JP2022087950A - Nickel-particle surface treatment method and nickel-powder producing method - Google Patents
Nickel-particle surface treatment method and nickel-powder producing method Download PDFInfo
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- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 title claims abstract description 333
- 239000002245 particle Substances 0.000 title claims abstract description 153
- 238000000034 method Methods 0.000 title claims abstract description 36
- 238000004381 surface treatment Methods 0.000 title abstract description 29
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 133
- 239000002879 Lewis base Substances 0.000 claims abstract description 67
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 48
- 150000007527 lewis bases Chemical class 0.000 claims abstract description 48
- 150000002815 nickel Chemical class 0.000 claims abstract description 27
- 238000002156 mixing Methods 0.000 claims abstract description 24
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 24
- 238000006722 reduction reaction Methods 0.000 claims abstract description 24
- 238000004519 manufacturing process Methods 0.000 claims description 25
- -1 nitrogen-containing Lewis base Chemical class 0.000 claims description 21
- 238000001035 drying Methods 0.000 claims description 19
- 238000002425 crystallisation Methods 0.000 claims description 13
- 230000008025 crystallization Effects 0.000 claims description 13
- 125000004432 carbon atom Chemical group C* 0.000 claims description 12
- DIOYAVUHUXAUPX-ZHACJKMWSA-N 2-[methyl-[(e)-octadec-9-enoyl]amino]acetic acid Chemical compound CCCCCCCC\C=C\CCCCCCCC(=O)N(C)CC(O)=O DIOYAVUHUXAUPX-ZHACJKMWSA-N 0.000 claims description 7
- 150000001875 compounds Chemical class 0.000 claims description 7
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- 108700004121 sarkosyl Proteins 0.000 claims description 6
- 125000000217 alkyl group Chemical group 0.000 claims description 5
- 125000003342 alkenyl group Chemical group 0.000 claims description 4
- 125000002947 alkylene group Chemical group 0.000 claims description 4
- NXLIWIHBINBLLP-UHFFFAOYSA-N 3-(pentadecylamino)propanoic acid Chemical compound C(CCNCCCCCCCCCCCCCCC)(=O)O NXLIWIHBINBLLP-UHFFFAOYSA-N 0.000 claims description 3
- 239000011362 coarse particle Substances 0.000 abstract description 28
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- 239000002002 slurry Substances 0.000 description 12
- 238000001914 filtration Methods 0.000 description 11
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 10
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- QMMRZOWCJAIUJA-UHFFFAOYSA-L nickel dichloride Chemical compound Cl[Ni]Cl QMMRZOWCJAIUJA-UHFFFAOYSA-L 0.000 description 7
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- 229910052802 copper Inorganic materials 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- DIOQZVSQGTUSAI-UHFFFAOYSA-N decane Chemical compound CCCCCCCCCC DIOQZVSQGTUSAI-UHFFFAOYSA-N 0.000 description 3
- 239000010419 fine particle Substances 0.000 description 3
- 239000008273 gelatin Substances 0.000 description 3
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- 235000011852 gelatine desserts Nutrition 0.000 description 3
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- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 3
- BFDHFSHZJLFAMC-UHFFFAOYSA-L nickel(ii) hydroxide Chemical compound [OH-].[OH-].[Ni+2] BFDHFSHZJLFAMC-UHFFFAOYSA-L 0.000 description 3
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- ZZSNKZQZMQGXPY-UHFFFAOYSA-N Ethyl cellulose Chemical compound CCOCC1OC(OC)C(OCC)C(OCC)C1OC1C(O)C(O)C(OC)C(CO)O1 ZZSNKZQZMQGXPY-UHFFFAOYSA-N 0.000 description 2
- VEQPNABPJHWNSG-UHFFFAOYSA-N Nickel(2+) Chemical compound [Ni+2] VEQPNABPJHWNSG-UHFFFAOYSA-N 0.000 description 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- GGBJHURWWWLEQH-UHFFFAOYSA-N butylcyclohexane Chemical compound CCCCC1CCCCC1 GGBJHURWWWLEQH-UHFFFAOYSA-N 0.000 description 2
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- MWKFXSUHUHTGQN-UHFFFAOYSA-N decan-1-ol Chemical compound CCCCCCCCCCO MWKFXSUHUHTGQN-UHFFFAOYSA-N 0.000 description 2
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- SNRUBQQJIBEYMU-UHFFFAOYSA-N dodecane Chemical compound CCCCCCCCCCCC SNRUBQQJIBEYMU-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229920001249 ethyl cellulose Polymers 0.000 description 2
- 235000019325 ethyl cellulose Nutrition 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 238000004898 kneading Methods 0.000 description 2
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- 229910001453 nickel ion Inorganic materials 0.000 description 2
- ZWRUINPWMLAQRD-UHFFFAOYSA-N nonan-1-ol Chemical compound CCCCCCCCCO ZWRUINPWMLAQRD-UHFFFAOYSA-N 0.000 description 2
- BKIMMITUMNQMOS-UHFFFAOYSA-N nonane Chemical compound CCCCCCCCC BKIMMITUMNQMOS-UHFFFAOYSA-N 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
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- 239000004332 silver Substances 0.000 description 2
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- QDKSGHXRHXVMPF-UHFFFAOYSA-N 2,2-dimethylundecane Chemical compound CCCCCCCCCC(C)(C)C QDKSGHXRHXVMPF-UHFFFAOYSA-N 0.000 description 1
- OAYXUHPQHDHDDZ-UHFFFAOYSA-N 2-(2-butoxyethoxy)ethanol Chemical compound CCCCOCCOCCO OAYXUHPQHDHDDZ-UHFFFAOYSA-N 0.000 description 1
- HBNHCGDYYBMKJN-UHFFFAOYSA-N 2-(4-methylcyclohexyl)propan-2-yl acetate Chemical compound CC1CCC(C(C)(C)OC(C)=O)CC1 HBNHCGDYYBMKJN-UHFFFAOYSA-N 0.000 description 1
- SGVYKUFIHHTIFL-UHFFFAOYSA-N 2-methylnonane Chemical compound CCCCCCCC(C)C SGVYKUFIHHTIFL-UHFFFAOYSA-N 0.000 description 1
- PLZDDPSCZHRBOY-UHFFFAOYSA-N 3-methylnonane Chemical compound CCCCCCC(C)CC PLZDDPSCZHRBOY-UHFFFAOYSA-N 0.000 description 1
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 1
- KRKIAJBQOUBNSE-GYSYKLTISA-N Isobornyl isobutyrate Chemical compound C1C[C@@]2(C)[C@H](OC(=O)C(C)C)C[C@@H]1C2(C)C KRKIAJBQOUBNSE-GYSYKLTISA-N 0.000 description 1
- 229910021607 Silver chloride Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- FAFMZORPAAGQFV-BREBYQMCSA-N [(1r,3r,4r)-4,7,7-trimethyl-3-bicyclo[2.2.1]heptanyl] propanoate Chemical compound C1C[C@@]2(C)[C@H](OC(=O)CC)C[C@@H]1C2(C)C FAFMZORPAAGQFV-BREBYQMCSA-N 0.000 description 1
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- 125000003277 amino group Chemical group 0.000 description 1
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- AQBOUNVXZQRXNP-UHFFFAOYSA-L azane;dichloropalladium Chemical compound N.N.N.N.Cl[Pd]Cl AQBOUNVXZQRXNP-UHFFFAOYSA-L 0.000 description 1
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Abstract
Description
本発明は、ニッケル粒子の表面処理方法およびニッケル粉末の製造方法に関する。 The present invention relates to a method for surface treatment of nickel particles and a method for producing nickel powder.
ニッケル粒子は、厚膜導電体を作製するための導電ペーストの材料として使用され、電気回路の形成や、積層セラミックコンデンサ（ｍｕｌｔｉｌａｙｅｒ ｃｅｒａｍｉｃ ｃａｐａｃｉｔｏｒｓ；ＭＬＣＣ）および多層セラミック基板等の積層セラミック部品の電極等に用いられている。 Nickel particles are used as a material for conductive paste for producing thick film conductors, and are used for forming electric circuits and electrodes for laminated ceramic parts such as multilayer ceramic capacitors (MLCCs) and multilayer ceramic substrates. It is used.
この電極が使用される積層セラミックコンデンサは、例えば、金属粉末にニッケル粒子を用いた場合は、次のような方法で製造される。 The monolithic ceramic capacitor in which this electrode is used is manufactured by the following method, for example, when nickel particles are used for the metal powder.
