JP7217675B2 - Aqueous dispersion of carbon black conductive material raw material, method for producing aqueous dispersion of carbon black conductive material raw material, method for producing conductive carbon black powder, and method for producing positive electrode material for lithium ion secondary battery - Google Patents

Description

The present invention provides an aqueous dispersion of conductive carbon black raw material, a method for producing an aqueous dispersion of conductive carbon black raw material, conductive carbon black powder, a method for producing conductive carbon black powder, and a lithium ion secondary battery. The present invention relates to a method for manufacturing a positive electrode material.

In recent years, with the spread of mobile phones, laptop computers, and the like, lithium-ion secondary batteries have been attracting attention, and their demand is increasing year by year. In the current lithium-ion secondary battery, in order to increase the efficiency of the battery reaction by increasing the electrode area, a coating mixed with an electrode active material, a binder, a conductive material, etc. is usually applied to the strip-shaped metal foil. Both electrodes are used, and after being wound together with a separator, they are housed in a battery can (Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2003-308845, etc.)).

Among them, the positive electrode uses a lithium-transition metal composite oxide or the like as an electrode active material. Such an electrode active material alone has poor electronic conductivity, that is, electrical conductivity, so in order to impart conductivity, conductive carbon black with a highly developed structure, and carbon such as graphite whose crystals exhibit significant anisotropy A material is added as a conductive material and dispersed in a non-aqueous solvent such as N-methyl-2-pyrrolidone together with a binder (binder) to prepare a slurry (see Patent Document 2 (Japanese Patent Application Laid-Open No. 2003-157846)). , the slurry is coated on a metal foil and dried to form a positive electrode.

By the way, the conductive material is required to be excellent in conductivity as well as to contain little metal impurities, particularly polyvalent metal ions, which cause deterioration of battery performance. In the case of carbon black, it is known that the content of metal impurities and conductivity vary depending on the manufacturing method, but when used as a conductive material, it has excellent conductivity like other conductive materials. It is required that the amount of metal impurities is small.

JP 2003-308845 A JP 2003-157846 A

Therefore, it is conceivable to employ acetylene black obtained by thermally decomposing acetylene gas as a conductive material, slurry it with a dispersant, and use it as a material for forming a positive electrode material for a lithium ion secondary battery.
Acetylene black has the advantages of high conductivity and less metal impurities than furnace black obtained by incomplete combustion of hydrocarbon oil in high-temperature gas.

However, acetylene black, which is a raw material, must be produced by pyrolysis of hydrocarbons or by a carbide method in which water acts on calcium carbide (carbide). There is a technical problem that it is difficult to simply and inexpensively produce an electrode material for a lithium ion secondary battery.

On the other hand, furnace black, which is commonly used as carbon black, contains a large amount of metal impurities derived from raw material oil, and therefore, when used as a conductive material, it tends to cause deterioration of battery performance.

Therefore, the present invention provides an aqueous dispersion of a conductive carbon black raw material that can easily and inexpensively produce a conductive material that has a reduced content of polyvalent metal ions and can exhibit excellent conductivity, and such a conductive carbon black raw material. It is an object of the present invention to provide a method for producing an aqueous dispersion of No. 1, a conductive carbon black powder, a method for producing a conductive carbon black powder, and a method for producing a positive electrode material for a lithium ion secondary battery.

Under such circumstances, the present inventors have made extensive studies and found that the nitrogen adsorption specific surface area N ₂ SA is 100 to 1500 m ² /g, and the value obtained by subtracting the statistical thickness specific surface area STSA from the nitrogen adsorption specific surface area N ₂ SA is 50 to 200 m ² /g, the DBP oil absorption is 100 to 500 ml/100 g, the average particle diameter is 100 to 500 nm, and the polyvalent metal content concentration after heat treatment is 10 to 100 ppm by mass. We have found that the above technical problems can be solved by an aqueous dispersion of a conductive carbon black raw material containing oxidized carbon black having a specific resistance of 0.05 to 0.23 Ω·cm, and based on this finding, we have completed the present invention. Completed.

That is, one embodiment of the present invention is
(1) a nitrogen adsorption specific surface area N ₂ SA of 200 to 300 m ² /g;
a value obtained by subtracting the statistical thickness specific surface area STSA from the nitrogen adsorption specific surface area N ₂ SA is 50 to 150 m ² /g;
DBP oil absorption of 100-500ml/100g,
An average particle size of 100 to 500 nm,
The polyvalent metal content concentration is 10 to 100 mass ppm,
An aqueous dispersion of a carbon black conductive material raw material, characterized by containing oxidized carbon black having a compression electrical resistivity of 0.05 to 0.23 Ω cm after heat treatment,
(2) Nitrogen adsorption specific surface area N ₂ SA is 200 to 300 m ² /g, the value obtained by subtracting the statistical thickness specific surface area STSA from the nitrogen adsorption specific surface area N ₂ SA is 50 to 150 m ² /g, DBP oil absorption is 100 to 500 ml/100 g, the average particle size is 100 to 500 nm, and an aqueous slurry of oxidized carbon black having one or more anionic functional groups on the surface,
An alkali metal hydroxide is mixed in the presence of one or more selected from a water-soluble chelating agent or a salt thereof and neutralized by heating, or an alkali metal hydroxide is mixed and neutralized by heating, and then a water-soluble chelating agent or its salt is added. A neutralization step of mixing one or more selected from salts;
A method for producing an aqueous dispersion of a carbon black conductive material raw material, characterized in that a separation and removal step of separating and removing a polyvalent metal ion chelate complex using a separation membrane is performed from the mixed solution obtained in the neutralization step,
(3) The aqueous dispersion of carbon black conductive material raw material according to (2) above, wherein in the neutralization step, the alkali metal hydroxide is mixed with the aqueous slurry of the oxidized carbon black so that the pH is 6 to 12. manufacturing method of
(4) The method for producing an aqueous dispersion of carbon black conductive material raw material according to (2) or (3) above, wherein the water-soluble chelating agent is an aminocarboxylic acid or a salt thereof;
(5) The oxidized carbon black having one or more anionic functional groups on its surface is one selected from water-soluble chelating agents or salts thereof under conditions of pH 2 to pH 4 after oxidizing the carbon black by a liquid phase method. The method for producing an aqueous dispersion of carbon black conductive material raw material according to any one of the above (2) to (4), which is obtained by mixing with the above and then preliminarily separating polyvalent metal ions using a separation membrane;
(6) The aqueous dispersion of carbon black conductive material raw material according to any one of (2) to (5) above, wherein the separation membrane is an ultrafiltration membrane (UF), a reverse osmosis membrane (RO) or an electrodialysis membrane. manufacturing method of
(7 ) A method for producing a conductive carbon black powder, which comprises heat-treating an aqueous dispersion of the conductive carbon black raw material according to (1) above.
( 8 ) Nitrogen adsorption specific surface area N ₂ SA is 200 to 300 m ² /g, the value obtained by subtracting the statistical thickness specific surface area STSA from the nitrogen adsorption specific surface area N ₂ SA is 50 to 150 m ² /g, DBP oil absorption is 100 to 500 ml/100 g, the average particle size is 100 to 500 nm, and an aqueous slurry of oxidized carbon black having one or more anionic functional groups on the surface,
An alkali metal hydroxide is mixed in the presence of one or more selected from a water-soluble chelating agent or a salt thereof and neutralized by heating, or an alkali metal hydroxide is mixed and neutralized by heating, and then a water-soluble chelating agent or its salt is added. A neutralization step of mixing one or more selected from salts;
An aqueous dispersion of the conductive carbon black raw material is prepared by subjecting the mixture obtained in the neutralization step to a separation and removal step of separating and removing the polyvalent metal ion chelate complex using a separation membrane, and then,
A method for producing conductive carbon black powder, characterized by subjecting the resulting aqueous dispersion of conductive carbon black raw material to a heat treatment to remove an anionic functional group of the oxidized carbon black.
( 9 ) The method for producing conductive carbon black powder according to ( 7 ) or ( 8 ) above, wherein the aqueous dispersion of conductive carbon black raw material is heat-treated at 500 to 600 ° C.,
( 10 ) The aqueous dispersion of the raw material for the carbon black conductive material according to (1) above, or the aqueous dispersion of the raw material for the carbon black conductive material obtained by the production method according to any one of (2) to (6) above. or the conductive carbon black powder obtained by the production method according to any one of ( 7 ) to ( 9 ) above,
mixed with at least an electrode active material and a binder;
Disclosed is a method for producing a positive electrode material for a lithium ion secondary battery, characterized by applying the material to an electrode substrate and drying the material.

