WO2019189284A1 - Composite material and method for producing same - Google Patents

Composite material and method for producing same Download PDF

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Publication number
WO2019189284A1
WO2019189284A1 PCT/JP2019/013052 JP2019013052W WO2019189284A1 WO 2019189284 A1 WO2019189284 A1 WO 2019189284A1 JP 2019013052 W JP2019013052 W JP 2019013052W WO 2019189284 A1 WO2019189284 A1 WO 2019189284A1
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Prior art keywords
graphite
composite material
resin
polymer
exfoliated graphite
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PCT/JP2019/013052
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French (fr)
Japanese (ja)
Inventor
尚代 河▲崎▼
和田　拓也
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積水化学工業株式会社
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Priority to JP2019519336A priority Critical patent/JPWO2019189284A1/en
Publication of WO2019189284A1 publication Critical patent/WO2019189284A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/20—Compounding polymers with additives, e.g. colouring
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • C08K3/04—Carbon
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L101/00—Compositions of unspecified macromolecular compounds

Definitions

  • the present invention relates to a composite material containing exfoliated graphite and a resin, and a method for producing the composite material.
  • Patent Document 1 discloses a composite material containing exfoliated graphite and a resin.
  • a composition containing graphite or primary exfoliated graphite and a polymer, in which the polymer is fixed to graphite or primary exfoliated graphite is prepared.
  • the polymer contained in the prepared composition is thermally decomposed to peel off the graphite or primary exfoliated graphite while leaving a part of the polymer.
  • Patent Document 1 describes that in the step of preparing the composition, a composition containing a thermally decomposable foaming agent may be prepared.
  • An object of the present invention is to provide a composite material having excellent conductivity and a method for producing the composite material.
  • the composite material according to the present invention is a composite material containing exfoliated graphite and a resin, and the ratio (A)% of the resin in the surface of the composite material and the ratio of the resin in the entire composite material ( B)
  • the ratio (A / B) to% by weight is 1.0 or less.
  • the ratio (A)% of the resin in the surface of the composite material is 40.0% or less.
  • the ratio (B) wt% of the resin in the entire composite material is 2.0 wt% or more and 80.0 wt% or less.
  • the exfoliated graphite is a partially exfoliated graphite having a graphite structure and a structure in which the graphite is partially exfoliated.
  • a method for producing a composite material according to the present invention is a method for producing a composite material according to the present invention, comprising graphite or primary exfoliated graphite and a polymer, wherein the polymer is converted into the graphite or primary exfoliated graphite.
  • a step of preparing a fixed composition a first heating step of heating the composition at a temperature of 50 ° C. to 600 ° C. in an inert gas atmosphere, and the first heating step. After that, the composition is heated at a temperature of 300 ° C. or more and 600 ° C. or less in an atmosphere having an inert gas concentration of 85% or more and 99% or less and an oxygen concentration of 1% or more and 15% or less.
  • a second heating step wherein in the first heating step and the second heating step, the polymer in the composition is thermally decomposed to leave a part of the polymer while the graphite or one To peel off the flake graphite.
  • FIG. 1 is a schematic cross-sectional view for explaining how to obtain the ratio (A)% of the resin in the surface of the composite material.
  • FIG. 2 is a field emission scanning electron microscope (FE-SEM) photograph of the composite material obtained in Example 1 at a magnification of 20,000 times.
  • FIG. 3 is a field emission scanning electron microscope (FE-SEM) photograph of the composite material obtained in Comparative Example 1 at a magnification of 20,000 times.
  • FIG. 4 is a schematic diagram for explaining how to obtain the conductivity.
  • the composite material according to the present invention includes exfoliated graphite and a resin.
  • exfoliated graphite and a resin are combined.
  • at least a part of the resin may be carbonized.
  • the ratio (A / B) of the ratio (A)% of the resin occupying the surface of the composite material to the ratio (B) wt% of the resin occupying the entire composite material is 0.0 or more, 1 0.0 or less.
  • the ratio (A)% of the resin occupying the surface of the composite material means the ratio of the portion where the resin is present on the surface of the composite material when the entire surface of the composite material is 100%.
  • the ratio (A)% of the resin occupying the surface of the composite material can be obtained by observing with a scanning electron microscope (SEM).
  • SEM scanning electron microscope
  • FE-SEM field emission scanning electron microscope
  • the cross section of the composite material sample is observed.
  • the composite material can be cut into a cross-section of the sample by a cross section Polinshire (manufactured by JEOL Ltd., product number “IB-09010CP”).
  • the cross section of the obtained sample is, for example, using FE-SEM (manufactured by Hitachi, Ltd., product number “S-4800”), acceleration voltage: 3 kV, signal: LA (Upper), and magnification: 20,000 times It can be measured under conditions.
  • the length of the outermost surface portion of the sample and the outermost surface portion are covered with the resin by distinguishing the graphite portion and the resin portion from the contrast obtained by the special signal.
  • the length of the part can be measured.
  • the ratio (A)% of the resin in the surface of the composite material can be determined from the ratio of the length of the portion covered with the resin in the outermost surface portion to the obtained length of the outermost surface portion.
  • FIG. 1 is a schematic cross-sectional view for explaining how to obtain the ratio (A)% of the resin in the surface of the composite material. 1 can be observed under a specific condition of the FE-SEM after preparing a cross section of a sample of a composite material sample using the cross section polisher. Further, the cross-sectional view as shown in FIG. 1 can be observed by using the special signal that allows the composition to be seen. Specifically, exfoliated graphite and resin can be distinguished from the contrast obtained with a special signal.
  • X is a portion where exfoliated graphite 2 is exposed on the surface.
  • X is described in two places, but the total of these is defined as a portion X where exfoliated graphite 2 is exposed on the surface.
  • Y is a portion where the resin 3 is exposed on the surface. Therefore, Y is a portion excluding X on the outer peripheral edge 1 a (surface) of the composite material 1.
  • the ratio (A)% of the resin 3 occupying the surface of the composite material 1 can be obtained from the following formula (1).
  • the ratio (B) wt% of the resin in the entire composite material can be obtained by thermal analysis measurement.
  • the thermal analysis measurement can be performed using, for example, a differential thermothermal gravimetric simultaneous measurement apparatus (product name “TG / DTA6300”, manufactured by SII Nano Technology). Separating the combustion temperature of exfoliated graphite and resin from the differential thermal analysis result obtained using such a differential thermothermal weight simultaneous measurement device, and the ratio of the resin to the entire composite material from the associated thermogravimetric change (B) % By weight can be determined.
  • exfoliated graphite and a resin are combined, so that, for example, when used as an electrode forming slurry of an electricity storage device, dispersibility in the electrode forming slurry can be improved.
  • exfoliated graphite and resin are compounded, aggregation and restacking can be suppressed, and thereby a decrease in conductivity can be suppressed.
  • the ratio (A / B) of the ratio (A)% of the resin occupying the surface of the composite material and the ratio (B) wt% of the resin occupying the entire composite material is within the above range. Since the ratio of the resin occupying the surface is reduced, the degree of exposure of exfoliated graphite is increased, and the conductivity can be effectively increased.
  • the ratio (A / B) is preferably 0.8 or less, more preferably 0.6 or less, and even more preferably 0.4 or less.
  • the lower limit of the ratio (A / B) is not particularly limited, but the ratio (A / B) is preferably 0.01 or more, more preferably 0.1 or more, from the viewpoint of further increasing the conductivity of the composite material. It is.
  • the ratio (A)% of the resin occupying the surface of the composite material is preferably 30.0% or less, more preferably 21.0% or less.
  • the conductivity can be further enhanced. Note that the resin may not be present on the surface of the composite material.
  • the ratio (B) wt% of the resin in the entire composite material is preferably 30.0 wt% or more, more preferably 50.0 wt% or more, preferably 70.0 wt% or less. Preferably it is 60.0 weight% or less.
  • the ratio (B)% by weight of the resin in the whole is not less than the above lower limit, the specific surface area of the composite material can be further increased.
  • the ratio (B)% by weight of the resin in the entire composite material is not more than the above upper limit, the conductivity can be further enhanced.
  • Exfoliated graphite is obtained by exfoliating the original graphite, and refers to a graphene sheet laminate that is thinner than the original graphite.
  • the number of graphene sheets laminated in exfoliated graphite should be less than the original graphite.
  • the number of graphene sheets stacked is preferably 1000 layers or less, more preferably 500 layers or less.
  • the specific surface area of exfoliated graphite can be further increased.
  • the exfoliated graphite is preferably partially exfoliated graphite having a graphite structure and a structure in which the graphite is partially exfoliated.
  • partially exfoliated graphite means that in the graphene laminate, the graphene layer is open from the edge to some extent inside, that is, a part of the graphite is exfoliated at the edge. In the central part, the graphite layer is laminated in the same manner as the original graphite or primary exfoliated graphite. Therefore, the part where the graphite is partially peeled off at the edge is continuous with the central part. Further, the partially exfoliated exfoliated graphite may include one exfoliated and exfoliated from the edge graphite.
  • the graphite layer is laminated in the central portion in the same manner as the original graphite or primary exfoliated graphite. Therefore, the degree of graphitization is higher than that of conventional graphene oxide and carbon black, and the conductivity can be further increased.
  • Such partially exfoliated exfoliated graphite includes graphite or primary exfoliated graphite and a polymer, and a composition in which the polymer is fixed to the graphite or primary exfoliated graphite by grafting or adsorption is prepared and thermally decomposed. Can be obtained.
  • a part of polymer, ie, resin, contained in the composition remains. That is, a resin-retained partially exfoliated graphite is preferable.
  • partially exfoliated graphite from which the resin (polymer) has been completely removed may be used.
  • the graphite used as a raw material is a laminate of a plurality of graphene sheets.
  • the graphite used as a raw material is preferably expanded graphite. Expanded graphite can be easily peeled off because the interlayer of the graphene layer is larger than that of normal graphite. Therefore, by using expanded graphite as the raw material graphite, it is possible to easily produce a resin-retained partially exfoliated exfoliated graphite.
  • the number of graphene layers is about 100,000 to 1,000,000, and the BET specific surface area has a value of 20 m 2 / g or less.
  • the number of graphene layers is preferably 3000 or less.
  • the BET specific surface area of the resin-retained partially exfoliated graphite is preferably 50 m 2 / g or more, and more preferably 70 m 2 / g or more.
  • the upper limit of the BET specific surface area of the resin-retained partially exfoliated graphite is usually 2500 m 2 / g or less.
  • primary exfoliated graphite may be used instead of graphite.
  • Examples of primary exfoliated graphite include exfoliated graphite obtained by exfoliating graphite by a conventionally known method, partially exfoliated graphite, and resin-retained partially exfoliated graphite. Since primary exfoliated graphite is obtained by exfoliating graphite, the specific surface area may be larger than that of graphite.
  • the resin contained in the resin-retained partially exfoliated exfoliated graphite is not particularly limited, and examples thereof include polyether resins, polyvinyl resins, and diene resins.
  • the polyether resin include polypropylene glycol, polyethylene glycol, polytetramethylene glycol and the like.
  • the polyvinyl resin include polyglycidyl methacrylate, polyvinyl acetate, polyvinyl butyral, polyacrylic acid, polystyrene, poly ⁇ -methylstyrene, polyethylene, polypropylene, and polyisobutylene.
  • the diene resin include polybutadiene, polyisoprene, and styrene butadiene rubber.
  • the resin contained in the resin-releasable partially exfoliated exfoliated graphite is preferably a resin that easily generates free radicals by thermal decomposition, such as polypropylene glycol, polyethylene glycol, polyglycidyl methacrylate, and polyvinyl acetate. More preferred are polyethers such as polypropylene glycol, polyethylene glycol, and polytetramethylene glycol. More preferred is polyethylene glycol.
  • the interlayer distance between the graphene layers is increased and the specific surface area is large.
  • the resin-retained partially exfoliated graphite has a structure in which the central portion has a graphite structure and the edge portion is exfoliated, and thus is easier to handle than conventional exfoliated graphite.
  • Resin-retained partially exfoliated graphite has high dispersibility in other resins because it contains a resin.
  • the other resin is a resin having a high affinity with the resin contained in the resin residual type exfoliated graphite, the dispersibility of the resin residual type partially exfoliated exfoliated graphite in the other resin is further increased. Will be enhanced.
  • the resin is desirably disposed between the graphene layers of the partially exfoliated graphite. But resin may adhere to the surface and edge part of partially exfoliation type exfoliated graphite. Further, it is desirable that the resin is grafted or adsorbed on the partially exfoliated exfoliated graphite.
  • the resin-retained partially exfoliated graphite can be obtained by a production method described in an example of the production method described later, and can be used as it is as an example of the composite material of the present invention.
  • exfoliated graphite and resin may be prepared separately and combined to obtain a composite material.
  • the resin is not particularly limited, and examples thereof include polyether resins, polyvinyl resins, and diene resins.
  • the polyether resin include polypropylene glycol, polyethylene glycol, polytetramethylene glycol and the like.
  • the polyvinyl resin include polyglycidyl methacrylate, polyvinyl acetate, polyvinyl butyral, polyacrylic acid, polystyrene, poly ⁇ -methylstyrene, polyethylene, polypropylene, and polyisobutylene.
  • the diene resin include polybutadiene, polyisoprene, and styrene butadiene rubber.
  • the resin is preferably a resin that easily generates free radicals by thermal decomposition of polypropylene glycol, polyethylene glycol, polyglycidyl methacrylate, polyvinyl acetate, or the like.
  • polyethers such as polypropylene glycol, polyethylene glycol, and polytetramethylene glycol. More preferred is polyethylene glycol.
  • the composite material of the present invention may contain other components as long as the effects of the present invention are not impaired.
  • antioxidants examples include additives such as antioxidants, ultraviolet absorbers, metal damage inhibitors, halogenated flame retardants, flame retardants, fillers, antistatic agents, stabilizers, pigments, and dyes.
  • antioxidant examples include phenol, phosphorus, amine, and sulfur.
  • ultraviolet absorber examples include benzotriazole-based or hydroxyphenyltriazine-based.
  • halogenated flame retardant examples include hexabromobiphenyl ether and decabromodiphenyl ether.
  • flame retardant ammonium polyphosphate, trimethyl phosphate, or the like may be used. These additives may be used alone or in combination.
  • a composition including graphite or primary exfoliated graphite and a polymer, and the polymer is fixed to the graphite or primary exfoliated graphite is first prepared.
  • the step of preparing this composition include the following first and second methods for fixing the polymer to graphite or primary exfoliated graphite by grafting the polymer to graphite or primary exfoliated graphite. .
  • First method In the first method, first, a mixture containing graphite or primary exfoliated graphite and a radical polymerizable monomer is prepared as a raw material. Next, the radically polymerizable monomer contained in the mixture is polymerized. Thereby, a polymer in which the radical polymerizable monomer is polymerized in the mixture is generated, and the polymer is grafted to graphite or primary exfoliated graphite.
  • a composition containing graphite or primary exfoliated graphite and a radical polymerizable monomer is prepared.
