Graphene inorganic particle composites, compositions, and formed products

Abstract

To provide graphene inorganic particle composites and compositions that can produce graphene-containing products with excellent corrosion resistance. [Solution] A graphene inorganic particle composite in which 10% to 100% of the surface area of ​​non-conductive inorganic particles is coated with surface-modified graphene.

Description

Technical Field

[0001] The present invention relates to a graphene inorganic particle composite, a composition using the same, and a formed product.

Background Art

[0002] Graphene is a two-dimensional crystal composed of carbon atoms and has been a highly regarded material since its discovery in 2004. The thin layer sheet structure of graphene has functions such as conductivity and thermal conductivity. As an example of an application utilizing the functions of graphene, a corrosion-resistant paint is cited, and by using graphene, a further improvement in corrosion resistance is expected (see, for example, Patent Document 1).

[0003] As a paint that particularly requires high corrosion resistance, a rust-preventive paint utilizing the sacrificial anticorrosion effect of zinc particles is used. Since graphene has electrical conductivity, by adding graphene to such a rust-preventive paint, the rust-preventive effect of zinc particles can be further enhanced (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] When graphene is applied to compositions such as paints, if the composition contains non-conductive particles, these particles can interfere with the connection between graphene particles, making it difficult for the properties of graphene, such as conductivity, to manifest. For example, paint compositions may contain non-conductive inorganic particles such as clay minerals called extender pigments. Because the thin sheet structure of graphene is more flexible than that of extender pigments, it can be hindered by the extender pigments, causing it to curl or fold, making it difficult to maintain the electrical network provided by the graphene. For example, Patent Document 2 proposes a system using zinc particles and graphene in combination. While the effect is achieved through the electrical connection between graphene and zinc particles, when actually applied to paint products, the composition may contain further extender pigments. As mentioned above, the extender pigments can hinder the electrical connection, and a sufficient graphene addition effect may not be obtained.

[0006] The inventors discovered that by coating the surface of non-conductive inorganic particles with graphene to give them conductivity, graphene can stably form conductive pathways through the surface of the non-conductive particles.

[0007] Graphene is expected to offer superior coverage and adhesion compared to carbon black and carbon nanotubes, as it can cover surfaces more effectively. However, to achieve uniform coverage that conforms to the surface of the substrate, it was necessary to use graphene with superior dispersibility.

[0008] In other words, the object of the present invention is to provide a composition that can yield an inorganic particle composite with excellent conductivity and a cured product with excellent corrosion resistance. [Means for solving the problem]

[0009] To solve the above problems, the present invention provides a graphene inorganic particle composite in which 10% to 100% of the surface area of ​​nonconductive inorganic particles is coated with surface-modified graphene. [Effects of the Invention]

[0010] The graphene inorganic particle composite of the present invention can provide a composition that has high conductivity and excellent corrosion resistance. [Modes for carrying out the invention]

[0011] <Graphene inorganic particle composite> The graphene inorganic particle composite of the present invention is a composite of surface-modified graphene and non-conductive inorganic particles, wherein 10% to 100% of the surface area of ​​the non-conductive inorganic particles is coated with graphene.

[0012] In this specification, "graphene" refers to graphene itself, and "graphene inorganic particle composite" refers to a composite of graphene and non-conductive inorganic particles. Furthermore, even if it further contains the surface treatment agent described later, it will also be referred to as a graphene inorganic particle composite.

[0013] In this invention, non-conductive inorganic particles have a volume resistivity of 1 × 10⁻¹⁶ according to JIS C2139 (2008). 6 These are inorganic particles with a density of Ω·cm or greater. Examples of such nonconductive inorganic particles include bentonite, talc, mica, kaolin, perlite, barium sulfate, barium carbonate, silica, alumina, potassium feldspar, soda feldspar, clay, diatomaceous earth, magnesium hydroxide, aluminum hydroxide, and may be mixtures of multiple types. Examples of inorganic particle shapes include spherical, flake-shaped, flaky, fibrous, and irregular shapes.

[0014] The graphene inorganic particle composite of the present invention is obtained by coating the surface of non-conductive inorganic particles with surface-modified graphene. By coating the surface of the non-conductive inorganic particles with graphene, conductivity is imparted, and conductive paths can be formed in a product obtained from a composition containing a curable resin and / or its precursor by the contact between the graphene inorganic particle composites.

[0015] From the viewpoint of facilitating the formation of conductive paths, the graphene coverage is 10% or more of the surface area of ​​the non-conductive inorganic particles. Furthermore, in order to form conductive paths with higher conductivity, the graphene coverage is preferably 20% or more, more preferably 50% or more, and even more preferably 60% or more. On the other hand, the graphene coverage when the entire surface of the non-conductive inorganic particles is covered is 100%, which is the maximum value. The graphene coverage of the present invention can be measured by the method described in Measurement Example 1 below. Note that the graphene coverage of the present invention can be easily adjusted by the concentration and solid-liquid ratio of the graphene dispersion liquid that comes into contact with the non-conductive inorganic particles.

[0016] In the present invention, the average particle size of the non-conductive inorganic particles is preferably 1 μm or more and 50 μm or less. By setting the average particle size of the non-conductive inorganic particles to 1 μm or more, the graphene does not overlap the surface of the non-conductive inorganic particles in multiple layers, and the surface of the non-conductive inorganic particles is uniformly coated. More preferably 5 μm or more, and even more preferably 10 μm or more. By setting the average particle size of the non-conductive inorganic particles to 50 μm or less, defects such as pinholes after curing of the composition containing the graphene inorganic particle composite and the curable resin and / or its precursor can be suppressed. From the viewpoint of further improving the corrosion resistance and conductivity of the cured product, 40 μm or less is more preferably, and even more preferably 30 μm or less.

[0017] The average particle size of non-conductive inorganic particles is determined by observation using a laser microscope, as follows: The non-conductive inorganic particles are diluted to 0.0065% by weight with an organic solvent, dropped onto a glass substrate, and dried. Next, the particle size of the non-conductive inorganic particles on the glass substrate is measured using a laser microscope. The length of the longest part (major axis) and the length of the shortest part (minor axis) of the particle are measured, and the value obtained by (major axis + minor axis) / 2 is taken as the particle size. In this way, the particle size of 50 non-conductive inorganic particles was measured randomly, and the average value was taken as the average particle size of the non-conductive inorganic particles. In the graphene inorganic particle composite after compounding with graphene, the thickness of the graphene is so thin that it is negligible compared to the average particle size of the non-conductive inorganic particles; therefore, in this invention, the particle size of the graphene inorganic particle composite can be considered as the average particle size of the non-conductive inorganic particles.

