JP3828727B2 - Iron oxide particles - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、酸化鉄粒子に関し、詳しくは黒色度、磁気特性、及び熱安定性に優れた、特に静電複写磁性トナー用材料粉、静電複写キャリア用材料粉、もしくは塗料用黒色顔料粉等に好適な酸化鉄粒子に関する。
【０００２】
【従来の技術及び発明が解決しようとする課題】
酸化鉄粒子は、各種分野、特に乾式電子複写機、プリンタ等の磁性トナー用材料粉、静電複写キャリア用材料粉、もしくは塗料用黒色顔料粉等の原料として広く利用されており、マグネタイト（Ｆｅ3 Ｏ4 ）粒子等がその代表的なものである。
【０００３】
昨今、上記各用途分野での酸化鉄粒子に対する要求特性はより高度なものになってきており、例えば、酸化鉄粒子を乾式電子複写機、プリンタ等の磁性トナー用材料粉に用いる際には、従来の文字以外にもグラフィックや写真等の出力も要求されており、複写機、プリンターの中には１インチ当たり１２００ドット以上の能力のものも現れ、感光体上の潜像はより緻密になってきている。そのため、現像での細線再現性を保ちつつ、画像濃度を高めることを目的として、黒色度が高く、かつ安定していることが要求されている。
【０００４】
上記酸化鉄粒子がマグネタイト等の単独の形態において、より高い黒色度を求める場合には、ＦｅＯ（もしくはＦｅ2+）含有率が高いことが重要視されており、例えば特公平１−４０９７６号公報には、黒色度はＦｅＯ含有率（量）と粒径によって異なり、ＦｅＯ含有率が低いと黒色度が低下する旨示されている。
【０００５】
そして、上記公報には用いられる磁性粉の代表としてマグネタイトが挙げられ、種々の特性を考慮し、ＦｅＯ含有率が１６〜２５重量％のものを使用するとされており、また一般的な湿式製造法によるマグネタイトのＦｅＯ含有率は２６〜２８重量％程度であるとされている。
【０００６】
しかし、このようなマグネタイト等の単独の形態の酸化鉄粒子においては、酸化鉄粒子中のＦｅＯ含有率が高いと良好な黒色度を有するものの、酸化によりその黒色度は劣化することが懸念され、ＦｅＯ含有率が低い場合には、一層要求される黒色度を満足するに至らないという弊害がある。
【０００７】
一方、ＦｅＯを含まない代表的な酸化鉄粒子としては、マグヘマイト（γ−Ｆｅ2 Ｏ3 ）等が挙げられるが、その色相は相当茶褐色を帯びていることが、特公平６−２４９８５号公報等に示されており、かかる材料においても、高い黒色度を有する等の上記高度な要求に十分応え得る酸化鉄粒子は未だ提案されていない。
【０００８】
従って、本発明の目的は、従来の酸化鉄粒子と同等もしくはそれ以上の黒色度、磁気特性を有し、かつ耐酸化性、特に熱安定性に優れた酸化鉄粒子を提供することにある。
【０００９】
【課題を解決するための手段】
本発明者等は、鋭意検討の結果、低ＦｅＯ含有率で、かつ色差計によるＬ値の低い酸化鉄粒子によって、上記目的が達成し得ることを知見し、本発明に至った。
【００１０】
本発明は、上記知見に基づきなされたもので、ＦｅＯ含有率が１６質量％未満であり、ＪＩＳ Ｋ５１０１−１９９１に準拠した粉体の黒色度測定において、色差計によるＬ値が３０以下であり、且つマグネタイト及びマグヘマイトを含有することを特徴とする酸化鉄粒子を提供するものである。
【００１１】
【発明の実施の形態】
以下、本発明の実施の形態を説明する。
