JP2016026983A - Carbon nanotube dispersion liquid comprising conductive polymer, carbon material and method for producing the dispersion liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon nanotube dispersion liquid having excellent dispersibility and a method for producing the same.SOLUTION: In an aqueous solution of a conductive polymer comprising a thiophene skeleton with a sulfo group, carbon nanotubes with a number average fiber diameter of 100 nm or more and carbon nanotubes with a number average fiber diameter of 30 nm or less are mixed with a wet jet mill, to obtain a carbon nanotube dispersion liquid having both carbon nanotubes dispersed in the aqueous solution.SELECTED DRAWING: None

Description

  The present invention relates to a dispersion of carbon nanotubes containing a conductive polymer, a carbon material, and a method for producing the dispersion.

  In Patent Document 1 (Japanese Patent Laid-Open No. 2011-178878), a conductive layer with few defects and foreign matters can be obtained by a simple method in terms of appearance and / or performance without impairing the characteristics of the carbon nanotube itself. In order to obtain a carbon nanotube composition having excellent long-term stability, a carbon nanotube-containing composition containing a carbon nanotube, a conductive polymer, and a solvent, and having a particle size distribution measured by a dynamic light scattering method Disclosed is a carbon nanotube-containing composition having a ratio ((I) / (II)) of 3.0 or more of a cumulative scattering intensity (I) of 1 nm or more and less than 1 μm and a cumulative scattering intensity (II) of 1 μm or more and less than 100 μm. ing. Furthermore, a carbon nanotube-containing conductive layer formed by applying a carbon nanotube-containing composition to a substrate and then drying it at room temperature or by heating is disclosed.

JP 2011-178878 A

However, there has been a problem that the carbon nanotubes obtained as aggregated particles do not exhibit sufficient dispersibility. In addition, a composition that is not sufficiently dispersed can be applied on a substrate to obtain a conductive layer, but since there is no attractive force between aggregated particles, it is not possible to form a conductive layer without a substrate. It was difficult.
This invention is made | formed in view of the said situation, Comprising: It aims at providing the dispersion liquid of a carbon nanotube with favorable dispersibility, a carbon material, and its manufacturing method.

  The present invention includes the following (1) to (6).

(1) Carbon nanotubes A having a number average fiber diameter of 100 nm or more and carbon nanotubes B having a number average fiber diameter of 30 nm or less are dispersed in an aqueous solution of a conductive polymer containing a thiophene skeleton having a sulfo group. A dispersion of carbon nanotubes characterized by comprising:
(2) The dispersion liquid according to (1), wherein 1 to 100 parts by mass of the carbon nanotube B is contained with respect to 100 parts by mass of the carbon nanotube A.
(3) The dispersion liquid according to (1) or (2), containing a total of 0.01 to 10% by mass of the carbon nanotubes A and B.
(4) The dispersion according to any one of (1) to (3), wherein the conductive polymer is contained in an amount of 0.1 to 50 parts by mass with respect to 100 parts by mass of the total amount of the carbon nanotubes A and B. .
(5) A carbon material obtained by removing water from the dispersion liquid according to any one of (1) to (4), wherein a plurality of the carbon nanotubes B adhere to the surface of the carbon nanotubes A. A carbon material having a structure in which the carbon nanotubes B straddle a plurality of the carbon nanotubes A.
(6) The carbon nanotubes according to any one of (1) to (4), wherein the carbon nanotubes A and B are mixed in an aqueous solution of the conductive polymer using a wet jet mill. A method for producing a dispersion liquid.

According to the present invention, a dispersion in which carbon nanotubes are finely dispersed and dispersibility is improved can be obtained.
Furthermore, by using the carbon nanotube dispersion of the present invention, it becomes easy to form a carbon material containing carbon nanotubes more uniformly, and can be used as, for example, an electronic component.

Scanning electron micrograph of the powder obtained in Example 13 (magnification: 50000 times)

The dispersion of the present invention comprises a carbon nanotube A having a number average fiber diameter of 100 nm or more and a carbon nanotube B having a number average fiber diameter of 30 nm or less in an aqueous solution of a conductive polymer containing a thiophene skeleton having a sulfo group. Is distributed. The dispersion of the present invention can be obtained by mixing the carbon nanotubes A and B in an aqueous solution of a conductive polymer containing a thiophene skeleton having a sulfo group using a wet jet mill.
In the present invention, “dispersed” refers to a state in which no precipitate is observed even when the dispersion is allowed to stand for one week or longer.

