JP2004323910A - Method of producing nickel powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing nickel powder which has excellent dispersibility in an organic vehicle in the preparation of electrically conductive paste, is suitable for preparing electrically conductive paste used for the formation of a thin internal electrode free from projections because of its sharp grain size distribution, can obtain a dry film having high density and reduced Ra after pasting and is suitably used for the production of a multilayer ceramic condenser. <P>SOLUTION: In the method of producing nickel powder, powder selected from the group consisting of nickel salt power and nickel hydroxide powder is suspended into polyol containing a noble metal compound catalyst and a dispersant, the powder is heated to a temperature sufficient for reducing the powder into nickel powder to produce nickel powder, and the produced flocculated nickel powder is subjected to crushing treatment so as to simply be dispersed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a nickel powder, and more specifically, because it is less agglomerated and close to a monodispersed state, has excellent dispersibility in an organic vehicle in the preparation of a conductive paste, and has a sharp particle size distribution, so that it is thin. Nickel powder that is suitable for the preparation of a conductive paste used to form internal electrodes without protrusions and that has a high dry film density and a small Ra after being made into a paste, and can be suitably used for the production of multilayer ceramic capacitors. And a method for producing the same.
[0002]
[Prior art]
It is known that when a nickel powder is produced by reducing a nickel salt powder or a nickel hydroxide powder by a polyol method, a nickel powder having a high purity, a high crystallinity and a uniform primary particle size can be obtained (for example, And Patent Document 1.).
[0003]
In addition, generally, any metal powder in a state as produced by a dry reaction or a wet reaction is agglomerated to varying degrees, and the problem of agglomeration is also great for nickel powder, particularly for conductive paste. At the time of preparation, dispersibility in an organic vehicle is an important point, and a nickel powder with less aggregation, that is, a so-called monodispersed state as close as possible has been demanded.
[0004]
[Patent Document 1]
Japanese Patent Publication No. 4-24402 [0005]
[Problems to be solved by the invention]
However, the nickel powder obtained by the polyol method is difficult to paste as it is because the primary particles are strongly agglomerated to form secondary particles, and a dried film obtained after the nickel powder is pasted. Has a low density and Ra tends to be poor.
[0006]
The present invention is used for the formation of an internal electrode which is thin and has no protrusion because the aggregation is small and close to a monodispersed state, so that the dispersibility in an organic vehicle is excellent in the preparation of a conductive paste, and the particle size distribution is sharp. An object of the present invention is to provide a method for producing nickel powder which is suitable for preparing a conductive paste, has a high density of a dried film obtained after pasting and has a small Ra, and can be suitably used for producing a multilayer ceramic capacitor. I have.
[0007]
[Means for Solving the Problems]
The present inventors have conducted intensive studies in order to achieve the above object, and as a result, the nickel powder produced by the polyol method is subjected to a wet crushing method or a dry crushing method, or a vibration fluidized dryer is used. It is found that a monodispersed nickel powder which is easy to paste, has a high density of a dried film obtained after pasting and has a small Ra, and can be suitably used for manufacturing a multilayer ceramic capacitor is obtained. Completed the invention.
[0008]
That is, the method for producing a nickel powder of the present invention comprises suspending a powder selected from the group consisting of a nickel salt powder and a nickel hydroxide powder in a polyol, and reducing the powder to a nickel powder. In this case, the powder is heated to a temperature sufficient to generate nickel powder, and the generated agglomerated nickel powder is crushed to be monodispersed.
[0009]
Further, the method for producing a nickel powder of the present invention comprises suspending a powder selected from the group consisting of a nickel salt powder and a nickel hydroxide powder in a polyol, and reducing the powder to a nickel powder. To a temperature sufficient to generate nickel powder, and wash the generated agglomerated nickel powder with an organic solvent having a boiling point of 100 ° C. or lower or a mixed solvent of the organic solvent and water, and fill a ball with a vibration dryer. It is characterized by drying in.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
As a noble metal compound catalyst that can be used in the production method of the present invention, palladium chloride, palladium nitrate, palladium acetate, ammonium palladium chloride, palladium compounds such as palladium oxide, silver nitrate, silver lactate, silver oxide, silver sulfate, silver cyclohexanoate, Silver compounds such as silver acetate; platinum compounds such as chloroplatinic acid, potassium chloroplatinate and sodium chloroplatinate; gold compounds such as chloroauric acid and sodium chloroaurate; and the cost and purity of nickel powder. From the viewpoint, palladium nitrate, palladium acetate, palladium oxide, silver nitrate, silver acetate, and silver oxide are preferred.
