JP2014065963A

JP2014065963A - Production method of silver powder and silver powder production apparatus

Info

Publication number: JP2014065963A
Application number: JP2012214217A
Authority: JP
Inventors: Shintaro Ishikawa; 進太郎石川
Original assignee: Sumitomo Metal Mining Co Ltd
Current assignee: Sumitomo Metal Mining Co Ltd
Priority date: 2012-09-27
Filing date: 2012-09-27
Publication date: 2014-04-17

Abstract

PROBLEM TO BE SOLVED: To produce a silver powder in which an average grain diameter from 0.1 μm to several μm, and grain size distribution is narrow, by high productivity and by low cost.SOLUTION: A silver powder production apparatus includes: a silver solution supply pipe 10 that supplies a silver solution A including a silver complex; a reducer solution pipe 20 that is disposed at an inside of a silver solution supply pipe 10, and supplies a reducer solution B; and a mixing pipe 30 that includes a tip side mix reaction area AR that mixes a silver solution A supplied through a silver solution supply pipe 10 and a reducer solution B supplied through a reducer solution pipe 20, wherein in a tip side mix reaction area AR, a mix reactIon pipe 40 in which at least one feed opening 31 that supplies a buffer fluid along an inner peripheral surface of a mixing pipe 30 is disposed is used, while a buffer fluid C is supplied in a mixing pipe 30 along an inner peripheral surface of a mixing pipe 30 through a feed opening 31, a silver solution A including a silver complex and a reducer solution B are supplied respectively by a quantitative and consecutive manner, and mixed, and a silver complex is reduced by a quantitative and consecutive manner in a reaction liquid to generate a silver grain.

Description

本発明は、電子機器の配線層や電極などの形成に利用される樹脂型銀ペーストや焼成型銀ペーストの主成分となる銀粉の製造に用いる銀粉の製造方法及び銀粉製造装置に関する。 The present invention relates to a silver powder production method and a silver powder production apparatus used for producing a silver powder that is a main component of a resin-type silver paste or a fired-type silver paste used for forming a wiring layer or an electrode of an electronic device.

電子機器における配線層や電極などの形成には、樹脂型銀ペーストや焼成型銀ペーストのような銀ペーストが多用されている。これらの銀ペーストは、塗布又は印刷した後、加熱硬化あるいは加熱焼成されることによって、配線層や電極などとなる導電膜を形成する。 Silver pastes such as resin-type silver paste and fired-type silver paste are frequently used to form wiring layers and electrodes in electronic devices. These silver pastes are applied or printed, and then heat-cured or heat-baked to form a conductive film that becomes a wiring layer, an electrode, or the like.

例えば、樹脂型銀ペーストは、銀粉、樹脂、硬化剤、溶剤などからなり、導電体回路パターン又は端子の上に印刷し、１００℃〜２００℃で加熱硬化させて導電膜とし、配線や電極を形成する。また、焼成型銀ペーストは、銀粉、ガラス、溶剤などからなり、導電体回路パターン又は端子の上に印刷し、６００℃〜８００℃に加熱焼成して導電膜とし、配線や電極を形成する。これらの銀ペーストで形成された配線や電極では、銀粉が連なることで電気的に接続した電流パスが形成されている。 For example, a resin-type silver paste is made of silver powder, resin, curing agent, solvent, etc., printed on a conductor circuit pattern or terminal, and cured by heating at 100 ° C. to 200 ° C. to form a conductive film. Form. The fired silver paste is made of silver powder, glass, solvent, etc., printed on a conductor circuit pattern or terminal, and heated and fired at 600 ° C. to 800 ° C. to form a conductive film to form wirings and electrodes. In wirings and electrodes formed of these silver pastes, electrically connected current paths are formed by continuous silver powder.

銀ペーストに使用される銀粉は、粒径が０．１μｍから数μｍであり、形成する配線の太さや電極の厚さによって使用される銀粉の粒径が異なる。また、ペースト中に均一に銀粉を分散させることにより、均一な太さの配線、均一な厚さの電極を形成することができる。 The silver powder used in the silver paste has a particle size of 0.1 μm to several μm, and the particle size of the silver powder used varies depending on the thickness of the wiring to be formed and the thickness of the electrode. Further, by uniformly dispersing silver powder in the paste, it is possible to form a wiring having a uniform thickness and an electrode having a uniform thickness.

銀ペースト用の銀粉に求められる特性としては、用途及び使用条件により様々であるが、一般的で且つ重要なことは、粒径が均一で凝集が少なく、ペースト中への分散性が高いことである。粒径が均一で、且つペースト中への分散性が高いと、硬化あるいは焼成が均一に進み、低抵抗で強度の大きい導電膜を形成できるからである。逆に粒径が不均一で分散性が悪いと、印刷膜中に銀粒子が均一に存在しないため、配線や電極の太さや厚さが不均一となるばかりか、硬化あるいは焼成が不均一となるため、導電膜の抵抗が大きくなったり、導電膜が脆く弱いものになったりしやすい。 The characteristics required for silver powder for silver paste vary depending on the application and use conditions, but the general and important point is that the particle size is uniform, there is little aggregation, and the dispersibility in the paste is high. is there. This is because if the particle size is uniform and the dispersibility in the paste is high, curing or firing proceeds uniformly, and a conductive film having low resistance and high strength can be formed. Conversely, if the particle size is uneven and the dispersibility is poor, the silver particles are not uniformly present in the printed film, so the thickness and thickness of the wiring and electrodes are not uniform, and curing or firing is not uniform. Therefore, the resistance of the conductive film tends to increase, or the conductive film tends to be brittle and weak.

更に、銀ペースト用の銀粉に求められる事項として、製造コストが低いことも重要である。銀粉はペーストの主成分であるため、ペースト価格に占める割合が大きいためである。製造コストの低減のためには、生産性が高いことや、使用する原料や材料の単価が低いだけでなく、廃液や排気の処理コストが低いことも重要となる。 Further, as a matter required for silver powder for silver paste, it is also important that the manufacturing cost is low. This is because silver powder is the main component of the paste and therefore has a large proportion of the paste price. In order to reduce manufacturing costs, it is important not only to have high productivity and low unit cost of raw materials and materials to be used, but also to have low waste liquid and exhaust treatment costs.

上記における銀ペーストに使用される銀粉の製造は、硝酸銀などの銀塩のアンミン錯体を含む溶液が入った槽内に還元剤溶液を投入して還元するバッチ式で行なわれることが多かった。しかしながら、バッチ式では、還元剤が投入された位置で局部的に還元反応が始まり、還元剤の投入開始から終了までの間で銀粒子の核が随時発生していくため、均一な粒径の銀粉を得ることは難しい。 The production of silver powder used in the silver paste in the above is often performed in a batch system in which a reducing agent solution is introduced into a tank containing a solution containing an ammine complex of silver salt such as silver nitrate. However, in the batch method, the reduction reaction starts locally at the position where the reducing agent is charged, and the nuclei of silver particles are generated from the start to the end of the charging of the reducing agent. It is difficult to obtain silver powder.

そこで、連続的に製造する方法として、１つの反応管に銀錯体を含む銀溶液と還元剤溶液をそれぞれ定量的かつ連続的に供給し、銀溶液と還元剤溶液を反応管内で混合して反応液中で銀錯体を定量的かつ連続的に還元する銀粉の製造方法が特開２００５−４８２３６号公報（特許文献１）などで提案されている。 Therefore, as a continuous production method, a silver solution containing a silver complex and a reducing agent solution are quantitatively and continuously supplied to one reaction tube, and the reaction is performed by mixing the silver solution and the reducing agent solution in the reaction tube. Japanese Patent Application Laid-Open No. 2005-48236 (Patent Document 1) and the like propose a method for producing silver powder in which a silver complex is quantitatively and continuously reduced in a liquid.