まず、ニッケル粒子と、エチルセルロース等の樹脂と、ターピネオール等の有機溶剤等とを混練して得られた導電ペーストを、厚さ１０μｍ以下の誘電体グリーンシート（セラミックグリーンシート）上にスクリーン印刷し、その後乾燥して内部電極用のニッケル塗膜を作製する。 First, a conductive paste obtained by kneading nickel particles, a resin such as ethyl cellulose, and an organic solvent such as tarpineol is screen-printed on a dielectric green sheet (ceramic green sheet) having a thickness of 10 μm or less. Then, it is dried to prepare a nickel coating film for an internal electrode.
次に、印刷された内部電極用のニッケル塗膜と誘電体グリーンシートが交互に重なるように積層し、圧着して積層体を作製する。 Next, the printed nickel coating film for the internal electrode and the dielectric green sheet are laminated so as to be alternately overlapped, and pressure-bonded to prepare a laminated body.
作製した積層体を所定の大きさにカットし、有機バインダとして使用したエチルセルロース等の樹脂の燃焼除去を行うための脱バインダ処理を行った後、１３００℃程度の高温焼成による誘電体、および内部電極（ニッケル膜）の焼結を進め、誘電体層と内部電極層が互いに積層したセラミック体を得る。そして、このセラミック体に外部電極を取り付け、積層セラミックコンデンサとする。 The prepared laminate is cut to a predetermined size, subjected to a binder removal treatment for burning and removing a resin such as ethyl cellulose used as an organic binder, and then a dielectric obtained by firing at a high temperature of about 1300 ° C. and an internal electrode. Sintering of the (nickel film) is advanced to obtain a ceramic body in which the dielectric layer and the internal electrode layer are laminated on each other. Then, an external electrode is attached to this ceramic body to form a monolithic ceramic capacitor.
なお、上記積層体の脱バインダ処理は、ニッケル粒子が酸化しないように、極めて微量の酸素を含んだ雰囲気下にて行われる。 The binder removal treatment of the laminated body is performed in an atmosphere containing an extremely small amount of oxygen so that the nickel particles are not oxidized.
一般に、ＭＬＣＣの内部電極に使用されるニッケルペーストは、ビヒクル中にニッケル粉末を混練して製造され、多くのニッケル粉末の凝集体を含んでいる。ニッケル粉末の製造プロセスでは、その最終段階に、ニッケル粉末の製造方法（気相法、液相法）を問わずに乾燥工程を有するのが通常である。この乾燥工程における乾燥処理がニッケル粒子の凝集を促すことから、得られるニッケル粉末には乾燥時に生じた凝集体が粗大粒子となって含まれていることが一般的である。 Generally, the nickel paste used for the internal electrode of MLCC is produced by kneading nickel powder in a vehicle and contains a large amount of agglomerates of nickel powder. In the nickel powder manufacturing process, the final step is usually to have a drying step regardless of the nickel powder manufacturing method (gas phase method, liquid phase method). Since the drying treatment in this drying step promotes the aggregation of nickel particles, it is common that the obtained nickel powder contains aggregates generated during drying as coarse particles.
近年のＭＬＣＣは、小型で大容量化を達成させるために、内部電極層を伴ったセラミックグリーンシートの積層数を、数百層から１０００層程度にまで増加させることが要求されている。このため、内部電極層の厚みを従来の数ミクロンレベルからサブミクロンレベルに薄層化する検討がなされており、それに伴い、内部電極用の電極材料のニッケル粉末の小粒径化が進められている。 In recent years, MLCCs are required to increase the number of layers of ceramic green sheets with internal electrode layers from several hundred layers to about 1,000 layers in order to achieve small size and large capacity. For this reason, studies have been made to reduce the thickness of the internal electrode layer from the conventional several micron level to the submicron level, and along with this, the nickel powder of the electrode material for the internal electrode has been reduced in particle size. There is.
しかしながら、小粒径になるほどニッケル粉末の表面積は大きくなり、それに伴い表面エネルギーが大きくなって、凝集体を形成し易くなる。また、ニッケル粉末等の金属粉末は、分散性が悪く、凝集体が存在するようになると、ＭＬＣＣ製造時における焼成工程でニッケル粉末が焼結する際にセラミックシート層を突き抜けてしまい、電極が短絡した不良品が発生するおそれがある。また、たとえセラミックシート層を突き抜けない場合であっても、ＭＬＣＣにおける電極間距離が短くなることで部分的な電流集中が発生する場合があり、この電流集中が積層セラミックコンデンサの寿命劣化の原因となっていた。このように、ＭＬＣＣにおいては、凝集体を含めた粗大粒子が少ないニッケルペーストを製造し、表面に凹凸がなく平滑な内部電極を得ることが重要となっている。また、ニッケル粒子の凝集体の存在により、製品不良を引き起こす可能性が懸念されていることから、凝集体が発生しないようニッケル粒子の表面状態の改善が望まれている。 However, the smaller the particle size, the larger the surface area of the nickel powder, and the larger the surface energy, which makes it easier to form aggregates. Further, metal powder such as nickel powder has poor dispersibility, and when aggregates are present, the nickel powder penetrates the ceramic sheet layer when the nickel powder is sintered in the firing process during MLCC production, and the electrodes are short-circuited. There is a risk that defective products will be generated. Further, even if the ceramic sheet layer cannot be penetrated, a partial current concentration may occur due to a short distance between the electrodes in the MLCC, and this current concentration causes deterioration of the life of the multilayer ceramic capacitor. It was. As described above, in MLCC, it is important to produce a nickel paste containing a small amount of coarse particles including aggregates and to obtain a smooth internal electrode having no unevenness on the surface. Further, since there is a concern that the presence of agglomerates of nickel particles may cause product defects, it is desired to improve the surface condition of nickel particles so that agglomerates do not occur.
特許文献１には、ニッケル粒子の表面の酸化処理についての技術が開示されており、液相法で作製したニッケル粉末を純水に添加してスラリー化してから、過酸化水素で酸化することの技術事項が開示されている。しかし、過酸化水素による表面酸化処理では、酸化処理を均一に制御することが難しい場合がある。 Patent Document 1 discloses a technique for oxidizing the surface of nickel particles. Nickel powder prepared by the liquid phase method is added to pure water to form a slurry, and then oxidized with hydrogen peroxide. The technical matters are disclosed. However, in the surface oxidation treatment with hydrogen peroxide, it may be difficult to uniformly control the oxidation treatment.
ニッケル粉末は、保管しておくと経時にて空気中の酸素により酸化されて表面に水酸化ニッケルを形成する場合がある。ニッケル粒子の粗大粒子は、表面の水酸化ニッケルによって隣接するニッケル粒子同士が強固に固められることによって発生する場合がある。そのため、特にＭＬＣＣに用いるニッケル粉末は、保管中の酸化による粗大粒子の発生によって不具合が生じないよう、ニッケル粉末の保管中の酸化を抑制することが重要となる。 If the nickel powder is stored, it may be oxidized by oxygen in the air over time to form nickel hydroxide on the surface. The coarse particles of nickel particles may be generated by firmly solidifying adjacent nickel particles with nickel hydroxide on the surface. Therefore, it is particularly important for the nickel powder used for MLCC to suppress the oxidation of the nickel powder during storage so that problems do not occur due to the generation of coarse particles due to the oxidation during storage.
本発明は、このような実情に鑑みて提案されたものであり、保管中の酸化による粗大粒子の発生が抑制されるニッケル粒子の表面処理方法およびニッケル粉末の製造方法を提供することを目的とする。 The present invention has been proposed in view of such circumstances, and an object of the present invention is to provide a surface treatment method for nickel particles and a method for producing nickel powder, in which the generation of coarse particles due to oxidation during storage is suppressed. do.
本発明者らは、上述した課題を解決するために鋭意検討を重ねた。その結果、水溶性ニッケル塩を還元させて晶析したニッケル粒子を、その表面が空気中の酸素と反応して表面が酸化しないように、一度も乾燥させずにルイス塩基化合物によりその表面を被覆することで、乾燥後の粉体状態におけるニッケル粒子の凝集を抑制でき、その結果として粗大粒子の発生を抑制できることを見出し、本発明を完成するに至った。 The present inventors have made extensive studies to solve the above-mentioned problems. As a result, the surface of the nickel particles crystallized by reducing the water-soluble nickel salt is coated with the Lewis base compound without being dried so that the surface does not react with oxygen in the air and the surface is not oxidized. By doing so, it was found that the aggregation of nickel particles in the powder state after drying can be suppressed, and as a result, the generation of coarse particles can be suppressed, and the present invention has been completed.
