JP2023000622A - Carbon nanotube aqueous dispersion and method for producing the same - Google Patents

Abstract

To provide a carbon nanotube aqueous dispersion having a large content of carbon nanotubes and allowing for its easy coating.SOLUTION: A carbon nanotube aqueous dispersion according to the present invention contains carbon nanotubes, carboxymethylcellulose, and water, wherein the content of carbon nanotubes is 2.5 mass% or more, and the viscosity measured using a B-type viscometer at 25°C and 60 rpm is 3000 cps or less.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a carbon nanotube aqueous dispersion and a method for producing the same.

A carbon nanotube has a structure in which a uniform planar graphene sheet is rolled into a cylinder. Since carbon nanotubes have such a unique structure, they have various properties and are expected to be applied in a wide range of fields.

For example, Patent Document 1 describes a method of producing a carbon nanotube dispersion by pressurizing a mixture of aggregates of carbon nanotubes and a dispersion medium, feeding the mixture into a plurality of narrow tube channels, and colliding and joining the mixture. Patent Document 1 describes that in a method for producing a carbon nanotube dispersion, the concentration of carbon nanotube aggregates is preferably 0.01% by mass to 1% by mass.

JP 2013-230951 A

It is desired to increase the content of carbon nanotubes in the carbon nanotube aqueous dispersion as described above. By increasing the content of carbon nanotubes, it is possible to enhance the performance specific to carbon nanotubes, such as electromagnetic wave shielding performance.

However, in a method of simply increasing the amount of carbon nanotubes added without using a dispersant such as a surfactant and repeating collision and confluence to disperse, the resulting carbon nanotube aqueous dispersion has too high a viscosity. Therefore, it has been difficult to prepare an aqueous carbon nanotube dispersion having excellent dispersibility of carbon nanotubes. Moreover, when the content of carbon nanotubes is increased, the viscosity of the aqueous carbon nanotube dispersion increases, making it difficult to apply the aqueous carbon nanotube dispersion to a substrate such as paper.

An object of some embodiments of the present invention is to provide a carbon nanotube aqueous dispersion that has a high carbon nanotube content and is easy to coat. Another object of some embodiments of the present invention is to provide a method for producing a carbon nanotube aqueous dispersion that has a large carbon nanotube content and is easy to apply.

One aspect of the carbon nanotube aqueous dispersion according to the present invention is
including carbon nanotubes, carboxymethyl cellulose, and water;
The content of the carbon nanotubes is 2.5% by mass or more,
The viscosity measured using a Brookfield viscometer under the conditions of 25° C. and 60 rpm is 3000 cps or less.

In one aspect of the carbon nanotube aqueous dispersion,
It may contain no dispersant other than the carboxymethyl cellulose.

In any aspect of the carbon nanotube aqueous dispersion,
The content of the carbon nanotubes may be 3.0% by mass or more.

In any aspect of the carbon nanotube aqueous dispersion,
The viscosity may be 2500 cps or less.

In any aspect of the carbon nanotube aqueous dispersion,
The viscosity may be 1000 cps or more.

In any aspect of the carbon nanotube aqueous dispersion,
The content of the carboxymethylcellulose may be 2.5% by mass or more.

In any aspect of the carbon nanotube aqueous dispersion,
The content of the carboxymethylcellulose may be 3.0% by mass or more.

In any aspect of the carbon nanotube aqueous dispersion,
It may be used as a coating agent for electromagnetic shielding seeds.

One aspect of the method for producing a carbon nanotube aqueous dispersion according to the present invention is
a step of preparing a first dispersion containing carbon nanotubes and water, wherein the content of the carbon nanotubes is 3.0% by mass or more;
preparing a second dispersion containing carbon nanotubes and water, wherein the content of the carbon nanotubes is less than 3.0% by mass;
mixing the first dispersion and the second dispersion to prepare a third dispersion;
including
In the step of preparing the first dispersion, an underwater facing collision method is performed with the number of passes of the wet atomization device set to 1 to prepare the first dispersion,
In the step of producing the second dispersion, the second dispersion is produced by performing an underwater facing collision method with the number of passes of the wet atomization device set to 2 or more.

In one aspect of the method for producing the carbon nanotube aqueous dispersion,
In the step of preparing the second dispersion, the number of passes of the wet atomization device may be set to 4 times.

In any aspect of the method for producing the carbon nanotube aqueous dispersion,
a step of subjecting the third dispersion to an underwater facing collision method with the number of passes of the wet atomization device set to two or more times to prepare a fourth dispersion;
a step of preparing a fifth dispersion containing carbon nanotubes and water, wherein the content of the carbon nanotubes is greater than that of the fourth dispersion;
mixing the fourth dispersion and the fifth dispersion to prepare a sixth dispersion;
including
In the step of producing the fifth dispersion, the fifth dispersion may be produced by performing an underwater facing collision method with one pass of the wet atomization device.

In any aspect of the method for producing the carbon nanotube aqueous dispersion,
In the step of preparing the fourth dispersion, the number of passes of the wet atomization device may be set to four.

In any aspect of the method for producing the carbon nanotube aqueous dispersion,
A step of subjecting the sixth dispersion to an underwater facing collision method with the number of passes of the wet atomization device set to two or more times to prepare a seventh dispersion;
preparing an eighth dispersion containing carbon nanotubes and water and having a higher content of carbon nanotubes than the seventh dispersion;
mixing the seventh dispersion and the eighth dispersion to prepare a ninth dispersion;
including
In the step of producing the eighth dispersion, the eighth dispersion may be produced by performing an underwater facing collision method with one pass of the wet atomization device.

In any aspect of the method for producing the carbon nanotube aqueous dispersion,
In the step of preparing the seventh dispersion, the number of passes of the wet atomization device may be set to four.

In any aspect of the method for producing the carbon nanotube aqueous dispersion,
The content of the carbon nanotubes in the first dispersion is 3.5% by mass or more,
A content of the carbon nanotubes in the second dispersion may be 2.5% by mass or less.

In any aspect of the method for producing the carbon nanotube aqueous dispersion,
In the step of preparing the third dispersion, the ratio of the mass of the first dispersion to the sum of the mass of the first dispersion and the mass of the second dispersion is 0.15 or more and 0.70 or less. The first dispersion and the second dispersion may be mixed so that

In any aspect of the method for producing the carbon nanotube aqueous dispersion,
The first dispersion and the second dispersion contain carboxymethyl cellulose,
The content of the carboxymethyl cellulose in the first dispersion is 3.0% by mass or more,
The content of the carboxymethylcellulose in the second dispersion may be less than 3.0% by mass.

In any aspect of the method for producing the carbon nanotube aqueous dispersion,
The content of the carboxymethyl cellulose in the first dispersion is 3.5% by mass or more,
The content of the carboxymethylcellulose in the second dispersion may be 2.5% by mass or less.