[0011]
Examples of the dispersant that can be used in the production method of the present invention include nitrogen-containing organic compounds such as polyvinylpyrrolidone, polyethyleneimine, polyacrylamide, and poly (2-methyl-2-oxazoline), and polyvinyl alcohol. .
[0012]
Examples of the polyol that can be used in the production method of the present invention include various polyols described in Japanese Patent Publication No. Hei 4-24402. Specifically, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene Examples thereof include glycol, 1,2-propanediol, dipropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, and mixtures thereof. In the production method of the present invention, a polyol which is liquid at the reaction temperature is used.
[0013]
Examples of the nickel salt and nickel hydroxide used in the production method of the present invention include nickel sulfate, nickel nitrate, nickel chloride, nickel bromide, nickel hydroxide and the like.
[0014]
In the production method of the present invention, in consideration of the reaction rate, a suspension in which a powder selected from the group consisting of nickel salt powder and nickel hydroxide powder is suspended is reduced to nickel powder. Need to be heated to a temperature sufficient to This heating temperature is preferably at least 85 ° C, more preferably at least 100 ° C. The upper limit of the heating temperature is limited by the boiling point or the decomposition temperature of the dispersant, or the lowest temperature among the boiling points of the polyol.
[0015]
In the production method of the present invention, it is preferable that the boiling point or the decomposition temperature of the dispersant is 100 ° C. or higher, and the heating temperature of the suspension is 85 ° C. or higher and lower than the boiling point or the decomposition temperature of the dispersant.
[0016]
In the production method of the present invention, the content of the dispersant is preferably 0.01% by mass or more of the amount of the polyol, and more preferably 0.05 to 5% by mass of the amount of the polyol. When the content of the dispersant is less than 0.01% by mass of the polyol, the effects aimed at in the present invention tend to be insufficient.
[0017]
In the production method of the present invention, as the crushing treatment, for example, a wet crushing method or a dry crushing method can be adopted, for example, a high-speed rotation method in which nickel powder is crushed by colliding with a rotating part rotating at a high speed. Collision crushing treatment, media stirring crushing treatment in which nickel powder is stirred and crushed with beads, etc., high water pressure crushing treatment in which a slurry of nickel particles collides and crushes from two directions with high water pressure, jet abutment treatment, etc. Can be mentioned.
[0018]
As a classification of a device for performing such a process, there are a high-speed moving body collision type air-flow type pulverizer, an impact type pulverizer, a cage mill, a medium stirring type mill, an axial flow mill, a jet abutment device, and the like. Specifically, a super hybrid mill (manufactured by Ishikawajima-Harima Heavy Industries), a jet mill (manufactured by Ebara Corporation), a supermass colloider (manufactured by Masuko Sangyo), a bead mill (manufactured by Irie Shokai), an optimizer (manufactured by Sugino Machine), an NC mill ( Ishii Pulverizer Co., Ltd., Disintegrator (Otsuka Iron Works), ACM Pulverizer (Hosokawa Micron), Turbo Mill (Matsubo), Supermicron (Hosokawa Micron), Micros (Nara Machinery), New Cosmomizer (Nara Machinery) ), Fine Victor Mill (Hosokawa Micron), Ecoplex (Hosokawa Micron), CF Mill (Ube Industries), Hybridizer (Nara Machinery), Pin Mill (Alpinay), Pressure Homogenizer (Nippon Seiki Seisakusho), Harel Homogenizer ( Domestic Seiko), mechanical Fusion system (Hosokawa Micron), there is a sand mill (Yodo made by casting), and the like.
[0019]
In the production method of the present invention, by carrying out under the above-mentioned conditions, since the aggregation is small and close to a monodispersed state, the dispersibility in the organic vehicle in preparing the conductive paste is excellent, and the particle size distribution is further improved. It has a sharp particle size distribution with a standard deviation σ of 0.18 or less and is suitable for preparing a conductive paste used for forming a thin and projection-free internal electrode. The density of a dried film obtained after the formation of the paste is 4.8 g. / Cm ³ or more, and Ra can be 0.20 μm or less, and monodispersed nickel powder which can be suitably used for production of a multilayer ceramic capacitor can be produced.
