JP7317852B2 - METHOD FOR MANUFACTURING ELECTRODE MATERIAL FOR ALUMINUM ELECTROLYTIC CAPACITOR - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an electrode material for an aluminum electrolytic capacitor.

Conventionally, aluminum electrolytic capacitors have been widely used in the energy field due to their properties. A capacitor is used. As described above, aluminum electrolytic capacitors are used in various applications, and are required to exhibit large-capacity characteristics at a voltage suitable for the application.

An aluminum electrolytic capacitor using an aluminum foil having fine aluminum powder adhered to its surface has been proposed (see Patent Document 1). Also, on one or both sides of a smooth aluminum foil with a foil thickness of 15 μm or more and less than 35 μm, aluminum that is self-similar in the length range of 2 μm to 0.01 μm and / or aluminum with an aluminum oxide layer formed on the surface. An electrolytic capacitor using an electrode foil to which aggregates of fine particles are attached is also known (see Patent Document 2).

However, the methods of attaching aluminum powder to an aluminum foil by plating and/or vapor deposition disclosed in these documents are at least insufficient for use in middle and high voltage capacitors.

Further, as an electrode material for aluminum electrolytic capacitors, an electrode material for aluminum electrolytic capacitors comprising a sintered body of at least one of aluminum and aluminum alloy is disclosed (see Patent Document 3). This sintered body has a unique structure obtained by sintering a laminate in which powder particles of aluminum or aluminum alloy are laminated while maintaining gaps between each other. It is said that a capacitance can be obtained (Patent Document 3, [0012] paragraph). The capacity of this electrode material can be increased by increasing the amount or thickness of the powder to be laminated.

However, in recent years, the performance required of capacitors has become more stringent. The above-mentioned electrode material has a problem that the electrostatic capacity of the electrode material is increased by increasing the thickness, but the electrostatic capacity per volume is becoming insufficient.

Also disclosed is a method for producing an electrode material for an aluminum electrolytic capacitor, in which a film made of a paste composition containing aluminum powder is formed on a substrate, the film is sintered, and the sintered film is etched. (see Patent Document 4). According to this production method, it is possible to produce an electrode material for an aluminum electrolytic capacitor that has a large capacitance per volume and can be made into a thin film, regardless of the average particle size of the aluminum powder used.

However, the method described above leaves room for consideration with regard to the increase in capacitance. When the sintered film is etched, the necking part between the powders that make up the film is dissolved by the etching treatment. There is a problem that the thickness of the film cannot be increased. Therefore, development of a manufacturing method capable of manufacturing an electrode material with a higher capacity is desired.

JP-A-2-267916 JP 2006-108159 A JP 2008-98279 A JP 2014-138159 A

SUMMARY OF THE INVENTION An object of the present invention is to provide a manufacturing method capable of easily manufacturing an electrode material for an aluminum electrolytic capacitor having a large capacitance.

As a result of intensive research to achieve the above object, the present inventors have found that a powder such as aluminum is subjected to an etching treatment, a film made of a paste composition containing the powder is formed on a substrate, and the film is baked. The inventors have found that the above-mentioned object can be achieved by the manufacturing method, and have completed the present invention.

That is, the present invention relates to the following method for producing an electrode material for an aluminum electrolytic capacitor.
1. A method for producing an electrode material for an aluminum electrolytic capacitor, comprising:
(1) a first step of subjecting powder of at least one of aluminum and aluminum alloy to an etching treatment;
(2) a second step of forming a film made of a paste composition containing the powder, a binder resin and a solvent on at least one surface of a substrate; and (3) a third step of sintering the film. A method for producing an electrode material for an aluminum electrolytic capacitor, characterized by:
2. Item 2. The manufacturing method according to item 1, wherein the etching treatment is chemical etching with an acid solution or an alkaline solution.
3. Item 2. The manufacturing method according to Item 1, wherein the etching treatment is chemical etching using an acid solution.
4. Item 4. The production method according to any one of items 1 to 3, wherein the powder has an average particle size D ₅₀ of 1 to 15 μm.
5. Item 5. The manufacturing method according to any one of Items 1 to 4, wherein the sintering temperature is 560°C or higher and 660°C or lower.
6. Item 6. The manufacturing method according to any one of Items 1 to 5, wherein the thickness of the film after the sintering is 30 to 2000 μm.
7. Item 7. The manufacturing method according to any one of Items 1 to 6, wherein the pore size of the coating after sintering is 1.3 μm or less.

