JP6834235B2 - Manufacturing method of nickel hydroxide particles - Google Patents
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Description
本発明は、水酸化ニッケル粒子及びその製造方法に関し、特に、硫黄やナトリウム等の不純物品位が低く、電子部品や固体酸化物形燃料電池の電極に用いられる酸化ニッケル微粉末の原料として好適な水酸化ニッケル粒子及びその製造方法に関する。 The present invention relates to nickel hydroxide particles and a method for producing the same, and in particular, water having a low impurity grade such as sulfur and sodium and suitable as a raw material for nickel oxide fine powder used for electronic parts and electrodes of solid oxide fuel cells. The present invention relates to nickel oxide particles and a method for producing the same.
一般に、酸化ニッケル微粉末は、硫酸ニッケル、硝酸ニッケル、炭酸ニッケル、水酸化ニッケル等のニッケル塩類又はニッケルメタル粉を、ロータリーキルン等の転動炉、プッシャー炉等のような連続炉、あるいはバーナー炉のようなバッチ炉を用いて酸化性雰囲気下で焼成することによって製造される。これらの酸化ニッケル微粉末は、電子部品用材料や固体酸化物形燃料電池の電極材料等の多様な用途に用いられている。例えば、電子部品用材料としての用途では、酸化ニッケル微粉末を酸化鉄や酸化亜鉛等の他の材料と混合した後、焼結することにより作製されるフェライト部品等が広く用いられている。 In general, nickel oxide fine powder is a nickel salt such as nickel sulfate, nickel nitrate, nickel carbonate, nickel hydroxide, or nickel metal powder, which is used in a rolling furnace such as a rotary kiln, a continuous furnace such as a pusher furnace, or a burner furnace. It is produced by firing in an oxidizing atmosphere using such a batch furnace. These nickel oxide fine powders are used in various applications such as materials for electronic parts and electrode materials for solid oxide fuel cells. For example, in applications as materials for electronic parts, ferrite parts and the like produced by mixing fine nickel oxide powder with other materials such as iron oxide and zinc oxide and then sintering them are widely used.
上記フェライト部品のように、複数の材料を混合して焼成することにより、これらを反応させて複合金属酸化物を製造する場合は、生成反応は固相の拡散反応で律速されるので、使用する原料としては一般に微細なものが好適に用いられている。その理由は、微細な原料を用いることで他材料との接触確率が高くなると共に粒子の活性が高くなるため、低温度且つ短時間でも反応を均一に進ませることができるからである。このように複合金属酸化物を製造する方法においては、原料となる粉体の粒径を小さくすることが効率向上の重要な要素となる。 When a composite metal oxide is produced by reacting a plurality of materials by mixing and firing a plurality of materials as in the above-mentioned ferrite component, the production reaction is rate-determined by the diffusion reaction of the solid phase, and thus is used. Generally, fine raw materials are preferably used. The reason is that by using a fine raw material, the probability of contact with other materials is increased and the activity of the particles is increased, so that the reaction can proceed uniformly even at a low temperature and for a short time. In the method for producing a composite metal oxide as described above, reducing the particle size of the powder as a raw material is an important factor for improving efficiency.
また、環境及びエネルギーの両面から新しい発電システムとして期待されている固体酸化物形燃料電池では、その電極材料として酸化ニッケル微粉末が用いられている。一般に、固体酸化物形燃料電池のセルスタックは、空気極、固体電解質及び燃料極からなる単セルが複数セル積層された構造を有している。この燃料極としては、例えばニッケル又は酸化ニッケルと、安定化ジルコニアからなる固体電解質とを混合したものが通常用いられている。燃料極は、発電時に水素や炭化水素等の燃料ガスにより還元されてニッケルメタルとなり、ニッケルと固体電解質と空隙からなる三相界面が燃料ガスと酸素の反応場となるため、フェライト部品として用いる場合と同様に原料となる粉体の粒径を小さくして微細にすることが発電効率向上の重要な要素となる。 Further, in a solid oxide fuel cell which is expected as a new power generation system from both aspects of environment and energy, nickel oxide fine powder is used as an electrode material thereof. Generally, a cell stack of a solid oxide fuel cell has a structure in which a plurality of single cells including an air electrode, a solid electrolyte, and a fuel electrode are stacked. As the fuel electrode, for example, a mixture of nickel or nickel oxide and a solid electrolyte made of stabilized zirconia is usually used. The fuel electrode is reduced to nickel metal by fuel gas such as hydrogen or hydrocarbon during power generation, and the three-phase interface consisting of nickel, solid electrolyte, and voids serves as a reaction field for fuel gas and oxygen, so when used as a ferrite component. Similarly, reducing the particle size of the raw material powder to make it finer is an important factor for improving power generation efficiency.
ところで、粉体が微細であることを測る指標としては、比表面積を用いることがある。また、粒径と比表面積には、下記の計算式１の関係があることが知られている。下記計算式１の関係は粒子が真球状であると仮定して導き出されたものであるため、計算式１から得られる粒径と実際の粒径との間にはいくらかの誤差を含むことになるが、比表面積が大きいほど粒径が小さくなることが分る。 By the way, the specific surface area may be used as an index for measuring the fineness of the powder. Further, it is known that the particle size and the specific surface area have a relationship of the following formula 1. Since the relationship of formula 1 below is derived on the assumption that the particles are spherical, some error is included between the particle size obtained from formula 1 and the actual particle size. However, it can be seen that the larger the specific surface area, the smaller the particle size.
［計算式１］
粒径＝６／（密度×比表面積）
[Calculation formula 1]
Particle size = 6 / (density x specific surface area)
近年、フェライト部品はますます高機能化する傾向にあり、また酸化ニッケル微粉末の用途はフェライト部品以外の電子部品等に広がっている。これに伴い、酸化ニッケル微粉末に含有される不純物元素の品位を低減することが求められている。不純物元素の中でも特に塩素や硫黄は、電極に利用されている銀と反応して電極劣化を生じさせたり、焼成炉を腐食させたりすることがあるため、できるだけ低減することが望ましい。 In recent years, ferrite parts have become more and more sophisticated, and the use of nickel oxide fine powder has expanded to electronic parts other than ferrite parts. Along with this, it is required to reduce the grade of impurity elements contained in the nickel oxide fine powder. Among the impurity elements, chlorine and sulfur may react with silver used for the electrodes to cause electrode deterioration and corrode the firing furnace, so it is desirable to reduce them as much as possible.
例えば特許文献１には、原料段階におけるフェライト粉の硫黄成分の含有量がＳ換算で３００〜９００ｐｐｍ且つ塩素成分の含有量がＣｌ換算で１００ｐｐｍであり、焼成後のフェライト焼結体の硫黄成分の含有量がＳ換算で１００ｐｐｍ以下且つ塩素成分の含有量がＣｌ換算で２５ｐｐｍ以下のフェライト材料が開示されている。このフェライト材料は、低温焼成においても添加物を用いることなく高密度化を図ることができ、これにより作製されたフェライト磁心及び積層チップ部品は、耐湿性と温度特性に優れていると記載されている。 For example, in Patent Document 1, the sulfur component content of the ferrite powder at the raw material stage is 300 to 900 ppm in S conversion, and the chlorine component content is 100 ppm in Cl conversion, and the sulfur component of the ferrite sintered body after firing is A ferrite material having a content of 100 ppm or less in terms of S and a chlorine component content of 25 ppm or less in terms of Cl is disclosed. It is stated that this ferrite material can be densified without using additives even in low-temperature firing, and that the ferrite core and laminated chip parts produced by this are excellent in moisture resistance and temperature characteristics. There is.
また、原料に硫酸ニッケルを用い、これを焙焼することで酸化ニッケル微粉末を製造する方法も提案されている。例えば、特許文献２には、原料としての硫酸ニッケルを、キルンなどを用いて酸化雰囲気中で９５０〜１０００℃で焙焼する第１段焙焼と、１０００〜１２００℃で焙焼する第２段焙焼とを行って酸化ニッケル粉末を製造する方法が提案されている。この製造方法によれば、平均粒径が制御され、且つ硫黄品位が５０質量ｐｐｍ以下である酸化ニッケル微粉末が得られると記載されている。 In addition, a method of producing nickel oxide fine powder by using nickel sulfate as a raw material and roasting it has also been proposed. For example, Patent Document 2 describes a first-stage roasting in which nickel sulfate as a raw material is roasted at 950 to 1000 ° C. in an oxidizing atmosphere using a kiln or the like, and a second-stage roasting in which the nickel sulfate is roasted at 1000 to 1200 ° C. A method of producing nickel oxide powder by roasting has been proposed. According to this production method, it is described that nickel oxide fine powder having an average particle size controlled and a sulfur grade of 50 mass ppm or less can be obtained.
