JP4679716B2 - Method for producing metal colloid solution - Google Patents
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- JP4679716B2 JP4679716B2 JP2000374144A JP2000374144A JP4679716B2 JP 4679716 B2 JP4679716 B2 JP 4679716B2 JP 2000374144 A JP2000374144 A JP 2000374144A JP 2000374144 A JP2000374144 A JP 2000374144A JP 4679716 B2 JP4679716 B2 JP 4679716B2
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【０００１】
【発明の属する技術分野】
本発明は、新規な金属コロイドの製造方法に関する。さらに詳しくは、均一な粒子径分布を有し、金属コロイド微粒子が単分散した溶液を容易に製造可能な方法に関する。
【０００２】
【発明の技術的背景】
従来、金属微粒子はその粒子径効果、高表面積効果、量子効果等のために触媒や電子機器等の分野において機能性材料として用いられている。例えばホウ化ニッケルコロイド微粒子を担体に担持して水素化触媒として用いることが知られている（帰山ら、日本化学会誌、１９８４（６）、ｐ．１００５〜１０１０）。また、金属微粒子は、電子機器等の分野として、陰極線管等の表示装置表面の帯電防止、電磁波遮蔽のために用いられている。
【０００３】
このような金属微粒子の製造方法としては、奥山、瀬戸ら、ケミカルエンジニアリング、Ｐ２２〜２７、(１９９３)には、気相プロセスによる超微粒子の製造方法が開示されている。
また本願出願人は、上記の乾式法とは別に、特開平１０−１８８６８１号公報にて、アルコール・水混合溶媒中で金属塩を還元剤あるいは電気的に還元する方法、および、金属微粒子または合金微粒子の分散液に、金属微粒子または合金微粒子よりも標準水素電極電位が高い金属の微粒子またはイオンを存在させて、金属微粒子または／および合金微粒子上に標準水素電極電位が高い金属を析出させる方法（湿式法）を提案している。
【０００４】
また、日本金属学会秋季大会シンポジウム講演概要集（１９９７）７０頁等には、貴金属イオン（Ａg+、Ａu3+、Ｐd2+、Ｐt2+、Ｐt4+等）を含み、必要に応じて界面活性剤等の有機化合物を添加した溶液に、不活性ガス雰囲気下で超音波を、例えば２００ｋＨz、６Ｗ／ｃｍ2の条件で照射することによって金属微粒子を調製する超音波照射直接還元法が提案されている。
【０００５】
しかしながら、乾式法で得られる金属微粒子は、凝集しやすく、分散媒に分散させても安定なコロイドが得にくく、また金属微粒子の粒子径は調節が困難であるとともに不均一であった。
また、湿式法および超音波照射直接還元法では、金属成分によっては粒子化が困難なものもあり、粒子化して金属微粒子が得られたとしても、必ずしも安定性が充分ではなく、粒子径の調節が困難であるとともに不均一であるなどの問題があった。
【０００６】
【発明の目的】
本発明は、安定な金属コロイド溶液を容易に得ることができるとともに、粒子径の制御が容易に行うことが可能な金属コロイド溶液の製造方法を提供することを目的としている。
【０００７】
【発明の概要】
本発明に係る金属コロイド溶液の製造方法は、
(a)標準水素電極電位が−０.８０〜＋１.２０ｅＶの範囲にある金属の塩（Ａ）、安定化剤、および溶媒を混合して金属コロイド溶液調製用母液を調製し、
(b)該金属コロイド溶液調製用母液を１０〜９５℃の温度に調整し、
(c)該金属コロイド溶液調製用母液に、標準水素電極電位が−０.２０〜＋１.５０ｅＶの範囲にあり、かつ前記金属の塩（Ａ）を構成する金属よりも標準水素電極電位が高い金属の塩（Ｂ）を添加したのち、
(d)還元剤を添加して金属塩（Ａ）および（Ｂ）を還元することを特徴としている。
【０００８】
本発明に係る製造方法では、(e)得られた金属コロイド溶液を、さらに５０〜１５０℃の範囲の温度で熟成することが望ましい。
前記(a)〜(d)または(a)〜(e)の工程は、非酸化雰囲気下で行われることが望ましい。
標準水素電極電位が−０.８０〜＋１.２０ｅＶの範囲にある金属の塩（Ａ）が、Ａｕ、Ａｇ、Ｃｕ、Ｎｉ、Ｃｏ、Ｆｅ、Ｒｕからなる群から選ばれる１種以上の金属の塩であり、
標準水素電極電位が−０.２０〜＋１.５０ｅＶの範囲にあり、かつ前記金属の塩（Ａ）を構成する金属よりも標準水素電極電位が高い金属の塩（Ｂ）が、Ｐｔ、Ｐｄ、Ｓｎからなる群から選ばれる１種以上の金属の塩であることが好ましい。
【０００９】
【発明の具体的な説明】
以下、本発明について具体的に説明する。なお、本発明でいう金属コロイド溶液とは金属コロイド微粒子が分散した溶液である。
(a) 金属コロイド溶液調製用母液の調製
本発明では、まず、標準水素電極電位が−０.８０〜＋１.２０ｅＶの範囲にある金属の塩（Ａ）、安定化剤、および溶媒を混合して金属コロイド溶液調製用母液を調製する。
【００１０】
本発明で用いる金属塩(A)としては、標準水素電極電位が−０.８０〜＋１.２０ｅＶ、好ましくは−０．６０〜＋１.１１ｅＶの範囲にある金属の塩を用いることが好ましい。具体的には、Ａu、Ａg、Ｎi、Ｃu、Ｆe、Ｃo、Ｒuからなる郡から選ばれる１種以上の金属の塩化物、硝酸塩、硫酸塩、リン酸塩、炭酸塩などの無機酸塩、有機酸塩などが挙げられる。また、金属塩(A)として、ヘキサアミンニッケル塩化物（(Ｎi(ＮＨ3)6)Ｃl2）、テトラアミン銅硫酸塩（(Ｃu(ＮＨ3)4)ＳＯ4・Ｈ2Ｏ）、ヘキサアミンルテニウム塩化物（(Ｒu(ＮＨ3)6)Ｃl2）などの錯塩も用いることができる。これらの塩は１種単独でも、または２種以上混合して使用される。
【００１１】
このような金属塩は、金属に換算して、金属コロイド溶液調製用母液中に０.１〜１０重量％、好ましくは０.５〜５重量％の範囲となるように用いることが好ましい。
金属塩の使用量が、金属に換算して、金属コロイド溶液調製用母液中に０.１重量％未満の場合は、金属塩濃度が低すぎて生産効率が低く、金属化合物の使用量が、金属に換算して、金属コロイド溶液調製用母液中に１０重量％を越えると、濃度が高すぎて得られる金属コロイド微粒子の単分散性が低下し、粒子径が不均一になる傾向がある。
【００１２】
安定化剤としては、蟻酸、クエン酸、フタル酸、リンゴ酸、マロン酸、ポリカルボン酸などの有機酸、ゼラチン、アラビアゴム、ポリビニールアルコール、ポリビニールピロリドン、ポリメチルビニールエーテルなどの親水性ポリマー、およびドデシルベンゼンスルホン酸ナトリウム、ラウリン酸ナトリウム等の界面活性剤、例えばデスパウント（東邦化学工業（株）商品名）などの界面活性剤が用いられる。中でもゼラチン、ポリビニールピロリドン、デスパウント界面活性剤が好ましい。