  • the blending ratio of graphite and radical polymerizable monomer is not particularly limited, but is preferably 1: 1 to 1: 100 by mass ratio. By setting the blending ratio in the above range, it is possible to effectively exfoliate graphite or primary exfoliated graphite and to obtain a composite material more effectively.
  • the method for preparing the composition is not particularly limited, and examples thereof include a method in which a radical polymerizable monomer is used as a dispersion medium and graphite or primary exfoliated graphite is dispersed in the radical polymerizable monomer.
  • a step of producing a polymer in which the radical polymerizable monomer is polymerized in the composition is performed by polymerizing the radical polymerizable monomer contained in the composition.
  • the radical polymerizable monomer generates a free radical.
  • the radical polymerizable monomer undergoes radical polymerization, thereby producing a polymer in which the radical polymerizable monomer is polymerized.
  • the graphite or primary exfoliated graphite contained in the composition has a radical trapping property because it is a laminate of a plurality of graphene layers. Therefore, when a radically polymerizable monomer is co-polymerized in the composition, the free radicals are adsorbed on the edge and surface of the graphene layer of the graphite or primary exfoliated graphite. Therefore, the polymer or radical polymerizable monomer having free radicals generated at the time of polymerization is grafted to the end portion and the surface of the graphene layer of graphite or primary exfoliated graphite.
  • Examples of the method for polymerizing the radical polymerizable monomer include a method in which the composition is heated to a temperature higher than the temperature at which the radical polymerizable monomer spontaneously starts polymerization. By heating the composition to the temperature or higher, free radicals can be generated in the radical polymerizable monomer contained in the composition. Thereby, the polymerization and grafting described above can be carried out.
  • the heating method is not particularly limited as long as the composition can be heated to the temperature or higher, and the composition can be heated by an appropriate method and apparatus. Moreover, in the case of the said heating, you may heat without sealing, ie, a normal pressure. However, it may be sealed and heated.
  • the temperature may be further maintained for a certain time after heating to a temperature equal to or higher than the temperature at which the radical polymerizable monomer spontaneously starts polymerization.
  • the time for maintaining the temperature in the vicinity of the above temperature is preferably in the range of 0.5 hours to 5 hours, although it depends on the kind and amount of the radical polymerizable monomer used.
  • the step of thermally decomposing the polymer is performed while heating the composition to the thermal decomposition temperature of the polymer while leaving a part of the polymer.
  • the thermal decomposition temperature of the polymer means a decomposition end point temperature dependent on TGA measurement. For example, if the polymer is polystyrene, the thermal decomposition temperature of the polymer is about 350 ° C.
  • the thermal decomposition start temperature and the thermal decomposition end temperature of the resin in the composite material obtained by thermal decomposition are higher than the thermal decomposition start temperature and the thermal decomposition end temperature of the resin before the composite, respectively.
  • the heating method is not particularly limited as long as it can be heated to the thermal decomposition temperature of the polymer, and the composition can be heated by an appropriate method and apparatus.
  • the thermal decomposition so that the resin remains can be achieved, for example, by adjusting the heating time. That is, the amount of residual resin can be increased by shortening the heating time. Also, the amount of residual resin can be increased by lowering the heating temperature.
  • the heating temperature and the heating time may be adjusted in the step of heating so that a part of the polymer (resin) remains.
  • the temperature is further increased after heating to a temperature equal to or higher than the thermal decomposition temperature of the polymer. You may maintain for a fixed time.
  • the time for maintaining the temperature in the vicinity of the above temperature is preferably in the range of 0.5 hours to 5 hours, although it depends on the kind and amount of the radical polymerizable monomer used.
  • the heat treatment for producing the polymer and the heat treatment for thermally decomposing the polymer are performed by the same method and apparatus. You may carry out continuously.
  • the polymer is first grafted to graphite or primary exfoliated graphite by heating the polymer in the presence of graphite or primary exfoliated graphite to a temperature in the temperature range of 50 ° C. or higher and 600 ° C. or lower.
  • the polymer obtained in advance is heated to the specific temperature range in the presence of graphite or primary exfoliated graphite.
  • polymer radicals generated by thermally decomposing the polymer can be directly grafted to graphite or primary exfoliated graphite.
  • a radical polymerizable monomer is polymerized in the presence of graphite or primary exfoliated graphite to produce a polymer, and grafting of the polymer onto graphite or primary exfoliated graphite has been attempted.
  • an appropriate pyrolytic radical generating polymer can be used as the polymer of the second method.
  • a polymer of a radical polymerizable monomer such as a vinyl monomer is preferably used.
  • vinyl monomers that is, vinyl group-containing monomers
  • examples of such vinyl monomers include monomers such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and benzyl acrylate.
  • styrene and glycidyl methacrylate are used.
  • the polymer formed by polymerizing the vinyl group-containing monomer include (meth) acrylic acid alkyl ester, polypropylene, polyvinyl phenol, polyphenylene sulfide, polyphenylene ether, and the like.
  • polymers containing halogen elements such as chlorine such as polyvinyl chloride, chlorinated vinyl chloride resin, ethylene fluoride resin, vinylidene fluoride resin, and vinylidene chloride resin can also be used.
  • Ethylene vinyl acetate copolymer (EVA) polyvinyl acetal, polyvinyl pyrrolidone and copolymers thereof can also be used.
  • Polymers obtained by cationic polymerization such as polyisobutylene and polyalkylene ether can also be used.
  • Polyurethane, epoxy resin, modified silicone resin, silicone resin, etc. formed by crosslinking oligomers can also be used.
  • Polyallylamine may be used, and in that case, an amino group can be grafted to graphite or primary exfoliated graphite.
  • Polyvinylphenol or polyphenols may be used, in which case the phenolic OH can be grafted to graphite or primary exfoliated graphite.
  • the phosphate group can be grafted.
  • condensation polymers such as polyester and polyamide may be used.
  • the decomposition product is grafted although the radical concentration obtained at the decomposition temperature is low.
  • a homopolymer of glycidyl methacrylate, polystyrene, polyvinyl acetate, polypropylene glycol, polyethylene glycol, polytetramethylene glycol, polyvinyl butyral, etc. are preferably used.
  • graphite or primary exfoliated graphite can be more effectively exfoliated.
  • a polyether such as polypropylene glycol, polyethylene glycol, or polytetramethylene glycol is more preferable. More preferred is polyethylene glycol.
  • the blending ratio of graphite or primary exfoliated graphite and polymer is not particularly limited, but it is desirable that the weight ratio is 1: 1 to 1:50. By setting the blending ratio within this range, it is possible to more effectively exfoliate graphite or primary exfoliated graphite and effectively obtain a composite material.
  • the graphite or primary exfoliated graphite can be more effectively exfoliated by heating that causes thermal decomposition of the polymer described later.
  • a specific method for preparing the composition is not limited, and examples thereof include a method in which a polymer and graphite or primary exfoliated graphite are put in an appropriate solvent or dispersion medium and heated. .
  • the polymer is grafted to graphite or primary exfoliated graphite by the above heating.
  • this heating temperature it is desirable to set it as the range of 50 to 600 degreeC.
  • the polymer can be effectively grafted onto the graphite.
  • graphite or primary exfoliated graphite can be more effectively exfoliated. The reason for this is considered as follows.
  • Third method As a third method, a method of dissolving or dispersing graphite and a polymer in an appropriate solvent can be mentioned.
  • a solvent tetrahydrofuran, methyl ethyl ketone, toluene, ethyl acetate, ethanol, water, or the like can be used.
  • a composition in which a polymer is adsorbed on graphite or primary exfoliated graphite in a solvent is prepared as the above composition.
  • the method for adsorbing the polymer to graphite or primary exfoliated graphite is not particularly limited. Since the polymer has adsorptivity to graphite, a method of mixing graphite or primary exfoliated graphite with the polymer in the above-described solvent can be used.
  • the polymer adsorption is considered to be due to the interaction between the surface energy of graphite and the polymer.
  • Exfoliation step of graphite or primary exfoliated graphite by thermal decomposition of polymer In any of the first method, the second method, and the third method, after preparing the composition as described above, the polymer contained in the composition is pyrolyzed. Thereby, graphite or primary exfoliated graphite is exfoliated while a part of the polymer remains, and a composite material can be obtained.
  • the composition may be heated to a temperature higher than the thermal decomposition temperature of the polymer. More specifically, it is heated to a temperature higher than the thermal decomposition temperature of the polymer, and the polymer is further baked. At this time, it is fired to such an extent that the polymer remains in the composition.
  • the thermal decomposition temperature of polystyrene is about 380 ° C. to 450 ° C.
  • the thermal decomposition temperature of polyglycidyl methacrylate is about 400 ° C. to 500 ° C.
  • the reason why the composite material can be obtained by thermal decomposition of the polymer is considered to be due to the above-described reason. That is, it is considered that when the polymer grafted on the graphite is baked, a large stress acts on the graft point, thereby increasing the distance between the graphenes.
  • the first method, the second method, and the third method can be appropriately selected and used.
  • the heating in the first heating step is performed in an inert gas atmosphere.
  • the inert gas examples include nitrogen, helium, argon, and carbon dioxide gas.
  • the inert gas is preferably nitrogen.
  • the oxygen concentration is preferably 1% or less, more preferably 0.1% or less. In this case, the defects of exfoliated graphite in the obtained composite material can be further reduced. Therefore, the conductivity of the composite material can be further increased.
  • the composition that has undergone the first heating step is heated at a temperature of 300 ° C. or higher and 600 ° C. or lower.
  • heating time it can be 10 minutes or more and 180 minutes or less, for example.
  • the heating in the second heating step is performed in an atmosphere having an inert gas concentration of 85% to 99% and an oxygen concentration of 1% to 15%.
  • the inert gas examples include nitrogen, helium, argon, and carbon dioxide gas.
  • the inert gas is preferably nitrogen.
  • the inert gas concentration is preferably 90% or more, and preferably 97% or less.
  • the oxygen concentration is preferably 3% or more, preferably 10% or less.
  • the resin on the surface of the composite material obtained can be selectively reduced as described later, and the conductivity of the composite material can be further enhanced.
  • oxygen concentration is below the said upper limit, the defect of exfoliated graphite in the composite material obtained can be decreased further, and the electroconductivity of a composite material can be improved further.
  • the polymer contained in the composition is heated in the first heating step (selected appropriately from the first method, the second method, and the third method).
  • the graphite or primary exfoliated graphite is peeled off while leaving a part of the polymer by thermally decomposing and compositing with graphite, whereby a composite material can be obtained.
  • the defect of exfoliated graphite in the composite material obtained can be decreased. Therefore, the conductivity of the composite material can be increased.
  • heating is performed in an atmosphere in which the inert gas concentration and the oxygen concentration are in the specific ranges, so that the ratio of the resin occupying the surface of the composite material is selectively reduced. Can do. Therefore, also from this point, conductivity can be effectively increased, and battery characteristics such as output characteristics of the electricity storage device can be improved.
  • the resin remains and the specific surface area is increased. Therefore, the capacity of the electricity storage device can be increased, and the battery characteristics can be improved from this point.
  • the electrical conductivity is enhanced by reducing the amount of resin on the surface while increasing the specific surface area by leaving the resin. Therefore, both output characteristics and capacity can be increased by using the electrode material for an electricity storage device or the like.
  • the composite material is obtained by pyrolyzing the polymer in the composition having a structure in which the polymer in which the radical polymerizable monomer is polymerized as described above is grafted to graphite or primary exfoliated graphite. It has gained.
  • the graphite may be further exfoliated as described above by using a composite material as a raw material.
  • you may implement the manufacturing method of the composite material of this invention by using the primary exfoliated graphite obtained by the exfoliation method of the other graphite as a raw material. Even in that case, a composite material having a larger specific surface area can be obtained.
  • a method for exfoliating graphite for example, a method for exfoliating graphite by electrochemical treatment or an adsorption-pyrolysis method can be used.
  • no thermally decomposable foaming agent is used during heating. Therefore, the amount of defects in exfoliated graphite can be reduced, and the conductivity can be further enhanced.
  • a pyrolytic foaming agent may be used during heating.
  • the composite material obtained by the example of the production method of the present invention is the above-mentioned resin-retained partially exfoliated graphite.
  • exfoliated graphite and resin may be prepared separately, and exfoliated graphite and resin may be combined by a method such as kneading to obtain a composite material.
  • Example 1 16 g of expanded graphite (trade name “PF Powder 8” manufactured by Toyo Tanso Co., Ltd.), 48 g of 1% carboxymethylcellulose aqueous solution and 480 g of pure water were mixed, and an ultrasonic crusher (trade name “UH-” manufactured by SMT Co., Ltd.) was mixed. 600S "), and ultrasonic treatment was performed for 5 hours in the intensity memory 6. As a result, a graphite / water dispersion in which graphite was dispersed in water was obtained.
  • PF Powder 8 manufactured by Toyo Tanso Co., Ltd.
  • the composition was heat-dried at a temperature of 150 ° C. for 3 hours to obtain a dried product. Thereafter, the obtained dried product is further heated to a temperature of 370 ° C. under a nitrogen atmosphere (oxygen concentration of 0.1% or less), maintained at a temperature of 370 ° C. for 2 hours, and the first heating step is performed. went. Subsequently, the composition subjected to the first heating step is further heated to a temperature of 400 ° C. in an atmosphere having a nitrogen concentration of 95% and an oxygen concentration of 5%, and is maintained at the temperature of 400 ° C. for 0.5 hour. A second heating step was performed.
  • the polyethylene glycol in the dried product was pyrolyzed, and the expanded graphite was peeled off.
  • a composite material which is a resin-retained partially exfoliated graphite was obtained.
  • FIG. 2 is a field emission scanning electron microscope (FE-SEM) photograph of the composite material obtained in Example 1 at a magnification of 20,000 times.
  • FIG. 3 is a field emission scanning electron microscope (FE-SEM) photograph of the composite material obtained in Comparative Example 1 at a magnification of 20,000.
  • the cross section of the obtained sample was measured using FE-SEM (manufactured by Hitachi, Ltd., product number “S-4800”) under the conditions of acceleration voltage: 3 kV, signal: LA (Upper), and magnification: 20,000 times. It was measured.
  • FIGS. 2 and 3 by observing under such conditions, the exfoliated graphite (graphite) portion and the resin portion were discriminated. Specifically, in FIGS. 2 and 3, the portion that appears white is the graphite portion, and the other gray portion is the resin portion.
  • the composite material that has undergone the second heating step is compared with FIG. 3 of the composition that has undergone only the first heating step (not through the second heating step). It can be seen that the amount of resin on the surface of the exfoliated graphite (graphite) portion is reduced.
  • the length of the outermost surface portion of the sample and the outermost surface portion are covered with the resin by distinguishing the graphite portion and the resin portion from the contrast obtained by the special signal.
  • the length of the part is measured.
  • the ratio (A)% of the resin in the surface of the composite material was determined from the ratio of the length of the portion covered with the resin in the outermost surface portion to the obtained length of the outermost surface portion.
  • the particle outermost surface portion in the cross section was visually observed to be 10 ⁇ m or more, and the graphite portion and the resin portion were distinguished.
  • (A)% was calculated
  • the ratio (A)% of the resin occupying the surface was similarly obtained for Comparative Example 1 that passed through only the first heating step (not passed through the second heating step).