According to the present invention, at least one powder of aluminum and an aluminum alloy is subjected to an etching treatment, and a film made of a paste composition containing the powder, a binder resin and a solvent is formed on at least one surface of a substrate, and the By sintering the film, it is possible to obtain an electrode material for an aluminum electrolytic capacitor having a large capacitance per volume. Therefore, it is possible to miniaturize a capacitor manufactured using the electrode material.

In addition, since the sintered film can be formed thickly, it is possible to obtain an electrode material for an aluminum electrolytic capacitor with a large electrostatic capacity as an electrode, and it is possible to increase the capacity of a capacitor manufactured using this electrode material. becomes.

FIG. 2 is a diagram showing a SEM photograph (secondary electron image) of powder (AHZL560F) before etching treatment in the first step of the manufacturing method of the present invention. FIG. 3 is a diagram showing an SEM photograph (secondary electron image) of powder (AHZL560F) after etching treatment in the first step of the manufacturing method of the present invention. FIG. 10 is a diagram showing measurement results of pore diameters of films after sintering of electrode materials for aluminum electrolytic capacitors of Example 2 and Comparative Example 2; The vertical axis indicates pore volume (Log Differential Intrusion (mL/g)), and the horizontal axis indicates pore size Diameter (μm). FIG. 5 is a diagram showing measurement results of pore diameters of films after sintering of electrode materials for aluminum electrolytic capacitors of Comparative Examples 2 and 14; The vertical axis indicates pore volume (Log Differential Intrusion (mL/g)), and the horizontal axis indicates pore size Diameter (μm).

The method for producing an electrode material for an aluminum electrolytic capacitor of the present invention comprises: (1) a first step of etching a powder of at least one of aluminum and an aluminum alloy; and (2) a paste composition containing the powder, a binder resin and a solvent. and (3) a third step of sintering the coating. Each step will be described below.

(First step)
The first step is a step of etching powder of at least one of aluminum and aluminum alloy.

As the raw material aluminum powder, for example, an aluminum powder having an aluminum purity of 99.8% by weight or more is preferable, and an aluminum purity of 99.9% by weight or more is more preferable. Examples of raw material aluminum alloy powder include silicon (Si), iron (Fe), copper (Cu), manganese (Mn), magnesium (Mg), chromium (Cr), zinc (Zn), titanium (Ti ), vanadium (V), gallium (Ga), nickel (Ni), boron (B) and zirconium (Zr). The content of these elements in the aluminum alloy is preferably 100 ppm by weight or less, particularly 50 ppm by weight or less.

The powder used preferably has an average particle size _D50 of 1 to 15 μm before sintering, more preferably 1.8 to 15 μm. In particular, when the average particle diameter _D50 of the powder is 3 to 9 μm, it can be suitably used as an electrode material for aluminum electrolytic capacitors with medium to high capacity.

The average particle diameter _D50 in the present specification refers to the number of particles corresponding to the 50th percentile of the total number of particles in a particle size distribution curve obtained by determining the particle size and the number of particles corresponding to that particle size by a laser diffraction method. particle size. Also, the average particle size _D50 of the powder after sintering is measured by observing the cross section of the sintered body with a scanning electron microscope. For example, the powder after sintering is partially melted or in a state where the powders are connected to each other, but the portions having a substantially circular shape can be approximately regarded as particles. That is, in the above observation, the maximum diameter (major diameter) of each particle having a substantially circular shape is defined as the particle diameter of the particle, and the particle diameters of 50 arbitrary particles are measured, and the arithmetic average of these particles after sintering is obtained. It is defined as the average particle size of the powder. The particle size of the powder obtained by such a method hardly changes compared to the particle size before sintering.

