Graphite production method and composition for producing graphite

Abstract

The purpose of the present invention is to provide a method for producing a graphite, said method utilizing a heat treatment at high temperatures and enabling the production of a graphite of high quality without using a resin as a starting material, or without being restricted to a specific resin even in cases where a resin is used as a starting material. The present invention relates to a method for producing a graphite, said method comprising a step in which a starting material is subjected to a heat treatment at a temperature of 2,400°C or higher, wherein: the starting material contains (A) a graphene oxide, while optionally containing (B) a resin; and the mass ratio of carbon to oxygen (C / O) in the graphene oxide (A) is from 0.1 to 20. The content of the graphene oxide (A) in the starting material may be from 0.3% by weight to 20% by weight, or may be from 50% by weight to 100% by weight. The average particle diameter of the graphene oxide (A) may be from 2 μm to 40 μm.

Description

[Technical Field]

[0001] The present invention relates to a method for producing graphite and to compositions for use in producing graphite. [Background technology]

[0002] Graphite is a material with excellent heat resistance, chemical resistance, and high thermal and electrical conductivity. In particular, graphite film, which is made from crystalline graphite, has recently been used as a heat dissipation material for semiconductor elements and other heat-generating components installed in various electronic and electrical devices such as computers and smartphones.

[0003] A known method for producing graphite film is the expanded graphite method. In this method, natural graphite is first immersed in a mixture of concentrated sulfuric acid and concentrated nitric acid and rapidly heated to form expanded graphite. The acid is then removed by washing, and the graphite film is then processed into a film using a high-pressure press. However, the graphite film produced by this method has low strength and insufficient physical properties, and also has problems such as the influence of residual acid.

[0004] To solve these problems, a method has been developed in which a special resin film is baked at high temperatures to form graphite (see, for example, Patent Document 1). Examples of resin films used in this method include films containing polyoxadiazole, polyimide, polyphenylene vinylene, polybenzimidazole, polybenzoxazole, polythiazole, and polyamide. This method is much simpler than the expanded graphitization method, and the resulting graphite film has the advantages of being essentially free of impurities such as acids and having excellent thermal conductivity and electrical conductivity properties close to those of single-crystal graphite.

[0005] Patent Document 2 describes a method of obtaining a heat-dissipating molded body by carbonizing the resin component in a molded body containing resin and expanded graphite powder. However, it only describes carbonization at a maximum temperature of 800°C, and does not describe or suggest graphitization, which requires high temperatures of 2400°C or higher. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-123506 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-122663 Summary of the Invention [Problem to be solved by the invention]

[0007] In conventional methods for producing highly crystalline graphite, which involve graphitizing resin through high-temperature heat treatment, the types of resin that can be used as raw materials are limited, and it has been necessary to use special types of resin.

[0008] In view of the above-described current situation, an object of the present invention is to provide a method for producing graphite by utilizing a heat treatment at high temperature, which method can realize the production of high-quality graphite without using a resin as a raw material, or, if a resin is used, without being limited to a special resin. [Means for solving the problem]

[0009] As a result of extensive research, the present inventors have found that when a raw material composed mainly of graphene oxide is heat-treated at high temperature, graphite with good qualities such as thermal diffusivity can be produced even if the raw material does not contain resin, or even if the raw material contains resin, without being limited to a special resin, and have arrived at the present invention.

[0010] That is, the present invention relates to a method for producing graphite, which includes a step of heat-treating a raw material at a temperature of 2400°C or higher, wherein the raw material contains graphene oxide (A), and the graphene oxide (A) has a mass ratio of carbon to oxygen (C / O) of 0.1 or more and 20 or less. Preferably, the raw material is composed of a resin composition further containing a resin (B). More preferably, the raw material has, in X-ray diffraction measurement, a graphene oxide orientation peak in a small angle region and a resin orientation peak in a high angle region. Preferably, the graphene oxide (A) has a mass ratio of carbon to oxygen (C / O) of 1.1 or more and less than 3.5. Preferably, the average particle size of the graphene oxide (A) is 2 μm or more and 40 μm or less. Preferably, the resin composition contains 0.3 to 20% by weight of graphene oxide (A) relative to 100% by weight of the resin composition. Preferably, the raw material is composed of 50 to 100% by weight of graphene oxide (A) and 0 to 50% by weight of resin (B). Preferably, resin (B) is one or more selected from the group consisting of polyacrylonitrile resin, polyvinyl alcohol resin, polyvinyl chloride resin, phenol resin, epoxy resin, melamine resin, acrylic resin, amide resin, amide-imide resin, and imide resin, more preferably, resin (B) is a phenol resin, and even more preferably, the phenol resin is a resole resin. Preferably, the step of heat-treating the raw material includes a step of performing heat treatment at a temperature of 2800° C. or higher. More preferably, the step of heat-treating the raw material includes a step of performing heat treatment at a temperature of 2800° C. or higher while applying a load to the raw material. Preferably, the raw material is in the form of a film, and more preferably, the thickness of the film is 10 nm to 1 mm. Preferably, the production method further includes a step of applying or casting a dispersion containing graphene oxide (A) onto a substrate to form the raw material. 16. The method according to claim 1, wherein the raw material is preferably produced by applying multiple layers to a thickness of 10 μm or less per application. The present invention also relates to a composition for producing graphite, the composition containing graphene oxide (A), in which the mass ratio of carbon to oxygen (C / O) of the graphene oxide (A) is 0.1 or more and 20 or less. Preferably, the composition further contains a resin (B). Preferably, the graphene oxide (A) has a mass ratio of carbon to oxygen (C / O) of 1.1 or more and less than 3.5. Preferably, the average particle size of the graphene oxide (A) is 2 μm or more and 40 μm or less. [Effects of the Invention]