[0020]
Next, a preferred method for producing a conductive paste for a multilayer ceramic capacitor will be described.
The conductive paste for a multilayer ceramic capacitor is composed of nickel powder, a resin, a solvent, and the like obtained by the production method of the present invention, and can further contain a dispersant, a sintering inhibitor, and the like, if necessary. Specifically, as a resin, a cellulose derivative such as ethyl cellulose, an acrylic resin, a polyvinyl butyral resin, a vinyl-based non-curable resin such as polyvinyl alcohol, and a thermosetting resin preferably used in combination with a peroxide such as epoxy and acrylic Can be used. In addition, terpineol, tetralin, butyl carbitol, carbitol acetate, and the like can be used alone or in combination as a solvent. Further, a glass frit may be added to this paste as needed. The conductive paste for a multilayer ceramic capacitor of the present invention is obtained by mixing and stirring the above raw materials using a mixing machine such as a ball mill or a three-roll mill.
[0021]
【Example】
Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples.
Example 1
30 kg of ethylene glycol (manufactured by Mitsui Chemicals, Inc.) and 0.81 kg of polyvinylpyrrolidone K30 (manufactured by Wako Pure Chemical Industries, Ltd.) were added to a 50 L tank, and the mixture was stirred with a small stirrer at a rotational speed of 350 rpm to obtain polyvinylpyrrolidone. K30 was dissolved (this solution is referred to as solution A for convenience).
[0022]
Next, 16.28 Kg of nickel hydroxide (manufactured by OM Group) and 10.6 mL of palladium nitrate solution (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) adjusted to 100 g / L were added to solution A (for convenience, this solution was used as a solution). B). This solution B was sent to a 200 L reaction tank, and 152.9 kg of ethylene glycol was further added thereto, followed by heating to 190 ° C. As the temperature rose, the liquid color in the reaction tank changed from green to black. In addition, water and organic substances by-produced were distilled off in a distillation line. After reaching 190 ° C., sampling was performed every hour, and the progress of the reaction was confirmed by XRD. It was confirmed that nickel powder was generated by complete reduction in 5 hours.
[0023]
After the completion of the reaction, the temperature was lowered to room temperature, and the supernatant was cut using a magnetic separator to obtain a slurry having a concentration of 80% by mass. This slurry was put in a 70 L tank, 30 L of pure water was added thereto, and the mixture was vigorously stirred. Then, the supernatant was cut using a magnetic separator. This operation was performed twice.
[0024]
Pure water was added to the obtained slurry to adjust the concentration to 10% by mass. Using a wet atomizer (Ultimizer system: manufactured by Sugino Machine Co., Ltd.), crushing was performed under the conditions of a pressure of 245 MPa.
[0025]
The average primary particle size (average primary particle size) of the nickel fine particles obtained by crushing and drying at 80 ° C. for 5 hours was 0.3 μm by SEM observation. As a result of the particle size distribution measured with a laser diffraction scattering particle size distribution analyzer X100 (manufactured by Microtrac _{Inc.), D 10} is 0.29 _{.mu.m, D 50} is 0.38 _{.mu.m, D 90} is 0.55 .mu.m, and _{D max} is 0.97 μm, and the standard deviation (σ) of the particle size distribution was 0.098. The true specific gravity was 8.61 g / cm ³ , the tap density was 3.8 g / cm ³ , and the specific surface area was 2.58 m ² / g.
[0026]
50 g of this nickel powder, 2.5 g of ethylcellulose and 47.5 g of terpineol were mixed, kneaded with a three-roll mill, and made into a paste. After forming a film with a coating machine, the film was dried at 80 ° C. The density of the obtained dried film was 5.23 g / cm ³ , and Ra was 0.12 μm.
[0027]
Example 2
Up to the reaction operation, the same operation as in Example 1 was performed to generate nickel powder.
After the completion of the reaction, the temperature was lowered to room temperature, and the supernatant was cut using a magnetic separator to obtain a slurry having a concentration of 80% by mass. This slurry was added to a 70 L tank, 30 L of pure water was added, and the mixture was vigorously stirred. The supernatant was cut using a magnetic separator. This operation was performed twice.
