JP7348745B2 - Method of manufacturing the composite - Google Patents

Description

The present invention relates to a method for manufacturing a composite. More specifically, the present invention relates to a method for producing a composite, a composite, a resin composition, and a heat dissipating material that can be suitably used to obtain a heat dissipating material that is installed in electronic communication equipment or placed around batteries.

BACKGROUND OF THE INVENTION In recent years, electronic communication devices have been widely used, and the importance of batteries has been rapidly increasing in many industries, from small portable devices to large-scale applications such as automobiles. Here, it is necessary to sufficiently dissipate the heat generated when electronic communication equipment and batteries are used, and heat dissipating materials having high thermal conductivity and sufficient electrical insulation properties are being researched and developed. Conventionally, such heat dissipation materials have been made by mixing an electrically insulating resin material with a thermally conductive filler. A suitable material that achieves both of these has not yet been found.

It is expected that boron nitride, which has high thermal conductivity and sufficient electrical insulation, will be used as such a thermally conductive filler. However, since boron nitride has almost no functional groups, it has low affinity with resins and does not have sufficient dispersibility in resins. Therefore, even if boron nitride is mixed into a resin, there is a problem in that the thermal conductivity and electrical insulation properties of boron nitride cannot be fully exhibited. Therefore, methods are being considered to improve the dispersibility in resin by modifying the surface of boron nitride.

For example, carbon-modified boron nitride, which has a sheet-like carbon layer on the surface of boron nitride particles, has been disclosed (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 2019-001701

However, the carbon-modified boron nitride described in Patent Document 1 mentioned above may not be sufficiently carbon-modified (combined with carbon), particularly depending on the type of boron nitride used as a raw material. It has been desired to enable sufficient carbon modification and to improve the dispersibility of boron nitride into the resin.

The present invention has been made in view of the above-mentioned current situation, and an object of the present invention is to provide a method that can suitably obtain a material that has both high thermal conductivity and sufficient electrical insulation.

The present inventors have studied various ways to suitably obtain materials that have both high thermal conductivity and sufficient electrical insulation, and have developed boron nitride, which has high thermal conductivity and sufficient electrical insulation. We focused on this research and investigated various ways to improve the affinity of boron nitride to resins. The present inventors also discovered that when mixing boron nitride and graphite oxide to produce a composite, the boron nitride and graphite oxide were dispersed so that the pH of the supernatant liquid after mixing was 6.5 or less. When mixed in a medium, even when using boron nitride that could not be composited with graphene oxide by the method described in Patent Document 1, the coloring derived from graphite oxide in the supernatant liquid after mixing is substantially reduced. We have discovered that graphite oxide and boron nitride can be highly composited, and boron nitride can be sufficiently modified with graphite oxide (composite with graphite oxide), and we have successfully solved the above problem. We have come up with a solution to this problem and have arrived at the present invention.

That is, the present invention is a method for producing a composite by mixing boron nitride and graphite oxide, and the method includes mixing boron nitride and graphite oxide so that the pH of the supernatant liquid after mixing is 6.5 or less. This is a method for producing a composite, characterized by including a step of mixing graphite with a dispersion medium.

By the method for producing a composite of the present invention, boron nitride and graphite oxide can be composited, and a resin-compatible composite that has both high thermal conductivity and sufficient electrical insulation can be obtained.

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

<Method for manufacturing composite>
The composite obtained by the method for producing a composite of the present invention is a composite of graphite oxide and boron nitride.

In the following, first, the step of mixing boron nitride and graphite oxide in a dispersion medium so that the pH of the supernatant liquid after mixing becomes 6.5 or less in the method for producing a composite of the present invention will be explained. After that, the oxidation step for obtaining oxidized graphite and other steps that may be performed between the oxidation step and the mixing step will be explained.

(Mixing process of mixing boron nitride and graphite oxide in a dispersion medium)
The manufacturing method of the present invention includes a step of mixing boron nitride and graphite oxide in a dispersion medium such that the pH of the supernatant liquid after mixing is 6.5 or less.
The pH of the supernatant liquid after mixing is preferably 6 or less, more preferably 5.5 or less, even more preferably 4.5 or less, and particularly preferably 3.5 or less. Although the lower limit of the pH is not particularly limited, it is preferably 1 or more, more preferably 2 or more, and even more preferably 2.5 or more.
In this specification, the supernatant liquid after mixing boron nitride and graphite oxide is the supernatant liquid after the dispersion is allowed to stand for one hour after the mixing step. Moreover, pH is measured at 25° C. using a pH meter AS800 (manufactured by As One Corporation).

The absorbance of the supernatant after mixing is preferably 0.5 or less, more preferably 0.2 or less, even more preferably 0.1 or less, and preferably 0.05 or less. Particularly preferred. If the absorbance of the supernatant liquid after mixing is low as described above, it can be said that graphene oxide does not substantially remain in the supernatant liquid and that graphene oxide is adsorbed on the surface of boron nitride. The lower limit of absorbance is not particularly limited, but is usually 0.001 or more.
The absorbance is measured by the method described in the example using the supernatant liquid after the dispersion is allowed to stand for 1 hour after the mixing step.

The dispersion medium is preferably an aqueous solvent. The aqueous dispersion only needs to contain water, and may further contain an organic dispersion medium that is miscible with water, but preferably does not contain an organic dispersion medium.

In the mixing step, boron nitride and graphite oxide are mixed in a dispersion medium. In addition, the dispersion medium may be a dispersion medium of boron nitride and/or graphite oxide before mixing, it may be a dispersion medium of boron nitride and graphite oxide, and it may be mixed alone separately from boron nitride and graphite oxide, or both of these may be used. Good too.
Further, in the above mixing step, graphite oxide may be added to a container containing boron nitride, boron nitride may be added to a container containing graphite oxide, or boron nitride and graphite oxide may be added to the container at the same time. You may.
Graphite oxide and boron nitride may be added all at once, in multiple portions, or continuously.
Furthermore, in this specification, the mixing method is not particularly limited, and can be appropriately carried out by any known method, such as stirring, shaking, ultrasonication, or using a known dispersion machine. It is preferable to uniformly disperse the solid content.

