JP2019118861A - Dispersant for carbon nano-tube, and carbon nano-tube dispersion liquid with use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dispersant capable of improving dispersibility of a carbon nanotube dispersion liquid and wettability to a PET film in one embodiment. In one embodiment, the present invention relates to a dispersant for carbon nanotubes, which comprises at least one of the following components A and B. Component A: Containing a constituent unit derived from acrylic acid and a constituent unit derived from a hydrophobic monomer, the content of the constituent unit derived from a hydrophobic monomer in all the constituent units is 0.5 mol% or more and 2.3 mol% or less. A copolymer having a number average molecular weight of 3,000 or more and 15,000 or less. Component B: Polyacrylic acid having a hydrophobic end group of 0.5 mol% or more and 2.3 mol% or less and having a number average molecular weight of 3,000 or more and 15,000 or less. [Selection diagram] None

Description

  The present disclosure relates to a dispersant for carbon nanotubes, and a carbon nanotube dispersion using the same.

  A carbon nanotube is a nano-carbon material having a shape in which one surface of graphite is wound substantially into a cylindrical shape, a single-walled carbon nanotube wound in one layer, and a multi-walled carbon nanotube wound coaxially in multilayer. It is said. Carbon nanotubes themselves have excellent intrinsic conductivity and are expected to be used as a conductive material.

  Since carbon nanotubes have a high aspect ratio and can form conductive paths with a small amount, they can be conductive materials that are superior in light transmittance and drop-off resistance to conventional conductive fine particles such as carbon black. For example, it is known to use carbon nanotubes as a transparent conductive thin film for optics.

In order to obtain a conductive film excellent in light transmittance using carbon nanotubes, a thick bundle (bundle) consisting of several tens of carbon nanotubes or strong aggregation is broken to make the carbon nanotubes highly disperse, and less carbon It is required to form conductive paths efficiently with the number of nanotubes. As a means for obtaining such a conductive film, for example, a method of applying a dispersion in which carbon nanotubes are highly dispersed in an aqueous medium to a substrate is known. In order to highly disperse carbon nanotubes in an aqueous medium, there is a method of dispersing using a dispersing agent. Among them, in order to disperse carbon nanotubes in a higher degree, a method of dispersing in an aqueous medium using a dispersant having both a hydrophilic group having an affinity for water and a hydrophobic group having a high affinity for carbon nanotubes. Are known (see, for example, Patent Documents 1 to 3).

JP, 2014-209471, A JP, 2016-190772, A WO 2014-002885

However, since the low molecular weight surfactant of sodium dodecylbenzene sulfonate is used in the technology described in Patent Document 1 and the sodium deoxycholate sodium is used in the technology described in Patent Document 2, the carbon nanotubes are dispersed. When the solution is vigorously stirred, a large amount of effervescence is generated, and when the dispersion is coated on a polyethylene terephthalate (PET) film, it may be uneven and adversely affect.
In the technology described in Patent Document 3, since a high molecular weight dispersant is used, foaming is suppressed. However, even if it coats on PET film, the wettability of the surface is bad and there existed a subject that it repelled and it could not coat well. In such a case, there is also a method of treating the surface of the PET film before coating, but this is disadvantageous in terms of process and cost.

  Thus, the present disclosure provides, in one aspect, a dispersant that can improve the dispersibility of a carbon nanotube dispersion and the wettability to a PET film.

The present disclosure relates, in one aspect, to a dispersant for carbon nanotubes, which comprises at least one of the following component A and component B.
Component A: containing a structural unit derived from acrylic acid and a structural unit derived from a hydrophobic monomer, and the content of the structural unit derived from the hydrophobic monomer in all the structural units is 0.5 mol% or more and 2.3 mol% or less, A copolymer having a number average molecular weight of 3,000 or more and 15,000 or less.
Component B: Polyacrylic acid having a hydrophobic end group of 0.5 mol% or more and 2.3 mol% or less and a number average molecular weight of 3,000 or more and 15,000 or less.

  The present disclosure relates, in one aspect, to a carbon nanotube dispersion comprising the dispersant of the present disclosure, carbon nanotubes, and an aqueous medium.

