WO2020194380A1 - Nanocarbon dispersion liquid, method for producing same, and nanocarbon dispersing agent - Google Patents

Nanocarbon dispersion liquid, method for producing same, and nanocarbon dispersing agent Download PDF

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Publication number
WO2020194380A1
WO2020194380A1 PCT/JP2019/012112 JP2019012112W WO2020194380A1 WO 2020194380 A1 WO2020194380 A1 WO 2020194380A1 JP 2019012112 W JP2019012112 W JP 2019012112W WO 2020194380 A1 WO2020194380 A1 WO 2020194380A1
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nanocarbon
dispersion
mass
cnc
dispersion liquid
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PCT/JP2019/012112
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French (fr)
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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Priority to PCT/JP2019/012112 priority Critical patent/WO2020194380A1/en
Priority to PCT/JP2020/011197 priority patent/WO2020195974A1/en
Priority to JP2021509058A priority patent/JP7177912B2/en
Publication of WO2020194380A1 publication Critical patent/WO2020194380A1/en

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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

Definitions

  • 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 describes a dispersion liquid in which nanocarbons such as carbon nanotubes are stably dispersed and has fluidity, a method for producing the dispersion liquid, and nanocarbon added to obtain the dispersion liquid. It is intended to provide a dispersant.
  • 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, 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.
  • a dispersion liquid in which nanocarbons such as carbon nanotubes are stably dispersed and have fluidity a method for producing the dispersion liquid, and a nanocarbon dispersant added to obtain the dispersion liquid. be able to.
  • 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, 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 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).

Abstract

The purpose of the present disclosure is to provide: a dispersion liquid in which nanocarbon such as carbon nanotubes is stably dispersed and which exhibits good fluidity, and a method for producing same; and a nanocarbon dispersing agent that is added in order to obtain the dispersion liquid. This nanocarbon dispersion liquid contains nanocarbon, cellulose nanocrystals and a dispersion medium.

Description

ナノカーボン分散液及びその製造方法並びにナノカーボン分散剤Nanocarbon dispersion liquid and its manufacturing method and nanocarbon dispersant
　本開示は、ナノカーボンとセルロースナノクリスタルとを含有するナノカーボン分散液及びその製造方法、並びにセルロースナノクリスタルを含有するナノカーボン分散剤に関する。 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.
　カーボンナノチューブ、ナノグラフェン等のナノカーボンは、表面エネルギーが高いため、媒体中にナノカーボンを分散させようとしても、ナノカーボン表面には強いファンデルワールス力が働く。したがって、ナノカーボンは凝集しやすい。このため、ナノカーボンを安定的に分散させることが要望されている。 Since 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.
　ナノカーボンの分散方法として、単糖又は少糖の結晶と、カーボンナノチューブと、非イオン又は陰イオン界面活性剤とを擂潰して得られる擂潰混合物に水を添加するカーボンナノチューブの分散方法が開示されている（例えば、特許文献１を参照。）。また、カルボキシメチルセルロースを分散剤とするカーボンナノチューブの分散方法が開示されている（例えば、特許文献２を参照。）。また、セルロースナノファイバーを分散剤とするカーボンナノチューブの分散方法が開示されている（例えば、特許文献３を参照。）。また、平均繊維外径が５０～１１０ｎｍの範囲である多層カーボンナノチューブをカルボキシメチルセルロースナトリウムで分散させる方法が開示されている（例えば、特許文献４を参照。）。 As 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).
特開２００８－２３０９３５号公報Japanese Unexamined Patent Publication No. 2008-230935 国際公開第２００５／０８２７７５号International Publication No. 2005/082775 国際公開第２０１４／１１５５６０号International Publication No. 2014/115560 特開２０１６－０２８１０９号公報Japanese Unexamined Patent Publication No. 2016-028109
　しかしながら、特許文献１に開示の方法では、上限値約５ｇ／Ｌの低濃度のカーボンナノチューブ分散液しか得られない問題がある。また、界面活性剤を使用しており、分散液に泡立ちの問題が生じやすい。特許文献２に開示の方法では、カルボキシメチルセルロースを用いるため分散液の粘度が高くなりやすく、分散機を用いて製造しようとすると、粘稠質の分散液によって分散機が閉塞する問題がある。特許文献３に開示の方法では、セルロースナノファイバーを用いるため分散液の粘度が高くなりやすく、実施例におけるカーボンナノチューブの濃度は、最高でも０．０５質量％に過ぎない。特許文献４に開示の方法は、特定の繊維径を有する多層カーボンナノチューブにしか適用できず、繊維径５０ｎｍ以下の繊維径が小さい（比表面積の大きい）カーボンナノチューブを安定的に分散させることは困難であった。 However, the method disclosed in 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. In addition, since a surfactant is used, the dispersion liquid tends to have a problem of foaming. In the method disclosed in Patent Document 2, since carboxymethyl cellulose is used, 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. In the method disclosed in 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.
　本開示は、このような問題に鑑み、カーボンナノチューブ等のナノカーボンが安定的に分散し、流動性を有する分散液及びその分散液の製造方法、並びにその分散液を得るために添加するナノカーボン分散剤を提供することを目的とする。 In view of these problems, the present disclosure describes a dispersion liquid in which nanocarbons such as carbon nanotubes are stably dispersed and has fluidity, a method for producing the dispersion liquid, and nanocarbon added to obtain the dispersion liquid. It is intended to provide a dispersant.
　本発明者らは、上記の課題を解決するために、鋭意検討した結果、セルロースナノクリスタルを用いることによって、前記課題を解決できることを見出し、本発明を完成させた。 As a result of diligent studies to solve the above problems, the present inventors have found that the above problems can be solved by using cellulose nanocrystals, and have completed the present invention.
　本発明に係るナノカーボン分散液は、ナノカーボンとセルロースナノクリスタルと分散媒とを含有することを特徴とする。 The nanocarbon dispersion liquid according to the present invention is characterized by containing nanocarbon, cellulose nanocrystals, and a dispersion medium.
