JP5285725B2 - Conductive powder - Google Patents
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本発明は、導電性粉末に関し、詳しくは、例えば、紙、プラスチック、ゴム、樹脂、塗料等に混入してこれらに導電性を付与する、酸化錫層が実質的にアンチモンを含まない導電性粉末に関するものである。 The present invention relates to a conductive Powder, particularly, for example, conductive free paper, plastic, rubber, resin, mixed in the paint or the like to impart conductivity thereto, the tin oxide layer is substantially antimony it relates to end gender powder.
近年、用途により、プラスチックにも導電性が求められてきている。例えば、ハウジング内の電気部品を大きな電磁界から遮蔽したり、帯電した部品を放電させたりする場合、ハウジング等に用いられるプラスチックは導電性のものであることが好ましい。このようにプラスチックに導電性を付与する方法としてはポリマーに導電性粉末を添加する方法が知られており、導電性粉末としては、例えば、金属粉末、カーボンブラック、アンチモン等をドープした酸化錫粉末等が知られている。 In recent years, conductivity has been required for plastics depending on applications. For example, when shielding an electrical component in the housing from a large electromagnetic field or discharging a charged component, the plastic used for the housing or the like is preferably conductive. Thus, as a method for imparting conductivity to a plastic, a method of adding a conductive powder to a polymer is known. Examples of the conductive powder include tin oxide powder doped with metal powder, carbon black, antimony, and the like. Etc. are known.
しかし、金属粉末やカーボンブラックをポリマーに添加すると得られるプラスチックが黒色になり、プラスチックの用途が限定されるため好ましくない。また、アンチモン等をドープした酸化錫粉末をポリマーに添加したものを用いると、導電性が高いためこの点では好ましいが、プラスチックが青黒色に着色するためカーボンブラック等と同様にプラスチックの用途が限定されると共に、アンチモン自体に毒性が懸念されるため、使用することが好ましくない。 However, the addition of metal powder or carbon black to the polymer is not preferable because the resulting plastic becomes black and the use of the plastic is limited. In addition, it is preferable to use a tin oxide powder doped with antimony or the like added to the polymer because of its high conductivity. However, since the plastic is colored blue-black, the use of the plastic is limited like carbon black. At the same time, there is a concern about the toxicity of antimony itself, which is not preferable.
これに対し、特許文献１（特許第２９９４０２０号公報）には、二酸化チタン等の粒子表面に、酸化スズの水和物からなる被覆層を形成され、得られた被覆処理物を非酸化性雰囲気中２５０〜６００℃で加熱処理する導電性二酸化チタン粉末の製造方法が開示されている。該方法によれば、得られる導電性二酸化チタン粉末は、白色度に優れ、毒性の危惧がないものとなる。 On the other hand, Patent Document 1 (Japanese Patent No. 2999420) discloses that a coating layer made of a hydrate of tin oxide is formed on the surface of particles of titanium dioxide or the like, and the resulting coating treatment is treated in a non-oxidizing atmosphere. The manufacturing method of the electroconductive titanium dioxide powder which heat-processes at 250-600 degreeC inside is disclosed. According to this method, the obtained conductive titanium dioxide powder is excellent in whiteness and has no risk of toxicity.
しかしながら、上記導電性二酸化チタン粉末は、粉体抵抗が低くてもせいぜい５８０Ω・ｃｍ程度であり、プラスチックの導電性を向上させるためには、粉体抵抗をさらに向上させることが望まれている現状では、導電性が十分に高いとはいえない。また、非酸化性雰囲気中２５０〜６００℃のような高温で焼成すると、導電性二酸化チタン粉末に酸素欠陥が増加するため導電性二酸化チタン粉末の体積抵抗を下げることができる点では好ましいが、一方で、導電性二酸化チタン粉末がメタル化する等により凝集が進んでしまうため塗料として使用する場合に該粉末の分散性が悪く、平滑な塗膜を形成することが困難であるという問題があった。従って、本発明の目的は、導電性、白色度及び分散性に優れ、毒性の危惧がない導電性粉末を提供することにある。 However, the conductive titanium dioxide powder is at most about 580 Ω · cm even if the powder resistance is low, and in order to improve the conductivity of the plastic, it is desired to further improve the powder resistance. However, it cannot be said that the conductivity is sufficiently high. Further, when firing at a high temperature such as 250 to 600 ° C. in a non-oxidizing atmosphere, oxygen defects are increased in the conductive titanium dioxide powder, which is preferable in terms of reducing the volume resistance of the conductive titanium dioxide powder. However, when the conductive titanium dioxide powder is agglomerated due to metalization, etc., when used as a paint, there is a problem that the dispersibility of the powder is poor and it is difficult to form a smooth coating film. . Accordingly, an object of the present invention is to provide a conductive powder that is excellent in conductivity, whiteness and dispersibility, and has no fear of toxicity.