[0018] The graphene used in this invention is surface-modified with a surface treatment agent. The surface treatment agent contributes to improving dispersibility by increasing the affinity of the graphene surface to the solvent. By using graphene with excellent dispersibility, the surface of non-conductive inorganic particles can be uniformly coated, and high adhesion can be obtained.

[0019] Graphene is said to be surface-modified with a surface treatment agent if the surface-treated graphene is dispersed in water at 25°C at a weight ratio of 100 to 25°C using a high-speed disperser (e.g., Primix Homodisper) at a rotation speed of 2000 rpm for 30 minutes, followed by a washing process of suction filtration using a vacuum pump, repeated five times, and then freeze-dried, after which the surface treatment agent remains in the surface-treated graphene. The presence of the surface treatment agent can be confirmed by measuring the dried surface-treated graphene using time-of-flight secondary ion mass spectrometry (TOF-SIMS; e.g., ION-TOF TOF.SIMS5), where the surface treatment agent molecules can be detected in the form of protonated molecules in the positive secondary ion spectrum. If the surface treatment agent is a neutralized salt, it can be detected as a protonated form of the surface treatment agent molecule after the anionic molecule has been removed.

[0020] From the viewpoint of enhancing the uniformity of the coating and the adhesion to the non-conductive inorganic particles, the surface treatment agent is preferably a nitrogen-containing compound. The nitrogen atom brings a positive charge to the surface treatment agent and can be electrostatically adsorbed to the negative charge of graphene. Further, such a positive charge can also be electrostatically adsorbed to the negative charge of the non-conductive inorganic particles, contributing to further enhancing the adhesion.

[0021] The nitrogen atom preferably originates from a primary amine, a secondary amine, a tertiary amine, a quaternary ammonium salt, or a nitrogen-containing ring. It may have two or more nitrogen atoms derived from these, or may have two or more nitrogen atoms derived from each of them.

[0022] The surface treatment agent may be a low molecular weight compound or a high molecular weight compound. From the viewpoint of further improving corrosion resistance, a low molecular weight compound is preferred, and from the viewpoint of further improving durability, a high molecular weight compound is preferred. Here, a low molecular weight compound refers to a compound having a molecular weight of less than 1000, and a high molecular weight compound refers to a compound having a molecular weight of 1000 or more. Two or more surface treatment agents may be used.

[0023] When the surface treatment agent is a low molecular weight compound, in order to facilitate the attachment of the surface treatment agent to graphene, it preferably has an aromatic ring, and an aromatic compound containing nitrogen is preferably used.

[0024] Examples of nitrogen-containing aromatic compounds include 2-halogenated anilines, 3-halogenated anilines, 4-halogenated anilines, benzylamine, phenylethylamine, 1-naphthylamine, 2-naphthylamine, aniline, p-toluidine, m-toluidine, o-toluidine, 1-aminoanthracene, 2-aminoanthracene, 9-aminoanthracene, 1-aminopyrene, N-methylaniline, N-ethylaniline, N-isopropylaniline, 4-ethylaniline, 4-isopropylaniline, N,N-dimethylaniline, 4-nitroaniline, diphenylamine, N-methyldiphenylamine, 2,4,6-trimethylaniline, 4-methoxyaniline, N-methylbenzylamine, N,N-dimethylbenzylamine, N,N-diethylbenzylamine, benzamide, dopamine, phenylalanine, tyrosine, tryptophan, histidine, and their salts.

[0025] Other examples of polyamines include 1,6-diaminopyrene, 1,8-diaminopyrene, 1,4-phenylenediamine, 1,3-phenylenediamine, 1,2-phenylenediamine, 1,4-diaminoanthraquinone, 1,5-diaminonaphthalene, 1,8-diaminonaphthalene, 2,3-diaminonaphthalene, p-xylenediamine, m-xylenediamine, and 1,2,4-triaminobenzene.

[0026] Linear or branched polyetheramines are also preferably used, and are preferably liquid or waxy at room temperature. Furthermore, the polyetheramine on the surface of graphene preferably has one or more amino groups, and more preferably two or more, from the viewpoint of improving dispersibility, corrosion resistance, and adhesion.

[0027] The weight-average molecular weight of the polyetheramine is preferably 140 or more and 10,000 or less. A weight-average molecular weight of 140 or more provides excellent adhesion to the graphene surface, more preferably 200 or more, and even more preferably 500 or more. Furthermore, a weight-average molecular weight of 10,000 or less reduces the concern of clumping due to excessive adhesion, more preferably 8,000 or less, and even more preferably 6,000 or less.

[0028] The polyetheramine preferably contains a polyoxyethylene and / or polyoxypropylene structure. These structures facilitate surfactant activity and enhance the affinity between the solvent or resin and graphene. Examples of commercially available products containing such structures include PEG #200, #300, #400, #600, #1000, #2000, "Uniox" (registered trademark) M-400, M-550, M-1000, and "Uniol" (registered trademark) D-200, D-250, D-400G, D-700, D-1000, D-1200, D-2000, D-4000, etc., manufactured by NOF Corporation.

[0029] The average thickness of the graphene in this invention is preferably 0.3 nm or more and 10 nm or less. The theoretical minimum average thickness of graphene particles is 0.3 nm, indicating that it is a single layer of graphene. On the other hand, by making the average thickness of the graphene 10 nm or less, the conformability and adhesion to the surface of non-conductive inorganic particles can be improved. The average thickness of the graphene particles is more preferably 5 nm or less, and even more preferably 2 nm or less. The average thickness of the graphene in this invention can be measured by the method described in Measurement Example 2 below.

[0030] The elemental ratio of oxygen to carbon (O / C ratio) in the graphene of the graphene inorganic particle composite of the present invention, as measured by X-ray photoelectron spectroscopy, is preferably 0.05 or more and 0.60 or less. The O / C ratio represents the amount of functional groups on the graphene and serves as an indicator of dispersibility and graphene functionality. Generally, the O / C ratio of graphene obtained by physical exfoliation is often less than 0.05, while the O / C ratio of graphene obtained by chemical exfoliation is often 0.05 or more and less than 0.40. From the viewpoint of further improving the dispersibility of graphene and improving adhesion with non-conductive inorganic particles, an O / C ratio of 0.08 or more is more preferable. Furthermore, from the viewpoint of further improving the functionality of graphene such as conductivity and thermal conductivity, an O / C ratio of 0.55 or less is more preferable, 0.30 or less is even more preferable, and 0.25 or less is even more preferable.