In the mixing step, for example, an acid may be further mixed in order to adjust the pH of the supernatant liquid after mixing. The acid is not particularly limited, and examples include mineral acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and boric acid; organic acids such as formic acid, acetic acid, propionic acid, butyric acid, lactic acid, and citric acid; One or more of these can be used. Among these, sulfuric acid is preferred.
The acid may be added as is, or may be added after being diluted with an aqueous solvent as appropriate for the purpose of facilitating pH adjustment.
The acid can be mixed as appropriate for the purpose of adjusting the pH within the above-mentioned preferred range, but the acid concentration in the dispersion is preferably 20 to 1000 ppm, more preferably 50 to 500 ppm. The content is more preferably 70 to 250 ppm.
In the above mixing step, when an acid is further mixed, the mixing order is not particularly limited, but it is preferable, for example, to add the acid to a dispersion of boron nitride, and then add graphite oxide or an aqueous dispersion thereof. .

The time for the mixing step is not particularly limited, but it is preferable to mix for 0.5 minutes or more and 300 minutes or less, for example.
The temperature of the dispersion medium in the mixing step is not particularly limited as long as the dispersion medium is liquid, and can be, for example, 10°C or more and 80°C or less.
The pressure conditions in the mixing step may be under increased pressure, normal pressure, or reduced pressure.

After the above mixing step, a step of purifying the complex can be performed by methods such as filtration, decantation, centrifugation, separation and extraction, and washing with water. Among these methods, filtration and separation/extraction are preferred, and filtration is more preferred.
After the purification step, a drying step of the complex may or may not be performed, but it is preferable to perform a drying step. Further, if necessary, the composite may be subjected to a pulverization process, a classification process, etc.
It is also a preferred embodiment of the present invention to heat-treat the composite simultaneously with or before or after the mixing step or the subsequent steps. When heat treatment is performed, graphene oxide on the surface of the composite can be partially reduced to obtain reduced graphene oxide.
The heat treatment temperature is preferably 80°C or higher, more preferably 100°C or higher, and even more preferably 120°C or higher. Further, the heat treatment temperature is preferably 500°C or lower, more preferably 400°C or lower, and even more preferably 300°C or lower.
The heat treatment time is not particularly limited, but is preferably 0.5 to 600 minutes, more preferably 1 to 400 minutes, and even more preferably 5 to 300 minutes.

The boron nitride used in the mixing step may have any crystal structure such as hexagonal or cubic, and hexagonal boron nitride is particularly preferred. Further, the average particle diameter of boron nitride is not particularly limited, but is preferably 1 μm or more, more preferably 2 μm or more, still more preferably 3 μm or more, even more preferably 5 μm or more, and even more preferably It is 15 μm or more, particularly preferably 20 μm or more. The average particle diameter is preferably 200 μm or less, more preferably 150 μm or less, even more preferably 100 μm or less, particularly preferably 50 μm or less.
The above-mentioned average particle diameter is a volume-based average particle diameter measured by a laser diffraction/scattering particle size distribution analyzer.

When the boron nitride used in the mixing step is dispersed in ultrapure water to form a 10% by mass aqueous dispersion, the pH of the supernatant liquid is preferably 9 or more. The pH of the supernatant liquid is more preferably 9.2 or higher. Further, the pH of the supernatant liquid is preferably 12 or less, more preferably 11 or less, and even more preferably 10 or less.
In this specification, the supernatant liquid when dispersed in ultrapure water to form a 10% by mass aqueous dispersion refers to the supernatant liquid that is dispersed in ultrapure water to become a 10% by mass aqueous dispersion, and then the dispersion is kept at room temperature. This is the supernatant liquid after standing for 24 hours. Further, the pH is measured at 25° C. using a pH meter AS800 (manufactured by As One).
Note that the ultrapure water used has a specific resistance of 18 MΩ·cm or more, and for example, one having a specific resistance of 18.2 MΩ·cm can be used.
Although it was difficult to combine such boron nitride with graphite oxide using the conventional technology described in Patent Document 1, the production method of the present invention can suitably combine the boron nitride and graphite oxide. A complexed complex can be obtained.

The oxidized graphite used in the above mixing step is one in which oxygen is bonded by oxidizing a graphite carbon material such as graphene or graphite (oxygen bonded to the carbon material); a graphite carbon material After oxidizing, it is partially reduced and has oxygen bonded to it (reduced oxidized graphite); Oxygen is bonded to it and organic chains such as hydrocarbon chains and Examples include those in which an inorganic chain is bonded (graphite oxide derivative), and the oxygen is present as a substituent such as a carboxyl group, carbonyl group, hydroxyl group, or epoxy group on the graphite carbon material.
The graphite oxide is preferably graphene oxide in which oxygen is bonded to carbon of graphene. Note that graphene oxide includes any graphene in which oxygen is bonded to carbon, and includes reduced graphene oxide, which is obtained by partially reducing graphene in which oxygen is bonded to carbon, and graphene oxide in which oxygen is bonded to carbon. It also includes graphene oxide derivatives that have a bonded structure and that are modified using various organic compounds, inorganic compounds, and the like. The form of modification in the graphene oxide derivative is not particularly limited; for example, a form in which an organic chain or the like is bonded via a bond (such as a covalent bond) formed by a reaction with an oxygen-containing functional group on the surface of graphene oxide; Preferred forms include a form in which an organic chain or the like is bound by a hydrogen bond with the functional group, or a form in which an organic chain or the like is bound by an electrostatic bond with a negative charge on the graphene oxide surface. Further, a graphene oxide derivative in which an organic chain having a hydrocarbon group at the end has a functional group and oxygen is also bonded is also a preferable form of the present invention. It can be obtained by modification with aromatic alcohol, amine, etc.

