Surface-treated graphene, surface-treated graphene organic solvent dispersion, composition, and formed product

Abstract

To provide surface-treated graphene with excellent dispersibility of graphene in organic solvent dispersions and in compositions containing resins, surface-treated graphene organic solvent dispersions, and compositions with excellent impermeability to substances. [Solution] Surface-treated graphene having an amine compound having an aromatic ring and an aliphatic amine compound on its surface.

Description

[Technical Field]

[0001] The present invention relates to surface-treated graphene and a dispersion of surface-treated graphene in an organic solvent, a composition, and a formed product using the same. [Background technology]

[0002] Graphene is a two-dimensional crystal composed of carbon atoms and has been a highly regarded material since its discovery in 2004. The thin sheet structure of graphene possesses functions such as electrical conductivity, thermal conductivity, and impermeability to materials. One example of an application utilizing the functions of graphene is the addition of graphene to resins and other materials to obtain functional materials that possess these properties. To efficiently obtain the properties of graphene, the dispersibility of graphene when mixed with other materials is important, and techniques for adjusting dispersibility by surface treating graphene are known. For example, Patent Document 1 describes chemically functionalizing the graphene surface to improve dispersibility. Furthermore, Patent Document 2 proposes surface-treated graphene to which a compound having a benzene-based aromatic group without a phenolic hydroxyl group or its neutralized salt is attached. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Special Publication No. 2021-523864 [Patent Document 2] International Publication No. 2017 / 154533 [Overview of the project] [Problems that the invention aims to solve]

[0004] The technology described in Patent Document 1 can improve dispersibility by chemically functionalizing a portion of the graphene surface, but since the amount that can be chemically functionalized is limited, there was room for further improvement in dispersibility. Similarly, the technology described in Patent Document 2 can improve the dispersibility of graphene in a dispersion, but there was room for improvement in maintaining the sheet shape of graphene in compositions containing resin and graphene. For example, graphene aggregates could form, and the resin could adhere to their surface, resulting in clumping. Because the resin has difficulty penetrating the graphene aggregates, the bonding between the resin and graphene becomes insufficient, leading to cracks at the interface and resulting in insufficient strength or difficulty in achieving the desired properties of graphene. Furthermore, if the clumps are coarse, defects in the coating film can occur, making it difficult to obtain the desired properties.

[0005] The present invention aims to provide surface-treated graphene with excellent dispersibility of graphene in organic solvent dispersions and in compositions containing resins, surface-treated graphene organic solvent dispersions, and compositions with excellent impermeability to substances. [Means for solving the problem]

[0006] The present invention and its preferred embodiments for solving the above problems have the following configuration. (1) Surface-treated graphene having an aromatic ring-containing amine compound and an aliphatic amine compound on the surface of the graphene. (2) The surface-treated graphene according to (1), wherein the aliphatic hydrocarbon group of the aliphatic amine compound has 3 to 20 carbon atoms. (3) The surface-treated graphene according to (1) or (2), wherein the total amount of the aromatic ring-containing amine compound and the aliphatic amine compound attached to the surface of the surface-treated graphene is 5 parts by mass or more and 100 parts by mass or less per 100 parts by mass of graphene. (4) Surface-treated graphene according to any one of (1) to (3), wherein the elemental ratio of oxygen to carbon (O / C ratio) of the surface-treated graphene, as measured by X-ray photoelectron spectroscopy, is 0.05 or more and 0.40 or less, and the elemental ratio of nitrogen to carbon (N / C ratio) of the surface-treated graphene is 0.010 or more and 0.200 or less. (5) The surface-treated graphene according to any one of (1) to (4), wherein the average thickness of the surface-treated graphene is 0.3 nm or more and less than 15 nm. (6) A dispersion of surface-treated graphene in an organic solvent, wherein the surface-treated graphene described in any of (1) to (5) is dispersed in an organic solvent. (7) A composition comprising a surface-treated graphene organic solvent dispersion as described in (6) and a curable resin and / or its precursor. (8) A formed product comprising surface-treated graphene as described in any of (1) to (5). [Effects of the Invention]

[0007] The surface-treated graphene of the present invention not only exhibits excellent dispersibility of graphene in dispersions, but also excellent dispersibility of graphene in mixtures with resins, making it possible to obtain compositions with excellent impermeability to substances. [Modes for carrying out the invention]

[0008] <Surface-treated graphene> The surface-treated graphene of the present invention has an amine compound having an aromatic ring and an aliphatic amine compound on the surface of the graphene.

[0009] Generally, graphene, in the narrow sense, refers to a thickness of one atom of sp². 2 While the term "graphene" generally refers to a sheet of bonded carbon atoms (single-layer graphene), in this invention, the term "graphene" also includes forms that are stacked in a flaky manner. Similarly, the term "graphene oxide," as described later, also includes forms that are stacked in a flaky manner.

[0010] In the present invention, the amine compound having an aromatic ring refers to a compound having one or more aromatic groups and one amino group.

[0011] The amine compound having an aromatic ring contributes to the graphene dispersibility in a dispersion or a composition and has an effect of suppressing unintentional aggregation.

[0012] As the amine compound having an aromatic ring, a compound represented by the following general formula (I) or its neutral salt is preferable.

[0013]

Chemical formula

[0014] In general formula (I), A: A benzene-based aromatic group with a condensation number of 1 to 4 R 1 : A direct bond, a divalent hydrocarbon group having 1 to 6 carbon atoms, or a divalent organic group having 1 to 6 carbon atoms having a structure selected from the group consisting of an ether bond, an ester bond, an alcohol structure, and a carbonyl structure R 2 and R 3 : Each independently, a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, or an organic group having 1 to 6 carbon atoms having a structure selected from the group consisting of an ether bond, an ester bond, an alcohol structure, and a carbonyl structure.

[0015] The benzene-based aromatic group represented by A in general formula (I) may contain a hetero atom. The benzene-based aromatic group may be monocyclic or polycyclic. By the condensation number of the benzene-based aromatic group being 1 or more and 4 or less, the dispersibility of graphene can be made more effectively higher.

[0016] Also, from the viewpoint of strengthening the effect of improving the affinity with the solvent by the amino group, in the above general formula (I), R 1 is preferably an alkylene group having 1 to 6 carbon atoms, an alkenoxyalkylene group having 2 to 6 carbon atoms, or a direct bond. More preferably, R 1is a compound in which is an alkylene group having 1 to 4 carbon atoms, an alkenyloxyalkylene group having 2 to 4 carbon atoms, or a direct bond. Among them, R with a lower molecular weight 1 A compound in which is an alkylene group having 1 to 2 carbon atoms, an alkenyloxyalkylene group having 2 carbon atoms, or a direct bond is particularly preferred because it can further enhance the dispersibility. In the present invention, the alkenyloxyalkylene group represents a divalent group in which one carbon atom of the alkylene group is substituted with an oxygen atom. That is, the alkenyloxyalkylene group represents a divalent group represented by the following general formula. -(CH2) p -O-(CH2) q - In the above general formula, p and q represent integers of 1 or more.

[0017] In general formula (I), R 1 When is a divalent hydrocarbon group having 1 to 6 carbon atoms, the hydrocarbon group may have a phenylene structure.

[0018] Examples of the acid that forms a neutral salt with the compound represented by the above general formula (I) include sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, propionic acid, oxalic acid, boric acid, hydrofluoric acid, hydrochloric acid, hydrobromic acid, and hydroiodic acid. Among them, hydrochloric acid, hydrobromic acid, and hydroiodic acid are particularly preferred because they have few side reactions, high stability, and ease of handling.