According to the present invention, an aqueous dispersion of a conductive carbon black raw material that can easily and inexpensively produce a conductive material that has a reduced content of polyvalent metal ions and can exhibit excellent conductivity, and such a conductive carbon black raw material. It is possible to provide a method for producing an aqueous dispersion of, conductive carbon black powder, a method for producing conductive carbon black powder, and a method for producing a positive electrode material for a lithium ion secondary battery.

<Aqueous dispersion of conductive carbon black raw material>
First, the aqueous dispersion of conductive carbon black raw material according to the present invention will be described.
The aqueous dispersion of the conductive carbon black raw material according to the present invention is
Nitrogen adsorption specific surface area N ₂ SA is 100 to 1500 m ² /g,
The value obtained by subtracting the statistical thickness specific surface area STSA from the nitrogen adsorption specific surface area N ₂ SA is 50 to 200 m ² /g,
DBP oil absorption of 100-500ml/100g,
An average particle size of 100 to 500 nm,
The polyvalent metal content concentration is 10 to 100 mass ppm,
It is characterized by containing oxidized carbon black having a compressive electrical resistivity of 0.05 to 0.23 Ω·cm after heat treatment.

The oxidized carbon black contained in the aqueous dispersion of the conductive carbon black raw material according to the present invention has a nitrogen adsorption specific surface area N ₂ SA of 100 to 1500 m from the viewpoint of increasing the number of particles per unit weight to obtain conductivity. ² /g, preferably 100 to 500 m ² /g from the viewpoint of suppressing viscosity increase during preparation of the aqueous dispersion, and 200 m 2 /g from the viewpoint of achieving both good conductivity and suppression of viscosity increase. More preferred is ~300 m ² /g.

In the aqueous dispersion of the conductive carbon black raw material 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 within the above range, so that it can be obtained by heat treatment. The conductive carbon black to be obtained also tends to have a similar nitrogen adsorption specific surface area N ₂ SA, and the number of particles per unit weight can be easily increased, so that the conductivity can be easily improved.

The nitrogen adsorption specific surface area N ₂ SA of the oxidized carbon black contained in the aqueous dispersion of the conductive carbon black raw material was determined according to JIS K 6217-2 using a fully automatic surface area measuring device (Gemini 2375 manufactured by Shimadzu Corporation). "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 the conductive carbon black raw material according to the present invention has pores on the surface to increase the number of particles per unit weight and obtain conductivity. The value obtained by subtracting the statistical thickness specific surface area (STSA) from the N ₂ SA is 50 to ^{200 m 2 /} g. Some is preferable, and from the viewpoint of achieving both the above-mentioned good conductivity and suppression of viscosity increase, those of 80 to 150 m ² /g are more preferable.

The statistical thickness specific surface area of the oxidized carbon black contained in the aqueous dispersion of the conductive carbon black raw material was determined according to JIS K 6217-7 using a fully automatic surface area measuring device (Gemini 2375 manufactured by Shimadzu Corporation). The value measured according to the prescribed "carbon black for rubber-basic properties-Part 7, rubber compound-multipoint method nitrogen specific surface area ( _N SA) and statistical thickness specific surface area (STSA)" means.

The oxidized carbon black contained in the aqueous dispersion of the conductive carbon black raw material according to the present invention has a DBP (dibutyl phthalate) oil absorption of 100 to 500 ml from the viewpoint of developing the structure structure of the carbon black and forming a conductive path. /100 g, preferably 100 to 300 ml/100 g from the viewpoint of suppressing the viscosity increase during preparation of the aqueous dispersion, and 150 to 250 ml from the viewpoint of achieving both the formation of the conductive path and the suppression of the viscosity increase. /100 g is more preferred.

In the aqueous dispersion of the conductive carbon black raw material according to the present invention, the DBP oil absorption of the oxidized carbon black contained in the aqueous dispersion is within the above range, so that the conductive carbon obtained by heat treatment Black also tends to have a similar DBP oil absorption, and conductive paths are easily formed, so that the conductivity can be easily improved.

The DBP oil absorption of the oxidized carbon black contained in the aqueous dispersion of the conductive carbon black raw material 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 aqueous dispersion of the conductive carbon black raw material according to the present invention has an average particle size of 100 to 500 nm from the viewpoint of obtaining good dispersibility, and from the viewpoint of further improving dispersibility. from 150 to 400 nm, and more preferably from 150 to 250 nm from the viewpoint of promoting the effect of removing impurity metals by a water-soluble chelating agent.

In the aqueous dispersion of the conductive carbon black raw material 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 conductive carbon obtained by heat treatment Agglomeration of black is also reduced, and the number of particles per unit weight can be easily increased, thereby easily improving electrical conductivity.

The average particle size of the oxidized carbon black contained in the aqueous dispersion of the conductive carbon black raw material 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).
When the oxidized carbon black is prepared using furnace black as a raw material, the obtained oxidized carbon black has the nitrogen adsorption specific surface area N ₂ SA, the statistical thickness specific surface area STSA, the DBP oil absorption and the average particle size. Therefore, according to the aqueous dispersion of conductive carbon black raw material according to the present invention, conductive carbon black can be obtained simply and inexpensively by heat-treating it.

The amount of acidic hydroxyl groups of the oxidized carbon black contained in the aqueous dispersion of the conductive carbon black raw material according to the present invention is preferably 300 μmol/g to 1200 μmol/g from the viewpoint of sufficiently oxidizing and obtaining dispersibility, and is more uniform. It is more preferably 500 μmol/g to 1000 μmol/g from the viewpoint of obtaining good dispersibility, and further preferably 800 μmol/g to 1000 μmol/g from the viewpoint of promoting the elution of metal impurities. The amount of acidic hydroxyl groups in oxidized carbon black contained in the aqueous dispersion of conductive carbon black raw material according to the present invention means the sum of the amount of carboxyl groups ( ^--COO- ) and the amount of hydroxyl groups (--O-- ⁾ in 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 obtained 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 0.1 mol/l NaOH 25 ml was titrated with 0.1 mol/l HCl V _Sample [ml]: Sample 25 ml was titrated 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 aqueous dispersion of conductive carbon black raw material 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.

The oxidized carbon black contained in the aqueous dispersion of the conductive carbon black raw material according to the present invention has a polyvalent metal content concentration of 10 to 100 from the viewpoint of suppressing metal elution into the system when used for the purpose. It is mass ppm, preferably 10 to 80 mass ppm, more preferably 10 to 50 mass ppm.

In the aqueous dispersion of the conductive carbon black raw material according to the present invention, the polyvalent metal content concentration after heat treatment of the oxidized carbon black contained in the aqueous dispersion is within the above range, so that the aqueous dispersion is Conductive carbon black obtained by heat treatment also has a similar concentration of polyvalent metals, and can easily suppress deterioration of battery performance when used as a positive electrode material for lithium secondary batteries.

The polyvalent metal content concentration of the oxidized carbon black contained in the aqueous dispersion of the conductive carbon black raw material means a value measured by a method based on JIS K 0133. An inductively coupled plasma emission spectrometer (ICPS-7510, manufactured by Shimadzu Corporation) is used as an apparatus to measure the content of each metal component. The metal components to be measured are Mg, Al, Ca, Cr, Mn, Fe, Ni, Cu, Zn, and Pb.

