JP7345742B2 - CNT dispersant and CNT dispersion liquid - Google Patents

Description

The present disclosure relates to CNT dispersants and CNT dispersions.

CNTs have high electrical conductivity. CNT dispersions are used to manufacture components containing CNTs. The CNT dispersion liquid includes CNTs, a solvent, and a CNT dispersant. A CNT dispersant is disclosed in Patent Document 1. For example, a member containing CNTs can be manufactured by applying a CNT dispersion onto a base material and volatilizing the solvent.

Japanese Patent Application Publication No. 2008-311642

When a CNT-containing member is manufactured using a CNT dispersion, the CNT dispersant remains in the CNT-containing member. It has not been easy to remove CNT dispersants from members containing CNTs. In the technique described in Patent Document 1, it was necessary to heat the member containing CNT in order to remove the CNT dispersant.

One aspect of the present disclosure is to provide a CNT dispersant and a CNT dispersion that can be easily removed from a member containing CNTs.

One aspect of the present disclosure is a CNT dispersant that includes silica particles and a hydrocarbon-bearing amide group bonded to the silica particles. The CNT dispersant, which is one aspect of the present disclosure, can be easily removed from a member containing CNTs.

FIG. 2 is an explanatory diagram showing the structure of a CNT dispersant.

Exemplary embodiments of the present disclosure will be described with reference to the drawings.
1. CNT Dispersant The CNT dispersant includes silica particles. Examples of silica particles include colloidal silica and silsesquioxane. Silsesquioxane is a siloxane-based organic-inorganic hybrid compound having 1.5 oxygen atoms in a unit composition.

The average particle diameter of the silica particles is preferably 0.3 nm or more and 200 nm or less, more preferably 1 nm or more and 200 nm or less. When the average particle diameter of the silica particles is 0.3 nm or more and 200 nm or less, hydrophobic groups are efficiently introduced onto the surface of the silica particles, and the dispersibility of CNTs is improved. When the average particle size of the silica particles is 1 nm or more and 200 nm or less, hydrophobic groups are more efficiently introduced onto the surface of the silica particles, and the dispersibility of CNTs is further improved. The method for measuring the average particle size of silica particles is the small-angle X-ray scattering method.
The CNT dispersant contains an amide group having a hydrocarbon (hereinafter referred to as a hydrocarbon-containing amide group). Hydrocarbon-containing amide groups are attached to the silica particles. For example, a plurality of hydrocarbon-containing amide groups are bonded to one silica particle.

The hydrocarbon contained in the hydrocarbon-containing amide group is preferably a chain hydrocarbon. When the hydrocarbon of the hydrocarbon-containing amide group is a chain hydrocarbon, the CNT dispersant can further disperse the CNTs in the CNT dispersion liquid.

The hydrocarbon contained in the hydrocarbon-containing amide group is preferably a chain saturated hydrocarbon. When the hydrocarbon of the hydrocarbon-containing amide group is a chain saturated hydrocarbon, the CNT dispersant can further disperse the CNTs in the CNT dispersion.

The hydrocarbon-containing amide group is represented by formula (1), for example.

式（１）において、Ｒ１は炭化水素である。Ｒ１は鎖式炭化水素であることが好ましい。Ｒ１が鎖式炭化水素である場合、ＣＮＴ分散剤は、ＣＮＴ分散液においてＣＮＴを一層分散させることができる。

In formula (1), R1 is a hydrocarbon. Preferably R1 is a chain hydrocarbon. When R1 is a chain hydrocarbon, the CNT dispersant can further disperse the CNTs in the CNT dispersion.

Preferably R1 is a chain saturated hydrocarbon. The number of carbon atoms in R1 is preferably 9 or more and 17 or less. When R1 is a chain saturated hydrocarbon, the CNT dispersant can further disperse the CNTs in the CNT dispersion. R2 is hydrogen or hydrocarbon. R3 is a hydrocarbon that binds to the silica particles. Silica particles to which hydrocarbon-containing amide groups are bonded are, for example, hydrophobic.

