Modified graphite manufacturing method, composition, thermal conductive material, and laminate

Abstract

To provide a method for manufacturing modified graphite which is excellent in adhesiveness to a resin, can be made to fill a resin sheet with high density, and can impart excellent heat conductivity to the resin sheet; a composition containing a modified graphite obtained by the method for manufacturing the modified graphite; a heat conductive material obtained using the composition; and a laminate having the modified graphite obtained by the method for manufacturing the modified graphite as a sheet.SOLUTION: There are provided a method for manufacturing modified graphite which includes a step (1) of mixing graphite and an oxidant in an aqueous solution with pH of 12.0 or more, and modifying the surface of the graphite in the aqueous solution; a composition; a heat conductive material; and a laminate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing modified graphite, a composition, a thermally conductive material, and a laminate. [Background technology]

[0002] Graphite has high heat dissipation properties and electrical conductivity, and is therefore used as a material for components of a wide range of electrical equipment, such as personal computers, general home appliances, and automobiles. In order to effectively utilize the properties of graphite, such as heat dissipation and electrical conductivity, in a desired application, techniques for processing graphite or its precursors have been investigated.

[0003] For example, Patent Document 1 describes a method for producing a flat carbon-based nanostructured material, which includes (a) mechanically attriting granular graphite in the presence of an alkaline reagent or a mixture containing an alkaline reagent, (b) exposing the graphite particles to an intercalation solvent so that the intercalation solvent penetrates between the carbon layers of the graphite, and (c) supplying ultrasonic energy to the graphite particle dispersion for a time sufficient to form a nanostructured material. The production method described in Patent Document 1 can be easily applied to the production of high-performance graphite materials for various applications, and is said to be able to produce uniform, thin, high-aspect-ratio, and uniformly flaky graphite microparticles with various surface chemical properties.

[0004] Patent Document 2 describes a method for producing a graphitic material, comprising: a hydroxide deposition step of contacting a graphite precursor with a water-soluble transition metal compound and an alkali in water to deposit the resulting transition metal hydroxide on the graphite precursor; an oxidation step of oxidizing the transition metal hydroxide deposited in the deposition step to a transition metal oxide with an oxidizing agent or oxidizing gas; and a graphitization step of heating the graphite precursor to which the transition metal oxide oxidized in the oxidation step is deposited at a temperature of 1500° C. or higher to graphitize it. The production method described in Patent Document 2 is said to provide a graphitic material that has a high discharge capacity as a negative electrode material for lithium-ion secondary batteries and that can be produced easily and inexpensively from an industrial perspective.

[0005] Patent Document 3 also describes a method for preparing graphene fluoride, which includes the steps of providing graphite, preparing graphene oxide using the graphite, and mixing the graphene oxide with a fluorine-containing compound in an oxygen-free environment at a mass ratio of 1:1 to 100:1, reacting the mixture at 200°C to 1000°C for 1 to 10 hours, and then cooling the mixture to obtain the graphene fluoride.The preparation method described in Patent Document 3 is said to make it possible to easily obtain graphene fluoride containing fluorine atoms and carbon atoms in a specific mass percentage. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-100219 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-263160 [Patent Document 3] Special Publication No. 2013-544223 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a method for producing modified graphite that has excellent adhesion to resins, can be densely packed into a resin sheet, and can impart excellent thermal conductivity to the resin sheet. Another object of the present invention is to provide a composition containing the modified graphite obtained by the method for producing modified graphite, and a thermally conductive material obtained using the composition. Another object of the present invention is to provide a laminate having, in the form of a sheet, the modified graphite obtained by the method for producing modified graphite. [Means for solving the problem]

[0008] The above-mentioned problems of the present invention have been solved by the following means. <1> A method for producing modified graphite, comprising: (1) mixing graphite with an oxidizing agent in an aqueous solution having a pH of 12.0 or higher, and modifying the surface of the graphite in the aqueous solution. <2> The standard redox potential of the oxidizing agent is 0.1 V or more. <1> 2. A method for producing the modified graphite according to claim 1. <3> The standard redox potential of the oxidizing agent is 1.0 V or more. <1> or <2> 2. A method for producing the modified graphite according to claim 1. <4> The standard redox potential of the oxidizing agent is 1.5 V or more. <1> ~ <3> 1. A method for producing the modified graphite according to any one of the above. <5> The standard redox potential of the oxidizing agent is 1.8 V or more. <1> ~ <4> 1. A method for producing the modified graphite according to any one of the above. <6> the oxidizing agent is a persulfate; <1> ~ <5> 1. A method for producing the modified graphite according to any one of the above. <7> a step (2) of contacting the modified graphite obtained in the step (1) with a surface modifier in the presence of at least one of water and an organic solvent, <1> ~ <6> 1. A method for producing the modified graphite according to any one of the above. <8> the surface modifier is at least one of a metal coupling agent, a curable compound, a carboxylic acid compound, an organic phosphonic acid compound, and an organic phosphate ester; <1> ~ <7> 1. A method for producing the modified graphite according to any one of the above. <9> the graphite is graphite particles; <1> ~ <8> 1. A composition comprising modified graphite particles obtained by the method for producing modified graphite according to any one of 1 to 8, and a resin binder or a precursor thereof. <10> <9> A thermally conductive material obtained by using the composition described in . <11> the graphite is a graphite sheet; <1> ~ <8> 1. A laminate comprising a modified graphite sheet obtained by the method for producing modified graphite according to any one of 1 to 8, and an adhesive layer on the modified graphite sheet.

[0009] In this specification, "modified graphite" means graphite whose surface has been modified in the step (1) defined in the present invention, or graphite obtained by further surface-modifying this surface-modified graphite. Note that graphite (raw material) before being subjected to the step (1) may be referred to as "raw graphite" or simply as "graphite." As used herein, "surface modification" refers to a state in which at least a portion of the surface of modified graphite (e.g., modified graphite particles or modified graphite sheets) is modified with an organic surface modifier. The surface modifier (organic compound) may be chemically bonded (chemisorbed) to the surface of the modified graphite, or may be adsorbed through physical interaction (physisorbed). Surface modification also includes a state in which organic groups obtained by partial detachment of the surface modifier are bonded to the surface of the modified graphite. The "bond" due to chemisorption or physisorption may be any bond, such as a covalent bond, a coordinate bond, an ionic bond, a metallic bond, a hydrogen bond, a van der Waals bond, or a hydrophilic-hydrophobic interaction. The surface modification may be performed so as to form a monolayer on at least a portion of the surface. A monolayer is a monolayer formed by the chemical adsorption of organic molecules and is known as a self-assembled monolayer (SAM). In this specification, the surface modification may be applied to only a portion of the surface of the modified graphite, or may be applied to the entire surface. In this specification, each component used in the method for producing modified graphite of the present invention may be used alone or in combination of two or more. [Effects of the Invention]

[0010] According to the method for producing modified graphite of the present invention, it is possible to obtain modified graphite that has excellent adhesiveness to resins, can be packed into a resin sheet at a high density, and can impart excellent thermal conductivity to the resin sheet. The composition, thermally conductive material, and laminate of the present invention have electrical conductivity and excellent thermal conductivity, and can be used in a wide range of applications. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Method for manufacturing modified graphite> The method for producing modified graphite of the present invention includes a step (1) of mixing graphite with an oxidizing agent in an aqueous solution having a pH of 12.0 or higher, and modifying the surface of the graphite in this aqueous solution. In addition to step (1), the method for producing modified graphite of the present invention preferably includes step (2) of contacting the surface-modified graphite obtained in step (1) with a surface modifier in the presence of at least one of water and an organic solvent. First, the "graphite," "oxidizing agent," "organic solvent," and "surface modifier" used in the method for producing modified graphite of the present invention will be described.

[0012] (graphite) The shape of the graphite used in step (1) is not particularly limited, and may be, for example, in the form of particles (graphite particles) or sheets (graphite sheets). The size of the graphite particles is not particularly limited, and for example, graphite particles having a volume-based median diameter of 1 to 200 μm as measured using a Mastersizer 2000 (trade name) manufactured by Malvern Panalytical can be used. The size of the graphite sheet is not particularly limited, and for example, a graphite sheet having a thickness of 10 to 500 μm can be used. For example, a graphite sheet having a length of 80 to 120 mm, a width of 80 to 120 mm, and a thickness of 50 to 200 μm can be used. The average interplanar spacing of graphite d 002 is 0.3354 to 0.3365, which is a different substance from the "graphite precursor" described in Patent Document 2. The "graphite precursor" is classified as amorphous carbon (one of the allotropes of carbon) and has a different crystal structure from graphite. The average interplanar spacing d 002 is 0.3366~0.35. Average spacing d 002 can be determined by X-ray diffraction method using CuKα rays as X-rays and high-purity silicon as the standard material [Otani Sugiro, Carbon Fiber, pp. 733-742 (1986), Kindai Hensha Publishing Co.].

[0013] (oxidizing agent) The oxidizing agent used in step (1) can be any of a wide range of oxidizing agents commonly used in the surface treatment of graphite. The oxidizing agent used in step (1) is preferably an oxidizing agent having a standard oxidation-reduction potential of 0.1 V or more, more preferably an oxidizing agent having a standard oxidation-reduction potential of 0.3 V or more, still more preferably an oxidizing agent having a standard oxidation-reduction potential of 1.0 V or more, still more preferably an oxidizing agent having a standard oxidation-reduction potential of 1.5 V or more, still more preferably an oxidizing agent having a standard oxidation-reduction potential of 1.7 V or more, and particularly preferably an oxidizing agent having a standard oxidation-reduction potential of 1.8 V or more, in order to introduce as many polar groups (for example, hydroxyl groups, carboxy groups, and epoxy groups) onto the surface of graphite. There is no particular upper limit to the standard oxidation-reduction potential, and practically, it is 4.0 V or less, and usually, it is 3.0 V or less. "Standard oxidation-reduction potential" is based on the standard hydrogen electrode.