The oxidized carbon black contained in the aqueous dispersion of the conductive carbon black raw material according to the present invention has a compressive electrical specific resistance of 0.05 to 0.23 Ω after heat treatment from the viewpoint of functioning as a conductive material in the positive electrode material. · cm, more preferably 0.05 to 0.20 Ω·cm, more preferably 0.05 to 0.10 Ω·cm from the viewpoint of obtaining conductivity even with a small amount of addition.

In the aqueous dispersion of the conductive carbon black raw material according to the present invention, the compression electrical resistivity after heat treatment of the oxidized carbon black contained in the aqueous dispersion is within the above range, so that the aqueous dispersion is heated. The conductive carbon black obtained by the treatment also has a similar compression electrical resistivity, and can easily suppress deterioration of battery performance when used as a positive electrode material for a lithium secondary battery.

The compressive electrical resistivity after heat treatment of the oxidized carbon black contained in the aqueous dispersion of the conductive carbon black raw material means a value measured by a method conforming to JIS K 1469-2003. A load cell Ezgraph manufactured by Shimadzu Corporation was used as an apparatus.

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

The acidic carbon black contained in the aqueous dispersion according to the present invention is used as a conductive carbon black raw material, and by separately removing the anionic functional group (acidic functional group) on the surface of the acidic carbon black, the conductivity having the desired characteristics is obtained. Carbon black can be obtained.

According to the present invention, it is possible to provide an aqueous dispersion of a conductive carbon black raw material that can easily and inexpensively produce a conductive material that has a reduced polyvalent metal ion content and exhibits excellent conductivity.

<Method for Producing Aqueous Dispersion of Conductive Carbon Black Raw Material>
Next, a method for producing an aqueous dispersion of conductive carbon black raw material according to the present invention will be described.
The method for producing an aqueous dispersion of conductive carbon black raw material according to the present invention is a method for producing an aqueous dispersion of conductive carbon black raw material according to the present invention, comprising:
the nitrogen adsorption specific surface area N ₂ SA is 100 to 1500 m ² /g, the value obtained by subtracting the statistical thickness specific surface area STSA from the nitrogen adsorption specific surface area N ₂ SA is 50 to 200 m ² /g,
For an aqueous slurry of oxidized carbon black having a DBP oil absorption of 100 to 500 ml/100 g, an average particle size of 100 to 500 nm, and having one or more anionic functional groups on the surface,
An alkali metal hydroxide is mixed in the presence of one or more selected from a water-soluble chelating agent or a salt thereof and neutralized by heating, or an alkali metal hydroxide is mixed and neutralized by heating, and then a water-soluble chelating agent or its salt is added. A neutralization step of mixing one or more selected from salts;
It is characterized by performing a separation removal step of separating and removing the polyvalent metal ion chelate complex from the mixed solution obtained in the neutralization step using a separation membrane.

In the method for producing an aqueous dispersion of conductive carbon black raw material according to the present invention, the aqueous slurry of oxidized carbon black has a nitrogen adsorption specific surface area N ₂ SA of 100 to 1500 m ² /g, and a nitrogen adsorption specific surface area N ₂ SA The value obtained by subtracting the statistical thickness specific surface area STSA is 50 to 200 m ² /g, the DBP oil absorption is 100 to 500 ml/100 g, the average particle size is 100 to 500 nm, and one or more anionic functional groups are formed on the surface. An aqueous slurry of oxidized carbon black is used.

In the method for producing an aqueous dispersion of a conductive carbon black raw material according to the present invention, the oxidized carbon black contained in the aqueous slurry has a nitrogen adsorption specific surface area N from the viewpoint of increasing the number of particles per unit weight and obtaining conductivity. ₂ SA is 100 to 1500 m ² /g, preferably 100 to 500 m ² /g from the viewpoint of suppressing the viscosity increase during preparation of the aqueous dispersion, and the above-mentioned good conductivity and viscosity increase. From the viewpoint of both suppression, it is more preferably 200 to 300 m ² /g.

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".

The oxidized carbon black contained in the aqueous dispersion of the conductive carbon black raw material according to the present invention has pores on the surface to increase the number of particles per unit weight and obtain conductivity. The value obtained by subtracting the statistical thickness specific surface area (STSA) from the N ₂ SA is 50 to ^{200 m 2 /} g. Some is preferable, and from the viewpoint of achieving both the above-mentioned good conductivity and suppression of viscosity increase, those of 80 to 150 m ² /g are more preferable.

The statistical thickness specific surface area of the oxidized carbon black contained in the aqueous dispersion of the conductive carbon black raw material was determined according to JIS K 6217-7 using a fully automatic surface area measuring device (Gemini 2375 manufactured by Shimadzu Corporation). The value measured according to the prescribed "carbon black for rubber-basic properties-Part 7, rubber compound-multipoint method nitrogen specific surface area ( _N SA) and statistical thickness specific surface area (STSA)" means.

In the method for producing an aqueous dispersion of a conductive carbon black raw material according to the present invention, the oxidized carbon black contained in the aqueous slurry is DBP (dibutyl phthalate) from the viewpoint of developing a carbon black structure and forming a conductive path. ) It has an oil absorption of 100 to 500 ml/100 g, preferably 100 to 300 ml/100 g from the viewpoint of suppressing viscosity increase during preparation of the aqueous dispersion, and suppression of formation of the conductive path and viscosity increase. 150 to 250 ml/100 g is more preferable from the viewpoint of satisfying both the above.

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, Determination of DBP absorption". means

In the method for producing an aqueous dispersion of conductive carbon black raw material according to the present invention, the oxidized carbon black contained in the aqueous slurry has an average particle size of 100 to 500 nm from the viewpoint of obtaining good dispersibility. Further, from the viewpoint of improving dispersibility, it is preferably 150 to 400 nm, and from the viewpoint of promoting the effect of removing impurity metals by a water-soluble chelating agent, it is more preferably 150 to 250 nm.

The average particle size of the oxidized carbon black contained in the aqueous slurry was 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 was 50%. Means particle size (volume average particle size D50).

In the method for producing an aqueous dispersion of conductive carbon black raw material according to the present invention, the nitrogen adsorption specific surface area N ₂ SA, DBP oil absorption, and average particle size of 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 and the separation and removal step, which will be described later, easily has the same nitrogen adsorption specific surface area N ₂ SA, statistical thickness specific surface area STSA, DBP oil absorption and average particle size. Become.

In the method for producing an aqueous dispersion of conductive carbon black raw material 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 as a raw material for oxidized carbon black preferably has a nitrogen adsorption specific surface area N ₂ SA of 100 to 1500 m ² /g from the viewpoint of increasing the number of particles per unit weight and obtaining conductivity. It is more preferably 100 to 500 m ² /g from the viewpoint of suppressing viscosity increase during preparation of the aqueous dispersion, and 200 to 300 m ² /g from the viewpoint of achieving both good conductivity and suppression of viscosity increase. is more preferred.
In addition, from the viewpoint of obtaining conductivity by increasing the number of particles per unit weight by having pores on the surface of carbon black, which is a raw material for oxidized carbon black, the statistical thickness is determined from the nitrogen adsorption specific surface area N ₂ SA. The value obtained by subtracting the specific surface area (STSA) is 50 to 200 m ² /g, and from the viewpoint of suppressing the viscosity increase during preparation of the aqueous dispersion, the value is preferably 50 to 150 m ² /g. From the viewpoint of achieving both good conductivity and suppression of viscosity increase, it is more preferably 80 to 150 m ² /g.
In addition, from the viewpoint of developing the structural structure of carbon black and forming a conductive path, the DBP (Dibutyl phthalate) oil absorption is 100 to 500 ml / 100 g, and suppresses the increase in viscosity during preparation of the aqueous dispersion. 100 to 300 ml/100 g is preferable from the viewpoint, and 150 to 250 ml/100 g is more preferable from the viewpoint of achieving both the formation of the conductive path and the suppression of viscosity increase.