　本発明に係るナノカーボン分散液では、前記ナノカーボンの濃度が１質量％以上であることが好ましい。ナノカーボンの濃度が１質量％以上であっても、ナノカーボン分散液の安定性及び流動性を良好にすることができる。 In the nanocarbon dispersion liquid according to the present invention, 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.
　本発明に係るナノカーボン分散液では、前記ナノカーボンと前記セルロースナノクリスタルとの質量基準の含有比率（ナノカーボン：セルロースナノクリスタル）が１：０．１～１：１０であることが好ましい。ナノカーボン分散液の安定性及び流動性をより良好にすることができる。 In the nanocarbon dispersion liquid according to the present invention, 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.
　本発明に係るナノカーボン分散液では、前記ナノカーボンの濃度が１質量％以上４質量％以下であり、かつ前記ナノカーボンと前記セルロースナノクリスタルとの合計濃度が１質量％を超えて１５質量％以下であることが好ましい。ナノカーボンの濃度が高くても、ナノカーボン分散液の安定性及び流動性をより良好にすることができる。 In the nanocarbon dispersion liquid according to the present invention, 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.
　本発明に係るナノカーボン分散液では、前記分散媒が極性溶媒であることが好ましい。分散性がより高いナノカーボン分散液を得ることができる。 In the nanocarbon dispersion liquid according to the present invention, it is preferable that the dispersion medium is a polar solvent. A nanocarbon dispersion having higher dispersibility can be obtained.
　本発明に係るナノカーボン分散液では、前記極性溶媒が、アルコール類、ケトン類若しくは水又はこれらの混合物であることが好ましい。分散性がさらに高いナノカーボン分散液を得ることができる。 In the nanocarbon dispersion according to the present invention, it is preferable that the polar solvent is alcohols, ketones, water, or a mixture thereof. A nanocarbon dispersion having even higher dispersibility can be obtained.
　本発明に係るナノカーボン分散液の製造方法は、ナノカーボンとセルロースナノクリスタルと分散媒とを含有する混合液を分散機で分散処理することを特徴とする。 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.
　本発明に係るナノカーボン分散液の製造方法では、前記混合液が、前記分散媒に前記セルロースナノクリスタルを添加して攪拌した後に前記ナノカーボンを添加して調製した混合液であることが好ましい。分散媒とナノカーボンとの相溶性が損なわれにくくなり、ナノカーボンが分散媒に浮きにくくなる。 In the method for producing a nanocarbon dispersion according to the present invention, it is preferable that 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.
　本発明に係るナノカーボン分散液の製造方法では、前記セルロースナノクリスタルがスプレードライ品であることが好ましい。セルロースナノクリスタルの濃度調整をしやすくすることができる。 In the method for producing a nanocarbon dispersion according to the present invention, it is preferable that the cellulose nanocrystal is a spray-dried product. It is possible to easily adjust the concentration of cellulose nanocrystals.
　本発明に係るナノカーボン分散液の製造方法では、前記分散機がホモジナイザーであることが好ましい。分散性がより安定したナノカーボン分散液を得ることができる。 In the method for producing a nanocarbon dispersion liquid according to the present invention, it is preferable that the disperser is a homogenizer. A nanocarbon dispersion with more stable dispersibility can be obtained.
　本発明に係るナノカーボン分散剤は、セルロースナノクリスタルを含有することを特徴とする。 The nanocarbon dispersant according to the present invention is characterized by containing cellulose nanocrystals.
　本開示によれば、カーボンナノチューブ等のナノカーボンが安定的に分散し、流動性を有する分散液及びその分散液の製造方法、並びにその分散液を得るために添加するナノカーボン分散剤を提供することができる。 According to the present disclosure, there are provided a dispersion liquid in which nanocarbons such as carbon nanotubes are stably dispersed and have fluidity, a method for producing the dispersion liquid, and a nanocarbon dispersant added to obtain the dispersion liquid. be able to.
　次に本発明について実施形態を示して詳細に説明するが、本発明はこれらの記載に限定して解釈されない。本発明の効果を奏する限り、実施形態は種々の変形をしてもよい。 Next, the present invention will be described in detail by showing embodiments, but the present invention is not construed as being limited to these descriptions. The embodiments may be modified in various ways as long as the effects of the present invention are exhibited.
（ナノカーボン分散液）
　本実施形態に係るナノカーボン分散液は、ナノカーボンとセルロースナノクリスタルと分散媒とを含有する。 (Nanocarbon dispersion)
The nanocarbon dispersion liquid according to the present embodiment contains nanocarbon, cellulose nanocrystals, and a dispersion medium.
　本実施形態において、ナノカーボンとは、カーボンナノチューブ（以下、ＣＮＴともいう。）、フラーレン、ＣＶＤ法又は機械的剥離法によるグラフェンナノプレートレット等のナノカーボンをいう。これらのナノカーボンは単層であっても２以上の多層の構造であってもよい。本実施形態では、これらのナノカーボンの分散液に関して説明するが、以下、代表例としてＣＮＴ分散液について詳細を述べる。 In the present embodiment, 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. These nanocarbons may have a single layer or a structure having two or more layers. In the present embodiment, these nanocarbon dispersions will be described, but the CNT dispersion will be described in detail below as a representative example.
　ＣＮＴは、フラーレンとグラフェンの導電性との中間的な導電性を有することから、工業的にも使用しやすい特徴を有する。ＣＮＴは、用途に応じて繊維長、繊維径及びＢＥＴ比表面積が異なるものが用いられ、例えば、その繊維長の範囲は、１μｍ～５００μｍであり、繊維径の範囲は、０．４ｎｍ～１５０ｎｍであり、ＢＥＴ比表面積の範囲は、１０ｍ２／ｇ～２５００ｍ２／ｇである。一般的に、比表面積が小さいものは繊維径が大きく、比較的分散しやすいが、比表面積が大きくなるにつれ（繊維径が小さくなるにつれ）、分散が困難となる傾向にある。ＣＮＴには、分散性を向上させるために表面にカルボキシル基等の官能基が導入されたものがあるが、そのようなＣＮＴにおいても比表面積が大きくなるにつれ（繊維径が小さくなるにつれ）、分散が困難となる傾向にある。具体的には、カルボキシル基等の官能基が導入されたＣＮＴのＢＥＴ比表面積が１００ｍ２／ｇを超えると、カルボキシメチルセルロース等の従来の分散剤では十分な分散が困難となることがあった。特に高濃度の分散液を得ることが困難となり、ＣＮＴ濃度が１質量％を超える分散液を得ることは困難であった。 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. As the CNT, those having different fiber lengths, fiber diameters and BET specific surface areas are used depending on the application. For example, the fiber length range is 1 μm to 500 μm, and the fiber diameter range is 0.4 nm to 150 nm. Yes, the range of BET specific surface area is 10 m 2 / g to 2500 m 2 / g. In general, 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.