本発明の酸化鉄粒子は、ＦｅＯ含有率が１６質量％未満であることが重要である。本発明の酸化鉄粒子の特徴は、ＦｅＯを多く含むマグネタイト等の単独の形態の酸化鉄粒子ではないので、ＦｅＯ含有率が低くなる。しかし、ＦｅＯ含有率の低下の影響は少ないものの、十分な黒色度を得ることを考慮した場合には、マグヘマイトの形態比率が少なく、ＦｅＯ含有率が１０質量％以上であることが好ましい。酸化鉄粒子のＦｅＯ含有率が１６質量％以上の場合には、耐酸化性に優れた酸化鉄形態が少ないことにより、従来技術によるマグネタイト等の単独形態の酸化鉄粒子と同様に酸化による黒色度の劣化は免れない。
【００１２】
本発明の酸化鉄粒子は、高い黒色度を有するという面から、マグヘマイトの含有率がマグネタイトの含有率に比べ低いことが好ましい。また、マグヘマイトは粒子内部に多く含有されていることが好ましい。この理由は、上記マグヘマイトが粒子表面、もしくは近傍に多く含まれているとやはり黒色度を損なうからである。
【００１３】
本発明の酸化鉄粒子は、ＪＩＳ Ｋ５１０１−１９９１に準拠した粉体の黒色度測定において、色差計によるＬ値が３０以下であり、好ましくは２５以下である。Ｌ値が３０を超える場合には、黒色顔料として黒味が劣る。
【００１４】
また、本発明の酸化鉄粒子は、平均粒子径が好ましくは０．０５〜１μｍ、より好ましくは０．１〜０．５μｍである。平均粒子径が０．０５μｍ未満では粉体の色が赤味が強く、黒色度に乏しいものとなり、平均粒子径が１μｍを超えると黒色顔料としての着色力が低下してしまう。
【００１５】
さらに、本発明の酸化鉄粒子は、外部磁場７９６ｋＡ／ｍにおける飽和磁化が好ましくは６５〜８５Ａｍ2 ／ｋｇ、より好ましくは７０〜８２Ａｍ2 ／ｋｇである。飽和磁化が６５Ａｍ2 ／ｋｇ未満の場合には、磁性材用途、特に静電複写磁性トナー用材料粉への供用に適さず、８５Ａｍ2 ／ｋｇを超える場合は、もはや酸化鉄粒子の成分をマグネタイトを主成分としながらも、マグヘマイトを含有する形態ではあり得ない。
【００１６】
また、本発明の酸化鉄粒子は、大気中で２００℃、１時間加熱した際のＦｅＯ変化率が１０％以下であることが好ましい。このＦｅＯ変化率が１０％を超える場合には、色味変化が大きく、耐熱性に劣るものとなる。
【００１７】
本発明の酸化鉄粒子は、必要な要求特性に応じて、粒子内部及び／又は粒子表面にＳｉ、Ａｌ、Ｍｎ、Ｚｎ、Ｎｉ、Ｃｕ、Ｍｇ、Ｔｉ、Ｃｏ、Ｚｒ、Ｗ、Ｍｏ、Ｐ等の成分を含む酸化物、水酸化物、酸化水酸化物、含水酸化物、及びこれらの混合物等の各種化合物を適宜含有もしくは被覆させてもよい。また、上記金属元素と鉄の複合酸化物を含有もしくは被覆させると、耐環境性に優れた酸化鉄粒子とすることができるのでより好ましい。
また、本発明の酸化鉄粒子は、分散性や樹脂等のなじみ改善のために、各種有機処理剤等により処理されていてもよい。
【００１８】
次に、本発明の酸化鉄粒子の好ましい製造方法について説明する。本発明の酸化鉄粒子の製造方法は、第一鉄塩水溶液をアルカリ水溶液と中和混合後、得られた水酸化第一鉄コロイドを含むスラリーに対して酸化反応を行う酸化鉄粒子の製造方法において、特定の反応温度、及び特定の反応溶液中の酸素存在量を調整することにより製造できる。
【００１９】
酸化鉄粒子を湿式法で製造する方法としては、Ｆｅ2+を含有する第一鉄塩水溶液をアルカリ水溶液で中和して得られた水酸化第一鉄コロイドを含む第一鉄塩スラリー（以下、単に反応スラリーという）に、酸素含有ガスを通気して酸化することにより酸化鉄粒子を得る方法が一般的である。
【００２０】
本発明者等は、この反応の際の反応スラリー中の酸素存在量を特定し、かつそれに応じて反応温度を調整することが、最終的な生成酸化鉄粒子中の酸化鉄形態に大きな影響を及ぼすことを知見した。
【００２１】
