JPS6051523B2 - Production method of silver powder - Google Patents

Description

【発明の詳細な説明】 本発明は酸化銀粉末からきわめて簡単な操作て粒度分
布幅の小さい均一な銀粉末を製造する方法に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing uniform silver powder with a narrow particle size distribution from silver oxide powder using extremely simple operations.

銀粉末は電子工業分野における高温焼成用銀塗料、リ
ード線接続用ペースト、導電性接着剤、電極用半田、電
池、電子回路用印刷インキなどに供せられるほか、焼結
合金用原料粉や自動車窓硝子結露防止用発熱体などにも
用いられている。Silver powder is used in high-temperature firing silver paint, lead wire connection paste, conductive adhesive, electrode solder, batteries, printing ink for electronic circuits, etc. in the electronics industry, as well as raw material powder for sintered alloys and automobiles. It is also used as a heating element to prevent condensation on window glass.

粒径が約１μｍ以上の銀粗粒の製造法としては機械的
に粉砕する方法が溶湯からノズルで溶射する方法などの
機械的操作による方法が知られているが、粒径が約１０
μｍ以下の比較的微細な銀粉末の場合には次のごとき化
学反応を利用した製造法が提案されている。（１）硝酸
銀水溶液に水素または一酸化炭素を吹き 込み銀粉を直
接還元させる方法、（２） 硝酸銀水溶液をアルカリで
中和後、ＮＨ、ＯＨ水で銀アンミン錯体を形成させ、ホ
ルマリン、蟻酸等の有機還元剤で銀粉を還元析出させる
方 法、（３） 硝酸銀水溶液をアルカリで中和し、酸
化銀沈澱を生成させ、次いでヒドラジン等の有機還元剤
を添加し、該酸化銀沈殿を還元する方法、（４）硝酸銀
水溶液をアルカリで中和し、生成した 酸化銀沈殿を枦
別後、５０℃以上の水素雰囲気に 置き還元する方法、
（５）硝酸銀水溶液をアルカリで中和し、生成した酸化
銀沈殿を濾別後、２５０’Ｃ以上で熱分解させ る方法
。As methods for producing coarse silver particles with a particle size of about 1 μm or more, methods using mechanical operations such as mechanical pulverization and thermal spraying from molten metal with a nozzle are known.
In the case of relatively fine silver powder of .mu.m or less, a manufacturing method using the following chemical reaction has been proposed. (1) Direct reduction of silver powder by blowing hydrogen or carbon monoxide into an aqueous silver nitrate solution, (2) After neutralizing the aqueous silver nitrate solution with an alkali, a silver ammine complex is formed with NH and OH water, and formalin, formic acid, etc. A method of reducing and precipitating silver powder with an organic reducing agent, (3) A method of neutralizing an aqueous silver nitrate solution with an alkali to form a silver oxide precipitate, and then adding an organic reducing agent such as hydrazine to reduce the silver oxide precipitate. , (4) a method in which an aqueous silver nitrate solution is neutralized with an alkali, the resulting silver oxide precipitate is separated, and then placed in a hydrogen atmosphere at 50°C or higher for reduction;
(5) A method in which an aqueous silver nitrate solution is neutralized with an alkali, the resulting silver oxide precipitate is filtered off, and then thermally decomposed at 250'C or higher.

これらの化学反応を利用した方法で得られる銀粉の一
次粒子は球状になることを特徴とするものてあるが、そ
れら一次粒子は凝集しやすく、塗料、ペースト、インキ
などの用途に使用した場合、容易に分散しないうえ、凝
集により０．２〜１０μｍのごとく粒径が広い範囲にわ
たつて分布し、それぞれの用途に要求される０．２〜０
．８μｍ） ２〜８μｍのごとぎ比較的粒径が揃い、鋭
い正規分布を示すような粒子が得られにくい。The primary particles of silver powder obtained by methods using these chemical reactions are characterized by their spherical shape, but these primary particles tend to aggregate, and when used in applications such as paints, pastes, and inks, In addition to not being easily dispersed, the particle size is distributed over a wide range of 0.2 to 10 μm due to agglomeration, and the particle size is 0.2 to 0.0 μm, which is required for each application.
．． (8 μm) It is difficult to obtain particles with relatively uniform particle sizes of 2 to 8 μm and exhibiting a sharp normal distribution.