【００１３】
このような安定化剤は、生成した金属コロイド微粒子の表面に吸着して、疎水性の金属コロイド微粒子が、水などの分散媒中で凝集することを抑制する。このため、分散安定性に優れた金属コロイド溶液を得ることができる。
安定化剤は、金属コロイド溶液調製用母液中の最終的な金属コロイド微粒子の重量（すなわち、金属塩（Ａ）および後述する金属塩（Ｂ）を金属に換算した合計重量）の０.１〜１０重量倍、好ましくは０.２〜５重量倍の範囲となるように用いることが好ましい。
【００１４】
安定化剤の使用量が、金属コロイド溶液調製用母液中の最終的な金属コロイド微粒子の重量の０.１重量倍未満の場合は、安定化剤量が希薄すぎて金属コロイド微粒子の単分散した金属コロイドが得にくく、得られたとしても金属コロイドの安定性がなく凝集し易い。また安定化剤の使用量が、金属コロイド溶液調製用母液中の最終的な金属コロイド微粒子の重量の１０重量倍を越えると、安定化剤の濃度が高すぎ溶液の粘度が増加したり、金属コロイド微粒子が安定化剤に覆われるため、触媒として使用する場合、触媒活性が充分発現しなかったり、導電性が充分発現しないことがある。
【００１５】
本発明で用いる溶媒としては、前記した標準水素電極電位が−０.８０〜＋１.２０ｅＶの範囲にある金属の塩（Ａ）および安定化剤、後述する標準水素電極電位が−０.２０〜＋１.５０ｅＶの範囲にある金属の塩（Ｂ）および還元剤を溶解することができるものであれば特に制限はなく従来公知の溶媒を用いることができる。
【００１６】
具体的には、水；メタノール、エタノール、プロパノール、ブタノール、ジアセトンアルコール、フルフリルアルコール、テトラヒドロフルフリルアルコール、エチレングリコール、ヘキシレングリコールなどのアルコール類；酢酸メチルエステル、酢酸エチルエステルなどのエステル類；ジエチルエーテル、エチレングリコールモノメチルエーテル、エチレングリコールモノエチルエーテル、エチレングリコールモノブチルエーテル、ジエチレングリコールモノメチルエーテル、ジエチレングリコールモノエチルエーテルなどのエーテル類；アセトン、メチルエチルケトン、アセチルアセトン、アセト酢酸エステルなどのケトン類などが挙げられる。これらは単独で使用してもよく、また２種以上混合して使用してもよい。なかでも水、アルコール類などの極性溶媒は、金属塩（Ａ）および（Ｂ）、安定化剤および還元剤を容易に溶解することができるので好ましい。
【００１７】
以上のような金属塩（Ａ）、安定化剤および溶媒を、公知の方法で混合する。混合方法としては、特に制限されるものではなく、たとえば、ミキサー、スターラーなどの公知の手法が挙げられる。混合して得られる金属コロイド溶液調製用母液のｐＨは３〜１０、好ましくは４〜９のｐＨの範囲にあることが望ましい。
金属コロイド溶液調製用母液のｐＨが３未満の場合は、還元剤の酸化反応によって水素イオン濃度が増大し、金属塩の還元反応の速度が低下し、金属微粒子の析出が遅くなる。
【００１８】
金属コロイド溶液調製用母液のｐＨが１０を越える場合は、金属塩の還元反応速度が増大して金属微粒子の凝集物が生成したり、あるいは金属の水酸化物の沈殿が生成しやくなることがある。
金属コロイド溶液調製用母液には、必要に応じてｐＨ緩衝剤が添加されていてもよい。ｐＨ緩衝剤を用いると金属の還元析出速度を一定にすることができるので金属コロイド微粒子が凝集することもなく、また粒子径をより均一に調整することができる。
【００１９】
このような緩衝剤としては、例えば酢酸、クエン酸、プロピオン酸、乳酸などの有機酸および有機酸塩が挙げられる。中でもクエン酸ナトリウム、酢酸ナトリウムなどの有機酸塩は好適に用いることができる。
このときの緩衝剤の使用量は、金属塩（Ａ）を金属に換算した重量の０．５〜３０重量％、さらには１〜２０重量％の範囲にあることが好ましい。
【００２０】
緩衝剤の添加量が、金属塩（Ａ）を金属に換算したときの重量の０．５重量％未満の場合は、緩衝作用が小さく金属コロイド溶液調製用母液ｐＨが変動することがあり金属微粒子が凝集物したり、粒子径が不均一になる傾向がある。また緩衝剤の添加量が、金属塩（Ａ）を金属に換算した重量の３０重量％を越えても緩衝効果はなんら向上しない。
【００２１】
(b) 金属コロイド溶液調製用母液の温度調整
次ぎに、金属コロイド溶液調製用母液を１０〜９５℃、好ましくは３０〜９０℃に調整する。
金属コロイド溶液調製用母液の温度が１０℃未満の場合は、温度が低すぎて金属の還元析出速度が遅くなることがあり、金属コロイド溶液調製用母液の温度が９５℃を越えると金属の還元析出速度が早すぎて、後述する標準水素電極電位が−０.２０〜＋１.５０ｅＶの範囲にある金属の塩（Ｂ）を添加する前に金属微粒子が析出し、このような金属微粒子は凝集したり、粒子径が不均一となることがある。
【００２２】
(c) 標準水素電極電位が−０ . ２０〜＋１ . ５０ｅＶの範囲にある金属の塩の添加
本発明では、上記金属コロイド溶液調製用母液に、標準水素電極電位が−０.２０〜＋１.５０ｅＶの範囲に金属の塩（Ｂ）を添加する。
本発明で用いる金属塩（Ｂ）としては、標準水素電極電位が−０.２０〜＋１.５０ｅＶ、好ましくは−０.１４〜＋１.２０eVの範囲にある金属の塩が望ましく、具体的には、Ｐt、Ｐd、Ｓn等の金属の塩化物、硝酸塩、硫酸塩、リン酸塩、炭酸塩などの無機酸塩、有機酸塩、錯塩などが挙げられる。これらの塩は１種単独でも、または２種以上混合して使用される。このような金属塩（Ｂ）としては、具体的に、塩化パラジウム、硝酸パラジウム、酢酸パラジウム、テトラクロロパラジウム酸ナトリウム、テトラクロロパラジウム酸アンモニウムなど各種パラジュウム化合物、塩化白金酸、塩化白金ナトリウム、ヘキサクロロ白金酸二アンモニウム、ヘキサクロロ白金酸二ナトリウムなど各種白金化合物、塩化スズ、スズ酸カリウム、蓚酸スズなど金属化合物が挙げられる。
【００２３】
このような金属塩（Ｂ）は前記金属塩（Ａ）を構成する金属の標準水素電極電位よりも高いために容易に還元され、金属微粒子として析出しやすい。このため、このような金属塩（Ｂ）の還元によって生成した金属微粒子が核粒子（種粒子）として作用し、引き続き金属塩（Ａ）が還元されて核粒子表面上に析出して単分散した金属コロイド微粒子か分散したコロイド溶液が得られる。金属塩（Ｂ）と金属塩（Ａ）とを構成する金属の標準水素電極電位の差は、特に制限されるものではないが、通常０.０４〜１.８ｅＶ、好ましくは０.２５〜１.２４ｅＶの範囲あることが好ましい。
【００２４】
このときの金属塩（Ｂ）の添加量は、金属に換算したときの重量（ＷB）と、金属塩（Ａ）を金属に換算したときの重量（ＷA）との重量比（ＷB／ＷA）が０.０００５〜０．２０、好ましくは０.００１〜０．１０の範囲にあることが望ましい。