  • the ratio (B) weight% of the resin in the entire composite material was determined by thermal analysis measurement.
  • the thermal analysis measurement was performed using a differential thermothermogravimetric simultaneous measurement device (TG-DTA, differential thermothermal gravimetric simultaneous measurement device (trade name “TG / DTA6300” manufactured by SII Nanotechnology)). Separating the combustion temperature of exfoliated graphite and resin from the differential thermal analysis results obtained using this differential thermothermal weight simultaneous measurement device, and the proportion of the resin in the entire composite material (B) wt% Asked.
  • the ratio (B) wt% of the resin in the entire composition was similarly determined for Comparative Example 1 that passed through only the first heating step (not passed through the second heating step).
  • the ratio (A / B) was determined from the ratio (A)% of the resin occupying the surface and the ratio (B)% by weight of the resin occupying the whole surface. The results are shown in Table 1 below.
  • Example 2 A composite material was obtained in the same manner as in Example 1 except that the heating time in the first heating step was changed from 2 hours to 1 hour.
  • Example 3 A composite material was obtained in the same manner as in Example 1 except that the heating time in the first heating step was changed from 2 hours to 4 hours.
  • Example 4 234 g of polyethylene glycol (trade name “PEG-600” manufactured by Sanyo Kasei Co., Ltd.) is added to 1 g of expanded graphite (trade name “PF Powder 8” manufactured by Toyo Tanso Co., Ltd.), and a homogenizer (trade name “MARK II” manufactured by Primix Co., Ltd.) is added. Graphite and resin were compounded by stirring at 8000 rpm for 30 minutes using Model 2.5 "). In this way, a composition in which polyethylene glycol was adsorbed on expanded graphite was prepared.
  • polyethylene glycol trade name “PEG-600” manufactured by Sanyo Kasei Co., Ltd.
  • expanded graphite trade name “PF Powder 8” manufactured by Toyo Tanso Co., Ltd.
  • a homogenizer trade name “MARK II” manufactured by Primix Co., Ltd.
  • the obtained dried product is further heated to a temperature of 370 ° C. under a nitrogen atmosphere (oxygen concentration of 0.1% or less), maintained at a temperature of 370 ° C. for 1 hour, and the first heating step is performed. went.
  • the composition that has undergone the first heating step is further heated to a temperature of 900 ° C. in a nitrogen atmosphere (oxygen concentration of 0.1% or less) and maintained at a temperature of 900 ° C. for 0.5 hours.
  • a second heating step was performed.
  • the polyethylene glycol in the dried product was pyrolyzed, and the expanded graphite was peeled off. Thereafter, potassium carbonate was removed by washing with water to obtain a composite material that was partially exfoliated graphite.
  • the electrical conductivity of the composite materials of Examples 3 to 4 and Comparative Examples 1 and 2 was measured. The results are shown in Table 1 below.
  • a method for measuring conductivity will be described with reference to FIG. First, as shown in FIG. 4, 1.0 g of the sample 5 was filled in the container 4 including the electrode 6. Next, the electrical resistance value when the sample 5 was compressed at a predetermined pressure was measured through the electrode 6 by the four-probe method. Thereby, the conductivity of the sample was measured. The conductivity was measured using a powder resistance device (Mitsubishi Chemical Corporation, product number: PD-51).

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Abstract

The present invention provides a composite material which has excellent electrical conductivity. A composite material which contains flake graphite and a resin, and which is configured such that the ratio of the occupancy (A) % of the resin in the surface of the composite material to the occupancy (B) % by weight of the resin in the whole composite material, namely A/B is 1.0 or less.

Description

複合材料及びその製造方法Composite material and manufacturing method thereof
　本発明は、薄片化黒鉛と樹脂とを含む、複合材料及び該複合材料の製造方法に関する。 The present invention relates to a composite material containing exfoliated graphite and a resin, and a method for producing the composite material.
　従来、導電性材料や熱伝導性材料として、炭素材料が広く用いられている。近年では、リチウムイオン二次電池などの二次電池やキャパシタなどの電極材料としての利用が検討されている。このような炭素材料としては、黒鉛、カーボンナノチューブ、グラフェン、又は薄片化黒鉛などが用いられている。薄片化黒鉛とは、元の黒鉛を剥離処理して得られるものであり、元の黒鉛よりも薄いグラフェンシート積層体である。 Conventionally, carbon materials have been widely used as conductive materials and heat conductive materials. In recent years, utilization as electrode materials for secondary batteries such as lithium ion secondary batteries and capacitors has been studied. As such a carbon material, graphite, carbon nanotube, graphene, exfoliated graphite, or the like is used. Exfoliated graphite is obtained by exfoliating the original graphite, and is a graphene sheet laminate that is thinner than the original graphite.
　下記の特許文献１には、薄片化黒鉛と樹脂とを含む複合材料が開示されている。特許文献１の複合材料の製造方法では、まず、黒鉛または一次薄片化黒鉛と、ポリマーとを含み、ポリマーが黒鉛または一次薄片化黒鉛に固定されている組成物を用意する。次に、用意した組成物中に含まれるポリマーを熱分解することにより、ポリマーの一部を残存させながら、黒鉛または一次薄片化黒鉛を剥離する。それによって、複合材料が製造されている。また、特許文献１においては、組成物を用意する工程において、熱分解性発泡剤を含む組成物を用意してもよい旨が記載されている。 The following Patent Document 1 discloses a composite material containing exfoliated graphite and a resin. In the method for producing a composite material disclosed in Patent Document 1, first, a composition containing graphite or primary exfoliated graphite and a polymer, in which the polymer is fixed to graphite or primary exfoliated graphite, is prepared. Next, the polymer contained in the prepared composition is thermally decomposed to peel off the graphite or primary exfoliated graphite while leaving a part of the polymer. Thereby, a composite material is produced. Patent Document 1 describes that in the step of preparing the composition, a composition containing a thermally decomposable foaming agent may be prepared.
国際公開第２０１４／０３４１５６号公報パンフレットInternational Publication No. 2014/034156 Pamphlet
　近年、特にハイブリッド自動車や電気自動車などの車載用途において、二次電池の更なる高性能化が求められている。それに伴い、二次電池の電極においても、より一層の低抵抗化が求められている。そのため、高い導電性を有する（抵抗値の低い）特許文献１の複合材料を用いた場合においても、なお十分ではなかった。 In recent years, there has been a demand for further enhancement of the performance of secondary batteries, particularly in in-vehicle applications such as hybrid vehicles and electric vehicles. Accordingly, there is a demand for further lower resistance in the electrodes of secondary batteries. Therefore, even when the composite material of Patent Document 1 having high conductivity (low resistance value) is used, it is still not sufficient.
　本発明の目的は、導電性に優れる、複合材料及び該複合材料の製造方法を提供することにある。 An object of the present invention is to provide a composite material having excellent conductivity and a method for producing the composite material.
　本発明に係る複合材料は、薄片化黒鉛と樹脂とを含む、複合材料であって、前記複合材料の表面に占める樹脂の割合（Ａ）％と、前記複合材料の全体に占める樹脂の割合（Ｂ）重量％との比（Ａ／Ｂ）が、１．０以下である。 The composite material according to the present invention is a composite material containing exfoliated graphite and a resin, and the ratio (A)% of the resin in the surface of the composite material and the ratio of the resin in the entire composite material ( B) The ratio (A / B) to% by weight is 1.0 or less.
　本発明に係る複合材料のある特定の局面では、前記複合材料の表面に占める樹脂の割合（Ａ）％が、４０．０％以下である。 In a specific aspect of the composite material according to the present invention, the ratio (A)% of the resin in the surface of the composite material is 40.0% or less.
　本発明に係る複合材料の他の特定の局面では、前記複合材料の全体に占める樹脂の割合（Ｂ）重量％が、２．０重量％以上、８０．０重量％以下である。 In another specific aspect of the composite material according to the present invention, the ratio (B) wt% of the resin in the entire composite material is 2.0 wt% or more and 80.0 wt% or less.
　本発明に係る複合材料のさらに他の特定の局面では、前記薄片化黒鉛が、グラファイト構造を有し、部分的にグラファイトが剥離している構造を有する、部分剥離型薄片化黒鉛である。 In yet another specific aspect of the composite material according to the present invention, the exfoliated graphite is a partially exfoliated graphite having a graphite structure and a structure in which the graphite is partially exfoliated.
　本発明に係る複合材料の製造方法は、本発明に従って構成される複合材料の製造方法であって、黒鉛または一次薄片化黒鉛と、ポリマーとを含み、前記ポリマーが前記黒鉛または一次薄片化黒鉛に固定されている組成物を用意する工程と、前記組成物を、不活性ガス雰囲気下において、５０℃以上、６００℃以下の温度で加熱する、第１の加熱工程と、前記第１の加熱工程の後に、前記組成物を、不活性ガス濃度が８５％以上、９９％以下、かつ酸素濃度が１％以上、１５％以下の雰囲気下において、３００℃以上、６００℃以下の温度で加熱する、第２の加熱工程と、を備え、前記第１の加熱工程及び第２の加熱工程において、前記組成物中のポリマーを熱分解することにより、前記ポリマーの一部を残存させながら、前記黒鉛または一次薄片化黒鉛を剥離する。 A method for producing a composite material according to the present invention is a method for producing a composite material according to the present invention, comprising graphite or primary exfoliated graphite and a polymer, wherein the polymer is converted into the graphite or primary exfoliated graphite. A step of preparing a fixed composition, a first heating step of heating the composition at a temperature of 50 ° C. to 600 ° C. in an inert gas atmosphere, and the first heating step. After that, the composition is heated at a temperature of 300 ° C. or more and 600 ° C. or less in an atmosphere having an inert gas concentration of 85% or more and 99% or less and an oxygen concentration of 1% or more and 15% or less. A second heating step, wherein in the first heating step and the second heating step, the polymer in the composition is thermally decomposed to leave a part of the polymer while the graphite or one To peel off the flake graphite.
　本発明によれば、導電性に優れる、複合材料及び該複合材料の製造方法を提供することができる。 According to the present invention, it is possible to provide a composite material excellent in conductivity and a method for producing the composite material.
図１は、複合材料の表面に占める樹脂の割合（Ａ）％の求め方を説明するための模式的断面図である。FIG. 1 is a schematic cross-sectional view for explaining how to obtain the ratio (A)% of the resin in the surface of the composite material. 図２は、実施例１で得られた複合材料の倍率２０，０００倍の電界放出形走査電子顕微鏡（ＦＥ－ＳＥＭ）写真である。FIG. 2 is a field emission scanning electron microscope (FE-SEM) photograph of the composite material obtained in Example 1 at a magnification of 20,000 times. 図３は、比較例１で得られた複合材料の倍率２０，０００倍の電界放出形走査電子顕微鏡（ＦＥ－ＳＥＭ）写真である。FIG. 3 is a field emission scanning electron microscope (FE-SEM) photograph of the composite material obtained in Comparative Example 1 at a magnification of 20,000 times. 図４は、導電率の求め方を説明するための模式図である。FIG. 4 is a schematic diagram for explaining how to obtain the conductivity.
　以下、本発明の詳細を説明する。 Hereinafter, the details of the present invention will be described.
　本発明に係る複合材料は、薄片化黒鉛と樹脂とを含む。上記複合材料においては、薄片化黒鉛と樹脂とが複合化されている。ここで、樹脂は、その少なくとも一部が炭化されていてもよい。 The composite material according to the present invention includes exfoliated graphite and a resin. In the composite material, exfoliated graphite and a resin are combined. Here, at least a part of the resin may be carbonized.
　本発明においては、複合材料の表面に占める樹脂の割合（Ａ）％と、複合材料の全体に占める樹脂の割合（Ｂ）重量％との比（Ａ／Ｂ）が、０．０以上、１．０以下である。 In the present invention, the ratio (A / B) of the ratio (A)% of the resin occupying the surface of the composite material to the ratio (B) wt% of the resin occupying the entire composite material is 0.0 or more, 1 0.0 or less.
　複合材料の表面に占める樹脂の割合（Ａ）％とは、複合材料の表面全体を１００％としたとき、複合材料の表面に樹脂が存在している部分の割合のことをいう。 The ratio (A)% of the resin occupying the surface of the composite material means the ratio of the portion where the resin is present on the surface of the composite material when the entire surface of the composite material is 100%.
　この複合材料の表面に占める樹脂の割合（Ａ）％は、走査電子顕微鏡（ＳＥＭ）により観察することにより求めることができる。走査電子顕微鏡としては、例えば、電界放出形走査電子顕微鏡（ＦＥ－ＳＥＭ）を用いることができる。 The ratio (A)% of the resin occupying the surface of the composite material can be obtained by observing with a scanning electron microscope (SEM). As the scanning electron microscope, for example, a field emission scanning electron microscope (FE-SEM) can be used.
　ＦＥ－ＳＥＭによる観察においては、複合材料の試料の断面を観察する。この際、例えば、クロスセクションポリンシャー（日本電子社製、品番「ＩＢ－０９０１０ＣＰ」）により複合材料を切削し、試料の断面とすることができる。 In the observation by FE-SEM, the cross section of the composite material sample is observed. At this time, for example, the composite material can be cut into a cross-section of the sample by a cross section Polinshire (manufactured by JEOL Ltd., product number “IB-09010CP”).
　得られた試料の断面は、例えば、ＦＥ－ＳＥＭ（日立製作所社製、品番「Ｓ－４８００」）を用いて、加速電圧：３ｋＶ、信号：ＬＡ（Ｕｐｐｅｒ）、及び倍率：２０，０００倍の条件で測定することができる。 The cross section of the obtained sample is, for example, using FE-SEM (manufactured by Hitachi, Ltd., product number “S-4800”), acceleration voltage: 3 kV, signal: LA (Upper), and magnification: 20,000 times It can be measured under conditions.
　このようにして観察した画像において、上記の特殊信号で得られたコントラストから黒鉛部分と樹脂部分とを区別することにより、試料の最表面部の長さ及び最表面部において樹脂で覆われている部分の長さを測定することができる。そして、得られた最表面部の長さに対する最表面部において樹脂で覆われている部分の長さの比から、複合材料の表面に占める樹脂の割合（Ａ）％を求めることができる。なお、表面に占める樹脂の割合（Ａ）％を求めるに際しては、試料の任意の箇所を上記クロスセクションポリンシャーで試料断面を作製の上、上記ＦＥ－ＳＥＭの特定条件にて断面観察する。 In the image observed in this manner, the length of the outermost surface portion of the sample and the outermost surface portion are covered with the resin by distinguishing the graphite portion and the resin portion from the contrast obtained by the special signal. The length of the part can be measured. And the ratio (A)% of the resin in the surface of the composite material can be determined from the ratio of the length of the portion covered with the resin in the outermost surface portion to the obtained length of the outermost surface portion. When determining the ratio (A)% of the resin occupying the surface, a cross section of the sample is prepared with the cross-section poli- nizer at any location of the sample, and the cross section is observed under the specific conditions of the FE-SEM.