The shape of the powder is not particularly limited, but any one of spherical, approximately spherical, and irregular shapes can be suitably used. The shape of the powder is preferably spherical or substantially spherical. Since the shape of the powder is spherical or substantially spherical, division by thin portions or thin portions during etching, which may occur when the shape is scale-like or fibrous, is further suppressed. .

As the powder, one manufactured by a known method can be used. Examples thereof include the atomization method, melt spinning method, rotating disk method, rotating electrode method, and rapid solidification method. For industrial production, the atomization method, particularly the gas atomization method, is preferred. That is, it is desirable to use powder obtained by atomizing molten metal.

The etching treatment is not particularly limited, but chemical etching with an acid solution or an alkaline solution is preferred. In particular, chemical etching with an acid solution can effectively increase the surface area and has good dispersibility, so that the paste composition in the second step can be mixed more easily. In the case of chemical etching with an alkaline solution, the surface area can be increased more effectively, but the powder tends to aggregate.

By performing these etching treatments, pores can be formed in the powder and the surface area can be further increased. The pore diameter of the pores formed in the powder is preferably 1.3 μm or less, more preferably 1.1 μm or less. By using a powder having a pore diameter within the above range, the surface area of the obtained capacitor electrode material can be further increased, and an electrode material for an aluminum electrolytic capacitor having a higher capacity and a higher capacity per volume can be obtained. Obtainable. Moreover, the pore diameter of the pores formed in the powder is preferably 0.3 μm or more, more preferably 0.6 μm or more. When a powder having a pore diameter within the above range is used, the capacitance of the obtained electrode material for a capacitor is further improved.

The acid solution used for chemical etching with the acid solution is not particularly limited, and a known acid solution such as a mixed acid aqueous solution containing one or more of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, etc. can be used. The concentration of the acidic solution is selected for the electrode material for aluminum electrolytic capacitors that exhibits high capacity in the low voltage range, the electrode material for aluminum electrolytic capacitors that exhibits high capacity in the high voltage range, or the electrode material for aluminum electrolytic capacitors that exhibits high capacity in both ranges. Although it may be appropriately set according to desired properties such as the electrode material, it is preferably 10 to 40% by mass. Also, the etching temperature and time may be appropriately adjusted according to the shape and average particle diameter of the powder, the pore diameter to be formed in the powder by etching, the number of pores, the distribution, the surface area, etc. is preferably about 1 to 210 minutes.

The alkaline solution used for chemical etching with the alkaline solution is not particularly limited, and for example, an alkaline solution (aqueous solution) such as caustic soda can be used. The concentration of the alkaline solution depends on the electrode material for aluminum electrolytic capacitors that exhibits high capacity in the low voltage range, the electrode material for aluminum electrolytic capacitors that exhibits high capacity in the high voltage range, or the electrode material for aluminum electrolytic capacitors that exhibits high capacity in both ranges. It may be appropriately set depending on the electrode material exhibiting the desired characteristics, such as an electrode material, but usually about 10 to 40% by mass is preferable. Also, the etching temperature and time may be appropriately adjusted according to the shape and average particle diameter of the powder, the pore diameter to be formed in the powder by etching, the number of pores, the distribution, the surface area, etc., but usually the temperature is 20. About 1 to 210 minutes at ~90°C is preferable.

An electrode material exhibiting desired characteristics can be obtained by performing the etching treatment. For example, chemical etching with an acid solution or an alkaline solution makes it possible to obtain an electrode material that exhibits high capacity and capacity per volume in a high voltage range of, for example, about 250 to 550V. The reason for this is considered as follows.

That is, chemical etching with an alkaline solution has a high ability to dissolve the surface and oxide film of aluminum, can reduce the average particle diameter _D50 of the aluminum powder of the electrode material, and improves the surface area of the electrode material. it is conceivable that. It is also believed that chemical etching with an acid solution dissolves the aluminum surface of the electrode material and simultaneously forms tunnel-like etching pits in the aluminum powder.

