WO2020195974A1 - Liquide de dispersion de nanocarbone, son procédé de production, agent de dispersion de nanocarbone, et matériau de protection contre les ondes électromagnétiques - Google Patents

Liquide de dispersion de nanocarbone, son procédé de production, agent de dispersion de nanocarbone, et matériau de protection contre les ondes électromagnétiques Download PDF

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WO2020195974A1
WO2020195974A1 PCT/JP2020/011197 JP2020011197W WO2020195974A1 WO 2020195974 A1 WO2020195974 A1 WO 2020195974A1 JP 2020011197 W JP2020011197 W JP 2020011197W WO 2020195974 A1 WO2020195974 A1 WO 2020195974A1
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nanocarbon
dispersion
mass
dispersion liquid
electromagnetic wave
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Japanese (ja)
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篤 田村
彰太 福島
英秋 込山
光次 田中
純司 根本
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北越コーポレーション株式会社
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/168—After-treatment
    • C01B32/174—Derivatisation; Solubilisation; Dispersion in solvents
    • 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
    • C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
    • C08L1/02—Cellulose; Modified cellulose

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  • the present disclosure relates to a nanocarbon dispersion liquid containing nanocarbon and cellulose nanocrystals, a method for producing the same, and a nanocarbon dispersant containing cellulose nanocrystals.
  • nanocarbons such as carbon nanotubes and nanographenes have high surface energy, a strong van der Waals force acts on the surface of the nanocarbons even if the nanocarbons are dispersed in the medium. Therefore, nanocarbons tend to aggregate. Therefore, it is required to stably disperse nanocarbon.
  • a method for dispersing nanocarbons a method for dispersing carbon nanotubes in which water is added to a crushed mixture obtained by crushing monosaccharide or low sugar crystals, carbon nanotubes, and a nonionic or anionic surfactant is disclosed. (See, for example, Patent Document 1). Further, a method for dispersing carbon nanotubes using carboxymethyl cellulose as a dispersant is disclosed (see, for example, Patent Document 2). Further, a method for dispersing carbon nanotubes using cellulose nanofibers as a dispersant is disclosed (see, for example, Patent Document 3). Further, a method of dispersing multi-walled carbon nanotubes having an average fiber outer diameter in the range of 50 to 110 nm with sodium carboxymethyl cellulose is disclosed (see, for example, Patent Document 4).
  • Patent Document 1 has a problem that only a low-concentration carbon nanotube dispersion liquid having an upper limit value of about 5 g / L can be obtained.
  • a surfactant since a surfactant is used, the dispersion liquid tends to have a problem of foaming.
  • the viscosity of the dispersion tends to be high, and when it is attempted to be produced using a disperser, there is a problem that the disperser is blocked by the viscous dispersion.
  • Patent Document 3 since cellulose nanofibers are used, the viscosity of the dispersion tends to be high, and the concentration of carbon nanotubes in the examples is only 0.05% by mass at the maximum.
  • the method disclosed in Patent Document 4 can be applied only to multi-walled carbon nanotubes having a specific fiber diameter, and it is difficult to stably disperse carbon nanotubes having a fiber diameter of 50 nm or less and a small fiber diameter (large specific surface area). Met.
  • the present disclosure is to obtain (1) a dispersion liquid in which nanocarbons such as carbon nanotubes are stably dispersed and have fluidity, a method for producing the dispersion liquid, and (2) a dispersion liquid. It is an object of the present invention to provide a nanocarbon dispersant to be added and (3) an electromagnetic wave shielding material.
  • the nanocarbon dispersion liquid according to the present invention is characterized by containing nanocarbon, cellulose nanocrystals, and a dispersion medium.
  • the concentration of the nanocarbon is preferably 1% by mass or more. Even if the concentration of nanocarbon is 1% by mass or more, the stability and fluidity of the nanocarbon dispersion can be improved.
  • the mass-based content ratio (nanocarbon: cellulose nanocrystal) of the nanocarbon and the cellulose nanocrystal is preferably 1: 0.1 to 1:10.
  • the stability and fluidity of the nanocarbon dispersion can be improved.
  • the concentration of the nanocarbon is 1% by mass or more and 4% by mass or less, and the total concentration of the nanocarbon and the cellulose nanocrystal exceeds 1% by mass and 15% by mass.
  • the following is preferable. Even if the concentration of nanocarbon is high, the stability and fluidity of the nanocarbon dispersion can be improved.
  • the dispersion medium is a polar solvent.
  • a nanocarbon dispersion having higher dispersibility can be obtained.
  • the polar solvent is alcohols, ketones, amides, water, or a mixture thereof.
  • a nanocarbon dispersion having even higher dispersibility can be obtained.