  In the carbon nanotube dispersion of the present invention, a conductive polymer containing a thiophene skeleton having a sulfo group is added as an additive. Carbon nanotubes are dispersed by using a conductive polymer containing a thiophene skeleton having a sulfo group as an additive.

As the conductive polymer of the present invention, a conductive polymer containing a thiophene skeleton having a sulfo group is used. This conductive polymer is preferably a water-soluble conductive polymer. In particular, the polymer is preferably a polymer having monomer units represented by the following general formulas (1) and (2). Of the general formulas (1) and (2), the general formula (1) is even more preferable.
Wherein R _1, R ₂ and R ₃ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 20 carbon atoms, or a linear or branched structure having 1 to 20 carbon atoms. Alkoxy group, linear or branched alkenyl group having 2 to 20 carbon atoms, linear or branched alkenyloxy group having 2 to 20 carbon atoms, hydroxyl group, halogen atom, nitro group, cyano group, trihalomethyl group, a phenyl group or _-SO ^3, - ^{M +} group (. ^{M +} is representing a hydrogen ion, an alkali metal ion or a quaternary ammonium ion,) .n representing the represents an integer of 1 to 20).

  Examples of the conductive polymer containing a thiophene skeleton having a sulfo group include polyalkyldioxythiophene derivatives and polyisothianaphthene derivatives, and in particular, poly (3,4-ethylenedioxythiophene) and polyisothianaphthenesulfonic acid. Is more preferable. Poly (3,4-ethylenedioxythiophene) is preferably added with polystyrene sulfonic acid as a dopant. Since polyisothianaphthenesulfonic acid is a self-doped conductive polymer, it is more preferably used.

  Specific examples of the conductive polymer containing a thiophene skeleton having a sulfo group include Espacer (registered trademark) # 100, Espacer # 300 manufactured by Showa Denko KK, Clevios (trademark) manufactured by Heraeus Co., Ltd., and Arakawa Chemical Industries, Ltd. Beamset 1700CP of Shin-Etsu Chemical Co., Ltd. (SEPLEGYDA (registered trademark), Sozo Chemical Co., Ltd. Verazol (registered trademark), polythiophene Baytron P) is preferably used, and Spacer # 100, Spacer # 300, Clevios and Baytron P are more preferable, Espacer # 100, Espacer # 300, and Clevios are more preferable, and Espacer is most preferable, where Espacer # 100 is a structure represented by the general formula (2). Including. Esupeisa ♯300 comprises a structure represented by the above general formula (1).

  In the carbon nanotube dispersion of the present invention, water is used as a dispersion medium. In the present invention, it is considered that the effect of dispersing carbon nanotubes in water is enhanced by using a conductive polymer containing a thiophene skeleton having a sulfo group as an additive.

  The carbon nanotubes A used in the present invention have a number average fiber diameter of 100 nm or more, preferably 100 to 1000 nm, more preferably 100 to 300 nm. The length is preferably 0.2 to 20 μm, more preferably 0.5 to 15 μm, and still more preferably 0.5 to 13 μm. Examples of such commercially available carbon nanotubes include VGCF (registered trademark) -H (number average fiber diameter 150 nm, number average fiber length: 10 to 20 μm, linear shape) manufactured by Showa Denko KK, Hodogaya Chemical Co., Ltd. Examples thereof include CT-12 (average fiber diameter: 110 nm), CT-25 (average fiber diameter: 150 nm), and the like.

  The carbon nanotubes B used in the present invention have a number average fiber diameter of 30 nm or less, preferably 1 to 30 nm, more preferably 5 to 20 nm. The length is preferably 0.1 to 10 μm, more preferably 0.2 to 8 μm, and still more preferably 0.2 to 5 μm. Examples of such commercially available carbon nanotubes A include VGCF (registered trademark) -X (number average fiber diameter 15 nm, non-linear shape) manufactured by Showa Denko KK, NC2100, NC2101, NC1100 manufactured by Nanosil Co., Ltd. Examples include MWNT MTC (fiber diameter 10-40 nm) manufactured by Meijo Nanocarbon.