Preferably, the CNT dispersant further contains an alkylcarboxylic acid. Alkylcarboxylic acids are, for example, by-products when producing silica particles to which hydrocarbon-containing amide groups are bonded. The CNT dispersant is, for example, a mixture containing silica particles to which hydrocarbon-containing amide groups are bonded and an alkylcarboxylic acid. When the CNT dispersant further includes an alkyl carboxylic acid, the CNT dispersant can further disperse the CNTs in the CNT dispersion.

The number of carbon atoms in the alkyl group of the alkyl carboxylic acid is preferably 9 or more and 17 or less. When the number of carbon atoms in the alkyl group of the alkylcarboxylic acid is 9 or more and 17 or less, the CNT dispersant can further disperse CNTs in the CNT dispersion liquid. The alkyl group of the alkylcarboxylic acid is preferably a chain hydrocarbon, more preferably a chain saturated hydrocarbon. When the alkyl group is a chain hydrocarbon, the CNT dispersant can further disperse the CNTs in the CNT dispersion.

Preferably, the CNT dispersant does not contain a surfactant. When the CNT dispersant does not contain a surfactant, the CNT dispersant can be more easily removed from a member containing CNTs. The hydrocarbon-containing amide group preferably does not contain an aromatic ring compound or a halogen. When the hydrocarbon-containing amide group does not contain an aromatic ring compound or a halogen, the CNT dispersant can be more easily removed from the member containing CNTs.

2. Manufacturing method of CNT dispersant Silica particles to which hydrocarbon-containing amide groups are bonded can be manufactured, for example, by the following first manufacturing method.
(First manufacturing method)
First, prepare silica particles. Examples of silica particles include acidic silica sol. Acidic silica sol can be produced, for example, by diluting sodium silicate with hydrochloric acid. Additionally, the silica particles may be commercially available colloidal silica.

Next, the silica particles and the silane coupling agent having an amino group are reacted under acidic conditions. Examples of the silane coupling agent having an amino group include 3-aminopropyltrimethoxysilane (APTMS). As a result, amino groups are introduced into the silica particles.

Next, the silica particles into which amino groups have been introduced are reacted with an acid chloride having an alkyl group. Examples of the acid chloride having an alkyl group include decanoyl chloride, lauroyl chloride, and stearoyl chloride. The number of carbon atoms in the alkyl group is preferably 9 or more and 17 or less. The alkyl group is preferably a chain hydrocarbon, more preferably a chain saturated hydrocarbon.

By reacting the amino group and the acid chloride to form an amide bond, silica particles to which a hydrocarbon-containing amide group is bonded can be obtained. The hydrocarbon-containing amide group contains the hydrocarbon that the acid chloride had and an amide bond. Alkyl carboxylic acids are produced as a by-product of the reaction of amino groups with acid chlorides.

Silica particles to which hydrocarbon-containing amide groups are bonded can also be produced, for example, by the second production method below.
(Second manufacturing method)
Silica particles into which amino groups have been introduced are obtained by polymerizing a silane coupling agent having amino groups. Examples of the silane coupling agent having an amino group include 3-aminopropyltrimethoxysilane (APTMS). Next, the silica particles into which amino groups have been introduced are reacted with an acid chloride having an alkyl group. Examples of the acid chloride having an alkyl group include decanoyl chloride, lauroyl chloride, and stearoyl chloride. The number of carbon atoms in the alkyl group is preferably 9 or more and 17 or less. The alkyl group is preferably a chain hydrocarbon, more preferably a chain saturated hydrocarbon.

By reacting the amino group and the acid chloride to form an amide bond, silica particles to which a hydrocarbon-containing amide group is bonded can be obtained. The hydrocarbon-containing amide group contains the hydrocarbon that the acid chloride had and an amide bond. Alkyl carboxylic acids are produced as a by-product of the reaction of amino groups with acid chlorides.

3. CNT Dispersion Liquid The CNT dispersion liquid contains a CNT dispersant, CNTs, and an organic solvent. The CNT dispersant is the one described in the section "1. CNT dispersant" above. Examples of CNTs include single-walled carbon nanotubes (SWCNTs). Examples of the organic solvent include 2-propanol (IPA), 2-butanone (MEK), tetrahydrofuran (THF), chloroform, toluene, and cyclohexane.