[0031] The O / C ratio of graphene can be measured by XPS after sampling graphene from the graphene inorganic particle composite. The main C1s peak based on carbon atoms is assigned to 284.3 eV, and the O1s peak based on oxygen atoms is assigned to a peak around 533 eV. The O / C ratio is calculated from the area ratio of each peak, and the obtained value is rounded to two decimal places. The O / C ratio of graphene can be easily adjusted to the aforementioned range, for example, by adjusting the degree of oxidation of the raw material graphene oxide or the degree of reduction due to the reduction reaction conditions. The O / C ratio of the graphene inorganic particle composite of the present invention can be measured by the method described in Measurement Example 3 below.

[0032] The atomic ratio of nitrogen to carbon (N / C ratio) in the graphene of the graphene inorganic particle composite of the present invention, measured by X-ray photoelectron spectroscopy, serves as an indicator of the amount of adhesion of the aforementioned surface treatment agent when it contains nitrogen atoms. The adhesion of the nitrogen-containing surface treatment agent to the graphene enhances dispersibility in the dispersion and improves the coating of graphene on non-conductive inorganic particles. The N / C ratio of graphene is preferably 0.005 or higher, more preferably 0.010 or higher, and even more preferably 0.050 or higher. On the other hand, from the viewpoint of suppressing unintended aggregation, the N / C ratio of graphene is preferably 0.200 or lower, and even more preferably 0.150 or lower.

[0033] The N / C ratio of graphene can be measured by XPS after sampling graphene from a graphene inorganic particle composite. The main C1s peak based on carbon atoms is assigned to 284.3 eV, and the N1s peak based on nitrogen atoms is assigned to a peak around 402 eV. The N / C ratio is calculated from the area ratio of each peak, and the obtained value is rounded to the third decimal place by the fourth decimal place. The N / C ratio of graphene can be easily adjusted to the aforementioned range, for example, by the amount of surface treatment agent applied. The N / C ratio of the graphene inorganic particle composite of the present invention can be measured by the method described in Measurement Example 4 below.

[0034] <Curable resins and / or their precursors> A composition comprising the graphene inorganic particle composite of the present invention together with a curable resin and / or its precursor is preferably used. The curable resin refers to a resin that hardens by the volatilization or reaction of a solvent, and examples include epoxy resins, urethane resins, acrylic resins, polyester resins, melamine resins, silicone resins, and alkyd resins. Commercially available curable resins for paint compositions can be suitably used. Two or more of these may be included. Among these, epoxy resins, urethane resins, and acrylic resins are preferred from the viewpoint of coating properties and handling ease.

[0035] Examples of epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, and modified versions thereof such as acrylic modified epoxy resin and urethane modified epoxy resin. Two or more of these may be included. Among these, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and novolac type epoxy resin are preferred.

[0036] The epoxy equivalent of the epoxy resin is preferably between 100 and 5000. If the epoxy equivalent is 100 or more, the strength of the coating film obtained from the composition can be improved. On the other hand, if the epoxy equivalent is 5000 or less, the composition can be cured efficiently.

[0037] When an epoxy resin is included as the curable resin, it is preferable to further include an epoxy resin curing agent. Examples of epoxy resin curing agents include polyfunctional amine compounds and polyamidoamine compounds, and commercially available epoxy resin curing agents can be used. Two or more of these may be included. The active hydrogen equivalent of the epoxy resin curing agent is preferably 30 to 5000. If the active hydrogen equivalent is 30 or more, the strength of the coating film obtained from the composition can be improved. On the other hand, if the active hydrogen equivalent is 5000 or less, the composition can be cured efficiently.

[0038] The composition of the present invention may further contain conductive inorganic particles. Conductive inorganic particles, when used in combination with the graphene inorganic particle composite, promote the formation of conductive paths and can be obtained to obtain higher conductivity. In this specification, conductive inorganic particles are defined as having a volume resistivity of 1 × 10⁻⁶ 6 This refers to particles with a conductivity of less than Ω·cm. Examples of conductive inorganic particles include zinc, graphite, carbon black, carbon nanotubes, fullerenes, carbon fibers, aluminum, iron, stainless steel, titanium, copper, tin, nickel, gold, silver, and platinum. Examples of conductive inorganic particle shapes include spherical, flake-shaped, flaky, fibrous, and irregular shapes.

[0039] When the composition of the present invention is used as a protective coating, the corrosion resistance of the formed object can be further improved by selecting a material with a high sacrificial corrosion protection effect, depending on the object to be protected. For example, when used as a protective coating for steel, among the conductive inorganic particles mentioned above, zinc, aluminum, and stainless steel are preferred, with zinc being more preferred, from the viewpoint of further improving corrosion resistance.

[0040] By combining graphene inorganic particle composites with conductive inorganic particles, the viscosity of the composition and the mechanical properties of the resulting coating can be easily adjusted to a desired range.

[0041] The average particle size of conductive inorganic particles is preferably 40 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less, from the viewpoint of suppressing defects such as pinholes and further improving the corrosion resistance of the formed product. On the other hand, from the viewpoint of enhancing the sacrificial corrosion protection effect by conductive inorganic particles and further improving the corrosion resistance and durability of the formed product, it is preferably 1.0 μm or more, more preferably 3.0 μm or more, and even more preferably 5.0 μm or more. The average particle size of conductive inorganic particles can be easily adjusted to the above range using known particle grinding techniques. Alternatively, commercially available conductive inorganic particles with the desired particle size can be purchased and used.

[0042] The composition of the present invention may further contain a solvent and / or optional additives. The solvent is preferably one that can dissolve the curable resin and / or its precursor and is volatile, and can be appropriately selected depending on the coating properties of the composition.

[0043] <Formation> The products formed by the present invention include the graphene inorganic particle composite of the present invention, and refer to those formed by molding the composition of the present invention into a desired shape on a substrate or the like. For example, these include coatings and cast bodies before and after drying. Specific examples are shown below.

[0044] Forms containing the graphene inorganic particle composite of the present invention are preferably used as anti-corrosion coatings and the like. For example, a composition containing the graphene inorganic particle composite of the present invention can be used as a base material, such as a sheet, film, or metal plate, and formed into a film on the base material to obtain a formed product.

[0045] The composition containing the graphene inorganic particle composite of the present invention can be molded by coating or casting, and then cured by drying or reaction to be used as a composite material that imparts the functions of graphene, such as conductivity, thermal conductivity, and barrier properties. Furthermore, the effects are more easily obtained by forming the composition as a film on a metal substrate.