ＷB／ＷAが０.０００５未満の場合は、核粒子の数が少ないために金属の析出が遅く、すなわち粒子の生成速度が長時間を要したり、得られる金属コロイド微粒子の粒子径が不均一になったり、粒子が凝集する傾向がある。ＷB／ＷAが０．２０を越えると、得られる金属コロイド微粒子は核粒子成分の割合が高いために所望の金属の特性（触媒特性や導電性等の金属特性）を発現しないことがある。
【００２５】
(d) 還元剤の添加
次ぎに、本発明では、金属コロイド溶液調製用母液に、還元剤を添加して、金属塩を還元する。
還元剤としては、次亜燐酸ナトリウム、水素化ホウ素ナトリウム、アルコール類、ヒドラジン、ホルムアルデヒド、ジメチルアミンボランなどが挙げられ、特に次亜燐酸ナトリウム、水素化ホウ素ナトリウム、ホルマリンが好ましい。これらは単独で使用してもよく、また２種以上混合して使用しても良い。
【００２６】
還元剤を添加することで、まず金属塩（Ｂ）が還元され、金属微粒子として析出し、生成した金属微粒子が核粒子（種粒子）として作用し、引き続き金属塩（Ａ）が還元されて核金属微粒子表面上に析出して単分散した金属コロイド微粒子が得られる。
還元剤の添加量としては、核金属粒子の種類や還元剤の還元力などによっても異なるが、金属塩（Ａ）および（Ｂ）を構成する金属の合計１モルに対し還元剤が０.１〜５モル、好ましくは０.５〜４モルの範囲にあることが好ましい。
【００２７】
還元剤の量が５モルを越えても還元速度がさらに速くなることもなく、還元剤の量が０.１モル未満の場合は、還元剤の量が少ないため、金属微粒子の析出が不充分となり、収率が低下するので好ましくない。
(e) 熟成処理
前記還元剤を添加したのち、金属コロイド溶液は、必要に応じて熟成してもよい。
【００２８】
熟成は、溶液の温度が５０〜１５０℃、好ましくは８〜１２０℃の温度で行うことが望ましい。また、熟成時間は、熟成温度によっても異なるが０.５〜１０時間、好ましくは１〜５時間の範囲にあることが望ましい。このような条件で熟成を行うことにより粒子径が均一で、安定な金属コロイド溶液を得ることができる。
前記熟成を行った金属コロイド溶液は用途によってはそのまま用いることもできるが、必要に応じて、洗浄および／または濃縮することが好ましい。
【００２９】
洗浄方法としては、金属コロイド溶液の安定性や収率を損なうことなく前記各添加剤に起因して随伴する不純物を除去できれば特に制限はなく、従来公知の方法を採用することができる。例えば、限外濾過膜を使用する方法、イオン交換樹脂を使用する方法、あるいはこれらの方法を組み合わせて洗浄する方法も好適に採用することができる。
【００３０】
また、濃縮する方法としては限外濾過膜を使用する方法、ロータリーエバポレーターを使用する方法等が挙げられる。また、濃縮時に、所望の溶媒に置換することもできる。
本発明における上記各工程は、少なくとも１部の工程を、非酸化雰囲気下で行うことが好ましい。具体的には、窒素、アルゴン、ヘリウムなどの不活性ガス雰囲気下で行うことが好ましい。酸化雰囲気下（たとえば酸素存在下）で上記工程を行うと金属コロイド溶液中の金属コロイド微粒子が酸化され、充分な触媒特性や導電性等の金属特性を発現しないことがある。
【００３１】
以上のような本発明に係る製造方法で得られた金属コロイド溶液は、標準水素電極電位が−０.２０〜＋１.５０ｅＶの範囲にある金属からなる核微粒子の表面に、前記核微粒子より標準水素電極電位が高く、かつ標準水素電極電位が−０.８０〜＋１.２０ｅＶの範囲にある金属が析出した複合金属微粒子が分散したコロイド溶液である。
【００３２】
このような金属コロイド溶液中の金属コロイド微粒子は単分散しており平均粒子径が３〜２００ｎｍの範囲にある。また、この金属コロイド微粒子は、平均粒子径±２０％の範囲内にある金属コロイド微粒子の割合が８０重量％以上であるので、粒径分布が狭く、大きさが揃っている。
なお、金属コロイド微粒子の平均粒子径、粒度分布は、マイクロトラック粒度分析計（日機装（株）製：ＵＰＡ９３４０）を用いて測定することができる。
【００３３】
【発明の効果】
本発明の金属コロイド溶液の製造方法は、標準水素電極電位が高い金属の塩（Ｂ）を用いて核粒子を形成させて、ついで標準水素電極電位が低い金属の塩（Ａ）を還元しての単分散金属コロイド溶液を調製しているので、極めて安定性の高い金属コロイド溶液を得ることができる。また得られた金属コロイド微粒子の粒子径も均一である。
【００３４】
得られる金属コロイド溶液は、各種触媒の他、各種回路素子、低抗体、コンデンサー、インダクター、相互配線導体、導電体用ペーストおよびこれを用いて得られる厚膜材料、機能素子、電磁波シールド、導電性接着剤、導電性フイラー、導電性塗料、磁性材料、磁気記録用材料、磁性流体材料、電極材料、電池材料など種々の用途に適用することができる。
【００３５】
【実施例】
以下、本発明を実施例により、さらに詳細に説明するが、本発明はこれらの実施に何ら限定されるものではない。
【００３６】
【実施例１】
金属塩（Ａ）として塩化ニッケル六水和物１５ｇおよび安定化剤として濃度２５重量％のゼラチン水溶液３.０ｇを、容量３Ｌの容器に秤量した。ついで、該容器に蒸留水５００ｇを加え、金属塩およびゼラチンを溶解して金属コロイド溶液調製用母液を調製したのち、窒素ガスを封入しながら４０℃に加温した。ついで、金属塩（Ｂ）として、Ｐｄ金属に換算したときの濃度が８.９７重量％のジクロロテトラアンミンパラジウムを１.０ｇ添加した。
【００３７】
均一に攪拌混合した後、還元剤としてホスフイン酸ナトリウム１水和物（化学式：ＮaＰＨ2Ｏ2・Ｈ2Ｏ）１０ｇ（０．０９モル／０．０６モル-生成金属微粒子）を添加して、金属コロイド溶液を調製した。ついで、限外濾過膜を使用し、金属重量に対し３００倍の蒸留水で洗浄し、濃縮して濃度３.０重量％の金属コロイド溶液（Ａ）を得た。
【００３８】
得られた金属コロイド溶液（Ａ）を還流器付きフラスコに入れ、８０℃、２時間熟成した。その後、金属コロイド微粒子の平均粒子径および粒子径の均一性（平均粒子径±２０重量％に含まれている粒子の量）を測定した。なお、平均粒子径および粒子径の均一性は、平均粒子径の±２０％に含まれている微粒子の重量％をマイクロトラック粒度分析計（日機装（株）製：UPA9340）で測定することによって評価した。
【００３９】
結果を表１に示す。
また、得られた金属コロイド溶液の分散安定性は、上記金属コロイド溶液調製後室温で放置した試料を１ヶ月間目視で観察し、以下の基準により評価した。
沈降物が全く認められず ：○
沈降物が僅かに認めらる ：△
沈降物が多量に認められる ：×
結果を表１に示す。
【００４０】
【実施例２】