  • the method for producing a nanocarbon dispersion according to the present invention is characterized in that a mixed solution containing nanocarbon, cellulose nanocrystals, and a dispersion medium is dispersed by a disperser.
  • the mixed solution is a mixed solution prepared by adding the cellulose nanocrystals to the dispersion medium, stirring the mixture, and then adding the nanocarbons.
  • the compatibility between the dispersion medium and the nanocarbon is less likely to be impaired, and the nanocarbon is less likely to float on the dispersion medium.
  • the cellulose nanocrystal is a spray-dried product. It is possible to easily adjust the concentration of cellulose nanocrystals.
  • the disperser is a homogenizer. A nanocarbon dispersion with more stable dispersibility can be obtained.
  • the nanocarbon dispersant according to the present invention is characterized by containing cellulose nanocrystals.
  • the electromagnetic wave shielding material according to the present invention has a base material and a coating layer provided on the surface of the base material, and the coating layer contains nanocarbon and cellulose nanocrystals in a mutually mixed state. It is characterized by.
  • the electromagnetic wave shielding material according to the present invention has the shape of a film, and the film is characterized by containing nanocarbon and cellulose nanocrystals in a mutually mixed state.
  • a dispersion liquid in which nanocarbons such as carbon nanotubes are stably dispersed and has fluidity and a method for producing the dispersion liquid and (2) nanocarbon dispersion added to obtain the dispersion liquid.
  • Agents and (3) electromagnetic wave shielding materials can be provided.
  • Nanocarbon dispersion liquid contains nanocarbon, cellulose nanocrystals, and a dispersion medium.
  • the nanocarbon refers to nanocarbon such as carbon nanotubes (hereinafter, also referred to as CNT), fullerenes, graphene nanoplatelets by a CVD method or a mechanical peeling method.
  • CNT carbon nanotubes
  • These nanocarbons may have a single layer or a structure having two or more layers.
  • these nanocarbon dispersions will be described, but the CNT dispersion will be described in detail below as a representative example.
  • CNT Since CNT has an intermediate conductivity between that of fullerene and that of graphene, it has a feature that it is easy to use industrially.
  • the CNT those having different fiber lengths, fiber diameters and BET specific surface areas are used depending on the application.
  • the fiber length range is 1 ⁇ m to 500 ⁇ m
  • the fiber diameter range is 0.4 nm to 150 nm.
  • the range of BET specific surface area is 10 m 2 / g to 2500 m 2 / g.
  • those having a small specific surface area have a large fiber diameter and are relatively easy to disperse, but as the specific surface area increases (as the fiber diameter decreases), dispersion tends to become difficult.
  • Some CNTs have a functional group such as a carboxyl group introduced on the surface in order to improve dispersibility, but even in such a CNT, as the specific surface area increases (as the fiber diameter decreases), the CNTs disperse. Tends to be difficult. Specifically, when the BET specific surface area of the CNT into which a functional group such as a carboxyl group has been introduced exceeds 100 m 2 / g, it may be difficult to sufficiently disperse the CNT with a conventional dispersant such as carboxymethyl cellulose. In particular, it has become difficult to obtain a dispersion having a high concentration, and it has been difficult to obtain a dispersion having a CNT concentration of more than 1% by mass.
  • a functional group such as a carboxyl group introduced on the surface in order to improve dispersibility, but even in such a CNT, as the specific surface area increases (as the fiber diameter decreases), the CNTs disperse. Tends to be difficult. Specifically, when the B
  • CNTs are dispersed by using cellulose nanocrystals (hereinafter, also referred to as CNC) as a dispersant.
  • the CNC is an acicular crystal obtained by subjecting a plant-derived cellulose fiber, particularly a wood-derived cellulose fiber, to a chemical treatment such as acid hydrolysis.
  • the number average fiber diameter of CNC is 4 nm to 70 nm
  • the number average fiber length is 25 nm to 1000 nm
  • the BET specific surface area is 100 m 2 / g to 500 m 2 / g
  • the aspect ratio is less than 50. is there.
  • the aspect ratio is a dimensionless number obtained by dividing the number average fiber length by the number average fiber diameter.
  • CNF Cellulose nanocrystals are also called cellulose nanowhiskers.
  • CNC cellulose nanofibers
  • CNF has a number average fiber diameter equivalent to that of CNC, but has a fiber length longer than that of CNC. It refers to a fibrous material having a fiber length of 10 times or more, generally 5 ⁇ m or more, and a CNC aspect ratio of more than 100.
  • CNC is an acicular crystal and does not have a large aspect ratio like a fibrous material such as CNF.
  • the major axis of CNC is also referred to as fiber length
  • the minor axis is also referred to as fiber diameter.