[0019] Also, in order to enhance the adhesion to graphene, R in the above general formula (I) 2 R 3 are each preferably a hydrogen atom, a phenyl group, an alkyl group having 1 to 6 carbon atoms, or an alkoxyalkyl group having 2 to 6 carbon atoms. More preferably, R 2 R 3 are each a compound in which is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxyalkyl group having 2 to 4 carbon atoms. Among them, a compound in which R 2 R 3 is a hydrogen atom is particularly preferred because it can further enhance the dispersibility. In general formula (I), R 2 R 3If the hydrocarbon group is a divalent hydrocarbon group having 1 to 6 carbon atoms, the hydrocarbon group may have a phenylene structure.

[0020] Specific examples of amine compounds having the aforementioned aromatic ring include 2-chloroaniline, 3-chloroaniline, 4-chloroaniline, benzylamine, 2-phenylethylamine, 1-naphthylamine, 2-naphthylamine, aniline, 4-chloroaniline, p-toluidine, m-toluidine, o-toluidine, N-methyl-p-toluidine, 1-aminoanthracene, 2-aminoanthracene, 9-aminoanthracene, 1-aminopyrene, 3-(2-naphthyl)-L-alanine, 2-(1-naphthyl)acetamide, N-methyl-1-naphthylmethylamine, N-methylaniline, N-ethylaniline, N-ylopropylaniline, 4-ethylaniline, 4-isopropylaniline, N,N-dimethylaniline, 4-nitroaniline, diphenylamine, N-methyldiphenylamine, 2-bromoaniline, 2,4-dibromoaniline, 2,3-dichloroaniline, 2 ,4-dichloroaniline, 2,5-dichloroaniline, 3,4-dichloroaniline, 3,5-dichloroaniline, 4-fluoroaniline, 3-fluoroaniline, 2-fluoroaniline, 2,6-difluoroaniline, 2-iodoaniline, 4-iodoaniline, 3-iodoaniline, N-methyl-1-naphthylamine, N,N-dimethyl-1-naphthylamine, N,N-dimethyl-2-naphthylamine, 2,4,6-trichloro Aniline, 2,4-dimethylaniline, 2,6-dimethylaniline, 3,4-dimethylaniline, 3,5-dimethylaniline, 4-cyanoaniline, N-phenyl-1-naphthylamine, N-phenyl-2-naphthylamine, 2,4,6-trimethylaniline, 4-methoxyaniline, 4-aminobenzenethiol, formanilide, 4-methylbenzylamine, N-methylbenzylamine, N,N-dimethylbenzylamine, N,Examples include N-diethylbenzylamine, N-tert-butylbenzylamine, N-isopropylbenzylamine, (S)-(-)-1-phenylethylamine, (R)-(+)-1-phenylethylamine, N-ethylbenzylamine, benzamide, 4-(1-aminoethyl)toluene, 4-fluorobenzylamine, chlorobenzylamine, 4-methylbenzamide, isophthalamide, N-ethyl-N-methylbenzylamine, 2-aminobenzylamine, 4-(aminomethyl)benzoic acid, tripenzylamine, 4-aminobenzamide, 2-chlorobenzamide, 4-chlorobenzamide, 2,4-dichlorobenzamide, N-benzylacetamide, N,N-dimethylbenzamide, 4-fluorobenzamide, and 1-(2,4-dichlorophenyl)ethylamine, dopamine, etc.

[0021] The amine compound having the aromatic ring may consist of only one compound or multiple compounds.

[0022] Among these, 3-chloroaniline, benzylamine, 2-phenylethylamine, 1-naphthylamine, dopamine, or their neutralized salts are particularly preferred.

[0023] In this invention, an aliphatic amine compound refers to a compound having one amino group in one molecule. The aliphatic amine compound has the effect of improving the miscibility between the resin and graphene, as well as strengthening the bonding with the resin.

[0024] The amino group of the aliphatic amine compound is preferably a primary amine represented by the following general formula in order to enhance its bonding ability with the resin. R 4 NH2 In the above general formula, R 4 is a saturated or unsaturated aliphatic hydrocarbon group. The aliphatic hydrocarbon group may contain a heteroatom and may be a linear, branched, or cyclic aliphatic hydrocarbon group.

[0025] From the viewpoint of further improving the dispersibility of graphene in the resin, it is preferable that the aliphatic hydrocarbon group of the aliphatic amine compound has 3 to 20 carbon atoms.

[0026] Specific examples of aliphatic amine compounds used in the present invention include ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, dodecylamine, stearylamine, and oleylamine.

[0027] In the present invention, the state in which graphene has the aromatic ring-containing amine compound and the aliphatic amine compound (hereinafter sometimes referred to as "surface treatment agent") on its surface means that the graphene and the surface treatment agent are present on the surface without forming a covalent bond. More specifically, this refers to the detection of molecules or fragments of the surface treatment agent in a temperature range of 100°C to 500°C, when approximately 2 mg of surface-treated graphene is analyzed by analytical methods such as thermal desorption GC-MS or TPD-MS, and the temperature is increased at a heating rate of 10°C / min under a helium flow atmosphere of 50 mL / min. If the surface treatment agent is bonded via a covalent bond, it will not be desorbed by such analytical methods and will be below the detection limit.

[0028] The surface treatment agent present on the surface of graphene can be analyzed for its structure, for example, by the following method.

[0029] Surface-treated graphene is dispersed in water at 25°C at a mass ratio of 100 times its mass using a high-speed disperser (e.g., Primix's "Labo-Solution"® Homodisper 2.5) at a rotation speed of 2000 rpm for 30 minutes. This washing process is repeated five times using a vacuum pump for suction filtration, and the filtrate is freeze-dried. The presence of residual surface treatment agent on the surface of the surface-treated graphene can be confirmed by measuring the freeze-dried surface-treated graphene using time-of-flight secondary ion mass spectrometry (TOF-SIMS; e.g., ION-TOF's TOF.SIMS5), where the surface treatment agent molecules can be detected in the form of protonated molecules in the positive secondary ion spectrum. If the surface treatment agent is a neutralized salt, it can be detected as a protonated form of the surface treatment agent molecule after the anionic molecule has been removed.

[0030] The total amount of the aromatic ring-containing amine compound and the aliphatic amine compound attached to the surface of the surface-treated graphene is preferably 5 parts by mass or more and 100 parts by mass or less per 100 parts by mass of graphene. By setting the total amount to 5 parts by mass or more, more preferably 30 parts by mass or more, the miscibility and bonding with the resin can be more effectively improved. By setting the total amount to 100 parts by mass or less, more preferably 80 parts by mass or less, the dispersibility can be more effectively improved.

[0031] The content of the aromatic ring-containing amine compound is preferably 40% by mass or more and 95% by mass or less relative to 100% by mass of the total amount of the aromatic ring-containing amine compound and the aliphatic amine compound. By setting the content of the aromatic ring-containing amine compound to 40% by mass or more, more preferably 50% by mass or more, unintended aggregation of graphene in the dispersion or composition can be suppressed. By setting the content of the aromatic ring-containing amine compound to 95% by mass or less, more preferably 90% by mass or less, the miscibility with the resin can be improved and the bonding strength can be strengthened.

[0032] The content of the aliphatic amine compound is preferably 5% by mass or more and 60% by mass or less relative to 100% by mass of the total amount of the aromatic ring-containing amine compound and the aliphatic amine compound. By setting the content of the aliphatic amine compound to 5% by mass or more, more preferably 10% by mass or more, the miscibility and bonding properties with the resin can be further effectively improved. By setting the content of the aliphatic amine compound to 60% by mass or less, more preferably 50% by mass or less, the dispersibility can be further effectively improved.