After the etching treatment, the powder is preferably further washed. Although the cleaning liquid is not particularly limited, for example, water, ethanol, toluene, ketones, esters, and other organic solvents can be used alone or in mixtures. It is preferable to wash with water from the viewpoint of cost. Additives such as surfactants and neutralizers may be added to the cleaning liquid as necessary. Although the number of times of washing is not particularly limited, it is preferable to wash several times. Also, when washing is performed a plurality of times, the washing liquid may be changed in the middle. Washing further suppresses deterioration of the characteristics of the electrode material for an aluminum electrolytic capacitor due to the acidic solution, the alkaline solution, or the reaction product of the powder and the solution remaining on the surface of the powder. can be done.

In the manufacturing method of the present invention, it is preferable that the powder is further dried after washing the powder in the first step.

Through the first step described above, the powder of at least one of aluminum and aluminum alloy is etched.

(Second step)
The second step is a step of forming a film of a paste composition containing the powder, binder resin and solvent on at least one surface of the substrate.

The paste composition contains a binder resin and a solvent in addition to the powder. All of these can use a well-known or commercially available thing.

The binder resin is not limited, and examples thereof include carboxy-modified polyolefin resins, vinyl acetate resins, vinyl chloride resins, vinyl chloride acetate copolymer resins, vinyl alcohol resins, butyral resins, vinyl fluoride resins, acrylic resins, polyester resins, urethane resins. Synthetic resins such as resins, epoxy resins, urea resins, phenolic resins, acrylonitrile resins, cellulose resins, paraffin waxes and polyethylene waxes, waxes, and natural resins and waxes such as tar, glue, sumac, rosin and beeswax can be preferably used. Depending on the molecular weight, type of resin, etc., some of these binder resins volatilize when heated, while others leave the residue together with the aluminum powder when thermally decomposed. .

A well-known thing can be used for the said solvent. For example, in addition to water, organic solvents such as ethanol, toluene, ketones and esters can be used.

The paste composition may contain other components such as a sintering aid and a surfactant, if necessary. Any of these can be known or commercially available. When the paste composition contains the above other components, the film can be formed more efficiently.

In the second step, a film is formed by applying the paste composition to at least one surface of a substrate. As the substrate, a wide range of known substrates can be used as long as they are used as substrates for electrode materials for aluminum electrolytic capacitors. In particular, aluminum foil can be preferably used.

The aluminum foil as the base material is not particularly limited, and for example, pure aluminum or an aluminum alloy can be used. The composition of the aluminum foil used in the present invention is silicon (Si), iron (Fe), copper (Cu), manganese (Mn), magnesium (Mg), chromium (Cr), zinc (Zn), titanium ( Ti), vanadium (V), gallium (Ga), nickel (Ni) and boron (B) are added within the required range, or the content of the above inevitable impurity elements is limited. Also includes aluminum that has been coated. The purity of the aluminum foil is preferably 99.8% by weight or more, more preferably 99.9% by weight or more. The purity of the aluminum foil may be the same as or different from the purity of the aluminum powder, but is preferably different in order to improve the strength after sintering between the aluminum foil and the powder.

Although the thickness of the aluminum foil is not particularly limited, it is preferably in the range of 5 μm or more and 100 μm or less, particularly 10 μm or more and 50 μm or less.

As the aluminum foil described above, one manufactured by a known method can be used. For example, a molten aluminum or aluminum alloy having the above-described predetermined composition is prepared, and an ingot obtained by casting it is appropriately homogenized. After that, the aluminum foil can be obtained by subjecting this ingot to hot rolling and cold rolling.

In the middle of the cold rolling step, intermediate annealing may be performed at a temperature of 50°C to 500°C, particularly 150°C to 400°C. Further, after the cold rolling step, the foil may be annealed at a temperature of 150° C. to 650° C., particularly 350° C. to 550° C. to obtain a soft foil.

A coating is formed on at least one side of the substrate. In the second step, the coating is preferably formed on both sides of the substrate. When the film is formed on both sides, it is preferable to arrange the film and the unformed portion symmetrically with the substrate sandwiched therebetween. By arranging them symmetrically, in the third step, peeling at the interface between the base material and the film due to sintering can be further suppressed, and warpage occurring in the film can be further suppressed.