　以下、図１に示す模式図を用いて、複合材料の表面に占める樹脂の割合（Ａ）％の求め方の一例について具体的に説明する。図１は、複合材料の表面に占める樹脂の割合（Ａ）％の求め方を説明するための模式的断面図である。なお、図１のような断面図は、複合材料の試料の任意の箇所を上記クロスセクションポリンシャーで試料断面を作製の上、上記ＦＥ－ＳＥＭの特定条件にて観察することができる。また、図１のような断面図は、組成をみることができる特殊な上記信号を用いて観察することができる。具体的には、特殊な信号で得られたコントラストから薄片化黒鉛と樹脂とを区別することができる。 Hereinafter, an example of how to obtain the ratio (A)% of the resin occupying the surface of the composite material will be specifically described with reference to the schematic diagram shown in FIG. FIG. 1 is a schematic cross-sectional view for explaining how to obtain the ratio (A)% of the resin in the surface of the composite material. 1 can be observed under a specific condition of the FE-SEM after preparing a cross section of a sample of a composite material sample using the cross section polisher. Further, the cross-sectional view as shown in FIG. 1 can be observed by using the special signal that allows the composition to be seen. Specifically, exfoliated graphite and resin can be distinguished from the contrast obtained with a special signal.
　図１に示すように、複合材料１の外周縁１ａ（表面）において、薄片化黒鉛２が表面に露出している部分をＸとする。なお、図１では、２か所にＸと記載しているが、これらの合計を薄片化黒鉛２が表面に露出している部分Ｘとする。また、複合材料１の外周縁１ａ（表面）において、樹脂３が表面に露出している部分をＹとする。従って、Ｙは、複合材料１の外周縁１ａ（表面）において、Ｘを除く部分である。このとき、複合材料１の表面に占める樹脂３の割合（Ａ）％は、以下の式（１）から求めることができる。 As shown in FIG. 1, in the outer peripheral edge 1a (surface) of the composite material 1, X is a portion where exfoliated graphite 2 is exposed on the surface. In FIG. 1, X is described in two places, but the total of these is defined as a portion X where exfoliated graphite 2 is exposed on the surface. Further, in the outer peripheral edge 1a (surface) of the composite material 1, Y is a portion where the resin 3 is exposed on the surface. Therefore, Y is a portion excluding X on the outer peripheral edge 1 a (surface) of the composite material 1. At this time, the ratio (A)% of the resin 3 occupying the surface of the composite material 1 can be obtained from the following formula (1).
　Ａ（％）＝Ｙ／（Ｘ＋Ｙ）×１００…式（１） A (%) = Y / (X + Y) × 100 Formula (1)
　また、複合材料の全体に占める樹脂の割合（Ｂ）重量％は、熱分析測定により求めることができる。熱分析測定は、例えば、示差熱熱重量同時測定装置（エスアイアイ・ナノテクノロジー社製、商品名「ＴＧ／ＤＴＡ６３００」）を用いて行うことができる。このような示差熱熱重量同時測定装置を用いて得られる示差熱分析結果から薄片化黒鉛と樹脂の燃焼温度を分離し、それに伴う熱重量変化から複合材料の全体に占める樹脂の割合（Ｂ）重量％を求めることができる。 Further, the ratio (B) wt% of the resin in the entire composite material can be obtained by thermal analysis measurement. The thermal analysis measurement can be performed using, for example, a differential thermothermal gravimetric simultaneous measurement apparatus (product name “TG / DTA6300”, manufactured by SII Nano Technology). Separating the combustion temperature of exfoliated graphite and resin from the differential thermal analysis result obtained using such a differential thermothermal weight simultaneous measurement device, and the ratio of the resin to the entire composite material from the associated thermogravimetric change (B) % By weight can be determined.
　本発明の複合材料では、薄片化黒鉛と樹脂が複合化されているので、例えば蓄電デバイスの電極形成用スラリーに用いたときに、電極形成用スラリー中での分散性を高めることができる。このように、本発明の複合材料では、薄片化黒鉛と樹脂が複合化されているので、凝集や再スタックを抑制することができ、それによって、導電性の低下を抑制することができる。 In the composite material of the present invention, exfoliated graphite and a resin are combined, so that, for example, when used as an electrode forming slurry of an electricity storage device, dispersibility in the electrode forming slurry can be improved. Thus, in the composite material of this invention, since exfoliated graphite and resin are compounded, aggregation and restacking can be suppressed, and thereby a decrease in conductivity can be suppressed.
　特に、本発明においては、複合材料の表面に占める樹脂の割合（Ａ）％と、複合材料の全体に占める樹脂の割合（Ｂ）重量％との比（Ａ／Ｂ）が、上記範囲内であり表面に占める樹脂の割合が低められているので、薄片化黒鉛の露出度が高くなり、導電性を効果的に高めることができる。 In particular, in the present invention, the ratio (A / B) of the ratio (A)% of the resin occupying the surface of the composite material and the ratio (B) wt% of the resin occupying the entire composite material is within the above range. Since the ratio of the resin occupying the surface is reduced, the degree of exposure of exfoliated graphite is increased, and the conductivity can be effectively increased.
　複合材料の導電性をより一層高める観点から、比（Ａ／Ｂ）は、好ましくは０．８以下、より好ましくは０．６以下、さらに好ましくは０．４以下である。比（Ａ／Ｂ）の下限値は、特に限定されないが、複合材料の導電性をより一層高める観点から、比（Ａ／Ｂ）が、好ましくは０．０１以上、より好ましくは０．１以上である。 From the viewpoint of further increasing the conductivity of the composite material, the ratio (A / B) is preferably 0.8 or less, more preferably 0.6 or less, and even more preferably 0.4 or less. The lower limit of the ratio (A / B) is not particularly limited, but the ratio (A / B) is preferably 0.01 or more, more preferably 0.1 or more, from the viewpoint of further increasing the conductivity of the composite material. It is.
　本発明においては、複合材料の表面に占める樹脂の割合（Ａ）％が、好ましくは３０．０％以下、より好ましくは２１．０％以下である。表面に占める樹脂の割合（Ａ）％が上記範囲内にある場合、導電性をより一層高めることができる。なお、複合材料の表面に樹脂が存在していなくてもよい。 In the present invention, the ratio (A)% of the resin occupying the surface of the composite material is preferably 30.0% or less, more preferably 21.0% or less. When the ratio (A)% of the resin in the surface is within the above range, the conductivity can be further enhanced. Note that the resin may not be present on the surface of the composite material.
　本発明においては、複合材料の全体に占める樹脂の割合（Ｂ）重量％が、好ましくは３０．０重量％以上、より好ましくは５０．０重量％以上、好ましくは７０．０重量％以下、より好ましくは６０．０重量％以下である。全体に占める樹脂の割合（Ｂ）重量％が上記下限以上である場合、複合材料の比表面積をより一層高めることができる。また、複合材料の全体に占める樹脂の割合（Ｂ）重量％が上記上限以下である場合、導電性をより一層高めることができる。 In the present invention, the ratio (B) wt% of the resin in the entire composite material is preferably 30.0 wt% or more, more preferably 50.0 wt% or more, preferably 70.0 wt% or less. Preferably it is 60.0 weight% or less. When the ratio (B)% by weight of the resin in the whole is not less than the above lower limit, the specific surface area of the composite material can be further increased. Moreover, when the ratio (B)% by weight of the resin in the entire composite material is not more than the above upper limit, the conductivity can be further enhanced.
　以下、本発明の複合材料を構成する各材料の詳細について説明する。 Hereinafter, details of each material constituting the composite material of the present invention will be described.
　（薄片化黒鉛）
　薄片化黒鉛とは、元の黒鉛を剥離処理して得られるものであり、元の黒鉛よりも薄いグラフェンシート積層体をいう。薄片化黒鉛におけるグラフェンシートの積層数は、元の黒鉛より少なければよい。 (Flaky graphite)
Exfoliated graphite is obtained by exfoliating the original graphite, and refers to a graphene sheet laminate that is thinner than the original graphite. The number of graphene sheets laminated in exfoliated graphite should be less than the original graphite.
　薄片化黒鉛において、グラフェンシートの積層数は、好ましくは１０００層以下であり、より好ましくは５００層以下である。グラフェンシートの積層数が上記上限以下である場合、薄片化黒鉛の比表面積をより一層大きくすることができる。 In the exfoliated graphite, the number of graphene sheets stacked is preferably 1000 layers or less, more preferably 500 layers or less. When the number of graphene sheets stacked is not more than the above upper limit, the specific surface area of exfoliated graphite can be further increased.
　薄片化黒鉛は、グラファイト構造を有し、部分的にグラファイトが剥離されている構造を有する部分剥離型薄片化黒鉛であることが好ましい。 The exfoliated graphite is preferably partially exfoliated graphite having a graphite structure and a structure in which the graphite is partially exfoliated.
　より具体的に、「部分的にグラファイトが剥離されている」とは、グラフェンの積層体において、端縁からある程度内側までグラフェン層間が開いており、すなわち端縁にてグラファイトの一部が剥離しており、中央側の部分ではグラファイト層が元の黒鉛又は一次薄片化黒鉛と同様に積層していることをいうものとする。従って、端縁にてグラファイトの一部が剥離している部分は、中央側の部分に連なっている。さらに、上記部分剥離型薄片化黒鉛には、端縁のグラファイトが剥離され薄片化したものが含まれていてもよい。 More specifically, “partially exfoliated graphite” means that in the graphene laminate, the graphene layer is open from the edge to some extent inside, that is, a part of the graphite is exfoliated at the edge. In the central part, the graphite layer is laminated in the same manner as the original graphite or primary exfoliated graphite. Therefore, the part where the graphite is partially peeled off at the edge is continuous with the central part. Further, the partially exfoliated exfoliated graphite may include one exfoliated and exfoliated from the edge graphite.
　このように、部分剥離型薄片化黒鉛は、中央側の部分において、グラファイト層が元の黒鉛又は一次薄片化黒鉛と同様に積層している。そのため、従来の酸化グラフェンやカーボンブラックより黒鉛化度が高く、より一層導電性を高めることができる。 As described above, in the partially exfoliated graphite, the graphite layer is laminated in the central portion in the same manner as the original graphite or primary exfoliated graphite. Therefore, the degree of graphitization is higher than that of conventional graphene oxide and carbon black, and the conductivity can be further increased.
　このような部分剥離型薄片化黒鉛は、黒鉛又は一次薄片化黒鉛と、ポリマーとを含み、ポリマーが黒鉛又は一次薄片化黒鉛にグラフト又は吸着により固定されている組成物を用意し、熱分解することにより得ることができる。なお、上記組成物中に含まれているポリマー、すなわち樹脂の一部は残存していることが好ましい。すなわち、樹脂残存型の部分剥離型薄片化黒鉛であることが好ましい。もっとも、樹脂（ポリマー）が完全に除去された部分剥離型薄片化黒鉛であってもよい。 Such partially exfoliated exfoliated graphite includes graphite or primary exfoliated graphite and a polymer, and a composition in which the polymer is fixed to the graphite or primary exfoliated graphite by grafting or adsorption is prepared and thermally decomposed. Can be obtained. In addition, it is preferable that a part of polymer, ie, resin, contained in the composition remains. That is, a resin-retained partially exfoliated graphite is preferable. However, partially exfoliated graphite from which the resin (polymer) has been completely removed may be used.
　原料として用いられる黒鉛は、複数のグラフェンシートの積層体である。原料として用いられる黒鉛は、膨張黒鉛が好ましい。膨張黒鉛は、通常の黒鉛よりもグラフェン層の層間が大きいため、容易に剥離され得る。そのため、原料黒鉛として膨張黒鉛を用いることにより、樹脂残存型の部分剥離型薄片化黒鉛を容易に製造することができる。 The graphite used as a raw material is a laminate of a plurality of graphene sheets. The graphite used as a raw material is preferably expanded graphite. Expanded graphite can be easily peeled off because the interlayer of the graphene layer is larger than that of normal graphite. Therefore, by using expanded graphite as the raw material graphite, it is possible to easily produce a resin-retained partially exfoliated exfoliated graphite.
　上記黒鉛では、グラフェンの積層数が１０万層～１００万層程度であり、ＢＥＴ比表面積は２０ｍ２／ｇ以下の値を有する。 In the graphite, the number of graphene layers is about 100,000 to 1,000,000, and the BET specific surface area has a value of 20 m 2 / g or less.
　一方、樹脂残存型の部分剥離型薄片化黒鉛では、グラフェンの積層数が３０００層以下であることが好ましい。樹脂残存型の部分剥離型薄片化黒鉛のＢＥＴ比表面積は、５０ｍ２／ｇ以上であることが好ましく、７０ｍ２／ｇ以上であることがより好ましい。なお、樹脂残存型の部分剥離型薄片化黒鉛におけるＢＥＴ比表面積の上限値は、通常、２５００ｍ２／ｇ以下である。 On the other hand, in the resin-retained partially exfoliated graphite, the number of graphene layers is preferably 3000 or less. The BET specific surface area of the resin-retained partially exfoliated graphite is preferably 50 m 2 / g or more, and more preferably 70 m 2 / g or more. The upper limit of the BET specific surface area of the resin-retained partially exfoliated graphite is usually 2500 m 2 / g or less.
　なお、原料としては、黒鉛の代わりに一次薄片化黒鉛を用いてもよい。一次薄片化黒鉛とは、従来公知の方法によって黒鉛を剥離することにより得られた薄片化黒鉛や、部分剥離型薄片化黒鉛、樹脂残存型の部分剥離型薄片化黒鉛が挙げられる。一次薄片化黒鉛は、黒鉛を剥離することにより得られるものであるため、その比表面積は、黒鉛よりも大きいものであればよい。 As a raw material, primary exfoliated graphite may be used instead of graphite. Examples of primary exfoliated graphite include exfoliated graphite obtained by exfoliating graphite by a conventionally known method, partially exfoliated graphite, and resin-retained partially exfoliated graphite. Since primary exfoliated graphite is obtained by exfoliating graphite, the specific surface area may be larger than that of graphite.
　樹脂残存型の部分剥離型薄片化黒鉛に含まれる樹脂としては、特に限定されず、例えば、ポリエーテル樹脂、ポリビニル樹脂、又はジエン系樹脂が挙げられる。ポリエーテル樹脂としては、ポリプロピレングリコール、ポリエチレングリコール、ポリテトラメチレングリコール等が挙げられる。ポリビニル樹脂としては、ポリグリシジルメタクリレート、ポリ酢酸ビニル、ポリビニルブチラール、ポリアクリル酸、ポリスチレン、ポリαメチルスチレン、ポリエチレン、ポリプロピレン、ポリイソブチレン等が挙げられる。ジエン系樹脂としては、ポリブタジエン、ポリイソプレン、スチレンブタジエンゴム等が挙げられる。 The resin contained in the resin-retained partially exfoliated exfoliated graphite is not particularly limited, and examples thereof include polyether resins, polyvinyl resins, and diene resins. Examples of the polyether resin include polypropylene glycol, polyethylene glycol, polytetramethylene glycol and the like. Examples of the polyvinyl resin include polyglycidyl methacrylate, polyvinyl acetate, polyvinyl butyral, polyacrylic acid, polystyrene, poly α-methylstyrene, polyethylene, polypropylene, and polyisobutylene. Examples of the diene resin include polybutadiene, polyisoprene, and styrene butadiene rubber.