The concentration of CNT in the CNT dispersion is preferably 0.01% by mass or more, more preferably 0.05% by mass or more. Preferably, the CNT dispersion does not contain a surfactant.
4. Examples (4-1) Materials and reagents used in Examples The materials and reagents used in Examples are as follows.
・No. 3 sodium silicate (SiO ₂ :29.03%, NaO ₂ :9.29%, molar ratio: 3.12)
・3-aminopropyltrimethoxysilane (APTMS) (reagent manufactured by Shin-Etsu Chemical Co., Ltd.)
・36% hydrochloric acid (Fuji Film Wako Pure Chemical Industries reagent)
・N,N-dimethylformamide (DMF) (Fuji Film Wako Pure Chemicals reagent)
・Triethylamine (Et ₃ N) (Fuji Film Wako Pure Chemical Industries reagent)
・Decanoyl chloride (reagent manufactured by Tokyo Kasei Kogyo Co., Ltd.)
・Lauroyl chloride (reagent manufactured by Tokyo Kasei Kogyo Co., Ltd.)
・Stearoyl chloride (reagent manufactured by Tokyo Kasei Kogyo Co., Ltd.)
・Chloroform (Reagent manufactured by Fuji Film Wako Pure Chemical Industries)
・Toluene (Fuji Film Wako Pure Chemicals reagent)
・Acetone (Fuji Film Wako Pure Chemical Industries reagent)
・Lauric acid (Fuji Film Wako Pure Chemical Industries reagent)
・2-Propanol (IPA) (Fuji Film Wako Pure Chemicals reagent)
・Cyclohexane (Fuji Film Wako Pure Chemical Industries reagent)
・2-Butanone (MEK) (Fuji Film Wako Pure Chemicals reagent)
・Tetrahydrofuran (THF) (Fuji Film Wako Pure Chemicals reagent)
・Chloroform (Reagent manufactured by Fuji Film Wako Pure Chemical Industries)
・Single-walled carbon nanotubes (SWCNT)
・Colloidal silica (ST-OXS) (Reagent manufactured by Nissan Chemical Industries, Ltd., SiO ₂ :10%, particle size: 5nm)
・Colloidal silica (ST-OS) (Reagent manufactured by Nissan Chemical Industries, Ltd., SiO ₂ :20%, particle size: 10nm)
・Colloidal silica (ST-OL) (Reagent manufactured by Nissan Chemical Industries, Ltd., SiO ₂ : 20%, particle size: 40-50 nm)
(4-2) Production of CNT dispersant A2 An aqueous solution of No. 3 sodium silicate was added dropwise to an aqueous hydrochloric acid solution that was being stirred under ice cooling. The volume of the hydrochloric acid aqueous solution was 10 mL. The concentration of hydrochloric acid in the aqueous hydrochloric acid solution was 3 mol/L. The aqueous solution of No. 3 sodium silicate was an aqueous solution in which 5.0 g of No. 3 sodium silicate was diluted with 12 mL of pure water.

Next, the mixture was stirred at room temperature for 15 minutes to obtain a colorless and transparent aqueous solution. Next, APTMS diluted with an aqueous hydrochloric acid solution was added and stirred for 1 hour. The amount of APTMS was 4.51 g. The concentration of the aqueous hydrochloric acid solution used for dilution was 1 mol/L, and the volume of the aqueous hydrochloric acid solution used for dilution was 36 mL.

The solvent was then evaporated by heating in an open system at a temperature of 60° C. overnight. As a result, silica particles A1 into which ammonium groups were introduced were obtained.
Next, 1.0 g of A1 was dissolved in 100 mL of 80° C. pure water. Next, the solvent was replaced with 10 mL of DMF. Next, 15 mmol of Et ₃ N was added to the solution. The mass of 15 mmol of Et ₃ N is 1.52 g.

Next, a DMF solution of lauroyl chloride was added. The DMF solution of lauroyl chloride was 10 mmol of lauroyl chloride dissolved in 2 mL of DMF.
Next, the mixture was stirred at room temperature for 10 minutes. Next, 30 mL of an aqueous hydrochloric acid solution having a concentration of 1 mol/L was added and stirred for 30 minutes. As a result, a white viscous substance was precipitated.