[0014] Specific examples of the oxidizing agent used in step (1) include the following. Although there are compounds for which the standard oxidation-reduction potential is not indicated, the standard oxidation-reduction potential of these compounds can be determined by a conventionally known method (for example, a method of measurement using an electrochemical analyzer (ALS660E (trade name) manufactured by ALS Corporation) or the like). Persulfates Sodium persulfate (standard redox potential: 2.01 V) Potassium persulfate (standard redox potential: 2.01 V) Ammonium persulfate (standard redox potential: 2.01 V) ·nitrate Cerium ammonium nitrate (standard redox potential: 1.74 V) Sodium nitrate (standard oxidation-reduction potential: 0.84 V) Ammonium nitrate (standard redox potential: 0.84 V) Peroxide Hydrogen peroxide (standard redox potential: 1.78 V) tert-butyl hydroperoxide Manganese compounds Potassium permanganate (standard redox potential: 1.7V) Manganese dioxide (standard redox potential: 1.23V) Chromium compounds potassium chromate Potassium dichromate (standard oxidation-reduction potential: 1.36 V) Iodine compounds Potassium iodate (standard redox potential: 1.20 V) Sodium iodate (standard redox potential: 1.20 V) Hypervalent iodine compounds Potassium periodate (standard redox potential: 1.60 V) Sodium periodate (standard redox potential: 1.60 V) Quinone compounds p-Benzoquinone (standard redox potential: 0.29 V) 1,2-Naphthoquinone (standard redox potential: 0.14 V) Anthraquinone Chloranil Amine oxide compounds N-Methylmorpholine N-oxide Salts of halogen oxoacids Sodium hypochlorite pentahydrate (standard oxidation-reduction potential: 1.63 V) Sodium chlorite (standard oxidation-reduction potential: 1.67V) ·Double salts Potassium peroxymonosulfate, potassium hydrogen sulfate, potassium sulfate (standard redox potential: 1.85 V) (e.g., DuPont OXONE) Among these, it is preferable to use a persulfate in step (1). These oxidizing agents may be used alone or in combination of two or more.

[0015] In step (1), a catalyst may be used to assist the action of the oxidizing agent. Specific examples of the catalyst include divalent iron compounds (such as FeSO4) and trivalent iron compounds. The catalyst may be used alone or in combination of two or more. The oxidizing agent and the catalyst may be hydrated.

[0016] (organic solvent) The organic solvent used in step (2) can be appropriately selected taking into consideration the type and amount of the surface modifier used in step (2). For example, alcohol solvents, nitrile solvents, ketone solvents, ester solvents, ether solvents, carbonate solvents, halogenated hydrocarbon solvents, etc. can be appropriately used. Preferred specific examples of the organic solvent include methanol, ethanol, 2-propanol, acetonitrile, cyclopentanone, cyclohexanone, ethyl acetate, methyl ethyl ketone, dichloromethane, and tetrahydrofuran.

[0017] (Surface modifier) The surface modifier used in step (2) is a compound capable of modifying the surface of the modified graphite obtained in step (1).

[0018] Examples of the surface modifier include common surface modifiers such as metal coupling agents, resins, curable compounds, carboxylic acid compounds (e.g., long-chain alkyl fatty acids (higher fatty acids)), organic phosphonic acid compounds, and organic phosphate esters. One or more types of surface modifiers can be used. As the surface modifier, for example, the surface modifiers described in JP 2009-502529 A, JP 2001-192500 A, Japanese Patent No. 4694929, WO 2018 / 004660, paragraphs

[0021] to

[0093] , WO 2019 / 013325, paragraphs

[0020] to

[0065] , WO 2019 / 013261, paragraphs

[0020] to

[0067] , and WO 2019 / 013323, paragraphs

[0020] to

[0087] can also be used. The metal coupling agent, resin, curable compound, carboxylic acid compound, organic phosphonic acid compound, and organic phosphate ester will be specifically described below.

[0019] Metal coupling agents Metal coupling agents are compounds that have a hydrolyzable group directly bonded to a metal atom. Examples of the metal atoms include Si, Ti, Zr, and Al. Examples of the hydrolyzable group include an alkoxy group (preferably having 1 to 10 carbon atoms) and a halogen atom such as a chlorine atom. The number of hydrolyzable groups contained in the metal coupling agent is preferably 1 or more, more preferably 2 or more, and even more preferably 3 or more. There is no particular upper limit to the number of hydrolyzable groups contained in the metal coupling agent, and it is, for example, 10,000.

[0020] It is also preferable that the metal coupling agent has a reactive group other than the hydrolyzable group and the hydroxyl group generated by hydrolysis of the hydrolyzable group. The reactive group is preferably a group reactive with, for example, a resin binder or a precursor thereof contained in the composition described below. Specific examples of the reactive group include an epoxy group, an oxetanyl group, a vinyl group, a (meth)acryloyl group, a styryl group, an amino group, an isocyanate group (isocyanato group), a mercapto group (sulfanyl group), and an acid anhydride group. The number of reactive groups contained in the metal coupling agent is preferably 1 or more, more preferably 2 or more, and even more preferably 3 or more. There is no particular upper limit to the number of reactive groups contained in the metal coupling agent, and it is, for example, 10,000.

[0021] Examples of metal coupling agents include silane coupling agents, titanium coupling agents, zirconium coupling agents, and aluminum coupling agents. Among these, the metal coupling agent is preferably a silane coupling agent.

[0022] Examples of silane coupling agents include: aminosilane-based silane coupling agents such as γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and trimethoxy[3-(phenylamino)propyl]silane; Epoxysilane-based silane coupling agents such as 3-glycidoxypropyltrimethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; vinylsilane-based silane coupling agents such as triethoxyvinylsilane and vinyl-tri(β-methoxyethoxy)silane; cationic silane-based silane coupling agents such as N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane hydrochloride; phenylsilane-based silane coupling agents such as phenyltrimethoxysilane and phenyltriethoxysilane; methacrylsilane-based silane coupling agents such as 3-methacryloxypropyltrimethoxysilane; acrylic silane-based silane coupling agents such as 3-acryloxypropyltrimethoxysilane; isocyanate silane-based silane coupling agents such as 3-isocyanate propyl triethoxy silane; isocyanurate silane-based silane coupling agents such as tris-(trimethoxysilylpropyl) isocyanurate; mercaptosilane-based silane coupling agents such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane; Ureidosilane-based silane coupling agents such as 3-ureidopropyltrimethylsilane; and styrylsilane-based silane coupling agents such as p-styryltrimethoxysilane; Examples include:

[0023] Examples of titanium coupling agents include PLENACT 38S, PLENACT TTS, PLENACT 46B, PLENACT 55, PLENACT 41B, PLENACT 138S, PLENACT 238S, PLENACT 338X, PLENACT 44, PLENACT 9SA and PLENACT ET (all trade names, manufactured by Ajinomoto Fine-Techno Co., Inc.).

[0024] Examples of zirconium coupling agents include Kenreact NZ01 (trade name, manufactured by Kenrich Co., Ltd.) and zirconium aluminate coupling agents.

[0025] An example of an aluminum coupling agent is PLENACT AL-M (trade name, manufactured by Ajinomoto Fine-Techno Co., Inc.).

[0026] The metal coupling agent may also be a polymer type metal coupling agent. The weight-average molecular weight of the polymer-type metal coupling agent is preferably 1,000 or more, more preferably 2,000 or more. The upper limit is preferably 100,000 or less, more preferably 10,000 or less. The reactive functional group equivalent capable of crosslinking with the resin binder or its precursor is preferably 1,000 g / mol or less, more preferably 500 g / mol or less.

[0027] When the metal coupling agent is brought into contact with the modified graphite obtained in step (1) (e.g., modified graphite particles or modified graphite sheet), the hydrolyzable groups in the metal coupling agent may be hydrolyzed in advance before the contact. In this case, it is also preferable to crosslink the metal coupling agent with the modified graphite obtained in the above step (1) by using hydroxyl groups generated by prior hydrolysis of the hydrolyzable groups in the metal coupling agent.

[0028] ·Curable compound As the surface modifier, a curable compound can also be used. The curable compound herein refers to a component different from the metal coupling agent described above.

[0029] The curable compound is preferably a compound that is soluble in the above organic solvent. The curable compound may be a high molecular weight compound (resin) or a low molecular weight compound. The molecular weight of the curable compound is, for example, 300 to 1,000,000, and when it is a polymer, the weight average molecular weight is, for example, 1,000 to 100,000. In this specification, the weight average molecular weight is a polystyrene-equivalent molecular weight obtained by gel permeation chromatography (GPC) measurement. Specifically, a GPC apparatus HLC-8320 (trade name, manufactured by Tosoh Corporation) is used, tetrahydrofuran is used as the eluent, and a column TSKgel Super HZM-H (trade name, manufactured by Tosoh Corporation) is used, and detection is performed with an RI detector at 23°C and a flow rate of 0.3 to 0.5 mL / min.

[0030] The curable compound, which is a resin, may or may not have thermoplasticity.

[0031] The curable compound has a reactive group (a group that causes a crosslinking reaction, a crosslinkable group). The crosslinkable group is also preferably a group capable of undergoing a crosslinking reaction with a resin binder or a precursor thereof (preferably a precursor of a resin binder) described below. The crosslinkable group is also preferably a group capable of undergoing a crosslinking reaction with a hydroxyl group. Examples of the crosslinkable group include an epoxy group, an oxetanyl group, a cyanate group (cyanato group), an isocyanate group, an ethylenic double bond-containing group (such as a (meth)acryloyl group), and a carboxy group. The number of crosslinkable groups contained in the curable compound is preferably 1 or more, more preferably 2 or more. There is no upper limit to the number, and it is, for example, 10,000.

[0032] Examples of curable compounds that are resins (resins having curable reactive groups) include epoxy resins, cyanate resins, phenolic resins, imide resins, isocyanate resins, benzoxazine resins, oxetane resins, amino resins, polyester resins, allyl resins, dicyclopentadiene resins, silicone resins, triazine resins, and melamine resins. Among these, the resin is preferably an epoxy resin or a cyanate resin, and more preferably an epoxy resin.

[0033] The epoxy resin is preferably an epoxy resin having one or more (preferably two or more) epoxy groups in one molecule. In this specification, phenoxy resins are also included in the epoxy resins. Examples of epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol AF type epoxy resins, bixylenol type epoxy resins, phenol novolac type epoxy resins, tert-butylcatechol type epoxy resins, naphthol type epoxy resins, naphthalene type epoxy resins, naphthalene type tetrafunctional epoxy resins, naphthylene ether type epoxy resins, glycidylamine type epoxy resins, glycidyl ester type epoxy resins, cresol novolac type epoxy resins, biphenyl type epoxy resins, biphenyl aralkyl type epoxy resins, dicyclopentadiene type epoxy resins, anthracene type epoxy resins, linear aliphatic epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, heterocyclic epoxy resins, spiro ring-containing epoxy resins, cyclohexanedimethanol type epoxy resins, trimethylol type epoxy resins, and halogenated epoxy resins.

[0034] Examples of cyanate resins include bisphenol-type cyanate resins such as novolac-type cyanate resins, bisphenol A-type cyanate resins, bisphenol E-type cyanate resins, and tetramethylbisphenol F-type cyanate resins, and prepolymers of these resins that have been partially converted to triazine.

