WO2023112472A1

WO2023112472A1 - Aqueous carbon black dispersion for electroconductive coating materials, and method for producing aqueous carbon black dispersion for electroconductive coating materials

Info

Publication number: WO2023112472A1
Application number: PCT/JP2022/039047
Authority: WO
Inventors: 義幸杉山; 大志桐山
Original assignee: 東海カーボン株式会社
Priority date: 2021-12-14
Filing date: 2022-10-20
Publication date: 2023-06-22
Also published as: TW202327996A

Abstract

The purpose of the present invention is to provide an aqueous carbon black dispersion for electroconductive coating materials, which makes it possible to form a coating film having an excellent blackness degree and excellent electroconductivity in a simple manner and at low cost.　Provided is an aqueous carbon black dispersion for electroconductive coating materials, which is characterized by containing a neutralization product of oxidized carbon black with sodium hydroxide that has at least one negative ion functional group on a surface having a nitrogen adsorption specific surface area N₂SA of 80 to 250 m²/g, a DBP oil absorption amount of 140 to 200 ml/100 g and an acidic hydroxyl group amount of 300 to 1200 μmol/g, in which the average particle diameter of the oxidized carbon black is preferably 100 to 300 nm.

Description

Aqueous Carbon Black Dispersion for Conductive Paint and Method for Producing Aqueous Carbon Black Dispersion for Conductive Paint

The present invention relates to a carbon black aqueous dispersion for conductive paint and a method for producing the carbon black aqueous dispersion for conductive paint.

In general, as a composite material for electric and electronic parts using a base material such as a metal substrate, a composite material is known in which conductivity is imparted by plating the surface of the metal substrate with gold or applying silver paste. For example, a gold-plated contact portion of a support metal plate of a semiconductor has been proposed (see Patent Document 1).

However, since the composite material is plated with gold, the manufacturing cost increases, making it difficult to use as a general-purpose product.
For this reason, there has been a demand for a conductive film that can be manufactured at low cost, is resistant to surface deterioration, and exhibits excellent conductivity.

In general, resin moldings are excellent in mechanical properties such as moldability, chemical resistance, tensile strength and bending strength, as well as abrasion resistance. It is used in a wide range of fields such as automobile parts.
However, in recent years, mainly in electrical/electronic parts and automobile parts, the use of electrically insulating resins in applications that require antistatic measures, applications that require electromagnetic wave shielding, and electrostatic coating applications centered on automobile exterior materials. There has been a demand for a conductive film (antistatic film) that can be easily formed on the surface of a molded product at low cost.

JP-A-2000-077477

As a material for forming the conductive film and antistatic film, the conductive film and antistatic film obtained are excellent in conductivity, and the presence or absence of film formation during film formation and the presence or absence of peeling of the film after film formation can be easily determined. Something visible is required.
In addition, as the material for forming the conductive film and the antistatic film, an aqueous dispersion using a water solvent is used, which is capable of reducing environmental load, suppressing odor, etc. during film formation, and improving workability. is desired.

In order to solve the above technical problems, the inventors of the present invention conducted intensive studies and found that an aqueous dispersion of oxidized carbon black having a high degree of blackness and excellent conductivity was applied to the surface of a substrate such as a metal substrate or a resin substrate. The inventors came up with the idea of forming a conductive film or an antistatic film by coating.
That is, an aqueous dispersion containing oxidized carbon black having a high degree of blackness, excellent conductivity, and excellent affinity for water solvents is prepared, and this is applied to a metal base material, a resin base material, etc. in the presence of a resin binder. The inventors came up with the idea of forming a conductive film or an antistatic film having excellent blackness and conductivity by coating the substrate surface to form a film.

However, conventionally, when an attempt is made to obtain a coating film excellent in blackness by using an oxidized carbon black aqueous dispersion, oxidized carbon black easily forms a smooth and dense coating film to reflect light, It has been believed that a DBP (dibutyl phthalate) with low oil absorption (low structure), which is easy to suppress scattering, is required.
On the other hand, when attempting to obtain a coating film of an oxidized carbon black aqueous dispersion with excellent conductivity, the oxidized carbon black has a large nitrogen adsorption specific surface area (N ₂ SA) (small primary particle size) and DBP (Dibutyl phthalate) High oil absorption (high structure) is required.
Thus, in oxidized carbon black, there is a trade-off relationship between blackness and conductivity, and it has been difficult to provide a carbon black aqueous dispersion for conductive paints that satisfies both of them.

Therefore, the present invention provides an aqueous carbon black dispersion for conductive paints that can easily and at low cost form a coating film excellent in blackness and conductivity, and a method for producing an aqueous carbon black dispersion for conductive paints. It is intended to

In order to solve the above technical problems, the inventors of the present invention conducted extensive studies and found that the nitrogen adsorption specific surface area N ₂ SA is 80 to 250 m ² /g, the DBP oil absorption is 140 to 200 ml/100 g, and the amount of acidic hydroxyl The above technical problems can be solved by an aqueous carbon black dispersion for conductive paint containing 300 to 1200 μmol/g of sodium hydroxide neutralized product of oxidized carbon black having one or more anionic functional groups on its surface. and completed the present invention based on this finding.

That is, the present invention
(1) having a nitrogen adsorption specific surface area N ₂ SA of 80 to 250 m ² /g, a DBP oil absorption of 140 to 200 ml/100 g, and an acidic hydroxyl group amount of 300 to 1200 μmol/g, and having one or more anionic functional groups on the surface; An aqueous carbon black dispersion for a conductive paint, characterized by containing a sodium hydroxide neutralized product of oxidized carbon black,
(2) The carbon black aqueous dispersion for conductive paint according to (1) above, wherein the oxidized carbon black has an average particle size of 100 to 300 nm.
(3) having a nitrogen adsorption specific surface area N ₂ SA of 80 to 250 m ² /g, a DBP oil absorption of 140 to 200 ml/100 g, and an acidic hydroxyl group amount of 300 to 1200 μmol/g, and having one or more anionic functional groups on the surface; For an aqueous slurry containing oxidized carbon black,
A method for producing a carbon black aqueous dispersion for a conductive paint, characterized by mixing sodium hydroxide and heating and neutralizing it,
(4) The method for producing a carbon black aqueous dispersion for conductive paint according to (3) above, wherein the oxidized carbon black has an average particle size of 100 to 300 nm.
(5) Production of carbon black aqueous dispersion for conductive paint according to (3) or (4) above, wherein the aqueous slurry containing the oxidized carbon black is mixed with the sodium hydroxide so as to have a pH of 6 to 12. Method,
It provides

According to the present invention, it is possible to provide an aqueous carbon black dispersion for conductive paints that can easily and at low cost form a coating film having excellent blackness and conductivity, and to provide an aqueous carbon black dispersion for conductive paints. A method of manufacturing a body can be provided.

<Carbon black aqueous dispersion for conductive paint>
First, the carbon black aqueous dispersion for conductive paint according to the present invention will be described.
The carbon black aqueous dispersion for conductive paint according to the present invention has a nitrogen adsorption specific surface area N ₂ SA of 80 to 250 m ² /g, a DBP oil absorption of 140 to 200 ml/100 g, and an acidic hydroxyl group amount of 300 to 1200 μmol/g. It is characterized by containing a sodium hydroxide neutralized product of oxidized carbon black having one or more anionic functional groups on its surface.

The oxidized carbon black contained in the carbon black aqueous dispersion for conductive paint according to the present invention has a nitrogen adsorption specific surface area N ₂ SA that improves the conductivity of the resulting coating film and suppresses the occurrence of coating film unevenness. , 80 to 250 m ² /g, preferably 80 to 240 m ² /g from the viewpoint of suppressing viscosity increase during preparation of the aqueous dispersion, and achieving both good conductivity and suppression of viscosity increase. 80 to 230 m ² /g is more preferable from the viewpoint of

In the aqueous dispersion of carbon black for conductive paint according to the present invention, the nitrogen adsorption specific surface area N ₂ SA of the oxidized carbon black contained in the aqueous dispersion is a high value within the above range. In the film, it is possible to easily exhibit good conductivity and to easily suppress the generation of coating film unevenness.

The nitrogen adsorption specific surface area N ₂ SA of the oxidized carbon black contained in the carbon black aqueous dispersion for conductive paint was measured using a fully automatic surface area measuring device (Gemini 2375 manufactured by Shimadzu Corporation), and according to JIS K 6217-2. "Carbon black for rubber - basic properties - Part 2, method for determining specific surface area - nitrogen adsorption method, single point method".