上記課題を解決するために、本発明のニッケル粒子の表面処理方法は、水溶性ニッケル塩を還元させて晶析したニッケル粒子を含む還元反応溶液と、窒素を含有するルイス塩基とを混合する混合工程を含む。 In order to solve the above problems, the surface treatment method for nickel particles of the present invention is a mixture of a reduction reaction solution containing nickel particles crystallized by reducing a water-soluble nickel salt and a nitrogen-containing Lewis base. Includes steps.
前記混合工程により、前記ルイス塩基が前記ニッケル粒子の表面に配位結合してもよい。 The Lewis base may be coordinate-bonded to the surface of the nickel particles by the mixing step.
前記ルイス塩基が、下記式（１）で表される化合物を含んでもよい。 The Lewis base may contain a compound represented by the following formula (1).
式（１）中、Ｒ１は炭素数が１～１８のアルキル基または炭素数が１～１８のアルケニル基を示し、Ｒ２は炭素数が１～６のアルキレン基を示し、Ｒ３およびＲ4はＨもしくはＣＨ３を示す。 In formula (1), R 1 represents an alkyl group having 1 to 18 carbon atoms or an alkenyl group having 1 to 18 carbon atoms, R 2 represents an alkylene group having 1 to 6 carbon atoms, and R 3 and R. 4 indicates H or CH 3 .
前記ルイス塩基が、Ｎ－オレオイルサルコシン、Ｎ－ラウロイルサルコシン、およびミリストイルメチル-β-アラニンから選択された１種類以上を含んでもよい。 The Lewis base may contain one or more selected from N-oleoyl sarcosine, N-lauroyl sarcosine, and myritoylmethyl-β-alanine.
また、上記課題を解決するために、本発明のニッケル粉末の製造方法は、還元反応溶液中で水溶性ニッケル塩を還元させてニッケル粒子を晶析させる晶析工程と、前記晶析工程後のニッケル粒子を含む還元反応溶液と、窒素を含有するルイス塩基とを混合する混合工程と、を含む。 Further, in order to solve the above-mentioned problems, the method for producing nickel powder of the present invention comprises a crystallization step of reducing a water-soluble nickel salt in a reduction reaction solution to crystallize nickel particles, and a crystallization step after the crystallization step. It comprises a mixing step of mixing a reduction reaction solution containing nickel particles and a Lewis base containing nitrogen.
前記混合工程後、表面処理されたニッケル粒子を乾燥させる乾燥工程を含んでもよい。 After the mixing step, a drying step of drying the surface-treated nickel particles may be included.
本発明によれば、保管中の酸化による粗大粒子の発生が抑制されるニッケル粒子の表面処理方法およびニッケル粉末の製造方法を提供することができる。 INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for surface-treating nickel particles and a method for producing nickel powder, in which the generation of coarse particles due to oxidation during storage is suppressed.
以下、本発明の実施の形態について、図面を参照しつつ詳細に説明する。図１は、本発明のニッケル粒子の表面処理方法とニッケル粉末の製造方法とを一連の工程として示したフロー図である。ただし、本発明は、以下の実施形態に限定されるものではない。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a flow chart showing a method for surface-treating nickel particles and a method for producing nickel powder of the present invention as a series of steps. However, the present invention is not limited to the following embodiments.
［ニッケル粉末の製造方法］
本発明のニッケル粉末の製造方法によって、ニッケル塩溶液に対してヒドラジン等の還元剤を用いた湿式還元法等のいわゆる湿式法により、ニッケル粉末を得ることができる。本発明のニッケル粉末の製造方法は、その一例として以下に説明する晶析工程と、混合工程とを含む。また、ニッケル塩水溶液調整工程、洗浄・ろ過工程および乾燥工程を含んでもよい。
[Manufacturing method of nickel powder]
By the method for producing nickel powder of the present invention, nickel powder can be obtained by a so-called wet method such as a wet reducing method using a reducing agent such as hydrazine with respect to a nickel salt solution. The method for producing nickel powder of the present invention includes, as an example thereof, a crystallization step and a mixing step described below. Further, it may include a nickel salt aqueous solution adjusting step, a washing / filtering step, and a drying step.
＜１：ニッケル塩水溶液調整工程＞
ニッケル塩水溶液は、塩化ニッケル、硫酸ニッケル、硝酸ニッケル等のニッケル塩化合物を溶解させた水溶液から適宜選んで用いることができる。少なからず合成されたニッケル粉末には、選ばれたニッケル塩の陰イオンに起因する元素が残留する場合があるため、残留しても性能に影響しない元素を考慮してニッケル塩を選べばよい。例えば、塩化ニッケルの塩素イオンは、ニッケル粉末の内部に取り込まれにくく、洗浄によって除去しやすいので、ニッケル塩としては塩化ニッケルが好ましい。また、湿式還元後の廃液の処理の容易性の観点からも、塩化ニッケルが好ましい。
<1: Nickel salt aqueous solution adjustment process>
The nickel salt aqueous solution can be appropriately selected from an aqueous solution in which nickel salt compounds such as nickel chloride, nickel sulfate and nickel nitrate are dissolved. Since elements due to the anions of the selected nickel salt may remain in the synthesized nickel powder, the nickel salt may be selected in consideration of the elements that do not affect the performance even if they remain. For example, nickel chloride is preferable as the nickel salt because the chlorine ions of nickel chloride are not easily taken into the inside of the nickel powder and are easily removed by washing. Further, nickel chloride is preferable from the viewpoint of ease of treatment of the waste liquid after wet reduction.
塩化ニッケルを選択した場合、その塩化ニッケル水溶液の濃度は、含まれるニッケルの濃度が５０～２００ｇ／リットルの範囲に調整されるような濃度が望ましい。このニッケルの濃度が低すぎると、相対的に大型の設備が必要となることや廃液量が増えるので効率的ではない。一方で、濃度が高すぎると、還元反応の制御が難しくなり、所望の粒子径のニッケル粒子を得ることが困難となるおそれがある。また、他のニッケル塩を用いる場合も、同理由によりニッケルの濃度が５０～２００ｇ／リットルの範囲となるように調整することが好ましい。 When nickel chloride is selected, the concentration of the aqueous nickel chloride solution is preferably such that the concentration of nickel contained is adjusted in the range of 50 to 200 g / liter. If the concentration of this nickel is too low, it is not efficient because relatively large equipment is required and the amount of waste liquid increases. On the other hand, if the concentration is too high, it becomes difficult to control the reduction reaction, and it may be difficult to obtain nickel particles having a desired particle size. Also, when other nickel salts are used, it is preferable to adjust the nickel concentration to be in the range of 50 to 200 g / liter for the same reason.
ニッケル塩水溶液の調整は、例えば純水等に所定量のニッケル塩を溶解させることで可能である。また、ニッケル塩水溶液の調整は自ら実施してもよく、調整されたニッケル塩水溶液を購入等により入手してもよい。 The nickel salt aqueous solution can be prepared, for example, by dissolving a predetermined amount of nickel salt in pure water or the like. Further, the nickel salt aqueous solution may be adjusted by oneself, or the adjusted nickel salt aqueous solution may be obtained by purchase or the like.
＜２：晶析工程＞
晶析工程では、還元反応溶液中で水溶性ニッケル塩を還元させてニッケル粒子を晶析させる。例えば、ニッケル塩水溶液に粒径制御剤を添加した後、還元剤を添加した還元反応溶液中で、水溶性ニッケル塩を還元させる還元処理が行われる。
<2: Crystallization process>
In the crystallization step, the water-soluble nickel salt is reduced in the reduction reaction solution to crystallize the nickel particles. For example, after adding a particle size control agent to an aqueous nickel salt solution, a reduction treatment is performed to reduce the water-soluble nickel salt in a reduction reaction solution to which a reducing agent is added.