The carbon nanotube aqueous dispersion according to the present invention contains carbon nanotubes, carboxymethyl cellulose, and water, and has a carbon nanotube content of 2.5% by mass or more. , the viscosity measured at a rotation speed of 60 rpm is 3000 cps or less. Therefore, the carbon nanotube aqueous dispersion according to the present invention has a large carbon nanotube content and is easy to apply. Further, according to the method for producing an aqueous carbon nanotube dispersion according to the present invention, it is possible to easily produce an aqueous carbon nanotube dispersion that has a large carbon nanotube content and is easy to coat.

4 is a flow chart for explaining a method for producing a carbon nanotube aqueous dispersion according to the present embodiment; 4 is a flowchart for explaining a first modification of the method for producing an aqueous carbon nanotube dispersion according to the present embodiment; 4 is a flowchart for explaining a second modification of the method for producing an aqueous carbon nanotube dispersion according to the present embodiment; 4 is a table showing the preparation conditions of the carbon nanotube aqueous dispersions of Examples 1 to 11 and Comparative Examples 1 and 2, and the evaluation results of the carbon nanotube content and viscosity.

Preferred embodiments of the present invention will be described in detail below with reference to the drawings. It should be noted that the embodiments described below do not unduly limit the scope of the invention described in the claims. Moreover, not all the configurations described below are essential constituent elements of the present invention.

1. Carbon nanotube aqueous dispersion 1.1. Content First, the carbon nanotube aqueous dispersion according to the present embodiment will be described. The carbon nanotube aqueous dispersion according to this embodiment contains carbon nanotubes (hereinafter also referred to as “CNT”), carboxymethyl cellulose (hereinafter also referred to as “CMC”), and water. Each content will be described below.

1.1.1. carbon nanotube (CNT)
The CNT contained in the CNT aqueous dispersion according to the present embodiment is a single-walled carbon nanotube (SWNT) in which a single six-membered ring network (graphene sheet) made of carbon is wound in a cylindrical shape. , multi-walled carbon nanotubes (MWNTs) in which a plurality of graphene sheets are concentrically wound. The aqueous CNT dispersion may contain only one or both of SWNTs and MWNTs, but considering the dispersibility of CNTs, it preferably contains only MWNTs as CNTs. Both ends of the CNT may be closed or open.

The CNTs as described above are produced to a desired size by, for example, an arc discharge method, a laser ablation method, a CVD (Chemical Vapor Deposition) method, or the like. The CNTs contained in the aqueous CNT dispersion according to this embodiment may be produced using any method.

The diameter of the CNT is, for example, 1 nm or more and 100 nm or less, preferably 5 nm or more and 50 nm or less, and more preferably 8 nm or more and 15 nm or less. If the diameter of the CNTs is 1 nm or more and 100 nm or less, the dispersibility of the CNTs can be improved. The diameter of CNT can be measured by SEM (Scanning Electron Microscope).

The fiber length of CNT is, for example, 0.5 μm or more and 50 μm or less, preferably 15 μm or more and 35 μm or less. If the fiber length of CNT is 0.5 μm or more and 50 μm or less, the dispersibility of CNT can be improved. The fiber length of CNT can be measured by SEM. The term "fiber length of CNT" refers to the length of CNTs bundled by van der Waals force, ie, the length of CNTs before being dispersed in a solvent.

The BET specific surface area of CNT is, for example, 50 m ² /g or more and 500 m ² /g or less, preferably 100 m ² /g or more and 300 m ² /g or less. If the BET specific surface area of CNTs is 50 m ² /g or more and 500 m ² /g or less, the dispersibility of CNTs can be improved. The "BET specific surface area" is a specific surface area measured by the BET (Brunauer Emmett Teller) method, and can be measured by an automatic specific surface area measuring device.

In the CNT aqueous dispersion, the CNT content is 2.5% by mass or more, preferably 3.0% by mass or more, and more preferably 3.5% by mass or more. If the content of CNT is 2.5% by mass or more, performance specific to CNT such as electromagnetic wave shielding performance can be enhanced. The CNT content is, for example, 10.0% by mass or less. If the CNT content is 10.0% by mass or less, the dispersibility of CNTs can be improved. The CNT content can be measured by thermal gravimetric analysis (TGA).

1.1.2. Carboxymethyl cellulose (CMC)
In the CNT aqueous dispersion according to this embodiment, CMC functions as a dispersant for dispersing CNTs. Only CMC is used as a CNT dispersant. That is, the CNT aqueous dispersion contains no dispersant other than CMC. The term “dispersant” refers to an additive that disperses CNTs in water and contributes to prevention of aggregation and settling of CNTs. By using only CMC as a CNT dispersant, air bubbles can be prevented from being mixed into the aqueous CNT dispersion, compared to, for example, adding an anionic surfactant or the like as a dispersant in addition to CMC. Therefore, when the CNT aqueous dispersion according to the present embodiment is used as a coating agent for an electromagnetic wave shield, by using only CMC as a CNT dispersant, it is possible to prevent air bubbles from entering the formed coating film. be able to.

The weight average molecular weight of CMC is, for example, 5,000 or more and 100,000 or less, preferably 10,000 or more and 60,000 or less, and more preferably 10,000 or more and 35,000 or less. When the weight-average molecular weight of CMC is 5000 or more, CMC is easily entangled with CNTs, and the dispersibility of CNTs can be improved. However, if the weight-average molecular weight is too large, the dispersibility deteriorates, so the molecular weight of CMC is preferably 100,000 or less. In addition, "weight average molecular weight" means the weight average molecular weight of polystyrene conversion measured by the gel permeation chromatography (GPC).

The degree of etherification of CMC is, for example, 0.6 or more and 1.2 or less, preferably 0.6 or more and 0.8 or less. If the degree of etherification of CMC is 0.6 or more and 1.2 or less, the dispersibility of CNTs can be improved.

In the CNT aqueous dispersion, the CMC content is 2.5% by mass or more, preferably 3.0% by mass or more, and more preferably 3.5% by mass or more. If the CMC content is 2.5% by mass or more, the dispersibility of CNTs can be improved. The content of CMC is, for example, 10.0% by mass or less. If the CMC content is 10.0% by mass or less, the viscosity of the aqueous CNT dispersion can be lowered. The higher the CMC content, the higher the viscosity of the CNT aqueous dispersion. The content of CMC can be measured by thermogravimetric analysis.