The oxidized carbon black contained in the aqueous dispersion of carbon black for conductive paint according to the present invention has a DBP (Dibutylphthalate) oil absorption that develops the structure structure of the oxidized carbon black, and the resulting coating film has excellent conductivity. From the viewpoint of easily exerting, it is 140 to 200 ml / 100 g, and from the viewpoint of suppressing the viscosity increase during preparation of the aqueous dispersion, it is preferable that it is 140 to 190 ml / 100 g. From the viewpoint of achieving both suppression, the content of 150 to 190 ml/100 g is more preferable.

In the aqueous dispersion of carbon black for conductive paint according to the present invention, the DBP oil absorption of the oxidized carbon black contained in the aqueous dispersion is a high value within the above range, so that the resulting coating film has a conductive You can easily improve the quality.

In addition, the DBP oil absorption of oxidized carbon black contained in the carbon black aqueous dispersion for conductive paint is defined in JIS K 6217-4 "Carbon black for rubber - basic properties - Part 4, Determination of DBP absorption means the value measured in accordance with

The oxidized carbon black contained in the carbon black aqueous dispersion for a conductive paint according to the present invention has an average particle size from the viewpoint of suppressing the occurrence of coating unevenness in the coating film obtained while exhibiting good dispersibility. It is preferably 100 to 300 nm, more preferably 100 to 250 nm from the viewpoint of improving dispersibility, and 100 to 200 nm from the viewpoint of suppressing the formation of unevenness in the coating film obtained with good dispersion performance. is more preferable.

In the carbon black aqueous dispersion for a conductive paint according to the present invention, the average particle size of the oxidized carbon black contained in the aqueous dispersion is within the above range, so that the coating can exhibit good dispersibility and can be obtained. It is possible to easily suppress the occurrence of coating film unevenness in the film.

The average particle size of the oxidized carbon black contained in the carbon black aqueous dispersion for conductive paint is the particle size of 50% of the cumulative particle size in the volume-based cumulative particle size distribution measured by a laser diffraction particle size distribution measuring device ( volume average particle diameter D50).

Oxidized carbon black that satisfies the above nitrogen adsorption specific surface area N ₂ SA, DBP oil absorption or average particle size can be easily prepared using, for example, furnace black as a raw material as described later. For example, the obtained oxidized carbon black can be used to easily and inexpensively prepare an aqueous carbon black dispersion for a conductive paint.

The amount of acidic hydroxyl groups of the oxidized carbon black contained in the carbon black aqueous dispersion for conductive paints according to the present invention is from 300 μmol/g to 300 μmol/g from the viewpoint of exhibiting sufficient affinity for aqueous media and obtaining excellent dispersibility. It is 1200 μmol/g, preferably 400 μmol/g to 1200 μmol/g from the viewpoint of obtaining uniform dispersibility, and more preferably 500 μmol/g to 1200 μmol/g to obtain particularly uniform dispersibility. .
The amount of acidic hydroxyl groups in the oxidized carbon black contained in the carbon black aqueous dispersion for conductive paint according to the present invention means the sum of the carboxyl group (—COO ⁻ ) amount and the hydroxyl group (—O ⁻ ) amount in the oxidized carbon black. do. Considering the dispersibility of oxidized carbon black in an aqueous medium, etc., acidic hydroxyl groups are important as functional groups on the surface of carbon black particles. The amount of acidic hydroxyl groups in the particles can be substantially regarded as the sum of the amount of carboxyl groups and the amount of hydroxyl groups.

The amount of acidic hydroxyl groups in oxidized carbon black means a value measured by the following method.
(Sample preparation: acid washing and standard solution addition)
The resulting aqueous dispersion of oxidized carbon black was dried at 110° C., pulverized with a mortar or the like, and 1.0 g of the powder was collected in a centrifuge tube. After shaking, solid-liquid separation is performed using a centrifuge. After performing this operation four times in total, the solid matter is transferred to a 100 ml beaker and dried at 110°C. The solid after drying was pulverized in a mortar, 1.0 g of oxidized carbon black was collected in an Erlenmeyer flask, 25 ml of 0.1 mol/l NaOH was added to the Erlenmeyer flask, and then the Erlenmeyer flask was shaken for 4 hours using a shaker. Shake. The shaken liquid is transferred to a centrifuge tube, and the supernatant liquid is collected as a measurement sample.
(Measurement procedure: titration method and acid value calculation method)
The acid value is measured by potentiometric titration using an automatic titrator (manufactured by Metrohm, 809 Titrando). Before the measurement of the sample obtained above, 25 ml of 0.1 mol/l NaOH was titrated with 0.1 mol/l HCl as a blank. Titrate with 1 mol/l HCl, and measure the dropwise amount of HCl required for neutralization. Substitute the obtained measured value into the following formula to obtain the acid value. The meanings of the symbols in the formula are shown below.
V _Blank [ml]: Drop amount required for neutralization when 25 ml of 0.1 mol/l NaOH was titrated with 0.1 mol/l HCl V _Sample [ml]: Titration of 25 ml of a measurement sample with 0.1 mol/l HCl Dropping amount required for neutralization N _HCl [mol/l]: concentration of HCl standard solution M _sample [g]: weight of oxidized carbon black in measurement sample Acid value [mmol/g]=(V _Blank − V _sample )×N _HCl /M _sample

In the carbon black aqueous dispersion for conductive paint according to the present invention, the amount of —SO ₃ H groups and —PO ₄ H ₂ groups of oxidized carbon black is not particularly limited.

In the carbon black aqueous dispersion for conductive paint according to the present invention, oxidized carbon black having one or more anionic functional groups on its surface is used as a sodium hydroxide neutralized product (in a state of being neutralized with sodium hydroxide). Dispersed in an aqueous medium.

As described above, conventionally, when an attempt is made to obtain a coating film of an oxidized carbon black dispersion having excellent blackness, the oxidized carbon black has a low DBP (dibutyl phthalate) oil absorption (low structure). and potassium hydroxide has been used as a neutralizing agent for oxidized carbon black in its aqueous dispersions.
This is because when an oxidized carbon black with a low DBP oil absorption (low structure) is used, it is easy to form a smooth and dense coating film, so it is easy to suppress the reflection and scattering of light. It is considered that when potassium hydroxide having a large ionic radius is used as the additive, a large number of voids are formed in the dense film, thereby improving light absorption.

On the other hand, as described above, when oxidized carbon black having a high DBP oil absorption of 140 to 200 ml/100 g (high structure) is used, the resulting coating film can exhibit the desired degree of blackness. First, it was considered that the use of a high DBP oil absorption of 140 to 200 ml/100 g tends to form projections on the surface of the resulting coating film, which tends to cause reflection and scattering of light.
Further, according to the studies of the present inventors, when oxidized carbon black having a high DBP oil absorption of 140 to 200 ml/100 g (high structure) is used, water is used as a neutralizing agent in the aqueous dispersion. It was found that even if potassium oxide is used, the reflection of light increases and the degree of blackness decreases.

Under such circumstances, the inventors of the present invention made further studies, and unexpectedly, even when oxidized carbon black having a high DBP oil absorption of 140 to 200 ml/100 g (high structure) was used, have found that when sodium hydroxide is used as a neutralizing agent in the aqueous dispersion, the desired blackness can be achieved in the resulting coating film.
The reason for this is not necessarily clear, but it is believed that when sodium hydroxide is used as the neutralizing agent, the convex portions on the surface of the resulting coating film are smoothed, making it easier to suppress reflection and scattering of light.

In the aqueous carbon black dispersion for conductive paint according to the present invention, examples of the aqueous solvent for dispersing oxidized carbon black include water and water-soluble organic solvents. Deionized water is preferred.

In the carbon black aqueous dispersion for conductive paint according to the present invention, the concentration of oxidized carbon black is 1 because it can easily exhibit suitable blackness and electrical conductivity when used in water-based paints and the like. It is preferably 0% by mass or more, and preferably 20.0% by mass or less from the viewpoint that suitable dispersibility can be easily exhibited when used in a water-based paint or the like, and 1.0 to It is more preferably 15.0% by mass, and even more preferably 1.0 to 10.0% by mass.

The carbon black aqueous dispersion for conductive paint according to the present invention can be suitably produced by the method for producing an aqueous carbon black dispersion for conductive paint described below.