The obtained slurry was dried at 80 ° C. for 5 hours to obtain a nickel powder. The obtained nickel powder was crushed using a hybridizer (manufactured by Nara Machinery Co., Ltd.).
[0028]
After the crushing treatment, the nickel particles had an average primary particle size (average particle size of primary particles) of 0.3 μm by SEM observation. As a result of the particle size distribution measured with a laser diffraction scattering particle size distribution analyzer X100 (manufactured by Microtrac _{Inc.), D 10} is 0.29 _{.mu.m, D 50} is 0.41 _{.mu.m, D 90} is 0.64 .mu.m, and _{D max} is The particle size distribution was 1.38 μm, and the standard deviation (σ) of the particle size distribution was 0.133. The true specific gravity was 8.71 g / cm ³ , the tap density was 3.5 g / cm ³ , and the specific surface area was 2.89 m ² / g.
[0029]
50 g of this nickel powder, 2.5 g of ethylcellulose and 47.5 g of terpineol were mixed, kneaded with a three-roll mill, and made into a paste. After forming a film with a coating machine, the film was dried at 80 ° C. The density of the obtained dried film was 5.02 g / cm ³ , and Ra was 0.13 μm.
[0030]
Example 3
Up to the reaction operation, the same operation as in Example 1 was performed to generate nickel powder.
After the completion of the reaction, the temperature was lowered to room temperature, and the supernatant was cut using a magnetic separator to obtain a slurry having a concentration of 80% by mass. This slurry was placed in a 70 L tank, 30 L of pure water was added, and the mixture was vigorously stirred, and the supernatant was cut using a magnetic separator. This operation was performed twice.
[0031]
This slurry was put into a 70 L tank, 30 L of methanol was further added, and vigorous stirring was performed. This operation was performed twice.
After washing the obtained slurry, the concentration was adjusted to 60% by mass, and the slurry was dried at 80 ° C. for 5 hours using a vibration fluidized drier (manufactured by Chuo Kakoki) filled with balls.
[0032]
The average primary particle size (average primary particle size) of the obtained nickel fine particles by SEM observation was 0.3 μm. As a result of the particle size distribution measured with a laser diffraction scattering particle size distribution analyzer X100 (manufactured by Microtrac _{Inc.), D 10} is 0.30 _{.mu.m, D 50} is 0.43 _{.mu.m, D 90} is 0.66 .mu.m, and _{D max} is 1.38 μm, and the standard deviation (σ) of the particle size distribution was 0.140. The true specific gravity was 8.65 g / cm ³ , the tap density was 3.4 g / cm ³ , and the specific surface area was 2.69 m ² / g.
[0033]
50 g of this nickel powder, 2.5 g of ethylcellulose and 47.5 g of terpineol were mixed, kneaded with a three-roll mill, and made into a paste. After forming a film with a coating machine, the film was dried at 80 ° C. The density of the obtained dried film was 4.91 g / cm ³ , and Ra was 0.18 μm.
[0034]
Comparative Example 1
The same operation as in Example 1 was performed except that the wet crushing treatment was not performed, to generate nickel powder.
After drying at 80 ° C. 5 hours, the results of the particle size distribution measured by a laser diffraction scattering particle size distribution analyzer X100 (manufactured by Microtrac _{Inc.), D 10} is 0.38 _{.mu.m, D 50} is 0.68 _{.mu.m, D 90} is 1.10 μm, D _max was 2.75 μm, and standard deviation (σ) was 0.270. Also, true specific gravity of 8.60 g / cm ^3, a tap density of 3.0 g / cm ^3, and specific surface area was 2.48m ² / g.
[0035]
50 g of this nickel powder, 2.5 g of ethylcellulose and 47.5 g of terpineol were mixed, kneaded with a three-roll mill, and made into a paste. After forming a film with a coating machine, the film was dried at 80 ° C. The density of the obtained dried film was 4.17 g / cm ³ , and Ra was 0.89 μm.
[0036]
Comparative Example 2
The same operation as in Example 2 was performed except that the dry crushing treatment was not performed, to generate nickel powder.