[0046] Conductive materials include, for example, coating materials such as corrosion-resistant paints and antistatic materials. Thermally conductive materials include, for example, thermally diffusive materials, heat dissipating materials, heat reflective materials, and heat-generating materials. Barrier materials include, for example, gas barrier films, impact-resistant films, and electromagnetic shielding films.

[0047] The graphene inorganic particle composite of the present invention exhibits excellent miscibility and bonding properties in resins, making it particularly effective when used in the form of coatings or films. When forming coatings or films, stress can be applied to the interface between the graphene inorganic particle composite and the resin due to shrinkage associated with resin curing, potentially leading to defects. However, by using the graphene inorganic particle composite of the present invention, the bonding properties between the graphene inorganic particle composite and the resin are enhanced, suppressing the occurrence of defects. Furthermore, because the graphene inorganic particle composite of the present invention exhibits excellent dispersibility and miscibility, the graphene inorganic particle composite can be uniformly distributed, allowing its functionality to be efficiently demonstrated.

[0048] Accordingly, compositions containing the graphene inorganic particle composite of the present invention can be suitably used, for example, as coating films, electrodes, antistatic materials, and thermal conductors. Examples of coating films include corrosion-resistant paints, waterproof paints, and impact-resistant films. Examples of electrodes include battery electrodes and sensor electrodes. Examples of thermal conductors include heat dissipation materials for electronic equipment, heat dissipation coatings for pipes, and cooling and antifreezing materials for buildings.

[0049] Examples of the aforementioned metal substrates include metal vapor-deposited films, electrode substrates such as aluminum foil and copper foil, metal housings and components for various electronic components, and steel housings and structures (vehicles such as automobiles and ships, structures such as bridges and steel bridges, factory equipment, etc.).

[0050] The composition of the present invention can be suitably used as a coating film formed by applying it to a substrate and drying it. Examples of application methods include applicator application, bar coating, spin coating, roller application, brush application, and spray application. The drying method can be appropriately selected depending on the solvent, resin, and application, and examples include natural drying, heat drying, and hot air drying.

[0051] The composition of the present invention may be used, for example, by injecting it into a crack and curing it by drying and / or a crosslinking reaction. Known methods can be used for injection and curing.

[0052] The composition of the present invention, formed in a film-like manner on a substrate, exhibits excellent corrosion resistance and durability. A low corrosion potential, which indicates resistance to corrosion, is preferable. Specifically, the corrosion potential measured by the method described in Measurement Example 8 below is preferably -0.9V or less, and more preferably -1.0V or less.

[0053] As an indicator of corrosion resistance and durability, it is preferable that the time to reach a score of 3 (width of red rust in the cut area is 2 mm) in a salt spray resistance test conducted by the method described in Measurement Example 9 below be longer. The time to reach a salt spray resistance score of 3 is preferably 700 hours or more, more preferably 800 hours or more, and even more preferably 1000 hours or more.

[0054] <Method for manufacturing graphene inorganic particle composites> The graphene inorganic particle composite of the present invention can be prepared by stirring and mixing non-conductive inorganic particles in a graphene dispersion, followed by filtration, concentration, washing, and drying. The graphene dispersion can be prepared, for example, by mixing graphene oxide and a surface treatment agent in a solvent, then micronizing the graphene oxide, and subsequently subjecting it to a reduction treatment. To further improve the dispersibility of graphene, it is preferable to have a filtration and concentration step and a redispersion step, which will be described later.

[0055] [Graphene oxide] Examples of methods for producing graphene oxide include the Hammers process. Alternatively, commercially available graphene oxide can be purchased. The following is an example of a method using the Hammers process for producing graphene oxide.

[0056] While in an ice bath, add graphite (calcium powder) and sodium nitrate to concentrated sulfuric acid and stir, gradually adding potassium permanganate while keeping the temperature from rising, and stirring for 0.2 to 5 hours while maintaining a temperature range of 25 to 50°C. Then, dilute with deionized water to make a suspension and stir at a temperature range of 80 to 100°C for 5 to 50 minutes. After that, add hydrogen peroxide and deionized water and stir for 1 to 30 minutes to obtain a graphene oxide aqueous dispersion. Filter and wash the obtained graphene oxide aqueous dispersion to obtain a graphene oxide wet cake.

[0057] Natural graphite is preferred as the graphite, and the mesh count is preferably 5000 or less. For 10g of natural graphite, the amount of sodium nitrate added is preferably 2-8g, the amount of concentrated sulfuric acid added is preferably 150-300ml, the amount of potassium permanganate added is preferably 10-40g, the amount of hydrogen peroxide added is preferably 40-80g, and the amount of deionized water added is preferably 10-20 times the amount of hydrogen peroxide added. The degree of oxidation of graphene oxide can be adjusted to a desired range by, for example, the amount of oxidizing agent added, such as sodium nitrate or potassium permanganate. Specifically, the ratio of the amount of sodium nitrate added to graphite (sodium nitrate / graphite) is preferably 0.200 to 0.800, and the ratio of the amount of potassium permanganate added to graphite (potassium permanganate / graphite) is preferably 1.0 to 4.0.

[0058] [Surface treatment process] Next, the graphene oxide and the surface treatment agent are mixed to allow the surface treatment agent to adhere to the graphene oxide. To ensure good mixing of the graphene oxide and the surface treatment agent, it is preferable to mix them while both are dispersed in the solvent. Ideally, both the graphene oxide and the surface treatment agent should be completely dissolved, but it is acceptable for some to remain dispersed as solids without dissolving. For mixing methods, dispersers employing dispersers such as the disperser stirring type or rotor / stator type are preferred. Examples of such dispersers include the "Labo-lution" (registered trademark) Homodisper 2.5 type (Primix Corporation), Disperser PH91 (SMT Corporation), and "Silverson Mixer" (registered trademark) L5M-A (Silverson Nippon Corporation).

[0059] [Refining process] Next, it is preferable to refine the graphene oxide in a solvent. Examples of refinement methods include applying ultrasound to a graphene oxide dispersion, colliding a pressured graphene oxide dispersion with ceramic balls, and using a liquid-liquid shear type wet jet mill to collide pressured graphene oxide dispersions with each other.

[0060] [Reduction Process] Next, graphene oxide is reduced in a solvent. Chemical reduction is preferred as the reduction method. In the case of chemical reduction, organic reducing agents and inorganic reducing agents can be used. Among these, inorganic reducing agents are preferred due to the ease of washing after reduction, and sodium dithionite and potassium dithionite are more preferred.