特に、最近の微細なプリント基板印刷回路などには銀粉
末が０．５μｍ前後の微細なものが要求されているが、
上記の化学反応を利用する方法では直接還元する方法お
よび酸化銀を経由する方法のいずれも還元時に生成する
銀粉末が凝集するので、所定の粒度範囲の微粉を得るた
めには分級を必要とし、従つて歩留りが低下ずろ。上記
方法のうち、（１），（２）の方法は直接還元する方法
であり、残りの（３），（４），（５）の方法は酸化銀
を経由する方法に属するものである。本発明者らは上記
の従来の酸化銀を経由する方法の問題点を解決し、酸化
銀粉末から粒度分布幅の小さい均一な銀粉末を製造する
方法を提供すべく検討した結果、従来の上記酸化銀を経
由する方法で得られた銀粉末の粒度分布の広がる原因を
、充電透過法粒度分布測定装置や走査型電子顕微鏡など
による観測の結果、酸化銀粉末から銀粉末への還元時に
発生する凝集または粒成長によるものであることを確認
し、本発明に到達した。In particular, fine silver powder of around 0.5 μm is required for recent fine printed circuit boards, etc.
In both the direct reduction method and the method using silver oxide, the silver powder produced during reduction agglomerates, so classification is required to obtain fine powder within a predetermined particle size range. Therefore, the yield will decrease. Among the above methods, methods (1) and (2) are direct reduction methods, and the remaining methods (3), (4), and (5) are methods that involve silver oxide. The present inventors solved the problems of the above-mentioned conventional method using silver oxide, and as a result of studying to provide a method for producing uniform silver powder with a small particle size distribution width from silver oxide powder, we found that The cause of the broadening of the particle size distribution of silver powder obtained by the method via silver oxide was determined by observation using a charged transmission particle size distribution measuring device and a scanning electron microscope, and it was found that the cause of the broadening of the particle size distribution of silver powder obtained by the method via silver oxide was that it occurs during the reduction of silver oxide powder to silver powder. It was confirmed that this was due to aggregation or grain growth, and the present invention was achieved.

すなわち、本発明の要旨とするところは、酸化銀粉末を
５０〜１０−３Ｔ０ｒｒの範囲の減圧下で５０〜３００
℃の温度範囲の熱媒油と接触させることを特徴とする銀
粉末の製造法、にある。本発明において出発物質として
使用する酸化銀粉末は硝酸銀水溶液をアルカリ水溶液で
中和して得られる酸化銀沈殿のごとき通常の製法で得ら
れる酸化銀沈殿を■別したものてある。That is, the gist of the present invention is that silver oxide powder is heated under reduced pressure in the range of 50 to 10-3 T0rr.
A method for producing silver powder, characterized in that it is brought into contact with a heat transfer oil in the temperature range of °C. The silver oxide powder used as a starting material in the present invention is obtained by separating the silver oxide precipitate obtained by a conventional manufacturing method, such as the silver oxide precipitate obtained by neutralizing a silver nitrate aqueous solution with an alkaline aqueous solution.