[0035] The carboxylic acid compound is preferably one that adsorbs to the surface of the modified graphite, and specific examples include long-chain carboxylic acids such as stearic acid, oleic acid, and linoleic acid. Other examples include polymers (polycarboxylic acids) obtained by polymerizing (meth)acrylic acid and maleic acid. The polymer is preferably a polycarboxylic acid containing at least one of a (meth)acrylic acid-derived component and a maleic acid-derived component in an amount of 80% by mass or more of the total components.

[0036] The organic phosphonic acid compound is preferably one that adsorbs to the surface of modified graphite. For example, alkylphosphonic acid is preferred as the organic phosphonic acid compound. Specific examples of preferred organic phosphonic acid compounds include n-octylphosphonic acid and its esters, n-decylphosphonic acid and its esters, 2-ethylhexylphosphonic acid and its esters, and camphylphosphonic acid and its esters.

[0037] The organic phosphate ester is preferably one that adsorbs to the surface of modified graphite. For example, an alkyl phosphate ester is preferred as the organic phosphate ester. Specific preferred examples of the organic phosphate ester include ethyl acid phosphate, butyl acid phosphate, butoxyethyl acid phosphate, 2-ethylhexyl acid phosphate, isotridecyl acid phosphate, oleyl acid phosphate, tetracosyl acid phosphate, ethylene glycol acid phosphate, 2-hydroxyethyl methacrylate acid phosphate, dibutyl phosphate, and bis(2-ethylhexyl) phosphate.

[0038] Furthermore, as the surface modifier (for example, a surface modifier that is a curable compound), a resin binder or a precursor thereof (preferably a precursor of a resin binder) described below may be used.

[0039] (Process (1)) In the method for producing modified graphite of the present invention, in step (1), graphite is brought into contact with an oxidizing agent in an aqueous solution having a pH of 12.0 or higher, and polar groups are introduced onto the surface of the graphite in this aqueous solution, thereby modifying the physicochemical properties of the surface. Known conventional methods for oxidizing the surface of graphite include, for example, the Brodie method, in which potassium chlorate and graphite are mixed in fuming nitric acid; the Staudenmaier method, in which potassium chlorate and graphite are mixed in fuming nitric acid and concentrated sulfuric acid; and the Hummers method, in which sodium nitrate, potassium permanganate, and graphite are mixed in concentrated sulfuric acid. However, these methods are undesirable from the viewpoint of safety during production because the oxidation reaction proceeds in a highly concentrated acid. Furthermore, the graphite must be washed with a large amount of water after surface treatment to remove the acid and oxidizing agent, resulting in poor production efficiency. For example, when oxidizing the surface of 100 g of graphite, approximately 14 L of water is used for washing after the oxidation reaction. In contrast, in the method for producing modified graphite of the present invention, the oxidation reaction proceeds in an aqueous solution with a pH of 12.0 or higher (step (1)). The base concentration in this aqueous solution is lower than the acid concentration in conventional acidic aqueous solutions, making it safer. Furthermore, the amount of water required to wash the graphite after surface treatment is small, resulting in higher production efficiency compared to the conventional methods. For example, when oxidizing the surface of 100 g of graphite, the base and oxidizing agent can be removed with 1 L of water. The present inventors have discovered that the surface of graphite can be highly efficiently modified with an oxidizing agent under basic conditions of pH 12.0 or higher, rather than under conventional strongly acidic conditions, and have thus completed the present invention. The pH may be 13.0 or higher, and there is no particular upper limit. The method for producing modified graphite of the present invention is effective even at a pH of about 14.0.

[0040] In step (1), the pH is controlled using a base, and the base may be an organic base or an inorganic base. Specific examples of organic bases include pyridine, diazabicycloundecene, triethylamine, and diisopropylethylamine, while specific examples of inorganic bases include sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide, and ammonia. In step (1), the order of adding the base, graphite, and oxidizing agent to water is not particularly limited, as long as the graphite and oxidizing agent can be brought into contact with each other in an aqueous solution having a pH of 12.0 or higher. For example, when graphite particles are used as raw graphite, a base can be added to water in advance to prepare an aqueous solution having a pH of 12.0 or higher, and then graphite and an oxidizing agent can be added to this aqueous solution and mixed. The graphite particles and the oxidizing agent can be added to the aqueous solution simultaneously or separately. When an aqueous solution having a pH of 12.0 or higher is prepared in advance, the pH of the aqueous solution is adjusted so that the pH of the aqueous solution is 12 or higher when the graphite particles and the oxidizing agent are added to the aqueous solution and mixed. Alternatively, the base and graphite particles may be added to water, and then the oxidizing agent may be added, followed by mixing. Alternatively, the base and oxidizing agent may be added to water, and then the graphite may be added, followed by mixing. Alternatively, the base, graphite, and oxidizing agent may be added to water at the same time and then mixed. The "mixing" can be carried out, for example, at 20 to 80°C for 0.1 to 10 hours (preferably 25 to 75°C for 1 to 8 hours, and more preferably 30 to 70°C for 2 to 6 hours). Stirring conditions can also be gentle enough so that the graphite particles do not collapse. When a graphite sheet is used as the raw graphite, for example, a base and an oxidizing agent are added to water in advance, either separately or simultaneously, to prepare an aqueous solution having a pH of 12.0 or higher, and the graphite sheet can be immersed in this aqueous solution at 20 to 80°C for 0.1 to 10 hours (preferably 20 to 80°C for 0.1 to 50 hours, and more preferably 30 to 70°C for 0.1 to 10 hours) to modify the surface of the graphite sheet.

[0041] The content of each component contained in the aqueous solution is not particularly limited as long as the raw graphite can be entirely immersed in the aqueous solution. The content of raw graphite in the aqueous solution can be, for example, 1.0 to 50 parts by mass, or 1.0 to 30 parts by mass, or 1.0 to 20 parts by mass, per 100 parts by mass of water in the aqueous solution. The content of the oxidizing agent in the aqueous solution can be, for example, 0.05 to 20 parts by mass, alternatively 0.1 to 20 parts by mass, alternatively 1.0 to 20 parts by mass, or alternatively 1.0 to 10 parts by mass, relative to 100 parts by mass of water in the aqueous solution. When the aqueous solution contains a catalyst, the content of the catalyst can be, for example, 0.005 to 2 parts by mass, or alternatively 0.01 to 2 parts by mass, or alternatively 0.1 to 2 parts by mass, per 100 parts by mass of water in the aqueous solution.

[0042] In step (1), for example, 1.0 to 800 parts by mass, 10 to 250 parts by mass, or 15 to 200 parts by mass of the oxidizing agent can be used relative to 100 parts by mass of raw graphite. When a catalyst is used in step (1), for example, the catalyst may be used in an amount of 0.01 to 15 parts by mass, 0.1 to 10 parts by mass, or 0.5 to 5 parts by mass per 100 parts by mass of raw graphite.

[0043] In step (1), components other than water, raw graphite, oxidizing agent, and catalyst may be used within the scope that does not impair the effects of the present invention. Examples of such components include organic solvents. When an organic solvent is used in step (1), the content of the organic solvent is, for example, preferably 5% by mass or less, more preferably 3% by mass or less, of the total of water and the organic solvent.

[0044] (Process (2)) The method for producing modified graphite of the present invention preferably includes step (2) of contacting the modified graphite obtained in step (1) with a surface modifier in the presence of at least one of water and an organic solvent, from the viewpoints of further improving the affinity between the modified graphite and the resin when the modified graphite is composited with the resin and further improving the thermal conductivity of the resulting resin sheet or the like. The modified graphite obtained in step (1) and the surface modifier may be added separately or simultaneously to at least one of water and an organic solvent (water, an organic solvent, or a mixture of water and an organic solvent). When graphite particles are used as the raw graphite, the "contact" can be carried out under conditions of, for example, 0 to 100°C for 0.1 to 10 hours (preferably 5 to 50°C for 0.2 to 6 hours, and more preferably 10 to 40°C for 0.3 to 3 hours). When a graphite sheet is used as the raw graphite, the "contact" can be carried out by immersing the graphite sheet obtained in step (1) in a solution containing a surface modifier at, for example, 0 to 100°C for 0.1 to 100 hours (preferably 5 to 50°C for 0.1 to 6 hours, and more preferably 10 to 40°C for 0.1 to 1 hour). By such a simple procedure, the surface of the modified graphite obtained in step (1) can be modified (organized) to the desired state.

[0045] In step (2), the quantitative ratio of each component used in step (2) is not particularly limited, as long as the surface of the modified graphite obtained in step (1) can be modified (organically modified) to a desired state. In step (2), for example, 0.01 to 100 parts by mass, 0.1 to 70 parts by mass, or 0.3 to 40 parts by mass of the surface modifier can be used per 100 parts by mass of raw graphite (based on 100 parts by mass of the raw graphite used in step (1)). In step (2), for example, 50 to 10,000 parts by mass, 100 to 9,500 parts by mass, or 150 to 9,000 parts by mass of water and organic solvent may be used in total relative to 100 parts by mass of raw graphite.

[0046] In step (2), components other than water, the organic solvent, the modified graphite obtained in step (1), and the surface modifier may be used within the scope of not impairing the effects of the present invention. Examples of such components include organic acids, organic bases, inorganic acids, and inorganic bases.

[0047] A washing step, a drying step, etc. may be carried out between steps (1) and (2) as long as the effects of the present invention are not impaired. The washing step can be performed by filtering the modified graphite from the aqueous solution containing the modified graphite obtained in step (1) as needed, and pouring the modified graphite into at least one of water, an acidic aqueous solution (pH 1 to 6), and an organic solvent. The organic solvent used in the washing step can be the same as that used in step (2). The amounts of water and organic solvent used in the washing step are not particularly limited. In the washing step, for example, 200 to 9,000 parts by mass, 500 to 8,000 parts by mass, or 750 to 7,000 parts by mass of water may be used relative to 100 parts by mass of raw graphite. For example, 200 to 5,000 parts by mass, 500 to 2,000 parts by mass, or 750 to 1,500 parts by mass of acidic aqueous solution may be used relative to 100 parts by mass of raw graphite. For example, 200 to 5,000 parts by mass, 500 to 2,000 parts by mass, or 750 to 1,500 parts by mass of organic solvent may be used relative to 100 parts by mass of raw graphite. The drying step can be carried out under conditions of, for example, 20 to 100°C, 0.1 to 100 hours (preferably 5 to 70°C, 1 to 70 hours, more preferably 10 to 60°C, 5 to 40 hours).