  • CNC having a fiber length shorter than that of CNF is suitable.
  • the number average fiber length of the CNC is preferably 25 nm to 500 nm, more preferably 100 nm to 400 nm, and most preferably 200 nm to 300 nm. If the average fiber length is less than 25 nm, the CNCs may aggregate with each other. If the number average fiber length exceeds 500 nm, the viscosity of the dispersion liquid tends to increase, and the fluidity of the dispersion liquid tends to be impaired when the concentration of CNTs is increased.
  • the viscosity measured with a B-type viscometer (20 ° C., 60 rpm, rotation time 1 minute) is 100 mPa ⁇ s or less in the case of a 2% by mass aqueous solution of CNC, and the fluidity is good, but CNF 2
  • the mass% aqueous solution often exceeds 10,000 mPa ⁇ s, resulting in impaired fluidity.
  • the number average fiber diameter of the CNC is preferably 5 nm to 60 nm, more preferably 10 nm to 50 nm, and most preferably 20 nm to 30 nm. If the average fiber diameter is less than 5 nm, the CNCs may aggregate with each other. If the number average fiber diameter exceeds 60 nm, the viscosity of the dispersion liquid may increase and the fluidity may decrease.
  • BET specific surface area of the CNC is preferably 120m 2 / g ⁇ 400m 2 / g, more preferably 150m 2 / g ⁇ 300m 2 / g, and most preferably 175m 2 / g ⁇ 250m 2 / g. If the BET specific surface area is less than 120 m 2 / g, the viscosity of the dispersion may increase and the fluidity may decrease. If the BET specific surface area exceeds 400 m 2 / g, the viscosity of the dispersion becomes high, and CNCs may aggregate with each other.
  • the aspect ratio of the CNC is preferably 5 to 40, more preferably 10 to 30, and most preferably 15 to 25. If the aspect ratio is less than 5, the CNCs may aggregate with each other. If the aspect ratio exceeds 40, the fluidity of the dispersion liquid when the CNT concentration is increased may decrease.
  • the number average fiber diameter and number average fiber length of CNC can be calculated according to the following. Using a transmission electron microscope (TEM, Transmission Electron Microscope) or a scanning electron microscope (SEM, Scanning Electron Microscope) on the surface of the CNC, at least three images of the CNC surface where the fields of view do not overlap are taken. To do. For the obtained image, two random axes are drawn vertically and horizontally for each image, and the fiber diameter and fiber length of the fibers intersecting the axes are visually read. At this time, the magnification is 5,000 times, 10,000 times, or 50,000 times depending on the size of the constituent fibers. The condition for the number of fibers intersecting the two axes is 20 or more.
  • TEM Transmission Electron Microscope
  • SEM Scanning Electron Microscope
  • CNC prepared by a chemical method such as acid hydrolysis using a strong acid with sulfuric acid, hydrochloric acid, hydrobromic acid or the like can be used for an aqueous suspension or slurry of cellulose fibers.
  • the strong acid is preferably sulfuric acid.
  • Negative charge is given by adding a sulfate ester group to the surface by hydrodispersing with sulfuric acid, and since the sulfate ester group has a large molecular weight, it also causes steric hindrance and has a large ability to disperse CNT. It is presumed that it will be.
  • the degree of polymerization of CNC is not particularly limited, but is preferably 100 to 500, and more preferably 200 to 400. If the degree of polymerization is less than 100, the dispersibility of CNTs may decrease. If the degree of polymerization exceeds 500, the viscosity of the dispersion liquid may increase and the fluidity may decrease.
  • CNT dispersion The details of the CNT dispersion have been described as a typical example of the nanocarbon dispersion, but even if the nanocarbon is another nanocarbon such as fullerene or graphene nanoplatelet, it is as good as the case of CNT. Nanocarbon dispersion can be obtained.
  • nanocarbons such as CNTs are stably dispersed in a dispersion medium.
  • CNTs having a BET specific surface area of 100 m 2 / g or more for example, CNTs having a BET specific surface area of 100 to 1000 m 2 / g can be stably dispersed.
  • the fiber diameter of CNTs having a BET specific surface area of 100 to 1000 m 2 / g is 30 nm or less, and many CNTs having such a fiber diameter are flexible and have excellent conductivity.
  • the concentration of nanocarbon is preferably 1% by mass or more. Even if the concentration of nanocarbon is 1% by mass or more, the stability and fluidity of the dispersion liquid of nanocarbon can be improved.
  • the content ratio contains more CNC than 1:10
  • the amount of nanocarbon is relatively small with respect to CNC, so that the effect of improving the dispersibility and stability of the nanocarbon dispersion has reached a plateau.
  • the upper limit of the concentration of nanocarbon is, for example, 4% by mass from the viewpoint of dispersibility.