　そこで、本実施形態においては、分散剤としてセルロースナノクリスタル（以下、ＣＮＣともいう。）を使用して、ＣＮＴを分散させる。ここで、ＣＮＣとは、植物由来特に木材由来のセルロース繊維を酸加水分解等の化学的処理を施すことで得られる針状結晶物である。一般的に、ＣＮＣの数平均繊維径は４ｎｍ～７０ｎｍであり、数平均繊維長は２５ｎｍ～１０００ｎｍであり、ＢＥＴ比表面積は１００ｍ２／ｇ～５００ｍ２／ｇであり、アスペクト比は５０未満である。ここでアスペクト比とは、数平均繊維長を数平均繊維径で除した無次元数である。セルロースナノクリスタルはセルロースナノウィスカーとも呼ばれる。なお、ＣＮＣとは別に、分散剤としてセルロースナノファイバー（以下、ＣＮＦともいう。）が知られているが、ＣＮＦとは、ＣＮＣと同等の数平均繊維径を有するが、ＣＮＣよりも繊維長が１０倍以上長く、一般的には繊維長が５μｍ以上である繊維状物をいい、ＣＮＦのアスペクト比は１００を超える。一方、ＣＮＣは針状結晶物であり、ＣＮＦ等の繊維状物のようにアスペクト比は大きくないが、本実施形態においては、ＣＮＣの長径を繊維長ともいい、短径を繊維径ともいう。 Therefore, in the present embodiment, CNTs are dispersed by using cellulose nanocrystals (hereinafter, also referred to as CNC) as a dispersant. Here, 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. Generally, 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, and the aspect ratio is less than 50. is there. Here, the aspect ratio is a dimensionless number obtained by dividing the number average fiber length by the number average fiber diameter. Cellulose nanocrystals are also called cellulose nanowhiskers. In addition to CNC, cellulose nanofibers (hereinafter, also referred to as CNF) are known as dispersants. 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 μm or more, and a CNC aspect ratio of more than 100. On the other hand, CNC is an acicular crystal and does not have a large aspect ratio like a fibrous material such as CNF. However, in the present embodiment, the major axis of CNC is also referred to as fiber length, and the minor axis is also referred to as fiber diameter.
　ＣＮＴの濃度が比較的高い分散液を得るには、繊維長がＣＮＦより短いＣＮＣが好適である。本実施形態において、ＣＮＣの数平均繊維長は、２５ｎｍ～５００ｎｍが好ましく、より好ましくは１００ｎｍ～４００ｎｍであり、最も好ましくは２００ｎｍ～３００ｎｍである。平均繊維長が２５ｎｍ未満であると、ＣＮＣ同士が凝集する可能性がある。数平均繊維長が５００ｎｍを超えると、分散液の粘度が高くなりやすく、ＣＮＴの濃度を高くした場合の分散液の流動性が損なわれやすくなる可能性がある。尚、ＣＮＦは繊維長が長すぎることから、ＣＮＴの分散が困難なだけでなく、分散液の流動性を大きく損ないやすいという特徴がある。例えば、Ｂ型粘度計（２０℃、６０ｒｐｍ、回転時間１分）で測定した粘度は、ＣＮＣの２質量％水溶液であれば１００ｍＰａ・ｓ以下であり、流動性は良好であるが、ＣＮＦの２質量％水溶液は、１００００ｍＰａ・ｓを超えることも多く、結果として流動性を損なう。 In order to obtain a dispersion liquid having a relatively high concentration of CNT, CNC having a fiber length shorter than that of CNF is suitable. In the present embodiment, 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. Since the fiber length of CNF is too long, not only is it difficult to disperse CNTs, but also the fluidity of the dispersion liquid is likely to be significantly impaired. For example, 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.
　本実施形態において、ＣＮＣの数平均繊維径は、５ｎｍ～６０ｎｍが好ましく、より好ましくは１０ｎｍ～５０ｎｍであり、最も好ましくは２０ｎｍ～３０ｎｍである。平均繊維径が５ｎｍ未満であると、ＣＮＣ同士が凝集する可能性がある。数平均繊維径が６０ｎｍを超えると、分散液の粘度が高くなり、流動性が低下する可能性がある。 In the present embodiment, 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.
　本実施形態において、ＣＮＣのＢＥＴ比表面積は、１２０ｍ２／ｇ～４００ｍ２／ｇが好ましく、より好ましくは１５０ｍ２／ｇ～３００ｍ２／ｇであり、最も好ましくは１７５ｍ２／ｇ～２５０ｍ２／ｇである。ＢＥＴ比表面積が１２０ｍ２／ｇ未満であると、分散液の粘度が高くなり、流動性が低下する可能性がある。ＢＥＴ比表面積が４００ｍ２／ｇを超えると、分散液の粘度が高くなり、ＣＮＣ同士が凝集する可能性がある。 In the present embodiment, 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.
　本実施形態において、ＣＮＣのアスペクト比は、５～４０が好ましく、より好ましくは１０～３０であり、最も好ましくは１５～２５である。アスペクト比が５未満であると、ＣＮＣ同士が凝集する可能性がある。アスペクト比が４０を超えると、ＣＮＴの濃度を高くした場合の分散液の流動性が低下する可能性がある。 In the present embodiment, 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.