[0033] The total amount of surface treatment agent attached to the graphene relative to its mass can be determined as follows: from the mass percentage of nitrogen measured by X-ray photoelectron spectroscopy (XPS) (a), the ratio of nitrogen derived from aliphatic amine compounds originating from the surface treatment agent measured by solid-state NMR (X), the molecular weight of the aromatic ring-containing amine compound (b1), the molecular weight of the aliphatic amine compound (b2), the formula weight of nitrogen in the aromatic ring-containing amine compound (c1), and the formula weight of nitrogen in the aliphatic amine compound (c2). Amount of amine compound containing an aromatic ring attached (Z1) = a × (1 - X) × b1 ÷ c1 Amount of aliphatic amine compound attached (Z2) = a × X × b2 ÷ c2 The total amount of surface treatment agent (parts by mass) per 100 parts by mass of graphene = (Z1 + Z2) ÷ (100 - Z1 - Z2) × 100.

[0034] The surface-treated graphene of the present invention preferably has an elemental ratio of oxygen to carbon (O / C ratio) of 0.05 or more and 0.40 or less, as measured by X-ray photoelectron spectroscopy (XPS). The O / C ratio represents the amount of functional groups on the surface-treated graphene and serves as an indicator of dispersibility and graphene functionality. From the viewpoint of further improving dispersibility, an O / C ratio of 0.05 or more, more preferably 0.08 or more, can more effectively improve dispersibility. Furthermore, an O / C ratio of 0.40 or less, more preferably 0.30 or less, and even more preferably 0.25 or less, can more effectively enhance the functionality of the surface-treated graphene, such as its impermeability to materials.

[0035] The O / C ratio of surface-treated graphene can be measured by XPS using an X-ray photoelectron spectroscopy analyzer as follows: monochromatic AlK as the excitation X-ray source. α1,2 A 1486.6 eV X-ray beam is used, with an X-ray diameter of 200 μm and a photoemission angle of 45°. The peak at 284.3 eV is assigned to the C1s main peak based on carbon atoms, and the peak around 533 eV is assigned to the O1s peak based on oxygen atoms. The O / C ratio is calculated from the area ratio of the O1s peak to the C1s peak, and the resulting value is rounded to two decimal places.

[0036] If the surface-treated graphene of the object to be measured is contained in a dispersion or composition, the surface-treated graphene is taken from there, powdered by vacuum drying, and then measured by XPS. The O / C ratio of the surface-treated graphene can be adjusted to the aforementioned range, for example, by adjusting the degree of oxidation of the raw material graphene oxide or the degree of reduction due to the reduction reaction conditions when using a chemical exfoliation method. In the case of the surface-treated graphene of the present invention, if the surface treatment agent attached to the graphene surface contains oxygen atoms, the ratio can also be adjusted by the amount of the attached agent.

[0037] The surface-treated graphene of the present invention preferably has an elemental ratio of nitrogen to carbon (N / C ratio) of 0.010 or more and 0.200 or less, as measured by XPS. The N / C ratio serves as an indicator of the amount of surface treatment agent adhering to the graphene. An N / C ratio of 0.010 or more, more preferably 0.015 or more, and even more preferably 0.020 or more, can more effectively improve miscibility and bonding with resin. Furthermore, an N / C ratio of 0.200 or less, more preferably 0.100 or less, and even more preferably 0.080 or less, can more effectively improve dispersibility.

[0038] The N / C ratio of surface-treated graphene can be measured by XPS using an X-ray photoelectron spectroscopy analyzer as follows: monochromatic AlK as the excitation X-ray source. α1,2A 1486.6 eV X-ray beam is used, with an X-ray diameter of 200 μm and a photoemission angle of 45°. The peak at 284.3 eV is assigned to the C1s main peak based on carbon atoms, and the peak around 402 eV is assigned to the N1s peak based on nitrogen atoms. The N / C ratio is calculated from the area ratio of the N1s peak and the C1s peak, and the resulting value is rounded to the third decimal place.

[0039] If the surface-treated graphene of the object to be measured is contained in a dispersion or composition, the surface-treated graphene can be taken from there, powdered by vacuum drying, and then measured by XPS.

[0040] The N / C ratio of surface-treated graphene can be adjusted to the aforementioned range, for example, by the amount of surface treatment agent applied.

[0041] The N / C ratio derived from aromatic ring-containing amine compounds and the N / C ratio derived from aliphatic amine compounds can be individually determined by integrating the ratio of the compound measured by solid-state NMR with the N / C ratio of surface-treated graphene measured by XPS.

[0042] If surface-treated graphene is included in the dispersion or composition of the object to be measured, the surface-treated graphene can be collected from there, powdered by vacuum drying, and then measured by solid-state NMR to determine the peak ratio of nitrogen atoms derived from aromatic ring-containing amine compounds and nitrogen atoms derived from aliphatic amine compounds.

[0043] The average thickness of the surface-treated graphene of the present invention is preferably 0.3 nm or more and less than 15 nm. An average thickness of 0.3 nm for surface-treated graphene is the theoretical minimum value for graphene and indicates that it is a single layer of graphene. On the other hand, by setting the average thickness of the surface-treated graphene to less than 15 nm, more preferably 12 nm or less, and even more preferably 10 nm or less, the dispersibility of the surface-treated graphene and its miscibility with resin can be more effectively improved, and functions such as impermeability of materials can be more effectively obtained.

[0044] The average thickness of surface-treated graphene is measured using a transmission electron microscope. In the case of a dispersion or composition, surface-treated graphene is sampled from there and measured using a transmission electron microscope. Surface-treated graphene embedded in resin is cross-sectioned by ion milling to prepare observation samples. Ten surface-treated graphene samples are randomly selected from the observation samples and observed using a transmission electron microscope. The entire cross-section of one surface-treated graphene is magnified to the maximum magnification that fits within the field of view, and the thickness is measured at five randomly selected locations on each surface-treated graphene. The arithmetic mean of the thicknesses at 50 locations (5 locations × 10 samples) is then calculated.

[0045] <Organic solvent dispersion> The surface-treated graphene of the present invention can be further dispersed in an organic solvent and used as a surface-treated graphene organic solvent dispersion. That is, the surface-treated graphene organic solvent dispersion of the present invention is obtained by dispersing the surface-treated graphene of the present invention in an organic solvent. The dispersion of the surface-treated graphene in the organic solvent may be carried out by dispersing the dry powder of the surface-treated graphene in the organic solvent, or by redispersing the concentrated wet cake of the surface-treated graphene in the organic solvent.

[0046] The aforementioned organic solvent is preferably volatile. Furthermore, when used as a mixed composition with the resin described later, it is preferable that the organic solvent is capable of dissolving the resin.

[0047] Examples of the aforementioned organic solvents include xylene, toluene, ethylbenzene, methyl isobutyl ketone, methyl ethyl ketone, acetone, butyl acetate, ethyl acetate, n-butanol, isobutanol, isopropyl alcohol, ethanol, N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide. Two or more of these may be included.

[0048] A weak solvent can also be used as the organic solvent. A weak solvent can be produced by refining crude oil and has the characteristic of having relatively weak dissolving power for resins and the like. By using a weak solvent, the effects of reducing odor and environmental impact can be obtained compared to aromatic organic solvents such as xylene and toluene. Examples of weak solvents include hydrocarbon organic solvents such as aliphatic organic solvents, naphthenic organic solvents, and aromatic naphtha organic solvents. Among these, aliphatic organic solvents are particularly preferred as weak solvents that have little odor and have little adverse impact on the environment.

[0049] Specific examples of the aforementioned weak solvents include, for example, cyclobutane, cyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, mineral spirits, white spirits, turpentine oil, mineral turpentine, isoparaffin, solvent kerosene, aromatic naphtha, and solvent naphtha.

[0050] The solid content concentration of the surface-treated graphene organic solvent dispersion is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less, from the viewpoint of further improving dispersibility. Furthermore, from the viewpoint of improving the convenience of the dispersion, it is preferable that it contains 0.1% by mass or more.