[0061] [Filtration and concentration process] Next, the graphene obtained in the reduction step is filtered and concentrated. The filtration and concentration step is a step in which a portion of the solvent in the reduced graphene dispersion is removed by filtration to obtain a graphene dispersion. Known methods can be used for filtration, and vacuum suction filtration is preferred from the viewpoint of suppressing graphene stacking. After the reduction step and before the solvent replacement step, a washing step may be performed in which the graphene is diluted with a solvent and filtered for the purpose of removing the reducing agent. This operation may also be repeated multiple times. In the present invention, it is preferable to perform the filtration and concentration step and the redispersion step described later two or more times. On the other hand, in the present invention, it is preferable to perform the filtration and concentration step and the redispersion step described later six or fewer times.

[0062] [Redispersion process] Next, the graphene dispersion obtained in the filtration and concentration step is redispersed in an organic solvent. In the present invention, it is preferable to filter and concentrate the graphene dispersion after the redispersion step again, which can eliminate stacking of graphene particles and further improve dispersibility.

[0063] In the redispersion process, it is preferable to stir the slurry, which is a mixture of the graphene dispersion and an organic solvent, using a disperser that employs a disperser stirring type, rotor / stator type, or the like. The higher the peripheral speed when stirring the slurry, the more efficiently the graphene layers stacked by shear force can be detached, thus eliminating stacks and further improving dispersibility. Examples of such dispersers include the Lab-Solution Homodisper 2.5, Disperser PH91, and Silverson Mixer L5M-A.

[0064] The solid content concentration of the graphene dispersion obtained in the redispersion process can be measured by the method described in Measurement Example 5 below.

[0065] [Composite formation process with non-conductive inorganic particles] Next, non-conductive inorganic particles are stirred and mixed into the graphene dispersion obtained in the redispersion step to coat the surface of the non-conductive inorganic particles with graphene, thereby obtaining a graphene-inorganic particle composite. In the composite step, it is preferable to stir the slurry of the graphene dispersion and non-conductive inorganic particles using a disperser, rotor / stator type, or the like. It is preferable to wash the graphene-inorganic particle composite by removing a portion of the solvent from the slurry containing the graphene-inorganic particle composite obtained in this way by filtration concentration, mixing in the solvent again and stirring, and then removing a portion of the solvent again by filtration concentration. In the present invention, it is preferable to wash the graphene-inorganic particle composite two or more times as described above. After washing, the slurry may be re-slurried using the solvent again, and then the solvent and excess graphene may be removed using a mesh finer than the particle size of the graphene-inorganic particle composite. The obtained graphene-inorganic particle composite is dried to remove the solvent and powderize it. Drying methods include hot air drying, vacuum drying, and freeze-drying.

[0066] <Method for producing the composition> Next, an example of a method for producing a composition using a graphene inorganic particle composite will be described. For example, a method of mixing the graphene inorganic particle composite with a curable resin and / or its precursor, conductive inorganic particles, and optionally a solvent and any additives may be used. The graphene inorganic particle composite and the conductive inorganic particles may be added and mixed simultaneously, or they may be added and mixed separately. From the viewpoint of further improving the dispersibility of the graphene inorganic particle composite, it is preferable to mix the graphene inorganic particle composite and the conductive inorganic particles in a solution in which the curable resin and / or its precursor are dissolved in a solvent.

[0067] Mixing equipment includes, for example, bead mills, homodispers, homomixers, planetary mixers, sand mills, and other mixers and kneaders.

[0068] If the composition of the present invention contains a curable resin precursor, the main component (e.g., epoxy resin) and the curing agent (e.g., epoxy resin curing agent) may be stored in separate containers until immediately before use. In this case, the graphene inorganic particle composite and the conductive inorganic particles may be contained in the main component or in the curing agent. [Examples]

[0069] The present invention will be described below using examples. First, the evaluation methods in each example and comparative example will be explained.

[0070] [Measurement Example 1: Graphene Coverage (%)] The graphene coverage of the graphene inorganic particle composites prepared according to each example and comparative example was measured by electron microscopy. Each graphene inorganic particle composite prepared according to each example and comparative example was diluted to 0.0065% by weight with n-butanol, and 1 μL was dropped onto aluminum foil and dried to adhere to the foil. Using a field emission scanning electron microscope (FE-SEM) S-5500 (Hitachi High-Tech Corporation), the magnification was adjusted so that the graphene inorganic particle composite on the aluminum foil filled the entire field of view. The coverage was calculated from the number of graphene pixels covering the surface of the graphene inorganic particle composite relative to the total number of pixels in the graphene inorganic particle composite image. The coverage of 20 randomly selected different graphene inorganic particle composites was measured, and the arithmetic mean was calculated.

[0071] [Measurement Example 2: Average thickness of graphene (nm)] The graphene inorganic particle composites prepared in each example and comparative example were diluted with N-methylpyrrolidone to a concentration of 0.001% by weight, and diluted using a Homodisper 2.5 type (Primix) at a rotation speed of 3000 rpm for 30 minutes to prepare a dilution. The prepared dilution was dropped onto a PET film, dried, and embedded in resin, then cross-sectioned by ion milling to prepare observation samples. The observation samples were observed using a transmission electron microscope JEM-F200 (JEOL Ltd.) at an accelerating voltage of 200 kV. The graphene layer on the surface of one graphene inorganic particle composite was magnified to an appropriate magnification so that it was within the field of view, and the thickness of the graphene particles was measured at five randomly selected locations on the graphene inorganic particle composite. The arithmetic mean was calculated, and the same analysis was performed on 10 randomly selected graphene inorganic particle composites. The arithmetic mean was calculated and rounded to the first decimal place.

[0072] [Measurement Example 3: O / C ratio of graphene] The graphene dispersions prepared according to each example and comparative example were subjected to photoelectron spectroscopy using the Quantera SXM X-ray photoelectron spectroscopy analyzer (ULVAC-PHI). The excitation X-ray was monochromatic AlK α1,2 The X-ray beam was set to 1486.6 eV, with an X-ray diameter of 200 μm and a photoemission angle of 45°. The main C1s peak, based on carbon atoms, was assigned to 284.3 eV, and the O1s peak, based on oxygen atoms, was assigned to a peak around 533 eV. The O / C ratio was calculated from the area ratio of the O1s peak to the C1s peak, and the resulting value was rounded to two decimal places.