  According to the present disclosure, in one or more embodiments, a dispersant capable of improving the dispersibility of the carbon nanotube dispersion and the wettability to a PET film can be provided.

  As a result of intensive studies, the present inventors dispersed a copolymer of acrylic acid and a specific hydrophobic monomer (component A) or a specific polyacrylic acid having a hydrophobic end group (component B). By using as an agent, it is found that carbon nanotubes can be favorably dispersed in an aqueous medium, wettability to a PET film is improved, and a carbon nanotube dispersion capable of forming a coating film on a PET film can be obtained. The present disclosure has been completed.

The details of the mechanism of the effects of the present disclosure are not clear, but are presumed as follows.
The component A and the component B used as the dispersant of the present disclosure have a polyethylene structure having a high affinity for carbon nanotubes that are strongly aggregated, and have a carboxyl group having a high affinity for water. It is considered that the dispersibility of the nanotubes is high. Furthermore, since it has a hydrophobic group (constituent unit derived from a hydrophobic monomer, or a hydrophobic end group) having high affinity with a PET film that is hydrophobic, the dispersibility of carbon nanotubes and the coatability to a PET film can be improved. It is considered to be compatible.
However, the present disclosure may not be interpreted as being limited to these mechanisms.

That is, the present disclosure relates, in one aspect, to a dispersant for carbon nanotubes, which comprises at least one of the following component A and component B.
Component A: containing a structural unit derived from acrylic acid and a structural unit derived from a hydrophobic monomer, and the content of the structural unit derived from the hydrophobic monomer in all the structural units is 0.5 mol% or more and 2.3 mol% or less, A copolymer having a number average molecular weight of 3,000 or more and 15,000 or less.
Component B: Polyacrylic acid having a hydrophobic end group of 0.5 mol% or more and 2.3 mol% or less and a number average molecular weight of 3,000 or more and 15,000 or less.

[Component A]
Component A which may be contained in the dispersant of the present disclosure is a structural unit derived from acrylic acid (hereinafter also referred to as “monomer a1”) (hereinafter also referred to as “constituent unit a1”) and a hydrophobic monomer (hereinafter referred to as “hydrophobic It is a copolymer including a constituent unit (hereinafter, also referred to as “constituent unit a2”) derived from “monomer a2”). Component A may be used individually by 1 type, and may use 2 or more types together. The copolymer of component A can be produced, for example, by polymerizing acrylic acid and a hydrophobic monomer.

  In the present disclosure, a hydrophobic monomer refers to a monomer having a solubility in water at 25 ° C. of less than 10% by mass. Dissolution indicates that the solute is mixed in a uniform solvent and exhibits a transparent state. Examples of hydrophobic monomers include methoxydipropylene glycol acrylate, phenoxydiethylene glycol acrylate, methyl acrylate, ethyl acrylate, butyl acrylate, phenyl acrylate and the like.

  The content of the structural unit a2 in all the structural units constituting the component A is 0.5 mol% or more, preferably 0.8 mol% or more, and 1 mol% or more from the viewpoint of wettability to PET and dispersibility. And from the same viewpoint, it is 2.3 mol% or less, preferably 2.1 mol% or less, and more preferably 1.8 mol% or less. More specifically, the content of the structural unit a2 is 0.5 mol% or more and 2.3 mol%, preferably 0.8 mol% or more and 2.1 mol% or less, and more preferably 1 mol% or more and 1.8 mol% or less. preferable.

  Component A may further include other constitutional units in one or more embodiments. In one or more embodiments, the total amount of structural unit a1 and structural unit a2 in all the structural units constituting component A is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably substantially It is 100 mass%.

  From the viewpoint of dispersibility, the number average molecular weight of the component A is 3,000 or more, preferably 3,500 or more, more preferably 4,000 or more, and from the same viewpoint, 15,000 or less. 14,000 or less is preferable, and 13,000 or less is more preferable. More specifically, the number average molecular weight of the component A is 3,000 or more and 15,000 or less, preferably 3,500 or more and 14,000 or less, and more preferably 4,000 or more and 13,000 or less. The number average molecular weight of the component A can be measured using gel permeation chromatography (hereinafter also referred to as “GPC”), and can be calculated specifically by the method described in the examples.