In the CNT aqueous dispersion, the ratio M _CMC /M _CNT of the mass M _CMC of CMC to the mass M _CNT of CNT is 1/5 or more and 5 or less (CNT:CMC=5:1 to 1:5), preferably 1/3 or more and 3 or less (CNT:CMC=3:1 to 1:3). If the ratio M _CMC /M _CNT is 1/5 or more, performance specific to CNT such as electromagnetic shielding performance can be enhanced. If the ratio M _CMC /M _CNT is 5 or less, the dispersibility of CNTs can be improved.

1.1.3. Water The CNT aqueous dispersion according to this embodiment contains water as a solvent. Examples of water include pure water such as ion-exchanged water, ultrafiltrated water, reverse osmosis water, and distilled water, and water from which ionic impurities are removed as much as possible, such as ultrapure water. Since the CNT aqueous dispersion uses water as a solvent, it is more environmentally friendly than the case where an organic solvent is used as a solvent. The CNT aqueous dispersion is C
It may contain only NT, CMC, and water. That is, the CNT aqueous dispersion may consist of CNTs, CMC, and water only.

1.1.4. Other Additives The aqueous CNT dispersion according to the present embodiment may further contain various additives such as preservatives, pH adjusters, colorants, and antifoaming agents, if necessary.

1.2. Viscosity In the CNT aqueous dispersion according to the present embodiment, the viscosity measured using a Brookfield viscometer at 25° C. and a rotation speed of 60 rpm is 3000 cps or less, preferably 1000 cps or more and 2500 cps or less, and more preferably. is 1500 cps or more and 2000 cps or less. Hereinafter, "viscosity measured using a Brookfield viscometer under conditions of 25°C and 60 rpm" is also simply referred to as "viscosity". Note that 1 cps=1 mPa·s.

If the viscosity of the aqueous CNT dispersion is 3000 cps or less, the aqueous CNT dispersion can be easily applied. Furthermore, the CNT aqueous dispersion can be applied with good uniformity. If the viscosity of the aqueous CNT dispersion is 1000 cps or more, the aqueous CNT dispersion can be applied more easily.

1.3. Applications The CNT aqueous dispersion according to the present embodiment can be applied to a predetermined substrate using, for example, a die coater, gravure coater, wire bar coater, knife coater, air coater, blade coater, roll coater, reverse roll coater, or the like. be engineered.

A CNT aqueous dispersion is used as a coating agent for an electromagnetic shield sheet for suppressing electromagnetic waves. An electromagnetic shielding sheet is produced, for example, by coating a substrate such as paper with an aqueous CNT dispersion and drying the coated aqueous CNT dispersion.

The application of the CNT aqueous dispersion is not limited to electromagnetic shielding sheets, and the CNT aqueous dispersion is used in a wide range of fields such as fuel cells, capacitors, semiconductor devices, medical instruments, automobiles, aircraft, and sporting goods. be done.

1.4. Effects The CNT aqueous dispersion according to the present embodiment contains CNTs, CMC, and water, has a CNT content of 2.5% by mass or more, and a viscosity of 3000 cps or less. Therefore, the CNT aqueous dispersion according to the present embodiment has a large CNT content and is easy to apply. If the viscosity is higher than 3000 cps, it becomes difficult to apply the aqueous CNT dispersion using the aforementioned die coater or the like.

2. Method for producing carbon nanotube aqueous dispersion 2.1. Overall Flow Next, a method for producing an aqueous CNT dispersion according to this embodiment will be described with reference to the drawings. FIG. 1 is a flow chart for explaining the method for producing an aqueous CNT dispersion according to this embodiment.

As shown in FIG. 1, the method for producing an aqueous CNT dispersion according to the present embodiment includes a step of producing a first dispersion having a CNT content of 3.0% by mass or more (step S1), and A step of preparing a second dispersion having a content of less than 3.0% by mass (step S2), and a step of mixing the first dispersion and the second dispersion to prepare a third dispersion (step S3 ) and including. Each step will be described below.

2.2. Step of preparing a first dispersion (Step S1)
2.2.1. Agitation of CMC and Water In the step of preparing the first dispersion, first, CMC and water are agitated. The stirring time is, for example, 0.1 hour or more and 3 hours or less, preferably 0.5 hour or more and 1.5 hours or less.

The content of CMC in the first dispersion is 3.0% by mass or more, preferably 3.5% by mass or more, more preferably 4.0% by mass or more, and even more preferably 5.0% by mass. % by mass or more. If the CMC content is 3.0% by mass or more, the dispersibility of CNTs in the first dispersion can be improved. The content of CMC in the first dispersion is, for example, 10.0% by mass or less. If the CMC content is 10.0% by mass or less, the viscosity of the mixture of CNTs, CMC, and water for preparing the first dispersion does not become too high, and the first dispersion is obtained by the underwater facing collision method. can be made. If the viscosity of the mixed liquid is too high, the nozzle holes of the wet micronization device will be clogged when performing the underwater facing impingement method.

2.2.2. Stirring of CNTs, CMC, and Water Next, CNTs are added to the stirred mixture of CMC and water, and the CNTs, CMC, and water are stirred. The stirring is performed at a higher speed than the stirring of CMC and water described above. The stirring time is, for example, 0.1 hour or more and 3 hours or less, preferably 0.5 hour or more and 1.5 hours or less.

The CNT content in the first dispersion is 3.0% by mass or more, preferably 3.5% by mass or more, more preferably 4.0% by mass or more, and even more preferably 5.0% by mass. % by mass or more. If the CNT content in the first dispersion is 3.0% by mass or more, a third dispersion having a large CNT content can be produced. The content of CNTs in the first dispersion is, for example, 10.0% by mass or less. If the content of CNTs in the first dispersion is 10.0% by mass or less, the viscosity of the mixture of CNTs, CMC, and water for preparing the first dispersion does not become too high, and the underwater facing collision method can be used. The first dispersion can be made by The higher the CNT content in the mixture, the higher the viscosity of the mixture.

In the first dispersion, the ratio M _CMC /M _CNT of the mass M _CMC of CMC to the mass M _CNT of CNT is 1/5 or more and 5 or less (CNT:CMC=5:1 to 1:5), preferably 1/3 or more and 3 or less (CNT:CMC=3:1 to 1:3). If the ratio M _CMC /M _CNT is 1/5 or more, a third dispersion having a large CNT content can be produced. If the ratio M _CMC /M _CNT is 5 or less, the dispersibility of CNTs in the first dispersion can be improved.

2.2.3. Screening Next, the mixed solution of the stirred CNTs, CMC, and water is screened to remove agglomerates of CNTs. Screening is performed, for example, by sieving. By performing the screen treatment, the underwater facing collision method can be performed smoothly.