金属塩（Ａ）として塩化ニッケル六水和物７．５ｇ、および安定化剤としてＰＶＰ(ポリビニールピロリドン)２．５ｇを、容量３Ｌの容器に秤量した。ついで、該容器に、蒸留水５００ｇを加え金属コロイド溶液調製用母液を調製し、窒素ガスを封入しながら４０℃に加温した。ついで、金属塩（B）として、Ｐｄ金属に換算したときの濃度が８.９７重量％のジクロロテトラアンミンパラジウムを０．５ｇ添加した。均一に攪拌混合した後、還元剤として水素化ホウ素ナトリウム（ＮaＢＨ4）を３.０ｇ（０．０８モル／０．０３モル-生成金属微粒子）添加してコロイド溶液を調製した。ついで、限外濾過膜を使用し、金属重量分に対し３００倍の蒸留水で洗浄し、濃縮して濃度３．５重量％の金属コロイド溶液（Ｂ）を得た。得られた金属コロイド溶液を還流器付きフラスコに入れ、８０℃、２時間熟成した。熟成後、金属コロイド溶液中の金属コロイド微粒子の平均粒子径、粒子径の均一性および分散安定性を測定した。
【００４１】
結果を表１に示す。
【００４２】
【実施例３】
金属塩（Ａ）として塩化ニッケル六水和物２４ｇと塩化銅二水和物４ｇ、および安定化剤としてＰＶＰ(ポリビニールピロリドン)１０．０ｇを、容量４Ｌの容器に秤量した。ついで該容器に、蒸留水５６０ｇを加え金属コロイド溶液調製用母液を調製し、窒素ガスを封入しながら４０℃に加温した。ついで、金属塩（Ｂ）としてＰｄ金属に換算したときの濃度が８.９７重量％のジクロロテトラアンミンパラジウムを２．０ｇ添加した。
【００４３】
均一に攪拌混合した後、還元剤として２重量％の水素化ホウ素ナトリウム（ＮaＢＨ4）水溶液４４０ｇ（０．２３モル／０．１２モル-生成金属微粒子）を７．３ｇ/分の速度で添加して金属コロイド溶液を調製した。ついで、限外濾過膜を使用し、金属重量分に対し３００倍の蒸留水で洗浄したのち、濃縮して濃度３．０重量％の金属コロイド溶液（Ｃ）を得た。
【００４４】
得られた金属コロイド溶液（Ｃ）を還流器付きフラスコに入れ、８０℃、２時間熟成した。熟成後、金属コロイド溶液中の金属コロイド微粒子の平均粒子径、粒子径の均一性および分散安定性を測定した。
結果を表１に示す。
【００４５】
【実施例４】
金属塩（Ａ）として塩化ルテニウム三水和物５．１ｇと、安定化剤としてクエン酸三ナトリウム二水和物５．０ｇと、ＰＶＰ(ポリビニールピロリドン)３ｇとを容量３Ｌの容器に秤量した。ついで該容器に、蒸留水１７５ｇを加え金属コロイド溶液調製用母液を調製し、窒素ガスを封入しながら４０℃に加温した。ついで、核形成用金属塩（Ｂ）としてＰｄ金属に換算したときの濃度が８.９７重量％のジクロロテトラアンミンパラジウムを１．０ｇ添加した。均一に攪拌混合した後、還元剤として１重量％の水素化ホウ素ナトリウム（ＮaＢＨ4）水溶液２２５ｇ（０．０２モル／０．０２モル-生成金属微粒子）を、７．３ｇ/分の速度で添加して金属コロイド溶液を調製した。ついで、限外濾過膜を使用し、金属重量分に対し３００倍の蒸留水で洗浄・濃縮して、濃度２．８重量％の金属コロイド溶液（Ｄ）を得た。
【００４６】
得られた金属コロイド溶液（Ｄ）を還流器付きフラスコに入れ、８０℃、２時間熟成した。金属コロイド溶液中の金属コロイド粒子の平均粒子径、粒子径の均一性および分散安定性を測定した。
結果を表１に示す。
【００４７】
【比較例１】
金属塩（Ａ）として塩化ニッケル六水和物１５ｇを、容量３Ｌの容器に秤量した。ついで該容器に、蒸留水５００ｇを加え金属コロイド溶液調製用母液を調製し、窒素ガスで封入しながら４０℃に加温した。ついで、金属塩（Ｂ）としてＰｄ金属に換算したときの濃度が８.９７重量％のジクロロテトラアンミンパラジウムを１．０ｇ添加した。
【００４８】
均一に攪拌混合した後、還元剤としてホスフィン酸ナトリウム１水和物（化学式：ＮaＰＨ2Ｏ2・Ｈ2Ｏ）１０ｇ（０．０９モル／０．０６モル-生成金属微粒子）を添加してニッケル金属微粒子の分散液（Ｅ）を調製した。得られたニッケル金属微粒子（Ｅ）は還元剤を添加した直後から凝集して沈降してしまい、平均粒子径、均一性は評価できなっかた。
【００４９】
【比較例２】
金属塩（Ａ）として塩化ニッケル六水和物１５ｇおよび安定化剤として濃度２５重量％のゼラチン水溶液３．０ｇを、容量３Ｌの容器に秤量した。ついで蒸留水５００ｇを加え金属コロイド溶液調製用母液を調製し、窒素ガスを封入しながら４０℃に加温した。均一に攪拌混合した後、還元剤としてホスフイン酸ナトリウム１水和物（化学式：ＮaＰＨ2Ｏ2・Ｈ2Ｏ）１０ｇ（０．０９モル／０．０６モル-生成金属微粒子）を添加して、濃度０.７重量％のニッケル金属微粒子の分散液（Ｆ）を調製した。ニッケル金属微粒子（Ｆ）の収率は約４０％と低く、得られたニッケル金属微粒子は凝集して沈降してしまい、平均粒子径および均一性は評価できなかった。
【００５０】
【表１】
BACKGROUND OF THE INVENTION
The present invention relates to a novel method for producing a metal colloid. More specifically, the present invention relates to a method capable of easily producing a solution having a uniform particle size distribution and monodispersed metal colloidal fine particles.
[0002]
TECHNICAL BACKGROUND OF THE INVENTION
Conventionally, metal fine particles have been used as functional materials in the fields of catalysts and electronic devices because of their particle size effect, high surface area effect, quantum effect, and the like. For example, it is known that nickel boride colloidal fine particles are supported on a carrier and used as a hydrogenation catalyst (Kaiyama et al., Journal of the Chemical Society of Japan, 1984 (6), p. 1005-1010). In addition, metal fine particles are used in the field of electronic equipment and the like for preventing charging of the surface of a display device such as a cathode ray tube and shielding electromagnetic waves.