[Component B]
Component B, which may be included in the dispersant of the present disclosure, is a polyacrylic acid having hydrophobic end groups. In the present disclosure, the hydrophobic end group indicates a group derived from a hydrophobic polymerization initiator and / or a hydrophobic chain transfer agent having a solubility in water at 25 ° C. of less than 10% by mass. Dissolution indicates a transparent state. In the present disclosure, “solubility in water at 25 ° C.” means that the hydrophobic polymerization initiator and / or the hydrophobic chain transfer agent starts to become cloudy when gradually added to water at 25 ° C. We say mass ratio. Polyacrylic acid having a hydrophobic end group can be obtained, for example, by polymerizing acrylic acid (monomer b) with a hydrophobic polymerization initiator and / or a hydrophobic chain transfer agent.

  The content of the hydrophobic end group in the component B is 0.5 mol% or more, preferably 0.8 mol% or more, more preferably 1 mol% or more, from the viewpoint of wettability and dispersibility to PET. From the same viewpoint, it is 2.3 mol% or less, preferably 2.1 mol% or less, and more preferably 1.8 mol% or less. More specifically, the content of the hydrophobic terminal group is 0.5 mol% or more and 2.3 mol% or less, preferably 0.8 mol% or more and 2.1 mol% or less, and 1 mol% or more and 1.8 mol% or less. Is more preferred. In the present disclosure, the content of the hydrophobic end group of the component B is, for example, the mass of the hydrophobic polymerization initiator and / or the hydrophobic chain transfer agent used for the polymerization relative to the total amount (100 mol%) of the monomers used for the polymerization. It can be regarded as

  From the viewpoint of dispersibility, the number average molecular weight of the component B is 3,000 or more, preferably 3,500 or more, more preferably 4,000 or more, and from the same viewpoint, it is 15,000 or less. 14,000 or less is preferable, and 13,000 or less is more preferable. More specifically, the number average molecular weight of the component B is 3,000 or more and 15,000 or less, preferably 3,500 or more and 14,000 or less, and more preferably 4,000 or more and 13,000 or less. The number average molecular weight of the component B can be measured using gel permeation chromatography (hereinafter also referred to as "GPC"), and can be calculated specifically by the method described in the examples.

  In the present disclosure, it is preferable that the component A and the component B have a low degree of neutralization from the viewpoint of improving the dispersibility. The degree of neutralization of the component A and the component B is preferably 25 mol% or less, preferably less than 25 mol%, with respect to 100 mol% of the neutralizable functional group (for example, carboxy group) contained in the component A or the component B. Some are more preferable, and from the viewpoint of improving the dispersibility, 10 mol% or less is more preferable, and it is more preferable that the resin is not substantially neutralized. Specifically, the degree of neutralization of Component A and Component B when not substantially neutralized is preferably 1 mol% or less, more preferably 0 mol%. The degree of neutralization can be calculated, for example, by pH measurement.

  The use form of the dispersant of the present disclosure may be the polymer of Component A and / or Component B itself, or may be in a state of being dissolved in an aqueous medium (aqueous solution). When the use form of the dispersant according to the present disclosure is an aqueous solution, the content of the dispersant in the aqueous solution is 20% by mass or more and 60% by mass from the viewpoint of ease of handling in one or more embodiments. The following are preferable, 25 mass% or more and 50 mass% or less are more preferable, and 30 mass% or more and 45 mass% or less are more preferable. The content of the dispersant in the aqueous solution can also be determined, for example, from the amount of raw materials charged, or can be determined by measuring the solid content in the aqueous solution.

