JP2020066569A - Process for producing carbon material composite - Google Patents

Abstract

To provide a process for easily producing high-quality graphite oxide.SOLUTION: Provided is a process for producing a carbon material composite composed by including amphoteric surfactant and graphite oxide, and said production process is characterized to include steps of: oxidizing graphite; mixing an amphoteric surfactant with an aqueous dispersion liquid in which graphite oxide obtained in the oxidization step is dispersed; and refining carbon material composite.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a carbon material composite. More specifically, catalysts, electrode active materials for batteries and capacitors, thermoelectric conversion materials, conductive materials, light emitting materials, lubricant additives, polymer (resin) additives, permeable membrane materials, antibacterial materials, water repellent materials. The present invention relates to a method for producing a carbon material composite which can be preferably used as an adsorbent material or the like.

Carbon materials are excellent in properties such as hardness and are used in various fields such as semiconductors, batteries, automobiles, information communication, and industrial equipment.
Graphite oxide, which is one type of carbon material, is obtained by oxidizing graphite having a layered structure in which carbon atoms bonded by sp ² bonds are arranged in a plane to give an oxygen-containing functional group. Many studies have been conducted due to their physical properties. Graphite oxide is a catalyst, electrode active material for batteries and capacitors, thermoelectric conversion material, conductive material, light emitting material, lubricant additive, polymer additive, permeable membrane material, antibacterial material, water repellent material, adsorbent material. It is expected to be used for various purposes such as.

As a manufacturing method of graphite oxide, a method of synthesizing graphite oxide by reacting graphite with a strong oxidizing agent in an acid solvent is generally used, and a Hummers method using sulfuric acid and potassium permanganate as an oxidizing agent is known. (See Non-Patent Document 1). Also known as other methods are the Brodie method using nitric acid and potassium chlorate, and the Staudenmeier method using sulfuric acid, nitric acid and potassium chlorate as oxidants.

For example, as a method for producing an oxidized graphite derivative, the solubility in water is 0.01% or more in a reaction liquid containing the oxidized graphite obtained in the oxidation step between the step of oxidizing graphite and the step of obtaining the oxidized graphite derivative. It is disclosed that the graphite oxide-containing composition is separated after the addition of a solvent that is immiscible with water (see Patent Document 1).
By the way, it is disclosed that graphene oxide (graphite oxide) is modified with a specific amine oxide (see Non-Patent Document 2). Further, it is disclosed that an aqueous solution of specific betaine is added to a suspension of graphene oxide (see Non-Patent Document 3).

International Publication No. 2017/082263

William S. Hummers, et.al, J. Am. Chem. Soc, 1958, 80, 1339. Wensheng Gao, et.al, RSC Adv. 2017, 7, 31085-31092 Zonghua Wang, et.al, Electrochimica Acta 160 (2015) 288-295

As described above, various methods are known as a method for producing graphite oxide, which is one type of carbon material, but it is common to purify graphite oxide from the reaction solution after obtaining graphite oxide in the oxidation step. Usually, the centrifugation is repeated or the reaction solution is filtered. In the former case, there is a problem that the process becomes complicated and the amount of waste liquid increases, and in the latter case, there is a problem that the filter is easily clogged. In either case, refining takes time, resulting in high cost, and there is room for improvement in terms of efficient production when producing graphite oxide. On the other hand, the method described in Patent Document 1 makes it possible to efficiently separate graphite oxide by liquid / liquid separation of an aqueous layer / organic layer, and easily obtain high-quality graphite oxide. It is possible. On the other hand, in industrially producing graphite oxide, there has been a strong demand for more efficient production of a graphite oxide separation step, particularly a filtration step, to more easily produce high-quality graphite oxide.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method capable of easily producing high-quality graphite oxide.

The present inventors have conducted various studies on a method capable of more easily producing high-quality graphite oxide, and when purifying graphite oxide from an aqueous dispersion liquid in which graphite oxide obtained in the oxidation step is dispersed. By the step of mixing the aqueous dispersion and the amphoteric surfactant, and the step of purifying the carbon material composite containing the amphoteric surfactant and graphite oxide, the acid remains in the aqueous dispersion. However, the action of the amphoteric surfactant aggregates the carbon material complex to form a large aggregate with low dispersibility, and even when the aqueous dispersion is filtered, the filter is unlikely to be clogged. It has been found that the carbon material composite can be purified very efficiently because the acid can be sufficiently removed while the length is shortened. The reason for this is considered as follows. First, regarding the action of the carbon material complex to aggregate by the action of the amphoteric surfactant even if the acid remains, the aqueous dispersion liquid in which the graphite oxide obtained in the oxidation step is dispersed is mixed with the amphoteric surfactant. Then, the graphite oxide and the amphoteric surfactant interact with each other to aggregate into a carbon material complex composed of the amphoteric surfactant and the graphite oxide, so that water-soluble impurities such as acids and salts can be easily formed. Can be separated. That is, the impurities can be easily removed by mixing the amphoteric surfactant with the aqueous dispersion liquid (reaction liquid) after the oxidation step. The present inventors have made it possible to easily produce a high-quality carbon material composite at low cost by such a purification method, and particularly when this method is applied to the industrial production of the carbon material composite. The inventors have found that the effect becomes remarkable, and have arrived at the present invention by thinking that the above problems can be solved satisfactorily.

Further, the present inventors have found that the carbon material composite obtained through the above-mentioned oxidation step, the above-mentioned mixing step, and the above-mentioned purification step can suitably separate the layers in the dispersion medium. The reason for this is that by modifying the surface of the graphite oxide with an amphoteric surfactant, hydrophobic groups and anion ionizing groups face the surface side of the graphite oxide, as described below, and with an organic dispersion medium of relatively high polarity. It is considered that this is because the carbon material composite including the amphoteric surfactant and the graphite oxide is dispersed in the organic dispersion medium due to the increased interaction, and the delamination of the graphite oxide becomes possible. To be
The present inventors have found that such a method makes it possible to easily produce a high-quality carbon material composite at low cost.

Further, the present inventors have added a step of mixing a nonionic surfactant in addition to an amphoteric surfactant to an aqueous dispersion liquid in which graphite oxide obtained in the oxidation step is dispersed, and a nonionic surfactant. , The amphoteric surfactant, and the step of purifying the carbon material composite containing graphite oxide, even if the acid remains in the aqueous dispersion, the nonionic surfactant and amphoteric surfactant Due to the action, the carbon material complex aggregates into a large aggregate with low dispersibility, and the filter does not easily become clogged even if the aqueous dispersion is filtered. It was found that the carbon material complex can be purified very efficiently. In addition, graphite oxide containing only amphoteric surfactant can be exfoliated particularly well in an organic solvent of relatively high polarity, whereas a mixture of nonionic surfactants can control polarity and hydrophobicity. It was found that it is particularly suitable for delamination in a highly polar dispersion medium such as water or methanol. The reason for this is that the aggregation of the carbon material composite with a nonionic surfactant having a weak cohesive force is not so strong, so even in a highly polar dispersion medium, the aggregation process can be easily broken down and dispersed again in the dispersion medium. It is thought that this can be done. That is, the dispersibility can be controlled by using a nonionic surfactant in addition to the amphoteric surfactant.

Furthermore, the present inventors have added a step of mixing a cationic surfactant in addition to an amphoteric surfactant to an aqueous dispersion liquid in which graphite oxide obtained in the oxidation step is dispersed, and a cationic surfactant. Of a cationic surfactant and an amphoteric surfactant even if an acid remains in the aqueous dispersion by the step of purifying a carbon material composite including an agent, an amphoteric surfactant, and graphite oxide. By the action of, the carbon material complex aggregates to become a large aggregate with low dispersibility, the filter is less likely to be clogged even if the aqueous dispersion is filtered, and the time required for purification is extremely short, and the acid It has been found that the carbon material composite can be sufficiently removed and the carbon material composite can be purified very efficiently. Also, graphite oxide containing only amphoteric surfactant can be exfoliated particularly well in an organic solvent of relatively high polarity, whereas the mixture of cationic surfactant can control polarity and hydrophobicity. It was found that it is particularly suitable for delamination in a medium polar dispersion medium such as a higher alcohol having about 4 to 12 carbon atoms.

Furthermore, the present inventors have added a nonionic surfactant and a cationic surfactant in addition to an amphoteric surfactant to an aqueous dispersion liquid in which graphite oxide obtained in the oxidation step is dispersed, By mixing the amphoteric surfactant, nonionic surfactant, and cationic surfactant in various ratios, it is possible to control the polarity and hydrophobicity of the carbon material composite by utilizing the above properties. I found that. For example, even in the case of a chain ester type dispersion medium which is not particularly suitable in the combination of an amphoteric surfactant alone, a combination of an amphoteric surfactant and a nonionic surfactant, and a combination of an amphoteric surfactant and a cationic surfactant. It has been found to be particularly suitable for delamination. That is, by mixing the amphoteric surfactant, the nonionic surfactant, and the cationic surfactant in various ratios, various solvents, for example, solvents having various functional groups, and particularly hydrophobic solvents and hydrophilic solvents are mixed. It can be stripped in a solvent such as a solvent, an amphipathic solvent, a low boiling point solvent, or a high boiling point solvent, and a dispersion of various solvents can be prepared.