  • the total concentration of nanocarbon and cellulose nanocrystals is preferably more than 1% by mass and 15% by mass or less. More preferably, it is 1.5% by mass or more and 13% by mass or less. Most preferably, it is 1.8% by mass or more and 5% by mass or less. If this total concentration is 1% by mass or less, nanocarbon may not be dispersed. If this total concentration exceeds 15% by mass, the viscosity of the dispersion liquid may increase and the fluidity may decrease.
  • the concentration of nanocarbon is 1% by mass or more and 4% by mass or less, and the total concentration of nanocarbon and cellulose nanocrystals is more than 1% by mass and 15% by mass or less. It is preferable to have. More preferably, the concentration of nanocarbon is 1% by mass or more and 3.5% by mass or less, and the total concentration of nanocarbon and cellulose nanocrystal is 1.5% by mass or more and 13% by mass or less. Most preferably, the concentration of nanocarbon is 1% by mass or more and 3% by mass or less, and the total concentration of nanocarbon and cellulose nanocrystal is 1.8% by mass or more and 5% by mass or less. Even if the concentration of nanocarbon is high, the stability and fluidity of the nanocarbon dispersion can be improved.
  • the dispersion medium can be arbitrarily selected depending on the intended use, but in order to fully exert the dispersion effect of CNC, it is preferable that the dispersion medium is a polar solvent in the nanocarbon dispersion liquid according to the present embodiment. ..
  • the polar solvent is preferably alcohols such as methanol and ethanol; ketones such as acetone and methyl ethyl ketone, amides such as N-methylpyrrolidone, water, or a mixture thereof. .. Water is particularly preferable. A nanocarbon dispersion having even higher dispersibility can be obtained.
  • the nanocarbon dispersion can contain various additives as long as the desired effect of the present invention is not impaired.
  • Additives include, for example, antioxidants, heat stabilizers, light stabilizers, UV absorbers, pigments, colorants, foaming agents, antistatic agents, flame retardants, lubricants, softeners, tackifiers, plasticizers, mold release agents. Agents, deodorants, fragrances or combinations thereof. Care must be taken when adding these additives, as they can affect the properties of nanocarbons.
  • the nanocarbon dispersion liquid according to the present embodiment can be applied to a substrate such as a film, dried and formed into a film, and the solvent can be directly removed from the dispersion liquid or put into a poor solvent.
  • a carbon nanotube / cellulose nanocrystal composite material can also be obtained by precipitating the solid content, filtering and drying.
  • the surfactant include a surfactant having a defoaming effect, a surfactant having a dispersing effect, and a surfactant having a viscosity adjusting effect.
  • the surfactant having a dispersing effect is used. It is preferable not to contain it. Surfactants with a dispersing effect can cause foaming.
  • the method for producing a nanocarbon dispersion liquid according to the present embodiment is characterized in that a mixed liquid containing nanocarbon, cellulose nanocrystals, and a dispersion medium is dispersed by a disperser.
  • CNC includes, for example, a slurry product dispersed in water and a spray-dried product obtained by drying the slurry product, both of which can be used.
  • the CNC is a spray-dried product.
  • CNC can be dispersed in water relatively easily even if it is a dried product, so that the concentration can be easily adjusted by using the dried product.
  • the order of addition of nanocarbon and CNC to the dispersion medium is not particularly limited, but in the method for producing a nanocarbon dispersion liquid according to the present embodiment, the mixed liquid simultaneously adds nanocarbon and CNC to the dispersion medium. It is preferable that the mixture is prepared by adding CNC to a dispersion medium and stirring, and then adding nanocarbon. Since nanocarbon has strong hydrophobicity, when the dispersion medium is water, if it is first added to the dispersion medium alone, it may float on the dispersion medium and easily impair compatibility.
  • the disperser used for the dispersion treatment is not particularly limited, and various known mechanical dispersion treatment machines can be used.
  • a stirrer equipped with an agitator, an ultrasonic disperser, a high shear stirrer, a biomixer or a homogenizer can be used.
  • Two or more kinds of these dispersers may be used in combination.
  • the mixed solution is pre-dispersed with an ultrasonic disperser and then dispersed with a homogenizer
  • the mixed solution is pre-dispersed with a biomixer, and then dispersed with a homogenizer. Dispersion processing of steps or more may be performed.
  • the disperser is a homogenizer.
  • the homogenizer includes, for example, an ultrasonic type, a stirring type, and a high pressure type, and a high pressure type, and a high pressure type homogenizer (high pressure homogenizer) is preferable.
  • the water jet method is preferable.
  • a water jet type high pressure homogenizer for example, there is Starburst (registered trademark) manufactured by Sugino Machine Limited.
