JP4454565B2 - Magnetite particles - Google Patents
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Abstract
Description
本発明は、銅及び／又はセリウムを含有するマグネタイト粒子に関し、詳しくは、湿式法による酸化反応時に、スラリーの粘度上昇を抑えることによって、粒度分布に優れ、かつ磁気特性、とりわけ保磁力の安定性に優れた、特に静電複写磁性トナー用、静電潜像現像用キャリア用及び塗料用黒色顔料粉等の用途に用いられるマグネタイト粒子に関する。 The present invention relates to magnetite particles containing copper and / or cerium, and more specifically, by suppressing an increase in the viscosity of a slurry during an oxidation reaction by a wet method, the particle size distribution is excellent, and magnetic properties, particularly the stability of coercive force. In particular, the present invention relates to magnetite particles used for applications such as electrostatic pigment magnetic toner, electrostatic latent image developing carrier and paint black pigment powder.
最近、電子複写機、プリンター等の磁性トナー用材料粉として、水溶液反応によるマグネタイト粒子が広く利用されている。磁性トナーとしては、各種の一般的現像特性が要求されるが、近年、電子写真技術の発達により、特にデジタル技術を用いた複写機、プリンターが急速に発達し、要求特性が高度なものになってきた。 Recently, magnetite particles by an aqueous solution reaction have been widely used as material powders for magnetic toners for electronic copying machines, printers and the like. As magnetic toner, various general development characteristics are required, but in recent years, due to the development of electrophotographic technology, especially copiers and printers using digital technology have rapidly developed, and the required characteristics have become advanced. I came.
すなわち、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の高さ、各環境下でも問題なく使用できること等が強く要求されている。 That is, 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 is more precise. It is becoming. For this reason, there are strong demands for high reproducibility of fine lines in development, and that they can be used without problems even in various environments.
このような要求に対して、マグネタイトを主に含有する酸化鉄粒子の改良が様々になされてきた。特に、酸化鉄粒子のバインダー樹脂への分散性についての改良が進められてきた。 In response to such demands, various improvements in iron oxide particles mainly containing magnetite have been made. In particular, improvements have been made on the dispersibility of iron oxide particles in a binder resin.
その中で、例えば特許文献１ないし８においては、酸化鉄粒子の平均粒子径とその標準偏差による式（１）の値が小さくなるような酸化鉄粒子について開示されている。 Among them, for example, Patent Documents 1 to 8 disclose iron oxide particles in which the value of the formula (1) based on the average particle diameter and standard deviation of the iron oxide particles is small.
これらの各公報に記載されている内容としては、粒子の大きさについて、粒度分布の優れた酸化鉄粒子を使用した磁性トナーは、トナーの評価において、様々な優位性が示されている。 As the contents described in each of these publications, magnetic toners using iron oxide particles having an excellent particle size distribution in terms of particle size have various advantages in toner evaluation.
しかし、磁性トナー用としての酸化鉄粒子の粒度分布については、更なる向上が求められている。最近は特にハーフトーンの再現性等、単純な白黒表現によりも階調性に対して、材料粉としての酸化鉄粒子の改良も求められてきている。 However, further improvement is required for the particle size distribution of iron oxide particles for magnetic toners. Recently, improvement of iron oxide particles as a material powder has also been demanded with respect to gradation by simple black and white expression such as halftone reproducibility.
上記従来技術の中には、このような更なる粒度分布の改良手段として、ケイ素を使用することが好ましい手段として開示されている。例えば、特許文献９によれば、水酸化第一鉄を含む懸濁液中に水可溶性ケイ酸塩（生成するマグネタイト粒子に対しＳｉＯ2 換算で０．１〜２．０重量％）を存在させると、生成するマグネタイト粒子の分布をさらによく
することができるので好ましいとされている。
In the above prior art, it is disclosed as a preferable means that silicon is used as a means for further improving the particle size distribution. For example, according to Patent Document 9, water-soluble silicate (0.1 to 2.0% by weight in terms of SiO 2 with respect to the generated magnetite particles) is present in a suspension containing ferrous hydroxide. And the distribution of the magnetite particles to be generated can be further improved.
