JP3578191B2 - Magnetic iron oxide particles, magnetic iron oxide particle powder for magnetic toner mainly comprising the particles, and magnetic toner using the magnetic iron oxide particle powder - Google Patents

Description

【０１３０】
【表２】

【０１３１】
比較例１で得られたマグネタイト粒子粉末は図３に示す電子顕微鏡写真（×５００００）から明らかな通り、六面体形状を有しているものであり、実施例１のマグネタイト粒子粉末に比べて樹脂混練物粒子表面からの脱落防止効果が十分ではなく、粒子表面に含有するＳｉが少ないため、流動性に劣るものである。
【０１３２】
＜被着処理＞
実施例４
実施例１で得られたマグネタイト粒子粉末１ｋｇを８０℃の水に分散させた後、攪拌しながら水酸化ナトリウム水溶液を滴下してｐＨを１１とした。次に、該粒子に対してＡｌ換算で１．００重量％の硫酸アルミニウム６３．４ｇを含む水溶液を滴下し、３．６Ｎの硫酸を滴下した後、ｐＨ７に調整し、３０分間攪拌した。その後、濾過、水洗した後、６０℃で乾燥して、粒子表面にアルミニウムの水酸化物が被着しているマグネタイト粒子粉末を得た。
【０１３３】
実施例５〜８、比較例８〜９
被処理粒子、処理物の種類及びその添加量を種々変化させた以外は実施例４と同様にして被着処理を行った。被着処理の条件及び得られた磁性酸化鉄粒子粉末の諸特性を表３に示した。
【０１３４】
【表３】

【０１３５】
＜疎水化処理＞
実施例９
前記実施の形態で得られたマグネタイト粒子粉末１０ｋｇとシランカップリング剤Ａ−１４３（日本ユニカ（株）製）１５ｇとをホイール型混練機（商品名：サンドミル （株）松本鋳造鉄工所製）に投入し、一時間作動させることにより、粒子表面にシランカップリング剤が被着しているマグネタイト粒子粉末を得た。
【０１３６】
実施例１０〜１５、比較例１０〜１１
被処理粒子、疎水化処理剤の種類及びその添加量を種々変化させた以外は実施例９と同様にして疎水化処理を行った。疎水化処理の条件及び得られた磁性酸化鉄粒子粉末の諸特性を表４に示した。
なお、上記以外の疎水化処理剤としては、チタネートカップリング剤 ブレンアクトＴＴＳ（味の素（株）製）、イソパルミチン酸（日産化学（株）製）を用いた。
【０１３７】
【表４】

【０１３８】
＜被着処理及び疎水化処理＞
実施例１６
前記実施の形態で得られた粒子表面にアルミニウムの水酸化物が被着しているマグネタイト粒子粉末１０ｋｇとシランカップリング剤Ａ−１４３（日本ユニカ（株）製）２０ｇとをホイール型混練機（商品名：サンドミル （株）松本鋳造鉄工所製）に投入し、一時間作動させることにより、さらに、粒子表面にシランカップリング剤が被着しているマグネタイト粒子粉末を得た。
【０１３９】
実施例１７〜２２
粒子表面に特定元素の酸化物等が被着している被処理粒子の種類、疎水化処理剤の種類及びその添加量を種々変化させた以外は実施例１６と同様にして疎水化処理を行った。疎水化処理の条件及び得られた磁性酸化鉄粒子粉末の諸特性を表５に示した。
【０１４０】
【表５】

【０１４１】
【発明の効果】
本発明に係る磁性トナー用磁性酸化鉄粒子粉末は、粒子サイズが０．０５〜０．５０μｍの微細粒子であり、粒子形状が粒状を基本とする角の丸い金平糖状であり、且つ、投影図上において粒子表面上の凸状突起物の数が２〜３０個の範囲である磁性酸化鉄粒子を個数割合で６０％以上含有することから、トナー粒子からの脱落がなく、Ｓｉを粒子表面に多く含有することから、トナーにしたときの流動性が良好であって、均一な帯電性が得られることから静電潜像現像において高解像度の画質が得られる磁性トナー用磁性酸化鉄粒子粉末として最適であり、さらに、発熱開始温度が１５０℃以上と高い場合には高い温度範囲での使用においても安定して使用でき、粒子表面の疎水性が十分であって吸油量が少ない場合には、樹脂への分散性を良好にすることができる。
【図面の簡単な説明】
【図１】本発明に係る磁性酸化鉄粒子の形態を拡大して模型的にした概念説明図である。
【符号の説明】
ａ 突起物の底辺の長さ
ｂ 突起物の高さ
ｃ 粒子径
【図２】本発明の実施の形態で得られたマグネタイト粒子粉末の粒子構造を示す電子顕微鏡写真（×５００００）である。
【図３】比較例１で得られたマグネタイト粒子粉末の粒子構造を示す電子顕微鏡写真（×５００００）である。
【図４】比較例２で得られたマグネタイト粒子粉末の粒子構造を示す電子顕微鏡写真（×５００００）である。
【図５】比較例５で得られたマグネタイト粒子粉末の粒子構造を示す電子顕微鏡写真（×５００００）である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a magnetic iron oxide particle powder for a magnetic toner, which does not fall off from toner particles and has good fluidity when formed into a toner, so that high-resolution image quality can be obtained in electrostatic latent image development. The present invention relates to a magnetic toner using iron oxide particles.
[0002]
[Prior art]
As one of the electrostatic latent image developing methods, a so-called “one-component magnetic toner” using, as a developer, composite particles in which magnetic particles such as magnetite particles are mixed and dispersed in a binder resin without using a carrier. Is widely known and widely used.
[0003]