In general, graphene is made up of carbon atoms bonded by ^sp2 bonds that are arranged in a single layer in a planar manner, rather than arranged three-dimensionally to form a cylindrical shape like carbon nanotubes (CNTs). Graphene oxide refers to a sheet consisting of a large number of laminated graphene sheets and is called graphite. However, the graphene oxide in the present invention does not only have a sheet consisting of one layer of carbon atoms, but also has a laminated structure of about 2 to 100 layers. Also includes things. It is preferable that the graphene oxide is a sheet consisting of only one layer of carbon atoms, or has a laminated structure of about 2 to 20 layers.
The graphite oxide may further have a functional group such as a sulfur-containing group or a nitrogen-containing group, but the content of carbon, hydrogen, and oxygen as constituent elements is 95 mol% or more based on all constituent elements. It is preferably 96 mol% or more, more preferably 97 mol% or more.

The graphite oxide preferably has a carbon/oxygen atomic ratio (C/O ratio) of 40/60 to 90/10. The C/O ratio is more preferably from 45/55 to 85/15, even more preferably from 50/50 to 80/20, even more preferably from 55/45 to 75/25, and even more preferably from 55/45 to 75/25. It is particularly preferable that the ratio is from /40 to 70/30.
The above C/O ratio is measured by the method described in Examples.

Only one type of graphite oxide may be used in the mixing step, or two or more types may be used that differ in any of the above average particle diameter, shape, etc.

The mass proportion of graphite oxide mixed with boron nitride in the mixing step is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, based on 100% by mass of boron nitride, More preferably, the content is 0.1% by mass or more. Further, the mass ratio is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 2% by mass or less, and 1% by mass or less, based on 100% by mass of boron nitride. % or less is particularly preferable.

Note that the dispersion medium may be, for example, an aqueous dispersion in which graphite oxide obtained in the oxidation step is dispersed. The aqueous dispersion medium may be the reaction composition immediately after the oxidation step, and may be used to remove sulfuric acid from the reaction composition in the subsequent graphite oxide purification step, or to add water to the reaction composition in the oxidation reaction quenching step. It may be a solution to which hydrogen peroxide is added, but it is preferable that the sulfuric acid concentration is reduced to 1% by mass or less by removing sulfuric acid from the reaction composition in a purification step, for example. .

The amount of the dispersion medium used in the mixing step is preferably 100 parts by mass or more, more preferably 300 parts by mass or more, and 500 parts by mass or more, for example, per 100 parts by mass of boron nitride. is even more preferable. Further, the amount of the dispersion medium is preferably 2000 parts by mass or less, more preferably 1500 parts by mass or less, and even more preferably 1200 parts by mass or less, based on 100 parts by mass of boron nitride.

(Oxidation process to obtain graphite oxide)
The manufacturing method of the present invention may further include a step of oxidizing graphite. In the step of oxidizing graphite, the method is not particularly limited as long as graphite is oxidized, and any graphite oxidation method such as Hummers method, Brodie method, Staudenmaier method, etc. may be used. It may be a step of adding permanganate to a mixed liquid containing graphite and sulfuric acid, which employs the oxidation method in the Hummers method.

In the method of oxidizing graphite described above, the oxidation step usually involves oxidizing graphite using an acid.
In addition, in the manufacturing method of the present invention, as a result of the acid used in the oxidation step remaining in the aqueous dispersion of graphite oxide used in the mixing step, the pH of the supernatant liquid after mixing in the mixing step is 6.5 or less. It may be.

Among these, it is one of the preferred embodiments of the present invention that the oxidation step is a step of adding permanganate to a mixed solution containing graphite and sulfuric acid.
In the 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, oxidized graphite can be efficiently produced by sufficiently preventing the reaction composition (mixture) from increasing in viscosity during the oxidation reaction. Further, by setting the mass ratio to 60 or less, the amount of waste liquid can be sufficiently reduced.

The graphite used in the oxidation step preferably has an average particle diameter of 3 μm or more and 80 μm or less. By using particles having such an average particle size, the oxidation reaction can proceed more efficiently. The average particle diameter 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 particle size distribution analyzer.

The shape of the graphite used in the oxidation step is not particularly limited, and examples thereof include fine powder, powder, granules, granules, scales, polyhedrons, rods, and shapes containing curved surfaces.

The content of graphite in the mixed liquid containing 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.1. 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, even more 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 that differ in any of the above average particle diameters, shapes, etc. may be used.

When the above oxidation step is a step of adding permanganate to a mixed solution containing graphite and sulfuric acid, the permanganate added in the above oxidation step includes sodium permanganate, potassium permanganate, permanganate. Examples include ammonium acid, silver permanganate, zinc permanganate, magnesium permanganate, calcium permanganate, barium permanganate, etc., and one or more of these can be used, but among them, sodium permanganate , potassium permanganate is preferred, and potassium permanganate is more preferred.

When the oxidation step is a step of adding permanganate to a mixed solution containing graphite and sulfuric acid, the total amount of permanganate added in the oxidation step is 100 parts by mass of graphite in the mixed solution. The amount is preferably 50 to 500 parts by mass. Thereby, graphite oxide can be produced safely and efficiently. Note that by changing the total amount of the oxidizing agent added, the amount of oxygen atoms introduced into the oxidized graphite can be adjusted.

When the above oxidation step is a step of adding permanganate to a mixed solution containing graphite and sulfuric acid, in the above oxidation step, permanganate may be added all at once, or may be added in multiple steps. Although it may be added continuously or it may be added continuously, it is preferable to add it in multiple portions or to add it continuously. This makes it possible to prevent the oxidation reaction from progressing rapidly, making it easier to control the reaction.
When the permanganate is added in multiple portions, the amount added per time may be the same or different.

When the oxidation step is a step of adding permanganate to a mixed solution containing graphite and sulfuric acid, in the oxidation step, permanganate is added while maintaining the temperature of the mixed solution within a range of 10 to 50°C. Preferably, salt is added. By maintaining the temperature within this range, the oxidation reaction can be controlled and allowed to proceed sufficiently.
Further, when the oxidation step is a step of adding permanganate to a mixed solution containing graphite and sulfuric acid, the oxidation step adds permanganate while maintaining the temperature change of the mixed solution at 30°C or less. Preferably, it is a step of adding. Thereby, the oxidation process can be performed more stably.

When the above oxidation step is a step of adding permanganate to a mixed solution containing graphite and sulfuric acid, in the above oxidation step, from the viewpoint of performing the oxidation step stably, the permanganate is added for 10 minutes to 10 hours. It is preferable to add it over a period of time.

