JP2010059493A - Nickel fine powder and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing nickel fine powder whose dispersibility is sufficiently secured and which is suitable as the material for an electronic component with high productivity also at a low cost. <P>SOLUTION: The method includes: a stage (A) where a nickel salt aqueous solution is neutralized with an alkali aqueous solution so as to produce nickel hydroxide precipitates, and next, nickel hydroxide powder is obtained; a stage (B) where the nickel hydroxide precipitates are roasted in a nonreducing atmosphere so as to produce nickel oxide powder; a stage (C) where the nickel oxide powder is granulated so as to obtain a granulated body of nickel oxide powder; a stage (D) where the granulated body of nickel oxide powder is dried; and a stage (E) where the granulated body of nickel oxide powder after the drying is reduced in a reducing gas atmosphere so as to obtain nickel fine powder. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a nickel fine powder and a method for producing the same, and more particularly to a method for producing a nickel fine powder having sufficiently ensured dispersibility suitable as an electronic component material with high productivity and low cost.

  Conventionally, nickel powder has been used as a material for a conductive paste for producing a thick film conductor. The thick film conductor is used for forming an electric circuit, an electrode of a multilayer ceramic component such as a multilayer ceramic capacitor and a multilayer ceramic substrate. In particular, increasing the number of layers is an effective way to improve the performance of multilayer ceramic capacitors. However, increasing the number of layers leads to an increase in the size of electronic components. It is necessary to reduce the thickness of the layer (thinning). For this reason, nickel fine powder having a particle size of 1.0 μm or less is widely used as a conductor forming material for electronic parts such as electrodes of multilayer ceramic capacitors.

  As described above, when the electrode layer of the multilayer ceramic capacitor is thinned, the nickel fine powder used as the internal electrode forming material is required to have a small particle diameter and high dispersibility. For example, when nickel fine powder in which a large number of particles are aggregated is used as the internal electrode forming material, the thickness of the formed electrode varies, which causes a short circuit between electrodes or a decrease in insulation resistance. Therefore, regarding the production of nickel fine powder for electronic component materials, securing the dispersibility of the obtained nickel fine powder is an important issue.

By the way, nickel fine powder having a particle size of 1.0 μm or less, which is generally used as an electronic component material, is manufactured by a known technique such as a gas phase reduction method, a wet reduction method, a spray pyrolysis method, or an evaporation aggregation method. Yes. However, further downsizing and higher efficiency of electronic components are further demanded, and the demand for particles having a smaller particle size and better dispersibility than before is increasing. Has become apparent and improvements have been demanded.
That is, in the gas phase particle synthesis method represented by the gas phase reduction method, the spray pyrolysis method, and the evaporation aggregation method, it is necessary to control the particle generation density to be small in order to produce particles having excellent dispersibility. Therefore, there is a problem that the manufacturing cost becomes large. On the other hand, when the production density is increased with emphasis on productivity, connected particles and coarse particles are likely to be generated, and in order to separate them, it is necessary to repeat the classification operation, which also increases the cost. The problem occurs.

  The wet reduction method is suitable as a method for producing particles having a fine particle diameter and excellent dispersibility. However, in this method, a method using a large amount of reducing agent and adsorbing a dispersing agent on the surface is generally used, which increases the quality of impurities or increases the processing cost of difficult-to-process waste liquid generated during production. There's a problem.

  On the other hand, as a manufacturing method that does not require complicated equipment and is relatively low in cost, there is an oxide powder reduction method. In this method, a nickel salt is neutralized by wet neutralization to crystallize nickel hydroxide, and the obtained nickel hydroxide is used as it is, or converted to an oxide by oxidative roasting, hydrogen, etc. The nickel fine powder is obtained by carrying out the reduction treatment in a reducing gas atmosphere. For example, in order to obtain nickel fine powder having a particle size of 1 μm or less using this oxide powder reduction method, a nickel-containing solution is continuously added to a slurry kept at a constant temperature as possible in the range of 40 to 80 ° C. And adding an alkaline solution so as to keep the slurry pH value as constant as possible in the range of 8.0 to 9.5 to produce nickel hydroxide, and then filtering the slurry. A method is proposed in which nickel powder is obtained by washing with water and drying to obtain nickel hydroxide, and then heating and reducing this using hydrogen gas at a temperature of 400 to 500 ° C. (see, for example, Patent Document 1). Has been. According to this method, the nickel powder produced at the time of reduction aggregates or sinters, and there is a problem that nickel powder excellent in dispersibility cannot be obtained.

  As a solution to this, in order to prevent the aggregation or sintering of nickel powder during reduction and improve dispersibility, a method of reducing a mixture of a nickel compound and a sintering inhibitor, for example, adding an alkali metal compound to an aqueous nickel solution Add to the neutralization reaction to form a slurry containing a nickel compound and a sintering inhibitor, a slurry adjustment step, dry the slurry obtained in the slurry adjustment step, a mixture of nickel compound and sintering inhibitor The resulting drying step, the mixture obtained in the drying step is subjected to hydrogen reduction, the reduction step forming a reduction product containing metallic nickel particles, and the reduction product obtained in the reduction step is subjected to leaching with an aqueous solution. A nickel powder manufacturing method including a wet processing step for obtaining metallic nickel particles (see, for example, Patent Document 2) is disclosed. However, since the nickel powder obtained by this method is as fine as an average particle size of less than 0.1 μm, it is not only limited in use as a material for electronic parts, but it also cleans a large amount of sintering inhibitor. There was a problem that it was necessary and it was not cheap.