2nd process WHEREIN: It is preferable that the film|membrane is not formed in the whole surface of a base material. That is, in a state in which a film is formed on the surface of the base material, when viewed from above in a direction perpendicular to the surface of the base material, the area of the base material is larger than the area of the film, and the film is formed on the surface of the base material. It is preferred that there is a portion that is not With this configuration, handling is further improved during roll-to-roll processing. Specifically, breakage of the substrate can be further suppressed during chemical conversion treatment for forming an oxide film on the surface of the electrode material for an aluminum electrolytic capacitor.

The total thickness of the coating is preferably 30-2000 μm, more preferably 60-2000 μm. The total thickness of the coating is preferably set so that the total thickness of the sintered body finally obtained through rolling and sintering is 30 to 2000 μm. These figures apply to either one or both sides of the substrate, but in the case of both sides, the thickness of the coating on one side is 1/1 of the total thickness (including the thickness of the substrate). It is preferably 3 or more.

The average thickness of the film was measured at 7 points with a micrometer, and the average value of 5 points excluding the maximum and minimum values.

The coating may optionally be dried at a temperature within the range of 20-300°C.

The method of forming the film is not particularly limited, and conventionally known methods can be employed. For example, the paste composition may be coated using a coating method such as roller, brush, spray, or dipping, or may be formed by a known printing method such as silk screen printing or die coating.

Through the above-described second step, a film made of a paste composition containing at least one powder of aluminum and an aluminum alloy, a binder resin and a solvent is formed on at least one surface of the substrate.

(Third step)
The third step is a step of sintering the film.

The sintering temperature is preferably 560 to 660°C, more preferably 570 to 650°C, even more preferably 580 to 620°C. The sintering time varies depending on the sintering temperature and the like, but can be appropriately determined within a range of about 5 to 24 hours.

The sintering atmosphere is not particularly limited, and may be, for example, a vacuum atmosphere, an inert gas atmosphere, an oxidizing gas atmosphere (air), a reducing atmosphere, or the like. preferable. Also, the pressure conditions may be normal pressure, reduced pressure or increased pressure.

In the manufacturing method of the present invention, it is preferable that the film is sintered in the third step, and that the substrate and the film after sintering are joined together. By adopting a structure in which the base material and the film after sintering are joined by sintering, the electrode material for an aluminum electrolytic capacitor can be produced more easily. As such a configuration, for example, an aluminum foil is used as a base material, a formed film is formed on at least one surface of the aluminum foil in the second step, the film is sintered in the third step, and the film after sintering and an aluminum foil are bonded together.

In the manufacturing method of the present invention, after the second step and prior to the third step, it is preferable to perform heat treatment (degreasing treatment) in advance at a temperature range of 100° C. or higher to 600° C. or lower for a holding time of 5 hours or longer. . The heat treatment atmosphere is not particularly limited, and may be, for example, a vacuum atmosphere, an inert gas atmosphere, or an oxidizing gas atmosphere. Also, the pressure conditions may be normal pressure, reduced pressure or increased pressure.

The film formed on at least one surface of the substrate is sintered by the third step described above.

An electrode material for an aluminum electrolytic capacitor is manufactured by the manufacturing method of the present invention. Since the electrode material for an aluminum electrolytic capacitor manufactured by the manufacturing method of the present invention has a large capacitance per volume, it is possible to miniaturize the capacitor manufactured using the electrode material. In addition, since the sintered film is formed thickly, it becomes an electrode material for an aluminum electrolytic capacitor having a large electrostatic capacity as an electrode, and it becomes possible to increase the capacity of a capacitor manufactured using the electrode material. .

The pore diameter of the sintered film sintered in the third step, that is, the pore diameter of the sintered film of the electrode material for an aluminum electrolytic capacitor produced by the production method of the present invention is 1.3 μm. The following is preferable, and 1.1 μm or less is more preferable. When the upper limit of the pore diameter of the film after sintering is within the above range, the surface area of the capacitor electrode material produced by the production method of the present invention can be further increased, and the capacity and capacity per volume can be further increased. It becomes an electrode material for high-quality aluminum electrolytic capacitors. Moreover, the pore diameter of the film after sintering is preferably 0.3 μm or more, more preferably 0.6 μm or more. When the lower limit of the pore diameter of the film after sintering is within the above range, the capacitance of the obtained electrode material for capacitors is further improved.