また、特許文献３には、４５０〜６００℃の仮焼による原料の硫酸ニッケルの脱水工程と、１０００〜１２００℃の焙焼による硫酸ニッケルの分解工程とを明確に分離した酸化ニッケル粉末の製造方法が提案されている。この製造方法によれば、硫黄品位が低く且つ平均粒径が小さい酸化ニッケル粉末を安定して製造できると記載されている。更に、特許文献４には、横型回転式製造炉を用いて、強制的に空気を導入しながら、最高温度を９００〜１２５０℃として硫酸ニッケルを焙焼する方法が提案されている。この製造方法によっても、不純物が少なく、硫黄品位が５００質量ｐｐｍ以下の酸化ニッケル粉末が得られると記載されている。 Further, Patent Document 3 describes a method for producing nickel oxide powder in which a step of dehydrating nickel sulfate as a raw material by calcining at 450 to 600 ° C. and a step of decomposing nickel sulfate by roasting at 1000 to 1200 ° C. are clearly separated. Has been proposed. According to this production method, it is described that nickel oxide powder having a low sulfur grade and a small average particle size can be stably produced. Further, Patent Document 4 proposes a method of roasting nickel sulfate at a maximum temperature of 900 to 1250 ° C. while forcibly introducing air using a horizontal rotary production furnace. It is described that nickel oxide powder having a small amount of impurities and a sulfur grade of 500 mass ppm or less can be obtained also by this production method.
上記の特許文献２や特許文献３の方法によれば不純物品位の低い酸化ニッケル微粉末が得られるが、熱処理を２回行うため生産コストが高くなってしまう。また、上記特許文献２〜４のいずれの方法においても、硫黄品位を低減するために焙焼温度を高くすると粒径が粗大になり、逆に粒子を微細にするために焙焼温度を下げると硫黄品位が高くなるため、粒径と硫黄品位を共に最適値に制御することは困難である。更に、加熱する際にＳＯｘを含むガスが大量に発生し、これを除害処理するために高価な設備が必要になるという問題を抱えている。 According to the methods of Patent Document 2 and Patent Document 3 described above, nickel oxide fine powder having a low impurity grade can be obtained, but the production cost is high because the heat treatment is performed twice. Further, in any of the methods of Patent Documents 2 to 4, when the roasting temperature is raised in order to reduce the sulfur grade, the particle size becomes coarse, and conversely, when the roasting temperature is lowered in order to make the particles finer. Since the sulfur grade is high, it is difficult to control both the particle size and the sulfur grade to the optimum values. Further, there is a problem that a large amount of gas containing SOx is generated during heating, and expensive equipment is required for detoxifying the gas.
酸化ニッケル微粉末を合成する方法として、硫酸ニッケルや塩化ニッケル等のニッケル塩を含む水溶液を、水酸化ナトリウム水溶液等のアルカリで中和して水酸化ニッケル粒子を晶析させ、これを焙焼する方法も提案されている。このように、水酸化ニッケル粒子を焙焼する場合は、陰イオン成分由来のガスの発生が少ないため、排ガス処理が不要となるか若しくは簡易な設備でよく、生産コストを抑えることが可能になると考えられる。 As a method for synthesizing nickel oxide fine powder, an aqueous solution containing a nickel salt such as nickel sulfate or nickel chloride is neutralized with an alkali such as an aqueous solution of sodium hydroxide to crystallize nickel hydroxide particles, which are then roasted. A method has also been proposed. In this way, when roasting nickel hydroxide particles, the generation of gas derived from anionic components is small, so exhaust gas treatment is not required or simple equipment is sufficient, and production costs can be suppressed. Conceivable.
例えば、特許文献５には、塩化ニッケル水溶液をアルカリで中和することで生成した水酸化ニッケル粒子を５００〜８００℃の温度で熱処理して酸化ニッケル粉末を生成し、得られた酸化ニッケル粉末に水を加えてスラリー化した後、湿式ジェットミルを用いて解砕すると同時に洗浄することにより、硫黄品位及び塩素品位が低く、且つ微細な酸化ニッケル微粉末を得る方法が提案されている。 For example, in Patent Document 5, nickel hydroxide particles produced by neutralizing an aqueous nickel chloride solution with alkali are heat-treated at a temperature of 500 to 800 ° C. to produce nickel oxide powder, and the obtained nickel oxide powder is used. A method has been proposed in which water is added to form a slurry, which is then crushed using a wet jet mill and simultaneously washed to obtain fine nickel oxide fine powder having low sulfur and chlorine grades.
上記の特許文献５の酸化ニッケル微粉末の製造方法は、原料に塩化ニッケルを用いているので硫黄品位の低減は可能であるが、硫黄品位を所定の範囲内に制御することは困難であった。また、湿式解砕を要件としているため、この湿式解砕後の乾燥時に粒子同士が凝集するおそれがある上、乾燥に要するエネルギーがコスト的に不利になることがあった。 In the method for producing nickel oxide fine powder of Patent Document 5 above, nickel chloride is used as a raw material, so that the sulfur grade can be reduced, but it is difficult to control the sulfur grade within a predetermined range. .. Further, since wet crushing is a requirement, particles may agglutinate during drying after the wet crushing, and the energy required for drying may be disadvantageous in terms of cost.
本発明は、上記した従来の問題点に鑑みてなされたものであり、ナトリウム等の総アルカリ金属及び硫黄等の不純物品位が低く、電子部品用材料や固体酸化物形燃料電池の電極材料として用いられる酸化ニッケル微粉末の原料として好適な水酸化ニッケル粒子及びその製造方法を提供することを目的とする。 The present invention has been made in view of the above-mentioned conventional problems, and is used as a material for electronic parts and an electrode material for a solid oxide fuel cell because it has a low grade of total alkali metals such as sodium and impurities such as sulfur. It is an object of the present invention to provide nickel hydroxide particles suitable as a raw material for nickel oxide fine powder and a method for producing the same.
すなわち、本発明の水酸化ニッケル粒子の製造方法は、ニッケル濃度が５０〜１５０ｇ／Ｌの硫酸ニッケル水溶液をアルカリ金属の水酸化物と炭酸ナトリウムとを含有するアルカリ水溶液によって連続晶析法を用いてｐＨ８.３〜９.０で中和することで水酸化ニッケル粒子を生成する中和工程を含み、前記アルカリ水溶液は炭酸ナトリウムの濃度が０.４〜０.８ｍｏｌ／Ｌであり、前記中和は反応時間を０.２〜５.０ｈとし、中和反応時の反応液の温度を５０〜７０℃の範囲内とすることを特徴としている。 That is, the method for producing nickel hydroxide particles of the present invention uses a continuous crystallization method using an aqueous solution of nickel sulfate having a nickel concentration of 50 to 150 g / L with an aqueous alkaline solution containing an alkali metal hydroxide and sodium carbonate. The alkaline aqueous solution includes a neutralization step of producing nickel hydroxide particles by neutralizing at pH 8.3 to 9.0, and the alkaline aqueous solution has a sodium carbonate concentration of 0.4 to 0.8 mol / L, and the neutralization. Is characterized in that the reaction time is 0.2 to 5.0 h and the temperature of the reaction solution at the time of the neutralization reaction is in the range of 50 to 70 ° C.
すなわち、本発明の水酸化ニッケル粒子の製造方法は、硫酸ニッケル水溶液をアルカリ金属の水酸化物と炭酸ナトリウムとを含有するアルカリ水溶液によって連続晶析法を用いてｐＨ８.３〜９.０で中和することで水酸化ニッケル粒子を生成する中和工程を含み、前記アルカリ水溶液は炭酸ナトリウムの濃度が０.４〜０.８ｍｏｌ／Ｌであり、前記中和は反応時間を０.２〜５.０ｈとすることを特徴としている。 That is, in the method for producing nickel hydroxide particles of the present invention, an aqueous solution of nickel sulfate is neutralized at pH 8.3 to 9.0 using an alkaline aqueous solution containing an alkali metal hydroxide and sodium carbonate by a continuous crystallization method. Including a neutralization step of producing nickel hydroxide particles by summing, the alkaline aqueous solution has a sodium carbonate concentration of 0.4 to 0.8 mol / L, and the neutralization has a reaction time of 0.2 to 5 It is characterized by setting it to .0h.
