JP5053925B2 - Silver oxide powder - Google Patents
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本発明は、特に導電性ペースト用のフィラーに適した微粒子酸化銀粉末とその製造方法に関する。 The present invention relates to a fine particle silver oxide powder particularly suitable as a filler for conductive paste and a method for producing the same.
従来技術として特開２００５−１０４８２５号公報及び特開２００３−３０８７３０号公報において、導電性フィラー用の微粒子酸化銀粉末の製法が提案されている。
先ず、特開２００５−１０４８２５号により得られる酸化銀粉末は、銀に還元する温度域も４００℃付近であることから、例えば、ポリエチレンテレフタレート（ＰＥＴ）のような低融点または耐熱温度が低い材料の基板上に配線や電極を形成する導電性ペーストに用いる導電性フィラーとしては適しておらず、導電性フィラーとして用いられる用途が限定されていた。また、酸化銀生成反応後に得られた微粒子酸化銀に対しては、乾燥工程を経てから更に有機溶媒中で湿式粉砕する処理工程が必要であって工程増となり、その上に、この工程から発生する廃液の処理工程も必要となり、これら工程などによってコスト増となるものであった。
JP-A-2005-104825 and JP-A-2003-308730 have proposed methods for producing fine-grain silver oxide powder for conductive fillers as conventional techniques.
First, since the silver oxide powder obtained by JP-A-2005-104825 has a temperature range for reduction to silver of around 400 ° C., for example, a material having a low melting point or a low heat resistance temperature such as polyethylene terephthalate (PET). It is not suitable as a conductive filler for use in a conductive paste for forming wirings or electrodes on a substrate, and its use as a conductive filler has been limited. In addition, the fine grain silver oxide obtained after the silver oxide production reaction requires a process step of wet pulverization in an organic solvent after passing through a drying step. In addition, a waste liquid treatment process is required, and these processes increase costs.
次に、特開２００３−３０８７３０号には、ペースト中の酸化銀粉末を１５０℃の加熱により銀に還元できることが開示されているが、この場合、ペースト中に還元剤を添加することが必要であり、さらに還元剤を添加することによってペーストが変質しやすくなってしまい保管中の品質変化が大きい、ことなどが工業的な問題として存在していた。
よって本発明の課題は、還元剤を共存させない場合でも、大気中にて従来よりも低い温度で加熱することにより酸化銀が還元して銀を生成する、導電性ペースト用フィラーに適した微細な酸化銀粉末を得ることである。さらには、有機溶媒等を用いた湿式粉砕処理工程を不要とする低コストで、従来よりも大気中低温加熱で銀に還元する酸化銀粉末の製造方法を提供することにある。 Therefore, the problem of the present invention is that even when a reducing agent is not present, the fineness suitable for a filler for conductive paste, in which silver oxide is reduced to form silver by heating at a lower temperature than in the past in the atmosphere. It is to obtain silver oxide powder. Furthermore, another object of the present invention is to provide a method for producing a silver oxide powder which is reduced to silver by heating at a lower temperature in the atmosphere than in the prior art at a low cost which does not require a wet pulverization process using an organic solvent or the like.
このような酸化銀粉末として、酸化銀微粒子表面を高分子有機物で被覆し、大気中にて８０℃以上１５０℃未満の温度域で加熱することにより、高分子有機物被膜の燃焼に伴う発熱エネルギーで酸化銀粉末中の酸素の解離を生じさせ、銀に還元させればよい。これを実現するため、すなわち、酸化銀粒子を被覆する有機物から十分な発熱エネルギーを得てこの発熱エネルギーにより酸化銀の還元を円滑に進めるため、（１）適切な有機物の選定、（２）酸化銀粒子表面を被覆する有機物量の設定、（３）酸化銀粒子の粒径が小さく且つ酸化銀粒子同士の凝集が少ない、ことを同時に達成することにより、大気中にて８０℃以上１５０℃未満で加熱することにより銀に還元する酸化銀粉末が得られるという知見を得て、本発明を完成するに至った。 As such silver oxide powder, the surface of silver oxide fine particles is coated with a polymer organic substance, and heated in the air at a temperature range of 80 ° C. or more and less than 150 ° C., thereby generating heat energy associated with the combustion of the polymer organic substance film. The oxygen in the silver oxide powder may be dissociated and reduced to silver. In order to achieve this, that is, in order to obtain sufficient exothermic energy from the organic substance covering the silver oxide particles and smoothly reduce silver oxide by this exothermic energy, (1) selection of appropriate organic substance, (2) oxidation By simultaneously setting the amount of organic matter covering the surface of the silver particles, (3) the silver oxide particles having a small particle size and little aggregation between the silver oxide particles, 80 ° C. or more and less than 150 ° C. in the air The present invention has been completed by obtaining the knowledge that a silver oxide powder that can be reduced to silver can be obtained by heating at a low temperature.
従来の方法では、銀塩含有水溶液(例えば硝酸銀水溶液)とアルカリ（例えば水酸化ナトリウム水溶液）を反応させて酸化銀粒子を生成する中和反応時において反応スラリー（酸化銀粒子含有スラリー）中に有機物が添加されており、この有機物が酸化銀粒子表面を被覆するものであった。この従来法では、酸化銀粒子表面を被覆する有機物量を十分に確保しようとするとスラリー中に添加する有機物量を多くする必要があり、この添加する有機物量が多い場合には酸化銀粉末が凝集してしまうという問題があった。凝集した場合には、後工程の解砕工程で酸化銀から銀への急激な還元が起こると同時に有機物が燃焼してしまい目的とする酸化銀粉末が得られないものであり、一方、添加する有機物量が前記凝集を生じない程度の量では、酸化銀粉末の大気中加熱時の還元温度が２００℃以下にならないというものであった。
さらには、従来の方法では酸化銀粒子表面を被覆した有機物の一部が、酸化銀粉末中の残留ナトリウムイオン等の不純物を除去する目的で行う純水による洗浄時において系外に排出されるため、有機物をその分多く添加する必要があった。
In the conventional method, an organic substance is contained in the reaction slurry (silver oxide particle-containing slurry) during a neutralization reaction in which a silver salt-containing aqueous solution (for example, silver nitrate aqueous solution) and an alkali (for example, sodium hydroxide aqueous solution) are reacted to form silver oxide particles. The organic substance covered the silver oxide particle surface. In this conventional method, it is necessary to increase the amount of organic matter added to the slurry in order to ensure a sufficient amount of organic matter covering the surface of the silver oxide particles. When the amount of added organic matter is large, the silver oxide powder is agglomerated. There was a problem of doing. In the case of agglomeration, a rapid reduction from silver oxide to silver occurs in the subsequent crushing step, and at the same time, the organic matter burns and the desired silver oxide powder cannot be obtained. When the amount of the organic substance is such that the aggregation does not occur, the reduction temperature when the silver oxide powder is heated in the atmosphere does not become 200 ° C. or lower.
Furthermore, in the conventional method, a part of the organic substance covering the surface of the silver oxide particles is discharged out of the system at the time of cleaning with pure water for the purpose of removing impurities such as residual sodium ions in the silver oxide powder. Therefore, it was necessary to add more organic matter.