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

The above liquid mixture can be obtained by mixing graphite, sulfuric acid, and other components as necessary. The above-mentioned mixing can be carried out appropriately by a known method, but it is preferable to uniformly disperse graphite by, for example, performing ultrasonic treatment or using a known disperser.

(Other steps that may be performed between the oxidation step and the mixing step)
The method for producing a carbon material composite of the present invention includes other steps such as an aging step, an oxidation reaction termination step, a purification step, and a peeling step between the above-mentioned graphite oxidizing step and the above-mentioned mixing step. You can stay there. As described above, for example, it is preferable to remove sulfuric acid from the reaction composition in the purification step and use a liquid whose sulfuric acid concentration is reduced to 1% by mass or less as an aqueous dispersion in the mixing step.

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

The oxidation reaction termination step may be performed in air or in an inert gas atmosphere such as nitrogen, helium, or argon. It may also be carried out in a vacuum.
In the oxidation reaction termination step, for example, the temperature of the reaction composition is set at 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. This can be done by adding. Alternatively, the reaction composition may be added to water or hydrogen peroxide solution set at 5 to 25°C.
The time for the oxidation reaction termination step can be, for example, 0.01 to 5 hours.

By appropriately removing acid and water from the reaction composition through the above purification step, the amount of acid and water can be adjusted within a suitable range. This step may include a solid-liquid separation step by centrifugation, static sedimentation, filtration, etc., a step of adding water, dilute hydrochloric acid, etc. to the obtained solid to redisperse it, and a concentration step such as vacuum concentration. Moreover, these steps may be completed only once, or may be repeated until a desired degree of purification is achieved. It is preferable to repeat the process until the sulfuric acid concentration in the treatment liquid becomes 1% by mass or less.

Further, it is preferable to exfoliate the obtained graphite oxide by applying mechanical shearing force using a homogenizer, high-pressure homogenizer, disperser, line mixer, or bead mill, or by irradiating it with ultrasonic waves.

<Complex>
The present invention also provides a composite comprising boron nitride and graphite oxide, the supernatant of which has a pH of 9 or more when dispersed in ultrapure water to form a 10% by mass aqueous dispersion. be.
According to the production method of the present invention, even when using boron nitride whose supernatant liquid has a pH of 9 or more when dispersed in ultrapure water to form a 10% by mass aqueous dispersion, the boron nitride and graphite oxide complexes can be obtained.

When the composite of the present invention is subjected to mapping measurement using a Raman spectrometer, it is preferable that absorption near 1600 cm ⁻¹ derived from graphene oxide is observed at at least 20 out of 25 arbitrary measurement points. In such a composite of the present invention, boron nitride is sufficiently coated with graphene oxide. It is more preferable that absorption near 1600 cm ^-1 derived from graphene oxide is observed at at least 23 of the 25 arbitrary measurement points, and absorption near 1600 cm ^-1 originating from graphene oxide is observed at at least 24 points. It is more preferable that absorption around 1600 cm ⁻¹ derived from graphene oxide be observed at all points.

The average particle diameter of the composite of the present invention is not particularly limited, but is preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 15 μm or more. When the average particle diameter is less than 5 μm, when a resin composition containing the composite of the present invention is made, there is a risk that the thermal conductivity will decrease due to an increase in grain boundaries. Further, the average particle diameter is usually 200 μm or less, preferably 150 μm or less. When the average particle diameter exceeds 200 μm, there is a possibility that sedimentation of the composite may easily occur during production of a resin composition containing the composite of the present invention.
The above-mentioned average particle diameter is a volume-based average particle diameter measured by a laser diffraction/scattering particle size distribution analyzer.
Particles with an average particle size in the above range can be obtained by, for example, pulverizing the particles with a pulverizer, screening the particles with a sieve, or a combination of these methods. It is possible to produce particles by optimizing the preparation conditions at the step of obtaining particles with a desired particle size.

The composite of the present invention includes the boron nitride and graphite oxide. The mass proportion of graphite oxide is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and 0.1 mass% or more based on 100 mass% of the boron nitride. More preferably. Further, the mass ratio is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 2% by mass or less, and 1% by mass or less, based on 100% by mass of boron nitride. % or less is particularly preferable.

The composite of the present invention may contain other components other than the boron nitride and graphite oxide, but the content of other components is 5% by mass or less in 100% by mass of the composite of the present invention. The content is preferably 1% by mass or less, and more preferably 1% by mass or less. It is further preferable that the composite of the present invention does not substantially contain the other components mentioned above.

<Resin composition>
The present invention also provides a resin composition characterized by containing the composite of the present invention and a resin.
The above resins include polyolefin resin, polycycloolefin resin, polystyrene resin, ABS resin (acrylonitrile-butadiene-styrene copolymer), polycarbonate resin, polyamide resin, polyimide resin, poly(meth)acrylate resin, polyethylene terephthalate resin, polyphenylene. Examples include sulfide resins, epoxy resins, urethane resins, silicone resins, phenol resins, and one or more of these can be used.

The amount of the composite of the present invention in the resin composition is preferably 1 to 80% by weight, more preferably 5 to 70% by weight, and even more preferably 10 to 60% by weight.
Further, the amount of the resin in the resin composition is preferably 20 to 99% by mass, more preferably 30 to 95% by mass, and even more preferably 40 to 90% by mass.
The resin composition of the present invention may further contain other components such as a curing agent, a crosslinking agent, a polymerization initiator, a filler, and a pigment, if necessary.

The resin composition of the present invention can be obtained by dispersing the composite of the present invention and, if necessary, other components in the resin by a conventionally known method.
Note that the composite of the present invention is a composite of graphite oxide and has excellent resin affinity, so that it can be suitably dispersed in the resin.

The present invention is a method for producing a resin composition containing a composite of boron nitride and graphite oxide, and a resin, and the production method is such that the pH of the supernatant after mixing is 6.5 or less. The method for producing a resin composition includes a step of mixing boron nitride and graphite oxide in a dispersion medium, and a step of dispersing the composite obtained in the mixing step in a resin.