When forming a conductive film or an antistatic film using the carbon black aqueous dispersion for conductive paint according to the present invention, for the carbon black aqueous dispersion for conductive paint according to the present invention, as a water-soluble resin, for example, After appropriately adding one or more selected from acrylic resins, polyester resins, epoxy resins, polyurethane resins, etc., an aqueous solvent is added as appropriate to prepare a conductive paint in which the concentration of oxidized carbon black is controlled to a desired concentration. What is necessary is just to apply|coat to an application target object.
Examples of the object to be coated with the above-described conductive paint include objects made of various metal materials (metal substrates) and objects made of various resins (resin substrates).

According to the present invention, it is possible to provide an aqueous carbon black dispersion for a conductive paint that can easily form a coating film with excellent blackness and conductivity at low cost.

<Method for producing carbon black aqueous dispersion for conductive paint>
Next, a method for producing an aqueous carbon black dispersion for conductive paint according to the present invention will be described.
The method for producing a carbon black aqueous dispersion for conductive paint according to the present invention has a nitrogen adsorption specific surface area N ₂ SA of 80 to 250 m ² /g, a DBP oil absorption of 140 to 200 ml/100 g, and an acidic hydroxyl group content of 300 to 1200 μmol. /g for an aqueous slurry containing oxidized carbon black having one or more anionic functional groups on its surface,
It is characterized by mixing sodium hydroxide and heating and neutralizing it.

In the method for producing an aqueous carbon black dispersion for conductive paint according to the present invention, the aqueous slurry of oxidized carbon black has a nitrogen adsorption specific surface area N ₂ SA of 80 to 250 m ² /g and a DBP oil absorption of 140 to 200 ml/g. 100 g of an aqueous slurry containing oxidized carbon black having one or more anionic functional groups on its surface with an acid hydroxyl content of 300-1200 μmol/g is used.

In the method for producing a carbon black aqueous dispersion for a conductive paint according to the present invention, the oxidized carbon black contained in the aqueous slurry has a nitrogen adsorption specific surface area N ₂ SA that improves the conductivity of the resulting coating film and causes unevenness in the coating film. is from 80 to 250 m ² ^/ g from the viewpoint of suppressing the occurrence of . From the viewpoint of simultaneously suppressing an increase in viscosity, one having a density of 80 to 230 m ² /g is more preferable.

In the method for producing an aqueous dispersion of carbon black for conductive paint according to the present invention, the nitrogen adsorption specific surface area N ₂ SA of the oxidized carbon black contained in the aqueous slurry is a high value within the above range. In the coating film, it is possible to easily exhibit good conductivity and to easily suppress the generation of unevenness in the coating film.

The nitrogen adsorption specific surface area N ₂ SA of the oxidized carbon black contained in the aqueous slurry was measured using a fully automatic surface area measuring device (Gemini 2375 manufactured by Shimadzu Corporation), and measured according to JIS K 6217-2 "Rubber Carbon black for commercial use-Basic properties-Part 2, Determination of specific surface area-Nitrogen adsorption method, single point method”.

In the method for producing an aqueous dispersion of carbon black for conductive paint according to the present invention, the oxidized carbon black contained in the aqueous slurry is obtained by increasing the DBP (Dibutylphthalate) oil absorption to develop the structure structure of the oxidized carbon black. It is preferably 140 to 200 ml/100 g from the viewpoint of easily exhibiting excellent conductivity in the coating film, and preferably 140 to 190 ml/100 g from the viewpoint of suppressing viscosity increase during preparation of the aqueous dispersion. From the viewpoint of achieving both the conductivity and suppression of viscosity increase, the amount of 150 to 190 ml/100 g is more preferable.

In the method for producing a carbon black aqueous dispersion for conductive paint according to the present invention, the DBP oil absorption of oxidized carbon black contained in the aqueous slurry is a high value within the above range, so that the resulting coating film, Conductivity can be easily improved.

The DBP oil absorption of the oxidized carbon black contained in the aqueous slurry is a value measured in accordance with JIS K 6217-4 "Carbon black for rubber - Basic properties - Part 4, How to determine the DBP absorption". means

In the method for producing an aqueous dispersion of carbon black for conductive coatings according to the present invention, the oxidized carbon black contained in the aqueous slurry has an average particle size that exhibits good dispersibility and the coating of the resulting coating film. It is preferably 100 to 300 nm from the viewpoint of suppressing the occurrence of film unevenness, and more preferably 100 to 250 nm from the viewpoint of improving dispersibility, and has good dispersion performance and coating film unevenness of the obtained coating film. From the viewpoint of suppressing the generation, one having a thickness of 100 to 200 nm is more preferable.

In the method for producing a carbon black aqueous dispersion for conductive paint according to the present invention, the average particle size of the oxidized carbon black contained in the aqueous slurry is within the above range, so that good dispersibility can be exhibited and obtained. It is possible to easily suppress the occurrence of coating film unevenness in the coating film obtained.

The average particle size of the oxidized carbon black contained in the aqueous slurry is measured by a laser diffraction particle size distribution measuring device (UPA150 manufactured by Microtrac Bell), and the cumulative particle size in the volume-based cumulative particle size distribution is 50%. Means particle size (volume average particle size D50).

In the method for producing an aqueous dispersion of carbon black for conductive paint according to the present invention, the nitrogen adsorption specific surface area N ₂ SA, the DBP oil absorption, and the average particle size of the oxidized carbon black contained in the aqueous slurry are each within the above ranges. As a result, the oxidized carbon black obtained after the neutralization step described below easily has similar nitrogen adsorption specific surface area N ₂ SA, DBP oil absorption and average particle size.

In the method for producing an aqueous dispersion of carbon black for conductive paint according to the present invention, the amount of acidic hydroxyl groups in the oxidized carbon black contained in the aqueous slurry exhibits sufficient affinity for the aqueous medium, resulting in excellent dispersion. It is preferably 300 μmol/g to 1200 μmol/g from the viewpoint of obtaining good dispersibility, preferably 400 μmol/g to 1200 μmol/g from the viewpoint of obtaining uniform dispersibility, and 500 μmol/g to 500 μmol/g from the viewpoint of obtaining particularly uniform dispersibility. More preferably 1200 μmol/g.
In the method for producing a carbon black aqueous dispersion for conductive paint according to the present invention, the amount of acidic hydroxyl groups of oxidized carbon black contained in the aqueous slurry is determined by the amount of carboxyl groups ( ^-COO- ) and hydroxyl groups (- O ⁻ ) means the sum of the quantities. Considering the dispersibility of oxidized carbon black in an aqueous medium, etc., acidic hydroxyl groups are important as functional groups on the surface of carbon black particles. The amount of acidic hydroxyl groups in the particles can be substantially regarded as the sum of the amount of carboxyl groups and the amount of hydroxyl groups.

The amount of acidic hydroxyl groups in oxidized carbon black means the value measured by the method described above.

In the method for producing an aqueous carbon black dispersion for conductive paint according to the present invention, the amount of —SO ₃ H groups and —PO ₄ H ₂ groups of oxidized carbon black is not particularly limited.

In the method for producing an aqueous dispersion of carbon black for conductive paints according to the present invention, the oxidized carbon black contained in the aqueous slurry can be easily prepared by introducing an anionic functional group into the carbon black.

Furnace black can be mentioned as the carbon black used as a raw material for the oxidized carbon black, and the carbon black may be acidic, neutral or basic. When the carbon black is acidic, it may be used as oxidized carbon black as it is, or may be used as oxidized carbon black after being oxidized to a desired extent.

Carbon black, which is a raw material for oxidized carbon black, has a nitrogen adsorption specific surface area N ₂ SA of 80 in order to improve the conductivity of a coating film obtained by applying a conductive paint and suppress the occurrence of coating film unevenness. It is preferably up to 250 m ² /g, more preferably 80 to 240 m ² /g from the viewpoint of suppressing viscosity increase during preparation of the aqueous dispersion, and achieves both good conductivity and suppression of viscosity increase. From the viewpoint, 80 to 230 m ² /g is more preferable.
In addition, as the carbon black to be the raw material of the oxidized carbon black, DBP (Dibutyl phthalate) oil absorption allows the structural structure of the oxidized carbon black to develop, and from the viewpoint of easily exhibiting excellent conductivity in the resulting coating film, It is preferably 140 to 200 ml/100 g, more preferably 140 to 190 ml/100 g from the viewpoint of suppressing viscosity increase during preparation of the aqueous dispersion, and 150 from the viewpoint of achieving both the above conductivity and viscosity increase suppression. More preferably ~190ml/100g.