本発明によれば、フェライト部品などの電子部品用材料や固体酸化物形燃料電池の電極材料として好適な、不純物品位が低くて微細な酸化ニッケル微粉末の原料となる水酸化ニッケル粒子を容易に作製することができる。 According to the present invention, nickel hydroxide particles which are suitable as materials for electronic parts such as ferrite parts and electrode materials for solid oxide fuel cells and which are raw materials for fine nickel oxide fine powder having low impurity grade can be easily produced. Can be made.
以下、本発明の水酸化ニッケル粒子の製造方法の一具体例について説明する。この本発明の一具体例の水酸化ニッケル粒子の製造方法は、原料としての硫酸ニッケル水溶液を炭酸ナトリウムを含んだアルカリ水溶液によって連続晶析法を用いてｐＨ８.３〜９.０で中和することで水酸化ニッケル粒子を生成する中和工程を含んでいる。 Hereinafter, a specific example of the method for producing nickel hydroxide particles of the present invention will be described. In the method for producing nickel hydroxide particles of one specific example of the present invention, an aqueous solution of nickel sulfate as a raw material is neutralized with an alkaline aqueous solution containing sodium carbonate at pH 8.3 to 9.0 using a continuous crystallization method. This includes a neutralization step to produce nickel hydroxide particles.
このように、本発明の一具体例の製造方法においては、原料のニッケル塩水溶液に硫酸ニッケルを使用することが重要である。すなわち、本発明者らは、硫黄成分の働きにより水酸化ニッケル粒子の熱処理時に熱処理温度が粒径に及ぼす影響を抑え得るとの知見を得、これに基づき原料に硫酸ニッケルを使用したところ、これにより生成される水酸化ニッケル粒子は、従来のニッケル塩の中和により生成した水酸化ニッケル粒子に比べて、後段の熱処理工程の温度を高温に設定しても微細な酸化ニッケル粉末が得られることを見出した。 As described above, in the production method of one specific example of the present invention, it is important to use nickel sulfate as the raw material nickel salt aqueous solution. That is, the present inventors have obtained the finding that the influence of the heat treatment temperature on the particle size can be suppressed during the heat treatment of nickel hydroxide particles by the action of the sulfur component, and based on this, nickel sulfate was used as a raw material. Compared to the conventional nickel hydroxide particles produced by neutralizing nickel salts, the nickel hydroxide particles produced by the above can obtain fine nickel oxide powder even if the temperature of the subsequent heat treatment step is set to a high temperature. I found.
更に、熱処理温度を特定の範囲で制御したところ、微細な粒径を維持したまま酸化ニッケル微粉末の硫黄品位を制御でき、電子部品用材料としての用途、特にフェライト部品の原料として用いる場合に好適な微細でかつ硫黄品位が制御された酸化ニッケル微粉末が得られることを見出した。しかも、この方法は塩化ニッケルを用いないため塩素が混入するおそれがなく、よって、原料に不可避的に含まれる不純物由来のもの以外は実質的に塩素を含有しない酸化ニッケル微粉末を得ることができる。 Furthermore, when the heat treatment temperature is controlled within a specific range, the sulfur grade of nickel oxide fine powder can be controlled while maintaining a fine particle size, which is suitable for use as a material for electronic parts, especially as a raw material for ferrite parts. It has been found that a fine nickel oxide fine powder having a controlled sulfur grade can be obtained. Moreover, since this method does not use nickel chloride, there is no risk of chlorine being mixed in, so that nickel oxide fine powder that does not substantially contain chlorine other than those derived from impurities inevitably contained in the raw material can be obtained. ..
上記方法で微細な粒径の酸化ニッケル微粉末が得られる明確な理由は不明であるが、硫酸ニッケルの分解温度は８４８℃と高温であるため、中和により晶析した水酸化ニッケル粒子の表面や界面に硫酸塩として巻きこまれた硫黄成分が酸化ニッケル粉末の焼結を高温まで抑制していると考えられる。この場合、硫酸ニッケルの分解温度より高温で熱処理すれば硫黄成分は揮発されるため、熱処理後の酸化ニッケル粉末の硫黄品位を低減することができる。 The clear reason why fine nickel oxide powder having a fine particle size can be obtained by the above method is unknown, but since the decomposition temperature of nickel sulfate is as high as 848 ° C., the surface of nickel hydroxide particles crystallized by neutralization. It is considered that the sulfur component caught as sulfate at the interface suppresses the sintering of nickel oxide powder to a high temperature. In this case, if the heat treatment is performed at a temperature higher than the decomposition temperature of nickel sulfate, the sulfur component is volatilized, so that the sulfur grade of the nickel oxide powder after the heat treatment can be reduced.
このように、水酸化ニッケル粒子内の水酸基の脱離により酸化ニッケル粉末の生成が行われる熱処理工程では、熱処理温度を適切に設定することによって、粒径の微細化と硫黄品位の制御が可能になる。具体的には、水酸化ニッケルの熱処理温度を、８５０℃を超え９５０℃未満の温度範囲、好ましくは８６０以上９００℃以下の温度範囲にすることで、酸化ニッケル微粉末の硫黄品位を２０質量ｐｐｍ以下に制御すると共に、比表面積を２ｍ２／ｇ以上４ｍ２／ｇ未満にすることができる。 In this way, in the heat treatment process in which the nickel oxide powder is produced by the desorption of the hydroxyl groups in the nickel hydroxide particles, the particle size can be made finer and the sulfur grade can be controlled by appropriately setting the heat treatment temperature. Become. Specifically, by setting the heat treatment temperature of nickel hydroxide in the temperature range of more than 850 ° C. and lower than 950 ° C., preferably in the temperature range of 860 or more and 900 ° C. or less, the sulfur grade of the nickel oxide fine powder is 20 mass ppm. While controlling as follows, the specific surface area can be 2 m 2 / g or more and less than 4 m 2 / g.
また、本発明の一具体例の製造方法においては、中和工程における中和反応の反応時間を０.２ｈ〜５ｈにすることで、総アルカリ金属の品位が低い水酸化ニッケル粒子を得ることができ、かつ最終的に酸化ニッケル微粉末中に残存する硫黄品位を２０質量ｐｐｍ以下、総アルカリ金属の品位を２０質量ｐｐｍ以下、より好ましくは１０質量ｐｐｍ以下に抑えることができる。この反応時間が５ｈを超えると、水酸化ニッケル中の総アルカリ金属の品位が５質量ｐｐｍを超え、その結果、酸化ニッケル微粉末中に残存する硫黄品位が２０質量ｐｐｍを超えることがある。以下、かかる本発明の一具体例の水酸化ニッケル粒子の製造方法が有する中和工程について詳細に説明する。 Further, in the production method of a specific example of the present invention, by setting the reaction time of the neutralization reaction in the neutralization step to 0.2 h to 5 h, nickel hydroxide particles having a low total alkali metal grade can be obtained. It is possible to suppress the grade of sulfur finally remaining in the nickel oxide fine powder to 20 mass ppm or less, and the grade of the total alkali metal to 20 mass ppm or less, more preferably 10 mass ppm or less. When this reaction time exceeds 5 hours, the grade of the total alkali metal in nickel hydroxide may exceed 5 mass ppm, and as a result, the sulfur grade remaining in the nickel oxide fine powder may exceed 20 mass ppm. Hereinafter, the neutralization step of the method for producing nickel hydroxide particles of a specific example of the present invention will be described in detail.
本発明の一具体例の製造方法が有する中和工程では、原料としての硫酸ニッケル水溶液を炭酸ナトリウムを含んだアルカリ水溶液で中和することで水酸化ニッケル粒子の析出を行う。原料として用いる硫酸ニッケルは、特に限定するものではないが、最終的に作製される酸化ニッケル微粉末が電子部品用材料や固体酸化物形燃料電池の電極材料として用いられることから、腐食を生じにくくするため、原料中に含まれる不純物が１００質量ｐｐｍ未満であることが望ましい。 In the neutralization step of the production method of one specific example of the present invention, nickel hydroxide particles are precipitated by neutralizing an aqueous solution of nickel sulfate as a raw material with an alkaline aqueous solution containing sodium carbonate. The nickel sulfate used as a raw material is not particularly limited, but since the nickel oxide fine powder finally produced is used as a material for electronic parts and an electrode material for a solid oxide fuel cell, corrosion is unlikely to occur. Therefore, it is desirable that the amount of impurities contained in the raw material is less than 100 mass ppm.
