RU2780325C1 - Surface-modified nanodiamond, a dispersed composition of nanodiamonds and a method for the production of surface-modified nanodiamond - Google Patents

Abstract

FIELD: nanotechnology.

SUBSTANCE: invention relates to the chemical industry and nanotechnology. The surface-modified nanodiamond contains nanodiamond particles and surface-modifying groups having a polyoxyalkylene chain and a silicon atom. To obtain a surface-modified nanodiamond, a nanodiamond particle is introduced into reaction with a silane binder containing a polyoxyalkylene chain. The surface-modified nanodiamond together with zirconium dioxide attached to it is used in the composite. To obtain a dispersed composition, the specified surface-modified nanodiamond is dispersed in a dispersion medium, while zirconium dioxide can be additionally introduced.

EFFECT: use of a silane binding agent having a polyoxyalkylene chain ensures the safety and high productivity of obtaining a surface-modified nanodiamond.

9 cl, 1 dwg, 8 ex

Description

Technical field

[0001]

The present invention relates to a surface-modified nanodiamond, a particulate nanodiamond composition, and a method for producing a surface-modified nanodiamond. In particular, the present invention relates to a surface-modified nanodiamond, a particulate nanodiamond composition comprising the above-mentioned surface-modified nanodiamond, and a method for producing the above-mentioned surface-modified nanodiamond. This patent application claims priority to Japanese Patent Application No. 2019-040189 filed in Japan on March 6, 2019, the contents of which are incorporated herein by reference.

State of the art

[0002]

Nanosized finely dispersed substances are known to have new characteristics that cannot be achieved in the bulk state. For example, nanodiamond particles (i.e., nanosized diamond particles) exhibit mechanical strength, high refractive index, thermal conductivity, insulating properties, anti-oxidation properties, and resin crystallization-promoting properties, and the like. However, nanodiamond particles usually have a large proportion of surface atoms, the sum of van der Waals forces that can act between the surface atoms of neighboring particles is large, and aggregation usually occurs. In addition, in the case of nanodiamond particles, the Coulomb interaction between the crystal surfaces of adjacent crystals can contribute to agglutination, which is a phenomenon in which the particles form a fairly strong cluster. Thus, it is extremely difficult to disperse nanodiamond particles so that they are in the state of primary particles in an organic solvent or resin. Therefore, the surface of the nanodiamond particles is modified so as to impart dispersibility to the nanodiamond particles to suppress aggregation.

[0003]

As surface-modified nanodiamonds, for example, nanodiamonds modified on the surface with polyethylene glycol chains (surface-modified nanodiamonds with polyethylene glycol chains) are known. Surface modification with polyethylene glycol chains can make nanodiamonds amphipathic.

[0004]

For example, Non-Patent Document 1 discloses a method for producing a nanodiamond surface modified with polyethylene glycol chains by reacting a nanodiamond having a hydroxyl group on the surface with thionyl chloride to form an acid chloride on the surface of the nanodiamond and introducing an alcohol or an amine having a polyethylene glycol chain into the subsequent reaction.

[0005]

In addition, Non-Patent Document 1 discloses a method for producing a nanodiamond surface-modified with poly-(PEGMA) by reacting the nanodiamond with 2-bromoisobutyryl bromide to introduce bromine onto the surface of the nanodiamond and subjecting polyethylene glycol methyl ester (PEGMA) methacrylate to the subsequent reaction, and polymerization.

In addition, Non-Patent Document 2 discloses a method for producing a nanodiamond surface-modified poly-(PEGMA) by introducing a specifically defined chain of a chain transfer agent onto the surface of the nanodiamond and then reacting and polymerizing the PEGMA.

[0006]

In addition, Patent Document 1, which is the closest analogue of the present invention, discloses a surface-modified nanodiamond and a method for its production, as well as a particulate composition containing a surface-modified nanodiamond. The nanodiamond surface modifying groups in Patent Document 1 contain a silicon atom and a terminal N-substituted or unsubstituted amino group, which are linked by an alkylene group. Such groups are reported in Patent Document 1 to have good reactivity with other compounds and dispersibility in dispersion media and resins. However, Patent Document 1 does not disclose nanodiamond surface modifying groups containing a polyoxyalkylene chain.

Citation list

Non-Patent Documents

[0007]

Non-Patent Document 1: Zhang, Xiaoyong. et al., Polymer, 53, 3178-3184: 2012.

Non-Patent Document 2: Zhang, Xiaoyong et al., Applied Surface Science 357, 2147-2153: 2015.

Patent Documents

Patent Document 1: WO 2018/186382 A1 (DAICEL CORP.), 10/11/2018.

The essence of the invention

Technical task

[0008]

However, the reaction with thionyl chloride disclosed in Non-Patent Document 1 is dangerous. Moreover, the reaction time is generally long. In addition, the PEGMA method disclosed in Non-Patent Documents 1 and 2 has reaction control problems due to the polymerization reaction. As described above, in the production of nanodiamond surface-modified with polyethylene glycol chains by known methods, there are problems such as hazard and poor productivity.

[0009]

Thus, it is an object of the present invention to provide a polyoxyalkylene chain surface-modified nanodiamond that is excellent in terms of safety during production and in terms of productivity. In addition, another object of the present invention is to develop a particulate nanodiamond composition in which the aforementioned surface-modified nanodiamond is dispersed. In addition, another object of the present invention is to provide a method for producing nanodiamond surface-modified with polyoxyalkylene chains, which is excellent in terms of safety and productivity.

The solution of the problem

[0010]

As a result of careful studies to achieve the above objects, it has been found that the use of a silane coupling agent having a polyoxyalkylene chain as a polyoxyalkylene chain-containing raw material that surface-modifies nanodiamond makes it possible to produce a surface-modified polyoxyalkylene nanodiamond in a manner that provides excellent safety during production and excellent performance. The present invention has been made on the basis of these discoveries.

[0011]

More specifically, the present invention provides a surface-modified nanodiamond comprising a nanodiamond particle and a surface-modifying group having a polyoxyalkylene chain and a silicon atom, wherein the nanodiamond particle is surface-modified with a surface-modifying group.

[0012]

The surface modifying group preferably contains a urethane bond.

[0013]

The polyoxyalkylene chain of the surface modifying group preferably has a number average molecular weight of 500 or more as a polyoxyalkylene.

[0014]

The surface modifying group is preferably one or more groups selected from the group consisting of groups represented by formula (1), groups represented by formula (2), and groups represented by formula (3):

[Chemical Formula 1]

In formulas (1)-(3), R ¹ is a hydrogen atom or an aliphatic hydrocarbon group. The R ² substituent is an alkylene group, and when there is more than one, any R ² substituents may be the same or different. Each of R ³ and R ⁴ , which may be the same or different, represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 3 carbon atoms, or a group represented by formula (a). X means a single bond or linking group. n means an integer 2 or more. The bonds shown by the wavy line in formulas (1)-(3) are related to the surface of the nanodiamond particle:

[Chemical formula 2]

In the formula (a) substituent R ^A means the fragment [-X-(OR ² ) _n -OR ¹ ] of the formulas (1)-(3) mentioned above. The substituents R ⁵ and R ⁶ , which may be the same or different, each represent a hydrogen atom or an aliphatic hydrocarbon group having 1 to 3 carbon atoms. Each of the indexes l and m, which may be the same or different, means an integer of 0 or more. The bond to the left of the silicon atom connects to the oxygen atom. The bond shown by the wavy line in formula (a) is connected to the surface of the nanodiamond particle. The order of linking the component link, denoted l, and the component link, denoted m, is not limited. In the case where one of l and m is an integer of 1 or more, while the other is an integer of 2 or more, the method of linking the component indicated by l and the component indicated by m may be any of random, alternating and block.

[0015]

X mentioned above includes a urethane bond.

[0016]

In addition, the present invention provides a surface-modified nanodiamond composite comprising the above-mentioned surface-modified nanodiamond and zirconia attached to the surface-modified nanodiamond.

[0017]

In addition, the present invention provides a particulate nanodiamond composition comprising a dispersion medium, wherein the surface-modified nanodiamond mentioned above is dispersed in the dispersion medium.

[0018]

The nanodiamond particulate composition mentioned above may also contain zirconium dioxide.

[0019]

In addition, the present invention provides a method for producing the aforementioned surface-modified nanodiamond, and this method includes modification by reacting the nanodiamond particle with a polyoxyalkylene chain-containing silane coupling agent.

Positive effects of the invention

[0020]

The surface-modified nanodiamond according to the present invention, in which the polyoxyalkylene chain modifies the surface, can be produced in a manner that provides excellent safety during production and excellent productivity.