Moreover, as a method for preventing aggregation or sintering of metal powder obtained by reducing the metal compound, a method of granulating the metal compound and reducing the granulated product, for example, a granulated product of iron compound powder A method for producing a metal magnetic powder, which is placed in a transport container having a structure capable of flowing gas, transports the transport container to a heat reduction reaction furnace, and heats and reduces the granulated product of the iron compound powder in the presence of a reducing gas. (For example, refer to Patent Document 3). According to this method, it is said that a metal magnetic powder free from changes in the shape of the iron particles and the sintering between the particles can be produced industrially advantageously. However, when this method is applied to nickel fine powder, the shape of the powder changes greatly during the reduction of nickel oxide powder, unlike the reduction of iron compound powder, so it is unclear whether the same method as that for iron compound powder can be applied. It is.
As described above, in the conventional technology, it has been difficult to achieve both uniform production of nickel fine powder having sufficiently dispersibility as a material for electronic parts and production with high productivity. .

JP 2003-213310 A (first page, second page) Japanese Patent Application Laid-Open No. 2004-323884 (first page, second page) JP-A-10-280013 (first page, second page)

  An object of the present invention is to provide a method for producing nickel fine powder having sufficient dispersibility suitable as an electronic component material with high productivity and low cost in view of the above-mentioned problems of the prior art. .

  In order to achieve the above object, the present inventors have focused on an oxide powder reduction method that does not require complicated equipment and can be expected to reduce costs, and a method for uniformly producing nickel fine powder having excellent dispersibility. As a result of intensive research, step (A) for obtaining nickel hydroxide powder, step (B) for producing nickel oxide powder, and step (C) for obtaining a granulated body of nickel oxide powder under specific conditions. When nickel fine powder is obtained by a series of steps including the step (D) of drying the granulated body of nickel oxide powder and the step (E) of obtaining nickel fine powder, the dispersibility suitable as a material for electronic parts is obtained. The inventors have found that sufficiently secured nickel fine powder can be produced at high productivity and at low cost, and the present invention has been completed.

  That is, according to the first invention of the present invention, the step (A) of producing a nickel hydroxide precipitate by neutralizing an aqueous nickel salt solution with an aqueous alkaline solution and then obtaining nickel hydroxide powder, and the nickel hydroxide precipitation A step (B) of producing a nickel oxide powder by granulation in a non-reducing atmosphere, a step (C) of granulating the nickel oxide powder to obtain a granulated body of the nickel oxide powder, and the nickel oxide Nickel comprising: a step (D) of drying a granulated product of powder, and a step (E) of obtaining a nickel fine powder by reducing the granulated product of nickel oxide powder after drying in a reducing gas atmosphere A method for producing a fine powder is provided.

  According to the second invention of the present invention, in the first invention, in the step (D), the content moisture content of the dried nickel oxide powder granule is 5% by mass or less. A method for producing a nickel fine powder is provided.

  In addition, according to the third invention of the present invention, in the first or second invention, when the nickel oxide powder is granulated in the step (C), the nickel oxide powder and the solvent are mixed to form a slurry. There is provided a method for producing nickel fine powder, characterized in that a granulated body is obtained by molding the resulting slurry.

  According to a fourth aspect of the present invention, there is provided the method for producing nickel fine powder according to the third aspect, wherein the solvent is pure water.

  According to a fifth invention of the present invention, in any one of the first to fourth inventions, in the step (C), the shape of the granulated body is any of a spherical shape, a spheroid shape, and a cylindrical shape. A method for producing a nickel fine powder is provided.

  Further, according to a sixth invention of the present invention, in the fifth invention, the size of the granulated body is 2-10 mm in diameter when the shape is spherical after drying, and when the shape is a spheroid, In the case of a diameter of 2 to 10 mm and a rotating shaft length of 2 to 50 mm, and in the case of a cylindrical shape, a method for producing nickel fine powder characterized by a diameter of 2 to 10 mm and a length of 2 to 50 mm is provided.

According to a seventh invention of the present invention, in any one of the first to sixth inventions, the apparent density of the granulated body is 1 to ³ g / cm ³ after drying. A method for producing a fine powder is provided.

  According to an eighth invention of the present invention, in any one of the first to seventh inventions, in the step (E), the reducing gas atmosphere is a gas containing hydrogen. A manufacturing method is provided.

  According to a ninth invention of the present invention, in any one of the first to eighth inventions, in the step (E), the reduction temperature is 300 to 500 ° C. Is provided.

  According to a tenth aspect of the present invention, in any one of the first to ninth aspects, in the step (A), the nickel salt aqueous solution contains a second group element that serves as a fusion inhibitor during reduction. A method for producing nickel fine powder is provided.

Moreover, according to the eleventh invention of the present invention, the nickel fine powder obtained by the method for producing nickel fine powder according to any one of the first to tenth inventions,
The particle size distribution measured by the laser scattering method provides a nickel fine powder characterized in that D90 is 0.95 μm or less.

  The nickel fine powder and the method for producing the same of the present invention can produce nickel fine powder having sufficiently ensured dispersibility suitable as a material for electronic components at high productivity and low cost. .

Hereinafter, the nickel fine powder of the present invention and the production method thereof will be described in detail.
The method for producing nickel fine powder of the present invention comprises a step (A) of neutralizing a nickel salt aqueous solution with an alkaline aqueous solution to form a nickel hydroxide precipitate, and then obtaining nickel hydroxide powder, and non-reducing the nickel hydroxide precipitate. A step (B) of baking in a neutral atmosphere to produce nickel oxide powder, a step (C) of granulating the nickel oxide powder to obtain a granulated body of nickel oxide powder, and a step of producing the nickel oxide powder. The method includes a step (D) of drying the granules, and a step (E) of reducing the dried nickel oxide powder granules in a reducing gas atmosphere to obtain nickel fine powder.