また、硫酸ニッケル水溶液中のニッケルの濃度は、特に限定するものではないが、生産性を考慮するとニッケル濃度で５０〜１５０ｇ／Ｌが好ましい。この濃度が５０ｇ／Ｌ未満では生産性が低下するおそれがある。逆に１５０ｇ／Ｌを超えると水溶液中の陰イオン濃度が高くなりすぎ、生成した水酸化ニッケル中の硫黄品位が高くなるため、最終的に得られる酸化ニッケル微粉末中の不純物品位が十分に低くならない場合がある。 The concentration of nickel in the nickel sulfate aqueous solution is not particularly limited, but the nickel concentration is preferably 50 to 150 g / L in consideration of productivity. If this concentration is less than 50 g / L, productivity may decrease. On the contrary, if it exceeds 150 g / L, the anion concentration in the aqueous solution becomes too high, and the sulfur grade in the produced nickel hydroxide becomes high, so that the impurity grade in the finally obtained nickel oxide fine powder is sufficiently low. It may not be.
中和に用いるアルカリ水溶液に含まれるアルカリ成分としては、反応液中に残留するニッケルの量を考慮してアルカリ金属の水酸化物を使用する。アルカリ金属の水酸化物には例えば水酸化ナトリウムや水酸化カリウムを挙げることができ、コストの面から水酸化ナトリウムが好ましい。中和に用いるアルカリ水溶液は、上記のアルカリ金属の水酸化物以外に更に炭酸ナトリウムを０.４〜０.８ｍｏｌ／Ｌの濃度で含んでいる。これにより、詳細は不明ではあるが、晶析した水酸化ニッケル粒子の界面や表面に巻き込まれるナトリウム等のアルカリ金属成分や硫黄成分の量を低減することができる。 As the alkaline component contained in the alkaline aqueous solution used for neutralization, an alkali metal hydroxide is used in consideration of the amount of nickel remaining in the reaction solution. Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide, and sodium hydroxide is preferable from the viewpoint of cost. The alkaline aqueous solution used for neutralization further contains sodium carbonate at a concentration of 0.4 to 0.8 mol / L in addition to the above-mentioned alkali metal hydroxide. This makes it possible to reduce the amount of alkali metal components such as sodium and sulfur components that are caught in the interface and surface of the crystallized nickel hydroxide particles, although the details are unknown.
上記アルカリ水溶液中の炭酸ナトリウム濃度を０.４〜０.８ｍｏｌ／Ｌとする理由は、アルカリ水溶液に含まれる炭酸ナトリウムの濃度を徐々に増やしていくと、水酸化ニッケル粒子中の硫黄品位は一旦増加するが、炭酸ナトリウムの濃度を更に増やすと硫黄品位は減少に転じ、０.４ｍｏｌ／Ｌ以上では炭酸ナトリウムを添加しない場合よりも硫黄品位が低くなるからである。また、水酸化ニッケル粒子中のナトリウム等のアルカリ金属の品位は、アルカリ水溶液中の炭酸ナトリウムの濃度を徐々に増やすことで低下させることができるが、アルカリ水溶液中の炭酸ナトリウムの濃度が０.８ｍｏｌ／Ｌより高くなると逆にナトリウム等のアルカリ金属の品位は高くなるからである。 The reason for setting the sodium carbonate concentration in the alkaline aqueous solution to 0.4 to 0.8 mol / L is that when the concentration of sodium carbonate contained in the alkaline aqueous solution is gradually increased, the sulfur grade in the nickel hydroxide particles is once improved. This is because the sulfur grade starts to decrease when the concentration of sodium carbonate is further increased, and the sulfur grade becomes lower at 0.4 mol / L or more than when sodium carbonate is not added. Further, the grade of alkali metal such as sodium in nickel hydroxide particles can be lowered by gradually increasing the concentration of sodium carbonate in the alkaline aqueous solution, but the concentration of sodium carbonate in the alkaline aqueous solution is 0.8 mol. This is because the quality of alkali metals such as sodium increases when the value is higher than / L.
このように、アルカリ水溶液中の炭酸ナトリウムの濃度が０.４ｍｏｌ／Ｌ未満では、中和により得られる水酸化ニッケル粒子の硫黄品位が炭酸ナトリウムを含有させない場合よりも高くなることがあり、０.８ｍｏｌ／Ｌを超えると、中和により得られる水酸化ニッケル粒子のナトリウム等のアルカリ金属の品位が炭酸ナトリウムを含有させない場合よりも高くなることがある。ナトリウム等のアルカリ金属は、後段の熱処理工程において高融点の硫酸塩を形成し、硫黄成分の分解や揮発を阻害する方向に働くので、水酸化ニッケル粒子のアルカリ金属の品位が高いと、酸化ニッケル微粉末の硫黄品位も高くなりやすい。 As described above, when the concentration of sodium carbonate in the alkaline aqueous solution is less than 0.4 mol / L, the sulfur grade of the nickel hydroxide particles obtained by neutralization may be higher than that in the case where sodium carbonate is not contained. If it exceeds 8 mol / L, the grade of the alkali metal such as sodium of the nickel hydroxide particles obtained by neutralization may be higher than that in the case where sodium carbonate is not contained. Alkali metals such as sodium form a high melting point sulfate in the subsequent heat treatment process and work in a direction to inhibit the decomposition and volatilization of sulfur components. Therefore, if the alkali metal grade of nickel hydroxide particles is high, nickel oxide The sulfur grade of fine powder tends to be high.
尚、上記中和反応の晶析により生成される水酸化ニッケル粒子は、硫黄品位が２質量％以下であるのが好ましい。下限については特に限定はないが、アルカリ水溶液中の炭酸ナトリウムの濃度が０.４〜０.８ｍｏｌ／Ｌの範囲では０.４質量％以上となる。アルカリ水溶液中の炭酸ナトリウム濃度を適宜調整することで、水酸化ニッケル粒子の硫黄品位をより好適な１.０〜２.０質量％に、最も好適な１.２〜１.８質量％にすることができる。 The nickel hydroxide particles produced by the crystallization of the neutralization reaction preferably have a sulfur grade of 2% by mass or less. The lower limit is not particularly limited, but the concentration of sodium carbonate in the alkaline aqueous solution is 0.4% by mass or more in the range of 0.4 to 0.8 mol / L. By appropriately adjusting the sodium carbonate concentration in the alkaline aqueous solution, the sulfur grade of the nickel hydroxide particles is adjusted to a more preferable 1.0 to 2.0% by mass and the most suitable 1.2 to 1.8% by mass. be able to.
上記中和工程では均質な水酸化ニッケル粒子を効率よく生産するため、反応槽内において十分に撹拌されている液に、予め調製しておいたニッケル塩水溶液である硫酸ニッケル水溶液とアルカリ水溶液とをいわゆるダブルジェット方式で添加する連続晶析法を採用している。即ち、反応槽内に予め準備したニッケル塩水溶液及びアルカリ水溶液のうちのいずれか一方に対して、もう一方を添加することで中和を行うのではなく、反応槽内において十分に攪拌されている乱流状態の液中に、好適には該攪拌を継続しながらニッケル塩水溶液とアルカリ水溶液とを同時並行的に且つ連続的に添加することで中和を行う。その際、反応槽内に予め入れておく液は、純水に上記アルカリ成分を添加して所定のｐＨに調整したものが好ましい。 In the above neutralization step, in order to efficiently produce homogeneous nickel hydroxide particles, a nickel sulfate aqueous solution and an alkaline aqueous solution, which are nickel salt aqueous solutions prepared in advance, are added to a solution that is sufficiently stirred in the reaction vessel. The continuous crystallization method of adding by the so-called double jet method is adopted. That is, one of the nickel salt aqueous solution and the alkaline aqueous solution prepared in advance in the reaction vessel is not neutralized by adding the other, but is sufficiently stirred in the reaction vessel. Neutralization is preferably carried out by adding a nickel salt aqueous solution and an alkaline aqueous solution to the turbulent liquid in parallel and continuously while continuing the stirring. At that time, it is preferable that the liquid to be put in the reaction vessel in advance is adjusted to a predetermined pH by adding the above alkaline component to pure water.