Recently, along with high performance such as miniaturization and high speed of electrostatic copying machines and printing equipment, the characteristics of magnetic toner as a developer have been improved, that is, durability that stable development performance can be obtained even under hard use conditions There is a strong demand for excellent magnetic toners. Further, there is a need for a magnetic toner capable of obtaining high resolution due to high fluidity.
[0004]
Usually, the magnetic toner is composed of magnetic particles and a binder resin, and the magnetic particles are uniformly dispersed in the toner particles. The magnetic particles exposed on the surface of the toner particles easily fall off from the toner particles due to friction or the like.In particular, the ratio of the magnetic particles exposed on the surface increases in a small particle size toner. In addition to the pulverization, the environment inside the device is deteriorated, and not only the uniform charging of the toner is hindered, but also the dropped magnetic particle powder is scattered during the electrostatic development to cause problems such as a decrease in developability. Therefore, there is a strong demand for magnetic particle powders that are hard to fall off even when exposed to the surface of toner particles and have excellent durability.
[0005]
The resolution at the time of developing an electrostatic latent image is described in Japanese Patent Application Laid-Open No. 63-139367, "In such a method using a dry developer, in order to form a visible image with good image quality, the developer is high. It is necessary to have fluidity and uniform chargeability. As described in "", the fluidity and uniform chargeability of toner particles as a developer are significantly involved. Therefore, in order to obtain a high-resolution image, a toner having high fluidity and uniform chargeability is required.
[0006]
The properties of the magnetic toner and the properties of the magnetic particle powder mixed and dispersed in the magnetic toner are closely related, and the fluidity of the magnetic toner depends on the surface condition of the magnetic particles exposed on the surface of the magnetic toner particles. Depends heavily. Therefore, as described in JP-A-5-72801, JP-A-5-213620 and JP-A-7-101731, the use of magnetic particle powder having Si on the surface reduces the fluidity of the magnetic toner. It is known to be effective in improving.
[0007]
The magnetic toner may be exposed to a high temperature of 150 ° C. or more when used, and in this case, it is required that the color tone is stable.
This fact is described in Japanese Patent Application Laid-Open No. 55-65406, entitled "Generally, such magnetic powder for a magnetic toner in the one-component system is required to have the following properties .... iv) Practical use The magnetic toner may contain a colorant, but it is preferable that the powder itself has a black color and no colorant is used.v) High heat resistance, color tone, In particular, it is necessary that the blackness and electromagnetic characteristics be sufficiently stable within a temperature range of about 0 to 150 ° C .... ”.