  In the present invention, the dried nickel oxide powder granule is reduced in a reducing gas atmosphere to obtain an important technical significance. That is, during the reduction, the generated water vapor greatly affects the dispersibility of the nickel fine powder, so that it is possible to suppress the amount of water vapor generated and efficiently discharge the generated water vapor. It is effective to obtain. For this reason, nickel oxide obtained by oxidative roasting of nickel hydroxide is used as a granulated product, and the granulated product is sufficiently dried and then subjected to a reduction treatment, whereby it can be produced with high productivity uniformly.

The technical features of the production method of the present invention will be described below in comparison with the conventional oxide powder reduction method.
In the conventional oxide powder reduction method, a nickel salt is neutralized by wet neutralization to crystallize nickel hydroxide, and the obtained nickel hydroxide is used as it is or converted to oxide by oxidation roasting. After that, it is a method to obtain nickel fine powder by reducing treatment in a reducing gas atmosphere such as hydrogen, and the nickel powder produced during the reduction aggregates or sinters, and the nickel powder with excellent dispersibility cannot be obtained There was a point.

  That is, in general, when nickel hydroxide powder is used as it is in a reduction treatment under a reducing gas atmosphere, nickel hydroxide is once converted into nickel oxide during the reduction treatment, and then nickel fine powder is generated. Moreover, when it reduces to oxide powder and carries out a reduction process, nickel fine powder produces | generates directly from nickel oxide powder. In either case, the nickel fine powder is produced by reducing the nickel oxide powder, but at this time, the nickel fine powder is not produced by being metallized while leaving the nickel oxide powder remains. That is, the nickel oxide powder is reduced from the surface and becomes a fine nickel powder with generation of fine nickel particles. For this reason, in the nickel fine powder obtained in this way, the activity of the surface of the generated nickel fine powder is increased, so compared to the case of other metal powders that are metallized while leaving the form, Aggregation or sintering is likely to occur. Further, when a large amount of water vapor is present in the atmosphere during the reduction, not only the contact of the nickel oxide powder with the reducing gas is hindered, but also the action of aggregating or sintering the metal particles possessed by the water vapor becomes greater.

  Accordingly, it is important to suppress the amount of water vapor generated during reduction and to discharge the generated water vapor out of the system. For this reason, from the viewpoint of improving gas flow and discharging water vapor outside the system, a method of reducing nickel oxide powder while flowing it using a rotary kiln or the like is considered effective, but in the case of reduction of nickel oxide powder. Is not suitable because there is a large difference in fluidity between the nickel oxide powder and the nickel fine powder obtained by reduction, so that the nickel fine powder tends to be unevenly distributed and easily becomes agglomerated or sintered nickel fine powder. For this reason, in the stationary reduction method, means for improving gas flow and discharging water vapor out of the system is used.

In the stationary reduction method, in order to discharge water vapor, for example, when nickel oxide powder is loaded in a heat-resistant container and reduced, it is possible to reduce the layer thickness of the loaded nickel oxide powder. There is a problem that productivity is significantly reduced.
On the other hand, if the granulated body of nickel oxide powder is reduced in a reducing gas atmosphere as in the method of the present invention, water vapor is sufficiently discharged by circulating the atmosphere gas between the granulated bodies. In addition, the amount of nickel oxide powder that can be reduced can be greatly increased. Furthermore, as in the method of the present invention, the nickel hydroxide powder is sufficiently oxidized and roasted to make it completely nickel oxide powder, and the granulated body before reduction is sufficiently dried to remove the contained moisture. Therefore, it is essential to suppress the amount of water vapor generated itself. That is, in the case of the reduction of nickel oxide powder, as described above, the surface activity of the nickel fine powder to be produced is high, and the particles are easily aggregated or sintered. This is because it is not sufficient to facilitate the discharge of water vapor, and it is necessary to suppress the amount of water vapor generated itself.

  As described above, in the production method of the present invention, nickel hydroxide powder is roasted in a non-reducing atmosphere to produce nickel oxide powder (B), and nickel oxide powder granulated body (C) ) And the step (D) of drying the nickel oxide powder granule, the amount of water vapor generated during the reduction can be suppressed and the generated water vapor can be discharged out of the system. Excellent and uniform nickel fine powder can be obtained with high productivity.

Below, the manufacturing method of the nickel fine powder of this invention is demonstrated for every process.
(1) Step (A)
The step (A) is a step of neutralizing an aqueous nickel salt solution with an aqueous alkaline solution to form a nickel hydroxide precipitate, and then obtaining nickel hydroxide powder.

  The aqueous nickel salt solution used in the step (A) is not particularly limited, and an aqueous solution containing a water-soluble nickel salt such as nickel chloride, nickel sulfate, nickel nitrate, or nickel organic acid salt is used. Thus, it is preferable to use an aqueous nickel chloride salt solution from the viewpoints of environmental effects such as ease of wastewater treatment and cost.

  If necessary, the nickel salt aqueous solution can contain a second group element of the periodic table such as magnesium, which serves as a fusion inhibitor during reduction, as a known technique. As a result, nickel fine powder having more excellent dispersibility can be obtained. That is, the effect can be further enhanced by using in combination with the present invention.

  The method for generating the nickel hydroxide precipitate used in the step (A) is not particularly limited, and a known technique can be used. For example, in the neutralization reaction between the nickel salt aqueous solution and the alkali, the pH is adjusted. If it is carried out while keeping constant, the rate of precipitation generation can be kept constant, which is preferable in order to obtain uniform precipitation.

