JP2016153367A - Carbon nanotube dispersion, manufacturing method therefor, carbon nanotube-containing thermoelectric transducer and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon nanotube dispersion by dispersing carbon nanotube with orientation and a manufacturing method therefor, and a carbon nanotube-containing thermoelectric transducer having high powder generating efficiency and a manufacturing method therefor.SOLUTION: A manufacturing method of a carbon nanotube-containing dispersion includes (a) a process of emulsion dispersing a first surfactant into a first water phase to prepare a first emulsion, (b) a process of emulsion dispersing the first emulsion and a second surfactant into a first oil phase to prepare a second emulsion, (c) a process of preparing a mixture by mixing carbon nanotube in an organic solvent to which a resin is dissolved and (d) a process of emulsion dispersing a mixture of the second emulsion and the mixture.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a carbon nanotube dispersion, a production method thereof, a carbon nanotube-containing thermoelectric conversion element, and a production method thereof.

  The carbon nanotube has a structure in which graphene in which six-membered rings of carbon atoms are continuously formed is rounded into a tubular shape, and a single-walled carbon nanotube (Single-Walled Carbon) Nanotube, SWCNT), and multi-walled carbon nanotubes (Multi-Walled Carbon Nanotube, MWCNT).

  Since carbon nanotubes exhibit various characteristics due to their special geometric structure, their application to various devices and functional materials has been studied in many technical fields. One of them has been studied for application to a thermoelectric conversion element. For example, Patent Document 1 discloses a process for preparing a dispersion for a thermoelectric conversion layer containing a nano-conductive material by subjecting a carbon nanotube and a dispersion medium to a high-speed rotating thin film dispersion method, and a prepared dispersion for a thermoelectric conversion layer. The manufacturing method of the thermoelectric conversion element which has the process of apply | coating to a base material and drying is disclosed.

  Patent Document 2 discloses a thermoelectric conversion element including a thermoelectric conversion member made of a thermoelectric conversion material containing a carbon nanotube mixture containing a semiconductor type with a purity of 70% or more with respect to the sum of a metal type and a semiconductor type. The thermoelectric conversion element formed by making the thermoelectric conversion member and the 2nd thermoelectric conversion member which consists of the 2nd thermoelectric conversion material from which thermoelectric conversion materials differ in thermoelectric conversion material electrically is disclosed.

JP 2014-209573 A JP 2014-239092 A

  In order to manufacture a thermoelectric conversion element containing carbon nanotubes, it is necessary to use a thermoelectric conversion member in which carbon nanotubes are dispersed. However, carbon nanotubes themselves do not dissolve in water or organic solvents, and these are simply mixed. By simply stirring, the carbon nanotubes exist as aggregates called bundles and are not uniformly dispersed in the mixed solution.

  Therefore, as a method for dispersing the surface of the carbon nanotube without chemically modifying it, various surfactants and conjugated compounds are added to the liquid in which the carbon nanotube is mixed as described in Patent Document 1 and Patent Document 2. In general, a method of dispersing carbon nanotubes in a solution by performing a dispersion process using a dispersing device (mixing device) or ultrasonic waves is generally known.

  However, even if the carbon nanotubes are dispersed by such a method, the orientation of the carbon nanotubes is not constant, and the carbon nanotubes are dispersed in an unspecified direction. When a thermoelectric conversion member is manufactured using such a dispersion, there is a problem in that it is difficult to obtain a high carbon nanotube conductive network desirable for manufacturing a thermoelectric conversion element with high power generation efficiency.

  An object of the present invention is to provide a carbon nanotube dispersion liquid in which carbon nanotubes are dispersed with orientation and a manufacturing method thereof, and to provide a carbon nanotube-containing thermoelectric conversion element having high power generation efficiency and a manufacturing method thereof. To do.

In order to achieve the above object, the present invention includes the following aspects.
(1) (a) a step of emulsifying and dispersing the first surfactant in the first aqueous phase to prepare a first emulsion;
(B) emulsifying and dispersing the first emulsion and the second surfactant in the first oil phase to prepare a second emulsion;
(C) preparing a mixed solution in which carbon nanotubes are mixed in an organic solvent in which a resin is dissolved;
(D) emulsifying and dispersing a mixed liquid of the second emulsion and the mixed liquid;
The manufacturing method of the carbon nanotube dispersion liquid containing this.
(2) The first surfactant includes a polymeric surfactant and a surfactant having an HLB of 5 to 18, and the second surfactant has a polymeric surfactant and an HLB of 10 The manufacturing method of the carbon nanotube dispersion liquid as described in said (1) containing the following surfactants.
(3) The emulsification dispersion method in at least one of the steps (a), (b) and (d) is a method in which a mixed liquid containing a dispersion medium and a dispersion medium is at least linear under a pressure of 50 MPa to 250 MPa. The method for producing a carbon nanotube dispersion according to (1) or (2), wherein the dispersion is emulsified and dispersed in the dispersion medium by passing through a pipe and a spiral pipe.
(4) The straight pipe has an inner diameter of 0.09 to 0.4 mm and a length of 0.1 to 500 mm, and the spiral pipe has an inner diameter of 0.2 to 0.4 mm and a length of 10 to 500 mm. The method for producing a carbon nanotube dispersion liquid according to (3), wherein the helical diameter is 5 to 10 mm.
(5) (A) a step of emulsifying and dispersing a carbon nanotube, a first organic solvent, and a first aqueous phase containing a first surfactant to prepare a third emulsion;
(B) emulsifying and dispersing a second organic solvent, a second surfactant, a resin, and the third emulsion to prepare a fourth emulsion;
(C) a step of subjecting the fourth emulsion to a high-pressure shear type emulsification dispersion treatment;
The manufacturing method of the carbon nanotube dispersion liquid containing this.
(6) The high-pressure shearing type emulsification dispersion processing method in the step (C) is performed by allowing a mixed liquid containing a dispersion medium and a dispersion medium to pass through at least a straight pipe and a helical pipe under a pressure of 50 MPa to 250 MPa. The dispersion is a method of emulsifying and dispersing the dispersion in the dispersion medium, wherein the straight pipe has an inner diameter of 0.09 to 0.4 mm, a length of 0.1 to 500 mm, and the spiral pipe has an inner diameter. Is 0.2 to 0.4 mm, the length is 10 to 500 mm, and the helical diameter is 5 to 10 mm. The method for producing a carbon nanotube dispersion liquid according to (5) above.
(7) An emulsion in which a first micelle assembly containing a first surfactant is micellized in a first oil phase with a second surfactant, and a mixed liquid in which carbon nanotubes are mixed in an organic solvent in which a resin is dissolved, A carbon nanotube dispersion liquid obtained by emulsifying and dispersing.
(8) The first surfactant includes a polymer surfactant and a surfactant having an HLB of 5 to 18, and the second surfactant has a polymer surfactant and an HLB of 10 The carbon nanotube dispersion liquid according to (7), including the following surfactant.
(9) A carbon nanotube dispersion liquid produced by the method according to any one of (1) to (6).
(10) A step of applying the carbon nanotube dispersion liquid according to any one of (7) to (9) on a flat plate;
Drying the coated carbon nanotube dispersion to form a carbon nanotube-dispersed resin film;
A step of arranging a plurality of the carbon nanotube-dispersed resin films so as to change the overlapping direction;
The manufacturing method of the carbon nanotube containing thermoelectric conversion element containing this.
(11) including a thermoelectric conversion member configured by stacking two or more carbon nanotube-dispersed resin films in which carbon nanotubes are dispersed;
A carbon nanotube-containing thermoelectric conversion element in which the two superposed adjacent carbon nanotube dispersed resin films of the thermoelectric conversion member have different overlapping directions.
(12) The carbon nanotube-containing thermoelectric conversion according to (11), wherein an angle formed by the overlapping direction of the two adjacent carbon nanotube-dispersed resin films overlapping each other is in a range of 30 ° to 90 °. element.

  According to the present invention, it is possible to provide a carbon nanotube dispersion liquid in which carbon nanotubes are dispersed with orientation and a method for producing the same, and provide a carbon nanotube-containing thermoelectric conversion element with high power generation efficiency and a method for producing the same. it can.