Further, the present inventors have found that the amphoteric surfactant is a group (such as a quaternary ammonium salt group) which is substantially ionized into a cation in an aqueous dispersion liquid in which graphite oxide obtained in the oxidation step is dispersed ( (Cationic ionization group), and substantially in an aqueous dispersion liquid in which graphite oxide obtained in the oxidation step, such as a carboxylic acid (salt) group, a sulfonic acid (salt) group, and a phosphoric acid (salt) group, is dispersed. In addition to a group that ionizes to an anion (anion ionizing group), by having a low polarity hydrophilic group having a relatively low polarity such as a polyoxyalkylene group, the degree of hydrophobicity and polarity can be adjusted. It has been found that such a specific amphoteric surfactant alone can exhibit the same effect as in the case where the amphoteric surfactant and the nonionic surfactant as described above are used in combination.

That is, the present invention is a method for producing a carbon material composite comprising an amphoteric surfactant and graphite oxide, which comprises a step of oxidizing graphite and a graphite oxide obtained in the oxidation step. Is a method for producing a carbon material composite, comprising a step of mixing an aqueous dispersion liquid in which is dispersed with an amphoteric surfactant, and a step of purifying the carbon material composite.
In the method for producing a carbon material composite according to the present invention, it is preferable that the mixing step further comprises mixing a nonionic surfactant and / or a cationic surfactant.
In the method for producing a carbon material composite of the present invention, the amphoteric surfactant is a cation ionizing group, an anion ionizing group, and a hydrophilic group having a lower polarity than the cation ionizing group or the anion ionizing group. It is preferable to have

The present invention is also a method for producing graphite oxide, which comprises a step of oxidizing graphite, an aqueous dispersion liquid in which the graphite oxide obtained in the oxidation step is dispersed, and an amphoteric surfactant. It is also a method for producing graphite oxide, which includes a step of mixing and a step of purifying graphite oxide.

In a preferred embodiment of the method for producing a carbon material composite of the present invention or the method for producing a graphite oxide of the present invention, the purification step comprises filtration, decantation, centrifugation, and separation extraction. It is a step of purifying the carbon material composite or the graphite oxide by at least one method selected.

According to the method for producing a carbon material composite of the present invention, a high quality carbon material composite can be easily obtained at low cost. The obtained carbon material composite can be dispersed very well in the dispersion medium. In addition, if necessary, by appropriately combining the surfactant according to the present invention, the polarity and hydrophobicity of the carbon material composite can be adjusted, and the carbon material composite is dispersed in an appropriate dispersion medium according to the application. It can be made to be suitable for removing or delamination. For example, a carbon material composite including a nonionic surfactant and / or a cationic surfactant, an amphoteric surfactant, and graphite oxide is dispersed in a highly polar dispersion medium containing water. Even in the case of allowing the layers, the layers can be suitably peeled off. The obtained carbon material composite can be dispersed very well in a resin-based dispersion medium. Due to the effects as described above, it can be dispersed very well not only in a general aqueous solvent or organic solvent, but also in a resin-based dispersion medium such as a monomer as a resin precursor. Similarly, if necessary, the polarity and hydrophobicity of the carbon material composite can be adjusted by appropriately combining the surfactant according to the present invention, and the carbon material composite can be prepared by using an appropriate resin-based dispersion medium according to the application. It may be suitable for dispersion in.

The present invention is described in detail below.
In addition, a form in which two or more preferable features of the present invention described in the paragraphs below are combined is also a preferable form of the present invention.

<Method for producing carbon material composite>
In the method for producing a carbon material composite of the present invention, the order of each step after the oxidation step is not particularly limited, but after performing an oxidation reaction termination (quenching) step described below, if necessary, the mixing step, It is particularly preferable to carry out the purification steps in this order. Further, a purification step of graphite oxide may be appropriately performed before the mixing step. For example, after performing an oxidation reaction stopping step as necessary, a purification step of graphite oxide, the mixing step, the purification step (carbon The purification step of the material complex) may be performed in this order. Further, the purification step may be performed in the middle of the mixing step as described later (for example, the step of mixing a part of the surfactant is the first mixing step, and the step of mixing the remaining surfactant is the first step). In the case of two mixing steps, the purification step may be performed between the first mixing step and the second mixing step), and after the oxidation reaction stopping step is performed if necessary, the first mixing step, The purification step and the second mixing step may be performed in this order.

The carbon material composite obtained by the method for producing a carbon material composite according to the present invention comprises an amphoteric surfactant and graphite oxide, and further contains a nonionic surfactant and / or a cationic surfactant. May be included.
Among them, in one preferred embodiment of the carbon material composite obtained by the method for producing a carbon material composite of the present invention, an amphoteric surfactant and a nonionic surfactant and / or a cationic surfactant and graphite oxide are used. It is configured to include.
For example, the carbon material composite obtained by the method for producing a carbon material composite according to the third aspect of the present invention comprises an amphoteric surfactant and graphite oxide, and further comprises a nonionic surfactant and / or a cation. It may contain a surface active agent.
The above-mentioned graphite oxide is one in which oxygen is bound by oxidizing a graphitic carbon material such as graphene or graphite (the one in which oxygen is bound to the carbon material), and the oxygen is a graphitic carbon material. On the other hand, it exists as a substituent such as a carboxyl group, a carbonyl group, a hydroxyl group, and an epoxy group.
The above graphite oxide is preferably graphene oxide in which oxygen is bonded to carbon of graphene.
Note that graphene generally refers to a sheet including one layer in which carbon atoms bonded by sp ² bonds are arranged in a plane, and a stack of a plurality of graphene sheets is referred to as graphite. Includes not only a sheet consisting of only one layer of carbon atoms but also a sheet having a structure in which about 2 to 100 layers are laminated. The graphene oxide is preferably a sheet composed of only one layer of carbon atoms, or has a structure in which about 2 to 20 layers are laminated.
The graphite oxide may further have a functional group such as a sulfur-containing group and a nitrogen-containing group, but the content ratio of carbon, hydrogen, and oxygen as constituent elements to all constituent elements is 97 mol% or more. Is preferable, 99 mol% or more is more preferable, and it is more preferable that the graphite oxide has carbon, hydrogen, and oxygen as the only constituent elements.

In the following, first, in the method for producing a carbon material composite of the present invention, an aqueous dispersion liquid in which graphite oxide obtained in the oxidation step is dispersed, an amphoteric surfactant, or an amphoteric surfactant and a nonionic interface. The mixing step of mixing the active agent and / or the cationic surfactant and the purification step of purifying the carbon material composite will be described in order, but the purification step may be performed during the mixing step as described later ( For example, when the step of mixing a part of the surfactant is the first mixing step and the step of mixing the remaining surfactant is the second mixing step, the purification step is the first mixing step and the second mixing step. Therefore, the purification step will be described in the description of the mixing step. Next, a step of separating the layers of graphite oxide contained in the carbon material composite body purified in the refining step and a step of oxidizing graphite before the refining step will be described.

(Mixing process)
The production method of the present invention includes a mixing step of mixing an aqueous dispersion liquid in which graphite oxide obtained in the oxidation step is dispersed with an amphoteric surfactant.
In the mixing step, an amphoteric surfactant may be added to the aqueous dispersion, an aqueous dispersion may be added to the amphoteric surfactant, and the aqueous dispersion and the amphoteric surfactant may be added to the container at the same time. You may. Further, in the present specification, the mixing method is not particularly limited and can be appropriately performed by a known method, for example, stirring or ultrasonic treatment, or by using a known disperser, solid It is preferable to disperse the components uniformly.

The aqueous dispersion obtained by dispersing the graphite oxide obtained in the oxidation step may be the reaction composition immediately after the oxidation step, and removes sulfuric acid from the reaction composition in the subsequent concentration step or stops the oxidation reaction. A liquid obtained by adding water and / or hydrogen peroxide solution to the reaction composition in the (quench) step may be used, but for example, water and / or hydrogen peroxide solution is added to the reaction composition in the oxidation reaction stopping step. It is preferable that it is a liquid.
The aqueous dispersion may contain water as a dispersion medium, and may further contain an organic dispersion medium which is miscible with water, but from the viewpoint of easiness of aggregation of the carbon material composite. It is preferable that no organic dispersion medium is contained.

In the present specification, the amphoteric surfactant has a cation ionizing group and an anion ionizing group as a hydrophilic group among compounds having a hydrophobic group and a hydrophilic group which are generally called a surfactant. In other words, in a water-based dispersion liquid in which graphite oxide obtained in the oxidation step is dispersed, it is substantially ionized into amphoteric ions.
Graphite oxide interacts with the cationic ionizing groups of such amphoteric surfactants. As a result, the hydrophobic groups and anionic ionizing groups of the amphoteric surfactant face outward, and the surface of the oxidized graphite becomes slightly anionic, which enhances the interaction with an organic dispersion medium having a relatively high polarity and enables delamination. To do.