　樹脂残存型の部分剥離型薄片化黒鉛に含まれる樹脂としては、好ましくは、ポリプロピレングリコールや、ポリエチレングリコール、ポリグリシジルメタクリレート、ポリ酢酸ビニル等の加熱分解により遊離基の発生しやすい樹脂が挙げられる。より好ましくは、ポリプロピレングリコールや、ポリエチレングリコール、ポリテトラメチレングリコール等のポリエーテルである。さらに好ましくは、ポリエチレングリコールである。 The resin contained in the resin-releasable partially exfoliated exfoliated graphite is preferably a resin that easily generates free radicals by thermal decomposition, such as polypropylene glycol, polyethylene glycol, polyglycidyl methacrylate, and polyvinyl acetate. More preferred are polyethers such as polypropylene glycol, polyethylene glycol, and polytetramethylene glycol. More preferred is polyethylene glycol.
　また、樹脂残存型の部分剥離型薄片化黒鉛では、グラフェン層間の層間距離が拡げられており、その比表面積が大きい。さらに、樹脂残存型の部分剥離型薄片化黒鉛は、中心部分がグラファイト構造を有し、エッジ部分が薄片化している構造を有することから、従来の薄片化黒鉛よりも取り扱いが容易である。また、樹脂残存型の部分剥離型薄片化黒鉛は、樹脂を含むため、他の樹脂中への分散性が高い。特に、他の樹脂が、樹脂残存型の薄片化黒鉛に含まれる樹脂と親和性の高い樹脂である場合、樹脂残存型の部分剥離型薄片化黒鉛の他の樹脂への分散性は、より一層高められることとなる。樹脂は、部分剥離型薄片化黒鉛のグラフェン層間に配置されていることが望ましい。もっとも、樹脂は、部分剥離型薄片化黒鉛の表面や端部に付着していてもよい。また、樹脂は、部分剥離型薄片化黒鉛にグラフト又は吸着していることが望ましい。 Also, in the resin-exfoliated partially exfoliated graphite, the interlayer distance between the graphene layers is increased and the specific surface area is large. Further, the resin-retained partially exfoliated graphite has a structure in which the central portion has a graphite structure and the edge portion is exfoliated, and thus is easier to handle than conventional exfoliated graphite. Resin-retained partially exfoliated graphite has high dispersibility in other resins because it contains a resin. In particular, when the other resin is a resin having a high affinity with the resin contained in the resin residual type exfoliated graphite, the dispersibility of the resin residual type partially exfoliated exfoliated graphite in the other resin is further increased. Will be enhanced. The resin is desirably disposed between the graphene layers of the partially exfoliated graphite. But resin may adhere to the surface and edge part of partially exfoliation type exfoliated graphite. Further, it is desirable that the resin is grafted or adsorbed on the partially exfoliated exfoliated graphite.
　樹脂残存型の部分剥離型薄片化黒鉛は、具体的には、後述の製造方法の一例の欄で説明する製造方法により得ることができ、そのまま本発明の複合材料の一例として用いることができる。もっとも、本発明においては、薄片化黒鉛と樹脂とを別々に用意し、複合化させることにより複合材料を得てもよい。 Specifically, the resin-retained partially exfoliated graphite can be obtained by a production method described in an example of the production method described later, and can be used as it is as an example of the composite material of the present invention. However, in the present invention, exfoliated graphite and resin may be prepared separately and combined to obtain a composite material.
　（樹脂）
　樹脂としては、特に限定されず、例えば、ポリエーテル樹脂、ポリビニル樹脂、又はジエン系樹脂が挙げられる。ポリエーテル樹脂としては、ポリプロピレングリコール、ポリエチレングリコール、ポリテトラメチレングリコール等が挙げられる。ポリビニル樹脂としては、ポリグリシジルメタクリレート、ポリ酢酸ビニル、ポリビニルブチラール、ポリアクリル酸、ポリスチレン、ポリαメチルスチレン、ポリエチレン、ポリプロピレン、ポリイソブチレン等が挙げられる。ジエン系樹脂としては、ポリブタジエン、ポリイソプレン、スチレンブタジエンゴム等が挙げられる。 (resin)
The resin is not particularly limited, and examples thereof include polyether resins, polyvinyl resins, and diene resins. Examples of the polyether resin include polypropylene glycol, polyethylene glycol, polytetramethylene glycol and the like. Examples of the polyvinyl resin include polyglycidyl methacrylate, polyvinyl acetate, polyvinyl butyral, polyacrylic acid, polystyrene, poly α-methylstyrene, polyethylene, polypropylene, and polyisobutylene. Examples of the diene resin include polybutadiene, polyisoprene, and styrene butadiene rubber.
　樹脂としては、好ましくは、ポリプロピレングリコールや、ポリエチレングリコール、ポリグリシジルメタクリレート、ポリ酢酸ビニル等の加熱分解により遊離基の発生しやすい樹脂が挙げられる。複合材料の導電性をより一層高める観点から、より好ましくは、ポリプロピレングリコールや、ポリエチレングリコール、ポリテトラメチレングリコール等のポリエーテルである。さらに好ましくは、ポリエチレングリコールである。 The resin is preferably a resin that easily generates free radicals by thermal decomposition of polypropylene glycol, polyethylene glycol, polyglycidyl methacrylate, polyvinyl acetate, or the like. From the viewpoint of further increasing the conductivity of the composite material, more preferred are polyethers such as polypropylene glycol, polyethylene glycol, and polytetramethylene glycol. More preferred is polyethylene glycol.
　（他の成分）
　本発明の複合材料には、本発明の効果を阻害しない範囲において、他の成分が含まれていてもよい。 (Other ingredients)
The composite material of the present invention may contain other components as long as the effects of the present invention are not impaired.
　他の成分としては、例えば、酸化防止剤、紫外線吸収剤、金属害防止剤、ハロゲン化難燃剤、難燃剤、充填剤、帯電防止剤、安定剤、顔料、染料等の添加剤が挙げられる。酸化防止剤としては、フェノール系、リン系、アミン系又はイオウ系等が挙げられる。紫外線吸収剤としては、ベンゾトリアゾール系又はヒドロキシフェニルトリアジン系等が挙げられる。ハロゲン化難燃剤としては、ヘキサブロモビフェニルエーテル又はデカブロモジフェニルエーテル等が挙げられる。また、難燃剤としては、ポリリン酸アンモニウム又はトリメチルフォスフェート等を用いてもよい。なお、これらの添加剤は、単独で用いてもよいし、複数を併用してもよい。 Examples of other components include additives such as antioxidants, ultraviolet absorbers, metal damage inhibitors, halogenated flame retardants, flame retardants, fillers, antistatic agents, stabilizers, pigments, and dyes. Examples of the antioxidant include phenol, phosphorus, amine, and sulfur. Examples of the ultraviolet absorber include benzotriazole-based or hydroxyphenyltriazine-based. Examples of the halogenated flame retardant include hexabromobiphenyl ether and decabromodiphenyl ether. Further, as the flame retardant, ammonium polyphosphate, trimethyl phosphate, or the like may be used. These additives may be used alone or in combination.
　以下、本発明の複合材料の製造方法の一例について説明する。 Hereinafter, an example of the method for producing the composite material of the present invention will be described.
　［複合材料の製造方法］
　複合材料の製造方法の一例として、上述の樹脂残存型の部分剥離型薄片化黒鉛の製造方法について説明する。なお、本発明においては、ポリマーの熱分解のための加熱工程を第１の加熱工程及び第２の加熱工程に分けて行うものとする。 [Production method of composite material]
As an example of a method for producing a composite material, a method for producing the above-mentioned resin-retained partially exfoliated graphite will be described. In the present invention, the heating process for the thermal decomposition of the polymer is divided into a first heating process and a second heating process.
　（第１の加熱工程）
　複合材料の一例としての製造方法では、黒鉛又は一次薄片化黒鉛と、ポリマーとを含み、ポリマーが黒鉛又は一次薄片化黒鉛に固定されている組成物をまず用意する。この組成物を用意する工程としては、例えば、ポリマーを黒鉛又は一次薄片化黒鉛にグラフト化することにより、ポリマーを黒鉛又は一次薄片化黒鉛に固定する以下の第１及び第２の方法が挙げられる。また、ポリマーを黒鉛又は一次薄片化黒鉛に吸着させることにより、ポリマーを黒鉛又は一次薄片化黒鉛に固定する第３の方法を用いてもよい。 (First heating step)
In the production method as an example of the composite material, a composition including graphite or primary exfoliated graphite and a polymer, and the polymer is fixed to the graphite or primary exfoliated graphite is first prepared. Examples of the step of preparing this composition include the following first and second methods for fixing the polymer to graphite or primary exfoliated graphite by grafting the polymer to graphite or primary exfoliated graphite. . Moreover, you may use the 3rd method of fixing a polymer to graphite or primary exfoliated graphite by making a polymer adsorb | suck to graphite or primary exfoliated graphite.
　第１の方法；
　第１の方法では、まず、原料として、黒鉛又は一次薄片化黒鉛と、ラジカル重合性モノマーとを含む混合物を用意する。次に、混合物に含まれているラジカル重合性モノマーを重合する。それによって、混合物中にラジカル重合性モノマーが重合しているポリマーを生成させるとともに、該ポリマーを黒鉛または一次薄片化黒鉛にグラフト化させる。 First method;
In the first method, first, a mixture containing graphite or primary exfoliated graphite and a radical polymerizable monomer is prepared as a raw material. Next, the radically polymerizable monomer contained in the mixture is polymerized. Thereby, a polymer in which the radical polymerizable monomer is polymerized in the mixture is generated, and the polymer is grafted to graphite or primary exfoliated graphite.
　第１の方法では、まず、黒鉛又は一次薄片化黒鉛と、ラジカル重合性モノマーとを含む組成物を用意する。 In the first method, first, a composition containing graphite or primary exfoliated graphite and a radical polymerizable monomer is prepared.
　黒鉛とラジカル重合性モノマーとの配合割合は特に限定されないが、質量比で１：１～１：１００の割合とすることが望ましい。配合割合を上記範囲とすることで、黒鉛又は一次薄片化黒鉛を効果的に剥離し、複合材料をより一層効果的に得ることができる。 The blending ratio of graphite and radical polymerizable monomer is not particularly limited, but is preferably 1: 1 to 1: 100 by mass ratio. By setting the blending ratio in the above range, it is possible to effectively exfoliate graphite or primary exfoliated graphite and to obtain a composite material more effectively.
　上記組成物を用意する方法は特に限定されないが、例えば、ラジカル重合性モノマーを分散媒として使用し、黒鉛又は一次薄片化黒鉛をラジカル重合性モノマー中に分散させる方法などが挙げられる。 The method for preparing the composition is not particularly limited, and examples thereof include a method in which a radical polymerizable monomer is used as a dispersion medium and graphite or primary exfoliated graphite is dispersed in the radical polymerizable monomer.
　次に、上記組成物に含まれるラジカル重合性モノマーを重合することにより、上記組成物中にラジカル重合性モノマーが重合しているポリマーを生成する工程を行う。 Next, a step of producing a polymer in which the radical polymerizable monomer is polymerized in the composition is performed by polymerizing the radical polymerizable monomer contained in the composition.
　このとき、ラジカル重合性モノマーはフリーラジカルを生成する。それによってラジカル重合性モノマーがラジカル重合することにより、ラジカル重合性モノマーが重合しているポリマーが生成する。一方、上記組成物中に含まれる黒鉛又は一次薄片化黒鉛は、複数のグラフェン層の積層体であるため、ラジカルトラップ性を有する。そのため、上記組成物中においてラジカル重合性モノマーを共存重合させると、上記フリーラジカルが上記黒鉛又は一次薄片化黒鉛のグラフェン層の端部及び表面に吸着される。従って、重合時に生じたフリーラジカルを有するポリマー又はラジカル重合性モノマーが、黒鉛又は一次薄片化黒鉛のグラフェン層の端部及び表面にグラフト化する。 At this time, the radical polymerizable monomer generates a free radical. As a result, the radical polymerizable monomer undergoes radical polymerization, thereby producing a polymer in which the radical polymerizable monomer is polymerized. On the other hand, the graphite or primary exfoliated graphite contained in the composition has a radical trapping property because it is a laminate of a plurality of graphene layers. Therefore, when a radically polymerizable monomer is co-polymerized in the composition, the free radicals are adsorbed on the edge and surface of the graphene layer of the graphite or primary exfoliated graphite. Therefore, the polymer or radical polymerizable monomer having free radicals generated at the time of polymerization is grafted to the end portion and the surface of the graphene layer of graphite or primary exfoliated graphite.
　ラジカル重合性モノマーを重合する方法としては、例えば、ラジカル重合性モノマーが自発的に重合を開始する温度以上に上記組成物を加熱する方法が挙げられる。上記組成物を上記温度以上に加熱することによって、上記組成物に含まれるラジカル重合性モノマーにフリーラジカルを生成することができる。それによって、上述の重合及びグラフト化を行うことができる。 Examples of the method for polymerizing the radical polymerizable monomer include a method in which the composition is heated to a temperature higher than the temperature at which the radical polymerizable monomer spontaneously starts polymerization. By heating the composition to the temperature or higher, free radicals can be generated in the radical polymerizable monomer contained in the composition. Thereby, the polymerization and grafting described above can be carried out.
　上記加熱方法としては、上記組成物を上記温度以上に加熱できる方法であれば特に限定されず、適宜の方法及び装置により上記組成物を加熱することができる。また、上記加熱の際には、密閉することなく、すなわち常圧下で加熱してもよい。もっとも、密閉して加熱してもよい。 The heating method is not particularly limited as long as the composition can be heated to the temperature or higher, and the composition can be heated by an appropriate method and apparatus. Moreover, in the case of the said heating, you may heat without sealing, ie, a normal pressure. However, it may be sealed and heated.
　また、ラジカル重合性モノマーを確実に重合させるために、ラジカル重合性モノマーが自発的に重合を開始する温度以上の温度まで加熱した後、上記温度をさらに一定時間維持してもよい。上記温度付近に維持する時間は、使用するラジカル重合性モノマーの種類及び量にもよるが、好ましくは０．５時間～５時間の範囲である。 In order to reliably polymerize the radical polymerizable monomer, the temperature may be further maintained for a certain time after heating to a temperature equal to or higher than the temperature at which the radical polymerizable monomer spontaneously starts polymerization. The time for maintaining the temperature in the vicinity of the above temperature is preferably in the range of 0.5 hours to 5 hours, although it depends on the kind and amount of the radical polymerizable monomer used.