ニッケル粉末の粒径制御剤となる金属は、ニッケルよりもイオン化傾向が小さい銅、パラジウム、プラチナ、ロジウム等から選べばよく、ニッケルと固溶するパラジウムや銅が望ましい。粒径制御剤となる金属は、ニッケル塩からニッケル粉末が合成される際の核として作用し、核数を制御することでニッケル粉末の粒径を制御することができる。ニッケルと固溶しない元素であっても、核として作用する金属と固溶できるのであれば、核を微細化し、一つのニッケル粒子に含まれるニッケル以外の金属含有量を減らすことができ、ニッケル粉末の高純度化が可能となるため、添加することが望ましい。 The metal used as the particle size control agent for nickel powder may be selected from copper, palladium, platinum, rhodium, etc., which have a lower ionization tendency than nickel, and palladium and copper, which are solidly soluble in nickel, are desirable. The metal serving as the particle size control agent acts as nuclei when nickel powder is synthesized from the nickel salt, and the particle size of the nickel powder can be controlled by controlling the number of nuclei. Even if it is an element that does not dissolve in nickel, if it can dissolve in a metal that acts as a nucleus, the nucleus can be made finer and the content of metals other than nickel contained in one nickel particle can be reduced, and nickel powder. It is desirable to add it because it enables high purification.
ニッケルと固溶する元素の添加量は、全ニッケル量に対して５００質量ｐｐｍよりも多く添加してもニッケル粉末は微細化できないので、５００質量ｐｐｍ以下であれば良い。銅やパラジウムといった核となる元素と固溶する元素は、全ニッケル量に対して５０質量ｐｐｍ以下であれば良い。それ以上添加しても核を微細化して、ニッケル粉末を微細化する効果は得られない。 The amount of the element that dissolves in solid with nickel may be 500 mass ppm or less because the nickel powder cannot be miniaturized even if it is added in an amount of more than 500 mass ppm with respect to the total amount of nickel. The element that dissolves in solid solution with the core element such as copper and palladium may be 50 mass ppm or less with respect to the total amount of nickel. Even if it is added more than that, the effect of refining the nucleus and refining the nickel powder cannot be obtained.
核となる金属の微粒子は、凝集していると実質的に核として作用する核数が少なくなり、一つのニッケル粉末の粒子に含まれる量が多くなることによってニッケル粉末の純度が下がり、更にはニッケル粉末の平均粒径が大きくなってしまうため、単分散であることが望ましい。 When the fine particles of the core metal are aggregated, the number of nuclei acting as nuclei is substantially reduced, and the amount contained in one nickel powder particle is increased, so that the purity of the nickel powder is lowered, and further, the purity of the nickel powder is lowered. Since the average particle size of the nickel powder becomes large, it is desirable that the nickel powder is monodisperse.
核となる金属の微粒子の凝集を抑制し単分散を保持するためには、保護コロイド作用を有する分子が還元反応溶液中に添加されていることが望ましい。保護コロイド作用を有する材料としては、ゼラチンやポリビニルピロリドンといった高分子材料や界面活性剤が適している。この材料を添加する量は、ニッケルに対して０．００２５～０．５質量％以下であることが望ましい。添加量が多すぎるとニッケルイオンの還元を阻害してしまうことがあり、添加量が少なすぎると所望の保護コロイド効果が得られない場合があるためである。 In order to suppress the aggregation of fine particles of the core metal and maintain the monodisperse, it is desirable that a molecule having a protective colloid action is added to the reduction reaction solution. As a material having a protective colloidal action, a polymer material such as gelatin or polyvinylpyrrolidone or a surfactant is suitable. The amount of this material added is preferably 0.0025 to 0.5% by mass or less with respect to nickel. This is because if the addition amount is too large, the reduction of nickel ions may be inhibited, and if the addition amount is too small, the desired protective colloid effect may not be obtained.
さらに、晶析工程でのニッケル塩水溶液には、ニッケルイオンと錯形成する錯化剤を添加することは有益である。錯化剤は、ニッケル錯体が形成できればよく、アミノ基、カルボキシル基、スルホ基、ヒドロキシル基、アルキル基等を有した化合物が適している。錯化剤の添加でニッケルが錯イオンを形成すると、晶析工程を経て得られるニッケル粉末の形状が球状となりやすくなる。 Furthermore, it is beneficial to add a complexing agent that complexes with nickel ions to the nickel salt aqueous solution in the crystallization step. As the complexing agent, a compound having an amino group, a carboxyl group, a sulfo group, a hydroxyl group, an alkyl group and the like is suitable as long as a nickel complex can be formed. When nickel forms complex ions by adding a complexing agent, the shape of the nickel powder obtained through the crystallization step tends to be spherical.
＜３：混合工程＞
混合工程では、晶析工程後のニッケル粒子を含む還元反応溶液と、窒素を含有するルイス塩基とを混合する。混合工程においてニッケル粒子の表面処理に使用する化合物として、窒素を含有するルイス塩基を使用することで、窒素を含有するルイス塩基の孤立電子対がニッケル粒子の表面に電子を与え配位結合した構造をとることが考えられる。窒素を含有するルイス塩基化合物は、ニッケル粒子の表面に効率的に吸着し、配位結合することが可能であり、ニッケル粒子の凝集による粗大粒子の発生を抑制することができる。
<3: Mixing process>
In the mixing step, the reduction reaction solution containing nickel particles after the crystallization step and the Lewis base containing nitrogen are mixed. By using a Lewis base containing nitrogen as a compound used for the surface treatment of nickel particles in the mixing step, a structure in which a lone electron pair of the Lewis base containing nitrogen gives an electron to the surface of the nickel particles and is coordinated. It is conceivable to take. The Lewis base compound containing nitrogen can be efficiently adsorbed on the surface of nickel particles and coordinate-bonded, and can suppress the generation of coarse particles due to the aggregation of nickel particles.
ルイス塩基でニッケル粉末を表面処理する方法としては、例えば析出したニッケル粒子を含む還元反応溶液と、窒素を含有するルイス塩基化合物を含む水又はアルコールを媒体としたルイス塩基溶液とを湿式混合させる方法が挙げられる。即ち、晶析工程によって得られたニッケル粒子を含む還元反応溶液と、窒素を含有するルイス塩基化合物の水もしくはアルコール溶液を混合してスラリー化することにより、ニッケル粉末の粒子表面にルイス塩基を均一に吸着させる。 As a method of surface-treating a nickel powder with a Lewis base, for example, a method of wet-mixing a reduction reaction solution containing precipitated nickel particles and a Lewis base solution containing water or an alcohol containing a Lewis base compound containing nitrogen as a medium. Can be mentioned. That is, by mixing a reduction reaction solution containing nickel particles obtained by the crystallization step with a nitrogen-containing Lewis base compound water or alcohol solution to form a slurry, the Lewis base is uniformly formed on the surface of the nickel powder particles. To be adsorbed to.
具体的には、ニッケル粒子を含む還元反応溶液を撹拌し、その中へ水溶性有機溶媒に溶解させた窒素を含有するルイス塩基化合物を添加し、撹拌を行う。この時、有機溶媒はアルコール等の有機溶媒を用いれば良く、攪拌中の表面処理温度は２０～５０℃で行うことが好ましい。処理温度が２０℃よりも低いとニッケル粒子への窒素を含有するルイス塩基化合物の付着速度が低下し、撹拌時間が長くかかるおそれがある。また、処理温度が５０℃より高いと水溶性有機溶媒の揮発が促進され、表面処理が困難となることがある。 Specifically, the reduction reaction solution containing nickel particles is stirred, and a Lewis base compound containing nitrogen dissolved in a water-soluble organic solvent is added thereto and stirred. At this time, an organic solvent such as alcohol may be used as the organic solvent, and the surface treatment temperature during stirring is preferably 20 to 50 ° C. If the treatment temperature is lower than 20 ° C., the adhesion rate of the Lewis base compound containing nitrogen to the nickel particles decreases, and the stirring time may be long. Further, if the treatment temperature is higher than 50 ° C., volatilization of the water-soluble organic solvent is promoted, which may make surface treatment difficult.
さらに、撹拌時間は０．５～２４時間にすることが好ましい。撹拌時間が０．５時間未満であると、ニッケル粒子へ窒素を含有するルイス塩基化合物の付着量が少なくなるおそれがある。また、撹拌時間を２４時間より長くしても、窒素を含有するルイス塩基化合物の付着量はほとんど増加せず、また、処理時間が長くなれば、その分ニッケル粉末の製造時間も長くなって、製造コストが高くなる可能性がある。 Further, the stirring time is preferably 0.5 to 24 hours. If the stirring time is less than 0.5 hours, the amount of nitrogen-containing Lewis base compound attached to the nickel particles may decrease. Further, even if the stirring time is longer than 24 hours, the amount of the Lewis base compound adhering to the nitrogen is hardly increased, and the longer the treatment time is, the longer the nickel powder production time is. Manufacturing costs can be high.