特開２００５−４８２３６号公報JP-A-2005-48236

しかしながら、先に提案されている従来の銀粉の製造方法では、連続的に銀粉を製造する場合に、反応路出口付近で析出する銀が次第に成長して反応管を閉塞させるために定期的に析出した銀を除去する必要があり、この問題により生産効率が抑制されている。 However, in the conventional silver powder production method proposed previously, when silver powder is produced continuously, the silver deposited in the vicinity of the reaction path outlet gradually grows and deposits periodically to block the reaction tube. It is necessary to remove the silver, and this problem limits production efficiency.

本発明の目的は、このような従来の事情に鑑み、平均粒径が０．１μｍから数μｍで粒度分布が狭い銀粉を、生産性が高く低コストで製造することのできる銀粉の製造方法及び銀粉製造装置を提供することにある。 In view of such conventional circumstances, an object of the present invention is to produce a silver powder having an average particle size of 0.1 μm to several μm and a narrow particle size distribution, which can be produced with high productivity and low cost, and The object is to provide an apparatus for producing silver powder.

本発明の他の目的、本発明によって得られる具体的な利点は、以下に説明される実施の形態の説明から一層明らかにされる。 Other objects of the present invention and specific advantages obtained by the present invention will become more apparent from the description of embodiments described below.

本発明者らは、上記目的を達成するために、鋭意検討を重ねた結果、反応管内の反応液中で成長した銀粒子が、反応管出口端面および反応管出口付近の内壁に付着しないようにするため、反応管出口付近の内壁と銀粒子を含む反応液の間にバッファとなる液体を流すことで、銀粒子の析出を抑制して閉塞問題を回避できることを見出し、本発明を完成した。 As a result of intensive studies to achieve the above object, the present inventors have made sure that silver particles grown in the reaction liquid in the reaction tube do not adhere to the reaction tube outlet end face and the inner wall near the reaction tube outlet. For this reason, the present inventors have found that by flowing a liquid serving as a buffer between the inner wall near the outlet of the reaction tube and the reaction liquid containing silver particles, precipitation of silver particles can be suppressed and the blockage problem can be avoided.

すなわち、本発明は、銀粉の製造方法であって、銀錯体を含む銀溶液を先端側混合反応領域に供給する銀溶液供給管と、上記銀溶液供給管の内側に配され、還元剤溶液を上記先端側混合反応領域に供給する還元剤溶液管と、上記銀溶液供給管を介して供給される銀溶液と上記還元剤溶液管を介して供給される還元剤溶液を混合する先端側混合反応領域を有する混合管とからなり、上記先端側混合反応領域において該混合管の内周面に沿ってバッファ液体を供給する供給口が１つ以上設けられた混合反応管を用い、上記混合管に、上記供給口を介して該混合管の内周面に沿ってバッファ液体を供給しながら、銀錯体を含む銀溶液と還元剤溶液をそれぞれ定量的かつ連続的に供給し、該銀溶液と該還元剤溶液を先端側混合反応領域で混合して反応液中で銀錯体を定量的かつ連続的に還元して銀粒子を生成させることを特徴とする。 That is, the present invention is a method for producing silver powder, comprising a silver solution supply pipe for supplying a silver solution containing a silver complex to a tip side mixed reaction region, and an inner side of the silver solution supply pipe. The reducing agent solution tube supplied to the leading end side mixing reaction region, the leading end side mixing reaction for mixing the silver solution supplied via the silver solution supplying tube and the reducing agent solution supplied via the reducing agent solution tube A mixing tube having a region, and using a mixing reaction tube provided with one or more supply ports for supplying a buffer liquid along the inner peripheral surface of the mixing tube in the front end side mixing reaction region. The silver solution containing the silver complex and the reducing agent solution are supplied quantitatively and continuously while supplying the buffer liquid along the inner peripheral surface of the mixing tube through the supply port, respectively. Reaction by mixing the reducing agent solution in the front end side mixing reaction area Characterized in that to produce a quantitatively and continuously reduced silver particles of silver complex with a medium.

本発明に係る銀粉の製造方法では、上記混合管の長手方向に１段以上設けられた供給口を介して、上記混合管の内周面に沿ってバッファ液体を供給することができる。 In the method for producing silver powder according to the present invention, the buffer liquid can be supplied along the inner peripheral surface of the mixing tube through a supply port provided in one or more stages in the longitudinal direction of the mixing tube.

さらに、本発明に係る銀粉の製造方法では、上記混合管の長手方向に２段以上設けられ、各段の供給口ピッチの位相をずらしてある複数の供給口を介して、上記混合管の内周面に沿ってバッファ液体を供給することができる。 Furthermore, in the method for producing silver powder according to the present invention, two or more stages are provided in the longitudinal direction of the mixing pipe, and the inside of the mixing pipe is provided via a plurality of supply ports whose phases of the supply port pitch of each stage are shifted. A buffer liquid can be supplied along the peripheral surface.

また、本発明は、銀錯体を含む銀溶液と還元剤溶液をそれぞれ定量的かつ連続的に反応管内に供給し、銀溶液と還元剤溶液を反応管内で混合して反応液中で銀錯体を定量的かつ連続的に還元して銀粒子を生成させる銀粉製造装置であって、銀錯体を含む銀溶液を先端側混合反応領域に供給する銀溶液供給管と、上記銀溶液供給管の内側に配され、還元剤溶液を上記先端側混合反応領域に供給する還元剤溶液管と、上記銀溶液供給管を介して供給される銀溶液と上記還元剤溶液管を介して供給される還元剤溶液を混合する上記先端側混合反応領域を有する混合管とからなる混合反応管を備え、上記混合管には、上記先端側混合反応領域において該混合管の内周面に沿ってバッファ液体を供給する供給口が１つ以上設けてあることを特徴とする。 In addition, the present invention supplies a silver solution containing a silver complex and a reducing agent solution into the reaction tube quantitatively and continuously, and mixes the silver solution and the reducing agent solution in the reaction tube to form the silver complex in the reaction solution. A silver powder production apparatus that produces silver particles quantitatively and continuously by reduction, a silver solution supply pipe that supplies a silver solution containing a silver complex to a front-end side mixed reaction region, and an inner side of the silver solution supply pipe A reducing agent solution pipe that is arranged and supplies the reducing agent solution to the tip side mixed reaction region, a silver solution supplied via the silver solution supply pipe, and a reducing agent solution supplied via the reducing agent solution pipe A mixing reaction tube comprising the mixing tube having the tip side mixing reaction region for mixing the liquid, and supplying a buffer liquid to the mixing tube along the inner peripheral surface of the mixing tube in the tip side mixing reaction region One or more supply ports are provided.

本発明に係る銀粉製造装置では、上記混合管の内周面に沿ってバッファ液体を供給する供給口が、上記混合管の長手方向に１段以上設けてあるものとすることができる。 In the silver powder manufacturing apparatus according to the present invention, one or more supply ports for supplying the buffer liquid along the inner peripheral surface of the mixing tube may be provided in the longitudinal direction of the mixing tube.

さらに、本発明に係る銀粉製造装置では、上記混合管の内周面に沿ってバッファ液体を供給する供給口が、上記混合管の長手方向に２段以上設けてあり、各段の供給口ピッチの位相をずらしてあるものとすることができる。 Furthermore, in the silver powder manufacturing apparatus according to the present invention, the supply ports for supplying the buffer liquid along the inner peripheral surface of the mixing tube are provided in two or more stages in the longitudinal direction of the mixing tube, and the supply port pitch of each stage Can be shifted in phase.