[0011] According to the present invention, there can be provided a method for producing graphite using a high-temperature heat treatment, which can produce high-quality graphite without using a resin as a raw material, or even if a resin is used, without being limited to a special resin. [Brief explanation of the drawings]

[0012] [Figure 1] X-ray diffraction measurement results for the raw material film of Example 2 DETAILED DESCRIPTION OF THE INVENTION

[0013] Specific embodiments of the present invention will be described in detail below. The present embodiment relates to a method for producing graphite by graphitizing a raw material containing graphene oxide (A) and, optionally, a resin (B) by heat-treating the raw material at a temperature of 2400° C. or higher. The raw material may be composed essentially of graphene oxide (A) alone, or may be composed of a resin composition containing graphene oxide (A) and a resin (B).

[0014] Graphene is a sheet-shaped substance composed of sp2-bonded carbon atoms and having a thickness of one to several carbon atoms. Graphene oxide (A) is graphene in which part of the graphene surface is substituted or modified with oxygen or oxygen-containing functional groups such as hydroxyl groups or carboxyl groups.

[0015] The graphene oxide (A) has a carbon to oxygen mass ratio (C / O) of 0.1 or more and 20 or less. If the mass ratio is less than 0.1, it becomes difficult to maintain the graphene structure. If the mass ratio exceeds 20, the oxygen content in the graphene oxide becomes low, making it difficult to produce good quality graphite, and in particular, it becomes difficult to produce graphite with high thermal diffusivity. The mass ratio is preferably 10 or less, more preferably 5 or less, particularly preferably less than 3.5, and most preferably 3.0 or less. The lower limit of the mass ratio is preferably 0.6 or more, more preferably 0.7 or more, and particularly preferably 1.1 or more.

[0016] In another embodiment, the mass ratio of carbon to oxygen (C / O) in the graphene oxide (A) may be 0.5 or more and less than 20. In this embodiment, the mass ratio is preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less. The lower limit of the mass ratio is preferably 0.6 or more, more preferably 0.7 or more, and even more preferably 1.0 or more.

[0017] The mass ratio of carbon to oxygen (C / O) of the graphene oxide (A) can be measured for a film obtained by drying the graphene oxide (A) using a CHN elemental analyzer (PE2400II manufactured by PerkinElmer).

[0018] The thickness of the graphene oxide (A) is not particularly limited, but is preferably 100 nm or less, more preferably 50 nm or less, even more preferably 10 nm or less, and particularly preferably 1 nm or less. The thickness of the graphene oxide (A) can be measured in tapping mode by applying a dispersion of the graphene oxide (A) to a silicon substrate and using a scanning probe microscope (SFM: AXS-type Dimension Icon manufactured by Bruker).

[0019] The average particle size of the graphene oxide (A) is not particularly limited, but is preferably 30 nm to 1 mm, more preferably 50 nm to 100 μm, even more preferably 100 nm to 50 μm, even more preferably 0.3 μm to 30 μm, and particularly preferably 2 μm to 40 μm. The average particle size of the graphene oxide (A) can be calculated by applying a dispersion of the graphene oxide (A) to a silicon substrate, measuring it using a scanning electron microscope (SEM: Zeiss ULTRAplus) at an accelerating voltage of 1 kV to obtain an SEM image, randomly picking out a certain number of particles (e.g., 100 particles) from the SEM image, measuring the particle size of each particle, and dividing the sum of the measured values ​​by the number of particles.