In addition, in the present application documents, N ₂ SA of carbon black is defined in JIS K 6217-2 "Carbon black for rubber - basic properties - Part 2, method for determining specific surface area - nitrogen adsorption method, single point method ”, and the DBP absorption of carbon black is a value measured according to JIS K 6217-4 “Carbon black for rubber-Basic properties-Part 4, Determination of DBP absorption” means

In addition, the average particle size of carbon black, which is the raw material of oxidized carbon black, is 100 to 300 nm from the viewpoint of suppressing the occurrence of coating film unevenness in the coating film obtained while exhibiting good dispersibility of oxidized carbon black. is preferable, more preferably 100 to 250 nm from the viewpoint of further improving dispersibility, and more preferably 100 to 200 nm from the viewpoint of suppressing the formation of unevenness in the coating film obtained with good dispersion performance. .

In the method for producing an aqueous carbon black dispersion for a conductive paint according to the present invention, the average particle size of the carbon black used as the raw material for the oxidized carbon black is within the above range, so that the oxidized carbon black exhibits good dispersibility. In addition, it is possible to easily suppress the occurrence of coating film unevenness in the coating film obtained.

In addition, in this application document, the average particle diameter of carbon black means a numerical value measured by a method based on ASTM No. D3846.

Specific examples of the carbon black include Toka Black #5500, Toka Black #4500, Toka Black #4400, Toka Black #3855, Toka Black #3845, Toka Black #3800 (manufactured by Tokai Carbon Co., Ltd.), # 3030, #3050, #3230, #3400 (manufactured by Mitsubishi Chemical Corporation), Conductex SC Ultra, Conductex K Ultra, Conductex 7097 Ultra, Conductex 7093, Conductex 7067 Ultra
, Conductex 7060 Ultra, Conductex 7055 Ultra, Conductex 7051 Ultra, Conductex 7054 Ultra, Conductex 7090, Conductex 7095 Ultra (Aditya Birla Group Columbian Chemicals Company company), ENASCO (R) 150G, ENASCO (R) ) 210G, ENASCO (R) 250G, ENASCO (R) 260G, ENASCO (R) 350G (manufactured by Imerys Graphite & Carbon), VULCAN XC 72, LITX (R) 200, LITX (R) 300, LITX (R) 50 ( Cabot), Ketjenblack EC300J, Ketjenblack EC600JD (all made by Lion Specialty Chemicals) and the like.

Examples of the method of preparing oxidized carbon black by introducing an anion exchange group into the carbon black include a method of oxidizing the carbon black with an oxidizing agent, a method of sulfonating the carbon black, a method of reacting with a diazonium salt, and the like. Anionic functional groups (acidic groups) can be introduced onto the carbon black surface by any of these methods.

　Oxidation treatment with an oxidizing agent can be carried out by known methods such as a liquid phase method and a gas phase method. In the case of oxidation treatment by a liquid phase method, oxidizing agents include, for example, peroxydioic acids such as nitric acid, sulfuric acid, chloric acid, peroxosulfuric acid, peroxoboric acid, peroxocarbonic acid and peroxolinic acid, permanganic acid, dichromic acid, Examples include chlorous acid, perchloric acid, hypohalous acid, hydrogen peroxide, phosphonic acid, phosphoric acid, phosphorous acid, hypophosphorous acid, and salts of these acids. Salts of alkali metals such as lithium, sodium and potassium, and ammonium salts are included.

In the liquid phase method, for example, carbon black having an anionic functional group (acidic group) on the surface can be obtained by adding carbon black to the dispersion liquid containing the oxidizing agent and stirring the mixture. As a solvent for dispersing the oxidizing agent, an aqueous medium is preferable, and examples of the aqueous medium include water and water-soluble organic solvents. Water, particularly deionized water, is preferable from the viewpoint of economy and safety. In order to uniformly disperse the carbon black particles, a surfactant may be added to the dispersion liquid containing the oxidizing agent. As the surfactant, an anionic, nonionic, or cationic surfactant may be used. be able to.

The degree of liquid-phase oxidation is controlled by adjusting the concentration of the oxidant in the dispersion liquid containing the oxidant, the ratio of the amount of carbon black particles added to the aqueous solution of the oxidant, the oxidation treatment temperature, the treatment time, the stirring speed, and the like. can be controlled.

The above-mentioned liquid-phase oxidation is carried out, for example, by adding carbon black particles in an appropriate amount ratio to an aqueous solution of an oxidizing agent whose concentration is adjusted, and mixing them to introduce anionic functional groups onto the surface of the carbon black. From the viewpoint of more efficiently introducing anionic functional groups onto the surface of carbon black, it is preferably carried out by stirring at a temperature of 60 to 90° C. for 1 to 20 hours to form a slurry. In the above liquid-phase oxidation treatment, the carbon black particles may be previously wet-oxidized or dry-oxidized, and by the preliminary wet-oxidation or dry-oxidation, the carbon black particles can be efficiently dispersed in the oxidizing agent aqueous solution, Uniform and efficient liquid-phase oxidation treatment is possible.

In addition, the method of introducing an anionic functional group (acidic group) onto the surface of carbon black by a method of reacting a diazonium salt includes the diazo coupling method on the surface of carbon black, and various -C ₆ H ₄ -COOH, -C ₆ H ₄ -SO ₃ H, -C ₆ H ₄ _-PO ^2- H ₂ , etc. , for example, as described in Japanese Unexamined Patent Application Publication No. 2000-512329.

The oxidation treatment by the gas phase method includes a method of exposing the carbon black particles to a gas atmosphere such as ozone, air, NOx, SOx, etc. According to the gas phase method, drying costs are not required. , and has the advantage of being easier to operate than the liquid phase method.

The oxidized carbon black thus obtained is preferably self-dispersing carbon black having acidic groups on its surface. Self-dispersing carbon black having an acidic group on its surface means that at least one hydrophilic group containing an acidic group is bonded directly to the surface of carbon black or through another atomic group, and is suspended in water. A stable dispersion state can be maintained without adding a surfactant or a polymer compound when it becomes cloudy and a dispersion liquid, and the surface tension of the dispersion liquid shows a value almost equivalent to that of water. .

In the method for producing an aqueous dispersion of carbon black for conductive paint according to the present invention, the oxidized carbon black is subjected to a neutralization step in the form of an aqueous slurry. Examples of the aqueous medium in which the oxidized carbon black is dispersed include water and water-soluble organic solvents, but water, particularly deionized water, is preferred from the standpoint of economy and safety.
In addition, the concentration of the oxidized carbon black in the aqueous slurry should be 1.0% by mass or more from the viewpoint that suitable blackness and electrical conductivity can be easily exhibited when used in a water-based paint or the like. is preferable, and when used in a water-based paint or the like, it is preferably 20.0% by mass or less from the point that suitable dispersibility can be easily exhibited, and it is 1.0 to 15.0% by mass. is more preferable, and 1.0 to 10.0% by mass is even more preferable.

In the method for producing an aqueous dispersion of carbon black for conductive paint according to the present invention, an aqueous slurry of oxidized carbon black having one or more anionic functional groups on its surface is mixed with sodium hydroxide and neutralized by heating. do.

The amount of sodium hydroxide used in the neutralization step can be appropriately determined according to the oxidized carbon black to be neutralized. The dissociation of the acidic functional groups and the electrical repulsion of the particle surface maintain the dispersion stability, so it is preferable to mix sodium hydroxide so that the pH is 6 or more, and the ion concentration in the dispersion is adjusted appropriately. It is preferable to mix sodium hydroxide so that the pH becomes 12 or less because it is easy to suppress aggregation due to salting out and destabilization of the dispersion pH due to absorption of carbon dioxide gas in the air. , it is more preferable to mix sodium hydroxide so that the pH is 7 to 12, and it is even more preferable to mix sodium hydroxide so that the pH is 8 to 12.

Sodium hydroxide is preferably added in the form of an aqueous solution to an aqueous slurry of oxidized carbon black having one or more anionic functional groups on its surface. However, water, especially deionized water, is preferred from the viewpoint of economy and safety.

In the neutralization step, an aqueous slurry of oxidized carbon black having one or more anionic functional groups on its surface is mixed with sodium hydroxide and subjected to heating and neutralization. The neutralization process proceeds gradually even at room temperature, but it is preferable to add a diluted neutralizing agent to the slurry in the reaction tank and heat it moderately so that the neutralization proceeds completely. The heating temperature for heat neutralization is preferably 30°C to 95°C, more preferably 60°C to 95°C, and even more preferably 80°C to 95°C.
Further, in the neutralization step, an aqueous slurry of oxidized carbon black having one or more anionic functional groups on the surface and sodium hydroxide are mixed, and the holding time is preferably 30 minutes to 12 hours, preferably 1 to 8 hours. More preferably, 2 to 5 hours is even more preferable.
Completion of the neutralization treatment can be confirmed by the fact that the pH does not fluctuate any more even if the heating is continued.