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 ", STSA of carbon black is defined in JIS K 6217-7 "Carbon black for rubber - basic properties - Part 7, rubber compound - multipoint method nitrogen specific surface area (N ₂ SA) and Statistical Thickness Specific Surface Area (STSA)” means the value measured according to the DBP absorption amount of carbon black is defined in JIS K 6217-4 “Carbon black for rubber - basic properties - Part 4, Determination of DBP Absorption" means the value measured according to

In addition, the average particle diameter of carbon black, which is the raw material of oxidized carbon black, is preferably 20 to 100 nm from the viewpoint of increasing the number of particles per unit weight to obtain conductivity, and from the viewpoint of further improving the density. , 20 to 50 nm.
In addition, in this application document, the average particle diameter of carbon black means the numerical value measured by the method based on ASTM number D3846.

Specific examples of 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（以上、三菱化学（株）製）、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 (manufactured by Aditya Birla Group Columbian Chemicals Company), ENASCO (registered trademark) 150G, ENASCO (registered trademark) 210G, ENASCO (registered trademark) 250G, ENASCO (registered trademark) 260G, ENASCO (registered trademark) 350G (manufactured by Imerys Graphite & Carbon), VULCAN XC 72, LITX (registered trademark) 200, LITX (registered trademark) 300, LITX (registered trademark) 50 (manufactured by Cabot) ), Ketjenblack EC300J, and Ketjenblack EC600JD (manufactured by Lion Specialty Chemicals).

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.

The oxidation treatment with an oxidizing agent can be performed by known methods such as a liquid phase method and a vapor 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 its surface can be obtained by adding carbon black to a dispersion 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 carbon black surface, 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 ₄ ^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 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 aqueous slurry of oxidized carbon black having one or more anionic functional groups on the surface obtained by the above oxidation treatment is subjected to oxidation treatment of carbon black by a liquid phase method, and then subjected to pH 2 to pH 4 conditions with a water-soluble chelating agent. Alternatively, it is preferably mixed with one or more selected from salts thereof, and then preliminarily separated from polyvalent metal ions using a separation membrane.

After the oxidized carbon black is produced by the liquid phase method, if the reduced salts (salts such as polyvalent metal ions) in the slurry produced by the liquid phase oxidation are removed by preliminary separation, the neutralization reaction process described later can be carried out smoothly. and can proceed efficiently. The reduction salt can be removed using a separation membrane such as an ultrafiltration membrane (UF), a reverse osmosis membrane (RO), an electrodialysis membrane, or the like. The extent to which the reducing salt is removed is desirably purified so that the electrical conductivity is less than 5 mS/cm when the carbon black dispersion concentration is 20% by mass, for example. Insufficient separation and purification causes deterioration of water dispersibility and dispersion stability, increase in viscosity of the dispersion, and corrosion of equipment due to the dispersion.

The removal treatment of the reducing salt is carried out by oxidizing the carbon black by a liquid phase method, and then preferably at pH 2 to pH 4, more preferably pH 2.1 to pH 3.9, further preferably pH 2.3 to pH 3.8. It is preferable to carry out the treatment after mixing the treatment liquid with one or more selected from water-soluble chelating agents and salts thereof. By forming one or more anionic functional groups (acidic functional groups) selected from -COO-, -SO ^3- and -PO ₄ ^2- groups on the carbon black surface, the pH in the liquid phase is ^adjusted to the above range. The range can be easily maintained and controlled. By controlling the pH within the above range, complexes of polyvalent metal ions and water-soluble chelating agents can be easily formed.

Although the water-soluble chelating agent is not particularly limited, it is preferably an aminocarboxylic acid or a salt thereof.

Examples of the above aminocarboxylic acids or salts thereof include ethylenediaminetetraacetic acid [EDTA], nitrilotriacetic acid, diethylenetriaminepentaacetic acid [DTPA], hydroxyethylethylenediaminetriacetic acid, triethylenetetraminehexaacetic acid [TTHA], 1,3-propanediamine. Tetraacetic acid, 1,3-diamino-2-hydroxypropanetetraacetic acid [CyDTA], hydroxyethyleneiminodiacetic acid, dihydroxyethylglycine, glycol ether diamine tetraacetic acid, ethylenediaminediorthohydroxyphenylacetic acid [EDDHA], ethylenediamine-N,N '-bis[(2-hydroxy-5-methylphenyl)acetic acid] [EDDHMA], N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-2acetic acid [HBED], N,N'- bis(2-hydroxy-5-methylbenzyl)ethylenediamine-N,N'-2acetic acid [HMBED], dicarboxymethylglutamic acid, ethylenediamine-N,N'-disuccinic acid, ethylenediaminetetrakis(methylenephosphonic acid) [EDTPO], nitrilotris(methylenephosphonic acid) [NTPO], propylenediaminetetra(methylenephosphonic acid) [PDTMP], 1-hydroxyethane-1,1-diphosphonic acid [HEDP], or one or more selected from salts thereof. can. Ethylenediaminetetraacetate is preferable as the aminocarboxylic acid or its salt, and specific examples of the ethylenediaminetetraacetate include sodium ethylenediaminetetraacetate and potassium ethylenediaminetetraacetate.

The contact amount of the water-soluble chelating agent or its salt with the oxidized carbon black is 0.1 part by mass or more with respect to 100 parts by mass of the solid content of the oxidized carbon black, from the viewpoint of forming a complex between the polyvalent metal ion and the water-soluble chelating agent. From the viewpoint of forming a complex more efficiently, it is more preferably 0.5 parts by mass or more, and even more preferably 1.0 parts by mass or more. On the other hand, the contact amount of the water-soluble chelating agent or its salt with the oxidized carbon black is 15 parts by mass or less with respect to 100 parts by mass of the solid content of oxidized carbon black, since a complex is not formed when the addition amount is more than the necessary and sufficient amount. From the viewpoint of economy, it is more preferably 12.5 parts by mass or less, and even more preferably 10 parts by mass or less.

When the dispersion obtained by oxidizing carbon black by a liquid phase method is brought into contact with the water-soluble chelating agent or its salt, a method of mixing the water-soluble chelating agent or its salt and stirring is mentioned. can be done.

When the dispersion is brought into contact with a water-soluble chelating agent or a salt thereof, the contact temperature is preferably 40°C or higher, more preferably 50°C, and 60°C from the viewpoint of promoting complex formation. is more preferred. Also, the contact time is preferably 30 minutes or longer, more preferably 1 hour or longer, and even more preferably 3 hours or longer.

By mixing the above dispersion with a water-soluble chelating agent or a salt thereof at pH 2 to 4, polyvalent metal ions, especially Fe ^{3 +} , Al ³⁺ , Cr ^{3 +} etc., containing the water-soluble chelating agent in the liquid phase. to form a polyvalent metal ion chelate complex, and this polyvalent metal ion chelate complex can also be preliminarily separated during the treatment for removing the reduced salt, so the polyvalent metal ion in the liquid phase content can be easily reduced.

The oxidized carbon black slurry obtained by the removal treatment (purification treatment) of the reducing salt described above has acidic functional groups such as —COO ^— groups, —SO ₃ ^— groups, and —PO ₄ ^2- groups formed on the surface of the carbon black. The pH is maintained at 2-4 even after purification. Therefore, even if a chelate complex with polyvalent metal ions, mainly trivalent metal ions, remains in the slurry after the reducing salt removal treatment, the water-soluble chelating agent and the polyvalent metal ions are chelate bond is maintained, and capture of polyvalent metal ions on the carbon black surface in the subsequent neutralization step can be suppressed.

The oxidized carbon black thus obtained is preferably self-dispersible 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 conductive carbon black raw material 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. Further, the solid content concentration of the oxidized carbon black in the aqueous slurry is preferably 1.0 to 20.0% by mass, more preferably 1.0 to 15.0% by mass, and 1.0% by mass. More preferably, it is up to 10.0% by mass.

In the method for producing an aqueous dispersion of conductive carbon black raw material according to the present invention, one selected from a water-soluble chelating agent or a salt thereof is added to an aqueous slurry of oxidized carbon black having one or more anionic functional groups on its surface. Neutralization by mixing alkali metal hydroxide in the presence of the above and neutralizing by heating, or by mixing alkali metal hydroxide and neutralizing by heating and then mixing one or more selected from water-soluble chelating agents or salts thereof. Apply the process.