[0048] Step (2) may be followed by a washing step, a drying step, or the like, as long as the effects of the present invention are not impaired. The washing step can be carried out by pouring the modified graphite obtained in step (2) into at least one of water and an organic solvent. The organic solvent used in the washing step can be the same as that used in step (2). The amounts of water and organic solvent used in the washing step are not particularly limited. In the washing step, for example, 50 to 1,000 parts by mass, 100 to 500 parts by mass, or 150 to 250 parts by mass of water may be used per 100 parts by mass of raw graphite, while for example, 50 to 9,000 parts by mass, 100 to 8,000 parts by mass, or 150 to 7,000 parts by mass of organic solvent may be used per 100 parts by mass of raw graphite. The drying step can be carried out under conditions of, for example, 20 to 100°C, 0.1 to 100 hours (preferably 5 to 70°C, 1 to 70 hours, more preferably 10 to 60°C, 5 to 40 hours).

[0049] The method for producing modified graphite of the present invention does not usually include a step of milling the raw graphite and the modified graphite, because milling the raw graphite and the modified graphite would significantly reduce the thermal conductivity of the final modified graphite. Therefore, when graphite particles are used as a raw material in the method for producing modified graphite of the present invention, the average primary particle size does not substantially change between the raw graphite particles and the resulting modified graphite particles. For example, if the average primary particle size of the raw graphite particles is 100, the average primary particle size of the resulting modified graphite particles can be in the range of 100±10. Similarly, when a graphite sheet is used as a raw material in the method for producing modified graphite of the present invention, the size of the graphite sheet does not change substantially. For example, if the volume of the raw graphite sheet is 100, the volume of the modified graphite sheet obtained in the end can be in the range of 100±10.

[0050] <Composition> The composition of the present invention contains modified graphite particles obtained by the method of producing modified graphite of the present invention, and a resin binder (for example, a solvent-soluble resin) or a precursor thereof (for example, a thermosetting resin before the curing reaction). A method for producing the composition of the present invention includes mixing modified graphite particles obtained by the method for producing modified graphite of the present invention with a resin binder (e.g., a solvent-soluble resin) or a precursor thereof (e.g., a thermosetting resin prior to the curing reaction). Hereinafter, the resin binder and its precursor contained in the composition of the present invention will also be collectively referred to as binder components.

[0051] The term "resin binder precursor" refers to one compound that will become a resin binder in a cured product obtained by a polymerization or crosslinking reaction alone, and two or more compounds (preferably 2 to 4, more preferably 2) that will react with each other to become a resin binder in a cured product. Specific examples of precursors include a combination of an epoxy compound and an active hydrogen group-containing compound, a combination of silicone compound A and silicone compound B, and polyamic acid (a precursor to a polyimide resin), as described below. Specific examples of precursors include a combination of a bisphenol F epoxy resin and a novolac phenolic resin, and a combination of a vinyl-terminated polydimethylsiloxane and a polymethylhydrosiloxane.

[0052] An example of a composition containing the resin binder itself is a composition containing a solvent, modified graphite particles obtained by the method of the present invention for producing modified graphite, and a resin binder that is a polymer (resin) dissolved or dispersed in the solvent. When the solvent in this composition evaporates, the resin binder precipitates, yielding a thermally conductive material, described below, in which the resin binder functions as a binder (binding agent). The solvent is preferably an organic solvent, such as cyclopentanone, cyclohexanone, ethyl acetate, methyl ethyl ketone, dichloromethane, or tetrahydrofuran.

[0053] Furthermore, when the composition of the present invention contains a thermoplastic resin as a resin binder, the composition of the present invention may be, for example, a composition containing modified graphite particles obtained by the method of producing modified graphite of the present invention and a thermoplastic resin, but not containing a solvent. This composition can be heated and melted, and then cooled and solidified in a desired form to obtain a thermally conductive material, described below, in which the thermoplastic resin functions as a binder (binding agent).

[0054] The resin binder precursor is a component that undergoes a polymerization reaction and / or a crosslinking reaction under predetermined conditions to become a resin binder (polymer and / or crosslinked product), for example, during the process of preparing the thermal conductive material described below from the composition of the present invention. The resin binder thus formed, which is a cured product, functions as a binder (binding agent) in the thermal conductive material described below. The precursor of the resin binder may be, for example, a curable compound. Examples of the curable compound include compounds that undergo a polymerization reaction and / or a crosslinking reaction by heat or light (such as ultraviolet light) to cure (become high molecular weight). That is, examples include thermosetting compounds and photocurable compounds. These compounds may be polymers or monomers. The curable compound may be a mixture of two or more compounds (for example, a base agent and a curing agent). The precursor of the resin binder may chemically react with a surface modifier.

[0055] Examples of resin binders (including resin binders formed from resin binder precursors) include binders composed of resins formed by chain polymerization of monomers having polymerizable double bonds, such as epoxy resins (crosslinked polymers formed by a curing reaction of an epoxy compound (resin binder precursor)), silicone resins, phenolic resins, polyimide resins, polyester resins, bismaleimide resins, melamine resins, isocyanate-based resins (polyurethane resins, polyurea resins, polyurethane urea resins, etc.), and radical polymers ((meth)acrylic resins, etc.).

[0056] Furthermore, the resin binder (including a resin binder formed from a resin binder precursor) may be, for example, a resin that has been made into a high molecular weight by a reaction between different monomers in the following combination (functional group 1 / functional group 2): (Functional group 1 / Functional group 2) = (polymerizable double bond / polymerizable double bond), (polymerizable double bond / thiol group (sulfanyl group)), (carboxylic acid halide group (carboxylic acid chloride group, etc.) / unsubstituted or monosubstituted amino group), (carboxy group / unsubstituted or monosubstituted amino group), (carboxylic acid anhydride group / unsubstituted or monosubstituted amino group), (carboxy group / aziridine group), (carboxy group / isocyanate group), (carboxy group / epoxy group), (carboxy group / halogenated benzyl group), (unsubstituted or monosubstituted amino group / isocyanate group), (unsubstituted, monosubstituted or bisubstituted (substituted amino group / halogenated benzyl group), (unsubstituted amino group / aldehydes (formyl group)), (isocyanate group / isocyanate group), (isocyanate group / hydroxyl group), (isocyanate group / epoxy group), (hydroxyl group / halogenated benzyl group), (hydroxyl group / carboxylic anhydride group), (hydroxyl group / alkoxysilyl group), (epoxy group / unsubstituted or monosubstituted amino group), (epoxy group / carboxylic anhydride group), (epoxy group / hydroxyl group), (epoxy group / epoxy group), (oxetanyl group / epoxy group), (alkoxysilyl group / alkoxysilyl group), etc. The polymerizable double bond refers to a double bond between carbon atoms that can undergo polymerization such as radical polymerization, and examples thereof include double bonds between carbon atoms in a (meth)acryloyl group and a vinyl group.

[0057] In particular, the composition of the present invention preferably contains, as a binder component, a precursor of a resin binder, more preferably a precursor of a resin binder capable of forming a cured epoxy resin product, and more preferably a precursor of a resin binder capable of forming a cured silicone resin product. The resin binder or precursor thereof contained in the composition of the present invention may be used alone or in combination of two or more. Preferable precursors of the resin binder contained in the composition of the present invention will be described below.

[0058] (epoxy resin precursor) Epoxy compounds An epoxy compound is a compound having at least one epoxy group in one molecule. The epoxy group may have a substituent other than the epoxy group (such as a linear or branched alkyl group having 1 to 5 carbon atoms).

[0059] The number of epoxy groups that the epoxy compound has is preferably 2 or more, more preferably 2 to 40, still more preferably 2 to 10, and particularly preferably 2, in one molecule. The molecular weight of the epoxy compound is preferably 150 to 10,000, more preferably 150 to 1,000, and even more preferably 200 to 290. The weight average molecular weight of the epoxy compound is preferably 150 to 10,000, more preferably 150 to 1,000, and even more preferably 200 to 290.

[0060] The epoxy group content of the epoxy compound is preferably from 2.0 to 20.0 mmol / g, more preferably from 5.0 to 15.0 mmol / g, and even more preferably from 5.5 to 14.0 mmol / g. The epoxy group content means the number of epoxy groups contained in 1 g of the epoxy compound. The epoxy compound preferably has an aromatic ring group (preferably an aromatic hydrocarbon ring group).

[0061] Other examples of epoxy compounds include glycidyl ethers of bisphenol A, F, S, AD, etc., such as bisphenol A epoxy compounds, bisphenol F epoxy compounds, bisphenol S epoxy compounds, and bisphenol AD ​​epoxy compounds; hydrogenated bisphenol A epoxy compounds, hydrogenated bisphenol AD ​​epoxy compounds, etc.; phenol novolac glycidyl ethers (phenol novolac epoxy compounds), cresol novolac glycidyl ethers (cresol novolac epoxy compounds), bisphenol A novolac glycidyl ethers, etc.; dicyclopentadiene glycidyl ethers (dicyclopentadiene epoxy compounds); dihydroxypentadiene glycidyl ethers (dihydroxypentadiene epoxy compounds); trisphenolmethane epoxy compounds; phenoxy resins, etc.; and acrylic resins having epoxy groups on their side chains. A compound in which one or more of the glycidyl ether groups and / or glycidyl ester groups in each of the above-mentioned compounds are replaced with a diglycidylamino group or a diglycidylaminoalkylene group (such as a diglycidylaminomethylene group) may be used as the epoxy compound. Each of the above compounds may have a substituent. For example, the aromatic ring group, cycloalkyl group, and / or alkylene group contained in each of the above compounds may have a substituent other than a glycidyl ether group, a glycidyl ester group, a diglycidylamino group, and / or a diglycidylaminoalkylene group.

[0062] Examples of the epoxy compound include polyhydroxy aromatic ring-type glycidyl ethers (polyhydroxy aromatic ring-type epoxy compounds) such as glycidyl ethers of dihydroxybenzenes such as resorcinol, and polycarboxy aromatic ring-type glycidyl esters (polycarboxy aromatic ring-type epoxy compounds). The polyhydroxy aromatic ring-type glycidyl ether is a compound having a structure in which two or more (preferably 2 to 6, more preferably 2 to 3, and even more preferably 2) hydroxyl groups in an aromatic ring having these two or more hydroxyl groups as substituents are glycidyl etherified. The polycarboxy aromatic ring type glycidyl ester is a compound having a structure in which two or more hydroxyl groups in an aromatic ring having two or more (preferably 2 to 6, more preferably 2 to 3, and even more preferably 2) carboxy groups as substituents are glycidyl esterified. The aromatic ring may be an aromatic hydrocarbon ring or an aromatic heterocycle, and is preferably an aromatic hydrocarbon ring. The aromatic ring may be a polycycle or a monocycle. The aromatic ring preferably has 5 to 15 ring members, more preferably 6 to 12 ring members, and more preferably 6 ring members. The aromatic ring may have a substituent other than a hydroxyl group. An example of the polyhydroxy aromatic ring type glycidyl ether is 1,3-phenylene bis(glycidyl ether). Compounds in which one or more of the glycidyl ether groups or glycidyl ester groups in the above-mentioned polyhydroxy aromatic ring-type glycidyl ethers and the above-mentioned polycarboxy aromatic ring-type glycidyl esters are replaced with diglycidylamino groups or diglycidylaminoalkylene groups (diglycidylaminomethylene groups, etc.) may be used as epoxy compounds.

