JP5194876B2 - Nickel oxide powder and method for producing the same - Google Patents

Description

  The present invention relates to nickel oxide powder and a method for producing the same, and more particularly relates to nickel oxide powder suitable for an electronic component material having a low sulfur grade and chlorine grade and being fine, and a method for producing the same.

  In general, the nickel oxide powder is a nickel salt such as nickel sulfate, nickel nitrate, nickel carbonate, nickel hydroxide or nickel metal powder, a rotary furnace such as a rotary kiln, a continuous furnace such as a pusher furnace, or a burner furnace. Manufactured by baking in an oxidizing atmosphere using a batch furnace. These nickel oxide powders are used in various applications. For example, in applications as electronic component materials, they are mixed with other materials such as iron oxide and zinc oxide and then sintered. Widely used as ferrite parts.

  In the case of producing a composite metal oxide by mixing and firing a plurality of materials as in the above ferrite parts, the production reaction is limited by a solid phase diffusion reaction. A fine material is used as a raw material to be used. This increases the probability of contact with other materials and increases the activity of the particles, so that it is known that the reaction proceeds uniformly at a low temperature for a short time. Accordingly, in such a method for producing a composite metal oxide, reducing the particle size of the raw material is an important factor for improving the efficiency.

In addition, a specific surface area is also used as an indicator that the powder is fine. It is known that there is a relationship of the following calculation formula 1 between the particle diameter and the specific surface area. Since the relationship of the following calculation formula 1 is based on the assumption that the particles are spherical, there is some error between the obtained particle size and the actual particle size. It can be seen that the larger the particle size, the smaller the particle size.
[Calculation Formula 1]
Particle size = 6 / (density × specific surface area)

  In recent years, reduction in impurity elements contained in nickel oxide powder has been demanded as ferrite parts have higher functionality and use of nickel oxide powder for electronic parts other than ferrite parts has been increasing. Among these impurity elements, particularly sulfur and chlorine react with silver used for the electrode to cause electrode deterioration and corrode the firing furnace, so it is desirable to reduce as much as possible.

  Conventionally, as a method for producing nickel oxide powder, a method of using nickel sulfate as a raw material and baking it has been proposed. For example, as described in Japanese Patent Application Laid-Open No. 2001-32002, first stage roasting using nickel sulfate as a raw material and using a kiln or the like to set the roasting temperature to less than 950 to 1000 ° C. in an oxidizing atmosphere; A method for producing nickel oxide powder that performs second-stage roasting at a roasting temperature of 1000 to 1200 ° C. has been proposed. According to this manufacturing method, nickel oxide powder having an average particle size controlled and a sulfur quality of 50 ppm by mass or less is obtained.

  Japanese Patent Application Laid-Open No. 2004-123488 proposes a method for producing nickel oxide powder in which a dehydration process by calcining at 450 to 600 ° C. and a decomposition process of nickel sulfate by roasting at 1000 to 1200 ° C. are clearly separated. Has been. According to this production method, nickel oxide powder having a low sulfur quality and a small average particle size can be produced stably.

  Furthermore, Japanese Patent Application Laid-Open No. 2004-189530 proposes a method of roasting at a maximum temperature of 900 to 1250 ° C. while forcibly introducing air using a horizontal rotary manufacturing furnace. According to this manufacturing method, it is said that nickel oxide powder with few impurities and sulfur quality of 500 mass ppm or less can be obtained.

  However, in any of the above methods, when the roasting temperature is increased to reduce the sulfur quality, the particle size becomes coarse, and when the roasting temperature is decreased to make the particles finer, the sulfur quality is increased. There is. Further, when heating, a gas containing SOx is generated, and expensive equipment is required to remove the gas.

  As a method for synthesizing nickel oxide powder, an aqueous solution containing nickel salts such as nickel sulfate and nickel chloride is neutralized with an alkali such as an aqueous sodium hydroxide solution to crystallize nickel hydroxide and roasted. A method is also conceivable. In this method of roasting nickel hydroxide, since there is no generation of the gas containing SOx described above, it is considered that low-cost production is possible. However, this production method provides sufficient quality of chlorine and sulfur. There is no report that a low and fine nickel oxide powder was obtained.

  For example, Japanese Patent Application Laid-Open No. 2005-2395 discloses that nickel oxide powder can be obtained by heat-treating nickel hydroxide in an oxidizing atmosphere, although it is an intermediate for producing nickel powder. ing. However, nothing is described about the quality and particle size of chlorine and sulfur contained in the obtained nickel oxide powder.