かかる実情において、本発明者は鋭意検討を行った結果、芯材を水中に分散させたスラリーに、水溶性錫化合物を添加後、酸又はアルカリを用いて中和反応を行い、前記芯材の表面に酸化錫水和物からなる被覆層が形成された導電性粉末前駆体を生成し、該前駆体を洗浄し、乾燥した後、酸化性雰囲気中２５０〜６００℃で仮焼して仮焼粉を得、該仮焼粉を粉砕後、非酸化性雰囲気中１５０〜２５０℃で焼成して、酸化錫層を還元によるメタル化をさせることなく酸素欠損を形成させて得られる、前記芯材の表面に酸化錫層が形成された導電性粉末であって、前記酸化錫層が実質的にアンチモンを含まない導電性粉末は、導電性、白色度及び分散性に優れ、毒性の危惧がないことを見出し、本発明を完成するに至った。 In such a situation, as a result of intensive studies, the present inventors have added a water-soluble tin compound to a slurry in which the core material is dispersed in water, and then performed a neutralization reaction using an acid or an alkali. A conductive powder precursor having a coating layer made of tin oxide hydrate formed on the surface is produced, the precursor is washed and dried, and then calcined at 250 to 600 ° C. in an oxidizing atmosphere. The core material obtained by obtaining a powder, pulverizing the calcined powder, firing at 150 to 250 ° C. in a non-oxidizing atmosphere, and forming an oxygen deficiency without metallizing the tin oxide layer by reduction A conductive powder having a tin oxide layer formed on the surface thereof, wherein the tin oxide layer is substantially free of antimony, has excellent conductivity, whiteness and dispersibility, and has no risk of toxicity. As a result, the present invention has been completed.
すなわち、本発明（１）は、芯材を水中に分散させたスラリーに、水溶性錫化合物を添加後、酸又はアルカリを用いて中和反応を行い、前記芯材の表面に酸化錫水和物からなる被覆層が形成された導電性粉末前駆体を生成し、該前駆体を洗浄し、乾燥した後、酸化性雰囲気中２５０〜６００℃で仮焼して仮焼粉を得、該仮焼粉を粉砕後、非酸化性雰囲気中１５０〜２５０℃で焼成して、酸化錫層を還元によりメタル化させずに酸素欠損を形成させて得られる、前記芯材の表面に酸化錫層が形成された導電性粉末であって、前記酸化錫層が実質的にアンチモンを含まず、体積抵抗率が１００Ω・ｃｍ未満であることを特徴とする導電性粉末を提供するものである。 That is, in the present invention (1), after adding a water-soluble tin compound to a slurry in which a core material is dispersed in water, a neutralization reaction is performed using an acid or an alkali, and the surface of the core material is hydrated with tin oxide. A conductive powder precursor having a coating layer made of a product is produced, the precursor is washed and dried, and calcined at 250 to 600 ° C. in an oxidizing atmosphere to obtain a calcined powder. After the pulverized powder is pulverized, it is fired at 150 to 250 ° C. in a non-oxidizing atmosphere, and the tin oxide layer is obtained by forming oxygen vacancies without metallizing the tin oxide layer by reduction. The conductive powder thus formed is characterized in that the tin oxide layer is substantially free of antimony and has a volume resistivity of less than 100 Ω · cm.
また、本発明（２）は、本発明（１）において、比表面積が５〜３００ｍ２／ｇであることを特徴とする導電性粉末を提供するものである。 Moreover, this invention (2) provides the electroconductive powder characterized by the specific surface area being 5-300 m < 2 > / g in this invention (1).
本発明（３）は、本発明（１）又は（２）において、前記芯材の材質が、硫酸バリウム、二酸化チタン、アルミナ又は二酸化珪素であることを特徴とする導電性粉末を提供するものである。 The present invention (3) provides the conductive powder according to the present invention (1) or (2), wherein the core material is barium sulfate, titanium dioxide, alumina or silicon dioxide. is there.
本発明に係る導電性粉末は、白色度が高いため樹脂、塗料等に添加しても導電性粉末自体の色で着色し難く、分散性が高いため樹脂、塗料等に添加しても平滑な塗膜を形成することができ、アンチモンを実質的に含まないため毒性の危惧がなく、導電性が高い。また、本発明に係る導電性粉末は、仮焼と本焼成との二段焼成を行うことにより得られるので、通常の一段焼成のものに比べて良好な分散性が付与された導電性粉末とすることができる。 Since the conductive powder according to the present invention has high whiteness, it is difficult to be colored with the color of the conductive powder itself even when added to a resin, paint, etc., and since it is highly dispersible, it is smooth even when added to a resin, paint, etc. A coating film can be formed, and since antimony is not substantially contained, there is no risk of toxicity and high conductivity. In addition, since the conductive powder according to the present invention can be obtained by performing two-stage firing of calcination and main firing, the conductive powder provided with better dispersibility compared to that of a normal one-stage firing can do.
本発明に係る導電性粉末は、芯材を水中に分散させたスラリーに、水溶性錫化合物を添加後、酸又はアルカリを用いて中和反応を行い、前記芯材の表面に酸化錫水和物からなる被覆層が形成された導電性粉末前駆体を生成し、該前駆体を洗浄し、乾燥した後、酸化性雰囲気中２５０〜６００℃で仮焼して仮焼粉を得、該仮焼粉を粉砕後、非酸化性雰囲気中１５０〜２５０℃で焼成して、酸化錫層を還元によるメタル化をさせることなく酸素欠損を形成させて得られる、前記芯材の表面に酸化錫層が形成された導電性粉末であって、実質的にアンチモンを含まず、体積抵抗率が１００Ω・ｃｍ未満であることを特徴とする。 In the conductive powder according to the present invention, a water-soluble tin compound is added to a slurry in which a core material is dispersed in water, and then a neutralization reaction is performed using an acid or an alkali to hydrate tin oxide on the surface of the core material. A conductive powder precursor having a coating layer made of a product is produced, the precursor is washed and dried, and calcined at 250 to 600 ° C. in an oxidizing atmosphere to obtain a calcined powder. A tin oxide layer formed on the surface of the core material obtained by pulverizing the calcined powder and firing it at 150 to 250 ° C. in a non-oxidizing atmosphere to form an oxygen deficiency without metallizing the tin oxide layer by reduction. The conductive powder is characterized by being substantially free of antimony and having a volume resistivity of less than 100 Ω · cm.