<Heat dissipation material>
The present invention also provides a heat dissipating material characterized by being obtained using the resin composition of the present invention.
The heat dissipating material of the present invention can be obtained by applying, drying, or molding the resin composition of the present invention. During drying and molding, heating may be applied if necessary.
The heat dissipating material of the present invention is one in which the composite of the present invention is sufficiently dispersed in a resin, and can fully exhibit excellent thermal conductivity and sufficient electrical insulation.
It is particularly preferable that the heat dissipating material of the present invention be installed in an electronic communication device or placed around a battery.
Note that the above-mentioned batteries include, for example, lithium ion secondary batteries, polymer electrolyte fuel cells, metal-air batteries, etc., which are used in electric vehicles.

The present invention is a method for manufacturing a heat dissipating material, which includes mixing boron nitride and graphite oxide in a dispersion medium such that the pH of the supernatant liquid after mixing is 6.5 or less. It is also a method for producing a resin composition, including a step, a step of dispersing the composite obtained in the mixing step in a resin, and a step of obtaining a heat dissipating material using the resin composition obtained in the mixing step.

The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples. In addition, unless otherwise specified, "parts" shall mean "parts by mass" and "%" shall mean "% by mass."

<Synthesis example 1>
(Preparation of graphene oxide dispersion)
10 g of flaky graphite powder Z-25 (manufactured by Ito Graphite Industries Co., Ltd.) was dispersed in 400 g of concentrated sulfuric acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.), and 35 g of potassium permanganate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was dispersed. In addition, the reaction mixture was stirred at 30° C. for 8 hours. After the reaction was completed, the reaction solution was slowly poured into 2000 g of stirred ion-exchanged water, and then 10 g of 30% hydrogen peroxide solution was added. The mixture was centrifuged, the supernatant was removed, and ion-exchanged water was added instead for redispersion. The steps of centrifugation, removal of supernatant liquid, and addition of ion-exchanged water were repeated four times to obtain a purified aqueous graphite oxide dispersion.

The purified graphite oxide aqueous dispersion was stirred at 10,000 rpm for 30 minutes using a homogenizer HG-200 (manufactured by As One) equipped with a shaft generator K-30 (manufactured by As One) to exfoliate the particles, and the graphene oxide aqueous dispersion was Obtained. When 1 g of graphene oxide aqueous dispersion was collected in an aluminum dish and heated in a blow oven at 105° C. for 1 hour, the evaporation residue was 1.2% by mass. The graphene oxide aqueous dispersion was diluted to 0.1% by mass with ultrapure water (specific resistance: 18.2 MΩ·cm, hereinafter the same), and the pH measured at 25° C. was 2.7. When the aqueous graphene oxide dispersion was diluted 100 times with ultrapure water, applied to a mica substrate, dried, and observed with an atomic force microscope (AFM), the length of the longest part of the sheet was 2.5 to 2.5 times. An image with a distribution of 15 μm and a thickness of 1 to 2 nm was confirmed. When a sample obtained by drying an aqueous graphene oxide dispersion at 50°C under vacuum for 48 hours was analyzed using an X-ray photoelectron spectrometer (XPS), the carbon/oxygen atomic ratio (C/O ratio) was 64/36. there were. In the X-ray diffraction (XRD) measurement, a strong peak appeared at the position of 2θ = 9.4°, which corresponds to the interlayer distance of 9.4 Å, and the 2θ = 9.4° position, which corresponds to the interlayer distance of 9.4 Å, was attributed to the graphite structure (interlayer distance of 3.3 to 3.4 Å). No peak was observed around 27°.

<Example 1>
(Preparation of graphene oxide-coated boron nitride)
20 g of hexagonal boron nitride powder HS (average particle size: 20 μm, manufactured by Dandong Chemical Engineering Institute Co., Ltd.) and 180 g of ultrapure water were thoroughly mixed and dispersed. When this mixture was allowed to stand for 24 hours, the pH of the supernatant was 9.5 (measurement temperature: 25°C, the same applies hereinafter). To this was added 3.50 g of 1% sulfuric acid prepared by diluting concentrated sulfuric acid 100 times with ultrapure water, and the mixture was stirred. Next, while stirring was continued, 3.33 g (0.040 g as graphene oxide) of the 1.2% by mass graphene oxide aqueous dispersion prepared in Synthesis Example 1 was added. Stirring was continued for an additional 10 minutes. Thereafter, stirring was stopped and the mixture was allowed to stand for 1 hour. The pH of the supernatant at this time was 3.0.

Upon visual inspection, the supernatant liquid was clear and colorless. Concentrated aqueous graphene oxide dispersions are colored black, and even dilute ones are brown, so graphene oxide is not substantially contained in the supernatant liquid, and almost all of it adsorbs to boron nitride and settles. I know what you did. Furthermore, when the supernatant after being left standing for 1 hour was placed in a quartz square cell with an optical path length of 10 mm and measured using an ultraviolet-visible spectrophotometer (UV-VIS), the absorbance at a wavelength of 400 nm was as low as 0.018.

When the reaction mixture was suction filtered using polytetrafluoroethylene filter paper PF-050 (manufactured by Advantech) with a filtration area of 9.62 cm ² , the entire amount of the liquid passed through within 1 minute. Since graphene oxide has a large aspect ratio, it is known that if even a small amount remains in the liquid, the filtration rate slows down, and this result means that there is almost no free graphene oxide in the reaction system. The amount of water-containing solids remaining on the filter paper was 29.7 g. The water-containing solid was dried at 50° C. under vacuum for 48 hours to obtain 19.9 g of cream-colored powder. Although the powder contained a small amount of agglomerates, they could be broken up by pressing lightly with a polyethylene spatula. When the crushed material was passed through a sieve with an opening of 106 μm, more than 99% passed through the sieve. When the powder that passed through the sieve was mapped using a Raman spectrometer, absorption at 1600 cm ^-1 derived from graphene oxide was observed at all 25 measurement points, indicating that the entire surface of the boron nitride was covered with graphene oxide. was confirmed. The average particle size of the composite that passed through the sieve was 21 μm.