[0051] The solid content concentration of the surface-treated graphene organic solvent dispersion can be calculated by measuring the mass after drying the solvent from the surface-treated graphene organic solvent dispersion and dividing the measured value by the mass of the surface-treated graphene organic solvent dispersion itself. Specifically, approximately 1 g of the surface-treated graphene organic solvent dispersion was placed in an aluminum cup of known mass and its mass was measured. Then, it was heated for 1.5 hours on a hot plate heated to the volatilization temperature of the organic solvent to evaporate the solvent. The solid content concentration of the surface-treated graphene organic solvent dispersion was calculated from the mass of the surface-treated graphene organic solvent dispersion before heating and the amount of solvent evaporated from the mass difference before and after heating. This process was repeated three times to calculate the average value.

[0052] The surface-treated graphene organic solvent dispersion of the present invention preferably has an absorbance of 1.0 or higher at a wavelength of 500 nm when the concentration of the surface-treated graphene is adjusted to 0.0065% by mass. The absorbance of surface-treated graphene changes depending on the peeling and aggregation state of the surface-treated graphene, with single-layer surface-treated graphene without aggregation having the highest absorbance, and the absorbance decreases with increasing number of layers and the formation of aggregation. An absorbance of 1.0 or higher, more preferably 1.4 or higher, and even more preferably 1.7 or higher at a wavelength of 500 nm means that the degree of peeling of the surface-treated graphene is high and that most of the surface-treated graphene is not laminated or aggregated. On the other hand, from the viewpoint of suppressing aggregation due to overdispersion of surface-treated graphene and improving dispersibility in the solvent, the absorbance of surface-treated graphene at a wavelength of 500 nm is preferably 2.5 or lower.

[0053] Means for adjusting the absorbance of the surface-treated graphene organic solvent dispersion to the aforementioned range include obtaining the surface-treated graphene organic solvent dispersion by the manufacturing method described later.

[0054] <Composition> The surface-treated graphene organic solvent dispersion of the present invention can be used further containing a resin. Preferably, a curable resin is used. That is, the composition of the present invention comprises the surface-treated graphene organic solvent dispersion of the present invention and a curable resin and / or its precursor.

[0055] In the present invention, a curable resin refers to a resin that hardens by the volatilization or reaction of a solvent. Examples of curable resins include epoxy resins, urethane resins, acrylic resins, polyester resins, melamine resins, silicone resins, and alkyd resins, and commercially available curable resins may also be used. Two or more of these may be included. Among these, epoxy resins, urethane resins, and acrylic resins are preferred from the viewpoint of excellent miscibility and bonding with the surface-treated graphene of the present invention, and epoxy resins or urethane resins with high bonding with polyfunctional amine compounds are more preferred.

[0056] Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, and modified versions thereof such as acrylic modified epoxy resin and urethane modified epoxy resin. Two or more of these may be included. Among these, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and novolac type epoxy resin are preferred.

[0057] The urethane resin is preferably an ester-based urethane resin, an ether-based urethane resin, or a carbonate-based urethane resin, with ester-based urethane resins and carbonate-based urethane resins being more preferred.

[0058] The acrylic resin preferably contains, for example, acrylic acid, methacrylic acid, or derivatives thereof as copolymerization components. Examples of derivatives of acrylic acid or methacrylic acid include esterified products of acrylic acid or methacrylic acid, acrylamide, methacrylamide, and alkyl fluoride acrylates. The copolymerization components may further include non-acrylic components such as styrene, or acrylate-functionalized polydimethylsiloxane.

[0059] The surface-treated graphene organic solvent dispersion of the present invention, containing the curable resin, preferably contains 0.05% by mass or more of surface-treated graphene relative to the total solid content of the curable resin, more preferably 0.1% by mass or more, and even more preferably 0.25% by mass or more, from the viewpoint of easily obtaining the effect of surface-treated graphene. Furthermore, from the viewpoint of making it less likely for aggregates to form due to the excessive addition of surface-treated graphene, it is preferably 20% by mass or less, and more preferably 10% by mass or less.

[0060] The composition of the present invention can be used as a composite material to which surface-treated graphene has been given functions such as impermeability to materials, by molding by coating or casting, and curing by drying or reaction.

[0061] The surface-treated graphene of the present invention exhibits excellent miscibility and bonding properties in resins, making it particularly effective when used in the form of coatings or films. When forming coatings or films, stress can be applied to the interface between the surface-treated graphene and the resin due to shrinkage and other effects associated with the resin, potentially leading to defects. However, by using the surface-treated graphene of the present invention, the bonding properties between the surface-treated graphene and the resin are enhanced, suppressing the occurrence of defects. Furthermore, because the surface-treated graphene of the present invention exhibits excellent dispersibility and miscibility, the uniform distribution of the surface-treated graphene allows for efficient expression of its functionality.

[0062] Furthermore, the compositions of the present invention can be used containing inorganic particles and, if necessary, any additives. For example, one method involves mixing a surface-treated graphene organic solvent dispersion with a curable resin and / or its precursor, inorganic particles, and, if necessary, a solvent and any additives, or by mixing graphene with a commercially available paint composition containing inorganic particles, a curable resin and / or its precursor. In the former method, the inorganic particles and the surface-treated graphene organic solvent dispersion may be added and mixed simultaneously, or they may be added and mixed separately.

[0063] Examples of the inorganic particles include extender pigments commonly used in paints. When the composition of the present invention is used as a protective coating, the corrosion resistance of the cured product can be further improved by selecting a material with a high sacrificial corrosion protection effect, depending on the object being protected. For example, when used as a protective coating for steel, selecting zinc particles as the inorganic material can further improve the corrosion resistance and durability of the cured product through the sacrificial corrosion protection effect.

[0064] The inorganic particles preferably include zinc, iron oxide, mica, talc, bentonite, silicon dioxide, titanium oxide, aluminum oxide, barium sulfate, stainless steel, glass, or aluminum. Two or more of these may be included.

[0065] Examples of the shapes of the inorganic particles include spherical, flake-shaped, flaky, fibrous, and irregular shapes.

[0066] Among these, mica, talc, bentonite, flaky titanium oxide, stainless steel flakes, glass flakes, and aluminum flakes have a high shielding effect due to their flattened shape, which can further improve the corrosion resistance of the cured product. In addition, zinc particles have a high sacrificial corrosion protection effect, which can further improve the corrosion resistance of the cured product. It is preferable to combine zinc particles with extender pigments such as talc and bentonite, or functional fillers such as glass flakes, which allows for easy adjustment of the viscosity of the composition and the mechanical properties of the coating obtained from the composition to a desired range.

[0067] The composition of the present invention can be suitably used as a coating film formed by applying it to a substrate and drying it. Examples of application methods include applicator application, bar coating, spin coating, roller application, brush application, and spray application. Drying methods can be appropriately selected depending on the solvent, resin, and application, and examples include natural drying, heat drying, and hot air drying. The composition of the present invention may also be used by injecting it into cracks, for example, and curing it by drying and / or crosslinking. Known methods can be used for injection and curing. Examples of the substrate include metal vapor-deposited films, electrode substrates such as aluminum foil and copper foil, metal housings and components of various electronic components, and steel housings and structures (vehicles such as automobiles and ships, structures such as bridges and iron bridges, factory equipment, etc.).

[0068] <Formation> The product formed by the present invention includes the surface-treated graphene of the present invention.

[0069] The formed products of the present invention can be suitably used, for example, as coating films, electrodes, antistatic materials, and thermal conductors. Examples of coating films include corrosion-resistant paints, waterproof paints, gas barrier films, impact-resistant films, and electromagnetic wave shielding films. Examples of electrodes include battery electrodes and sensor electrodes. Examples of thermal conductors include heat dissipation materials for electronic equipment, heat dissipation coatings for pipes, and cooling and antifreezing materials for buildings.