（本発明に係る導電性粉末の実施の形態）
まず、本発明に係る導電性粉末の実施の形態について説明する。本形態で用いられる芯材は、その表面に酸化錫層を形成することが可能な実質的に粒状、フレーク状又は針状の芯材である。芯材の材質としては、例えば、硫酸バリウム、二酸化チタン、アルミナ、二酸化珪素、雲母、タルク、ホウ酸アルミニウム、酸化亜鉛（ＺｎＯ）及びチタン酸アルカリ金属塩等が挙げられる。
(Embodiment of conductive powder according to the present invention)
First, an embodiment of the conductive powder according to the present invention will be described. The core material used in this embodiment is a substantially granular, flaky or needle-like core material capable of forming a tin oxide layer on the surface thereof. Examples of the core material include barium sulfate, titanium dioxide, alumina, silicon dioxide, mica, talc, aluminum borate, zinc oxide (ZnO), and alkali metal titanate.
芯材は、粒度Ｄ５０が通常０．０１〜１００μｍ、好ましくは０．１〜１０μｍである。芯材の粒径が該範囲内にあると、酸化錫層を形成して得られる導電性粉末の粒度が樹脂等中に分散し易いものとなるため好ましい。本明細書において粒度Ｄ５０とは、レーザー回折散乱法で求められる体積平均粒径をいう。 The core material, particle size D 50 is usually 0.01 to 100 [mu] m, preferably 0.1 to 10 [mu] m. It is preferable that the particle diameter of the core material be within this range since the particle diameter of the conductive powder obtained by forming the tin oxide layer is easily dispersed in the resin or the like. In the present specification, the particle size D 50 refers to a volume average particle size determined by a laser diffraction scattering method.
芯材は、比表面積が通常０．１〜１５０ｍ２／ｇ、好ましくは１０〜５０ｍ２／ｇである。芯材の比表面積が該範囲内にあると、酸化錫層を形成して得られる導電性粉末の粒度が樹脂等中に分散し易いものとなるため好ましい。一方、該比表面積が０．１ｍ２／ｇ未満であると、導電性粉末の粒子が大きいことから塗料化したときに均一な塗膜を得られ難いため好ましくない。また、該比表面積が１５０ｍ２／ｇを超えると、酸化錫の粒径と同じ大きさに近くなることから密着性の良いコート層を形成し難くなるため好ましくない。 The core material has a specific surface area of usually 0.1 to 150 m 2 / g, preferably 10 to 50 m 2 / g. It is preferable that the specific surface area of the core material be within this range because the particle size of the conductive powder obtained by forming the tin oxide layer is easily dispersed in the resin or the like. On the other hand, when the specific surface area is less than 0.1 m 2 / g, since the conductive powder particles are large, it is difficult to obtain a uniform coating film when formed into a paint, which is not preferable. On the other hand, if the specific surface area exceeds 150 m 2 / g, it becomes difficult to form a coat layer with good adhesion because it is close to the same size as the particle size of tin oxide.
本発明に係る導電性粉末は、上記芯材の表面に酸化錫層が形成される。酸化錫層は、酸化錫ＳｎＯ２の微粒子が芯材の表面を実質的に隙間なく被覆して形成される表面が略平滑な層であって、実質的にアンチモンを含まないものである。なお、本明細書において実質的にアンチモンを含まないとは、アンチモンを不純物として含まないことを意味し、具体的には酸化錫層中のアンチモンの含有量が重量基準で１０００ｐｐｍ未満であることを意味する。本発明に係る導電性粉末は、このように実質的にアンチモンを含まないため、毒性の危惧がないものとなる。 In the conductive powder according to the present invention, a tin oxide layer is formed on the surface of the core material. The tin oxide layer is a layer having a substantially smooth surface formed by covering the surface of the core material with fine particles of tin oxide SnO 2 substantially without any gap, and is substantially free of antimony. In the present specification, “substantially free of antimony” means that antimony is not contained as an impurity. Specifically, the content of antimony in the tin oxide layer is less than 1000 ppm on a weight basis. means. Since the conductive powder according to the present invention does not substantially contain antimony as described above, there is no risk of toxicity.
本発明に係る導電性粉末は、導電性粉末中における前記酸化錫層の含有量が、通常１０〜９０重量％、好ましくは２０〜８０重量％である。上記含有量が該範囲内にあると、導電性粉末の導電性が高いと共に、芯材と酸化錫層との結合が比較的強く導電性粉末を樹脂等に混練しても酸化錫層が剥離し難いものとなるため好ましい。一方、上記含有量が１０重量％未満であると、酸化錫の量が少なく、導電性粉末の導電性が不十分になり易いため好ましくない。また、上記含有量が９０重量％を超えると、導電性粉末の凝集が強くなり、塗膜の平滑性が失われることによりコート粉のメリットがなくなり易いため好ましくない。 In the conductive powder according to the present invention, the content of the tin oxide layer in the conductive powder is usually 10 to 90% by weight, preferably 20 to 80% by weight. When the above content is within the above range, the conductive powder has high conductivity, and the core and tin oxide layer have a relatively strong bond, and even if the conductive powder is kneaded with resin or the like, the tin oxide layer peels off. This is preferable because it is difficult to perform. On the other hand, if the content is less than 10% by weight, the amount of tin oxide is small, and the conductivity of the conductive powder tends to be insufficient. Moreover, when the said content exceeds 90 weight%, since aggregation of electroconductive powder will become strong and the smoothness of a coating film will be lost, since the merit of coat powder is easy to be lost, it is unpreferable.