Next, the white viscous material was washed with pure water, centrifuged, and the supernatant removed three times. Next, 2.4 g of a white powdery product was obtained by vacuum drying overnight.
Next, the white powdery product was dissolved in 100 to 200 mL of MEK, and the soluble portion was extracted and cooled to precipitate a white crystalline product. Next, 1.5 g of CNT dispersant A2 was obtained by vacuum drying the white crystalline product overnight.

CNT dispersant A2 contains silica particles to which hydrocarbon-containing amide groups are bonded and lauric acid. Silica particles to which hydrocarbon-containing amide groups are bonded have a structure in which hydrocarbon-containing amide groups 3 are bonded to silica particles 1, as shown in FIG. Among the hydrocarbon-containing amide groups 3, the hydrocarbon corresponding to R1 in formula (1) is a chain saturated hydrocarbon and has 11 carbon atoms.

(4-3) Production of CNT dispersant B2 15.0 g of colloidal silica ST-OXS was stirred at room temperature for 15 minutes. Next, APTMS diluted with hydrochloric acid was added to the colloidal silica ST-OXS while stirring, and the mixture was stirred for 1 hour. The amount of APTMS was 4.67g. The concentration of the aqueous hydrochloric acid solution used for dilution was 1 mol/L, and the volume of the aqueous hydrochloric acid solution used for dilution was 36 mL.

The solvent was then evaporated by heating in an open system at a temperature of 60° C. for 5 hours. As a result, silica particles B1 into which ammonium groups were introduced were obtained. The yield of B1 was 6.0 g.

Next, 1.0 g of B1 was dissolved in 100 mL of 80° C. pure water. Next, the solvent was replaced with 10 mL of DMF. Next, 15 mmol of Et ₃ N was added to the solution. The mass of 15 mmol of Et ₃ N is 1.52 g.

Next, a DMF solution of lauroyl chloride was added. The DMF solution of lauroyl chloride was 10 mmol of lauroyl chloride dissolved in 2 mL of DMF.
Next, the mixture was stirred at room temperature for 10 minutes. Next, 30 mL of an aqueous hydrochloric acid solution having a concentration of 1 mol/L was added and stirred for 30 minutes. As a result, a white viscous substance was precipitated.

Next, the white viscous material was washed with pure water, centrifuged, and the supernatant removed three times. Next, about 2.5 g of CNT dispersant B2 was obtained by vacuum drying overnight. CNT dispersant B2 basically has the same structure as CNT dispersant A2. However, in CNT dispersant B2, silica particles 1 are colloidal silica.

Note that even if 7.5 g of colloidal silica ST-OS is used instead of 15.0 g of colloidal silica ST-OXS, a CNT dispersant similar to CNT dispersant B2 can be obtained. Further, even if 7.5 g of colloidal silica ST-OL is used instead of 15.0 g of colloidal silica ST-OXS, a CNT dispersant similar to CNT dispersant B2 can be obtained.

(4-4) Production of CNT dispersant C2 90 mL of an aqueous hydrochloric acid solution with a concentration of 0.5 mol/L was added to 5.6 g of APTMS, and the mixture was stirred at room temperature for 2 hours. 5.6 g of APTMS is 30 mmol. The amount of hydrochloric acid contained in 90 mL of an aqueous solution of hydrochloric acid having a concentration of 0.5 mol/L is 45 mmol.

The solvent was then evaporated by heating in an open system at a temperature of 90° C. for 3.5 hours. As a result, a colorless and transparent film-like product was obtained. Next, the colorless and transparent film-like product was washed with acetone and separated by suction filtration three times. Next, the residue was vacuum dried overnight to obtain 4.7 g of C1. C1 is an ammonium group-containing ladder type polysilsesquioxane. C1 was hydrophilic.

Next, 2.9 g of C1 was dissolved in 150 mL of pure water at 80°C. Next, the solvent was replaced with 10 mL of DMF. Next, 50 mmol of Et ₃ N was added to the solution. The mass of 50 mmol of Et ₃ N is 5.06 g.