本発明によれば、混合反応管に、供給口を介して混合管の内周面に沿ってバッファ液体を供給しながら、銀錯体を含む銀溶液と還元剤溶液をそれぞれ定量的かつ連続的に供給して混合し、反応液中で銀錯体を定量的かつ連続的に還元して銀粒子を生成させているので、混合反応管の出口付近で生じる銀粒子の析出を抑制して、混合管出口における閉塞状態を回避することができる。 According to the present invention, the silver solution containing the silver complex and the reducing agent solution are quantitatively and continuously supplied to the mixing reaction tube along the inner peripheral surface of the mixing tube via the supply port. Since the silver complex is produced by quantitatively and continuously reducing the silver complex in the reaction solution in a reaction solution, the precipitation of silver particles that occurs near the outlet of the mixing reaction tube is suppressed, and the mixing tube A blocked state at the outlet can be avoided.

さらに、本発明により製造される銀粉は、適度な粒径を有するとともに粒度分布が狭く、電子機器の配線層や電極などの形成に利用される樹脂型銀ペーストや焼成型銀ペーストなどのペースト用銀粉として好適であり、その工業的価値は極めて大きいものである。 Furthermore, the silver powder produced by the present invention has an appropriate particle size and a narrow particle size distribution, and is used for pastes such as resin-type silver paste and fired-type silver paste used for forming wiring layers and electrodes of electronic devices. It is suitable as silver powder, and its industrial value is extremely large.

本発明を適用した銀粉製造装置の構成を示す外観斜視図である。It is an external appearance perspective view which shows the structure of the silver powder manufacturing apparatus to which this invention is applied. 銀粉製造装置の要部縦断側面図である。It is a principal part vertical side view of a silver powder manufacturing apparatus. 銀粉製造装置の要部縦断正面図である。It is a principal part vertical front view of a silver powder manufacturing apparatus.

以下、本発明の実施の形態について、図面を参照しながら詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

本実施の形態に係る銀粉の製造方法は、銀錯体を含む銀溶液と還元剤溶液とを混合して反応液とし、その反応液中の銀錯体を還元して銀粒子スラリーを得た後、濾過、洗浄、乾燥の各工程を経て銀粉を製造する方法である。 In the method for producing silver powder according to the present embodiment, a silver solution containing a silver complex and a reducing agent solution are mixed to form a reaction solution, and after the silver complex in the reaction solution is reduced to obtain a silver particle slurry, This is a method for producing silver powder through each step of filtration, washing and drying.

特に、本実施の形態に係る製造方法では、銀溶液と還元剤溶液とを定量的に且つ連続的に一定の空間に供給し、これらを混合することによって還元反応を生じせしめ、還元反応が終了した還元後液、すなわち銀粒子スラリーを定量的かつ連続的に排出するようにする。 In particular, in the manufacturing method according to the present embodiment, the silver solution and the reducing agent solution are quantitatively and continuously supplied to a constant space, and these are mixed to cause a reduction reaction, thereby completing the reduction reaction. The reduced post-reduction liquid, that is, the silver particle slurry is quantitatively and continuously discharged.

このように、定量的かつ連続的に各溶液を供給して還元させることで、還元反応場の銀錯体の濃度と還元剤の濃度が一定に保たれ、一定の粒子成長を図ることができる。そして、これにより、得られる銀粒子の大きさが揃い、粒度分布がシャープな均一な粒径を有する銀粉を得ることができる。さらに、銀溶液と還元剤溶液の供給と銀粒子スラリーの排出を連続的に行うことで、連続的に銀粉を得ることができ、高い生産性でもって銀粉を製造することができる。 Thus, by supplying each solution quantitatively and continuously and reducing it, the concentration of the silver complex and the concentration of the reducing agent in the reduction reaction field can be kept constant, and constant particle growth can be achieved. And thereby, the silver particle which has the uniform particle diameter with which the magnitude | size of the silver particle obtained is uniform and a particle size distribution is sharp can be obtained. Further, by continuously supplying the silver solution and the reducing agent solution and discharging the silver particle slurry, the silver powder can be continuously obtained, and the silver powder can be produced with high productivity.

ここで、銀溶液は、還元されて銀となる銀錯体を含む溶液であり、塩化銀や硝酸銀等の各種銀塩を銀の原料として用いることができる。その中でも、塩化銀をアンモニア水に溶解することにより得たものであることが好ましい。このように、塩化銀を原料とすることにより、硝酸銀を出発原料とする方法で必要とされた亜硝酸ガスの回収装置や廃水中の硝酸系窒素の処理装置を設置する必要がなく、環境への影響も少ないプロセスとなり、製造コストの低減を図ることができる。また、塩化銀を用いることにより、粒径制御と反応液中の銀の高濃度化を容易に行うことができる。 Here, the silver solution is a solution containing a silver complex that is reduced to silver, and various silver salts such as silver chloride and silver nitrate can be used as a raw material of silver. Among these, it is preferable that it is obtained by dissolving silver chloride in aqueous ammonia. Thus, by using silver chloride as a raw material, there is no need to install a nitrite gas recovery device and a treatment system for nitrate nitrogen in wastewater, which are required in the method using silver nitrate as a starting material. Therefore, the manufacturing cost can be reduced. In addition, by using silver chloride, it is possible to easily control the particle size and increase the concentration of silver in the reaction solution.

還元剤溶液は、銀溶液に含まれる銀錯体を還元して銀粒子を生成させる還元剤を含む溶液である。その還元剤としては、特に限定されるものではなく、一般的なヒドラジンやホルマリン等を用いることもできるが、その中でもアスコルビン酸を用いることが好ましい。アスコルビン酸は、その還元作用が緩やかであるため、銀粒子中の結晶粒が成長し易く、また銀濃度が高濃度の反応液中でも粒径制御を容易に行うことができる。 The reducing agent solution is a solution containing a reducing agent that reduces silver complexes contained in the silver solution to generate silver particles. The reducing agent is not particularly limited, and general hydrazine, formalin, and the like can be used. Among them, ascorbic acid is preferably used. Since ascorbic acid has a slow reducing action, the crystal grains in the silver particles are likely to grow, and the particle diameter can be easily controlled even in a reaction solution having a high silver concentration.

また、還元剤溶液としては、溶液中に銀核を添加したものを用いてもよい。この銀核を含有した還元剤溶液（核含有還元剤溶液）を用いて銀溶液と反応させることにより、核生成とその後の粒子成長を還元剤の標準電極電位によって制御することができ、より効果的に、均一で所望とする粒径の粒子を得ることができる。具体的には、還元力の強い強還元剤を含む溶液に銀錯体を含む核生成用銀溶液を添加して得た銀核溶液に、その強還元剤よりも標準電極電位が高い弱還元剤を添加して核含有還元剤溶液とする。 Moreover, as a reducing agent solution, you may use what added the silver nucleus in the solution. By reacting with a silver solution using this silver nucleus-containing reducing agent solution (nucleus-containing reducing agent solution), the nucleation and subsequent particle growth can be controlled by the standard electrode potential of the reducing agent, which is more effective. In particular, particles having a uniform and desired particle diameter can be obtained. Specifically, a weak reducing agent having a standard electrode potential higher than that of a strong reducing agent in a silver nucleus solution obtained by adding a silver solution for nucleation containing a silver complex to a solution containing a strong reducing agent having a strong reducing power. To obtain a core-containing reducing agent solution.