本発明に係る導電性粉末は、粒度Ｄ５０が通常０．０１〜１００μｍ、好ましくは０．０５〜５０μｍ、さらに好ましくは０．１〜１０μｍ、特に好ましくは０．２〜３．０μｍである。導電性粉末の粒径が該範囲内にあると、樹脂等中に分散し易いものとなるため好ましい。 The conductive powder according to the present invention has a particle size D50 of usually 0.01 to 100 μm, preferably 0.05 to 50 μm, more preferably 0.1 to 10 μm, and particularly preferably 0.2 to 3.0 μm. It is preferable for the particle size of the conductive powder to fall within this range because it becomes easy to disperse in a resin or the like.
本発明に係る導電性粉末は、比表面積が通常１〜３００ｍ２／ｇ、好ましくは５〜２００ｍ２／ｇ、さらに好ましくは１０〜１００ｍ２／ｇである。導電性粉末の比表面積が該範囲内にあると、樹脂等中に分散し易いものとなるため好ましい。一方、該比表面積が１ｍ２／ｇ未満であると、導電性粉末の粒子が大きいことから塗料化したときに均一な塗膜を得られ難いため好ましくない。また、該比表面積が３００ｍ２／ｇを超えると、酸化錫の粒径と同じ大きさに近くなることから密着性の良いコート層を形成し難くなるため好ましくない。本発明に係る導電性粉末は、体積抵抗率が通常１００Ω・ｃｍ未満、好ましくは５０Ω・ｃｍ未満にあり、導電性が高い。 The conductive powder according to the present invention has a specific surface area of usually 1 to 300 m 2 / g, preferably 5 to 200 m 2 / g, more preferably 10 to 100 m 2 / g. It is preferable that the specific surface area of the conductive powder is within this range because it becomes easy to disperse in a resin or the like. On the other hand, if the specific surface area is less than 1 m 2 / g, the conductive powder particles are large, so that it is difficult to obtain a uniform coating film when made into a paint, which is not preferable. On the other hand, when the specific surface area exceeds 300 m 2 / g, it becomes difficult to form a coat layer with good adhesion because it is close to the same particle size as that of tin oxide. The conductive powder according to the present invention has a volume resistivity of generally less than 100 Ω · cm, preferably less than 50 Ω · cm, and has high conductivity.
本発明に係る導電性粉末は、塗膜抵抗が低い。具体的には、塗膜抵抗が、通常１．０×１０８Ω／□未満、好ましくは６．０×１０７Ω／□未満である。ここで、塗膜抵抗は、試料粉体を三菱レイヨン株式会社製アクリル樹脂ＬＲ１６７に固形分重量で７０重量％混合し、これをペイントシェーカーにて１時間分散した後、バーコーターを用いてＰＥＴフィルムの上に塗布し、乾燥して厚さ１μｍの塗膜を形成し、該塗膜の表面抵抗を三菱化学株式会社製ロレスタＨＰを用いて測定した値である。 The conductive powder according to the present invention has low coating film resistance. Specifically, the coating film resistance is usually less than 1.0 × 10 8 Ω / □, preferably less than 6.0 × 10 7 Ω / □. Here, the coating film resistance was obtained by mixing the sample powder with acrylic resin LR167 manufactured by Mitsubishi Rayon Co., Ltd. at 70% by weight in solid content, and dispersing this with a paint shaker for 1 hour, and then using a bar coater. This is a value obtained by applying a coating film on the substrate and drying to form a 1 μm-thick coating film, and measuring the surface resistance of the coating film using Loresta HP manufactured by Mitsubishi Chemical Corporation.
上記本発明に係る導電性粉末は、下記の方法により製造することができる。本発明に係る導電性粉末は、芯材を水中に分散させたスラリーに、水溶性錫化合物を添加後、酸又はアルカリを用いて中和反応を行い、前記芯材の表面に酸化錫水和物からなる被覆層が形成された導電性粉末前駆体を生成し、該前駆体を洗浄し、乾燥した後、酸化性雰囲気中２５０〜６００℃で仮焼して仮焼粉を得、次いで該仮焼粉を粉砕後、非酸化性雰囲気中１５０〜２５０℃で焼成して、酸化錫層を還元によるメタル化をさせることなく酸素欠損を形成させる。 The conductive powder according to the present invention can be produced by the following method. In the conductive powder according to the present invention, a water-soluble tin compound is added to a slurry in which a core material is dispersed in water, and then a neutralization reaction is performed using an acid or an alkali to hydrate tin oxide on the surface of the core material. A conductive powder precursor having a coating layer made of a product is produced, the precursor is washed and dried, and then calcined at 250 to 600 ° C. in an oxidizing atmosphere to obtain a calcined powder, After calcining the calcined powder, it is fired at 150 to 250 ° C. in a non-oxidizing atmosphere to form oxygen vacancies without metallizing the tin oxide layer by reduction.