反応スラリー中の酸素存在量は、基本的には連続的に反応スラリー中に導入される酸素含有ガスによる反応スラリー中の未溶解酸素量と反応スラリー中に存在する溶存酸素量の和で表現されるが、反応スラリー中の溶存酸素量は、基本的には反応スラリーの温度に左右される。即ち、反応スラリー温度が低いほど溶存酸素濃度は高く、高いほど溶存酸素濃度は低くなる。この反応スラリー中の溶存濃度の測定は、工業規模の生産上困難であるが、酸化雰囲気を調整するためには、反応スラリー中の酸素存在量、ひいては反応スラリーへの酸素供給量を反応温度に合わせて調整すればよいと考えられる。
【００２２】
ところで、通常の酸素含有ガス、経済性の面から利用される空気を用いて７０℃以上で酸化反応を行った場合には、基本的にはＦｅＯが１６質量％以上のマグネタイトを主成分とする酸化鉄粒子が生成する。この際、マグネタイトがより多く析出させるには、反応温度が高温であればよく、反応ｐＨがどのレベルであっても安定的で他形態の酸化鉄は生成しにくい。
【００２３】
本発明においては、溶存酸素濃度を高くし、反応スラリー中に局部的に過酸化雰囲気を形成することにより、上記通常の空気酸化により生成するマグネタイトの一部をマグヘマイト化し、かつマグネタイト中に均一かつ微細に固溶、もしくは分散析出させることができるものと推察した。
【００２４】
具体的には、反応スラリー温度が６０℃以上７０℃未満の低温度の場合には、空気を使用して酸化反応を行う。また、７０〜７５℃の場合には、空気、酸素、窒素の内１種又は２種以上で調製される空気より酸素濃度の高い酸素含有ガスにて酸化反応を行う。この際、反応スラリー温度が６０℃未満では、ゲーサイトの発生が著しく、反応スラリー温度が７５℃を超える場合には、マグネタイトが単独で安定的に生成し、共に目的とする本発明の酸化鉄粒子を得るのが困難である。
【００２５】
なお、上述したように、反応スラリー中の溶存酸素濃度を測定することは困難であるが、酸化還元電位計（ＯＲＰ計）を用いて反応スラリー中の酸化雰囲気を観察することは有効で、具体的には−２００〜０ｍＶにて酸化雰囲気を、観察制御するのが好ましい。
【００２６】
上記製造方法によって得られる本発明のマグネタイト及びマグヘマイトを含有する酸化鉄粒子は、単にマグネタイト粒子を表面酸化（自然酸化、意図的な酸化処理の何れをも含む）して得られた低ＦｅＯ含有率酸化鉄粒子や、マグヘマイトを被覆した低ＦｅＯ含有率酸化鉄粒子等とは異なり、黒色度が優れていると同時に、各種環境中での劣化が殆どない。
【００２７】
また、粒子内部及び／又は粒子表面にＳｉ、Ａｌ、Ｍｎ、Ｚｎ、Ｎｉ、Ｃｕ、Ｍｇ、Ｔｉ、Ｃｏ、Ｚｒ、Ｗ、Ｍｏ、Ｐ等の成分を含む酸化物、水酸化物、酸化水酸化物、含水酸化物、及びこれらの混合物等の各種化合物を適宜含有もしくは被覆させる場合には、上記成分の可溶性塩を出発原料となる第一鉄塩水溶液やアルカリ水溶液、もしくは反応スラリー中、もしくはコア粒子生成スラリー中に添加して、酸化反応、中和反応処理等を行えばよく、第一鉄塩を含む湿式スラリー状態において、上記成分の可溶性塩を添加し、酸化反応を行えば、上記金属元素と鉄の複合酸化物形態で、酸化鉄粒子に含有もしくは被覆させることができる。また、酸化反応終了後のスラリーを濾過、洗浄、乾燥して得られた酸化鉄粒子と、予め用意した上記各種化合物や各種有機処理剤等を混合して機械的処理を行い、表面被覆酸化鉄粒子とすることもできる。
【００２８】
【実施例】
以下、実施例等に基づいて、本発明を具体的に説明する。
【００２９】
〔実施例１〕
表１に示すように、Ｆｅ2+を２．０ｍｏｌ／ｌ含有する硫酸第一鉄水溶液５０リットルと４．０ｍｏｌ／ｌの水酸化ナトリウム５０リットルとを混合撹拌し、水酸化第一鉄コロイドを含む第一鉄塩水溶液を得た。この反応水溶液の温度を６０℃に保ちながら、１０リットル／ｍｉｎの空気を通気し、酸化反応を行った。得られた酸化鉄粒子スラリーを通常の濾過、洗浄、乾燥、粉砕工程により処理し、酸化鉄粒子を得た。得られた酸化鉄粒子について、以下の方法で諸特性を評価した。その結果を表２に示す。