[0020] As the graphene oxide (A), a commercially available product or an appropriately synthesized product may be used.

[0021] The method for synthesizing the graphene oxide (A) is not particularly limited, and examples thereof include a method of oxidizing graphite with an oxidizing agent and then exfoliating it, or a method of performing electrolysis using graphite as a working electrode and then exfoliating it. Examples of the method of oxidation with an oxidizing agent include the Brodie method (using nitric acid and potassium chlorate), the Staudenmaier method (using nitric acid, sulfuric acid, and potassium chlorate), and the Hummers-Offeman method (using sulfuric acid, sodium nitrate, and potassium permanganate). Examples of the electrolysis method include a method using an aqueous solution of an acidic substance such as sulfuric acid, nitric acid, or perchloric acid as an electrolyte solution. Examples of the exfoliation method include a method of applying a mechanical external force, a method of performing heat treatment, and a method of using ultrasonic irradiation.

[0022] The resin (B) is not particularly limited as long as it is an organic resin that can form a mixture with graphene oxide (A) and can be graphitized by heat treatment at 2400°C or higher. By using the resin (B) in combination with graphene oxide (A), graphite with a good appearance can be easily obtained. While either a thermosetting resin or a thermoplastic resin may be used, a thermosetting resin is preferred because it can be easily mixed with graphene oxide (A) to form a film. The thermosetting resin may be used in combination with a curing agent, a curing accelerator, a curing catalyst, etc., as needed.

[0023] Specific examples of the resin (B) include polyacrylonitrile resin, polyvinyl alcohol resin, polyvinyl chloride resin, phenol resin, epoxy resin, melamine resin, acrylic resin, amide resin, amide-imide resin, and imide resin. These may be used alone or in combination of two or more. Polyacrylonitrile resin or phenol resin is preferred, and phenol resin is more preferred, because it is easy to mix with graphene oxide (A) and form into a film, and is inexpensive.

[0024] The phenolic resin is a resin obtained by condensation polymerization of phenol and formaldehyde. The phenolic resin obtained by the condensation polymerization in the presence of an acid catalyst is a novolac resin, which is a thermoplastic resin. The phenolic resin obtained using an alkali catalyst is a resole resin. Since resole resins have self-reactive functional groups, they can be cured by heating and generally exhibit the properties of a thermosetting resin. As the phenolic resin, a resole resin is preferred because it can be easily mixed with graphene oxide (A) to form a film.

[0025] The viscosity of the resin (B) is not particularly limited, but is preferably 100 mPa·s or more, more preferably 200 mPa·s or more, and even more preferably 300 mPa·s or more.

[0026] The contents of graphene oxide (A) and resin (B) in the resin composition are not particularly limited. In one embodiment, the content of graphene oxide (A) is preferably 0.3 to 20 wt % and the content of resin (B) is preferably 80 to 99.7 wt % relative to 100 wt % of the resin composition. When the content of graphene oxide (A) is 0.3 to 20 wt %, it is possible to produce graphite of higher quality. More preferably, the content of graphene oxide (A) is 1 to 15 wt %, the content of resin (B) is 85 to 99 wt %, and even more preferably, the content of graphene oxide (A) is 1 to 10 wt %, and the content of resin (B) is 90 to 99 wt %.

[0027] In another embodiment, the content of graphene oxide (A) is preferably 50 to 100% by weight and the content of resin (B) is preferably 0 to 50% by weight, relative to 100% by weight of the raw materials. When the content of graphene oxide (A) is 50% by weight or more, graphite of good quality is more likely to be obtained. More preferably, the content of graphene oxide (A) is 80 to 100% by weight and the content of resin (B) is 0 to 20% by weight, and even more preferably, the content of graphene oxide (A) is 90 to 100% by weight and the content of resin (B) is 0 to 10% by weight. In this embodiment, the resin (B) does not have to be included in the raw materials.

[0028] In the production method of this embodiment, first, a raw material substantially composed of graphene oxide (A) alone or a raw material composed of a resin composition containing graphene oxide (A) and resin (B) is prepared. While the specific method for producing the raw material is not particularly limited, examples include a method in which graphene oxide (A), optionally resin (B), and, if necessary, a solvent or dispersion medium are mixed to obtain a liquid mixture or dispersion, and then the mixture or dispersion is applied or cast onto a substrate to form a thin film, dried, and the formed film is peeled off from the substrate. However, when a commercially available graphene oxide dispersion is used as graphene oxide (A), the solvent or dispersion medium does not need to be added separately. Furthermore, when a liquid resin, resin solution, or resin dispersion is used as resin (B), the solvent or dispersion medium does not need to be added separately.