JP 2001-3002 A JP 2004-123488 A JP 2004-189530 A JP 2005-2395 A

  The present invention has been made in view of the above-mentioned problems of the prior art, and aims to provide a nickel oxide powder suitable for an electronic component material having a low sulfur quality and a low chlorine quality and a fine particle size, and a method for producing the same. It is what.

  In order to achieve the above object, the present inventor has focused on nickel chloride as a nickel salt containing no sulfur in a method for producing nickel oxide powder by roasting nickel hydroxide obtained by neutralizing nickel chloride. As a result of extensive research, neutralization was achieved by adding a small amount of magnesium to nickel chloride, and the resulting nickel hydroxide was roasted at a specific temperature to form nickel oxide, which was then washed with an aqueous solution containing an organic acid. Thus, it has been found that a fine nickel oxide powder having a low sulfur quality and a chlorine quality can be obtained, and the present invention has been completed.

  That is, the method for producing nickel oxide powder of the present invention comprises a step A for obtaining nickel hydroxide by neutralizing a nickel chloride aqueous solution containing an alkaline earth metal with an alkali, and a step B for washing the obtained nickel hydroxide. The step C includes heat treatment of the cleaned nickel hydroxide to nickel oxide, and step D of washing the obtained nickel oxide with an aqueous solution containing an organic acid.

  In the manufacturing method of the nickel oxide powder by the said invention, it is preferable to provide the process E which crushes the nickel oxide obtained by the process C between the said process C and the said process D. FIG. Moreover, the said process E and the said process D can also be performed simultaneously.

  In the method for producing nickel oxide powder according to the present invention, the organic acid in Step D is preferably at least one of ascorbic acid, glutamic acid, and citric acid, and the alkaline earth metal in Step A is magnesium. Preferably there is.

  Moreover, in the manufacturing method of the said nickel oxide powder by this invention, it is preferable to use alkaline aqueous solution in the washing | cleaning of the said process B, Furthermore, as said alkaline aqueous solution, sodium hydroxide and / or potassium hydroxide aqueous solution are preferable. Moreover, it is preferable that the heat processing temperature in the said process C is 450-650 degreeC.

The nickel oxide powder provided by the present invention is a nickel oxide powder obtained by the above-described method for producing a nickel oxide powder of the present invention, having a specific surface area of 6 to 12 m ² / g, a chlorine quality of 300 mass ppm or less , and Sulfur quality is 30 mass ppm or less . Moreover, it is preferable that D90 measured by the laser scattering method is 1 micrometer or less in the nickel oxide powder of this invention.

  According to the present invention, a fine nickel oxide powder having a low sulfur quality and a low chlorine quality can be obtained. Furthermore, the nickel oxide powder of the present invention is finer than that obtained by the conventional method, is suitable as an electronic component material such as a ferrite component, and its manufacturing method is easy, so its industrial value. Is extremely large.

  The method for producing nickel oxide powder according to the present invention comprises a step A for obtaining nickel hydroxide by neutralizing a nickel chloride aqueous solution containing an alkaline earth metal with an alkali, a step B for washing the obtained nickel hydroxide, and a washing And a step D of washing the obtained nickel oxide with an aqueous solution of an organic acid. In the method of the present invention, it is particularly important to add a specific amount of an alkaline earth metal to the nickel chloride aqueous solution in the step A and to wash the nickel oxide with an organic acid aqueous solution in the step D.

  In the above step A, by adding an alkaline earth metal to the nickel chloride aqueous solution, the nickel oxide powder obtained by the heat treatment in the subsequent step C becomes fine. The reason why a fine nickel oxide powder can be obtained is unclear, but during the heat treatment, alkaline earth metal is oxidized prior to nickel to become an oxide, and when nickel is oxidized, the fusion is suppressed and the nickel oxide is coarse. It seems to suppress the conversion.

  The alkaline earth metal to be used is not particularly limited, but magnesium is preferable in consideration of the effect and cost of adding a small amount. Further, the addition amount of the alkaline earth metal is preferably more than 200 ppm by mass and less than 1000 ppm by mass, and more preferably 300 to 600 ppm by mass. When the addition amount is 200 ppm by mass or less, the nickel oxide is not sufficiently refined and the finally obtained nickel oxide powder may be coarsened. Moreover, when 1000 mass ppm or more is added, magnesium remaining as an impurity in the nickel oxide powder increases, which is not preferable for an electronic component such as a ferrite component.