本形態では、まず、芯材を水中に分散させてスラリーを調製する。ここで、芯材としては、本発明に係る導電性粉末で説明したものと同様のものを用いる。 In this embodiment, first, a core material is dispersed in water to prepare a slurry. Here, as a core material, the thing similar to what was demonstrated with the electroconductive powder which concerns on this invention is used.
上記スラリーは、例えば、芯材を水に芯材の粗粒がなくなるまで分散させる方法により得られる。該スラリーの生成に用いる水としては、特に限定されないが、純水等を用いると、不純物含有量の少ない酸化錫水和物を生成することにより、最終的に得られる導電性粉末の塗料分散性が良くなるため好ましい。 The slurry is obtained, for example, by a method in which the core material is dispersed in water until there are no coarse core material particles. The water used for the production of the slurry is not particularly limited. However, when pure water or the like is used, it is possible to produce tin oxide hydrate having a low impurity content, thereby finally obtaining a paint dispersibility of the conductive powder obtained. Is preferable.
上記スラリー中における水と芯材との配合比率は、水１ｌに対して芯材が、通常１０〜１００ｇ、好ましくは３０〜８０ｇである。上記配合比率が該範囲内にあると、均一な酸化錫被覆層が得られ易いため好ましい。 The mixing ratio of water and the core material in the slurry is usually 10 to 100 g, preferably 30 to 80 g, of the core material with respect to 1 l of water. It is preferable for the blending ratio to fall within this range because a uniform tin oxide coating layer can be easily obtained.
次に、該スラリーに、水溶性錫化合物を添加する。本形態で用いられる水溶性錫化合物としては、芯材の表面に酸化錫水和物からなる被覆層を形成することができるものであればよく特に限定されないが、例えば、錫酸ナトリウム、四塩化錫等が挙げられる。このうち、錫酸ナトリウム及び四塩化錫は水への溶解が容易であるため好ましい。 Next, a water-soluble tin compound is added to the slurry. The water-soluble tin compound used in the present embodiment is not particularly limited as long as it can form a coating layer made of tin oxide hydrate on the surface of the core material. For example, sodium stannate, tetrachloride Tin etc. are mentioned. Of these, sodium stannate and tin tetrachloride are preferable because they are easily dissolved in water.
また、上記スラリー中における水と水溶性錫化合物との配合比率は、水に対する水溶性錫化合物中のＳｎ濃度が、通常１〜２０重量％、好ましくは３〜１０重量％である。上記配合比率が該範囲内にあると、均一な酸化錫被覆層が得られ易いため好ましい。 The mixing ratio of water and the water-soluble tin compound in the slurry is such that the Sn concentration in the water-soluble tin compound relative to water is usually 1 to 20% by weight, preferably 3 to 10% by weight. It is preferable for the blending ratio to fall within this range because a uniform tin oxide coating layer can be easily obtained.
次に、水溶性錫化合物を添加したスラリーに、酸又はアルカリを用いて中和反応を行う。中和反応を行う方法としては、該スラリーに酸性物質やアルカリ性物質を添加する方法が挙げられる。ここで、酸性物質としては、例えば、硫酸、硝酸、酢酸等が挙げられる。硫酸は、希硫酸であると均一な酸化錫被覆層が得られ易いため好ましい。希硫酸の濃度は、通常１０〜５０容量％である。また、アルカリ性物質としては、例えば、水酸化ナトリウム、アンモニア水等が挙げられる。このうち、水酸化ナトリウムは濃度を管理し易いため好ましい。 Next, the slurry to which the water-soluble tin compound is added is subjected to a neutralization reaction using an acid or an alkali. Examples of a method for performing the neutralization reaction include a method of adding an acidic substance or an alkaline substance to the slurry. Here, examples of the acidic substance include sulfuric acid, nitric acid, acetic acid and the like. Sulfuric acid is preferably dilute sulfuric acid because a uniform tin oxide coating layer is easily obtained. The concentration of dilute sulfuric acid is usually 10-50% by volume. Examples of the alkaline substance include sodium hydroxide and aqueous ammonia. Among these, sodium hydroxide is preferable because the concentration can be easily controlled.
中和を行う際、スラリーのｐＨは、通常ｐＨ０．５〜５、好ましくはｐＨ２．０〜４．０、さらに好ましくはｐＨ２．０〜３．０とする。中和の際のｐＨを該範囲内にすることにより、水溶性錫化合物をスラリーに溶解して得られた錫酸が酸化錫水和物を生成し、芯材の表面に酸化錫水和物（ＳｎＯ２・ｎＨ２Ｏ）からなる被覆層が形成された導電性粉末前駆体が生成する。 When neutralization is performed, the pH of the slurry is usually 0.5 to 5, preferably 2.0 to 4.0, and more preferably 2.0 to 3.0. By making the pH during neutralization within this range, stannic acid obtained by dissolving the water-soluble tin compound in the slurry produces tin oxide hydrate, and tin oxide hydrate is formed on the surface of the core material. A conductive powder precursor having a coating layer made of (SnO 2 · nH 2 O) is generated.
次に、該導電性粉末前駆体を洗浄する。洗浄した導電性粉末前駆体は、脱水濾過後、乾燥させる。乾燥方法としては特に限定されない。 Next, the conductive powder precursor is washed. The washed conductive powder precursor is dried after dehydration filtration. It does not specifically limit as a drying method.