本発明に係る酸化銀粉末は、予めｐＨを１２程度（好ましくはｐＨ１２±１.５）のアルカリ性に調整した水溶液中に、銀塩を６ｍｏｌ／リットル（Ｌで表わす。）以下の量で含む水溶液と、この銀塩に対し１ｍｏｌ当量以上のアルカリを含む水溶液とを同時投入して反応を行い、一次粒子の小さな酸化銀微粒子を析出させる。なお、この一次粒子はその１００個の長辺をＳＥＭによって測定した値の平均値が１００ｎｍ以下のものが得られる。この酸化銀粒子含有スラリーを洗浄して得られた酸化銀粒子を水に懸濁させたスラリー中に、溶媒に溶解させた高分子有機物を、酸化銀粉末中に含有される銀量に対して０.１〜２.５質量％の範囲で添加することにより、十分な量の有機物を酸化銀粒子に被覆させる。その後、固液分離し乾粉とすることにより、微粒子酸化銀粉末を得ることができる。この酸化銀粒子に被覆させる有機物として、ゼラチンを主成分とする高分子有機物を選択することにより、大気中で８０℃以上１５０℃未満の温度で加熱することにより銀に還元する平均粒径１０〜２００ｎｍの酸化銀粉末を得ることができる。 The silver oxide powder according to the present invention is an aqueous solution containing a silver salt in an amount of 6 mol / liter or less (expressed as L) in an aqueous solution whose pH is adjusted to about 12 (preferably pH 12 ± 1.5) in advance. And an aqueous solution containing 1 mol equivalent or more of alkali with respect to the silver salt is reacted simultaneously to precipitate silver oxide fine particles having small primary particles. In addition, as for this primary particle, the average value of the value which measured 100 long sides by SEM is obtained with 100 nm or less. In the slurry in which the silver oxide particles obtained by washing the silver oxide particle-containing slurry are suspended in water, the polymer organic matter dissolved in the solvent is added to the amount of silver contained in the silver oxide powder. By adding in the range of 0.1 to 2.5% by mass, a sufficient amount of organic matter is coated on the silver oxide particles. Thereafter, solid-liquid separation is performed to obtain a dry powder, whereby a fine particle silver oxide powder can be obtained. As the organic substance to be coated on the silver oxide particles, an average particle diameter of 10 to 10 reduced to silver by heating at a temperature of 80 ° C. or higher and lower than 150 ° C. in the air by selecting a high molecular organic substance mainly composed of gelatin. A 200 nm silver oxide powder can be obtained.
本発明により、大気中で従来よりも低温域の加熱で銀に還元する酸化銀粉末を得ることができる。本発明で得られる酸化銀粉末は、還元剤を共存させなくても８０℃以上１５０℃未満の温度で銀に還元することから、低温焼成可能な導電性ペーストの品質安定性を向上することができ、ＰＥＴの様な低融点または耐熱温度が低い材料の基板への応用が期待出来る。
また既存の銀系ペーストへ本発明の微粒子酸化銀粉末を最適量添加した場合には、低い焼成温度で従来では得られなかった密着性や抵抗値を得ることが可能となり、工業的用途が大幅に拡大する。
さらに、本発明の酸化銀粉末は、製造時に有機溶媒等の処理に要するコストが不要で、導電性ペーストに還元剤を添加する必要がないことから、安価な銀系の導電回路を形成するための導電性ペーストおよび導電性ペースト用フィラーを供給することが可能となる。
According to the present invention, it is possible to obtain a silver oxide powder that is reduced to silver by heating in the air at a lower temperature than in the past. Since the silver oxide powder obtained by the present invention reduces to silver at a temperature of 80 ° C. or higher and lower than 150 ° C. without the presence of a reducing agent, the quality stability of the conductive paste that can be fired at low temperature can be improved. In addition, application to a substrate made of a material having a low melting point or a low heat resistance temperature such as PET can be expected.
In addition, when an optimal amount of the fine grain silver oxide powder of the present invention is added to an existing silver paste, it becomes possible to obtain adhesion and resistance values that could not be obtained conventionally at a low firing temperature, greatly increasing industrial applications. Expand to.
Furthermore, the silver oxide powder of the present invention does not require the cost required for the treatment of an organic solvent or the like at the time of manufacture, and it is not necessary to add a reducing agent to the conductive paste, so that an inexpensive silver-based conductive circuit is formed. It becomes possible to supply the conductive paste and the conductive paste filler.
本発明における製造プロセスにより、安価に銀系ペースト原料を提供することができる。
すなわち、本発明に従う微粒子酸化銀粉末は、ｐＨを制御したアルカリ溶液中に銀塩溶液とアルカリ溶液を同時に投入することによってｐＨの変動を抑えることにより、均一な酸化銀核発生と核成長・粒子成長を行う方法によって製造することができる。また、粒径を制御するために保護コロイドとなる高分子有機物を使用する。
前記工程までは特開２００５−１０４８２５号（特許文献１）と同様であるが、本発明では更に、酸化銀粒子生成反応後の酸化銀粒子含有スラリーを洗浄し、この酸化銀粒子を水に懸濁させたスラリーに最適量の高分子有機物を添加することにより、酸化銀粒子表面に有機物被膜を形成させ、乾燥・解砕工程を経て微粒子酸化銀粉末を得る。
The silver paste material can be provided at low cost by the manufacturing process of the present invention.
That is, the fine grain silver oxide powder according to the present invention suppresses fluctuations in pH by simultaneously introducing a silver salt solution and an alkaline solution into an alkaline solution whose pH is controlled, thereby generating uniform silver oxide nuclei and nuclear growth / particles. It can be manufactured by a method of growing. Moreover, in order to control a particle size, the high molecular organic substance used as a protective colloid is used.
The steps up to this step are the same as in JP-A-2005-104825 (Patent Document 1). In the present invention, the silver oxide particle-containing slurry after the silver oxide particle generation reaction is further washed, and the silver oxide particles are suspended in water. An organic polymer film is formed on the surface of the silver oxide particles by adding an optimal amount of high molecular weight organic matter to the turbid slurry, and a fine silver oxide powder is obtained through a drying and crushing process.
微粒子酸化銀粒子表面に高分子有機物を被覆する効果として、微粒子酸化銀粉末を導電性ペーストとして用いた場合、８０℃以上１５０℃未満の温度範囲における被覆有機物の分解に伴い酸素解離が生ずることにより、銀前駆体を形成させることが出来る。この時の発熱エネルギーにおいて、ペースト中の溶剤とバインダーの一部が分解する。 As an effect of coating the surface of fine silver oxide particles with a polymer organic matter, when fine silver oxide powder is used as a conductive paste, oxygen dissociation occurs due to decomposition of the coated organic matter in a temperature range of 80 ° C. or higher and lower than 150 ° C. A silver precursor can be formed. In the heat generation energy at this time, a part of the solvent and the binder in the paste is decomposed.
予め反応スラリー中に多量の高分子有機物を添加する場合には、高分子有機物の被覆層中に、スラリー中のナトリウムイオン等が多く残留する。この場合、高分子有機物が粘着材の様に作用し、反応後の酸化銀微粒子含有スラリー洗浄が困難となる為、有効に残留不純物を除去することが困難となる。これに対し、酸化銀粒子生成反応後に高分子有機物を含有する溶液で酸化銀粒子を処理する場合には、酸化銀粒子生成反応後の有機物被覆量が少なくて済むため、スラリー中のナトリウムイオン等の不純物が高分子有機物層中に多く含まれることはなく、酸化銀粒子生成反応後の洗浄が容易になる。これも、本発明の製法の利点となっている。 When a large amount of high molecular organic substance is added to the reaction slurry in advance, a large amount of sodium ions or the like in the slurry remain in the high molecular organic substance coating layer. In this case, the polymer organic substance acts like an adhesive material, and it becomes difficult to wash the slurry containing silver oxide fine particles after the reaction, so it is difficult to effectively remove residual impurities. On the other hand, when silver oxide particles are treated with a solution containing a polymer organic substance after the silver oxide particle generation reaction, the amount of organic matter coating after the silver oxide particle generation reaction can be small, so that sodium ions in the slurry, etc. The impurities are not contained in the polymer organic material layer in a large amount, and the cleaning after the silver oxide particle generation reaction becomes easy. This is also an advantage of the manufacturing method of the present invention.
その製造方法は、要するところ、銀塩に保護コロイドを適量添加し、アルカリを水中で反応させて酸化銀沈殿物を得る工程（酸化銀粒子生成工程）、得られた酸化銀沈殿物を水洗する工程、水洗後の酸化銀粒子含有スラリーに更に高分子有機物を添加する工程、そのスラリーを固液分離・乾燥する工程、乾燥物を解砕して酸化銀粉末を得る工程からなる。以下にさらに詳細に説明する。 The manufacturing method is, as necessary, a step of adding a suitable amount of protective colloid to a silver salt, reacting an alkali in water to obtain a silver oxide precipitate (silver oxide particle generating step), and washing the obtained silver oxide precipitate with water The step includes a step of further adding a polymer organic substance to the silver oxide particle-containing slurry after washing, a step of solid-liquid separation and drying the slurry, and a step of crushing the dried product to obtain a silver oxide powder. This will be described in more detail below.