  • the pressure homogenized dispersion treatment condition is preferably a pressure of 100 to 250 MPa and 1 to 10 passes. A nanocarbon dispersion cannot be obtained without dispersion treatment. If the pressure is less than 100 MPa, the dispersion may be insufficient. If the pressure exceeds 250 MPa or the number of passes exceeds 10, the dispersion does not proceed and the high temperature of the dispersion liquid may rise.
  • the nanocarbon dispersant is an agent for dispersing nanocarbon.
  • the nanocarbon dispersant according to the present embodiment contains cellulose nanocrystals.
  • Examples of the form of the nanocarbon dispersant include a slurry product in which cellulose nanocrystals are dispersed in water (hereinafter referred to as Form L), and a spray-dried product of cellulose nanocrystals obtained by drying the slurry product (hereinafter referred to as Form L).
  • Form L a slurry product in which cellulose nanocrystals are dispersed in water
  • Form L a spray-dried product of cellulose nanocrystals obtained by drying the slurry product
  • the nanocarbon dispersion liquid in which the dispersion medium is water can be easily prepared by adding the nanocarbon to the slurry product in the form L.
  • the form of use is, for example, adding nanocarbon and the nanocarbon dispersant to the dispersion medium at the same time, or in a liquid in which the nanocarbon is dispersed in the dispersion medium.
  • Nanocarbon dispersants may be added.
  • the dispersion medium is water, it is preferable to add the nanocarbon and the nanocarbon dispersant to the dispersion medium at the same time from the viewpoint of the hydrophobicity of the nanocarbon.
  • the nanocarbon dispersant is of form N, by adding nanocarbon to the dispersion of form N, a nanocarbon dispersion in which the dispersion medium is a dispersion medium other than water can be easily prepared.
  • the electromagnetic wave shielding material having a base material and a coating layer
  • the electromagnetic wave shielding material according to the present embodiment has a base material and a coating layer provided on the surface of the base material, and the coating layer contains nanocarbon and cellulose nanocrystals in a mutually mixed state. ..
  • the base material is, for example, a plate or non-woven fabric made of paper, rubber, or resin.
  • the material of the base material can be changed according to the form of the electromagnetic wave shielding material.
  • the base material has a single layer or a plurality of layers.
  • a form of the plurality of layers for example, there is a paper in which a pigment coating layer is provided on a high-quality paper which is a support, or a laminated paper which is made by laminating.
  • the thickness of the coating layer is preferably 0.1 ⁇ m to 15.0 ⁇ m, more preferably 2.0 ⁇ m to 10.0 ⁇ m, and further preferably 3.5 ⁇ m to 5.0 ⁇ m. If it is less than 0.1 ⁇ m, the electromagnetic wave shielding property of the electromagnetic wave shielding material may not be sufficiently obtained. If it is larger than 15.0 ⁇ m, it may be difficult to prepare an electromagnetic wave shielding material.
  • the dispersion liquid will be impregnated into the base material. Then, when the dispersion medium of the dispersion liquid evaporates, a coating layer is formed on the inner wall of the base material. In this case, even if the thickness of the coating layer is small, there is a possibility that the electromagnetic wave shielding property can be imparted if the base material is sufficiently impregnated with the dispersion liquid. For example, when the dispersion liquid permeates substantially uniformly in the thickness direction of the base material and the permeation depth into the base material exceeds 10.0 ⁇ m, electromagnetic wave shielding property can be imparted even if the thickness of the coating layer is small. there is a possibility.
  • the depth at which the coating layer is present is preferably 1.0 ⁇ m to 15.0 ⁇ m, more preferably 2.0 ⁇ m to 10.0 ⁇ m.
  • the nanocarbons in the coating layer are unevenly distributed and the cellulose nanocrystals are unevenly distributed, the nanocarbons are uniformly distributed, and the cellulose nanocrystals are unevenly distributed.
  • a state a state in which nanocarbons are unevenly distributed and cellulose nanocrystals are uniformly distributed, or a state in which nanocarbons are uniformly distributed and cellulose nanocrystals are uniformly distributed.
  • the nanocarbons in the coating layer are uniformly distributed and the cellulose nanocrystals are uniformly distributed.
  • An electromagnetic wave shielding material having a high electromagnetic wave shielding property can be obtained.
  • the electromagnetic wave shielding material can be produced by applying a nanocarbon dispersion liquid to a base material, evaporating the dispersion medium contained in the nanocarbon dispersion liquid, and providing a coating layer.
  • the mass-based content ratio of the nanocarbon and the cellulose nanocrystal contained in the coating layer is the same as the mass-based content ratio of the nanocarbon and the cellulose nanocrystal contained in the nanocarbon dispersion. ..