1 is a schematic configuration diagram of a high-pressure shearing type emulsifying dispersion device according to an embodiment of the present invention. (A) is a micrograph showing the CNT network of the CNT-dispersed resin film of the example, and (b) is a micrograph of the CNT-dispersed resin film obtained from a dispersion in which the CNTs are not dispersed while maintaining their orientation. . (A) is a graph showing the relationship between the type of CNT, the inner diameter of the first tubule, and the volume resistance value of the obtained CNT-dispersed resin film, and (b) is the type of CNT, the inner diameter of the second tubule. It is a graph which shows the relationship with the volume resistance value of the CNT dispersion | distribution resin film. (A) is an electron micrograph of a CNT dispersion with a high performance CNT dispersion resin film, and (b) is an electron micrograph of a CNT dispersion with a low performance CNT dispersion resin film. It is a graph which shows the relationship between the frequency | count of a coating of a CNT dispersion | distribution resin film, and the electromotive force of the obtained lamination | stacking CNT containing thermoelectric conversion element.

(Embodiment 1)
Embodiment 1 (Embodiment 1) of a method for producing a carbon nanotube dispersion, a carbon nanotube dispersion, a carbon nanotube-containing thermoelectric conversion element, and a carbon nanotube-containing thermoelectric conversion element production method according to the present invention will be described below.

(carbon nanotube)
The carbon nanotubes (hereinafter also referred to as “CNT”) used in Embodiment 1 are preferably single-walled CNTs, and more preferably single-walled CNTs containing as much semiconductor-type single-walled CNTs as possible. The structure of a carbon nanotube can be represented by a chiral vector (Ch = na1 + ma2) represented by a basic vector (a1 and a2) of a six-membered ring of carbon, and (n, m) is called a chiral index. Semiconductor chiral CNTs whose (nm) of this chiral index is not a multiple of 3 are.

  When a CNT is manufactured by a manufacturing method in which the type of the generated CNT is not specified, a CNT in which a semiconductor type and a metal type are mixed at a ratio of 2 to 1 is generated. As the CNT used in the first embodiment, a semiconductor CNT concentrated from a mixture of semiconductor CNT and metal CNT may be used, or a manufacturing method (chemical vapor deposition method or the like) mainly generating semiconductor CNT. CNT produced by the above method may be used.

(Manufacture of CNT dispersion)
A method for producing the CNT dispersion according to the first embodiment will be described. First, a method for preparing a dispersion medium for dispersing CNTs will be described. The dispersion medium according to Embodiment 1 is a multilayer emulsion in which a surfactant is further oriented around the micelle of the surfactant to form micelles.

(Preparation of dispersion medium)
Specifically, a multilayer emulsion as a carbon nanotube dispersion medium is prepared by the following process.
(Step 1) A first emulsion is prepared by mixing and emulsifying the first surfactant in the first aqueous phase.
(Process 2) A 1st oil phase and a 2nd surfactant are mixed with a 1st emulsion, and a 2nd emulsion is prepared by emulsifying.

  In addition, in each said process, the order which adds each component is not specifically limited. For example, in step 2, the first oil phase and the second surfactant may be sequentially added to the first emulsion to emulsify, or the first oil phase and the second surfactant may be mixed in advance. You may emulsify in addition to a 1st emulsion.

  Further, a second aqueous phase and a third surfactant may be further mixed into the second emulsion and emulsified to prepare a third emulsion, which may be used as a carbon nanotube dispersion medium. As the third surfactant, the same surfactant as the hydrophilic surfactant (described later) contained in the first surfactant can be used. Moreover, the same kind as the upper first water phase can be used as the second water phase.

  In the first emulsion, the first micelles in which the first surfactant is oriented and assembled with the hydrophilic portion facing outward are dispersed in the first aqueous phase (O / W emulsion). The second emulsion is a fine first aqueous phase droplet containing a plurality of first micelles, in which second micelles in which the second surfactant is oriented with the hydrophobic portion facing outward are dispersed in the first oil phase. (O / W / O emulsion).

  The first surfactant used in step 1 preferably includes a polymer surfactant and a hydrophilic surfactant. By using such a combination, a fine and uniform first emulsion can be obtained. In addition, the mixing amount of the first surfactant may be an amount that becomes a critical micelle concentration or more. The mixing ratio of the polymeric surfactant and the hydrophilic surfactant is 30:70 to 98: 2 by weight, preferably 40:60 to 95: 5, more preferably 60:40. ~ 90: 10.

  As the hydrophilic surfactant contained in the first surfactant, a surfactant having an HLB value (Hydrophile-Lipophile Balance) of 5 to 18, particularly 6 to 12 is preferable. Specifically, tetraisostearate polyoxyethylene sorbite, tetraoleate polyoxyethylene sorbite, monolaurate polyoxyethylene sorbitol, polyisoethylene stearate polyoxyethylene glyceryl, polyoxyethylene oleate glyceryl, monolaurate polyethylene glycol, monoolein Polyethylene glycol acid, polyethylene glycol diisostearate, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene hydrogenated castor oil, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monolaurate (16.7), polyoxyethylene sorbitan isostearate, triole Phosphate polyoxyethylene sorbitan, polyglycerin isostearic acid ester, polyglycerin laurate, polyglycerin oleate ester, polyvinyl alcohol, polyethylene glycol and the like. These may be used alone or in combination of two or more. There are several calculation methods for obtaining the HLB value, and any of the above calculation methods may be used.

  Examples of the polymeric surfactant contained in the first surfactant include sodium sulfonate formalin condensate (for example, sodium naphthalene sulfonate formalin condensate), sodium polycarboxylate, styrene-maleic acid half ester copolymer ammonium salt. Ionic polymer type surfactants such as ammonium salt of styrene-maleic acid copolymer, sodium polyacrylate, ammonium polyacrylate, sodium carboxymethylcellulose, and the like.

  The second surfactant used in step 2 preferably includes a polymer surfactant and a hydrophobic surfactant. By using such a combination, a fine and uniform second emulsion can be obtained. In addition, the mixing amount of the second surfactant may be an amount that becomes a critical micelle concentration or more. The mixing ratio of the polymeric surfactant and the hydrophobic surfactant is 30:70 to 98: 2 by weight, preferably 40:60 to 95: 5, and more preferably 60:40. ~ 90: 10.

  As the hydrophobic surfactant contained in the second surfactant, those having an HLB value of 10 or less are preferred, those having 7 or less are more preferred, and those having 1 to 5 are particularly preferred. Specific examples include glycerin fatty acid esters, sucrose fatty acid esters, sorbitan fatty acid esters, and lecithins.

  Specific examples of glycerol fatty acid esters include monoglycerol monocaprylate, monoglycerol monocaprate, monoglycerol dicaprylate, monoglycerol dicaprate, monoglycerol dilaurate, and monoglycerol dimyristate. , Monoglycerin distearate, monoglycerin dioleate, monoglycerin dierucate, monoglycerin dibehenate, monoglycerin fatty acid ester, monoglycerin caprylic acid succinate, monoglycerin stearate citrate , Monoglycerol stearate acetate, monoglycerol stearate succinate, monoglycerol stearate lactate, monoglycerol Fatty acid partial glycerides such as monoglycerin fatty acid organic acid esters such as diacetyltartaric acid ester of mono-tearate, monoglycerin oleic acid citrate; hexaglycerin monocaprylic acid ester, hexaglycerin dicaprylic acid ester, decaglycerin monocaprylic acid ester, triglycerin Monolaurate, Tetraglycerol monolaurate, Pentaglycerol monolaurate, Hexaglycerol monolaurate, Decaglycerol monolaurate, Triglycerol monomyristate, Pentaglycerol monomyristate, Pentaglycerol trimyristate, Hexa Glycerin monomyristic acid ester, decaglycerin monomyristic acid ester, jig Serine monooleate, triglycerol monooleate, tetraglycerol monooleate, pentaglycerol monooleate, hexaglycerol monooleate, decaglycerol monooleate, diglycerol monostearate, triglycerol Monostearic acid ester, tetraglycerin monostearic acid ester, pentaglycerin monostearic acid ester, pentaglycerin tristearic acid ester, hexaglycerin monostearic acid ester, hexaglycerin tristearic acid ester, hexaglycerin distearic acid ester, decaglycerin monostearate Acid ester, decaglycerin distearate, decaglycerin tristearate And polyglycerin fatty acid esters such as tetra; polyglycerin condensed ricinoleic acid esters such as tetraglycerin condensed ricinoleic acid ester, pentaglycerin condensed ricinoleic acid ester and hexaglycerin condensed ricinoleic acid ester.