しかしながら、このようなケイ酸塩を使用することは、電子写真の分野において、温度や湿度の変化に対する環境依存性が問題となり易く、磁気特性面でも劣ることが推定できる。 However, the use of such a silicate can be presumed to be inferior in terms of magnetic properties in the field of electrophotography, in which the environmental dependency with respect to changes in temperature and humidity tends to be a problem.
従って、粒度分布に優れ、なおかつ上記環境依存性や磁気特性等の他の諸特性を損なわない酸化鉄粒子は、いまだ十分なものが示されていない。 Accordingly, iron oxide particles that are excellent in particle size distribution and do not impair other characteristics such as the above-mentioned environmental dependence and magnetic characteristics have not been shown yet.
一方、湿式で酸化鉄粒子を製造する場合には、第一鉄塩水溶液とアルカリ水溶液を中和混合して得られた水酸化第一鉄スラリーを酸素含有ガスにて酸化する方法が一般によく利用されるが、この酸化反応の際に、スラリー粘度はかなり上昇する。 On the other hand, when producing iron oxide particles by wet method, a method of oxidizing ferrous hydroxide slurry obtained by neutralizing and mixing ferrous salt aqueous solution and alkaline aqueous solution with oxygen-containing gas is generally used. However, during this oxidation reaction, the slurry viscosity rises considerably.
この粘度上昇が著しい場合には、酸化反応にかかわる酸素含有ガスのスラリー中での分散が不良となり、その結果生成する微細粒子の粒度分布が悪くなり、その後の反応で粒度分布を改善することは難しい。 If this viscosity increase is significant, the dispersion of the oxygen-containing gas involved in the oxidation reaction in the slurry will be poor, resulting in poor particle size distribution of the fine particles produced, and improving the particle size distribution in subsequent reactions. difficult.
スラリー粘度上昇を防ぐ手段としては、スラリー濃度を下げる方法や、酸化反応を一旦止めて微細粒子の生成を制御する方法等が有効であるが、湿式製造法はバッチ式が殆どなので生産性の面から見て非常に不都合である。 As a means to prevent an increase in slurry viscosity, a method of reducing the slurry concentration or a method of temporarily controlling the production of fine particles by temporarily stopping the oxidation reaction, etc. are effective. It is very inconvenient to see from.
また、目標とする酸化鉄粒子の粒径がフェレ径の平均粒径が０．３μｍ以下の小粒径の場合には、上記粘度上昇現象の影響で、得られた酸化鉄粒子の粒度分布はさらにブロードとなり易い。 In addition, when the target particle size of the iron oxide particles is a small particle size with a ferret average particle size of 0.3 μm or less, the particle size distribution of the obtained iron oxide particles is Furthermore, it is easy to become broad.
上述の通り、粒径が小さくても粒度分布がシャープな酸化鉄粒子を得ることは難しく、その製造方法について具体的な提案は上記従来技術においてはなされていない。 As described above, it is difficult to obtain iron oxide particles having a sharp particle size distribution even if the particle size is small, and no specific proposal has been made regarding the production method in the above-described conventional technology.
また、マグネタイトのようにＦｅＯを含有する形態では、空気中の酸素及び熱によって酸化し易く、このような形態からなる酸化鉄粒子に要求される特性としては、使用前における酸化鉄粒子中のＦｅＯの安定性や熱可塑性樹脂との熱混練時における耐熱性が求められる。 Moreover, in the form containing FeO like magnetite, it is easily oxidized by oxygen and heat in the air, and the characteristics required for the iron oxide particles having such a form include FeO in the iron oxide particles before use. Stability and heat resistance during thermal kneading with a thermoplastic resin are required.
酸化鉄粒子の粒径が小さい場合には、より酸化による影響を受け易く、具体的には粒度分布の悪い酸化鉄粒子においては、粒径の小さな粒子の存在によって含有ＦｅＯの劣化が著しいといった問題が発生する。 When iron oxide particles have a small particle size, they are more susceptible to oxidation. Specifically, in iron oxide particles having a poor particle size distribution, the content of FeO is significantly deteriorated due to the presence of particles having a small particle size. Will occur.