[0003]
As a method for producing such metal fine particles, Okuyama, Seto et al., Chemical Engineering, P22-27, (1993) discloses a method for producing ultrafine particles by a gas phase process.
In addition to the dry method described above, the applicant of the present invention disclosed in JP-A-10-188681 a method for reducing a metal salt or a metal salt in an alcohol / water mixed solvent, and metal fine particles or alloys. A method in which metal fine particles or ions having a higher standard hydrogen electrode potential than metal fine particles or alloy fine particles are present in the fine particle dispersion to deposit a metal having a higher standard hydrogen electrode potential on the metal fine particles or / and alloy fine particles ( Wet method).
[0004]
In addition, the 70th Symposium of the Symposium of the Annual Meeting of the Japan Institute of Metals (1997) includes noble metal ions (Ag + , Au 3+ , Pd 2+ , Pt 2+ , Pt 4+ etc.) Proposed the ultrasonic irradiation direct reduction method that prepares metal fine particles by irradiating a solution to which an organic compound such as a surfactant is added with an ultrasonic wave in an inert gas atmosphere at, for example, 200 kHz and 6 W / cm 2. Has been.
[0005]
However, the metal fine particles obtained by the dry method are easy to aggregate, and even when dispersed in a dispersion medium, it is difficult to obtain a stable colloid, and the particle size of the metal fine particles is difficult to adjust and is not uniform.
In addition, in the wet method and the direct reduction method with ultrasonic irradiation, there are some metal components that are difficult to be formed into particles, and even if metal particles are obtained by forming into particles, the stability is not always sufficient, and the particle size is adjusted. There are problems such as being difficult and non-uniform.
[0006]
OBJECT OF THE INVENTION
It is an object of the present invention to provide a method for producing a metal colloid solution that can easily obtain a stable metal colloid solution and that can easily control the particle size.
[0007]
Summary of the Invention
The method for producing a metal colloid solution according to the present invention includes:
(a) A metal salt (A) having a standard hydrogen electrode potential in the range of −0.80 to +1.20 eV, a stabilizer, and a solvent are mixed to prepare a mother colloid solution for preparing a metal colloid solution,
(b) adjusting the metal colloid solution preparation mother liquor to a temperature of 10 to 95 ° C,
(c) The standard hydrogen electrode potential in the metal colloid solution preparing mother liquor is in the range of −0.20 to +1.50 eV, and the standard hydrogen electrode potential is higher than the metal constituting the metal salt (A). After adding the metal salt (B)
(d) It is characterized by adding a reducing agent to reduce the metal salts (A) and (B).
[0008]
In the production method according to the present invention, it is desirable that (e) the obtained metal colloid solution is further aged at a temperature in the range of 50 to 150 ° C.
The steps (a) to (d) or (a) to (e) are preferably performed in a non-oxidizing atmosphere.
The metal salt (A) having a standard hydrogen electrode potential in the range of −0.80 to +1.20 eV is made of one or more metals selected from the group consisting of Au, Ag, Cu, Ni, Co, Fe, and Ru. Salt,
A metal salt (B) having a standard hydrogen electrode potential in the range of −0.20 to +1.50 eV and having a standard hydrogen electrode potential higher than the metal constituting the metal salt (A) is Pt, Pd, It is preferably a salt of one or more metals selected from the group consisting of Sn.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described. In the present invention, the metal colloid solution is a solution in which metal colloidal fine particles are dispersed.
(a) Preparation of mother liquid for preparing metal colloid solution In the present invention, first, a metal salt (A) having a standard hydrogen electrode potential in the range of -0.80 to +1.20 eV, a stabilizer, and A mother liquor for preparing a colloidal metal solution is prepared by mixing the solvent.
[0010]
As the metal salt (A) used in the present invention, it is preferable to use a metal salt having a standard hydrogen electrode potential in the range of −0.80 to +1.20 eV, preferably −0.60 to +1.11 eV. Specifically, inorganic acid salts such as chlorides, nitrates, sulfates, phosphates and carbonates of one or more metals selected from the group consisting of Au, Ag, Ni, Cu, Fe, Co and Ru, Organic acid salt etc. are mentioned. Further, as the metal salt (A), hexaamine nickel chloride ((Ni (NH 3 ) 6 ) Cl 2 ), tetraamine copper sulfate ((Cu (NH 3 ) 4 ) SO 4 .H 2 O), hexaamine Complex salts such as ruthenium chloride ((Ru (NH 3 ) 6 ) Cl 2 ) can also be used. These salts may be used alone or in combination of two or more.
[0011]
Such a metal salt is preferably used so as to be in the range of 0.1 to 10% by weight, preferably 0.5 to 5% by weight, in terms of metal, in the mother liquid for preparing the metal colloid solution.
When the amount of metal salt used is less than 0.1% by weight in terms of metal in the mother colloid solution preparation, the metal salt concentration is too low and the production efficiency is low. When converted to metal and exceeds 10% by weight in the metal colloid solution preparation mother liquor, the monodispersity of the resulting metal colloidal fine particles is lowered and the particle size tends to be non-uniform.
[0012]
Stabilizers include organic acids such as formic acid, citric acid, phthalic acid, malic acid, malonic acid and polycarboxylic acid, and hydrophilic polymers such as gelatin, gum arabic, polyvinyl alcohol, polyvinyl pyrrolidone and polymethyl vinyl ether. , And surfactants such as sodium dodecylbenzenesulfonate and sodium laurate, for example, surfactants such as Despound (trade name of Toho Chemical Industry Co., Ltd.) are used. Of these, gelatin, polyvinyl pyrrolidone, and a despont surfactant are preferable.
[0013]
Such a stabilizer is adsorbed on the surface of the generated metal colloidal fine particles and suppresses aggregation of the hydrophobic metal colloidal fine particles in a dispersion medium such as water. For this reason, the metal colloid solution excellent in dispersion stability can be obtained.
The stabilizer is 0.1 to 0.1 of the weight of the final metal colloid fine particles in the mother liquid for preparing the metal colloid solution (that is, the total weight of the metal salt (A) and the metal salt (B) described later converted to metal). It is preferably used so as to be in the range of 10 times by weight, preferably 0.2 to 5 times by weight.
[0014]
When the amount of the stabilizer used is less than 0.1 times the weight of the final metal colloid particles in the mother liquid for preparing the metal colloid solution, the amount of the stabilizer is too dilute and the metal colloid particles are monodispersed. It is difficult to obtain a metal colloid, and even if it is obtained, the metal colloid is not stable and easily aggregates. If the amount of the stabilizer used exceeds 10 times the final weight of the metal colloidal fine particles in the metal colloid solution preparation mother liquor, the concentration of the stabilizer is too high and the viscosity of the solution increases, Since the colloidal fine particles are covered with a stabilizer, when used as a catalyst, the catalytic activity may not be sufficiently developed or the conductivity may not be sufficiently developed.
[0015]
As the solvent used in the present invention, the metal salt (A) and the stabilizer in which the standard hydrogen electrode potential is in the range of −0.80 to +1.20 eV, the standard hydrogen electrode potential described later is −0.20 to There is no particular limitation as long as it can dissolve the metal salt (B) and the reducing agent in the range of +1.50 eV, and a conventionally known solvent can be used.