[0063] The epoxy compound also includes a compound in which the epoxy group is fused to a ring, such as 3,4:8,9-diepoxybicyclo[4.3.0]nonane.

[0064] In addition, the epoxy compounds described in paragraphs

[0051] to

[0134] of WO 2020 / 067364 can also be used as the epoxy compound.

[0065] When the composition of the present invention contains an epoxy compound as a resin binder precursor, the content thereof is preferably 1 to 40% by volume, more preferably 3 to 30% by volume, and even more preferably 6 to 20% by volume, based on the total solid content of the composition (typically, components other than the solvent). The epoxy compounds may be used alone or in combination of two or more.

[0066] ·Compounds containing active hydrogen groups The composition of the present invention preferably contains a combination of an epoxy compound and an active hydrogen group-containing compound, which can be reacted to prepare a resin binder as a cured product. The active hydrogen group-containing compound is a compound having one or more (preferably two or more, more preferably 2 to 10) groups having active hydrogen (active hydrogen groups). Examples of the active hydrogen group include a hydroxyl group, an unsubstituted or monosubstituted amino group, and a mercapto group, and among these, a hydroxyl group is preferred. The active hydrogen group-containing compound is preferably a polyol having two or more (preferably three or more, more preferably three to six) hydroxyl groups.

[0067] Among these, the active hydrogen group-containing compound used in combination with the epoxy compound is preferably a phenol compound. That is, the composition of the present invention preferably contains an epoxy compound and a phenol compound as precursors of the epoxy resin binder. The phenol compound is a compound having one or more (preferably two or more, more preferably three or more, and even more preferably three to six) phenolic hydroxyl groups (hydroxyl groups directly bonded to carbon atoms constituting a benzene ring).

[0068] Preferred examples of the active hydrogen group-containing compound include benzene polyols such as benzenetriol, biphenyl aralkyl phenol resins, phenol novolac resins, cresol novolac resins, aromatic hydrocarbon formaldehyde resin-modified phenol resins, dicyclopentadiene phenol addition resins, phenol aralkyl resins, polyhydric phenol novolac resins synthesized from polyhydric hydroxy compounds and formaldehyde, naphthol aralkyl resins, trimethylolmethane resins, tetraphenylolethane resins, naphthol novolac resins, naphtholphenol co-condensed novolac resins, naphthol-cresol co-condensed novolac resins, biphenyl-modified phenol resins, biphenyl-modified naphthol resins, aminotriazine-modified phenol resins, and alkoxy group-containing aromatic ring-modified novolac resins.

[0069] As the active hydrogen group-containing compound, the phenol compounds described in paragraphs

[0037] to

[0059] of WO 2020 / 158259 can also be used.

[0070] The hydroxyl group content of the active hydrogen group-containing compound is preferably 3.0 mmol / g or more, more preferably 4.0 mmol / g or more, while the hydroxyl group content is preferably 25.0 mmol / g or less, more preferably 20.0 mmol / g or less. The hydroxyl group content refers to the number of hydroxyl groups (preferably phenolic hydroxyl groups) contained in 1 g of the active hydrogen group-containing compound. In addition, the active hydrogen group-containing compound may have an active hydrogen-containing group (such as a carboxy group) capable of polymerizing with an epoxy compound in addition to a hydroxyl group. The active hydrogen content (total content of hydrogen atoms in the hydroxyl group, carboxy group, etc.) of the active hydrogen group-containing compound is preferably 3.0 mmol / g or more, more preferably 4.0 mmol / g or more. On the other hand, the active hydrogen content is preferably 25.0 mmol / g or less, more preferably 20.0 mmol / g or less. The active hydrogen content refers to the number of active hydrogen atoms contained in 1 g of the active hydrogen group-containing compound.

[0071] The molecular weight of the active hydrogen group-containing compound is preferably 2000 or less, more preferably 1500 or less, and even more preferably 1000 or less. On the other hand, the molecular weight of the active hydrogen group-containing compound is preferably 110 or more, and more preferably 300 or more. The weight average molecular weight of the active hydrogen group-containing compound is preferably 2000 or less, more preferably 1500 or less, and even more preferably 1000 or less. On the other hand, the weight average molecular weight of the active hydrogen group-containing compound is preferably 110 or more, and more preferably 300 or more.

[0072] When the composition of the present invention contains an active hydrogen group-containing compound, the content thereof is preferably 1 to 40% by volume, more preferably 3 to 30% by volume, and even more preferably 5 to 20% by volume, based on the total solid content of the composition of the present invention. The active hydrogen group-containing compound may be used alone or in combination of two or more.

[0073] When the composition of the present invention contains an epoxy compound and an active hydrogen group-containing compound, the ratio of the content of the epoxy compound to the content of the active hydrogen group-containing compound is such that the equivalent ratio ("number of epoxy groups" / "number of active hydrogen groups") of the epoxy group of the epoxy compound to the active hydrogen groups (preferably hydroxyl groups, more preferably phenolic hydroxyl groups) of the active hydrogen group-containing compound is preferably 30 / 70 to 70 / 30, more preferably 40 / 60 to 60 / 40, and even more preferably 45 / 55 to 55 / 45. When the composition of the present invention contains an epoxy compound and an active hydrogen group-containing compound, the total content of the epoxy compound and the active hydrogen group-containing compound is preferably 20 to 100% by volume, more preferably 60 to 100% by volume, and even more preferably 90 to 100% by volume, of the total binder components.

[0074] (Silicone resin precursor) When the composition of the present invention contains a precursor of a silicone resin, it may be a combination of an addition reaction curable silicone resin and a condensation curable silicone resin. In this specification, precursors capable of forming a silicone resin as a cured product (the above-mentioned addition reaction curable silicone resin and condensation curable silicone resin) are also referred to as silicone compounds.

[0075] The silicone resin precursor is preferably a combination of silicone compound A and silicone compound B described below.

[0076] An organopolysiloxane having two or more alkenyl groups is used as the silicone compound A. The organopolysiloxane having two or more alkenyl groups is preferably an organopolysiloxane having two or more vinyl groups, and more preferably an organopolysiloxane having vinyl groups at both ends. Examples of organopolysiloxanes having vinyl groups at both ends include polydimethylsiloxane having vinyl groups at both ends, polyphenylmethylsiloxane having vinyl groups at both ends, a copolymer of dimethylsiloxane having vinyl groups at both ends and diphenylsiloxane, a copolymer of dimethylsiloxane having vinyl groups at both ends and phenylmethylsiloxane, and a copolymer of dimethylsiloxane having vinyl groups at both ends and diethylsiloxane. The weight average molecular weight of the organopolysiloxane having two or more alkenyl groups is preferably 4,000 to 50,000, and more preferably 7,500 to 25,000. The silicone compound A may be used alone or in combination of two or more.

[0077] The silicone compound B may be any compound capable of crosslinking the silicone compound A, and may include compounds having two or more hydrosilyl groups (SiH). Polyorganosiloxanes having two or more hydrosilyl groups (hereinafter also referred to as "hydrosilyl group-containing polyorganosiloxanes") are preferred. Polyorganosiloxanes having three or more hydrosilyl groups (for example, 3 to 1000) are more preferred. Examples of hydrosilyl group-containing polyorganosiloxanes include methylhydrosiloxane-dimethylsiloxane copolymers, polymethylhydrosiloxanes, polyethylhydrosiloxanes, and methylhydrosiloxane-phenylmethylsiloxane copolymers. These may or may not have hydrosilyl groups at their ends, and for example, both ends may be capped with trimethylsilyl groups or triethylsilyl groups. The weight average molecular weight of the hydrosilyl group-containing polyorganosiloxane is preferably 800 to 5,000, more preferably 1,500 to 4,000. In the composition of the present invention, the content of silicone compound B relative to 100 parts by mass of silicone compound A is, for example, 0.1 to 250 parts by mass, preferably 10 to 200 parts by mass, more preferably 50 to 150 parts by mass, and even more preferably 70 to 150 parts by mass. In the composition of the present invention, the volume ratio of silicone compound A to silicone compound B is preferably 30 / 70 to 70 / 30, more preferably 40 / 60 to 60 / 40, and even more preferably 45 / 55 to 55 / 45. The silicone compound B may be used alone or in combination of two or more. In the composition of the present invention, silicone compound A and silicone compound B may be partially reacted.

[0078] In the composition of the present invention, the content of the binder component is preferably 5 to 90% by volume, more preferably 10 to 80% by volume, even more preferably 10 to 70% by volume, still more preferably 15 to 65% by volume, and particularly preferably 15 to 60% by volume, based on the total solid content of the composition.

[0079] In the composition of the present invention, the content of the modified graphite particles obtained by the method for producing modified graphite of the present invention is preferably 10 to 95% by volume, more preferably 30 to 85% by volume, and even more preferably 50 to 75% by volume, based on the total solid content of the composition of the present invention. The composition of the present invention may contain components other than the modified graphite particles and binder component, as long as the effects of the present invention are not impaired. Examples of such components include an organic solvent, a curing accelerator, a viscosity modifier, a dispersant, a polymerization initiator, and a flame retardant.

[0080] When the composition of the present invention is a curable composition containing components that can react with each other, such as a resin binder precursor, it is preferable to store the composition at a low temperature at which the reaction between the components does not occur or is sufficiently suppressed so that the components are maintained in a stable state. For example, the composition can be stored at 10°C or below, preferably 5°C or below, more preferably 3°C or below, and even more preferably 0°C or below. If necessary, the composition can be stored in a dark place.

[0081] <Thermal conductive materials> The thermally conductive material of the present invention can be obtained by a conventional method except for using the composition of the present invention. Specifically, for example, the composition of the present invention can be applied to a substrate such as polyethylene terephthalate (PET), followed by a heating step (e.g., 5 to 90 minutes) at 80 to 200°C and a cooling step (e.g., 10 to 90 minutes) at 20 to 40°C as needed to obtain a thermally conductive material of the present invention having a desired shape. The heating and cooling steps may be repeated, and pressure (e.g., 1 to 20 MPa) may be applied as needed. The shape of the thermally conductive material of the present invention is not particularly limited, but is usually in the form of a sheet. Since the modified graphite particles contained in the thermally conductive material of the present invention have electrical conductivity, the thermally conductive material of the present invention can also be used as an electrically conductive material. The use of the thermally conductive material of the present invention is not particularly limited, and the thermally conductive material of the present invention is suitable for heat dissipation applications of power semiconductor devices used in various electrical equipment such as personal computers, general home appliances, and automobiles.