このような耐酸化性や耐熱性の向上のために、粒子表面に耐熱性を付与する処理を行うことが従来技術にも開示されている。この中には、Ｓｉ、Ａｌ、Ｚｎ成分等による被覆によって、耐熱性が向上したことが示されているが、このような元素を粒子表面に被覆すると、粉末の吸湿性が高くなったり、粉体の色相や分散性に悪い影響を与える。 In order to improve such oxidation resistance and heat resistance, it has been disclosed in the prior art to perform a treatment for imparting heat resistance to the particle surface. In this, it is shown that the heat resistance is improved by coating with Si, Al, Zn components, etc., but if such an element is coated on the particle surface, the hygroscopicity of the powder increases or the powder increases. It adversely affects the hue and dispersibility of the body.
従って、本発明の目的は、粒径分布に優れ、磁気特性、とりわけ保磁力の安定性に優れ、かつ含有ＦｅＯの安定性や耐熱性に優れたマグネタイト粒子を提供することにある。 Accordingly, an object of the present invention is excellent in particle size distribution, the magnetic properties, especially excellent stability of coercive force, and to provide excellent magnetite particles stability and heat resistance of containing FeO.
本発明者等は、上記従来技術を踏まえ、マグネタイト粒子に特定量の銅及び／又はセリウム成分を含有させることにより、上記目的を達成し得ることを知見した。 The present inventors have found that the above object can be achieved by incorporating magnetite particles with a specific amount of copper and / or cerium component based on the above prior art.
本発明は、上記知見に基づきなされたもので、セリウムを酸化鉄粒子総量に対して０．００１〜０．５重量％含有することを特徴とするマグネタイト粒子を提供するものである。 The present invention has been made based on the above finding, there is provided a magnetite particles characterized in that it contains 0.001 to 0.5 wt% of cell helium against the iron oxide particles total volume.
また、本発明は、第一鉄塩を含有する水溶液とアルカリ水溶液とを中和して得られた水酸化第一鉄スラリーの酸化反応を行い、酸化反応の途中に水可溶性の銅塩を添加することで得られたマグネタイト粒子であって、銅を酸化鉄粒子総量に対して０．０４８〜０．５重量％含有することを特徴とするマグネタイト粒子を提供するものである。 In addition, the present invention performs an oxidation reaction of a ferrous hydroxide slurry obtained by neutralizing an aqueous solution containing ferrous salt and an aqueous alkaline solution, and a water-soluble copper salt is added during the oxidation reaction. It is a magnetite particle obtained by carrying out, Comprising: The magnetite particle | grains which contain 0.048 to 0.5 weight% of copper with respect to the iron oxide particle total amount are provided.
本発明のマグネタイト粒子は、銅及び／又はセリウム成分を含有することによって、粒度分布に優れ、磁気特性、とりわけ保磁力の安定性に優れ、かつ含有ＦｅＯの安定性や耐熱性に優れており、特に静電複写磁性トナー用材料粉、静電潜像現像用キャリア用材料粉、塗料用黒色顔料粉等の用途に最適である。また、添加する銅及び／又はセリウムによる酸化反応時のスラリー粘度低下作用により、マグネタイト粒子の粒度を揃えるのみならず、工業的な酸化鉄粒子製造における生産性も向上する。 The magnetite particles of the present invention contain a copper and / or cerium component, so that the particle size distribution is excellent, the magnetic properties, particularly the stability of the coercive force, and the stability and heat resistance of the contained FeO are excellent. In particular, it is optimal for applications such as electrostatic copying magnetic toner material powder, electrostatic latent image developing carrier material powder, and black pigment powder for paint. Moreover, not only the particle size of magnetite particles is made uniform but also the productivity in industrial iron oxide particle production is improved by the action of reducing the viscosity of the slurry during the oxidation reaction with added copper and / or cerium .
以下、本発明の実施の形態を説明する。
本発明は、マグネタイト（Ｆｅ3 Ｏ4 ）粒子に係るものである。マグネタイト粒子は、分散性を向上させるために、ＳｉやＡｌ、あるいは有機処理剤等による表面処理を施したものであってもよい。以下の説明でマグネタイト粒子という時には、その内容によって個々の粒子又はその集合のいずれも意味する。
Embodiments of the present invention will be described below.
This onset Ming is according to magnetite (Fe 3 O 4) particles. Magnetite particles, in order to improve dispersibility, or may be subjected to surface treatment with Si or Al or an organic treatment agent. By the time that the following description hoax Gunetaito particles, to mean any of the individual particles or aggregate thereof by its contents.