【００３０】
〔測定方法〕
（１）粒子形状と粒径測定
走査型電子顕微鏡を用い、倍率２００００倍にて粒子形状観察及び２００個の粒子についてフェレ径の測定を行い、平均粒径を求めた。
（２）比表面積
島津−マイクロメリテックス社製２２００型ＢＥＴ計にて測定した。
（３）ＸＲＤプロファイル
Ｘ線回折装置によって、各化合物（Ｆｅ3 Ｏ4 、γ−Ｆｅ2 Ｏ3 、α−Ｆｅ2 Ｏ3 ）のピークを同定した。
（４）ＦｅＯ含有率
試料を硫酸にて溶解し、過マンガン酸カリウム標準溶液を使用して酸化還元滴定にて測定した。
（５）磁気特性
東英工業社製、振動型磁力計ＶＳＭ−Ｐ７型を使用し、外部磁場７９６ｋＡ／ｍ及び７９．６ｋＡ／ｍにて測定した。
（６）測色（黒色度、色相）
試料２．０ｇにヒマシ油１．４ｃｃを加え、フーバー式マーラーで練り込む。この練り込んだサンプル２．０ｇにラッカー７．５ｇを加え、さらに練り込んだ後、これをミラーコート紙上に４ｍｉｌのアプリケータを用いて塗布し、乾燥後、色差計（東京電色社製、カラーアナライザーＴＣ−１８００型）にて測色した。
（７）耐熱性試験
試料を時計皿に入れ、通風型乾燥機（タバイエスペック製オーブン、ＰＨ−２０１型）にて、１５０℃、１時間保持し、ＦｅＯの劣化を測定した。
【００３１】
〔実施例２〜６及び比較例１〜２〕
表１に示す条件を設定した以外は、実施例１と同様の方法で酸化鉄粒子を得た。得られた酸化鉄粒子について、実施例１と同様の方法で諸特性を評価した。その結果を表２に示す。
【００３２】
【表１】
【表２】
表２の結果から明らかなように、実施例１〜６の酸化鉄粒子は、ＦｅＯ含有率は低いものの、大気中での加熱試験後のＦｅＯ劣化率が小さく、黒色度も十分優れている。また、飽和磁化も十分高く、プリンタ等の磁性トナー用材料粉、静電複写キャリア用材料粉の使用にも適している。また、ＸＲＤプロファイルから、Ｆｅ3 Ｏ4 とγ−Ｆｅ2 Ｏ3 とを含有していることが判った。
【００３５】
これに対し、比較例１の酸化鉄粒子は、ＦｅＯ含有率が高く、黒色度も優れているが、大気中での加熱試験後のＦｅＯ劣化率が大きく、耐酸化性に著しく劣るものであった。また、比較例２の酸化鉄粒子は、Ｌ値が大きすぎ、黒色顔料としての黒味に劣ったものであった。
【００３６】
【発明の効果】
以上説明したように、本発明の酸化鉄粒子は、低ＦｅＯ含有率で、かつ色差計によるＬ値の低いことにより、従来の酸化鉄粒子と同等もしくはそれ以上の黒色度、磁気特性を有し、かつ耐酸化性、特に熱安定性に優れており、静電複写磁性トナー用材料粉、静電複写キャリア用材料粉、もしくは塗料用黒色顔料粉等に好適である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to iron oxide particles, and in particular, excellent in blackness, magnetic properties, and thermal stability, in particular, electrostatic powder magnetic toner material powder, electrostatic copy carrier material powder, or black pigment powder for paint, etc. It is related with the iron oxide particle suitable for.