また、本発明において使用する熱媒油は鉱物油、動植物
油、シリコーン油およびフッ素油よりなるものであり、
これらの油はいずれも水素原子を有し、かつ上記還元条
件下において、出発物質の酸化銀粉末および還元によつ
て生成した銀粉末とは反応せず、またそれ自体劣化しな
いものであればよい。本発明は以上のように、酸化銀粉
末を上記熱媒油に添加し、５０〜１０−３Ｔ０ｒｒの減
圧下で５０〜３００℃の範囲に加熱するという構成をと
るものである。この構成によつて、酸化銀粉末は次式の
ごとく還元されて、酸素を放出し、銀粉末となる。，Ａ
ｇ２Ｏ→Ａｇ＋１１２０２この反応において、上記熱媒
油は単なる熱分解の媒体となるばかりでなく、熱媒油中
に含まれる水素原子が上記酸化銀粉末の還元の促進に寄
与するものと推察される。Further, the heat transfer oil used in the present invention consists of mineral oil, animal and vegetable oil, silicone oil and fluorine oil,
All of these oils have hydrogen atoms and do not react with the starting silver oxide powder and the silver powder produced by reduction under the above reducing conditions, and do not deteriorate themselves. . As described above, the present invention has a configuration in which silver oxide powder is added to the heat transfer oil and heated to a temperature in the range of 50 to 300° C. under a reduced pressure of 50 to 10 −3 T0rr. With this configuration, silver oxide powder is reduced as shown in the following equation, releases oxygen, and becomes silver powder. ,A
g2O→Ag+11202 In this reaction, it is presumed that the heat transfer oil not only serves as a medium for thermal decomposition, but also that the hydrogen atoms contained in the heat transfer oil contribute to promoting the reduction of the silver oxide powder.

従つて、この還元時には特に水素を存在させる必要はな
い。また、これら熱媒油は上記還元反応時に生成した銀
粒子を覆うために、銀粒子の凝集または粒成長を防止す
ることもできる。さらに、上記還元反応において、放出
された酸素は該熱媒油中に溶存するので、減圧雰囲気に
よつて系外に取り除かれ、それによつて上記還元を効率
的に進行させかつ熱媒油自体の劣化を低減させることが
できる。上記熱媒油の加熱温度は５０〜３００℃の範［
召である。Therefore, there is no particular need for hydrogen to be present during this reduction. Furthermore, since these thermal oils cover the silver particles produced during the above-mentioned reduction reaction, they can also prevent agglomeration or grain growth of the silver particles. Furthermore, in the above reduction reaction, the released oxygen is dissolved in the heat transfer oil, so it is removed from the system by the reduced pressure atmosphere, thereby allowing the above reduction to proceed efficiently and reducing the heat transfer oil itself. Deterioration can be reduced. The heating temperature of the above heat transfer oil is in the range of 50 to 300°C [
It is a calling.

加熱温度が５０℃未満では上記酸１し銀粉末の還元反応
の進行がきわめて遅く、工業的に不適当であり、また３
００′Ｃを越えると、酸化銀の分解反応が激しく反応は
爆発的に進行し、かつ熱媒油自体の劣化も激化する。加
熱温度が５０〜３００℃の範囲であれば、該加熱温度が
使用した熱媒油の沸点に達する場合でも、反応装置に冷
却還流手段を設ければ特に差支えはない。本発明の反応
系内の圧力は５０−１０−３Ｔ０ｒｒの範囲の減圧雰囲
気である。If the heating temperature is lower than 50°C, the reduction reaction of the acid 1 and silver powder will proceed extremely slowly, which is industrially unsuitable.
When the temperature exceeds 00'C, the decomposition reaction of silver oxide is intense and the reaction proceeds explosively, and the deterioration of the heat transfer oil itself is also intensified. As long as the heating temperature is in the range of 50 to 300°C, there is no particular problem even if the heating temperature reaches the boiling point of the heat transfer oil used, as long as the reaction apparatus is provided with cooling reflux means. The pressure within the reaction system of the present invention is a reduced pressure atmosphere in the range of 50-10-3T0rr.

圧力が５０Ｔ′０ＴＴを越えると、熱媒油中に溶存する
上記酸素の除去が容易でなく、熱媒油も劣化しやすくな
る。また、１０−３Ｔ０ｒｒ未満ではそのような真空度
を得るための設備費用が高くなり、コスト的に不利であ
る。When the pressure exceeds 50T'0TT, it is not easy to remove the oxygen dissolved in the heat transfer oil, and the heat transfer oil also tends to deteriorate. Moreover, if it is less than 10-3T0rr, the equipment cost for obtaining such a degree of vacuum becomes high, which is disadvantageous in terms of cost.