[0082] <Laminate> The laminate of the present invention comprises a modified graphite sheet obtained by the method of producing modified graphite of the present invention and an adhesive layer (adhesive sheet) on the modified graphite sheet. The laminate of the present invention may have the adhesive layer on one side or both sides of the modified graphite sheet. The adhesive layer may be, for example, a layer containing at least one type of adhesive compound (such as a resin and / or a low-molecular-weight compound). The adhesive layer may contain components other than the adhesive compound, such as a filler, as needed. The adhesive compound is preferably a compound that is insulating and / or flexible when adhered to an object. Among these, from the viewpoint of adhesiveness and insulating properties, it is preferable to contain at least one selected from the group consisting of polyimide resin, modified polyimide resin, polyamideimide resin, modified polyamideimide resin, and epoxy compound. Specific examples include an epoxy resin layer (a layer formed by curing an epoxy compound), a polyimide resin layer, a modified polyimide resin layer, a polyamideimide resin layer, and a modified polyamideimide resin layer. The epoxy compound may be an epoxy resin containing an acrylic-modified rubber. In addition, for example, an adhesive layer made of an acrylic adhesive, an olefin adhesive, a silicone adhesive, a natural rubber adhesive, or a synthetic rubber adhesive (preferably a (meth)acrylic compound adhesive layer, a polyolefin adhesive layer, a silicone compound adhesive layer, a natural rubber adhesive layer, or a synthetic rubber adhesive layer) can also be used as the adhesive layer. Among the above-mentioned resin binders and resin binders obtained from precursors of resin binders, those having adhesive or tackiness can also be formed into a layer and used as an adhesive layer. The thickness of the adhesive layer is not particularly limited and can be, for example, 1 to 30 μm. The laminate of the present invention may further include a release film, a substrate, and a protective film in addition to the modified graphite sheet and adhesive layer, provided that the effects of the present invention are not impaired. The method for producing the laminate of the present invention comprises laminating a modified graphite sheet obtained by the method for producing modified graphite of the present invention and an adhesive layer. The adhesive layer can be obtained, for example, by applying an adhesive layer composition (a composition containing components that form an adhesive layer, such as an epoxy compound) onto a substrate and drying (drying temperature: 80 to 150°C).

[0083] Since the modified graphite sheet contained in the laminate of the present invention has electrical conductivity, the laminate of the present invention can also be used as an electrically conductive material. The use of the laminate of the present invention is not particularly limited, and the laminate of the present invention is suitable as an electromagnetic wave shielding member or an antistatic member in, for example, mobile phones, liquid crystal displays, car navigation devices, notebook computers, etc. [Example]

[0084] The present invention will be described in more detail based on examples. However, the present invention is not to be construed as being limited by the examples except as defined in the present invention.

[0085] <Production and evaluation of modified graphite particles using graphite particles> Modified graphite particles were produced using graphite particles (powder) (particle size: 95% passing through 45 μm) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. The median diameter of graphite particles manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. is 20 μm (measured using a Mastersizer 2000 (trade name) manufactured by Malvern Panalytical).

[0086] [Production of graphite particles] Example 1A Graphite particles (50 g) were added to an aqueous NaOH solution (40 g NaOH / 400 mL water) and stirred at 25°C for 30 minutes to obtain an aqueous solution. A sodium persulfate solution (9.6 g sodium persulfate / 100 mL water) was then added to this aqueous solution, and the temperature was raised to 50°C. The solution was stirred for 3 hours to obtain graphite particle-containing water (step (1)). The pH of the aqueous solution was measured immediately after the start of the "3-hour stirring" and it was confirmed that this pH had not changed immediately after the "3-hour stirring" period had ended. The obtained pH values ​​are listed in Table 3 below. A Three-One Motor manufactured by Shinto Scientific Co., Ltd. was used for stirring at 150 rpm. The same stirring was used in the following Examples and Comparative Examples. The graphite particle-containing water was allowed to stand until the temperature reached 30°C, and the graphite particles were filtered and washed with water (500 mL) and acetonitrile (250 mL) in that order. The washed graphite particles were dried in an oven at 40°C for 24 hours to obtain modified graphite particles A1 (Gr-A1). Example 1B While the modified graphite particles A1 obtained in the same manner as in Example 1A were stirred in acetonitrile (100 mL), a hydrolyzed solution (solution of hydrolyzed silane coupling agent) (1.25 g) of a silane coupling agent (KBM-573 (trade name), manufactured by Shin-Etsu Chemical Co., Ltd.) was added to the acetonitrile. After the addition, the mixture was stirred at 25°C for 1 hour (step (2): step of contacting graphite with a surface modifier). The graphite particles in the acetonitrile were filtered, and then the filtered modified graphite particles were washed with acetonitrile (100 mL) and dried in an oven at 40°C for 24 hours to obtain modified graphite particles B1 (Gr-B1). The hydrolysis solution of the silane coupling agent was prepared by mixing the silane coupling agent (1 g), ethanol (500 μL), 2-propanol (500 μL), water (720 μL), and acetic acid (100 μL), and stirring the mixture for 30 minutes at 25° C. In the following examples and comparative examples, a hydrolysis solution of the silane coupling agent prepared in the same manner was used unless otherwise specified.

[0087] Example 2A Graphite particles (50 g) were added to an aqueous NaOH solution (40 g NaOH / 400 mL water) and stirred at 25°C for 30 minutes to obtain an aqueous solution. To this solution, sodium persulfate solution (9.6 g sodium persulfate / 100 mL water) and iron sulfate heptahydrate (1.1 g) were added, and the mixture was heated to 50°C and stirred for 3 hours to obtain graphite particle-containing water (step (1)). The pH of the aqueous solution was measured immediately after the start of the "3-hour stirring" and confirmed to be unchanged immediately after the "3-hour stirring" period. The obtained pH values ​​are listed in Table 3 below. The graphite particle-containing water was allowed to stand until it reached room temperature (25°C), and then the graphite particles were filtered out from the graphite particle-containing water. The filtered graphite particles were washed with 1N hydrochloric acid (500 mL), water (500 mL), and acetonitrile (250 mL) in that order, and then dried in an oven at 40°C for 24 hours to obtain modified graphite particles A2 (Gr-A2). Example 2B) While stirring the modified graphite particles A2 obtained in the same manner as in Example 2A in acetonitrile (100 mL), a hydrolyzed solution (1.25 g) of a silane coupling agent (KBM-573) was added to the acetonitrile, and the mixture was stirred at room temperature for 1 hour (step (2): contacting graphite with a surface modifier). The modified graphite particles in the acetonitrile were filtered, washed with acetonitrile (100 mL), and dried in an oven at 40°C for 24 hours to obtain modified graphite particles B2 (Gr-B2).

[0088] Example 3A Graphite particles (50 g) were added to water (400 mL) and stirred to obtain a mixed solution. A sodium hypochlorite aqueous solution (sodium hypochlorite pentahydrate: 9.6 g / water: 100 mL) was added to the mixed solution, and the resulting aqueous solution was heated to 50°C and stirred for 3 hours to obtain graphite particle-containing water (step (1)). The pH of the aqueous solution was measured immediately after the start of the "3-hour stirring" and it was confirmed that this pH had not changed immediately after the "3-hour stirring" period had ended. The obtained pH values ​​are listed in Table 3 below. The graphite particle-containing water was allowed to stand until it reached room temperature, and then the graphite particles were filtered out from the graphite particle-containing water. The filtered graphite particles were washed with water (500 mL) and acetonitrile (250 mL) in that order, and dried in an oven at 40°C for 24 hours to obtain modified graphite particles A3 (Gr-A3). Example 3B While stirring the modified graphite particles A3 obtained in the same manner as in Example 3A in acetonitrile (100 mL), a hydrolyzed solution of a silane coupling agent (KBM-573) (1.25 g) was added to the acetonitrile, and the mixture was stirred at 25°C for 1 hour (step (2): contacting graphite with a surface modifier). The modified graphite particles in the acetonitrile were filtered, washed with acetonitrile (100 mL), and dried in an oven at 40°C for 24 hours to obtain modified graphite particles B3 (Gr-B3).

[0089] Example 4A Graphite particles (50 g) were added to an aqueous NaOH solution (40 g NaOH / 400 mL water) and stirred at 25°C for 30 minutes to obtain an aqueous solution. A cerium ammonium nitrate solution (9.6 g cerium ammonium nitrate / 100 mL water) was then added to this aqueous solution, and the temperature was raised to 50°C. The solution was stirred for 3 hours to obtain graphite particle-containing water (step (1)). The pH of the aqueous solution was measured immediately after the start of the "3-hour stirring" and it was confirmed that this pH had not changed immediately after the "3-hour stirring" period had ended. The obtained pH values ​​are listed in Table 3 below. The graphite particle-containing water was allowed to stand until it reached room temperature, and then the graphite particles were filtered out from the graphite particle-containing water. The filtered graphite particles were washed with 1 N hydrochloric acid (500 mL), water (500 mL), and acetonitrile (250 mL) in that order, and then dried in an oven at 40°C for 24 hours to obtain modified graphite particles A4 (Gr-A4). Example 4B The modified graphite particles A4 obtained in the same manner as in Example 4A were stirred in acetonitrile (100 mL), while the hydrolyzed solution of a silane coupling agent (KBM-573) (1.25 g) in acetonitrile was added thereto, followed by stirring at 25°C for 1 hour (step (2): contacting graphite with a surface modifier). The modified graphite particles were filtered out from the graphite particle-containing water, washed with acetonitrile (100 mL), and dried in an oven at 40°C for 24 hours to obtain modified graphite particles B4 (Gr-B4).

[0090] Examples 5A and 5B Modified graphite particles A5 (Gr-A5) and modified graphite particles (Gr-B5) were obtained in the same manner as in Examples 1A and 1B, except that the aqueous sodium persulfate solution having a composition of "sodium persulfate: 9.6 g / water: 100 mL" in Example 1A was changed to an aqueous sodium persulfate solution having a composition of "sodium persulfate: 48 g / water: 100 mL."

[0091] Examples 6A and 6B Modified graphite particles A6 (Gr-A6) and modified graphite particles B6 (Gr-B6) were obtained in the same manner as in Examples 1A and 1B, except that the aqueous NaOH solution having a composition of "NaOH: 40 g / water: 400 mL" in Example 1A was changed to an aqueous NaOH solution having a composition of "NaOH: 2 g / water: 400 mL."