上記中和反応時は、反応槽内の反応液のｐＨを８.３〜９.０の範囲内に調整する。このｐＨが８.３より低いと、水酸化ニッケル粒子中に残存する硫酸イオン等の陰イオン成分の濃度が増大し、これらは水酸化ニッケル粒子を熱処理して酸化ニッケル粉末を生成する際に大量のＳＯｘ等となって炉体を傷めるおそれがある。逆にこのｐＨが９.０を超えると、析出する水酸化ニッケル粒子が微細になりすぎ、この水酸化ニッケル粒子を含むスラリーを例えば濾過装置で固液分離する際に濾過性が低下することがある。更に、後段の熱処理工程で焼結が進みすぎて、微細な酸化ニッケル微粉末を得ることが困難になることがある。 During the above neutralization reaction, the pH of the reaction solution in the reaction vessel is adjusted within the range of 8.3 to 9.0. When this pH is lower than 8.3, the concentration of anionic components such as sulfate ions remaining in the nickel hydroxide particles increases, and these are abundant when the nickel hydroxide particles are heat-treated to produce nickel oxide powder. There is a risk of damaging the furnace body due to SOx and the like. On the contrary, when this pH exceeds 9.0, the precipitated nickel hydroxide particles become too fine, and the filterability may be lowered when the slurry containing the nickel hydroxide particles is solid-liquid separated by, for example, a filtration device. is there. Further, sintering may proceed too much in the heat treatment step in the subsequent stage, making it difficult to obtain fine nickel oxide fine powder.
上記した好適な中和条件であるｐＨ９.０以下では反応後の水溶液中に僅かにニッケル成分が残存することがあるが、この場合は、上記の中和工程による晶析がほぼ完了した後にｐＨを１０程度まで上げることによって、上記の濾過により得られる濾液中のニッケル成分を低減させることができる。中和反応時は、ｐＨをほぼ一定に保つことが好ましく、特にその変動幅が設定値を中心として絶対値で０.２以内となるように一定に制御することが好ましい。ｐＨの変動幅がこれより大きくなると、不純物が増大したり酸化ニッケル微粉末の比表面積が低下したりするおそれがある。 At pH 9.0 or lower, which is the above-mentioned suitable neutralization condition, a small amount of nickel component may remain in the aqueous solution after the reaction. In this case, the pH is almost completed after the crystallization by the above-mentioned neutralization step is almost completed. The nickel component in the filtrate obtained by the above filtration can be reduced by increasing the pH to about 10. During the neutralization reaction, it is preferable to keep the pH substantially constant, and it is particularly preferable to control the fluctuation range to be within 0.2 in absolute value around the set value. If the fluctuation range of pH is larger than this, impurities may increase or the specific surface area of the nickel oxide fine powder may decrease.
上記の中和反応時の反応液の温度には特に制約がなく、室温で行うことも可能であるが、水酸化ニッケル粒子を十分に成長させるためには５０〜７０℃の範囲内が好ましい。水酸化ニッケル粒子を十分に成長させることで、水酸化ニッケル粒子中への硫黄の過度の含有を防止することができる。また、水酸化ニッケル粒子中へのナトリウムなどの不純物の巻き込みを抑制し、最終的に得られる酸化ニッケル微粉末の不純物を低減することができる。この液温が５０℃未満では水酸化ニッケル粒子の成長が不十分になって、水酸化ニッケル中への硫黄等の不純物の巻き込みが多くなるおそれがある。逆に液温が７０℃を超えると水の蒸発量が増加し、水溶液中の硫黄等の不純物濃度が高くなるため、生成した水酸化ニッケル粒子中の硫黄等の不純物品位が高くなるおそれがある。 The temperature of the reaction solution at the time of the above neutralization reaction is not particularly limited, and it can be carried out at room temperature, but it is preferably in the range of 50 to 70 ° C. in order to sufficiently grow the nickel hydroxide particles. By sufficiently growing the nickel hydroxide particles, it is possible to prevent excessive inclusion of sulfur in the nickel hydroxide particles. In addition, it is possible to suppress the entrainment of impurities such as sodium in the nickel hydroxide particles and reduce the impurities of the nickel oxide fine powder finally obtained. If the liquid temperature is less than 50 ° C., the growth of nickel hydroxide particles will be insufficient, and impurities such as sulfur may be more involved in nickel hydroxide. On the contrary, when the liquid temperature exceeds 70 ° C., the amount of evaporation of water increases and the concentration of impurities such as sulfur in the aqueous solution increases, so that the grade of impurities such as sulfur in the generated nickel hydroxide particles may increase. ..
上記の中和工程では、中和の反応時間を０.２〜５時間にしている。ここで中和の反応時間とは、所定の中和反応条件が維持される時間であり、例えば連続式完全混合槽型の反応槽で中和反応を行う場合は、その有効容量を硫酸ニッケル水溶液とアルカリ水溶液との合計供給量で除して得られる時間であり、この場合は中和工程に要する平均時間に相当する。例えば、オーバーフロー口を設けることで有効容積が１０Ｌに維持されている反応槽に硫酸ニッケル水溶液とアルカリ水溶液とを合計２０Ｌ／ｈで供給する場合、反応時間は１０／２０＝０.５時間になる。 In the above neutralization step, the neutralization reaction time is set to 0.2 to 5 hours. Here, the neutralization reaction time is a time during which a predetermined neutralization reaction condition is maintained. For example, when a neutralization reaction is carried out in a continuous complete mixing tank type reaction tank, the effective capacity thereof is set to an aqueous nickel sulfate solution. It is the time obtained by dividing by the total supply amount of the alkaline aqueous solution and the alkali aqueous solution, and in this case, it corresponds to the average time required for the neutralization step. For example, when a nickel sulfate aqueous solution and an alkaline aqueous solution are supplied at a total of 20 L / h to a reaction vessel whose effective volume is maintained at 10 L by providing an overflow port, the reaction time is 10/20 = 0.5 hours. ..
上記反応時間が０.２ｈ未満では、水酸化ニッケル粒子中に残存する硫黄量が増加して、その硫黄品位が２.０質量％を超えることがある。水酸化ニッケル粒子の硫黄品位が２.０質量％を超えると、熱処理条件等を制御しても酸化ニッケル微粉末の硫黄品位が２０質量ｐｐｍ以下とならないことがある。逆に反応時間が５ｈを超えると、水酸化ニッケル粒子中に残存する総アルカリ金属の量が増加して１０質量ｐｐｍ以上となることがある。水酸化ニッケル粒子の総アルカリ金属の品位が１０質量ｐｐｍ以上になると、熱処理条件等を制御しても酸化ニッケル微粉末の総アルカリ金属の品位が２０質量ｐｐｍ以下とはならないことがあり、その結果、硫黄品位が２０質量ｐｐｍを超えることがある。また、水酸化ニッケル粒子の総アルカリ金属品位をより低くすることが求められる場合は、反応時間を０.２〜２.５時間とするのが好ましく、一方、水酸化ニッケル粒子の硫黄品位をより低くすることが求められる場合は、反応時間を３.５〜５時間とするのが好ましい。 If the reaction time is less than 0.2 h, the amount of sulfur remaining in the nickel hydroxide particles may increase, and the sulfur grade may exceed 2.0% by mass. If the sulfur grade of the nickel hydroxide particles exceeds 2.0 mass%, the sulfur grade of the nickel oxide fine powder may not be 20 mass ppm or less even if the heat treatment conditions and the like are controlled. On the contrary, when the reaction time exceeds 5 hours, the amount of total alkali metal remaining in the nickel hydroxide particles may increase to 10 mass ppm or more. When the total alkali metal grade of the nickel hydroxide particles is 10 mass ppm or more, the total alkali metal grade of the nickel oxide fine powder may not be 20 mass ppm or less even if the heat treatment conditions are controlled, and as a result. , Sulfur grade may exceed 20 mass ppm. When it is required to lower the total alkali metal grade of the nickel hydroxide particles, the reaction time is preferably 0.2 to 2.5 hours, while the sulfur grade of the nickel hydroxide particles is higher. When lowering is required, the reaction time is preferably 3.5 to 5 hours.
