JP4127477B2 - Method for producing anhydrous nickel chloride and nickel ultrafine powder - Google Patents

Description

【００１９】
（実施例１〜１１）
用いた無水塩化ニッケルは、塩化ニッケル含有率が９８質量％以上であり、鉄含有率は０．００４質量％以下と低く、水分は０．４質量％以下である。実施例１〜１１では質量平均粒径が０．２５〜２．９ｍｍ、粒径４ｍｍ以上が１．１質量％以下、粒径０．３ｍｍ以下が１．１〜５７．０質量％、粒径０．１ｍｍ以下は０．５〜９．３質量％、嵩密度は０．９５〜１．３４ｋｇ／Ｌの無水塩化ニッケルを用いた。これらはいずれも反応装置への原料の切出しは安定しており、また、反応装置内の堆積物は少なく．製造運転はトラブル頻度も小さく、順調に推移した。気相反応法で製造したニッケル超微粉は、Ｎｉ収率が９６質量％以上であり、鉄含有率は０．００１８質量％以下であった。
（比較例１〜６）
用いた無水塩化ニッケルは、塩化ニッケル含有率が９５．０〜９７．０質量％で９８質量％を下廻っており、鉄含有率は０．００６質量％以上と高く、水分も０．７質量％以上と高い。
【００２０】
気相反応法で製造したニッケル超微粉は、Ｎｉ収率が８１〜９２質量％と低く、鉄含有率は０．００３０質量％以上と高い。また、反応装置内の堆積物により、製造運転が途中で中止になるトラブルが多い。
【００２１】
比較例全般に、原料を反応装置に供給するトラブルや、反応装置内に堆積物が生成し製造運転が途中で中止になるなどのトラブルが発生した。また、Ｎｉの回収率が比較的低く鉄含有率が高くなるなどの結果になった。なお、ニッケル超微粉の平均粒径が実施例より比較的小さいのは、Ｎｉ収率が比較的低いことやトラブルが発生しやすかったことによるものと考えられる。
【００２２】
【発明の効果】
本発明の無水塩化ニッケルを使用することにより、気相化学法によるニッケル超微粉の製造のトラブルが低減され、Ｎｉ収率が高く、鉄含有率が低いなどの効果が得られる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to anhydrous nickel chloride used in a process for vaporizing anhydrous nickel chloride and producing nickel ultrafine powder by reaction of nickel chloride in a gas phase with hydrogen gas, and a method for producing nickel ultrafine powder using the same. .
[0002]
[Prior art]
In the multilayer ceramic capacitor, hundreds of layers of dielectric electrodes mainly composed of nickel ultrafine powder and barium titanate are alternately laminated. At the time of manufacture, it is fired at a high temperature of about 1300 ° C. Therefore, the internal electrode and the dielectric are preferably materials that are physically and chemically independent and stable. The dielectric is mainly composed of barium titanate, but the actual composition contains calcium oxide, magnesium oxide, zirconium oxide, manganese oxide, silicon oxide, rare earth oxide, etc., in a small amount or in a minute amount, strictly controlled. . Therefore, when a different substance enters the dielectric from the internal electrode, the characteristics as the dielectric are hindered, and the multilayer ceramic capacitor becomes a defective product.
[0003]
The content of nickel chloride in anhydrous nickel chloride is preferably 98% by mass or more. When the content is low, the productivity of the nickel ultrafine powder is reduced, and the remainder accumulates in the reaction apparatus to induce manufacturing trouble, and more impurities are contained in the nickel ultrafine powder. Absent. As described above, anhydrous nickel chloride as a raw material for nickel ultrafine powder must have characteristics suitable for the purity, impurity content, moisture content, and particle size of anhydrous nickel chloride.
[0004]
Regarding anhydrous nickel chloride for the production of nickel powder for multilayer ceramic capacitors, Japanese Patent Application Laid-Open No. 11-228145 discloses that high-purity and particularly low-sulfur metal nickel is heated to 500 ° C. or more and 1000 ° C. or less, and chlorine gas is used. A technique for condensing and recovering after generating nickel chloride vapor by chlorination is disclosed. The anhydrous nickel chloride obtained by this method has a description that the moisture content is 1% or less and the sulfur content is 100 ppm or less, but the content of nickel chloride, the content of iron, the bulk density, the average particle size, There is no description such as existence rate. Since it is described as condensation recovery, it is presumed to be fine nickel chloride anhydrous.
[0005]
Japanese Patent Laid-Open No. 11-263625 discloses a method in which nickel chloride hexahydrate crystals are heat-treated at a temperature of 160 ° C. or higher and 200 ° C. or lower. It is described that it can be effectively reduced. The use is described for producing Ni powder for multilayer ceramic capacitors. The anhydrous nickel chloride obtained by this method has a description that the content of NiO is 0.1% or more and 1% or less, but the content of nickel chloride, the content of iron, the bulk density, the average particle size and the fine powder There is no description of the existence rate of. The moisture content is described as 4% in Comparative Example 2, but is not described in the examples.
[0006]
[Problems to be solved by the invention]
In recent years, nickel ultrafine powder for multilayer ceramic capacitors has been increasingly required to have higher quality and lower price in response to downsizing, higher capacity, and thinner internal electrodes.
[0007]
The present invention reduces nickel ultrafine powder production problems in the vapor phase chemical method (CVD method) in which nickel chloride gas and hydrogen gas in a gas phase are reacted to produce nickel ultrafine powder. An object of the present invention is to provide a method for producing anhydrous nickel chloride and nickel ultrafine powder, which can improve the temperature.
[0008]
[Means for Solving the Problems]
The present invention is anhydrous, characterized in that the nickel chloride content is 98% by mass or more, the iron content is 0.005% by mass or less, the moisture content is 0.5% by mass or less, the weight average particle size is 3 mm or less, and 0.2 mm or more. Nickel chloride. Anhydrous nickel chloride is preferably qualitatively and economically preferable in that metallic nickel is dissolved in hydrochloric acid, and the nickel chloride solution from which impurities are removed is dehydrated and / or dried, and then the particle size is adjusted by a granulator. This anhydrous nickel chloride is particularly suitable as a raw material used when producing ultrafine nickel powder (average particle size of 1 to 0.1 μm) for multilayer ceramic capacitors by a gas phase chemical method.
[0009]
The content of nickel chloride in anhydrous nickel chloride is 98% by mass or more. If the content is lower than this, the productivity of the ultrafine nickel powder will decrease, and the residue will accumulate in the reactor, causing manufacturing troubles, and more impurities will be contained in the ultrafine nickel powder. It is not preferable.
[0010]