  Examples of the sucrose fatty acid esters include those obtained by esterifying one or more hydroxyl groups of sucrose with fatty acids having 6 to 18 carbon atoms, preferably 6 to 12 carbon atoms, and specifically, sucrose palmitic acid. Examples include acid esters and sucrose stearates.

  Examples of sorbitan fatty acid esters include those obtained by esterifying one or more hydroxyl groups of sorbitans with fatty acids having 6 to 18 carbon atoms, preferably 6 to 12 carbon atoms, and specifically, sorbitan monostearic acid. Examples thereof include esters and sorbitan monooleate.

  Specific examples of lecithins include egg yolk lecithin, soybean lecithin, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, sphingomyelin, dicetylphosphate, stearylamine, phosphatidylglycerol, phosphatidic acid, phosphatidylinositolamine, cardiolipin, ceramide phosphorylethanolamine, ceramide Examples include phosphorylglycerol, lysolecithin, and mixtures thereof.

  Examples of the polymeric surfactant contained in the second surfactant include sodium sulfonate formalin condensate (for example, sodium naphthalene sulfonate formalin condensate), sodium polycarboxylate, styrene-maleic acid half ester copolymer ammonium salt, Examples thereof include ionic polymer type surfactants such as ammonium salt of styrene-maleic acid copolymer, sodium polyacrylate, ammonium polyacrylate, sodium carboxymethylcellulose and the like.

  The organic solvent as the first oil phase used in step 2 is not particularly limited as long as it is a volatile organic solvent that can dissolve other oil phase components and is immiscible with water. Specific examples include dichloromethane, chloroform, ethyl acetate, 1.2-dichloroethane, toluene and the like. These may be used alone or in combination of two or more.

  In step 2, the charge ratio of the aqueous phase to the oil phase, that is, the charge ratio of the first emulsion to the first oil phase (including the second surfactant) is not particularly limited, but the mass ratio of the water phase / oil phase is The ratio is preferably 0.01 / 99.99 to 50/50, more preferably 0.1 / 99.9 to 30/70, and particularly preferably 1/99 to 20/80.

  Moreover, tap water, purified water, distilled water, ion-exchanged water, or the like can be used as the first aqueous phase used in step 1. Moreover, you may add a small amount of hydrophilic organic solvents and additives. The hydrophilic organic solvent is not particularly limited as long as it is easily soluble in an aqueous phase; ketones such as acetone and methyl ethyl ketone; methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol , Isobutyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3 -Alcohols such as butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, glycerin; nitriles such as acetonitrile, propionitrile, succinonitrile, butyronitrile, isobutyronitrile : Diethyl ether, methyl tert-butyl ether, aniso Can be exemplified Le, ethers such as dioxane and tetrahydrofuran, and the like. Additives include pH adjusters, antifoaming agents, magnetic powders, fillers, flocking agents, curing agents, leveling agents, fluidity promoters, fluidity control agents, plasticizers, stabilizers, gas generation inhibitors, An antioxidant, a light stabilizer, a thickener, etc. are mentioned.

  Here, it is preferable that each micelle has a diameter (particle diameter) as small as possible and is distributed in a narrow range, that is, the particle diameter is as uniform as possible. When the particle diameters are distributed over a wide range, that is, when the particle diameters are not uniform, the effect of dispersing the single-walled CNTs with orientation decreases.

  Specifically, the volume average particle diameter is preferably adjusted to 0.1 to 20 μm, more preferably 0.1 to 10 μm.

(High pressure shearing type emulsification dispersion treatment)
In order to produce a multilayer emulsion containing fine micelle particles having a uniform particle size as much as possible, the emulsion is prepared by emulsifying a mixture of a dispersion to be emulsified and a dispersion medium as a medium by high-pressure shearing type emulsification dispersion treatment. . The high-pressure shearing type emulsification dispersion treatment in the first embodiment is an emulsification dispersion treatment method in which a mixture of a material to be dispersed, a dispersion medium, and a surfactant appropriately selected as necessary is passed through a capillary tube under high pressure. In the first embodiment, as a thin tube, both a finer micelle and a uniform micelle particle size are achieved by combining a linear first thin tube and a helical second thin tube for continuous treatment. That is, in the linear first tubule, the back pressure (resistance force) from the inner wall of the tubule becomes a shearing force, and the micelle particles are refined. In addition, in the spiral second tubule, the micelle particles receive a rotational force when the dispersion flows in the tubule, and the particle size is gradually made uniform by repeating dispersion and coalescence.

  The treatment pressure in the high-pressure shear type emulsification dispersion treatment is 50 MPa to 250 MPa. The first capillary has an inner diameter of 0.1 mm to 2.0 mm, and an overall length of 0.1 mm to 500 mm. The second capillary has an inner diameter of 0.1 mm to 2.0 mm, an overall length of 10 mm to 500 mm, and a helical diameter of 5 mm to 10 mm. The pressure at the outlet of the second thin tube is not particularly limited, but is preferably atmospheric pressure.

  In addition, you may use the nozzle connected and connected to the inlet side and / or outlet side of a 1st thin tube and / or a 2nd thin tube. Although the nozzle is not particularly limited, the nozzle on the outlet side of the second capillary tube performs multi-stage pressure reduction in which the liquid pressure is reduced in multiple stages and reduced to a pressure at which no bubbling occurs even when released to the atmosphere at the outlet. preferable. As such a nozzle, for example, a diamond nozzle (manufactured by Miki Co., Ltd.) can be mentioned. The diamond nozzle has a structure in which a diamond sandwiches a flow path having a length of 0.4 mm. The flow path can be set to 0.1 mm to 1 mm, and the diameter (width) can be set to 0.09 to 0.13 mm. This diamond nozzle is similar to the energy application of the conventional collision type high-pressure emulsification apparatus, but cavitation hardly occurs because the pressure is returned from high pressure to normal pressure in multiple stages.

  You may repeat the continuous process by a 1st thin tube and a 2nd thin tube twice or more. By repeating, the degree of miniaturization and homogenization is improved, and a finer and more uniform emulsified dispersion can be obtained.

(Preparation of CNT organic solvent mixture)
The CNT to be dispersed is first stirred and mixed in an organic solvent in which a resin is dissolved. The organic solvent only needs to dissolve the resin. The resin has a role as a base material for fixing the CNTs finally dispersed with orientation while maintaining the orientation. Therefore, the resin concentration in the organic solvent only needs to ensure a film-like thickness when the dispersion is applied and dried, and is, for example, 0.1 to 20% by weight, and is 1 to 10% by weight. It is more preferable. The CNT concentration is, for example, 0.1 to 20% by weight, and more preferably 1 to 10% by weight. The weight ratio between the resin amount and the CNT amount is preferably 1: 9 to 9: 1, more preferably 1: 4 to 4: 1, and 2: 3 to 3: 2. Most preferred. These mixed solutions are stirred to obtain a CNT organic solvent mixed solution. At this stage, it is not always necessary to emulsify.

  As the organic solvent for preparing the CNT organic solvent mixed solution, for example, the organic solvents mentioned above as the organic solvent used as the first oil phase can be used.