  The number average fiber diameter is the number average value of 100 fibers observed with a transmission electron microscope (TEM) in both the carbon nanotubes A and B. This can be calculated by averaging the values obtained by photographing 100 fibers and binarizing them by image processing. In the carbon nanotube A, the number average fiber length is a number average value of 100 fibers observed with a transmission electron microscope (TEM). This can be calculated by averaging the values obtained by photographing 100 fibers and binarizing them by image processing.

  It is preferable that 1-100 mass parts of carbon nanotubes B are contained with respect to 100 mass parts of carbon nanotubes A in the dispersion liquid of the present invention. The content of the carbon nanotube B is more preferably 4 to 30 parts by mass, and more preferably 8 to 14 parts by mass in order to further improve the conductivity of the electrode material configured using the dispersion liquid of the present invention. More preferably.

  The total content of carbon nanotubes A and B in the dispersion of the present invention is preferably 0.01 to 10% by mass. More preferably, it is 0.05-7 mass%, More preferably, it is 0.1-5 mass%.

  The content of the conductive polymer containing a thiophene skeleton having a sulfo group in the dispersion of the present invention is preferably 0.1 to 50 parts by mass with respect to 100 parts by mass of the total amount of carbon nanotubes A and B. 0.5 to 10 parts by mass is more preferable, and 0.5 to 2 parts by mass is even more preferable.

  The carbon material from which water has been removed from the dispersion of the present invention preferably has a structure in which a plurality of carbon nanotubes B adhere to the surface of the carbon nanotubes A and the carbon nanotubes B straddle the plurality of carbon nanotubes A. The structure of the carbon material can be confirmed by observation with a transmission electron microscope (TEM), a scanning electron microscope (SEM), or the like.

  The dispersion of the present invention can be obtained, for example, by mixing carbon nanotubes A and B with an aqueous solution of a conductive polymer containing a thiophene skeleton having a sulfo group using a wet jet mill.

As a wet jet mill, Nanojet Pal (registered trademark) manufactured by Joko, Nanomaker manufactured by Advanced Nanotechnology, Nanomizer (registered trademark) manufactured by Nanomizer, Starburst (registered trademark) manufactured by Sugino Machine, Yoshida Kogyo Co., Ltd. A company-made ultra-high pressure wet micronizer can be used.
The pressure during mixing by the wet jet mill is preferably 100 MPa or more, and more preferably 150 to 250 MPa.

By mixing the carbon nanotubes A and B having different average diameters by the above method, the aggregated carbon nanotubes B are loosened and dispersed.
Preferably, the carbon material obtained by mixing by the above-described method until the average particle diameter (D50) of the particles in the dispersion described later is 2 times or less, preferably 1 time or less, of the average fiber length of the carbon nanotube A The conductivity becomes better.

  When mixing with a mixer, ball mill, or the like, there is a problem that when the mixing energy is small, the degree of loosening of the agglomerates is small, and when the mixing energy is large, the fiber is cut because too much shearing force is applied to the fiber. In that respect, when the above-described wet jet mill method is used, an appropriate mixing energy can be given to the aggregates of the carbon nanotubes A and B, so that the aggregates can be loosened.

The dispersion of the present invention thus obtained can be used for surface coating, vapor deposition and pressure bonding of composite materials, antistatic agents, resin additives, metal additives, and aluminum (including foil).
The dispersion itself can also be used as a lubricant.

The dispersion of the present invention obtained as described above can be dehydrated and formed into a sheet by a conventional method.
As the dehydration method, filtration (preferably suction filtration or centrifugal filtration), paper making, pressurization, or the like can be used. The carbon material obtained by dehydration using these methods may be compressed under pressure as necessary, and water remaining in the carbon material may be removed by drying at room temperature or by heating and vacuum drying. good. Here, the carbon material refers to a structure obtained by removing water from the dispersion of the present invention. At this time, the conductive polymer may remain in the carbon material or may be removed together with water.

  The obtained carbon material has a structure in which loose carbon nanotube fibers are entangled with other carbon fibers, and carbon nanotubes B having a small fiber diameter straddle a plurality of carbon nanotubes A. As a result, the shaped carbon material can maintain its shape without problems during subsequent handling, and can be made to withstand use in the intended application.