Brief description of the drawings

[0021]

FIG. 1 is an enlarged schematic diagram illustrating an example of a surface-modified nanodiamond according to an embodiment of the present invention, where the surface-modified HA (ND) [1] has a surface-modifying group [3] including a polyoxyalkylene chain-containing group [4], on surface of the ND particle [2] (not shown in full).

Description of Embodiments

[0022]

Surface modified nanodiamond

A surface-modified nanodiamond according to an embodiment of the present invention (hereinafter, nanodiamond may be referred to as "ND") includes nanodiamond particles and a surface-modifying group having a polyoxyalkylene chain and a silicon atom, wherein the surface-modifying group modifies the surface of the nanodiamond particle . It should be noted that in this description, the aforementioned group having a polyoxyalkylene chain and a silicon atom may be referred to as a "surface-modifying group according to an embodiment of the present invention". The surface-modified HA according to an embodiment of the present invention may have only one type of surface-modifying groups according to the present invention, or may have two or more types thereof.

[0023]

FIG. 1 is an enlarged schematic diagram illustrating an example of a surface-modified HA according to an embodiment of the present invention, wherein the surface-modified HA [1] has a surface-modifying group (a surface-modifying group according to an embodiment of the present invention) [3], including a group containing a polyoxyalkylene chain [4] on the surface of an ND particle [2].

[0024]

The HA particle constituting the surface-modified HA preferably contains a primary nanodiamond particle. In addition, a secondary particle may be included in which several to tens of primary particles are aggregated (agglutinated). Moreover, the surface of the surface-modified HA may have one or more other surface functional groups (eg, an amino group, a hydroxyl group, and a carboxyl group) in addition to the surface-modifying group according to an embodiment of the present invention.

[0025]

As the above-mentioned HA particles, for example, detonation HA (i.e., HA produced by a detonation method) and HA of a high temperature, high pressure process (i.e., HA produced by a high temperature and high pressure method) can be used. Of these, from the point of view of excellent dispersibility in the dispersion medium, that is, from the point of view that the particle diameter of the primary particle is one digit nanometer, detonation HA is preferable.

[0026]

The detonation HA mentioned above includes air-cooled detonation HA (ie, air-cooled detonation HA) and water-cooled detonation HA (ie, water-cooled detonation HA). Of these, air-cooled detonation HA is preferable in terms of obtaining smaller primary particles compared to water-cooled detonation HA.

[0027]

The surface modifying group according to an embodiment of the present invention is a group having a polyoxyalkylene chain and a silicon atom. In the surface-modifying group according to an embodiment of the present invention, the silicon atom mentioned above is preferably located between the polyoxyalkylene chain and the HA particle which is surface-modified. The silicon atom mentioned above in the surface modifying group according to an embodiment of the present invention is preferably present as a Si-O bond. The surface-modified HA according to an embodiment of the present invention preferably has a structure where a silicon atom in the surface-modifying group according to an embodiment of the present invention is bonded to the HA particle with an oxygen atom inserted between them.

[0028]

Examples of the above polyoxyalkylene chain include a polyethylene glycol chain, a polypropylene glycol chain, a polytetramethylene glycol chain, and a polybutylene glycol chain. In addition, in each surface-modifying group according to an embodiment of the present invention, the polyoxyalkylene chain may be composed of only one type of oxyalkylene, or composed of two or more types of oxyalkylenes. Examples of a polyoxyalkylene chain composed of two or more oxyalkylenes include a polyethylene glycol-polypropylene glycol chain. In the case where the surface modifying group according to an embodiment of the present invention is composed of two or more oxyalkylenes, the bonded form of the two or more oxyalkylenes may be a random, alternating, or block form.

[0029]

The surface modifying group of an embodiment of the present invention preferably has a structure where the end of the polyoxyalkylene chain is closed with an aliphatic hydrocarbon group. More specifically, the hydrogen atom in the hydroxyl group at one end of the polyoxyalkylene chain is preferably substituted with an aliphatic hydrocarbon group.

[0030]

The aliphatic hydrocarbon group with which the end of the polyoxyalkylene chain is closed is preferably an aliphatic hydrocarbon group having 1 to 10 carbon atoms, more preferably an aliphatic hydrocarbon group having 1 to 6 carbon atoms. Examples of the aliphatic hydrocarbon group having 1 to 10 carbon atoms include straight or branched alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, t-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, and a decyl group; linear or branched alkenyl groups such as vinyl and allyl groups; and alkynyl groups such as an ethynyl group and a propynyl group. Of these groups, linear or branched alkyl groups are preferred.

[0031]

The polyoxyalkylene chain in the surface modifying group of an embodiment of the present invention has a number average molecular weight as polyoxyalkylene, preferably 100 or more (e.g., 100 to 10,000), more preferably 200 or more (e.g., 200 to 5,000), even more preferably 300 or more (eg 300 to 4000), even more preferably 400 or more (eg 400 to 2500), particularly preferably 500 or more (eg 500 to 3000).

[0032]

The average polymerization degree (number average polymerization degree) of the oxyalkylene groups in the polyoxyalkylene chain is preferably 2 to 50, more preferably 4 to 45, even more preferably 6 to 40. When the average polymerization degree is 2 or more, the steric hindrance between the surface modifying groups according to an embodiment of the present invention, it is sufficient and dispersion in the dispersion medium is facilitated. When n is 50 or less, the surface modifying groups according to an embodiment of the present invention are kept from intertwining, and dispersion in the dispersion medium is facilitated. In addition, properties as a diamond material are less likely to be degraded.

[0033]

The surface modifying group according to an embodiment of the present invention preferably includes a urethane bond. The aforementioned urethane bond is preferably between the silicon atom and the polyoxyalkylene chain in the surface modifying group according to an embodiment of the present invention.

[0034]

The surface modifying group according to an embodiment of the present invention is preferably one or more groups selected from the group consisting of the groups represented by the formula (1) below, the groups represented by the formula (2) below, and the groups represented by the formula (3) below ). The bonds shown by the wavy line in formulas (1)-(3) are connected to the surfaces of nanodiamond particles.

[0035]

[Chemical Formula 3]

[0036]

In the formulas (1)-(3) mentioned above, the substituent R ¹ means a hydrogen atom or an aliphatic hydrocarbon group. The aliphatic hydrocarbon group mentioned above is preferably an aliphatic hydrocarbon group having 1 to 10 carbon atoms, more preferably an aliphatic hydrocarbon group having 1 to 6 carbon atoms. Examples of the aliphatic hydrocarbon group having 1 to 10 carbon atoms include straight or branched alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, t-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, and a decyl group; linear or branched alkenyl groups such as vinyl and allyl groups; and alkynyl groups such as an ethynyl group and a propynyl group. Of these groups, linear or branched alkyl groups are preferred.

[0037]

In the formulas (1) to (3) mentioned above, R ² is an alkylene group, and is preferably an alkylene group having 1 to 4 carbon atoms. Examples of an alkylene group having 1 to 4 carbon atoms include an ethylene group, an isopropylene group, an isobutylene group, and a tetramethylene group. Of these, an ethylene group and an isopropylene group are preferable. The plurality of any R ² substituents may be the same or different. In the case where a plurality of R ² are different, the linkage form of the oxyalkylene chains (-OR ² ) mentioned above may be random, alternating or block form.

[0038]

In the formulas (1) to (3) mentioned, n means the average degree of polymerization (number average degree of polymerization) of oxyalkylene chains (-OR ² ) and is an integer of 2 or more. The index n is preferably an integer from 2 to 50, more preferably an integer from 4 to 45, even more preferably an integer from 6 to 40. When n is 2 or more, the steric hindrance between surface modifying groups according to an embodiment of the present the invention is sufficient, and dispersion in the dispersion medium is simplified. When n is 50 or less, the surface modifying groups according to an embodiment of the present invention are kept from intertwining, and dispersion in the dispersion medium is facilitated. In addition, properties as a diamond material are less likely to be degraded.

[0039]

In the formulas (1)-(3) mentioned above, X means a single bond or a linking group (a divalent group having one or more atoms). Examples of the linking group include a divalent hydrocarbon group, a urethane bond, a carbonyl group, an ether bond, an ester bond, a carbonate group, an amide group, and a group in which one or more groups and bonds are connected.

[0040]

Examples of the divalent hydrocarbon group include a linear or branched alkylene group having 1 to 18 carbon atoms and a divalent alicyclic hydrocarbon group. Examples of a linear or branched alkylene group having 1 to 18 carbon atoms include a methylene group, a methylmethylene group, a dimethylmethylene group, an ethylene group, a propylene group, and a trimethylene group. Examples of the divalent alicyclic hydrocarbon group include a cycloalkylene group (including a cycloalkylidene group) such as a 1,2-cyclopentylene group, a 1,3-cyclopentylene group, a cyclopentylidene group, a 1,2-cyclohexylene group, a 1,3-cyclohexylene group, 1 ,4-cyclohexylene group; and cyclohexylidene group. The number of carbon atoms in the divalent hydrocarbon group is preferably 1 to 10, more preferably 2 to 6.