次に、乾燥した導電性粉末前駆体を酸化性雰囲気中で仮焼する。ここで、酸化性雰囲気としては、例えば、大気雰囲気、酸素雰囲気等が挙げられる。このうち、大気雰囲気は、操作が容易であるため好ましい。 Next, the dried conductive powder precursor is calcined in an oxidizing atmosphere. Here, examples of the oxidizing atmosphere include an air atmosphere and an oxygen atmosphere. Among these, an air atmosphere is preferable because it is easy to operate.
仮焼温度としては、通常２５０〜６００℃、好ましくは２７０〜５５０℃であり、仮焼時間としては、通常５〜１８０分、好ましくは３０〜９０分である。仮焼条件が、上記範囲内にあると、十分に酸化でき、且つ凝集を起こし難いため好ましい。上記の工程を行うと、導電性粉末前駆体の表面にある酸化錫水和物（ＳｎＯ２・ｎＨ２Ｏ）からなる被覆層が酸化され、酸化錫からなる被覆層が形成される。該被覆層は、後述の本焼成を行うことにより還元されて酸素欠損を有する酸化錫層を形成するものであるが、本工程の仮焼を行って酸化錫水和物を一旦酸化しておくことにより、次工程の本焼成を低温で行うことができるため、凝集させずに分散性の良い導電性粉末を製造することができる。 The calcination temperature is usually 250 to 600 ° C., preferably 270 to 550 ° C., and the calcination time is usually 5 to 180 minutes, preferably 30 to 90 minutes. It is preferable for the calcining conditions to be within the above range because sufficient oxidization can be achieved and aggregation is difficult to occur. When the above process is performed, the coating layer made of tin oxide hydrate (SnO 2 .nH 2 O) on the surface of the conductive powder precursor is oxidized, and a coating layer made of tin oxide is formed. The coating layer is reduced by performing the main firing described later to form a tin oxide layer having oxygen vacancies. However, the coating layer is temporarily calcined to oxidize the tin oxide hydrate. Thus, the main firing in the next step can be performed at a low temperature, so that conductive powder with good dispersibility can be produced without agglomeration.
次に、仮焼した導電性粉末前駆体を適宜粉砕した後、非酸化性雰囲気中で焼成する。ここで粉砕方法としては特に限定されない。また、非酸化性雰囲気としては、水素を含有した窒素雰囲気とする。水素を含有した窒素雰囲気は、安価であるため好ましい。また、水素を含有した窒素雰囲気の場合、水素の含有量は、１〜３体積％である。水素の含有量が該範囲内にあると、酸化錫層について還元によるメタル化をさせずに酸素欠損を形成させ易いため好ましい。 Next, the calcined conductive powder precursor is appropriately pulverized and then fired in a non-oxidizing atmosphere. Here, the grinding method is not particularly limited. As the non-oxidizing atmosphere, it shall be the nitrogen Kiri囲gas containing the hydrogen. Nitrogen atmosphere containing hydrogen is preferable because it is inexpensive. In the case of a nitrogen atmosphere containing hydrogen, the hydrogen content is 1 to 3% by volume. It is preferable for the hydrogen content to fall within this range because it is easy to form oxygen vacancies without metallizing the tin oxide layer by reduction.
焼成温度としては、通常１５０〜２５０℃、好ましくは１８０〜２２０℃である。上記の工程を行うことにより、本発明に係る導電性粉末を製造することができる。 As a calcination temperature, it is 150-250 degreeC normally, Preferably it is 180-220 degreeC. By performing the above steps, the conductive powder according to the present invention can be produced.
上記本発明に係る導電性粉末は、例えば、紙、プラスチック、ゴム、樹脂、塗料等に混入してこれらに導電性を付与する導電性フィラーとして、また、電池等の電極改質剤として使用することができる。上記樹脂としては、例えば、アクリル樹脂、エポキシ樹脂、ポリエステル等が挙げられる。 The conductive powder according to the present invention is used, for example, as a conductive filler that imparts conductivity to paper, plastic, rubber, resin, paint, etc., and as an electrode modifier for batteries and the like. it is possible. The upper SL resins, such as acrylic resin, epoxy resin, polyester or the like.
本発明に係る導電性粉末は、上記樹脂や水等の液状媒体に対する分散性が良好であり、その指標として、導電性粉末を純水に７０重量％分散し、ペイントシェーカーを用いて分散処理した場合の分散粒度Ｄ５０が、通常０．０５〜０．４５μｍ、好ましくは０．１〜０．４μｍである。分散粒度Ｄ５０が該範囲内にあると、平滑であり透明性の高い膜が得られ易いため好ましい。また、本発明に係る導電性粉末は、上記樹脂に分散させたときの塗膜抵抗が低くなる。 The conductive powder according to the present invention has good dispersibility in the liquid medium such as the resin and water, and as an index thereof, the conductive powder is dispersed in 70% by weight in pure water and dispersed using a paint shaker. In this case, the dispersed particle size D 50 is usually 0.05 to 0.45 μm, preferably 0.1 to 0.4 μm. It is preferable that the dispersed particle size D 50 is in this range because a smooth and highly transparent film can be easily obtained. In addition, the conductive powder according to the present invention has low coating film resistance when dispersed in the resin.
以下に実施例を示すが、本発明はこれらに限定されて解釈されるものではない。 Examples are shown below, but the present invention is not construed as being limited thereto.