[0029] Alternatively, a film containing graphene oxide (A) and resin (B) may be produced by mixing graphene oxide (A), a precursor of resin (B), optionally a reaction accelerator or catalyst, and optionally a solvent or dispersion medium to obtain a liquid mixture or dispersion, and then applying or casting the mixture or dispersion onto a substrate in the form of a thin film, followed by drying and allowing the precursor to react to form resin (B).

[0030] The solvent or dispersion medium is not particularly limited, but examples thereof include water, DMF, DMAc, DMSO, dichlorobenzene, toluene, xylene, methoxybenzene, ethanol, propanol, and pyridine.

[0031] The substrate may be a substrate or a film, or may be an endless belt, a stainless steel drum, or the like. Examples of the coating method include a method using spin coating or a method using bar coating. The coating may be performed once, or may be performed multiple times to perform multiple coatings. When a resin-containing film produced by multiple coatings is used as a raw material, graphite with a higher thermal diffusivity can be produced. When multiple coatings are performed, it is preferable that the coating thickness per coating be 10 μm or less.

[0032] Furthermore, when producing a resin-containing film, if the resin (B) is a thermoplastic resin, a method can also be used in which graphene oxide (A) and the resin (B) are melt-kneaded in an extruder, then extruded into a film from a T-die and cooled and solidified. Examples of such melt-kneading methods include methods using kneading devices such as a twin-screw kneader such as a plastomill, a single-screw extruder, a twin-screw extruder, a Banbury mixer, and a roll. Furthermore, the melt-kneaded mixture may be processed into a film by pressing.

[0033] The shape of the raw material containing graphene oxide (A) and optionally resin (B) is not particularly limited, but is preferably a film. The thickness of the film is not particularly limited, but is, for example, 10 nm to 1 mm, preferably 0.1 μm to 500 μm, and more preferably 1 to 300 μm.

[0034] Next, the raw material is heat-treated at a temperature of 2400°C or higher to produce graphite. Heat treatment at 2400°C or higher releases oxygen atoms from the graphene oxide (A), promoting graphitization, and carbonization of the resin (B), followed by graphitization. In one embodiment, the raw material contains graphene oxide (A) in addition to the resin (B). This allows the graphene oxide (A) to act as a nucleating material that increases the crystallinity of the resin (B). This makes it possible to produce high-quality graphite even when the resin (B) is a type of resin that could not be used in conventional polymer graphitization methods. In another embodiment, high-quality graphite can be produced even when the raw material does not contain resin (B) or contains only a small amount of resin (B). When the raw material is in the form of a film, a high-quality graphite film can be produced.

[0035] The heat treatment process will be specifically described. First, a raw material containing graphene oxide (A) and, optionally, a resin (B) is preheated in a non-oxidizing atmosphere such as nitrogen gas and carbonized. This allows for the production of glassy carbon. The carbonization process can be carried out by raising the temperature to a temperature of typically 80°C or higher (preferably 90°C or higher) and 1500°C or lower (e.g., 1000°C). The rate of temperature increase is not particularly limited, but is preferably 0.1°C / min to 10°C / min. For example, when raising the temperature to 1000°C at a rate of 10°C / min, it is desirable to maintain the temperature in the 1000°C temperature range for approximately 30 minutes. The carbonization process may be carried out under reduced pressure or while flowing an inert gas. The carbonization process may also be carried out while applying a load to the raw material that is small enough not to cause damage to the raw material.

[0036] The resulting carbon is then placed in an ultra-high temperature furnace and graphitized. In the graphitization process, rearrangement of graphite layers in the carbon proceeds, resulting in the formation of highly crystalline graphite. The carbonization and graphitization processes may be carried out consecutively in the same furnace, or may be carried out separately with a step of cooling the carbon after the carbonization process interposed therebetween.

[0037] The heating temperature during the graphitization step may be 2400°C or higher, preferably 2700°C or higher, and more preferably 2800°C or higher. The graphitization step is desirably carried out in an inert gas. The inert gas is not particularly limited, but argon is preferred, and argon containing a small amount of helium is more preferred. The rate of temperature increase during the graphitization step is not particularly limited, but is preferably 0.1°C / min to 10°C / min, for example. The graphitization step may be carried out under reduced pressure or while flowing an inert gas.

[0038] The graphitization step may be carried out while applying a load to the carbon using a press or the like. When the graphitization step is carried out while applying a load, graphite with a higher thermal diffusivity and a better appearance can be produced. The load is preferably 1 kg / cm. 2 More preferably, 10 kg / cm 2 More preferably, 50 kg / cm 2 That's all.