As the hydrophobic group of the amphoteric surfactant, for example, a hydrocarbon group such as an aliphatic hydrocarbon group or an aromatic hydrocarbon group is preferable. The hydrocarbon group preferably has 3 or more carbon atoms, more preferably 4 or more carbon atoms, and particularly preferably 5 or more carbon atoms. The hydrocarbon group preferably has, for example, 24 or less carbon atoms. In addition, the amphoteric surfactant contains a cationic ionizing group and an anionic ionizing group as the hydrophilic group. Preferred examples of the cation ionizing group include a quaternary ammonium base, a pyridinium base and an amine group. Preferred examples of the anion ionizing group include a carboxylic acid (salt) group, a sulfonic acid (salt) group, and a phosphoric acid (salt) group. Furthermore, the hydrophobic group, the cation ionizing group, and the anion ionizing group do not have to be one type each. For example, an amphoteric surfactant includes a cation ionizing group and an anion ionizing group (both are highly polar hydrophilic groups), as well as a polyoxyalkylene group (eg, polyoxyethylene group, polyoxypropylene group), ether in the same molecule. It may have a functional group having a relatively small polarity (a low-polar hydrophilic group) such as a group, an ester group, and a hydroxyl group. The amphoteric surfactant has a cation ionizing group, an anion ionizing group, and a hydrophilic group having a lower polarity than the cation ionizing group or the anion ionizing group, thereby adjusting the degree of hydrophobicity or polarity. It is possible to achieve the same effect as in the case where the amphoteric surfactant and the nonionic surfactant as described above are mixed with only one molecule (amphoteric surfactant). That is, the amphoteric surfactant preferably has a cation ionizing group, an anion ionizing group, and a hydrophilic group having a lower polarity than the cation ionizing group or the anion ionizing group. Examples of the hydrophilic group having a low polarity include a polyoxyalkylene group, an ether group, an ester group, a hydroxyl group and the like, and a polyoxyalkylene group having an alkylene group having 2 to 3 carbon atoms is preferable. In addition, for example, the amphoteric surfactant having a plurality of cationic ionizing groups can also adjust the degree of hydrophobicity and polarity, and such a specific amphoteric surfactant alone can be used together with the above-mentioned amphoteric surfactant. It is possible to exhibit the same effect as when the ionic surfactant is used in combination.

Examples of the amphoteric surfactant include alkyldimethylaminoacetic acid betaine, alkyldimethylamine oxide, alkylcarboxymethylimidazolinium betaine, alkylamidopropyl betaine, alkylsulfobetaine, and the like, and one or more of these may be used. Can be used. Among these amphoteric surfactants, alkyldimethylaminoacetic acid betaine is preferable, and lauryldimethylaminoacetic acid betaine (laurylbetaine) is more preferable. When the cation ionizing group is a salt, the salt preferably includes a halide and a hydroxide, and among the halides, a chloride is preferable. When the anion ionizing group is a salt, the salt is preferably an alkali metal salt, and among the alkali metal salts, sodium salt and potassium salt are preferable.

The amount of the amphoteric surfactant to be mixed with the aqueous dispersion liquid in which graphite oxide is dispersed in the above mixing step may be set appropriately, but with respect to 100% by mass of graphite oxide in the aqueous dispersion liquid in which graphite oxide is dispersed. It is preferably 10 to 1000% by mass. The amount of the amphoteric surfactant is more preferably 20 to 700% by mass, further preferably 25 to 600% by mass, relative to 100% by mass of the graphite oxide in the aqueous dispersion liquid in which graphite oxide is dispersed. , And particularly preferably 30 to 500% by mass.

In the production method of the present invention, it is preferable that in the mixing step, a nonionic surfactant and / or a cationic surfactant is further mixed. As a result, as described above, in the subsequent purification step, the time required for purification can be shortened, the acid can be removed more sufficiently, and the carbon material composite can be purified extremely efficiently. In addition, it becomes possible to delaminate graphite oxide contained in the carbon material composite in various dispersion media.
When the above-mentioned mixing step further mixes a nonionic surfactant and / or a cationic surfactant, the order of mixing is not particularly limited, but for example, an aqueous dispersion in which graphite oxide obtained in the oxidation step is dispersed. First mixing step of mixing a liquid with a nonionic surfactant and / or a cationic surfactant, and a dispersion of the nonionic surfactant and / or cationic surfactant and graphite oxide It may include a second mixing step of mixing the water-based dispersion liquid and the amphoteric surfactant, and the non-ionic interface is added to the water-based dispersion liquid in which the graphite oxide obtained in the oxidation step is dispersed. An active agent and / or a cationic surfactant and an amphoteric surfactant may be mixed at the same time.

You may perform a refinement | purification process in the middle of the said mixing process. That is, when the step of mixing a part of the surfactant is the first mixing step and the step of mixing the remaining surfactants is the second mixing step, the purification step is the first mixing step and the second mixing step. You may go to and from. For example, the mixing step is a first mixing step of mixing an aqueous dispersion liquid in which graphite oxide obtained in the oxidation step is dispersed with a nonionic surfactant and / or a cationic surfactant, and In the case of including the second mixing step of mixing the nonionic surfactant and / or the cationic surfactant, and the aqueous dispersion liquid in which graphite oxide is dispersed with the amphoteric surfactant, the first mixing step and A carbon material composite including a nonionic surfactant and / or a cationic surfactant and graphite oxide from the mixed solution obtained in the first mixing step between the second mixing step and the second mixing step. It may include a step of purifying the body. The purification step is not particularly limited, and a conventionally known method can be appropriately used, for example, purification by at least one method selected from the group consisting of filtration, decantation, centrifugation, and separation extraction. It is preferable that the step is In this way, the sulfuric acid may be sufficiently washed off in advance between the first mixing step and the second mixing step, which causes the acid groups of the oxidized graphite to be ionized in the subsequent second mixing step, resulting in amphoteric surface activity. The interaction with the agent becomes stronger, and as a result, the effect of separating the layers of the graphite oxide in the organic dispersion medium becomes remarkable. Further, between the first mixing step and the second mixing step, the carbon material complex is purified by at least one method selected from the group consisting of filtration, decantation, centrifugation, and liquid separation extraction. After that, you may wash with water as needed. The purification process will be described in detail after the description of the mixing process.

In the first mixing step, a nonionic surfactant and / or a cationic surfactant may be added to the aqueous dispersion liquid, and the nonionic surfactant and / or the cationic surfactant may be added. The aqueous dispersion may be added to the surfactant, or the aqueous dispersion and the nonionic surfactant and / or the cationic surfactant may be simultaneously added to the container. . The same applies to the second mixing step, which may be one in which an amphoteric surfactant is added to the aqueous dispersion, or one in which the aqueous dispersion is added to the amphoteric surfactant. The aqueous dispersion and the amphoteric surfactant may be added at the same time.

When a nonionic surfactant and / or a cationic surfactant and an amphoteric surfactant are simultaneously mixed with an aqueous dispersion liquid in which graphite oxide obtained in the above oxidation step is dispersed, for example, an aqueous system A nonionic surfactant and / or a cationic surfactant and an amphoteric surfactant may be simultaneously added to the dispersion liquid, and the aqueous dispersion liquid and the nonionic surfactant and / or the container may be added to the container. The cationic surfactant and the amphoteric surfactant may be added simultaneously.

When a nonionic surfactant and / or a cationic surfactant and an amphoteric surfactant are simultaneously mixed with an aqueous dispersion liquid in which graphite oxide obtained in the above oxidation step is dispersed, for example, an aqueous system A nonionic surfactant and / or a cationic surfactant and an amphoteric surfactant may be simultaneously added to the dispersion liquid, and the aqueous dispersion liquid and the nonionic surfactant and / or the container may be added to the container. The cationic surfactant and the amphoteric surfactant may be added simultaneously.

In the present specification, the nonionic surfactant is an aqueous system in which graphite oxide obtained in the oxidation step is dispersed among compounds having a hydrophobic group and a hydrophilic group, which are generally called surfactants. It does not substantially ionize ions in the dispersion. Further, in the present specification, the cationic surfactant has a cationic ionizing group as a hydrophilic group among compounds having a hydrophobic group and a hydrophilic group generally called a surfactant, and It does not have an anion ionizing group, in other words, it substantially ionizes into cations in an aqueous dispersion liquid in which graphite oxide obtained in the oxidation step is dispersed.
Graphite oxide undergoes hydrophobic interaction and / or ionic interaction with such nonionic surfactant and / or cationic surfactant, and aggregates. Thereby, the purification process such as filtration can be efficiently performed, and the production cost of the carbon material composite can be reduced.

Examples of the hydrophobic group of the nonionic surfactant and the cationic surfactant include hydrocarbon groups such as aliphatic hydrocarbon groups and aromatic hydrocarbon groups as preferable ones. The hydrocarbon group preferably has 3 or more carbon atoms, more preferably 4 or more carbon atoms, even more preferably 5 or more carbon atoms, still more preferably 6 or more carbon atoms, and 9 or more carbon atoms. Is particularly preferable. The hydrocarbon group preferably has, for example, 24 or less carbon atoms. In addition, as the hydrophilic group of the nonionic surfactant and the cationic surfactant, for example, an alkylene oxide group, an ether group, an ester group, an amide group, a hydroxyl group and the like are preferable. More preferably, the alkylene oxide group is an ethylene oxide group.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkenyl ether, polyoxyethylene alkyl phenyl ether, higher fatty acid alkanolamide or ethylene oxide adduct thereof, sucrose fatty acid ester, alkylglycoxide, Fatty acid glycerin monoester, alcohol ethoxylate, sorbitan esters, polyoxyethylene sorbitan esters, derivatives thereof and the like are mentioned as preferable ones, and one or more of these can be used. For example, the nonionic surfactant has a hydroxyl group (-OH) at the end of the (poly) ethylene glycol chain of alcohol ethoxylate (for example, Softanol 50, Softanol 120 [manufactured by Nippon Shokubai Co., Ltd.]), poly Particularly preferred are oxyethylene sorbitan esters (for example, Newcol 85 [manufactured by Nippon Emulsifier Co., Ltd.]).

