Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/15—Nano-sized carbon materials
  • C01B32/182—Graphene
  • C01B32/184—Preparation
  • C01B32/19—Preparation by exfoliation

Definitions

• the present invention relates to a graphene composition, a method for producing the same, and a conductive film.
• Graphene exhibits unique properties that are not found in existing materials in terms of electronic properties, optical properties, thermal properties, chemical properties, and mechanical properties. Therefore, in recent years, it has attracted a great deal of attention, and research and development has been promoted in various fields.
• Patent Document 1 describes a graphene dispersion containing multilayer graphene, a polymer having a nonionic group, and a ketone organic solvent.
• Patent Document 2 describes that graphene is rolled into a cylindrical shape and used as a carbon nanotube.
• An object of the present invention is to provide a graphene composition excellent in dispersibility, a graphene composition excellent in dispersibility, a method for producing the same, and a conductive film.
• the present inventors can obtain a composition of graphene in one or more layers and in a flat form as it is, without using a dispersing agent, a polymer, or the like, a highly conductive conductive film can be obtained. I thought it would be obtained. However, it has been found that graphene is very likely to aggregate when no dispersant or polymer is used. Therefore, as a result of intensive research conducted by the present inventors, agglomeration of graphene can be achieved by forming flat graphene in one layer or two layers using bubbles having an average diameter of 500 nm or less. The present invention has been completed.
• the following graphene compositions and the like are provided.
• a graphene composition comprising bubbles having an average diameter of 500 nm or less, and
• 3. 3 The graphene composition according to 1 or 2, wherein the component (a) has an average major axis of 2 to 100 ⁇ m. 4).
• the number ratio of single layer graphene or two or more layers of graphene having a thickness of 0.3 to 30 nm is 70% or more.
• a conductive film having excellent conductivity can be obtained, and a graphene composition having excellent dispersibility, a method for producing the same, and a conductive film can be provided.
• the graphene composition of the present invention comprises (a) a single-layer graphene or two or more layers of graphene (hereinafter also referred to as “component (a)”) having an average thickness of 0.3 to 30 nm, (b) Bubbles having an average diameter of 500 nm or less (hereinafter also referred to as “component (b)”) and (c) a solvent (hereinafter referred to as “component (c)”) that is water, an organic solvent, or a mixed solvent of water and an organic solvent.
• component (a) a single-layer graphene or two or more layers of graphene
• component (b) Bubbles having an average diameter of 500 nm or less
• component (c) a solvent
• component (c) that is water, an organic solvent, or a mixed solvent of water and an organic solvent.
• the graphene composition of the present invention is preferably a dispersion.
• the dispersion is, for example, a dispersion in which component (a) does not settle.
• Graphene is generally a layer of a carbon hexagonal network structure formed by sp2 bonds between carbon atoms, and may be a single-layer graphene or a graphene (multilayer graphene) in which two or more layers are stacked.
• the shape of the component (a) is preferably a flat plate from the viewpoint of conductivity and thermal conductivity.
• the flat sheet may have a deformed shape, for example, a corrugated plate shape, a saddle shape, a spiral shape, a saddle shape, or a folded shape.
• the average number of layers of the component (a) is preferably 1 to 100 layers, more preferably 1 to 80 layers, further preferably 1 to 30 layers, particularly preferably 1 to 10 layers, from the viewpoint of dispersibility. Is most preferred.
• the average thickness of the component (a) is 0.3 to 30 nm. From the viewpoint of dispersibility, 0.3 to 24 nm is preferable, 0.3 to 9 nm is more preferable, and 0.3 to 3 nm is more preferable. Particularly preferred is 0.3 to 1.5 nm.
• the number ratio of single layer graphene or two or more layers of graphene having a thickness of 0.3 to 30 nm with respect to the total graphene composition excluding component (b) and component (c) depends on dispersibility and From the viewpoint of uniformity, 70% or more is preferable, 80% or more is more preferable, and 90% or more is particularly preferable. By being within the above range, performance such as transparency, conductivity, thermal conductivity, and capacitor characteristics can be exhibited.
• the average thickness of the component (a) can be determined by, for example, a field emission scanning electron microscope (FE-SEM).
• the average major axis of the component (a) is preferably from 0.1 to 500 ⁇ m, more preferably from 1 to 100 ⁇ m, further preferably from 2 to 100 ⁇ m, particularly preferably from 2 to 50 ⁇ m, most preferably from 2 to 40 ⁇ m. By being within the above range, aggregation can be suppressed and dispersibility can be maintained.