<Example 2>
Graphene oxide-coated boron nitride powder was produced in the same manner as in Example 1 except that the amount of 1% sulfuric acid was changed to 1.31 g. Graphene oxide was added and stirred, and the pH of the supernatant measured 1 hour after the stirring was stopped was 5.3. The supernatant liquid was colorless and transparent, and the absorbance at a wavelength of 400 nm measured by UV-VIS was as low as 0.048. In the filtration, the entire amount of liquid passed through within 1 minute, and the amount of water-containing solids remaining on the filter paper was 29.6 g. After drying, 19.8 g of cream-colored powder was obtained. Although the powder contained a small amount of agglomerates, they could be broken up by pressing lightly with a polyethylene spatula. When the crushed material was passed through a sieve with an opening of 106 μm, more than 99% passed through the sieve. When the powder that passed through the sieve was mapped using a Raman spectrometer, absorption at 1600 cm ^-1 derived from graphene oxide was observed at all 25 measurement points, indicating that the entire surface of the boron nitride was covered with graphene oxide. was confirmed. The average particle size of the composite that passed through the sieve was 20 μm.

<Comparative example 1>
Graphene oxide-coated boron nitride powder was produced in the same manner as in Example 1 except that the amount of 1% sulfuric acid was changed to 0.47 g. Graphene oxide was added and stirred, and the pH of the supernatant measured 1 hour after the stirring was stopped was 7.9. The supernatant liquid was colored brown, and the absorbance at a wavelength of 400 nm measured by UV-VIS was as high as 0.665. Filtration required 5 minutes for the entire amount of liquid to pass through. All of these mean that free graphene oxide remains in the supernatant, that is, the adsorption to boron nitride is insufficient. The amount of water-containing solids remaining on the paper after filtration was 29.6 g. After drying, 19.9 g of cream-colored powder was obtained. Although the powder contained a small amount of agglomerates, they could be broken up by pressing lightly with a polyethylene spatula. When the crushed material was passed through a sieve with an opening of 106 μm, more than 99% passed through the sieve. When the powder that passed through the sieve was mapped and measured using a Raman spectrometer, absorption at 1600 cm ^-1 originating from graphene oxide was observed at only 15 out of 25 measurement points, and part of the boron nitride surface was due to graphene oxide. It was confirmed that it was not covered with The average particle size of the composite that passed through the sieve was 21 μm.

<Comparative example 2>
Graphene oxide-coated boron nitride powder was produced in the same manner as in Example 1 except that 1% sulfuric acid was not added. Graphene oxide was added and stirred, and the pH of the supernatant measured 1 hour after the stirring was stopped was 8.9. The supernatant liquid was colored deep brown, and the absorbance at a wavelength of 400 nm measured by UV-VIS was as high as 2.038. Filtration required 10 minutes for the entire amount of liquid to pass through. All of these mean that free graphene oxide remains in the supernatant, that is, the adsorption to boron nitride is insufficient. The amount of water-containing solids remaining on the paper after filtration was 29.1 g. After drying, 19.8 g of cream-colored powder was obtained. Although the powder contained a small amount of agglomerates, they could be broken up by pressing lightly with a polyethylene spatula. When the crushed material was passed through a sieve with an opening of 106 μm, more than 99% passed through the sieve. When the powder that passed through the sieve was mapped and measured using a Raman spectrometer, absorption at 1600 cm ^-1 originating from graphene oxide was observed at only 8 out of 25 measurement points, and most of the boron nitride surface was due to graphene oxide. It was confirmed that it was not covered with The average particle size of the composite that passed through the sieve was 20 μm.

<Example 3>
20 g of hexagonal boron nitride powder HSL (average particle size: 35 μm, manufactured by Dandong Chemical Engineering Institute Co., Ltd.) and 180 g of ultrapure water were thoroughly mixed and dispersed. When this mixture was allowed to stand for 24 hours, the pH of the supernatant was 9.6. To this was added 3.55 g of 1% sulfuric acid prepared by diluting concentrated sulfuric acid 100 times with ultrapure water, and the mixture was stirred. Next, while stirring was continued, 3.33 g (0.040 g as graphene oxide) of the 1.2% by mass graphene oxide aqueous dispersion prepared in Synthesis Example 1 was added. Stirring was continued for an additional 10 minutes. Thereafter, stirring was stopped and the mixture was allowed to stand for 1 hour. The pH of the supernatant at this time was 2.9.

Upon visual inspection, the supernatant liquid was clear and colorless. Concentrated aqueous graphene oxide dispersions are colored black, and even dilute ones are brown, so graphene oxide is not substantially contained in the supernatant liquid, and almost all of it adsorbs to boron nitride and settles. I know what you did. Furthermore, when the supernatant after being left standing for 1 hour was placed in a quartz square cell with an optical path length of 10 mm and measured using an ultraviolet-visible spectrophotometer (UV-VIS), the absorbance at a wavelength of 400 nm was as low as 0.037.

When the reaction mixture was suction filtered using polytetrafluoroethylene filter paper PF-050 (manufactured by Advantech) with a filtration area of 9.62 cm ² , the entire amount of the liquid passed through within 1 minute. Since graphene oxide has a large aspect ratio, it is known that if even a small amount remains in the liquid, the filtration rate slows down, and this result means that there is almost no free graphene oxide in the reaction system. The amount of water-containing solids remaining on the filter paper was 30.5 g. The water-containing solid was dried at 50° C. under vacuum for 48 hours to obtain 19.8 g of cream-colored powder. Although the powder contained a small amount of agglomerates, they could be broken up by pressing lightly with a polyethylene spatula. When the crushed material was passed through a sieve with an opening of 125 μm, more than 99% passed through the sieve. When the powder that passed through the sieve was mapped using a Raman spectrometer, absorption at 1600 cm ^-1 derived from graphene oxide was observed at all 25 measurement points, indicating that the entire surface of the boron nitride was covered with graphene oxide. was confirmed. The average particle size of the composite that passed through the sieve was 36 μm.