　ＣＮＣの数平均繊維径及び数平均繊維長は、次に従って算出することができる。ＣＮＣの表面部分に対し、透過型電子顕微鏡（ＴＥＭ、Ｔｒａｎｓｍｉｓｓｉｏｎ　Ｅｌｅｃｔｒｏｎ　Ｍｉｃｒｏｓｃｏｐｅ）又は走査型電子顕微鏡（ＳＥＭ、Ｓｃａｎｎｉｎｇ　Ｅｌｅｃｔｒｏｎ　Ｍｉｃｒｏｓｃｏｐｅ）を用いて、最低３枚の視野が重なっていないＣＮＣ表面部分の画像を撮影する。得られた画像に対し、１枚の画像あたり縦横２本ずつの無作為な軸を引き、軸に交差する繊維の繊維径及び繊維長を目視で読み取っていく。このとき、構成する繊維の大きさに応じて５０００倍、１００００倍、５００００倍のいずれかの倍率で行う。なお、２本の軸と交差する繊維数の条件は２０本以上とする。各々２本の軸に交差する繊維の繊維径及び繊維長の値を読み取る。したがって、最低２０本×２×３＝１２０個の繊維情報が得られる。こうして得られた繊維径及び繊維長のデータから数平均繊維径及び数平均繊維長を算出する。ＣＮＴの数平均繊維径及び数平均繊維長を算出する場合についても同様である。 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. Read the fiber diameter and fiber length values of the fibers that intersect each of the two axes. Therefore, information on at least 20 fibers × 2 × 3 = 120 fibers can be obtained. The number average fiber diameter and the number average fiber length are calculated from the fiber diameter and fiber length data thus obtained. The same applies to the case of calculating the number average fiber diameter and the number average fiber length of CNTs.
　本実施形態では、例えば、セルロース繊維の水懸濁液またはスラリーを、硫酸、塩酸、臭化水素酸等による強酸を用いた酸加水分解等の化学的手法で調製したＣＮＣを使用することができる。強酸としては好ましくは硫酸である。硫酸で加水分散することにより表面に硫酸エステル基が付加されることで負の電荷が付与されるとともに、硫酸エステル基は分子量としても大きいことから立体障害にもなり、ＣＮＴを分散させる能力が大きくなるものと推察される。 In this embodiment, for example, 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.
　ＣＮＣの重合度は、特に限定するものではないが、１００～５００が好ましく、より好ましくは２００～４００である。重合度が１００未満であると、ＣＮＴの分散性が低下する可能性がある。重合度が５００を超えると、分散液の粘度が高くなり、流動性が低下する可能性がある。 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.
　ナノカーボン分散液の代表例として、ＣＮＴ分散液について詳細を述べたが、ナノカーボンがフラーレン、グラフェンナノプレートレット等の他のナノカーボンである場合であっても、ＣＮＴである場合と同様に良好なナノカーボン分散液が得られる。 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.
　本実施形態のナノカーボン分散液では、このようなＣＮＣを分散剤として用いることにより、ＣＮＴ等のナノカーボンを分散媒に安定的に分散させる。特に、ＢＥＴ比表面積が１００ｍ２／ｇ以上のナノカーボン、例えばＢＥＴ比表面積が１００～１０００ｍ２／ｇのＣＮＴであっても安定的に分散させることが可能となる。ＢＥＴ比表面積が１００～１０００ｍ２／ｇのＣＮＴの繊維径は３０ｎｍ以下になると考えられ、このような繊維径のＣＮＴは柔軟で導電性にも優れるものが多い。 In the nanocarbon dispersion liquid of the present embodiment, by using such CNC as a dispersant, nanocarbons such as CNTs are stably dispersed in a dispersion medium. In particular, even nanocarbons 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. It is considered that 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.
　本実施形態では、ナノカーボンの濃度が１質量％以上であることが好ましい。ナノカーボンの濃度が１質量％以上であっても、ナノカーボンの分散液の安定性及び流動性を良好にすることができる。 In this embodiment, 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.
　本実施形態に係るナノカーボン分散液では、ナノカーボン分散液におけるナノカーボンとＣＮＣの含有比率は、特に限定するものではないが、ナノカーボンが安定的に分散した分散液とするには、質量基準で、ナノカーボン：セルロースナノクリスタル＝１：０．１～１：１０が好ましい。より好ましくは、ナノカーボン：セルロースナノクリスタル＝１：０．５～１：５である。含有比率１：０．１よりも、セルロースナノクリスタルが少なく含有される含有比率であっても（例えば、ナノカーボン：セルロースナノクリスタル＝１：０．０１）、ナノカーボンの分散性の向上に効果があるが、ナノカーボンの濃度が例えば１質量％以上となるような比較的高い場合に、沈降物が生じやすくなる可能性がある。一方、１：１０よりも、ＣＮＣが多く含有される含有比率であると、ナノカーボンがＣＮＣに対して相対的に少なくなるため、ナノカーボン分散液の分散性及び安定性の向上効果は頭打ちとなる。ナノカーボンの濃度の上限値は、分散性の観点から、例えば４質量％である。 In the nanocarbon dispersion liquid according to the present embodiment, the content ratio of nanocarbon and CNC in the nanocarbon dispersion liquid is not particularly limited, but in order to obtain a dispersion liquid in which nanocarbon is stably dispersed, a mass standard is used. Therefore, nanocarbon: cellulose nanocrystal = 1: 0.1 to 1:10 is preferable. More preferably, nanocarbon: cellulose nanocrystal = 1: 0.5 to 1: 5. Even if the content ratio contains less cellulose nanocrystals than 1: 0.1 (for example, nanocarbon: cellulose nanocrystals = 1: 0.01), it is effective in improving the dispersibility of nanocarbons. However, when the concentration of nanocarbon is relatively high, for example, 1% by mass or more, sediment may easily occur. On the other hand, when 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. Become. The upper limit of the concentration of nanocarbon is, for example, 4% by mass from the viewpoint of dispersibility.