In the method for producing an aqueous carbon black dispersion for a conductive paint according to the present invention, oxidized carbon black with a high DBP oil absorption (high structure), which was conventionally thought to be difficult to improve blackness, was used. However, by neutralizing with heating using sodium hydroxide as a neutralizing agent, a coating film having a high degree of blackness can be easily formed using the obtained carbon black aqueous dispersion for conductive paint. .

In the method for producing an aqueous dispersion of carbon black for conductive paints according to the present invention, the preferred range of the amount of acidic hydroxyl groups in the oxidized carbon black in the resulting aqueous dispersion is the carbon black for conductive paints of the present invention described above. It is the same as the preferred range of the amount of acidic hydroxyl groups in the oxidized carbon black contained in the black aqueous dispersion.

Further, in the method for producing an aqueous dispersion of carbon black for conductive paint according to the present invention, the amount of —SO ₃ H groups and —PO ₄ H ₂ groups of oxidized carbon black in the obtained aqueous dispersion is particularly limited. The method for measuring the amount of acidic hydroxyl groups is the same as that described in the explanation of the oxidized carbon black contained in the aqueous dispersion of the carbon black for conductive paints of the present invention.

In the method for producing an aqueous dispersion of carbon black for conductive paint according to the present invention, the nitrogen adsorption specific surface area N ₂ SA, the DBP oil absorption, and the preferred ranges of the average particle size of the obtained oxidized carbon black are also as described above. The preferred ranges for the nitrogen adsorption specific surface area N ₂ SA, DBP oil absorption and average particle size of the oxidized carbon black contained in the aqueous dispersion of carbon black for conductive paints of the present invention are the same as those described above.
Moreover, the measurement methods for these are the same as those described in the explanation of the oxidized carbon black contained in the aqueous dispersion of the carbon black for conductive paints of the present invention.

According to the present invention, as described above, the desired conductive carbon black aqueous dispersion can be easily prepared using, for example, furnace black as a raw material. Carbon black aqueous dispersions for coatings can be prepared.

According to the present invention, it is possible to provide a method for producing a carbon black aqueous dispersion for a conductive paint, which can easily form a coating film with excellent blackness and conductivity at low cost.

(Example)
The contents of the present invention will be described below with reference to specific examples together with comparative examples. However, the present invention is not limited to these examples. In the following examples and comparative examples, the pH was obtained by the method specified in JIS Z 8802.

(Example 1)
(1) Preparation of oxidized carbon black-containing aqueous slurry As carbon black, 150 g of furnace carbon black (having a nitrogen adsorption specific surface area N ₂ SA of 225 m ² /g, a DBP oil absorption of 155 ml/100 g, and an average particle diameter of 183 nm). was added to 3000 ml of a 2.0 N aqueous solution of sodium persulfate using deionized water, and the reaction temperature was 90° C. and the stirring speed was 300 rpm for 3 hours to liquid-phase oxidize the carbon black surface.
By the above-mentioned liquid-phase oxidation treatment, the surface having a nitrogen adsorption specific surface area N ₂ SA of 225 m ² /g, a DBP oil absorption of 155 ml/100 g, an average particle diameter of 183 nm, and an acidic hydroxyl group amount of 900 μmol/g was added to the surface. An oxidized carbon black-containing aqueous slurry containing oxidized carbon black having functional groups was obtained.
The oxidized carbon black concentration in the obtained oxidized carbon black-containing aqueous slurry was 5% by mass.

(2) Neutralization treatment To the aqueous slurry containing oxidized carbon black obtained in <Preparation of slurry containing oxidized carbon black>, an aqueous sodium hydroxide solution is added so that the pH of the slurry becomes 10, and the reaction temperature is 95°C. , and the neutralization reaction was carried out for 3 hours at a stirring speed of 300 rpm.
By the above neutralization treatment, anions on the surface having a nitrogen adsorption specific surface area N ₂ SA of 225 m ² /g, a DBP oil absorption of 155 ml/100 g, an average particle diameter of 183 nm, and an acidic hydroxyl group amount of 900 μmol/g An aqueous dispersion of carbon black for conductive paint containing oxidized carbon black having functional groups was prepared.
The content of neutralized oxidized carbon black in the obtained aqueous dispersion of carbon black for conductive paint was 20% by mass.

(Comparative example 1)
In the neutralization treatment of Example 1 (2), instead of adding an aqueous sodium hydroxide solution to the carbon black-containing aqueous slurry so that the pH of the slurry became 10, potassium hydroxide was added so as to achieve the same pH. In the same manner as in Example 1 except that the aqueous solution was added, the nitrogen adsorption specific surface area N ₂ SA was 225 m ² /g, the DBP oil absorption was 155 ml/100 g, the average particle diameter was 183 nm, and the amount of acidic hydroxyl groups was An aqueous dispersion of carbon black for conductive coatings containing 900 μmol/g of oxidized carbon black with anionic functional groups on its surface was prepared.
The content of neutralized oxidized carbon black in the obtained aqueous dispersion of carbon black for conductive paint was 20% by mass.

(Example 2)
(1) Preparation of oxidized carbon black-containing aqueous slurry As carbon black, 150 g of furnace carbon black (having a nitrogen adsorption specific surface area N ₂ SA of 168 m ² /g, a DBP oil absorption of 163 ml/100 g, and an average particle diameter of 132 nm). was added to 3000 ml of a 2.0 N aqueous solution of sodium persulfate using deionized water, and the reaction temperature was 90° C. and the stirring speed was 300 rpm for 3 hours to liquid-phase oxidize the carbon black surface.
By the above-mentioned liquid-phase oxidation treatment, the surface having a nitrogen adsorption specific surface area N ₂ SA of 168 m ² /g, a DBP oil absorption of 163 ml/100 g, an average particle diameter of 132 nm, and an acidic hydroxyl group amount of 670 μmol/g was added to the surface. An oxidized carbon black-containing aqueous slurry containing oxidized carbon black having functional groups was obtained.
The oxidized carbon black concentration in the obtained oxidized carbon black-containing aqueous slurry was 5% by mass.

(2) Neutralization treatment To the aqueous slurry containing oxidized carbon black obtained in <Preparation of slurry containing oxidized carbon black>, an aqueous sodium hydroxide solution is added so that the pH of the slurry becomes 10, and the reaction temperature is 95°C. , and the neutralization reaction was carried out for 3 hours at a stirring speed of 300 rpm.
By the above neutralization treatment, anions on the surface having a nitrogen adsorption specific surface area N ₂ SA of 168 m ² /g, a DBP oil absorption of 163 ml/100 g, an average particle diameter of 132 nm, and an acidic hydroxyl group amount of 670 μmol/g An aqueous dispersion of carbon black for conductive paint containing oxidized carbon black having functional groups was prepared.
The content of neutralized oxidized carbon black in the obtained aqueous dispersion of carbon black for conductive paint was 20% by mass.

(Comparative example 2)
Example 2 (2) In the neutralization treatment, instead of adding an aqueous sodium hydroxide solution to the carbon black oxide-containing aqueous slurry so that the pH of the slurry became 10, potassium hydroxide was added so as to achieve the same pH. In the same manner as in Example 2 except that the aqueous solution was added, the nitrogen adsorption specific surface area N ₂ SA was 168 m ² /g, the DBP oil absorption was 163 ml/100 g, the average particle diameter was 132 nm, and the amount of acidic hydroxyl groups was An aqueous dispersion of carbon black for conductive paint was prepared containing oxidized carbon black with anionic functional groups on its surface at 670 μmol/g.
The content of neutralized oxidized carbon black in the obtained aqueous dispersion of carbon black for conductive paint was 20% by mass.

(Example 3)
(1) Preparation of oxidized carbon black-containing aqueous slurry As carbon black, 150 g of furnace carbon black (having a nitrogen adsorption specific surface area N ₂ SA of 133 m ² /g, a DBP oil absorption of 152 ml/100 g, and an average particle diameter of 156 nm). was added to 3000 ml of a 2.0 N aqueous solution of sodium persulfate using deionized water, and the reaction temperature was 90° C. and the stirring speed was 300 rpm for 3 hours to liquid-phase oxidize the carbon black surface.
By the above-mentioned liquid-phase oxidation treatment, the surface having a nitrogen adsorption specific surface area N ₂ SA of 133 m ² /g, a DBP oil absorption of 152 ml/100 g, an average particle diameter of 156 nm, and an acidic hydroxyl group amount of 530 μmol/g was added to the surface. An oxidized carbon black-containing aqueous slurry containing oxidized carbon black having functional groups was obtained.
The oxidized carbon black concentration in the obtained oxidized carbon black-containing aqueous slurry was 5% by mass.