As the cationic surfactant, for example, benzalkonium salt, tributylmethyl ammonium salt, dimethyl distearyl ammonium salt, trimethyl stearyl ammonium salt, benzyl tributyl ammonium salt, tris (polyoxyalkylene) dodecyl ammonium salt (for example, Texnol L7 (manufactured by Nippon Emulsifier Co., Ltd.)); quaternary ammonium salts; lauryl (dodecyl) pyridinium salts, cetylpyridinium salts, and other pyridinium salts; stearamidepropyldimethylamine, stearamidoethyldiethylamine, and other fatty acid amide amines; Alkyl ether amines such as propyl dimethyl amine; polyoxyethylene alkyl amines, alkyl imidazolines and the like are mentioned as preferable ones, and one or two of these Or more can be used. Among them, the cationic surfactant is preferably a quaternary ammonium salt or a pyridinium salt. Examples of the quaternary ammonium salt and pyridinium salt include halides and hydroxides, and chlorides are preferable among the halides.

The amount of the nonionic surfactant and / or the cationic surfactant mixed with the aqueous dispersion in the mixing step may be appropriately set, but is 10 to 10% by mass of graphite oxide in the aqueous dispersion. It is preferably 1000% by mass. The amount of the nonionic surfactant and / or the cationic surfactant is more preferably 20 to 700% by mass based on 100% by mass of oxidized graphite in the aqueous dispersion containing the oxidized graphite, and further preferably Is 30 to 600% by mass, and particularly preferably 40 to 500% by mass.
The amount of the nonionic surfactant and / or the cationic surfactant is the total amount when the nonionic surfactant and the cationic surfactant are used in combination.

In the method for producing a carbon material composite according to the present invention, the aqueous dispersion mixed with the amphoteric surfactant preferably contains 1 mass% or more of sulfate ion based on 100 mass% of the aqueous dispersion.
The content of the sulfate ion is more preferably 3% by mass or more, further preferably 5% by mass or more. Further, the content of the sulfate ion is preferably 90% by mass or less, and more preferably 70% by mass or less.
The content of sulfate ions is the total content of sulfate ions derived from sulfuric acid and sulfate ions derived from sulfate salts.
Further, the pH of the above aqueous dispersion is preferably 2 or less, more preferably 1.5 or less. Although the lower limit of pH is not particularly limited, it is usually -1 or higher.
In the method for producing a carbon material composite of the present invention, when a nonionic surfactant and / or a cationic surfactant is further mixed in the mixing step, in the presence of a strong acid such as sulfuric acid used in the oxidation step, The surprising effect that the nonionic surfactant and / or the cationic surfactant interacts with the graphite oxide and aggregates is exhibited, and the effect of the present invention can be more remarkably exhibited.

In the method for producing a carbon material composite according to the present invention, the aqueous dispersion liquid (the aqueous dispersion liquid before mixing with the surfactant) in which the graphite oxide obtained in the oxidation step is dispersed is 100% by mass of the aqueous dispersion liquid. On the other hand, the water concentration is preferably 20% by mass or more.
The water concentration is more preferably 25% by mass or more, further preferably 30% by mass or more, and particularly preferably 35% by mass or more.
By setting it within such a water concentration range, even in the presence of sulfuric acid used in the oxidation step, etc., the amphoteric surfactant interacts with the graphite oxide and aggregates more unexpectedly. However, the effect of the present invention becomes more excellent.
Further, the water concentration is, for example, preferably 99% by mass or less, and more preferably 95% by mass or less.

In the method for producing a carbon material composite of the present invention, when a nonionic surfactant and / or a cationic surfactant is further mixed in the mixing step, in the presence of a strong acid such as sulfuric acid used in the oxidation step, The unexpected effect that the nonionic surfactant interacts with the graphite oxide and aggregates is further developed, and the effect of the present invention is further enhanced. Above all, when a nonionic surfactant is further mixed in the mixing step, the above-mentioned action is further manifested, and the effect of the present invention is further excellent and is remarkable.

As described above, the purification step may be performed in the middle of the mixing step. For example, in the production method of the present invention, an aqueous dispersion liquid in which the graphite oxide obtained in the oxidation step is dispersed and a nonionic surfactant are used. And / or a cationic surfactant in a first mixing step, and a nonionic surfactant and / or a cationic surfactant, and an aqueous dispersion liquid in which graphite oxide is dispersed and amphoteric When the second mixing step of mixing with the surfactant is included, the mixed solution obtained in the first mixing step may be purified between the first mixing step and the second mixing step as described above. Thereby, in the subsequent second mixing step, the interaction between the graphite oxide and the amphoteric surfactant becomes stronger. For example, an aqueous dispersion in which a nonionic surfactant and / or a cationic surfactant and graphite oxide are dispersed contains 10% by mass or less of sulfate ion based on 100% by mass of the aqueous dispersion. It is preferable. The content of the sulfate ion is more preferably 5% by mass or less, further preferably 1% by mass or less, and particularly preferably 0.1% by mass or less. The lower limit of the content of the sulfate ion is not particularly limited and may be 0% by mass.
The pH of the aqueous dispersion liquid in which the nonionic surfactant and / or the cationic surfactant and the graphite oxide are dispersed is preferably 2 to 10, and more preferably 9 or less. , 8 or less is more preferable.

In the method for producing a carbon material composite according to the present invention, the nonionic surfactant and / or the cationic surfactant, and the aqueous dispersion in which graphite oxide is dispersed are 100% by mass of the aqueous dispersion. The water concentration is preferably 20% by mass or more.
The water concentration is more preferably 25% by mass or more, further preferably 30% by mass or more, and particularly preferably 35% by mass or more.
Further, the water concentration is, for example, preferably 99% by mass or less, and more preferably 95% by mass or less.

In the mixing step, the aqueous dispersion liquid obtained by dispersing the graphite oxide obtained in the oxidation step and the amphoteric surfactant are first mixed, and then the nonionic surfactant and / or the cationic surfactant is used. It may be a mixture of agents. In that case as well, various preferable embodiments include the above-mentioned mixing step in which the aqueous dispersion liquid in which the oxidized graphite obtained in the oxidation step is dispersed and a nonionic surfactant and / or a cationic surfactant are used. It is similar to the case of mixing first and then the amphoteric surfactant.

(Purification process of carbon material composite)
In the method for producing a carbon material composite of the present invention, after mixing the aqueous dispersion liquid containing at least graphite oxide and the amphoteric surfactant in the mixing step, or as described above, the mixing step is the first mixing step. When the second mixing step is included, a step of purifying the carbon material composite body is performed between the first mixing step and the second mixing step. The purification step is not particularly limited, and a conventionally known method can be appropriately used, for example, purification by at least one method selected from the group consisting of filtration, decantation, centrifugation, and separation extraction. It is preferable that the step is
In addition, it is preferable to carry out the purification step after completing the mixing step of the aqueous dispersion and the surfactant. When performing the refining step between the first mixing step and the second mixing step, the remaining surfactant is further mixed with the carbon material composite obtained by the refining step, and thus the refining step is performed. The carbon material composite according to the present invention is different from the carbon material composite finally obtained by the production method of the present invention in that it does not contain the remaining surfactant.
By using these methods, sulfuric acid in the aqueous dispersion can be efficiently and sufficiently removed, and the carbon material composite can be purified in a short time. As a result, it is possible to sufficiently prevent the reactive oxygen-containing functional group of the graphite oxide contained in the carbon material composite from being reduced and / or inactivated during the purification of the carbon material composite, which results in high quality. It is possible to obtain a complex carbon material composite. In the present specification, the purification step means a step of removing solid impurities (for example, an oxidizing agent such as permanganate) and / or a solvent (such as a strong acid such as sulfuric acid) during the oxidation reaction from the aqueous dispersion. To tell.
Among these methods, filtration and liquid separation extraction are more preferable, and filtration is more preferable. According to the above purification step, aggregation of the carbon material composite particles is promoted in the aqueous dispersion liquid by the action of the amphoteric surfactant, and the carbon material composite particles become large aggregates, and as a result, the aqueous dispersion liquid is filtered. However, the filter is unlikely to become clogged and the time required for filtration is extremely short. Further, when a nonionic surfactant and / or a cationic surfactant is further mixed in the mixing step, the aggregation of the carbon material composite by the nonionic surfactant having a weak cohesive force is not so strong. The water can enter the agglomerate and the sulfuric acid can be thoroughly washed away. In addition, for example, when a cationic surfactant is mixed in the mixing step, graphite oxide interacts with the cationic ionizing group of the cationic surfactant, so that the hydrophobic group of the cationic surfactant is changed. When the surface side of the oxidized graphite becomes hydrophobic when facing outward, the hydrophobicity can be utilized to drive out highly polar sulfuric acid. Therefore, by using filtration as a method for purifying the carbon material composite, a high quality carbon material composite can be obtained very easily.

The carbon material complex to be purified may contain an amphoteric surfactant and graphite oxide, and may be further mixed with a nonionic surfactant and / or a cationic interface in the mixing step before the purification step. When the active agent is mixed, it may further contain a nonionic surfactant and / or a cationic surfactant.

In the method for producing a carbon material composite of the present invention, from the viewpoint of more easily obtaining the carbon material composite, the purification step is preferably performed by two or less of the methods described above, and one method. More preferably, Further, it is one of the preferable modes in the manufacturing method of the present invention that the above method is completed in one step without repeating.
Further, from the viewpoint of more sufficiently purifying the carbon material composite, the above method is preferably repeated. Among them, repeating at least one method selected from the group consisting of filtration, decantation, centrifugation, and liquid separation extraction is one of the preferable modes in the production method of the present invention.
The purification step may be performed in air or in an inert gas atmosphere such as nitrogen, helium or argon. Further, it may be carried out under pressure, normal pressure or reduced pressure.