なお、銀溶液又は還元剤溶液には、ポリビニルアルコール等の分散剤をさらに添加してもよい。これにより、得られる銀粒子の凝集を抑制することができる。 In addition, you may further add dispersing agents, such as polyvinyl alcohol, to a silver solution or a reducing agent solution. Thereby, aggregation of the silver particle obtained can be suppressed.

ところで、従来の銀粉の製造方法では、上述のように連続的に銀粒子スラリーを生成させようとした場合に、反応路の出口付近で析出生成する銀粒子が次第に成長し、反応管を閉塞させることがあった。そのため、析出した銀粒子を定期的に除去する必要が生じ、生産効率を著しく損なわせていた。 By the way, in the conventional silver powder manufacturing method, when the silver particle slurry is continuously generated as described above, the silver particles precipitated and formed in the vicinity of the outlet of the reaction path gradually grow and block the reaction tube. There was a thing. For this reason, it is necessary to periodically remove the precipitated silver particles, and production efficiency is significantly impaired.

そこで、本実施の形態に係る銀粉の製造方法においては、例えば図１に示すような構成の銀粉製造装置１００を用いて行うことを特徴としている。 Therefore, the silver powder manufacturing method according to the present embodiment is characterized in that it is performed using, for example, a silver powder manufacturing apparatus 100 configured as shown in FIG.

この銀粉製造装置１００は、図１に示すように、銀溶液供給管１０と、還元剤溶液供給管２０と、混合管３０とからなる混合反応管４０を備える。 As shown in FIG. 1, the silver powder production apparatus 100 includes a mixed reaction tube 40 including a silver solution supply tube 10, a reducing agent solution supply tube 20, and a mixing tube 30.

銀溶液供給管１０は、銀錯体を含む銀溶液Ａを定量的に且つ連続的に先端側混合反応領域ＡＲに供給する供給管である。この銀溶液供給管１０の材質としては、特に限定されず、供給する銀溶液Ａと反応しない材質を選択すればよく、例えば塩化ビニル、ポリプロピレン、ポリエチレン等から選択することができる。 The silver solution supply pipe 10 is a supply pipe that supplies the silver solution A containing the silver complex quantitatively and continuously to the front end side mixed reaction region AR. The material of the silver solution supply pipe 10 is not particularly limited, and a material that does not react with the supplied silver solution A may be selected. For example, it can be selected from vinyl chloride, polypropylene, polyethylene, and the like.

還元剤溶液供給管２０は、銀溶液供給管１０の内側に配され、還元剤溶液Ｂを定量的に且つ連続的に先端側混合反応領域ＡＲに供給する供給管である。この還元剤溶液供給管２０の材質についても、特に限定されず、還元剤溶液Ｂと反応しない材質を選択すればよく、例えば塩化ビニル、ポリプロピレン、ポリエチレン等から選択することができる。 The reducing agent solution supply pipe 20 is a supply pipe that is arranged inside the silver solution supply pipe 10 and supplies the reducing agent solution B quantitatively and continuously to the front end side mixed reaction area AR. The material of the reducing agent solution supply pipe 20 is not particularly limited, and a material that does not react with the reducing agent solution B may be selected. For example, vinyl chloride, polypropylene, polyethylene, or the like can be selected.

これら銀溶液供給管１０、還元剤溶液供給管２０を介して、それぞれ銀溶液Ａ、還元剤溶液Ｂを後述する混合管３０に供給する手段としては、一般的な定量ポンプ等を用いることができるが、脈動の小さいものが好ましい。 As means for supplying the silver solution A and the reducing agent solution B to the mixing tube 30 described later via the silver solution supply pipe 10 and the reducing agent solution supply pipe 20, respectively, a general metering pump or the like can be used. However, a thing with small pulsation is preferable.

また、それぞれの供給管１０，２０を介して供給する銀溶液と還元剤溶液の流量としては、特に限定されず、所望とする粒径の大きさに応じて適宜設定することができるが、一方が他方の１０倍以下であることが好ましい。各溶液の流量に１０倍以上の差があると、均一に混合されにくいという問題がある。各溶液の流量は、特に限定されないが、０．１Ｌ／ｍｉｎ以上、１０Ｌ／ｍｉｎ以下とすることが好ましい。流量が０．１Ｌ／ｍｉｎ未満の場合では、生産性が悪化するため好ましくない。一方で、流量が１０Ｌ／ｍｉｎより多い場合では、均一に混合され難くなり、還元反応が不十分になる可能性がある。
また。各溶液の流速についても、特に限定されないが、０．０２ｍ／ｓｅｃ以上、２．２０ｍ／ｓｅｃ以下とすることが好ましい。流速が０．０２ｍ／ｓｅｃ未満の場合では、生産性が悪化するため好ましくない。一方で、流速が２．２０ｍ／ｓｅｃより多い場合では、均一に混合され難くなり、還元反応が不十分になる可能性がある。 Further, the flow rates of the silver solution and the reducing agent solution supplied through the respective supply pipes 10 and 20 are not particularly limited, and can be appropriately set according to the desired particle size. Is preferably 10 times or less of the other. If there is a difference of 10 times or more in the flow rate of each solution, there is a problem that uniform mixing is difficult. The flow rate of each solution is not particularly limited, but is preferably 0.1 L / min or more and 10 L / min or less. When the flow rate is less than 0.1 L / min, productivity deteriorates, which is not preferable. On the other hand, when the flow rate is higher than 10 L / min, it is difficult to mix uniformly, and the reduction reaction may be insufficient.
Also. The flow rate of each solution is not particularly limited, but is preferably 0.02 m / sec or more and 2.20 m / sec or less. When the flow rate is less than 0.02 m / sec, productivity deteriorates, which is not preferable. On the other hand, when the flow rate is higher than 2.20 m / sec, it is difficult to mix uniformly, and the reduction reaction may be insufficient.

混合管３０は、銀溶液供給管１０を介して供給される銀溶液Ａと、還元剤溶液管２０を介して供給される還元剤溶液Ｂとを混合する先端側混合反応領域ＡＲを有し、供給された各溶液による還元反応の反応場となって、定量的に且つ連続的に銀粒子を生成させる。この混合管３０の材質としては、特に限定されないが、銀溶液Ａや還元剤溶液Ｂと反応しないことと、還元反応により生成した銀粒子が付着しないことが選択上重要であり、特にガラスであることが好ましい。 The mixing tube 30 has a front-end side mixing reaction area AR that mixes the silver solution A supplied via the silver solution supply tube 10 and the reducing agent solution B supplied via the reducing agent solution tube 20. It becomes a reaction field for a reduction reaction by each supplied solution and produces silver particles quantitatively and continuously. The material of the mixing tube 30 is not particularly limited, but it is important for selection that it does not react with the silver solution A or the reducing agent solution B and that silver particles generated by the reduction reaction do not adhere, and is particularly glass. It is preferable.

また、この混合管３０には、先端側混合反応領域ＡＲにおいて、この混合管３０の内周面に沿ってバッファ液体Ｃを供給する供給口３１が１つ以上設けられている。 Further, the mixing tube 30 is provided with one or more supply ports 31 for supplying the buffer liquid C along the inner peripheral surface of the mixing tube 30 in the front end side mixing reaction region AR.