　上記ポリマーを生成する工程の後に、上記組成物をポリマーの熱分解温度まで加熱することにより、ポリマーの一部を残存させながら、ポリマーを熱分解する工程を行う。それによって、上記組成物に含まれるポリマー、並びに黒鉛又は一次薄片化黒鉛のグラフェン層の端部及び表面にグラフト化している上記ポリマー等が熱分解する。なお、本発明において、ポリマーの熱分解温度とは、ＴＧＡ測定依存の分解終点温度をいう。例えば、ポリマーがポリスチレンである場合には、ポリマーの熱分解温度は約３５０℃である。 After the step of producing the polymer, the step of thermally decomposing the polymer is performed while heating the composition to the thermal decomposition temperature of the polymer while leaving a part of the polymer. Thereby, the polymer contained in the composition, the polymer grafted on the end portion and the surface of the graphene layer of graphite or primary exfoliated graphite, and the like are thermally decomposed. In the present invention, the thermal decomposition temperature of the polymer means a decomposition end point temperature dependent on TGA measurement. For example, if the polymer is polystyrene, the thermal decomposition temperature of the polymer is about 350 ° C.
　このとき、黒鉛又は一次薄片化黒鉛のグラフェン層の端部及び表面にグラフト化しているポリマー等が熱分解する際に、グラフェン層間に剥離力が生じる。従って、ポリマー等を熱分解することによって、黒鉛又は一次薄片化黒鉛のグラフェン層間を剥離し、薄片化黒鉛を得ることができる。 At this time, when the polymer or the like grafted on the end portion and the surface of the graphene layer of graphite or primary exfoliated graphite is thermally decomposed, peeling force is generated between the graphene layers. Therefore, by pyrolyzing a polymer or the like, the graphene layer of graphite or primary exfoliated graphite can be peeled off to obtain exfoliated graphite.
　また、この熱分解によっても、一部のポリマー、すなわち樹脂は組成物中に残存している。そして、熱分解によって得られる複合材料における樹脂の熱分解開始温度及び熱分解終了温度は、それぞれ、複合化前の樹脂の熱分解開始温度及び熱分解終了温度よりも高くなる。 Further, even by this thermal decomposition, a part of the polymer, that is, the resin remains in the composition. Then, the thermal decomposition start temperature and the thermal decomposition end temperature of the resin in the composite material obtained by thermal decomposition are higher than the thermal decomposition start temperature and the thermal decomposition end temperature of the resin before the composite, respectively.
　上記加熱方法としては、ポリマーの熱分解温度まで加熱できる方法であれば特に限定されず、適宜の方法及び装置により上記組成物を加熱することができる。樹脂を残存させるように熱分解させるには、例えば加熱時間を調整することにより達成することができる。すなわち、加熱時間を短くすることにより残存樹脂量を多くすることができる。また、加熱温度を低めることにより残存樹脂量を多くすることもできる。 The heating method is not particularly limited as long as it can be heated to the thermal decomposition temperature of the polymer, and the composition can be heated by an appropriate method and apparatus. The thermal decomposition so that the resin remains can be achieved, for example, by adjusting the heating time. That is, the amount of residual resin can be increased by shortening the heating time. Also, the amount of residual resin can be increased by lowering the heating temperature.
　後述の第２の方法及び第３の方法においても、ポリマー（樹脂）の一部を残存させるように加熱する工程においては、加熱温度及び加熱時間を調整すればよい。 In the second method and the third method described later, the heating temperature and the heating time may be adjusted in the step of heating so that a part of the polymer (resin) remains.
　ポリマーの一部を上記組成物中に残存させつつ、ポリマーの一部が残存するようにしてポリマーを熱分解させることができれば、ポリマーの熱分解温度以上の温度まで加熱した後、上記温度をさらに一定時間維持してもよい。上記温度付近に維持する時間は、使用するラジカル重合性モノマーの種類及び量にもよるが、好ましくは０．５時間～５時間の範囲である。 If the polymer can be thermally decomposed so that a part of the polymer remains while part of the polymer remains in the composition, the temperature is further increased after heating to a temperature equal to or higher than the thermal decomposition temperature of the polymer. You may maintain for a fixed time. The time for maintaining the temperature in the vicinity of the above temperature is preferably in the range of 0.5 hours to 5 hours, although it depends on the kind and amount of the radical polymerizable monomer used.
　また、上記ポリマーを生成する工程において、加熱によりラジカル重合性モノマーを重合させる場合には、ポリマー生成する際の加熱処理と、ポリマーを熱分解する際の加熱処理とを、同一の方法及び装置により連続して行ってもよい。 Further, in the step of producing the polymer, when the radical polymerizable monomer is polymerized by heating, the heat treatment for producing the polymer and the heat treatment for thermally decomposing the polymer are performed by the same method and apparatus. You may carry out continuously.
　第２の方法；
　第２の方法では、まず、ポリマーを黒鉛又は一次薄片化黒鉛の存在下で、５０℃以上、６００℃以下の温度範囲の温度に加熱することにより、ポリマーを黒鉛又は一次薄片化黒鉛にグラフト化させる。このように、第２の方法では、予め得られたポリマーを黒鉛又は一次薄片化黒鉛の存在下で上記特定の温度範囲に加熱する。それによって、ポリマーを熱分解することにより生成したポリマーラジカルを直接黒鉛又は一次薄片化黒鉛にグラフトさせることができる。なお、第１の方法では、黒鉛又は一次薄片化黒鉛の存在下でラジカル重合性モノマーを重合してポリマーを生成するとともにポリマーの黒鉛又は一次薄片化黒鉛へのグラフト化が図られていた。 Second method;
In the second method, the polymer is first grafted to graphite or primary exfoliated graphite by heating the polymer in the presence of graphite or primary exfoliated graphite to a temperature in the temperature range of 50 ° C. or higher and 600 ° C. or lower. Let As described above, in the second method, the polymer obtained in advance is heated to the specific temperature range in the presence of graphite or primary exfoliated graphite. Thereby, polymer radicals generated by thermally decomposing the polymer can be directly grafted to graphite or primary exfoliated graphite. In the first method, a radical polymerizable monomer is polymerized in the presence of graphite or primary exfoliated graphite to produce a polymer, and grafting of the polymer onto graphite or primary exfoliated graphite has been attempted.
　第２の方法のポリマーとしては、適宜の熱分解ラジカル生成ポリマーを用いることができる。 As the polymer of the second method, an appropriate pyrolytic radical generating polymer can be used.
　ほとんどの有機ポリマーが分解温度でラジカルを発生する。従って、上記分解温度付近でラジカルを形成するポリマーとしては多くの有機ポリマーを用いることができる。もっとも、好ましくは、ビニル系モノマーなどのラジカル重合性モノマーの重合体が好適に用いられる。このようなビニル系モノマー、すなわちビニル基含有モノマーとしては、エチルアクリレート、ブチルアクリレート、２－エチルヘキシルアクリレート、ベンジルアクリレートなどのモノマーが挙げられる。好ましくは、スチレンやグリシジルメタクリレートが挙げられる。また、上記ビニル基含有モノマーを重合してなるポリマーとしては、（メタ）アクリル酸アルキルエステル、ポリプロピレン、ポリビニルフェノール、ポリフェニレンサルファイド、ポリフェニレンエーテルなどを挙げることができる。 Most organic polymers generate radicals at the decomposition temperature. Therefore, many organic polymers can be used as the polymer that forms radicals near the decomposition temperature. However, a polymer of a radical polymerizable monomer such as a vinyl monomer is preferably used. Examples of such vinyl monomers, that is, vinyl group-containing monomers, include monomers such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and benzyl acrylate. Preferably, styrene and glycidyl methacrylate are used. Examples of the polymer formed by polymerizing the vinyl group-containing monomer include (meth) acrylic acid alkyl ester, polypropylene, polyvinyl phenol, polyphenylene sulfide, polyphenylene ether, and the like.
　また、ポリ塩化ビニル、塩素化塩化ビニル樹脂、フッ化エチレン樹脂やフッ化ビニリデン樹脂、塩化ビニリデン樹脂など、塩素などのハロゲン元素を含有するポリマーなども使用可能である。エチレン酢酸ビニル共重合体（ＥＶＡ）、ポリビニルアセタール、ポリビニルピロリドンやそれらの共重合体も、使用可能である。ポリイソブチレンやポリアルキレンエーテルなどのカチオン重合によって得られたポリマーも使用可能である。 In addition, polymers containing halogen elements such as chlorine, such as polyvinyl chloride, chlorinated vinyl chloride resin, ethylene fluoride resin, vinylidene fluoride resin, and vinylidene chloride resin can also be used. Ethylene vinyl acetate copolymer (EVA), polyvinyl acetal, polyvinyl pyrrolidone and copolymers thereof can also be used. Polymers obtained by cationic polymerization such as polyisobutylene and polyalkylene ether can also be used.
　オリゴマーを架橋してなる、ポリウレタン、エポキシ樹脂、変性シリコーン樹脂やシリコーン樹脂なども使用可能である。 Polyurethane, epoxy resin, modified silicone resin, silicone resin, etc. formed by crosslinking oligomers can also be used.
　ポリアリルアミンを用いてもよく、その場合には黒鉛又は一次薄片化黒鉛にアミノ基をグラフトすることができる。ポリビニルフェノールやポリフェノール類を用いてもよく、その場合には、フェノール性ＯＨを黒鉛又は一次薄片化黒鉛にグラフトすることができる。また、リン酸基を有するポリマーを用いると、リン酸基をグラフトすることができる。 Polyallylamine may be used, and in that case, an amino group can be grafted to graphite or primary exfoliated graphite. Polyvinylphenol or polyphenols may be used, in which case the phenolic OH can be grafted to graphite or primary exfoliated graphite. Further, when a polymer having a phosphate group is used, the phosphate group can be grafted.
　また、ポリエステル、ポリアミドなどの縮合系ポリマーを用いてもよい。その場合には、分解温度で得られるラジカル濃度は低いけれども、分解物がグラフトされる。 Also, condensation polymers such as polyester and polyamide may be used. In that case, the decomposition product is grafted although the radical concentration obtained at the decomposition temperature is low.
　上記予め用意したポリマーとして、グリシジルメタクリレートのホモポリマー、ポリスチレン、ポリ酢酸ビニル、ポリプロピレングリコール、ポリエチレングリコール、ポリテトラメチレングリコール、ポリビニルブチラールなどが好適に用いられる。これらのポリマーを用いることにより、黒鉛又は一次薄片化黒鉛をより一層効果的に剥離することができる。得られる複合材料の導電性をより一層高める観点から、より好ましくは、ポリプロピレングリコールや、ポリエチレングリコール、ポリテトラメチレングリコール等のポリエーテルである。さらに好ましくは、ポリエチレングリコールである。 As the polymer prepared in advance, a homopolymer of glycidyl methacrylate, polystyrene, polyvinyl acetate, polypropylene glycol, polyethylene glycol, polytetramethylene glycol, polyvinyl butyral, etc. are preferably used. By using these polymers, graphite or primary exfoliated graphite can be more effectively exfoliated. From the viewpoint of further increasing the conductivity of the resulting composite material, a polyether such as polypropylene glycol, polyethylene glycol, or polytetramethylene glycol is more preferable. More preferred is polyethylene glycol.
　第２の方法において、黒鉛又は一次薄片化黒鉛とポリマーとの配合割合は特に限定されないが、重量比で１：１～１：５０の割合とすることが望ましい。配合割合をこの範囲内とすることにより、黒鉛又は一次薄片化黒鉛をより効果的に剥離し、複合材料を効果的に得ることができる。 In the second method, the blending ratio of graphite or primary exfoliated graphite and polymer is not particularly limited, but it is desirable that the weight ratio is 1: 1 to 1:50. By setting the blending ratio within this range, it is possible to more effectively exfoliate graphite or primary exfoliated graphite and effectively obtain a composite material.
　第２の方法においても、第１の方法の場合と同様に、後述するポリマーの熱分解を引き起こす加熱により、黒鉛又は一次薄片化黒鉛をより一層効果的に剥離することができる。 Also in the second method, similarly to the first method, the graphite or primary exfoliated graphite can be more effectively exfoliated by heating that causes thermal decomposition of the polymer described later.
　第２の方法においても、組成物を用意する具体的な方法は限定されないが、例えば、ポリマーと黒鉛又は一次薄片化黒鉛とを適宜の溶媒もしくは分散媒中に投入し、加熱する方法が挙げられる。 Also in the second method, a specific method for preparing the composition is not limited, and examples thereof include a method in which a polymer and graphite or primary exfoliated graphite are put in an appropriate solvent or dispersion medium and heated. .
　上記加熱によりポリマーが黒鉛又は一次薄片化黒鉛にグラフトされる。この加熱温度については、５０℃以上、６００℃以下の範囲とすることが望ましい。温度をこの範囲内とすることにより、ポリマーを黒鉛に効果的にグラフトさせることができる。それによって、黒鉛又は一次薄片化黒鉛をより一層効果的に剥離することができる。この理由については、以下の通りと考えられる。 The polymer is grafted to graphite or primary exfoliated graphite by the above heating. About this heating temperature, it is desirable to set it as the range of 50 to 600 degreeC. By setting the temperature within this range, the polymer can be effectively grafted onto the graphite. Thereby, graphite or primary exfoliated graphite can be more effectively exfoliated. The reason for this is considered as follows.
　上記ラジカル重合性モノマーを重合して得られたポリマーを加熱することにより、ポリマーの一部が分解し、黒鉛又は一次薄片化黒鉛のグラフェン層にラジカルトラップされる。従って、ポリマーが黒鉛又は一次薄片化黒鉛にグラフトされることになる。そして、後述する加熱工程においてポリマーを分解し、焼成すると、ポリマーの黒鉛又は一次薄片化黒鉛にグラフトされているグラフト面に大きな応力が加わる。そのため、剥離力がグラフト点を起点として作用し、グラフェン層間が効果的に拡げられることになると考えられる。 When the polymer obtained by polymerizing the radical polymerizable monomer is heated, a part of the polymer is decomposed and radical trapped in the graphene layer of graphite or primary exfoliated graphite. Therefore, the polymer will be grafted to graphite or primary exfoliated graphite. And if a polymer is decomposed | disassembled and baked in the heating process mentioned later, a big stress will be added to the graft surface currently grafted by the graphite or primary exfoliated graphite of a polymer. Therefore, it is considered that the peeling force acts starting from the graft point, and the graphene layer is effectively expanded.
　第３の方法；
　第３の方法としては、黒鉛と、ポリマーとを適宜の溶媒に溶解もしくは分散させる方法を挙げることができる。このような溶媒としては、テトラヒドロフラン、メチルエチルケトン、トルエン、酢酸エチル、エタノール、水などを用いることができる。 Third method;
As a third method, a method of dissolving or dispersing graphite and a polymer in an appropriate solvent can be mentioned. As such a solvent, tetrahydrofuran, methyl ethyl ketone, toluene, ethyl acetate, ethanol, water, or the like can be used.
　また、第３の方法では、上記組成物として、溶媒中において、ポリマーが黒鉛もしくは一次薄片化黒鉛に吸着されている組成物を用意する。ポリマーを黒鉛もしくは一次薄片化黒鉛に吸着させる方法は特に限定されない。ポリマーが黒鉛に対して吸着性を有するため、上述した溶媒中において、黒鉛もしくは一次薄片化黒鉛をポリマーと混合する方法を用いることができる。 In the third method, a composition in which a polymer is adsorbed on graphite or primary exfoliated graphite in a solvent is prepared as the above composition. The method for adsorbing the polymer to graphite or primary exfoliated graphite is not particularly limited. Since the polymer has adsorptivity to graphite, a method of mixing graphite or primary exfoliated graphite with the polymer in the above-described solvent can be used.