また、反応系内の雰囲気としては、アルゴンガスのごと
き不活性ガス雰囲気であれば、さらに好適である。第１
図は本発明の一実施例に使用する実験装置の配置図、第
２図は実施例４の場合の異なる加熱温度における反応時
間と試料中の銀含有量との関係を示すグラフ図である。Further, as the atmosphere in the reaction system, an inert gas atmosphere such as argon gas is more suitable. 1st
The figure is a layout diagram of an experimental apparatus used in an example of the present invention, and FIG. 2 is a graph showing the relationship between reaction time and silver content in a sample at different heating temperatures in Example 4.

第１図において、酸化銀粉末を添加した熱媒油１をアル
ゴンガス２の雰囲気内でロータリポンプ７と拡散ポンプ
８とによる５０〜１０−３Ｔ０ｒｒの範囲の減圧下で電
熱器３によつて５０〜３０００Ｃの範囲に茄熱して熱媒
油１に懸濁した酸化銀粉末を還元して銀粉末とする。In FIG. 1, heating medium oil 1 to which silver oxide powder has been added is heated in an atmosphere of argon gas 2 by an electric heater 3 under reduced pressure in the range of 50 to 10-3 T0rr by a rotary pump 7 and a diffusion pump 8. The silver oxide powder suspended in heat transfer oil 1 is reduced to silver powder by heating to a temperature in the range of ~3000C.

４は攪拌棒５回転用モータ、６は冷却還流管、９は冷却
水である。4 is a motor for rotating the stirring rod five times, 6 is a cooling reflux pipe, and 9 is cooling water.

第２図は比較例としての加熱温度４０℃の場合では反応
速度がおそく試料中の銀含有量が少ないことおよび加熱
温度３５０℃の場合では反応が爆発的に進行することを
示している。FIG. 2 shows that, as a comparative example, when the heating temperature is 40°C, the reaction rate is slow and the silver content in the sample is low, and when the heating temperature is 350°C, the reaction proceeds explosively.

本発明は上記構成をとることによつて、酸化銀粉末から
きわめて簡単な還元操作で原料の酸化銀粉末の形状、粒
径をそのまま保持した状態で凝集することなく粒度分布
幅の小さい均一な銀粉末を安定して製造することを可能
ならしめる銀粉末の製造法を提供するもので、その工業
的価値はきわめて大きい。By adopting the above structure, the present invention can produce uniform silver with a narrow particle size distribution without agglomeration while maintaining the shape and particle size of the raw material silver oxide powder by a very simple reduction operation from silver oxide powder. The present invention provides a method for producing silver powder that enables stable production of the powder, and its industrial value is extremely large.

次に、本発明を実施例によつてさらに具体的に説明する
が、本発明はその要旨を越えない限り、以下の実施例に
よつて限定されるものではない。Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

実施例１銀３４０ｙ／ｅの濃度の硝酸銀水溶液１ｅを△
の水酸化ナトリウム水溶液２′に滴下し、生成した酸化
銀沈殿を戸別し、次いで１１０℃で乾燥して得た微細な
酸化銀粉末３９０ｙを真空ポンプオイル（日本真空製Ｕ
ＬＶＯＩＬＢ−４）１ｆに懸濁させ、ロータリポンプで
１０−１Ｔ０ｒｒに減圧しながら１８０Ｃに加熱し、６
吟間放置した。Example 1 Silver nitrate aqueous solution 1e with a concentration of 340y/e of silver was mixed with △
was added dropwise to an aqueous sodium hydroxide solution 2', the resulting silver oxide precipitate was separated, and then dried at 110°C to obtain 390y of fine silver oxide powder.
Suspend in LVOILB-4) 1f, heat to 180C while reducing the pressure to 10-1T0rr with a rotary pump,
I left it alone for a while.

次いで、該酸化銀粉末を真空ポンプオイルから淵別し、
Ｘ線回折パターンを観測したところ、銀のピークパター
ンが得られ、またミクロンフオトサイザーで粒度分布を
測定したところ、０．８〜１．２μｍの均一な粒子であ
ることがわかつた。この銀粉末６５ｑにグリセリン１３
ｑ１低融点ガラス粉１２ｙ１テレピン油１０ｙを混合し
てペーストを調製したのち、平滑度２μｍのガラス板上
にセロテープで枠を作り、上記ペーストをアプリケータ
ーで塗布した。Next, the silver oxide powder is separated from the vacuum pump oil,
When the X-ray diffraction pattern was observed, a silver peak pattern was obtained, and when the particle size distribution was measured using a micron photosizer, it was found that the particles were uniform particles with a size of 0.8 to 1.2 μm. 65q of this silver powder and 13g of glycerin
After preparing a paste by mixing q1 low melting point glass powder 12y1 turpentine oil 10y, a frame was made with cellophane tape on a glass plate having a smoothness of 2 μm, and the paste was applied with an applicator.