The pore diameter of the film after sintering the electrode material for an aluminum electrolytic capacitor is measured, for example, by a mercury intrusion method. Other measuring methods such as the gas adsorption method are not excluded, and a suitable measuring method is selected according to the pore diameter. Although the pore size usually has a distribution, the pore size at the peak of the large pore volume is adopted as the pore size of the object to be measured. When there are multiple pore volume peaks, the pore diameter closest to the pore diameter measured by, for example, electron microscope observation is adopted.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples and comparative examples. However, the present invention is not limited to the examples.

Electrode materials of Examples and Comparative Examples were produced according to the following procedure. The capacitance of the obtained electrode material was measured by the following measuring method.

(capacitance)
After subjecting the electrode material to chemical conversion treatment in an aqueous boric acid solution (50 g/L) at voltages of 250, 550 and 700 V, the capacitance was measured using an aqueous ammonium borate solution (3 g/L). The measurement projected area was 10 cm ² .

(pore size)
The pore size of the film after sintering the electrode material was measured using a pore size distribution analyzer (AutoPore IV 9500 manufactured by Micromeritics). Among the obtained measurement results, the pore size diameter (μm) of the peak with the largest pore volume (Log Differential Intrusion (mL/g)) was taken as the pore diameter of the film after sintering the electrode material. .

<Examples and Comparative Examples>
Comparative example 1
Aluminum powder (JIS A1080, manufactured by Toyo Aluminum Co., Ltd., AHZL530C) having an average particle diameter _D50 of 15.0 μm, an ethyl cellulose binder resin and a solvent (butyl acetate) were mixed to obtain a paste composition. This composition is symmetrically applied to both sides of a 30 μm thick aluminum foil substrate (SB material, purity 99.99% by weight) using a comma coater so that the thickness of each film after sintering is 50 μm. The coating was then dried in an air atmosphere at 100°C for 1.5 minutes. An electrode material of Comparative Example 1 was produced by sintering this aluminum foil at a temperature of 600° C. for 10 hours in an argon gas atmosphere. The thickness of the electrode material after sintering was about 120 μm.

For the average particle size of the aluminum powder, Microtrac MT3300EXII (manufactured by Nikkiso Co., Ltd.) was used to measure the particle size distribution on a volume basis by laser analysis, and the average particle size _D50 was calculated.

Comparative example 2
Aluminum powder (JIS A1080, manufactured by Toyo Aluminum Co., Ltd., AHZL560F) having an average particle diameter _D50 of 9.0 μm, an ethyl cellulose binder resin and a solvent (butyl acetate) were mixed to obtain a paste composition. This composition is symmetrically applied to both sides of a 30 μm thick aluminum foil substrate (SB material, purity 99.99% by weight) using a comma coater so that the thickness of each film after sintering is 50 μm. The coating was then dried in an air atmosphere at 100°C for 1.5 minutes. An electrode material of Comparative Example 2 was produced by sintering this aluminum foil at a temperature of 600° C. for 10 hours in an argon gas atmosphere. The thickness of the electrode material after sintering was about 120 μm.

Comparative example 3
Aluminum powder (JIS A1080, manufactured by Toyo Aluminum Co., Ltd., AHZL58FN) having an average particle diameter _D50 of 3.0 μm was mixed with an ethyl cellulose binder resin and a solvent (butyl acetate) to obtain a paste composition. This composition is symmetrically applied to both sides of a 30 μm thick aluminum foil substrate (SB material, purity 99.99% by weight) using a comma coater so that the thickness of each film after sintering is 50 μm. The coating was then dried in an air atmosphere at 100°C for 1.5 minutes. An electrode material of Comparative Example 3 was produced by sintering this aluminum foil at a temperature of 600° C. for 10 hours in an argon gas atmosphere. The thickness of the electrode material after sintering was about 120 μm.