〈窒素を含有するルイス塩基〉
表面処理に使用する化合物としては、窒素を含有するルイス塩基化合物を使用する。本発明によるニッケル粉末の製造方法によって、窒素を含有するルイス塩基の孤立電子対がニッケル粒子の表面に電子を与え配位結合した構造をとることが考えられる。窒素を含有するルイス塩基化合物は、ニッケル粒子の表面に効率的に吸着し、配位結合することが可能であり、ニッケル粒子の凝集による粗大粒子の発生を抑制することができる。
<Lewis base containing nitrogen>
As the compound used for the surface treatment, a Lewis base compound containing nitrogen is used. According to the method for producing nickel powder according to the present invention, it is conceivable that a lone electron pair of a Lewis base containing nitrogen gives an electron to the surface of nickel particles to form a coordinate bond. The Lewis base compound containing nitrogen can be efficiently adsorbed on the surface of nickel particles and coordinate-bonded, and can suppress the generation of coarse particles due to the aggregation of nickel particles.
この窒素を含有するルイス塩基化合物の添加量としては、表面処理前のニッケル粒子１００質量％に対して０．１６質量％以上３．０質量％以下の範囲であることが好ましい。窒素を含有するルイス塩基化合物の含有量がニッケル粒子１００質量％に対して０．１６質量％以上であることにより、ニッケル粒子に対する吸着量を高めることができ、結果としてニッケル微粒子の分散性をより高めることができる。一方で、窒素を含有するルイス塩基化合物の含有量が３．０質量％以下であることにより、窒素を含有するルイス塩基化合物の量の増加に伴うニッケルペーストの粘度の変化を防止することができる。 The amount of the Lewis base compound containing nitrogen is preferably in the range of 0.16% by mass or more and 3.0% by mass or less with respect to 100% by mass of the nickel particles before the surface treatment. When the content of the Lewis base compound containing nitrogen is 0.16% by mass or more with respect to 100% by mass of the nickel particles, the amount of adsorption to the nickel particles can be increased, and as a result, the dispersibility of the nickel fine particles is further improved. Can be enhanced. On the other hand, when the content of the Lewis base compound containing nitrogen is 3.0% by mass or less, it is possible to prevent the change in the viscosity of the nickel paste due to the increase in the amount of the Lewis base compound containing nitrogen. ..
窒素を含有するルイス塩基としては、例えば下記式（１）で表される化合物を含むものが挙げられる。 Examples of the Lewis base containing nitrogen include those containing a compound represented by the following formula (1).
式（１）中、Ｒ１は炭素数が１～１８のアルキル基または炭素数が１～１８のアルケニル基を示し、Ｒ２は炭素数が１～６のアルキレン基を示し、Ｒ３およびＲ４はＨもしくはＣＨ３を示す。 In formula (1), R 1 represents an alkyl group having 1 to 18 carbon atoms or an alkenyl group having 1 to 18 carbon atoms, R 2 represents an alkylene group having 1 to 6 carbon atoms, and R 3 and R. 4 indicates H or CH 3 .
特に、ニッケル粒子をスラリー化できる溶媒に溶解可能なルイス塩基として、Ｎ－オレオイルサルコシン、Ｎ－ラウロイルサルコシン、およびミリストイルメチル-β-アラニンから選択された１種類以上をルイス塩基として用いることができる。下記一般式（２）～（４）に、Ｎ－オレオイルサルコシン、Ｎ－ラウロイルサルコシン、およびミリストイルメチル-β-アラニンの構造を示す。 In particular, one or more selected from N-oleoyl sarcosine, N-lauroyl sarcosine, and myritoylmethyl-β-alanine can be used as the Lewis base as a Lewis base that can be dissolved in a solvent capable of making nickel particles into a slurry. .. The following general formulas (2) to (4) show the structures of N-oleoyl sarcosine, N-lauroyl sarcosine, and myristylmethyl-β-alanine.
（溶剤）
表面処理対象となるニッケル粒子を分散してスラリー化させるための溶剤、および窒素を含有するルイス塩基を溶解させる溶剤としては、ニッケル粒子を分散させることができ、前記ルイス塩基が溶解可能なものであれば、特に限定されない。具体的には、例えば、ターピネオール、ジヒドロターピネオール、ジヒドロターピネオールアセテート、イソボルニルプロピオナート、イソボルニルイソブチレート、ミネラルスピリット、０号ソルベント、ブチルカルビトール、酢酸イソブチル、メチルエチルケトン、シクロヘキサン、ヘキサン、エタノール、ノナン、ノナノール、デカノール等が挙げられる。さらには、ＣｎＨ２ｎ＋２、ＣｎＨ２ｎ、ＣｎＨ２ｎ－２で示される脂肪族炭化水素、ＣｎＨ２ｎ－６で示される芳香族炭化水素等を用いることもでき、具体的には、ジメチルオクタン、エチルメチルシクロヘキサン、メチルプロピルシクロヘプタン、トリメチルヘキサン、ブチルシクロヘキサン、トリデカン、テトラデカン、メチルノナン、エチルメチルヘプタン、トリメチルデカン、ペンチルシクロヘキサン、デカン、ウンデカン、ドデカン、トルエン等が挙げられる。これらの有機溶剤は、１種単独で、あるいは２種以上を併せて用いることができる。
(solvent)
As a solvent for dispersing nickel particles to be surface-treated and forming a slurry, and a solvent for dissolving a Lewis base containing nitrogen, nickel particles can be dispersed and the Lewis base can be dissolved. If there is, there is no particular limitation. Specifically, for example, tarpineol, dihydroterpineol, dihydroterpineol acetate, isobornylpropionate, isobornylisobutyrate, mineral spirit, No. 0 solvent, butyl carbitol, isobutyl acetate, methyl ethyl ketone, cyclohexane, hexane, etc. Examples thereof include ethanol, nonane, nonanol, decanol and the like. Further, aliphatic hydrocarbons represented by C n H 2n + 2 , C n H 2n , C n H 2n-2 , aromatic hydrocarbons represented by C n H 2n-6 , and the like can also be used, and specifically. Examples thereof include dimethyloctane, ethylmethylcyclohexane, methylpropylcycloheptane, trimethylhexane, butylcyclohexane, tridecane, tetradecane, methylnonane, ethylmethylheptane, trimethyldecane, pentylcyclohexane, decane, undecane, dodecane, toluene and the like. These organic solvents may be used alone or in combination of two or more.
＜４：洗浄・ろ過工程＞
本発明のニッケル粉末の製造方法では、乾燥工程の前に、洗浄・ろ過工程を行ってもよい。具体的には、上記したニッケル粒子の表面処理方法を実施した後は、ルイス塩基により表面処理されたニッケル粒子が分散したスラリーが得られるため、まず、このスラリーを、吸引ろ過器を用いて減圧ろ過する。そして、ろ過によってろ紙に残ったニッケル粒子を上記の溶剤と混合し、周速２～５ｍ／秒の条件で０．５～３時間撹拌して洗浄する。この洗浄作業とろ過作業を繰り返して、未反応のルイス塩基や不純物をニッケル粒子から除去することができる。さらに、得られたろ液の赤外分光分析を行い、未反応のルイス塩基が検出されないことを確認し、洗浄作業を終了することが出来る。
<4: Cleaning / filtration process>
In the method for producing nickel powder of the present invention, a washing / filtering step may be performed before the drying step. Specifically, after the above-mentioned method for surface-treating nickel particles is carried out, a slurry in which nickel particles surface-treated with a Lewis base are dispersed can be obtained. Therefore, first, this slurry is depressurized using a suction filter. Filter. Then, the nickel particles remaining on the filter paper by filtration are mixed with the above solvent, and the mixture is stirred and washed at a peripheral speed of 2 to 5 m / sec for 0.5 to 3 hours. By repeating this cleaning operation and filtration operation, unreacted Lewis bases and impurities can be removed from the nickel particles. Further, infrared spectroscopic analysis of the obtained filtrate can be performed to confirm that no unreacted Lewis base is detected, and the cleaning operation can be completed.