2.2.4. Treatment with Homogenizer Next, as a pretreatment for the underwater facing collision method, the mixture of CNT, CMC and water is treated with a homogenizer. The homogenizer may be an ultrasonic type that causes cavitation with ultrasonic waves, a stirring type that agitates the mixed liquid, or a pressure type that applies pressure to the mixed liquid. By performing treatment with a homogenizer, aggregates of CNTs can be reduced, and the underwater facing collision method can be performed smoothly. The treatment time with the homogenizer is, for example, 1 minute or more and 30 minutes or less, preferably 3 minutes or more and 10 minutes or less.

2.2.5. Underwater Counter-Collision Method Next, the mixed solution of CNT, CMC, and water is subjected to the underwater counter-collision method by setting the number of passes of the wet micronization device to one. Only CMC is used as a dispersing agent in the step of preparing the first dispersion. Even if only CMC is used as a dispersant, the dispersibility of CNTs can be improved by performing the underwater facing collision method. This makes it possible to prepare a first dispersion having excellent CNT dispersibility.

In the underwater facing collision method, a mixed liquid containing CNTs is discharged at high pressure from a pair of nozzle holes (a first nozzle hole and a second nozzle hole) arranged to face each other, and the mixed liquid discharged from the first nozzle hole, The CNTs are dispersed by colliding with the liquid mixture discharged from the second nozzle hole. Preferably, in the underwater facing collision method, the CNTs contained in the liquid mixture discharged from the first nozzle hole collide with the CNTs contained in the liquid mixture discharged from the second nozzle hole to disperse the CNTs. In the underwater facing collision method, as long as the central axis of the first nozzle hole and the central axis of the second nozzle hole intersect each other, both central axes may be on a straight line or may be inclined to each other. . Alternatively, a method of colliding the liquid mixture against a ceramic ball or the like through a nozzle hole may be used.

In the underwater facing collision method, for example, the mixed liquids are ejected from nozzle holes having a diameter of 50 μm or more and 200 μm or less, preferably 80 μm or more and 120 μm or less, more preferably 100 μm, so that the mixed liquids collide with each other. If the diameter of the nozzle hole is 50 μm or more, even a mixed liquid with a relatively high viscosity can be discharged from the nozzle hole. If the diameter of the nozzle hole is 200 μm or less, the collision energy between the liquid mixtures can be increased.

In the underwater confronting collision method, for example, the mixed liquid is discharged at a pressure of 150 MPa or more and 250 MPa or less, preferably 180 MPa or more and 220 MPa or less, more preferably 200 MPa, to cause the mixed liquids to collide with each other. If the pressure is 150 MPa or higher, the collision energy between the liquid mixtures can be increased. If the pressure is 250 MPa or less, it is possible to suppress breakage of CNT fibers due to too high collision energy.

Specifically, the underwater counter-impingement method is performed using a wet atomization apparatus "Starburst Lab" (model name: HJP-25005) manufactured by Sugino Machine Co., Ltd. The wet atomization apparatus has a higher energy density than, for example, an ultrasonic homogenizer or a ball mill, and can produce a first dispersion having excellent CNT dispersibility in a short period of time. Furthermore, the wet-type atomization apparatus can minimize the contamination of impurities, and can produce the first dispersion with extremely little contamination of impurities.

In the step of preparing the first dispersion, the first dispersion is prepared by performing the underwater facing collision method with one pass of the wet atomization device. Here, "the number of passes of the liquid mixture in the wet atomization apparatus" means the number of circulation times of the liquid mixture in the wet atomization apparatus. This means that the mixture is circulated twice so that . Thus, the number of passes corresponds to the number of collisions of CNTs contained in the mixed liquid. Furthermore, the number of passes is proportional to the processing time in the wet atomization device. If the processing time in the wet atomization device is long, the number of times the liquid mixture is circulated increases.

The first dispersion has a high CNT content of 3.0% by mass or more, and therefore has a high viscosity. The viscosity of the first dispersion is, for example, 9000 cps or more, preferably 9500 cps or more, more preferably 10000 cps or more. Even if one more attempt is made to perform the underwater facing collision method with a wet atomization device for such a high-viscosity first dispersion (that is, the underwater facing collision method is performed with the number of passes set to two times, 1 dispersion liquid), the first dispersion liquid clogs the nozzle hole of the wet atomization device, and the underwater counter-collision method cannot be performed. Therefore, in the step of preparing the first dispersion, it is difficult to pass the wet atomization apparatus twice. Used for making the third dispersion.

Through the steps described above, the first dispersion containing CNTs, CMC, and water, and having a CNT content and a CMC content of 3.0% by mass or more can be produced.

In the above description, an example in which the underwater facing collision method is performed on the mixed liquid of CNT, CMC, and water was explained. The first dispersion may be prepared by adding CMC to the mixed liquid subjected to the facing collision method. However, considering the dispersibility of CNTs, it is preferable to subject the mixture of CNTs, CMC, and water to the underwater facing collision method.

2.3. Step of preparing a second dispersion (Step S2)
2.3.1. Agitation of CMC and Water In the step of preparing the second dispersion, first, CMC and water are agitated. The stirring time is, for example, 0.1 hour or more and 3 hours or less, preferably 0.5 hour or more and 1.5 hours or less.

The content of CMC in the second dispersion is less than 3.0% by mass, preferably 2.5% by mass or less, and more preferably 2.3% by mass or less. If the CMC content is less than 3.0% by mass, the viscosity of the second dispersion can be lowered. The content of CMC in the second dispersion is, for example, 1.0% by mass or more. If the CMC content is 1.0% by mass or more, the dispersibility of CNTs in the second dispersion can be improved.

2.3.2. Stirring of CNTs, CMC, and Water Next, CNTs are added to the stirred mixture of CMC and water, and the CNTs, CMC, and water are stirred. The stirring is performed at a higher speed than the stirring of CMC and water described above. The stirring time is, for example, 0.1 hour or more and 3 hours or less, preferably 0.5 hour or more and 1.5 hours or less.

The content of CNTs in the second dispersion is less than 3.0% by mass, preferably 2.5% by mass or less, and more preferably 2.3% by mass or less. If the CNT content is less than 3.0% by mass, the viscosity of the second dispersion can be lowered. The content of CNTs in the second dispersion is, for example, 1.0% by mass or more. If the CNT content is 1.0% by mass or more, a third dispersion having a high CNT content can be produced.

In the second dispersion, the ratio M _CMC /M _CNT of the mass M _CMC of CMC to the mass M _CNT of CNT is 1/5 or more and 5 or less (CNT:CMC=5:1 to 1:5), preferably 1/3 or more and 3 or less (CNT:CMC=3:1 to 1:3). If the ratio M _CMC /M _CNT is 1/5 or more, a third dispersion having a large CNT content can be produced. If the ratio M _CMC /M _CNT is 5 or less, the dispersibility of CNTs in the second dispersion can be improved.