  The resin for preparing the CNT organic solvent mixed solution is not particularly limited as long as the resin is soluble in the organic solvent. Specifically, acrylic ester resin, methacrylic ester resin, acrylic ester-methacrylic ester copolymer, acrylic acid resin, maleic acid resin, copolymer of styrene and maleic ester, styrene and acrylic acid or Copolymer with ester, copolymer of styrene and methacrylic acid or ester, urea resin, polyvinyl butyral, polyvinyl acetal, polyamide resin, ester gum, polyester resin, alkyd resin, polyurethane resin, epoxy resin, polyvinyl alkyl Ether, coumarone-indene resin, polyterpene, rosin resin and its hydrogenated product, ketone resin, terpene-phenol copolymer, polyacrylic acid polymethacrylic acid copolymer, phenol resin, polyethylene oxide, polyvinyl Pyrrolidone, N- vinyl acetamide, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, ethyl hydroxyethyl cellulose, and copolymers thereof and various derivatives thereof. These resins may be used alone or in combination of two or more.

(Preparation of CNT dispersion)
The above CNT organic solvent mixed solution and the above-described multi-layer emulsion subjected to the high-pressure shearing type emulsifying dispersion treatment are mixed, and the mixed solution is subjected to the above-described high-pressure shearing type emulsifying dispersion treatment for emulsification, thereby CNT dispersion. Prepare the solution. That is, a mixture of a CNT organic solvent mixed solution and a multilayer emulsion is continuously emulsified and dispersed with a first capillary and a second capillary under a pressure of 50 MPa to 250 MPa to prepare a CNT dispersion.

  The mixing ratio of the CNT organic solvent mixed solution and the multilayer emulsion is 100: 1 to 1: 1 by weight ratio, more preferably 50: 1 to 5: 1, depending on the CNT content. : More preferably, it is 1-5: 1.

  In the CNT dispersion produced by such a method, it is considered that the orientation directions of the respective CNTs are aligned and dispersed. The inventor speculates as follows for this reason. In this CNT dispersion, micelle fine particles having a uniform particle diameter are arranged over the entire CNTs. Since the micelle fine particles repel each other, the CNTs arranged with the micelle fine particles repel each other and do not aggregate.

  In addition, it is not part of the CNTs that are arranged with micelle particles with a uniform particle size, but because they are arranged throughout, a large number of CNTs are dispersed in the same direction without being crossed and repelling. It becomes. In this way, the CNTs can be dispersed while maintaining their orientation (directed in the same direction). A solution in which CNTs are dispersed in such a state is referred to as a CNT dispersion in which CNTs are dispersed with their orientation.

(CNT-containing thermoelectric conversion member)
The performance of the thermoelectric conversion member is represented by a figure of merit (Z) or a dimensionless figure of merit ZT = S ² T / ρκ obtained by multiplying this by the operating temperature T. Here, S is the Seebeck coefficient [V / K], ρ is the electrical resistivity [Ωm], and κ is the thermal conductivity [W / mK]. From this, in order to obtain a thermoelectric conversion member with high performance, it is better that the Seebeck coefficient is large, and that the electrical resistivity and thermal conductivity are small.

  Therefore, it is preferable that the thermoelectric conversion member used for the CNT-containing thermoelectric conversion element has a good conductive network between the CNTs in order to reduce the electrical resistivity (increase conductivity), and also has a low thermal conductivity as the whole element. .

  The thermoelectric conversion member according to Embodiment 1 is formed by stacking a plurality of resin thin films (hereinafter referred to as “CNT-dispersed resin films”) in which a CNT dispersion liquid in which CNTs are dispersed with the orientation thereof is fixed. To do. The inventors have found that when a CNT dispersion liquid in which CNTs are dispersed with their orientation is fixed with a resin, the CNTs are fixed while forming a three-dimensional network.

  Further, the two overlapping layers are preferably overlapped so that the orientation directions of the CNTs are different from each other. Specifically, the two layers are stacked so that the angle formed by the CNT alignment directions is 30 ° to 90 °. More preferably, it is 60 ° to 90 °, and most preferably, CNT dispersion is performed so that the orientation direction of CNTs in the CNT dispersed resin film overlapping (adjacent) vertically is 90 ° ± 5 ° (substantially orthogonal). This is a structure in which a plurality of resin films are stacked.

  By configuring as described above, a large number of contact points per unit area of CNTs between two adjacent CNT dispersed resin films are formed to form a good conductive network, and a plurality of CNT dispersed resin films are stacked. Thus, it is considered that the volume of the resin having a relatively low thermal conductivity increases, and the thermal conductivity of the entire device can be reduced.

  A CNT-containing thermoelectric conversion element can be obtained by attaching electrodes to both ends of the CNT-containing thermoelectric conversion member formed as described above.

(Method for producing CNT-containing thermoelectric conversion element)
Next, the preferable manufacturing method of the CNT containing thermoelectric conversion element using a CNT dispersion liquid is demonstrated. First, a CNT dispersion liquid containing resin in which CNTs are dispersed with their orientation is applied on a flat plate. Any coating method may be used. For example, the CNT dispersion liquid is dropped on a flat plate and is thinly stretched into a film with a casting knife or the like.

  Next, the CNT dispersion applied on the flat plate is dried by heating for 5 to 10 minutes at 80 to 90 ° C. (resin Tg (glass transition point) ± 10 ° C. as a guide) with the flat plate. Thereby, the volatile / evaporable medium in the dispersion is volatilized / evaporated, and a CNT-dispersed resin film in which the CNTs are fixed in the resin while maintaining a three-dimensional network is obtained.

  A plurality of CNT-dispersed resin films obtained as described above are stacked so that the orientation directions of CNTs are different to produce a CNT-containing thermoelectric conversion member. That is, the second CNT-dispersed resin film is stacked on the first CNT-dispersed resin film so that the CNT alignment directions are different. Next, the third CNT-dispersed resin film is overlaid so that the CNT alignment direction is different from the CNT-aligned direction of the second CNT-dispersed resin film. In this way, a plurality of CNT-dispersed resin films are sequentially stacked. In addition, since the CNT orientation directions of the CNT dispersed resin films obtained by the same production method are the same, the CNT dispersed resin films obtained by the same production method may be sequentially stacked while changing their directions.

  Finally, the CNT-containing thermoelectric conversion member is completed by applying pressure to the stacked CNT-dispersed resin film layers to bring them into close contact.

  Next, a conductive film layer is formed as an electrode on a CNT-containing thermoelectric conversion member shaped into a predetermined shape using a material such as ITO, gold, or aluminum. For example, a gold electric wire can be formed on both ends of a CNT-containing thermoelectric conversion member by a printing method, a vapor deposition method, or the like to form an electrode terminal. Thus, a CNT-containing thermoelectric conversion element is manufactured.

The produced CNT-containing thermoelectric conversion element measures the voltage and current by giving a temperature difference, and seebeck coefficient (S [V / K]: electromotive force per unit temperature difference) and power factor (PF = S ² / ρ, ρ can evaluate the performance of the element by obtaining the electrical resistivity [Ωm]).

(Embodiment 2)
Embodiment 2 (Embodiment 2) of a method for preparing a CNT dispersion liquid and a method for manufacturing a CNT-containing thermoelectric conversion element using a CNT dispersion resin film prepared from the CNT dispersion liquid according to the present invention will be described below. To do. In addition, about the part which overlaps with Embodiment 1, it demonstrates centering on a different part.

  The CNT used in the second embodiment is preferably a single-walled CNT, as in the case of the CNT used in the first embodiment, and more preferably a single-walled CNT containing as much semiconductor-type single-walled CNTs as possible.

A method for producing the CNT dispersion according to the second embodiment will be described. In Embodiment 2, a CNT dispersion liquid is manufactured through the following steps.
(Step (A)) CNT, a first organic solvent, and a first aqueous phase containing a first surfactant are emulsified and dispersed to prepare a third emulsion (first emulsification).
(Step (B)) A second organic solvent, a second surfactant, a resin, and a third emulsion are emulsified and dispersed to prepare a fourth emulsion (secondary emulsification).
(Step (C)) A CNT dispersion is produced by subjecting the fourth emulsion to high-pressure shear emulsification dispersion treatment and further emulsification dispersion.