In the production method of the present invention, for example, after purifying the carbon material complex by at least one method selected from the group consisting of filtration, decantation, centrifugation, and separation extraction, other purification such as washing with water. The process may be included. In the case where the washing step is repeated after the above-mentioned purification step, the number of washing steps is, for example, once from the viewpoint of more sufficiently removing sulfuric acid and more suitably peeling the graphite oxide layer in the peeling step described later. It is preferably at least 2 times, more preferably at least twice. Further, from the viewpoint of not removing too much the surfactant used from the carbon material composite obtained by the production method of the present invention, the number of times of water washing is preferably 10 times or less, and preferably 7 times or less. More preferable. From the viewpoint of not removing too much the used surfactant, washing may be performed with a mixed solution of water and the used surfactant instead of water. Furthermore, it is possible to adjust the ratio of graphite oxide and various surfactants in the finally obtained carbon material composite by adjusting the cleaning liquid.

(Peeling process)
Further, it is preferable that the production method of the present invention further include a step of peeling the layers of the graphite oxide contained in the carbon material composite purified in the purification step. The peeling step is a step of peeling the layers of the graphite oxide as described above, and can be performed by ultrasonic treatment, homogenizer treatment, or the like, and usually, the carbon material composite containing graphite oxide whose layers are peeled by the peeling step. The body disperses in the dispersion medium. The exfoliation step is constituted by the amphoteric surfactant alone or the amphoteric surfactant and the nonionic surfactant and / or cationic surfactant purified in the purification step, and graphite oxide. The complex can be carried out after mixing with the dispersion medium.
When the purification step is performed between the first mixing step and the second mixing step, the peeling step may be performed after the purification step and before the second mixing step, but after the second mixing step ( The stripping step is preferably performed (after the mixing step is completed).

The dispersion medium used in the peeling step in the method for producing a carbon material composite according to the present invention will be described. In the composite of amphoteric surfactant alone and graphite oxide, an organic dispersion medium (which may contain water) can be used as the dispersion medium, and the organic dispersion medium is, for example, methanol, ethanol, 1-propanol, 2-propanol. Preferred are lower alcohols having 1 to 3 carbon atoms such as acetone, acetone, methyl ethyl ketone (MEK), acetonitrile, diacetone alcohol, acetylacetone, and tetrahydrofuran. One or more of these mixed dispersion media can be used. Further, in the case of containing one or more of these mixed dispersion media, it is possible to appropriately mix even nonpolar dispersion media such as toluene and hexane other than the above-mentioned preferred dispersion media. It is also a preferred form of the invention. Further, in the composite of the amphoteric surfactant, the nonionic surfactant and graphite oxide, the dispersion medium is either an aqueous dispersion medium containing water or an organic dispersion medium (which may contain water). However, lower alcohols having 1 to 3 carbon atoms such as methanol, ethanol, 1-propanol and 2-propanol, acetone, methyl ethyl ketone, acetonitrile, diacetone alcohol, acetylacetone, tetrahydrofuran, water and the like are preferable. One or more of these mixed dispersion media can be used. Further, in the case of containing one or more mixed dispersion media, even nonpolar dispersion media such as toluene and hexane other than the above-mentioned preferred dispersion media can be appropriately mixed. It is also a preferred form of the invention. Further, in the composite of the amphoteric surfactant, the cationic surfactant, and the graphite oxide, the dispersion medium is either an aqueous dispersion medium containing water or an organic dispersion medium (which may contain water). However, acetone, methyl ethyl ketone, methyl isobutyl ketone, acetonitrile, diacetone alcohol, acetylacetone, tetrahydrofuran, propylene carbonate, butanol, pentanol, hexanol, and other aliphatic alcohols having 4 to 12 carbon atoms are preferable. One or more of these mixed dispersion media can be used. Further, in the case of containing one or more of these mixed dispersion media, it is possible to appropriately mix even nonpolar dispersion media such as toluene and hexane other than the above-mentioned preferred dispersion media. It is also a preferred form of the invention. Further, in the complex of the amphoteric surfactant, the nonionic surfactant, the cationic surfactant, and the graphite oxide, the dispersion medium is an aqueous dispersion medium containing water, an organic dispersion medium (including water). Or any of), and an aliphatic alcohol having 4 to 12 carbon atoms such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetonitrile, diacetone alcohol, acetylacetone, tetrahydrofuran, propylene carbonate, butanol, pentanol, and hexanol. Chain ester solvents such as methyl acetate, ethyl acetate and butyl acetate, and glycol derivatives such as glycol ether and glycol ester are preferable. One or more of these mixed dispersion media can be used. Further, in the case of containing one or more of these mixed dispersion media, it is possible to appropriately mix even nonpolar dispersion media such as toluene and hexane other than the above-mentioned preferred dispersion media. It is also a preferred form of the invention.
Sulfuric acid can be sufficiently removed by the above purification step, that the graphite oxide having the amphoteric surfactant bound to the surface interacts favorably with the organic dispersion medium, and in addition to the amphoteric surfactant, a nonionic surfactant and / or Alternatively, since the graphite oxide bound to the surface of the cationic surfactant also interacts favorably with both the aqueous dispersion medium and the organic dispersion medium, the layer of the graphite oxide is very suitably peeled in the peeling step, As a result, the carbon material composite can be dispersed in the dispersion medium.

A liquid polymer compound is also preferable as the dispersion medium. Examples of the liquid polymer compound include polyethylene glycol, polypropylene glycol, silicone oil and the like, and one or more of these can be used.

Further, a resin precursor (monomer) is also preferable as the dispersion medium. The resin precursor may be a hydrophilic (water-based) resin precursor or a lipophilic (organic-based) resin precursor, and is a conventionally known thermoplastic resin precursor or thermosetting resin precursor. A precursor of a photocurable resin or the like can be used as appropriate.

Examples of the thermoplastic resin include olefin resins such as polyethylene, polypropylene, ethylene-olefin copolymers (ethylene-propylene copolymer, etc.), polymethylpentene; poly (meth) acrylate resins, poly (meth) acryl. (Meth) acrylic resin such as acid resin and poly (meth) acrylonitrile resin; polystyrene, AS resin (acrylonitrile-styrene resin), ABS resin (acrylonitrile-butadiene-styrene resin), ACS resin (chlorinated polyethylene-acrylonitrile-styrene) Resin), AES resin (acrylonitrile-ethylene-styrene resin) and other styrene-based resins; polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride and other halogenated vinyl resins; aliphatic polyamide, aromatic polyamide, etc. Resins; vinyl acetate resins such as polyvinyl acetate and ethylene-vinyl acetate copolymers; other vinyl resins such as polyvinyl alcohol resins, polyvinyl acetal resins, polyvinyl ether resins, polyvinyl ketone resins; polyethylene terephthalate, polybutylene terephthalate, polyethylene Polyester resin such as phthalate; PPE resin (polyphenylene ether resin), modified PPE resin, phenylene group-containing resin such as polyphenylene oxide, polyphenylene sulfide; fluorine resin such as polytetrafluoroethylene; polyether ether ketone, polyether ketone, polyether Polyether resin such as sulfone and polyether nitrile; polycarbonate; silicone resin; polysulfone resin; liquid crystal polymer; to obtain these resins Copolymers based on a proper combination of monomers used and the like.

Examples of the thermosetting resin include epoxy resin, phenol resin, cyanate ester resin, melamine resin, polyimide resin, bismaleimide resin, urea resin, alkyd resin, silicone resin, vinyl ester resin, benzoxazine resin, urethane resin and the like. Is mentioned.

Examples of the photocurable resin include photocurable (meth) acrylic resins such as urethane (meth) acrylic resin and epoxy (meth) acrylic resin; polyvinyl carbonate resins such as polyvinyl acetate resin.

As the resin precursor, a monomer used to obtain the above-described resin (for example, a thermoplastic resin, a thermosetting resin, a photocurable resin) can be used, and among them, a monomer having an ethylenically unsaturated double bond. (Vinyl monomer) and epoxy compound (epoxy monomer) are preferable.
The monomer having an ethylenically unsaturated double bond may be monofunctional or polyfunctional, and examples thereof include (meth) acrylic acid ester, (meth) acrylic acid and (meth) acrylonitrile. (Meth) acrylic monomers: Styrene monomers such as styrene and divinylbenzene, and other vinyl monomers such as vinyl acetate, vinyl chloride, vinyl ether, and butadiene, and the like, and one or more of these can be used.
Examples of the epoxy compound include alicyclic epoxy compounds, aromatic epoxy compounds, hydrogenated epoxy compounds and the like, and one or more of these can be used.

Further, the dispersion medium may be a mixed dispersion medium in which at least two kinds selected from the group consisting of water, an organic dispersion medium, a liquid polymer compound, and a resin precursor are combined.
For example, the liquid polymer compound or the resin precursor described above may be dissolved or dispersed in an aqueous dispersion medium or an organic dispersion medium.