(2) Neutralization treatment To the aqueous slurry containing oxidized carbon black obtained in <Preparation of slurry containing oxidized carbon black>, an aqueous sodium hydroxide solution is added so that the pH of the slurry becomes 10, and the reaction temperature is 95°C. , and the neutralization reaction was carried out for 3 hours at a stirring speed of 300 rpm.
By the above neutralization treatment, anions on the surface having a nitrogen adsorption specific surface area N ₂ SA of 133 m ² /g, a DBP oil absorption of 152 ml/100 g, an average particle diameter of 156 nm, and an acidic hydroxyl group amount of 530 μmol/g An aqueous dispersion of carbon black for conductive paint containing oxidized carbon black having functional groups was prepared.
The content of neutralized oxidized carbon black in the obtained aqueous dispersion of carbon black for conductive paint was 20% by mass.

(Comparative Example 3)
Example 3 (2) In the neutralization treatment, instead of adding an aqueous sodium hydroxide solution to the carbon black oxide-containing aqueous slurry so that the pH of the slurry became 10, potassium hydroxide was added so as to achieve the same pH. In the same manner as in Example 3 except that the aqueous solution was added, the nitrogen adsorption specific surface area N ₂ SA was 133 m ² /g, the DBP oil absorption was 152 ml/100 g, the average particle diameter was 156 nm, and the amount of acidic hydroxyl groups was An aqueous dispersion of carbon black for conductive coatings containing 530 μmol/g of oxidized carbon black with anionic functional groups on its surface was prepared.
The content of neutralized oxidized carbon black in the obtained aqueous dispersion of carbon black for conductive paint was 20% by mass.

(Example 4)
(1) Preparation of oxidized carbon black-containing aqueous slurry As carbon black, 150 g of furnace carbon black (having a nitrogen adsorption specific surface area N ₂ SA of 91 m ² /g, a DBP oil absorption of 185 ml/100 g, and an average particle diameter of 211 nm). was added to 3000 ml of a 2.0 N aqueous solution of sodium persulfate using deionized water, and the reaction temperature was 90° C. and the stirring speed was 300 rpm for 3 hours to liquid-phase oxidize the carbon black surface.
By the above-mentioned liquid-phase oxidation treatment, the surface having a nitrogen adsorption specific surface area N ₂ SA of 91 m ² /g, a DBP oil absorption of 185 ml/100 g, an average particle diameter of 211 nm, and an acidic hydroxyl group amount of 360 μmol/g was formed on the surface. An oxidized carbon black-containing aqueous slurry containing oxidized carbon black having functional groups was obtained.
The oxidized carbon black concentration in the obtained oxidized carbon black-containing aqueous slurry was 5% by mass.

(2) Neutralization treatment To the aqueous slurry containing oxidized carbon black obtained in <Preparation of slurry containing oxidized carbon black>, an aqueous sodium hydroxide solution is added so that the pH of the slurry becomes 10, and the reaction temperature is 95°C. , and the neutralization reaction was carried out for 3 hours at a stirring speed of 300 rpm.
By the above neutralization treatment, anions on the surface having a nitrogen adsorption specific surface area N ₂ SA of 91 m ² /g, a DBP oil absorption of 185 ml/100 g, an average particle diameter of 211 nm, and an acidic hydroxyl group content of 360 μmol/g An aqueous dispersion of carbon black for conductive paint containing oxidized carbon black having functional groups was prepared.
The content of neutralized oxidized carbon black in the obtained aqueous dispersion of carbon black for conductive paint was 20% by mass.

(Comparative Example 4)
Example 4 (2) In the neutralization treatment, instead of adding an aqueous sodium hydroxide solution to the carbon black-containing aqueous slurry so that the pH of the slurry became 10, potassium hydroxide was added so as to achieve the same pH. In the same manner as in Example 4 except that the aqueous solution was added, the nitrogen adsorption specific surface area N ₂ SA was 91 m ² /g, the DBP oil absorption was 185 ml/100 g, the average particle diameter was 211 nm, and the amount of acidic hydroxyl groups was An aqueous dispersion of carbon black for conductive paint was prepared containing oxidized carbon black with anionic functional groups on its surface at 360 μmol/g.
The content of neutralized oxidized carbon black in the obtained aqueous dispersion of carbon black for conductive paint was 20% by mass.

(Comparative Example 5)
(1) Preparation of oxidized carbon black-containing aqueous slurry As carbon black, 150 g of furnace carbon black (having a nitrogen adsorption specific surface area N ₂ SA of 57 m ² /g, a DBP oil absorption of 185 ml/100 g, and an average particle diameter of 325 nm). was added to 3000 ml of a 2.0 N aqueous solution of sodium persulfate using deionized water, and the reaction temperature was 90° C. and the stirring speed was 300 rpm for 3 hours to liquid-phase oxidize the carbon black surface.
By the liquid-phase oxidation treatment, an anion is formed on the surface having a nitrogen adsorption specific surface area N ₂ SA of 57 m ² /g, a DBP oil absorption of 185 ml/100 g, an average particle diameter of 325 nm, and an acidic hydroxyl group amount of 230 μmol/g. An oxidized carbon black-containing aqueous slurry containing oxidized carbon black having functional groups was obtained.
The oxidized carbon black concentration in the obtained oxidized carbon black-containing aqueous slurry was 5% by mass.

(2) Neutralization treatment To the aqueous slurry containing oxidized carbon black obtained in <Preparation of slurry containing oxidized carbon black>, an aqueous potassium hydroxide solution is added so that the pH of the slurry becomes 10, and the reaction temperature is 95°C. , and the neutralization reaction was carried out for 3 hours at a stirring speed of 300 rpm.
By the above neutralization treatment, anions on the surface having a nitrogen adsorption specific surface area N ₂ SA of 57 m ² /g, a DBP oil absorption of 185 ml/100 g, an average particle diameter of 325 nm, and an acidic hydroxyl group content of 230 μmol/g An aqueous dispersion of carbon black for conductive paint containing oxidized carbon black having functional groups was prepared.
The content of neutralized oxidized carbon black in the obtained aqueous dispersion of carbon black for conductive paint was 20% by mass.

(Comparative Example 6)
(1) Preparation of oxidized carbon black-containing aqueous slurry As carbon black, 150 g of furnace carbon black (having a nitrogen adsorption specific surface area N ₂ SA of 31 m ² /g, a DBP oil absorption of 153 ml/100 g, and an average particle diameter of 393 nm). was added to 3000 ml of a 2.0 N aqueous solution of sodium persulfate using deionized water, and the reaction temperature was 90° C. and the stirring speed was 300 rpm for 3 hours to liquid-phase oxidize the carbon black surface.
By the above-mentioned liquid-phase oxidation treatment, the surface having a nitrogen adsorption specific surface area N ₂ SA of 31 m ² /g, a DBP oil absorption of 153 ml/100 g, an average particle diameter of 393 nm, and an acidic hydroxyl group content of 130 μmol/g was coated with anions. An oxidized carbon black-containing aqueous slurry containing oxidized carbon black having functional groups was obtained.
The oxidized carbon black concentration in the obtained oxidized carbon black-containing aqueous slurry was 5% by mass.

(2) Neutralization treatment To the aqueous slurry containing oxidized carbon black obtained in <Preparation of slurry containing oxidized carbon black>, an aqueous potassium hydroxide solution is added so that the pH of the slurry becomes 10, and the reaction temperature is 95°C. , and the neutralization reaction was carried out for 3 hours at a stirring speed of 300 rpm.
By the above neutralization treatment, anions on the surface having a nitrogen adsorption specific surface area N ₂ SA of 31 m ² /g, a DBP oil absorption of 153 ml/100 g, an average particle diameter of 393 nm, and an acidic hydroxyl group amount of 130 μmol/g An aqueous dispersion of carbon black for conductive paint containing oxidized carbon black having functional groups was prepared.
The content of neutralized oxidized carbon black in the obtained aqueous dispersion of carbon black for conductive paint was 20% by mass.