[0070] <Method for producing a surface-treated graphene organic solvent dispersion> The surface-treated graphene of the present invention may use commercially available graphene as a raw material, or it may be obtained by using graphene oxide as a raw material and performing a reduction treatment (chemical exfoliation method). From the viewpoint of further improving dispersibility, it is preferable to use the chemical exfoliation method.

[0071] The method for manufacturing surface-treated graphene will be explained using a chemical exfoliation method as an example. The chemical exfoliation method preferably includes, in this order, a step of obtaining graphene oxide by oxidative exfoliation of graphite (graphite exfoliation step), and a reduction step (reduction step). The surface treatment agent may be applied to the graphene after reduction, or it may be applied to graphene oxide and then subjected to a reduction treatment to obtain surface-treated graphene.

[0072] Aromatic ring-containing amine compounds and aliphatic amine compounds may be added separately or simultaneously, but it is preferable to add them separately to facilitate control of the adhesion ratio of the two and to minimize impairing dispersibility. From the viewpoint of minimizing impairing dispersibility, it is preferable to add the aromatic ring-containing amine compound first, followed by the aliphatic amine compound, in the order of adding the surface treatment agents.

[0073] For example, when graphene oxide is used as the starting material, the following process example is preferred.

[0074] 1) Graphene oxide is mixed with an amine compound having an aromatic ring, then an aliphatic amine compound is mixed in, and the mixture is reduced to obtain surface-treated graphene.

[0075] 2) Graphene oxide is mixed with an amine compound having an aromatic ring, reduced, and then mixed with an aliphatic amine compound to obtain surface-treated graphene.

[0076] 3) After reducing graphene oxide, an amine compound having an aromatic ring is mixed in, and then an aliphatic amine compound is mixed in to obtain surface-treated graphene.

[0077] Furthermore, the process may include a step to wash away any excess surface treatment agent or reducing agent after reduction. If water is used as the solvent when dispersing graphene oxide, a solvent replacement step may be included after reduction. If a step to add a surface treatment agent is included after reduction, it is preferable to add the surface treatment agent after the washing step and solvent replacement step. In addition, a drying step to remove moisture may be included as needed.

[0078] [Graphite removal process] In this process, graphite is oxidized and exfoliated to obtain graphene oxide. Examples of methods for producing graphene oxide include the Hammers process. Alternatively, commercially available graphene oxide may be purchased. The following example illustrates the use of the Hammers process as a method for producing graphene oxide.

[0079] While in an ice bath, graphite (calcium powder) and sodium nitrate are added to concentrated sulfuric acid and stirred. Potassium permanganate is gradually added to prevent the temperature from rising, and the mixture is stirred for 0.2 to 5 hours while maintaining a temperature range of 25 to 50°C. Then, deionized water is added to dilute the mixture into a suspension, and the mixture is stirred for 5 to 50 minutes at a temperature range of 80 to 100°C. After that, hydrogen peroxide and deionized water are added and stirred for 1 to 30 minutes to obtain a graphene oxide aqueous dispersion. The obtained graphene oxide aqueous dispersion is filtered and washed to obtain a graphene oxide wet cake.

[0080] Natural graphite is preferred as the graphite, and the mesh count is preferably 5000 or less. For 10g of natural graphite, the amount of sodium nitrate added is preferably 2-8g, the amount of concentrated sulfuric acid added is preferably 150-300ml, the amount of potassium permanganate added is preferably 10-40g, and the amount of hydrogen peroxide added is preferably 40-80g. The amount of deionized water added is preferably 10-20 times the amount of hydrogen peroxide added. The degree of oxidation of graphene oxide can be adjusted to a desired range by, for example, the amount of oxidizing agent sodium nitrate or potassium permanganate added. Specifically, the more sodium nitrate and potassium permanganate used relative to the graphite in the oxidation reaction, the higher the degree of oxidation, and the less, the lower the degree of oxidation. The ratio of the amount of sodium nitrate added to graphite (sodium nitrate / graphite) is preferably 0.200 to 0.800, and the ratio of the amount of potassium permanganate added to graphite (potassium permanganate / graphite) is preferably 1.0 to 4.0.

[0081] [Surface treatment agent mixing process] As mentioned above, there are several possible timings for adding the surface treatment agent, but in this process, graphene oxide or graphene is mixed with the surface treatment agent to adhere the surface treatment agent to the graphene oxide or graphene. To ensure good mixing of graphene oxide and the surface treatment agent, it is preferable to mix them while both are dispersed in the solvent. Ideally, both graphene oxide and the surface treatment agent should be completely dissolved, but it is acceptable for some to remain dispersed as solids without dissolving. As for the mixing method, a disperser that employs a disperser stirring type or a rotor / stator type is preferred. Examples of such dispersers include the "Labo-lution" (registered trademark) Homodisper 2.5 type, Disperser PH91 (manufactured by SMT Co., Ltd.), and the "Silverson Mixer" (registered trademark) L5M-A (manufactured by Silverson Nippon Co., Ltd.). Among these, a rotor / stator type disperser is preferred because it can obtain a higher dispersion force through the shear force due to the rotor peripheral speed and the shear force due to the stator slits. In the present invention, it is preferable to mix graphene oxide with an amine compound having an aromatic ring in this surface treatment step.

[0082] [Reduction Process] In this process, graphene oxide is reduced. Chemical reduction is preferred as the reduction method. In the case of chemical reduction, organic reducing agents and inorganic reducing agents can be used, but inorganic reducing agents are more preferred due to the ease of washing after reduction.

[0083] Examples of organic reducing agents include aldehyde-based reducing agents, hydrazine derivative reducing agents, and alcohol-based reducing agents. Among these, alcohol-based reducing agents are particularly preferred because they can reduce substances relatively gently. Examples of alcohol-based reducing agents include methanol, ethanol, propanol, isopropyl alcohol, butanol, benzyl alcohol, phenol, ethanolamine, ethylene glycol, propylene glycol, and diethylene glycol.

[0084] Examples of inorganic reducing agents include sodium dithionite, potassium dithionite, phosphorous acid, sodium borohydride, and hydrazine. Among these, sodium dithionite and potassium dithionite are preferred because they can reduce the material while relatively retaining acidic groups, allowing for the production of graphene with high dispersibility in solvents.

[0085] [Filtration and concentration process] Next, the surface-treated graphene obtained in the reduction step is filtered and concentrated. The filtration and concentration step is a step in which a portion of the solvent in the reduced surface-treated graphene dispersion is removed by filtration to obtain a surface-treated graphene dispersion. Known methods can be used for filtration, and vacuum suction filtration is preferred from the viewpoint of suppressing stacking of surface-treated graphene. After the reduction step and before the solvent replacement step, a washing step may be performed in which the surface-treated graphene is diluted with a solvent and filtered for the purpose of removing the reducing agent. This operation may also be repeated multiple times. In the present invention, it is preferable to perform the filtration and concentration step and the redispersion step described later two or more times each.

[0086] [Drying process] After completing the surface treatment and / or reduction steps, the surface-treated graphene of the present invention can be obtained by drying and removing the solvent. Suitable drying methods include vacuum drying, freeze-drying, or spray drying. Freeze-drying or spray drying is preferred from the viewpoint of suppressing irreversible aggregation. This step yields a dried powder of surface-treated graphene.