水３．５ｌに硫酸バリウム２００ｇを硫酸バリウムの粗粒がなくなるまで分散させてスラリーを生成した。該スラリーにＳｎ含有量４１重量％の錫酸ナトリウム３８４ｇを投入し、錫酸ナトリウムを溶解させた。該スラリーに２０％希硫酸をスラリーのｐＨが２．５になるまで９８分間かけて添加して中和した。該反応液を温水を用いて洗浄した。洗浄終了後は、脱水濾過を行い、濾滓（ケーキ）を回収した。
次に、得られた濾滓を１５０℃の雰囲気中に１５時間放置して、乾燥させた。得られた乾燥ケーキをアトマイザーを用いて解砕し、該解砕物について大気中において、３００℃で６０分仮焼を行った。得られた仮焼粉を、アトマイザーを用いて粉砕した後、水素を２体積％含有した窒素ガスを流通させながら、２３０℃で３０分間焼成を行った。
得られた粉末について、被覆率（導電性粉末中における酸化錫層の含有量）、体積抵抗率、粒度Ｄ５０比表面積、分散粒度Ｄ５０及び塗膜抵抗を下記の方法により測定した。測定結果を表１に示す。
200 g of barium sulfate was dispersed in 3.5 l of water until no coarse particles of barium sulfate disappeared to form a slurry. The slurry was charged with 384 g of sodium stannate having a Sn content of 41% by weight to dissolve the sodium stannate. The slurry was neutralized by adding 20% dilute sulfuric acid over 98 minutes until the pH of the slurry reached 2.5. The reaction solution was washed with warm water. After the completion of washing, dehydration filtration was performed, and a filter cake (cake) was collected.
Next, the obtained filter cake was left in an atmosphere of 150 ° C. for 15 hours to be dried. The obtained dried cake was pulverized using an atomizer, and the pulverized product was calcined at 300 ° C. for 60 minutes in the air. The obtained calcined powder was pulverized using an atomizer and then calcined at 230 ° C. for 30 minutes while flowing nitrogen gas containing 2% by volume of hydrogen.
About the obtained powder, the coverage (content of the tin oxide layer in the conductive powder), volume resistivity, particle size D 50 specific surface area, dispersed particle size D 50 and coating film resistance were measured by the following methods. The measurement results are shown in Table 1.
（体積抵抗率）：試料粉体を三菱化学株式会社製ロレスタＰＡＰＤ−４１を用いて５００ｋｇｆ／ｃｍ２に加圧した状態で、三菱化学株式会社製ロレスタＡＰを用いた測定値を体積抵抗率として求めた。
（粒度Ｄ５０）：２００ｃｃのサンプル容器に試料約０．１ｇを採り、０．２ｇ／ｌのヘキサメタリン酸ソーダを１０ｍｌ添加混合後、純水９０ｍｌを添加し、超音波分散機日本精機株式会社製ＵＳ−３００Ｔにより１０分間分散しサンプル液を調整した。日機装株式会社製マイクロトラックＨＲＡを用いて測定した。
（比表面積）：ユアサアイオニクス株式会社製モノソーブを用いて測定したＢＥＴ比表面積を用いた。
（分散粒度Ｄ５０）：試料粉体を純水に３０重量％分散した後、ペイントシェーカーを用いて分散処理を３０分間行い、得られたスラリーの分散粒度Ｄ５０を日機装株式会社製マイクロトラックＨＲＡを用いて測定した。
（塗膜抵抗）：試料粉体を三菱レイヨン株式会社製アクリル樹脂ＬＲ１６７に固形分重量で７０重量％混合し、これをペイントシェーカーにて１時間分散した後、バーコーターを用いてＰＥＴフィルムの上に塗布し、乾燥して厚さ１μｍの塗膜を形成し、該塗膜の表面抵抗を三菱化学株式会社製ロレスタＨＰを用いて測定した。
(Volume resistivity): In a state where the sample powder was pressurized to 500 kgf / cm 2 using Loresta PAPD-41 manufactured by Mitsubishi Chemical Corporation, the measured value using Loresta AP manufactured by Mitsubishi Chemical Corporation was used as volume resistivity. Asked.
(Particle size D 50 ): About 0.1 g of a sample is put in a 200 cc sample container, 10 ml of 0.2 g / l sodium hexametaphosphate is added and mixed, and then 90 ml of pure water is added, and an ultrasonic dispersing machine manufactured by Nippon Seiki Co., Ltd. A sample solution was prepared by dispersing for 10 minutes with US-300T. Measurement was performed using Microtrack HRA manufactured by Nikkiso Co., Ltd.
(Specific surface area): The BET specific surface area measured using the monosorb by Yuasa Ionics Co., Ltd. was used.
(Dispersion particle size D 50 ): After 30% by weight of the sample powder was dispersed in pure water, dispersion treatment was performed for 30 minutes using a paint shaker, and the dispersion particle size D 50 of the resulting slurry was changed to Microtrack HRA manufactured by Nikkiso Co., Ltd. It measured using.
(Film resistance): The sample powder was mixed with acrylic resin LR167 manufactured by Mitsubishi Rayon Co., Ltd. at a solid weight of 70% by weight and dispersed for 1 hour with a paint shaker. The film was dried to form a coating film having a thickness of 1 μm, and the surface resistance of the coating film was measured using Loresta HP manufactured by Mitsubishi Chemical Corporation.
焼成温度を１７０℃とし、被覆率が４０重量％となるようにした以外は実施例１と同様にして導電性粉末を得た。測定結果を表１に示す。 A conductive powder was obtained in the same manner as in Example 1 except that the firing temperature was 170 ° C. and the coverage was 40% by weight. The measurement results are shown in Table 1.