  In the first embodiment, the second emulsion not containing CNT is prepared as a dispersion medium, and the CNT is dispersed by mixing the CNT, the organic solvent in which the resin is dissolved, and the second emulsion. In the second embodiment, the CNT is dispersed. A third emulsion is prepared by mixing and emulsifying an oil phase containing water and an aqueous phase, a fourth emulsion is prepared by mixing and emulsifying the third emulsion and an oil phase containing a resin, and then the fourth emulsion is subjected to high-pressure shear emulsification. It is further emulsified and dispersed by a dispersion treatment.

  In the third emulsion, first micelles in which the first surfactant is oriented and assembled with the lipophilic part facing the outside of the fine droplets of the first oil phase are dispersed in the first water phase (O / W emulsion). In the fourth emulsion, the second micelle in which the second surfactant is oriented with the hydrophobic portion facing outward is dispersed in the second oil phase in the minute first aqueous phase droplets including a plurality of first micelles. (O / W / O emulsion). It is considered that the CNTs are dispersed by arranging the second micelles around the CNTs.

  As the step (A), for example, a third emulsion is prepared by mixing and emulsifying and dispersing a first oil phase in which CNT and a first organic solvent are mixed, and a first aqueous phase in which an aqueous solution and a first surfactant are mixed. Can be prepared. However, it is not limited to this method.

  As the step (B), for example, a fourth emulsion is prepared by mixing and emulsifying and dispersing a second oil phase in which a second surfactant and a resin are mixed and dissolved in a second organic solvent, and the third emulsion. be able to. However, it is not limited to this method.

  The emulsification dispersion process in the step (A) and the step (B) can be performed using various mixers and stirring devices. The emulsification dispersion process in the step (C) performs the high-pressure shearing type emulsion dispersion process described in the first embodiment. The emulsification dispersion process in the step (A) and the process (B) may also be a high pressure shearing type emulsification dispersion process.

  The first surfactant used in the step (A) preferably includes a high molecular weight surfactant and a hydrophilic surfactant, like the first surfactant shown in the first embodiment. By using such a combination, a fine and uniform third emulsion can be obtained. In addition, the mixing amount of the first surfactant may be an amount that becomes a critical micelle concentration or more. The mixing ratio of the polymeric surfactant and the hydrophilic surfactant is 30:70 to 98: 2 by weight, preferably 40:60 to 95: 5, more preferably 60:40. ~ 90: 10.

  As the hydrophilic surfactant contained in the first surfactant, a surfactant having an HLB value (Hydrophile-Lipophile Balance) of 5 to 18, particularly 6 to 12 is preferable. Specifically, the hydrophilic surfactant described in Embodiment 1 can be used.

  Further, as the polymeric surfactant contained in the first surfactant, the polymeric surfactant described in the first embodiment can be used.

  The second surfactant used in the step (B) preferably contains a high molecular weight surfactant and a hydrophobic surfactant in the same manner as the second surfactant described in the first embodiment. By using such a combination, a fine and uniform fourth emulsion can be obtained. In addition, the mixing amount of the second surfactant may be an amount that becomes a critical micelle concentration or more. The mixing ratio of the polymeric surfactant and the hydrophobic surfactant is 30:70 to 98: 2 by weight, preferably 40:60 to 95: 5, and more preferably 60:40. ~ 90: 10.

  As described in Embodiment 1, the hydrophobic surfactant contained in the second surfactant is preferably one having an HLB value of 10 or less, more preferably 7 or less, and 1 to 5 Is particularly preferred. Specific examples include glycerin fatty acid esters, sucrose fatty acid esters, sorbitan fatty acid esters, and lecithins.

  As specific examples of glycerin fatty acid esters, sucrose fatty acid esters, sorbitan fatty acid esters, and lecithins, the types described in Embodiment 1 can be used.

  As the polymer surfactant contained in the second surfactant, the polymer surfactant described in Embodiment 1 can be used.

  The first organic solvent used in the step (A) and the second organic solvent used in the step (B) are particularly limited as long as they can dissolve other oil phase components and are not miscible with water. Not. Specific examples include dichloromethane, chloroform, ethyl acetate, 1.2-dichloroethane, toluene and the like. These may be used alone or in combination of two or more.

  The second organic solvent is preferably one that can dissolve the resin used in the step (B). The resin has a role as a base material for fixing the CNTs in which the CNTs are dispersed one by one while maintaining the state. Therefore, the resin concentration in the organic solvent only needs to ensure a film thickness when the dispersion is applied and dried. The type of resin described in Embodiment 1 can be used.

  The CNT concentration in the second organic solvent is, for example, 0.1 to 20% by weight, and more preferably 0.5 to 10% by weight. The weight ratio of the resin amount to the CNT amount is preferably 1: 9 to 9: 1, more preferably 1: 4 to 4: 1, and 2: 3 to 3: 2. Most preferred.

  In the step (A), the charging ratio of the first water phase (including the first surfactant) to the first oil phase (including CNT) is not particularly limited, but the mass of the first oil phase / first water phase The ratio is preferably 10/90 to 90/10, more preferably 20/80 to 60/40, and particularly preferably 30/70 to 50/50.

  In the step (B), the charging ratio of the third emulsion to the second oil phase (including the second surfactant and the resin) is not particularly limited, but the mass ratio of the third emulsion / second oil phase is 0.01 / It is preferably 99.99 to 50/50, more preferably 0.1 / 99.9 to 30/70, and particularly preferably 1/99 to 20/80.

  Further, as the aqueous solution used in the step (A), the same type as the first aqueous phase described in Embodiment 1 can be used.

  Here, it is preferable that each micelle has a diameter (particle diameter) as small as possible and is distributed in a narrow range, that is, the particle diameter is as uniform as possible. When the particle diameters are distributed over a wide range, that is, when the particle diameters are not uniform, the effect of dispersing the single-walled CNTs separately is reduced.

  Specifically, the volume average particle diameter is preferably adjusted to 0.1 to 20 μm, more preferably 0.1 to 10 μm.

  At least in the step (C), the fourth emulsion is further emulsified by high-pressure shearing type emulsification dispersion treatment. As described in the first embodiment, the high-pressure shearing type emulsification dispersion treatment is an emulsification dispersion treatment in which a mixture of a material to be dispersed, a dispersion medium, and a surfactant appropriately selected as necessary is passed through a capillary under high pressure. Is the method.

  In the second embodiment, both the micronization of the micelles and the uniformization of the micelle particle size are achieved by combining the straight first thin tubes and the helical second thin tubes as the thin tubes and continuously processing them. That is, in the linear first tubule, the back pressure (resistance force) from the inner wall of the tubule becomes a shearing force, and the micelle particles are refined. In addition, in the spiral second tubule, the micelle particles receive a rotational force when the dispersion flows in the tubule, and the particle size is gradually made uniform by repeating dispersion and coalescence.

  The treatment pressure in the high-pressure shear type emulsification dispersion treatment is 50 MPa to 250 MPa. The first capillary has an inner diameter of 0.1 mm to 2.0 mm, and an overall length of 0.1 mm to 500 mm. The second capillary has an inner diameter of 0.1 mm to 2.0 mm, an overall length of 10 mm to 500 mm, and a helical diameter of 5 mm to 10 mm. The pressure at the outlet of the second thin tube is not particularly limited, but is preferably atmospheric pressure.

  In addition, you may use the nozzle connected and connected to the inlet side and / or outlet side of a 1st thin tube and / or a 2nd thin tube.

  You may repeat the continuous process by a 1st thin tube and a 2nd thin tube twice or more. By repeating, the degree of miniaturization and homogenization is improved, and a finer and more uniform emulsified dispersion can be obtained.

  In the CNT dispersion liquid produced by such a method, it is considered that the aggregated state of CNTs is eliminated and the respective CNTs are dispersed apart.

  Next, a method for producing a CNT-containing thermoelectric conversion element from the CNT dispersion will be described. First, the CNT dispersion liquid obtained as described above is applied in a predetermined amount or thickness on a flat plate such as glass by an arbitrary method, for example, a method of extending it into a thin film with a casting knife or the like, and dried. A thin CNT-containing resin film is prepared. The dried CNT-containing resin film is peeled off from the flat plate. A plurality of CNT-containing resin films are produced by the same method.