• the average major axis of the component (a) can be measured using a polarizing microscope, for example.
• the major axis of component (a) refers to the dimension of component (a) that is the longest.
• the carbon purity of the component (a) is preferably 95% by mass or more, more preferably 96 to 100% by mass, and further preferably 97 to 100% by mass. By being 95 mass% or more, the electroconductivity of the electrically conductive film obtained can be improved.
• the content of the component (a) is preferably 0.01 to 60% by mass and more preferably 0.05 to 50% by mass in the total graphene composition.
• the content of the component (a) is preferably 95% by mass or more, more preferably 96% by mass or more, still more preferably 97% by mass or more, excluding the component (b) and the component (c).
• 98 mass% or more is especially preferable, and 99 mass% or more is the most preferable.
• the average diameter of the component (b) is 500 nm or less, and is preferably 10 to 400 nm, more preferably 10 to 300 nm, from the viewpoint of generation and dispersion of thin graphene.
• the number density of the component (b) is preferably 1700 pieces / ml or more, more preferably 2000 to 4 billion pieces / ml. By being 1700 pieces / ml or more, a thin layer of graphene can be generated.
• the average diameter and number density of the component (b) are determined using, for example, NS500 (manufactured by NanoSight) by the nanoparticle tracking analysis method, and SALD7100HH (manufactured by Shimadzu Corporation) by the laser diffraction / scattering method. Can be measured.
• component gas species examples include air, nitrogen gas, oxygen gas, carbon dioxide gas, and hydrogen gas.
• a single gas may be used, or a mixed gas may be used.
• component (c) a gas type that tends to be supersaturated is preferable. This is because a large amount of fine bubbles can be generated.
• the component (c) is water, an organic solvent, or a mixed solvent of water and an organic solvent, and a mixed solvent of water and an organic solvent is preferable from the viewpoint of ease of production.
• the surface tension of the component (c) at room temperature (20 to 25 ° C.) is preferably 20 to 74 mN / m, more preferably 30 to 50 mN / m.
• the mixed solvent is preferably a water: organic solvent in a mass ratio of 7: 1 to 1: 7, and is preferably 6: 2 to 2: 6, so that it is easy to produce and disperse thin graphene.
• Organic solvents include isopropyl alcohol, 2-methoxyethanol, N-methyl-2-pyrrolidone, methyl ethyl ketone, acetone, methyl isobutyl ketone, 1-methoxy-2-propyl acetate or N, N-dimethylformamide, 1,3-propane
• Examples include diol, toluene, tetralin, tetradecane, and ethylene glycol monoethyl ether. Isopropyl alcohol and N-methyl-2-pyrrolidone are preferred.
• Organic solvents may be used alone or in combination of two or more.
• Component (c) is preferably an organic solvent from the viewpoint of film formation on a hydrophobic surface.
• the component (c) is preferably water from the viewpoint of film formation on a hydrophilic surface.
• the water may be replaced with an organic solvent.
• the organic solvent may be replaced with water after preparing using a mixed solvent of water and an organic solvent containing the component (b).
• the content of the component (c) is preferably 40 to 99.99% by mass and more preferably 50 to 99.95% by mass in the total graphene composition. By being in the said range, the electroconductivity of the electrically conductive film obtained can be improved.
• the graphene composition of the present invention consists essentially of the component (a), the component (b) and the component (c), and may contain other inevitable impurities as long as the effects of the present invention are not impaired.
• the graphene composition of the present invention has, for example, 80 to 100% by mass, 90 to 100% by mass, 95 to 100% by mass, 98 to 100% by mass, or 100% by mass of component (a), component (b) and c) It may consist of components.
• graphite, bubbles having an average diameter of 500 nm or less, and water, an organic solvent, or a solvent that is a mixed solvent of water and an organic solvent are mixed to obtain a mixed solution.
• the above-mentioned graphene composition can be obtained by subjecting the mixed solution to ultrasonic treatment, mechanical shearing treatment, or ultrasonic treatment and mechanical shearing treatment.
• graphite, bubbles having an average diameter of 500 nm or less, and a solvent that is a mixed solvent of water and an organic solvent are mixed to obtain a mixed solution, and mixed.
• the liquid is subjected to ultrasonic treatment, mechanical shearing treatment, or ultrasonic treatment and mechanical shearing treatment, and the mixed liquid after the treatment is further replaced with an organic solvent.
• a certain above-mentioned graphene composition can be obtained.