[0092] Examples 7A and 7B Modified graphite particles A7 (Gr-A7) and modified graphite particles B7 (Gr-B7) were obtained in the same manner as in Examples 1A and 1B, except that the aqueous sodium persulfate solution having a composition of "sodium persulfate: 9.6 g / water: 100 mL" in Example 1A was changed to an aqueous potassium iodate solution having a composition of "potassium iodate: 9.6 g / water: 100 mL."

[0093] Examples 8A and 8B Modified graphite particles A8 (Gr-A8) and modified graphite particles B8 (Gr-B8) were obtained in the same manner as in Examples 1A and 1B, except that the aqueous sodium persulfate solution having a composition of "sodium persulfate: 9.6 g / water: 100 mL" in Example 1A was changed to an aqueous potassium persulfate solution having a composition of "potassium persulfate: 9.6 g / water: 100 mL."

[0094] Examples 9A and 9B Modified graphite particles A9 (Gr-A9) and modified graphite particles B9 (Gr-B9) were obtained in the same manner as in Examples 1A and 1B, except that the aqueous sodium persulfate solution having a composition of "sodium persulfate: 9.6 g / water: 100 mL" in Example 1A was changed to an aqueous ammonium persulfate solution having a composition of "ammonium persulfate: 9.6 g / water: 100 mL."

[0095] Examples 10A and 10B Modified graphite particles A10 (Gr-A10) and modified graphite particles B10 (Gr-B10) were obtained in the same manner as in Examples 1A and 1B, except that the silane coupling agent in Example 1B was changed to a titanium coupling agent (Plenact-38S (trade name), manufactured by Ajinomoto Fine-Techno Co., Inc.). The modified graphite particles A10 (Gr-A10) are the same as the modified graphite particles A1 (Gr-A1).

[0096] Comparative Example 1 In Comparative Example 1, graphite particles (powder) (particle size: 95% passing through 45 μm) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. were used.

[0097] Comparative Example 2 Untreated graphite particles (graphite particles not subjected to the surface modification in step (1)) were subjected to step (2) using the hydrolysis solution of the silane coupling agent described in Example 1B to obtain surface-treated graphite particles C1 (Gr-C1).

[0098] [Preparation of Epoxy Resin Composition Containing Modified Graphite Particles] Components (A) to (D) were mixed in the order shown in Table 1 below so as to obtain the contents shown in Table 1, and then component (E) was added to the resulting mixture. The resulting mixture was mixed at room temperature for 5 minutes using a planetary centrifugal mixer (THINKY Corporation, Awatori Rentaro ARE-310 (trade name)) to prepare a composition having the formulation shown in Table 1 below.

[0099] [Table 1]

[0100] (Table notes) Component (A): Cyclopentanone Component (B): Novolac phenolic resin (MEH-7500 (trade name), manufactured by Showa Kasei Co., Ltd.) Component (C): Bisphenol F type epoxy resin (EPICLON 830-S (trade name), manufactured by DIC Corporation) Component (D): Triphenylphosphine Component (E): Compositions e1A to e10B and Comparative Example e2c used the modified graphite particles prepared above in Examples 1A to 10B and Comparative Example 2. For Composition e1c, graphite particles (powder) (particle size: 95% passing through 45 μm) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. were used as is.

[0101] The content of components (B) to (E) is the percentage (volume %) of the content of each component in the total solid content in the composition (total content of components (B) to (E)).

[0102] [Preparation of resin sheet using epoxy resin composition listed in Table 1] [Resin sheet e1A] Using an applicator, composition e1A was uniformly applied onto the release surface of a release-treated polyester film (NP-100A (trade name), manufactured by Panac Corporation, film thickness 100 μm), and the film was left to stand at 120°C for 5 minutes to obtain a semi-cured sheet (semi-cured film). The resulting semi-cured sheet was heat-pressed in air (pressed at a hot plate temperature of 180°C and a pressure of 5 MPa for 5 minutes, then left to stand at 180°C for 90 minutes under normal pressure) to cure the coating, yielding a laminate of the cured sheet and polyester film. The polyester film was peeled off from the laminate to yield a cured sheet (resin sheet e1A) with an average thickness of 120 μm.

[0103] [Resin sheets e1B to e10B, e1c and e2c] Resin sheets e1B to e10B, e1c and e2c were produced in the same manner as resin sheet e1A, except that compositions e1B to e10B, e1c and e2c were used instead of composition e1A.

[0104] [Preparation of Silicone Resin Composition Containing Modified Graphite Particles] Components (E), (F), and (G) shown in Table 2 below were mixed at 25°C for 5 minutes using a planetary centrifugal mixer (THINKY Corporation, Awatori Rentaro ARE-310 (trade name)) so that the components were in the amounts shown in Table 2 below, thereby preparing a composition having the formulation shown in Table 2 below.

[0105] [Table 2]

[0106] (Table notes) Component (F): 1:1 (volume ratio) of component A and component B of "KE-1012 A / B (product name, manufactured by Shin-Etsu Chemical Co., Ltd.)," a precursor to a silicone resin binder. Component (G): Toluene Component (E): Compositions s1A to s10B and Comparative Example s2c used the modified graphite particles or surface-treated modified graphite particles prepared above in Examples 1A to 10B and Comparative Example 2. For composition s1c, graphite particles (powder) (particle size: 95% passing through 45 μm) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. were used as is.

[0107] The contents of components (F) and (E) are the proportions of the content of each component relative to the total solid content in the composition (total content of components (F) and (E)).

[0108] [Preparation of resin sheets using silicone resin compositions listed in Table 2] [Resin sheet s1A] Using an applicator, composition s1A was uniformly applied to a release surface of a release-treated polyester film (NP-100A (trade name), manufactured by Panac Corporation, film thickness 100 μm) to a thickness of 1 mm, and the coating was then allowed to stand at 80°C for 30 minutes to obtain a coating film. A new polyester film was laminated onto the coating of the coated polyester film thus obtained, with the release surface facing the coating, to obtain a laminate having a "polyester film-coating-polyester film" structure. The laminate was heat-pressed (hot plate temperature: 100°C) in air under conditions such that the thickness of the resulting resin sheet was 500 µm. The polyester films on both sides of the laminate were peeled off to obtain a resin sheet s1A (cured coating film, average film thickness: 500 µm).

[0109] [Resin sheets s1B to s10B, s1c and s2c] Resin sheets s1B to s10B, s1c and s2c were produced in the same manner as for the resin sheet s1A, except that compositions s1B to s10B, s1c and s2c were used instead of composition s1A. The resin sheet obtained was subjected to the following tests, and the results are summarized in Table 3 below.

[0110] [Test example] [Test Example 1: Filling Evaluation] The specific gravity of the resin sheet was measured by the Archimedes method (using a solid specific gravity measurement kit) using a Mettler Toledo XS204 balance. The higher the specific gravity, the fewer voids there are in the resin sheet (meaning that the modified graphite particles are densely packed in the resin sheet). For resin sheets eA1 to e10B, the specific gravity of each sheet was substituted for the specific gravity of "resin sheet eX" in the following formula e) to obtain a value (increase in specific gravity), which was then evaluated according to the evaluation criteria described below. A grade of "C" or higher is considered acceptable. Formula e) Increase = specific gravity of resin sheet eX - specific gravity of resin sheet e1c The resin sheets sA1 to s10B were evaluated by substituting the specific gravity of each of the resin sheets sA1 to s10B for the specific gravity of "resin sheet sX" in the following formula s) to obtain a value (increase) according to the evaluation criteria described below. A grade of "C" or higher is acceptable. Formula s) Increase amount = specific gravity of resin sheet sX - specific gravity of resin sheet s1c -Evaluation criteria- "AA": Increase amount is 0.05 or more "A": The increase is 0.04 or more but less than 0.05 "B": The increase is 0.02 or more but less than 0.04 "C": The increase is greater than 0 and less than 0.02 "D":0 The resin sheets e1c and s1c used as the reference were rated "D."

[0111] [Test Example 2: Thermal Conductivity Evaluation] For each resin sheet, the thermal conductivity (W / m·k) was calculated using the following procedure, and the thermal conductivity was evaluated according to the evaluation criteria described below. (1) Using "LFA467" (trade name) manufactured by NETZSCH, the thermal diffusivity of the resin sheet in the thickness direction was measured by the laser flash method. (2) Using a balance "XS204" (product name) manufactured by Mettler-Toledo, the specific gravity of the resin sheet was measured by the Archimedes method (using a "solid specific gravity measurement kit"). (3) Using a Seiko Instruments Inc. "DSC320 / 6200" (trade name), the specific heat of the resin sheet at 25°C was determined under the condition of a temperature increase of 10°C / min. (4) The thermal conductivity (W / m·k) of the resin sheet was calculated by multiplying the obtained thermal diffusivity by the specific gravity and specific heat. (5) The thermal conductivity of each resin sheet obtained in (4) was substituted into the "thermal conductivity of resin sheet" in the following formula H), and the obtained value (increased heat quantity) was evaluated according to the evaluation criteria described below. A grade of "C" or higher is considered acceptable. Formula H) Increased heat (W / m·k) = Thermal conductivity of resin sheet - Thermal conductivity of reference resin sheet The "reference resin sheet" is a resin sheet produced in the same manner as each resin sheet described in Table 3, except that graphite particles (powder) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. were used instead of the modified graphite particles in the preparation of each composition used to produce each resin sheet described in Table 3. The thermal conductivity evaluation of the resin sheets e1c and s1c produced without using modified graphite particles was "D" in the following evaluation criteria. -Evaluation criteria- "AA": Increased heat quantity is 1.5W / mK or more "A": Increase in heat is 1.0W / mK or more but less than 1.5W / mK "B": Increase in heat is 0.5W / mK or more but less than 1.0W / mK "C": Increase in heat is greater than 0 W / mK and less than 0.5 W / mK "D":0

[0112] [Table 3]

[0113] (Table notes) Gr: Graphite particles (powder) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. KBM-573: Trade name, manufactured by Shin-Etsu Chemical Co., Ltd., N-phenyl-3-aminopropyltrimethoxysilane 38S: PLENACT 38S (titanium coupling agent, manufactured by Ajinomoto Fine-Techno Co., Ltd.) ≧14.0: means 14.0 or greater. In Comparative Example 1, Gr is listed in the column for modified graphite particles to facilitate comparison with Examples. Similarly, in Comparative Example 2, the surface-treated graphite particles are listed in the column for modified graphite particles.