酸化銀粒子生成工程において、銀塩としては硝酸銀などを使用することができる。アルカリとしては水酸化カリウムや水酸化ナトリウムの他、水酸化リチウムなどの塩基を使用することが出来るが、例えばアミン等の有機塩基を用いることも可能である。中和処理はアルカリ水溶液と銀塩の水溶液を同時添加し、反応液のｐＨを一定（例えばｐＨ１２程度）にすることにより、溶液中への銀の溶出を低く抑えることができるので、アルカリ水溶液に対して、銀塩の水溶液およびアルカリ水溶液を添加する方法がコスト的に有利となる。 In the silver oxide particle production step, silver nitrate or the like can be used as the silver salt. In addition to potassium hydroxide and sodium hydroxide, bases such as lithium hydroxide can be used as the alkali. For example, organic bases such as amines can also be used. In the neutralization treatment, an alkaline aqueous solution and an aqueous silver salt solution are added simultaneously, and the pH of the reaction solution is kept constant (for example, about pH 12), so that elution of silver into the solution can be kept low. On the other hand, a method of adding an aqueous solution of silver salt and an aqueous alkaline solution is advantageous in terms of cost.
アルカリ水溶液の濃度は０.５ｍｏｌ／Ｌ以下とし、銀塩溶液の濃度は６ｍｏｌ／Ｌ以下、好ましくは３ｍｏｌ／Ｌ以下、銀塩溶液と同時添加するアルカリ水溶液は、反応中のｐＨ変動を少なくする為に、銀塩に対し１ｍｏｌ当量以上であるのがよい。銀塩溶液濃度を低くすると粒径の小さい酸化銀粉末を製造できる。銀塩溶液濃度を６ｍｏｌ／Ｌより高くすると粒径の大きい酸化銀粉末が生成する。 The concentration of the alkaline aqueous solution is 0.5 mol / L or less, the concentration of the silver salt solution is 6 mol / L or less, preferably 3 mol / L or less, and the alkaline aqueous solution added simultaneously with the silver salt solution reduces pH fluctuation during the reaction. Therefore, it is good that it is 1 mol equivalent or more with respect to the silver salt. When the silver salt solution concentration is lowered, a silver oxide powder having a small particle size can be produced. When the silver salt solution concentration is higher than 6 mol / L, a silver oxide powder having a large particle size is produced.
反応中に保護コロイドを共存させることによって、酸化銀粒子の粒成長を抑え、比表面積を高くすることができる。保護コロイドとしては、ゼラチン、アラビアゴム、デキストリン、ポリビニルアルコール、ロジン、アミノ酸、寒天など公知のものを使用することができる。保護コロイドは銀塩の水溶液中に含有銀量に対して５質量％以下、好ましくは２質量％以下含有させるのがよい。５質量％より多いと逆に結着材の働きをしてしまい凝集粒となる。 By allowing the protective colloid to coexist during the reaction, the growth of silver oxide particles can be suppressed and the specific surface area can be increased. As the protective colloid, known materials such as gelatin, gum arabic, dextrin, polyvinyl alcohol, rosin, amino acid, and agar can be used. The protective colloid is contained in an aqueous silver salt solution in an amount of 5% by mass or less, preferably 2% by mass or less based on the amount of silver contained. On the other hand, when the amount is more than 5% by mass, it acts as a binder and becomes aggregated particles.
保護コロイドの添加は、反応後に得られる粒子表面に均一な被膜が形成される様、反応前に予め銀塩水溶液中に溶解しておくことが好ましい。反応時のｐＨは１２.０±１.５の範囲であるのが良い。更に好ましくはｐＨ１２.０±０.５の範囲が望ましい。その理由としては、溶液中への銀の溶解度がｐＨ１２.０付近で極小となるからである。その範囲外では、溶解・析出による粒成長が発生し、銀が系外に逃げてしまい酸化銀粉末の収率が悪化するという問題が出てくる。中和処理における反応温度は外気温の変化に対しての制御しやすさとコスト面から、３０℃以上５０℃以下が好ましい。反応温度が５０℃を超えた場合は、反応槽内壁に銀膜が発生するため好ましくなく、一方、３０℃未満の場合には酸化銀の一次粒子が肥大化するため好ましくない。 The addition of the protective colloid is preferably preliminarily dissolved in the aqueous silver salt solution before the reaction so that a uniform film is formed on the surface of the particles obtained after the reaction. The pH during the reaction is preferably in the range of 12.0 ± 1.5. More preferably, the pH is in the range of 12.0 ± 0.5. The reason for this is that the solubility of silver in the solution is minimized near pH 12.0. Outside this range, grain growth occurs due to dissolution / precipitation, and silver escapes out of the system, resulting in a problem that the yield of silver oxide powder deteriorates. The reaction temperature in the neutralization treatment is preferably 30 ° C. or higher and 50 ° C. or lower from the viewpoint of ease of control with respect to changes in the outside air temperature and cost. When the reaction temperature exceeds 50 ° C., a silver film is generated on the inner wall of the reaction tank, which is not preferable.
酸化銀粒子生成反応終了後は、得られた酸化銀沈殿物を熟成してから固液分離するのが好ましい。酸化銀沈殿物の熟成は中和反応後の酸化銀粒子含有スラリーをその温度で５〜１２０分間撹拌を保持する。これにより酸化銀沈殿物が均一化される。次いで撹拌を止め、この酸化銀粒子含有スラリーを静置することにより沈降させ、スラリー中の残留ナトリウムイオンを除去する目的で、電気伝導度が２ｍＳ／ｍ以下となるまでデカンテーション洗浄を行う。 After completion of the silver oxide particle formation reaction, it is preferable to solid-liquid separate after aging the obtained silver oxide precipitate. In the ripening of the silver oxide precipitate, the silver oxide particle-containing slurry after the neutralization reaction is kept stirred at that temperature for 5 to 120 minutes. Thereby, the silver oxide precipitate is homogenized. Then, the stirring is stopped, and the silver oxide particle-containing slurry is allowed to settle, and decantation washing is performed until the electric conductivity becomes 2 mS / m or less for the purpose of removing residual sodium ions in the slurry.
その後、純水洗浄上澄み液を廃棄し、固液質量比（酸化銀：純水）１：１から１：２８、更に好ましくは１：５から１：１０の範囲となる酸化銀粒子含有スラリーとし、そのスラリー中に、溶媒中に最適量溶解させた高分子有機物を撹拌混合させる。その理由としては、高分子有機物は一度溶媒に溶解させている為、酸化銀粒子表面に被覆されていない余剰分が系外に排出されやすいからである。よってデカンテーション洗浄の際に出来るだけ洗浄上澄液を廃棄し、固液比を規定したスラリー中に添加することにより、排水として排出される高分子有機物量を極力少なくすることができ、スラリー中に残留させる有機物を制御し易いからである。また量産時における排水処理費用も最小限に抑えることが可能となる。 Thereafter, the supernatant of the pure water washing is discarded to form a slurry containing silver oxide particles in a solid-liquid mass ratio (silver oxide: pure water) of 1: 1 to 1:28, more preferably 1: 5 to 1:10. In the slurry, the polymer organic substance dissolved in the optimum amount in the solvent is stirred and mixed. The reason is that the polymer organic substance is once dissolved in the solvent, so that the surplus portion not coated on the surface of the silver oxide particles is easily discharged out of the system. Therefore, by discarding the washing supernatant as much as possible during decantation washing and adding it to the slurry with a defined solid-liquid ratio, the amount of polymer organic matter discharged as waste water can be reduced as much as possible. This is because it is easy to control the organic matter remaining in the substrate. In addition, wastewater treatment costs during mass production can be minimized.