  Although it does not specifically limit as pH at the time of neutralizing used at the said process (A), 7-9.5 are preferable and 8-9 are more preferable. That is, if the pH is less than 7, the nickel salt may not be sufficiently neutralized. On the other hand, when the pH exceeds 9.5, fine colloidal nickel hydroxide particles are formed, and solid-liquid separation becomes very difficult, and nickel oxide powder is agglomerated or sintered by the subsequent oxidation roasting. However, the dispersibility of the finally obtained nickel fine powder may not be sufficient.

  The method for neutralization used in the step (A) is not particularly limited, and while adding a nickel salt aqueous solution and an alkaline aqueous solution in a double-jet method in a well-stirred reaction vessel. It is effective to produce nickel hydroxide having uniform characteristics. Here, pure water can be used as the liquid previously placed in the reaction tank, but it is more preferable to use a liquid obtained by adjusting the filtrate once used for neutralization to a predetermined pH with an alkali.

  The alkaline aqueous solution used in the above step (A) is not particularly limited, and for example, an aqueous solution of an alkali metal hydroxide such as an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution is preferable. A sodium hydroxide aqueous solution is more preferable. In addition, although alkaline compounds, such as sodium hydroxide and potassium hydroxide, can be used directly instead of the alkaline aqueous solution, precipitation may be uneven.

In the step (A), the generated nickel hydroxide precipitate is recovered by dehydration by filtration to obtain a filter cake.
Here, as the filtration operation, it is preferable to use means capable of sufficiently reducing the residual chlorine concentration. For this reason, the following methods (a) to (c) are used.
(B) Repeat filtration and repulp washing several times.
(B) As a method of increasing the slurry concentration while lowering the residual chlorine concentration, cross flow filtration is used.
(C) As a method of washing so as to reduce the residual chlorine concentration while eliminating the gel of the obtained nickel hydroxide precipitate, washing is performed using an acid such as sulfuric acid.

  Among these, the method (c) uses acid such as sulfuric acid to efficiently reduce the chlorine remaining in the nickel hydroxide precipitate by washing while eliminating the gel of the nickel hydroxide precipitate obtained. This is more preferable. For example, in this method, it is particularly preferable to wash the produced nickel hydroxide precipitate with sulfuric acid or a sulfate aqueous solution having a concentration of 0.0004 to 0.0015 mol / L, and then with water. Here, when the concentration of sulfuric acid or sulfate aqueous solution is less than 0.0004 mol / L, a sufficient cleaning effect cannot be obtained, and when the concentration exceeds 0.0015 mol / L, the cleaning effect cannot be improved. The residual sulfur concentration becomes too high, and the resulting nickel fine powder may be unsuitable as an electronic material.

In the method (c), the temperature of the liquid at the time of cleaning can be room temperature, but may be heated to enhance the cleaning effect.
In the method (c), the amount of sulfuric acid or sulfate aqueous solution added to the nickel hydroxide precipitate is not particularly limited, and may be an amount that can sufficiently reduce residual chlorine. In order to disperse well, the concentration of the nickel hydroxide powder in the sulfuric acid or sulfate aqueous solution is preferably about 100 g / L. In addition, the cleaning time is not particularly limited, and may be a cleaning time in which the residual chlorine concentration is sufficiently reduced depending on the cleaning conditions. Moreover, it does not specifically limit as an apparatus used for washing | cleaning, The apparatus similar to water washing can be used.

  In the method (c), it is preferable to prepare an aqueous solution in which the concentration of sulfuric acid or sulfate is adjusted in advance, and add nickel hydroxide precipitate thereto while stirring. In addition, nickel hydroxide powder obtained by drying once can be added instead of nickel hydroxide precipitation, but it is easier to perform uniform treatment by using a cake-like product with water content. This not only improves the efficiency of the process, but also shortens the process.

Here, for uniform treatment, first, a small amount of water is added to a nickel hydroxide filter cake to form a slurry, and then a sulfuric acid or sulfate aqueous solution adjusted to have a predetermined concentration after the addition is added. It is preferable to add at a time while stirring.
The moisture content of the nickel hydroxide cake is not particularly limited, and is preferably 10 to 40% by mass, more preferably about 30% by mass. That is, when the water content is less than 10% by mass, there are restrictions such that it is difficult to uniformly disperse in an aqueous solution, the cleaning efficiency is deteriorated, and that more severe dehydration is required to reduce the water content. On the other hand, when the moisture content exceeds 40% by mass, the handling property of nickel hydroxide is poor, and uniform processing may be hindered, and the processing amount necessary to obtain a certain amount of nickel hydroxide increases. End up.

  The washed nickel hydroxide precipitate obtained in the step (A) can be dried by a known method such as air drying or vacuum drying. Thereby, the nickel hydroxide powder in which the residual chlorine concentration is sufficiently reduced is obtained.

(2) Process (B)
The step (B) is a step of firing the nickel hydroxide powder obtained in the step (A) in a non-reducing atmosphere to generate nickel oxide powder.
In the above step (B), the method for roasting is not particularly limited, and is a general method such as a stationary roasting furnace, a rolling furnace, a burner furnace, a conveying continuous furnace, a fluidized roasting furnace. However, in order to obtain the desired excellent dispersibility and uniform nickel fine powder, in this step, the characteristics are uniform and sufficiently in the form of nickel oxide. It is important to obtain converted nickel oxide powder. That is, if the conversion to the nickel oxide form is insufficient, nickel hydroxide remains, water vapor is generated by the decomposition of nickel hydroxide during the subsequent reduction process, and aggregation or sintering between the nickel particles does not occur. As a result, nickel fine powder having excellent dispersibility cannot be obtained.