本発明のマグネタイト粒子の形状は、トナー用に適した特性を付与できるものであれば特に限定されないが、トナー用材料粉として一般的な粒状品（球状、八面体状、六面体状等）が好ましい。 The shape of the magnetite particles of the present invention is not particularly limited as long as it can give properties suitable for toner, but general granular products (spherical, octahedral, hexahedral, etc.) are preferable as toner powder. .
また、粒子の大きさとしては、粒子のフェレ径の平均粒径として０．０５〜１μｍ、より好ましくは０．０８〜０．５μｍ、さらに好ましくは０．１〜０．３μｍである。 The particle size is 0.05 to 1 μm, more preferably 0.08 to 0.5 μm, and still more preferably 0.1 to 0.3 μm, as an average particle diameter of the ferret diameter of the particles.
本発明のマグネタイト粒子は、セリウムをマグネタイト粒子総量に対して０．００１〜０．５重量％含有することを特徴とするものである。セリウムの含有量は、好ましくは０．００２〜０．４重量％であり、より好ましくは０．００４〜０．３重量％である。また本発明のマグネタイト粒子は、銅をマグネタイト粒子総量に対して０．０４８〜０．５重量％含有することを特徴とするものである。 Magnetite particles of the present invention is characterized in that it contains 0.001 to 0.5 wt% of cell potassium respect magnetite particles the total amount. The content of Se helium is preferably 0.002 to 0.4 wt%, more preferably from 0.004 to 0.3 wt%. The magnetite particles of the present invention are characterized by containing copper in an amount of 0.048 to 0.5% by weight based on the total amount of magnetite particles.
マグネタイト粒子に銅及び／又はセリウムを含有させることによる効果については後述するが、基本的には粒度分布の改善にあり、この含有率が０．００１重量％未満（セリウムの場合）又は０．０４８重量％未満（銅の場合）の場合には、粒度分布改善効果が得られず、０．５重量％を超える場合には、磁気特性の劣化、特に飽和磁化の低下等が生じ、またその他特性への弊害が生じる。 The effect of including copper and / or cerium in the magnetite particles will be described later. Basically, the particle size distribution is improved. This content is less than 0.001% by weight (in the case of cerium) or 0.048. If the amount is less than wt% (in the case of copper) , the effect of improving the particle size distribution cannot be obtained. If the amount exceeds 0.5 wt%, the magnetic properties deteriorate, particularly the saturation magnetization decreases, and other properties. Harmful to.
また、本発明のマグネタイト粒子は、熱可塑性樹脂との混練物を粉砕して得られるトナー粒子粉末の外部磁場１０ｋＯｅにおける保磁力のバラツキが５Ｏｅ以下であることを特徴とする。 The magnetite particles of the present invention are characterized in that the variation in coercive force in an external magnetic field of 10 kOe of a toner particle powder obtained by pulverizing a kneaded product with a thermoplastic resin is 5 Oe or less.
この特徴は、粒子に特定の銅及び／又はセリウムを含有することにより得られるもので、粒度分布が格段に優れていることにより、保磁力の安定化を図ることが可能となる。 This characteristic is obtained by containing specific copper and / or cerium in the particles, and the coercive force can be stabilized because the particle size distribution is remarkably excellent.
また、本発明のマグネタイト粒子を乾燥する際、真空乾燥した試料と、空気中、５０℃で１２時間乾燥した試料のＦｅＯ含有率の差が５重量％以下であることが望ましい。さらに好ましくはこのＦｅＯ含有率の差が３重量％以下であり、より好ましくは１重量％以下である。このことによって、含有ＦｅＯの安定性や耐熱性に優れる。 Moreover, when drying the magnetite particles of the present invention, it is desirable that the difference in FeO content between the sample dried in vacuum and the sample dried in air at 50 ° C. for 12 hours is 5% by weight or less. More preferably, the difference in the FeO content is 3% by weight or less, more preferably 1% by weight or less. Thereby, the stability and heat resistance of the contained FeO are excellent.