As the water-soluble chelating agent, one or more selected from those that can be used in the preliminary separation described above can be used. The contact amount of the water-soluble chelating agent or its salt with respect to 100 parts by mass of the solid content of oxidized carbon black is also the same as the contact amount described above.

In the neutralization step,
(i) After mixing one or more water-soluble chelating agents or salts thereof with an aqueous slurry of oxidized carbon black having one or more anionic functional groups on the surface, an alkali metal hydroxide is mixed and heated. You can process the sum,
(ii) An aqueous slurry of oxidized carbon black having one or more anionic functional groups on the surface thereof is heated and neutralized by simultaneously mixing one or more selected from water-soluble chelating agents or salts thereof and an alkali metal hydroxide. You may
(iii) An aqueous slurry of oxidized carbon black having one or more anionic functional groups on its surface is mixed with an alkali metal hydroxide and heat-neutralized, and then one or more selected from water-soluble chelating agents or salts thereof. may be mixed.

In the neutralization step, the mixing timing of the aqueous slurry of oxidized carbon black having one or more anionic functional groups on its surface and one or more selected from water-soluble chelating agents or salts thereof is the above (i) to (iii). The metal impurity components contained in the oxidized carbon black are gradually eluted and exchanged with alkali metals by the heat neutralization treatment in the neutralization step.

As the alkali metal hydroxide used in the neutralization step, one or more selected from sodium hydroxide, lithium hydroxide and potassium hydroxide can be used.

The amount of alkali metal hydroxide to be used in the neutralization step can be appropriately determined according to the oxidized carbon black to be neutralized. It is preferable to mix an alkali metal, more preferably to mix an alkali metal hydroxide to pH 7 to pH 12, and more preferably to mix an alkali metal hydroxide to pH 8 to pH 12.

An alkali metal hydroxide is mixed with an aqueous slurry of oxidized carbon black to a pH of 6 to 12 and neutralized by heating to remove polyvalent metal ions, particularly divalent metal ions ( divalent iron ions, zinc ions, nickel ions, magnesium ions, calcium ions, etc.) are eluted and exchanged with alkali hydroxide, and the eluted polyvalent metal ions form polyvalent metal ion chelate complexes with water-soluble chelating agents. Since it becomes water-soluble and dissolves in the slurry, it can be easily removed by membrane separation.

The alkali metal 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. organic solvents can be used, but water, especially deionized water, is preferred from the viewpoint of economy and safety.

In the neutralization step, alkali hydroxide is mixed with an aqueous slurry of oxidized carbon black having one or more anionic functional groups on its surface, and the mixture is neutralized by heating. 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, an alkali hydroxide and a water-soluble chelating agent are mixed and maintained for a period of preferably 30 minutes to 12 hours, 1 to 8 hours is more preferred, and 2 to 5 hours is even more preferred.

Polyvalent metal ions captured on the surface of oxidized carbon black by mixing an aqueous slurry of oxidized carbon black with an alkali metal hydroxide so as to have a pH of 6 to 12 and performing a neutralization treatment at the above temperature and time; In particular, divalent metal ions (divalent iron ions, zinc ions, nickel ions, magnesium ions, calcium ions, etc.) are exchanged with alkali metal ions, and the polyvalent metal ions exchanged with these alkali metal ions become water-soluble chelating agents. In order to form a polyvalent metal ion chelate complex, it can be easily removed by the subsequent step of separation and removal.

In the method for producing an aqueous dispersion of conductive carbon black raw material according to the present invention, after the neutralization step is performed, the polyvalent metal ion chelate complex is separated from the mixed liquid obtained in the neutralization step using a separation membrane. A separation removal step is performed to remove.

The separation membrane used in the separation and removal step is not particularly limited, but is preferably an ultrafiltration membrane (UF), a reverse osmosis membrane (RO) or an electrodialysis membrane. The above separation membrane can separate and remove polyvalent metal ions captured on the surface of oxidized carbon black as a polyvalent metal ion chelate complex, and at the same time, can remove residual salts due to excess alkali hydroxide out of the system. In addition, it is also effective in suppressing reaggregation of oxidized carbon black particles.

The separation treatment in the separation and removal step may be performed to such an extent that the polyvalent metal ion chelate complex and the residual salt due to excess alkali hydroxide can be sufficiently removed from the system. When it is % by mass, it is preferable to carry out until the electrical conductivity of the aqueous dispersion becomes 5 mS/cm or less, more preferably 2 mS/cm or less.

In the method for producing an aqueous dispersion of a conductive carbon black raw material according to the present invention, the preferred ranges of the acidic hydroxyl group content, carboxyl group equivalent weight and hydroxyl group content of the oxidized carbon black in the resulting aqueous dispersion are as described above. The preferred ranges of the acidic hydroxyl group amount, carboxyl group equivalent weight and hydroxyl group amount of the oxidized carbon black contained in the aqueous dispersion of the conductive carbon black raw material of the present invention are the same as those described above.

In the method for producing an aqueous dispersion of conductive carbon black raw material according to the present invention, the amount of —SO ₃ H groups and —PO ₄ H ₂ groups of oxidized carbon black in the resulting aqueous dispersion is not particularly limited, and , and the measuring method thereof is the same as that described in the explanation of the oxidized carbon black contained in the aqueous dispersion of the conductive carbon black raw material of the present invention.

In the method for producing an aqueous dispersion of a conductive carbon black raw material 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 in the obtained oxidized carbon black are also described above. It is the same as the preferred ranges of 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 the conductive carbon black raw material of the present invention.

In the method for producing an aqueous dispersion of conductive carbon black raw material according to the present invention, the preferred ranges of polyvalent metal content concentration and compression electrical resistivity in the obtained heat-treated oxidized carbon black are also described above. The preferred range of the polyvalent metal content concentration of the oxidized carbon black contained in the aqueous dispersion of the conductive carbon black raw material of the present invention and the carbon oxide contained in the above aqueous dispersion of the conductive carbon black raw material of the present invention This is the same as the preferred range of compressive electrical resistivity after heat treatment for black.

The acidic carbon black in the aqueous dispersion obtained by the production method according to the present invention serves as a conductive carbon black raw material, and the desired properties are obtained by separately removing the anionic functional group (acidic functional group) on the surface of the acidic carbon black. It is possible to obtain conductive carbon black having

According to the present invention, there is provided a method for producing an aqueous dispersion of a conductive carbon black raw material, which can easily and inexpensively produce a conductive material having a reduced content of polyvalent metal ions and exhibiting excellent conductivity. can be done.

<Conductive carbon black powder>
Next, the conductive carbon black powder according to the present invention will be explained.
The conductive carbon black powder according to the present invention is
Nitrogen adsorption specific surface area N ₂ SA is 100 to 1500 m ² /g,
The value obtained by subtracting the statistical thickness specific surface area STSA from the nitrogen adsorption specific surface area N ₂ SA is 50 to 200 m ² /g,
DBP oil absorption of 100-500ml/100g,
an average particle size of 20 to 100 nm,
polyvalent metal content concentration is 10 to 100 mass ppm,
Compressive electrical resistivity is 0.05 to 0.23 Ω cm
It is characterized by being

The conductive carbon black powder according to the present invention has a nitrogen adsorption specific surface area N ₂ SA of 100 to 1500 m ² /g from the viewpoint of increasing the number of particles per unit weight to obtain conductivity, It is preferably 100 to 500 m ² /g from the viewpoint of suppressing viscosity increase during preparation of the aqueous dispersion, and 200 to 300 m ² /g from the viewpoint of achieving both good conductivity and suppression of viscosity increase. more preferred.

In the conductive carbon black powder according to the present invention, when the nitrogen adsorption specific surface area N ₂ SA is within the above range, the number of particles per unit weight can be easily increased, and the conductivity can be easily improved. .