[0041]

The linking group in the above X preferably includes, in particular, a urethane bond, and more preferably a group in which the urethane bond is bonded to a divalent hydrocarbon group (especially a linear or branched alkylene group). In addition, silicon atoms and divalent hydrocarbon groups (particularly straight or branched alkylene groups) in X in the formulas (1) to (3) mentioned above are preferably directly bonded. That is, X is preferably -(CH ₂ ) _k -NH-C(=O)- (C at the left end and C at the right end are linked respectively to silicon and O in the polyoxyalkylene chain). It should be noted that in the above formulas, k is an integer from 1 to 18 and preferably an integer from 1 to 6, more preferably an integer from 1 to 3.

[0042]

In the formula (1) mentioned above, the substituents R ³ and R ⁴ , which may be the same or different, each represent a hydrogen atom, an aliphatic hydrocarbon group having 1 to 3 carbon atoms, or a group represented by formula (a) below. Examples of the above aliphatic hydrocarbon group having 1 to 3 carbon atoms 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 an ethynyl group and a propynyl group. Of these groups, linear or branched alkyl groups are preferred. Note that the R ³ substituent in formula (2) is the same group as the R ³ substituent in formula (1).

[0043]

[Chemical formula 4]

[0044]

In the formula (a) mentioned above, the substituent R ^A means the fragment [-X-(OR ² ) _n -OR ¹ ]. X, R ¹ , R ² and n in R ^A each have the same meanings as those illustrated and described in the formulas (1)-(3) mentioned above, and their preferred aspects are the same. In addition, the form of binding in the presence of two or more (OR ² ) is also the same as described above. It should be noted that the bond passing to the left of the silicon atom is connected to the oxygen atom. The bond shown by the wavy line in formula (a) is bonded to the surface of the nanodiamond particle.

[0045]

In the formula (a) mentioned above, the substituents R ⁵ and R ⁶ , which may be the same or different, each represent a hydrogen atom or an aliphatic hydrocarbon group having 1 to 3 carbon atoms. Examples of the above aliphatic hydrocarbon group having 1 to 3 carbon atoms 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 an ethynyl group and a propynyl group. Of these groups, linear or branched alkyl groups are preferred.

[0046]

In the formula (a) mentioned above, the indices l and m, which may be the same or different, each represent an integer of 0 or more. The linking order of the subunit denoted l and the subunit denoted m is not particularly limited. More specifically, the silicon atom in formula (a) to be bonded to the oxygen atom in formula (1) or (2) may be the silicon atom in the subunit denoted l, or may be the silicon atom in the subunit denoted m. Similarly, the oxygen atom in formula (a) to be bonded to the R ⁶ substituent in formula (a) may be the oxygen atom in the subunit denoted l, or may be the oxygen atom in the subunit denoted m. In addition, in the case where one of l and m is an integer 1 or more, while the other is an integer 2 or more, the associated form of the constituent unit indicated by l and the constituent unit indicated by m may be any of statistical, interleaved and block.

[0047]

In the case where the surface-modified HA according to an embodiment of the present invention has a plurality of R ¹ -R ⁶ , X, l, m or n, the plurality of R ¹ -R ⁶ , X, l, m and n may be the same or different .

[0048]

It should be noted that in the formulas (1) and (2) mentioned above, the structure in which the R ³ and R ⁴ substituents are hydrogen atoms indicates the structure in which the unreacted alkoxysilyl group in the surface modifying group of the embodiment of the present invention associated with the HA particle is hydrolyzed, and the like. In addition, the structure in which the R ³ and R ⁴ substituents are aliphatic hydrocarbon groups having 1 to 3 carbon atoms indicates a structure in which the unreacted alkoxysilyl group remains in the surface modifying group according to the embodiment of the present invention, linked with an HA particle. In addition, the structure in which the substituents R ³ and R ⁴ are the groups represented by the formula (a) mentioned above indicates the structure obtained by reacting the unreacted alkoxysilyl group in the surface modifying group of the embodiment of the present invention associated with the HA particle , and another alkoxysilyl group in the surface-modifying group of an embodiment of the present invention bonded to the unreacted polyoxyalkylene chain-containing silane coupling agent described later and/or the HA particle by dehydration condensation and the like.

[0049]

The surface-modified HA according to an embodiment of the present invention may have zirconia attached (attached). A surface-modified nanodiamond according to an embodiment of the present invention with zirconia attached thereto may be referred to as a "surface-modified nanodiamond composite according to an embodiment of the present invention". More specifically, the surface-modified HA composite of an embodiment of the present invention comprises a surface-modified nanodiamond according to an embodiment of the present invention and zirconia attached to a surface-modified nanodiamond according to an embodiment of the present invention. It should be noted that the attached state of zirconia may be physical attachment (bonding, adhesion, or the like), may be chemical attachment (covalent bonding to the HA particle or surface modifying group according to an embodiment of the present invention, covalent bonding to modifying the surface groups of the present invention, bonding due to intermolecular forces, hydrogen bonding, ionic bonding, or the like), or may be both. Only one type of zirconia may be used, or two or more types of zirconia may be used.

[0050]

The surface-modified HA of an embodiment of the present invention will exhibit amphipathicity such that the surface-modifying group of an embodiment of the present invention modifies the surfaces of hydrophilic HA particles, exhibiting affinity for both water and organic solvents, or provides dispersibility with respect to different dispersion media and resin affinity such that the polarity of the HA particles is controlled by the branched structure of the polyoxyalkylene chain or the length of the alkylene chain. For this reason, surface-modified HA can be used in engineering applications such as CMP polishes, surface dressing materials, corrosion-resistant electrode coating materials for fuel cells, high hardness surface coating materials for cutting tools, etc. etc., and materials with high temperature resistance and high thermal conductivity. In addition, the surface-modified HA according to an embodiment of the present invention also exhibits high dispersibility under high salt conditions and is acceptable for use in the medical field.

[0051]

The particle size (D50) of the surface-modified HA according to an embodiment of the present invention is, for example, 400 nm or less, preferably 300 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less. The lower limit of particle size (D50) of surface-modified HA is, for example, 5 nm. In addition, the particle size (D90) is, for example, 500 nm or less, preferably 180 nm or less, more preferably 170 nm or less. The lower limit of particle size (D90) of surface-modified NA is, for example, 50 nm. The smaller particle size of surface-modified HA is preferred in terms of achieving high transparency of the composite material described below. It should be noted that the (average) particle size of the surface-modified HA can be measured using the dynamic light scattering method.

[0052]

Dispersed composition of nanodiamond

The nanodiamond particulate composition (ND particulate composition) according to an embodiment of the present invention includes a dispersion medium and a surface-modified HA according to an embodiment of the present invention dispersed in the dispersion medium.

[0053]

The dispersion medium mentioned above is a dispersion medium for surface-modified HA according to an embodiment of the present invention, and examples of the dispersion medium include water, organic solvents, and ionic liquids. Only one type of dispersion medium may be used, or two or more types of dispersion media may be used.

[0054]

Examples of the organic solvents mentioned above include aliphatic hydrocarbon solvents such as hexane, heptane and octane (especially linear saturated aliphatic hydrocarbon solvents); aromatic hydrocarbon solvents such as benzene, toluene and xylene; alicyclic hydrocarbon solvents such as cyclohexane and methylcyclohexane; aprotic polar solvents such as dimethylformamide (DMF (DMF)), dimethylacetamide, N-methylpyrrolidone and dimethylsulfoxide; halogenated hydrocarbon solvents such as chloroform, dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene and trifluoromethylbenzene; linear or cyclic ethers such as diethyl ether, diisopropyl ether, dimethoxyethane, tetrahydrofuran (THF (THF)) and dioxane; esters such as ethyl acetate and butyl acetate; linear ketones such as methyl ethyl ketone (MEK) and methyl isobutyl ketone; and nitriles such as acetonitrile. Of these solvents, cyclic ethers or linear ketones are preferred because they are particularly excellent in terms of dispersibility of the surface-modified HA of an embodiment of the present invention, and linear ketones are especially preferred.

[0055]

The HA particulate composition according to an embodiment of the present invention may include zirconia. In the case where the HA particulate composition according to an embodiment of the present invention includes zirconia, the HA particulate composition according to an embodiment of the present invention may include surface-modified HA according to an embodiment of the present invention and zirconia alone or as a composite of surface-modified ON in accordance with an embodiment of the present invention. Only one type of zirconia may be used, or two or more types of zirconia may be used.