Next, a DMF solution of lauroyl chloride was added. The DMF solution of lauroyl chloride was 30 mmol of lauroyl chloride dissolved in 2 mL of DMF.
Next, the mixture was stirred at room temperature for 10 minutes. Next, 100 mL of an aqueous hydrochloric acid solution having a concentration of 1 mol/L was added and stirred for 30 minutes. As a result, a white viscous substance was precipitated.

Next, the operation of washing the white viscous material with pure water and centrifuging it was repeated three times. Next, the white viscous material was washed with acetone and centrifuged, which was repeated three times.
Next, the residue was dissolved in 100 to 200 mL of toluene, and the soluble portion was extracted and cooled to precipitate a white crystalline product. Next, the white crystalline product was vacuum dried overnight to obtain 4.3 g of CNT dispersant C2. CNT dispersant C2 basically has the same structure as CNT dispersant A2. However, in CNT dispersant C2, silica particles 1 are polysilsesquioxane.

(4-5) Production of CNT dispersant D2 The method for producing CNT dispersant D2 is basically the same as the method for producing CNT dispersant A2. However, the difference is that the method for producing CNT dispersant A2 uses lauroyl chloride, whereas the method for producing CNT dispersant D2 uses decanoyl chloride.

Further, in the manufacturing method of CNT dispersant A2, MEK was used as an extraction solvent after water washing, whereas in the manufacturing method of CNT dispersant D2, THF is used.
CNT dispersant D2 basically has the same structure as CNT dispersant A2. However, in the CNT dispersant D2, the number of carbon atoms in the hydrocarbon corresponding to R1 in formula (1) is 9 . Further, the alkylcarboxylic acid contained in the CNT dispersant D2 is decanoic acid.

(4-6) Production of CNT dispersant E2 The method for producing CNT dispersant E2 is basically the same as the method for producing CNT dispersant A2. However, the difference is that the method for producing CNT dispersant A2 uses lauroyl chloride, whereas the method for producing CNT dispersant E2 uses stearoyl chloride.

Further, in the manufacturing method of CNT dispersant A2, MEK was used as an extraction solvent after water washing, whereas in the manufacturing method of CNT dispersant E2, toluene was used.
CNT dispersant E2 basically has the same structure as CNT dispersant A2. However, in the CNT dispersant E2, the hydrocarbon corresponding to R1 in formula (1) has 17 carbon atoms. Further, the alkylcarboxylic acid contained in the CNT dispersant E2 is stearic acid.

(4-7) CNT dispersibility evaluation test The CNT dispersibility of each of the CNT dispersants A2 to E2 and the dispersant R1 of the comparative example was evaluated by the following method. Dispersant R1 consists only of lauric acid.

Into a 10 mL glass sample container, first the CNT dispersant was charged, then 10 mL of the organic solvent, and finally the SWCNTs. As a result, a CNT dispersion was obtained. The concentration of the CNT dispersant in the CNT dispersion was 1% by mass. The type of organic solvent was selected from IPA, MEK, THF, chloroform, toluene, and cyclohexane. The concentration of SWCNT in the CNT dispersion was varied in the range of 0.01 to 0.05% by mass.

Next, the CNT dispersion liquid was subjected to a dispersion treatment for 15 minutes using an ultrasonic homogenizer (manufactured by Ieda Boeki Co., Ltd., VCX-500). The output of the ultrasonic homogenizer was 100W. During the dispersion process, 1 second on and 1 second off were alternately repeated. On means that the ultrasonic homogenizer is operating. Off is a state in which the ultrasonic homogenizer is stopped.

Next, the dispersion state of SWCNTs in the CNT dispersion liquid was visually confirmed to confirm the presence or absence of SWCNT aggregates. The evaluation results are shown in Table 1.

評価基準は以下のとおりである。

The evaluation criteria are as follows.

◎: There were no aggregates when the SWCNT concentration was 0.05% by mass.
○: There were no aggregates when the SWCNT concentration was 0.01% by mass, and there were aggregates when the SWCNT concentration was 0.05% by mass.

x: Aggregates were present when the SWCNT concentration was 0.01% by mass.
By using CNT dispersants A2 to E2 in combination with any of the organic solvents, it was possible to produce a CNT dispersion in which aggregates are less likely to occur.