[0008]
As is well known, the phenomenon in which the color tone changes from black to brown is that the blackness of the magnetite particles is Fe²⁺Depends on the content of Fe²⁺The higher the content, the better the blackness tends to be. However, when exposed to a high temperature of 150 ° C., particularly about 200 ° C., the Fe²⁺Is oxidized to Fe³⁺It is caused by transformation into maghemite.
[0009]
In addition, the magnetic particle powder generally has a hydrophilic particle surface, which makes it difficult to disperse the resin in the resin, and the content of the magnetic particles among the magnetic toner particles becomes non-uniform. Magnetic agglomeration is likely to occur around the large amount of magnetic toner particles. This results in an increase in the oil absorption of the magnetic particle powder.
Therefore, in order to obtain a magnetic toner capable of high resolution, it is required that the particle surface of the magnetic particle powder is hydrophobic and the oil absorption is small in order to improve the dispersibility of the magnetic particle powder in the resin. I have.
[0010]
The magnetite particle powder used as the magnetic particle powder for the magnetic toner includes octahedral magnetite particle powder (JP-B-44-668) and spherical magnetite particles (JP-B-62-51208). Further, magnetite particles having a hexahedral shape (Japanese Unexamined Patent Publication No. Hei 3-201509) are known.
[0011]
Further, as characteristic particle shapes, magnetite particles having granular projections on the particle surface (JP-A-5-345616) and magnetite particles having a polyhedron having at least 10 or more surface surfaces (JP-A-Hei. -43253).
[0012]
Conventionally, a production method of adding Si during a magnetite generation reaction to improve the properties of magnetite particles has been studied. For example, a silicon component is added to a ferrous salt solution, and 1.0% of iron is added. After mixing with ~ 1.1 equivalents of alkali, the oxidation reaction is carried out while maintaining the pH at 7 ~ 10, and in the middle of the reaction, 0.9 ~ 1.2 equivalents of insufficient iron to the initial alkali is added. A method of obtaining magnetite particles by carrying out an oxidation reaction while maintaining the pH at 6 to 10 (JP-A-5-213620);²⁺When magnetite particles are formed by passing an oxygen-containing gas through a ferrous salt reaction aqueous solution containing a ferrous hydroxide colloid obtained by reacting 0.80 to 0.99 equivalents of alkali hydroxide with respect to A method of obtaining a spherical magnetite particle powder by adding a water-soluble silicate to Fe in an amount of 0.1 to 5.0 atomic% in terms of Si based on a two-step reaction (Japanese Patent Publication No. 3-9045). ), An aqueous solution of an equivalent amount or more is added to the ferrous salt solution, and during the oxidation reaction to the magnetite particles after the production of ferrous hydroxide, the hydroxosilicate solution is added to Fe in the reaction solution.²⁺/ Fe³⁺When the ratio is 10 to 1.0, Si / Fe₃O₄And a method for producing a magnetite pigment which is added at a ratio of 0.5 to 3.0% by weight (Japanese Patent Publication No. 1-36864).
[0013]
Also, a method of forming a coating layer made of a hydroxide or a hydrated oxide such as Si, Al, Ti or the like to improve heat resistance (Japanese Patent Application Laid-Open No. 8-133745), an oil absorption by making the particle surface hydrophobic. In order to reduce the water content, there is a method of performing a hydrophobic treatment with a hydrophobizing agent such as a coupling agent, silicone or a higher fatty acid (JP-A-7-277738).
[0014]
[Problems to be solved by the invention]
Magnetic iron oxide particles for magnetic toner that can be obtained with high resolution in electrostatic latent image development because they do not fall off from the toner particles, have good fluidity when formed into toner, and can obtain uniform chargeability. Although the powder is most demanded at present, such a magnetic iron oxide particle powder for a magnetic toner has not been provided yet.