酸化銀粒子含有スラリー中に添加する高分子有機物の主成分としてゼラチンを用い、その単体でも十分に目的の還元温度を得ることが出来るが、更にアラビアゴム、デキストリン、ポリビニルアルコール、ロジン、アミノ酸、寒天など公知の高分子材料も併せて添加することにより、酸化銀から銀への還元温度を更に低くすることが可能となる。
高分子有機物の最適添加量としては、スラリー中の理論銀量に対し、０.１質量％以上、２.５質量％以下で添加することが望ましく、更に好ましくは１.０〜１.５質量％の範囲で添加させるのがよい。０.１質量％未満であると、８０℃以上１５０℃未満での発熱エネルギー量が少なくなり、その条件で得た微粒子酸化銀粉末を２００℃まで加熱しても銀への還元が確認出来ないからである。また、２.５質量％を越えた場合、酸化銀粒子含有スラリー乾燥後の解砕工程において、解砕機の解砕エネルギーにより酸化銀から銀への還元が一挙に起こり、爆発的に有機物が燃焼する場合があるので好ましくない。
Gelatin is used as the main component of the organic polymer added to the silver oxide particle-containing slurry, and the desired reduction temperature can be sufficiently obtained by itself. Further, gum arabic, dextrin, polyvinyl alcohol, rosin, amino acid, agar By adding a known polymer material such as the above, the reduction temperature from silver oxide to silver can be further lowered.
The optimum addition amount of the high molecular weight organic material is desirably 0.1% by mass or more and 2.5% by mass or less, more preferably 1.0 to 1.5% by mass with respect to the theoretical silver amount in the slurry. It is good to add in the range of%. When the amount is less than 0.1% by mass, the amount of heat generated at 80 ° C. or more and less than 150 ° C. is reduced, and reduction to silver cannot be confirmed even when the fine particle silver oxide powder obtained under the conditions is heated to 200 ° C. Because. In addition, when the content exceeds 2.5% by mass, reduction of silver oxide to silver occurs at once by the crushing energy of the crusher in the crushing process after drying the slurry containing silver oxide particles, and the organic matter burns explosively. This is not preferable.
その後酸化銀粒子含有スラリーを固液分離させ、真空減圧乾燥機にて好ましくは３０℃以上９０℃以下、更に好ましくは４０℃以上６０℃以下の範囲で１０時間以上乾燥させ、黒茶色の乾燥物を得る。この時の乾燥温度を９０℃超とした場合は、高分子有機成分が一部熱により分解し、乾燥機内で爆発的に燃焼する場合があるので好ましくない。乾燥装置として真空減圧乾燥機を用いる理由としては、大気循環型乾燥機を用いた場合より、高温で且つ（同じ乾燥温度でも）短時間で乾燥が可能であるからである。
前記の製造工程により、ＢＥＴ１点法による比表面積が１〜３０ｍ2／ｇ、（二次粒子の）平均粒径が１０〜２００ｎｍの酸化銀粉末を製造することが出来る。
また、この微粒子酸化銀粉末を大気中にて８０℃以上１５０℃未満の温度域で加熱処理を行うと、微粒子酸化銀粉末の酸素離脱による発熱と、高分子有機物被膜の燃焼とにより、茶黒色の微粒子酸化銀粉末が銀白色に変化し、銀に還元されていることが確認出来る。
なお、酸化銀粉末の大気中での熱分解温度が８０℃未満の場合は、酸化銀粉末の取り扱い時やペースト製造工程において銀への還元が生じてしまうので好ましくない。
Thereafter, the silver oxide particle-containing slurry is solid-liquid separated and dried in a vacuum reduced pressure dryer preferably at 30 ° C. or higher and 90 ° C. or lower, more preferably at 40 ° C. or higher and 60 ° C. or lower for 10 hours or longer. Get. If the drying temperature at this time exceeds 90 ° C., the high molecular organic component may be partially decomposed by heat and explosively burned in the dryer, which is not preferable. The reason why a vacuum reduced pressure dryer is used as the drying device is that drying can be performed at a higher temperature and in a shorter time (even at the same drying temperature) than when an air circulation dryer is used.
According to the above production process, a silver oxide powder having a specific surface area of 1 to 30 m 2 / g by BET single point method and an average particle size (secondary particles) of 10 to 200 nm can be produced.
Further, when this fine particle silver oxide powder is heat-treated in the air at a temperature range of 80 ° C. or higher and lower than 150 ° C., heat generation due to oxygen desorption of the fine particle silver oxide powder and combustion of the polymer organic matter film cause brown black It can be confirmed that the fine silver oxide powder changed to silver white and was reduced to silver.
In addition, when the thermal decomposition temperature in air | atmosphere of silver oxide powder is less than 80 degreeC, since reduction to silver arises at the time of handling of silver oxide powder or a paste manufacturing process, it is not preferable.
［実施例１］１６０ｇの純水に銀濃度３８.０質量％の硝酸銀水溶液４６７ｇを添加した硝酸銀水溶液を調整した。前記硝酸銀水溶液中の銀量を酸化銀換算した理論酸化銀量に対し１.０質量％となるポリビニルアルコール（和光純薬製試薬、重合度２０００)１.９ｇを溶解させた水溶液を前記硝酸銀水溶液に添加し、マグネットスターラーを用いて１０分間混合を行った。
中和剤として市販の４８％水酸化ナトリウム水溶液１５０.３ｇを準備した。
反応槽は５Ｌビーカーを用い、予め３.６Ｌに定量した純水を、温度調節器にて４９±１℃とした後、市販の４８％水酸化ナトリウム水溶液６.８ｇを添加した。その時のｐＨは１１.８であった。
温度調節とｐＨ制御を行った水酸化ナトリウム水溶液を撹拌している中に、先に準備していた硝酸銀とポリビニルアルコールの混合水溶液と、中和剤である４８％水酸化ナトリウム水溶液とを同時に添加した。この時の添加速度は、硝酸銀とポリビニルアルコール混合水溶液を毎分１４５ｇ、４８％水酸化ナトリウム水溶液を毎分３０ｇとし、約５分で全量添加できる様、添加速度を調整した。全量添加後のｐＨは１１.９であった。
その後、１０分間撹拌を継続し、中和澱物（酸化銀粒子）の熟成を行った。その時のｐＨは１１.９であった。
Example 1 A silver nitrate aqueous solution was prepared by adding 467 g of a silver nitrate aqueous solution having a silver concentration of 38.0% by mass to 160 g of pure water. An aqueous solution in which 1.9 g of polyvinyl alcohol (reagent manufactured by Wako Pure Chemical Industries, degree of polymerization 2000), which is 1.0% by mass with respect to the theoretical silver oxide amount obtained by converting the silver amount in the silver nitrate aqueous solution to 1.0 mass%, is dissolved in the silver nitrate aqueous solution. And mixed for 10 minutes using a magnetic stirrer.
As a neutralizing agent, 150.3 g of a commercially available 48% aqueous sodium hydroxide solution was prepared.
The reaction vessel was a 5 L beaker, and pure water quantified to 3.6 L in advance was adjusted to 49 ± 1 ° C. with a temperature controller, and then 6.8 g of a commercially available 48% aqueous sodium hydroxide solution was added. The pH at that time was 11.8.
While stirring sodium hydroxide aqueous solution with temperature control and pH control, the previously prepared mixed aqueous solution of silver nitrate and polyvinyl alcohol and 48% sodium hydroxide aqueous solution as neutralizing agent are added simultaneously did. At this time, the addition rate was adjusted so that the silver nitrate / polyvinyl alcohol mixed aqueous solution was 145 g / min and the 48% sodium hydroxide aqueous solution was 30 g / min, and the total amount could be added in about 5 minutes. The pH after addition of the entire amount was 11.9.
Thereafter, stirring was continued for 10 minutes, and the neutralized starch (silver oxide particles) was aged. The pH at that time was 11.9.