[0073] When extracting and measuring graphene from a graphene inorganic particle composite, prepare an N-methylpyrrolidone dilution of the graphene inorganic particle composite in the same manner as in Measurement Example 2. Centrifuge at 5000 rpm using a small centrifuge H-112 (Kokusan Co., Ltd.), collect the supernatant, concentrate it by vacuum filtration, and vacuum dry it to extract graphene from the graphene inorganic particle composite. The graphene obtained in this way is then measured in the same manner.

[0074] [Measurement Example 4: N / C ratio of graphene] The graphene dispersions prepared according to each example and comparative example were subjected to photoelectron spectroscopy using an X-ray photoelectron spectroscopy analyzer, Quantera SXM (ULVAC-PHI). The excitation X-ray was monochromatic AlK α1,2 The X-ray beam was set to 1486.6 eV, with an X-ray diameter of 200 μm and a photoelectron escape angle of 45°. The main C1s peak, based on carbon atoms, was assigned to 284.3 eV, and the N1s peak, based on nitrogen atoms, was assigned to a peak around 402 eV. The N / C ratio was calculated from the area ratio of the N1s peak to the C1s peak, and the resulting value was rounded to the third decimal place.

[0075] When extracting and measuring graphene from a graphene inorganic particle composite, prepare an N-methylpyrrolidone dilution of the graphene inorganic particle composite in the same manner as in Measurement Example 2. Centrifuge at 5000 rpm using a small centrifuge H-112 (Kokusan Co., Ltd.), collect the supernatant, concentrate it by vacuum filtration, and vacuum dry it to extract graphene from the graphene inorganic particle composite. The graphene obtained in this way is then measured in the same manner.

[0076] [Measurement example 5: Solid content concentration (wt%)] The graphene dispersions prepared according to each example and comparative example were placed in aluminum cups of known weight and their weight was measured. The dispersions were then heated on a hot plate set to 120°C for 1.5 hours to evaporate the solvent. The solid content concentration of the graphene dispersion was calculated from the weight of the dispersion before heating and the amount of solvent evaporated (calculated from the weight difference before and after heating). This process was repeated three times, and the average value was calculated.

[0077] The solid content concentration of the graphene oxide wet cake prepared according to Synthesis Example 1 was measured in the same manner as the measurement of the solid content concentration of the graphene dispersion, except that the temperature was adjusted to 100°C.

[0078] [Measurement example 6: Paint film resistance (Ω cm)] The compositions prepared according to each example and comparative example were spray-applied onto a 50 μm thick A4-sized PET film, dried at room temperature, and allowed to cure for one week to form a 100 μm thick cured film. The coating resistance of the obtained cured film was measured using a resistivity meter "Highresta-UX" (registered trademark) MCP-HT800 (Nitto Seikou Analytech Co., Ltd.).

[0079] [Measurement Example 7: Number of Defects] In the same manner as in Measurement Example 6, the material was applied to a 50 μm thick A4-sized PET film using a spray, dried at room temperature, and allowed to harden for one week to form a 70 μm thick cured film. The surface of the obtained cured film was observed at 100x magnification using an optical microscope, and the presence or absence of defects such as cracks and pinholes was observed at 10 randomly selected locations. The corrosion resistance was evaluated based on the number of locations where defects were observed. The fewer the locations where defects were observed, the better the corrosion resistance.

[0080] [Measurement Example 8: Corrosion Potential (V)] The compositions prepared according to each example and comparative example were applied using a spray gun to a sandblasted general structural rolled steel sheet (material: SS400) measuring 15 cm × 7 cm × 0.8 cm thick, dried at room temperature, and left to stand for one day to form a cured film. The thickness of the cured film was adjusted to 70 ± 10 μm. For exposed areas of the substrate where the cured film had not formed, a commercially available rust-preventive paint (Nippon Paint Co., Ltd. "Zinky" (registered trademark) 8000HB) was applied using a brush, dried, and left to stand for one week to cure, obtaining a test plate. The test plate was connected to the working electrode of a potentiostat Model 1480A (Solartron analytical), a platinum electrode to the counter electrode, and a silver-silver chloride electrode to the reference electrode. The test plate was immersed in 300 mL of a 3.5 wt% sodium chloride aqueous solution (pH=7) at room temperature in a 500 mL beaker, and measurements were started. The measurement was performed by first stabilizing the circuit in an open circuit for an initial 900 seconds, and then sweeping the voltage from -0.2V to +0.5V at a speed of 0.003V / s in voltage sweep mode, measuring the current value. The absolute values ​​of the obtained current values ​​were plotted, and the voltage at which the current value was minimum was defined as the corrosion potential. The lower the corrosion potential (the larger the absolute value), the better the corrosion resistance.

[0081] [Measurement Example 9: Saltwater spray resistance time (h)] A test plate was obtained in the same manner as in Measurement Example 8. A straight cut 5 cm long and 0.5 to 1.0 mm deep was made in the center of the test plate, and it was set in a salt spray test apparatus (STP-30, Suga Test Instruments Co., Ltd.). After starting the salt spray test using a 5 wt% sodium chloride aqueous solution (pH=7) heated to 35°C, each sample was scored according to the rust formation status as described below, the change over time was recorded, and the durability was evaluated from the time it took to reach a score of 3. Score 0: Close to the initial state, with no red rust observed. If zinc is used, white rust may be seen due to the sacrificial corrosion protection effect, but no red rust is observed. Score 1: Red rust is visible throughout the cut area. Score 2: Red rust less than 2 mm wide is observed throughout the cut area, and there is at least one area around the cut where blistering of the hardened film or pitting corrosion outside the cut area has occurred and red rust is observed. Score 3: Multiple blisters and pitting corrosion are observed around the cut area, and the width of the red rust at the cut area is 2 mm or more.

[0082] [Synthesis Example 1: Method for preparing a graphene oxide dispersion] Using 1500-mesh natural graphite powder (Shanghai Yifan Graphite Co., Ltd.) as the raw material, 10 g of natural graphite powder was placed in an ice bath, to which 220 ml of 98% concentrated sulfuric acid, 5 g of sodium nitrate, and 30 g of potassium permanganate were added and stirred for 1 hour, maintaining the temperature of the mixture below 20°C. This mixture was removed from the ice bath and stirred in a 35°C water bath for 4 hours, then 500 ml of deionized water was added, and the resulting suspension was stirred at 90°C for a further 15 minutes. Finally, 600 ml of deionized water and 50 ml of hydrogen peroxide were added, and the mixture was stirred for 5 minutes to obtain a graphene oxide dispersion. The obtained graphene oxide dispersion was filtered, metal ions were washed with dilute hydrochloric acid solution, and the acid was washed with deionized water. The washing was repeated until the pH reached 7, and the mixture was concentrated by suction filtration to prepare a graphene oxide wet cake. The solid content concentration of the prepared graphene oxide wet cake, as measured according to Measurement Example 5, was 45% by weight. 11.1 g of the obtained graphene oxide wet cake (5.0 g of graphene oxide solids) was mixed with 988.9 g of deionized water, and stirred for 30 minutes at a rotation speed of 10,000 rpm using a rotor / stator type Silverson mixer L5M-A to obtain 1,000 g of graphene oxide dispersion with a graphene oxide concentration of 0.5% by weight.