  The method for producing Component A and Component B in the present disclosure can be produced by a known polymerization method. For polymerization, known polymerization initiators, chain transfer agents and the like can be used. As a polymerization initiator, for example, 2,2-azobis (isobutyronitrile) (hydrophobic), 2,2-azobis (2,4-dimethylvaleronitrile) (hydrophobic), 2,2-azobis [N Azo-initiated polymerization agents such as-(2-carboxyethyl) -2-methylpropionamidine] hydrate (water-soluble), 2,2-azobis [2-methylpropionamidine] dihydrochloride (water-soluble), etc. . Examples of chain transfer agents include 3-mercaptopropionic acid (hydrophilic), mercaptopropanediol (water-soluble), 1-octanethiol (hydrophobic) and the like. It is preferred that at least one of the polymerization initiator and the chain transfer agent used for the production of component B be hydrophobic.

[Carbon nanotube dispersion liquid]
The present disclosure, in one aspect, comprises a carbon nanotube dispersion (hereinafter, also referred to as “the CNT dispersion of the present disclosure”), including the dispersant of the present disclosure, the carbon nanotube (hereinafter, also referred to as “CNT”), and an aqueous medium. About. According to the present disclosure, it is possible to provide a carbon nanotube dispersion having excellent dispersibility and wettability to a PET film.

<Carbon nanotube>
In the present disclosure, carbon nanotubes (CNTs) mean an aggregate including a plurality of carbon nanotubes. The form of the carbon nanotubes may not be particularly limited. For example, the plurality of carbon nanotubes may be independent of one another, or the plurality of carbon nanotubes may be in the form of bundles or entanglements, or the like. May be mixed. The carbon nanotubes may be carbon nanotubes of various layer numbers or diameters. The CNTs can include impurities (eg, catalysts and amorphous carbon) from processes in the production of carbon nanotubes.

  In one or more embodiments, the carbon nanotube has a shape in which one surface of graphite is wound into a cylindrical shape, and one wound into one layer is wound into a single-walled carbon nanotube and two layers. A double-walled carbon nanotube, one wound into three or more layers is also referred to as a multi-walled carbon nanotube. For the carbon nanotube dispersion and the coating film obtained by applying the dispersion, any single-wall, two-layer, multi-wall carbon nanotube and a mixture thereof can be used according to the required application properties. In particular, it is preferable to use a single-walled carbon nanotube in order to obtain a conductive film having high light transmittance.

  The length of the carbon nanotube may not be particularly limited, and is preferably 0.5 μm or more from the viewpoint of conductivity, more preferably 1 μm or more, and preferably 30 μm or less from the viewpoint of dispersibility.

  The content of the impurities in the CNT is preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 20% by mass or less, and still more preferably 10% by mass or less, from the viewpoint of increasing the effective concentration of CNTs. And substantially 0% by mass is more preferable.

<Aqueous medium>
The aqueous medium includes water or a mixed medium of water and a water-soluble organic solvent. Examples of water include distilled water, ion exchanged water, ultrapure water and the like. Examples of the water-soluble organic solvent include at least one selected from methanol, ethanol, isopropyl alcohol, butyl alcohol, benzyl alcohol, acetone, ethylene glycol, polyethylene glycol, propylene glycol, and butyl cellosolve, and the point of improvement of dispersibility From the above, at least one selected from ethanol, isopropyl alcohol, acetone, propylene glycol, and butyl cellosolve is preferable. When a mixed medium is used as the aqueous medium, the water-soluble organic solvent may be added (blended) separately from water, or may be added (blended) simultaneously with water. The content of water in the aqueous medium is preferably 90% by mass or more from the viewpoint of improving the dispersibility.

  From the viewpoint of increasing the concentration of the active component, the blending amount of CNT in the CNT dispersion liquid of the present disclosure is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and 0.15% by mass or more Is more preferably 0.5% by mass or less, more preferably 0.4% by mass or less, and still more preferably 0.3% by mass or less from the viewpoint of easy handling viscosity of the dispersion.

  From the viewpoint of dispersibility, the blending amount of the dispersant of the present disclosure in the CNT dispersion of the present disclosure is preferably 50% by mass or more, more preferably 60% by mass or more, and 70% by mass or more with respect to 100% by mass of CNTs. Is more preferable, and from the viewpoint of dispersibility, 500% by mass or less is preferable, 400% by mass or less is more preferable, and 300% by mass or less is more preferable.