[0016]
Specifically, water; alcohols such as methanol, ethanol, propanol, butanol, diacetone alcohol, furfuryl alcohol, tetrahydrofurfuryl alcohol, ethylene glycol and hexylene glycol; esters such as acetic acid methyl ester and acetic acid ethyl ester Ethers such as diethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether and diethylene glycol monoethyl ether; ketones such as acetone, methyl ethyl ketone, acetylacetone and acetoacetate . These may be used singly or in combination of two or more. Of these, polar solvents such as water and alcohols are preferable because the metal salts (A) and (B), the stabilizer and the reducing agent can be easily dissolved.
[0017]
The above metal salt (A), stabilizer and solvent are mixed by a known method. The mixing method is not particularly limited, and examples thereof include known methods such as a mixer and a stirrer. It is desirable that the pH of the metal colloid solution preparing mother liquor obtained by mixing is in the range of 3 to 10, preferably 4 to 9.
When the pH of the mother liquor for preparing the metal colloid solution is less than 3, the hydrogen ion concentration increases due to the oxidation reaction of the reducing agent, the reduction rate of the metal salt reduction reaction decreases, and the precipitation of the metal fine particles becomes slow.
[0018]
When the pH of the mother colloid solution for metal colloid solution preparation exceeds 10, the reduction reaction rate of the metal salt is increased, and aggregates of metal fine particles are formed, or precipitation of metal hydroxide is likely to be generated. is there.
A pH buffering agent may be added to the metal colloid solution preparing mother liquor as necessary. When a pH buffer is used, the metal reduction deposition rate can be made constant, so that the metal colloidal fine particles do not aggregate and the particle diameter can be adjusted more uniformly.
[0019]
Examples of such buffering agents include organic acids and organic acid salts such as acetic acid, citric acid, propionic acid, and lactic acid. Of these, organic acid salts such as sodium citrate and sodium acetate can be preferably used.
The amount of the buffer used at this time is preferably in the range of 0.5 to 30% by weight, more preferably 1 to 20% by weight of the weight of the metal salt (A) converted to metal.
[0020]
When the added amount of the buffering agent is less than 0.5% by weight of the metal salt (A) converted to metal, the buffering action is small and the pH of the mother colloid solution preparation may fluctuate. Tend to agglomerate and the particle size tends to be non-uniform. Moreover, even if the addition amount of a buffering agent exceeds 30 weight% of the weight which converted metal salt (A) into the metal, a buffering effect will not improve at all.
[0021]
(b) Temperature adjustment of the metal colloid solution preparing mother liquor Next, the metal colloid solution preparing mother liquor is adjusted to 10 to 95C, preferably 30 to 90C.
If the temperature of the mother liquid for preparing the metal colloidal solution is less than 10 ° C, the temperature may be too low and the reduction rate of the metal may be reduced. If the temperature of the mother liquor for preparing the metal colloidal solution exceeds 95 ° C, the reduction of the metal Precipitation rate is too fast, and metal fine particles are precipitated before adding a metal salt (B) having a standard hydrogen electrode potential in the range of −0.20 to +1.50 eV, which will be described later. Or the particle size may be non-uniform.
[0022]
(c) the standard hydrogen electrode potential -0. In 20 + 1. metal additives <br/> present invention salts in the range of 50 eV, the above-mentioned metal colloid solution prepared for mother liquor, the standard hydrogen electrode potential -0. The metal salt (B) is added in the range of 20 to +1.50 eV.
The metal salt (B) used in the present invention is desirably a metal salt having a standard hydrogen electrode potential in the range of −0.20 to +1.50 eV, preferably −0.14 to +1.20 eV. Inorganic acid salts such as chlorides, nitrates, sulfates, phosphates, carbonates, organic acid salts, complex salts, and the like of metals such as Pt, Pd, and Sn. These salts may be used alone or in combination of two or more. Specific examples of such a metal salt (B) include various palladium compounds such as palladium chloride, palladium nitrate, palladium acetate, sodium tetrachloropalladate, ammonium tetrachloropalladate, chloroplatinic acid, sodium platinum chloride, hexachloroplatinum. Examples include various platinum compounds such as diammonium acid and disodium hexachloroplatinate, and metal compounds such as tin chloride, potassium stannate, and tin oxalate.
[0023]
Since such a metal salt (B) is higher than the standard hydrogen electrode potential of the metal constituting the metal salt (A), it is easily reduced and easily precipitated as metal fine particles. For this reason, the metal fine particles generated by the reduction of the metal salt (B) act as core particles (seed particles), and the metal salt (A) is subsequently reduced and deposited on the surface of the core particles and monodispersed. A colloidal solution in which metal colloidal fine particles are dispersed is obtained. The difference in the standard hydrogen electrode potential of the metal constituting the metal salt (B) and the metal salt (A) is not particularly limited, but is usually 0.04 to 1.8 eV, preferably 0.25-1. A range of .24 eV is preferred.
[0024]
The addition amount of the metal salt of this case (B), the weight ratio of the weight (W B) when converted to the metal, the weight (W A) of when the metal salt (A) in terms of metal (W B / W A ) is in the range of 0.0005 to 0.20, preferably 0.001 to 0.10.
When W B / W A is less than 0.0005, the number of core particles is small, so that the precipitation of the metal is slow, that is, the generation rate of the particles takes a long time, or the particle size of the obtained metal colloidal fine particles is There is a tendency to become non-uniform and to aggregate the particles. When W B / W A exceeds 0.20, the resulting metal colloidal fine particles may not exhibit desired metal characteristics (catalytic characteristics, metal characteristics such as conductivity) due to a high ratio of the core particle component. .
[0025]
(d) Addition of reducing agent Next, in the present invention, the reducing agent is added to the mother liquor for preparing the metal colloid solution to reduce the metal salt.
Examples of the reducing agent include sodium hypophosphite, sodium borohydride, alcohols, hydrazine, formaldehyde, dimethylamine borane and the like, and sodium hypophosphite, sodium borohydride, and formalin are particularly preferable. These may be used singly or in combination of two or more.
[0026]
By adding a reducing agent, the metal salt (B) is first reduced and precipitated as metal fine particles, and the generated metal fine particles act as nucleus particles (seed particles), and subsequently the metal salt (A) is reduced to form nuclei. Metal colloidal fine particles that are monodispersed by depositing on the surface of the metal fine particles are obtained.
The amount of the reducing agent added varies depending on the kind of the core metal particles and the reducing power of the reducing agent, but the reducing agent is 0.1 per 1 mol in total of the metals constituting the metal salts (A) and (B). It is preferable to be in the range of -5 mol, preferably 0.5-4 mol.
[0027]
Even if the amount of the reducing agent exceeds 5 mol, the reduction rate is not further increased, and when the amount of the reducing agent is less than 0.1 mol, the amount of the reducing agent is small and the metal fine particles are not sufficiently precipitated. This is not preferable because the yield decreases.
(e) Aging treatment After adding the reducing agent, the metal colloid solution may be aged if necessary.
[0028]
The aging is desirably performed at a temperature of the solution of 50 to 150 ° C, preferably 8 to 120 ° C. Further, the aging time varies depending on the aging temperature, but it is desirably 0.5 to 10 hours, preferably 1 to 5 hours. By aging under such conditions, a stable metal colloid solution having a uniform particle diameter can be obtained.