The conditions for roasting used in the step (B) are not particularly limited, and may be arbitrarily set according to the characteristics of the furnace so that characteristics such as the particle diameter of the target nickel fine powder can be obtained. However, in order to carry out a uniform treatment, it is preferably carried out in a gas stream.
As an atmosphere of the roasting, there is no problem as long as it is in a non-reducing atmosphere, and an inert gas or an oxidizing gas is used as the atmosphere gas. Among these, use of air is cost and ease of handling. This is preferable.

  The roasting temperature is not particularly limited, and a temperature that can be sufficiently converted into the form of nickel oxide is selected. However, in the case of a general static roasting furnace, 350 to 550 is used. It is preferable to set it as ° C, and it is more preferable to set it as 400-500 ° C. That is, when the roasting temperature is less than 350 ° C., the conversion to the nickel oxide form is not sufficient and nickel hydroxide may remain. On the other hand, when the roasting temperature exceeds 550 ° C., the nickel oxide powder is agglomerated or sintered, and the nickel fine powder particles obtained by the reduction treatment are coarsened and the dispersibility may not be sufficient.

  The roasting time is not particularly limited, and in consideration of the roasting temperature, the processing amount, the equipment to be used, etc., the nickel hydroxide powder is sufficiently converted into the nickel oxide form, and the nickel hydroxide powder Conditions are selected that allow the corpse to remain.

(3) Process (C)
The said process (C) is a process of granulating the nickel oxide powder obtained at the process (B), and obtaining the granulated body of nickel oxide powder.

  Here, by granulating the nickel oxide powder, the reduction reaction in the subsequent step (E) can be progressed uniformly, and the resulting nickel fine powder has good dispersibility and uniform characteristics. Can be. And productivity can be improved significantly compared with the case where it does not granulate. In other words, in order to make the reduction reaction proceed uniformly, the contact interface between the reducing gas such as hydrogen and the raw material nickel oxide powder should be increased so that the entire raw material starts to react as uniformly as possible. In addition, the water vapor generated by the reaction hinders the reduction reaction of the unreacted raw material and satisfies the two requirements of prompt removal from the reaction system in order to promote the aggregation or sintering of the produced nickel particles. However, by granulating the nickel oxide powder in this process, even if the amount of nickel oxide powder to be reduced is increased, the macroscopic contact interface can be increased and the gas flow path can be increased. Therefore, nickel fine powder with uniform characteristics can be obtained.

In order to satisfy the above requirements, it is preferable to appropriately adjust the characteristics of the granulated body of nickel oxide powder. That is, when granulating the nickel oxide powder, it is important to suppress variations in the density and size of individual granulated bodies as much as possible and to avoid changes in the particle diameter, fine structure, etc. of the raw nickel oxide powder.
Therefore, as the granulation method, a wet method is suitable. For example, a method in which nickel oxide powder and a solvent are mixed to form a slurry, and the resulting slurry is molded to obtain a granulated body is preferable. Here, the nickel oxide powder and the solvent are mixed and slurried so as to obtain properties such as viscosity suitable for molding.

  The solvent is not particularly limited, and any organic solvent can be used, and a binder component such as a resin can be added. However, in consideration of the effect on the reduction reaction in the next step, pure water is used. It is preferable to use it. In addition, when an organic solvent is used as the solvent, it is necessary to remove it in advance in order to prevent carbon or the like from remaining in the subsequent step (E). For this reason, it is possible to add a process under an appropriate condition before the reduction process in the step (E), for example, a process of heat treatment in an air atmosphere at a temperature of 300 to 400 ° C.

  In the slurrying, a general kneader or a stirrer can be used. For example, an arbitrary method such as a twin screw kneader or a rotation / revolution stirrer can be used depending on the scale and characteristics. Moreover, when shaping | molding, a general shaping | molding machine can be used, for example, a uniaxial extrusion molding machine, a roll press machine, etc. can be used.

  The shape of the granulated body is not particularly limited, and is preferably a spherical shape, a spheroid or a cylindrical shape for the strength of the molded body or a uniform reaction with gas. In other words, the angular shape tends to be broken during handling and may cause dust generation, and the gas contact interface and the gas flow path may not be sufficiently secured.

  Although it does not specifically limit as a dimension of the said granule, It is preferable that a diameter is 2-10 mm in the case of a sphere after drying, and a diameter is 2 in the case of a spheroid. 10 to 10 mm and the rotation axis length is preferably 2 to 50 mm. In the case of a cylindrical shape, the diameter is preferably 2 to 10 mm and the length is preferably 2 to 50 mm. That is, when the diameter of the granulated body after drying exceeds 10 mm, the reaction between the inside and outside of the granulated body becomes non-uniform during the reduction reaction, resulting in variations in characteristics. On the other hand, when the diameter of the granulated body after drying is less than 2 mm, the granulation effect may not be sufficiently obtained in the reduction reaction in the subsequent step (E). In the case of a spheroid or cylindrical shape, if the length is out of the above range, the granulated body collapses and causes dust generation during handling such as reduction treatment in the subsequent step (E).

Although it does not specifically limit as an apparent density of the said granulated body, In order to advance the reductive reaction in a subsequent process (E) uniformly with the whole granulated body, ^1-3 g / cm < ³ > after drying. It is preferable that That is, when the apparent density of the granulated body exceeds ³ g / cm ³ , the reaction between the central part and the outer peripheral part of the granulated body becomes non-uniform during the reduction reaction, which may cause variation in characteristics. In addition, if an excessive compressive force is applied at the time of molding in order to increase the apparent density of the granulated body, characteristics such as the particle size and microstructure of the nickel oxide powder are changed, and the target nickel fine powder cannot be obtained. On the other hand, if the apparent density of the granulated body is less than 1 g / cm ³ , sufficient strength cannot be obtained in the granulated body, the granulated body may collapse, and the granulation effect may not be sufficiently obtained. In addition, there is a possibility of dust generation due to collapse.