このものを１５０℃の予熱器で予熱したのち、６００℃
で３紛間焼成したところ、得られた焼成体の比抵抗は３
×１０−５Ω・ｄであつた。実施例２銀１７０ｙ／ｅの
濃度の硝酸銀水溶液１ｅを１Ｎの水酸化カリウム水溶液
２ｆに滴下し、４０℃に加温し、生成した酸化銀沈殿を
枦別後、１１０゜Ｃに乾燥して得た酸化銀粉末１９５Ｖ
をシリコーン油（信越化学製ＫＦ９６）１ｅに懸濁させ
、アスピレーターで１０１′０ｒｒに減圧しながら２５
０℃に加熱し、ｌ紛間放置した。After preheating this in a 150℃ preheater, heat it to 600℃.
When 3 powders were fired at
×10-5Ω·d. Example 2 Silver nitrate aqueous solution 1e having a concentration of 170 y/e of silver was added dropwise to 1N potassium hydroxide aqueous solution 2f, heated to 40°C, the resulting silver oxide precipitate was separated, and dried at 110°C to obtain a silver oxide powder 195V
was suspended in silicone oil (KF96 manufactured by Shin-Etsu Chemical) 1e, and heated to 25 ml while reducing the pressure to 101'0rr with an aspirator.
The mixture was heated to 0°C and left to stand for 1 hour.

次いで、該酸化銀粉末をシリコーン油からＰ別し、Ｘ線
回折パターンを観測したところ、銀のピークパターンが
得られ、またミクロンフオトサイザーて粒度分布を測定
したところ、１〜４μｍの均一な粒子であることがわか
つた。この銀粉末５ｙをｍ気圧の圧力で１『φのペレッ
トに圧粉化し、４端子法抵抗測定を行つたところ、該ペ
レットの比抵抗は５×１０−６Ω・〔であつた。実施例
３ 銀１７０ｙ／ｆの濃度の硝酸銀水溶液１′を０．５Ｎの
水酸化ナトリウム水溶液２′に滴下し、生成した酸化銀
沈殿を沖別後、６０℃て真空乾燥して得た酸化銀粉末１
９５ｙをフッ素油（タイキン工業製ダイフロイル＃１）
１ｅに懸濁させ、ロータリーポンプで５ｘ１０−３Ｔ０
ｒｒに減圧しながら１００℃に加熱し４時間放置した。Next, when the silver oxide powder was separated from the silicone oil and the X-ray diffraction pattern was observed, a silver peak pattern was obtained, and when the particle size distribution was measured using a micron photosizer, uniform particles of 1 to 4 μm were observed. It turns out that it is. This silver powder 5y was compacted into pellets of 1"φ at a pressure of m atm, and the resistivity of the pellets was measured by the 4-terminal method, and the specific resistance of the pellets was 5.times.10@-6 .OMEGA.. Example 3 A silver nitrate aqueous solution 1' having a concentration of silver 170y/f was dropped into a 0.5N sodium hydroxide aqueous solution 2', and the resulting silver oxide precipitate was separated and vacuum dried at 60°C to obtain silver oxide. powder 1
95y with fluorine oil (Taikin Kogyo Daifloil #1)
1e and 5x10-3T0 with a rotary pump.
The mixture was heated to 100° C. under reduced pressure to rr and left for 4 hours.