[0039] By carrying out the above steps, graphite with high thermal diffusivity can be produced by heat treating the raw material at a high temperature, even if the raw material does not contain a resin, or even if the raw material contains a resin, without being limited to a special resin. [Example]

[0040] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0041] (Method for measuring the thermal diffusivity of graphite) The thermal diffusivity of graphite was measured in an atmosphere of 20°C using a thermal diffusivity measuring device (Thermowave Analyzer TA-3, manufactured by Bethel Co., Ltd.) on a sample cut into a shape of 40 x 40 mm from the graphite.

[0042] (Method for evaluating the orientation of raw materials) The orientation of the raw material was evaluated using an X-ray diffractometer (Rigaku Corporation, SmartLab). X-rays were irradiated onto the edge of the raw material film, and WADX was measured. The measurement conditions were as follows: tube voltage and current were 40 kV and 50 mA, scan axis was 2θ (incident angle 0°), measurement mode was exposure, camera length was 25 mm, exposure time was 5 min, X-ray source was CuKα (λ = 1.54186 Å), goniometer length was 300 mm, and the optical system was set to parallel beam (double pinhole). The incident optical system was set to a first pinhole (selection slit) of φ0.3 mm, incident solar was open, second pinhole (collimator) of φ0.1 mm, third pinhole of φ1 mm, and the attachment was set to a 2D-SAXS / WAXS attachment + φ base. The receiving optical system was set to no receiving slit 1, no parallel slit analyzer, no receiving solar, and open receiving slit 2. The detector used was a two-dimensional detector HyPix-3000, monochromatic (parabolic multilayer mirror).

[0043] (How to check the appearance after graphitization) The appearance after graphitization was visually inspected, and a flat and uniform appearance was rated as "A," a very slight appearance with bubbles or unevenness was rated as "B," a slight appearance with bubbles or unevenness was rated as "C," and an appearance with bubbles or unevenness was rated as "D."

[0044] Example 1 A solution of graphene oxide (average particle size 1 μm, C / O ratio 1.2) in DMF (concentration approximately 2%) and a phenolic resin in methanol (a resol resin in methanol, concentration approximately 65%, viscosity 200 mPa·s) was mixed in a solids ratio of 10:90 (by weight). The mixture was applied to aluminum foil to a thickness of 30 μm after drying and then dried at room temperature. After drying, the aluminum foil was removed with hydrochloric acid, and the film was washed with water and dried to obtain a 30 μm thick raw film. The obtained raw material film was sandwiched between graphite plates and heated in a nitrogen atmosphere from room temperature to 1000°C at 1°C / min, and then held at 1000°C for 10 minutes to carbonize. The obtained carbonized film was then sandwiched between graphite plates and heated in a vacuum from room temperature to 2000°C at 2.5°C / min, then in argon from 2000°C to 2950°C at 2.5°C / min, and then held at 2950°C for 10 minutes to graphitize. The thermal diffusivity of the obtained graphite was 5.7 cm 2 / s.

[0045] [Table 1]

[0046] Example 2 A DMF solution (approximately 2% concentration) of graphene oxide (average particle size 1 μm, C / O ratio 1.2) and a methanol solution of phenolic resin (a methanol solution of resol resin, approximately 65% ​​concentration, viscosity approximately 200 mPa·s) were mixed at a solids ratio of 10:90 (by weight). This solution was applied to aluminum foil in four separate applications to a dry thickness of 30 μm. The drying temperatures after application were 60°C and 120°C. After final drying, the aluminum foil was removed with hydrochloric acid, and the film was washed with water and dried to obtain a 30 μm-thick raw film. The orientation of the resulting raw film is shown in Figure 1. There was a graphene oxide orientation peak in the small-angle region (2θ less than 5°) and a resin orientation peak in the high-angle region (2θ greater than 15°), confirming the orientation of the graphene oxide and resin. The obtained raw film was graphitized in the same manner as in Example 1. The thermal diffusivity of the obtained graphite was 7.6 cm 2 / s.

[0047] Example 3 Graphite was produced in the same manner as in Example 1, except that graphene oxide (average particle size 10 μm, C / O ratio 1.2) was used. The thermal diffusivity of the obtained graphite was 6.0 cm 2 / s.

[0048] Example 4 Graphite was produced in the same manner as in Example 2, except that graphene oxide (average particle size 10 μm, C / O ratio 1.2) was used. The thermal diffusivity of the obtained graphite was 7.8 cm 2 / s.

[0049] Examples 5 to 7 In Examples 5, 6, and 7, graphite was prepared in the same manner as in Example 3, except that the proportion (by weight) of graphene oxide was changed to 5%, 1%, and 20%. The thermal diffusivity of the obtained graphite was 5.5 cm 2 / s, 5.2cm 2 / s, 6.0cm 2 / s.