　本実施形態に係るナノカーボン分散液では、ナノカーボンとセルロースナノクリスタルとの合計濃度が１質量％を超えて１５質量％以下であることが好ましい。より好ましくは１．５質量％以上１３質量％以下である。最も好ましくは、１．８質量％以上５質量％以下である。この合計濃度が１質量％以下であると、ナノカーボンが分散できない可能性がある。この合計濃度が１５質量％を超えると、分散液の粘度が高くなり、流動性が低下する可能性がある。 In the nanocarbon dispersion liquid according to the present embodiment, 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.
　本実施形態に係るナノカーボン分散液では、ナノカーボンの濃度が１質量％以上４質量％以下であり、かつナノカーボンとセルロースナノクリスタルとの合計濃度が１質量％を超えて１５質量％以下であることが好ましい。より好ましくは、ナノカーボンの濃度が１質量％以上３．５質量％以下であり、かつナノカーボンとセルロースナノクリスタルとの合計濃度が１．５質量％以上１３質量％以下である。最も好ましくは、ナノカーボンの濃度が１質量％以上３質量％以下であり、かつナノカーボンとセルロースナノクリスタルとの合計濃度が１．８質量％以上５質量％以下である。ナノカーボンの濃度が高くても、ナノカーボン分散液の安定性及び流動性をより良好にすることができる。 In the nanocarbon dispersion liquid according to the present embodiment, 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.
　分散媒は、用途に応じて任意に選択することができるが、ＣＮＣの分散効果を十分に発揮させるには、本実施形態に係るナノカーボン分散液では、分散媒が極性溶媒であることが好ましい。 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. ..
　本実施形態に係るナノカーボン分散液では、極性溶媒が、メタノール、エタノール等のアルコール類；アセトン、メチルエチルケトン等のケトン類若しくは水又はこれらの混合物であることが好ましい。特に好ましくは水である。分散性がさらに高いナノカーボン分散液を得ることができる。 In the nanocarbon dispersion according to the present embodiment, the polar solvent is preferably alcohols such as methanol and ethanol; ketones such as acetone and methyl ethyl ketone, water, or a mixture thereof. Water is particularly preferable. A nanocarbon dispersion having even higher dispersibility can be obtained.
　ナノカーボン分散液は、本発明の目的とする効果を損ねない範囲で、各種添加剤を含有することができる。添加剤は、例えば酸化防止剤、熱安定剤、光安定剤、紫外線吸収剤、顔料、着色剤、発泡剤、帯電防止剤、難燃剤、滑剤、軟化剤、粘着付与剤、可塑剤、離型剤、防臭剤、香料又はそれらの組合せである。これらの添加剤は、ナノカーボンの特性に影響を与える可能性があるため、添加の際には注意を要する。本実施形態に係るナノカーボン分散液は、フィルム等の基材に塗布、乾燥して、成膜することができるほか、分散液から直接、溶媒を除去するか、又は貧溶媒に投入して、固形分を析出させ、ろ過、乾燥することで、カーボンナノチューブ／セルロースナノクリスタル複合材料を得ることもできる。界面活性剤としては、例えば消泡効果を有する界面活性剤、分散効果を有する界面活性剤、又は粘度調整効果を有する界面活性剤があるが、本実施形態では、分散効果を有する界面活性剤を含有しないことが好ましい。分散効果を有する界面活性剤は泡立ちの発生の原因となる可能性がある。 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. Examples of the surfactant include a surfactant having a defoaming effect, a surfactant having a dispersing effect, and a surfactant having a viscosity adjusting effect. In the present embodiment, the surfactant having a dispersing effect is used. It is preferable not to contain it. Surfactants with a dispersing effect can cause foaming.
（ナノカーボン分散液の製造方法）
　本実施形態に係るナノカーボン分散液の製造方法は、ナノカーボンとセルロースナノクリスタルと分散媒とを含有する混合液を分散機で分散処理することを特徴とする。 (Manufacturing method of nanocarbon dispersion)
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には、例えば、水に分散させた状態のスラリー品と、スラリー品を乾燥させて得たスプレードライ品が存在するが、そのどちらも使用することができる。本実施形態では、ＣＮＣがスプレードライ品であることが好ましい。ＣＮＣはＣＮＦとは異なり、乾燥品でも比較的容易に水中に分散させることができるため、乾燥品を用いることで濃度調整を行いやすくすることができる。 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. In this embodiment, it is preferable that the CNC is a spray-dried product. Unlike CNF, 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.
　ナノカーボンとＣＮＣの分散媒への添加順は特に限定するものではないが、本実施形態に係るナノカーボン分散液の製造方法では、混合液が、ナノカーボンとＣＮＣとを分散媒に同時に添加して調製した混合液であるか、又は分散媒にＣＮＣを添加して攪拌した後にナノカーボンを添加して調製した混合液であることが好ましい。ナノカーボンは疎水性が強いため、分散媒が水である場合、分散媒に単独で最初に添加すると、分散媒に浮いてしまい、相溶性を損ないやすい可能性がある。混合液の流動性は、ナノカーボンとＣＮＣとの合計濃度及び質量基準の含有比率により異なるが、例えば質量基準でＣＮＴ：ＣＮＣ＝１：１の場合は、ＣＮＴとＣＮＣとの合計濃度を２～６質量％とすると、適度な流動性を保て、次工程の分散処理に好適となる。 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 fluidity of the mixed solution varies depending on the total concentration of nanocarbon and CNC and the content ratio based on mass. For example, when CNT: CNC = 1: 1 on a mass basis, the total concentration of CNT and CNC is 2 to 2. When it is set to 6% by mass, it is suitable for the dispersion treatment in the next step while maintaining an appropriate fluidity.