[0015]
That is, although the magnetite particle powder described in the above-mentioned Japanese Patent Application Laid-Open No. 5-345616 has granular projections on the particle surface, the individual projections are fine and are inferior in the effect of sufficiently preventing falling off. Things.
[0016]
The magnetite particle powder described in the above-mentioned JP-A-5-43253 is composed of particles having 10 or more surfaces, but does not have an effect of preventing the particles from falling off the toner surface because it has no irregularities.
[0017]
The magnetite particles described in JP-A-5-213620 mentioned above add 1.0 to 1.1 equivalents of alkali to ferrous iron in the primary reaction, and the obtained magnetite particles are nearly spherical. And a particle having a large particle size distribution and a uniform particle size cannot be obtained.
[0018]
The magnetite particles described in Japanese Patent Publication No. 3-9045 mentioned above have no pH adjustment at the time of the primary reaction, have a low pH of less than 8.0, and have a spherical shape.
[0019]
The magnetite particles described in Japanese Patent Publication No. 36864/1993 are octahedral in shape and have no irregularities, and thus do not have an effect of preventing the particles from falling off the toner surface.
[0020]
Accordingly, the present invention provides a magnetic recording medium that can be obtained with high resolution in electrostatic latent image development because it does not fall off from the toner particles, has good fluidity when formed into toner, and has uniform charging properties. It is a technical object to provide a magnetic iron oxide particle powder for a toner and a magnetic toner using the magnetic iron oxide particle powder.
[0021]
[Means for solving the problem]
The technical problem can be achieved by the present invention as described below.
[0022]
That is, the present invention is a magnetite particle having a particle diameter of 0.05 to 0.50 μm and containing 0.9 to 6.5 atomic% of silicon with respect to Fe in terms of Si, and the particle shape is granular. Is a rounded confetti-like shape based on the following formula, and on the particle surface, oxides, hydroxides, and water-containing one or more elements selected from Al, Ti, Mg, Si, Co, Zr, Mn, and Zn. The magnetic iron oxide particles, wherein any one of oxides or a mixture thereof is adhered, and the number of convex protrusions on the particle surface is in a range of 2 to 30 on a projection view. .
[0023]
The present invention also relates to magnetite particles having a particle diameter of 0.05 to 0.50 μm and containing 0.9 to 6.5 atomic% of silicon with respect to Fe in terms of Si, wherein the particle shape is granular. And the surface of the particle is coated with a hydrophobizing agent, and the number of convex protrusions on the particle surface is in the range of 2 to 30 on the projection view. It is a magnetic iron oxide particle characterized by the above-mentioned.
[0024]
The present invention also relates to magnetite particles having a particle diameter of 0.05 to 0.50 μm and containing 0.9 to 6.5 atomic% of silicon with respect to Fe in terms of Si, wherein the particle shape is granular. Is a rounded confetti-like shape based on the following formula, and on the particle surface, oxides, hydroxides, and water-containing one or more elements selected from Al, Ti, Mg, Si, Co, Zr, Mn, and Zn. Either an oxide or a mixture thereof is adhered, and further, a hydrophobizing agent is adhered, and the number of convex protrusions on the particle surface is in a range of 2 to 30 on a projection view. The magnetic iron oxide particles are characterized in that:
[0025]
The present invention also provides the magnetite particle powder having an average particle diameter of 0.05 to 0.50 μm and containing 0.9 to 6.5 atomic% of silicon with respect to Fe in terms of Si. A magnetic iron oxide particle powder for a magnetic toner, wherein the powder contains at least 60% by number of any of the particles.
[0026]
Further, the present invention provides the magnetic iron oxide particle powder for a magnetic toner.And binder resinToner.
[0027]
The configuration of the present invention will be described in more detail as follows.
First, the magnetic iron oxide particles according to the present invention will be described.