The nitrogen adsorption specific surface area N ₂ SA of the conductive carbon black powder was measured using a fully automatic surface area measuring device (Gemini 2375 manufactured by Shimadzu Corporation), as defined in JIS K 6217-2 "Carbon black for rubber - Basic properties - Part 2, Determination of specific surface area - Nitrogen adsorption method, single point method".

_The conductive carbon black powder according to the present invention has pores on the surface, so that the number of particles per unit weight is increased and conductivity is obtained. The value obtained by subtracting the surface area (STSA) is 50 to 200 m ² /g, preferably 50 to 150 m ² /g from the viewpoint of suppressing the viscosity increase during preparation of the aqueous dispersion, and the above good conductivity. It is more preferably 80 to 150 m ² /g from the viewpoint of achieving both good properties and suppression of viscosity increase.

The statistical thickness specific surface area of the conductive carbon black powder was measured using a fully automatic surface area measuring device (Gemini 2375 manufactured by Shimadzu Corporation), as defined in JIS K 6217-7 "Carbon black for rubber - Basic Properties--Part 7, Rubber Compounds--Determination of Multipoint Nitrogen Specific Surface Area (N ₂ SA) and Statistical Thickness Specific Surface Area (STSA)".

The conductive carbon black powder according to the present invention has a DBP (Dibutyl phthalate) oil absorption of 100 to 500 ml / 100 g from the viewpoint of developing a carbon black structure and forming a conductive path. It is preferably 100 to 300 ml/100 g from the viewpoint of suppressing the viscosity increase during preparation of the dispersion, and more preferably 150 to 250 ml/100 g from the viewpoint of achieving both the formation of the conductive path and the suppression of the viscosity increase.

When the DBP oil absorption of the conductive carbon black powder according to the present invention is within the above range, conductive paths are easily formed and the conductivity can be easily improved.

The DBP oil absorption of the conductive carbon black powder means a value measured in accordance with JIS K 6217-4 "Carbon black for rubber - Basic properties - Part 4, Determination of DBP absorption". .

The conductive carbon black powder according to the present invention has an average particle diameter of 20 to 100 nm from the viewpoint of increasing the number of particles per unit weight to obtain conductivity, and from the viewpoint of further improving the density. , preferably 20 to 80 nm, more preferably 20 to 50 nm.

When the average particle size of the conductive carbon black powder according to the present invention is within the above range, the number of particles per unit weight can be easily increased, and the conductivity can be easily improved.

In addition, the average particle size of the conductive carbon black powder means a numerical value measured by a method based on ASTM No. D3846.

The conductive carbon black powder according to the present invention has a polyvalent metal content concentration of 10 to 100 mass ppm from the viewpoint of suppressing metal elution into the system when used for the purpose. It is preferably up to 80 mass ppm, more preferably 10 to 50 mass ppm.

When the concentration of the polyvalent metal contained in the conductive carbon black powder according to the present invention is within the above range, deterioration in battery performance can be easily suppressed when used as a positive electrode material for lithium secondary batteries.

The polyvalent metal content concentration of the conductive carbon black powder means a value measured by a method conforming to JIS K 0133. An inductively coupled plasma emission spectrometer (ICPS-7510, manufactured by Shimadzu Corporation) is used as an apparatus to measure the content of each metal component. The metal components to be measured are Mg, Al, Ca, Cr, Mn, Fe, Ni, Cu, Zn, and Pb.

The conductive carbon black powder according to the present invention has a compressive electrical resistivity of 0.05 to 0.23 Ω cm from the viewpoint of functioning as a conductive material in the positive electrode material, and is conductive even when added in a small amount. From the viewpoint of obtaining properties, it is preferably 0.05 to 0.20 Ω·cm, more preferably 0.05 to 0.10 Ω·cm.

Since the conductive carbon black powder according to the present invention has a compressive electrical resistivity within the above range, deterioration of battery performance can be easily suppressed when used as a positive electrode material for a lithium secondary battery.

The compressive electrical resistivity of the conductive carbon black powder means a value measured by a method conforming to JIS K 1469-2003. A load cell Ezgraph manufactured by Shimadzu Corporation was used as an apparatus.

The amount of acidic hydroxyl groups in the conductive carbon black powder according to the present invention is preferably 50 μmol/g to 300 μmol/g, more preferably 50 μmol/g to 250 μmol/g, from the viewpoint of removal of surface anionic groups. is more preferable, and 50 μmol/g to 200 μmol/g is even more preferable. The amount of acidic hydroxyl groups in oxidized carbon black contained in the conductive carbon black powder according to the present invention means the sum of the amount of carboxyl groups ( ^--COO.sup.- ) and the amount of hydroxyl groups ( ^--O.sup.- ) in oxidized carbon black.

The amount of acidic hydroxyl groups in the conductive carbon black powder means the value obtained by the following measuring method.
(Sample preparation: acid washing and standard solution addition)
1.0 g of conductive carbon black powder is collected in a centrifuge tube, 5.0 g of 0.5 mol/l hydrochloric acid is added, shaken several times, and solid-liquid separated by 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 the resulting carbon black powder was collected in an Erlenmeyer flask, 25 ml of 0.1 mol / l NaOH was added to the Erlenmeyer flask, and then the Erlenmeyer was shaken using a shaker. Shake the flask for 4 hours. 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. Titration was performed with 1 mol/l HCl, and the dropwise amount of HCl required for neutralization was measured. The obtained measured value was substituted 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 0.1 mol/l NaOH 25 ml was titrated with 0.1 mol/l HCl V _Sample [ml]: Sample 25 ml was titrated 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 conductive carbon black in measurement sample Acid value [mmol/g] = (V _Blank −V _sample )×N _HCl /M _sample

The amounts of —SO ₃ H groups and —PO ₄ H ₂ groups in the conductive carbon black powder according to the present invention are not particularly limited.

The conductive carbon black powder according to the present invention can be suitably prepared by the method for producing the conductive carbon black powder according to the present invention described below.

ADVANTAGE OF THE INVENTION According to the present invention, it is possible to provide a conductive carbon black powder which is useful as a conductive material, which can exhibit excellent conductivity with a reduced content of polyvalent metal ions, and which can be produced inexpensively and easily. .

<Method for producing conductive carbon black powder>
Next, a method for producing conductive carbon black powder according to the present invention will be described.

The method for producing conductive carbon black powder according to the present invention (hereinafter referred to as powder production method 1 according to the present invention) is characterized by heat-treating an aqueous dispersion of the conductive carbon black raw material according to the present invention. and

The details of the aqueous dispersion of conductive carbon black raw material according to the present invention are as described above.

In order to obtain the conductive carbon black powder according to the present invention, when the aqueous dispersion of the conductive carbon black raw material according to the present invention is heat-treated, the heat treatment conditions include oxidized carbon black as the conductive carbon black raw material. There are no particular limitations as long as the conditions are such that the anionic functional group (acidic functional group) of is sufficiently removed.
As the heat treatment conditions, heat treatment at 500° C. to 600° C. in an inert atmosphere is preferable, and heat treatment at 500° C. to 550° C. is more preferable from the viewpoint of shortening the heating time.
The heat treatment time is preferably 30 to 600 minutes, more preferably 30 to 180 minutes, and even more preferably 60 to 120 minutes.
The type of gas used for the inert atmosphere is not particularly limited, and one or more selected from inert gases such as nitrogen gas, argon gas, and helium gas can be used.
Anionic functional groups (acidic functional groups) on the surface of acidic carbon black, which is a raw material of conductive carbon black, are suitably removed by the heat treatment, and conductive carbon black powder having desired properties can be obtained.