<Example 4>
A graphene oxide-coated boron nitride powder was produced in the same manner as in Example 3 except that the amount of 1% sulfuric acid was changed to 1.44 g. Graphene oxide was added and stirred, and the pH of the supernatant measured 1 hour after the stirring was stopped was 3.4. The supernatant liquid was colorless and transparent, and the absorbance at a wavelength of 400 nm measured by UV-VIS was as low as 0.087. In the filtration, the entire amount of liquid passed through within 1 minute, and the amount of water-containing solids remaining on the filter paper was 30.3 g. After drying, 19.6 g of cream-colored powder was obtained. Although the powder contained a small amount of agglomerates, they could be broken up by pressing lightly with a polyethylene spatula. When the crushed material was passed through a sieve with an opening of 125 μm, more than 99% passed through the sieve. When the powder that passed through the sieve was mapped using a Raman spectrometer, absorption at 1600 cm ^-1 derived from graphene oxide was observed at all 25 measurement points, indicating that the entire surface of the boron nitride was covered with graphene oxide. was confirmed. The average particle size of the composite that passed through the sieve was 36 μm.

<Example 5>
Graphene oxide-coated boron nitride powder was produced in the same manner as in Example 3 except that the amount of 1% sulfuric acid was changed to 0.47 g. Graphene oxide was added and stirred, and the pH of the supernatant measured 1 hour after the stirring was stopped was 4.8. The supernatant liquid was almost colorless and transparent, and the absorbance at a wavelength of 400 nm measured by UV-VIS was as low as 0.334. In filtration, the entire amount of liquid passed through in 1 minute, and the amount of water-containing solids remaining on the filter paper was 30.0 g. After drying, 19.8 g of cream-colored powder was obtained. Although the powder contained a small amount of agglomerates, they could be broken up by pressing lightly with a polyethylene spatula. When the crushed material was passed through a sieve with an opening of 125 μm, more than 99% passed through the sieve. When the powder that passed through the sieve was mapped using a Raman spectrometer, absorption at 1600 cm ^-1 derived from graphene oxide was observed at all 25 measurement points, indicating that the entire surface of the boron nitride was covered with graphene oxide. was confirmed. The average particle size of the composite that passed through the sieve was 35 μm.

<Comparative example 3>
Graphene oxide-coated boron nitride powder was produced in the same manner as in Example 3 except that 1% sulfuric acid was not added. Graphene oxide was added and stirred, and the pH of the supernatant measured 1 hour after the stirring was stopped was 6.8. The supernatant liquid was colored deep brown, and the absorbance at a wavelength of 400 nm measured by UV-VIS was as high as 1.164. Filtration required 11 minutes for the entire amount of liquid to pass through. All of these mean that free graphene oxide remains in the supernatant, that is, the adsorption to boron nitride is insufficient. The amount of water-containing solids remaining on the paper after filtration was 30.1 g. After drying, 19.9 g of cream-colored powder was obtained. Although the powder contained a small amount of agglomerates, they could be broken up by pressing lightly with a polyethylene spatula. When the crushed material was passed through a sieve with an opening of 125 μm, more than 99% passed through the sieve. When the powder that passed through the sieve was mapped and measured using a Raman spectrometer, absorption at 1600 cm ^-1 originating from graphene oxide was observed at only 16 out of 25 measurement points, and part of the boron nitride surface was due to graphene oxide. It was confirmed that it was not covered with The average particle size of the composite that passed through the sieve was 35 μm.

< Reference example 1 >
20 g of hexagonal boron nitride powder UHP-2 (average particle size: 11 μm, manufactured by Showa Denko K.K.) and 180 g of ultrapure water were thoroughly mixed and dispersed. When this mixture was allowed to stand for 24 hours, the pH of the supernatant was 8.6. While stirring the mixture, 3.33 g (0.040 g as graphene oxide) of the 1.2% by mass graphene oxide aqueous dispersion prepared in Synthesis Example 1 was added. Stirring was continued for an additional 10 minutes. Thereafter, stirring was stopped and the mixture was allowed to stand for 1 hour. The pH of the supernatant at this time was 4.5.

Upon visual inspection, the supernatant liquid was clear and colorless. Concentrated aqueous graphene oxide dispersions are colored black, and even dilute ones are brown, so graphene oxide is not substantially contained in the supernatant liquid, and almost all of it adsorbs to boron nitride and settles. I know what you did. Furthermore, when the supernatant after being left standing for 1 hour was placed in a quartz square cell with an optical path length of 10 mm and measured using an ultraviolet-visible spectrophotometer (UV-VIS), the absorbance at a wavelength of 400 nm was as low as 0.018.

When the reaction mixture was suction filtered using polytetrafluoroethylene filter paper PF-050 (manufactured by Advantech) with a filtration area of 9.62 cm ² , the entire amount of the liquid passed through within 1 minute. Since graphene oxide has a large aspect ratio, it is known that if even a small amount remains in the liquid, the filtration rate slows down, and this result means that there is almost no free graphene oxide in the reaction system. The amount of water-containing solids remaining on the filter paper was 29.7 g. The water-containing solid was dried at 50° C. under vacuum for 48 hours to obtain 19.9 g of cream-colored powder. Although the powder contained a small amount of agglomerates, they could be broken up by pressing lightly with a polyethylene spatula. When the crushed material was passed through a sieve with an opening of 90 μm, more than 99% passed through the sieve. When the powder that passed through the sieve was mapped using a Raman spectrometer, absorption at 1600 cm ^-1 derived from graphene oxide was observed at all 25 measurement points, indicating that the entire surface of the boron nitride was covered with graphene oxide. was confirmed. The average particle size of the composite that passed through the sieve was 11 μm.

< Reference example 2 >
20 g of hexagonal boron nitride powder Platelets-012 (average particle size: 11 μm, manufactured by 3M) and 180 g of ultrapure water were thoroughly mixed and dispersed. When this mixture was allowed to stand for 24 hours, the pH of the supernatant was 8.6. While stirring the mixture, 3.33 g (0.040 g as graphene oxide) of the 1.2% by mass graphene oxide aqueous dispersion prepared in Synthesis Example 1 was added. Stirring was continued for an additional 10 minutes. Thereafter, stirring was stopped and the mixture was allowed to stand for 1 hour. The pH of the supernatant at this time was 4.0.