  From the viewpoint of wettability, the viscosity of the CNT dispersion liquid of the present disclosure is preferably 100 mPa · s or more, more preferably 150 mPa · s or more, still more preferably 200 mPa · s or more, and from the same viewpoint, 2000 mPa · s or less. Is preferable, 1500 mPa · s or less is more preferable, and 1000 mPa · s or less is more preferable. More specifically, the viscosity of the CNT dispersion liquid of the present disclosure is preferably 100 mPa · s or more and 2000 mPa · s or less, more preferably 150 mPa · s or more and 1500 mPa · s or less, and still more preferably 200 mPa · s or more and 1000 mPa · s or less .

[Method of producing carbon nanotube dispersion (CNT dispersion)]
The CNT dispersion of the present disclosure can be produced, for example, by blending the dispersant of the present disclosure, CNTs and an aqueous medium by a known method. Therefore, the present disclosure, in one aspect, includes a dispersion step of mixing the dispersant of the present disclosure, CNTs, and an aqueous medium, and dispersing the CNTs in the aqueous medium, a method of producing a CNT dispersion (hereinafter referred to as “the present disclosure (Also referred to as “the CNT dispersion liquid production method”). According to the CNT dispersion manufacturing method of the present disclosure, a CNT dispersion having excellent dispersibility and wettability to PET can be manufactured. As the CNT and the aqueous medium used in the dispersion liquid production method of the present disclosure, the same ones as the CNT dispersion liquid of the present disclosure described above can be used.

  In the dispersion step, a CNT dispersion can be produced using a general mixing and dispersing machine for producing a paint. Examples of the mixing and dispersing machine include at least one selected from an ultrasonic homogenizer, a vibration mill, a jet mill, a ball mill, a bead mill, a bead mill, a sand mill, a roll mill, a homogenizer, a high pressure homogenizer, an ultrasonic device, an attritor, a dissolver, and a paint shaker. Can be mentioned. In the dispersion step, it is preferable to disperse using ultrasonic waves from the viewpoint of improving the dispersibility. The state of CNTs used for dispersion may be in a dry state or in a state containing an aqueous medium. In the dispersion step, the preferable blending amount of each component can be the same as the preferred blending amount of the CNT dispersion liquid of the present disclosure described above.

  Hereinafter, the present disclosure will be described in more detail by way of examples, but these are illustrative and the present disclosure is not limited to these examples.

1. Measurement Method of Number Average Molecular Weight The number average molecular weight of Component A and Component B was measured using gel permeation chromatography (hereinafter also referred to as “GPC”) method.
That is, the sample was diluted with N, N-dimethylformamide, and a solution having a solid concentration of 0.3% by mass of the sample was prepared as a sample solution, and 100 μL of the solution was subjected to measurement. A solution of phosphoric acid and lithium bromide dissolved in N, N-dimethylformamide so as to have concentrations of 60 mmol / L and 50 mmol / L, respectively, is used as an eluent, GPC [apparatus: "HLC-8120 GPC" manufactured by Tosoh Corporation, Detector: Differential refractometer (apparatus attachment), column: Tosoh Corp. "TSK-GEL alpha-M" x 2 pieces, column temperature: It measured by 40 degreeC, eluent flow rate: 1 mL / min].
As a standard substance, polystyrene (manufactured by Tosoh Corp .: molecular weight 5.26 × 10 ² , 1.02 × 10 ⁵ , 8.42 × 10 ⁶ ; manufactured by Nishio Kogyo Co., Ltd .: molecular weight 4.0 × 10 ³ , 3. 0 × 10 ⁴ , 9.0 × 10 ⁵ ) were used.