The aged colloidal metal solution can be used as it is depending on the application, but it is preferable to wash and / or concentrate as necessary.
[0029]
The cleaning method is not particularly limited as long as impurities accompanying the additives can be removed without impairing the stability and yield of the metal colloid solution, and a conventionally known method can be employed. For example, a method using an ultrafiltration membrane, a method using an ion exchange resin, or a method of washing by combining these methods can be suitably employed.
[0030]
Examples of the concentration method include a method using an ultrafiltration membrane and a method using a rotary evaporator. In addition, a desired solvent can be substituted during the concentration.
In each of the steps in the present invention, it is preferable to perform at least one part of the step in a non-oxidizing atmosphere. Specifically, it is preferable to carry out in an inert gas atmosphere such as nitrogen, argon or helium. When the above process is performed in an oxidizing atmosphere (for example, in the presence of oxygen), the metal colloidal fine particles in the metal colloid solution may be oxidized, and metal characteristics such as sufficient catalytic properties and conductivity may not be exhibited.
[0031]
The colloidal metal solution obtained by the production method according to the present invention as described above is more standard than the nuclear fine particles on the surface of the core fine particles made of metal having a standard hydrogen electrode potential in the range of −0.20 to +1.50 eV. This is a colloidal solution in which composite metal fine particles in which metal having a high hydrogen electrode potential and a standard hydrogen electrode potential in the range of −0.80 to +1.20 eV are dispersed are dispersed.
[0032]
The metal colloidal fine particles in such a metal colloid solution are monodispersed and have an average particle diameter in the range of 3 to 200 nm. Further, since the proportion of the metal colloidal fine particles within the range of the average particle size ± 20% is 80% by weight or more, the metal colloidal fine particles have a narrow particle size distribution and uniform sizes.
The average particle size and particle size distribution of the metal colloidal fine particles can be measured using a Microtrac particle size analyzer (manufactured by Nikkiso Co., Ltd .: UPA9340).
[0033]
【The invention's effect】
In the method for producing a metal colloid solution of the present invention, a core particle is formed using a metal salt (B) having a high standard hydrogen electrode potential, and then a metal salt (A) having a low standard hydrogen electrode potential is reduced. Since a monodispersed metal colloid solution is prepared, a highly stable metal colloid solution can be obtained. The obtained metal colloidal fine particles have a uniform particle size.
[0034]
In addition to various catalysts, the resulting colloidal metal solution includes various circuit elements, low antibodies, capacitors, inductors, interconnectors, conductor pastes and thick film materials, functional elements, electromagnetic wave shields, and electrical conductivity obtained using these. The present invention can be applied to various uses such as adhesives, conductive fillers, conductive paints, magnetic materials, magnetic recording materials, magnetic fluid materials, electrode materials, and battery materials.
[0035]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these implementations at all.
[0036]
[Example 1]
15 g of nickel chloride hexahydrate as a metal salt (A) and 3.0 g of a gelatin aqueous solution having a concentration of 25% by weight as a stabilizer were weighed in a 3 L container. Next, 500 g of distilled water was added to the container to dissolve the metal salt and gelatin to prepare a mother liquor for preparing a metal colloid solution, and then heated to 40 ° C. while sealing with nitrogen gas. Subsequently, 1.0 g of dichlorotetraammine palladium having a concentration of 8.97 wt% when converted to Pd metal was added as the metal salt (B).
[0037]
After stirring and mixing uniformly, sodium phosphinate monohydrate (chemical formula: NaPH 2 O 2 .H 2 O) 10 g (0.09 mol / 0.06 mol-generated metal fine particles) was added as a reducing agent, A metal colloid solution was prepared. Subsequently, an ultrafiltration membrane was used, washed with distilled water 300 times the metal weight, and concentrated to obtain a metal colloid solution (A) having a concentration of 3.0% by weight.
[0038]
The obtained metal colloid solution (A) was placed in a flask equipped with a reflux condenser and aged at 80 ° C. for 2 hours. Thereafter, the average particle size of the metal colloidal fine particles and the uniformity of the particle size (the amount of particles contained in the average particle size ± 20% by weight) were measured. The average particle size and the uniformity of the particle size are evaluated by measuring the weight percentage of fine particles contained in ± 20% of the average particle size with a Microtrac particle size analyzer (manufactured by Nikkiso Co., Ltd .: UPA9340). did.
[0039]
The results are shown in Table 1.
The dispersion stability of the obtained metal colloid solution was evaluated by visually observing a sample left at room temperature after preparation of the metal colloid solution for one month and by the following criteria.
No sediment was observed: ○
Sediment is slightly observed: △
A large amount of sediment is observed: ×
The results are shown in Table 1.
[0040]
[Example 2]
7.5 g of nickel chloride hexahydrate as a metal salt (A) and 2.5 g of PVP (polyvinylpyrrolidone) as a stabilizer were weighed in a 3 L container. Next, 500 g of distilled water was added to the vessel to prepare a mother colloid solution for preparing a metal colloid solution, which was heated to 40 ° C. while nitrogen gas was sealed. Subsequently, 0.5 g of dichlorotetraammine palladium having a concentration of 8.97 wt% when converted to Pd metal was added as the metal salt (B). After stirring and mixing uniformly, 3.0 g (0.08 mol / 0.03 mol-generated metal fine particles) of sodium borohydride (NaBH 4 ) was added as a reducing agent to prepare a colloidal solution. Next, an ultrafiltration membrane was used, washed with distilled water 300 times the metal weight, and concentrated to obtain a metal colloid solution (B) having a concentration of 3.5% by weight. The obtained metal colloid solution was put into a flask equipped with a reflux condenser and aged at 80 ° C. for 2 hours. After aging, the average particle size, uniformity of particle size and dispersion stability of the metal colloid fine particles in the metal colloid solution were measured.
[0041]
The results are shown in Table 1.
[0042]
[Example 3]
24 g of nickel chloride hexahydrate and 4 g of copper chloride dihydrate as the metal salt (A) and 10.0 g of PVP (polyvinylpyrrolidone) as the stabilizer were weighed in a 4 L container. Next, 560 g of distilled water was added to the container to prepare a mother colloid solution for preparing a metal colloid solution, and the mixture was heated to 40 ° C. while nitrogen gas was sealed. Subsequently, 2.0 g of dichlorotetraammine palladium having a concentration of 8.97 wt% when converted to Pd metal as the metal salt (B) was added.
[0043]
After uniformly stirring and mixing, 440 g (0.23 mol / 0.12 mol-generated metal fine particles) of a 2 wt% sodium borohydride (NaBH 4 ) aqueous solution as a reducing agent was added at a rate of 7.3 g / min. Thus, a metal colloid solution was prepared. Subsequently, an ultrafiltration membrane was used, washed with distilled water 300 times the metal weight, and concentrated to obtain a metal colloid solution (C) having a concentration of 3.0% by weight.
[0044]
The obtained metal colloid solution (C) was put into a flask equipped with a reflux condenser and aged at 80 ° C. for 2 hours. After aging, the average particle size, uniformity of particle size and dispersion stability of the metal colloid fine particles in the metal colloid solution were measured.
The results are shown in Table 1.