Upon visual inspection, the supernatant liquid was clear and colorless. Concentrated aqueous graphene oxide dispersions are colored black, and even dilute ones are brown, so graphene oxide is not substantially contained in the supernatant liquid, and almost all of it adsorbs to boron nitride and settles. I know what you did. Further, when the supernatant after being left standing for 1 hour was placed in a quartz square cell with an optical path length of 10 mm and measured using an ultraviolet-visible spectrophotometer (UV-VIS), the absorbance at a wavelength of 400 nm was as low as 0.030.

When the reaction mixture was suction filtered using polytetrafluoroethylene filter paper PF-050 (manufactured by Advantech) with a filtration area of 9.62 cm ² , the entire amount of the liquid passed through within 1 minute. Since graphene oxide has a large aspect ratio, it is known that if even a small amount remains in the liquid, the filtration rate slows down, and this result means that there is almost no free graphene oxide in the reaction system. The amount of water-containing solids remaining on the filter paper was 31.7 g. The water-containing solid was dried at 50° C. under vacuum for 48 hours to obtain 19.6 g of cream-colored powder. Although the powder contained a small amount of agglomerates, they could be broken up by pressing lightly with a polyethylene spatula. When the crushed material was passed through a sieve with an opening of 90 μm, more than 99% passed through the sieve. When the powder that passed through the sieve was mapped using a Raman spectrometer, absorption at 1600 cm ^-1 derived from graphene oxide was observed at all 25 measurement points, indicating that the entire surface of the boron nitride was covered with graphene oxide. was confirmed. The average particle size of the composite that passed through the sieve was 11 μm.

< Reference example 3 >
20 g of hexagonal boron nitride powder XGP (average particle size: 30 μm, manufactured by Denka Corporation) and 180 g of ultrapure water were thoroughly mixed and dispersed. When this mixture was allowed to stand for 24 hours, the pH of the supernatant was 8.9. While stirring the mixture, 3.33 g (0.040 g as graphene oxide) of the 1.2% by mass graphene oxide aqueous dispersion prepared in Synthesis Example 1 was added. Stirring was continued for an additional 10 minutes. Thereafter, stirring was stopped and the mixture was allowed to stand for 1 hour. The pH of the supernatant at this time was 4.5.

Upon visual inspection, the supernatant liquid was clear and colorless. Concentrated aqueous graphene oxide dispersions are colored black, and even dilute ones are brown, so graphene oxide is not substantially contained in the supernatant liquid, and almost all of it adsorbs to boron nitride and settles. I know what you did. Further, when the supernatant after being left standing for 1 hour was placed in a quartz square cell with an optical path length of 10 mm and measured using an ultraviolet-visible spectrophotometer (UV-VIS), the absorbance at a wavelength of 400 nm was as low as 0.042.

When the reaction mixture was suction filtered using polytetrafluoroethylene filter paper PF-050 (manufactured by Advantech) with a filtration area of 9.62 cm ² , the entire amount of the liquid passed through within 1 minute. Since graphene oxide has a large aspect ratio, it is known that if even a small amount remains in the liquid, the filtration rate slows down, and this result means that there is almost no free graphene oxide in the reaction system. The amount of water-containing solids remaining on the filter paper was 29.1 g. The water-containing solid was dried at 50° C. under vacuum for 48 hours to obtain 19.9 g of cream-colored powder. Although the powder contained a small amount of agglomerates, they could be broken up by pressing lightly with a polyethylene spatula. When the crushed material was passed through a sieve with an opening of 125 μm, more than 99% passed through the sieve. When the powder that passed through the sieve was mapped using a Raman spectrometer, absorption at 1600 cm ^-1 derived from graphene oxide was observed at all 25 measurement points, indicating that the entire surface of the boron nitride was covered with graphene oxide. was confirmed. The average particle size of the composite that passed through the sieve was 30 μm.

<Example 9>
A graphene oxide-coated boron nitride powder was produced in the same manner as in Example 1, except that the amount of the 1.2% by mass aqueous graphene oxide dispersion was changed to 8.33 g (0.100 g as graphene oxide). Graphene oxide was added and stirred, and the pH of the supernatant measured 1 hour after the stirring was stopped was 3.0. The supernatant liquid was colorless and transparent, and the absorbance at a wavelength of 400 nm measured by UV-VIS was as low as 0.025. In the filtration, the entire amount of liquid passed through within 1 minute, and the amount of water-containing solids remaining on the filter paper was 30.6 g. After drying, 19.7 g of cream-colored powder was obtained. Although the powder contained a small amount of agglomerates, they could be broken up by pressing lightly with a polyethylene spatula. When the crushed material was passed through a sieve with an opening of 106 μm, more than 99% passed through the sieve. When the powder that passed through the sieve was mapped using a Raman spectrometer, absorption at 1600 cm ^-1 derived from graphene oxide was observed at all 25 measurement points, indicating that the entire surface of the boron nitride was covered with graphene oxide. was confirmed. The average particle size of the composite that passed through the sieve was 22 μm.

The composites obtained in each of the above-mentioned Examples have excellent dispersibility in the resin because the entire surface of boron nitride is covered with graphene oxide, and the composite and the resin composition containing the resin are excellent. It is thought that the properties of the composite (for example, thermal conductivity) can be fully exhibited in products. For example, it is considered that a high-quality heat dissipating material can be suitably obtained by applying and drying or molding the resin composition.

Claims (4)

A method for producing a composite by mixing boron nitride and graphite oxide, the method comprising:
This manufacturing method involves mixing boron nitride whose supernatant liquid has a pH of 9 or more when dispersed in ultrapure water to form a 10% by mass aqueous dispersion, and graphite oxide, and which has a supernatant liquid whose pH after mixing is 6. A method for producing a composite, the method comprising the step of mixing in a dispersion medium so that the number of particles is 5 or less. A complex comprising boron nitride and graphite oxide whose supernatant liquid has a pH of 9 or more when dispersed in ultrapure water to form a 10% by mass aqueous dispersion,
A complex characterized in that, when the complex is subjected to mapping measurement using a Raman spectrometer, absorption near 1600 cm ^-1 derived from graphene oxide is observed at at least 20 out of 25 arbitrary measurement points. A resin composition comprising the composite according to claim 2 and a resin. A heat dissipating material obtained using the resin composition according to claim 3.