(Comparative Example 7)
(1) Preparation of oxidized carbon black-containing aqueous slurry As carbon black, 150 g of furnace carbon black (having a nitrogen adsorption specific surface area N ₂ SA of 113 m ² /g, a DBP oil absorption of 139 ml/100 g, and an average particle diameter of 160 nm). was added to 3000 ml of a 2.0 N aqueous solution of sodium persulfate using deionized water, and the reaction temperature was 90° C. and the stirring speed was 300 rpm for 3 hours to liquid-phase oxidize the carbon black surface.
By the above-mentioned liquid-phase oxidation treatment, the surface having a nitrogen adsorption specific surface area N ₂ SA of 113 m ² /g, a DBP oil absorption of 139 ml/100 g, an average particle diameter of 160 nm, and an acidic hydroxyl group amount of 450 μmol/g was formed on the surface. An oxidized carbon black-containing aqueous slurry containing oxidized carbon black having functional groups was obtained.
The oxidized carbon black concentration in the obtained oxidized carbon black-containing aqueous slurry was 5% by mass.

(2) Neutralization treatment To the aqueous slurry containing oxidized carbon black obtained in <Preparation of slurry containing oxidized carbon black>, an aqueous potassium hydroxide solution is added so that the pH of the slurry becomes 10, and the reaction temperature is 95°C. , and the neutralization reaction was carried out for 3 hours at a stirring speed of 300 rpm.
By the above neutralization treatment, anions on the surface having a nitrogen adsorption specific surface area N ₂ SA of 113 m ² /g, a DBP oil absorption of 139 ml/100 g, an average particle diameter of 160 nm, and an acidic hydroxyl group amount of 450 μmol/g An aqueous dispersion of carbon black for conductive paint containing oxidized carbon black having functional groups was prepared.
The content of neutralized oxidized carbon black in the obtained aqueous dispersion of carbon black for conductive paint was 20% by mass.

(Comparative Example 8)
(1) Preparation of oxidized carbon black-containing aqueous slurry As carbon black, 150 g of furnace carbon black (having a nitrogen adsorption specific surface area N ₂ SA of 244 m ² /g, a DBP oil absorption of 76 ml/100 g, and an average particle diameter of 77 nm). was added to 3000 ml of a 2.0 N aqueous solution of sodium persulfate using deionized water, and the reaction temperature was 90° C. and the stirring speed was 300 rpm for 3 hours to liquid-phase oxidize the carbon black surface.
By the above-mentioned liquid-phase oxidation treatment, the surface having a nitrogen adsorption specific surface area N ₂ SA of 244 m ² /g, a DBP oil absorption of 76 ml/100 g, an average particle diameter of 77 nm, and an acidic hydroxyl group amount of 980 μmol/g was added to the surface. An oxidized carbon black-containing aqueous slurry containing oxidized carbon black having functional groups was obtained.
The oxidized carbon black concentration in the obtained oxidized carbon black-containing aqueous slurry was 5% by mass.

(2) Neutralization treatment To the aqueous slurry containing oxidized carbon black obtained in <Preparation of slurry containing oxidized carbon black>, an aqueous potassium hydroxide solution is added so that the pH of the slurry becomes 10, and the reaction temperature is 95°C. , and the neutralization reaction was carried out for 3 hours at a stirring speed of 300 rpm.
By the above neutralization treatment, anions on the surface having a nitrogen adsorption specific surface area N ₂ SA of 244 m ² /g, a DBP oil absorption of 76 ml/100 g, an average particle diameter of 77 nm, and an acidic hydroxyl group amount of 980 μmol/g An aqueous dispersion of carbon black for conductive paint containing oxidized carbon black having functional groups was prepared.
The content of neutralized oxidized carbon black in the obtained aqueous dispersion of carbon black for conductive paint was 20% by mass.

(Comparative Example 9)
(1) Preparation of oxidized carbon black-containing aqueous slurry As carbon black, 150 g of furnace carbon black (having a nitrogen adsorption specific surface area N ₂ SA of 30 m ² /g, a DBP oil absorption of 71 ml/100 g, and an average particle diameter of 235 nm). was added to 3000 ml of a 2.0 N aqueous solution of sodium persulfate using deionized water, and the reaction temperature was 90° C. and the stirring speed was 300 rpm for 3 hours to liquid-phase oxidize the carbon black surface.
By the above-mentioned liquid-phase oxidation treatment, the surface having a nitrogen adsorption specific surface area N ₂ SA of 30 m ² /g, a DBP oil absorption of 71 ml/100 g, an average particle diameter of 235 nm, and an acidic hydroxyl group amount of 120 μmol/g was added to the surface. An oxidized carbon black-containing aqueous slurry containing oxidized carbon black having functional groups was obtained.
The oxidized carbon black concentration in the obtained oxidized carbon black-containing aqueous slurry was 5% by mass.

(2) Neutralization treatment To the aqueous slurry containing oxidized carbon black obtained in <Preparation of slurry containing oxidized carbon black>, an aqueous potassium hydroxide solution is added so that the pH of the slurry becomes 10, and the reaction temperature is 95°C. , and the neutralization reaction was carried out for 3 hours at a stirring speed of 300 rpm.
By the above neutralization treatment, anions on the surface having a nitrogen adsorption specific surface area N ₂ SA of 30 m ² /g, a DBP oil absorption of 71 ml/100 g, an average particle diameter of 235 nm, and an acidic hydroxyl group amount of 120 μmol/g An aqueous dispersion of carbon black for conductive paint containing oxidized carbon black having functional groups was prepared.
The content of neutralized oxidized carbon black in the obtained aqueous dispersion of carbon black for conductive paint was 20% by mass.

(Comparative Example 10)
(1) Preparation of Aqueous Slurry Containing Oxidized Carbon Black As carbon black, 150 g of acetylene black (having a nitrogen adsorption specific surface area N ₂ SA of 80 m ² /g and a DBP oil absorption of 216 ml/100 g) was added to deionized water. The surface of the carbon black was liquid-phase oxidized by adding it to 3000 ml of a 2.0 N aqueous solution of sodium persulfate and treating it at a reaction temperature of 90° C. and a stirring speed of 300 rpm for 3 hours.
Carbon oxide having a nitrogen adsorption specific surface area N ₂ SA of 80 m ² /g, a DBP oil absorption of 216 ml/100 g, and an acidic hydroxyl group amount of 320 μmol/g by the liquid phase oxidation treatment, and having an anionic functional group on the surface. An oxidized carbon black-containing aqueous slurry containing black was obtained.
The oxidized carbon black concentration in the obtained oxidized carbon black-containing aqueous slurry was 5% by mass.

(2) Neutralization treatment To the aqueous slurry containing oxidized carbon black obtained in <Preparation of slurry containing oxidized carbon black>, an aqueous sodium hydroxide solution is added so that the pH of the slurry becomes 10, and the reaction temperature is 95°C. , and the neutralization reaction was carried out for 3 hours at a stirring speed of 300 rpm.
Carbon oxide having an anionic functional group on its surface having a nitrogen adsorption specific surface area N ₂ SA of 80 m ² /g, a DBP oil absorption of 216 ml/100 g, and an acidic hydroxyl group amount of 320 μmol/g by the above neutralization treatment. An aqueous dispersion of carbon black for conductive coating containing black was prepared.
The content of neutralized oxidized carbon black in the obtained aqueous dispersion of carbon black for conductive paint was 20% by mass.

(Comparative Example 11)
(1) Preparation of oxidized carbon black-containing aqueous slurry As carbon black, 150 g of furnace carbon black (having a nitrogen adsorption specific surface area N ₂ SA of 262 m ² /g and a DBP oil absorption of 150 ml/100 g) was mixed with deionized water. It was added to 3000 ml of a 2.0 N aqueous solution of sodium persulfate used and treated at a reaction temperature of 90° C. and a stirring speed of 300 rpm for 3 hours to liquid-phase oxidize the surface of the carbon black.
Carbon oxide having an anionic functional group on its surface having a nitrogen adsorption specific surface area N ₂ SA of 262 m ² /g, a DBP oil absorption of 150 ml/100 g, and an acidic hydroxyl group amount of 1050 μmol/g by the liquid phase oxidation treatment. An oxidized carbon black-containing aqueous slurry containing black was obtained.
The oxidized carbon black concentration in the obtained oxidized carbon black-containing aqueous slurry was 5% by mass.

(2) Neutralization treatment To the aqueous slurry containing oxidized carbon black obtained in <Preparation of slurry containing oxidized carbon black>, an aqueous sodium hydroxide solution is added so that the pH of the slurry becomes 10, and the reaction temperature is 95°C. , and the neutralization reaction was carried out for 3 hours at a stirring speed of 300 rpm.
Carbon oxide having an anionic functional group on its surface having a nitrogen adsorption specific surface area N ₂ SA of 262 m ² /g, a DBP oil absorption of 150 ml/100 g, and an acidic hydroxyl group amount of 1050 μmol/g by the above neutralization treatment. An aqueous dispersion of carbon black for conductive coating containing black was prepared.
The content of neutralized oxidized carbon black in the obtained aqueous dispersion of carbon black for conductive paint was 20% by mass.