熟成終了後、酸化銀粒子含有スラリーに純水を加えた。次に、酸化銀粒子を５Ｌビーカーの底に沈殿させ、残留ナトリウムイオンを除去する目的で、このビーカーを傾けて上澄み液だけを排出（デカンテーション）した。１回のデカンテーションで使用する純水量は約３Ｌとし、最終的に排水中の電気伝導率が２ｍＳ／ｍ以下となるまで合計１４回繰り返した。
その後３０分静置させ完全に中和澱物を沈降させた後、純水量と中和澱物である酸化銀粉末との固液質量比(酸化銀：水)が１：７になる様、上澄み液を排出した。
スラリー中の理論銀量に対し、１.２５質量％となるゼラチン(ゼライス株式会社製、銘柄：Ｅ−２００)２.２ｇを１１０ｇの純水中に溶解させ、撹拌中の固液質量比１：７(酸化銀：水)のスラリー内に投入し、１０分間撹拌混合を行なった。その後速やかにヌッチェにて固液分離を行い、濃茶色の酸化銀ウエットケーキを得た。
その酸化銀ウエットケーキを５５℃に設定した真空減圧乾燥機内にて約１２時間乾燥させ、得られた乾固粉をコーヒーミルで解砕させることにより、目的の微粒子酸化銀粉末を得た。
After ripening, pure water was added to the silver oxide particle-containing slurry. Next, for the purpose of precipitating silver oxide particles on the bottom of a 5 L beaker and removing residual sodium ions, the beaker was tilted and only the supernatant was discharged (decantation). The amount of pure water used in one decantation was about 3 L, and the process was repeated a total of 14 times until the electrical conductivity in the wastewater finally became 2 mS / m or less.
Then, after standing still for 30 minutes to completely settle the neutralized starch, the solid-liquid mass ratio (silver oxide: water) between the pure water amount and the silver oxide powder as the neutralized starch is 1: 7. The supernatant was drained.
2.2 g of gelatin (brand: E-200, manufactured by Zerais Co., Ltd.), which is 1.25% by mass with respect to the theoretical silver amount in the slurry, is dissolved in 110 g of pure water, and the solid-liquid mass ratio during stirring is 1 : 7 (silver oxide: water) and the mixture was stirred and mixed for 10 minutes. Thereafter, solid-liquid separation was performed immediately with Nutsche to obtain a dark brown silver oxide wet cake.
The silver oxide wet cake was dried in a vacuum reduced pressure drier set at 55 ° C. for about 12 hours, and the resulting dried solid powder was crushed with a coffee mill to obtain the desired fine grain silver oxide powder.
そこで得られた微粒子酸化銀粉末を、示差熱分析測定装置（ブルカーエイエックス社製ＴＧ−ＤＴＡ２０００）にて、大気中５００℃まで、毎分５℃の昇温速度で測定したところ、高分子有機物被膜の燃焼と酸素の解離による、１４６℃での発熱ピークが確認できた。
また、得られた微粒子酸化銀粉末を加熱器にて大気中１４６℃まで加熱し、１分間保持したところ、濃茶色の酸化銀粉末が銀白色に変化した。
変色後の銀白色粉末をＸ線回折装置(リガク社製Ｒｏｔａｆｌｅｘ)にてＣｕＫα線２θ角で定性分析を行ったところ、メインピークが３８°にあることを確認した。その回折線角度からＪＣＰＤＳ−ＩＣＤＤにて物質同定したところ、銀のメインピークであることを確認した。本発明では、酸化銀粉末を大気中で加熱した物質を前記のＸ線回折測定し、メインピークが３８°である場合、酸化銀が銀に還元したと判断した。本発明では、酸化銀粉末を前記方法で加熱して前記方法でＸ線回折測定を行った際、メインピークが銀のピークであれば、その酸化銀粉末の熱分解温度は前記加熱温度以下であるとした。
さらに前記加熱温度が８０℃の場合には、酸化銀粉末を加熱後にＸ線回折測定した結果、３３°付近に相対強度比１００となるピークを確認し、その回折線角度からＪＣＰＤＳ−ＩＣＤＤにて物質同定したところ、酸化銀のメインピークであることを確認した。この結果は後記の実施例２においても同様であった。
The fine particle silver oxide powder thus obtained was measured with a differential thermal analysis measuring device (TG-DTA2000 manufactured by Bruker Ax) at a heating rate of 5 ° C. per minute up to 500 ° C. in the atmosphere. An exothermic peak at 146 ° C. due to the combustion of the coating and the dissociation of oxygen was confirmed.
Moreover, when the obtained fine particle silver oxide powder was heated to 146 degreeC in air | atmosphere with the heater and was hold | maintained for 1 minute, the dark brown silver oxide powder changed to silver white.
A qualitative analysis was performed on the silver white powder after discoloration using a CuKα ray 2θ angle with an X-ray diffractometer (Rotaflex, manufactured by Rigaku Corporation), and it was confirmed that the main peak was at 38 °. When the substance was identified by JCPDS-ICDD from the diffraction line angle, it was confirmed to be the main peak of silver. In the present invention, the substance obtained by heating silver oxide powder in the atmosphere was measured by the X-ray diffraction, and when the main peak was 38 °, it was determined that the silver oxide was reduced to silver. In the present invention, when silver oxide powder is heated by the above method and X-ray diffraction measurement is performed by the above method, if the main peak is a silver peak, the thermal decomposition temperature of the silver oxide powder is below the heating temperature. It was supposed to be.
Further, when the heating temperature is 80 ° C., X-ray diffraction measurement was performed after the silver oxide powder was heated, and as a result, a peak having a relative intensity ratio of 100 was confirmed around 33 °. When the substance was identified, it was confirmed to be the main peak of silver oxide. This result was the same in Example 2 described later.
また、５０ｍｇの前記微粒子酸化銀粉末を、２０ｇの０.２％ヘキサメタリン酸ナトリウム水溶液中にて、ホモジナイザーを用いて１０分間超音波分散を行った後、粒度分布測定装置（日機装社製、商品名：マイクロトラックＨＲＡ）にて平均粒径（二次粒径）を測定したところ０.０８８μｍであった（本発明で、平均粒径とは、前記粒度分布測定装置を用い前記方法で測定した平均粒径Ｄ５０の値を示す）。
また、比表面積測定装置（ＱＵＡＮＴＡ ＣＨＲＯＭＥ社製、装置名：ＭＯＮＯＳＯＲＢ）を用い、脱気条件を６０℃１５分として、比表面積をＢＥＴ１点法にて測定したところ、１０.６ｍ2／ｇであった（本発明で、比表面積とは、前記装置、方法で測定した値を示す）。
さらに、得られた微粒子酸化銀粉末中の不純物分析をイオンクロマトグラフ(ＤＩＯＮＥＸ社製)にて残留ナトリウムイオン量を測定したところ、１０ｐｐｍ未満であった。
Further, 50 mg of the fine silver oxide powder was ultrasonically dispersed in 20 g of 0.2% sodium hexametaphosphate aqueous solution using a homogenizer for 10 minutes, and then a particle size distribution measuring apparatus (trade name, manufactured by Nikkiso Co., Ltd.). The average particle size (secondary particle size) measured by Microtrac HRA was 0.088 μm (in the present invention, the average particle size is the average measured by the above method using the particle size distribution measuring device). The value of the particle size D50 is shown).
Further, when the specific surface area was measured by the BET one-point method using a specific surface area measuring apparatus (manufactured by QUANTA CHROME, apparatus name: MONOSORB) at a degassing condition of 60 ° C. for 15 minutes, it was 10.6 m 2 / g. (In the present invention, the specific surface area is a value measured by the above apparatus and method).
Furthermore, when the amount of residual sodium ions was measured with an ion chromatograph (manufactured by DIONEX) for impurity analysis in the obtained fine particle silver oxide powder, it was less than 10 ppm.
