nanodiamond aggregate) obtained through decantation after acid treatment, This slurry was subjected to heat treatment for 48 hours under reflux under normal pressure conditions. The heating temperature in this oxidation treatment is 140 to 160 ° C. Next, after cooling, the solid content (including the nanodiamond aggregate) was washed with water by decantation. When the supernatant liquid was colored at the beginning of washing with water, the solid content was repeatedly washed with water by decantation until the supernatant liquid became transparent visually.

Next, 1000 mL of the nanodiamond-containing liquid obtained through the above water washing treatment was subjected to spray drying using a spray drying device (trade name "Spray dryer B-290", manufactured by Nippon Büch Co., Ltd.) (drying Process). As a result, 50 g of nanodiamond powder was obtained.

0.3 g of the nanodiamond particles obtained in the above drying step was weighed into a reaction container, 13.5 g of MIBK and 1.2 g of hexyltrimethoxysilane as a silane compound were added, and the mixture was stirred for 10 minutes.

After stirring, 36 g of zirconia beads (registered trademark “YTZ”, manufactured by Tosoh Corporation, diameter 30 μm) was added. After the addition, use an ultrasonic disperser (model "UP-400s", manufactured by Heelscher) while cooling in ice water, and with the tip of the ultrasonic disperser vibrator immersed in the solution in the reaction vessel for more than 20 hours. The ND particles were reacted with the silane compound by sonication. At first, it was gray, but the particle size gradually decreased and the dispersion state improved, and finally it became a uniform, black liquid. This is because the ND particles are sequentially disintegrated (disintegrated) from the ND particle aggregates, the silane compound acts on and bonds to the ND particles in the dissociated state, and the surface-modified ND particles are dispersed and stabilized in MIBK. It is thought that it is because there is. In this way, an ND dispersion liquid (MIBK dispersion liquid) was obtained.

(Preparation of ND dispersion composition)
To 10 g of the surface-modified ND dispersion obtained above, 0.2 g of a dispersant was added and stirred, and then MIBK was distilled off by a rotary evaporator, and a dispersion medium was added to make the total weight 10 g. In this way, an ND dispersion composition was prepared. The nanodiamond concentration of the ND dispersion composition was 2% by mass. The nanodiamond concentration was determined from the absorbance at 350 nm. The dispersant and dispersion medium used in Examples 1 to 5 are as follows. The dispersants used in Examples 1 to 5 all have a structure derived from polyalkylene glycol monoalkyl ether.
Example 1
Dispersant: Mass average molecular weight 1000, amine number 19, having a structure derived from polyethylene glycol monoalkyl ether, dispersion medium: hexane Example 2
Dispersant: Dispersion medium having a mass average molecular weight of 3600, an amine value of 48, a structure derived from polypropylene glycol monoalkyl ether, a carbamate structure, and a structure derived from polycaprolactone: Hexane Example 3
Dispersant: mass average molecular weight 700, amine value 66, having a structure derived from polypropylene glycol monoalkyl ether, dispersion medium: hexane Example 4
Dispersant: Mass average molecular weight 1400, amine value 44, having a structure derived from polyethylene glycol monoalkyl ether, dispersion medium: POE
Example 5
Dispersant: Dispersion medium having a mass average molecular weight of 3600, an amine value of 48, a structure derived from polypropylene glycol monoalkyl ether, a carbamate structure, and a structure derived from polycaprolactone: POE

Comparative Examples 1 and 2
An ND dispersion composition was prepared in the same manner as in the Example except that the following was used as the dispersion medium without using the dispersant.
Comparative Example 1
Dispersion medium: Hexane Comparative Example 2
Dispersion medium: POE

(Evaluation)
Each ND dispersion composition obtained in the examples and comparative examples was evaluated as follows. The evaluation results are shown in the table.

(1) Haze value The ND dispersion compositions obtained in Examples and Comparative Examples were measured using a haze measuring device (trade name "Hazemeter 300A", manufactured by Nippon Denshoku Industries Co., Ltd.). Each sample solution used for measurement was subjected to ultrasonic cleaning for 10 minutes by an ultrasonic cleaning machine. The thickness (inner dimension) of the measuring glass cell filled with the sample liquid and used for the measurement is 1 mm, and the optical path length in the sample relating to the measurement is 1 mm. In addition, "-" in the table indicates that the measurement was not performed.