得られた水酸化ニッケル粒子に粗大粒子が存在すると、これを中間原料として酸化ニッケル粒子を生成した場合に該酸化ニッケル粒子も粗大粒子となり、電子部品用材料や固体酸化物形燃料電池の電極材料として使用するには不適となる。粒子の大きさを測る指標としてはＤ９０があり、これは粒径をレーザー散乱法により測定し、その粒度分布から体積積算９０％での粒径を求めることで得られる。上記の中和工程で生成する水酸化ニッケル粒子は、Ｄ９０が６０μｍ以下であるのが好ましく、５０μｍ以下がより好ましい。Ｄ９０の下限値については特に限定はなく、上記中和反応による晶析では５μｍ程度が下限となるが、後段の濾過を考慮すると２５μｍ以上とするのがより好ましい。 If coarse particles are present in the obtained nickel hydroxide particles, when nickel oxide particles are generated using these as intermediate raw materials, the nickel oxide particles also become coarse particles, and are used as materials for electronic parts and electrode materials for solid oxide fuel cells. It is not suitable for use as. There is D90 as an index for measuring the size of particles, which can be obtained by measuring the particle size by a laser scattering method and obtaining the particle size at a volume integration of 90% from the particle size distribution. The nickel hydroxide particles produced in the above neutralization step preferably have a D90 of 60 μm or less, more preferably 50 μm or less. The lower limit of D90 is not particularly limited, and in the crystallization by the above neutralization reaction, the lower limit is about 5 μm, but it is more preferably 25 μm or more in consideration of the subsequent filtration.
尚、水酸化ニッケル粒子のＤ９０を６０μｍ以下にするためには、上記中和反応時の反応槽内の液を、中和反応の開始時から中和反応が進行して晶析により生成した水酸化ニッケル粒子を含むスラリーになるまで常に乱流状態となるように流動させるのが好ましく、これは例えば撹拌翼の回転数を調整する等、公知の方法を用いて行うことができる。 In order to reduce the D90 of the nickel hydroxide particles to 60 μm or less, the liquid in the reaction vessel during the neutralization reaction is water produced by crystallization as the neutralization reaction proceeds from the start of the neutralization reaction. It is preferable to flow the slurry so that it is always in a turbulent state until it becomes a slurry containing nickel oxide particles, and this can be performed by using a known method such as adjusting the rotation speed of the stirring blade.
上記中和反応の終了後は、析出した水酸化ニッケル粒子を含むスラリーを濾過等の固液分離手段により固液分離して該水酸化ニッケル粒子を濾過ケーキ等の湿潤状態の固形分の形態で回収する。この湿潤状態の固形分は、次の熱処理工程で処理する前に洗浄することが好ましい。洗浄はレパルプ洗浄とすることが好ましく、その場合に用いる洗浄液としては水が好ましく、純水がより好ましい。 After the completion of the neutralization reaction, the slurry containing the precipitated nickel hydroxide particles is solid-liquid separated by a solid-liquid separation means such as filtration, and the nickel hydroxide particles are separated into wet solids such as a filtration cake. to recover. The wet solid content is preferably washed before being treated in the next heat treatment step. The cleaning is preferably repulp cleaning, and water is preferable and pure water is more preferable as the cleaning liquid used in that case.
洗浄時の水酸化ニッケルと水との混合割合は特に限定がないが、ニッケル塩に含まれるナトリウム等のアルカリ金属成分が十分に除去できる混合割合が好ましい。具体的には、残留するアルカリ金属等の不純物が十分に低減でき且つ水酸化ニッケル粒子を良好に分散させるため、５０〜１５０ｇの水酸化ニッケルに対して１Ｌの洗浄液を混合することが好ましく、１００ｇ程度の水酸化ニッケルに対して１Ｌの洗浄液を混合するのがより好ましい。 The mixing ratio of nickel hydroxide and water at the time of washing is not particularly limited, but a mixing ratio that can sufficiently remove alkali metal components such as sodium contained in the nickel salt is preferable. Specifically, in order to sufficiently reduce residual impurities such as alkali metals and to disperse nickel hydroxide particles satisfactorily, it is preferable to mix 1 L of the cleaning liquid with 50 to 150 g of nickel hydroxide, preferably 100 g. It is more preferable to mix 1 L of the cleaning solution with respect to the degree of nickel hydroxide.
尚、洗浄時間については、上記の洗浄液の量や温度などの洗浄条件に応じて適宜定めることができ、残留不純物が十分に低減可能な時間とすればよい。また、１回の洗浄でアルカリ金属等の不純物が十分に低減しない場合は、複数回繰り返して洗浄することが好ましい。特に、ナトリウム等のアルカリ金属は酸化ニッケル粉末を生成する際の熱処理によっても除去できないため、この洗浄によって十分に除去することが好ましい。洗浄液に純水を用いる場合は、例えば洗浄後に測定した洗浄液の導電率が所定の値以下になるまで洗浄を繰り返すことで、不純物品位のばらつきを抑えることができる。 The cleaning time can be appropriately determined according to the cleaning conditions such as the amount and temperature of the cleaning liquid, and may be a time during which residual impurities can be sufficiently reduced. Further, when impurities such as alkali metal are not sufficiently reduced by one cleaning, it is preferable to repeat the cleaning a plurality of times. In particular, alkali metals such as sodium cannot be removed by heat treatment when producing nickel oxide powder, so it is preferable to sufficiently remove them by this cleaning. When pure water is used as the cleaning liquid, for example, by repeating the cleaning until the conductivity of the cleaning liquid measured after the cleaning becomes a predetermined value or less, the variation in the impurity grade can be suppressed.
上記の製造方法により作製される水酸化ニッケル粒子は、原料から不可避不純物として混入する以外に塩素が混入する工程を含まないので、塩素品位が極めて低い。加えて、硫黄品位が制御されると共に、ナトリウム等の総アルカリ金属の品位が低い。具体的には、塩素品位が２０質量ｐｐｍ以下、総アルカリ金属の品位が１０質量ｐｐｍ未満である。また硫黄品位は２.０質量％以下に制御される。硫黄品位の下限については特に限定されないが、アルカリ水溶液中の炭酸ナトリウムの混合割合が０.４〜０.８ｍｏｌ／Ｌの範囲では０.４質量％以上となる。またより好ましくは硫黄品位が１.０〜２.０質量％、更に好ましくは１.２〜１.８質量％となる。また、水酸化ニッケル粒子のＴＡＰ密度は０.６ｇ／ｃｍ３以上となる。従って、電子部品用、特にフェライト部品用の材料や固体酸化物形燃料電池の電極用材料に用いられる酸化ニッケル微粉末の原料に好適である。 The nickel hydroxide particles produced by the above production method do not include a step of mixing chlorine other than being mixed as an unavoidable impurity from the raw material, and therefore have an extremely low chlorine grade. In addition, the sulfur grade is controlled and the grade of total alkali metals such as sodium is low. Specifically, the chlorine grade is 20 mass ppm or less, and the total alkali metal grade is less than 10 mass ppm. The sulfur grade is controlled to 2.0% by mass or less. The lower limit of the sulfur grade is not particularly limited, but the mixing ratio of sodium carbonate in the alkaline aqueous solution is 0.4% by mass or more in the range of 0.4 to 0.8 mol / L. Further, the sulfur grade is more preferably 1.0 to 2.0% by mass, and further preferably 1.2 to 1.8% by mass. Further, the TAP density of the nickel hydroxide particles is 0.6 g / cm 3 or more. Therefore, it is suitable as a raw material for nickel oxide fine powder used as a material for electronic parts, particularly for ferrite parts, and as a material for electrodes of solid oxide fuel cells.
上記水酸化ニッケル粒子は、所定の熱処理温度で熱処理を施すことで水酸基が離脱して酸化ニッケル粉末となる。この熱処理では、ある程度焼結が進行するので熱処理後はこの形成された焼結体を解砕して酸化ニッケル微粉末とするのが好ましい。上記熱処理は非還元性雰囲気中で行うのが好ましく、熱処理温度は８５０℃を超え９５０℃未満が好ましい。解砕はジェットミル等の流体エネルギーを利用した解砕装置を用いるのが好ましく、乾式解砕とするのがより好ましい。 The nickel hydroxide particles are desorbed from hydroxyl groups by heat treatment at a predetermined heat treatment temperature to become nickel oxide powder. Since sintering proceeds to some extent in this heat treatment, it is preferable to crush the formed sintered body to obtain nickel oxide fine powder after the heat treatment. The heat treatment is preferably performed in a non-reducing atmosphere, and the heat treatment temperature is preferably more than 850 ° C and lower than 950 ° C. For crushing, it is preferable to use a crushing device using fluid energy such as a jet mill, and it is more preferable to use dry crushing.