  Moreover, in the said process D, the chlorine quality which remains in the nickel oxide powder obtained can be reduced significantly by wash | cleaning nickel oxide with the aqueous solution (cleaning liquid) containing an organic acid. Although the effect of the organic acid is not necessarily clear, it is considered that residual chlorine can be efficiently removed by exchange adsorption with chlorine. In the present invention, since nickel chloride not containing sulfur is basically used as a raw material, nickel oxide having sufficiently low sulfur quality and chlorine quality can be obtained only by the process D for reducing residual chlorine.

  The organic acid to be added to the cleaning liquid is not particularly limited. However, since the cleaning effect of ascorbic acid, glutamic acid, and citric acid is large, it is preferable to use an aqueous solution containing at least one of them. It is particularly preferable to use an aqueous solution containing an acid. The organic acid concentration in the cleaning liquid is preferably 1 to 200 g / liter. When the concentration of the organic acid is less than 1 g / liter, the cleaning effect is not sufficient, and residual chlorine may not be reduced. Also, there is no particular problem if the concentration of the organic acid is higher than 200 g / liter, but it is not economical because no further improvement in the cleaning effect is observed.

  In addition, it is considered that when an organic acid is added to the cleaning liquid, the ionic strength increases and the electrostatic repulsive force between the particles decreases. However, sedimentation of the particles is promoted, and the filterability is improved. That is, for example, when the concentration of the organic acid is less than 2 g / liter, the effect of reducing chlorine by washing can be sufficiently exhibited, but the sedimentation property of the particles is poor, and the workability may be reduced. Therefore, the concentration of the organic acid is more preferably in the range of 2 to 200 g / liter.

  Next, the method for producing nickel oxide of the present invention will be described in detail for each step. First, step A is a step of neutralizing a nickel chloride aqueous solution containing an alkaline earth metal with an alkali to form a precipitate of nickel hydroxide, and known techniques can be applied to the concentration and neutralization conditions. The nickel chloride used as a raw material is not particularly limited, but it is preferable that the sulfur quality contained as an impurity is sufficiently low, specifically 30 ppm by mass or less. By limiting the sulfur derived from the raw material, the sulfur quality of the nickel oxide powder finally obtained can be made 30 mass ppm or less.

  As an alkali used for neutralization, sodium hydroxide, potassium hydroxide, or the like is used, but sodium hydroxide is preferable in consideration of cost. The alkali may be added to the nickel chloride aqueous solution in a solid or liquid state, but it is preferable to use an aqueous solution for ease of handling. In order to obtain nickel hydroxide with uniform characteristics, it is effective to add a nickel chloride aqueous solution and an alkaline aqueous solution into a sufficiently stirred reaction tank by a double jet method. At that time, pure water can be used as the liquid previously placed in the reaction tank, but it is preferable to use the filtrate after neutralization and adjustment to a predetermined pH with an alkali.

  Step B is a step of washing the nickel hydroxide obtained in Step A. Specifically, the nickel hydroxide produced in the above step A is dehydrated by filtration, and the resulting filter cake is washed. Since it is preferable to sufficiently reduce the residual chlorine quality by this washing, repeated filtration and repulp washing are repeated several times. However, it is also effective to use cross-flow filtration as a method of increasing the slurry concentration while lowering the residual chlorine quality. It is particularly preferable to use a continuous pressure cross flow filtration method. As a continuous pressure cross flow filtration type filtration device, for example, a rotary filter (manufactured by Kotobuki Industries Co., Ltd.) can be mentioned.

  Although water can be used for washing, washing with an aqueous solution containing an alkali (alkaline aqueous solution) is preferable in order to further reduce residual chlorine and make the nickel oxide after heat treatment finer. The alkali to be used is not particularly limited, but sodium hydroxide or potassium hydroxide is preferable from the viewpoint of cost. Moreover, when it wash | cleans with alkaline aqueous solution, it is preferable to wash with water again after that for impurity reduction.

  For example, when washing is performed using an aqueous sodium hydroxide solution, the concentration of the aqueous sodium hydroxide solution is preferably set to 0.01 to 0.15 mol / liter. If the concentration is less than 0.01 mol / liter, a sufficient cleaning effect cannot be obtained. Further, even if the concentration exceeds 0.15 mol / Lill, not only can the cleaning effect be improved, but also the residual sodium concentration tends to be high, and the resulting nickel powder may be inappropriate as an electronic material. This is not preferable. The temperature of the aqueous solution at the time of washing may be room temperature, but heating is preferable in order to enhance the washing effect.