  Carbon fibers may be added to maintain the shape. In particular, when a carbon material having a large shape is formed, the strength of the carbon material is increased and effective. The carbon fiber to be added has a number average fiber diameter of 1 to 100 μm, preferably 3 to 50 μm, more preferably 5 to 30 μm. In particular, when the shape of the carbon material is plate-like, the number average fiber length of the carbon fibers is preferably 1 mm to 0.9 * D, more preferably, relative to the diameter D of the maximum inner circle of the maximum surface of the carbon material. It is 2-0.5 * D, More preferably, it is 3-0.3 * D. Such carbon fibers can be selected from commercially available products.

  When the number average fiber diameter of the carbon fiber is 1 μm or more or the number average fiber length is 1 mm or more, the strength reinforcing performance of the carbon material is good, and the number average fiber diameter of the carbon fiber is 100 μm or less or the number average fiber length is D * 0. In the case of .9 or less, it is easy to form a uniform film and hardly break.

The carbon fiber content is preferably 0.1 to 50 parts by mass, more preferably 1 to 30 parts by mass, and 3 to 15 parts by mass with respect to 100 parts by mass of the total amount of carbon nanotubes A and B. More preferably, it is a part.
Carbon fibers may be added at the same time as mixing the carbon nanotubes, but in order to mix them efficiently with a jet mill, the carbon nanotubes A and B are added to the dispersion after mixing with the jet mill and mixed. Is preferred. As a mixing method, a general method can be used. For example, a stirring or kneading apparatus such as an ultrasonic wave, a homogenizer, a spiral mixer, a planetary mixer, a disperser, or a hybrid mixer can be used.
The carbon fiber in the above range functions to increase the strength of the formed carbon material and facilitate handling.

  In addition, the carbon material obtained by removing water from the dispersion of the present invention can be used in medicine / medical / biotechnology, large transport field, environment field, electrical / electronic field, sports / leisure field, industrial material, catalyst, sliding / lubrication. It can be suitably used as a material or a magnetic material. Specifically, it can be used as a battery electrode, in particular, in place of a carbon electrode, for example, an electrode such as a Li battery, a Li-air battery, a metal-air battery, a catalyst such as a fuel cell catalyst or a photocatalyst, an electric double layer It can be used for electrode materials for capacitors and solid capacitors, cathode materials for optical devices such as flat fluorescent tubes and cold cathode tubes, transparent electrode materials such as touch panels and solar cells, and hydrogen storage agents. When it is used for an electrode or a catalyst, it is preferable to perform compression molding in order to increase conductivity. Thereby, a contact point increases between the fibers of adjacent carbon nanotubes, and a suitable conductive path can be formed. On the other hand, since carbon nanotubes having different fiber diameters are dispersed to form appropriate gaps, the carbon material can have voids through which a reaction medium such as an electrolyte or a reaction gas can easily pass. The number of contact points of the conductive path and the number of voids through which the reaction medium passes can be suitably controlled by, for example, the types of carbon nanotubes to be mixed and the above compression molding conditions.

  Further, a field emission display including the carbon material of the present invention on an electrode substrate, a hyper building using the carbon material of the present invention as a composite material, a cable for a large bridge, an automobile, an aircraft, a spacecraft, etc. Is also considered as an example.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited only to a following example.

<Example 1>
(Preparation of dispersion)
In water (100 ml) of dispersion medium, Espacer (registered trademark) # 300 (weight average molecular weight (gel permeation chromatography method / polystyrene sulfonic acid conversion) 12000, 1% by mass aqueous solution, which is polyisothianaphthenesulfonic acid as an additive 3 g) was dissolved to obtain an Espacer aqueous solution.
To this solution, VGCF (registered trademark) -H (number average fiber diameter 150 nm, number average fiber length 10 μm, 1.80 g) manufactured by Showa Denko KK as carbon nanotube A and VGCF (registered trademark) -X (number) as carbon nanotube B Average fiber diameter 15 nm, 0.20 g) was added.
Next, the solution was mixed using a wet jet mill at a pressure of 170 MPa for 10 minutes, and this mixing operation was repeated three times. Furthermore, this solution was dispersed using Nanomizer (registered trademark), and this dispersion operation was repeated 10 times to obtain a dispersion of Example 1.
(Average particle size measurement)
In order to confirm the dispersibility of the obtained dispersion, the average particle diameter (D50) of the particles in the dispersion was measured. The results are shown in Table 1.
The average particle size (D50) is a volume in the particle size distribution of an aggregate of spherical particles showing a scattering pattern equivalent to the light scattering pattern measured with a Nikkiso laser diffraction / scattering particle size distribution meter (Microtrac MT3000). The particle size is 50% fraction.
(Observation with a scanning electron microscope)
In order to investigate the dispersion state, the obtained dispersion liquid was filtered under reduced pressure, and a dried powder was obtained using a hot air dryer. An appropriate amount of this powder was collected and observed with a scanning electron microscope (FIG. 1).