  • the electromagnetic wave shielding material according to the present embodiment has the shape of a film, and the film contains nanocarbon and cellulose nanocrystals in a mutually mixed state.
  • the thickness of the film is preferably 30 ⁇ m to 160 ⁇ m, more preferably 40 ⁇ m to 160 ⁇ m. If it is less than 30 ⁇ m, it may be necessary to increase the CNT concentration contained in the film in order to obtain sufficient electromagnetic wave shielding property. If it is larger than 160 ⁇ m, the electromagnetic wave shielding property of the electromagnetic wave shielding material is saturated, and the thickened electromagnetic wave shielding property may not be improved.
  • the mixed state is, for example, a state in which nanocarbons in the film are unevenly distributed and cellulose nanocrystals are unevenly distributed, a state in which nanocarbons are uniformly distributed and cellulose nanocrystals are unevenly distributed. It is a state in which nanocarbons are unevenly distributed and cellulose nanocrystals are uniformly distributed, or a state in which nanocarbons are uniformly distributed and cellulose nanocrystals are uniformly distributed.
  • the nanocarbons in the film are uniformly distributed and the cellulose nanocrystals are uniformly distributed.
  • the nanocarbons in the film can be uniformly distributed, and the cellulose nanocrystals can be uniformly distributed.
  • the electromagnetic wave shielding material can be produced by evaporating the dispersion medium contained in the nanocarbon dispersion liquid.
  • the mass-based content ratio of the nanocarbon and the cellulose nanocrystal contained in the film is the same as the mass-based content ratio of the nanocarbon and the cellulose nanocrystal contained in the nanocarbon dispersion.
  • the obtained suspension was concentrated by centrifugation, and then ion-exchanged water was added to adjust the solid content concentration to 2% by mass to obtain a second suspension.
  • the second suspension was defibrated by an ultrasonic homogenizer (US300E, manufactured by Nippon Seiki Seisakusho), and then water was removed by a spray dry method to obtain a powdery CNC.
  • CNT Carbon nanotube
  • A Carbon nanotube (trade name: K-nanos100P, multi-walled CNT, manufactured by Kumho Petrochemical, fiber length (Bundle Diameter) 3 ⁇ m, fiber diameter 8 to 15 nm, specific surface area 220 m 2 / g)
  • B Carbon nanotube (trade name: nanocil-7000, multi-walled CNT, manufactured by nanocil, number average fiber length 1.5 ⁇ m, number average fiber diameter 9.5 nm, specific surface area 250 to 300 m 2 / g)
  • Example 1 The obtained CNC was added to ion-exchanged water as a dispersant and stirred, and then CNT (A) was gradually added together with ion-exchanged water to obtain a mixed solution.
  • the concentration of CNC in the mixed solution was 2% by mass, and the concentration of CNT (A) was 2% by mass.
  • the obtained mixed solution was dispersed for 30 minutes using a biomixer (BM-2 type, Nissei Tokyo Office), filtered through a 60-mesh sieve, and then a high-pressure homogenizer (trade name: Ultimizer, manufactured by Sugino Machine Limited).
  • a carbon nanotube dispersion was obtained by passing the mixture 10 times at a pressure of 200 MPa.
  • Example 2 A carbon nanotube dispersion was obtained in the same manner as in Example 1 except that CNC was added so that the concentration of CNC in the mixed solution was 0.2% by mass.
  • Example 3 A carbon nanotube dispersion was obtained in the same manner as in Example 1 except that CNC was added so that the concentration of CNC in the mixed solution was 10% by mass.
  • Example 4 Same as in Example 1 except that CNT (A) was added so that the concentration of CNT (A) in the mixed solution was 1% by mass, and CNC was added so that the concentration of CNC was 1% by mass. A carbon nanotube dispersion was obtained.
  • Example 5 Same as in Example 1 except that CNT (A) was added so that the concentration of CNT (A) in the mixed solution was 1% by mass, and CNC was added so that the concentration of CNC was 0.1% by mass. A carbon nanotube dispersion was obtained.
  • Example 6 Same as in Example 1 except that CNT (A) was added so that the concentration of CNT (A) in the mixed solution was 1% by mass, and CNC was added so that the concentration of CNC was 10% by mass. A carbon nanotube dispersion was obtained.
  • Example 7 Change CNT (A) to CNT (B), add CNT (A) so that the concentration of CNT (B) in the mixed solution is 1.5% by mass, and the concentration of CNC is 1.5% by mass.
  • a carbon nanotube dispersion was obtained in the same manner as in Example 1 except that CNC was added so as to become.