次に、本発明のマグネタイト粒子の製造方法は、第一鉄塩を含有する水溶液とアルカリ水溶液とを中和して得られた水酸化第一鉄スラリーを酸化するマグネタイト粒子の製造方法において、第一鉄塩の酸化反応率が１〜３０％の間に水可溶性の銅及び／又はセリウム塩を添加することを特徴とする。 Next, the method for producing magnetite particles according to the present invention is the method for producing magnetite particles for oxidizing a ferrous hydroxide slurry obtained by neutralizing an aqueous solution containing a ferrous salt and an alkaline aqueous solution. A water-soluble copper and / or cerium salt is added while the oxidation reaction rate of the ferrous salt is 1 to 30%.
本発明においては、上記のように水酸化第一鉄スラリー中の第一鉄塩の酸化反応率が１〜３０％において、水可溶性の銅及び／又はセリウム塩を添加することが重要であり、特に酸化反応率が２〜２０％においての添加が好ましい。上記添加時期において第一鉄塩の酸化反応率が１％未満の場合には、反応当初よりマグネタイト微細粒子の生成が抑制を受け易く、かえって粒度分布への悪影響が生じることとなるし、第一鉄塩の酸化反応率が３０％を超える場合には、スラリー粘度が落ち着いた状態なので粒度分布改善効果が期待できない。 In the present invention, as described above, when the oxidation reaction rate of the ferrous salt in the ferrous hydroxide slurry is 1 to 30%, it is important to add water-soluble copper and / or cerium salt, Addition at an oxidation reaction rate of 2 to 20% is particularly preferable. If the oxidation reaction rate of the ferrous salt is less than 1% at the addition time, the formation of magnetite fine particles is likely to be suppressed from the beginning of the reaction, which adversely affects the particle size distribution. When the oxidation reaction rate of the iron salt exceeds 30%, the effect of improving the particle size distribution cannot be expected because the slurry viscosity is settled.
本発明に用いられる水可溶性の銅及び／又はセリウム塩としては、硫酸銅（II）、硝酸銅（II）や硫酸セリウム、硝酸セリウム等が例示される。また、水可溶性の銅及び／又はセリウム塩の添加方法は、一括添加でも、徐々に添加しても構わないが、効果の持続性や作業の容易さから考えると、一括添加の方が好ましい。 Examples of the water-soluble copper and / or cerium salt used in the present invention include copper (II) sulfate, copper (II) nitrate, cerium sulfate, and cerium nitrate. Moreover, the addition method of water-soluble copper and / or cerium salt may be added all at once or gradually, but in view of the sustainability of the effect and the ease of work, the batch addition is more preferable.
マグネタイト粒子を始めとする酸化鉄粒子に銅を含有させる技術については、特公平３−５３２５７号公報、特公平３−２４４１２号公報、特開平９−５９０２４号公報、及び特開平９−５９０２５号公報等に開示されているが、いずれも銅以外の多くの元素も含む成分群の中から選択する事例であり、本発明が目的とする粒度分布の改善効果を示してはいない。また、酸化鉄粒子にセリウムを含有させる技術については、全く公知技術は見当たらない。 With regard to the technology for containing copper in iron oxide particles including magnetite particles, Japanese Patent Publication No. 3-53257, Japanese Patent Publication No. 3-24121, Japanese Patent Application Laid-Open No. 9-59024, and Japanese Patent Application Laid-Open No. 9-59025 are disclosed. However, all are examples selected from a group of components including many elements other than copper, and do not show the effect of improving the particle size distribution intended by the present invention. In addition, there is no known technique for incorporating cerium into iron oxide particles.
マグネタイト粒子に銅及び／又はセリウムを含有させることによって、何故に粒度分布改善に効果があるかについては定かではないが、本発明者等は酸化反応時に、反応スラリー中に銅及び／又はセリウム成分を添加した際のスラリー粘度が低下する現象に着目した。 Although it is not clear why the inclusion of copper and / or cerium in the magnetite particles is effective in improving the particle size distribution, the present inventors have determined that the copper and / or cerium component in the reaction slurry during the oxidation reaction. Attention was paid to the phenomenon that the viscosity of the slurry was reduced when selenium was added.