  The CNT dispersion liquid obtained by the method of Embodiment 1 may be used. Moreover, the method of apply | coating on a flat plate is not restricted to the casting knife method, You may apply using a coater etc.

  A plurality of the produced CNT-containing resin films are overlapped and stacked such that the directions of two adjacent CNT-containing resin films are changed, and are adhered to each other to produce a CNT-containing thermoelectric conversion member.

  Specifically, the overlapping is performed so that the angle formed by the overlapping (adjacent) CNT dispersed resin films is 30 ° to 90 °. More preferably, the angle is 60 ° to 90 °, and the most preferable is a structure in which a plurality of CNT-dispersed resin films are stacked so as to be 90 ° ± 5 ° (substantially orthogonal).

  By arranging and laminating the produced CNT-containing resin film so as to have the above-mentioned angular relationship, a CNT-containing thermoelectric conversion member in which the dispersed CNTs are in point contact at many positions can be produced.

  The CNT-containing thermoelectric conversion member produced by overlapping in this way is shaped, and electrodes are attached to both ends to produce a CNT-containing thermoelectric conversion element.

  The CNT-containing resin films may be prepared one by one, and a desired number of CNT-containing resin films may be prepared and then stacked. However, the present invention is not limited to this. After the first CNT-containing resin film is formed on the flat plate and dried, the orientation of the flat plate is changed according to the above-described angular relationship without peeling off the first CNT-containing resin film, The second layer may be formed by directly applying the CNT dispersion and drying. In this way, the necessary number of CNT-containing resin films are formed in different directions, and finally the whole is peeled off from the flat plate (may be further pressure-bonded) and shaped, and an electrode is attached to form a CNT-containing thermoelectric conversion element. Good.

The thus produced CNT-containing thermoelectric conversion element measures the voltage and current by giving a temperature difference, and seebeck coefficient (S [V / K]: electromotive force per unit temperature difference) and power factor (PF = S ² / ρ and ρ are electric resistivity [Ωm]), whereby the performance of the element can be evaluated.

  In addition, by measuring the resistance value or electromotive force of a plurality of CNT-containing resin films or CNT-containing thermoelectric conversion members prepared from CNT dispersions prepared under different conditions, respectively, the manufacturing conditions of the CNT dispersion and its It is possible to relatively compare and evaluate the relationship of the high ability of the CNT-containing thermoelectric conversion element that can be manufactured from the CNT dispersion.

Example 1
Below, one example of manufacture of a CNT dispersion liquid and a CNT containing thermoelectric conversion element is demonstrated.

(Preparation of multilayer emulsion as dispersion medium)
1 g of sodium naphthalene sulfonate formalin condensate (Labelin (registered trademark), Daiichi Kogyo Seiyaku Co., Ltd.) as a polymeric surfactant, polyoxyethylene sorbitan monolaurate (RHEODOL (registered trademark)) as a hydrophilic surfactant (TW-L120, Kao Co., Ltd.) 5 g and 100 g of water were mixed and emulsified and dispersed at room temperature using a high-pressure shearing type emulsifying dispersion device to obtain a first emulsion.

  As shown in FIG. 1, the high-pressure shear type emulsifying and dispersing apparatus used in this example includes a pump 10 (BERYU MINI, Beautiful Grain Co., Ltd.) that pressurizes and discharges a liquid mixture, a liquid mixture reservoir 15, and nozzles 21 to 21. 24, the 1st thin tube 30, the 2nd thin tube 40, the coolers 51 and 52 which cool the 1st thin tube 30 and the 2nd thin tube 40, and the liquid receiving part 60 are comprised.

  The first thin tube 30 is a straight thin tube having an inner diameter of 0.4 mm and an overall length of 100 mm, and is cooled to 10 to 15 ° C. by the cooler 51. The second thin tube 40 is a helical thin tube having an inner diameter of 0.3 mm, an overall length of 300 mm, and a helical diameter of 5 mm, and is cooled to 10 to 15 ° C. by the cooler 52. Nozzles 21 and 22 are provided at both ends of the first thin tube 30, and nozzles 23 and 24 are provided at both ends of the second thin tube 40, respectively. The nozzle is a diamond nozzle (Bigrain Co., Ltd.), and is a straight pipe having a rectangular parallelepiped inner hole. The upper and lower holes are made of diamond. A nozzle having a cross-sectional shape of 1 mm.

  In the present embodiment, the mixed liquid is pressurized and discharged from the mixed liquid storage unit 15 to 100 MPa using the pump 10, and is passed through the first thin tube 30 and the second thin tube 40 at a flow rate of 30 ml / m to the liquid receiving unit 60. The continuous treatment received was repeated 5 times to obtain a first emulsion.

  Next, 151 g of the first emulsion, 1 g of sodium naphthalene sulfonate formalin condensate (Labelin (registered trademark), Daiichi Kogyo Seiyaku Co., Ltd.) which is a polymeric surfactant, glycerin fatty acid ester (hydrophobic surfactant) SY Grister CR-310, Sakamoto Yakuhin Kogyo Co., Ltd. (5 g) and toluene (special grade, Kanto Chemical Co., Ltd.) 450 g are mixed and subjected to emulsification dispersion treatment at room temperature using the above-described high-pressure shear type emulsification dispersion apparatus. An emulsion was obtained. The apparatus and processing conditions are the same as above.

(Preparation of CNT organic solvent mixture)
Next, 5.0 g of semiconducting single-walled carbon nanotubes (SGCNT, National Institute of Advanced Industrial Science and Technology), 5.0 g of polystyrene (atactic type, molecular weight of about 280000, Kanto Chemical Co., Ltd.), 290 g of toluene (Kanto Chemical Co., Ltd.) A CNT organic solvent mixture was prepared by mixing and stirring at room temperature using a high-pressure shearing type emulsifying dispersion device. The apparatus and processing conditions are the same as above.

(Preparation of CNT dispersion)
Next, 10 g of the second emulsion and 100 g of the CNT organic solvent mixture were mixed and subjected to an emulsification dispersion treatment at room temperature using the high-pressure shear type emulsification dispersion apparatus to prepare a CNT dispersion. The apparatus and processing conditions are the same as above. The continuous treatment with the first and second capillaries was repeated 20 times.

(Production of CNT-dispersed resin film)
Next, an appropriate amount of the above CNT dispersion was dropped onto a glass plate and spread with a casting knife to form a liquid film having a thickness of 0.5 mm. This was put together with the glass plate in a hot air drier, dried at 90 ° C. for 10 minutes, and then peeled off from the glass plate to obtain a CNT-dispersed resin film. FIG. 2A is a photomicrograph showing the CNT network of the CNT-dispersed resin film of this example. In addition, in FIG.2 (b), the microscope picture of the CNT dispersion | distribution resin film obtained from the dispersion liquid which CNT does not disperse | distribute with the orientation is shown as a comparative example. In FIG.2 (b), it turns out that CNT does not comprise a three-dimensional network but has overlapped and aggregated.

(Manufacture of CNT-containing thermoelectric conversion members)
Next, the five CNT-dispersed resin films produced as described above are cut into the same size (about 10 cm × 10 cm), and sequentially so that the orientation directions of the CNTs in the CNT-dispersed resin film are alternately orthogonal. Stacked up. If the CNT-dispersed resin films are manufactured by the same film-forming method, the orientation directions of the CNTs are the same. Therefore, the CNT-dispersed resin films manufactured by the same method are stacked so as to be alternately orthogonal.

  Next, the stacked CNT-dispersed resin films were pressed and pressure-bonded at 0.1 MPa using a hydraulic press machine to obtain a CNT-containing thermoelectric conversion member.

(Production of CNT-containing thermoelectric conversion elements)
Next, gold was vapor-deposited in a rectangular shape on both ends of the CNT-containing thermoelectric conversion member using a high vacuum vapor deposition device to form electrode terminals, thereby obtaining a CNT-containing thermoelectric conversion element.