Further, the dispersion medium may include a resin, for example, the dispersion medium contains water and / or organic dispersion medium, the water and / or organic dispersion medium, the resin is dissolved or It may be dispersed. Examples of the resin include the above-mentioned thermoplastic resins, thermosetting resins, and photocurable resins, and one or more of these can be used. For example, one in which a water-soluble resin is dissolved in water, one in which emulsion particles are dispersed in water, and one in which a polymer such as a vinyl resin is dissolved in an organic dispersion medium can be preferably used as the dispersion medium.
As the organic dispersion medium, it is preferable to use the preferable organic dispersion medium in the peeling step described above.

In summary, the dispersion medium may be one kind selected from the group consisting of water, an organic dispersion medium, a liquid polymer compound, a resin, and a resin precursor, and at least two kinds are appropriately combined. It may be a mixed dispersion medium.

As described above, as the resin dispersion medium containing the resin and / or the resin precursor among the above dispersion media, for example, an epoxy compound (epoxy monomer), an epoxy resin, a monomer having an ethylenically unsaturated double bond is used. (Vinyl monomer), vinyl resin, a copolymer obtained by combining two or more kinds of these monomers, and a mixed dispersion medium of two or more kinds of these are preferable. Further, the resin dispersion medium may further contain an organic dispersion medium and / or water.

The content of sulfuric acid in the dispersion medium in the peeling step is preferably 0.1% by mass or less with respect to 100% by mass of the dispersion medium.

The peeling step can be performed, for example, in air or in an atmosphere of an inert gas such as nitrogen, helium, or argon. The temperature condition of the peeling step is not particularly limited, but it is preferably carried out within the range of 10 to 50 ° C, for example. Moreover, the pressure condition of the peeling step is not particularly limited, and may be performed under any of a pressure condition, a normal pressure condition, and a reduced pressure condition, but it is preferably performed under a normal pressure condition, for example. .
The time of the peeling step may be appropriately adjusted depending on the total amount of the carbon material composite dispersion liquid and the size of the peeling device, and can be, for example, 1 minute to 120 hours. Further, it is preferably 1 to 100 minutes, and more preferably 2 to 80 minutes.

(Process of oxidizing graphite)
The method of oxidizing the graphite is not particularly limited as long as the graphite is oxidized, and any method of oxidizing graphite may be used, such as the Hummers method, Brodie method, or Staudenmaire method. It may be a step of adding permanganate to a mixed liquid containing graphite and sulfuric acid, which employs the Hummers oxidation method.

In the above-mentioned method of oxidizing graphite, the above-mentioned oxidation step usually oxidizes graphite using acid.
In the production method of the present invention, the acid remains in the aqueous dispersion that is subjected to the purification step, but even if the acid remains, the amphoteric surfactant interacts with the graphite oxide and aggregates the acid, etc. The surprising effect is that the impurities can be easily removed. As a result, a high-quality carbon material composite can be easily manufactured.

Among them, it is one of preferred embodiments of the present invention that the oxidation step is a step of adding permanganate to a mixed liquid containing graphite and sulfuric acid.
In the above-mentioned oxidation step, the amount of sulfuric acid used is preferably such that the mass ratio of sulfuric acid to graphite (sulfuric acid / graphite) is 25 to 60. When the mass ratio is 25 or more, it is possible to sufficiently prevent the reaction composition (mixed liquid) from becoming highly viscous during the oxidation reaction and to efficiently produce oxidized graphite. Further, when the mass ratio is 60 or less, the amount of waste liquid can be sufficiently reduced.

The graphite used in the oxidation step preferably has an average particle size of 3 μm or more and 80 μm or less. By using the one having such an average particle diameter, the oxidation reaction can be promoted more efficiently. The average particle size of graphite is more preferably 3.2 μm or more and 70 μm or less.
As the average particle diameter, it is preferable to adopt a volume-based average particle diameter measured by a laser diffraction / scattering type particle size distribution measuring device.

The shape of graphite used in the oxidation step is not particularly limited, and examples thereof include fine powder, powder, granules, granules, scales, polyhedrons, rods, and curved surface-containing shapes. Incidentally, the particles having an average particle diameter in the above-mentioned range are, for example, a method of pulverizing the particles with a pulverizer, a method of selecting the particle diameter by sieving the particles, a combination of these methods, and producing particles. The production conditions can be optimized by the method of obtaining particles having a desired particle size and the like.

The content of graphite in the mixed liquid containing the above graphite and sulfuric acid is preferably 0.5% by mass or more, more preferably 1% by mass or more, based on 100% by mass of the mixed liquid. It is more preferably 5% by mass or more, and particularly preferably 2% by mass or more. The graphite content is preferably 10% by mass or less, more preferably 8% by mass or less, further preferably 7% by mass or less, and particularly preferably 6% by mass or less.
Only one type of graphite may be used in the oxidation step in the production method of the present invention, or two or more types of graphite having different average particle diameters or shapes may be used.

When the oxidation step is a step of adding permanganate to a mixed solution containing graphite and sulfuric acid, the permanganate added in the oxidation step may be sodium permanganate, potassium permanganate, or permanganate. Ammonium acid, silver permanganate, zinc permanganate, magnesium permanganate, calcium permanganate, barium permanganate and the like can be mentioned, and one or more of these can be used, among which sodium permanganate , Potassium permanganate is preferable, and potassium permanganate is more preferable.

When the oxidizing step is a step of adding permanganate to a mixed solution containing graphite and sulfuric acid, the total addition amount of the permanganate in the oxidizing step is 100% by mass of the graphite in the mixed solution. On the other hand, it is preferably 50 to 500 mass%. Thereby, graphite oxide can be manufactured safely and efficiently. The amount of oxygen atoms introduced into the oxidized graphite can be adjusted by changing the total amount of the oxidizing agent added.

When the oxidation step is a step of adding permanganate to a mixed solution containing graphite and sulfuric acid, in the oxidation step, permanganate may be added all at once, or added in multiple times. Alternatively, it may be added continuously, but it is preferable to add it in plural times or to add it continuously. This makes it possible to suppress the rapid progress of the oxidation reaction and make it easier to control the reaction.
When the above-mentioned permanganate is added in a plurality of times, the addition amount per one time may be the same or different.

When the oxidizing step is a step of adding permanganate to a mixed solution containing graphite and sulfuric acid, in the oxidizing step, permanganic acid is maintained while maintaining the temperature of the mixed solution within the range of 10 to 50 ° C. It is preferred to add salt. By maintaining such a temperature range, the oxidation reaction can be progressed sufficiently while being controlled.
When the oxidizing step is a step of adding permanganate to a mixed solution containing graphite and sulfuric acid, the oxidizing step removes the permanganate while maintaining the temperature change of the mixed solution at 30 ° C or lower. The step of adding is preferable. Thereby, the oxidation process can be performed more stably.

In the case where the oxidation step is a step of adding permanganate to a mixed liquid containing graphite and sulfuric acid, in the oxidation step, permanganate is added for 10 minutes to 10 hours from the viewpoint of stably performing the oxidation step. It is preferable to add it during the period.

The oxidation step is preferably performed with stirring using a known stirrer or the like.
The oxidation step can be performed, for example, in air or in an atmosphere of an inert gas such as nitrogen, helium, or argon. The pressure condition of the oxidation step is not particularly limited and may be any of pressurized condition, normal pressure condition and reduced pressure condition, but it is preferably carried out under normal pressure condition, for example.
The above oxidation step may be performed continuously or intermittently.

The mixed solution can be obtained by mixing graphite, sulfuric acid, and, if necessary, other components. The above mixing can be appropriately performed by a known method, but it is preferable to uniformly disperse the graphite by, for example, performing ultrasonic treatment or using a known disperser.

The method for producing a carbon material composite according to the present invention may include other steps such as an aging step, an oxidation reaction stopping step, and a concentrating step between the above-mentioned graphite oxidizing step and the above-mentioned purification step. . As described above, for example, it is preferable to use a liquid obtained by adding water and / or hydrogen peroxide solution to the reaction composition in the oxidation reaction stopping step as an aqueous dispersion in the refining step.

In the aging step, the temperature and time for aging the reaction composition obtained in the oxidation step may be appropriately selected, but it is preferable to maintain the reaction composition at a temperature of 0 to 90 ° C.
The time for aging is preferably 0.1 to 24 hours.

The oxidation reaction stopping step may be performed in air or in an inert gas atmosphere such as nitrogen, helium, or argon. It may also be performed in vacuum.
In the oxidation reaction stopping step, for example, the temperature of the reaction composition is set to 5 to 15 ° C., water is added to the reaction composition, and then hydrogen peroxide solution is added as a reducing agent, or only hydrogen peroxide solution is added. Can be added. Alternatively, the reaction composition may be added to water or hydrogen peroxide solution set at 5 to 25 ° C.
The time of the oxidation reaction stopping step can be set to, for example, 0.01 to 5 hours.

By appropriately removing the acid and water from the reaction composition in the concentration step, the amount of acid and water can be adjusted within a suitable range. This step can be performed by using a method such as centrifugation, redispersion with addition of water or the like, filtration, or vacuum concentration. Further, although these steps may be repeated, it is preferable to complete them in one step without repeating.

After the purification step, the production method of the present invention is a graphite oxide derivative obtained by reacting graphite oxide contained in the carbon material complex purified in the purification step with a compound that reacts with an oxygen-containing functional group of graphite oxide. May be included.
The compound that reacts with the oxygen-containing functional group of the graphite oxide preferably contains, for example, at least one selected from the group consisting of alcohols, silane compounds, fatty acids (salts), fatty acid esters, isocyanate compounds, and amines. . The silane compound preferably has a siloxy group and / or an alkoxy group directly bonded to a silicon atom from the viewpoint of improving the reactivity with the oxygen-containing functional group of graphite oxide.