[0056]

The relative content of HA particles in the HA particulate composition according to the embodiment of the present invention is not particularly limited, but is, for example, from 0.1 wt.h./million to 10% of the mass.

[0057]

The relative abundance of HA particles mentioned above can be calculated from the absorbance at 350 nm. It should be noted that in the case where the relative content of surface-modified HA means a low concentration (for example, less than or equal to 2000 ppm mass), the compound in which the HA particles are surface-modified can be detected using high-frequency emission spectroscopy. with inductively coupled plasma (ICP emission spectroscopy), and the percentage can be determined based on the amount detected.

[0058]

The content of the dispersion medium in the dispersed HA composition according to the embodiment of the present invention is, for example, from 90 to 99.9999% of the mass. It should be noted that the upper limit is equal to 100% of the mass.

[0059]

The relative content of zirconia in the HA particulate composition according to an embodiment of the present invention is, for example, 0.001 to 10% by mass, preferably 0.01 to 1.0% by mass, more preferably 0.05 to 0.5 % wt.

[0060]

The relative content of zirconia can be determined based on the measured amount of Zr determined by inductively coupled plasma high frequency emission spectroscopy (ICP emission spectroscopy), using as a reference a dispersion for which the relative content of Zr is known.

[0061]

The weight ratio (first/last) of zirconia to surface-modified HA particles in the HA particulate composition of an embodiment of the present invention is, for example, from 0.01 to 1.0, preferably from 0.05 to 0.75, more preferably from 0.1 to 0.5. When the weight ratio is 0.2 or more, the effect of incorporating zirconia may be more pronounced. When the weight ratio is 3.0 or less, the effect of the surface-modified HA particles can be more pronounced.

[0062]

The HA particulate composition according to an embodiment of the present invention may only include the surface-modified HA according to an embodiment of the present invention and the dispersion medium, or may contain other components. Examples of other components include, in addition to the zirconia described above, surfactants, thickeners, binders, dispersants, rust inhibitors, corrosion inhibitors, freezing point depressants, antifoam agents, antiwear additives, antiseptics, and colorants. The relative content of other components to the total amount of the dispersed composition ON according to the embodiment of the present invention is, for example, 30% of the mass. or less, preferably 20% of the mass. or less, more preferably 10% of the mass. or less, even more preferably 5% of the mass. or less, particularly preferably 1% of the mass. or less. Accordingly, the total relative content of surface-modified HA and the dispersion medium to the total amount of the dispersed HA composition in accordance with an embodiment of the present invention is, for example, 70 wt%. or more, preferably 80% of the mass. or more, more preferably 90% of the mass. or more, even more preferably 95% of the mass. or more, particularly preferably 99% of the mass. or more.

[0063]

The HA particulate composition according to an embodiment of the present invention includes the surface-modified HA according to an embodiment of the present invention in a highly dispersed state. The average particle size (D50) of the HA particles in the HA particulate composition of the present invention is, for example, 100 nm or less, preferably 60 nm or less, more preferably 50 nm or less, even more preferably 30 nm or less. The lower limit of the average size of the dispersed particles of the above-mentioned HA particles is, for example, 10 nm.

[0064]

The HA particulate composition according to an embodiment of the present invention has a haze value of preferably 5 or less, more preferably 3 or less, even more preferably 1 or less. The HA particulate composition of an embodiment of the present invention is excellent in terms of dispersibility of the surface-modified HA according to an embodiment of the present invention, and is therefore capable of producing an HA particulate composition with the above haze value. The haze value can be measured according to JIS K 7136.

[0065]

The HA particulate composition according to an embodiment of the present invention can preferably be used, for example, as an additive to composite materials to impart characteristics of fine HA particles (such as, for example, mechanical strength, high refractive index, thermal conductivity, insulating properties, antioxidant properties, a crystallization-promoting action and a dendritic-suppressing action) resin or the like. (for example, photocurable resins and thermoplastic resins). In addition, the composition obtained by adding the HA particulate composition of the present invention to the resin can preferably be used as a material such as a functional hybrid material, thermally functional (heat resistant, heat storage, heat/electrical conductive, heat insulating, etc.). ) material, photonic material (organic electroluminescent (EL) element, light-emitting diode (LED), liquid crystal display, optical disc, etc.), bio/biocompatible material, coating material, film material (such as hard coating film for touch screen , various displays, etc., and thermal barrier film), sheet material, shielding material (such as a transmissive type transparent screen), filler material (such as fillers for heat radiation or to improve mechanical properties), heat-resistant plastic substrate material ( such as flexible display substrate) and material for lithium-ion batteries containers. In addition, the HA particulate composition of an embodiment of the present invention can also be preferably used for medical applications and as a friction reducing agent or lubricant applied to a sliding portion or the like. mechanical part (for example, a car or an airplane).

[0066]

Method for the production of surface-modified nanodiamond and nanodiamond dispersed composition

The surface-modified HA of an embodiment of the present invention can be produced, for example, by modifying interacting HA particles and a polyoxyalkylene chain-containing silane coupling agent.

[0067]

The HA particles which react with the silane coupling agent preferably have hydroxyl groups on the surface. It should be noted that HA particles that are not surface modified tend to have hydroxyl groups (-OH) on the surface. As HA particles, only one type of HA particles may be used, or two or more types of HA particles may be used.

[0068]

The polyoxyalkylene chain-containing silane coupling agent is preferably a compound represented by formula (1') below. As the polyoxyalkylene chain-containing silane coupling agent, only one silane coupling agent may be used, or two or more types of silane coupling agents may be used.

[0069]

[Chemical Formula 5]

[0070]

In the above formula (1'), R ¹ , R ² , X and n each have the same meanings as those shown and described in the formulas (1) to (3) mentioned above, and their preferred aspects are also same. When two or more compounds represented by formula (1') are used, the plurality of R ¹ , R ² , X and n may be the same or different.

[0071]

In the above formula (1'), the R ⁷ substituents, which may be the same or different, represent an aliphatic hydrocarbon group having 1 to 3 carbon atoms. Examples of the above aliphatic hydrocarbon group having 1 to 3 carbon atoms 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 an ethynyl group and a propynyl group. Of these groups, linear or branched alkyl groups are preferred.

[0072]

The above modification is preferably carried out in a solvent. Examples of the solvent mentioned above include the solvents mentioned and described as the dispersion medium mentioned above. Of these solvents, the preferred solvent for use in the dispersion composition described above is HA, a cyclic ether (eg, THF), and a linear ketone (eg, MEK, MIBK). As the above solvent, only one type of solvent may be used, or two or more types of solvent may be used.

[0073]

The above modification is carried out in such a manner that a mixed solution containing the dried nanodiamond, the silane coupling agent and the solvent is stirred in the reaction vessel.

[0074]

In the aforementioned modification, in the case where aggregates (agglutinates) of HA particles with HA particles agglutinated to form secondary particles are incorporated into HA particles, a reaction between the polyoxyalkylene chain-containing silane coupling agent and the HA particles can proceed upon disintegration or dispersion of the HA particles. Therefore, aggregates of HA particles can be broken down into primary particles, the surface of HA primary particles can be modified, and the dispersibility of HA particles can be improved.

[0075]

Examples of the method for disintegrating or dispersing HA particles include methods that process HA particles using a high shear mixer, high shear mixer, homomixer, ball mill, bead mill, high pressure homogenizer, ultrasonic homogenizer, colloid mill, or jet mill . Of these, it is preferable to implement the ultrasonic treatment in the presence of a grinding medium (such as, for example, zirconia beads). It should be noted that the use of zirconia beads as the grinding medium results in the production of a composite of surface-modified HA according to an embodiment of the present invention and a particulate composition of HA containing zirconia. The ultrasonic treatment causes cavitation (microbubbles) and the jet shock that occurs during the destruction of the cavitation imparts a sufficiently large kinetic energy to the grinding medium. The grinding medium then collides with the HA aggregates and provides impact energy to release the HA particles from the HA aggregates (disintegration). The silane coupling agent then acts on and binds to the dissociated HA particles. In the case where the HA particles include HA agglutinates formed by agglutination of the HA particles, the HA agglutinates can be disintegrated to form primary particles, the surface of the HA primary particles can be modified, and surface-modified HA with excellent dispersibility can be obtained.

[0076]

The diameter of the grinding media (such as zirconia beads) is, for example, 15 to 500 µm, preferably 15 to 300 µm, and particularly preferably 15 to 100 µm.

[0077]

The ratio of HA particles to silane coupling agent (first:last, weight ratio) fed to the interaction is, for example, from 2:1 to 1:80. Moreover, the concentration of HA particles in the solvent is, for example, 0.5 to 10% by mass, and the concentration of the silane coupling agent in the solvent is, for example, 5 to 60% by mass.