　分散処理に用いる分散機は特に限定するものではなく、各種公知の機械的分散処理機を用いることができ、例えば、アジテーターを備えた攪拌機、超音波分散機、高剪断攪拌機、バイオミキサー又はホモジナイザーを用いることができる。これらの分散機は２種以上を組み合わせて用いてもよい。例えば、混合液を超音波分散機でプレ分散処理をし、その後、ホモジナイザーで分散処理を行うこと、混合液をバイオミキサーでプレ分散処理をし、その後、ホモジナイザーで分散処理を行うこと等の２段階以上の分散処理を行ってもよい。 The disperser used for the dispersion treatment is not particularly limited, and various known mechanical dispersion treatment machines can be used. For example, a stirrer equipped with an agitator, an ultrasonic disperser, a high shear stirrer, a biomixer or a homogenizer can be used. Can be used. Two or more kinds of these dispersers may be used in combination. For example, 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.
　本実施形態に係るナノカーボン分散液の製造方法では、分散機がホモジナイザーであることが好ましい。ホモジナイザーで分散処理をすることで、より分散性の安定したナノカーボン分散液を得ることができる。また、ホモジナイザーには、例えば、超音波式、攪拌式、高圧式があるが、高圧式のホモジナイザー（高圧ホモジナイザー）が好ましい。また、高圧ホモジナイザーの中でもウォータージェット方式が好適である。ウォータージェット方式の高圧ホモジナイザーとしては、例えばスギノマシン製のスターバースト（登録商標）がある。高圧ホモジナイズドの分散処理条件は圧力１００～２５０ＭＰａ、１～１０パスが好ましい。分散処理しないと、ナノカーボン分散液が得られない。圧力１００ＭＰａ未満であると、分散不十分となる可能性がある。圧力２５０ＭＰａを超えるか、又はパス回数１０回を超えると、分散が進まなくなり、分散液の高温が上昇する可能性がある。 In the method for producing a nanocarbon dispersion liquid according to the present embodiment, it is preferable that the disperser is a homogenizer. By performing the dispersion treatment with a homogenizer, a more stable nanocarbon dispersion can be obtained. Further, the homogenizer includes, for example, an ultrasonic type, a stirring type, and a high pressure type, and a high pressure type homogenizer (high pressure homogenizer) is preferable. Further, among the high pressure homogenizers, the water jet method is preferable. As 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.
（ナノカーボン分散剤）
　ナノカーボン分散剤は、ナノカーボンを分散させるための薬剤である。本実施形態に係るナノカーボン分散剤は、セルロースナノクリスタルを含有する。ナノカーボン分散剤の形態としては、例えば、セルロースナノクリスタルを水に分散させた状態のスラリー品（以下、形態Ｌという。）、該スラリー品を乾燥させて得られるセルロースナノクリスタルのスプレードライ品（以下、形態Ｍという。）、又は該スラリー品の分散媒を水以外の分散媒に置換した分散液（以下、形態Ｎという。）がある。ナノカーボン分散剤が、形態Ｌである場合、ナノカーボンを形態Ｌのスラリー品に添加することによって、分散媒が水であるナノカーボン分散液を容易に調製することができる。ナノカーボン分散剤が、形態Ｍである場合、使用の形態としては、例えば、ナノカーボンとナノカーボン分散剤とを分散媒に同時に添加すること、又はナノカーボンを分散媒に分散させた液中にナノカーボン分散剤を添加することがある。ここにおいて、分散媒が水ならば、ナノカーボンの疎水性の観点から、ナノカーボンとナノカーボン分散剤とを分散媒に同時に添加することが好ましい。ナノカーボン分散剤が、形態Ｎである場合、ナノカーボンを形態Ｎの分散液に添加することによって、分散媒が水以外の分散媒であるナノカーボン分散液を容易に調製することができる。 (Nanocarbon dispersant)
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). Hereinafter, there is a dispersion liquid (hereinafter, referred to as Form N) in which the dispersion medium of the slurry product is replaced with a dispersion medium other than water. When the nanocarbon dispersant is in the form L, 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. When the nanocarbon dispersant is in the form M, 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. Here, if 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. When 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.
　以下、本発明について実施例に基づき具体的に説明するが、本発明はこれら実施例に限定されるものではない。なお、以下の説明において、量を表す「％」及び「部」は、特に断らない限り、質量基準である。 Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the following description, "%" and "part" representing the amount are based on mass unless otherwise specified.
（ＣＮＣの製造）
　針葉樹サルファイトパルプのシートを乾式で粗粉砕して綿状繊維とし、この綿状繊維の固形分濃度が３質量％となるように、６４％硫酸水溶液に綿状繊維を添加して第１の懸濁液を調製し、懸濁液中にて４５℃で６０分間綿状繊維を加水分解させた。第１の懸濁液をイオン交換水により５倍に希釈し、懸濁物を沈降させて上澄み液を除く操作を、上澄み液のｐＨが５以上になるまで繰り返した。得られた懸濁物を遠心分離により濃縮し、その後イオン交換水を添加して固形分濃度を２質量％に調整し、第２の懸濁液を得た。第２の懸濁液を超音波ホモジナイザー（ＵＳ３００Ｅ、日本精機製作所製）により解繊処理し、次いでスプレードライ方式により水を除去しパウダー状のＣＮＣを得た。 (Manufacturing of CNC)
A sheet of coniferous sulfite pulp is roughly crushed by a dry method to obtain cotton-like fibers, and cotton-like fibers are added to a 64% sulfuric acid aqueous solution so that the solid content concentration of the cotton-like fibers becomes 3% by mass. A suspension was prepared and the cotton fibers were hydrolyzed in the suspension at 45 ° C. for 60 minutes. The operation of diluting the first suspension with ion-exchanged water 5-fold, allowing the suspension to settle and removing the supernatant was repeated until the pH of the supernatant became 5 or higher. 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）
　各実施例及び比較例で用いるカーボンナノチューブは下記のとおりである。尚、各カーボンナノチューブは市販品である。
　ＣＮＴ（Ａ）：カーボンナノチューブ
（商品名：Ｋ－ｎａｎｏｓ１００Ｐ、多層型ＣＮＴ、Ｋｕｍｈｏ Ｐｅｔｒｏｃｈｅｍｉｃａｌ社製、繊維長（Ｂｕｎｄｌｅ Ｄｉａｍｅｔｅｒ）３μｍ、繊維径８～１５ｎｍ、比表面積２２０ｍ２／ｇ）
　ＣＮＴ（Ｂ）：カーボンナノチューブ
（商品名：ｎａｎｏｃｙｌ－７０００、多層型ＣＮＴ、ｎａｎｏｃｙｌ社製、数平均繊維長１．５μｍ、数平均繊維径９．５ｎｍ、比表面積２５０～３００ｍ２／ｇ） (CNT)
The carbon nanotubes used in each Example and Comparative Example are as follows. Each carbon nanotube is a commercially available product.