In the present invention, the content of iron in anhydrous nickel chloride is limited to 0.005% by mass or less. This is because when the anhydrous nickel chloride is vaporized in the reaction apparatus, the iron content is easily vaporized and is entrained in the vapor phase nickel chloride, so that it is finally contained in the ultrafine nickel powder. Iron content penetrates into the dielectric during firing at a maximum temperature of about 1300 ° C., adversely affects the dielectric crystals, and adversely affects the characteristics of the multilayer ceramic capacitor. The iron content in anhydrous nickel chloride is preferably zero, but 0.005% by mass or less, which has little influence on the dielectric, is preferable when producing a large amount at an economical price.
[0011]
The moisture in anhydrous nickel chloride is 0.5% by mass or less. Moisture generally behaves in an oxidative manner, and when anhydrous nickel chloride is heated, nickel chloride is oxidized and transformed into nickel oxide, resulting in a decrease in Ni content to be vaporized. In addition, since nickel oxide is more stable than nickel chloride, the deposition gradually increases in the reaction apparatus, thereby obstructing vaporization of nickel chloride and causing damage such as shutdown of the reaction apparatus. Of course, the water content is preferably zero, but anhydrous nickel chloride has a high hygroscopic property, and when it absorbs moisture, it becomes a relatively stable compound water, which makes it difficult to reduce it. The amount of moisture in anhydrous nickel chloride is less than 0.5% by mass that has little influence on the production of nickel ultrafine powder.
[0012]
The particle size of anhydrous nickel chloride is 3 to 0.2 mm, more preferably 3 to 0.5 mm in terms of weight average diameter. When supplying anhydrous nickel chloride into the gas phase chemical reactor, the supply amount per hour is continuously controlled using a feeder, so if the particle size is too large, a large machine is used as the feeder itself. It is necessary to do so and it is uneconomical in terms of equipment. On the other hand, when the particle size is large, the number of anhydrous nickel chloride particles supplied per unit time decreases, and the particles are intermittently supplied into the reactor. This is because the evaporation of anhydrous nickel chloride is intermittent and the production of nickel ultrafine powder fluctuates, and the particle size and characteristics of the nickel ultrafine powder fluctuate. In order to vaporize anhydrous nickel chloride, heat supply from the outside is required, and anhydrous nickel chloride particles are heated from the surface. Granular anhydrous nickel chloride having a large particle size has a relatively small specific surface area and tends to have a relatively long vaporization time due to external heat supply. For this reason, the amount of vaporization per hour is reduced, and the productivity of nickel ultrafine powder is reduced. Considering vaporization alone, the particle size of anhydrous nickel chloride should be smaller. However, when powdered anhydrous nickel chloride is produced, hydrates are more likely to be generated due to moisture absorption from the atmosphere, and dust generation during handling is suppressed. The particle size of anhydrous nickel chloride is 3 to 0. 3 in terms of weight average diameter for reasons such as easy cutting out from the feeder and prevention of adhesion and clogging of the extracted anhydrous nickel chloride in the path to the reactor. 2 mm.
[0013]
The portion of 4 mm or more is preferably zero, but it is preferably 1% by mass or less because it may be mixed industrially. Moreover, regarding a fine powder part, it is suitable that a 0.3 mm or less part is 60 mass% or less, and a 0.1 mm or less part is 15 mass% or less. More preferably, the portion of 0.3 mm or less is 10 mass% or less, and the portion of 0.1 mm or less is 3 mass% or less.
[0014]
The bulk density of anhydrous nickel chloride is preferably 1.5 to 0.9 kg / L. Anhydrous nickel chloride is transported, stored or stored in a container. At this time, if the bulk density is large, the size of the container can be reduced, which is advantageous in terms of equipment and transportation. If the bulk density is too high, a small volume of nickel chloride is cut out per hour when supplying the reactor, and precise control is required.
[0015]
As described above, the anhydrous nickel chloride of the present invention has a specific range of purity, impurity content, moisture, and particle size. As a means for producing such anhydrous nickel chloride, metallic nickel with moderately low impurities such as iron is dissolved in industrial 35% hydrochloric acid at 50 ° C. or higher. The produced nickel chloride solution deposits iron, cobalt, etc. in the solution by chemical treatment, and is filtered and removed. The recovered nickel chloride solution is dehydrated and / or dried by a concentrator, a separator, and a dryer to recover anhydrous nickel chloride. Since the particle size is not suitable as it is, the desired anhydrous nickel chloride can be produced by crushing and sieving at the time of the above-mentioned anhydrous nickel chloride recovery, or by adjusting the particle size with a general granulator and sieving device. Can do. In order to prevent contamination by impurities, it is desirable to consider materials such as acid resistance and wear resistance for the above-described equipment.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Table 1 shows the results of the inventors using various anhydrous nickel chlorides to produce ultrafine nickel powders by a gas phase chemical method. In order to produce a nickel ultrafine powder suitable for a multilayer ceramic capacitor, it has been found that the purity, iron content, moisture, and particle size of nickel chloride are appropriate.
[0017]
The ultrafine nickel powder was produced by the vapor phase chemical method at a vaporization temperature of 1050 ° C., a reaction temperature of 1050 ° C., an anhydrous nickel chloride supply rate of 1 kg / hr, and a hydrogen gas flow rate of 20 L / min. At this time, data on the frequency of troubles in supplying anhydrous nickel chloride and the recovery rate of Ni were collected. Moreover, the average particle diameter and iron content of the recovered nickel ultrafine powder were measured.
[0018]
[Table 1]