[0028]
The magnetic iron oxide particles according to the present invention are composed of magnetite particles ((FeO) X.Fe₂O₃, 0 <x ≦ 1), and one or more metal elements selected from Mn, Zn, Ni, Cu, Al, and Ti in a total amount of 10 atomic% or less with respect to Fe, other than iron. May be included.
[0029]
The magnetic iron oxide particles according to the present invention contain 0.9 to 6.5 atomic%, preferably 1.3 to 5.3 atomic% of Si with respect to Fe.
[0030]
The magnetic iron oxide particles according to the present invention have a particle diameter of 0.05 to 0.50 μm, preferably 0.10 to 0.30 μm.
[0031]
The magnetic iron oxide particles according to the present invention are spinous particles with rounded corners based on a granular shape, and 2 to 30, preferably 5 to 20 convex protrusions on the particle surface on a projection view. Have
When the particle shape is conventionally well-known, such as spherical, octahedral, hexahedral, or polyhedral, it tends to fall off when exposed to the toner particle surface.
When the number of the protrusions is less than 2, the effect of preventing the protrusions from falling off the surface of the toner particles is small. If the number exceeds 30, the number of contact portions with the resin on the surface of the toner particles increases, but the size of each protrusion becomes small, and a sufficient effect of preventing falling off cannot be obtained.
[0032]
The convex projection in the present invention satisfies the following conditions.
That is, on a projection view of a magnetic iron oxide particle (a transmission electron micrograph or the like),
(1) Both ends of the projection are concave.
(2) When two or more protruding portions are overlapped, only the tip portion is used as a protruding object.
(3) The length (a), height (b), and particle diameter (c) of the base of the protrusion satisfy the following expression.
i) 10 ≦ a / c × 100 ≦ 40
ii) 5 ≦ b / c × 100 ≦ 30
[0033]
(1) and (2) are visually determined on the projection view (transmission electron micrograph, etc.).
Regarding (3), the length (a), height (b), and length of the base of each of the protrusions on the particle surface of the magnetic iron oxide particles in the projection view (transmission electron micrograph, etc.) Is measured and a / c and b / c are calculated to determine whether or not conditions i) and ii) are satisfied.
[0034]
FIG. 1 is a conceptual explanatory view in which the form of the magnetic iron oxide particles satisfying the above conditions (1) to (3) is enlarged and modeled, and the “both ends are concave” in the above (1). Refers to the portion indicated by the arrow A, and “only the tip portion” in the above (2) refers to the portion indicated by the arrow B, and “length (a), height (b) and The “particle diameter (c)” is a, b, and c in FIG.
[0035]
An oxide or hydroxide of one or more elements (hereinafter, referred to as “specific elements”) selected from Al, Ti, Mg, Si, Co, Zr, Mn, and Zn on the particle surface according to the present invention; The amount of Al, Ti, Mg, Si, Co, Zr, Mn, and Zn deposited on the surface of the magnetic iron oxide particles to which any of the hydrated oxides or their mixtures is deposited is preferably 0.02 to 10% by weight.
[0036]
One or more hydrophobizing agents selected from coupling agents, silicones, and higher fatty acids are coated on the surface of the magnetic iron oxide particles having the hydrophobizing agent adhered to the particle surface according to the present invention. It is preferable to wear it.
[0037]
As the coupling agent, a silane coupling agent, a titanate coupling agent, an aluminate coupling agent and the like can be used.
As the silicone, silicone oil or the like can be used.
As the higher fatty acid, stearic acid, isostearic acid, palmitic acid, isopalmitic acid, oleic acid and the like can be used.
[0038]
The amount of the hydrophobic treatment agent to be applied is preferably 0.1 to 10.0% by weight, more preferably 0.2 to 5.0% by weight.
[0039]
Any one of the oxides, hydroxides, hydrated oxides, and mixtures thereof of the specific element is adhered to the particle surface according to the present invention, and further, a magnetic iron oxide to which a hydrophobizing agent is adhered. The amount of the specific element deposited on the particle surface of the particles is preferably 0.02 to 10% by weight. Further, the amount of the hydrophobizing agent applied is preferably 0.1 to 10.0% by weight, more preferably 0.2 to 5.0% by weight.