2. Preparation of Dispersants 1 to 13 The following components were used in the preparation of Dispersants 1 to 13 shown in Table 1.
<Hydrophobic monomer>
MPG2A: Methoxydipropylene glycol acrylate (Kyoei Kagaku "Light acrylate DPM-A", solubility in water at 25 ° C: 2% by mass)
PhEG2A: phenoxydiethylene glycol acrylate (Kyoei Kagaku Co., Ltd. "Light acrylate P2H-A, solubility in water at 25 ° C: less than 1% by mass")
MA: methyl acrylate (Wako Pure Chemical Industries, Ltd., solubility in water at 25 ° C .: 5% by mass)
<Polymerization initiator>
V-65B: 2,2-azobis (2,4-dimethylvaleronitrile) ("V-65B" manufactured by Wako Pure Chemical Industries, Ltd., hydrophobic, solubility in water at 25 ° C: less than 1% by mass)
VA-057: 2,2-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] tetrahydrate (Wako Pure Chemical Industries, Ltd. “VA-057”)
<Chain transfer agent>
MPA: 3-mercaptopropionic acid (Wako Pure Chemical Industries, reagent, hydrophilic)
OcSH: 1-octanethiol (Wako Pure Chemical Industries, Ltd. reagent, hydrophobicity, solubility in water at 25 ° C .: less than 1% by mass)

[Synthesis of Dispersant 1 (aqueous solution)]
15.0 g of distilled water was previously charged in a 1 L four-neck separable flask, and two dropping funnels, a reflux condenser, a thermometer, and a stirrer were attached. After nitrogen substitution, while stirring at 150 rpm, the temperature is raised to 80 ° C., and while maintaining the temperature, 80 mass% acrylic acid aqueous solution (monomer a1): 60.6 g and PhEGH2A (hydrophobic monomer a2): 1.5 g A mixed solution and a mixed solution of 1.41 g of VA-057 (polymerization initiator), 1.66 g of MPA (chain transfer agent) and 47.8 g of distilled water were separately added dropwise over 60 minutes. After completion of the dropwise addition, the temperature was kept at 80 ° C. for 60 minutes and then cooled. The solid content concentration of the obtained aqueous solution of dispersant 1 was 44.5% by mass, and the polystyrene reduced number average molecular weight by GPC was 7100.

[Synthesis of Dispersants 2 to 7, 9, 11 to 13 (aqueous solution)]
Synthesis of Dispersant 1 aqueous solution except that the type of hydrophobic monomer, composition ratio of copolymer, type and amount of polymerization initiator, and type and amount of chain transfer agent are changed as shown in Table 1 The aqueous solution of the dispersants 2-7, 9 and 11-13 was prepared in the same manner as in the above. The solid content concentration and number average molecular weight of the resulting aqueous dispersant solution are shown in Table 1.

[Synthesis of Dispersant 8 (aqueous solution)]
15.0 g of acetone was previously charged in a 1 L four-neck separable flask, and two dropping funnels, a reflux condenser, a thermometer, and a stirrer were attached. After nitrogen substitution, while stirring at 150 rpm, the temperature is raised to 60 ° C., and while maintaining the temperature, 80 mass% acrylic acid aqueous solution (monomer b): 62.5 g and V-65 B (hydrophobic polymerization initiator): A mixed solution of 0.69 g and 1.02 g of OcSH (hydrophobic chain transfer agent) and 47.5 g of acetone was separately added dropwise over 60 minutes. After completion of the dropwise addition, the temperature was kept at 60 ° C. for 60 minutes and then cooled. The solid content concentration of the obtained aqueous solution of dispersant 8 was 51.0% by mass, and the polystyrene reduced number average molecular weight by GPC was 12,800.

[Synthesis of Dispersant 10 (aqueous solution)]
15.0 g of ethanol was previously charged in a 1-L four-neck separable flask, and two dropping funnels, a reflux condenser, a thermometer, and a stirrer were attached. After nitrogen substitution, while stirring at 150 rpm, the temperature is raised to 80 ° C., and while maintaining the temperature, 80 mass% acrylic acid aqueous solution (monomer a1): 56.3 g and PhEGH2A (hydrophobic monomer a2): 5.0 g A mixed solution and a mixed solution of V-65B (hydrophobic polymerization initiator): 2.41 g, MPA (chain transfer agent): 4.12 g and ethanol: 48.8 g were separately dropped over 60 minutes. After completion of the dropwise addition, the temperature was kept at 80 ° C. for 60 minutes and then cooled. The solid content concentration of the obtained aqueous solution of dispersant 10 was 43.1% by mass, and the polystyrene reduced number average molecular weight by GPC was 1,500.