[0019]
(Examples 1 to 11)
The used anhydrous nickel chloride has a nickel chloride content of 98% by mass or more, an iron content as low as 0.004% by mass or less, and a water content of 0.4% by mass or less. In Examples 1 to 11, the mass average particle size is 0.25 to 2.9 mm, the particle size of 4 mm or more is 1.1% by mass or less, the particle size of 0.3 mm or less is 1.1 to 57.0% by mass, the particle size Anhydrous nickel chloride having a thickness of 0.1 to 0.5 mm and a bulk density of 0.95 to 1.34 kg / L was used. All of these materials are stable in cutting out the raw material into the reactor, and there are few deposits in the reactor. Manufacturing operation was smooth with less frequent trouble. The nickel ultrafine powder produced by the gas phase reaction method had a Ni yield of 96% by mass or more and an iron content of 0.0018% by mass or less.
(Comparative Examples 1-6)
The anhydrous nickel chloride used had a nickel chloride content of 95.0-97.0% by mass, less than 98% by mass, an iron content as high as 0.006% by mass, and a moisture content of 0.7% by mass. More than that.
[0020]
The nickel ultrafine powder produced by the gas phase reaction method has a low Ni yield of 81 to 92 mass% and a high iron content of 0.0030 mass% or more. In addition, there are many troubles that the production operation is interrupted due to deposits in the reactor.
[0021]
In general comparative examples, troubles such as supplying raw materials to the reaction apparatus and deposits formed in the reaction apparatus and the production operation was stopped in the middle occurred. In addition, the Ni recovery rate was relatively low and the iron content was high. In addition, it is thought that the average particle diameter of nickel ultrafine powder is comparatively smaller than an Example because Ni yield was comparatively low and trouble was easy to generate | occur | produce.
[0022]
【The invention's effect】
By using the anhydrous nickel chloride of the present invention, troubles in the production of ultrafine nickel powder by a gas phase chemical method are reduced, and effects such as high Ni yield and low iron content can be obtained.

Claims (5)

Anhydrous nickel chloride having a nickel chloride content of 98% by mass or more, an iron content of 0.005% by mass or less, a moisture content of 0.5% by mass or less, and a weight average particle size of 3 mm or less, 0.2 mm or more. 2. The anhydrous nickel chloride according to claim 1, wherein particles having a particle size of 4 mm or more are 1% by mass or less and particles having a particle size of 0.3 mm or less are 60% by mass or less. 3. Anhydrous nickel chloride according to claim 2, wherein particles having a particle size of 0.1 mm or less are 15% by mass or less. The anhydrous nickel chloride according to any one of claims 1 to 3, wherein a bulk density is 1.5 to 0.9 kg / L. A method for producing nickel ultrafine powder, comprising vaporizing the anhydrous nickel chloride according to any one of claims 1 to 4 and reacting vapor phase nickel chloride with hydrogen gas to produce nickel ultrafine powder.