　ポリマーの吸着は、黒鉛の表面エネルギーとポリマーとの相互作用によると考えられる。 The polymer adsorption is considered to be due to the interaction between the surface energy of graphite and the polymer.
　ポリマーの熱分解による黒鉛又は一次薄片化黒鉛の剥離工程；
　上記第１の方法、第２の方法、及び第３の方法のいずれにおいても、上記のようにして組成物を用意したのち、組成物中に含まれるポリマーを熱分解する。それによって、ポリマーの一部を残存させながら、黒鉛又は一次薄片化黒鉛が剥離され、複合材料を得ることができる。この場合のポリマーの熱分解を果たすために、上記組成物をポリマーの熱分解温度以上に加熱すればよい。より具体的には、ポリマーの熱分解温度以上に加熱し、さらにポリマーを焼成する。このとき、組成物中にポリマーが残存する程度に焼成する。それによって、複合材料を得ることができる。例えば、ポリスチレンの熱分解温度は３８０℃～４５０℃程度であり、ポリグリシジルメタクリレートの熱分解温度は４００℃～５００℃程度である。 Exfoliation step of graphite or primary exfoliated graphite by thermal decomposition of polymer;
In any of the first method, the second method, and the third method, after preparing the composition as described above, the polymer contained in the composition is pyrolyzed. Thereby, graphite or primary exfoliated graphite is exfoliated while a part of the polymer remains, and a composite material can be obtained. In order to achieve thermal decomposition of the polymer in this case, the composition may be heated to a temperature higher than the thermal decomposition temperature of the polymer. More specifically, it is heated to a temperature higher than the thermal decomposition temperature of the polymer, and the polymer is further baked. At this time, it is fired to such an extent that the polymer remains in the composition. Thereby, a composite material can be obtained. For example, the thermal decomposition temperature of polystyrene is about 380 ° C. to 450 ° C., and the thermal decomposition temperature of polyglycidyl methacrylate is about 400 ° C. to 500 ° C.
　上記ポリマーの熱分解により複合材料を得ることができるのは、前述した理由によると考えられる。すなわち、黒鉛にグラフトしているポリマーが焼成されると、グラフト点に大きな応力が作用し、それによってグラフェン間の距離が拡がるためと考えられる。 The reason why the composite material can be obtained by thermal decomposition of the polymer is considered to be due to the above-described reason. That is, it is considered that when the polymer grafted on the graphite is baked, a large stress acts on the graft point, thereby increasing the distance between the graphenes.
　第１の加熱工程においては、上記第１の方法、第２の方法、及び第３の方法を、適宜選択して用いることができる。また、第１の加熱工程における加熱は、不活性ガス雰囲気下において行うものとする。 In the first heating step, the first method, the second method, and the third method can be appropriately selected and used. The heating in the first heating step is performed in an inert gas atmosphere.
　不活性ガスとしては、例えば、窒素、ヘリウム、アルゴン、炭酸ガスが挙げられる。なかでも、不活性ガスとしては、窒素であることが好ましい。また、酸素濃度は、好ましくは１％以下、より好ましくは０．１％以下である。この場合、得られる複合材料における薄片化黒鉛の欠陥をより一層少なくすることができる。そのため、複合材料の導電性をより一層高めることができる。 Examples of the inert gas include nitrogen, helium, argon, and carbon dioxide gas. Among these, the inert gas is preferably nitrogen. Further, the oxygen concentration is preferably 1% or less, more preferably 0.1% or less. In this case, the defects of exfoliated graphite in the obtained composite material can be further reduced. Therefore, the conductivity of the composite material can be further increased.
　（第２の加熱工程）
　第２の加熱工程においては、上記第１の加熱工程を経た組成物を、３００℃以上、６００℃以下の温度で加熱する。加熱時間としては、例えば、１０分以上、１８０分以下とすることができる。また、第２の加熱工程における加熱は、不活性ガス濃度が８５％以上、９９％以下、かつ酸素濃度が１％以上、１５％以下の雰囲気において行うものとする。 (Second heating step)
In the second heating step, the composition that has undergone the first heating step is heated at a temperature of 300 ° C. or higher and 600 ° C. or lower. As heating time, it can be 10 minutes or more and 180 minutes or less, for example. The heating in the second heating step is performed in an atmosphere having an inert gas concentration of 85% to 99% and an oxygen concentration of 1% to 15%.
　不活性ガスとしては、例えば、窒素、ヘリウム、アルゴン、炭酸ガスが挙げられる。なかでも、不活性ガスとしては、窒素であることが好ましい。なお、不活性ガス濃度は、好ましくは９０％以上、好ましくは９７％以下である。 Examples of the inert gas include nitrogen, helium, argon, and carbon dioxide gas. Among these, the inert gas is preferably nitrogen. The inert gas concentration is preferably 90% or more, and preferably 97% or less.
　また、酸素濃度は、好ましくは３％以上、好ましくは１０％以下である。酸素濃度が上記下限以上である場合、後述するように得られる複合材料の表面における樹脂を選択的により一層少なくすることができ、複合材料の導電性をより一層高めることができる。また、酸素濃度が上記上限以下である場合、得られる複合材料における薄片化黒鉛の欠陥をより一層少なくすることができ、複合材料の導電性をより一層高めることができる。 The oxygen concentration is preferably 3% or more, preferably 10% or less. When the oxygen concentration is at least the above lower limit, the resin on the surface of the composite material obtained can be selectively reduced as described later, and the conductivity of the composite material can be further enhanced. Moreover, when oxygen concentration is below the said upper limit, the defect of exfoliated graphite in the composite material obtained can be decreased further, and the electroconductivity of a composite material can be improved further.
　上記のように、本発明においては、第１の加熱工程（第１の方法、第２の方法、及び第３の方法から適宜選択して）で加熱することにより、組成物中に含まれるポリマーを熱分解して黒鉛に複合化することでポリマーの一部を残存させながら、黒鉛又は一次薄片化黒鉛が剥離され、複合材料を得ることができる。また、本発明では、第１の加熱工程において、不活性ガス雰囲気下で加熱するので、得られる複合材料における薄片化黒鉛の欠陥を少なくすることができる。そのため、複合材料の導電性を高めることができる。 As described above, in the present invention, the polymer contained in the composition is heated in the first heating step (selected appropriately from the first method, the second method, and the third method). The graphite or primary exfoliated graphite is peeled off while leaving a part of the polymer by thermally decomposing and compositing with graphite, whereby a composite material can be obtained. Moreover, in this invention, since it heats in inert gas atmosphere in a 1st heating process, the defect of exfoliated graphite in the composite material obtained can be decreased. Therefore, the conductivity of the composite material can be increased.
　さらに、本発明では、第２の加熱工程で、不活性ガス濃度及び酸素濃度が上記特定の範囲にある雰囲気下で加熱するので、複合材料の表面に占める樹脂の割合を選択的に小さくすることができる。従って、この点からも導電性を効果的に高めることができ、蓄電デバイスの出力特性などの電池特性を高めることができる。 Furthermore, in the present invention, in the second heating step, heating is performed in an atmosphere in which the inert gas concentration and the oxygen concentration are in the specific ranges, so that the ratio of the resin occupying the surface of the composite material is selectively reduced. Can do. Therefore, also from this point, conductivity can be effectively increased, and battery characteristics such as output characteristics of the electricity storage device can be improved.
　また、得られる複合材料には、樹脂が残存しており、比表面積が高められている。そのため、蓄電デバイスの容量を大きくすることができ、この点からも電池特性を高めることができる。 In the composite material obtained, the resin remains and the specific surface area is increased. Therefore, the capacity of the electricity storage device can be increased, and the battery characteristics can be improved from this point.
　このように、本発明の複合材料では、樹脂を残存させ比表面積を高めつつ、表面の樹脂量を少なくすることにより導電性が高められている。そのため、蓄電デバイスなどの電極材料に用いることにより、出力特性と容量の双方を大きくすることができる。 Thus, in the composite material of the present invention, the electrical conductivity is enhanced by reducing the amount of resin on the surface while increasing the specific surface area by leaving the resin. Therefore, both output characteristics and capacity can be increased by using the electrode material for an electricity storage device or the like.
　（他の変形例）
　なお、本発明においては、上記のようにラジカル重合性モノマーが重合しているポリマーが黒鉛又は一次薄片化黒鉛にグラフト化している構造を有する組成物中のポリマーを熱分解することにより複合材料を得ている。本発明では、さらに、他の方法により黒鉛を薄片化する工程を施してもよい。例えば、上記のように、複合材料を原料として用い、従来知られているような他の黒鉛の薄片化方法をさらに実施してもよい。あるいは、他の黒鉛の薄片化方法で得られた一次薄片化黒鉛を原料として本発明の複合材料の製造方法を実施してもよい。その場合においても、より一層比表面積の大きい複合材料を得ることができる。このような他の黒鉛の薄片化方法としては、例えば、電気化学的処理による黒鉛の薄片化方法、あるいは吸着－熱分解法を用いることができる。 (Other variations)
In the present invention, the composite material is obtained by pyrolyzing the polymer in the composition having a structure in which the polymer in which the radical polymerizable monomer is polymerized as described above is grafted to graphite or primary exfoliated graphite. It has gained. In this invention, you may give the process of exfoliating graphite by another method further. For example, as described above, the graphite may be further exfoliated as described above by using a composite material as a raw material. Or you may implement the manufacturing method of the composite material of this invention by using the primary exfoliated graphite obtained by the exfoliation method of the other graphite as a raw material. Even in that case, a composite material having a larger specific surface area can be obtained. As such another method for exfoliating graphite, for example, a method for exfoliating graphite by electrochemical treatment or an adsorption-pyrolysis method can be used.
　また、上記本発明の製造方法の一例では、加熱の際に熱分解性発泡剤が用いられていない。そのため、薄片化黒鉛の欠陥量を少なくすることができ、導電性をより一層高めることができる。もっとも、本発明においては、加熱の際に熱分解発泡剤が用いられていてもよい。 Further, in the example of the production method of the present invention, no thermally decomposable foaming agent is used during heating. Therefore, the amount of defects in exfoliated graphite can be reduced, and the conductivity can be further enhanced. However, in the present invention, a pyrolytic foaming agent may be used during heating.
　なお、上記本発明の製造方法の一例で得られた複合材料は、上述の樹脂残存型の部分剥離型薄片化黒鉛である。もっとも、本発明においては、薄片化黒鉛と樹脂とを別々に用意し、薄片化黒鉛と樹脂とを混練などの方法により複合化させることによって複合材料を得てもよい。 The composite material obtained by the example of the production method of the present invention is the above-mentioned resin-retained partially exfoliated graphite. However, in the present invention, exfoliated graphite and resin may be prepared separately, and exfoliated graphite and resin may be combined by a method such as kneading to obtain a composite material.
　次に、本発明の具体的な実施例及び比較例を挙げることにより本発明を明らかにする。なお、本発明は以下の実施例に限定されるものではない。 Next, the present invention will be clarified by giving specific examples and comparative examples of the present invention. In addition, this invention is not limited to a following example.
　（実施例１）
　膨張黒鉛（東洋炭素社製、商品名「ＰＦパウダー８」）１６ｇと、１％濃度のカルボキシメチルセルロース水溶液４８ｇおよび純水４８０ｇとを混合し、超音波破砕機（エスエムテー社製、商品名「ＵＨ－６００Ｓ」）を用いて、強度メモリ６で５時間の超音波処理を行った。これにより黒鉛が水に分散した黒鉛／水分散液を得た。 Example 1
16 g of expanded graphite (trade name “PF Powder 8” manufactured by Toyo Tanso Co., Ltd.), 48 g of 1% carboxymethylcellulose aqueous solution and 480 g of pure water were mixed, and an ultrasonic crusher (trade name “UH-” manufactured by SMT Co., Ltd.) was mixed. 600S "), and ultrasonic treatment was performed for 5 hours in the intensity memory 6. As a result, a graphite / water dispersion in which graphite was dispersed in water was obtained.
　このようにして得られた黒鉛／水分散液に対してポリエチレングリコール（三洋化成社製、商品名「ＰＥＧ－１５４０」）３２０ｇを添加し、ホモジナイザー（プライミクス社製、商品名「ＭＡＲＫＩＩ　Ｍｏｄｅｌ２．５」）を用いて８０００ｒｐｍ、３０分の攪拌処理により黒鉛と樹脂を複合化した。このようにして、ポリエチレングリコールが膨張黒鉛に吸着されている組成物を用意した。 320 g of polyethylene glycol (trade name “PEG-1540”, manufactured by Sanyo Chemical Co., Ltd.) was added to the graphite / water dispersion thus obtained, and a homogenizer (trade name “MARK II Model 2.5” manufactured by Primics Co., Ltd.) was added. ) And a composite of graphite and resin by stirring for 30 minutes at 8000 rpm. In this way, a composition in which polyethylene glycol was adsorbed on expanded graphite was prepared.
　次に、上記組成物を温度１５０℃で３時間加熱乾燥し、乾燥物を得た。その後、得られた乾燥物を、窒素雰囲気下（酸素濃度０．１％以下）で、３７０℃の温度となるまでさらに加熱し、３７０℃の温度で２時間維持し、第１の加熱工程を行った。続いて、第１の加熱工程を経た組成物を、窒素濃度９５％及び酸素濃度５％の雰囲気下で、４００℃の温度となるまでさらに加熱し、４００℃の温度で０．５時間維持し、第２の加熱工程を行った。第１の加熱工程及び第２の加熱工程を経て、上記乾燥物中のポリエチレングリコールを熱分解し、上記膨張黒鉛を剥離した。以上のようにして、樹脂残存型の部分剥離型薄片化黒鉛である複合材料を得た。 Next, the composition was heat-dried at a temperature of 150 ° C. for 3 hours to obtain a dried product. Thereafter, the obtained dried product is further heated to a temperature of 370 ° C. under a nitrogen atmosphere (oxygen concentration of 0.1% or less), maintained at a temperature of 370 ° C. for 2 hours, and the first heating step is performed. went. Subsequently, the composition subjected to the first heating step is further heated to a temperature of 400 ° C. in an atmosphere having a nitrogen concentration of 95% and an oxygen concentration of 5%, and is maintained at the temperature of 400 ° C. for 0.5 hour. A second heating step was performed. Through the first heating step and the second heating step, the polyethylene glycol in the dried product was pyrolyzed, and the expanded graphite was peeled off. As described above, a composite material which is a resin-retained partially exfoliated graphite was obtained.
　（比較例１）
　第２の加熱工程を実施しなかったこと以外は、実施例１と同様にして複合材料を得た。 (Comparative Example 1)
A composite material was obtained in the same manner as in Example 1 except that the second heating step was not performed.