[0002]
[Prior art and problems to be solved by the invention]
Iron oxide particles are widely used as raw materials for various fields, in particular, powders for magnetic toners for dry electronic copying machines and printers, powders for electrostatic copying carriers, and black pigment powders for paints. 3 O 4 ) particles are typical examples.
[0003]
Recently, the required characteristics for iron oxide particles in each of the above application fields have become more advanced. For example, when iron oxide particles are used in magnetic toner material powders for dry electronic copying machines, printers, etc., In addition to conventional characters, output of graphics and photographs is also required, and some copiers and printers have a capacity of 1200 dots or more per inch, and the latent image on the photoconductor becomes more precise. It is coming. For this reason, high blackness and stability are required for the purpose of increasing the image density while maintaining fine line reproducibility in development.
[0004]
When the iron oxide particles require a higher blackness in a single form such as magnetite, it is important to have a high FeO (or Fe 2+ ) content. For example, Japanese Patent Publication No. 1-40976 Indicates that the blackness varies depending on the FeO content (amount) and the particle size, and that the blackness decreases when the FeO content is low.
[0005]
And in the above publication, magnetite is mentioned as a representative of the magnetic powder used, and in consideration of various characteristics, it is said that a FeO content of 16 to 25% by weight is used, and a general wet manufacturing method The magnetite has a FeO content of about 26 to 28% by weight.
[0006]
However, in such a single form of iron oxide particles such as magnetite, although there is a good blackness when the FeO content in the iron oxide particles is high, there is concern that the blackness will deteriorate due to oxidation, When the FeO content is low, there is a problem that the required blackness is not satisfied.
[0007]
On the other hand, typical iron oxide particles that do not contain FeO include maghemite (γ-Fe 2 O 3 ) and the like, and the color of the iron oxide is considerably brownish, for example, Japanese Patent Publication No. 6-24985. Even in such materials, iron oxide particles that can sufficiently meet the above high demands such as having high blackness have not been proposed yet.
[0008]
Accordingly, an object of the present invention is to provide iron oxide particles having blackness and magnetic properties equivalent to or higher than those of conventional iron oxide particles and excellent in oxidation resistance, particularly thermal stability.
[0009]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have found that the above object can be achieved by iron oxide particles having a low FeO content and a low L value by a color difference meter, and have reached the present invention.
[0010]
The present invention has been made based on the above findings, a FeO content is less than 16 mass%, in the black measurement of powder conforming to JIS K5101-1991, L value by the color difference meter is Ri der 30 or less , in which and provides iron oxide particles characterized that you containing magnetite and maghemite.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
It is important that the iron oxide particles of the present invention have an FeO content of less than 16% by mass. The feature of the iron oxide particles of the present invention is not the iron oxide particles in a single form such as magnetite containing a large amount of FeO, so the FeO content is low. However, although the influence of the decrease in the FeO content is small, in consideration of obtaining sufficient blackness, it is preferable that the maghemite has a small form ratio and the FeO content is 10% by mass or more. When the FeO content of the iron oxide particles is 16% by mass or more, the blackness due to oxidation is the same as the iron oxide particles in a single form such as magnetite according to the prior art due to the small number of iron oxide forms excellent in oxidation resistance. Degradation is inevitable.