[0045]
[Example 4]
As a metal salt (A), 5.1 g of ruthenium chloride trihydrate, 5.0 g of trisodium citrate dihydrate as a stabilizer, and 3 g of PVP (polyvinylpyrrolidone) were weighed in a 3 L container. . Next, 175 g of distilled water was added to the vessel to prepare a mother colloid solution for preparing a metal colloid solution, and heated to 40 ° C. while nitrogen gas was sealed. Subsequently, 1.0 g of dichlorotetraammine palladium having a concentration of 8.97 wt% when converted to Pd metal as the nucleation metal salt (B) was added. After stirring and mixing uniformly, 225 g of a 1% by weight sodium borohydride (NaBH 4 ) aqueous solution as a reducing agent (0.02 mol / 0.02 mol-generated metal fine particles) was added at a rate of 7.3 g / min. Thus, a metal colloid solution was prepared. Subsequently, an ultrafiltration membrane was used and washed and concentrated with distilled water 300 times the metal weight to obtain a metal colloid solution (D) having a concentration of 2.8% by weight.
[0046]
The obtained metal colloid solution (D) was placed in a flask equipped with a reflux condenser and aged at 80 ° C. for 2 hours. The average particle size, uniformity of particle size, and dispersion stability of the metal colloid particles in the metal colloid solution were measured.
The results are shown in Table 1.
[0047]
[Comparative Example 1]
As a metal salt (A), 15 g of nickel chloride hexahydrate was weighed into a 3 L container. Next, 500 g of distilled water was added to the vessel to prepare a mother colloid solution for preparing a metal colloid solution, which was heated to 40 ° C. while being sealed with nitrogen gas. Subsequently, 1.0 g of dichlorotetraammine palladium having a concentration of 8.97 wt% when converted to Pd metal as the metal salt (B) was added.
[0048]
After stirring and mixing uniformly, sodium phosphinate monohydrate (chemical formula: NaPH 2 O 2 .H 2 O) 10 g (0.09 mol / 0.06 mol-generated metal fine particles) was added as a reducing agent, and nickel was added. A dispersion (E) of metal fine particles was prepared. The obtained nickel metal fine particles (E) aggregated and settled immediately after the addition of the reducing agent, and the average particle diameter and uniformity could not be evaluated.
[0049]
[Comparative Example 2]
15 g of nickel chloride hexahydrate as a metal salt (A) and 3.0 g of a gelatin aqueous solution having a concentration of 25% by weight as a stabilizer were weighed in a 3 L container. Next, 500 g of distilled water was added to prepare a mother liquor for preparing a metal colloid solution, and the mixture was heated to 40 ° C. while nitrogen gas was sealed. After stirring and mixing uniformly, sodium phosphinate monohydrate (chemical formula: NaPH 2 O 2 .H 2 O) 10 g (0.09 mol / 0.06 mol-generated metal fine particles) was added as a reducing agent, A dispersion (F) of nickel metal fine particles having a concentration of 0.7% by weight was prepared. The yield of nickel metal fine particles (F) was as low as about 40%, and the obtained nickel metal fine particles aggregated and settled, and the average particle diameter and uniformity could not be evaluated.
[0050]
[Table 1]
Claims (3)
(b)該金属コロイド溶液調製用母液を１０〜９５℃の温度に調整し、
(c)該金属コロイド溶液調製用母液に、標準水素電極電位が−０.２０〜＋１.５０ｅＶの範囲にあり、かつ前記金属の塩（Ａ）を構成する金属よりも標準水素電極電位が高い金属の塩（Ｂ）を、金属塩（A）と金属塩（B）とをそれぞれ金属に換算したときの重量W A 、W B とし、その重量比（W B /W A ）＝0.0005〜0.20の比率となるように添加したのち、
(d)還元剤を添加して金属塩（Ａ）および（Ｂ）を還元し、
(e)得られた金属コロイド溶液を、さらに５０〜１５０℃の範囲の温度で熟成することを特徴とする金属コロイド溶液の製造方法。(a) the standard hydrogen electrode potential metal salt in the range of -0.80~ + 1.20eV (A), a stabilizer, and solvent were mixed to prepare a metal colloid solution prepared for mother liquor, stabilizer The amount of addition of is 0.1 to 10 times the weight of the final metal colloidal fine particles (total weight of metal salt (A) and metal salt (B) converted to metal),
(b) adjusting the metal colloid solution preparation mother liquor to a temperature of 10 to 95 ° C,
(c) The metal colloid solution preparation mother liquid has a standard hydrogen electrode potential in the range of −0.20 to +1.50 eV, and has a higher standard hydrogen electrode potential than the metal constituting the metal salt (A). the metal salt (B), and a metal salt (a) and the weight when the metal salt (B) respectively in terms of metal W a, and W B, the weight ratio (W B / W a) = 0.0005~0.20 After adding so that the ratio of
(d) adding a reducing agent to reduce the metal salts (A) and (B);
(e) A method for producing a metal colloid solution, wherein the obtained metal colloid solution is further aged at a temperature in the range of 50 to 150 ° C.
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| JP2004075703A (en) * | 2002-08-09 | 2004-03-11 | Nippon Paint Co Ltd | Method of preparing metal colloidal solution and metal colloidal solution |
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| WO2006026026A2 (en) * | 2004-07-30 | 2006-03-09 | Acrymed, Inc. | Antimicrobial silver compositions |
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| CN101312800B (en) | 2005-12-08 | 2011-05-25 | 住友金属矿山株式会社 | Liquid colloidal dispersion of silver particles, coating liquid for forming silver film, manufacturing method and silver film |
| CN100457330C (en) * | 2005-12-27 | 2009-02-04 | 上海沪正纳米科技有限公司 | Nano-grained metal and preparation method thereof |
| JP5535071B2 (en) * | 2007-08-01 | 2014-07-02 | ロード コーポレイション | Non-precipitating glycol-based magnetorheological fluid |
| JP5376292B2 (en) * | 2008-11-07 | 2013-12-25 | 株式会社豊田中央研究所 | Colloidal solution of metal compound and method for producing the same |
| CN102472748A (en) * | 2009-07-29 | 2012-05-23 | 学校法人工学院大学 | Alloyed metal colloid |
| JP5874086B2 (en) * | 2012-01-20 | 2016-03-01 | 日本アトマイズ加工株式会社 | Method for producing metal nanoparticles and conductive material |
| JP6201153B2 (en) | 2014-09-11 | 2017-09-27 | 石原ケミカル株式会社 | Nickel colloidal catalyst solution for electroless nickel or nickel alloy plating and electroless nickel or nickel alloy plating method |
| JP6407850B2 (en) * | 2015-12-22 | 2018-10-17 | 石福金属興業株式会社 | Method for producing platinum powder |
| CN108031468A (en) * | 2017-10-31 | 2018-05-15 | 佛山中科先创电子科技有限公司 | The preparation method of electrochemical gas sensor catalyst |
| JP2021028308A (en) * | 2019-08-09 | 2021-02-25 | 株式会社日本触媒 | Aqueous dispersion for cosmetics, dispersion protective agent, and manufacturing method of cosmetics |
| JP6843455B1 (en) * | 2020-04-27 | 2021-03-17 | 石原ケミカル株式会社 | Nickel colloid catalyst solution for electroless nickel or nickel alloy plating and electroless nickel or nickel alloy plating method |
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