なお、ニッケル粒子のろ過には、汎用の固液分離装置を用いることができ、具体的には、デンバーろ過器、フィルタープレス、遠心分離機、デカンター等が挙げられるがこれらに限定されない。また、洗浄作業後に、更にスプレードライヤー等を用いて、ニッケル粒子から溶剤を飛ばして除去してもよい。 A general-purpose solid-liquid separator can be used for filtering the nickel particles, and specific examples thereof include, but are not limited to, a Denver filter, a filter press, a centrifuge, and a decanter. Further, after the cleaning operation, the solvent may be further removed from the nickel particles by using a spray dryer or the like.
＜５：乾燥工程＞
本発明のニッケル粉末の製造方法では、混合工程後、表面処理されたニッケル粒子を乾燥させる乾燥工程を含んでもよい。例えば、洗浄・ろ過工程の次に乾燥工程を行うことができる。
<5: Drying process>
The method for producing nickel powder of the present invention may include a drying step of drying the surface-treated nickel particles after the mixing step. For example, a drying step can be performed after the washing / filtering step.
例えば、ニッケルが酸化ないよう、不活性ガス雰囲気乾燥機および真空乾燥機等の汎用の乾燥装置を用いて５０～３００℃、好ましくは、８０～１５０℃で乾燥し、ニッケル粉末を得ることができる。また、必要に応じてニッケル粉末をメッシュパスさせてもよい。 For example, nickel powder can be obtained by drying at 50 to 300 ° C., preferably 80 to 150 ° C. using a general-purpose drying device such as an inert gas atmosphere dryer and a vacuum dryer so that nickel does not oxidize. .. Further, if necessary, nickel powder may be mesh-passed.
なお、必要に応じて、洗浄・ろ過工程を行ってニッケル粉末含水ケーキとし、さらにこのケーキ中の付着水をエタノール等の低温揮発性の有機溶剤に置換した後、上記不活性ガス雰囲気乾燥機や真空乾燥機で乾燥して、水の大きな表面張力に起因して乾燥中に生じるニッケル粒子間の乾燥凝集を弱めることも可能である。 If necessary, a washing and filtration step is performed to obtain a nickel powder water-containing cake, and after replacing the adhering water in the cake with a low-temperature volatile organic solvent such as ethanol, the above-mentioned inert gas atmosphere dryer or It is also possible to dry in a vacuum dryer to weaken the drying agglomeration between the nickel particles that occurs during drying due to the high surface tension of the water.
［ニッケル粒子の表面処理方法］
次に、本発明のニッケル粒子の表面処理方法の一例について説明する。本方法は、水溶性ニッケル塩を還元させて晶析したニッケル粒子を含む還元反応溶液と、窒素を含有するルイス塩基とを混合する混合工程を含む。
[Surface treatment method for nickel particles]
Next, an example of the surface treatment method for nickel particles of the present invention will be described. The method comprises a mixing step of mixing a reduction reaction solution containing nickel particles crystallized by reducing a water-soluble nickel salt with a nitrogen-containing Lewis base.
例えば、先述のニッケル粉末の製造方法における晶析工程を実施して水溶性ニッケル塩を還元させて晶析したニッケル粒子を含む還元反応溶液を得てもよく、また、購入する等により当該還元反応溶液を得てもよい。 For example, a reduction reaction solution containing nickel particles crystallized by reducing a water-soluble nickel salt by carrying out a crystallization step in the above-mentioned method for producing nickel powder may be obtained, or the reduction reaction may be obtained by purchasing the solution. A solution may be obtained.
そして、混合工程は先述のニッケル粉末の製造方法における混合工程と同様の工程であり、この工程により、ルイス塩基がニッケル粒子の表面に配位結合すると考えられる。 The mixing step is the same as the mixing step in the above-mentioned method for producing nickel powder, and it is considered that the Lewis base is coordinated to the surface of the nickel particles by this step.
また、ルイス塩基が、先述のニッケル粉末の製造方法と同様に、上記式（１）で表される化合物を含んでもよく、式（１）中、Ｒ１は炭素数が１～１８のアルキル基または炭素数が１～１８のアルケニル基を示し、Ｒ２は炭素数が１～６のアルキレン基を示し、Ｒ３およびＲ4はＨもしくはＣＨ３を示す。 Further, the Lewis base may contain a compound represented by the above formula (1) in the same manner as in the above-mentioned method for producing a nickel powder, and in the formula (1), R 1 is an alkyl group having 1 to 18 carbon atoms. Alternatively, R 2 indicates an alkenyl group having 1 to 18 carbon atoms, R 2 indicates an alkylene group having 1 to 6 carbon atoms, and R 3 and R 4 indicate H or CH 3 .
ルイス塩基が、先述のニッケル粉末の製造方法と同様に、Ｎ－オレオイルサルコシン、Ｎ－ラウロイルサルコシン、およびミリストイルメチル-β-アラニンから選択された１種類以上を含んでもよい。 The Lewis base may contain one or more selected from N-oleoyl sarcosine, N-lauroyl sarcosine, and myritoylmethyl-β-alanine, as in the method for producing nickel powder described above.
［ルイス塩基含有ニッケル粉末］
上記した本発明のニッケル粉末の製造方法またはニッケル粒子の表面処理方法によって、ルイス塩基含有ニッケル粉末を得ることができる。
[Lewis base-containing nickel powder]
The Lewis base-containing nickel powder can be obtained by the above-mentioned method for producing nickel powder or the method for surface-treating nickel particles of the present invention.
本発明のルイス塩基含有ニッケル粒子は、窒素を含有するルイス塩基がニッケル粒子の表面に存在しており、ルイス塩基とニッケル粒子との質量比が、０．１６～３．０：１００であることが好ましい。かかる質量比が０．１６未満：１００の場合、ニッケル粒子の表面に酸化し得る領域が残って経時にて水酸化ニッケルが生成し、粗大粒子が発生するおそれがある。また、かかる質量比が３．０：１００を超えてルイス塩基を存在させることは難しく、３．０：１００の質量比がルイス塩基の存在量の上限と考えられる。 In the Lewis base-containing nickel particles of the present invention, the Lewis base containing nitrogen is present on the surface of the nickel particles, and the mass ratio of the Lewis base to the nickel particles is 0.16 to 3.0: 100. Is preferable. When the mass ratio is less than 0.16: 100, a region that can be oxidized remains on the surface of the nickel particles, nickel hydroxide is generated over time, and coarse particles may be generated. Further, it is difficult for the Lewis base to be present in such a mass ratio exceeding 3.0: 100, and the mass ratio of 3.0: 100 is considered to be the upper limit of the abundance of the Lewis base.
窒素を含有するルイス塩基の孤立電子対がニッケル粒子の表面に電子を与え配位結合した構造をとることにより、ルイス塩基がニッケル粒子の表面に配位結合すると考えられる。窒素を含有するルイス塩基化合物は、ニッケル粒子の表面に効率的に吸着し、配位結合することが可能であり、ニッケル粒子の凝集による粗大粒子の発生を抑制することができる。 It is considered that the Lewis base is coordinate-bonded to the surface of the nickel particle by having a structure in which the lone electron pair of the Lewis base containing nitrogen gives an electron to the surface of the nickel particle and is coordinate-bonded. The Lewis base compound containing nitrogen can be efficiently adsorbed on the surface of nickel particles and coordinate-bonded, and can suppress the generation of coarse particles due to the aggregation of nickel particles.
ルイス塩基含有ニッケル粒子は、近年の積層セラミックコンデンサの内部電極の薄層化に対応するという観点から、数平均粒径が０．０３μｍ～０．４μｍであることが好ましい。なお、数平均粒径は、ニッケル粒子の走査電子顕微鏡写真（ＳＥＭ像）から求めた数平均の粒径である。 The Lewis base-containing nickel particles preferably have a number average particle size of 0.03 μm to 0.4 μm from the viewpoint of corresponding to the recent thinning of the internal electrode of the laminated ceramic capacitor. The number average particle size is the number average particle size obtained from a scanning electron micrograph (SEM image) of nickel particles.
また、同様に薄層化に対応するという観点から、粒子形状が略球状であることが好ましく、略球状の形状には、真球のみならず、所定の断面（例えば粒子の中心を通る断面）において短径と長径との比（短径／長径）が０．８～１．０となる楕円形状となる楕円体等も含む。 Similarly, from the viewpoint of corresponding to thinning, the particle shape is preferably substantially spherical, and the substantially spherical shape includes not only a true sphere but also a predetermined cross section (for example, a cross section passing through the center of the particle). Also includes an ellipsoid having an ellipsoidal shape in which the ratio of the minor axis to the major axis (minor axis / major axis) is 0.8 to 1.0.