［実施例２］実施例１と同様にしてデカンテーション後の中和澱物を経て、純水量と中和澱物である酸化銀との固液質量比(酸化銀：水)が１：７のスラリーを得た。
このスラリー中の理論銀量に対し１.５質量％となるゼラチン２.７ｇを１３２ｇの純水中に溶解させた。同じくスラリー中の理論銀量に対し０.２質量％となるポリビニルアルコール０.３５ｇを１８ｇの純水中に溶解させ、撹拌中の固液重量比１：７（酸化銀：水）のスラリー内にこれらのゼラチン溶液とポリビニルアルコール溶液を同時投入し、１０分間撹拌混合を行なった。その後速やかに固液分離を行い、濃茶色のウエットケーキを得た。
そのウエットケーキを５５℃に設定した真空乾燥機内にて１２時間乾燥させ、乾固粉をコーヒーミルで解砕させることにより、目的の微粒子酸化銀粉末を得た。
[Example 2] In the same manner as in Example 1, after passing through the neutralized starch after decantation, the solid-liquid mass ratio (silver oxide: water) between the pure water amount and the silver oxide as the neutralized starch was 1: 7. A slurry of was obtained.
2.7 g of gelatin which is 1.5% by mass with respect to the theoretical silver content in the slurry was dissolved in 132 g of pure water. Similarly, 0.35 g of polyvinyl alcohol which is 0.2% by mass with respect to the theoretical silver amount in the slurry is dissolved in 18 g of pure water, and the solid-liquid weight ratio during stirring is 1: 7 (silver oxide: water). These gelatin solution and polyvinyl alcohol solution were simultaneously added to and mixed with stirring for 10 minutes. Thereafter, solid-liquid separation was performed promptly to obtain a dark brown wet cake.
The wet cake was dried in a vacuum dryer set at 55 ° C. for 12 hours, and the dried solid powder was crushed with a coffee mill to obtain the intended fine grain silver oxide powder.
そこで得られた微粒子酸化銀粉末を、示差熱分析測定装置（ブルカーエイエックス社製ＴＧ−ＤＴＡ２０００）にて、大気中５００℃まで、毎分５℃の昇温速度で測定したところ、高分子有機物被膜の燃焼と酸素の解離による、１４３℃での発熱ピークが確認できた。
また、得られた微粒子酸化銀粉末を加熱器にて１４３℃まで加熱したところ、濃茶色の酸化銀粉末が灰色に変化した。
変色後の灰色粉末をＸ線回折装置(リガク社製Ｒｏｔａｆｌｅｘ)にてＣｕＫα線２θ角で定性分析を行ったところ、メインピークが３８°にあることを確認した。その回折線角度からＪＣＰＤＳ−ＩＣＤＤにて物質同定したところ、銀のメインピークであることを確認した。
The fine particle silver oxide powder thus obtained was measured with a differential thermal analysis measuring device (TG-DTA2000 manufactured by Bruker Ax) at a heating rate of 5 ° C. per minute up to 500 ° C. in the atmosphere. An exothermic peak at 143 ° C. due to combustion of the coating and dissociation of oxygen was confirmed.
Moreover, when the obtained fine particle silver oxide powder was heated to 143 ° C. with a heater, the dark brown silver oxide powder turned gray.
A qualitative analysis of the discolored gray powder with a CuKα ray 2θ angle using an X-ray diffractometer (Rotaflex, manufactured by Rigaku Corporation) confirmed that the main peak was at 38 °. When the substance was identified by JCPDS-ICDD from the diffraction line angle, it was confirmed to be the main peak of silver.
また、粒度分布測定装置（日機装社製、商品名：マイクロトラックＨＲＡ）にて平均粒径（二次粒径）を測定したところ０.０９３μｍであった。また、比表面積をＢＥＴ１点法にて測定したところ、１１.４ｍ2／ｇであった。
さらに、得られた微粒子酸化銀粉末中の不純物分析をイオンクロマトグラフ(ＤＩＯＮＥＸ社製)にて残留ナトリウムイオン量を測定したところ、１０ｐｐｍ未満であった。
The average particle size (secondary particle size) was measured with a particle size distribution measuring apparatus (trade name: Microtrac HRA, manufactured by Nikkiso Co., Ltd.) and found to be 0.093 μm. Moreover, it was 11.4 m < 2 > / g when the specific surface area was measured by the BET 1 point method.
Furthermore, when the amount of residual sodium ions was measured with an ion chromatograph (manufactured by DIONEX) for impurity analysis in the obtained fine particle silver oxide powder, it was less than 10 ppm.
［比較例１］１６０ｇの純水に銀濃度３８.０質量％の硝酸銀水溶液４６６ｇを添加した硝酸銀水溶液を調整した。前記硝酸銀水溶液中の銀量を酸化銀換算した理論酸化銀量に対し１.０質量％となるポリビニルアルコール(和光純薬製試薬、重合度２０００)１.９ｇを溶解させた水溶液を前記硝酸銀水溶液に添加して、マグネットスターラーを用いて１０分間混合を行った。
中和剤として市販の４８％水酸化ナトリウム水溶液１５０.３ｇを準備した。
反応槽は５Ｌビーカーを用い、予め３.６Ｌに定量した純水を、温度調節器にて４９±１℃とした後、市販の４８％水酸化ナトリウム水溶液６.８ｇを添加した。その時のｐＨは１１.８であった。
温度調節とｐＨ制御を行った水酸化ナトリウム水溶液を撹拌している中に、先に準備していた硝酸銀とポリビニルアルコールの混合水溶液と、中和剤である４８％水酸化ナトリウム水溶液とを同時に添加する。この時の添加速度は、硝酸銀とポリビニルアルコール混合水溶液を毎分１４５ｇ、４８％水酸化ナトリウム水溶液を毎分３０ｇとし、約５分で全量添加できる様、添加速度を調整した。全量添加後のｐＨは１１.９であった。
その後、１０分間撹拌を継続し、中和澱物の熟成を行った。その時のｐＨは１１.９であった。
[Comparative Example 1] A silver nitrate aqueous solution prepared by adding 466 g of a silver nitrate aqueous solution having a silver concentration of 38.0% by mass to 160 g of pure water was prepared. An aqueous solution in which 1.9 g of polyvinyl alcohol (reagent manufactured by Wako Pure Chemicals, degree of polymerization 2000) is 1.0% by mass with respect to the theoretical silver oxide amount obtained by converting the silver amount in the aqueous silver nitrate solution to silver oxide is the silver nitrate aqueous solution. And mixed for 10 minutes using a magnetic stirrer.
As a neutralizing agent, 150.3 g of a commercially available 48% aqueous sodium hydroxide solution was prepared.
The reaction vessel was a 5 L beaker, and pure water quantified to 3.6 L in advance was adjusted to 49 ± 1 ° C. with a temperature controller, and then 6.8 g of a commercially available 48% aqueous sodium hydroxide solution was added. The pH at that time was 11.8.
While stirring sodium hydroxide aqueous solution with temperature control and pH control, the previously prepared mixed aqueous solution of silver nitrate and polyvinyl alcohol and 48% sodium hydroxide aqueous solution as neutralizing agent are added simultaneously To do. At this time, the addition rate was adjusted so that the silver nitrate / polyvinyl alcohol mixed aqueous solution was 145 g / min and the 48% sodium hydroxide aqueous solution was 30 g / min, and the total amount could be added in about 5 minutes. The pH after addition of the entire amount was 11.9.
Thereafter, stirring was continued for 10 minutes to age the neutralized starch. The pH at that time was 11.9.
熟成終了後、残留ナトリウムイオンを除去する目的で、純水にてデカンテーションを行った。１回のデカンテーションで使用する純水量は約３Ｌとし、最終的に排水中の電気伝導率が２ｍＳ／ｍ以下となるまで合計１４回繰り返した。
その後３０分静置させ完全に中和澱物を沈降させた後、純水量と中和澱物である酸化銀粉末との固液質量比(酸化銀：水)が１：７になる様、上澄み液を排出した。
得られたスラリーをヌッチェにて固液分離し十分水洗した後、５５℃の真空乾燥機内にて約１２時間乾燥させ乾固粉を得、更にその乾固粉をコーヒーミルにて解砕し、微粒子酸化銀粉末を得た。
After completion of aging, decantation was performed with pure water for the purpose of removing residual sodium ions. The amount of pure water used in one decantation was about 3 L, and the process was repeated a total of 14 times until the electrical conductivity in the wastewater finally became 2 mS / m or less.