• graphite, bubbles having an average diameter of 500 nm or less, and an organic solvent or a solvent that is a mixed solvent of water and an organic solvent are mixed to obtain a mixed solution. Then, the mixed solution is subjected to ultrasonic treatment, mechanical shearing treatment, or ultrasonic treatment and mechanical shearing treatment, and the solvent is replaced with water in the mixed solution after treatment.
• a certain above-mentioned graphene composition can be obtained.
• Bubbles having an average diameter of 500 nm or less are the same as the component (b) described above.
• the solvent is the same as the component (c) described above.
• Water, organic solvent, and mixed solvent are as described above.
• a known graphite can be used.
• Examples of graphite include natural graphite, scaly graphite, scaly graphite, artificial graphite, pyrolytic graphite, expanded graphite, and expanded graphite. These may be used alone or in combination of two or more.
• the blending amount of graphite is preferably the same as the content of the component (a).
• the mixing method is not particularly limited, and examples thereof include a mixing method using a mixer such as a mechanical stirrer, a magnetic stirrer, an ultrasonic disperser, a planetary mill, a ball mill, a reactor, and a three roll. Thereby, a liquid mixture can be obtained.
• a mixer such as a mechanical stirrer, a magnetic stirrer, an ultrasonic disperser, a planetary mill, a ball mill, a reactor, and a three roll.
• bubbles having an average diameter of 500 nm or less and part or all of the solvent may be premixed and used for the above-mentioned mixing.
• bubbles having an average diameter of 500 nm or less may be preliminarily produced using a part or all of the solvent and used for the above-mentioned mixing.
• water is preferable as a part of the solvent.
• Examples of the method for producing bubbles having an average diameter of 500 nm or less include a pore blowing stirring method, a pressure dissolution method, a shear method, and a rotating liquid flow method.
• a pressure dissolution method that can generate a large amount of fine bubbles is preferable.
• the pressure dissolution method can be carried out under known conditions using an ultra fine bubble generator FZ1N-02 (manufactured by IDEC Corporation) or the like.
• the ultrasonic treatment is preferably performed by an apparatus that applies ultrasonic vibration to the mixed solution.
• the sonication time is preferably 30 seconds to 20 minutes, more preferably 1 to 15 minutes.
• the frequency of the ultrasonic treatment is preferably 20 to 80 kHz, more preferably 30 to 50 kHz.
• the mechanical shearing treatment is preferably performed with a shear mixer, a stone mill type grinder, a grinder, a thin film swirl type high speed mixer or the like. Among these, it is more preferable to carry out with a thin film swirl type high speed mixer.
• the shear gap of the mechanical shearing treatment is preferably 2 ⁇ m to 5 mm, and more preferably 2 ⁇ m to 2 mm. If it is within the above range, it can be done in a shorter time.
• the mixer turbine speed of the mechanical shearing treatment is preferably 1 to 100 m / s, and more preferably 1 to 40 m / s.
• the mechanical shearing time is, for example, 5 to 180 seconds.
• the substitution with water or the substitution with an organic solvent can use a known method, for example, distillation, pervaporation, decantation, liquid-liquid extraction.
• a two-phase separation column can be used.
• the conductive film of the present invention can be manufactured using the graphene composition described above.
• the above-mentioned graphene composition can be applied onto a substrate such as a PET (polyethylene terephthalate) film by a known method and dried to obtain the conductive film of the present invention.
• a known method can be used as the drying method.
• the drying temperature is, for example, 60 to 100 ° C.
• the drying time is, for example, 1 to 30 minutes.
• the film thickness of the conductive film of the present invention is, for example, 0.5 to 200 ⁇ m.
• the conductive film of the present invention can be used for display elements such as liquid crystal displays, plasma displays, mobile phones, touch panels, electrodes for lithium ion batteries, lithium ion capacitors, fuel cells, solar cells, electromagnetic wave absorbing sheets, antistatic sheets for resins, etc. Can be used.
• the conductive film of the present invention may be used for a heat radiating sheet, heat radiating grease, or the like that efficiently radiates heat generated inside the device.
• NS500 manufactured by NanoSight
• bubbles with a diameter of 100 nm are present at a number density of 100 million / mL or more. It was confirmed that Further, the total number of bubbles and the bubble size of bubbles with a diameter of 100 nm did not change greatly for 3 days after production, and the bubbles with a diameter of 100 nm were stably present in water.
• Example 1 Manufacture of graphene composition
• Scale-like graphite X-100 average thickness of about 2 ⁇ m, manufactured by Ito Graphite Industries Co., Ltd.