(2) D50
The ND dispersion compositions obtained in Examples and Comparative Examples were diluted with a dispersion medium to 0.1% by mass, and the particle size distribution of ND particles was measured by a device manufactured by Malvern (trade name "Zetasizer Nano ZS"). ) Was used to measure by a dynamic light scattering method (non-contact backscattering method).

(3) Dispersibility The ND dispersion compositions obtained in Examples and Comparative Examples were diluted with a dispersion medium to 0.1% by mass, and the dispersibility was visually evaluated based on the following evaluation criteria. ..
◯: Transparent and no aggregation is observed.
Δ: A little cloudy, but no aggregation could be confirmed.
X: It was cloudy and clear aggregation could be confirmed.

(4) Viscosity The ND dispersion compositions obtained in Examples and Comparative Examples were measured using an EMS viscometer (trade name “EMS1000”, manufactured by Kyoto Electronics Manufacturing Co., Ltd.). 500 μL of sample and φ2 mm aluminum balls were put in a test tube, and the temperature was 25 ° C. and the rotation speed was 1000 rpm, and measurement was performed.

As a summary of the above, the configuration of the present invention and variations thereof will be additionally described below.
[1] Organic dispersion medium,
Nanodiamond particles dispersed in the organic dispersion medium,
A dispersant having a mass average molecular weight of 500 or more and an amine value of 15 mgKOH / g or more;
A nanodiamond dispersion composition comprising:
[2] The nanodiamond dispersion composition according to [1], wherein the average dispersed particle diameter of the nanodiamond particles is 2 to 240 nm (preferably 4 to 200 nm, more preferably 10 to 180 nm, further preferably 20 to 150 nm). ..
[3] The nanodiamond dispersion composition according to [1] or [2], which has a haze value of 5 or less (preferably 3 or less, more preferably 1 or less, still more preferably 0.5 or less).
[4] The nanodiamond dispersion composition according to any one of [1] to [3], wherein the SP value of the organic dispersion medium is 6.0 to 12.0 (cal / cm) ^1/2 .
[5] The viscosity according to any one of [1] to [4], which has 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). Nano diamond dispersion composition.

[6] Any of [1] to [5], wherein the dispersant contains a compound having a structure derived from polyalkylene glycol monoalkyl ether (preferably derived from polyethylene glycol monoalkyl ether or polypropylene glycol alkyl ether). The nanodiamond dispersion composition as described in 1.
[7] The nanodiamond dispersion composition according to any one of [1] to [6], wherein the dispersant contains a compound having a carbamate structure.
[8] The nanodiamond dispersion composition according to any one of [1] to [7], wherein the dispersant contains a compound having a structure derived from polycaprolactone.
[9] The dispersant has a structure derived from polyalkylene glycol monoalkyl ether (preferably derived from polyethylene glycol monoalkyl ether or derived from polypropylene glycol alkyl ether), a carbamate structure, and a structure derived from polycaprolactone [1 ] The nano diamond dispersion composition as described in any one of [5].
[10] The nanodiamond dispersion composition according to any one of [1] to [9], wherein the dispersant has a mass average molecular weight of 650 or more (preferably 950 or more).
[11] The nanodiamond dispersion composition according to any one of [1] to [10], wherein the dispersant has a mass average molecular weight of 20,000 or less (preferably 10,000 or less).
[12] The nanodiamond dispersion according to any one of [1] to [11], wherein the dispersant has an amine value of 18 mgKOH / g or more (preferably 20 mgKOH / g or more, more preferably 30 mgKOH / g or more). Composition.
[13] The nanodiamond dispersion according to any one of [1] to [12], wherein the amine value of the dispersant is 100 mgKOH / g or less (preferably 90 mgKOH / g or less, more preferably 60 mgKOH / g or less). Composition.