[0078]

The interaction time of the HA particles and the silane coupling agent is, for example, from 4 to 20 hours. Moreover, the reaction preferably occurs while removing the generated heat using ice water or the like.

[0079]

As described above, a surface-modified HA according to an embodiment of the present invention and an HA particulate composition according to an embodiment of the present invention in which the surface-modified HA according to an embodiment of the present invention is dispersed in a dispersion medium are obtained. It should be noted that in the case where HA agglutinates remain at the end of the reaction, the liquid formed after the completion of the reaction is kept at rest, the supernatant is preferably collected and used as the dispersion composition of HA. In addition, in the case where a solvent that is preferable for the reaction in the case of surface treatment is used in the modification, once the dispersion of surface-modified HA particles is obtained, the dispersion medium in the dispersion is distilled off with an evaporator or the like, after which it is mixed again. with a new dispersion medium and mix. In other words, the HA particulate composition according to the embodiment of the present invention can also be produced by changing the solvent.

[0080]

It should be noted that HA particles can be produced, for example, by detonation. Examples of the detonation method include an air-cooled detonation method and a water-cooled detonation method. Of these, the air-cooled detonation method is preferred in terms of the ability to produce HA particles having finer primary particles compared to the water-cooled detonation method.

[0081]

In addition, 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.

[0082]

An example of a method for producing HA particles is described below; however, the HA particles used in the embodiment of the present invention are not limited to particles obtained by the following production method.

[0083]

Formation

First, a molded explosive bonded to an electric detonator is placed inside a high-pressure resistant detonation vessel, and the vessel is hermetically sealed in a state where normal-pressure atmospheric composition gas and the explosive used coexist inside the vessel. The vessel is, for example, made of iron, and the volume of the vessel is, for example, 0.5 to 40 m ³ . A mixture of trinitrotoluene (TNT) and cyclotrimethylenetrinitramine, i.e. RDX, can be used as an explosive. The weight ratio of TNT to RDX (TNT:RDX) is, for example, in the range from 40:60 to 60:40.

[0084]

The detonator is then triggered during formation to detonate the explosive in the vessel. "Detonation" refers to an explosion, including explosions associated with a chemical reaction in which the surface of the flame where the reaction occurs moves at a high speed, greater than the speed of sound. During detonation, the explosive used undergoes partial combustion and releases carbon, and this carbon is used as a starting material for the production of HA particles due to the action of pressure and energy of shock waves that arise during the explosion. Due to the Coulomb interaction between the crystal planes, as well as van der Waals forces between adjacent primary particles or crystallites, the ND-produced particles undergo very strong aggregation to form agglutinates.

[0085]

Further, during formation, the vessel and its interior are kept at rest for about 24 hours at room temperature and thereby cooled. After cooling, the crude HA particle product (comprising the soot and HA particle agglutinates formed as described above) adhering to the inner wall of the vessel is scraped off with a spatula, and as a result, the crude HA particle product is collected. By the method described above, a crude product from HA particles (crude product of HA particles) can be obtained. In addition, by performing the nanodiamond formation process described above several times as needed, a desired amount of crude product from the HA particles can be obtained.

[0086]

acid treatment

In acid treatment, a strong acid acts on the crude product of the HA particles, which is the raw material, for example, in an aqueous solvent, to remove the metal oxide. The crude HA particle product obtained by the detonation method tends to include a metal oxide, and the metal oxide is an oxide of Fe, Co, Ni or the like obtained from a vessel or the like used in the detonation method. The metal oxide can be dissolved and removed from the crude product of the HA particles, for example by treating it with a strong acid in an aqueous solvent. The strong acid used in the acid treatment is preferably a mineral acid, and examples thereof include hydrochloric acid, hydrofluoric acid, sulfuric acid, nitric acid, and aqua regia. A single type of strong acid may be used, or two or more types of strong acids may be used. The concentration of strong acid used in the acid treatment is, for example, from 1 to 50 wt%. The acid treatment temperature is, for example, 70 to 150°C. The duration of the acid treatment is, for example, from 0.1 to 24 hours. In addition, the acid treatment can be carried out under reduced pressure, at atmospheric pressure, or under pressure. After such an acid treatment, the solid content (consisting of nanodiamond agglutinates) is washed with water, for example by decanting. Preferably, the solid is washed with water by multiple decantations until the pH of the precipitated solution reaches, for example, a value of 2 to 3. If the metal oxide content of the crude HA particle product obtained by the detonation process is low, the acid treatment described above can be omitted.

[0087]

Oxidative treatment

Oxidation treatment is a process for removing graphite from the crude product of HA particles using an oxidizing agent. The crude product of the HA particles produced by the detonation process includes graphite, and this graphite is formed from carbon that has not crystallized the HA particles, this carbon being the carbon released as a result of the partially incomplete combustion of the explosive used. Graphite can be removed from the crude product of the HA particles by exposing the product to an oxidizing agent in an aqueous solvent. Moreover, due to the action of the oxidizing agent on the product, an oxygen-containing group, such as a carboxyl group or a hydroxyl group, can be introduced onto the surface of the HA particles.

[0088]

Examples of the oxidizing agent used in the oxidizing treatment include chromic acid, chromic anhydride, dichromic acid, permanganic acid, perchloric acid, nitric acid, and mixtures thereof, a mixed acid of at least one acid selected from them, and another acid ( e.g. sulfuric acid) and their salts. Of these, a mixed acid (particularly a mixed acid of sulfuric acid and nitric acid) is preferably used because such a mixed acid is environmentally friendly and exhibits excellent performance in oxidizing and removing graphite.

[0089]

The mixing ratio of sulfuric acid to nitric acid (first/last, weight ratio) in the above-described mixed acid is preferably 60:40 to 95:5, for example, because when the mixing ratio is in this range, graphite can be effectively oxidized. and removed, for example, at a temperature of 130°C or higher (particularly preferably at 150°C or higher, while the upper limit is, for example, 200°C) even at a pressure close to normal pressure (for example, from 0.5 to 2 atm). The lower limit of the mixing ratio is preferably 65:35 and more preferably 70:30. The upper limit of the mixing ratio is preferably 90:10, more preferably 85:15 and even more preferably 80:20. When the mixing ratio is not less than 60:40, the content of sulfuric acid having a high boiling point is high, and therefore the reaction temperature becomes, for example, 120° C. or higher at a pressure close to normal pressure, and hence the removal efficiency graphite is generally improved. When the mixing ratio is less than or equal to 95:5, nitric acid, which contributes greatly to the oxidation of graphite, is contained in a larger amount, and hence the graphite removal efficiency is generally improved.

[0090]

The amount of oxidizing agent (particularly a mixed acid) used is, for example, 10 to 50 parts by mass, preferably 15 to 40 parts by mass. and particularly preferably from 20 to 40 wt.h. per 1 wt.h. crude product ON particles. In addition, 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 from 15 to 30 wt.h. per 1 wt.h. crude product ON particles. In addition, 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 from 5 to 8 wt.h. per 1 wt.h. crude product ON particles.

[0091]

In addition, when using a mixed acid as an oxidizing agent, a catalyst can be used along with the mixed acid. By using a catalyst, the graphite removal efficiency can be further improved. Examples of the catalyst include copper(II) carbonate. The amount of catalyst used is, for example, from about 0.01 to 10 parts by weight. per 100 wt.h. crude product ON particles.

[0092]

The temperature of the oxidative treatment is in the range, for example, from 100 to 200°C. The duration of the oxidative treatment is, for example, from 1 to 24 hours. The oxidative treatment may be carried out under reduced pressure, at atmospheric pressure, or under pressure.

[0093]

Treatment with alkali and hydrogen peroxide

When the metal oxide is not completely removed and remains on the HA particles even after the acid treatment described above, agglutinates (secondary particles) are formed due to the very strong interaction between the primary particles, leading to aggregation. In this case, alkali and hydrogen peroxide are exposed to the HA particles in an aqueous solvent. Therefore, the metal oxide remaining on the HA particles can be removed and the separation of the primary particles from the agglutinates can be promoted. Examples of the alkali used in this treatment include sodium hydroxide, ammonia and potassium hydroxide. When treating with alkali and hydrogen peroxide, the concentration of alkali is, for example, from 0.1 to 10% by mass, the concentration of hydrogen peroxide is, for example, from 1 to 15% by mass, the temperature during treatment is in the range, for example, from 40 to 100 °C, and the processing time is, for example, from 0.5 to 5 hours. In addition, the treatment with alkali and hydrogen peroxide can be carried out under reduced pressure, at atmospheric pressure, or under pressure.