2.3.3. Screening Next, the mixture of CNT, CMC, and water is screened in the same manner as in the above-described step of preparing the first dispersion (step S1).

2.3.4. Treatment with Homogenizer Next, the mixture of CNT, CMC, and water is treated with a homogenizer in the same manner as in the above-described step of preparing the first dispersion (step S1).

2.3.5. Underwater Counter Collision Method Next, the mixed solution of CNT, CMC, and water is subjected to the underwater counter collision method by setting the number of passes of the wet micronization device to 2 or more. In the step of preparing the second dispersion, the underwater facing collision method is performed in the same manner as in the step of preparing the first dispersion (step S1), except for the number of passes.

The mixed liquid of CNT, CMC, and water in the step of preparing the second dispersion has a low viscosity because the CNT content is as small as less than 3.0% by mass. Therefore, in the step of preparing the second dispersion, the underwater counter-collision method can be performed by setting the number of passes of the wet micronization device to 2 or more. By setting the number of passes to 2 or more, the viscosity of the second dispersion can be made lower than when the number of passes is 1. As a result, it is possible to prepare a third dispersion having a viscosity suitable for coating while maintaining a high CNT content. The number of passes is preferably three times, more preferably four times. The higher the number of passes, the lower the viscosity of the second dispersion. The number of passes may be 5 times or more, but 4 times is preferable in consideration of shortening the processing time by the wet micronization device.

The viscosity of the second dispersion is, for example, 10 cps or more and 2000 cps or less, preferably 15 cps or more and 1500 cps or less, more preferably 20 cps or more and 1000 cps or less, still more preferably 25 cps or more and 500 cps or less, still more preferably 30 cps or more and 150 cps or less. . If the viscosity is 10 cps or more and 2000 cps or less, a third dispersion having a viscosity suitable for coating can be produced.

Through the steps described above, a second dispersion containing CNTs, CMC, and water, and having a CNT content and a CMC content of less than 3.0% by mass can be produced.

The order of the step of preparing the first dispersion (step S1) and the step of preparing the second dispersion (step S2) is not particularly limited.

2.4. Step of preparing a third dispersion (step S3)
In the step of producing the third dispersion, the first dispersion and the second dispersion are mixed to produce the third dispersion. Mixing of the first dispersion and the second dispersion is performed by, for example, a high-speed disperser or homogenizer. When using a high-speed disperser, it may be a stirring type that agitates the mixed liquid, and when using a homogenizer, it may be an ultrasonic type that causes cavitation with ultrasonic waves, or pressure is applied to the mixed liquid. It may be a pressure type. The treatment time with a high-speed disperser or homogenizer is, for example, 10 minutes or more and 240 minutes or less, preferably 30 minutes or more and 120 minutes or less.

In the step of preparing the third dispersion, the ratio M ₁ /M _SUM of the mass M ₁ of the first dispersion to the sum M _SUM of the mass of the first dispersion and the mass of the second dispersion is, for example, 0.5. The first dispersion and the second dispersion are mixed so that the ratio is 15 or more and 0.70 or less, preferably 0.20 or more and 0.65 or less, more preferably 0.25 or more and 0.60 or less. If the ratio M ₁ /M _SUM is 0.15 or more and 0.70 or less, a third dispersion having a CNT content of 2.5% by mass or more and a viscosity of 3000 cps or less can be produced. The CNT content in the third dispersion is less than the CNT content in the first dispersion and greater than the CNT content in the second dispersion. The viscosity of the third dispersion is lower than the viscosity of the first dispersion and higher than the viscosity of the second dispersion.

Through the steps described above, the third dispersion as the CNT aqueous dispersion can be produced.

2.5. Effects In the method for producing an aqueous CNT dispersion according to the present embodiment, the steps of producing a first dispersion containing CNTs and water and having a CNT content of 3.0% by mass or more; and mixing the first and second dispersions to prepare a third dispersion; and including. In the step of preparing the first dispersion, the first dispersion is prepared by performing the underwater facing collision method with one pass of the wet atomization device. In the step of producing the second dispersion, the second dispersion is produced by performing the underwater facing collision method with the number of passes of the wet atomization device set to 2 or more.

As described above, the second dispersion has a CNT content of less than 3.0% by mass and is produced by performing the underwater facing collision method with the number of passes of the wet atomization device set to 2 or more, Low viscosity. Then, since the first dispersion having a high CNT content and the second dispersion having a low viscosity are mixed, an aqueous CNT dispersion having a high CNT content and a viscosity set for coating is prepared. be able to. Therefore, in the method for producing an aqueous CNT dispersion according to the present embodiment, it is possible to easily produce an aqueous CNT dispersion that has a large CNT content and is easy to coat.

2.6. First modification 2.6.1. Overall Flow Next, a first modified example of the method for producing an aqueous CNT dispersion according to the present embodiment (hereinafter also simply referred to as "first modified example of the production method") will be described with reference to the drawings. FIG. 2 is a flow chart for explaining a first modification of the manufacturing method.

In the first modification of the manufacturing method, as shown in FIG. 2, after the step of preparing the third dispersion (step S3), the third dispersion is subjected to the underwater facing collision method to produce the fourth dispersion. a step of preparing (step S4); a step of preparing a fifth dispersion having a higher CNT content than the fourth dispersion (step S5); and a step of preparing a 6 dispersion (step S6). Each step will be described below.

2.6.2. Step of preparing a fourth dispersion (step S4)
In the step of producing the fourth dispersion, the third dispersion is subjected to the underwater facing collision method with the number of passes of the wet atomization device set to two or more times to produce the fourth dispersion. In the step of preparing the fourth dispersion, the underwater facing collision method is performed in the same manner as in the step of preparing the first dispersion (Step S1), except for the number of passes. Although the third dispersion has a high CNT content, it has a low viscosity. Therefore, the underwater facing collision method can be performed with two or more passes of the wet atomization device.

By setting the number of passes of the wet atomization apparatus to two or more times, the viscosity of the fourth dispersion can be made lower than when the number of passes is one. The number of passes is preferably three times, more preferably four times.

The viscosity of the fourth dispersion is lower than the viscosity of the third dispersion. The viscosity of the fourth dispersion is, for example, from 10 cps to 2000 cps, preferably from 15 cps to 1000 cps, more preferably from 20 cps to 500 cps, and even more preferably from 30 cps to 300 cps. If the viscosity is 10 cps or more and 2000 cps or less, a sixth dispersion having a viscosity suitable for coating can be produced.