また、本発明のルイス塩基含有ニッケル粒子は、粒径が０．８μｍを超える粒子の含有量が２００質量ｐｐｍ以下であり、粒径が１．２μｍを超える粒子の含有量が１００質量ｐｐｍ以下であることが好ましい。 Further, in the Lewis base-containing nickel particles of the present invention, the content of particles having a particle size of more than 0.8 μm is 200% by mass or less, and the content of particles having a particle size of more than 1.2 μm is 100% by mass or less. It is preferable to have.
ニッケル粒子の粗大粒子の影響は、ニッケル粒子が用いられる積層セラミックコンデンサの内部電極層の膜厚により左右されるが、近年の薄層化された内部電極層では、粒径が０．８μｍを超える粗大粒子の含有量が４００質量ｐｐｍを超えたり、粒径が１．２μｍを超える粗大粒子の含有量が２００質量ｐｐｍを超えると、電極間ショートの発生が顕著となることがある。ニッケル粒子において、粗大粒子の含有量が少ないほど良好であるのは言うまでもなく、粒径が０．８μｍを超える粗大粒子の含有量を２００質量ｐｐｍ以下とし、粒径が１．２μｍを超える粗大粒子の含有量が１００質量ｐｐｍ以下とすれば、電極間ショートの発生率を十分に低減することができる。なお、粗大粒子の粒径は、ＳＥＭ像から求めた短軸径とすればよい。 The influence of the coarse particles of the nickel particles depends on the film thickness of the internal electrode layer of the laminated ceramic capacitor in which the nickel particles are used, but the particle size of the thinned internal electrode layer in recent years exceeds 0.8 μm. If the content of the coarse particles exceeds 400 mass ppm or the content of the coarse particles having a particle size of more than 1.2 μm exceeds 200 mass ppm, the occurrence of short circuit between electrodes may become remarkable. Needless to say, the smaller the content of the coarse particles is, the better the nickel particles are. When the content of the particles is 100% by mass or less, the occurrence rate of short circuit between electrodes can be sufficiently reduced. The particle size of the coarse particles may be the minor axis diameter obtained from the SEM image.
以下、実施例によって本発明を更に詳細に説明するが、本発明は、これらの実施例によって何ら限定されるものではない。 Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.
［実施例１］
ニッケルを還元するためのアルカリ性コロイド溶液の作製は、具体的には、次のように行った。まず、純水６Ｌに０．１２ｇのゼラチンを溶解させた後、ヒドラジンの濃度が０．０２ｇ／Ｌとなるようにヒドラジンを混合した。次に、パラジウム含有率１００ｇ／Ｌのテトラアンミンパラジウム(II)ジクロライド溶液１０ｍｇと、銀含有率５０ｇ／Ｌのジアンミン銀（Ｉ）クロライド溶液０．５ｍｇとの混合溶液を作製した。そして、この混合溶液２ｍｌをゼラチンとヒドラジンが含まれる前記溶液に滴下して、コロイド溶液を得た。
[Example 1]
Specifically, the preparation of the alkaline colloidal solution for reducing nickel was carried out as follows. First, 0.12 g of gelatin was dissolved in 6 L of pure water, and then hydrazine was mixed so that the concentration of hydrazine was 0.02 g / L. Next, a mixed solution of 10 mg of a tetraammine palladium (II) dichloride solution having a palladium content of 100 g / L and 0.5 mg of a diammine silver (I) chloride solution having a silver content of 50 g / L was prepared. Then, 2 ml of this mixed solution was added dropwise to the solution containing gelatin and hydrazine to obtain a colloidal solution.
このコロイド溶液に、水酸化ナトリウムを添加し、ｐＨを１０以上とした後、さらに、ヒドラジンの濃度が２６ｇ／Ｌとなるまでヒドラジンを添加して、パラジウムと微量の銀からなる複合コロイド粒子が混合されたアルカリ性ヒドラジン溶液を作製し、ニッケルを還元するためのアルカリ性コロイド溶液とした。 Sodium hydroxide is added to this colloidal solution to raise the pH to 10 or more, and then hydrazine is further added until the hydrazine concentration reaches 26 g / L, and the composite colloidal particles composed of palladium and a trace amount of silver are mixed. The prepared alkaline hydrazine solution was prepared and used as an alkaline colloidal solution for reducing nickel.
そして、このアルカリ性コロイド溶液に、ニッケル塩水溶液としてニッケル濃度が１００ｇ／Ｌの塩化ニッケル水溶液を０．５Ｌ滴下して、ニッケルの還元を行い、ニッケル粉末を得た。 Then, 0.5 L of a nickel chloride aqueous solution having a nickel concentration of 100 g / L was added dropwise to this alkaline colloidal solution as a nickel salt aqueous solution to reduce nickel, and a nickel powder was obtained.
＜ニッケル粒子の表面処理＞
析出したニッケル粒子１０ｇを含む還元反応溶液約１００ｇに、ジヒドロターピネオール１０ｇにＮ－オレオイルサルコシン０．０５ｇを溶解させた溶液を加え、スリーワンモータにより３００ｒｐｍで１時間撹拌し、室温２５℃で３時間撹拌し、ニッケル粒子スラリーとした。このスラリーを濾過により固液分離し、窒素雰囲気下１２０℃で乾燥処理、目的とするニッケル粒子を得た。
<Surface treatment of nickel particles>
To about 100 g of the reduction reaction solution containing 10 g of the precipitated nickel particles, a solution prepared by dissolving 0.05 g of N-oleoyl sarcosine in 10 g of dihydroterpineol was added, and the mixture was stirred with a three-one motor at 300 rpm for 1 hour and at room temperature 25 ° C. for 3 hours. The mixture was stirred to obtain a nickel particle slurry. This slurry was separated into solid and liquid by filtration and dried at 120 ° C. under a nitrogen atmosphere to obtain the desired nickel particles.
［実施例２］
析出したニッケル粒子１０ｇを含む還元反応溶液約１００ｇに、ジヒドロターピネオール１０ｇにラウロイルサルコシン０．０５ｇを溶解させた溶液を加え、スリーワンモータにより３００ｒｐｍで１時間撹拌し、室温２５℃で３時間撹拌し、ニッケル粒子スラリーとした。このスラリーを濾過により固液分離し、窒素雰囲気下１２０℃で乾燥処理、目的とするニッケル粒子を得た。その他の条件や手順は、実施例１と同様とした。
[Example 2]
A solution prepared by dissolving 0.05 g of lauroyl sarcosine in 10 g of dihydroterpineol was added to about 100 g of a reduction reaction solution containing 10 g of precipitated nickel particles, and the mixture was stirred at 300 rpm for 1 hour with a three-one motor and at room temperature of 25 ° C. for 3 hours. It was made into a nickel particle slurry. This slurry was separated into solid and liquid by filtration and dried at 120 ° C. under a nitrogen atmosphere to obtain the desired nickel particles. Other conditions and procedures were the same as in Example 1.
［実施例３］
析出したニッケル粒子１０ｇを含む還元反応溶液約１００ｇに、ジヒドロターピネオール１０ｇにミリストイルメチル-β-アラニン０．０５５ｇを溶解させた溶液を加え、スリーワンモータにより３００ｒｐｍで１時間撹拌し、室温２５℃で３時間撹拌し、ニッケル粒子スラリーとした。このスラリーを濾過により固液分離し、窒素雰囲気下１２０℃で乾燥処理、目的とするニッケル粒子を得た。その他の条件や手順は、実施例１と同様とした。
[Example 3]
To about 100 g of the reduction reaction solution containing 10 g of the precipitated nickel particles, a solution prepared by dissolving 0.055 g of myristylmethyl-β-alanine in 10 g of dihydroterpineol was added, and the mixture was stirred at 300 rpm for 1 hour by a three-one motor and 3 at room temperature 25 ° C. The mixture was stirred for a time to obtain a nickel particle slurry. This slurry was separated into solid and liquid by filtration and dried at 120 ° C. under a nitrogen atmosphere to obtain the desired nickel particles. Other conditions and procedures were the same as in Example 1.
（比較例１）
Ｎ－オレオイルサルコシンのジヒドロターピネオール溶液を混合する工程を除き、実施例１と同様の条件とした。すなわち、ルイス塩基による表面処理を実施せずにニッケル粒子を製造した。
(Comparative Example 1)
The conditions were the same as in Example 1 except for the step of mixing the dihydroterpineol solution of N-oleoyl sarcosine. That is, nickel particles were produced without surface treatment with a Lewis base.