[0094]

After the above-described oxidative treatment or treatment with alkali and hydrogen peroxide, it is preferable to remove the supernatant liquid, for example, by decanting. In addition, during decantation, the solid content is preferably washed with water. The supernatant is colored after the initial water wash, and therefore the solid content is preferably washed with water repeatedly until the supernatant is visually clear.

[0095]

Disintegrating treatment

The HA particles can be subjected to a disintegrating treatment if necessary. The disintegrating treatment can be carried out using, for example, a high shear mixer, high shear mixer, homomixer, ball mill, bead mill, high pressure homogenizer, ultrasonic homogenizer or colloid mill. It should be noted that the disintegration treatment may be carried out by a wet method (for example, a disintegration treatment in a suspended state in water or the like) or may be carried out by a dry method. When the disintegration treatment is carried out in a dry manner, drying is preferably carried out before the disintegration treatment. In addition, in the case of carrying out an oxidizing treatment or a hydrogenation treatment, a disintegrating treatment may be carried out after such treatment.

[0096]

Drying

Drying is preferably carried out after treatment with alkali and hydrogen peroxide. For example, spray dryer or evaporator, etc. used for evaporating the liquid content from the solution containing HA particles obtained by treatment with alkali and hydrogen peroxide, after which the obtained solid content is dried by heating and drying in an oven. The heating and drying temperature is, for example, 40 to 150°C. As a result of such drying, HA particles are obtained.

[0097]

In addition, if necessary, the HA particles can be subjected to an oxidative treatment (eg, oxygen oxidation) or reductive treatment (eg, hydrogenation treatment) in the gas phase, if necessary. By carrying out the oxidative treatment in the gas phase, HA particles are obtained having a large number of C=O groups on the surface. In addition, by carrying out the reduction treatment in the gas phase, HA particles are obtained having a large number of C-H groups on the surface.

Example

[0098]

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

[0099]

Example 1

Surface-modified HA particles and nanodiamond dispersed composition are produced in the following way.

[0100]

Production of surface-modified HA particles

First of all, nanodiamonds are formed by the detonation method. In this formation, first, a molded explosive bonded to an electric detonator is placed inside a detonation pressure-resistant vessel, and the vessel is hermetically sealed. The vessel is made of iron and has a capacity of 15 m ³ . The explosive used is 0.50 kg of a mixture of TNT and RDX. The mass ratio of TNT and RDX (TNT:RDX) in the explosive is 50:50. An electric detonator is initiated to detonate the explosive in the vessel (detonation-forming nanodiamond). The container and its interior are then left alone for 24 hours at room temperature and cooled as a result. After cooling, the crude nanodiamond product (containing the HA particle agglutinate and soot generated by the above detonation method) that has adhered to the inner wall of the vessel is scraped off with a spatula, and the crude nanodiamond product is collected.

[0101]

The crude product of nanodiamond particles obtained by repeatedly carrying out the above-described formation is then subjected to acid treatment. More specifically, the suspension obtained by adding 6 L of 10% (wt.) hydrochloric acid to 200 g of the crude nanodiamond product is subjected to heat treatment under reflux at normal pressure for 1 hour. The heating temperature in this acid treatment is 85 to 100°C. Then, after cooling, the solid (containing nanodiamond agglutinates and carbon black) is washed with water by decanting. The solid is washed repeatedly with water until the pH of the precipitated solution reaches 2 on the low pH side.

[0102]

Then an oxidative treatment is carried out. That is, 6 L of 98% (w/w) sulfuric acid and 1 L of 69% (w/w) nitric acid are added to the precipitate solution (containing the nanodiamond aggregate) obtained by decanting after the acid treatment to form a slurry, and then the suspension is subjected to heat treatment at reflux at normal pressure for 48 hours. The heating temperature in such an oxidative treatment is 140 to 160°C. Then, after cooling, the solid (containing nanodiamond agglutinates) is washed with water by decantation. The initial supernatant from the aqueous wash is colored, so washing the solid with water by decantation is repeated until the supernatant is visually clear.

[0103]

Then, the precipitate solution (solution containing nanodiamond agglutinate) obtained by the above-described aqueous washing is subjected to drying to obtain a dried powder (nanodiamond agglutinate). In drying, evaporation to dryness by means of an evaporator is used as the drying treatment method.

[0104]

Then, 10 mmol of polyalkylene glycol (trade name "UNIOX M-1000" from NOF Corporation) was dissolved in 100 ml of THF, and 60 mmol of triethylamine was slowly added to the solution. In addition, 10 mmol of isocyanatepropyltrimethoxysilane (3-(trimethoxysilyl)propylisocyanate) (from Tokyo Chemical Industry Co., Ltd.) was added to the solution, and with the distillation tube connected, the mixture was reacted at 80°C for 48 hours. After completion of the reaction, THF is distilled off by distillation under reduced pressure with an evaporator, and triethylamine is also completely removed by keeping at 110° C. for 24 hours in a vacuum dryer. A polyoxyalkylene chain-containing silane coupling agent ([(MeO) ₃ SiC ₃ H ₆ NHC(=O)-PEG], ending: aliphatic hydrocarbon group; number average molecular weight as polyoxyalkylene: 1000) is obtained.

[0105]

In a reaction vessel, 0.30 g ^of the nanodiamond agglutinate obtained by the above drying was weighed, and 15 cm µm, from Tosoh Corporation). After adding the HA, the particles and the silane coupling agent were ultrasonicated for 15 hours using an ultrasonic dispersing machine (Model "UH-600S" from SMT Co., Ltd.) under ice water cooling under conditions where the tip of the oscillator of the ultrasonic dispersing machine was immersed. into the solution in the reaction vessel. As a result, the nanodiamond particles and the silane coupling agent containing the polyoxyalkylene chain react. The mixture initially has a gray color; however, the particle diameter gradually becomes smaller and the dispersion state becomes better. And finally, the mixture becomes a homogeneous black liquid. It is believed that this occurs because the nanodiamond particles are sequentially destroyed from the nanodiamond aggregate (disintegration), the polyoxyalkylene chain-containing silane coupling agent acts on the dissociated nanodiamond particles and binds to the particles, and the surface-modified nanodiamond particles are stably dispersed in the toluene solvent. The resulting dispersion is subjected to centrifugation at 13,000 g for 15 minutes to obtain a supernatant. As a result, a dispersion of surface-modified nanodiamond is obtained. In the resulting dispersion of surface-modified nanodiamond, the median size (particle size D50) of surface-modified nanodiamond particles measured by the above-mentioned method is 32 nm.

[0106]

Then, after adding 5 ml of acetonitrile to 1 ml of the resulting dispersion of surface-modified nanodiamond, the mixture was stirred for 5 minutes in an ultrasonic cleaner, and the appearance after one day's aging was observed to establish the optimal state of the dispersion, which was maintained. In addition, in the case where N-methylpyrrolidone is used instead of acetonitrile, the same procedure is carried out to successfully confirm the maintenance of the optimum state of the dispersion.

[0107]

Example 2

The nanodiamond particles and the polyoxyalkylene chain-containing silane coupling agent were reacted by sonication for 15 hours in the same manner as in Example 1, except for using 8 g of the polyoxyalkylene chain-containing silane coupling agent ([(MeO) ₃ SiC ₃ H ₆ NHC(=O)-PEG], ending: aliphatic hydrocarbon group; number average molecular weight as polyoxyalkylene: 2000) synthesized using 10 mmol "UNIOX M-2000" (trade name, from NOF Corporation) instead of 10 mmol "UNIOX M-1000" (trade name, from NOF Corporation) used in the modification of example 1, and using 15 cm ³ tetrahydrofuran instead of 15 cm ³ methyl ethyl ketone. After ultrasonic treatment for 15 hours, the resulting dispersion is centrifuged at 13,000 g for 15 minutes to obtain a supernatant. The median size (particle size D50) of surface-modified nanodiamond particles measured by the above method is 80 nm.

[0108]

Then, after adding 5 ml of acetonitrile to 1 ml of the resulting dispersion of surface-modified nanodiamond, the mixture was stirred for 5 minutes in an ultrasonic cleaner, and the appearance after one day's aging was observed to establish the optimal state of the dispersion, which was maintained. In addition, in the case where N-methylpyrrolidone is used instead of acetonitrile, the same procedure is carried out to successfully confirm the maintenance of the optimum state of the dispersion.

[0109]

Example 3

The nanodiamond particles and the polyoxyalkylene chain-containing silane coupling agent were reacted by sonication for 15 hours in the same manner as in Example 1, except for using 4 g of the polyoxyalkylene chain-containing silane coupling agent ([(MeO) ₃ SiC ₃ H ₆ NHC(=O)-PPG], ending: aliphatic hydrocarbon group; number average molecular weight as polyoxyalkylene: 700) synthesized using 10 mmol "UNILUBE MB-7" (trade name, from NOF Corporation) instead of 10 mmol "UNIOX M-1000" (trade name, from NOF Corporation) used in the modification of Example 1. After sonication for 15 hours, the resulting dispersion was centrifuged at 13,000 g for 15 minutes to obtain a supernatant. The median size (particle size D50) of surface-modified nanodiamond particles, measured by the method described above after 15 hours of ultrasonic treatment, is 35 nm.