　［評価］
　図２は、実施例１で得られた複合材料の倍率２０，０００倍の電界放出形走査電子顕微鏡（ＦＥ－ＳＥＭ）写真である。また、図３は、比較例１で得られた複合材料の倍率２０，０００倍の電界放出形走査電子顕微鏡（ＦＥ－ＳＥＭ）写真である。 [Evaluation]
FIG. 2 is a field emission scanning electron microscope (FE-SEM) photograph of the composite material obtained in Example 1 at a magnification of 20,000 times. FIG. 3 is a field emission scanning electron microscope (FE-SEM) photograph of the composite material obtained in Comparative Example 1 at a magnification of 20,000.
　なお、ＦＥ－ＳＥＭによる観察においては、クロスセクションポリンシャー（日本電子社製、品番「ＩＢ－０９０１０ＣＰ」）を用いて、複合材料及び第１の加熱工程のみを経た組成物をそれぞれ切削し、試料の断面とした。 In the observation with the FE-SEM, a cross section porinshire (manufactured by JEOL Ltd., product number “IB-09010CP”) was used to cut the composite material and the composition that had undergone only the first heating step, respectively. The cross section was taken.
　得られた試料の断面は、ＦＥ－ＳＥＭ（日立製作所社製、品番「Ｓ－４８００」）を用いて、加速電圧：３ｋＶ、信号：ＬＡ（Ｕｐｐｅｒ）、及び倍率：２０，０００倍の条件で測定した。図２及び図３では、このような条件で観察することにより、薄片化黒鉛（黒鉛）部分及び樹脂部分を判別した。具体的に、図２及び図３において、白色で見える部分が黒鉛部分であり、それ以外のグレー部分が樹脂部分である。 The cross section of the obtained sample was measured using FE-SEM (manufactured by Hitachi, Ltd., product number “S-4800”) under the conditions of acceleration voltage: 3 kV, signal: LA (Upper), and magnification: 20,000 times. It was measured. In FIGS. 2 and 3, by observing under such conditions, the exfoliated graphite (graphite) portion and the resin portion were discriminated. Specifically, in FIGS. 2 and 3, the portion that appears white is the graphite portion, and the other gray portion is the resin portion.
　図２及び図３の比較より、第２の加熱工程を経た複合材料の図２では、第１の加熱工程のみを経た（第２の加熱工程を経ていない）組成物の図３と比較して、薄片化黒鉛（黒鉛）部分の表面における樹脂量が少なくなっていることがわかる。 2 and 3, the composite material that has undergone the second heating step is compared with FIG. 3 of the composition that has undergone only the first heating step (not through the second heating step). It can be seen that the amount of resin on the surface of the exfoliated graphite (graphite) portion is reduced.
　また、このようにして観察した画像において、上記の特殊信号で得られたコントラストから黒鉛部分と樹脂部分とを区別することにより、試料の最表面部の長さ及び最表面部において樹脂で覆われている部分の長さを測定した。そして、得られた最表面部の長さに対する最表面部において樹脂で覆われている部分の長さの比から、複合材料の表面に占める樹脂の割合（Ａ）％を求めた。なお、表面に占める樹脂の割合（Ａ）％を求めるに際しては、試料の任意の箇所を上記クロスセクションポリンシャーで試料断面を作製の上、上記ＦＥ－ＳＥＭの特定条件にて断面観察し、粒子断面における粒子最表面部を目視で１０μｍ以上観察し、黒鉛部分と樹脂部分を判別した。観察した表面長さに対する樹脂と判別した長さの割合から（Ａ）％を求めた。なお、比較のため、第１の加熱工程のみを経た（第２の加熱工程を経ていない）比較例１についても同様にして表面に占める樹脂の割合（Ａ）％を求めた。 Moreover, in the image observed in this way, the length of the outermost surface portion of the sample and the outermost surface portion are covered with the resin by distinguishing the graphite portion and the resin portion from the contrast obtained by the special signal. The length of the part is measured. Then, the ratio (A)% of the resin in the surface of the composite material was determined from the ratio of the length of the portion covered with the resin in the outermost surface portion to the obtained length of the outermost surface portion. When determining the ratio (A)% of the resin in the surface, a cross section of the sample was prepared with the cross section porincher at any location of the sample, and the cross section was observed under the specific conditions of the FE-SEM. The particle outermost surface portion in the cross section was visually observed to be 10 μm or more, and the graphite portion and the resin portion were distinguished. (A)% was calculated | required from the ratio of the length discriminate | determined from resin with respect to the observed surface length. For comparison, the ratio (A)% of the resin occupying the surface was similarly obtained for Comparative Example 1 that passed through only the first heating step (not passed through the second heating step).
　また、熱分析測定により複合材料の全体に占める樹脂の割合（Ｂ）重量％を求めた。熱分析測定は、示差熱熱重量同時測定装置（ＴＧ－ＤＴＡ、示差熱熱重量同時測定装置（エスアイアイ・ナノテクノロジー社製、商品名「ＴＧ／ＤＴＡ６３００」））を用いて行った。この示差熱熱重量同時測定装置を用いて得られる示差熱分析結果から薄片化黒鉛と樹脂の燃焼温度を分離し、それに伴う熱重量変化から複合材料の全体に占める樹脂の割合（Ｂ）重量％を求めた。なお、比較のため、第１の加熱工程のみを経た（第２の加熱工程を経ていない）比較例１についても同様にして組成物全体に占める樹脂の割合（Ｂ）重量％を求めた。 Also, the ratio (B) weight% of the resin in the entire composite material was determined by thermal analysis measurement. The thermal analysis measurement was performed using a differential thermothermogravimetric simultaneous measurement device (TG-DTA, differential thermothermal gravimetric simultaneous measurement device (trade name “TG / DTA6300” manufactured by SII Nanotechnology)). Separating the combustion temperature of exfoliated graphite and resin from the differential thermal analysis results obtained using this differential thermothermal weight simultaneous measurement device, and the proportion of the resin in the entire composite material (B) wt% Asked. For comparison, the ratio (B) wt% of the resin in the entire composition was similarly determined for Comparative Example 1 that passed through only the first heating step (not passed through the second heating step).
　また、得られた表面に占める樹脂の割合（Ａ）％及び全体に占める樹脂の割合（Ｂ）重量％から、比（Ａ／Ｂ）を求めた。結果を下記の表１に示す。 Also, the ratio (A / B) was determined from the ratio (A)% of the resin occupying the surface and the ratio (B)% by weight of the resin occupying the whole surface. The results are shown in Table 1 below.
　（実施例２）
　第１の加熱工程における加熱時間を、２時間から１時間に変更したこと以外は、実施例１と同様にして複合材料を得た。 (Example 2)
A composite material was obtained in the same manner as in Example 1 except that the heating time in the first heating step was changed from 2 hours to 1 hour.
　（実施例３）
　第１の加熱工程における加熱時間を、２時間から４時間に変更したこと以外は、実施例１と同様にして複合材料を得た。 Example 3
A composite material was obtained in the same manner as in Example 1 except that the heating time in the first heating step was changed from 2 hours to 4 hours.
　（比較例２）
　第２の加熱工程を実施しなかったこと以外は、実施例２と同様にして複合材料を得た。 (Comparative Example 2)
A composite material was obtained in the same manner as in Example 2 except that the second heating step was not performed.
　（実施例４）
　膨張黒鉛（東洋炭素社製、商品名「ＰＦパウダー８」）１ｇに、ポリエチレングリコール（三洋化成社製、商品名「ＰＥＧ－６００」）２３４ｇを添加し、ホモジナイザー（プライミクス社製、商品名「ＭＡＲＫＩＩ　Ｍｏｄｅｌ２．５」）を用いて８０００ｒｐｍ、３０分の攪拌処理により黒鉛と樹脂を複合化した。このようにして、ポリエチレングリコールが膨張黒鉛に吸着されている組成物を用意した。 Example 4
234 g of polyethylene glycol (trade name “PEG-600” manufactured by Sanyo Kasei Co., Ltd.) is added to 1 g of expanded graphite (trade name “PF Powder 8” manufactured by Toyo Tanso Co., Ltd.), and a homogenizer (trade name “MARK II” manufactured by Primix Co., Ltd.) is added. Graphite and resin were compounded by stirring at 8000 rpm for 30 minutes using Model 2.5 "). In this way, a composition in which polyethylene glycol was adsorbed on expanded graphite was prepared.
　次に、上記組成物に顆粒状の炭酸カリウム４７０ｇを添加し、よく攪拌して均一化した。その後、得られた乾燥物を、窒素雰囲気下（酸素濃度０．１％以下）で、３７０℃の温度となるまでさらに加熱し、３７０℃の温度で１時間維持し、第１の加熱工程を行った。続いて、第１の加熱工程を経た組成物を、窒素雰囲気下（酸素濃度０．１％以下）で、９００℃の温度となるまでさらに加熱し、９００℃の温度で０．５時間維持し、第２の加熱工程を行った。第１の加熱工程及び第２の加熱工程を経て、上記乾燥物中のポリエチレングリコールを熱分解し、上記膨張黒鉛を剥離した。その後、水洗にて炭酸カリウムを除去し、部分剥離型薄片化黒鉛である複合材料を得た。 Next, 470 g of granular potassium carbonate was added to the above composition, and the mixture was stirred well and homogenized. Thereafter, the obtained dried product is further heated to a temperature of 370 ° C. under a nitrogen atmosphere (oxygen concentration of 0.1% or less), maintained at a temperature of 370 ° C. for 1 hour, and the first heating step is performed. went. Subsequently, the composition that has undergone the first heating step is further heated to a temperature of 900 ° C. in a nitrogen atmosphere (oxygen concentration of 0.1% or less) and maintained at a temperature of 900 ° C. for 0.5 hours. A second heating step was performed. Through the first heating step and the second heating step, the polyethylene glycol in the dried product was pyrolyzed, and the expanded graphite was peeled off. Thereafter, potassium carbonate was removed by washing with water to obtain a composite material that was partially exfoliated graphite.
　［評価］
　実施例２～４及び比較例１～２について、実施例１と同様にして、表面に占める樹脂の割合（Ａ）％及び全体に占める樹脂の割合（Ｂ）重量％を得て、比（Ａ／Ｂ）を求めた。結果を下記の表１に示す。なお、表１では、表面に露出している樹脂及び薄片化黒鉛それぞれの割合を表面（ＦＥ－ＳＥＭ）と記載している。 [Evaluation]
For Examples 2 to 4 and Comparative Examples 1 and 2, the ratio (A)% of the resin occupying the surface and the ratio (B) wt% of the resin occupying the whole were obtained in the same manner as in Example 1, and the ratio (A / B). The results are shown in Table 1 below. In Table 1, the ratio of the resin exposed on the surface and the exfoliated graphite is indicated as the surface (FE-SEM).
　また、実施例３～４及び比較例１～２の複合材料について、導電率を測定した。結果を下記の表１に示す。以下、導電率の測定方法について、図４を参照して説明する。
　まず、図４に示すように、電極６を備える容器４に試料５を１．０ｇ充填した。次に、所定の圧力で試料５を圧縮したときの電気抵抗値を、電極６を介して４探針法により測定した。それによって、試料の導電率を測定した。導電率の測定は、粉体抵抗装置（三菱化学株式会社製、品番：ＰＤ－５１）を用いて行った。 The electrical conductivity of the composite materials of Examples 3 to 4 and Comparative Examples 1 and 2 was measured. The results are shown in Table 1 below. Hereinafter, a method for measuring conductivity will be described with reference to FIG.
First, as shown in FIG. 4, 1.0 g of the sample 5 was filled in the container 4 including the electrode 6. Next, the electrical resistance value when the sample 5 was compressed at a predetermined pressure was measured through the electrode 6 by the four-probe method. Thereby, the conductivity of the sample was measured. The conductivity was measured using a powder resistance device (Mitsubishi Chemical Corporation, product number: PD-51).
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
１…複合材料
１ａ…外周縁
２…薄片化黒鉛
３…樹脂
４…容器
５…試料
６…電極 DESCRIPTION OF SYMBOLS 1 ... Composite material 1a ... Outer periphery 2 ... Exfoliated graphite 3 ... Resin 4 ... Container 5 ... Sample 6 ... Electrode

Claims (5)

  1. 　薄片化黒鉛と樹脂とを含む、複合材料であって、
    　前記複合材料の表面に占める樹脂の割合（Ａ）％と、前記複合材料の全体に占める樹脂の割合（Ｂ）重量％との比（Ａ／Ｂ）が、１．０以下である、複合材料。     A composite material comprising exfoliated graphite and a resin,
    The composite material in which the ratio (A / B) of the ratio (A)% of the resin occupying the surface of the composite material to the ratio (B) wt% of the resin occupying the entire composite material is 1.0 or less. .
  2. 　前記複合材料の表面に占める樹脂の割合（Ａ）％が、４０．０％以下である、請求項１に記載の複合材料。 The composite material according to claim 1, wherein a ratio (A)% of the resin occupying the surface of the composite material is 40.0% or less.
  3. 　前記複合材料の全体に占める樹脂の割合（Ｂ）重量％が、２．０重量％以上、８０．０重量％以下である、請求項１または２に記載の複合材料。 The composite material according to claim 1 or 2, wherein the ratio (B) wt% of the resin to the entire composite material is 2.0 wt% or more and 80.0 wt% or less.
  4. 　前記薄片化黒鉛が、グラファイト構造を有し、部分的にグラファイトが剥離している構造を有する、部分剥離型薄片化黒鉛である、請求項１～３のいずれか１項に記載の複合材料。 The composite material according to any one of claims 1 to 3, wherein the exfoliated graphite is a partially exfoliated exfoliated graphite having a graphite structure and a structure in which the graphite is partially exfoliated.
  5. 　請求項１～４のいずれか１項に記載の複合材料の製造方法であって、
    　黒鉛または一次薄片化黒鉛と、ポリマーとを含み、前記ポリマーが前記黒鉛または一次薄片化黒鉛に固定されている組成物を用意する工程と、
    　前記組成物を、不活性ガス雰囲気下において、５０℃以上、６００℃以下の温度で加熱する、第１の加熱工程と、
    　前記第１の加熱工程の後に、前記組成物を、不活性ガス濃度が８５％以上、９９％以下、かつ酸素濃度が１％以上、１５％以下の雰囲気下において、３００℃以上、６００℃以下の温度で加熱する、第２の加熱工程と、を備え、
    　前記第１の加熱工程及び第２の加熱工程において、前記組成物中のポリマーを熱分解することにより、前記ポリマーの一部を残存させながら、前記黒鉛または一次薄片化黒鉛を剥離する、複合材料の製造方法。     A method for producing a composite material according to any one of claims 1 to 4,
    Providing a composition comprising graphite or primary exfoliated graphite and a polymer, wherein the polymer is fixed to the graphite or primary exfoliated graphite;
    A first heating step of heating the composition at a temperature of 50 ° C. or higher and 600 ° C. or lower in an inert gas atmosphere;
    After the first heating step, the composition is heated to 300 ° C. or higher and 600 ° C. or lower in an atmosphere having an inert gas concentration of 85% to 99% and an oxygen concentration of 1% to 15%. A second heating step of heating at a temperature of
    In the first heating step and the second heating step, a composite material that exfoliates the graphite or primary exfoliated graphite while thermally decomposing the polymer in the composition while leaving a part of the polymer. Manufacturing method.
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