一般に、第一鉄塩水溶液とアルカリ水溶液を中和混合して得られた水酸化第一鉄スラリーを酸化するマグネタイト粒子の製造方法においては、酸化反応開始よりスラリー中の第一鉄塩の酸化反応率が３０％程度となるまで粘度が一旦上昇する。この上昇はスラリー中に反応で生じたマグネタイト粒子が微細であるがゆえ起こるものであり、粒子の成長が進むにつれ、収まるものと推測される。 In general, in the method for producing magnetite particles that oxidize ferrous hydroxide slurry obtained by neutralizing and mixing ferrous salt aqueous solution and alkaline aqueous solution, oxidation reaction of ferrous salt in the slurry from the start of the oxidation reaction The viscosity increases once until the rate reaches about 30%. This rise occurs because the magnetite particles generated by the reaction in the slurry are fine, and it is assumed that the rise will be settled as the particles grow.
本発明においては、銅やセリウムの酸化還元による価数変化（Ｃｕ2+−Ｃｕ+ やＣｅ4+−Ｃｕ3+）が、Ｆｅ2+からＦｅ3+への酸化速度を適度に調整することにより、過剰で不均一な微細マグネタイト粒子の生成を妨害する作用があるのではないかと考えた。つまり、微細なマグネタイト粒子の発生を抑えることにより、反応スラリーの粘度が下がり、粒度分布の改善に寄与するのである。また、銅やセリウムは比較的フェライトを形成しにくい元素として知られており、少量の添加でもスラリー中に残留して、持続的なスラリー粘度の低減効果を奏するものと考えられる。 In the present invention, the valence change (Cu 2+ -Cu + or Ce 4+ -Cu 3+ ) due to redox of copper or cerium appropriately adjusts the oxidation rate from Fe 2+ to Fe 3+ . Therefore, it was thought that there may be an action that hinders the generation of excessive and non-uniform fine magnetite particles. That is, by suppressing the generation of fine magnetite particles, the viscosity of the reaction slurry is lowered, contributing to the improvement of the particle size distribution. Further, copper and cerium are known as elements that are relatively difficult to form ferrite, and even if added in a small amount, they remain in the slurry, and are considered to exert a continuous slurry viscosity reducing effect.
本発明のマグネタイト粒子の製造方法によれば、特に工業的規模での低濃度スラリー反応下において、反応槽内の均一化、核生成と結晶成長の制御が困難であった従来の製造方法に対し、簡易な手段で粒度分布の優れたマグネタイト粒子を製造することができる。 According to the method for producing magnetite particles of the present invention, particularly in the case of a low concentration slurry reaction on an industrial scale, compared with the conventional production method in which homogenization in the reaction vessel, nucleation and crystal growth are difficult to control. Thus, magnetite particles having an excellent particle size distribution can be produced by simple means.
以下、実施例等に基づき本発明を具体的に説明する。 Hereinafter, the present invention will be specifically described based on examples and the like.
〔実施例１〕
表１に示されるように、Ｆｅ2+を２．５ｍｏｌ／ｌ含有する硫酸第一鉄水溶液４０リットルと、ＮａＯＨを８．０ｍｏｌ／ｌ含有する水酸化ナトリウム水溶液２５．５リットルとを中和混合した。混合後のスラリーの液温を８５℃、及び温水を用いてスラリー液量を１００リットルになるように調整した後、スラリーを撹拌しながら２０リットル／ｍｉｎにて空気を通気して酸化反応を行った。反応中にスラリー中の最高粘度（ＴＯＫＩＭＥＣ．ＩＮＣ．製、ＶＩＳＣＯＭＥＴＥＲ ＭＯＤＥＬ ＢＭ型にて測定）及び未反応Ｆｅ2+の測定を行った。酸化反応の途中、酸化反応率が２０％に達したところでセリウムを０．１ｍｏｌ／ｌ含有する溶液を３リットル添加した。酸化反応終了後、得られたマグネタイトスラリーを通常の濾過、洗浄、乾燥、粉砕工程を経てマグネタイト粒子を得た。
[Example 1]
As shown in Table 1, 40 liters of ferrous sulfate aqueous solution containing 2.5 mol / l Fe 2+ and 25.5 liters sodium hydroxide aqueous solution containing 8.0 mol / l NaOH were neutralized and mixed. did. Adjust the slurry temperature after mixing to 85 ° C and the volume of the slurry to 100 liters using hot water, and then conduct the oxidation reaction by aeration of air at 20 liters / min while stirring the slurry. It was. During the reaction, the maximum viscosity in the slurry (manufactured by TOKIMEC. INC., Measured with VISCOMETER MODEL BM type) and unreacted Fe 2+ were measured. During the oxidation reaction, when the oxidation reaction rate reached 20%, 3 liters of a solution containing 0.1 mol / l of cerium was added. After the oxidation reaction, the obtained magnetite slurry was subjected to normal filtration, washing, drying, and pulverization steps to obtain magnetite particles.