[0110]

Then, after adding 5 ml of acetonitrile to 1 ml of the resulting dispersion of surface-modified nanodiamond, the mixture was stirred for 5 minutes in an ultrasonic cleaner, and the appearance after one day's aging was observed to establish the optimal state of the dispersion, which was maintained. In addition, in the case where N-methylpyrrolidone is used instead of acetonitrile, the same procedure is carried out to successfully confirm the maintenance of the optimum state of the dispersion.

[0111]

Example 4

The nanodiamond particles and the polyoxyalkylene chain-containing silane coupling agent were reacted by sonication for 15 hours in the same manner as in Example 1, except for using 4 g of the polyoxyalkylene chain-containing silane coupling agent ([(MeO) ₃ SiC ₃ H ₆ NHC(=O)-PPG], ending: aliphatic hydrocarbon group; number average molecular weight as polyoxyalkylene: 1000) synthesized using 10 mmol "UNILUBE MB-11" (trade name, from NOF Corporation) instead of 10 mmol "UNIOX M-1000" (trade name, from NOF Corporation) used in the modification of Example 1. After sonication for 15 hours, the resulting dispersion was centrifuged at 13,000 g for 15 minutes to obtain a supernatant. The median size (particle size D50) of surface-modified nanodiamond particles measured by the above method is 104 nm.

[0112]

Then, after adding 5 ml of acetonitrile to 1 ml of the resulting dispersion of surface-modified nanodiamond, the mixture was stirred for 5 minutes in an ultrasonic cleaner, and the appearance after one day's aging was observed to establish the optimal state of the dispersion, which was maintained. In addition, in the case where N-methylpyrrolidone is used instead of acetonitrile, the same procedure is carried out to successfully confirm the maintenance of the optimum state of the dispersion.

[0113]

Example 5

The nanodiamond particles and the polyoxyalkylene chain-containing silane coupling agent were reacted by sonication for 15 hours in the same manner as in Example 1, except for using 8 g of the polyoxyalkylene chain-containing silane coupling agent ([(MeO) ₃ SiC ₃ H ₆ NHC(=O)-PPG], ending: aliphatic hydrocarbon group; number average molecular weight as polyoxyalkylene: 2300) synthesized using 10 mmol "UNILUBE MB-370" (trade name, from NOF Corporation) instead of 10 mmol "UNIOX M-1000" (trade name, from NOF Corporation) used in the modification of example 1, and using 15 cm ³ tetrahydrofuran instead of 15 cm ³ methyl ethyl ketone. After ultrasonic treatment for 15 hours, the resulting dispersion is centrifuged at 13,000 g for 15 minutes to obtain a supernatant. The median size (particle size D50) of surface-modified nanodiamond particles measured by the above method is 328 nm.

[0114]

Then, after adding 5 ml of acetonitrile to 1 ml of the resulting dispersion of surface-modified nanodiamond, the mixture was stirred for 5 minutes in an ultrasonic cleaner, and the appearance after one day's aging was observed to establish the optimal state of the dispersion, which was maintained. In addition, in the case where N-methylpyrrolidone is used instead of acetonitrile, the same procedure is carried out to successfully confirm the maintenance of the optimum state of the dispersion.

[0115]

Example 6

The nanodiamond particles and the polyoxyalkylene chain-containing silane coupling agent were reacted by sonication for 15 hours in the same manner as in Example 1, except for using 8 g of the polyoxyalkylene chain-containing silane coupling agent ([(MeO) ₃ SiC ₃ H ₆ NHC(=O)-PPG-PEG], ending: aliphatic hydrocarbon group; number average molecular weight as polyoxyalkylene: 550; bound form of PPG and PEG: block), synthesized using 10 mM "UNIOX M-550" (trade name, from NOF Corporation) instead of 10 mmol "UNIOX M-1000" (trade name, from NOF Corporation) used in the modification of example 1, and using 15 cm ³ tetrahydrofuran instead of 15 cm ³ methyl ethyl ketone. After ultrasonic treatment for 15 hours, the resulting dispersion is centrifuged at 13,000 g for 15 minutes to obtain a supernatant. The median size (particle size D50) of surface-modified nanodiamond particles measured by the above method is 48 nm.

[0116]

Then, after adding 5 ml of acetonitrile to 1 ml of the resulting dispersion of surface-modified nanodiamond, the mixture was stirred for 5 minutes in an ultrasonic cleaner, and the appearance after one day's aging was observed to establish the optimal state of the dispersion, which was maintained. In addition, in the case where N-methylpyrrolidone is used instead of acetonitrile, the same procedure is carried out to successfully confirm the maintenance of the optimum state of the dispersion.

[0117]

Example 7

The nanodiamond particles and the polyoxyalkylene chain-containing silane coupling agent were reacted by sonication for 15 hours in the same manner as in Example 1, except for using 4 g of the polyoxyalkylene chain-containing silane coupling agent ([(MeO) ₃ SiC ₃ H ₆ NHC(=O)-PPG-PEG], ending: aliphatic hydrocarbon group; number average molecular weight as polyoxyalkylene: 1000; bound form of PPG and PEG: block), synthesized using 10 mM "UNILUBE 50MB-11" (trade name, from NOF Corporation) instead of 10 mmol "UNIOX M-1000" (trade name, from NOF Corporation) used in the modification of example 1. After ultrasonic treatment for 15 hours, the resulting dispersion was subjected to centrifugation at 13,000 g for 15 minutes, get the supernatant. The median size (particle size D50) of surface-modified nanodiamond particles measured by the above method is 63 nm.

[0118]

Then, after adding 5 ml of acetonitrile to 1 ml of the resulting dispersion of surface-modified nanodiamond, the mixture was stirred for 5 minutes in an ultrasonic cleaner, and the appearance after one day's aging was observed to establish the optimal state of the dispersion, which was maintained. In addition, in the case where N-methyl-pyrrolidone is used instead of acetonitrile, the same procedure is carried out to successfully confirm that the dispersion state is maintained in an optimal state.

[0119]

Example 8

The nanodiamond particles and the polyoxyalkylene chain-containing silane coupling agent were reacted by sonication for 15 hours in the same manner as in Example 1, except for using 3 g of "Dynasylan 4150" (trade name, from Evonik Industries, [(MeO ) ₃ SiC ₃ H ₆ -PEG] ending: aliphatic hydrocarbon group; number average molecular weight as polyoxyalkylene: 500) instead of 8 g of the polyoxyalkylene chain-containing silane coupling agent used in Example 1 and using 15 cm ^{3 of} tetrahydrofuran instead of 15 cm ³ methyl ethyl ketone. After ultrasonic treatment for 15 hours, the resulting dispersion is subjected to centrifugation at 13,000 g for 15 minutes to obtain a supernatant. The median size (particle size D50) of surface-modified nanodiamond particles measured by the above method is 140 nm.

[0120]

Then, after adding 5 ml of acetonitrile to 1 ml of the resulting dispersion of surface-modified nanodiamond, the mixture was stirred for 5 minutes in an ultrasonic cleaner, and the appearance after one day's aging was observed to establish the optimal state of the dispersion, which was maintained. In addition, in the case where N-methylpyrrolidone is used instead of acetonitrile, the same procedure is carried out to confirm that the HA particles are aggregated and precipitated.

[0121]

Comparative Example 1

The nanodiamond particles and the alkyl chain-containing silane coupling agent were reacted by sonication for 15 hours in the same manner as in Example 1, except for using 1.2 g of hexyl-trimethoxysilane instead of 8 g of the polyoxyalkylene chain-containing silane coupling agent used in example 1, and using 15 cm ³ tetrahydrofuran instead of 15 cm ³ methyl ethyl ketone. After ultrasonic treatment for 15 hours, the resulting dispersion is centrifuged at 13,000 g for 15 minutes to obtain a supernatant. The median size (particle size D50) of surface-modified nanodiamond particles measured by the above method is 21 nm.

[0122]

Then, after adding 5 ml of acetonitrile to 1 ml of the obtained surface-modified nanodiamond dispersion, the mixture was stirred for 5 minutes in an ultrasonic cleaner, and the appearance after one day's aging was observed to confirm that the HA particles were aggregated and deposited. In addition, in the case where N-methylpyrrolidone is used instead of acetonitrile, the same procedure is carried out to confirm that the HA particles are aggregated and precipitated.