[0012]
The iron oxide particles of the present invention preferably have a lower maghemite content than the magnetite content in terms of having high blackness. Further, it is preferable that a large amount of maghemite is contained inside the particles. This is because if the maghemite is contained in a large amount on or near the particle surface, the blackness is deteriorated.
[0013]
The iron oxide particles of the present invention have an L value of 30 or less, preferably 25 or less, as measured by a color difference meter in measuring the blackness of powder according to JIS K5101-1991. When L value exceeds 30, blackness is inferior as a black pigment.
[0014]
The iron oxide particles of the present invention preferably have an average particle size of 0.05 to 1 μm, more preferably 0.1 to 0.5 μm. If the average particle size is less than 0.05 μm, the powder color is strongly reddish and poor in blackness. If the average particle size exceeds 1 μm, the coloring power as a black pigment is reduced.
[0015]
Furthermore, the iron oxide particles of the present invention preferably have a saturation magnetization at an external magnetic field of 796 kA / m of 65 to 85 Am 2 / kg, more preferably 70 to 82 Am 2 / kg. When the saturation magnetization is less than 65 Am 2 / kg, it is not suitable for use as a magnetic material, particularly as a material powder for electrostatic copying magnetic toner. When the saturation magnetization exceeds 85 Am 2 / kg, the iron oxide particle component is no longer magnetized. However, it cannot be in a form containing maghemite.
[0016]
The iron oxide particles of the present invention preferably have a FeO change rate of 10% or less when heated in the atmosphere at 200 ° C. for 1 hour. When the FeO change rate exceeds 10%, the color change is large and the heat resistance is poor.
[0017]
The iron oxide particles of the present invention have Si, Al, Mn, Zn, Ni, Cu, Mg, Ti, Co, Zr, W, Mo, P, etc. inside the particle and / or on the particle surface, depending on the required required properties. Various compounds such as oxides, hydroxides, oxide hydroxides, hydrated oxides, and mixtures thereof containing these components may be appropriately contained or coated. Further, it is more preferable to contain or coat the above complex oxide of metal element and iron since iron oxide particles having excellent environmental resistance can be obtained.
In addition, the iron oxide particles of the present invention may be treated with various organic treatment agents or the like in order to improve dispersibility and compatibility of resins and the like.
[0018]
Next, the preferable manufacturing method of the iron oxide particle of this invention is demonstrated. Manufacturing method of the iron oxide particles of the present invention, the production of iron oxide particles to carry out an oxidation reaction of ferrous salt aqueous solution was neutralized mixture with an alkaline aqueous solution, relative to slurries containing ferrous hydroxide colloid obtained In the method, it can be produced by adjusting the specific reaction temperature and the amount of oxygen present in the specific reaction solution.
[0019]
As a method for producing iron oxide particles by a wet method, a ferrous salt slurry containing a ferrous hydroxide colloid obtained by neutralizing a ferrous salt aqueous solution containing Fe 2+ with an alkaline aqueous solution (hereinafter referred to as a ferrous hydroxide slurry) Generally, a method of obtaining iron oxide particles by oxidizing an oxygen-containing gas through a reaction slurry) is generally performed.
[0020]
The inventors of the present invention specify the amount of oxygen present in the reaction slurry during this reaction, and adjust the reaction temperature accordingly, greatly affecting the form of iron oxide in the final iron oxide particles. I found out that
[0021]
The amount of oxygen present in the reaction slurry is basically expressed as the sum of the amount of undissolved oxygen in the reaction slurry and the amount of dissolved oxygen present in the reaction slurry due to the oxygen-containing gas continuously introduced into the reaction slurry. However, the amount of dissolved oxygen in the reaction slurry basically depends on the temperature of the reaction slurry. That is, the lower the reaction slurry temperature, the higher the dissolved oxygen concentration, and the higher, the lower the dissolved oxygen concentration. Although it is difficult to measure the dissolved concentration in the reaction slurry on an industrial scale, in order to adjust the oxidizing atmosphere, the amount of oxygen present in the reaction slurry, and hence the amount of oxygen supplied to the reaction slurry, is set to the reaction temperature. It may be necessary to adjust them together.