CNT (A): Carbon nanotube (trade name: K-nanos100P, multi-walled CNT, manufactured by Kumho Petrochemical, fiber length (Bundle Diameter) 3 μm, fiber diameter 8 to 15 nm, specific surface area 220 m 2 / g)
CNT (B): Carbon nanotube (trade name: nanocil-7000, multi-walled CNT, manufactured by nanocil, number average fiber length 1.5 μm, number average fiber diameter 9.5 nm, specific surface area 250 to 300 m 2 / g)
（実施例１）
　得られたＣＮＣを分散剤としてイオン交換水に添加して攪拌し、次いでＣＮＴ（Ａ）をイオン交換水と共に徐々に添加し、混合液を得た。混合液中のＣＮＣの濃度は２質量％であり、ＣＮＴ（Ａ）の濃度は２質量％であった。得られた混合液を、バイオミキサー（ＢＭ－２型、日本精機製作所）を用いて３０分間分散処理し、６０メッシュ篩で濾した後、高圧ホモジナイザー（商品名：アルティマイザー、スギノマシン社製）により２００ＭＰａの圧力にて１０回パスさせカーボンナノチューブ分散液を得た。 (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.
（実施例２）
　混合液中のＣＮＣの濃度が０．２質量％になるようにＣＮＣを添加した以外は実施例１と同様にしてカーボンナノチューブ分散液を得た。 (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.
（実施例３）
　混合液中のＣＮＣの濃度が１０質量％になるようにＣＮＣを添加した以外は実施例１と同様にしてカーボンナノチューブ分散液を得た。 (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.
（実施例４）
　混合液中のＣＮＴ（Ａ）の濃度が１質量％になるようにＣＮＴ（Ａ）を添加し、ＣＮＣの濃度が１質量％になるようにＣＮＣを添加した以外は実施例１と同様にしてカーボンナノチューブ分散液を得た。 (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.
（実施例５）
　混合液中のＣＮＴ（Ａ）の濃度が１質量％になるようにＣＮＴ（Ａ）を添加し、ＣＮＣの濃度が０．１質量％になるようにＣＮＣを添加した以外は実施例１と同様にしてカーボンナノチューブ分散液を得た。 (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.
（実施例６）
　混合液中のＣＮＴ（Ａ）の濃度が１質量％になるようにＣＮＴ（Ａ）を添加し、ＣＮＣの濃度が１０質量％になるようにＣＮＣを添加した以外は実施例１と同様にしてカーボンナノチューブ分散液を得た。 (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.
（実施例７）
　ＣＮＴ（Ａ）をＣＮＴ（Ｂ）に変更し、混合液中のＣＮＴ（Ｂ）の濃度が１．５質量％になるようにＣＮＴ（Ａ）を添加し、ＣＮＣの濃度が１．５質量％になるようにＣＮＣを添加した以外は実施例１と同様にしてカーボンナノチューブ分散液を得た。 (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.
（比較例１）
　ＣＮＣを、広葉樹クラフトパルプを機械的に解繊処理（処理機：スーパーマスコロイダー、増幸産業社製）することにより得られたセルロースナノファイバーに変更した以外は実施例１と同様にして、カーボンナノチューブ分散液を得た。 (Comparative 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.
（比較例２）
　ＣＮＣをカルボキシメチルセルロース（ＣＭＣ、セロゲンＰＲ、第一工業製薬製）に変更した以外は実施例１と同様にして処理したが、高圧ホモジナイザー処理中に粘度が上昇し、高圧ホモジナイザー内が閉塞して目的とするカーボンナノチューブ分散液を得ることができなかった。 (Comparative 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.
（比較例３）
　ＣＮＣをカルボキシメチルセルロース（ＣＭＣ、セロゲンＷＳ－Ｃ、第一工業製薬製）に変更し、混合液中のＣＮＴ（Ａ）の濃度が１．５質量％になるようにＣＮＴ（Ａ）を添加し、カルボキシメチルセルロースの濃度が１．５質量％になるようにカルボキシメチルセルロースを添加した以外は実施例１と同様にして処理したが、高圧ホモジナイザー処理中に粘度が上昇し、高圧ホモジナイザー内が閉塞して目的とするカーボンナノチューブ分散液を得ることができなかった。 (Comparative Example 3)
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. 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.
（比較例４）
　混合液にＣＮＣを添加しなかった以外は実施例１と同様にして、カーボンナノチューブ分散液を得た。 (Comparative 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.
（比較例５）
　ＣＮＣを、分散効果を有する界面活性剤（ドデシル硫酸ナトリウム、東京化成工業社製）に変更した以外は実施例１と同様としたが、バイオミキサーでの分散処理の段階で多量の泡が発生し、高圧ホモジナイザーでの処理を行うことができなかった。 (Comparative 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.
　各実施例及び比較例で得たナノカーボン分散液の組成及び評価を表１に記載した。尚、ナノカーボン分散液の評価は、それぞれ以下の方法を用いた。 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.
（分散性）
　分散処理して得られたナノカーボン分散液をＣＮＴ濃度が０．０５質量％となるようイオン交換水で希釈し、ガラス製バイアル瓶で１時間放置した後に目視観察にて以下の基準で評価した。
　Ａ：凝集物の沈降及びＣＮＴと水との分離が無く良好である。
　Ｂ：凝集物の沈降は無く、ＣＮＴと水との分離が僅かであり良好である。
　Ｃ：細かい凝集物があり、ＣＮＴと水との小さな分離も確認できる（実用下限）。
　Ｄ：凝集物の殆どが大きく、水との分離も大きい（実用不可）。 (Dispersiveness)
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).