  The amount of the cleaning liquid (water or alkaline aqueous solution) with respect to the nickel hydroxide powder is not particularly limited, and may be an amount that can sufficiently reduce residual chlorine, but in order to disperse the nickel hydroxide powder satisfactorily. The mixing ratio of nickel hydroxide powder / cleaning liquid is preferably about 100 g / liter. Also, the cleaning time is not particularly limited, and the cleaning time may be set so that the residual chlorine concentration is sufficiently reduced depending on the cleaning conditions.

  When nickel hydroxide is washed, the water content of the nickel hydroxide filter cake is preferably 10 to 40% by mass, more preferably about 30% by mass. When the water content is lower than 10% by mass, the filter cake is difficult to uniformly disperse in the aqueous solution, so that the efficiency of washing is deteriorated, and there is a restriction that a severe dehydration treatment is required to reduce the water content. There is not preferable. On the other hand, when the moisture content is higher than 40% by mass, the handling property of nickel hydroxide is poor, and the uniform treatment may be hindered, and the processing amount necessary for obtaining a certain amount of nickel hydroxide is not sufficient. There are inconveniences such as an increase.

Step C is a step in which the nickel hydroxide after washing obtained in Step B is heat-treated to form nickel oxide. A general roasting furnace can be used for the heat treatment. Moreover, as heat treatment conditions, the treatment temperature and time can be set according to the nickel oxide to be obtained, but the specific surface area of the nickel oxide powder finally obtained is 6 to 12 m ² / g. It should be set as follows. The specific surface area of the nickel oxide powder finally obtained by pulverization is a change amount that increases by about 1 m ² / g with respect to the specific surface area of the nickel oxide powder after the heat treatment. Judging by the specific surface area, the processing conditions can be set.

  Specifically, the heat treatment temperature is preferably in the range of 450 to 650 ° C. When the heat treatment temperature is lower than 450 ° C., the spheroidization and refinement of the plate-like primary particles do not proceed sufficiently. Conversely, when the heat treatment temperature is higher than 650 ° C., the sintering of the particles becomes remarkable, and a fine nickel oxide powder can be obtained. It can be difficult. The heat treatment is preferably performed in an air atmosphere, but there is no problem if it is performed in another atmosphere as long as it is a non-reducing atmosphere.

  Step D is a step of washing the nickel oxide powder obtained in Step C with an aqueous solution containing an organic acid. As described above, the residual chlorine concentration can be greatly reduced by washing the nickel oxide powder with an aqueous solution of an organic acid.

  The nickel oxide powder is washed in Step D by dispersing the nickel oxide powder in an organic acid aqueous solution, which is a washing liquid, and maintaining the slurry in a slurry state. In order to reduce the residual chlorine quality, the residual chlorine can be reduced to a lower concentration as the temperature of the cleaning liquid is higher. The washing temperature is preferably 30 to 90 ° C, and more preferably 40 to 90 ° C. When the washing temperature exceeds 90 ° C., there is a problem in safety and it is disadvantageous in terms of energy. Further, if the washing temperature is less than 30 ° C., the reaction is not sufficient and the residual chlorine quality may not be reduced.

  The mixing ratio of the nickel oxide powder and the cleaning liquid is not particularly limited and can be appropriately changed depending on the scale to be implemented, but the mixing ratio of the nickel oxide powder / cleaning liquid is preferably 50 to 500 g / liter. . When this mixing ratio exceeds 500 g / liter, the dispersion of the nickel oxide powder may be deteriorated and cleaning may not be performed sufficiently. On the other hand, when the mixing ratio is less than 50 g / liter, a large amount of chemical solution is required for cleaning, and there is a problem in economical efficiency and operability. In addition, the cleaning time is not particularly limited, and the cleaning time may be a time for sufficiently reducing the residual chlorine quality depending on the concentration of nickel oxide powder in the slurry, the concentration of organic acid, and the cleaning conditions.

  In addition, the apparatus used for washing | cleaning is not specifically limited, A normal wet reaction tank can be used. During the washing, it is preferable to stir the slurry containing nickel oxide powder. For example, ultrasonic stirring or mechanical stirring can be used.