The method for producing a conductive carbon black powder according to the present invention (hereinafter referred to as powder production method 2 according to the present invention) has a nitrogen adsorption specific surface area N ₂ SA of 100 to 1500 m ² /g, a nitrogen adsorption specific surface area N ₂ A value obtained by subtracting the statistical thickness specific surface area STSA from SA is 50 to 200 m ² /g, the DBP oil absorption is 100 to 500 ml/100 g, the average particle size is 100 to 500 nm, and one or more anions are present on the surface For an aqueous slurry of oxidized carbon black having functional groups,
An alkali metal hydroxide is mixed in the presence of one or more selected from a water-soluble chelating agent or a salt thereof and neutralized by heating, or an alkali metal hydroxide is mixed and neutralized by heating, and then a water-soluble chelating agent or its salt is added. A neutralization step of mixing one or more selected from salts;
An aqueous dispersion of the conductive carbon black raw material is prepared by subjecting the mixture obtained in the neutralization step to a separation and removal step of separating and removing the polyvalent metal ion chelate complex using a separation membrane, and then,
The method is characterized by subjecting the resulting aqueous dispersion of the conductive carbon black raw material to a heat treatment to remove the anionic functional groups of the oxidized carbon black.

In the powder production method 2 according to the present invention, the contents up to the preparation of the aqueous dispersion of the conductive carbon black raw material by subjecting the aqueous slurry of oxidized carbon black to the neutralization step and the separation and removal step are included in the present invention. Since this method is common to the method for producing an aqueous dispersion of conductive carbon black raw material, the details thereof are the same as those described above.

In the powder production method 2 according to the present invention, an aqueous dispersion of conductive carbon black raw material obtained by subjecting an aqueous slurry of oxidized carbon black to a neutralization step and a separation and removal step is heat-treated to perform the oxidation. A functional group removal step is performed to remove the anionic functional groups of the carbon black.

In the powder production method 2 according to the present invention, the heat treatment conditions in the functional group removal step are conditions that can sufficiently remove the anionic functional group (acidic functional group) of the oxidized carbon black that is the raw material of the conductive carbon black. There is no particular limitation if any.
As the heat treatment conditions, heat treatment at 500° C. to 600° C. in an inert atmosphere is preferable, and heat treatment at 500° C. to 550° C. is more preferable from the viewpoint of shortening the heating time.
The heat treatment time is preferably 30 to 600 minutes, more preferably 30 to 180 minutes, and even more preferably 60 to 120 minutes.
The type of gas used for the inert atmosphere is not particularly limited, and one or more selected from inert gases such as nitrogen gas, argon gas, and helium gas can be used.
Anionic functional groups (acidic functional groups) on the surface of acidic carbon black, which is a raw material of conductive carbon black, are suitably removed by the heat treatment, and conductive carbon black powder having desired properties can be obtained.

According to the present invention, the content of polyvalent metal ions is reduced, and conductive carbon black powder useful as a conductive material capable of exhibiting excellent conductivity can be produced easily and inexpensively. A manufacturing method can be provided.

<Method for producing positive electrode material for lithium ion secondary battery>
Next, a method for producing a positive electrode material for lithium ion secondary batteries according to the present invention will be described.

The method for producing a positive electrode material for a lithium ion secondary battery according to the present invention includes an aqueous dispersion of the conductive carbon black raw material according to the present invention, and an aqueous dispersion of the conductive carbon black raw material obtained by the production method according to the present invention. , the conductive carbon black powder according to the present invention or the conductive carbon black powder obtained by the method according to the present invention,
mixed with at least an electrode active material and a binder;
It is characterized in that it is applied to an electrode substrate and dried.

In the method for producing a positive electrode material for a lithium ion secondary battery according to the present invention, the aqueous dispersion of the conductive carbon black raw material according to the present invention, and the aqueous dispersion of the conductive carbon black raw material obtained by the production method according to the present invention The details of the conductive carbon black powder according to the present invention or the conductive carbon black powder obtained by the method according to the present invention are as described above.

ADVANTAGE OF THE INVENTION According to the present invention, a positive electrode for a lithium-ion secondary battery is made of a conductive carbon black powder, which has a reduced content of polyvalent metal ions, exhibits excellent conductivity, and can be produced easily and inexpensively as a conductive material. It is possible to provide a method for manufacturing materials.

(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)
<Preparation of slurry containing oxidized carbon black>
Carbon black (furnace carbon black, manufactured by Tokai Carbon Co., Ltd., TB #5500, nitrogen adsorption specific surface area N ₂ SA is 225 m ² /g, nitrogen adsorption specific surface area N ₂ SA minus statistical thickness specific surface area (STSA) 90 m ² /g, DBP oil absorption of 155 ml/100 g, average particle size of 200 nm) was added to 3000 ml of a 2.0 N sodium persulfate aqueous solution using deionized water, and the reaction temperature was 90 ° C. and the stirring speed was The surface of the carbon black was subjected to liquid phase oxidation by treatment at 300 rpm for 3 hours.
Next, the reduced salt in the resulting slurry was washed with water using an ultrafiltration membrane (manufactured by Asahi Kasei Co., Ltd., AHP-1010, molecular weight cut off: 50,000) until the conductivity fell below 3 mS/cm, and was desalted and purified. . The pH of the resulting slurry containing oxidized carbon black was pH3.
To the slurry containing the oxidized carbon black washed with water (oxidized carbon black solid content concentration 5% by mass), sodium dihydrogen ethylenediaminetetraacetate is added per oxidized carbon black solid content (per oxidized carbon black solid content 100% by mass). 5 mass % was added and reacted for 15 minutes at a reaction temperature of 25° C. and a stirring speed of 300 rpm.
The carbon black slurry obtained by the reaction with sodium dihydrogendihydrogendiaminetetraacetate is washed with water through an ultrafiltration membrane (AHP-1010 manufactured by Asahi Kasei Co., Ltd., molecular weight cut off: 50000) until the electric conductivity falls below 3 mS/cm. The nitrogen adsorption specific surface area N ₂ SA is 225 m ² /g, and the value obtained by subtracting the statistical thickness specific surface area (STSA) from the nitrogen adsorption specific surface area N ₂ SA, in which polyvalent metal ions were preliminarily separated by desalting and purification. is 90 m ² /g, the DBP oil absorption is 155 ml/100 g, the average particle diameter is 200 nm, and the amount of acidic hydroxyl groups is 900 μmol/g. A slurry was obtained.

<Neutralization treatment>
Sodium dihydrogen ethylenediaminetetraacetate was added to the oxidized carbon black-containing slurry obtained in <Preparation of oxidized carbon black-containing slurry> in which polyvalent metal ions were preliminarily separated, per oxidized carbon black solid content (oxidized carbon black solid content 5% by mass (based on 100% by mass) was added, and an aqueous sodium hydroxide solution was added so that the pH of the slurry became 11, and the neutralization reaction was carried out at a reaction temperature of 95°C and a stirring speed of 300 rpm for 3 hours.

<Separation removal treatment>
The mixed solution obtained by performing the neutralization reaction in the above <neutralization treatment> is again subjected to an ultrafiltration membrane (AHP-1010 manufactured by Asahi Kasei Co., Ltd., molecular weight cutoff 50000) to remove remaining salts and chelate complexes. The nitrogen adsorption specific surface area N ₂ SA is 225 m ² /g, and the value obtained by subtracting the statistical thickness specific surface area (STSA) from the nitrogen adsorption specific surface area N ₂ SA is 90 m ² /g. , a conductive carbon black raw material containing 20% by mass of oxidized carbon black having an anionic functional group on its surface, having a DBP oil absorption of 155 ml/100 g, an average particle size of 200 nm, and an acidic hydroxyl group content of 900 μmol/g. was prepared.

<Functional group removal treatment>
Next, the aqueous dispersion of the conductive carbon black raw material obtained in the <separation and removal treatment> was heat-treated in a dryer at 110 ° C. for 720 minutes to remove moisture, and then the dried product obtained in the graphite crucible. and heat-treated at 500 ° C. for 1 hour in an N ₂ gas atmosphere to remove the anionic functional groups on the surface of the carbon black conductive carbon black powder (nitrogen adsorption specific surface area N ₂ SA 225 m ² /g , the value obtained by subtracting the statistical thickness specific surface area (STSA) from the nitrogen adsorption specific surface area N ₂ SA is 90 m ² /g, the DBP oil absorption is 155 ml / 100 g, the average particle diameter is 25 nm, and the amount of acidic hydroxyl groups is 100 μmol / g). prepared.