• NMP N-methyl-2-pyrrolidone
• the mixture was stirred for 1 minute with a stirrer to obtain a mixed solution.
• the obtained liquid mixture is processed every 10 ml for about 30 seconds at a mixer turbine speed of 10 m / s using a thin film swirl type high speed mixer, Filmix 30-L type (manufactured by Primics Co., Ltd., shear gap 2 mm), and a graphene composition Got.
• the entire graphene composition was uniformly blackened in a state where the graphene particles were dispersed without being settled (dispersion).
• the graphene composition described above was applied onto a PET film substrate and dried at 100 ° C. for 10 minutes to obtain a conductive film having a thickness of 32 ⁇ m.
• the film thickness of the conductive film was obtained by measuring five points using LEXT OLS3500 (manufactured by Olympus Corporation) and calculating the arithmetic average.
• Example 2 A graphene composition and a conductive film were produced and evaluated in the same manner as in Example 1 except that the mixer turbine speed was 30 m / s. The results are shown in Table 1. Further, when the obtained graphene composition was visually observed, the entire graphene composition was uniformly blackened in a state where the graphene particles were dispersed without being settled (dispersion).
• Example 3 A graphene composition and a conductive film were produced and evaluated in the same manner as in Example 1 except that the UFB water was changed to 60 g and NMP 60 g was changed to 20 g of isopropyl alcohol (IPA). The results are shown in Table 1. Further, when the obtained graphene composition was visually observed, the entire graphene composition was uniformly blackened in a state where the graphene particles were dispersed without being settled (dispersion).
• IPA isopropyl alcohol
• Example 4 A graphene composition and a conductive film were produced and evaluated in the same manner as in Example 2 except that the UFB water was changed to 60 g and NMP 60 g was changed to IPA 20 g. The results are shown in Table 1. Further, when the obtained graphene composition was visually observed, the entire graphene composition was uniformly blackened in a state where the graphene particles were dispersed without being settled (dispersion).
• Example 5 0.8 g of X-100, 30 g of UFB water obtained in Production Example 1 and 50 g of NMP were mixed (stirring with a magnetic stirrer for 1 minute) to obtain a mixed solution.
• the obtained mixed solution was subjected to ultrasonic treatment for 5 minutes using ASU-6D (manufactured by ASONE Co., Ltd.) under the condition of a frequency of 43 kHz.
• the mixed solution after the ultrasonic treatment was improved in the shear gap of the Fillmix 30-L type to 3 ⁇ m and treated at a mixer turbine speed of 1 m / s for 60 seconds to obtain a graphene composition.
• the obtained graphene composition was evaluated in the same manner as in Example 1.
• the electrically conductive film was manufactured and evaluated like Example 1 using the obtained graphene composition.
• the results are shown in Table 1. Further, when the obtained graphene composition was visually observed, the entire graphene composition was uniformly blackened in a state where the graphene particles were dispersed without being settled (dispersion).
• Comparative Example 1 A graphene composition and a conductive film were produced and evaluated in the same manner as in Example 1 except that pure water was used instead of UFB water. The results are shown in Table 1. Moreover, when the obtained graphene composition was observed visually, many graphite particles were settled. Since the conductive film could not be formed, the film thickness and conductivity of the conductive film could not be measured.
• Comparative Example 2 A graphene composition and a conductive film were produced and evaluated in the same manner as in Example 2 except that pure water was used instead of UFB water. The results are shown in Table 1. Moreover, when the obtained graphene composition was observed visually, many graphite particles were settled. Since the conductive film could not be formed, the film thickness and conductivity of the conductive film could not be measured.
• Comparative Example 3 A graphene composition and a conductive film were produced and evaluated in the same manner as in Example 1 except that the treatment with the Fillmix 30-L type was not performed. The results are shown in Table 1. Further, when the obtained graphene composition was visually observed, half of the graphite particles settled and the other half floated on the liquid surface.
• Example 6 In the same manner as in Example 3, mixing and treatment with Fillmix 30-L type were performed. In the mixed solution after the treatment with the Fillmix 30-L type, the solvent was replaced with water to obtain a graphene composition. When the obtained graphene composition was visually observed, the entire graphene composition was uniformly blackened with the graphene particles dispersed.
• the obtained graphene composition was evaluated in the same manner as in Example 1. Moreover, the electrically conductive film was manufactured and evaluated like Example 1 using the obtained graphene composition. The results are shown in Table 2.

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