The CNT content in the fourth dispersion is greater than the CNT content in the second dispersion and less than the CNT content in the fifth dispersion. The CNT content in the fourth dispersion is, for example, the same as the CNT content in the third dispersion. The content of CNTs in the fourth dispersion is, for example, 2.7% by mass or more and 10.0% by mass or less, preferably 3.0% by mass or more and 8.0% by mass or less, more preferably 3.0% by mass or more and 8.0% by mass or less. It is 2 mass % or more and 5.0 mass % or less. If the CNT content is 2.7% by mass or more, a sixth dispersion having a high CNT content can be produced. If the CNT content is 10.0% by mass or less, the viscosity of the fourth dispersion can be lowered.

2.6.3. Step of preparing a fifth dispersion (step S5)
In the step of producing a fifth dispersion, a fifth dispersion containing CNTs and water and having a higher CNT content than the fourth dispersion is produced. The description of the step of preparing the fifth dispersion can be applied by replacing the “first dispersion” with the “fifth dispersion” in the description of the step of preparing the first dispersion (step S1). can. Therefore, description thereof is omitted.

The order of the step of preparing the fourth dispersion (step S4) and the step of preparing the fifth dispersion (step S5) is not particularly limited.

2.6.4. Step of preparing a sixth dispersion (step S6)
In the step of producing the sixth dispersion, the fourth dispersion and the fifth dispersion are mixed to produce the sixth dispersion. The description of the step of preparing the sixth dispersion is as follows: In the step of preparing the third dispersion (step S3) described above, the “first dispersion”, the “second dispersion”, and the “third dispersion” are They can be applied in place of "fourth dispersion", "fifth dispersion", and "sixth dispersion", respectively. Therefore, description thereof is omitted.

Through the above steps, the sixth dispersion as the CNT water dispersion can be produced.

2.6.5. Effect In the first modification of the production method, in addition to the steps of producing the first to third dispersions, the number of passes of the wet atomization device for the third dispersion is set to 2 or more times, and the underwater facing is performed. performing a collision method to prepare a fourth dispersion; preparing a fifth dispersion that contains CNTs and water and has a higher CNT content than the fourth dispersion; and the fourth dispersion. and mixing with the fifth dispersion to form a sixth dispersion. In the step of preparing the fifth dispersion, the wet atomization device is passed once, and the underwater facing collision method is performed to prepare the fifth dispersion. Therefore, in the first modification of the manufacturing method, it is possible to prepare, as the aqueous CNT dispersion, the sixth dispersion having a higher CNT content than the third dispersion.

2.7. Second modification 2.7.1. Overall Flow Next, a second modified example of the method for producing an aqueous CNT dispersion according to the present embodiment (hereinafter also simply referred to as "second modified example of the production method") will be described with reference to the drawings. FIG. 3 is a flow chart for explaining a second modification of the manufacturing method.

In the second modification of the manufacturing method, as shown in FIG. 3, after the step of preparing the sixth dispersion (step S6), the sixth dispersion is subjected to the underwater facing collision method to produce the seventh dispersion. a step of preparing (step S7); a step of preparing an eighth dispersion having a CNT content higher than that of the seventh dispersion (step S8); and a step of preparing a 9 dispersion (step S9). Each step will be described below.

2.7.2. Step of preparing a seventh dispersion (step S7)
In the step of producing the seventh dispersion, the sixth dispersion is subjected to the underwater facing collision method with the number of passes of the wet atomization device set to two or more times to produce the seventh dispersion. In the step of preparing the seventh dispersion, the underwater facing collision method is performed in the same manner as in the step of preparing the first dispersion (step S1), except for the number of passes. Although the sixth dispersion has a high CNT content, it has a low viscosity. Therefore, the underwater facing collision method can be performed with two or more passes of the wet atomization device.

By setting the number of passes of the wet atomization apparatus to 2 or more, the viscosity of the seventh dispersion can be made lower than when the number of passes is 1. The number of passes is preferably three times, more preferably four times.

The viscosity of the seventh dispersion is lower than the viscosity of the sixth dispersion. The viscosity of the seventh dispersion is, for example, from 10 cps to 2000 cps, preferably from 15 cps to 1000 cps, more preferably from 20 cps to 500 cps, and even more preferably from 30 cps to 300 cps. If the viscosity is 10 cps or more and 2000 cps or less, the ninth dispersion having a viscosity suitable for coating can be produced.

The CNT content in the seventh dispersion is higher than the CNT content in the fourth dispersion and lower than the CNT content in the eighth dispersion. The CNT content in the seventh dispersion is, for example, the same as the CNT content in the sixth dispersion. The content of CNTs in the seventh dispersion is, for example, 3.0% by mass or more and 10.0% by mass or less, preferably 3.2% by mass or more and 8.0% by mass or less, and more preferably 3.2% by mass or more and 8.0% by mass or less. It is 5 mass % or more and 5.0 mass % or less. If the CNT content is 3.0% by mass or more, a ninth dispersion having a high CNT content can be produced. If the CNT content is 10.0% by mass or less, the viscosity of the seventh dispersion can be lowered.

2.7.3. Step of preparing an eighth dispersion (step S8)
In the step of producing an eighth dispersion, an eighth dispersion containing CNTs and water and having a higher CNT content than the seventh dispersion is produced. The description of the step of preparing the eighth dispersion can be applied by replacing the “first dispersion” with the “eighth dispersion” in the description of the step of preparing the first dispersion (Step S1). can. Therefore, description thereof is omitted.

The order of the step of preparing the seventh dispersion (step S7) and the step of preparing the eighth dispersion (step S8) is not particularly limited.

2.7.4. Step of preparing a ninth dispersion (Step S9)
In the step of producing the ninth dispersion, the seventh dispersion and the eighth dispersion are mixed to produce the ninth dispersion. The description of the step of preparing the ninth dispersion is as follows: In the step of preparing the third dispersion (step S3), the “first dispersion”, the “second dispersion”, and the “third dispersion” are They can be applied in place of "seventh dispersion", "eighth dispersion", and "ninth dispersion", respectively. Therefore, description thereof is omitted.

Through the steps described above, the ninth dispersion as an aqueous CNT dispersion can be produced.

2.7.5. Effect In the second modification of the production method, in addition to the steps of preparing the first to sixth dispersions of the first modification, the number of passes of the wet atomization device for the sixth dispersion is two or more times. A step of producing a seventh dispersion by performing an underwater facing collision method as a step of producing an eighth dispersion containing CNTs and water and having a higher CNT content than the seventh dispersion; and mixing the dispersion and the eighth dispersion to form a ninth dispersion. In the step of preparing the eighth dispersion, the number of passes of the wet atomization device is set to one, and the underwater facing collision method is performed to prepare the eighth dispersion. Therefore, in the second modification of the manufacturing method, the ninth dispersion having a higher CNT content than the sixth dispersion can be produced as the aqueous CNT dispersion.