(Comparative example 1)
In the <Preparation of slurry containing oxidized carbon black> and <Neutralization treatment> of Example 1, the concentration of oxidized carbon black was adjusted in the same manner as in Example 1, except that neither sodium dihydrogen ethylenediaminetetraacetate was added. After preparing an aqueous dispersion of 20% by mass of conductive carbon black raw material, the functional group removal treatment was performed in the same manner as in Example 1, and the nitrogen adsorption specific surface area N ₂ SA225 m ² /g, the nitrogen adsorption specific surface area N ₂ Conductivity having a value obtained by subtracting the statistical thickness specific surface area (STSA) from SA of 90 m ² /g, a DBP oil absorption of 155 ml/100 g, an average particle size of 200 nm, and an acidic hydroxyl group content of 100 μmol/g A carbon black powder was prepared.

(Comparative example 2)
Nitrogen adsorption specific surface area N ₂ SA 225 m ² /g, nitrogen adsorption ratio The value obtained by subtracting the statistical thickness specific surface area (STSA) from the surface area N ₂ SA is 90 m ² /g, the DBP oil absorption is 155 ml/100 g, the average particle size is 200 nm, and the amount of acidic hydroxyl groups is 900 μmol/g. A conductive carbon black powder was prepared.

<Method for measuring content of metal component>
In Example 1 and Comparative Examples 1 and 2, the aqueous dispersion of each conductive carbon black raw material obtained after the <separation removal treatment> was diluted with nitric acid solution, and then subjected to an inductively coupled plasma atomic emission spectrometer (( Shimadzu Corporation, ICPS-7510) was used to measure the content of each polyvalent metal component.
For comparison, the content of polyvalent metal components in carbon black (TB#5500) used as a raw material was also measured in the same manner.

Table 1 shows the results obtained.
The numerical values in the table are the total amount (mass ppm) of polyvalent metals contained in the carbon black. As polyvalent metals, Mg, Al, Ca, Cr, Mn, Fe, Ni, Cu, Zn, and Pb were measured.

<Method for measuring compressive electrical resistance of carbon black powder>
The compression electrical resistance of the conductive carbon black powders obtained in Example 1 and Comparative Examples 1 and 2 was measured according to JIS K 1469-2003.
For comparison, the compressive electrical resistance of carbon black (TB#5500) used as a raw material was similarly measured.
Table 1 shows the results.

From Table 1, the conductive carbon black powder obtained in Example 1 is derived from furnace black, but after forming a complex with a water-soluble chelating agent, the polyvalent metal is separated and removed. Therefore, compared to the carbon black used as a raw material, the polyvalent metal concentration is significantly reduced to about 2.0% ((49/2000) × 100), and the compressive electrical resistivity is 0 It can be seen that it is suitable as a material for forming a positive electrode material for a lithium ion secondary battery because it can exhibit excellent conductivity as low as 20 Ω·cm.
On the other hand, from Table 1, the polyvalent metal was not sufficiently removed in Comparative Example 1, and the anionic functional group (acidic functional group) was not sufficiently removed in Comparative Example 2. It can be seen that none of them is suitable as a material for forming a positive electrode material for a lithium ion secondary battery, since the compression electrical resistivity is high.

According to the present invention, an aqueous dispersion of a conductive carbon black raw material that can easily and inexpensively produce a conductive material that has a reduced content of polyvalent metal ions and can exhibit excellent conductivity, and such a conductive carbon black raw material. It is possible to provide a method for producing an aqueous dispersion of, conductive carbon black powder, a method for producing conductive carbon black powder, and a method for producing a positive electrode material for a lithium ion secondary battery.

Claims (10)

a nitrogen adsorption specific surface area N ₂ SA of 200 to 300 m ² /g;
The value obtained by subtracting the statistical thickness specific surface area STSA from the nitrogen adsorption specific surface area N ₂ SA is 50 to 150 m ² /g,
DBP oil absorption of 100-500ml/100g,
An average particle size of 100 to 500 nm,
The polyvalent metal content concentration is 10 to 100 mass ppm,
Compressive electrical resistivity after heat treatment is 0.05 to 0.23 Ω cm
Contains oxidized carbon black
An aqueous dispersion of a carbon black conductive material raw material characterized by: The nitrogen adsorption specific surface area N ₂ SA is 200 to 300 m ² /g, the value obtained by subtracting the statistical thickness specific surface area STSA from the nitrogen adsorption specific surface area N ₂ SA is 50 to 150 m ² /g, and the DBP oil absorption is 100 to 500 ml/g. 100 g of an aqueous slurry of oxidized carbon black having an average particle size of 100 to 500 nm and having one or more anionic functional groups on the surface,
An alkali metal hydroxide is mixed in the presence of one or more selected from a water-soluble chelating agent or a salt thereof and neutralized by heating, or an alkali metal hydroxide is mixed and neutralized by heating, and then a water-soluble chelating agent or its salt is added. A neutralization step of mixing one or more selected from salts;
A method for producing an aqueous dispersion of a raw material for a carbon black conductive material, characterized by subjecting the mixture obtained in the neutralization step to a separation-removal step of separating and removing a polyvalent metal ion chelate complex using a separation membrane. 3. The method for producing an aqueous dispersion of a carbon black conductive material raw material according to claim 2, wherein in the neutralization step, the alkali metal hydroxide is mixed with the aqueous slurry of the oxidized carbon black so that the pH is 6 to 12. 4. The method for producing an aqueous dispersion of a carbon black conductive material raw material according to claim 2 or 3, wherein the water-soluble chelating agent is an aminocarboxylic acid or a salt thereof. The oxidized carbon black having one or more anionic functional groups on its surface is mixed with one or more water-soluble chelating agents or salts thereof under conditions of pH 2 to pH 4 after oxidizing the carbon black by a liquid phase method. 5. The method for producing an aqueous dispersion of carbon black conductive material raw material according to any one of claims 2 to 4, wherein polyvalent metal ions are preliminarily separated using a separation membrane. The method for producing an aqueous dispersion of carbon black conductive material raw material according to any one of claims 2 to 5, wherein the separation membrane is an ultrafiltration membrane (UF), a reverse osmosis membrane (RO) or an electrodialysis membrane. A method for producing a conductive carbon black powder, which comprises heat-treating an aqueous dispersion of the conductive carbon black raw material according to claim 1 . The nitrogen adsorption specific surface area N ₂ SA is 200 to 300 m ² /g, the value obtained by subtracting the statistical thickness specific surface area STSA from the nitrogen adsorption specific surface area N ₂ SA is 50 to 150 m ² /g, and the DBP oil absorption is 100 to 500 ml/g. 100 g of an aqueous slurry of oxidized carbon black having an average particle size of 100 to 500 nm and having one or more anionic functional groups on the surface,
An alkali metal hydroxide is mixed in the presence of one or more selected from a water-soluble chelating agent or a salt thereof and neutralized by heating, or an alkali metal hydroxide is mixed and neutralized by heating, and then a water-soluble chelating agent or its salt is added. A neutralization step of mixing one or more selected from salts;
An aqueous dispersion of the conductive carbon black raw material is prepared by subjecting the mixture obtained in the neutralization step to a separation and removal step of separating and removing the polyvalent metal ion chelate complex using a separation membrane, and then,
A method for producing conductive carbon black powder, which comprises subjecting the resulting aqueous dispersion of conductive carbon black raw material to a heat treatment to remove an anionic functional group of the oxidized carbon black. The method for producing conductive carbon black powder according to claim 7 or 8, wherein the heat treatment of the aqueous dispersion of the conductive carbon black raw material is performed at 500 to 600°C. The conductive material aqueous dispersion of carbon black raw material according to claim 1, the aqueous dispersion of carbon black conductive material raw material obtained by the production method according to any one of claims 2 to 6, or claims 7 to 7. Conductive carbon black powder obtained by the production method according to any one of 9,
mixed with at least an electrode active material and a binder;
A method for producing a positive electrode material for a lithium-ion secondary battery, comprising applying the material to an electrode substrate and drying the material.