このようにして酸化ニッケル微粉末を生成することで、硫黄品位が２０質量ｐｐｍ以下、塩素品位が２０質量ｐｐｍ以下、総アルカリ金属の品位が２０質量ｐｐｍ以下、比表面積が２ｍ２／ｇ以上４ｍ２／ｇ未満の酸化ニッケル微粉末が得られ、電子部品用、特にフェライト部品用の材料や固体酸化物形燃料電池の電極用材料に好適に用いることができる。尚、固体酸化物形燃料電池の電極用材料としては、硫黄品位が１００質量ｐｐｍ以下であることが好ましいとされている。 By producing the nickel oxide fine powder in this way, the sulfur grade is 20 mass ppm or less, the chlorine grade is 20 mass ppm or less, the total alkali metal grade is 20 mass ppm or less, and the specific surface area is 2 m 2 / g or more and 4 m. A fine powder of nickel oxide of less than 2 / g can be obtained, and it can be suitably used as a material for electronic parts, particularly for ferrite parts, and a material for electrodes of solid oxide fuel cells. As a material for electrodes of solid oxide fuel cells, it is said that the sulfur grade is preferably 100 mass ppm or less.
次に、実施例及び比較例を挙げて本発明を説明するが、本発明はこれらの実施例等によってなんら限定されるものではない。尚、以下の実施例及び比較例の塩素品位の分析は、分析対象物を塩素の揮発を抑制できる密閉容器内にてマイクロ波照射下で硝酸に溶解し、硝酸銀を加えて塩化銀を沈殿させ、得られた沈殿物中の塩素を蛍光Ｘ線定量分析装置（ＰＡＮａｌｙｔｉｃａｌ社製 Ｍａｇｉｘ）を用いて検量線法で評価することによって行った。硫黄品位の分析は、分析対象物を硝酸に溶解した後、ＩＣＰ発光分光分析装置（セイコー社製 ＳＰＳ−３０００）によって行った。ナトリウム品位の分析は、分析対象物を硝酸に溶解した後、原子吸光装置（日立ハイテク社製 Ｚ−２３００）により評価することによって行った。試料の粒径は、レーザー散乱法により測定し、その粒度分布から体積積算９０％での粒径Ｄ９０を求めた。ＴＡＰ密度は、振とう比重測定器（（株）蔵持化学器械製作所、ＫＲＳ−４０９）を用いて、５００回タッピングした後の試料の質量／タッピング後の体積で求められた値とした。比表面積の分析は、窒素ガス吸着によるＢＥＴ法により求めた。 Next, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples and the like. In the chlorine grade analysis of the following examples and comparative examples, the object to be analyzed is dissolved in nitric acid under microwave irradiation in a closed container capable of suppressing the volatilization of chlorine, and silver nitrate is added to precipitate silver chloride. , Chlorine in the obtained precipitate was evaluated by a calibration beam method using a fluorescent X-ray quantitative analyzer (Magic manufactured by PANalytical Co., Ltd.). The sulfur grade was analyzed by dissolving the analysis object in nitric acid and then using an ICP emission spectroscopic analyzer (SPS-3000 manufactured by Seiko Corporation). The sodium grade analysis was performed by dissolving the analysis object in nitric acid and then evaluating it with an atomic absorption spectrophotometer (Z-2300 manufactured by Hitachi High-Tech). The particle size of the sample was measured by a laser scattering method, and the particle size D90 at a volume integration of 90% was determined from the particle size distribution. The TAP density was determined by the mass of the sample after tapping 500 times / the volume after tapping using a shaking specific gravity measuring instrument (Kuramochi Chemical Instruments Mfg. Co., Ltd., KRS-409). The analysis of the specific surface area was determined by the BET method by adsorbing nitrogen gas.
［実施例１］
邪魔板とオーバーフロー口を有する攪拌機構付きの有効容積４Ｌの反応槽に純水を入れてから炭酸ナトリウムと水酸化ナトリウムを添加して十分に攪拌し、炭酸ナトリウム濃度０.６ｍｏｌ／Ｌ、ｐＨ８.５の混合水溶液４Ｌを調製した。また、硫酸ニッケルを純水に溶解してニッケル濃度１２０ｇ／Ｌに調整したニッケル水溶液と、水酸化ナトリウム及び濃度０.６ｍｏｌ／Ｌに調整された炭酸ナトリウムを含む添加用混合水溶液とを用意した。これらニッケル水溶液と添加用混合水溶液とを、前述の炭酸ナトリウムと水酸化ナトリウムとを含む反応槽内の混合水溶液に同時並行的且つ連続的に添加して混合させ、中和反応を行った。この時、両供給ノズル出口部からそれぞれ供給を行ったニッケル水溶液及び添加用混合水溶液は、各々供給先の反応槽内において乱流状態で混合されていた。
[Example 1]
Pure water is put into a reaction vessel having an effective volume of 4 L with a stirrer plate and an overflow port, and then sodium carbonate and sodium hydroxide are added and sufficiently stirred. Sodium carbonate concentration 0.6 mol / L, pH 8. 4 L of the mixed aqueous solution of 5 was prepared. Further, a nickel aqueous solution prepared by dissolving nickel sulfate in pure water to adjust the nickel concentration to 120 g / L and an additive mixed aqueous solution containing sodium hydroxide and sodium carbonate adjusted to a concentration of 0.6 mol / L were prepared. These nickel aqueous solutions and the mixed aqueous solution for addition were added simultaneously and continuously to the above-mentioned mixed aqueous solution in the reaction vessel containing sodium carbonate and sodium hydroxide and mixed to carry out a neutralization reaction. At this time, the nickel aqueous solution and the mixed aqueous solution for addition, which were supplied from the outlets of both supply nozzles, were mixed in a turbulent state in the reaction tank of the supply destination, respectively.
この中和反応の際、反応槽内の反応液はｐＨ８.５を中心としてその変動幅が絶対値で０.２以内となるように調整した。また、ニッケル水溶液を７５ｍＬ／分の流量で添加することによって、添加用混合水溶液の流量と合わせて中和の反応時間を０.５時間に調整した。更に、反応槽内では反応液の温度を６０℃とし、攪拌翼を用いて７００ｒｐｍで撹拌した。 At the time of this neutralization reaction, the reaction solution in the reaction vessel was adjusted so that the fluctuation range centered on pH 8.5 was within 0.2 in absolute value. Further, by adding the nickel aqueous solution at a flow rate of 75 mL / min, the reaction time of neutralization was adjusted to 0.5 hours in combination with the flow rate of the mixed aqueous solution for addition. Further, in the reaction vessel, the temperature of the reaction solution was set to 60 ° C., and the mixture was stirred at 700 rpm using a stirring blade.
上記の連続晶析法により水酸化ニッケル粒子を連続的に晶析させた。この晶析により生成した水酸化ニッケル粒子の沈殿物を含むスラリーをオーバーフローにより連続的に回収し、ヌッチェによる濾過と保持時間３０分の純水レパルプを１０回繰り返して、水酸化ニッケル粒子の濾過ケーキを得た。この濾過ケーキを送風乾燥機を用いて１３０℃の大気中にて２４時間かけて乾燥し、水酸化ニッケル粒子を得た。この水酸化ニッケル粒子に対して硫黄（Ｓ）品位、塩素（Ｃｌ）品位、ナトリウム（Ｎａ）品位、ＴＡＰ密度、及びＤ９０を測定した。 Nickel hydroxide particles were continuously crystallized by the above continuous crystallization method. The slurry containing the precipitate of nickel hydroxide particles produced by this crystallization is continuously recovered by overflow, and filtration by Nutche and pure water repulp with a holding time of 30 minutes are repeated 10 times to filter the nickel hydroxide particles. Got This filtered cake was dried in the air at 130 ° C. for 24 hours using a blower dryer to obtain nickel hydroxide particles. Sulfur (S) grade, chlorine (Cl) grade, sodium (Na) grade, TAP density, and D90 were measured for the nickel hydroxide particles.
次に、この水酸化ニッケル粒子を原料として９００℃の大気で５時間かけて熱処理した後、ナノグライディングミル（登録商標、徳寿工作所製）にてプッシャーノズル圧力１.０ＭＰａ、グライディング圧力０.９ＭＰａにて粉砕して酸化ニッケル微粒子を生成した。得られた酸化ニッケル微粒子の硫黄品位は１５質量ｐｐｍ、塩素品位は２０質量ｐｐｍ未満、ナトリウム品位は１０質量ｐｐｍ未満、比表面積は３.２ｍ２／ｇ、Ｄ９０は０.８１μｍであり、電子部品材料や固体酸化物形燃料電池の電極材料として好適な不純物品位が低く且つ微細な酸化ニッケル微粉末が得られることが分った。 Next, the nickel hydroxide particles are heat-treated in the atmosphere at 900 ° C. for 5 hours, and then a pusher nozzle pressure of 1.0 MPa and a gliding pressure of 0.9 MPa are used in a nanogliding mill (registered trademark, manufactured by Tokuju Kosakusho). To produce nickel oxide fine particles. The obtained nickel oxide fine particles have a sulfur grade of 15 mass ppm, a chlorine grade of less than 20 mass ppm, a sodium grade of less than 10 mass ppm, a specific surface area of 3.2 m 2 / g, and a D90 of 0.81 μm. It was found that a fine nickel oxide fine powder having a low impurity grade suitable as a material or an electrode material for a solid oxide fuel cell can be obtained.