In the above, an example including the steps of producing the first to ninth dispersions has been described, but the method for producing an aqueous CNT dispersion according to the present invention further includes the number of passes for the ninth dispersion. A dispersion prepared by performing the underwater facing collision method with two or more passes (low-concentration dispersion), and a dispersion prepared by performing the underwater facing collision method with the number of passes set to 1 (low-concentration dispersion A CNT aqueous dispersion may be produced by mixing a high-concentration dispersion larger than the liquid). Thus, in the method for producing an aqueous CNT dispersion according to the present invention, the aqueous CNT dispersion may be produced by repeating mixing of the low-concentration dispersion and the high-concentration dispersion. The number of repetitions of the mixing is not particularly limited. The greater the number of repetitions of the mixing, the more the CNT aqueous dispersion with a higher CNT content can be produced.

3. EXAMPLES AND COMPARATIVE EXAMPLES Examples and comparative examples are shown below to describe the present invention more specifically. The present invention is by no means limited by the following examples and comparative examples.

3.1. Preparation of CNT aqueous dispersion 3.1.1. Example 1
(1) First liquid CMC was added to water and stirred. CMC was added so that the content in the first liquid was 4.0% by mass. As CMC, "Celogen 5A" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. was used. The CMC has a molecular weight of 11000-15000 and a degree of etherification of 0.7. Only CMC was used as a dispersant.

Next, CNTs were added to the stirred mixture of CMC and water and stirred for 1 hour. The stirring was performed at a higher speed than the stirring of the mixture of CMC and water. CNTs were added so that the content in the first liquid was 4.0% by mass. As CNT, "K-Nanos-100P" manufactured by KUMHO PETROCHEMICAL was used. The CNTs are MWNTs, diameter 8 nm to 15 nm, fiber length 27 μm (bundle), BET specific surface area 220 m ² /g.

Next, the mixed solution was treated with a homogenizer “Biomixer BM-2” manufactured by Nippon Seiki Seisakusho Co., Ltd. The treatment time was 5 minutes.

Next, the above mixed solution was subjected to an underwater facing collision method. The underwater counter-impingement method was performed using a wet atomization apparatus "Starburst Lab" (model name: HJP-25005) manufactured by Sugino Machine Co., Ltd. The diameter of the nozzle hole through which the mixed liquid is discharged was set to 100 μm, and the discharging pressure of the mixed liquid was set to 200 MPa. The number of passes of the mixed liquid by the wet atomization device was set to one.

The first liquid was produced through the above steps. The viscosity of the first liquid was 10000 cps or more. The viscosity was measured using a B-type viscometer "BM" manufactured by Tokyo Keiki Co., Ltd. under the conditions of 25° C. and 60 rpm.

(2) Second liquid CMC was added so that the content in the second liquid was 2.3% by mass. CNTs were added so that the content in the second liquid was 2.3% by mass. The mixed liquid of CNT, CMC and water was passed four times by the wet atomization device.

Except for the above, the second liquid was prepared in the same manner as the first liquid described above. The viscosity of the second liquid was 150 cps. The viscosity of the second liquid was measured under the same conditions as the first liquid.

(3) Mixing the first liquid and the second liquid Next, the first liquid and the second liquid are mixed with a high-speed dispersing machine "Homo Disper 2.5 type" manufactured by Primix Co., Ltd. to obtain the first liquid. A mixture of the liquid and the second liquid was prepared. The treatment time was 60 minutes. The ratio of the mass of the first liquid to the mass of the second liquid was adjusted so that the CNT content in the mixed liquid was 3.0%.

Through the above steps, a mixed liquid as a CNT aqueous dispersion was prepared. FIG. 4 is a table showing conditions for preparing the mixtures of Examples 1 to 11 and Comparative Examples 1 and 2. As shown in FIG. In FIG. 4, the "mass ratio of the first liquid" is the ratio of the mass of the first liquid to the sum of the mass of the first liquid and the mass of the second liquid.

3.1.2. Examples 2 and 3
In Examples 2 and 3, the first liquid and the first liquid were mixed in the same manner as in the first embodiment except that the CNT content and the CMC content in the first liquid were changed as shown in FIG. A mixture of the two liquids was prepared.

3.1.3. Examples 4 and 5
In Examples 4 and 5, the CNT content and CMC content in the first liquid and the CNT content and CMC content in the second liquid were changed as shown in FIG. A mixed liquid of the first liquid and the second liquid was prepared in the same manner as in the first embodiment.

3.1.4. Example 6
In Example 6, the mixed liquid of Example 1 prepared as described above was subjected to the underwater facing collision method with four passes by the wet atomization device, and the liquid was used as the second liquid. A mixed liquid of the first liquid and the second liquid was prepared in the same manner as in the first example described above, except that the mass ratio of one liquid was set to 0.40.

3.1.5. Example 7
In Example 7, the mixed liquid of Example 6 prepared as described above was subjected to the underwater facing collision method with the number of passes by the wet atomization apparatus set to 4 times, and the liquid was used as the second liquid, and A mixed liquid of the first liquid and the second liquid was prepared in the same manner as in the first example described above, except that the mass ratio of the first liquid was set to 0.34.

3.1.6. Examples 8 and 9
In Examples 8 and 9, the first liquid and the second liquid were prepared in the same manner as in the above-described first example, except that the CMC content in the first liquid or the second liquid was changed as shown in FIG. A liquid mixture was prepared.

3.1.7. Example 10
In Example 10, the mixed liquid of Example 9 prepared as described above was subjected to the underwater facing collision method with four passes by the wet atomization device, and the liquid was used as the second liquid, and A mixed liquid of the first liquid and the second liquid was prepared in the same manner as in the first example described above, except that the mass ratio of the first liquid was set to 0.30.

3.1.8. Example 11
In Example 11, the first liquid and the second liquid were prepared in the same manner as in the first example except that the CMC contents in the first liquid and the second liquid were changed as shown in FIG. A mixed solution was prepared.

3.1.9. Comparative example 1
In Comparative Example 1, a mixed liquid of the first liquid and the second liquid was prepared in the same manner as in the first example described above, except that only water was used as the second liquid. That is, in Comparative Example 1, the first liquid having a CNT content of 4.0% by mass was diluted with water so that the CNT content was 3.0% by mass.

3.1.10. Comparative example 2
In Comparative Example 2, only water was used as the second liquid. A mixed liquid of the first liquid and the second liquid was prepared in the same manner as in the above-described first example, except that the mass ratio of was adjusted. That is, in Comparative Example 2, the first liquid having a viscosity of 10000 cps or more was diluted with water so that the viscosity became 1500 cps.

3.2. Evaluation Results of CNT Content and Viscosity in Mixed Liquid FIG. 4 shows evaluation results of CNT content and viscosity in the mixed liquids of Examples 1 to 11 and Comparative Examples 1 and 2.