  • Example 1 Carbon nanotubes in the same manner as in Example 1 except that the CNC was changed to cellulose nanofibers obtained by mechanically defibrating hardwood kraft pulp (processing machine: Super Mascoroider, manufactured by Masuko Sangyo Co., Ltd.). A dispersion was obtained.
  • Example 2 The treatment was carried out in the same manner as in Example 1 except that the CNC was changed to carboxymethyl cellulose (CMC, cellogen PR, manufactured by Dai-ichi Kogyo Seiyaku), but the viscosity increased during the high-pressure homogenizer treatment, and the inside of the high-pressure homogenizer was blocked for the purpose. It was not possible to obtain the carbon nanotube dispersion liquid.
  • CMC carboxymethyl cellulose
  • CNC was changed to carboxymethyl cellulose (CMC, cellogen WS-C, manufactured by Dai-ichi Kogyo Seiyaku), and CNT (A) was added so that the concentration of CNT (A) in the mixed solution was 1.5% by mass.
  • CMC carboxymethyl cellulose
  • A carboxymethyl cellulose
  • the treatment was carried out in the same manner as in Example 1 except that carboxymethyl cellulose was added so that the concentration of carboxymethyl cellulose became 1.5% by mass, but the viscosity increased during the high-pressure homogenizer treatment, and the inside of the high-pressure homogenizer was blocked for the purpose. It was not possible to obtain the carbon nanotube dispersion liquid.
  • Example 4 A carbon nanotube dispersion was obtained in the same manner as in Example 1 except that CNC was not added to the mixed solution.
  • Example 5 The same as in Example 1 except that the CNC was changed to a surfactant having a dispersing effect (sodium dodecyl sulfate, manufactured by Tokyo Chemical Industry Co., Ltd.), but a large amount of bubbles were generated at the stage of the dispersion treatment with the biomixer. , The treatment with the high pressure homogenizer could not be performed.
  • a surfactant having a dispersing effect sodium dodecyl sulfate, manufactured by Tokyo Chemical Industry Co., Ltd.
  • Table 1 shows the composition and evaluation of the nanocarbon dispersions obtained in each Example and Comparative Example. The following methods were used for the evaluation of the nanocarbon dispersion.
  • the nanocarbon dispersion obtained by the dispersion treatment was diluted with ion-exchanged water so that the CNT concentration was 0.05% by mass, left in a glass vial for 1 hour, and then evaluated by visual observation according to the following criteria. .. A: It is good because there is no sedimentation of aggregates and separation of CNT and water. B: There is no sedimentation of aggregates, and the separation between CNT and water is slight and good. C: There are fine aggregates, and a small separation between CNT and water can be confirmed (lower limit of practical use). D: Most of the agglomerates are large, and the separation from water is also large (not practical).
  • the viscosity of the nanocarbon dispersion obtained by the dispersion treatment was adjusted to 20 ° C. using a B-type viscometer (No. 1 to 4 rotor) (trade name: B-type viscometer, model: BM, manufactured by Tokyo Keiki Seisakusho). The viscosity was measured by rotating at a rotation speed of 60 rpm for 1 minute, and the value was evaluated according to the following criteria A to D.
  • B B-type viscosity is 1000 mPa ⁇ s or less, and the fluidity is good.
  • B-type viscosity is 2000 mPa ⁇ s or less, and fluidity can be confirmed (practical lower limit).
  • D B-type viscosity exceeds 5000 mPa ⁇ s and lacks fluidity (not practical).
  • Dispersion 1 corresponding to the dispersion of Example 6
  • dispersion 2 corresponding to the dispersion of Example 3
  • dispersion 3 corresponding to the dispersion of Example 1
  • dispersion corresponding to the dispersion of Example 5 Liquid 4 was prepared respectively.
  • the carbon nanotubes used in the preparation of the dispersion liquids 1 to 4 were CNT (A), and the dispersant was CNC.
  • Paper with a pigment coating layer on high-quality paper that is a support (“Mucoat Neos” (registered trademark) manufactured by Hokuetsu Corporation, basis weight 157 g / m 2 ) is prepared as a "paper base material” and dispersed. After the liquid 1 was coated on the paper with a bar coater, it was dried at 120 ° C. for 3 minutes to evaporate the water content, and a coated paper was prepared. That is, the "coated paper” is a paper base material provided with a coating layer containing CNT and CNC. For each of the dispersion liquid 2, the dispersion liquid 3, and the dispersion liquid 4, coated paper was prepared by the same operation as in the case of the dispersion liquid 1. Regarding the coating amount, the coating amount was adjusted so that the theoretical thickness of the coating layer of each coated paper was constant.