[0050] (Examples 8 to 11) For Examples 8, 9, 10, and 11, graphite was produced in the same manner as in Example 3, except that the graphene oxide (average particle size 10 μm, C / O ratio 1.2) in Example 3 was changed to graphene oxide having an average particle size of 30 μm and a C / O ratio of 1.2 in Example 8, graphene oxide having an average particle size of 50 μm and a C / O ratio of 1.2 in Example 9, graphene oxide having an average particle size of 10 μm and a C / O ratio of 1.0 in Example 10, and graphene oxide having an average particle size of 10 μm and a C / O ratio of 3.5 in Example 11. The thermal diffusivity of the resulting graphite was 5.9 cm 2 / s, 5.6cm 2 / s, 5.9cm 2 / s, 5.7cm 2 / s.

[0051] [Table 2]

[0052] Example 12 The same raw material film as in Example 3 was sandwiched between graphite plates, and the four sides of the graphite plates were fixed with screws and carbonized. The resulting carbonized film was then sandwiched between graphite plates, and the four sides of the graphite plates were fixed with screws. Graphite was produced in the same manner as in Example 3, except that the maximum temperature during graphitization was changed to 2900°C. The thermal diffusivity of the resulting graphite was 6.7 cm.2 / s.

[0053] Example 13 The same raw film as in Example 3 was sandwiched between graphite plates, and the four sides of the graphite plates were fixed with screws and carbonized. The resulting carbonized film was then sandwiched between the graphite plates and subjected to a pressure of 1 kg / cm. 2 Graphite was produced in the same manner as in Example 3, except that a weight of 1.0 kgf / cm was added and the maximum temperature during graphitization was changed to 2900°C. The thermal diffusivity of the obtained graphite was 7.0 cm 2 / s.

[0054] Example 14 The same raw film as in Example 3 was sandwiched between graphite plates, and the four sides of the graphite plates were fixed with screws and carbonized. The resulting carbonized film was then sandwiched between the graphite plates and subjected to a pressure of 50 kg / cm. 2 Graphite was produced in the same manner as in Example 3, except that a weight of 1.0 kgf / cm2 was added and the maximum temperature during graphitization was changed to 2900°C. The thermal diffusivity of the obtained graphite was 7.3 cm 2 / s.

[0055] Example 15 The same raw film as in Example 4 was sandwiched between graphite plates, and the four sides of the graphite plates were fixed with screws and carbonized. The resulting carbonized film was then sandwiched between the graphite plates and subjected to a pressure of 50 kg / cm. 2 Graphite was produced in the same manner as in Example 4, except that a weight of 1.0 kgf / cm2 was added and the maximum temperature during graphitization was changed to 2900°C. The thermal diffusivity of the obtained graphite was 7.9 cm 2 / s.

[0056] Example 16 Graphite was prepared in the same manner as in Example 3, except that the methanol solution of phenolic resin was replaced with a methanol solution of resol resin (concentration approximately 65%, viscosity 400 mPa s). The thermal diffusivity of the obtained graphite was 6.1 cm 2 / s.

[0057] [Table 3]

[0058] Example 17 Graphite was produced in the same manner as in Example 4, except that the raw materials used were a solution of graphene oxide (average particle size: 10 μm, C / O ratio: 1.2) in DMF (concentration: approximately 2%) and a polyacrylonitrile resin in DMF (concentration: approximately 10%) in a solids ratio of 10:90 (by weight). The thermal diffusivity of the resulting graphite was 5.8 cm. 2 / s.

[0059] Example 18 Graphite was produced in the same manner as in Example 15, except that the raw materials used were a solution of graphene oxide (average particle size: 10 μm, C / O ratio: 1.2) in DMF (concentration: approximately 2%) and a polyacrylonitrile resin in DMF (concentration: approximately 10%) in a solids ratio of 10:90 (by weight). The thermal diffusivity of the resulting graphite was 6.5 cm. 2 / s.

[0060] (Comparative Example 1) Graphite was produced in the same manner as in Example 1, except that expanded graphite (average particle size: 10 μm) was used instead of graphene oxide. The thermal diffusivity of the obtained graphite was 0.5 cm 2 / s.

[0061] (Comparative Example 2) Graphite was produced in the same manner as in Example 1, except that graphene (average particle size: 10 μm, C / O ratio: 25 or more) was used instead of graphene oxide. The thermal diffusivity of the obtained graphite was 0.5 cm 2 / s.