[0040]
Next, the magnetic iron oxide particles for magnetic toner according to the present invention will be described.
[0041]
The magnetic iron oxide particles for a magnetic toner according to the present invention are composed of magnetite particles ((FeO) X.Fe₂O₃, 0 <x ≦ 1), and as shown in the electron micrograph of FIG. 2 described below, the particles are in the shape of confetti with rounded corners based on granules, and 2 to 30 convex protrusions are formed on the surface of the particles. This is a particle powder containing 60% or more, preferably 70% or more of the magnetic iron oxide particles in a number ratio. When the number ratio is less than 60%, the effect of preventing the toner particles from falling off the surface of the toner particles is small.
Here, the convex protrusion means one that satisfies the above conditions (1) to (3).
[0042]
The number ratio was calculated by measuring the number of magnetic iron oxide particles satisfying the above conditions (1) to (3) in a transmission electron micrograph, and calculating the ratio to the total number of measured particles. The total number of particles to be measured at this time is 30 or more, preferably 50 or more.
[0043]
The magnetic toner magnetic iron oxide particles according to the present invention have an average particle diameter of 0.05 to 0.50 μm, preferably 0.10 to 0.30 μm. When the average particle diameter is less than 0.05 μm, the number of particles in a unit volume becomes too large, and the number of contacts between the particles increases, so that the adhesive force between the powder layers increases, and when the magnetic toner is used, Dispersibility in the binder resin becomes poor. If it exceeds 0.50 μm, the number of magnetic iron oxide particles contained in one toner particle decreases, and the distribution of the magnetic iron oxide particles in each toner particle is biased. Sex is impaired.
[0044]
The magnetic iron oxide particle powder for a magnetic toner according to the present invention has a BET specific surface area of 3 to 30 m.²/ G, preferably 5-20 m²/ G.
[0045]
The magnetic iron oxide particle powder for a magnetic toner according to the present invention has a saturation magnetization value of 80 to 92.Am ² / Kg, Preferably 82 to 90Am ² / KgRange. 92Am ² / KgIs the theoretical value of magnetite, and does not exceed this value. 80Am ² / KgIf less than, Fe in the particles²⁺As the amount decreases, the powder becomes reddish, which is not preferable as magnetic iron oxide particles for magnetic toner.
[0046]
The magnetic iron oxide particle powder for a magnetic toner according to the present invention is Fe Fe²⁺The content is 12 to 24% by weight, preferably 17 to 24% by weight, based on the total weight of the magnetic iron oxide particles. If the amount is less than 12% by weight, sufficient blackness cannot be obtained. If it exceeds 24% by weight, it is easily oxidized and becomes environmentally unstable.
[0047]
The magnetic iron oxide particles for a magnetic toner according to the present invention contain 0.9 to 6.5 atomic%, preferably 1.3 to 5.3 atomic% of Si with respect to Fe. When the content of Si is less than 0.9 atomic%, the amount of Si contained on the surface decreases, resulting in poor fluidity. When the content is 6.5 atomic% or more, the amount of Si contained increases, so that the hygroscopicity increases, and when the toner is used, the environmental stability of the toner may be affected. In addition, Si present independently from the magnetic iron oxide particle powder may inhibit uniform charging and degrade charging stability.
Further, the Si content of the particle surface is 0.05 to 1.0 at%, preferably 0.08 to 0.80 at% with respect to Fe. If the content is less than 0.05 atomic%, good fluidity cannot be obtained when the toner is used. When the content exceeds 1.0 atomic%, the hygroscopicity is increased, and when the toner is used, the environmental stability of the toner may be affected.
[0048]
According to the present invention, for a magnetic toner containing at least 60% by number of magnetic iron oxide particles in which any one of an oxide, a hydroxide, a hydrated oxide, and a mixture thereof is adhered to the particle surface. The coating amount of Al, Ti, Mg, Si, Co, Zr, Mn, and Zn on the surface of the magnetic iron oxide particles is preferably 0.02 to 10% by weight. If it is less than 0.02% by weight, sufficient heat resistance cannot be obtained. If the content exceeds 10% by weight, all of the Si present on the surface of the particles is covered, and the fluidity is undesirably reduced.