[0022]
By the way, when an oxidation reaction is performed at 70 ° C. or higher using a normal oxygen-containing gas and air utilized from the economical aspect, basically, the main component is magnetite having FeO of 16% by mass or higher. Iron oxide particles are generated. At this time, in order to deposit more magnetite, the reaction temperature may be high, and it is stable and hardly forms other forms of iron oxide regardless of the reaction pH.
[0023]
In the present invention, by increasing the dissolved oxygen concentration and locally forming a peroxidation atmosphere in the reaction slurry, a part of the magnetite generated by the normal air oxidation is converted into maghemite, and the magnetite is uniformly and It was inferred that it could be finely dissolved or dispersed and precipitated.
[0024]
Specifically, when the reaction slurry temperature is a low temperature of 60 ° C. or higher and lower than 70 ° C., the oxidation reaction is performed using air. Moreover, in the case of 70-75 degreeC, an oxidation reaction is performed by oxygen-containing gas whose oxygen concentration is higher than the air prepared by 1 type, or 2 or more types in air, oxygen, and nitrogen. At this time, when the reaction slurry temperature is less than 60 ° C., goethite is remarkably generated, and when the reaction slurry temperature exceeds 75 ° C., magnetite is stably generated alone, and the target iron oxide of the present invention is used together. It is difficult to obtain particles.
[0025]
As described above, it is difficult to measure the dissolved oxygen concentration in the reaction slurry, but it is effective to observe the oxidizing atmosphere in the reaction slurry using an oxidation-reduction potentiometer (ORP meter). Specifically, it is preferable to control the observation of the oxidizing atmosphere at −200 to 0 mV.
[0026]
The iron oxide particles containing magnetite and maghemite of the present invention obtained by the above production method are obtained by simply oxidizing the surface of the magnetite particles (including both natural oxidation and intentional oxidation treatment). Unlike iron oxide particles, low FeO content iron oxide particles coated with maghemite, etc., the blackness is excellent and at the same time, there is almost no deterioration in various environments.
[0027]
Also, oxides, hydroxides, and oxyhydroxides containing components such as Si, Al, Mn, Zn, Ni, Cu, Mg, Ti, Co, Zr, W, Mo, and P inside the particle surface and / or the particle surface Products, hydrated oxides, and mixtures thereof, as appropriate, or in the case of coating or coating, soluble salts of the above components are used as starting materials in ferrous salt aqueous solutions, alkaline aqueous solutions, reaction slurries, or cores It may be added to the particle generation slurry to perform oxidation reaction, neutralization reaction treatment, etc. In the wet slurry state containing ferrous salt, if the soluble salt of the above components is added and oxidation reaction is performed, the above metal It can be contained or coated on the iron oxide particles in the form of complex oxide of element and iron. Further, the iron oxide particles obtained by filtering, washing, and drying the slurry after completion of the oxidation reaction are mixed with the above-mentioned various compounds and various organic treatment agents, etc., and subjected to mechanical treatment to obtain a surface-coated iron oxide. It can also be a particle.
[0028]
【Example】
Hereinafter, based on an example etc., the present invention is explained concretely.
[0029]
[Example 1]
As shown in Table 1, 50 liters of ferrous sulfate aqueous solution containing 2.0 mol / l of Fe 2+ and 50 liters of 4.0 mol / l sodium hydroxide were mixed and stirred, and the ferrous hydroxide colloid was mixed. An aqueous ferrous salt solution was obtained. While maintaining the temperature of the reaction aqueous solution at 60 ° C., 10 liter / min of air was vented to carry out the oxidation reaction. The obtained iron oxide particle slurry was processed by normal filtration, washing, drying, and pulverization processes to obtain iron oxide particles. Various characteristics of the obtained iron oxide particles were evaluated by the following methods. The results are shown in Table 2.
[0030]
〔Measuring method〕
(1) Particle shape and particle size measurement Using a scanning electron microscope, the particle shape was observed at a magnification of 20000 and the ferret diameter was measured for 200 particles, and the average particle size was determined.