  It is preferable to provide the process E which crushes the nickel oxide obtained at the process C between the above-mentioned process C and the process D. This step E is not an indispensable step, but it is easy to adjust to the desired particle size distribution by crushing the agglomerated particles by firing, to increase the surface area or to form a new interface. Thus, the chlorine removal efficiency in the next step D can be improved. As a result, by passing through the crushing step E, a nickel oxide powder having excellent dispersibility suitable as a ferrite part can be finally obtained.

  In this step E, the nickel oxide powder obtained in step C is crushed by a ball mill, a bead mill or the like. In consideration of operability, the bead mill is excellent, but considering the contamination of impurities from the crushing media, a ball mill capable of soft crushing is preferable. In addition, yttria-stabilized zirconia is preferably used for the ball and ball mill pot lining from the viewpoint of strength and wear resistance. The crushing conditions are not particularly limited, and can be appropriately set according to the specific surface area and particle size of the nickel oxide powder to be obtained.

  Specifically, when a ball mill is used, the ratio of the nickel oxide powder to the crushing media is set to 1: 1 to 1:15, so that crushing can proceed while suppressing impurity contamination to nickel oxide. It is preferable because it is possible. In consideration of the fact that the energy required for crushing is not so large, the diameter of the media used for crushing is preferably 0.5 to 3 mm. If the media diameter is larger than 3 mm, crushing may become uneven or contamination of impurities may increase. Conversely, if the media diameter is smaller than 0.5 mm, the operation for separating the powder from the media is possible. May be difficult.

  Furthermore, by performing the crushing of the process E and the cleaning of the process D at the same time, it is possible to perform an efficient process at a low cost. That is, for example, by performing crushing with a ball mill or the like in the cleaning liquid, cleaning with crushing can effectively reduce the residual chlorine quality.

The nickel oxide powder of the present invention produced by the above method is suitable as a material for electronic parts because it has low chlorine and sulfur grades and a large specific surface area. Specifically, the residual chlorine quality is preferably 300 ppm by mass or less, and more preferably 100 ppm by mass or less. The sulfur quality is preferably 30 mass ppm or less. Moreover, it is preferable that a specific surface area is the range of 6-12 m < ² > / g.

  Further, the nickel oxide powder of the present invention preferably has a D90 (particle diameter at 90% cumulative particle amount in the particle size distribution curve) measured by a laser scattering method of 1 μm or less. The D90 measured by the laser scattering method is crushed and reduced when mixed with other materials during the manufacture of electronic components and the like, but the specific surface area is unlikely to be increased by crushing. It is important that the specific surface area of itself is large.

  Furthermore, in the method for producing nickel oxide powder according to the present invention, since nickel hydroxide produced by a wet method is heat-treated, harmful SOx is not generated, and therefore expensive equipment for removing this is unnecessary. Therefore, the manufacturing cost can be kept low.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by these Examples. The analysis of chlorine quality in Examples and Comparative Examples was carried out by dissolving nickel oxide powder in nitric acid under microwave irradiation in a sealed container capable of suppressing volatilization of chlorine, adding silver nitrate to precipitate silver chloride, Chlorine in the product was evaluated by a calibration curve method using a fluorescent X-ray quantitative analyzer (Magnix manufactured by PANalytical). In addition, the sulfur quality and the zirconium quality were analyzed by an ICP emission spectroscopic analyzer (SEPS SPS-3000) after being dissolved in nitric acid.

The particle size of the nickel oxide particles is measured by laser diffusion method, the particle diameter D ₁₀ at 10% cumulative from the particle size _{distribution,} particle diameter D ₅₀ of an integration of _50%, was determined the particle size D ₉₀ of at cumulative 90% . Moreover, the specific surface area was calculated | required by BET method by gas adsorption.

[Example 1]
A nickel chloride aqueous solution containing magnesium of 0.04 g / liter and having a nickel concentration of 60 g / liter and a 24 mass% sodium hydroxide aqueous solution were continuously added and mixed so as to have a pH of 8.3. A precipitate of nickel oxide was produced (step A).

  Thereafter, filtration and pure water repulping for 30 minutes were repeated three times to obtain a nickel hydroxide filter cake having a water content of 30% by mass. The obtained filter cake was washed with a 0.1 mol / liter sodium hydroxide aqueous solution heated to 50 ° C., washed again with water to reduce residual sodium, and then filtered to obtain a filter cake having a water content of 30% by mass ( Step B).