(4-8) Evaluation of dispersant removability The dispersant removability of each of the CNT dispersants A2 to E2 and the comparative dispersant R2 was evaluated in the following manner. Dispersant R2 was polyvinylpyrrolidone (PVP).

A CNT dispersion containing a dispersion solvent, a dispersant, and SWCNT was prepared. The types of dispersion solvents were as shown in Table 2.

ＣＮＴ分散液における分散剤の濃度は１質量％とした。ＣＮＴ分散液におけるＳＷＣＮＴの濃度は０．０５質量％とした。

The concentration of the dispersant in the CNT dispersion was 1% by mass. The concentration of SWCNT in the CNT dispersion was 0.05% by mass.

Next, the CNT dispersion liquid was applied to the surface of the base material using a bar coat and air-dried to form a CNT film. A #6 wire bar was used in the bar coat. The material of the base material was polyethylene terephthalate (PET). The CNT film corresponds to a member containing CNT. The morphology of the CNT film was a thin film.

Next, the surface resistance value of the CNT film was measured using a 4-terminal resistance meter (Loresta GP MCP-T610, manufactured by Mitsubishi Chemical Analytech). The measured value at this time will hereinafter be referred to as the measured value before cleaning.

Next, the CNT film was washed. The cleaning method was to immerse the CNT film in a cleaning solution for 10 minutes. The washing liquid is shown in Table 2 above. The washing liquid was the same as the dispersion solvent contained in the CNT dispersion.

Next, the CNT film was removed from the cleaning solution and air-dried. Next, the surface resistance value of the CNT film was measured using the same measuring method as before cleaning. The measured value at this time is hereinafter referred to as the measured value after cleaning. The measured values before washing and after washing are shown in Table 2 above.

When CNT dispersants A2 to E2 were used, the measured values after washing were significantly lower than the measured values before washing. This indicates that CNT dispersants A2-E2 can be easily removed from the CNT film.

5. Effects of CNT dispersant and CNT dispersion liquid (1A) A member containing CNTs can be manufactured using the CNT dispersion liquid of the present disclosure. The CNT dispersant of the present disclosure can be easily removed from a member containing CNTs.

(1B) The CNT dispersion of the present disclosure does not easily form CNT aggregates. By using the CNT dispersant of the present disclosure and an organic solvent together, it is possible to produce a CNT dispersion liquid in which CNT aggregates are less likely to occur.

6. Other Embodiments Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented with various modifications.

(1) The function of one component in each of the above embodiments may be shared among multiple components, or the function of multiple components may be performed by one component. Further, a part of the configuration of each of the above embodiments may be omitted. Further, at least a part of the configuration of each of the above embodiments may be added to, replaced with, etc. in the configuration of other embodiments.

(2) In addition to the above-mentioned CNT dispersant, the present disclosure can also be realized in various forms, such as a product containing the CNT dispersant as a component, a method for producing a CNT dispersant, and the like.

1...Silica particles, 3...Hydrocarbon-containing amide group

Claims (5)

silica particles or silsesquioxane ;
an amide group having a hydrocarbon bonded to the silica particles or the silsesquioxane ;
including;
The amide group having a hydrocarbon is represented by the following formula (1),
R1 is a chain saturated hydrocarbon having 9 or more and 17 or less carbon atoms,
R2 is hydrogen or hydrocarbon;
R3 is a CNT dispersant that is a hydrocarbon bonded to the silica particles or the silsesquioxane.

The CNT dispersant according to claim 1,
A CNT dispersant further comprising an alkyl carboxylic acid. The CNT dispersant according to claim 2,
The CNT dispersant wherein the alkyl group of the alkyl carboxylic acid has 9 or more and 17 or less carbon atoms. The CNT dispersant according to any one of claims 1 to 3,
The silica particles are a CNT dispersant that is colloidal silica. A CNT dispersion liquid comprising the CNT dispersant according to any one of claims 1 to 4 , CNTs, and an organic solvent.

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