このようにして得られたマグネタイト粒子を以下に示す方法にて特性、性状を評価し、得られた結果を表２に示す。また、上記により測定したスラリー中の最高粘度を併せて表２に示す。 The properties and properties of the thus obtained magnetite particles were evaluated by the methods shown below, and the results obtained are shown in Table 2. Table 2 also shows the maximum viscosity in the slurry measured as described above.
〔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、平均粒径と粒径の標準偏差及び変動係数を求めた。
（２）比表面積
島津−マイクロメリテックス製２２００型ＢＥＴ計にて測定した。
（３）磁気特性
東英工業製振動型磁力計ＶＳＭ−Ｐ７型を使用し、外部磁場１０ｋＯｅにて測定した。
（４）化学分析
サンプルを酸に溶解し、ＩＣＰにて測定した。
（５）樹脂との混練物における保磁力の安定性評価
マグネタイト粒子を使用したトナーを試作し、飽和磁化値のバラツキにより、保磁力の安定性の評価を行った。
マグネタイト粒子、スチレン−アクリル系熱可塑性樹脂（三洋化成（株）製、ＴＢ−１０００Ｆ）、帯電制御剤（オリエント化学製、ボントロン Ｓ−３４）及びワックス（三洋化成（株）製、ビスコール ５５０Ｐ）をそれぞれ、重量比１００：１００：１：２にて計量し、ヘンシェルミキサーにて混合し、さらに２軸のニーダーを使用して１８０℃にて溶融混練を行った。得られた混練物を冷却し、バンタムミルにて粗粉砕を、さらにジェットミルにて微粉砕を行って、大きさの異なる２種類の粉砕品の粉末粒子を得た。
得られた２種類の粉末粒子中の磁気特性について、外部磁場１０ｋＯｅでの保磁力を、それぞれの粉砕品において異なる５ヶ所のサンプリングによって繰り返し測定を行い、計１０回の測定での粉末の最高保磁力値と最低保磁力値の差の大きさ（保磁力値のバラツキ）をもって保磁力の安定性の評価とした。
（６）マグネタイト粒子の乾燥によるＦｅＯ劣化試験
湿式法にて得られたマグネタイト粒子の濾過、洗浄したケーキの一部を、室温で真空デシケーター中にて乾燥させたサンプルと、上記ケーキの一部を空気中で５０℃の箱型乾燥機（タバイエスペック製、オーブンＰＨ−２０１）にて１２時間乾燥したサンプルについて、それぞれ硫酸に溶解した後、過マンガン酸カリウム標準液にて酸化還元滴定を行い、それぞれのサンプルのＦｅＯ含有量（重量％）を測定した。
〔Measuring method〕
(1) Particle shape and particle size measurement Using a scanning electron microscope, observe the particle shape at a magnification of 20000 times and measure the ferret diameter of 200 particles, and calculate the average particle diameter, standard deviation of particle diameter and coefficient of variation. Asked.
(2) Specific surface area Measured with a 2200 type BET meter made by Shimadzu-Micromeritex.
(3) Magnetic properties Measured with an external magnetic field of 10 kOe using a vibration magnetometer VSM-P7 manufactured by Toei Kogyo.
(4) Chemical analysis The sample was dissolved in acid and measured by ICP.
(5) Stability evaluation of coercive force in a kneaded product with a resin A toner using magnetite particles was prototyped, and the stability of the coercive force was evaluated based on variations in saturation magnetization values.