具体的な構造例として、図２に先端側混合反応領域ＡＲ部分の要部縦断側面図を示し、図３に図２の要部縦断側面図におけるＸ−Ｘ’線断面図を示す。例えば、この図２及び図３に示すように、混合管３０には、混合管３０の出口から５ｍｍの位置に、銀析出防止用のバッファ液体Ｃを注入するための１段目の供給口３１Ａが周方向に９０度間隔で４ヶ所設けられている。さらに、この混合管３０には、例えばその出口から１５ｍｍの位置に、銀析出防止用のバッファ液体Ｃを注入するための２段目の供給口３１Ｂが１段目の供給口３１Ａに対して４５度ピッチをずらして周方向に９０度間隔で４ヶ所設けられている。 As a specific structural example, FIG. 2 shows a vertical cross-sectional side view of the main part of the tip-side mixed reaction region AR, and FIG. 3 shows a cross-sectional view taken along line X-X ′ in the vertical vertical side view of FIG. For example, as shown in FIGS. 2 and 3, the first-stage supply port 31 </ b> A for injecting the buffer liquid C for preventing silver deposition into the mixing tube 30 at a position 5 mm from the outlet of the mixing tube 30. Are provided at intervals of 90 degrees in the circumferential direction. Further, in the mixing tube 30, for example, a second-stage supply port 31B for injecting the buffer liquid C for preventing silver deposition at a position 15 mm from the outlet of the mixing tube 30 is 45 with respect to the first-stage supply port 31A. The four pitches are provided at 90 ° intervals in the circumferential direction by shifting the pitch.

本実施の形態に係る銀粉の製造方法においては、例えば、上述した２段構成の８ヶ所の供給口３１Ａ，３１Ｂから水等のバッファ液体Ｃを混合管３０の内周面に沿って供給しながら、各溶液を定量的に且つ連続的に供給して混合させるようにする。すると、混合管３０では、内周面に沿ってバッファ液体Ｃが供給されることで、そのバッファ液体Ｃによるバッファ層が混合管３０の出口付近の全周囲に亘って形成されるようになり、混合管３０の出口付近で銀粒子が析出することを抑制し、混合管３０の出口が閉塞状態になることを回避することができる。 In the silver powder manufacturing method according to the present embodiment, for example, while supplying the buffer liquid C such as water along the inner peripheral surface of the mixing tube 30 from the eight supply ports 31A and 31B having the two-stage configuration described above. Each solution is supplied quantitatively and continuously to be mixed. Then, in the mixing tube 30, the buffer liquid C is supplied along the inner peripheral surface, so that a buffer layer of the buffer liquid C is formed over the entire periphery near the outlet of the mixing tube 30. It is possible to prevent the silver particles from being deposited in the vicinity of the outlet of the mixing tube 30 and to prevent the outlet of the mixing tube 30 from being closed.

このように、混合管３０の内周面に沿ってバッファ液体Ｃを供給しながら、銀溶液Ａと還元剤溶液Ｂをそれぞれ定量的かつ連続的に供給して混合させ、反応液中で銀錯体を還元して銀粒子を生成させることにより、混合反応管３０の出口付近で生じる銀粒子の析出を抑制して、混合管出口における閉塞状態を回避することができ、長時間に亘って効率よく銀粒子を生成させることができる。 As described above, while supplying the buffer liquid C along the inner peripheral surface of the mixing tube 30, the silver solution A and the reducing agent solution B are supplied quantitatively and continuously to be mixed, and the silver complex is mixed in the reaction solution. Is reduced to produce silver particles, so that the precipitation of silver particles generated near the outlet of the mixing reaction tube 30 can be suppressed, and the blockage state at the outlet of the mixing tube can be avoided, and it can be efficiently performed over a long period of time. Silver particles can be generated.

なお、混合管３０におけるバッファ液体Ｃを注入するための供給口の設置位置や設置数、設置段数等については、上述した構造例に限定されず、その混合管３０の内周面に沿ってバッファ液をする供給する供給口を少なくとも１つ以上設けていればよい。 In addition, the installation position, the number of installations, the number of installation stages, and the like of the supply port for injecting the buffer liquid C in the mixing tube 30 are not limited to the above-described structure example, and the buffer is provided along the inner peripheral surface of the mixing tube 30. It is only necessary to provide at least one supply port for supplying the liquid.

また、上述した反応混合管４０における混合管３０の下流側には、蛇管等を接続させるようにしてもよい。これにより、反応場が十分な長さとすることができ、還元反応を１００％終了させるようにすることにより、未還元の銀錯体が残留して粗大な銀粒子が生成されることを防止できる。 A serpentine tube or the like may be connected to the downstream side of the mixing tube 30 in the reaction mixing tube 40 described above. Thereby, a reaction field can be made into sufficient length, and it can prevent that an unreduced silver complex remains and a coarse silver particle is produced | generated by making a reduction reaction complete | finish 100%.

また、混合反応管４０内で銀溶液Ａと還元剤溶液Ｂとが混合されて還元反応が終了した反応液は、一旦、所定の槽に受けるようにしてもよい（以下、この槽を「受槽」という）。なお、受槽内では、還元により生成した銀粒子が沈降しないように攪拌することが必要になる。銀粒子が沈降すると、銀粒子同士が凝集体を形成し分散性が悪くなってしまい好ましくない。受槽内での攪拌は、銀粒子が沈降しない程度の能力で攪拌すればよく、一般的な攪拌機を用いて攪拌すればよい。受槽に入った反応液は、ポンプによりフィルタープレス等の濾過機に送液され、連続的に次の工程へと流すことができる。 Further, the reaction solution in which the silver solution A and the reducing agent solution B are mixed in the mixed reaction tube 40 and the reduction reaction is completed may be once received in a predetermined tank (hereinafter, this tank is referred to as “receiving tank”). "). In the receiving tank, it is necessary to stir so that the silver particles produced by the reduction do not settle. When the silver particles settle, the silver particles form an aggregate and the dispersibility is deteriorated, which is not preferable. Stirring in the receiving tank may be performed with an ability not to allow silver particles to settle, and may be performed using a general stirrer. The reaction liquid entering the receiving tank is sent to a filter such as a filter press by a pump, and can be continuously flowed to the next step.

以上のようにして銀粉製造装置１００にて銀粒子スラリーを生成すると、続いて、その銀粒子スラリーを濾過した後、洗浄し、乾燥することによって銀粉を生成する。 When the silver particle slurry is generated in the silver powder manufacturing apparatus 100 as described above, the silver particle slurry is subsequently filtered, washed, and dried to generate silver powder.

洗浄方法としては、特に限定されるものではないが、例えば銀粒子を水に投入し、攪拌機又は超音波洗浄器を使用して攪拌した後、フィルタープレス等で濾過して回収する方法が用いられる。この洗浄方法において、水への投入、攪拌洗浄及び濾過からなる操作を、数回繰り返して行うことが好ましい。また、洗浄に用いる水は、銀粉に対して有害な不純物元素を含有していない水を使用し、特に純水を使用することが好ましい。 The washing method is not particularly limited, and for example, a method is used in which silver particles are put into water, stirred using a stirrer or ultrasonic cleaner, and then filtered and collected by a filter press or the like. . In this washing method, it is preferable to repeat the operation consisting of charging into water, stirring washing and filtration several times. The water used for washing is water that does not contain an impurity element harmful to silver powder, and it is particularly preferable to use pure water.

次に、洗浄後の銀粉を乾燥させて、水分を蒸発させる。乾燥方法としては、特に限定されるものではないが、例えば洗浄後の銀粒子をステンレスバット上に置き、大気オーブン又は真空乾燥機等の市販の乾燥装置を用いて、４０〜８０℃程度の温度で加熱することにより行うことができる。 Next, the washed silver powder is dried to evaporate water. Although it does not specifically limit as a drying method, For example, the silver particle after washing | cleaning is set | placed on a stainless steel bat, and about 40-80 degreeC temperature is used using commercially available drying apparatuses, such as an atmospheric oven or a vacuum dryer. It can be performed by heating with.