After drying at 80 ° C. for 5 hours, the particle size distribution was measured with a laser diffraction / scattering type particle size distribution analyzer X100 (manufactured by Microtrac Co., Ltd.). As a result, D ₁₀ was 0.35 μm, D ₅₀ was 0.69 μm, and D ₉₀ was 1.26 μm, D _max was 5.50 μm, and standard deviation (σ) was 0.346. The true specific gravity was 8.71 g / cm ³ , the tap density was 2.9 g / cm ³ , and the specific surface area was 2.75 m ² / g.
[0037]
50 g of this nickel powder, 2.5 g of ethylcellulose and 47.5 g of terpineol were mixed, kneaded with a three-roll mill, and made into a paste. After forming a film with a coating machine, the film was dried at 80 ° C. The density of the obtained dried film was 4.02 g / cm ³ , and Ra was 1.15 μm.
[0038]
Comparative Example 3
Except that the treatment with methanol was not performed, the same operation as in Example 3 was performed to generate nickel powder.
After drying at 80 ° C. 5 hours, the results of the particle size distribution measured by a laser diffraction scattering particle size distribution analyzer X100 (manufactured by Microtrac _{Inc.), D 10} is 0.48 _{.mu.m, D 50} is 0.84 _{.mu.m, D 90} is 1.31 μm, D _max was 3.27 μm, and standard deviation (σ) was 0.314. Also, true specific gravity of 8.64 g / cm ^3, a tap density of 2.8 g / cm ^3, and specific surface area was 2.57m ² / g.
[0039]
This nickel powder (50 g), ethyl cellulose (2.5 g) and terpineol (47.5 g) were mixed and kneaded with a three-roll mill to form a paste. After forming a film with a coating machine, the film was dried at 80 ° C. The density of the obtained dried film was 4.11 g / cm ³ , and Ra was 1.21 μm.
[0040]
As is clear from the data of the above Examples and Comparative Examples, in Comparative Examples 1 to 3 in which the crushing treatment was not performed, since there was aggregation, the standard deviation σ was large, and the particle size distribution was broad. Yes, the density of the dried film obtained after pasting is low, and Ra is high.
[0041]
On the other hand, in the production methods of the present invention of Examples 1 to 3, the agglomeration is small, close to a monodispersed state, and the standard deviation σ of the particle size distribution is a sharp particle size distribution of 0.18 or less. The density of the obtained dried film is 4.8 g / cm ³ or more, and Ra is 0.20 μm or less, and monodispersed nickel powder which can be suitably used for production of a multilayer ceramic capacitor can be produced.
[0042]
【The invention's effect】
Since the monodispersed nickel powder obtained by the production method of the present invention has little aggregation and is close to a monodispersed state, it has excellent dispersibility in an organic vehicle in the preparation of a conductive paste, and further has a standard deviation σ of particle size distribution of 0. Since it has a sharp particle size distribution of .18 or less, it is suitable for preparing a conductive paste used for forming a thin and projection-free internal electrode, and the density of a dried film obtained after the formation of the paste is 4.8 g / cm ³ or more. It is a monodispersed nickel powder that can be made and has a Ra of 0.20 μm or less, and can be suitably used for manufacturing a multilayer ceramic capacitor.

Claims (5)

In a polyol containing a noble metal compound catalyst and a dispersant, a powder selected from the group consisting of a nickel salt powder and a nickel hydroxide powder is suspended, and sufficient to reduce the powder to nickel powder. A method for producing nickel powder, characterized in that the powder is heated to a temperature to generate nickel powder, and the generated agglomerated nickel powder is crushed and monodispersed. The method for producing nickel powder according to claim 1, wherein the crushing treatment is performed by a wet crushing method or a dry crushing method. In a polyol containing a noble metal compound catalyst and a dispersant, a powder selected from the group consisting of a nickel salt powder and a nickel hydroxide powder is suspended, and sufficient to reduce the powder to nickel powder. The powder is heated to a temperature to generate nickel powder, and the generated agglomerated nickel powder is washed with an organic solvent having a boiling point of 100 ° C. or lower or a mixed solvent of the organic solvent and water, and dried in a vibration drier filled with balls. A method for producing nickel powder. The method for producing nickel powder according to any one of claims 1 to 3, wherein monodisperse nickel powder having a standard deviation σ of particle size distribution of 0.18 or less is produced. 5. A monodisperse nickel powder capable of producing a dried film having a density of at least 4.8 g / cm < ³ > and a Ra of at most 0.20 [mu] m after the nickel powder is made into a paste. Production method of nickel powder.