(Performance measurement of CNT-containing thermoelectric conversion element)
A temperature difference was produced at both ends of the thus produced CNT-containing thermoelectric conversion element, the generated current was measured, and the electromotive force was calculated. The generated voltage is proportional to the temperature difference between the electrodes. The Seebeck coefficient was calculated from this proportionality coefficient. The electrical resistivity was calculated by measuring the current flowing with a predetermined voltage. As a result, the Seebeck coefficient was 65 μV / K, the electrical resistivity was 4.1 × 10 ⁻³ Ωcm, and the power factor was 90 μW / mK ² .

(Example 2)
A CNT dispersion was prepared by the method of steps (A) to (C) of Embodiment 2. In addition, in order to evaluate the change in the volume resistance value of the CNT-dispersed resin film depending on the processing conditions of the high-pressure shear type emulsification dispersion process in step (C) and the type of CNT (single layer, multilayer), single-layer CNT and multilayer type After the steps (A) and (B) were performed under the same conditions using CNTs and a plurality of samples of the fourth emulsion were prepared, the obtained samples (Nos. 1 to 15) were separated from the conditions of the different steps (C) ( Dispersion treatment was performed under high pressure shear type emulsification dispersion conditions).

  The method for preparing the fourth emulsion is as follows. 100 g of 1 wt% toluene solution of each CNT is poured into an aqueous solution in which 5 g of polyoxyethylene sorbitan monolaurate (RHEODOL (registered trademark) TW-L120, Kao Corporation) as a surfactant is dissolved in 200 g of water, and a high-speed stirring device (A foam-less mixer, Sojitz Machinery Co., Ltd.) was dispersed and mixed at 5000 rpm for 5 minutes and emulsified to obtain a third emulsion (O / W emulsion) (step (A)).

  The obtained third emulsion was poured into a toluene solution prepared by dissolving 11 g of polyglycerol fatty acid ester (Sakamoto Yakuhin Kogyo Co., Ltd., SY Glyster CR-310) as a surfactant and 0.5 g of polystyrene resin in 400 g of toluene. Using a stirrer (bubble-less mixer, Sojitz Machinery Co., Ltd.), dispersed and mixed at 1500 rpm for 5 minutes and emulsified to obtain a fourth emulsion (O / W / O type multilayer emulsion) (step (B)). .

  In the obtained fourth emulsion, the particle size of the second micelles was non-uniform. This fourth emulsion (sample Nos. 1 to 15) was subjected to a high-pressure shearing type emulsification dispersion treatment as follows (step (C)).

Sample No. 1 to 15 are pressurized with a pump 10 (BERYU MINI, Co., Ltd., pump discharge pressure 100 MPa) as shown in FIG. 1, and the first narrow tube 30 (straight pipe) having the conditions shown in Table 1 and its downstream side The second thin tube 40 (spiral pipe, the diameter of the helix is fixed at 5 mm) is circulated (passed) as many times as shown in Table 1 under the condition of a flow rate of 200 cm ³ / min, and collected in the liquid receiving part 60. Thus, a CNT dispersion was obtained. The 1st thin tube 30 and the 2nd thin tube 40 were cooled to 10-15 degreeC with the cooler 51 and the cooler 52, respectively. Nozzles 21 and 22 are provided at both ends of the first thin tube 30, and nozzles 23 and 24 are provided at both ends of the second thin tube 40, respectively. The first capillary 30 having a length of 0.1 mm is one in which the second capillary 40 is connected 0.1 mm downstream from the nozzle having the pipe inner diameter shown in Table 1.

  Using the obtained CNT dispersion, a CNT-dispersed resin film was prepared by the method described below, and the surface resistance value (Ω / □) and the film thickness (mm) were measured. A volume resistance value (Ω · cm) was calculated from the obtained surface resistance value and film thickness. The smaller the volume resistance value, the higher the electromotive force, which means that the performance as a thermoelectric conversion element is high.

The method for producing the CNT-dispersed resin film and the method for calculating the volume resistance value are as follows.
(1) A CNT dispersion sample was taken with about 2 mL Eppendorf and filtered through a 25φ membrane filter. 2 mL of the sample was collected on the filtration surface and filtered at a reduced pressure.
(2) The filtered residue was dried together with the filter for about 30 seconds.
(3) The film thickness of the dried residue was measured with a digital caliper including a membrane filter. The film thickness shown in Table 1 is a numerical value including this membrane filter. The thickness of the membrane filter itself was 60 μm.
(4) The surface resistance value was measured by 4-probe resistance measurement.
(5) The thickness of the membrane filter was subtracted from the film thickness of 60 μm to obtain the CNT dispersed resin film thickness, and the volume resistance value was calculated by multiplying the measured surface resistance value by the CNT dispersed resin film thickness. In the case where the film thickness was less than 60 μm, the CNT-dispersed resin film thickness was calculated as 3 μm.

  Table 1 shows the high-pressure shear emulsification dispersion conditions for preparing the CNT dispersion and the volume resistance value of the produced CNT dispersion resin film.

Table 1 High-pressure shear type emulsification dispersion treatment conditions and volume resistance value of CNT-dispersed resin film

  FIG. 3A is a graph showing the relationship between the type of CNT, the inner diameter of the first capillary, and the volume resistance value of the obtained CNT-dispersed resin film. As shown, the single-walled CNT generally has a lower volume resistance value than the multi-walled CNT (higher performance as a thermoelectric conversion element). In addition, when single-walled CNT is used, the relationship between the inner diameter of the first capillary and the volume resistance value is not necessarily clear, but in the range of the inner diameter of 0.13 to 0.4 (mm), the volume resistance increases as the inner diameter increases. The value tends to increase.

  FIG. 3B is a graph showing the relationship between the type of CNT, the inner diameter of the second capillary, and the volume resistance value of the obtained CNT-dispersed resin film. As shown, the single-walled CNT generally has a lower volume resistance value than the multi-walled CNT (higher performance as a thermoelectric conversion element). In addition, when single-walled CNT is used, the relationship between the inner diameter of the second capillary and the volume resistance value is not necessarily clear, but in the range of 0.2 to 0.4 (mm), the volume resistance increases as the inner diameter increases. The value tends to increase.

  Other parameters may not be fixed between the number of passes, which is the number of passes through the first and second capillaries, and the volume resistance value, and no clear relationship was found. Other parameters are considered to have a larger influence on the volume resistance value than the difference in the number of passes from 1 to 5.

  In addition, other parameters may not be fixed for the pipe length of the first capillary tube and the pipe length of the second capillary tube, and the volume resistance value is large even when comparing the samples processed with the same pipe length. Different results were obtained, and no particularly clear tendency was observed between the volume resistance values. It is considered that the parameters other than the pipe lengths of the first thin tube and the second thin tube have a larger influence on the volume resistance value.

(Comparative Example 1)
Among the high-pressure shearing type emulsification dispersion treatment, the CNT dispersion state of the CNT dispersion treated only with the first capillary (straight pipe) without using the second capillary (spiral pipe) is shown in both the first capillary and the second capillary. The CNT dispersion of the CNT dispersion treated with CNT was compared with the CNT dispersion status.

  4A shows a sample No. in Table 1. 6 is an electron micrograph of a CNT dispersion liquid according to the present invention prepared under condition 6. FIG. 4 (b) is an electron micrograph at the same magnification of a CNT dispersion of Comparative Example prepared using only 0.3φ, 100 mm straight piping and not using the second capillary. The volume resistance value of the CNT-dispersed resin film produced using the CNT dispersion shown in FIG. It is considerably larger than the volume resistance value of the CNT-dispersed resin film produced using the CNT dispersion liquid No. 6.

  Sample No. In FIG. 4 (a), which is an electron micrograph of FIG. 6, CNTs that appear black are dispersed uniformly (as a whole), whereas in FIG. 4 (b) of the comparative example, CNTs are uniformly dispersed. It can be seen that there are many portions that remain agglomerated. As can be seen from these electron micrographs, in order to produce a CNT-dispersed resin film having a small volume resistance value, a CNT dispersion liquid in which CNTs are uniformly dispersed as a whole is prepared, and such a CNT dispersion liquid is used. It is more preferable to produce a CNT-dispersed resin film.