[0062] (Comparative Example 3) Graphite was produced in the same manner as in Example 1, except that the raw film was produced using only a methanol solution of phenolic resin, without using a DMF solution of graphene oxide. The thermal diffusivity of the obtained graphite was 0.1 cm 2 / s.

[0063] Example 19 An aqueous solution (concentration: approximately 1%) of graphene oxide (average particle size: 1 μm, C / O ratio: 1.2) was applied to aluminum foil so that the thickness after drying would be 50 μm, and then dried at room temperature. After drying, the aluminum foil was removed with hydrochloric acid, and after washing with water and drying, a raw film with a thickness of 50 μm was obtained. The obtained raw material film was sandwiched between graphite plates and heated in a nitrogen atmosphere from room temperature to 1000°C at 1°C / min, and then held at 1000°C for 10 minutes to carbonize. The obtained carbonized film was then sandwiched between graphite plates and heated in a vacuum from room temperature to 2000°C at 2.5°C / min, then in argon from 2000°C to 2950°C at 2.5°C / min, and then held at 2950°C for 10 minutes to graphitize. The thermal diffusivity of the obtained graphite was 6.5cm 2 / s.

[0064] [Table 4]

[0065] Example 20 Graphite was prepared in the same manner as in Example 19, except that an aqueous solution (concentration: approximately 1%) of graphene oxide (average particle size: 10 μm, C / O ratio: 1.2) was used. The thermal diffusivity of the obtained graphite was 6.8 cm 2 / s.

[0066] Example 21 Graphite was produced in the same manner as in Example 19, except that an aqueous solution (concentration: approximately 1%) of graphene oxide (average particle size: 30 μm, C / O ratio: 1.2) was used. The thermal diffusivity of the obtained graphite was 6.9 cm 2 / s.

[0067] Example 22 Graphite was produced in the same manner as in Example 19, except that an aqueous solution (concentration: approximately 1%) of graphene oxide (average particle size: 50 μm, C / O ratio: 1.2) was used. The thermal diffusivity of the obtained graphite was 6.8 cm 2 / s.

[0068] Example 23 Graphite was produced in the same manner as in Example 19, except that the raw materials used were a solution of graphene oxide (average particle size: 10 μm, C / O ratio: 1.2) in DMF (concentration: approximately 2%) and a polyacrylonitrile resin in DMF (concentration: approximately 10%) in a solids ratio of 95:5 (by weight). The thermal diffusivity of the resulting graphite was 6.4 cm. 2 / s.

[0069] Example 24 Graphite was produced in the same manner as in Example 19, except that the raw materials used were a DMF solution (concentration: approximately 2%) of graphene oxide (average particle size: 30 μm, C / O ratio: 1.2) and a methanol solution of phenolic resin (methanol solution of resol resin, concentration: approximately 65%, viscosity: approximately 200 mPa s) mixed in a solids ratio of 90:10 (by weight). The thermal diffusivity of the resulting graphite was 6.7 cm. 2 / s.

[0070] Example 25 The same raw material film as in Example 19 was sandwiched between graphite plates, and the four sides of the graphite plates were fixed with screws and carbonized. The resulting carbonized film was then sandwiched between graphite plates, and the four sides of the graphite plates were fixed with screws. Graphite was produced in the same manner as in Example 20, except that the maximum temperature during graphitization was changed to 2900°C. The thermal diffusivity of the resulting graphite was 7.7 cm 2 / s.

[0071] Example 26 The same raw film as in Example 19 was sandwiched between graphite plates, and the four sides of the graphite plates were fixed with screws and carbonized. The resulting carbonized film was then sandwiched between the graphite plates and subjected to a pressure of 1 kg / cm. 2 Graphite was produced in the same manner as in Example 20, except that a weight of 1.0 kgf / cm2 was added and the maximum temperature during graphitization was changed to 2900°C. The thermal diffusivity of the obtained graphite was 7.9 cm 2 / s.

[0072] [Table 5]

[0073] Example 27 The same raw film as in Example 19 was sandwiched between graphite plates, and the four sides of the graphite plates were fixed with screws and carbonized. The resulting carbonized film was then sandwiched between the graphite plates and subjected to a pressure of 50 kg / cm. 2 Graphite was produced in the same manner as in Example 20, except that a weight of 1.0 kgf / cm2 was added and the maximum temperature during graphitization was changed to 2900°C. The thermal diffusivity of the obtained graphite was 8.1 cm 2 / s.

[0074] Example 28 Graphite was prepared in the same manner as in Example 27, except that an aqueous solution (concentration: approximately 1%) of graphene oxide (average particle size: 30 μm, C / O ratio: 1.2) was used. The thermal diffusivity of the obtained graphite was 8.2 cm 2 / s.