  In addition, the size and the apparent density of the granulated body are defined by the numerical values after drying, when the granulation is performed under a certain condition by the above granulation method, the change in the size and the apparent density of the granulated body before and after the drying is Since it is stable, the size and apparent density after drying are easily within the above range by determining the granulation conditions by granulating with a small amount of sample in consideration of the solvent amount, shape, granulation pressure, etc. This is because it can be controlled.

(4) Process (D)
The said process (D) is a process of drying the granulated body of the nickel oxide powder obtained at the process (C). Here, by sufficiently drying the granulated body, nickel powder having uniform characteristics and excellent dispersibility can be obtained by the reduction treatment in the next step (E). That is, when the granulated body is not sufficiently dried, water vapor is generated during the reduction treatment, and the aggregation or sintering of the nickel fine powder generated as described above is promoted to obtain nickel fine powder with excellent dispersibility. Absent.

  In the step (D), the moisture content of the granulated nickel oxide powder after drying is not particularly limited, but is preferably 5% by mass or less, and 3% by mass or less. Is more preferable. That is, if the moisture content exceeds 5% by mass, nickel fine powder having excellent dispersibility may not be obtained due to the influence of the generation of water vapor.

  The drying method used in the step (D) is not particularly limited, and a general stationary dryer may be used, or a vibration dryer may be used. However, when using a vibratory dryer, it is necessary to pay attention to the collapse of the molded body, and it is necessary to set appropriate conditions for the strength and shape of the molded body.

  The drying temperature and time used in the step (D) are not particularly limited, and normal conditions are selected. For example, the drying temperature is preferably 60 to 200 ° C. It should be noted that if the drying temperature is too high, the granulated body may be collapsed. Further, the drying time may be a time that can be sufficiently dried in consideration of the drying temperature and the processing amount.

(5) Process (E)
The said process (E) is a process of reducing the granulated body of the nickel oxide powder after drying in a reducing gas atmosphere, and obtaining nickel fine powder.
As the processing conditions used in the above step (E), the processing temperature, time, etc. can be appropriately set according to the target particle diameter and the like. For example, in the same manner as in the step (B), In order to obtain uniform nickel fine powder, it is preferable to carry out and give a uniform air flow to the granulated body as much as possible. In addition, it is preferable to increase the flow rate as long as the temperature does not vary and decrease, because the gas exchange efficiency can be improved.

  The reduction temperature used in the step (E) is not particularly limited, and is preferably 300 to 500 ° C. in order to obtain nickel fine powder having a particle diameter of 1 μm or less. That is, as the reduction temperature is higher and the reduction time is set longer, the particle size tends to increase. Therefore, in order to obtain nickel fine powder having a mean particle diameter of 0.5 μm or less, which is a more preferable average particle diameter for electronic component materials, the reduction temperature is more preferably 380 to 480 ° C. Here, when the reduction temperature is less than 300 ° C., nickel oxide is not sufficiently reduced, and the oxygen content of the obtained nickel fine powder may increase. On the other hand, when the reduction temperature exceeds 500 ° C., the nickel fine powder is agglomerated or sintered, and the dispersibility may deteriorate.

  Although it does not specifically limit as reducing atmosphere used at the said process (E), In order to prevent mixing of impurities, such as carbon, in the nickel fine powder obtained, it is preferable to set it as hydrogen or a hydrogen containing gas atmosphere. . Here, the hydrogen-containing gas atmosphere is preferably a mixed gas atmosphere with an inert gas such as nitrogen. In that case, the hydrogen content is preferably 10 to 50% by volume. That is, when the hydrogen content is less than 10% by volume, the reduction reaction rate becomes slow, and aggregation or connection of nickel fine powder occurs. On the other hand, if the hydrogen content exceeds 50% by volume, the reaction proceeds rapidly and the amount of water vapor generated increases, which again causes aggregation or connection of nickel fine powder.

  The method of the reduction treatment used in the step (E) is not particularly limited, and for example, the reduction can be performed by placing the granulated body in a heat-resistant open container placed in a reduction furnace. The reduction furnace is not particularly limited, but a stationary reduction furnace is preferable, and for example, a batch-type atmosphere firing furnace, a conveyance type continuous furnace, or the like is used. In addition, a fluidized bed type reduction furnace such as a kiln system is not preferable because the nickel oxide granulated body may be collapsed.

  The reduction time used in the step (E) is not particularly limited, and may be appropriately set according to the particle size of the target nickel fine powder depending on the reduction temperature and the treatment amount, but as short as possible. It is preferable that

  In the step (E), the granulated product after the reduction can be easily dispersed and a nickel fine powder can be obtained. However, in order to further improve the dispersibility, it is preferable to provide a crushing step after the reduction. . Here, the crushing method is not particularly limited, and a normal method is used, but a vibrating sieve, a jet mill, or the like is preferably used.

As described above, the nickel fine powder production method of the present invention reduces nickel hydroxide produced by a wet method, and thus does not include complicated steps, and a uniform nickel fine powder with good dispersibility can be obtained. Therefore, the manufacturing cost can be kept low.
The nickel fine powder obtained by the above manufacturing method is excellent in dispersibility, and is suitable as a material for electronic components. That is, as specific characteristics, by setting the conditions optimally, the particle size distribution measured by the laser scattering method is such that D90 is 0.95 μm or less and uniform nickel fine powder can be obtained.

Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples. The specific surface area, particle dispersibility, oxygen, granule size, apparent density of the granule and moisture content used in the examples and comparative examples are as follows.
(1) Measurement of specific surface area: It was measured by the BET single point method by nitrogen gas adsorption.
(2) Evaluation of particle dispersibility: Particle size distribution is measured by laser light diffraction / scattering type particle size distribution measurement, 10% volume diameter (hereinafter referred to as D10), 50% volume diameter (hereinafter referred to as D50). , 90% volume diameter (hereinafter referred to as D90) was obtained and used as an indicator of the dispersion state.
(3) Analysis of oxygen (mass%): measured by inert gas melting-infrared absorption method. This value was used as an index of the reduction state.
(4) Measurement of granule dimensions: Diameter and length were measured using a micrometer.
(5) Measurement of apparent density of granulated body: Based on the measurement results of the above dimensions, the apparent density is obtained by dividing the weight by the volume of the granulated body calculated as a cylindrical or spherical shape, and granulated. The average value of the measurement results of 10 bodies was used.
(6) Measurement of moisture content: Using a heat drying method measuring instrument (MX-50, manufactured by A & D Co., Ltd.), the moisture content was determined from the weight loss during heating up to 120 ° C.

Example 1
The following steps (A) to (E) were sequentially performed to produce nickel fine powder.
(1) Step (A)
First, a nickel chloride aqueous solution containing 0.04 g / L of magnesium serving as a fusion inhibitor at the time of reduction, and a sodium hydroxide aqueous solution having a concentration of 24% by mass in a reaction vessel, with a nickel concentration of 60 g / L. While adjusting the pH to 8.3, it was continuously added to form a nickel hydroxide precipitate. Thereafter, filtration and 30-minute pure water repulp were repeated three times to obtain a nickel hydroxide filter cake having a water content of 30% by mass. Next, after adding a small amount of water to 3 kg of the obtained filter cake, sulfuric acid whose concentration was adjusted to 10 L of 0.0015 mol / L sulfuric acid in total with the previously added water was added and washed with stirring for 30 minutes. did. After washing, it was filtered, washed again with pure water and dried to obtain nickel hydroxide powder.
(2) Process (B)
30 kg of the nickel hydroxide powder obtained in the step (A) was charged in an amount of 300 g at a time into an alumina koji bowl and charged into a conveying continuous firing furnace. Here, while introducing air at a flow rate of 27 L / min per heating zone, oxidation roasting was performed at a temperature of 480 ° C. for 2 hours to obtain nickel oxide powder.

(3) Steps (C) and (D)
To 120 g of nickel oxide powder obtained in the step (B), 42 ml of pure water was added and mixed by a rotating / revolving mixer to obtain a clay-like slurry. This operation was repeated to produce about 4 kg of pure water slurry of nickel oxide powder, granulated using a uniaxial granulator (manufactured by Akira Kiko, model AX-75), and then at a temperature of 120 ° C. by a stationary dryer. Was dried to obtain a cylindrical granulated body of nickel oxide powder. Here, a screen having a diameter of 4 mm was used for molding.
When the dimensions of the obtained cylindrical granule after drying were measured, the diameter was about 3.8 mm and the length was about 5 to 20 mm. Moreover, the apparent density after the drying was 2.2 g / cm ³ and the moisture content was 2% by mass.
(4) Process (E)
The dried nickel oxide powder 132g obtained in step (D) was charged in 33g each to four 150mm square alumina pots, and 25L was placed using a static atmosphere firing furnace. While introducing a mixed gas of 80% nitrogen and 20% hydrogen at a flow rate of / min and holding at a temperature of 410 ° C. for 2 hours, reduction treatment, after reduction treatment, crushing in an agate mortar, nickel A fine powder was obtained. Here, the addition ratio (hydrogen equivalent) with respect to the amount of hydrogen necessary for the reduction reaction of nickel oxide during the temperature holding was 15 times the reaction equivalent.
Thereafter, the particle size distribution (D10, D50, D90), specific surface area, and oxygen quality were measured for the obtained nickel fine powder. The results are shown in Table 1.

(Example 2)
In step (E), 200 g of the dried nickel oxide powder granules obtained in step (D) were each charged into four 150 mm square alumina pots and reduced. And the hydrogen equivalent at the time of temperature holding was performed similarly to Example 1 except that it was 10 times, and nickel fine powder was obtained.
Thereafter, the particle size distribution (D10, D50, D90), specific surface area, and oxygen quality were measured for the obtained nickel fine powder. The results are shown in Table 1.

(Example 3)
In step (E), 264 g of the dried nickel oxide powder granules obtained in step (D) were each charged in 4 pieces of about 150 mm square alumina pots and reduced, respectively. And the hydrogen equivalent at the time of temperature maintenance was carried out similarly to Example 1 except having been 7.6 times, and obtained nickel fine powder.
Thereafter, the particle size distribution (D10, D50, D90), specific surface area, and oxygen quality were measured for the obtained nickel fine powder. The results are shown in Table 1.

Example 4
In step (E), the dried nickel oxide powder granulate 132g obtained in step (D) was charged into an approximately 150 mm square alumina pot and reduced, It carried out like Example 1 and obtained nickel fine powder.
Thereafter, the particle size distribution (D10, D50, D90), specific surface area, and oxygen quality were measured for the obtained nickel fine powder. The results are shown in Table 1.

(Example 5)
Nickel was formed in the same manner as in Example 1 except that it was granulated into a spherical shape with a diameter of about 4 mm using a high-performance automatic round machine (manufactured by Akira Kiko, PT6025) in steps (C) and (D). A fine powder was obtained. In addition, the dimension after drying of the obtained granulated body is a spherical shape having a diameter of about 4.1 mm, its apparent density is 2.3 g / cm ³ , and the moisture content is 1.8% by mass. there were.
Thereafter, the particle size distribution (D10, D50, D90), specific surface area, and oxygen quality were measured for the obtained nickel fine powder. The results are shown in Table 1.