Comparative example 4
Aluminum powder (JIS A1080, manufactured by Toyo Aluminum Co., Ltd., AHU091) having an average particle diameter _D50 of 1.8 μm, an ethyl cellulose binder resin, and a solvent (butyl acetate) were mixed to obtain a paste composition. This composition is symmetrically applied to both sides of a 30 μm thick aluminum foil substrate (SB material, purity 99.99% by weight) using a comma coater so that the thickness of each film after sintering is 50 μm. The coating was then dried in an air atmosphere at 100°C for 1.5 minutes. An electrode material of Comparative Example 4 was produced by sintering this aluminum foil at a temperature of 600° C. for 10 hours in an argon gas atmosphere. The thickness of the electrode material after sintering was about 120 μm.

Example 1
An electrode material was produced in the same manner as in Comparative Example 1, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (30% concentration), temperature: 25°C, time: 60 min

Example 2
An electrode material was produced in the same manner as in Comparative Example 2, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (30% concentration), temperature: 25°C, time: 60 min

Example 3
An electrode material was produced in the same manner as in Comparative Example 3, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (30% concentration), temperature: 25°C, time: 60 min

Example 4
An electrode material was produced in the same manner as in Comparative Example 4, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (30% concentration), temperature: 25°C, time: 60 min

Table 1 shows the results.

Example 5
An electrode material was produced in the same manner as in Comparative Example 1, except that the aluminum powder was etched under the following conditions.
Etchant: sulfuric acid (concentration 40%), temperature: 25°C, time: 60 min

Example 6
An electrode material was produced in the same manner as in Comparative Example 2, except that the aluminum powder was etched under the following conditions.
Etchant: sulfuric acid (concentration 40%), temperature: 25°C, time: 60 min

Example 7
An electrode material was produced in the same manner as in Comparative Example 3, except that the aluminum powder was etched under the following conditions.
Etchant: sulfuric acid (concentration 40%), temperature: 25°C, time: 60 min

Example 8
An electrode material was produced in the same manner as in Comparative Example 4, except that the aluminum powder was etched under the following conditions.
Etchant: sulfuric acid (concentration 40%), temperature: 25°C, time: 60 min

Table 2 shows the results.

Example 9
An electrode material was produced in the same manner as in Comparative Example 1, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (concentration 10%), temperature: 25°C, time: 210 min

Example 10
An electrode material was produced in the same manner as in Comparative Example 2, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (concentration 10%), temperature: 25°C, time: 210 min

Example 11
An electrode material was produced in the same manner as in Comparative Example 3, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (concentration 10%), temperature: 25°C, time: 210 min

Example 12
An electrode material was produced in the same manner as in Comparative Example 4, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (concentration 10%), temperature: 25°C, time: 210 min

Table 3 shows the results.

Example 13
An electrode material was produced in the same manner as in Comparative Example 1, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (concentration 10%), temperature: 80°C, time: 60min

Example 14
An electrode material was produced in the same manner as in Comparative Example 2, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (concentration 10%), temperature: 80°C, time: 60min

Example 15
An electrode material was produced in the same manner as in Comparative Example 3, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (concentration 10%), temperature: 80°C, time: 60min

Example 16
An electrode material was produced in the same manner as in Comparative Example 4, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (concentration 10%), temperature: 80°C, time: 60min

Table 4 shows the results.

Comparative example 5
An electrode material was prepared in the same manner as in Comparative Example 1, except that the composition was applied symmetrically on both sides of the aluminum foil substrate so that the thickness of the film after sintering was 30 μm.

Comparative example 6
An electrode material was produced in the same manner as in Comparative Example 2, except that the composition was applied symmetrically on both sides of the aluminum foil substrate so that the thickness of each film after sintering was 30 μm.

Comparative example 7
An electrode material was produced in the same manner as in Comparative Example 3, except that the composition was applied symmetrically to both surfaces of the aluminum foil substrate so that the thickness of the film after sintering was 30 μm.

Comparative example 8
An electrode material was produced in the same manner as in Comparative Example 4, except that the composition was applied symmetrically on both sides of the aluminum foil substrate so that the thickness of the film after sintering was 30 μm.