[0087] [Solvent replacement process] If a drying step is not performed, it is preferable to have a step of replacing the aqueous solvent in the filtered and concentrated cake after the washing step with an organic solvent. Solvent replacement may be performed by repeatedly redispersing the filtered and concentrated cake in an organic solvent, filtering and concentrating it, and then redispersing it again in an organic solvent and filtering and concentrating it again, or by redispersing the filtered and concentrated cake in an organic solvent and distilling off the water. This step yields an organic solvent wet cake of surface-treated graphene. In the present invention, it is preferable to repeat the step of mixing an aliphatic amine compound with the surface-treated graphene in this solvent replacement step, filtering and concentrating it, and then redispersing it again in an organic solvent and filtering and concentrating it again two or more times. This step is preferable because it removes excess aliphatic amine that did not adhere to the surface of the graphene, thereby suppressing adverse effects on the dispersion and composition due to the inclusion of aliphatic amine.

[0088] [Solvent dispersion process] When obtaining a surface-treated graphene organic solvent dispersion by dispersing the dried powder or organic solvent wet cake of the surface-treated graphene of the present invention in an organic solvent, it is preferable to stir the slurry obtained by mixing the organic solvent wet cake with the organic solvent using a disperser, rotor / stator type, or the like. The higher the peripheral speed when stirring the slurry, the easier it is to peel off the stacked surface-treated graphene by shear force, thereby eliminating stacks and further improving dispersibility. Examples of such dispersers include the Labo-Solution® HomoDisperser 2.5, Disperser PH91, and Silverson Mixer L5M-A. Among these, a rotor / stator type disperser is preferred as it can obtain higher dispersion force due to the shear force from the rotor peripheral speed and the shear force from the stator slits. In the present invention, it is preferable to filter and concentrate the redispersed surface-treated graphene organic solvent dispersion again, thereby eliminating stacks between the surface-treated graphene particles and further improving dispersibility.

[0089] <Method for producing the composition> Next, an example of a method for producing a composition using a surface-treated graphene organic solvent dispersion will be described. For example, a method of mixing the surface-treated graphene organic solvent dispersion with a curable resin and / or its precursor, and optionally with a solvent and any additives. From the viewpoint of further improving the dispersibility of surface-treated graphene, it is preferable to mix the surface-treated graphene organic solvent dispersion with a solution in which the curable resin and / or its precursor is dissolved in a solvent.

[0090] Mixing equipment used in the production of compositions includes, for example, bead mills, homodispers, homomixers, planetary mixers, sand mills, and other mixers and kneaders.

[0091] If the composition of the present invention contains a curable resin precursor, the main component (e.g., epoxy resin) and the curing agent (e.g., epoxy resin curing agent) may be stored in separate containers until immediately before use. In this case, the surface-treated graphene organic solvent dispersion may be contained in the main component or in the curing agent. [Examples]

[0092] The present invention will be described below using examples. First, the measurement and evaluation methods in each example and comparative example will be explained.

[0093] [Measurement and Evaluation Methods] (1) Amount of surface treatment agent applied The total amount of aromatic ring-containing amine compounds and aliphatic amine compounds attached to the surface of surface-treated graphene prepared according to each example and comparative example was determined by XPS and solid-state NMR. Measurements were performed on surface-treated graphene prepared according to each example and comparative example, which was washed five times by diluting it with water to 0.5% by mass, suction filtration, and then freeze-dried. XPS measurements were performed using an X-ray photoelectron spectrometer (Quantera SXM, ULVAC-PHIE). Monochromatic AlK was used as the excitation X-ray source. α1,2 A 1486.6 eV X-ray beam was used, with an X-ray diameter of 200 μm and a photoelectron escape angle of 45°.

[0094] The amount of surface treatment agent deposited was determined from the mass percentage value of nitrogen measured by XPS (a), the N / C ratio of nitrogen derived from aliphatic compounds originating from the surface treatment agent measured by solid-state NMR spectrometer (JNM-ECZ400R, JEOL Ltd.) (X), the molecular weight of the aromatic ring-containing amine compound (b1), the molecular weight of the aliphatic amine compound (b2), the formula weight of nitrogen in the aromatic ring-containing amine compound (c1), and the formula weight of nitrogen in the aliphatic amine compound (c2). Amount of amine compound containing an aromatic ring attached (Z1) = a × (1 - X) × b1 ÷ c1 Amount of aliphatic amine compound attached (Z2) = a × X × b2 ÷ c2 The total amount of surface treatment agent attached to the graphene relative to its mass (mass %) = (Z1 + Z2) ÷ (100 - Z1 - Z2) × 100.

[0095] (2) O / C ratio of surface-treated graphene The photoelectron spectra of surface-treated graphene prepared according to each example and comparative example were measured using an X-ray photoelectron spectroscopy analyzer (Quantera SXM). Monochromatic AlK was used as the excitation X-ray source. α1,2 A 1486.6 eV X-ray beam was used, with an X-ray diameter of 200 μm and a photoemission angle of 45°. The peak at 284.3 eV was assigned to the C1s main peak based on carbon atoms, and the peak around 533 eV was assigned to the O1s peak based on oxygen atoms. The O / C ratio was calculated from the area ratio of the O1s peak to the C1s peak, and the resulting value was rounded to two decimal places to obtain the O / C ratio.

[0096] (3) N / C ratio of surface-treated graphene The surface-treated graphene prepared according to each example and comparative example was subjected to photoelectron spectroscopy using an X-ray photoelectron spectrometer (Quantera SXM). Monochromatic AlK was used as the excitation X-ray source. α1,2 A 1486.6 eV X-ray beam was used, with an X-ray diameter of 200 μm and a photoelectron escape angle of 45°. The peak at 284.3 eV was assigned to the C1s main peak based on carbon atoms, and the peak around 402 eV was assigned to the N1s peak based on nitrogen atoms. The N / C ratio was calculated from the area ratio of the N1s peak to the C1s peak, and the resulting value was rounded to the third decimal place to obtain the N / C ratio.

[0097] (4) Average thickness of surface-treated graphene The surface-treated graphene prepared in each example and comparative example was diluted with N-methylpyrrolidone to 0.001% by mass, and a dilution was prepared by stirring at 3000 rpm for 30 minutes using a high-speed disperser (Labo-Solution® HomoDisper 2.5, manufactured by Primix). The prepared dilution was dropped onto a PET film, dried, and embedded in resin. A cross-section was prepared from the embedding by ion milling to create observation samples. The observation samples were observed using a transmission electron microscope (JEM-F200, manufactured by JEOL Ltd.) at an accelerating voltage of 200 kV, and 10 surface-treated graphene samples were randomly selected from the observation samples. The entire cross-section of one surface-treated graphene was magnified to the maximum magnification that allowed it to fit in the field of view, and the thickness was measured at 5 randomly selected locations per surface-treated graphene. The arithmetic mean of 50 locations (5 locations × 10 samples) was calculated and rounded to the first decimal place in nm.

[0098] (5) Solid content concentration (mass%) Approximately 1 g of each surface-treated graphene organic solvent dispersion prepared according to the examples and comparative examples was placed in an aluminum cup of known mass and its mass was measured. The mixture was then heated on a hot plate set to the volatilization temperature of the organic solvent for 1.5 hours to evaporate the solvent. The solid content concentration of the surface-treated graphene organic solvent dispersion was calculated from the mass of the dispersion before heating and the amount of solvent evaporated, calculated from the mass difference before and after heating. This process was repeated three times, and the average value was calculated.

[0099] The solid content concentration of the graphene oxide wet cake described later was measured in the same manner as the method for measuring the solid content concentration of the surface-treated graphene organic solvent dispersion described above, except that the temperature was adjusted to 100°C.

[0100] The solid content concentration of the surface-treated graphene dispersion obtained by the filtration and concentration process described later was measured in the same manner as the method for measuring the solid content concentration of the surface-treated graphene organic solvent dispersion described above, except that the temperature was adjusted to 120°C.