  This filter cake was dried in the air at 160 ° C. for 48 hours by an air dryer, and 400 g of the obtained nickel hydroxide powder was supplied to an atmosphere firing furnace, and air was introduced at a flow rate of 20 liter / min. After heating up with time, it heat-processed at 600 degreeC for 2 hours, and obtained the nickel oxide powder (process C).

  80 g of the obtained nickel oxide powder was put into a ball mill pot (volume 400 cc, inner diameter 75 mm) lined with yttria-stabilized zirconia together with 400 g of yttria-stabilized zirconia balls 2 mm in diameter and 240 ml of a 150 g / liter aqueous citric acid solution. It was rotated at 68 rpm for 6 hours (Steps D and E).

  The obtained slurry was taken out from the ball mill pot, the balls were separated using a sieve, filtered, and then repulped with pure water. Further, filtration was performed and vacuum drying was performed at 105 ° C. to obtain a nickel oxide fine powder.

The obtained nickel oxide powder of Example 1 had a chlorine quality of 55 ppm by mass, a sulfur quality of less than 30 ppm, and a zirconium quality derived from a ball mill of 100 ppm. The specific surface area was 7.8 m ² / g, D10 was 0.25 μm, D50 was 0.35 μm, and D90 was 0.48 μm.

[Example 2]
The blending at the time of crushing and cleaning by the ball mill (steps D and E) was the same as in Example 1 except that the nickel oxide powder was 70 g, the yttria stabilized zirconia balls were 350 g, and the citric acid aqueous solution was 210 ml in concentration of 150 g / liter. Thus, nickel oxide powder was obtained.

The obtained nickel oxide powder of Example 2 had a chlorine quality of 65 ppm by mass, a sulfur quality of less than 30 ppm, and a zirconium quality of 90 ppm. The specific surface area was 7.4 m ² / g, D10 was 0.27 μm, D50 was 0.38 μm, and D90 was 0.54 μm.

[Example 3]
The composition at the time of crushing and washing by the above ball mill (steps D and E) was the same as in Example 1 except that nickel oxide powder 100 g, yttria stabilized zirconia balls 500 g, and citric acid aqueous solution 300 ml having a concentration of 50 g / liter were used. A nickel oxide powder was obtained.

The obtained nickel oxide powder of Example 3 had a chlorine quality of 94 ppm by mass, a sulfur quality of less than 30 ppm, and a zirconium quality of 80 ppm. The specific surface area was 7.3 m ² / g, D10 was 0.26 μm, D50 was 0.36 μm, and D90 was 0.49 μm.

[Example 4]
The composition at the time of crushing and washing by the ball mill (steps D and E) was the same as in Example 1 except that the nickel oxide powder was 100 g, the yttria stabilized zirconia balls were 500 g, and the citric acid aqueous solution was 300 ml with a concentration of 17 g / liter. A nickel oxide powder was obtained.

The obtained nickel oxide powder of Example 4 had a chlorine quality of 95 ppm by mass, a sulfur quality of less than 30 ppm, and a zirconium quality of 80 ppm. The specific surface area was 7.2 m ² / g, D10 was 0.27 μm, D50 was 0.37 μm, and D90 was 0.52 μm.

[Example 5]
The same as in Example 1 except that the blending at the time of crushing and cleaning by the ball mill (steps D and E) was nickel oxide powder 100 g, yttria-stabilized zirconia balls 500 g, and a citric acid aqueous solution 300 ml having a concentration of 1.7 g / liter. Thus, nickel oxide powder was obtained.

The obtained nickel oxide powder of Example 5 had a chlorine quality of 92 ppm by mass, a sulfur quality of less than 30 ppm, and a zirconium quality of 180 ppm. The specific surface area was 7.1 m ² / g, D10 was 0.24 μm, D50 was 0.34 μm, and D90 was 0.46 μm.

[Example 6]
Crushing with the above ball mill (step E) is not performed, but 20 g of unwashed nickel oxide is dispersed in 60 ml of an aqueous citric acid solution having a concentration of 17 g / liter, mixed and washed for 6 hours by mechanical stirring (step D) Produced nickel oxide powder in the same manner as in Example 1 above.

The obtained nickel oxide powder of Example 6 had a chlorine quality of 140 mass ppm, a sulfur quality of less than 30 ppm, and a zirconium quality of 50 ppm. The specific surface area was 6.6 m ² / g, D10 was 0.35 μm, D50 was 0.96 μm, and D90 was 14.0 μm.