As shown in FIG. 4, the mixed liquids of Examples 1 to 11 had a CNT content of 2.5% by mass or more and a viscosity of 3000 cps or less. Comparative Example 1 had a CNT content of 2.5% by mass or more, but had a viscosity higher than 3000 cps. Comparative Example 2 had a viscosity of 3000 cps or less, but a CNT content of less than 2.5% by mass.

By comparing Example 1 and Comparative Example 1, even if the CNT content in the mixed liquid is the same 3.0% by mass, Comparative Example 1 using water as the second liquid has a significantly higher viscosity. found to be higher.

By comparing Example 1 and Comparative Example 2, even if the mixed liquid has the same viscosity of 1500 cps, Comparative Example 2 using water as the second liquid has a significantly smaller CNT content. all right.

By comparing Example 1 and Example 6, it was found that the CNT content can be increased by using the mixed liquid of Example 5 as the second liquid. Furthermore, by comparing Example 6 and Example 7, it was found that the CNT content can be increased by using the mixed liquid of Example 6 as the second liquid. In this way, by repeating the use of the prepared mixed solution of this example as the second liquid, the CNT content in the mixed solution can be brought infinitely close to 4.0% by mass.

According to Examples 8, 9 and 11, even if the ratio M _CMC /M _CNT of the mass M _CMC of CMC to the mass M _CNT of CNT is not 1 (CNT:CMC=1:1), the content of CNT It was found that a mixture having an amount of 2.5% by mass or more and a viscosity of 3000 cps or less could be prepared.

The above-described embodiments and modifications are examples, and the present invention is not limited to these. For example, it is also possible to appropriately combine each embodiment and each modification.

The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments. "Substantially the same configuration" means, for example, a configuration having the same function, method, and result, or a configuration having the same purpose and effect. Moreover, the present invention includes configurations in which non-essential portions of the configurations described in the embodiments are replaced. Moreover, the present invention includes a configuration that achieves the same effects as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the present invention includes configurations obtained by adding known techniques to the configurations described in the embodiments.

Claims (18)

including carbon nanotubes, carboxymethyl cellulose, and water;
The content of the carbon nanotubes is 2.5% by mass or more,
An aqueous carbon nanotube dispersion having a viscosity of 3000 cps or less as measured using a Brookfield viscometer at 25° C. and a rotation speed of 60 rpm. 2. The carbon nanotube aqueous dispersion according to claim 1, which does not contain a dispersing agent other than the carboxymethyl cellulose. 3. The carbon nanotube aqueous dispersion according to claim 1, wherein the carbon nanotube content is 3.0% by mass or more. The carbon nanotube aqueous dispersion according to any one of claims 1 to 3, wherein said viscosity is 2500 cps or less. The carbon nanotube aqueous dispersion according to any one of claims 1 to 4, wherein said viscosity is 1000 cps or more. The carbon nanotube aqueous dispersion according to any one of claims 1 to 5, wherein the carboxymethylcellulose content is 2.5% by mass or more. The carbon nanotube aqueous dispersion according to any one of claims 1 to 6, wherein the carboxymethylcellulose content is 3.0% by mass or more. 8. The carbon nanotube aqueous dispersion according to any one of claims 1 to 7, which is used as a coating agent for electromagnetic shielding seeds. a step of preparing a first dispersion containing carbon nanotubes and water, wherein the content of the carbon nanotubes is 3.0% by mass or more;
preparing a second dispersion containing carbon nanotubes and water, wherein the content of the carbon nanotubes is less than 3.0% by mass;
mixing the first dispersion and the second dispersion to prepare a third dispersion;
including
In the step of preparing the first dispersion, an underwater facing collision method is performed with the number of passes of the wet atomization device set to 1 to prepare the first dispersion,
The method for producing an aqueous carbon nanotube dispersion, wherein in the step of producing the second dispersion, the second dispersion is produced by performing an underwater facing collision method with the number of passes of the wet atomization device set to 2 or more. 10. The method for producing an aqueous carbon nanotube dispersion according to claim 9, wherein in the step of preparing the second dispersion, the wet atomization device is passed four times. a step of subjecting the third dispersion to an underwater facing collision method with the number of passes of the wet atomization device set to two or more times to prepare a fourth dispersion;
a step of preparing a fifth dispersion containing carbon nanotubes and water, wherein the content of the carbon nanotubes is greater than that of the fourth dispersion;
mixing the fourth dispersion and the fifth dispersion to prepare a sixth dispersion;
including
11. The carbon nanotube water according to claim 9 or 10, wherein in the step of preparing the fifth dispersion, the fifth dispersion is prepared by performing an underwater facing collision method with one pass of the wet atomization device. A method for producing a dispersion. 12. The method for producing an aqueous carbon nanotube dispersion according to claim 11, wherein in the step of preparing the fourth dispersion, the wet atomization device is passed four times. A step of subjecting the sixth dispersion to an underwater facing collision method with the number of passes of the wet atomization device set to two or more times to prepare a seventh dispersion;
a step of preparing an eighth dispersion containing carbon nanotubes and water, wherein the content of the carbon nanotubes is greater than that of the seventh dispersion;
mixing the seventh dispersion and the eighth dispersion to prepare a ninth dispersion;
including
13. The carbon nanotube water according to claim 11 or 12, wherein in the step of producing the eighth dispersion, the eighth dispersion is produced by performing an underwater facing collision method with one pass of the wet atomization device. A method for producing a dispersion. 14. The method for producing an aqueous carbon nanotube dispersion according to claim 13, wherein in the step of preparing the seventh dispersion, the wet atomization device is passed four times. The content of the carbon nanotubes in the first dispersion is 3.5% by mass or more,
15. The method for producing an aqueous carbon nanotube dispersion according to any one of claims 9 to 14, wherein the content of said carbon nanotubes in said second dispersion is 2.5% by mass or less. In the step of preparing the third dispersion, the ratio of the mass of the first dispersion to the sum of the mass of the first dispersion and the mass of the second dispersion is 0.15 or more and 0.70 or less. 16. The method for producing an aqueous carbon nanotube dispersion according to any one of claims 9 to 15, wherein said first dispersion and said second dispersion are mixed so as to obtain. The first dispersion and the second dispersion contain carboxymethyl cellulose,
The content of the carboxymethyl cellulose in the first dispersion is 3.0% by mass or more,
17. The method for producing an aqueous carbon nanotube dispersion according to any one of claims 9 to 16, wherein the content of said carboxymethylcellulose in said second dispersion is less than 3.0% by mass. The content of the carboxymethyl cellulose in the first dispersion is 3.5% by mass or more,
18. The method for producing an aqueous carbon nanotube dispersion according to claim 17, wherein the content of said carboxymethyl cellulose in said second dispersion is 2.5% by mass or less.

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