  • the dispersion liquid 1, the dispersion liquid 2, the dispersion liquid 3 and the dispersion liquid 4 were each placed in a petri dish having a diameter of 8.5 cm and dried at 50 ° C. overnight to evaporate the water content, respectively, to prepare a dried film. That is, the "dry film” is a sheet containing CNT and CNC, and is not provided on a base material such as paper. After production, the film-forming property of each of the obtained dry films was observed.
  • the specific evaluation criteria are as follows. A: A solid substance having the shape and flexibility of a film, having no cracks, and containing nanocarbon and cellulose nanocrystals in a mutually mixed state was formed on the entire surface of the petri dish.
  • a solid substance having the shape and flexibility of a film and containing nanocarbon and cellulose nanocrystals in a mutually mixed state was formed on the entire surface of the petri dish, but cracks were generated in this solid substance. It was.
  • C A solid substance having the shape and flexibility of the film, having no cracks, and containing nanocarbon and cellulose nanocrystals in a mutually mixed state was formed only in the black spot portion of the petri dish.
  • (Evaluation result of film formation property) 1a to 1d are images of the appearance of a dried film obtained by putting a carbon nanotube dispersion in a petri dish and drying it at 50 ° C. overnight.
  • Table 2 shows the evaluation results of the film-forming property of the dried film.
  • the dispersion liquids 1 to 3 have better CNT dispersibility than the dispersion liquid 4, and therefore have good film forming properties.
  • FIG. 4 is a graph in which "S 21 " is plotted against “mass ratio of CNT to total mass of CNT and CNC” shown in Table 2.
  • the “mass ratio of CNT to the total mass of CNT and CNC” is the ratio (mass%) occupied by CNT when the total of the mass of CNT and the mass of CNC is 100% by mass.
  • Table 2 shows the thickness of the coating layer of the dispersion liquid.
  • the thickness of the coating layer of the dispersion liquid means the thickness of the coating layer obtained by drying the dispersion liquid.
  • the thickness of the coating layer of the dispersion was measured by SEM analysis. Specifically, the thickness was obtained by subtracting the thickness of the paper base material (thickness of the woodfree paper and the thickness of the pigment coating layer) from the thickness of the entire coated paper.
  • the coated paper prepared from the dispersion liquids 1 to 3 has a frequency of both 300 MHz and 7 GHz as the mass ratio of CNT to the total mass of CNT and CNC increases.
  • the absolute value of "S 21 " has increased.
  • the coated paper prepared using the dispersion liquid 4 had a smaller absolute value of "S 21 " at both frequencies of 300 MHz and 7 GHz than the coated paper prepared using the dispersion liquid 3.
  • the absolute value of "S 21 " of the coated paper produced using the dispersion liquid 4 is smaller than the absolute value of "S 21 " of the coated paper produced using the dispersion liquid 3 as described above.
  • the dispersibility of the dispersion liquid 4 is poorer than that of the dispersion liquid 3, and it is considered that the electromagnetic wave shielding property is lowered.
  • each profile shown by the numerical value of 0.3 ⁇ m to 4.5 ⁇ m is the profile of the coated paper which has the coating layer of the dispersion liquid by the thickness, and is shown by the numerical value of 158 ⁇ m.
  • the profile is a profile of a dry film having a thickness of 158 ⁇ m.
  • a network analyzer "ZVA67” manufactured by ROHDE & SCHWARZ and a test fixture “TF-18C” manufactured by KEYCOM were used as the testing machine.
  • the measurement frequency was 500 MHz to 18 GHz.
  • FIG. 9 is a graph showing the evaluation results of electromagnetic wave absorption by the microstrip line method.
  • the vertical axis “Rtp” in FIG. 9 indicates the transmission attenuation factor. The larger the absolute value of the transmission attenuation factor, the higher the electromagnetic wave absorption.
  • the coated paper provided with the coating layer containing CNT and CNC has higher electromagnetic wave absorption than the paper base material and the aluminum foil. By this evaluation, it was possible to confirm the electromagnetic wave absorption of the coated paper containing CNT.

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Abstract

L'objet de la présente invention consiste à fournir : (1) un liquide de dispersion dans lequel un nanocarbone tel que des nanotubes de carbone est dispersé de manière stable et fait preuve d'une bonne fluidité, et un procédé pour le produire; (2) un agent de dispersion de nanocarbone qui est ajouté afin d'obtenir le liquide de dispersion; et (3) un matériau de protection contre les ondes électromagnétiques. Ce liquide de dispersion de nanocarbone contient du nanocarbone, des nanocristaux de cellulose et un milieu de dispersion.
PCT/JP2020/011197 2019-03-22 2020-03-13 Liquide de dispersion de nanocarbone, son procédé de production, agent de dispersion de nanocarbone, et matériau de protection contre les ondes électromagnétiques WO2020195974A1 (fr)

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