[Example 7]
Crushing washing with the ball (Step D, E) the formulation of time in the same manner as in Example 4, first milled in pure water in place of citric acid solution, the resulting nickel oxide powder 20g to the above-described In the same manner as in Example 6, it was stirred and washed with an aqueous citric acid solution .

The obtained nickel oxide powder of Example 7 had a chlorine quality of 100 mass ppm, a sulfur quality of less than 30 ppm, and a zirconium quality of 220 ppm. The specific surface area was 7.1 m ² / g, D10 was 0.27 μm, D50 was 0.38 μm, and D90 was 0.52 μm.

[Comparative Example 1]
Nickel oxide powder was obtained in the same manner as in Example 7 except that after pulverization with pure water, washing with an aqueous citric acid solution (Step D ) was not performed.

The obtained nickel oxide powder of Comparative Example 1 had a chlorine quality of 470 mass ppm, a sulfur quality of less than 30 ppm, and a zirconium quality of 240 ppm. The specific surface area was 7.1 m ² / g, D10 was 0.28 μm, D50 was 0.39 μm, and D90 was 0.55 μm.

For Examples 1 to 7 and Comparative Example 1 described above, together with the concentration of the aqueous citric acid solution used in Steps D and E and the presence or absence of crushing in Step E, the chlorine quality, sulfur quality and zirconium quality of the obtained nickel oxide powder Are summarized in Table 1 below. The specific surface area and D10, D50, and D90 are summarized in Table 2 below.

  As can be seen from the above results, the chlorine quality is 300 ppm by mass or less because all the examples are washed with an aqueous citric acid solution. Particularly in Examples 1 to 5 and 7, since cleaning and crushing with an aqueous citric acid solution are simultaneously performed, the chlorine quality is 100 mass ppm or less. Moreover, since the raw material containing the sulfur which is an impurity is not used, in any Example, sulfur quality is less than 30 mass ppm.

In Example 6, since the crushing process of the process E was not performed, it is thought that particle | grains have aggregated, D50 and D90 of nickel oxide powder are large compared with above-mentioned Examples 1-5. . However, since the specific surface area is almost the same as in Examples 1 to 5 and in the range of 6 to 12 m ² / g, it can be seen that fine nickel oxide powder is obtained. Moreover, the cleaning effect of the process D is also slightly lowered as compared with the above-described Examples 1 to 5.

  In each of the examples described above, an aqueous citric acid solution was used for washing nickel oxide, but almost the same washing effect could be obtained when an aqueous solution of ascorbic acid or glutamic acid was used.

  On the other hand, in Comparative Example 1, the particle size and specific surface area of the nickel oxide powder are almost the same as those in the above example, but since the cleaning treatment with the citric acid aqueous solution is not performed, the chlorine quality becomes extremely high at 470 mass ppm. ing.

Claims (10)

  Step A for obtaining nickel hydroxide by neutralizing an aqueous nickel chloride solution containing an alkaline earth metal with alkali; Step B for washing the obtained nickel hydroxide; And a step D of washing the obtained nickel oxide with an aqueous solution containing an organic acid.   The method for producing nickel oxide powder according to claim 1, further comprising a step E of crushing the nickel oxide obtained in the step C between the step C and the step D. The method for producing nickel oxide powder according to claim 2, wherein the step E and the step D are performed simultaneously.   The method for producing nickel oxide powder according to any one of claims 1 to 3, wherein the organic acid in the step D is at least one of ascorbic acid, glutamic acid, and citric acid.   The method for producing a nickel oxide powder according to claim 1, wherein the alkaline earth metal in the step A is magnesium. The method for producing nickel oxide powder according to claim 1 , wherein an alkaline aqueous solution is used in the cleaning in the step B.   The method for producing nickel oxide powder according to claim 6, wherein the aqueous alkaline solution is an aqueous sodium hydroxide and / or potassium hydroxide solution.   The method for producing a nickel oxide powder according to claim 1, wherein the heat treatment temperature in the step C is 450 to 650 ° C. The nickel oxide powder obtained by the production method according to claim 1, having a specific surface area of 6 to 12 m ² / g, a chlorine quality of 300 mass ppm or less , and a sulfur quality of 30 mass ppm or less. Nickel oxide powder characterized by   The nickel oxide powder according to claim 9, wherein D90 measured by a laser scattering method is 1 μm or less.