Then, after standing still for 30 minutes to completely settle the neutralized starch, the solid-liquid mass ratio (silver oxide: water) between the pure water amount and the silver oxide powder as the neutralized starch is 1: 7. The supernatant was drained.
The resulting slurry was solid-liquid separated with Nutsche and washed thoroughly with water, then dried in a vacuum dryer at 55 ° C. for about 12 hours to obtain a dry solid powder, and the dry solid powder was further crushed with a coffee mill, A fine grain silver oxide powder was obtained.
そこで得られた微粒子酸化銀粉末を粒度分布測定装置（商品名：マイクロトラックＨＲＡ、日機装社製）にて平均粒径を測定したところ０.０９μｍであった。また、比表面積をＢＥＴ１点法にて測定したところ、７.３ｍ2／ｇであった。
また、示差熱分析測定装置（ブルカーエイエックス社製ＴＧ−ＤＴＡ２０００）にて、大気中５００℃まで、毎分５℃の昇温速度で測定したところ、３９２.６℃での吸熱ピークが確認されたが、それ以下の温度域での発熱ピークは確認出来なかった。
さらに、大気中２００℃以下での加熱試験でも灰色変色を確認出来ず、リガク社製Ｘ線回折装置にてＣｕＫα線２θ角で定性分析を行ったところ、３３°付近に相対強度比１００となるピークを確認し、その回折線角度からＪＣＰＤＳ−ＩＣＤＤにて物質同定したところ、酸化銀のメインピークであることを確認した。
The fine particle silver oxide powder thus obtained was measured to have an average particle size of 0.09 μm using a particle size distribution analyzer (trade name: Microtrac HRA, manufactured by Nikkiso Co., Ltd.). Moreover, it was 7.3 m < 2 > / g when the specific surface area was measured by the BET 1 point method.
In addition, an endothermic peak at 392.6 ° C. was confirmed by measuring with a differential thermal analysis measuring device (TG-DTA2000 manufactured by Bruker Ax) to 500 ° C. in the atmosphere at a rate of temperature increase of 5 ° C. per minute. However, no exothermic peak in a temperature range below that was confirmed.
Furthermore, gray discoloration could not be confirmed even in a heating test at 200 ° C. or less in the atmosphere, and a qualitative analysis was performed with a CuKα ray 2θ angle using a Rigaku X-ray diffractometer, and a relative intensity ratio of about 33 ° was 100. When the peak was confirmed and the substance was identified by JCPDS-ICDD from the diffraction line angle, it was confirmed to be the main peak of silver oxide.
［比較例２］１６０ｇの純水に銀濃度３８.０質量％の硝酸銀水溶液４６６ｇを添加した硝酸銀水溶液を調整した。前記硝酸銀水溶液中の銀量を酸化銀換算した理論酸化銀量に対し１.５質量％となるポリビニルアルコール(和光純薬製試薬、重合度２０００)２.９ｇを純水１００ｇに溶解させた以外は比較例１と同様のプロセスにて酸化銀粒子含有スラリーを得た。
スラリー中の残留ナトリウムイオンを除去する目的で、純水にてデカンテーションを行った。１回のデカンテーションで使用する純水量は約３Ｌとし、最終的に排水中の電気伝導率が２ｍＳ／ｍ以下となるまで合計１４回繰り返した。
その後３０分静置させ完全に中和澱物を沈降させた後、純水量と中和澱物である酸化銀粉末との固液質量比(酸化銀：水)が１：７になる様、上澄み液を排出した。
得られた酸化銀粒子含有スラリーをヌッチェにて固液分離し十分水洗した後、５５℃での真空乾燥機内にて約１２時間乾燥させ乾固粉を得、更にその乾固粉をコーヒーミルにて解砕し、微粒子酸化銀粉末を得た。
[Comparative Example 2] A silver nitrate aqueous solution prepared by adding 466 g of a silver nitrate aqueous solution having a silver concentration of 38.0% by mass to 160 g of pure water was prepared. Except for dissolving 2.9 g of polyvinyl alcohol (reagent manufactured by Wako Pure Chemicals, degree of polymerization 2000) which is 1.5% by mass with respect to the theoretical amount of silver oxide in terms of silver oxide in the silver nitrate aqueous solution in 100 g of pure water. Obtained a slurry containing silver oxide particles by the same process as in Comparative Example 1.
Decantation was performed with pure water for the purpose of removing residual sodium ions in the slurry. The amount of pure water used in one decantation was about 3 L, and the process was repeated a total of 14 times until the electrical conductivity in the wastewater finally became 2 mS / m or less.
Then, after standing still for 30 minutes to completely settle the neutralized starch, the solid-liquid mass ratio (silver oxide: water) between the pure water amount and the silver oxide powder as the neutralized starch is 1: 7. The supernatant was drained.
The resulting silver oxide particle-containing slurry is solid-liquid separated with a Nutsche and sufficiently washed with water, and then dried in a vacuum dryer at 55 ° C. for about 12 hours to obtain a dried solid powder. To obtain fine-grain silver oxide powder.
そこで得られた微粒子酸化銀粉末を粒度分布測定装置（商品名：マイクロトラックＨＲＡ、日機装社製）にて平均粒径を測定したところ０.１５μｍであった。また、比表面積をＢＥＴ１点法にて測定したところ、６.９ｍ2／ｇであった。
また、示差熱分析測定装置（ブルカーエイエックス社製ＴＧ−ＤＴＡ２０００）にて、大気中５００℃まで、毎分５℃の昇温速度で測定したところ、３８２℃での吸熱ピークが確認されたが、それ以下の温度域での発熱ピークは確認出来なかった。
さらに、大気中２００℃以下での加熱試験でも灰色変色を確認出来ず、リガク社製Ｘ線回折装置にてＣｕＫα線２θ角で定性分析を行ったところ、３３°付近に相対強度比１００となるピークを確認し、その回折線角度からＪＣＰＤＳ−ＩＣＤＤにて物質同定したところ、酸化銀のメインピークであることを確認した。
The average particle size of the fine particle silver oxide powder thus obtained was measured by a particle size distribution measuring device (trade name: Microtrac HRA, manufactured by Nikkiso Co., Ltd.) and found to be 0.15 μm. Moreover, it was 6.9 m < 2 > / g when the specific surface area was measured by the BET 1 point method.
In addition, an endothermic peak at 382 ° C. was confirmed when measured with a differential thermal analyzer (TG-DTA2000 manufactured by Bruker Ax) at 500 ° C. in the atmosphere at a rate of temperature increase of 5 ° C. per minute. An exothermic peak in a temperature range below that could not be confirmed.
Furthermore, gray discoloration could not be confirmed even in a heating test at 200 ° C. or less in the atmosphere, and a qualitative analysis was performed with a CuKα ray 2θ angle using a Rigaku X-ray diffractometer, and a relative intensity ratio of about 33 ° was 100. When the peak was confirmed and the substance was identified by JCPDS-ICDD from the diffraction line angle, it was confirmed to be the main peak of silver oxide.