[14] The SP value of the organic dispersion medium is 6.0 to 8.2 (cal / cm) ^1/2 (preferably 6.5 to 8.0 (cal / cm) ^1/2 ) [1] ~ The nanodiamond dispersion composition according to any one of [13].
[15] The SP value of the organic dispersion medium is 9.0 to 12.0 (cal / cm) ^1/2 (preferably 9.2 to 12.0 (cal / cm) ^1/2 ) [1] ~ The nanodiamond dispersion composition according to any one of [13].
[16] The content ratio of the dispersant is 90 mass% or more (95 mass% or more, more preferably 99 mass% or more) with respect to the total amount of the dispersant in the nanodiamond dispersion composition [1]. The nanodiamond dispersion composition according to any one of to [15].
[17] The content of the dispersant in the nanodiamond dispersion composition is 10 to 10000 parts by mass (preferably 50 to 1000 parts by mass) based on 100 parts by mass of the total amount of the nanodiamond particles in the nanodiamond dispersion composition. The nanodiamond dispersion composition according to any one of [1] to [16], which is a mass part, more preferably 70 to 300 mass parts.
[18] The content ratio of the nanodiamond particles is 0.01 to 5.0% by mass (preferably 0.1 to 4.0% by mass, more preferably 0.25 to 3.0% by mass, still more preferably 0.1. The nanodiamond dispersion composition according to any one of [1] to [17], which is 5 to 2.0% by mass).
[19] The content ratio of the nanodiamond particles in the nanodiamond dispersion composition is 0.1 to 2000 mass ppm, and the content of the dispersant is 1000 with respect to 100 parts by mass of the total amount of the nanodiamond particles. The nanodiamond dispersion composition according to any one of [1] to [16], which is ˜1,000,000 parts by mass (preferably 2,000 to 100,000 parts by mass, more preferably 3,000 to 50,000 parts by mass).
[20] The total content ratio of the nanodiamond particles, the dispersant, and the organic dispersion medium is 70% by mass or more (preferably 80% by mass or more, and more preferably, based on the total amount of the nanodiamond dispersion composition. 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 99% by mass or more), the nanodiamond dispersion composition according to any one of [1] to [19].

[21] The nanodiamond dispersion composition according to any one of [1] to [20], wherein the nanodiamond particles are surface-modified nanodiamonds having a silane compound bonded to the surface.
[22] The nanodiamond dispersion composition according to [21], wherein the silane compound contains a compound represented by the following formula (1-1).

[In the formula (1-1), R ¹ , R ² and R ³ are the same or different and each represents an aliphatic hydrocarbon group having 1 to 3 carbon atoms. R ⁴ represents an aliphatic hydrocarbon group having 1 or more carbon atoms. ]
[23] The nanodiamond dispersion composition according to [22], wherein R ⁴ is an aliphatic hydrocarbon group having 4 or more carbon atoms (preferably an aliphatic hydrocarbon group having 6 or more carbon atoms).
[24] The R ⁴ is an aliphatic hydrocarbon group having 25 or less carbon atoms (preferably an aliphatic hydrocarbon group having 20 or less carbon atoms, more preferably an aliphatic hydrocarbon group having 12 or less carbon atoms) [22] Alternatively, the nanodiamond dispersion composition according to [23].
[25] Any of [22] to [24], wherein the aliphatic hydrocarbon group for R ⁴ is a linear or branched alkyl group or an alkenyl group (preferably a linear or branched alkyl group). The nanodiamond dispersion composition as described in 1 above.

Claims (10)

1. An organic dispersion medium,
   Nanodiamond particles dispersed in the organic dispersion medium,
   A dispersant having a mass average molecular weight of 500 or more and an amine value of 15 mgKOH / g or more;
   A nanodiamond dispersion composition comprising:
2. The nanodiamond dispersion composition according to claim 1, wherein the average dispersed particle diameter of the nanodiamond particles is 20 to 150 nm.
3. The nanodiamond dispersion composition according to claim 1 or 2, which has a haze value of 5 or less.
4. 4. The nanodiamond dispersion composition according to claim 1, wherein the SP value of the organic dispersion medium is 6.0 to 12.0 (cal / cm) ^1/2 .
5. The nanodiamond dispersion composition according to any one of claims 1 to 4, which has a viscosity at 25 ° C of 20 to 90 mPa · s.
6. The nanodiamond dispersion composition according to any one of claims 1 to 5, wherein the dispersant contains a compound having a structure derived from polyalkylene glycol monoalkyl ether.
7. The nanodiamond dispersion composition according to any one of claims 1 to 6, wherein the dispersant contains a compound having a carbamate structure.
8. The nanodiamond dispersion composition according to any one of claims 1 to 7, wherein the dispersant contains a compound having a structure derived from polycaprolactone.
9. The nanodiamond dispersion composition according to any one of claims 1 to 8, wherein the content ratio of the nanodiamond particles is 0.01 to 5.0% by mass.
10. The nanodiamond dispersion composition according to any one of claims 1 to 9, wherein the nanodiamond particles are surface-modified nanodiamonds having a silane compound bonded to the surface.