［実施例２〜７］
中和工程の反応時間を０.５時間に代えてそれぞれ０.２時間（実施例２）、１.０時間（実施例３）、１.５時間（実施例４）、２.５時間（実施例５）、３.５時間（実施例６）、５.０時間（実施例７）に調整した以外は実施例１と同様にして水酸化ニッケル粒子を得ると共に分析、測定を行った。
[Examples 2 to 7]
The reaction time of the neutralization step was changed from 0.5 hours to 0.2 hours (Example 2), 1.0 hours (Example 3), 1.5 hours (Example 4), and 2.5 hours (Example 4), respectively. Nickel hydroxide particles were obtained and analyzed and measured in the same manner as in Example 1 except that the time was adjusted to 3.5 hours (Example 6) and 5.0 hours (Example 7).
更に、実施例５及び実施例７で得られた水酸化ニッケル粒子については、実施例１と同じ条件で酸化ニッケル微粉末を生成した。実施例５の水酸化ニッケル粒子より得られた酸化ニッケル微粉末の硫黄品位は２０質量ｐｐｍ、塩素品位は２０質量ｐｐｍ未満、ナトリウム品位は１０質量ｐｐｍ未満、比表面積は３.４ｍ２／ｇ、Ｄ９０は０.８５μｍであり、実施例７の水酸化ニッケル粒子より得られた酸化ニッケル微粉末の硫黄品位は２０質量ｐｐｍ、塩素品位は２０質量ｐｐｍ未満、ナトリウム品位は１０質量ｐｐｍ未満、比表面積は３.８ｍ２／ｇ、Ｄ９０は０.８４μｍであった。これらの結果より、電子部品材料や固体酸化物形燃料電池の電極材料として好適な不純物品位が低く且つ微細な酸化ニッケル微粉末が得られることが分った Further, for the nickel hydroxide particles obtained in Examples 5 and 7, nickel oxide fine powder was produced under the same conditions as in Example 1. The nickel oxide fine powder obtained from the nickel hydroxide particles of Example 5 had a sulfur grade of 20 mass ppm, a chlorine grade of less than 20 mass ppm, a sodium grade of less than 10 mass ppm, and a specific surface area of 3.4 m 2 / g. D90 is 0.85 μm, and the nickel oxide fine powder obtained from the nickel hydroxide particles of Example 7 has a sulfur grade of 20 mass ppm, a chlorine grade of less than 20 mass ppm, a sodium grade of less than 10 mass ppm, and a specific surface area. Was 3.8 m 2 / g, and D90 was 0.84 μm. From these results, it was found that fine nickel oxide fine powder with low impurity grade suitable for electronic component materials and electrode materials for solid oxide fuel cells can be obtained.
［比較例１〜３］
中和工程の反応時間を０.５時間に代えてそれぞれ０.１時間（比較例１）、６.０時間（比較例２）、１０.０時間（比較例３）に調整した以外は実施例１と同様にして水酸化ニッケル粒子を得ると共に分析、測定を行った。更に、比較例２で得られた水酸化ニッケル粒子については、実施例１と同じ条件で酸化ニッケル微粉末を生成した。得られた酸化ニッケル微粉末の硫黄品位は７０質量ｐｐｍ、塩素品位は２０質量ｐｐｍ未満、ナトリウム品位は１０質量ｐｐｍ、比表面積は３.９ｍ２／ｇ、Ｄ９０は０.８７μｍであり、硫黄品位とナトリウム品位が高いことが確認された。
[Comparative Examples 1 to 3]
The reaction time of the neutralization step was changed to 0.1 hour (Comparative Example 1), 6.0 hours (Comparative Example 2) and 10.0 hours (Comparative Example 3), respectively, instead of 0.5 hours. Nickel hydroxide particles were obtained, analyzed and measured in the same manner as in Example 1. Further, for the nickel hydroxide particles obtained in Comparative Example 2, nickel oxide fine powder was produced under the same conditions as in Example 1. The obtained nickel oxide fine powder has a sulfur grade of 70 mass ppm, a chlorine grade of less than 20 mass ppm, a sodium grade of 10 mass ppm, a specific surface area of 3.9 m 2 / g, and a D90 of 0.87 μm. It was confirmed that the sodium grade was high.
［比較例４］
中和反応時のｐＨを８.５に代えてｐＨ８.０に調整した以外は実施例５と同様にして水酸化ニッケル粒子を得ると共に分析、測定を行った。
[Comparative Example 4]
Nickel hydroxide particles were obtained and analyzed and measured in the same manner as in Example 5 except that the pH at the time of the neutralization reaction was adjusted to pH 8.0 instead of 8.5.
［実施例８］
中和反応時のｐＨを８.５に代えてｐＨ９.０に調整した以外は実施例５と同様にして水酸化ニッケル粒子を得ると共に分析、測定を行った。
[Example 8]
Nickel hydroxide particles were obtained and analyzed and measured in the same manner as in Example 5 except that the pH at the time of the neutralization reaction was adjusted to pH 9.0 instead of 8.5.
［実施例９、１０］
撹拌回転数を６００ｒｐｍ（実施例９）、４５０ｒｐｍ（実施例１０）に調整した以外は実施例５と同様にして水酸化ニッケル粒子を得ると共に分析、測定を行った。上記の実施例１〜１０及び比較例１〜４の水酸化ニッケル粒子の分析、測定結果を表１にまとめて示す。
[Examples 9 and 10]
Nickel hydroxide particles were obtained and analyzed and measured in the same manner as in Example 5 except that the stirring rotation speed was adjusted to 600 rpm (Example 9) and 450 rpm (Example 10). Table 1 summarizes the analysis and measurement results of the nickel hydroxide particles of Examples 1 to 10 and Comparative Examples 1 to 4 above.
上記表１の結果から分るように、実施例1〜１０の水酸化ニッケル粒子はいずれも硫黄品位が０.４〜２.０質量％に制御されている上、塩素品位は２０質量ｐｐｍ未満、ナトリウム品位が１０質量ｐｐｍ未満と、ＴＡＰ密度が０.６ｇ／ｃｍ３以上になっている。また、実施例１、実施例５、及び実施例７の水酸化ニッケル粒子を原料として作製した酸化ニッケル微粉末は、電子部品用材料や固体酸化物形燃料電池の電極材料として好適であることも確認できた。更に実施例１、実施例９、及び実施例１０より、中和反応時の反応槽の撹拌翼の回転数を多くすることで水酸化ニッケル粒子のＤ９０を小さくできることが分った。これに対して、比較例１〜４では、硫黄品位、ナトリウム品位、及びＴＡＰ密度のうちの少なくともいずれかが上記の範囲から外れており、電子部品用材料や固体酸化物形燃料電池の電極材料として好適な酸化ニッケル微粉末の原料として適切でないことが分る。
As can be seen from the results in Table 1 above, all of the nickel hydroxide particles of Examples 1 to 10 have a sulfur grade controlled to 0.4 to 2.0 mass% and a chlorine grade of less than 20 mass ppm. , The sodium grade is less than 10 mass ppm, and the TAP density is 0.6 g / cm 3 or more. Further, the nickel oxide fine powder produced from the nickel hydroxide particles of Examples 1, 5 and 7 as raw materials may be suitable as a material for electronic parts or an electrode material for a solid oxide fuel cell. It could be confirmed. Further, from Examples 1, 9, and 10, it was found that the D90 of the nickel hydroxide particles can be reduced by increasing the rotation speed of the stirring blade of the reaction tank during the neutralization reaction. On the other hand, in Comparative Examples 1 to 4, at least one of the sulfur grade, the sodium grade, and the TAP density is out of the above range, and the material for electronic parts and the electrode material of the solid oxide fuel cell It can be seen that it is not suitable as a raw material for nickel oxide fine powder.
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