以上、詳細に説明したように、本実施の形態に係る銀粉の製造方法では、銀溶液と還元剤溶液とを定量的かつ連続的に供給して混合することによって反応液とし、その反応液中で銀錯体を還元して銀粒子を成長させるようにする。このように、各溶液を定量的かつ連続的に供給して混合させることで、還元反応場の銀錯体の濃度と還元剤の濃度が一定に保たれ、一定の粒子成長を図ることができ、微粒を含まず、均一な粒径を有する銀粉を製造することができる。 As described above in detail, in the method for producing silver powder according to the present embodiment, a silver solution and a reducing agent solution are quantitatively and continuously supplied and mixed into a reaction solution, and the reaction solution contains The silver complex is reduced to grow silver particles. Thus, by supplying and mixing each solution quantitatively and continuously, the concentration of the silver complex and the concentration of the reducing agent in the reduction reaction field can be kept constant, and constant particle growth can be achieved. Silver powder having a uniform particle size without containing fine particles can be produced.

具体的には、例えば、走査型電子顕微鏡観察による一次粒子の平均粒径が０．３〜２．０μｍであり、粒径の相対標準偏差（標準偏差σ／平均粒径ｄ）が０．３以下、好ましくは０．２５以下の銀粉を製造することができる。なお、ここで言う一次粒子とは、外見上から判断して、単位粒子と考えられるものを意味する。このような均一で粒度分布が狭い銀粉は、電子機器の配線層や電極等の形成に利用される樹脂型銀ペーストや焼成型銀ペースト等のペースト用銀粉として好適に用いることができる。 Specifically, for example, the average particle diameter of primary particles by observation with a scanning electron microscope is 0.3 to 2.0 μm, and the relative standard deviation of particle diameter (standard deviation σ / average particle diameter d) is 0.3. In the following, it is possible to produce a silver powder of preferably 0.25 or less. In addition, the primary particle said here means what can be considered as a unit particle judging from appearance. Such a silver powder having a uniform and narrow particle size distribution can be suitably used as a silver powder for a paste such as a resin-type silver paste or a fired-type silver paste used for forming a wiring layer or an electrode of an electronic device.

また、このような定量的に且つ連続的な製造方法によれば、高い生産性でもって効率的に銀粉を製造することができる。 Moreover, according to such a quantitative and continuous manufacturing method, silver powder can be efficiently manufactured with high productivity.

しかも、本実施の形態に係る銀粉の製造方法では、上述したような反応混合管４０を用いて、その混合管３０の内周面に沿ってバッファ液体Ｃを供給しながら、銀溶液Ａと還元剤溶液Ｂをそれぞれ定量的かつ連続的に供給して先端側混合反応領域ＡＲで混合させ、銀粒子を生成させるようにしている。 Moreover, in the method for producing silver powder according to the present embodiment, using the reaction mixing tube 40 as described above, while supplying the buffer liquid C along the inner peripheral surface of the mixing tube 30, the silver solution A and the reduction are reduced. The agent solution B is supplied quantitatively and continuously and mixed in the front end side mixing reaction area AR to generate silver particles.

このような製造方法によれば、混合反応管３０の出口付近で生じる銀粒子の析出を抑制し、その銀粒子の析出による混合管出口における閉塞状態を回避することができ、長時間に亘って銀粉を効率よく製造することができる。 According to such a manufacturing method, it is possible to suppress the precipitation of silver particles generated in the vicinity of the outlet of the mixing reaction tube 30 and to avoid the clogged state at the outlet of the mixing tube due to the precipitation of the silver particles. Silver powder can be produced efficiently.

以下に、本発明の実施例及び比較例によって本発明をさらに詳細に説明するが、本発明は、これらの実施例によってなん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 and comparative examples of the present invention, but the present invention is not limited to these examples.

（実施例１）
３８℃の温浴中において液温３６℃に保持した２５％アンモニア水１６６ｍＬと純水３．２１Ｌの混合液に、塩化銀８．３１ｇ（住友金属鉱山（株）製、純度９９．９９９９％）を攪拌しながら投入して核生成用銀溶液（溶液中の銀濃度１．５ｇ／Ｌ）を作製した。次に、分散剤のポリビニルアルコール４１ｇ（（株）クラレ製、ＰＶＡ２０５）を３６℃の純水６．４８Ｌに溶解し、そこへ強還元剤であるヒドラジン一水和物１．６２ｍＬ（核生成用銀溶液中の銀量に対して２．５当量）を添加して得られた還元剤溶液を、温浴中において３６℃に保持した。そして、還元剤溶液中に、５６ｍＬ／ｍｉｎの流量で核生成用銀溶液を添加して銀核を生成させて銀核溶液とした。 Example 1
In a mixed solution of 166 mL of 25% ammonia water and 3.21 L of pure water kept at a liquid temperature of 36 ° C. in a 38 ° C. bath, 8.31 g of silver chloride (Sumitomo Metal Mining Co., Ltd., purity 99.9999%) was added. A nucleation silver solution (silver concentration in solution: 1.5 g / L) was prepared while stirring. Next, 41 g of polyvinyl alcohol as a dispersant (manufactured by Kuraray Co., Ltd., PVA205) was dissolved in 6.48 L of pure water at 36 ° C., and 1.62 mL of hydrazine monohydrate as a strong reducing agent (for nucleation) The reducing agent solution obtained by adding 2.5 equivalents to the amount of silver in the silver solution was kept at 36 ° C. in a warm bath. Then, a nucleation silver solution was added to the reducing agent solution at a flow rate of 56 mL / min to produce silver nuclei, thereby obtaining a silver nucleation solution.

次に、得られた銀核溶液に、弱還元剤であるアスコルビン酸６６５ｇ（下記の粒子成長用銀溶液中の銀量に対して１．４当量）を添加して核含有還元剤溶液とした。 Next, 665 g of ascorbic acid as a weak reducing agent (1.4 equivalents with respect to the amount of silver in the silver solution for particle growth described below) was added to the obtained silver core solution to obtain a core-containing reducing agent solution. .

一方、３３℃の温浴中において液温３２℃に保持した２５％アンモニア水１８Ｌに、塩化銀９４７ｇ（住友金属鉱山（株）製、純度９９．９９９９％）を攪拌しながら投入して粒子成長用銀溶液（溶液中の銀濃度３５ｇ／Ｌ）を作製した。消泡剤（（株）アデカ製、アデカノールＬＧ−１２６）を体積比で１００倍に希釈し、この消泡剤希釈液８．３ｍＬを粒子成長用銀溶液に添加して温浴中において３２℃に保持した。なお、核含有還元剤溶液に添加したポリビニルアルコールの添加量は、粒子成長用銀溶液中の銀量に対して３．５質量％となる。 On the other hand, 947 g of silver chloride (manufactured by Sumitomo Metal Mining Co., Ltd., purity 99.9999%) was added to 18 L of 25% aqueous ammonia maintained at a liquid temperature of 32 ° C. in a 33 ° C. bath for particle growth. A silver solution (silver concentration in the solution: 35 g / L) was prepared. An antifoaming agent (manufactured by Adeka Co., Ltd., Adecanol LG-126) was diluted 100 times by volume, and 8.3 mL of this antifoaming agent dilution was added to the silver solution for particle growth, and the temperature was increased to 32 ° C. in a warm bath. Retained. The addition amount of polyvinyl alcohol added to the core-containing reducing agent solution is 3.5% by mass with respect to the silver amount in the particle growth silver solution.