<Carbon material composite>
The present invention is a carbon material composite including an amphoteric surfactant and graphite oxide. The carbon material composite of the present invention can be suitably dispersed in an organic dispersion medium. A preferred form of the carbon material composite of the present invention is a carbon material composite containing a nonionic surfactant and / or a cationic surfactant, an amphoteric surfactant, and graphite oxide. . Another preferred form of the carbon material composite of the present invention is a carbon material composite containing an amphoteric surfactant and graphite oxide, wherein the amphoteric surfactant is a cationic ionizing group. And a carbon material composite having an anion ionizing group and a hydrophilic group having a lower polarity than the cation ionizing group or the anion ionizing group. These carbon material composites can be suitably dispersed in both an aqueous dispersion medium and an organic dispersion medium.
The graphite oxide preferably has a ratio of the number of carbon atoms to the number of oxygen atoms (C / O) of 5.5 or less. The ratio is preferably 5 or less, more preferably 4 or less. Further, it is preferably 1 or more.
The ratio of the number of carbon atoms to the number of oxygen atoms can be confirmed by the ratio of the total peak area of the O1s region and the total peak area of the C1s region obtained by XPS measurement.
The carbon material composite of the present invention can be obtained by the method for producing a carbon material composite of the present invention.

<Dispersion>
The present invention is also a dispersion obtained by dispersing the carbon material composite of the present invention in a dispersion medium. The dispersion medium in which the carbon material composite of the present invention (complex of an amphoteric surfactant and a nonionic surfactant and / or a cationic surfactant and graphite oxide) is dispersed is an aqueous dispersion medium or an organic dispersion medium. Any of (may contain water), a lower alcohol having 1 to 3 carbon atoms such as methanol, ethanol, 1-propanol, and 2-propanol, and a carbon number having 4 to 12 carbon atoms such as butanol, pentanol, and hexanol. A chain ester solvent such as aliphatic alcohol, acetone, methyl ethyl ketone (MEK), acetonitrile, diacetone alcohol, acetylacetone, tetrahydrofuran, propylene carbonate, methyl acetate, ethyl acetate, butyl acetate and the like are preferable. The dispersion medium for dispersing the composite of amphoteric surfactant alone and graphite oxide is an organic dispersion medium having a relatively high polarity (may include water), and an organic dispersion medium having a relatively high polarity. As the medium, for example, lower alcohols having 1 to 3 carbon atoms such as methanol, ethanol, 1-propanol and 2-propanol, acetone, methyl ethyl ketone, acetonitrile, diacetone alcohol and acetylacetone are preferable.
In addition, 1 type of these dispersion media or 2 or more types of mixed dispersion media can be used.

As the dispersion medium, water, an organic dispersion medium, or the liquid polymer compound, resin, or resin precursor described above can be preferably used. As the liquid polymer compound, the resin, and the resin precursor, those described in the description of the peeling step can be used, and the preferable ones are the same as those described above in the description of the peeling step.
Suitable examples of the liquid polymer compound include polyethylene glycol and polypropylene glycol.
Preferred examples of the resin include vinyl resins such as (meth) acrylic resin and epoxy resins.
Examples of suitable resin precursors include vinyl monomers such as (meth) acrylic monomers and epoxy monomers.
The dispersion medium may be a mixed dispersion medium in which at least two kinds selected from the group consisting of water, an organic dispersion medium, a liquid polymer compound, a resin, and a resin precursor are appropriately combined. A preferable combination is as described above in the peeling step.
As the organic dispersion medium, it is preferable to use the preferable organic dispersion medium in the peeling step described above.
The content ratio of the carbon material composite of the present invention in the dispersion of the present invention can be appropriately adjusted.

As described above, the dispersion of the present invention may be a dispersion of the carbon material composite of the present invention in a resin and / or a resin precursor (resin dispersion). The resin dispersion may further contain at least one selected from the group consisting of water, an organic dispersion medium, and a liquid polymer compound as a dispersion medium.

The form of the resin dispersion may be a liquid or gel composition, or a solid form (for example, a molded body).
The resin dispersion is, for example, a dispersion obtained by dispersing the carbon material composite of the present invention in an aqueous dispersion medium or an organic dispersion medium, or the carbon material composite itself (powder) of the present invention. It can be obtained through a step of kneading with a resin (thermoplastic resin, thermosetting resin, or photocurable resin) (preferably, melting the resin before kneading).
Further, the molded body can be obtained by using, for example, a resin dispersion of the present invention, which is a liquid or gel composition, and for example, coating or film-forming the composition, It can be obtained by molding or by polymerizing and curing the resin precursor or the like in the composition.
Examples of the resin dispersion of the present invention include a liquid or gel composition; a solid composition such as a film (film), a sheet, a fiber, a pellet, and a particle.
Examples of the film include a coating film and a self-supporting film.

<Method for producing graphite oxide>
The present invention is a method for producing graphite oxide, which comprises a step of oxidizing graphite, an aqueous dispersion liquid in which the graphite oxide obtained in the oxidation step is dispersed, and an amphoteric surfactant. And a method for producing graphite oxide, the method including the step of purifying the graphite oxide.
In a preferred embodiment of the method for producing graphite oxide of the present invention, the purification step is a carbon material complex by at least one method selected from the group consisting of filtration, decantation, centrifugation, and liquid separation extraction. Is a step of purifying.
The method for producing the graphite oxide of the present invention can be performed by the same method as the method for producing the carbon material composite of the present invention described above. For example, the specific purification step described above is repeatedly performed, or the purification step After that, by repeatedly washing with water, the oxide oxide can be obtained by removing the surfactant used together with the impurities. From the viewpoint of removing the surfactant, washing with water containing no surfactant (the above-mentioned washing with water) is preferable. The method for producing graphite oxide of the present invention can easily obtain high-quality graphite oxide.
For example, the step of purifying the graphite oxide can be rephrased as the step of removing the amphoteric surfactant so that the amphoteric surfactant does not substantially remain.
The phrase "the amphoteric surfactant does not substantially remain" means that the mass ratio of the amphoteric surfactant is 1000 ppm or less.

The carbon material composite obtained by the method for producing a carbon material composite of the present invention, the carbon material composite of the present invention, the dispersion of the present invention, any of the graphite oxide obtained by the method of producing the graphite oxide of the present invention, a catalyst Suitable for use as battery, capacitor electrode active material, thermoelectric conversion material, conductive material, light emitting material, lubricant additive, polymer additive, permeable membrane material, antibacterial material, water repellent material, adsorbent material, etc. You can
Since the carbon material composite and the graphite oxide obtained by the production method of the present invention are preferably dispersed in an organic dispersion medium, the carbon material composite and the graphite oxide can be particularly preferably used for applications where the presence of water or moisture is not desirable.
Note that examples of the battery include a lithium ion secondary battery, a polymer electrolyte fuel cell, and a metal-air battery.
Examples of the thermoelectric conversion device using the thermoelectric conversion material include, for example, geothermal / hot spring heat generators, solar heat generators, waste heat generators such as factories and automobiles, generators such as body temperature generators, and at least the generator as a power source. Examples include various electric products, electric motors, artificial satellites, etc. used as one.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. In addition, "part" means "part by mass" and "%" means "% by mass" unless otherwise specified.

<Synthesis of aqueous dispersion containing graphite oxide>
(Synthesis example 1)
Graphite oxide was synthesized by the following steps. 15 g of graphite (Z-25 manufactured by Ito Graphite Co., Ltd.) and 640 g of sulfuric acid (manufactured by Wako Pure Chemical Industries, Ltd.) were placed in a reaction vessel in advance, and potassium permanganate (manufactured by Wako Pure Chemical Industries, Ltd.) was adjusted at 30 ° C. 45g was put. After the addition, the temperature was raised to 35 ° C. for 30 minutes and the reaction was performed for 2 hours. After the reaction, 1070 ml of water and 42 ml of 30% hydrogen peroxide solution (manufactured by Wako Pure Chemical Industries, Ltd.) were added to the reaction solution to stop the reaction, and an aqueous dispersion containing graphite oxide (total water mass 1812 g, raw material graphite conversion concentration 0.83%). , Water concentration 61%, sulfate ion concentration 36%) were obtained. The C / O of the graphite oxide in the obtained graphite oxide-containing aqueous dispersion was 1.8.

<Evaluation of purification efficiency>
(Example 1)
0.75 mass equivalent of lauryl betaine (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added to the raw material graphite to the aqueous dispersion containing graphite oxide (100 g) obtained in Synthesis Example 1 to cause aggregation. When filtered after stirring, the filterability was very good (filtering was completed within 10 minutes). Further, when water was added to the filtered wet cake and then filtered and washed with water, good filterability was maintained (filtering was completed within 10 minutes). Washing with water was carried out twice, and good filterability was maintained both times.

(Example 2)
Examples except that 0.75 mass equivalent of lauryl betaine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the amphoteric surfactant, instead of 0.75 mass equivalent of lauryl dimethylamine oxide (manufactured by Kao Corporation). When the filterability was confirmed as in the method described in 1, the filterability was good.

(Example 3)
Except that 0.75 mass equivalent of lauryl betaine (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was used as an amphoteric surfactant in place of 0.75 mass equivalent of raw material graphite, but the same equivalent of lauryl sulfobetaine (manufactured by Tokyo Chemical Industry Co., Ltd.) was used. When the filterability was confirmed in the same manner as in the method described in Example 1, the filterability was good.