Example 17
An electrode material was produced in the same manner as in Comparative Example 5, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (30% concentration), temperature: 25°C, time: 60 min

Example 18
An electrode material was produced in the same manner as in Comparative Example 6, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (30% concentration), temperature: 25°C, time: 60 min

Example 19
An electrode material was produced in the same manner as in Comparative Example 7, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (30% concentration), temperature: 25°C, time: 60 min

Example 20
An electrode material was produced in the same manner as in Comparative Example 8, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (30% concentration), temperature: 25°C, time: 60 min

Table 5 shows the results.

Comparative example 9
An electrode material was produced in the same manner as in Comparative Example 1, except that the composition was applied symmetrically on both sides of the aluminum foil substrate so that the thickness of each film after sintering was 1000 μm.

Comparative example 10
An electrode material was produced in the same manner as in Comparative Example 2, except that the composition was applied symmetrically on both sides of the aluminum foil substrate so that the thickness of the film after sintering was 1000 μm.

Comparative example 11
An electrode material was produced in the same manner as in Comparative Example 3, except that the composition was applied symmetrically on both sides of the aluminum foil substrate so that the thickness of the film after sintering was 1000 μm.

Comparative example 12
An electrode material was produced in the same manner as in Comparative Example 4, except that the composition was applied symmetrically on both sides of the aluminum foil substrate so that the thickness of the film after sintering was 1000 μm.

Example 21
An electrode material was produced in the same manner as in Comparative Example 9, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (30% concentration), temperature: 25°C, time: 60 min

Example 22
An electrode material was produced in the same manner as in Comparative Example 10, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (30% concentration), temperature: 25°C, time: 60 min

Example 23
An electrode material was produced in the same manner as in Comparative Example 11, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (30% concentration), temperature: 25°C, time: 60 min

Example 24
An electrode material was produced in the same manner as in Comparative Example 12, except that the aluminum powder was etched under the following conditions.
Etching solution: hydrochloric acid (30% concentration), temperature: 25°C, time: 60 min

Table 6 shows the results.

Comparative Example 13 (Example 1 of JP-A-2014-138159)
An electrode material was produced in the same manner as in Comparative Example 3, except that the sintered electrode material was etched under the following conditions.
Etching solution: mixed solution of hydrochloric acid and sulfuric acid (hydrochloric acid concentration: 1 mol/L, sulfuric acid concentration: 3 mol/L, concentration 15%), temperature: 40 ° C., time: 2 min

Table 7 shows the results.

Comparative Example 14 (Example 9 of JP-A-2014-138159)
An electrode material was produced in the same manner as in Comparative Example 2, except that the sintered electrode material was subjected to an etching treatment under the following conditions.
Etching solution: mixed solution of hydrochloric acid and sulfuric acid (hydrochloric acid concentration: 1 mol/L, sulfuric acid concentration: 3 mol/L, concentration 15%), temperature: 40 ° C., time: 2 min

Table 8 shows the results.

[result]
As shown in Tables 1 to 8, it was confirmed that the electrode materials of each example had excellent capacitance required for capacitors compared to the corresponding electrode materials of the comparative examples.

Claims (7)

A method for producing an electrode material for an aluminum electrolytic capacitor, comprising:
(1) a first step of subjecting powder of at least one of aluminum and aluminum alloy to an etching treatment;
(2) a second step of forming a film made of a paste composition containing the powder, a binder resin and a solvent on at least one surface of a substrate; and (3) a third step of sintering the film. A method for producing an electrode material for an aluminum electrolytic capacitor, characterized by: 2. The manufacturing method according to claim 1, wherein said etching treatment is chemical etching with an acid solution or an alkaline solution. 2. The manufacturing method according to claim 1, wherein said etching treatment is chemical etching with an acid solution. The production method according to any one of claims 1 to 3, wherein the powder has an average particle size D ₅₀ of 1 to 15 µm. The manufacturing method according to any one of claims 1 to 4, wherein the sintering temperature is 560°C or higher and 660°C or lower. The manufacturing method according to any one of claims 1 to 5, wherein the thickness of the film after sintering is 30 to 2000 µm. The manufacturing method according to any one of claims 1 to 6, wherein the pore size of the coating after sintering is 1.3 µm or less.

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