焼成温度を２００℃とし、被覆率が６０重量％となるようにした以外は実施例１と同様にして導電性粉末を得た。測定結果を表１に示す。 A conductive powder was obtained in the same manner as in Example 1 except that the firing temperature was 200 ° C. and the coverage was 60% by weight. The measurement results are shown in Table 1.
焼成温度を２００℃とし、被覆率が８０重量％となるようにした以外は実施例１と同様にして導電性粉末を得た。測定結果を表１に示す。 A conductive powder was obtained in the same manner as in Example 1 except that the firing temperature was 200 ° C. and the coverage was 80% by weight. The measurement results are shown in Table 1.
硫酸バリウム２００ｇに代えて二酸化珪素２００ｇを用い、焼成温度を２００℃とし、被覆率が５０重量％となるようにした以外は実施例１と同様にして導電性粉末を得た。測定結果を表１に示す。 Conductive powder was obtained in the same manner as in Example 1 except that 200 g of silicon dioxide was used instead of 200 g of barium sulfate, the firing temperature was 200 ° C., and the coverage was 50% by weight. The measurement results are shown in Table 1.
硫酸バリウム２００ｇに代えて二酸化チタン２００ｇを用い、焼成温度を２００℃とし、被覆率が５０重量％となるようにした以外は実施例１と同様にして導電性粉末を得た。測定結果を表１に示す。 Conductive powder was obtained in the same manner as in Example 1 except that 200 g of titanium dioxide was used instead of 200 g of barium sulfate, the firing temperature was 200 ° C., and the coverage was 50% by weight. The measurement results are shown in Table 1.
［比較例１］
仮焼を行わず、焼成温度を３５０℃とし、焼成時間を１２０分とし、被覆率が５０重量％となるようにした以外は実施例１と同様にして導電性粉末を得た。測定結果を表１に示す。
[Comparative Example 1]
A conductive powder was obtained in the same manner as in Example 1 except that calcination was not performed, the firing temperature was 350 ° C., the firing time was 120 minutes, and the coverage was 50% by weight. The measurement results are shown in Table 1.
［比較例２］
仮焼を行わず、焼成温度を６００℃とし、焼成時間を６０分とし、被覆率が８０重量％となるようにした以外は実施例１と同様にして導電性粉末を得た。測定結果を表１に示す。
[Comparative Example 2]
A conductive powder was obtained in the same manner as in Example 1 except that calcining was not performed, the firing temperature was 600 ° C., the firing time was 60 minutes, and the coverage was 80% by weight. The measurement results are shown in Table 1.
［比較例３］
硫酸バリウム２００ｇに代えて二酸化珪素２００ｇを用い、仮焼を行わず、焼成温度を６００℃とし、焼成時間を６０分とし、被覆率が５０重量％となるようにした以外は実施例１と同様にして導電性粉末を得た。測定結果を表１に示す。
[Comparative Example 3]
Similar to Example 1 except that 200 g of silicon dioxide was used instead of 200 g of barium sulfate, no calcination was performed, the firing temperature was 600 ° C., the firing time was 60 minutes, and the coverage was 50% by weight. Thus, a conductive powder was obtained. The measurement results are shown in Table 1.
［比較例４］
硫酸バリウム２００ｇに代えて二酸化チタン２００ｇを用い、仮焼を行わず、焼成温度を６００℃とし、焼成時間を６０分とし、被覆率が５０重量％となるようにした以外は実施例１と同様にして導電性粉末を得た。測定結果を表１に示す。
[Comparative Example 4]
The same as Example 1 except that 200 g of titanium dioxide was used instead of 200 g of barium sulfate, calcining was not performed, the firing temperature was 600 ° C., the firing time was 60 minutes, and the coverage was 50% by weight. Thus, a conductive powder was obtained. The measurement results are shown in Table 1.
表１より、仮焼を行わない比較例の導電性粉末は、体積抵抗が高くて導電性が悪く、分散粒度Ｄ５０が大きく、塗膜抵抗が高いことが判る。 From Table 1, a conductive powder of the comparative example does not perform calcination has poor conductivity higher volume resistivity, large dispersed particle size D 50, it is seen that the coating film resistance is high.
本発明に係る導電性粉末は、精密電子機器の静電気障害防止、静電気災害の発生防止、防塵等のためのハウジング、建材、繊維、機械部品；電池等の用途に用いることができる。 Conductive Powder according to the present invention, precision electronic devices static hazard prevention, prevention of static electricity disasters, housing for the dustproof like, building materials, fibers, mechanical parts; can be used in applications such as a battery.
Claims (3)
前記酸化錫層が実質的にアンチモンを含まず、体積抵抗率が１００Ω・ｃｍ未満であることを特徴とする導電性粉末。 After adding the water-soluble tin compound to the slurry in which the core material is dispersed in water, a neutralization reaction was performed using an acid or alkali, and a coating layer made of tin oxide hydrate was formed on the surface of the core material. After producing a conductive powder precursor, washing and drying the precursor, calcining in an oxidizing atmosphere at 250 to 600 ° C. to obtain calcined powder, grinding the calcined powder, hydrogen 1 A tin oxide layer is formed on the surface of the core material obtained by firing at 150 to 250 ° C. in a nitrogen atmosphere containing 3% by volume to form an oxygen deficiency without metallizing the tin oxide layer by reduction. Conductive powder,
The conductive powder characterized in that the tin oxide layer is substantially free of antimony and has a volume resistivity of less than 100 Ω · cm.
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