[0101] (6) Absorbance The absorbance of the surface-treated graphene organic solvent dispersions prepared according to each example and comparative example was measured using a spectrophotometer (UV7, Mettler Toledo). A quartz cell with a path length of 10 mm was used. To each example and comparative example, the organic solvent used in each example and comparative example was added to the surface-treated graphene organic solvent dispersion prepared according to each example and comparative example so that the graphene concentration was 0.0065% by mass. The mixture was then shaken for 10 minutes at the "High" setting using an ultrasonic cleaner (ASU-6M, AS ONE Corporation) with an output of 130 W and an oscillation frequency of 40 kHz. Using the baseline measured from the organic solvent used for concentration adjustment, the absorbance of the diluted solution obtained by the shaking treatment was measured as a sample.

[0102] (7) Number of defects The compositions containing the surface-treated graphene organic solvent dispersion and the curable resin and / or its precursor prepared in each example and comparative example were applied to a 50 μm thick A4-sized PET film using a 500 μm applicator to form a coating film, which was left to stand overnight at room temperature. Subsequently, the coating film was dried in a hot air oven at 100°C for 2 hours to cure it and form a cured film. The surface of the obtained cured film was observed under an optical microscope at 100x magnification, and the presence or absence of defects such as cracks and pinholes was observed at 10 randomly selected locations, and the number of locations where defects were found was recorded. The fewer the locations where defects were found, the better the conductivity, thermal conductivity, and impermeability of materials.

[0103] [Example 1] (Preparation of graphene oxide dispersion) Using 1500-mesh natural graphite powder (manufactured by Shanghai Yifan Graphite Co., Ltd.) as the raw material, 10 g of natural graphite powder was placed in an ice bath, to which 220 ml of 98% concentrated sulfuric acid, 4.7 g of sodium nitrate, and 27.0 g of potassium permanganate were added and stirred for 1 hour, maintaining the temperature of the mixture below 20°C. This mixture was removed from the ice bath and stirred in a 35°C water bath for 4 hours, after which 500 ml of deionized water was added, and the resulting suspension was stirred further at 90°C for 15 minutes. Finally, 600 ml of deionized water and 50 ml of hydrogen peroxide were added and stirred for 5 minutes to obtain a graphene oxide dispersion. After filtering the obtained graphene oxide dispersion, metal ions were washed with dilute hydrochloric acid solution, and the acid was washed with deionized water. These washings were repeated until the pH reached 7, and the mixture was concentrated by suction filtration to prepare a graphene oxide wet cake. The solid content concentration of the prepared graphene oxide wet cake was 45% by mass. 11.1 g of the obtained graphene oxide wet cake (5.0 g of graphene oxide solids) was mixed with 988.9 g of deionized water, and stirred for 30 minutes at a rotation speed of 10,000 rpm using a rotor / stator type Silverson mixer (L5M-A) to obtain 1,000 g of graphene oxide dispersion with a graphene oxide concentration of 0.5% by mass.

[0104] The elemental ratio of oxygen atoms to carbon atoms (O / C ratio) of the synthesized graphene oxide, as measured by X-ray photoelectron spectroscopy, was 0.11.

[0105] (Surface treatment agent mixing process) To 1000 g of the above graphene oxide dispersion, an aqueous sodium hydroxide solution was added to adjust the pH to 8.5. 1.5 g of dopamine hydrochloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as an aromatic ring-containing amine compound, and the mixture was stirred for 30 minutes at a rotation speed of 10,000 rpm using a rotor / stator type Silverson mixer (L5M-A).

[0106] (Reduction process) 25.0 g of sodium dithionite (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to the graphene oxide dispersion after the surface treatment agent mixing step, and the mixture was kept warm at 40°C. A reduction reaction was carried out by stirring at 10,000 rpm for 30 minutes using a rotor / stator type Silverson mixer (L5M-A) to obtain a surface-treated graphene dispersion.

[0107] (filtration concentration process) The obtained surface-treated graphene dispersion was filtered using a vacuum suction filter to obtain a surface-treated graphene dispersion. 100 g of the obtained surface-treated graphene dispersion was mixed with 1000 g of deionized water, and the mixture was redispersed by stirring at 10,000 rpm for 10 minutes using a rotor / stator type Silverson mixer (L5M-A).

[0108] The obtained surface-treated graphene redispersion was subjected to a second filtration and concentration step to obtain a surface-treated graphene dispersion using water as the dispersion medium. The solid content concentration of the surface-treated graphene dispersion was 3.0% by mass.

[0109] (Redispersion process) 50 g of the obtained surface-treated graphene dispersion was mixed with 300 g of methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 0.075 g of propylamine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as an aliphatic amine compound. The mixture was stirred for 10 minutes at a rotation speed of 10,000 rpm using a rotor / stator type Silverson mixer (L5M-A) to perform the first redispersion, and a surface-treated graphene redispersion solution with methanol as the main dispersion medium was obtained.

[0110] The obtained surface-treated graphene redispersion was filtered and concentrated. 48 g of the resulting graphene dispersion was mixed with 288 g of a 1:1 mass mixture of xylene and isopropanol. The mixture was then stirred for 10 minutes at 10,000 rpm using a rotor / stator type Silverson mixer (L5M-A) to perform a second redispersion using the xylene-isopropanol mixture as the main dispersion medium.

[0111] The second redispersion obtained was filtered and concentrated to obtain a surface-treated graphene dispersion with a solid content of 3.0% by mass. Xylene was added to the obtained graphene dispersion as an organic solvent to obtain a solid content of 1% by mass. The mixture was stirred for 5 minutes at 5000 rpm using a high-speed disperser (Labo-Solution® HomoDisper 2.5 type) to obtain a surface-treated graphene organic solvent dispersion with xylene as the dispersion medium.

[0112] The obtained surface-treated graphene organic solvent dispersion was vacuum-dried overnight to produce a powder, and the physical properties of the surface-treated graphene measured by measurement and evaluation methods (1) to (4), as well as the absorbance of the surface-treated graphene organic solvent dispersion adjusted to 0.0065% by mass with xylene as the organic solvent, are shown in Tables 1 to 3.

[0113] The obtained 1% by mass dispersion of surface-treated graphene organic solvent was filtered and concentrated to obtain a surface-treated graphene dispersion with a solid content of 3.0% by mass.

[0114] (Creation of a portrait) 8.2 g of bisphenol A type epoxy resin ("Epiclon"® 1050, manufactured by DIC Corporation) with an epoxy equivalent weight of 450-500 g / eq was weighed, 8.2 g of xylene was added, and the mixture was heated to 90°C to dissolve it. The mixture was then stirred for 20 minutes at 3000 rpm using a high-speed disperser (Labo-Solution® HomoDisper 2.5). 5.5 g of the above surface-treated graphene organic solvent dispersion (concentration 3% by mass) was added, and the mixture was stirred for 30 minutes at 3000 rpm using a high-speed disperser (Labo-Solution® HomoDisper 2.5). As an epoxy resin curing agent, 11.7 g of polyamidoamine (Newmid 515 (trade name), manufactured by Harima Chemicals Group Co., Ltd.) with an active hydrogen equivalent of 185 (solid content 70% by mass, solid mass 8.2 g) was added, and the mixture was homogenized by stirring at 3000 rpm for 10 minutes using a high-speed disperser (Labo-Solution® Homodisper 2.5 type) to prepare a composition in which the mass ratio of surface-treated graphene to total solid content was 1% by mass.

[0115] Table 3 shows the evaluation results of the number of defects in the cured film obtained from the compositions.