3. Preparation of Carbon Nanotube Dispersion (CNT Dispersion) The prepared dispersants 1 to 13, CNTs, and an aqueous medium (distilled water) were mixed to prepare CNT dispersions of Examples 1 to 8 and Comparative Examples 1 to 5. .
Specifically, 30 g of a dispersant aqueous solution and distilled water were measured in a 60 mL screw tube, and then 0.08 g of a CNT composition was measured. Then, after stirring at 300 rpm for 1 hour with a 2 cm length stirrer chip, it was dispersed for 5 minutes with an ultrasonic homogenizer (300 μA) while cooling with ice. As the ultrasonic homogenizer, US-300 manufactured by Nippon Seiki Co., Ltd. was used.
The blending amount of the dispersant in the CNT dispersion was 0.3% by mass, and the blending amount of CNTs was 0.2% by mass. The content of distilled water is the balance excluding the dispersant and CNT (including impurities). The compounding amount of CNT is an amount excluding impurities in CNT.
As the CNT, “TUBALL” (single-walled carbon nanotube having a purity of 75%, one or two layers, length 5 μm or more) manufactured by OCSiAl was used.

4. Evaluation
[CNT dispersibility (appearance)]
Evaluation of the dispersed state was judged by visual observation and viscosity.
(Visually)
It was confirmed whether aggregates of carbon nanotubes were observed on the wall of the screw tube. The results are shown in Table 1.
<Evaluation criteria>
A: Almost no aggregates B: Some aggregates are seen C: Many aggregates D: Not dispersed at all

[Viscosity at a shear rate of 10 s ^-1 ]
Brookfield viscometer cone plate type (cone radius 12 mm, cone angle 3 °), the viscosity after rotating for 60 seconds at a shear rate of 10 s ^-1 was read. The measurement temperature was 25 ° C. The results are shown in Table 1.

[Wettability to PET film]
As a commercially available PET film, Toyobo Co., Ltd. Cosmo Shine A4100 (length 20 cm ×
10 cm in width was used. The prepared CNT dispersion was applied to the spiral bar coater No. 1 with respect to the easy adhesion treated surface. After coating using 3 and drying for 1 minute with a blower dryer at 100 ° C., the coated surface was observed. The evaluation criteria are shown below. The evaluation results are shown in Table 1. In Table 1, when evaluation criteria are A and B, it is judged that the wettability to a PET film is favorable.
<Evaluation criteria>
A: No Hajiki can be seen B: One or two Hajiki can be seen C: Three or 10 Hajiki can be seen D: Many Hajiki (more than 11) can be seen

  From the results of Table 1, it was found that the CNT dispersions of Examples 1 to 8 were excellent in dispersibility and wettability to PET film.

  By using the dispersant of the present disclosure, a CNT dispersion having excellent dispersibility and wettability to a PET film can be manufactured.

Claims (5)

The dispersing agent for carbon nanotubes which contains at least one of the following component A and the component B.
Component A: containing a structural unit derived from acrylic acid and a structural unit derived from a hydrophobic monomer, and the content of the structural unit derived from the hydrophobic monomer in all the structural units is 0.5 mol% or more and 2.3 mol% or less, A copolymer having a number average molecular weight of 3,000 or more and 15,000 or less.
Component B: Polyacrylic acid having a hydrophobic end group of 0.5 mol% or more and 2.3 mol% or less and a number average molecular weight of 3,000 or more and 15,000 or less.   The dispersing agent of Claim 1 whose neutralization degree of the component A and the component B is 25 mol% or less.   The dispersant according to claim 1, wherein the carbon nanotube is a single-walled carbon nanotube.   A carbon nanotube dispersion comprising the dispersant according to any one of claims 1 to 3, a carbon nanotube, and an aqueous medium.   The carbon nanotube dispersion liquid according to claim 4, wherein a content of water in the aqueous medium is 90% by mass or more.