(2) Specific surface area Measured with a 2200 type BET meter manufactured by Shimadzu-Micromeritex.
(3) by XRD profile X-ray diffraction apparatus, the compound (Fe 3 O 4, γ- Fe 2 O 3, α-Fe 2 O 3) was identified peaks.
(4) FeO content rate sample was dissolved in sulfuric acid and measured by redox titration using a potassium permanganate standard solution.
(5) Magnetic properties Using a vibration type magnetometer VSM-P7 manufactured by Toei Kogyo Co., Ltd., measurement was performed with an external magnetic field of 796 kA / m and 79.6 kA / m.
(6) Colorimetry (blackness, hue)
Add 1.4 cc of castor oil to 2.0 g of sample and knead with Hoover-type Mahler. After adding 7.5 g of lacquer to 2.0 g of this kneaded sample and further kneading, this was applied onto a mirror-coated paper using a 4 mil applicator, dried, and then a color difference meter (manufactured by Tokyo Denshoku Co., Ltd., Color measurement was performed using a color analyzer TC-1800 type).
(7) The heat resistance test sample was put in a watch glass, and kept at 150 ° C. for 1 hour in a ventilated dryer (Tabba Espec oven, PH-201 type) to measure the deterioration of FeO.
[0031]
[Examples 2-6 and Comparative Examples 1-2]
Iron oxide particles were obtained in the same manner as in Example 1 except that the conditions shown in Table 1 were set. Various properties of the obtained iron oxide particles were evaluated in the same manner as in Example 1. The results are shown in Table 2.
[0032]
[Table 1]
[Table 2]
As is clear from the results in Table 2, the iron oxide particles of Examples 1 to 6 have a low FeO content, but have a small rate of deterioration of FeO after a heating test in the atmosphere and are sufficiently excellent in blackness. Further, the saturation magnetization is sufficiently high, and it is also suitable for the use of magnetic toner material powder for printers and electrostatic copying carrier material powder. Further, it was found from the XRD profile that Fe 3 O 4 and γ-Fe 2 O 3 were contained.
[0035]
On the other hand, the iron oxide particles of Comparative Example 1 have a high FeO content and excellent blackness, but have a large deterioration rate of FeO after a heating test in the air and are extremely inferior in oxidation resistance. It was. Moreover, the iron oxide particles of Comparative Example 2 had an L value that was too large and was inferior in blackness as a black pigment.
[0036]
【The invention's effect】
As described above, the iron oxide particles of the present invention have a low FeO content and a low L value by a color difference meter, thereby having blackness and magnetic properties equivalent to or higher than those of conventional iron oxide particles. In addition, it has excellent oxidation resistance, particularly thermal stability, and is suitable for electrostatic copying magnetic toner material powder, electrostatic copying carrier material powder, paint black pigment powder, and the like.
Claims (4)
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| JP2000236656A JP3828727B2 (en) | 2000-08-04 | 2000-08-04 | Iron oxide particles |
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| ITMI20020567A1 (en) * | 2002-03-18 | 2003-09-18 | Sud Chemie S R L | PROCESS FOR THE PREPARATION OF IRON OXIDES |
| JP4603943B2 (en) * | 2004-10-08 | 2010-12-22 | キヤノン株式会社 | Magnetic toner |
| JP4590319B2 (en) * | 2005-07-11 | 2010-12-01 | キヤノン株式会社 | Two-component developer |
| JP5037982B2 (en) * | 2007-03-23 | 2012-10-03 | Ｄｏｗａエレクトロニクス株式会社 | Carrier core material for electrophotographic developer and method for producing the same, carrier for electrophotographic developer, and electrophotographic developer |
| JP5038002B2 (en) * | 2007-04-10 | 2012-10-03 | Ｄｏｗａエレクトロニクス株式会社 | Carrier core material for electrophotographic developer and method for producing the same, carrier for electrophotographic developer, and electrophotographic developer |
| JP5588826B2 (en) * | 2010-10-29 | 2014-09-10 | 三井金属鉱業株式会社 | Magnetic iron oxide particle dispersion and method for producing the same |
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