［比較例３］１６０ｇの純水に銀濃度３８.０質量％の硝酸銀水溶液４６６ｇを添加した硝酸銀水溶液を調整し、硝酸銀水溶液中の銀量を酸化銀換算した理論酸化銀量に対し１.５質量％となるゼラチン（ゼライス株式会社製、銘柄：Ｅ−２００)２.９ｇを純水に溶解させた以外は、比較例１と同様のプロセスにて酸化銀粒子含有スラリーを得た。
酸化銀粒子含有スラリー中の残留ナトリウムイオンを除去する目的で、純水にてデカンテーションを行った。１回のデカンテーションで使用する純水量は約３Ｌとし、最終的に排水中の電気伝導率が２ｍＳ／ｍ以下となるまで合計１４回繰り返した。
その後３０分静置させ完全に中和澱物を沈降させた後、純水量と中和澱物である酸化銀粉末との固液質量比(酸化銀：水)が１：７になる様、上澄み液を排出した。
得られた酸化銀粒子含有スラリーをヌッチェにて固液分離し十分水洗した後、５５℃での真空乾燥機内にて約１２時間乾燥させ乾固粉を得、更にその乾固粉をコーヒーミルにて解砕し微粒子酸化銀粉末を得た。
[Comparative Example 3] A silver nitrate aqueous solution prepared by adding 466 g of a silver nitrate aqueous solution having a silver concentration of 38.0% by mass to 160 g of pure water was prepared, and the silver amount in the silver nitrate aqueous solution was 1.5 with respect to the theoretical silver oxide amount in terms of silver oxide. A silver oxide particle-containing slurry was obtained in the same process as in Comparative Example 1 except that 2.9 g of gelatin (made by Zelice Co., Ltd., brand: E-200) in mass% was dissolved in pure water.
Decantation was performed with pure water for the purpose of removing residual sodium ions in the silver oxide particle-containing slurry. The amount of pure water used in one decantation was about 3 L, and the process was repeated a total of 14 times until the electrical conductivity in the wastewater finally became 2 mS / m or less.
Then, after standing still for 30 minutes to completely settle the neutralized starch, the solid-liquid mass ratio (silver oxide: water) between the pure water amount and the silver oxide powder as the neutralized starch is 1: 7. The supernatant was drained.
The resulting silver oxide particle-containing slurry is solid-liquid separated with a Nutsche and sufficiently washed with water, and then dried in a vacuum dryer at 55 ° C. for about 12 hours to obtain a dried solid powder. To obtain fine-grain silver oxide powder.
そこで得られた微粒子酸化銀粉末を粒度分布測定装置（商品名：マイクロトラックＨＲＡ、日機装社製）にて平均粒径を測定したところ０.１２μｍであった。また、比表面積をＢＥＴ１点法にて測定したところ、７.２ｍ2／ｇであった。
また、示差熱分析測定装置（ブルカーエイエックス社製ＴＧ−ＤＴＡ２０００）にて、大気中５００℃まで、毎分５℃の昇温速度で測定したところ、３９９℃での吸熱ピークが確認されたが、それ以下の温度域での発熱ピークは確認出来なかった。
また、大気中２００℃以下での加熱試験でも灰色変色を確認出来ず、リガク社製Ｘ線回折装置にてＣｕＫα線２θ角で定性分析を行ったところ、３３°付近に相対強度比１００となるピークを確認し、その回折線角度からＪＣＰＤＳ−ＩＣＤＤにて物質同定したところ、酸化銀のメインピークであることを確認した。
The average particle size of the fine particle silver oxide powder thus obtained was measured by a particle size distribution measuring device (trade name: Microtrac HRA, manufactured by Nikkiso Co., Ltd.) and found to be 0.12 μm. Moreover, it was 7.2 m < 2 > / g when the specific surface area was measured by the BET 1 point method.
In addition, an endothermic peak at 399 ° C. was confirmed when measured with a differential thermal analyzer (TG-DTA2000 manufactured by Bruker Ax) at 500 ° C. in the atmosphere at a rate of temperature increase of 5 ° C. per minute. An exothermic peak in a temperature range below that could not be confirmed.
Further, even in a heating test at 200 ° C. or less in the atmosphere, gray discoloration could not be confirmed, and when a qualitative analysis was performed with a CuKα ray 2θ angle using an Rigaku X-ray diffractometer, the relative intensity ratio was 100 around 33 °. When the peak was confirmed and the substance was identified by JCPDS-ICDD from the diffraction line angle, it was confirmed to be the main peak of silver oxide.
［比較例４］１６０ｇの純水に銀濃度３８.０質量％の硝酸銀水溶液４６６ｇを添加した硝酸銀水溶液を調整した。前記硝酸銀水溶液中の銀量を酸化銀換算した理論酸化銀量に対し６.０質量％となるポリビニルアルコール(和光純薬製試薬、重合度２０００)１１.４ｇを純水に溶解させた以外は、比較例１と同様のプロセスにて酸化銀粒子含有スラリーを得た。
酸化銀粒子含有スラリー中の残留ナトリウムイオンを除去する目的で、ヌッチェにて濾過を行ったが、銀塩に添加した添加物が粘着剤として作用し、スラリーを濾過させるのに４時間、３Ｌの純水を用いての洗浄に約６時間費やした為、作業性を考慮して２回目以降の純水洗浄を断念した。
その酸化銀ウエットケーキを５５℃に設定した真空減圧乾燥機内にて約１２時間乾燥させ、得られた乾固粉をコーヒーミルで解砕させたところ、その解砕エネルギーにより微粒子酸化銀粉末が瞬間的に還元し（酸化銀を被覆する有機物が瞬時に燃焼し）、酸化銀粉末を得ることが出来なかった。
[Comparative Example 4] A silver nitrate aqueous solution was prepared by adding 466 g of a silver nitrate aqueous solution having a silver concentration of 38.0% by mass to 160 g of pure water. Except for dissolving 11.4 g of polyvinyl alcohol (reagent manufactured by Wako Pure Chemical Industries, degree of polymerization 2000), which is 6.0% by mass with respect to the theoretical silver oxide amount in terms of silver oxide, based on the silver amount in the silver nitrate aqueous solution. A silver oxide particle-containing slurry was obtained by the same process as in Comparative Example 1.
For the purpose of removing residual sodium ions in the slurry containing silver oxide particles, filtration was performed with Nutsche, but the additive added to the silver salt acted as an adhesive, and 4 L for 3 hours to filter the slurry. Since it took about 6 hours for cleaning with pure water, the second and subsequent cleaning with pure water was abandoned in consideration of workability.
The silver oxide wet cake was dried in a vacuum vacuum dryer set at 55 ° C. for about 12 hours, and the resulting dried powder was crushed with a coffee mill. Reduction (the organic substance covering the silver oxide burned instantly), and silver oxide powder could not be obtained.
［比較例５］硝酸銀水溶液に添加する物質をポリビニルアルコールからゼラチン(ゼライス株式会社製、銘柄：Ｅ−２００)に変更した以外は、比較例４の方法で微粒子酸化銀粉末を得た。
酸化銀粒子含有スラリー中の残留ナトリウムイオンを除去する目的で、ヌッチェにて濾過を行ったが、銀塩に添加した添加物が粘着剤として作用し、スラリーを濾過させるのに４時間、３Ｌの純水を用いての洗浄に約６時間費やした為、作業性を考慮して２回目以降の純水洗浄を断念した。
その酸化銀ウエットケーキを５５℃に設定した真空減圧乾燥機内にて１２時間乾燥させ、得られた乾固粉をコーヒーミルで解砕させた所、その解砕エネルギーにより微粒子酸化銀粉末が瞬間的に還元し（酸化銀を被覆する有機物が瞬時に燃焼し）、酸化銀粉末を得ることが出来なかった。
[Comparative Example 5] Fine silver oxide powder was obtained by the method of Comparative Example 4 except that the substance added to the aqueous silver nitrate solution was changed from polyvinyl alcohol to gelatin (manufactured by Zerais Co., Ltd., brand: E-200).
For the purpose of removing residual sodium ions in the slurry containing silver oxide particles, filtration was performed with Nutsche, but the additive added to the silver salt acted as an adhesive, and 4 L for 3 hours to filter the slurry. Since it took about 6 hours for cleaning with pure water, the second and subsequent cleaning with pure water was abandoned in consideration of workability.
The silver oxide wet cake was dried in a vacuum vacuum dryer set at 55 ° C. for 12 hours, and the resulting dried solid powder was crushed with a coffee mill. (Organic material covering silver oxide burned instantaneously), and silver oxide powder could not be obtained.
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