[0075] Example 29 Graphite was produced in the same manner as in Example 20, except that an aqueous solution (concentration: approximately 1%) of graphene oxide (average particle size: 10 μm, C / O ratio: 1.0) was used. The thermal diffusivity of the obtained graphite was 6.7 cm 2 / s.

[0076] Example 30 Graphite was produced in the same manner as in Example 20, except that an aqueous solution (concentration: approximately 1%) of graphene oxide (average particle size: 10 μm, C / O ratio: 3.5) was used. The thermal diffusivity of the obtained graphite was 6.4 cm 2 / s.

[0077] Example 31 Graphite was prepared in the same manner as in Example 26, except that the raw materials used were a solution of graphene oxide (average particle size: 30 μm, C / O ratio: 1.2) in DMF (concentration: approximately 2%) and a phenolic resin in methanol (concentration: approximately 65%, viscosity: approximately 200 mPa s) mixed in a solids ratio of 90:10 (by weight). The thermal diffusivity of the resulting graphite was 7.7 cm. 2 / s.

[0078] Comparative Example 4 Graphite was prepared in the same manner as in Example 20, except that an aqueous solution of graphene (average particle size: 10 μm, C / O ratio: >25) was used. The thermal diffusivity of the obtained graphite was 5.5 cm 2 / s.

Claims

1. A method for producing graphite, comprising a step of heat treating a raw material at a temperature of 2400°C or higher, The raw material is composed of a resin composition containing graphene oxide (A) and a resin (B), The graphene oxide (A) has a mass ratio of carbon to oxygen (C / O) of 0.6 or more and 3.5 or less.

2. The method according to claim 1 , wherein the raw material has an orientation peak of graphene oxide in a small angle region and an orientation peak of resin in a high angle region in X-ray diffraction measurement.

3. The method according to claim 1 or 2, wherein the graphene oxide (A) has a mass ratio of carbon to oxygen (C / O) of 1.1 or more and less than 3.

5.

4. The method according to any one of claims 1 to 3, wherein the graphene oxide (A) has an average particle size of 2 µm or more and 40 µm or less.

5. The method according to any one of claims 1 to 4, wherein the resin composition contains 0.3 to 20% by weight of the graphene oxide (A) relative to 100% by weight of the resin composition.

6. 5. The method for producing graphite according to claim 1, wherein the raw material is composed of 50% by weight or more and less than 100% by weight of graphene oxide (A) and more than 0% by weight and 50% by weight or less of resin (B).

7. The method according to any one of claims 1 to 6, wherein the resin (B) is at least one selected from the group consisting of polyacrylonitrile resin, polyvinyl alcohol resin, polyvinyl chloride resin, phenolic resin, epoxy resin, melamine resin, acrylic resin, amide resin, amide-imide resin, and imide resin.

8. The method according to claim 7, wherein the resin (B) is a phenolic resin.

9. The method of claim 8, wherein the phenolic resin is a resole resin.

10. The manufacturing method according to any one of claims 1 to 9, wherein the step of heat treating the raw material includes a step of performing heat treatment at a temperature of 2800°C or higher.

11. The manufacturing method according to claim 10 , wherein the step of heat-treating the raw material includes a step of performing heat treatment at a temperature of 2800° C. or higher while applying a load to the raw material.

12. The method according to any one of claims 1 to 11, wherein the raw material is in the form of a film.

13. The method of claim 12, wherein the film has a thickness of 10 nm to 1 mm.

14. The method according to any one of claims 1 to 13, further comprising the step of applying or casting a dispersion containing graphene oxide (A) onto a substrate to form the raw material.

15. The method according to any one of claims 1 to 14, wherein the raw material is produced by applying multiple coats to a thickness of 10 µm or less per coat.

16. A method for producing graphite, comprising a step of heat treating a raw material at a temperature of 2400°C or higher, the raw material contains graphene oxide (A) and is produced by applying multiple layers to a coating thickness of 10 μm or less per layer, The graphene oxide (A) has a mass ratio of carbon to oxygen (C / O) of 0.6 or more and 3.5 or less.

17. 1. A composition for producing graphite, comprising: The composition contains graphene oxide (A) and a resin (B), The graphene oxide (A) has a mass ratio of carbon to oxygen (C / O) of 0.6 or more and 3.5 or less.

18. The composition according to claim 17, wherein the graphene oxide (A) has a mass ratio of carbon to oxygen (C / O) of 1.1 or more and less than 3.

5.

19. The composition according to claim 17 or 18, wherein the graphene oxide (A) has an average particle size of 2 μm or more and 40 μm or less.

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