［ニッケル粒子の評価］
〈ニッケル粒子表面の炭素量の評価〉
炭素量は、炭素・硫黄分析装置（ＬＥＣＯ社製ＣＳ８４４）により測定した。
[Evaluation of nickel particles]
<Evaluation of carbon content on the surface of nickel particles>
The amount of carbon was measured by a carbon / sulfur analyzer (CS844 manufactured by LECO).
<ニッケル粒子表面処理状態の解析>
吸引ろ過により固液分離後のジヒドロターピネオールおよび、ニッケル粒子を洗浄後のジヒドロターピネオールを回収し、これらを分析のための濃度調製のためにメタノールで希釈し、液体クロマトグラフィー質量分析装置（アジレント社製１２９０ ｉｎｆｉｎｉｔｙ２－アジレント社製６５３０）)により、表面処理に消費されなかったルイス塩基の含有量を定量化した。この値を用いて、以下に示す式（５）、（６）から表面処理後のニッケル粒子に含まれるルイス塩基含有量を算出した。
<Analysis of nickel particle surface treatment state>
Dihydroterpineol after solid-liquid separation by suction filtration and dihydroterpineol after washing nickel particles were recovered, diluted with methanol to adjust the concentration for analysis, and liquid chromatographic mass spectrometer (manufactured by Azilent). The content of Lewis bases not consumed in the surface treatment was quantified by 1290 infinity2-Azilent Co., Ltd. 6530)). Using this value, the Lewis base content contained in the nickel particles after the surface treatment was calculated from the following formulas (5) and (6).
［数１］
表面処理後のＮｉ粒子に含まれるルイス塩基量
＝（使用したルイス塩基全量－表面処理に消費されなかったルイス塩基量） ・・・（５）
[Number 1]
Amount of Lewis base contained in Ni particles after surface treatment = (total amount of Lewis base used-amount of Lewis base not consumed in surface treatment) ... (5)
［数２］
表面処理後のＮｉ粒子に含まれるルイス塩基含有量（質量％）
＝（表面処理後のＮｉ粒子に含まれるルイス塩基量／表面処理後のＮｉ粒子量）×１００ ・・・（６）
[Number 2]
Lewis base content (% by mass) contained in Ni particles after surface treatment
= (Amount of Lewis base contained in Ni particles after surface treatment / Amount of Ni particles after surface treatment) × 100 ... (6)
〈平均粒径の測定〉
ニッケル粒子の平均粒径は、ニッケル粉末の走査電子顕微鏡（ＳＥＭ、ＪＳＭ－６３６０、日本電子製）を用いた観察像（ＳＥＭ像）の画像解析の結果から求めた粒径を測定し、数平均の粒径として算出した。
<Measurement of average particle size>
The average particle size of the nickel particles is obtained by measuring the particle size obtained from the result of image analysis of the observation image (SEM image) using a scanning electron microscope (SEM, JSM-6360, manufactured by JEOL Ltd.) of the nickel powder, and the number average. It was calculated as the particle size of.
〈粗大粒子の含有量の測定〉
表面処理操作後のニッケル粉末を、１００ｍｌハイベッセル容器（近畿容器株式会社製ＢＨＢ－１００）に入れ、常温で大気雰囲気下１日放置後の実施例１～３、比較例１のニッケル粒子について、走査型電子顕微鏡（ＳＥＭ、ＪＳＭ－６３６０、日本電子製）を用い、倍率５０００倍のＳＥＭ像の写真を得た。そして、画像解析ソフトＭａｃ－Ｖｉｅｗ（株式会社マウンテック製）を用いて、得られたＳＥＭ像の写真内の粒子形状の全様が見える粒子の面積と個数を計測し、これらから各粒子の直径を求め、直径が０．８μｍ以上、および１．２μｍ以上のものを粗大粒子としてカウントした。そして、ニッケル粉末中に含まれる粗大粒子の含有量（粒径０．８μｍを超える場合、および、粒径１．２μｍを超える場合）を、初期値として求めた。
<Measurement of coarse particle content>
Regarding the nickel particles of Examples 1 to 3 and Comparative Example 1 after the nickel powder after the surface treatment operation was placed in a 100 ml high vessel container (BHB-100 manufactured by Kinki Container Co., Ltd.) and left at room temperature for 1 day in an air atmosphere. Using a scanning electron microscope (SEM, JSM-6360, manufactured by JEOL Ltd.), photographs of SEM images at a magnification of 5000 were obtained. Then, using the image analysis software Mac-View (manufactured by Mountech Co., Ltd.), the area and number of particles in which the entire particle shape can be seen in the photograph of the obtained SEM image are measured, and the diameter of each particle is calculated from these. The particles having a diameter of 0.8 μm or more and 1.2 μm or more were counted as coarse particles. Then, the content of the coarse particles contained in the nickel powder (when the particle size exceeds 0.8 μm and when the particle size exceeds 1.2 μm) was determined as an initial value.
また、ＳＥＭ像を撮影後、実施例１～２、比較例１のニッケル粒子を常温で大気雰囲気下において、１８０日間放置した後、同様に粗大粒子の含有量を測定した。１８０日放置後の粗大粒子の含有量の結果を、表１に示す。 Further, after taking an SEM image, the nickel particles of Examples 1 and 2 and Comparative Example 1 were left at room temperature in an air atmosphere for 180 days, and then the content of coarse particles was measured in the same manner. The results of the content of coarse particles after being left for 180 days are shown in Table 1.
ニッケル粒子表面の炭素量、平均粒径および粗大粒子の含有量についての結果を、表１に示す。また、図２に、実施例１、比較例１における初期および１８０日放置後のニッケル粒子のＳＥＭ写真を示す。 The results regarding the carbon content, average particle size and content of coarse particles on the surface of the nickel particles are shown in Table 1. In addition, FIG. 2 shows SEM photographs of nickel particles in the initial stage and after being left for 180 days in Example 1 and Comparative Example 1.
実施例１～３、および比較例１の結果より、表面処理によってニッケル粒子の平均粒径は大幅に変化せず、粗大粒子の増加も認められなかった（表１、図２）。また、表面処理によって大気雰囲気下で１８０日後の粗大粒子の増加を抑制できた。 From the results of Examples 1 to 3 and Comparative Example 1, the average particle size of the nickel particles did not change significantly by the surface treatment, and no increase in the coarse particles was observed (Table 1, FIG. 2). In addition, the surface treatment was able to suppress the increase of coarse particles after 180 days in the atmospheric atmosphere.
ただし、比較例１のニッケル粒子の結果より、ルイス塩基による表面処理をしなかった場合には、大気雰囲気下で１８０日後の粗大粒子の増加が認められた。 However, from the results of the nickel particles of Comparative Example 1, when the surface treatment with the Lewis base was not performed, an increase in coarse particles after 180 days was observed in the atmospheric atmosphere.
また、図２の比較例１の１８０日後のＳＥＭ画像では、中央部において複数の粒子が潰れて癒着したように見える色の濃い塊となった領域が認められた。この領域が酸化による粗大粒子１個とカウントすることができる。 Further, in the SEM image of Comparative Example 1 in FIG. 2 after 180 days, a region of dark-colored lumps in which a plurality of particles seemed to be crushed and adhered was observed in the central portion. This region can be counted as one coarse particle due to oxidation.
［まとめ］
以上のとおり、本発明のニッケル粒子の表面処理方法およびニッケル粉末の製造方法であれば、窒素を含有するルイス塩基によってニッケル粒子を表面処理することにより、保管中の酸化による粗大粒子の発生を抑制できることは、明らかである。
[summary]
As described above, in the nickel particle surface treatment method and the nickel powder production method of the present invention, the nickel particles are surface-treated with a nitrogen-containing Lewis base to suppress the generation of coarse particles due to oxidation during storage. It's clear what you can do.
Claims (6)
前記晶析工程後のニッケル粒子を含む還元反応溶液と、窒素を含有するルイス塩基とを混合する混合工程と、
を含む、ニッケル粉末の製造方法。 A crystallization step of reducing a water-soluble nickel salt in a reduction reaction solution to crystallize nickel particles,
A mixing step of mixing a reduction reaction solution containing nickel particles after the crystallization step and a Lewis base containing nitrogen, and a mixing step.
A method for producing nickel powder, including.
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