[0116] [Example 2] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 5.8 g, and the amount of potassium permanganate added was changed to 37.0 g. In addition, 1.5 g of 1,4-phenylenediamine was used as an aromatic ring-containing amine compound in the surface treatment agent mixing step. Surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0117] [Example 3] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 5.0 g, and the amount of potassium permanganate added was changed to 30.0 g. In addition, 0.075 g of oleylamine was used as the aliphatic amine compound in the redispersion step. Except for these changes, surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0118] [Example 4] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 7.5 g, and the amount of potassium permanganate added was changed to 37.4 g. In addition, 0.75 g of 2-phenylethylamine hydrochloride was used as an aromatic ring-containing amine compound in the surface treatment agent mixing step, and 0.15 g of oleylamine was used as an aliphatic amine compound in the redispersion step. Surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0119] [Example 5] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 7.7 g, and the amount of potassium permanganate added was changed to 38.0 g. In addition, 1.5 g of 1,4-phenylenediamine was used as an aromatic ring-containing amine compound in the surface treatment agent mixing step, and 0.3 g of octylamine was used as an aliphatic amine compound in the redispersion step. Surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0120] [Example 6] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 6.3 g, and the amount of potassium permanganate added was changed to 34.0 g. In addition, the amount of aromatic ring-containing amine compound mixed in the surface treatment agent mixing step was changed to 2.5 g, and 0.15 g of oleylamine was used as the aliphatic amine compound in the redispersion step. Except for these changes, surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0121] [Example 7] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 4.3 g, and the amount of potassium permanganate added was changed to 24.0 g. In addition, 3.5 g of 1,4-phenylenediamine was used as an aromatic ring-containing amine compound in the surface treatment agent mixing step, and 1.05 g of oleylamine was used as an aliphatic amine compound in the redispersion step. Surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0122] [Example 8] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 4.3 g, and the amount of potassium permanganate added was changed to 24.0 g. In addition, 0.5 g of 1,4-phenylenediamine was used as the aromatic ring-containing amine compound in the surface treatment agent mixing step, and the amount of aliphatic amine compound added in the redispersion step was changed to 1.5 g. Surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0123] [Example 9] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 4.3 g, and the amount of potassium permanganate added was changed to 24.0 g. In addition, 2.5 g of 1,4-phenylenediamine was used as an aromatic ring-containing amine compound in the surface treatment agent mixing step, and 0.015 g of dodecylamine was used as an aliphatic amine compound in the redispersion step. Surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0124] [Example 10] Surface-treated graphene, a dispersion of surface-treated graphene using an organic solvent, and a composition were prepared in the same manner as in Example 1, except that xylene was replaced with toluene as the organic solvent used as the dispersion medium in the redispersion process. The evaluation results are shown in Tables 1 to 3.

[0125] [Example 11] Surface-treated graphene, a dispersion of surface-treated graphene using an organic solvent, and a composition were prepared in the same manner as in Example 1, except that xylene was replaced with ethylbenzene as the organic solvent used as the dispersion medium in the redispersion process. The evaluation results are shown in Tables 1 to 3.

[0126] [Example 12] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 5.8 g, and the amount of potassium permanganate added was changed to 37.0 g. In addition, 0.11 g of 1,4-phenylenediamine was used as the aromatic ring-containing amine compound in the surface treatment agent mixing step, and the amount of aliphatic amine compound added in the redispersion step was changed to 0.024 g. Surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0127] [Example 13] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 5.8 g, and the amount of potassium permanganate added was changed to 37.0 g. In addition, 0.17 g of 1,4-phenylenediamine was used as the aromatic ring-containing amine compound in the surface treatment agent mixing step, and the amount of aliphatic amine compound added in the redispersion step was changed to 0.036 g. Surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0128] [Example 14] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 5.8 g, and the amount of potassium permanganate added was changed to 37.0 g. In addition, 0.10 g of 1,4-phenylenediamine was used as the aromatic ring-containing amine compound in the surface treatment agent mixing step, and the amount of aliphatic amine compound added in the redispersion step was changed to 0.14 g. Surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0129] [Example 15] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 7.7 g, and the amount of potassium permanganate added was changed to 38.0 g. In addition, 2.33 g of 1,4-phenylenediamine was used as the aromatic ring-containing amine compound in the surface treatment agent mixing step, and the amount of aliphatic amine compound added in the redispersion step was changed to 0.15 g. Surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0130] [Example 16] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 7.7 g, and the amount of potassium permanganate added was changed to 38.0 g. In addition, 0.51 g of 1,4-phenylenediamine was used as the aromatic ring-containing amine compound in the surface treatment agent mixing step, and the amount of aliphatic amine compound added in the redispersion step was changed to 0.86 g. Surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0131] [Example 17] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 5.8 g, and the amount of potassium permanganate added was changed to 37.0 g. In addition, 1,4-phenylenediamine was used as the aromatic ring-containing amine compound in the surface treatment agent mixing step at 1.21 g, and the amount of aliphatic amine compound added in the redispersion step was changed to 0.25 g. Surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0132] [Example 18] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 5.8 g, and the amount of potassium permanganate added was changed to 37.0 g. In addition, 0.15 g of 1,4-phenylenediamine was used as the aromatic ring-containing amine compound in the surface treatment agent mixing step, and the amount of aliphatic amine compound added in the redispersion step was changed to 1.70 g. Surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0133] [Example 19] Surface-treated graphene, a dispersion of surface-treated graphene using an organic solvent, and a composition were prepared in the same manner as in Example 1, except that xylene was replaced with a weak solvent, mineral spirit, as the organic solvent used as the dispersion medium in the redispersion process. The evaluation results are shown in Tables 1 to 3.

[0134] [Comparative Example 1] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 5.0 g, and the amount of potassium permanganate added was changed to 30.0 g. In addition, the amine compound having an aromatic ring was not mixed in the surface treatment agent mixing step, and the amount of aliphatic amine compound added in the redispersion step was changed to 0.75 g. Surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0135] [Comparative Example 2] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 4.3 g, and the amount of potassium permanganate added was changed to 24.0 g. In addition, the amount of aromatic ring-containing amine compound mixed in the surface treatment agent mixing step was changed to 0.5 g, and the aliphatic amine compound was not added in the redispersion step. Surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0136] [Comparative Example 3] In the preparation of the graphene oxide dispersion, the amount of sodium nitrate added was changed to 4.3 g, and the amount of potassium permanganate added was changed to 24.0 g. In addition, an amine compound having an aromatic ring was not mixed in the surface treatment agent mixing step, and an aliphatic amine compound was not added in the redispersion step. Surface-treated graphene, surface-treated graphene organic solvent dispersion, and composition were prepared in the same manner as in Example 1. The evaluation results are shown in Tables 1 to 3.

[0137] [Table 1]

[0138] [Table 2]

[0139] [Table 3]

Claims

1. Surface-treated graphene having aromatic ring-containing amine compounds and aliphatic amine compounds on its surface.

2. The surface-treated graphene according to claim 1, wherein the aliphatic hydrocarbon group of the aliphatic amine compound has 3 to 20 carbon atoms.

3. The surface-treated graphene according to claim 1, wherein the total amount of the aromatic ring-containing amine compound and the aliphatic amine compound attached to the surface of the surface-treated graphene is 5 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the graphene.

4. The surface-treated graphene according to claim 1, wherein the elemental ratio of oxygen to carbon (O / C ratio) of the surface-treated graphene, as measured by X-ray photoelectron spectroscopy, is 0.05 or more and 0.40 or less, and the elemental ratio of nitrogen to carbon (N / C ratio) of the surface-treated graphene is 0.010 or more and 0.200 or less.

5. The surface-treated graphene according to claim 1, wherein the average thickness of the surface-treated graphene is 0.3 nm or more and less than 15 nm.

6. A dispersion of surface-treated graphene in an organic solvent, wherein the surface-treated graphene described in any one of claims 1 to 5 is dispersed in an organic solvent.

7. A composition comprising a surface-treated graphene organic solvent dispersion according to claim 6 and a curable resin and / or its precursor.

8. A formed product comprising surface-treated graphene according to any one of claims 1 to 5.

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