(Example 4)
Into the graphite oxide-containing aqueous dispersion (100 g) obtained in Synthesis Example 1 above, 0.45 mass equivalent of nonionic surfactant Softanol 120 (manufactured by Nippon Shokubai Co., Ltd.) and amphoteric surfactant relative to raw material graphite. 0.30 mass equivalent of lauryl betaine (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added and aggregated. When filtered after stirring, the filterability was very good (filtering was completed within 10 minutes). Further, when water was added to the filtered wet cake and then filtered and washed with water, good filterability was maintained (filtering was completed within 10 minutes). Washing with water was carried out twice, and good filterability was maintained both times.

(Example 5)
0.45 mass equivalent of laurylpyridinium chloride (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), which is a cationic surfactant, is added to the raw material graphite in the aqueous dispersion containing graphite oxide (100 g) obtained in Synthesis Example 1 above. Then, 0.30 mass equivalent of lauryl betaine (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), which is an amphoteric surfactant, was charged and aggregated. When filtered after stirring, the filterability was very good (filtering was completed within 10 minutes). Further, when water was added to the filtered wet cake and then filtered and washed with water, good filterability was maintained (filtering was completed within 10 minutes). Washing with water was carried out twice, and good filterability was maintained both times.

(Example 6)
Into the graphite oxide-containing aqueous dispersion (100 g) obtained in Synthesis Example 1 above, 0.15 mass equivalent of nonionic surfactant Softanol 120 (manufactured by Nippon Shokubai Co., Ltd.) with respect to raw material graphite, 0.30 mass Lauryl pyridinium chloride (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) which is an equivalent amount of cationic surfactant, and 0.30 mass equivalent of lauryl betaine (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) which is an amphoteric surfactant. Was charged to agglomerate. When filtered after stirring, the filterability was very good (filtering was completed within 10 minutes). Further, when water was added to the filtered wet cake and then filtered and washed with water, good filterability was maintained (filtering was completed within 10 minutes). Washing with water was carried out twice, and good filterability was maintained both times.

(Comparative Example 1)
When the filterability was confirmed in the same manner as in Example 1 except that the amphoteric surfactant (lauryl betaine) was not added as a coagulant-free one, the filterability was very poor and the filter paper was clogged. , Could not be filtered.

(Comparative example 2)
As an anionic surfactant was used instead of the amphoteric surfactant, 0.75 mass equivalent of lauryl betaine (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) to the raw material graphite was replaced with the same equivalent amount of linear dodecyl. When the filterability was confirmed in the same manner as in Example 1 except that sodium benzenesulfonate (manufactured by Wako Pure Chemical Industries, Ltd.) was used, the filterability was very poor and the filter paper was clogged and filtration was impossible. there were.

<Dispersion of graphite oxide composite>
(Example 7)
100 g of acetone was added to the wet cake containing graphite oxide composite obtained in Example 1 (corresponding to 1 g of raw material graphite), stirred, and then ultrasonic waves were applied for 30 minutes to prepare an acetone dispersion of the graphite oxide composite. . When the acetone dispersion was allowed to stand for 24 hours, phase separation did not occur, a uniform appearance was maintained, and very good dispersibility was exhibited.

(Example 8)
Acetone dispersion of graphite oxide composite was prepared in the same manner as in Example 7 except that the used graphite oxide composite-containing wet cake was obtained in Example 2, and then allowed to stand for 24 hours. As a result, the acetone dispersion maintained a uniform appearance and exhibited very good dispersibility.

(Example 9)
After the acetone dispersion of the graphite oxide composite was prepared in the same manner as in Example 7, except that the used graphite oxide composite-containing wet cake was the one obtained in Example 3, and then allowed to stand for 24 hours. As a result, the acetone dispersion maintained a uniform appearance and exhibited very good dispersibility.

(Example 10)
A 2-propanol dispersion of an oxidized graphite composite was prepared in the same manner as in Example 9 except that the dispersion medium used was 2-propanol, and the mixture was allowed to stand for 24 hours. Maintained a uniform appearance and exhibited very good dispersibility.

(Example 11)
A methanol dispersion of an oxidized graphite composite was prepared in the same manner as in Example 9 except that the dispersion medium used was methanol, and the mixture was allowed to stand for 24 hours. The methanol dispersion maintained a uniform appearance. And showed good dispersibility.

(Example 12)
Acetone dispersion of graphite oxide composite was prepared in the same manner as in Example 7 except that the used graphite oxide composite-containing wet cake was obtained in Example 4, and then allowed to stand for 24 hours. As a result, the acetone dispersion maintained a uniform appearance and exhibited very good dispersibility.

(Example 13)
A methanol dispersion of the oxidized graphite composite was prepared in the same manner as in Example 12 except that the dispersion medium used was methanol, and the mixture was allowed to stand for 24 hours. The methanol dispersion maintained a uniform appearance. And showed very good dispersibility. Further, when compared with Example 11 using only the zwitterionic surfactant, a better dispersibility was exhibited.

(Example 14)
Acetone dispersions of the graphite oxide composite were prepared in the same manner as in Example 7 except that the used graphite oxide composite-containing wet cake was obtained in Example 5, and then allowed to stand for 24 hours. As a result, the acetone dispersion maintained a uniform appearance and exhibited very good dispersibility.

(Example 15)
A 1-hexanol dispersion of an oxidized graphite composite was prepared in the same manner as in Example 14 except that the dispersion medium used was 1-hexanol. Maintained a uniform appearance and exhibited very good dispersibility.

(Example 16)
After the acetone dispersion of the graphite oxide composite was prepared in the same manner as in Example 7, except that the used graphite oxide composite-containing wet cake was obtained in Example 6, and allowed to stand for 24 hours. As a result, the acetone dispersion maintained a uniform appearance and exhibited very good dispersibility.

(Example 17)
A 1-hexanol dispersion of an oxidized graphite composite was prepared in the same manner as in Example 16 except that the dispersion medium used was 1-hexanol, and the mixture was allowed to stand for 24 hours. Maintained a uniform appearance and exhibited very good dispersibility.

(Example 18)
When an ethyl acetate dispersion of a graphite oxide composite was prepared in the same manner as in Example 16 except that the dispersion medium used was ethyl acetate, the mixture was allowed to stand for 24 hours, and the ethyl acetate dispersion was uniform. The appearance was maintained and the dispersion was very good.

(Examples 19 to 28)
10 parts of the dispersion obtained in Example 8 was treated with liquid epoxy jER828US (Example 19), Nippon Kayaku Co., Ltd. epoxy curing acid anhydride KAYAHARED MCD (Example 20), acrylic acid (Example 21), Butyl acrylate (Example 22), 2-ethylhexyl acrylate (Example 23), methacrylic acid (Example 24), methyl methacrylate (Example 25), cyclohexyl methacrylate (Example 26), vinyl acetate (Example) Example 27) and styrene (Example 28) were each mixed with 90 parts to prepare a dispersion having each monomer as a main dispersion medium. Each of the resulting dispersions was very well dispersed and no agglomerates were generated. Further, there was no effect on the subsequent curing characteristics.
From this, it is understood that the carbon material composite of the present invention is well dispersed without aggregation even with respect to the monomer.

From the results of Examples 1 to 6 and Comparative Examples 1 and 2, good purification efficiency was shown by adding the amphoteric surfactant before the purification step. Further, from the results of Examples 7 to 28, the carbon material composites (graphite oxide composites) obtained by the above-described purification method showed good dispersibility in various dispersion media. According to the method for producing a carbon material composite of the present invention, a high quality carbon material composite can be easily obtained at low cost. Further, the carbon material composite of the present invention can be dispersed in various solvents by adjusting each surfactant, and carbon material composite dispersions of various solvents can be obtained.

Claims (9)

A method for producing a carbon material composite comprising an amphoteric surfactant and graphite oxide,
The manufacturing method comprises a step of oxidizing graphite,
A step of mixing an aqueous dispersion liquid in which graphite oxide obtained in the oxidation step is dispersed, and an amphoteric surfactant, and
A method for producing a carbon material composite, comprising a step of purifying the carbon material composite. The purification step is a step of purifying the carbon material complex by at least one method selected from the group consisting of filtration, decantation, centrifugation, and liquid separation extraction. A method for producing the carbon material composite as described above. The method for producing a carbon material composite according to claim 1 or 2, wherein in the mixing step, a nonionic surfactant and / or a cationic surfactant is further mixed. The carbon material composite according to any one of claims 1 to 3, wherein the manufacturing method further includes a step of separating the layers of the graphite oxide contained in the carbon material composite purified in the refining step. Body manufacturing method. The method for producing a carbon material composite according to any one of claims 1 to 4, wherein the aqueous dispersion contains 1 mass% or more of sulfate ions with respect to 100 mass% of the aqueous dispersion. A carbon material composite comprising a nonionic surfactant and / or a cationic surfactant, an amphoteric surfactant, and graphite oxide. A dispersion comprising the carbon material composite according to claim 6 dispersed in a dispersion medium. A method for producing graphite oxide, comprising:
The manufacturing method comprises a step of oxidizing graphite,
A step of mixing an aqueous dispersion liquid in which graphite oxide obtained in the oxidation step is dispersed, and an amphoteric surfactant, and
A method for producing graphite oxide, comprising the step of purifying graphite oxide. The purification step is a step of purifying graphite oxide by at least one method selected from the group consisting of filtration, decantation, centrifugation, and liquid separation extraction. Method for producing graphite oxide.