[0083] [Example 1] (Method for preparing graphene dispersion) Surface treatment agent mixing step: 1000 g of graphene oxide dispersion prepared according to Synthesis Example 1 was mixed with an aqueous sodium hydroxide solution to adjust the pH to 8.5, and 2.5 g of dopamine hydrochloride (Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a surface treatment agent. The mixture was then stirred for 30 minutes at a rotation speed of 10,000 rpm using a rotor / stator type Silverson mixer L5M-A.

[0084] Miniaturization process: The graphene oxide dispersion after surface treatment was subjected to ultrasonic waves at an output of 300W for 30 minutes using an ultrasonic device UP400S (Hielscher).

[0085] Reduction process: 25.0 g of sodium dithionite (Fujifilm Wako Pure Chemical Industries) was added to the graphene oxide dispersion after micronization treatment, and the mixture was kept warm at 40°C. The mixture was then stirred for 30 minutes at 10,000 rpm using a rotor / stator type Silverson mixer L5M-A to carry out the reduction reaction and obtain a graphene dispersion.

[0086] Filtration and Concentration Step: The obtained graphene dispersion was filtered using a vacuum suction filter to obtain a graphene dispersion. 100.0 g of the obtained graphene dispersion was mixed with 1000 g of deionized water, and redispersion was performed by stirring at 10,000 rpm for 10 minutes using a rotor / stator type Silverson mixer L5M-A. The resulting redispersed graphene solution was subjected to a second filtration and concentration step to obtain a graphene dispersion. The solid content concentration of the graphene dispersion measured according to Measurement Example 5 was 3.0% by weight.

[0087] Redispersion step: 50.0 g of the obtained graphene dispersion was mixed with 300.0 g of n-butanol (Fujifilm Wako Pure Chemical Industries, Ltd.), and the mixture was stirred for 10 minutes at 10,000 rpm using a rotor / stator type Silverson mixer L5M-A to perform the first redispersion. The obtained graphene redispersion was filtered and concentrated, and 48.0 g of the obtained graphene dispersion was mixed with 288.0 g of n-butanol, and the mixture was stirred for 10 minutes at 10,000 rpm using a rotor / stator type Silverson mixer L5M-A to perform the second redispersion. The obtained second redispersion was filtered and concentrated to obtain a graphene dispersion with a solid content of 3.0 wt%. The obtained graphene dispersion was mixed with n-butanol to a solid content of 1.5 wt%, and the mixture was stirred for 5 minutes at 5,000 rpm using a Lab-Solution Homodisper 2.5 to obtain a graphene dispersion.

[0088] The physical properties of the obtained graphene dispersion were measured using the methods described in Measurement Example 3 and Measurement Example 4, and the results are shown in Table 2.

[0089] (Method for fabricating graphene inorganic particle composites) 67 g of the obtained graphene dispersion (1.0 g graphene solid weight) was mixed with 50 g of "Talcan Powder" (registered trademark) PK-C (average particle size 12.1 μm) manufactured by Hayashi Co., Ltd. as talc, and stirred with a magnetic stirrer at 400 rpm for 30 minutes. The obtained graphene-talc mixture was filtered and concentrated, and 200 g of N-methylpyrrolidone was added to the concentrate, and stirred with a Lab-Solution Homodisper 2.5 at 3000 rpm for 30 minutes. The obtained graphene-talc mixture was filtered and concentrated again, and dried at 120°C for 2 hours to obtain a graphene inorganic particle composite.

[0090] The physical properties of the obtained graphene inorganic particle composites were measured using the methods described in Measurement Example 1 and Measurement Example 2, and the results are shown in Tables 1 and 2.

[0091] (Method for preparing the composition) 8.2 g of "Epiclon" (registered trademark) 1050 (bisphenol A type epoxy resin, epoxy equivalent 450-500 g / eq, DIC Corporation) was weighed out as the epoxy resin, 18 g of xylene and 2 g of n-butanol were added, and the mixture was heated to 90°C to dissolve. The mixture was then stirred for 20 minutes at 3000 rpm using a Lab-Solution Homodisper 2.5 type. 3.6 g of bentonite and 40 g of graphene inorganic particle composite were added to the resulting solution and the mixture was stirred for 20 minutes at 3000 rpm using a Lab-Solution Homodisper 2.5 type. 40 g of zinc powder (average particle size 10 μm, Hayashi Pure Chemical Industries, Ltd.) was further added and the mixture was stirred for 30 minutes at 3000 rpm using a Lab-Solution Homodisper 2.5 type. 11.7 g of Newmid 515 (trade name, Harima Chemicals Group Co., Ltd.) (polyamidoamine, active hydrogen equivalent 185, solid content 70% by weight, solid weight 8.2 g) was added as an epoxy resin curing agent, and the mixture was further homogenized by stirring at 3000 rpm for 10 minutes using a Lab-Solution Homodisper 2.5 type to prepare the composition.

[0092] The corrosion resistance and durability of the obtained compositions were evaluated using the methods described in Measurement Examples 6 to 9, and the results are shown in Table 2.