Magnetite particles, styrene-acrylic thermoplastic resin (manufactured by Sanyo Chemical Co., Ltd., TB-1000F), charge control agent (manufactured by Orient Chemical Co., Ltd., Bontron S-34) and wax (manufactured by Sanyo Chemical Co., Ltd., Viscol 550P) Each was weighed at a weight ratio of 100: 100: 1: 2, mixed with a Henschel mixer, and further melt-kneaded at 180 ° C. using a biaxial kneader. The obtained kneaded product was cooled, coarsely pulverized with a bantam mill, and further finely pulverized with a jet mill to obtain powder particles of two types of pulverized products having different sizes.
Regarding the magnetic properties in the two kinds of powder particles obtained, the coercive force at an external magnetic field of 10 kOe is repeatedly measured by sampling at five different points in each pulverized product, and the maximum retention of the powder in a total of 10 measurements. The magnitude of the difference between the magnetic force value and the minimum coercive force value (variation of coercive force value) was used to evaluate the stability of the coercive force.
(6) FeO degradation test by drying magnetite particles A sample of a cake obtained by filtering and washing a portion of the cake obtained by filtration and washing of the magnetite particles obtained by a wet method, and a portion of the cake described above. Samples dried for 12 hours in a box dryer (Obay PH-201, manufactured by Tabai Espec, Inc.) in air were each dissolved in sulfuric acid and then subjected to redox titration with a potassium permanganate standard solution. The FeO content (% by weight) of each sample was measured.
〔実施例２〜８〕
実施例１と同様に、表１に示される条件にてマグネタイト粒子を製造し、実施例１と同様に評価した結果を表２に示す。
[Examples 2 to 8 ]
As in Example 1, magnetite particles were produced under the conditions shown in Table 1, and the results evaluated in the same manner as in Example 1 are shown in Table 2.
〔比較例１〜４〕
表１に示されるように、銅又はセリウム成分を添加することなくマグネタイト粒子を製造し、実施例１と同様に評価した結果を表２に示す。
[Comparative Examples 1-4]
As shown in Table 1, magnetite particles were produced without adding a copper or cerium component, and the results evaluated in the same manner as in Example 1 are shown in Table 2.
表２から明らかなように、銅及び／又はセリウム成分を添加した実施例１〜８のマグネタイト粒子は、これらを添加しない比較例１〜４のマグネタイト粒子に対して、酸化反応時のスラリーの最高粘度が低く、また、粒径の変動係数も小さいことが判る。これは、酸化反応時の粘度の低下が、スラリー全体の均一な酸化反応にとって効果があるものと思われる。 As is clear from Table 2, the magnetite particles of Examples 1 to 8 to which copper and / or cerium components were added were the highest in the slurry during the oxidation reaction compared to the magnetite particles of Comparative Examples 1 to 4 to which these were not added. It can be seen that the viscosity is low and the coefficient of variation in particle size is also small. This is considered that the reduction in viscosity during the oxidation reaction is effective for the uniform oxidation reaction of the entire slurry.
さらに、比較例１〜４のマグネタイト粒子に比べ、実施例１〜８のマグネタイト粒子は、樹脂との混練物において保磁力のバラツキが小さく、粒度分布の改善により、樹脂中でのマグネタイト粒子の分散性が優れていることが判る。また、乾燥条件の相違に基づくＦｅＯ含有率の差が小さいことから、実施例１〜８のマグネタイト粒子は、含有ＦｅＯの安定性や耐熱性に優れている。特に、比較例１のような粒子径の小さなマグネタイト粒子は、酸化の影響を受け易く、ＦｅＯの差が大きい。しかし、実施例１を見ても明らかな通り、本発明のマグネタイト粒子では、小粒径でもＦｅＯの差は小さく酸化の影響を受けにくいことが判る。
Furthermore, compared with the magnetite particles of Comparative Examples 1 to 4, the magnetite particles of Examples 1 to 8 have less variation in coercive force in the kneaded product with the resin, and the dispersion of the magnetite particles in the resin by improving the particle size distribution. It can be seen that the properties are excellent. Moreover, since the difference of the FeO content based on the difference in drying conditions is small, the magnetite particles of Examples 1 to 8 are excellent in the stability and heat resistance of the contained FeO. In particular, the magnetite particles having a small particle diameter as in Comparative Example 1 are easily affected by oxidation and have a large difference in FeO. However, as is clear from Example 1, it can be seen that the magnetite particles of the present invention have a small difference in FeO even with a small particle size and are not easily affected by oxidation.
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