次いで、該酸化銀粉末を油から洒別し、Ｘ線回折パター
ンを観測したところ、銀のピークパターンが得られ、ま
たミクロンフオトサイザーで粒度分布を測定したところ
、０．５〜０．９μｍの均一な粒子であることがわかつ
た。実施例４銀３４０ｙ／′の濃度の硝酸銀水溶液１ｅ
を歩の水酸化ナトリウム水溶液２′に滴下し、生成した
酸化銀沈殿を洒別し、該沈殿を１１０℃で乾燥して得た
酸化銀粉末３９０ｑを真空ポンプ油（日本真空製ＵＬＶ
ＯＩＬＢ−４）１′に懸濁させ、ロータリーポンプで１
Ｔ０ｒｒに減圧しながら、各加熱温度における反応時間
と試料中の銀含有量との関係を求めたところ、結果は第
２図の如く得られた。Next, when the silver oxide powder was separated from the oil and the X-ray diffraction pattern was observed, a silver peak pattern was obtained, and when the particle size distribution was measured with a micron photosizer, it was found to be 0.5 to 0.9 μm. It was found that the particles were uniform. Example 4 Silver nitrate aqueous solution 1e with a concentration of 340y/' silver
was added dropwise to Ayumu's aqueous sodium hydroxide solution 2', the resulting silver oxide precipitate was separated, and the precipitate was dried at 110°C to obtain 390q of silver oxide powder.
Suspend in OILB-4)1' and pump with a rotary pump.
The relationship between the reaction time at each heating temperature and the silver content in the sample was determined while reducing the pressure to T0rr, and the results were obtained as shown in FIG. 2.

図において加熱温度が４０゜Ｃの場合と３５０℃の場合
は上述したように、それぞれ比較例を示すものである。
比較例 試薬特級酸化銀粉末１０７ｙをナタネ油１ｆに懸濁させ
て４０℃に加熱し、４時間後に粉末を油から戸別し、Ｘ
線回折パターンから銀と酸化銀（Ａｇ２Ｏ）の組成比を
測定したところ銀が２０％、酸化銀が８０％（モル）で
あつた。In the figure, the cases where the heating temperature is 40° C. and 350° C. respectively show comparative examples, as described above.
Comparative Example Reagent special grade silver oxide powder 107y was suspended in 1f rapeseed oil and heated to 40°C. After 4 hours, the powder was separated from the oil and
When the composition ratio of silver and silver oxide (Ag2O) was measured from a line diffraction pattern, it was found that silver was 20% and silver oxide was 80% (mol).

また、９（ロ）間後には銀が５０％、酸化銀が５０％（
モル）であり、還元反応の進行は認められたが、きわめ
て緩やかで、１工業的には不適当であることがわかつた
。Also, after 9 (b), 50% silver and 50% silver oxide (
Although the reduction reaction was observed to proceed, it was found to be extremely slow and unsuitable for industrial use.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は本発明の一実施例に使用する実験装置の配置図
、第２図は熱媒油として真空ポンプ油を用い、１Ｔ０ｒ
Ｉ′の減圧下で加熱を行なう実施例４の・場合と異なる
加熱温度における反応時間と試料中の銀含有量との関係
を示すグラフ図である。Figure 1 is a layout diagram of the experimental equipment used in one embodiment of the present invention, and Figure 2 is a 1T0r
FIG. 3 is a graph showing the relationship between the reaction time and the silver content in the sample at different heating temperatures from that of Example 4 in which heating was performed under reduced pressure in I'.

Claims (1)

【特許請求の範囲】 １ 酸化銀粉末を５０〜１０＾−＾３Ｔｏｒｒの範囲の
減圧下で５０〜３００℃の温度範囲の熱媒油と接触させ
ることを特徴とする銀粉末の製造法。 ２ 前記熱媒油は鉱物油、動植物油、シリコーン油およ
びフッ素油よりなる群の中から選ばれた少なくとも一種
である特許請求の範囲第１項に記載の銀粉末の製造法。[Scope of Claims] 1. A method for producing silver powder, which comprises bringing silver oxide powder into contact with heat transfer oil having a temperature range of 50 to 300° C. under a reduced pressure of 50 to 10 to 3 Torr. 2. The method for producing silver powder according to claim 1, wherein the heat transfer oil is at least one selected from the group consisting of mineral oil, animal and vegetable oil, silicone oil, and fluorine oil.