[0114] Table 3 reveals the following: Resin sheets e1c and s1c made using raw graphite particles were inferior in specific gravity and thermal conductivity. Resin sheets e2c and s2c made using surface-treated graphite particles that were subjected only to step (2) of the manufacturing method of the present invention, without undergoing step (1), also had inferior specific gravity and thermal conductivity. In contrast, resin sheets e1A to e10B and s1A to s10B (thermal conductive material of the present invention) produced using modified graphite particles obtained by the modified graphite production method of the present invention passed all the tests for specific gravity and thermal conductivity.

[0115] <Production and evaluation of modified graphite sheets using graphite sheets> A modified graphite sheet was produced using 1.5 g of a graphite sheet (length 90 mm, width 115 mm, thickness 70 μm, manufactured by Panasonic Corporation, product name: EYGS091207).

[0116] Example 11A An aqueous solution of sodium persulfate (2.4 g of sodium persulfate / 25 mL of water) was added to an aqueous solution of NaOH (10 g of NaOH / 100 mL of water), and the temperature of the solution was then raised to 50°C. The graphite sheet was then immersed in the solution for 1 hour (step (1)). The pH of the solution was measured immediately after the temperature was raised to 50°C, and it was confirmed that the pH had not changed even after the "1-hour immersion." The pH is shown in Table 4 below. After immersion, the graphite sheet was taken out, washed with 100 mL of water, and then dried in an oven at 40°C for 24 hours to obtain modified graphite sheet A11 (GrS-A11). Example 11B A modified graphite sheet A11 obtained in the same manner as in Example 11A was immersed in a mixture of 100 mL of acetonitrile and 1.25 g of a hydrolyzed solution of a silane coupling agent at 25°C for 10 minutes (step (2): contacting graphite with a surface modifier). The graphite sheet was removed, washed with 100 mL of acetonitrile, and dried in an oven at 40°C for 24 hours to obtain a modified graphite sheet B11 (GrS-B11).

[0117] Example 12A An aqueous sodium hypochlorite solution (2.4 g sodium hypochlorite pentahydrate / 25 mL water) was added to 100 mL of water, and the solution was heated to 50°C. The graphite sheet was then immersed in the solution for 1 hour (step (1)). The pH of the solution was measured immediately after heating to 50°C, and it was confirmed that the pH had not changed even after the "1-hour immersion." The pH is shown in Table 4 below. After immersion, the graphite sheet was taken out, washed with 100 mL of water, and then dried in an oven at 40°C for 24 hours to obtain modified graphite sheet A12 (GrS-A12). Example 12B Modified graphite sheet A12 obtained in the same manner as in Example 12A was immersed in a mixture of 100 mL of acetonitrile and 1.25 g of a hydrolyzed solution of a silane coupling agent at 25°C for 10 minutes (step (2): contacting graphite with a surface modifier). The graphite sheet was removed, washed with 100 mL of acetonitrile, and dried in an oven at 40°C for 24 hours to obtain modified graphite sheet B12 (GrS-B12).

[0118] Examples 13A and 13B Modified graphite sheet A13 (GrS-A13) and modified graphite sheet B13 (GrS-B13) were obtained in the same manner as in Examples 11A and 11B, except that the aqueous sodium persulfate mixture in Example 11A was changed to an aqueous sodium persulfate mixture of 12 g sodium persulfate and 25 mL water.

[0119] Examples 14A and 14B Modified graphite sheet A14 (GrS-A14) and modified graphite sheet B14 (GrS-B14) were obtained in the same manner as in Examples 11A and 11B, except that the aqueous sodium persulfate mixture in Example 11A (2.4 g sodium persulfate / 25 mL water) was changed to the aqueous potassium persulfate mixture in Example 11A (2.4 g potassium persulfate / 25 mL water).

[0120] Examples 15A and 15B Modified graphite sheet A15 (GrS-A15) and modified graphite sheet B15 (GrS-B15) were obtained in the same manner as in Examples 11A and 11B, except that the aqueous sodium persulfate having a blend of "sodium persulfate: 2.4 g / water: 25 mL" in Example 11A was changed to an aqueous ammonium persulfate having a blend of "ammonium persulfate: 2.4 g / water: 25 mL."

[0121] Examples 16A and 16B Modified graphite sheet A16 (GrS-A16) and modified graphite sheet B16 (GrS-B16) were obtained in the same manner as in Examples 11A and 11B, except that the silane coupling agent in Example 11B was changed to a titanium coupling agent (Plenact-38S (trade name), manufactured by Ajinomoto Fine-Techno Co., Inc.). The modified graphite sheet A16 (GrS-A16) is the same as the modified graphite sheet A11 (GrS-A11).

[0122] Comparative Example 3 In Comparative Example 3, a graphite sheet manufactured by Panasonic Corporation (length 90 mm, width 115 mm, thickness 70 μm, product name: EYGS091207) was used.

[0123] Comparative Example 4 An untreated graphite sheet (a graphite sheet that has not been subjected to the surface modification in step (1)) was subjected to step (2) using the hydrolysis solution of the silane coupling agent described in Example 11B to obtain a surface-treated graphite sheet C1 (GrS-C1).

[0124] [Test Example 3: Adhesion Evaluation] (Preparation of test specimens) Cyclopentanone (76 g), novolac-type phenolic resin (MEH-7500 (trade name), manufactured by Showa Kasei Co., Ltd.) (7.2 g), bisphenol F-type epoxy resin (EPICLON 830-S (trade name), manufactured by DIC Corporation) (12 g), and triphenylphosphine (0.4 g) were mixed in this order at room temperature for 20 minutes to obtain a composition for the adhesive layer. The adhesive layer composition was spin-coated onto one side of an electrolytic copper foil (20 mm × 100 mm, thickness: 35 μm) and dried at 120° C. for 1 minute to obtain a copper foil with an adhesive layer. The thickness of the adhesive layer was 10 μm. The adhesive layer composition was spin-coated onto one side of an aluminum plate (30 mm × 60 mm, thickness: 1 mm) and dried at 120 ° C. for 1 minute to obtain an aluminum plate with an adhesive layer. The thickness of the adhesive layer was 10 μm. A 20 mm × 60 mm strip was cut out from each of the modified graphite sheets of Examples 11A to 16B, the graphite sheet of Comparative Example 3, and the surface-treated graphite sheet of Comparative Example 4. The strip was sandwiched between a copper foil with an adhesive layer and an aluminum plate with an adhesive layer, with the adhesive layers of the copper foil and the aluminum plate in contact with the graphite sheet. The resulting laminate was subjected to a heat press treatment in air (heat plate temperature 180°C, pressure 5 MPa, 5 minutes) to obtain test pieces 11A to 16B, c3, and c4.

[0125] (Peel test (measuring peel strength)) The peel strength when peeling the copper foil from the modified graphite sheet or graphite sheet of each test piece was measured using a digital force gauge (ZTS-200N (trade name), manufactured by Imada Co., Ltd.) and a 90-degree peel test jig (P90-200N-BB (trade name), manufactured by Imada Co., Ltd.) according to the method for measuring peel strength under normal conditions described in JIS C 6481-1996. In the peel strength test, the copper foil was peeled at an angle of 90° to the aluminum plate with the copper foil attached, at a peel rate of 50 mm / min. Peeling occurred between the modified graphite sheet or graphite sheet and the adhesive layer on the copper foil. The peel strength (N / cm) of each test piece was substituted into the "peel strength of the test piece" in the following formula P), and the obtained value (increased peel strength) was evaluated according to the evaluation criteria described below. A grade of "B" or higher is considered a pass level. Formula P) Increased peel strength (N / cm) = Peel strength of test piece - Peel strength of test piece 3c The peel strength evaluation of test piece 3c, which was produced without using modified graphite particles, was rated "C" in the following evaluation criteria. "AA": Increase of 2.0N / cm or more "A": Increase of 1.5N / cm or more but less than 2.0N / cm "B": An increase of 0.5N / cm or more but less than 1.5N / cm "C": 0 or an increase of less than 0.5 N / cm

[0126] [Table 4]

[0127] (Table notes) GrS: Panasonic graphite sheet (length 90 mm, width 115 mm, thickness 70 μm, product name: EYGS091207) KBM-573: Trade name, manufactured by Shin-Etsu Chemical Co., Ltd. 38S: Plainact 38S (product name, manufactured by Ajinomoto Fine-Techno Co., Ltd.) ≧14.0: means 14.0 or greater. In Comparative Example 3, GrS is listed in the modified graphite sheet column to facilitate comparison with the Examples. Similarly, in Comparative Example 4, the surface-treated graphite sheet is listed in the modified graphite sheet column.

[0128] Table 4 reveals the following: Test piece 3c, which was made using the raw graphite sheet, had poor adhesiveness. Test piece 4c, which was made using a surface-treated graphite sheet that had been subjected only to step (2) of the manufacturing method of the present invention, without undergoing step (1), also had poor adhesiveness. In contrast, all of the test pieces 11A to 16B (laminates of the present invention) made using modified graphite sheets obtained by the method for producing modified graphite of the present invention passed the test for adhesiveness.

Claims

1. a step (1) of mixing graphite with an oxidizing agent in an aqueous solution having a pH of 12.0 or more, and modifying a surface of the graphite in the aqueous solution; The method for producing modified graphite, wherein the oxidizing agent has a standard oxidation-reduction potential of 1.0 V or more.

2. 2. The method for producing modified graphite according to claim 1, wherein the oxidizing agent has a standard oxidation-reduction potential of 1.5 V or more.

3. 3. The method for producing modified graphite according to claim 2, wherein the oxidizing agent has a standard oxidation-reduction potential of 1.8 V or more.

4. The method for producing modified graphite according to any one of claims 1 to 3, wherein the oxidizing agent is a persulfate.

5. 5. The method for producing modified graphite according to claim 1, further comprising: a step (2) of contacting the modified graphite obtained in step (1) with a surface modifier in the presence of at least one of water and an organic solvent.

6. 6. The method for producing modified graphite according to claim 5, wherein the surface modifier is at least one of a metal coupling agent, a curing compound, a carboxylic acid compound, an organic phosphonic acid compound, and an organic phosphate ester.

7. the graphite is graphite particles; A method for producing a composition, comprising obtaining modified graphite particles by the method for producing modified graphite according to any one of claims 1 to 6, and mixing the obtained modified graphite particles with a resin binder or a precursor thereof.

8. A method for producing a thermally conductive material, comprising obtaining a composition by the method for producing a composition according to claim 7 and applying the obtained composition onto a substrate.

9. the graphite is a graphite sheet; A method for producing a laminate, comprising: obtaining a modified graphite sheet by the method for producing modified graphite according to any one of claims 1 to 6; and laminating the obtained modified graphite sheet and an adhesive layer.

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