  In a CNT-dispersed resin film prepared using a CNT dispersion liquid in which CNTs are uniformly dispersed as a whole, the CNTs are fixed with resin in a three-dimensional and spatially dispersed state, and the CNTs are located at a number of positions. It is thought that they are in point contact. As described above, since the CNTs are three-dimensionally and spatially dispersed to form a point-contact network, it is considered that a favorable thermoelectric conversion element having a high electric conductivity and a low thermal conductivity can be manufactured. .

(Comparative Example 2)
A step (A) and a step (B) are performed, and the step (C) is not performed (the high-pressure shear type emulsification dispersion treatment is not performed). A CNT-dispersed resin film is prepared using a CNT mixed solution, and the surface resistance value (Ω / □) and film thickness (mm) were measured. However, many of the obtained CNT-dispersed resin films have voids or bubbles mixed therein, and the measured surface resistance values greatly fluctuated. Furthermore, as a result of calculating the volume resistance value (Ω · cm) from the measured surface resistance value and film thickness, the volume resistance value is 0.73 to 1.82 (Ω · cm) in the case of single-walled CNT, In the case of multilayer CNT, it was 2.03 to 3.30 (Ω · cm). As can be seen from this result, the volume resistance value of the CNT dispersion resin film prepared from the CNT dispersion prepared without performing the step (C) is the CNT dispersion prepared from the CNT dispersion prepared by performing the step (C). The value is about one digit larger than the volume resistance value of the resin film, and is a level that cannot be used as a thermoelectric conversion element.

(Example 3)
Samples A to E of CNT (all single-walled CNTs) were processed by the method described in Example 2 to prepare a fourth emulsion. A CNT dispersion was obtained by treatment under the conditions of high-pressure shearing type emulsification dispersion treatment shown in 4 or 6. Each of the obtained CNT dispersions was coated on a 10 cm × 10 cm glass plate at 0.2 mm / second using a desktop coater and dried to obtain a CNT dispersed resin film. While the obtained dry CNT-dispersed resin film was placed on a glass plate, terminals were connected to both ends, and a temperature difference (16 ° C.) was given between both terminals to measure the electromotive force of the CNT-dispersed resin film. Next, the electrode was removed, the glass plate was rotated 90 degrees, the second coating was performed in the same manner, and dried to obtain a laminated CNT dispersed resin film. Terminals were connected to both ends of the obtained laminated CNT-dispersed resin film, and an electromotive force was measured by giving a temperature difference. Thereafter, the coating was rotated by 90 degrees up to 10 coats and dried to produce a laminated CNT-dispersed resin film, terminals were connected to both ends, and a temperature difference was given to measure the electromotive force.

  Table 2 and FIG. 5 show the relationship between the number of coatings (the number of laminated layers) of the CNT-dispersed resin film produced as described above and the electromotive force (mV) of the obtained laminated CNT-containing thermoelectric conversion element. A larger electromotive force means higher performance as a thermoelectric conversion element.

Table 2 Number of coatings of CNT-dispersed resin film and electromotive force of CNT-containing thermoelectric conversion element

  As shown in Table 2 and FIG. 5, the electromotive force increased in each sample when the number of coatings was twice or three times than once. Thereafter, there were many samples that exhibited the same performance until 3 to 6 times, but some samples such as Sample D and Sample E were also reduced. When it was 7 times or more, the electromotive force tended to decrease in any sample. Any sample shows the largest electromotive force around 3 to 4 coatings.

  From FIG. 5, the number of times (the number of laminated layers) for laminating the CNT dispersed resin film is preferably 2 to 6 times (sheets), more preferably 2 to 5 times (sheets), and further preferably 3 to 4 times (sheets). I understand.

DESCRIPTION OF SYMBOLS 10 Pump 15 Mixed liquid storage part 21-24 Nozzle 30 1st thin tube 40 2nd thin tube 51, 52 Cooler 60 Liquid receiving part

Claims (12)

(A) a step of emulsifying and dispersing the first surfactant in the first aqueous phase to prepare a first emulsion;
(B) emulsifying and dispersing the first emulsion and the second surfactant in the first oil phase to prepare a second emulsion;
(C) preparing a mixed solution in which carbon nanotubes are mixed in an organic solvent in which a resin is dissolved;
(D) emulsifying and dispersing a mixed liquid of the second emulsion and the mixed liquid;
The manufacturing method of the carbon nanotube dispersion liquid containing this.   The first surfactant includes a polymer surfactant and a surfactant having an HLB of 5 to 18, and the second surfactant is an interface having a polymer surfactant and an HLB of 10 or less. The manufacturing method of the carbon nanotube dispersion liquid of Claim 1 containing an activator.   The emulsification and dispersion method in at least one of the steps (a), (b) and (d) is a method in which a mixed liquid containing a material to be dispersed and a dispersion medium is spiraled at least with a straight pipe under a pressure of 50 MPa to 250 MPa. The manufacturing method of the carbon nanotube dispersion liquid of Claim 1 or 2 which makes the said to-be-dispersed material emulsify-disperse in the said dispersion medium by allowing it to pass through a pipe.   The straight pipe has an inner diameter of 0.09 to 0.4 mm and a length of 0.1 to 500 mm, and the spiral pipe has an inner diameter of 0.2 to 0.4 mm, a length of 10 to 500 mm, and a spiral diameter. The manufacturing method of the carbon nanotube dispersion liquid of Claim 3 whose is 5-10 mm. (A) emulsifying and dispersing carbon nanotubes, a first organic solvent, and a first aqueous phase containing a first surfactant to prepare a third emulsion;
(B) emulsifying and dispersing a second organic solvent, a second surfactant, a resin, and the third emulsion to prepare a fourth emulsion;
(C) a step of subjecting the fourth emulsion to a high-pressure shear type emulsification dispersion treatment;
The manufacturing method of the carbon nanotube dispersion liquid containing this.   In the high-pressure shearing type emulsification dispersion treatment method in the step (C), the mixed liquid containing the dispersion and the dispersion medium is passed through at least a straight pipe and a helical pipe under a pressure of 50 MPa to 250 MPa, so that In this method, the dispersion is emulsified and dispersed in the dispersion medium. The straight pipe has an inner diameter of 0.09 to 0.4 mm, a length of 0.1 to 500 mm, and the spiral pipe has an inner diameter of 0.1 mm. The manufacturing method of the carbon nanotube dispersion liquid of Claim 5 which is 2-0.4mm, length is 10-500mm, and a helix diameter is 5-10mm.   An emulsion in which a first micelle assembly containing a first surfactant is micellized in a first oil phase with a second surfactant and a mixed solution in which carbon nanotubes are mixed in an organic solvent in which a resin is dissolved are emulsified. Dispersed carbon nanotube dispersion.   The first surfactant includes a polymer surfactant and a surfactant having an HLB of 5 to 18, and the second surfactant is an interface having a polymer surfactant and an HLB of 10 or less. The carbon nanotube dispersion liquid according to claim 7, comprising an activator.   The carbon nanotube dispersion liquid manufactured by the method as described in any one of Claims 1-6. Applying the carbon nanotube dispersion according to any one of claims 7 to 9 on a flat plate;
Drying the coated carbon nanotube dispersion to form a carbon nanotube-dispersed resin film;
A step of arranging a plurality of the carbon nanotube-dispersed resin films so as to change the overlapping direction;
The manufacturing method of the carbon nanotube containing thermoelectric conversion element containing this. Including a thermoelectric conversion member formed by stacking two or more carbon nanotube-dispersed resin films in which carbon nanotubes are dispersed;
A carbon nanotube-containing thermoelectric conversion element in which the two superposed adjacent carbon nanotube dispersed resin films of the thermoelectric conversion member have different overlapping directions.   The carbon nanotube-containing thermoelectric conversion element according to claim 11, wherein an angle formed by the overlapping direction of the two adjacent carbon nanotube-dispersed resin films that are adjacently overlapped is in a range of 30 ° to 90 °.