<Examples 2-12, Comparative Examples 1-3>
Dispersions were obtained in the same manner as in Example 1 except that the types and masses of the conductive polymer, carbon nanotube A, and carbon nanotube B were changed as shown in Table 1.
The average particle size (D50) of the obtained dispersion was measured in the same manner as in Example 1. The results are shown in Table 1.

  From Table 1, the average particle diameter (D50) is 9.8 to 18.5 μm in Examples 1 to 12, whereas it is 27.3 to 28.2 μm in Comparative Examples 1 to 3. In Examples 1 to 12, it was confirmed that the dispersibility of the dispersion was higher than those in Comparative Examples 1 to 3, and in Example 1, the dispersibility was higher. The reason why such a result was obtained may be that the aggregate of carbon nanotubes B was loosened moderately in the dispersion of carbon nanotubes.

<Example 13>
To the dispersion liquid obtained in Example 1, 100 g of carbon short fibers (Donna Carbo Chop S-232, manufactured by Osaka Gas Co., Ltd.) was added and mixed using a mixer (ULTRA-TURRAX UTC 80 manufactured by IKA Co., Ltd.).
Using 3 liters of this slurry mixed with carbon short fibers, the slurry was poured into a rectangular filter having a width of 210 mm and a length of 300 mm, and suction filtered to prepare a cake. The obtained cake was compressed by applying a total load of 20 tons, and a weight was placed on the cake and dried in a 200 ° C. drier. The dried carbon material had a thickness of 5 mm and a total weight of 56 g. Even if a shape such as a part of this carbon material was cut out, cracking did not occur, and a carbon material with good handleability could be obtained.

<Comparative Examples 4-5>
Carbon short fibers were added to the dispersions of Comparative Examples 1 and 2, and a carbon material was obtained in the same manner as in Example 13. The thickness of the dried carbon material was 5 mm, and the total weight was 56 g and 55 g, respectively. However, in all cases, cracks occurred when the obtained carbon material was taken out of the dryer or when it was cut out.

  By using the carbon nanotube dispersion liquid of the present invention, it becomes easy to form a carbon material containing carbon nanotubes more uniformly, and can be used, for example, as an electronic component.

Claims (6)

In an aqueous solution of a conductive polymer containing a thiophene skeleton having a sulfo group,
A carbon nanotube A having a number average fiber diameter of 100 nm or more;
Carbon nanotubes B having a number average fiber diameter of 30 nm or less,
A dispersion of carbon nanotubes, characterized in that is dispersed. The dispersion liquid according to claim 1, wherein the carbon nanotube B is contained in an amount of 1 to 100 parts by mass with respect to 100 parts by mass of the carbon nanotube A. The dispersion liquid according to claim 1 or 2, comprising a total of 0.01 to 10 mass% of the carbon nanotubes A and B. The dispersion liquid as described in any one of Claims 1-3 which contains the said conductive polymer 0.1-50 mass parts with respect to 100 mass parts of total amounts of the said carbon nanotubes A and B. A carbon material obtained by removing water from the dispersion according to any one of claims 1 to 4, wherein a plurality of the carbon nanotubes B adhere to the surface of the carbon nanotubes A, and the carbon nanotubes B Is a carbon material having a structure straddling between the plurality of carbon nanotubes A. 5. The carbon nanotube dispersion according to claim 1, wherein the carbon nanotubes A and B are mixed with the aqueous conductive polymer solution using a wet jet mill. Method.