[0123]

Particle diameter D50

The median sizes (particle sizes D50) of the nanodiamond dispersions according to the Examples and Comparative Examples obtained as described above are measured from the nanodiamond particle size distributions obtained by the dynamic light scattering method. More specifically, nanodiamond particle size distributions are determined by dynamic light scattering (non-contact backscattering method) using a "Zetasizer Nano ZS" (trade name) available from Malvern Panalytical Ltd.

[0124]

In summary, the configurations of the present invention and variations thereof are described below.

[Note 1] A surface-modified nanodiamond comprising a nanodiamond particle and a surface-modifying group having a polyoxyalkylene chain and a silicon atom, in which the nanodiamond particle is surface-modified with a surface-modifying group.

[Note 2] The surface-modified nanodiamond according to Note 1, in which the silicon atom is present as a Si-O bond in the surface-modifying group.

[Note 3] A surface-modified nanodiamond according to Note 1 or 2, in which the silicon atom has a structure associated with the nanodiamond particle, with an oxygen atom inserted between them.

[Note 4] The surface-modified nanodiamond according to any one of Notes 1 to 3, wherein the polyoxyalkylene chain includes one or more groups selected from the group consisting of a polyethylene glycol chain, a polypropylene glycol chain, a polytetramethylene glycol chain, and a polybutylene glycol chain.

[Note 5] The surface-modified nanodiamond according to any one of Notes 1 to 4, wherein the surface-modifying group has a structure with a polyoxyalkylene chain end closed with an aliphatic hydrocarbon group.

[Note 6] The surface-modified nanodiamond according to Note 5, wherein the aliphatic hydrocarbon group is an aliphatic hydrocarbon group having 1 to 10 carbon atoms (preferably an aliphatic hydrocarbon group having 1 to 6 carbon atoms, more preferably linear or branched alkyl group).

[Note 7] The surface-modified nanodiamond according to any one of Notes 1 to 6, wherein the surface-modifying group includes a urethane bond.

[Note 8] A surface-modified nanodiamond according to Note 7 having a urethane bond between a silicon atom and a polyoxyalkylene chain in the surface-modifying group.

[Note 9] The surface-modified nanodiamond according to any one of Notes 1 to 8, wherein the polyoxyalkylene chain in the surface-modifying group has, as polyoxyalkylene, a number average molecular weight of 100 or more (e.g., 100 to 10,000}, preferably 200 or more (e.g. 200 to 5000), more preferably 300 or more (e.g. 300 to 4000), even more preferably 400 or more (e.g. 400 to 2500), particularly preferably 500 or more (e.g. 500 to 3000).

[Note 10] The surface-modified nanodiamond according to any one of Notes 1 to 9, wherein the average polymerization degree (number average polymerization degree) of the oxyalkylene groups in the polyoxyalkylene chain is 2 to 50 (preferably 4 to 45, more preferably 6 to 40).

[Note 11] The surface-modified nanodiamond according to any one of Notes 1 to 10, wherein the surface-modifying group is one or more groups selected from the group consisting of groups represented by formula (1), groups represented by formula (2 ), and groups represented by formula (3):

[Chemical Formula 1]

where in formulas (1)-(3) R ¹ means a hydrogen atom or an aliphatic hydrocarbon group,

R ² is an alkylene group, and when there is more than one, any R ² may be the same or different,

each of R ³ and R ⁴ , which may be the same or different, represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 3 carbon atoms, or a group represented by formula (a) below,

X means a single bond or linking group,

n means integer 2 or more,

the bonds shown by the wavy line in formulas (1)-(3) are attached to the surface of the nanodiamond particle:

[Chemical Formula 2]

where in the formula (a) R ^A means the fragment [-X-(OR ² )n-OR ¹ ] in the formulas (1)-(3) mentioned above,

each of R ⁵ and R ⁶ , which may be the same or different, represents a hydrogen atom or an aliphatic hydrocarbon group having 1 to 3 carbon atoms,

each of l and m, which may be the same or different, means an integer 0 or greater,

the bond to the left of the silicon atom connects to the oxygen atom,

the bond shown by the wavy line in formula (a) is connected to the surface of the nanodiamond particle,

the order of linking the component link, designated l, and the component link, designated m, is not limited,

in the case where one of l and m is an integer of 1 or more, while the other is an integer of 2 or more, the linking method for the component indicated by l and the component indicated by m may be any of statistical, alternating and block.

[Note 12] The surface-modified nanodiamond according to Note 11, wherein the aforementioned X includes a urethane bond.

[Note 13] The surface modified nanodiamond according to any one of Notes 1 to 12, wherein the nanodiamond particle includes a detonation nanodiamond (preferably an air-cooled detonation nanodiamond).

[Note 14] The surface-modified nanodiamond according to any one of Notes 1 to 13, wherein a particle size (D50) is 400 nm or less (preferably 300 nm or less, more preferably 100 nm or less, even more preferably 50 nm or less).

[Note 15] The surface-modified nanodiamond according to any one of Notes 1 to 14, wherein the particle size (D90) is 500 nm or less (preferably 180 nm or less, more preferably 170 nm or less).

[Note 16] A surface-modified nanodiamond composite comprising the surface-modified nanodiamond described in any one of Notes 1 to 15 and zirconia attached to the surface-modified nanodiamond.

[Note 17] A dispersed nanodiamond composition comprising a dispersion medium and a surface-modified nanodiamond described in any one of Notes 1 to 15, wherein the surface-modified nanodiamond is dispersed in the dispersion medium.

[Note 18] The nanodiamond particulate composition according to Note 17, also including zirconia.

[Note 19] The method for producing the surface-modified nanodiamond described in any one of Notes 1 to 15, and this method includes modification by reacting the nanodiamond particle with a polyoxyalkylene chain-containing silane coupling agent.

List of reference positions

[0125]

1 Surface modified nanodiamond

2 Nanodiamond particle

3 Surface modifying group according to an embodiment of the present invention

4 Polyoxyalkylene chain containing group.

Claims (26)

1. A surface-modified nanodiamond containing nanodiamond particles and surface-modifying groups having a polyoxyalkylene chain and a silicon atom, where the nanodiamond particles are surface-modified with surface-modifying groups. 2. Surface-modified nanodiamond according to claim 1, wherein the surface-modifying group contains a urethane bond. 3. A surface modified nanodiamond according to claim 1 or 2, wherein the polyoxyalkylene chain in the surface modifying group has a number average molecular weight of 500 or more as a polyoxyalkylene. 4. The surface-modified nanodiamond according to claim 1 or 3, wherein the surface-modifying group is one or more groups selected from the group consisting of groups represented by formula (1), groups represented by formula (2), and groups represented by formula (3):

where in formulas (1)-(3) R ¹ means a hydrogen atom or an aliphatic hydrocarbon group, R ² is an alkylene group, and when there is more than one, any R ² may be the same or different, each of R ³ and R ⁴ , which may be the same or different, represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 3 carbon atoms, or a group represented by formula (a), X means a simple bond or a linking group, or a linking group that is a divalent hydrocarbon group, a urethane bond, a carbonyl group, an ether bond, an ester bond, a carbonate group, an amide group, and a group in which one or more groups and bonds are connected, n means an integer 2 or more, and the bonds shown by the wavy line in formulas (1)-(3) are attached to the surface of the nanodiamond particle;

where in formula (a) R ^A means a fragment [-X-(OR ² )n-OR ¹ ] of formulas (1)-(3), each of R ⁵ and R ⁶ , which may be the same or different, represents a hydrogen atom or an aliphatic hydrocarbon group having 1 to 3 carbon atoms, each of l and m, which may be the same or different, means an integer 0 or greater, the bond to the left of the silicon atom is connected to the oxygen atom, the bond shown by the wavy line in formula (a) is associated with the surface of the nanodiamond particle, the linking order of the subunit denoted l and the subunit denoted m is not limited, and in the case where one of l and m is an integer of 1 or more, while the other is an integer of 2 or more, the linking method for the component indicated by l and the component indicated by m may be any of statistical, alternating and block. 5. Surface-modified nanodiamond according to claim 4, wherein X contains a urethane bond. 6. Composite surface-modified nanodiamond containing surface-modified nanodiamond according to any one of paragraphs. 1-5 and zirconia attached to a surface-modified nanodiamond. 7. Dispersed nanodiamond composition containing a dispersion medium and a surface-modified nanodiamond according to any one of paragraphs. 1-5, and the surface-modified nanodiamond is dispersed in a dispersion medium. 8. Dispersed nanodiamond composition according to claim 7, additionally containing zirconium dioxide. 9. Method for the production of surface-modified nanodiamond according to any one of paragraphs. 1-5, including modification by introducing a nanodiamond particle into a reaction with a silane coupling agent containing a polyoxyalkylene chain.

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