チューブポンプ（ＭＡＳＴＥＲＦＬＥＸ製）を使用し、粒子成長用銀溶液と核含有還元剤溶液とを、それぞれ２．７Ｌ／ｍｉｎ、０．９０Ｌ／ｍｉｎで、図１に示すような銀粉製造装置１００の混合反応管４０内に供給して混合することで反応液とした。 Using a tube pump (manufactured by MASTERFLEX), the silver solution for particle growth and the core-containing reducing agent solution are mixed at a rate of 2.7 L / min and 0.90 L / min, respectively, as shown in FIG. A reaction solution was prepared by supplying the mixture into the reaction tube 40 and mixing them.

混合反応管４０は、全体の長さが２５０ｍｍ（混合管３０の長さ：１５０ｍｍ）で、銀溶液供給管１０は内径１０ｍｍで、還元剤溶液供給管２０は内径３ｍｍのＬ字形で銀溶液供給管１０の中心に銀溶液供給管内部の長さ４０ｍｍの構造を有したガラス製のものを用いた。混合反応管４０から出た反応液は、混合反応管４０の後段に接続した内径１２ｍｍ、長さ１０ｍポリプロピレン製チューブ内で還元反応を完全に終了させた後、銀錯体を還元して得られた銀粒子スラリーとして受槽内に貯留した。２液の送液が終了した後、受槽内での攪拌は３０分継続した。 The total length of the mixing reaction tube 40 is 250 mm (the length of the mixing tube 30: 150 mm), the silver solution supply tube 10 has an inner diameter of 10 mm, and the reducing agent solution supply tube 20 has an L shape of 3 mm inner diameter and supplies the silver solution. The thing made from glass which has the structure of length 40mm inside a silver solution supply pipe | tube in the center of the pipe | tube 10 was used. The reaction solution exiting from the mixed reaction tube 40 was obtained by reducing the silver complex after completely completing the reduction reaction in a polypropylene tube having an inner diameter of 12 mm and a length of 10 m connected to the subsequent stage of the mixed reaction tube 40. It was stored in a receiving tank as a silver particle slurry. After the feeding of the two liquids was completed, stirring in the receiving tank was continued for 30 minutes.

また、混合反応管４０には、出口から５ｍｍの位置に１段目の銀析出防止用の注入水の供給口３１Ａを周方向に９０度間隔で４ヶ所設け、さらに出口から１５ｍｍの位置に２段目の銀析出防止用の注入水の供給口３１Ｂを１段目に対して４５度ずつ（半ピッチ）ずらして周方向に９０度間隔で４ヶ所設けた。各供給口３１Ａ，３１Ｂの内径は４ｍｍとし、各供給口３１Ａ，３１Ｂを介して混合反応管の内周面に沿って注入水を０．０３６Ｌ／ｍｉｎの流量で供給しながら各溶液を混合させた。 Further, the mixing reaction tube 40 is provided with four supply ports 31A for the first stage of silver precipitation prevention at 90 ° intervals in the circumferential direction at a position 5 mm from the outlet, and 2 at a position 15 mm from the outlet. The supply ports 31B for injection water for preventing silver precipitation at the stage were provided at four positions at intervals of 90 degrees in the circumferential direction by shifting by 45 degrees (half pitch) with respect to the first stage. The inner diameters of the supply ports 31A and 31B are 4 mm, and the solutions are mixed while supplying the injection water at a flow rate of 0.036 L / min along the inner peripheral surface of the mixing reaction tube via the supply ports 31A and 31B. It was.

そして、混合反応管４０において、粒子成長用銀溶液と核含有還元剤溶液を供給するポンプに圧力センサーを装備し、出口付近に銀が析出して閉塞状態となったことを示す信号が圧力センサーから発せられるようにした状態で銀粉の製造を行った。 The mixing reaction tube 40 is equipped with a pressure sensor in the pump for supplying the particle growth silver solution and the nucleus-containing reducing agent solution, and a signal indicating that silver is deposited near the outlet and is in a closed state is a pressure sensor. The silver powder was produced in a state where it was emitted from the

その結果、混合反応管４０を８時間連続で使用しても、混合反応管４０の出口付近で閉塞現象は発生せず、閉塞状態となったことを示す信号が発せられることはなかった。 As a result, even when the mixed reaction tube 40 was used continuously for 8 hours, no clogging phenomenon occurred near the outlet of the mixed reaction tube 40, and no signal indicating that the clogged state was reached was generated.

このようにして製造した銀粒子スラリーは、受槽内での攪拌を終了した後、フィルタープレスで濾過し、銀粒子を固液分離した。続いて、回収した銀粒子を０．０５ｍｏｌ／ＬのＮａＯＨ水溶液２３Ｌ中に投入し、そこへステアリン酸エマルジョン（中京油脂（株）製、セロゾール９２０）１７．８ｇを添加し、１５分間攪拌した後、フィルタープレスで濾過して回収した。０．０５ｍｏｌ／ＬのＮａＯＨ水溶液への投入、攪拌、及び濾過からなる操作を更に２回繰返した後、回収した銀粒子を純水２３Ｌ中に投入し、１５分間の攪拌による洗浄と、フィルタープレスによる濾過からなる操作を行った。その後、銀粒子をステンレスバットに移し、真空乾燥機にて６０℃で１０時間乾燥して銀粉を得た。１ロット製造途中で一時製造を中断した。そのため、反応管および反応管の後段に接続したポリプロピレン製チューブを交換した後に、製造を再開して実施例と同量の１ロット分の銀粉を得た。 The silver particle slurry produced in this manner was stirred in the receiving tank and then filtered with a filter press to separate the silver particles into solid and liquid. Subsequently, the collected silver particles were put into 23 L of 0.05 mol / L NaOH aqueous solution, and 17.8 g of stearic acid emulsion (manufactured by Chukyo Yushi Co., Ltd., Cellosol 920) was added thereto and stirred for 15 minutes. It was recovered by filtration with a filter press. After repeating the operations of adding 0.05 mol / L NaOH aqueous solution, stirring and filtration two more times, the recovered silver particles were put into 23 L of pure water, washed by stirring for 15 minutes, and filter press An operation consisting of filtration by was performed. Thereafter, the silver particles were transferred to a stainless bat and dried at 60 ° C. for 10 hours in a vacuum dryer to obtain silver powder. Temporary production was suspended during the production of one lot. Therefore, after exchanging the reaction tube and the polypropylene tube connected to the latter stage of the reaction tube, the production was resumed to obtain one lot of silver powder in the same amount as in the example.

得られた銀核と銀粉の双方ともに、均一な粒子からなるものであった。また、ＳＥＭ像より３００個以上の一次粒子の粒径を測長して粒子数で平均することで求めた銀核と銀粉の平均粒径は、それぞれ０．１１μｍと０．８１μｍであり、測定結果より得られた銀粉の粒径の相対標準偏差（標準偏差σ／平均粒径ｄ）は０．１８であり、均一で微粒がないことが確認された。 Both the obtained silver nucleus and silver powder consisted of uniform particles. Moreover, the average particle diameters of silver nuclei and silver powder obtained by measuring the particle diameters of 300 or more primary particles from the SEM image and averaging them by the number of particles are 0.11 μm and 0.81 μm, respectively. The relative standard deviation (standard deviation σ / average particle diameter d) of the particle diameter of the silver powder obtained from the results was 0.18, and it was confirmed that the silver powder was uniform and free of fine particles.