（流動性）
　分散処理して得られたナノカーボン分散液の粘度をＢ型粘度計（Ｎｏ．１～４ローター）（商品名：Ｂ型粘度計、型式：ＢＭ、東京計器製作所製）を用い、２０℃にて回転数６０ｒｐｍで１分間回転させて粘度を測定し、その数値から下記Ａ～Ｄの基準で評価した。
　Ａ：Ｂ型粘度は１００ｍＰａ・ｓ以下であり、流動性が非常に良好である。
　Ｂ：Ｂ型粘度は１０００ｍＰａ・ｓ以下であり、流動性が良好である。
　Ｃ：Ｂ型粘度は２０００ｍＰａ・ｓ以下であり、流動性が確認できる（実用下限）。
　Ｄ：Ｂ型粘度は５０００ｍＰａ・ｓを超え、流動性に欠ける（実用不可）。 (Liquidity)
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.
A: B type viscosity is 100 mPa · s or less, and the fluidity is very good.
B: B-type viscosity is 1000 mPa · s or less, and the fluidity is good.
C: 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).
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１の結果より、実施例１～７では、安定的に分散し、流動性の良好なカーボンナノ材料分散液が得られた。比較例１はＣＮＣの代わりにＣＮＦを用いたが分散性、流動性ともに悪いものとなった。比較例２及び比較例３では、分散剤としてＣＮＣの代わりにＣＭＣを用いたため、粘度が高くかつ粘調質となり分散機器を閉塞させ分散液を得ることができなかった。比較例４ではＣＮＣを使用しなかったため、疎水性の高いＣＮＴ単独では分散できず、大きな凝集体となり沈降を生じた。比較例５では分散剤としてＣＮＣの代わりに界面活性剤を用いたため、分散処理の際、泡立ちが生じ処理を進めることができなかった。
 
  From the results shown in Table 1, in Examples 1 to 7, carbon nanomaterial dispersions having stable dispersion and good fluidity were obtained. In Comparative Example 1, CNF was used instead of CNC, but both dispersibility and fluidity were poor. In Comparative Example 2 and Comparative Example 3, since CMC was used as the dispersant instead of CNC, the viscosity was high and the viscosity became viscous, and the dispersion equipment was clogged and the dispersion liquid could not be obtained. Since CNC was not used in Comparative Example 4, CNTs having high hydrophobicity alone could not be dispersed, resulting in large aggregates and sedimentation. In Comparative Example 5, since a surfactant was used instead of CNC as the dispersant, foaming occurred during the dispersion treatment and the treatment could not proceed.

Claims (11)

  1. 　ナノカーボンとセルロースナノクリスタルと分散媒とを含有することを特徴とするナノカーボン分散液。 A nanocarbon dispersion characterized by containing nanocarbon, cellulose nanocrystals, and a dispersion medium.
  2. 　前記ナノカーボンの濃度が１質量％以上であることを特徴とする請求項１に記載のナノカーボン分散液。 The nanocarbon dispersion according to claim 1, wherein the concentration of the nanocarbon is 1% by mass or more.
  3. 　前記ナノカーボンと前記セルロースナノクリスタルとの質量基準の含有比率（ナノカーボン：セルロースナノクリスタル）が１：０．１～１：１０であることを特徴とする請求項１又は２に記載のナノカーボン分散液。 The nanocarbon according to claim 1 or 2, wherein the content ratio (nanocarbon: cellulose nanocrystal) based on the mass of the nanocarbon and the cellulose nanocrystal is 1: 0.1 to 1:10. Dispersion solution.
  4. 　前記ナノカーボンの濃度が１質量％以上４質量％以下であり、かつ前記ナノカーボンと前記セルロースナノクリスタルとの合計濃度が１質量％を超えて１５質量％以下であることを特徴とする請求項１～３のいずれか１つに記載のナノカーボン分散液。 The claim is characterized in that 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 is more than 1% by mass and 15% by mass or less. The nanocarbon dispersion according to any one of 1 to 3.
  5. 　前記分散媒が極性溶媒であることを特徴とする請求項１～４のいずれか１つに記載のナノカーボン分散液。 The nanocarbon dispersion liquid according to any one of claims 1 to 4, wherein the dispersion medium is a polar solvent.
  6. 　前記極性溶媒が、アルコール類、ケトン類若しくは水又はこれらの混合物であることを特徴とする請求項５に記載のナノカーボン分散液。 The nanocarbon dispersion according to claim 5, wherein the polar solvent is an alcohol, a ketone, water, or a mixture thereof.
  7. 　ナノカーボンとセルロースナノクリスタルと分散媒とを含有する混合液を分散機で分散処理することを特徴とするナノカーボン分散液の製造方法。 A method for producing a nanocarbon dispersion, which comprises dispersing a mixture containing nanocarbon, cellulose nanocrystals, and a dispersion medium with a disperser.
  8. 　前記混合液が、前記分散媒に前記セルロースナノクリスタルを添加して攪拌した後に前記ナノカーボンを添加して調製した混合液であることを特徴とする請求項７に記載のナノカーボン分散液の製造方法。 The production of the nanocarbon dispersion according to claim 7, wherein the mixture is a mixture prepared by adding the cellulose nanocrystals to the dispersion medium, stirring the mixture, and then adding the nanocarbons. Method.
  9. 　前記セルロースナノクリスタルがスプレードライ品であることを特徴とする請求項７又は８に記載のナノカーボン分散液の製造方法。 The method for producing a nanocarbon dispersion according to claim 7 or 8, wherein the cellulose nanocrystal is a spray-dried product.
  10. 　前記分散機がホモジナイザーであることを特徴とする請求項７～９のいずれか１つに記載のナノカーボン分散液の製造方法。 The method for producing a nanocarbon dispersion liquid according to any one of claims 7 to 9, wherein the disperser is a homogenizer.
  11. 　セルロースナノクリスタルを含有することを特徴とするナノカーボン分散剤。 A nanocarbon dispersant characterized by containing cellulose nanocrystals.
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