(Comparative Example 12)
(1) Preparation of oxidized carbon black-containing aqueous slurry As carbon black, 150 g of furnace carbon black (having a nitrogen adsorption specific surface area N ₂ SA of 31 m ² /g, a DBP oil absorption of 153 ml/100 g, and an average particle diameter of 393 nm). was added to 3000 ml of a 2.0 N aqueous solution of sodium persulfate using deionized water, and the reaction temperature was 90° C. and the stirring speed was 300 rpm for 3 hours to liquid-phase oxidize the carbon black surface.
By the above-mentioned liquid-phase oxidation treatment, the surface having a nitrogen adsorption specific surface area N ₂ SA of 31 m ² /g, a DBP oil absorption of 153 ml/100 g, an average particle diameter of 393 nm, and an acidic hydroxyl group content of 130 μmol/g was coated with anions. An oxidized carbon black-containing aqueous slurry containing oxidized carbon black having functional groups was obtained.
The oxidized carbon black concentration in the obtained oxidized carbon black-containing aqueous slurry was 5% by mass.

(2) Neutralization treatment To the aqueous slurry containing oxidized carbon black obtained in <Preparation of slurry containing oxidized carbon black>, an aqueous sodium hydroxide solution is added so that the pH of the slurry becomes 10, and the reaction temperature is 95°C. , and the neutralization reaction was carried out for 3 hours at a stirring speed of 300 rpm.
By the above neutralization treatment, anions on the surface having a nitrogen adsorption specific surface area N ₂ SA of 31 m ² /g, a DBP oil absorption of 153 ml/100 g, an average particle diameter of 393 nm, and an acidic hydroxyl group amount of 130 μmol/g An aqueous dispersion of carbon black for conductive paint containing oxidized carbon black having functional groups was prepared.
The content of neutralized oxidized carbon black in the obtained aqueous dispersion of carbon black for conductive paint was 20% by mass.

(Comparative Example 13)
(1) Preparation of oxidized carbon black-containing aqueous slurry As carbon black, 150 g of furnace carbon black (having a nitrogen adsorption specific surface area N ₂ SA of 113 m ² /g, a DBP oil absorption of 139 ml/100 g, and an average particle diameter of 160 nm). was added to 3000 ml of a 2.0 N aqueous solution of sodium persulfate using deionized water, and the reaction temperature was 90° C. and the stirring speed was 300 rpm for 3 hours to liquid-phase oxidize the carbon black surface.
By the above-mentioned liquid-phase oxidation treatment, the surface having a nitrogen adsorption specific surface area N ₂ SA of 113 m ² /g, a DBP oil absorption of 139 ml/100 g, an average particle diameter of 160 nm, and an acidic hydroxyl group amount of 450 μmol/g was formed on the surface. An oxidized carbon black-containing aqueous slurry containing oxidized carbon black having functional groups was obtained.
The oxidized carbon black concentration in the obtained oxidized carbon black-containing aqueous slurry was 5% by mass.

(2) Neutralization treatment To the aqueous slurry containing oxidized carbon black obtained in <Preparation of slurry containing oxidized carbon black>, an aqueous sodium hydroxide solution is added so that the pH of the slurry becomes 10, and the reaction temperature is 95°C. , and the neutralization reaction was carried out for 3 hours at a stirring speed of 300 rpm.
By the above neutralization treatment, anions on the surface having a nitrogen adsorption specific surface area N ₂ SA of 113 m ² /g, a DBP oil absorption of 139 ml/100 g, an average particle diameter of 160 nm, and an acidic hydroxyl group amount of 450 μmol/g An aqueous dispersion of carbon black for conductive paint containing oxidized carbon black having functional groups was prepared.
The content of neutralized oxidized carbon black in the obtained aqueous dispersion of carbon black for conductive paint was 20% by mass.

<Formation of coating film>
(1) Preparation of conductive paint Using the aqueous dispersions of conductive carbon black obtained in Examples 1 to 4 and Comparative Examples 1 to 11, conductive paints having the following composition were prepared. bottom.
Oxidized carbon black neutralized product (solid content) 3.0% by mass
Water-based varnish (manufactured by Wasin Paint) (solid content) 12.0% by mass
Wetting agent (Olfine E1010 manufactured by Nissin Chemical Industry Co., Ltd.) 1.0% by mass
Pure water 84.0% by mass

(2) Application of conductive paint Each conductive paint obtained in (1) is applied onto one main surface of a PET (polyethylene terephthalate) film using a bar coater (No. 6) to obtain a PET film. A coating film having a thickness of 2 μm (containing 20% by mass of neutralized carbon black oxide in terms of solid content) was formed thereon.

(3) Measurement of surface resistivity In each PET film with a coating film formed on one main surface obtained in (2), a resistivity meter (Hiresta UX MCP-HT800 manufactured by Nitto Seiko Analytic Co., Ltd.) Surface resistivity was measured. Table 1 shows the results.

(4) Measurement of blackness In each PET film having a coating film formed on one main surface obtained in (2), a spectrophotometer (CM-26dG manufactured by Konica Minolta Co., Ltd.) was used to measure diffuse reflectance. R was measured, and the optical density (blackness) OD was calculated by the following formula.
OD = -log ₁₀ R
Table 1 shows the results.

From Table 1, the carbon black aqueous dispersions for conductive paints obtained in Examples 1 to 4 have a nitrogen adsorption specific surface area N ₂ SA of 80 to 250 m ² /g and a DBP oil absorption of 140 to 200 ml/100 g. , a sodium hydroxide-neutralized product of oxidized carbon black having one or more anionic functional groups on its surface and having an acidic hydroxyl group amount of 300 to 1200 μmol/g. Therefore, when these aqueous carbon black dispersions for conductive paints are used in conductive paints, it is possible to easily form a coating film having low surface resistance, excellent conductivity, and excellent blackness at low cost. I understand.

On the other hand, from Table 1, the carbon black aqueous dispersions for conductive paint obtained in Comparative Examples 1 to 13 have a nitrogen adsorption specific surface area of N ₂ as a neutralized product of acidic carbon black contained in the aqueous dispersion. SA outside the range of 80 to 250 m ² /g (Comparative Examples 5, 6, 9, 11, 12) and DBP oil absorption outside the range of 140 to 200 ml/100 g (Comparative Examples 7 to 10, Comparative Example 13), and those having an acidic hydroxyl group content outside the range of 300 to 1200 μmol / g (Comparative Examples 5, 6, 9, 12), , KOH neutralized products (Comparative Examples 1 to 9). For this reason, when these aqueous carbon black dispersions for conductive paints are used in conductive paints, the surface resistance of the resulting coating film is high and the conductivity is poor (Comparative Examples 5 to 9, Comparative Example 12, Comparative Example 13), poor blackness (Comparative Examples 1 to 7, Comparative Examples 9 to 13), uneven coating film (Comparative Example 5, Comparative Example 6, Comparative Example 9, Comparative Example 12).

Claims

Oxidized carbon black having a nitrogen adsorption specific surface area N 2 SA of 80 to 250 m 2 /g, a DBP oil absorption of 140 to 200 ml/100 g, and an acidic hydroxyl group content of 300 to 1200 μmol/g, and having one or more anionic functional groups on its surface. An aqueous carbon black dispersion for a conductive paint, characterized by containing a sodium hydroxide neutralized product.
The carbon black aqueous dispersion for conductive paint according to claim 1, wherein the oxidized carbon black has an average particle size of 100 to 300 nm.
Oxidized carbon black having a nitrogen adsorption specific surface area N 2 SA of 80 to 250 m 2 /g, a DBP oil absorption of 140 to 200 ml/100 g, and an acidic hydroxyl group content of 300 to 1200 μmol/g, and having one or more anionic functional groups on its surface. For an aqueous slurry containing
A method for producing an aqueous carbon black dispersion for a conductive paint, which comprises mixing sodium hydroxide and heating and neutralizing it.
The method for producing an aqueous carbon black dispersion for conductive paint according to claim 3, wherein the oxidized carbon black has an average particle size of 100 to 300 nm.
The method for producing an aqueous carbon black dispersion for conductive paint according to claim 3 or claim 4, wherein the aqueous slurry containing the oxidized carbon black is mixed with the sodium hydroxide so as to have a pH of 6 to 12.