（比較例１）
銀析出防止用の注入水の供給口を設けず、注入水を供給せずに銀粉の製造を行ったこと以外は、上述の実施例１と同様の反応管を用い、その他の製造条件も同様にして銀粉を製造した。 (Comparative Example 1)
The same reaction tube as in Example 1 described above was used, and the other manufacturing conditions were the same except that the injection port for supplying silver for preventing silver precipitation was not provided and the silver powder was manufactured without supplying the injection water. Thus, silver powder was produced.

その結果、得られた銀粉は、粒径の相対標準偏差は０．１８で、実施例１と同様に、均一で微粒がない銀粉が製造された。 As a result, the obtained silver powder had a relative standard deviation of the particle size of 0.18, and as in Example 1, uniform and fine silver powder was produced.

しかしながら、粒子成長用銀溶液と核含有還元剤溶液を供給するポンプに設けられた圧力センサーから連続操業４時間程度で出口付近に銀が析出して閉塞状態となったことを示す信号が発せられ、１ロット製造途中で一時製造を中断した。そのため、反応管および反応管の後段に接続したポリプロピレン製チューブを交換した後に、製造を再開して実施例１と同量の１ロット分の銀粉を得た。 However, a signal indicating that silver is deposited near the outlet and becomes closed in about 4 hours from the pressure sensor provided in the pump for supplying the silver solution for particle growth and the nucleus-containing reducing agent solution is emitted. Temporary production was interrupted during the production of one lot. Therefore, after replacing the reaction tube and the polypropylene tube connected to the latter stage of the reaction tube, the production was resumed to obtain one lot of silver powder in the same amount as in Example 1.

１０銀溶液供給管、２０還元剤溶液供給管、３０混合管、３１，３１Ａ，３１Ｂ供給口、４０混合反応管、１００銀粉製造装置、Ａ銀溶液、Ｂ還元剤溶液、Ｃバッファ液体、ＡＲ先端側混合反応領域 10 Silver solution supply pipe, 20 Reducing agent solution supply pipe, 30 Mixing pipe, 31, 31A, 31B Supply port, 40 Mixing reaction pipe, 100 Silver powder production device, A Silver solution, B Reducing agent solution, C Buffer liquid, AR Tip Side mixing reaction zone

Claims

銀錯体を含む銀溶液を先端側混合反応領域に供給する銀溶液供給管と、上記銀溶液供給管の内側に配され、還元剤溶液を上記先端側混合反応領域に供給する還元剤溶液管と、上記銀溶液供給管を介して供給される銀溶液と上記還元剤溶液管を介して供給される還元剤溶液を混合する先端側混合反応領域を有する混合管とからなり、上記先端側混合反応領域において該混合管の内周面に沿ってバッファ液体を供給する供給口が１つ以上設けられた混合反応管を用い、
上記混合管に、上記供給口を介して該混合管の内周面に沿ってバッファ液体を供給しながら、銀錯体を含む銀溶液と還元剤溶液をそれぞれ定量的かつ連続的に供給し、該銀溶液と該還元剤溶液とを先端側混合反応領域で混合して反応液中で銀錯体を定量的かつ連続的に還元して銀粒子を生成させることを特徴とする銀粉の製造方法。 A silver solution supply pipe for supplying a silver solution containing a silver complex to the front end side mixed reaction area; and a reducing agent solution pipe that is arranged inside the silver solution supply pipe and supplies a reducing agent solution to the front end side mixed reaction area; A mixing tube having a tip side mixing reaction region for mixing the silver solution supplied through the silver solution supply tube and the reducing agent solution supplied through the reducing agent solution tube, and the tip side mixing reaction Using a mixing reaction tube provided with one or more supply ports for supplying a buffer liquid along the inner peripheral surface of the mixing tube in the region;
While supplying a buffer liquid along the inner peripheral surface of the mixing tube to the mixing tube through the supply port, a silver solution containing a silver complex and a reducing agent solution are respectively supplied quantitatively and continuously, A method for producing silver powder, characterized in that a silver solution and the reducing agent solution are mixed in a front end side mixed reaction region, and a silver complex is quantitatively and continuously reduced in the reaction solution to produce silver particles.

上記混合管の長手方向に１段以上設けられた供給口を介して、上記混合管の内周面に沿ってバッファ液体を供給することを特徴とする請求項１記載の銀粉の製造方法。 The method for producing silver powder according to claim 1, wherein the buffer liquid is supplied along the inner peripheral surface of the mixing tube through a supply port provided in one or more stages in the longitudinal direction of the mixing tube.

上記混合管の長手方向に２段以上設けられ、各段の供給口ピッチの位相をずらしてある複数の供給口を介して、上記混合管の内周面に沿ってバッファ液体を供給することを特徴とする請求項１記載の銀粉の製造方法。 Two or more stages are provided in the longitudinal direction of the mixing tube, and the buffer liquid is supplied along the inner peripheral surface of the mixing tube through a plurality of supply ports whose phases of the supply port pitch of each stage are shifted. The method for producing silver powder according to claim 1, wherein

銀錯体を含む銀溶液と還元剤溶液をそれぞれ定量的かつ連続的に反応管内に供給し、銀溶液と還元剤溶液を反応管内で混合して反応液中で銀錯体を定量的かつ連続的に還元して銀粒子を生成させる銀粉製造装置であって、
銀錯体を含む銀溶液を先端側混合反応領域に供給する銀溶液供給管と、
上記銀溶液供給管の内側に配され、還元剤溶液を上記先端側混合反応領域に供給する還元剤溶液管と、
上記銀溶液供給管を介して供給される銀溶液と上記還元剤溶液管を介して供給される還元剤溶液を混合する上記先端側混合反応領域を有する混合管とからなる混合反応管を備え、
上記混合管には、上記先端側混合反応領域において該混合管の内周面に沿ってバッファ液体を供給する供給口が１つ以上設けてあることを特徴とする銀粉製造装置。 A silver solution containing a silver complex and a reducing agent solution are supplied into the reaction tube quantitatively and continuously, and the silver solution and the reducing agent solution are mixed in the reaction tube to quantitatively and continuously form the silver complex in the reaction solution. A silver powder production apparatus that produces silver particles by reduction,
A silver solution supply pipe for supplying a silver solution containing a silver complex to the front side mixed reaction region;
A reducing agent solution tube that is arranged inside the silver solution supply tube and supplies the reducing agent solution to the tip side mixed reaction region;
A mixing reaction tube comprising a silver solution supplied via the silver solution supply tube and a mixing tube having the tip side mixing reaction region for mixing the reducing agent solution supplied via the reducing agent solution tube;
1. The silver powder production apparatus according to claim 1, wherein the mixing tube is provided with one or more supply ports for supplying a buffer liquid along an inner peripheral surface of the mixing tube in the front end side mixing reaction region.

上記混合管の内周面に沿ってバッファ液体を供給する供給口が、上記混合管の長手方向に１段以上設けてあることを特徴とする請求項４記載の銀粉製造装置。 The silver powder manufacturing apparatus according to claim 4, wherein one or more supply ports for supplying a buffer liquid along the inner peripheral surface of the mixing tube are provided in the longitudinal direction of the mixing tube.

上記混合管の内周面に沿ってバッファ液体を供給する供給口が、上記混合管の長手方向に２段以上設けてあり、各段の供給口ピッチの位相をずらしてあることを特徴とする請求項４記載の銀粉製造装置。 Two or more supply ports for supplying the buffer liquid along the inner peripheral surface of the mixing tube are provided in the longitudinal direction of the mixing tube, and the phase of the supply port pitch of each step is shifted. The silver powder manufacturing apparatus according to claim 4.