(Comparative Example 1)
As in Example 1, except that the steps (C) and (D) were omitted, the nickel oxide powder was reduced without granulation, and the reduction temperature was 400 ° C. in the step (E). And nickel fine powder was obtained. In addition, when the moisture content of the nickel oxide powder was measured, it was 1.7% by mass.
Thereafter, the particle size distribution (D10, D50, D90), specific surface area, and oxygen quality were measured for the obtained nickel fine powder. The results are shown in Table 1.

(Comparative Example 2)
The steps (C) and (D) were omitted, and the nickel oxide powder was not granulated, and the reduction treatment amount was reduced to 66 g at 4 koji, and the reduction temperature was 400 ° C. in step (E). This was carried out in the same manner as in Example 1 except that the hydrogen equivalent at the time of holding the temperature was 7.6 equivalents to obtain nickel fine powder.
Thereafter, the particle size distribution (D10, D50, D90), specific surface area, and oxygen quality were measured for the obtained nickel fine powder. The results are shown in Table 1.

(Comparative Example 3)
A nickel fine powder was obtained in the same manner as in Comparative Example 1 except that 132 g of nickel oxide powder was charged in a koji bowl and reduced.
Thereafter, the particle size distribution (D10, D50, D90), specific surface area, and oxygen quality were measured for the obtained nickel fine powder. The results are shown in Table 1.

  From Table 1, in Examples 1-5, since it was performed according to the method of the present invention in steps (A) to (E), the efficiency of the reducing gas was improved, uniform treatment was possible, and dispersibility was improved. It turns out that a good uniform nickel fine powder is obtained. In particular, it can be seen that the effect is large when the reduction treatment amount is increased. Specifically, in any case where the amount of loaded raw material per koji bowl is increased, the oxygen quality hardly changes, and no change is observed in the reduced state. Moreover, there is no big change also in D50 and D90, generation | occurrence | production of the coarse grain by sintering of particle | grains is not confirmed, and favorable dispersibility is obtained.

  On the other hand, in Comparative Examples 1 to 3, it was found that the reduction treatment without granulating the nickel oxide powder did not meet these conditions, so that satisfactory results in dispersibility could not be obtained. Specifically, in Comparative Examples 1 and 2, the oxygen quality increased due to an increase in the amount of treatment, and even when compared with the same hydrogen equivalent, the oxygen quality was higher than in the examples, so the reduction was insufficient. That is confirmed. Further, D50 and D90 increased, and D90 exceeded 0.95 μm, and generation of coarse particles due to particle sintering was observed. That is, due to the increase in the processing amount, the uniformity of the reduction treatment is lost and the dispersibility is also reduced.

  As is clear from the above, the nickel fine powder production method of the present invention can be produced at low cost because nickel fine powder with good dispersibility can be produced uniformly even when the production amount is increased. Further, the obtained nickel fine powder is suitable as an electronic component material, particularly suitable as a wiring material, an electrode material, and the like, and can be used stably as a paste.

Claims (11)

  A step (A) of producing a nickel hydroxide precipitate by neutralizing an aqueous nickel salt solution with an alkaline aqueous solution, and then obtaining the nickel hydroxide powder, and roasting the nickel hydroxide precipitate in a non-reducing atmosphere to produce nickel oxide A step (B) of generating powder, a step (C) of granulating the nickel oxide powder to obtain a granulated body of the nickel oxide powder, and a step (D) of drying the granulated body of the nickel oxide powder. And a step (E) of obtaining a nickel fine powder by reducing the granulated nickel oxide powder in a reducing gas atmosphere after drying.   In the said process (D), the moisture content of the granulated body of the nickel oxide powder after drying is 5 mass% or less, The manufacturing method of the nickel fine powder of Claim 1 characterized by the above-mentioned.   In the step (C), when the nickel oxide powder is granulated, the nickel oxide powder and a solvent are mixed to form a slurry, and the resulting slurry is molded to obtain a granulated body. The manufacturing method of the nickel fine powder of 2.   4. The method for producing nickel fine powder according to claim 3, wherein the solvent is pure water.   In the said process (C), the shape of a granule is either spherical shape, a spheroidal shape, or a cylindrical shape, The manufacturing method of the nickel fine powder in any one of Claims 1-4 characterized by the above-mentioned.   The size of the granule is 2 to 10 mm in diameter when the shape is spherical after drying, 2 to 10 mm in diameter and 2 to 50 mm in rotation axis length in the case of a spheroid, and in the case of a cylindrical shape The method for producing nickel fine powder according to claim 5, wherein the diameter is 2 to 10 mm and the length is 2 to 50 mm. The method for producing nickel fine powder according to any one of claims 1 to 6, wherein the apparent density of the granulated body is 1 to ³ g / cm3 after drying.   In the said process (E), reducing gas atmosphere is the gas containing hydrogen, The manufacturing method of the nickel fine powder in any one of Claims 1-7 characterized by the above-mentioned.   In the said process (E), reduction temperature is 300-500 degreeC, The manufacturing method of the nickel fine powder in any one of Claims 1-8 characterized by the above-mentioned.   In the said process (A), nickel salt aqueous solution contains the 2nd group element used as the fusion inhibitor at the time of reduction | restoration, The manufacturing method of the nickel fine powder in any one of Claims 1-9 characterized by the above-mentioned. It is nickel fine powder obtained by the manufacturing method of nickel fine powder in any one of Claims 1-10,
Nickel fine powder, wherein the particle size distribution measured by the laser scattering method is such that D90 is 0.95 μm or less.