[0093] [Example 2] In the preparation of the graphene inorganic particle composite in Example 1, the amount of graphene dispersion was changed to 50 g (graphene solid weight 0.75 g), and 17 g of n-butanol was added as the solvent, but otherwise the graphene inorganic particle composite was prepared in the same manner. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0094] [Example 3] In the preparation of the graphene inorganic particle composite in Example 1, the only difference was that the amount of graphene dispersion mixed was changed to 33.5 g (0.5 g graphene solid weight) and 33.5 g of n-butanol was added as the solvent. The graphene inorganic particle composite was prepared in the same manner as in Example 1. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0095] [Example 4] In the preparation of the graphene inorganic particle composite in Example 1, the amount of graphene dispersion was changed to 13.3 g (graphene solid weight 0.2 g), and 53.7 g of n-butanol was added as the solvent, but otherwise the graphene inorganic particle composite was prepared in the same manner. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0096] [Example 5] In the preparation of the graphene inorganic particle composite in Example 1, the amount of graphene dispersion was changed to 8.0 g (graphene solid weight 0.12 g), and 59.0 g of n-butanol was added as the solvent, but otherwise the graphene inorganic particle composite was prepared in the same manner. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0097] [Example 6] In the preparation of the graphene dispersion in Example 1, the graphene dispersion was prepared in the same manner as in Example 1, except that the surface treatment agent was changed to 1,4-phenylenediamine (Tokyo Chemical Industries Co., Ltd.) in the surface treatment agent mixing step. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0098] [Example 7] In the preparation of the graphene dispersion in Example 1, the graphene dispersion was prepared in the same manner as in Example 1, except that the surface treatment agent was changed to phenylethylamine hydrochloride (Tokyo Chemical Industries Co., Ltd.) in the surface treatment agent mixing step. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0099] [Example 8] In the preparation of the graphene dispersion in Example 1, the graphene dispersion was prepared in the same manner as in Example 1, except that the amount of surface treatment agent mixed in the surface treatment agent mixing step was changed to 0.04 g. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0100] [Example 9] In the preparation of the graphene oxide dispersion in Synthesis Example 1, the degree of oxidation was changed by using 4.0 g of sodium nitrate and 21.0 g of potassium permanganate, but otherwise the same procedure was followed to prepare the graphene oxide dispersion. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0101] [Example 10] In the preparation of the graphene dispersion in Example 1, the degree of oxidation was changed by using 2.0 g of sodium dithionite, but otherwise the graphene dispersion was prepared in the same manner. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0102] [Example 11] In the preparation of the graphene oxide dispersion for Synthesis Example 1, the degree of oxidation was changed by using 4.3 g of sodium nitrate and 24.0 g of potassium permanganate, but otherwise the same procedure was followed to prepare the graphene oxide dispersion. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0103] [Example 12] In the preparation of the graphene oxide dispersion for Synthesis Example 1, the degree of oxidation was changed by using 5.8 g of sodium nitrate and 37.0 g of potassium permanganate, but otherwise the same procedure was followed to prepare the graphene oxide dispersion. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0104] [Example 13] In the preparation of the graphene oxide dispersion for Synthesis Example 1, the degree of oxidation was changed by using 7.7 g of sodium nitrate and 38.0 g of potassium permanganate, but otherwise the same procedure was followed to prepare the graphene oxide dispersion. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0105] [Example 14] In the preparation of the graphene oxide dispersion for Synthesis Example 1, the degree of oxidation was changed by using 7.5 g of sodium nitrate and 37.4 g of potassium permanganate, but otherwise the same procedure was followed to prepare the graphene oxide dispersion. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0106] [Example 15] In the preparation of the graphene dispersion of Example 1, the surface treatment agent was changed to 1,5-diaminonaphthalene (Tokyo Chemical Industries Co., Ltd.) in the surface treatment agent mixing step, and the amount of surface treatment agent mixed was changed to 0.075 g. The graphene dispersion was prepared in the same manner as in Example 1. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0107] [Example 16] In the preparation of the graphene dispersion in Example 1, the surface treatment agent was changed to tryptophan (Fujifilm Wako Pure Chemical Industries, Ltd.) in the surface treatment agent mixing step, and the amount of surface treatment agent mixed was changed to 17.5 g. The graphene dispersion was prepared in the same manner as in Example 1. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0108] [Example 17] In the preparation of the graphene dispersion in Example 1, the graphene dispersion was prepared in the same manner as in Example 1, except that the amount of surface treatment agent mixed in the surface treatment agent mixing step was changed to 3.75 g. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0109] [Example 18] In the preparation of the graphene dispersion in Example 1, the surface treatment agent was changed to benzamide (Tokyo Chemical Industries Co., Ltd.) in the surface treatment agent mixing step, and the amount of surface treatment agent mixed was changed to 12.5 g, but otherwise the graphene dispersion was prepared in the same manner. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0110] [Example 19] In the preparation of the graphene inorganic particle composite in Example 1, the talc was replaced with KHP-25 (average particle size 4.8 μm) manufactured by Hayashi Co., Ltd., except that the same procedure was followed. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0111] [Example 20] In the preparation of the graphene inorganic particle composite in Example 1, the talc was replaced with general-purpose mica J-31M (average particle size 35.0 μm) manufactured by Yamaguchi Mica Co., Ltd., in the same manner as in Example 1. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0112] [Comparative Example 1] The composition was prepared in the same manner as in Example 1, except that the graphene inorganic particle composite was replaced with talc that was not coated with graphene. The results of evaluating the obtained composition using the method described above are shown in Table 2.

[0113] [Comparative Example 2] In the preparation of the graphene dispersion in Example 1, the graphene dispersion was prepared in the same manner as in Example 1, except that the surface treatment agent was not mixed in the surface treatment agent mixing step. The results of evaluating the obtained graphene dispersion, graphene inorganic particle composite, and composition using the method described above are shown in Table 2.

[0114] [Table 1]

[0115] [Table 2]

Claims

1. A graphene inorganic particle composite in which 10% to 100% of the surface area of ​​non-conductive inorganic particles is coated with surface-modified graphene.

2. The graphene inorganic particle composite according to claim 1, wherein 60% to 100% of the surface area of ​​the nonconductive inorganic particles is coated with surface-modified graphene.

3. The graphene inorganic particle composite according to claim 1, wherein the average thickness of the graphene is 0.3 nm or more and 10 nm or less.

4. The graphene inorganic particle composite according to claim 1, wherein the elemental ratio of oxygen to carbon (O / C ratio) of the graphene, as measured by X-ray photoelectron spectroscopy, is 0.05 or more and 0.60 or less.

5. The graphene inorganic particle composite according to claim 1, wherein the graphene is surface-modified with a nitrogen-containing compound.

6. The graphene inorganic particle composite according to claim 5, wherein the elemental ratio of nitrogen to carbon (N / C ratio) of the graphene, as measured by X-ray photoelectron spectroscopy, is 0.005 or more and 0.200 or less.

7. The graphene inorganic particle composite according to claim 1, wherein the average particle size of the nonconductive inorganic particles is 1 μm or more and 50 μm or less.

8. A composition comprising a graphene inorganic particle composite according to any one of claims 1 to 7, and a curable resin and / or its precursor.

9. The composition according to claim 8, further comprising conductive inorganic particles.

10. A structure comprising the graphene inorganic particle composite according to any one of claims 1 to 7.

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