[0049]
According to the present invention, a coupling agent, a silicone and a silicone agent are provided on the surface of the magnetic iron oxide particles for magnetic toner containing at least 60% by number of magnetic iron oxide particles having a hydrophobizing agent adhered to the particle surface. Preferably, one or more hydrophobizing agents selected from higher fatty acids are adhered.
[0050]
The amount of the hydrophobic treatment agent to be applied is preferably 0.1 to 10.0% by weight, more preferably 0.2 to 5.0% by weight. If it is less than 0.1% by weight, the hydrophobicity is not sufficient. If the content exceeds 10.0% by weight, the Si on the particle surface is entirely covered and the fluidity is lowered, which is not preferable.
[0051]
Any one of the oxides, hydroxides, hydrated oxides, and mixtures thereof of the specific element is adhered to the particle surface according to the present invention, and further, a magnetic iron oxide to which a hydrophobizing agent is adhered. The deposition amount of the specific element on the particle surface of the magnetic iron oxide particle powder for magnetic toner containing 60% or more of the particles in number ratio is preferably 0.02 to 10% by weight. If it is less than 0.02% by weight, sufficient heat resistance cannot be obtained. If the content exceeds 10% by weight, all of the Si present on the surface of the particles is covered, and the fluidity is undesirably reduced. Further, the amount of the hydrophobizing agent applied is preferably 0.1 to 10.0% by weight, more preferably 0.2 to 5.0% by weight. If it is less than 0.1% by weight, the hydrophobicity is not sufficient. If the content exceeds 10.0% by weight, the Si on the particle surface is entirely covered and the fluidity is lowered, which is not preferable.
[0052]
The magnetic iron oxide particle powder for a magnetic toner according to the present invention has a fluidity index of 50 or less, preferably 45 or less, and has good fluidity.
[0053]
The magnetic iron oxide particle powder for a magnetic toner according to the present invention has a charge amount of +20 to −60 μC / g, preferably +10 to −50 μC / g.
[0054]
The magnetic iron oxide particle powder for a magnetic toner containing 60% or more by number of magnetic iron oxide particles having a hydrophobizing agent adhered to the particle surface according to the present invention preferably has an oil absorption of 20 ml / 100 g or less. , More preferably 18 ml / 100 g or less.
[0055]
The magnetic toner according to the present invention, which comprises at least 60% by number of magnetic iron oxide particles in which the oxide, hydroxide, hydrated oxide, or a mixture thereof is adhered on the particle surface. The magnetic iron oxide particles for use preferably have an exothermic onset temperature of 150 ° C. or higher.
[0056]
Next, a method for producing the magnetic iron oxide particle powder for a magnetic toner according to the present invention as described above will be described.
[0057]
Examples of the aqueous ferrous salt solution in the first-stage reaction of the present invention include an aqueous ferrous sulfate solution and an aqueous ferrous chloride solution.
[0058]
Examples of the aqueous alkali hydroxide solution in the first step reaction of the present invention include aqueous solutions of hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, hydroxides of alkaline earth metals such as magnesium hydroxide and calcium hydroxide. , An aqueous solution of an alkali carbonate such as sodium carbonate, potassium carbonate and ammonium carbonate, and aqueous ammonia.
[0059]
The amount of the aqueous alkali hydroxide used before the pH adjustment in the first-stage reaction is determined by the amount of Fe in the aqueous ferrous salt solution.²⁺0.80 to 0.99 equivalents. Preferably it is in the range of 0.90 to 0.99 equivalents. If it is less than 0.80 equivalent, goethite is mixed in the product, and the desired magnetite particles cannot be obtained as a single phase. If it exceeds 0.99 equivalents, the particle size distribution becomes large and a uniform particle size cannot be obtained.
[0060]
The reaction temperature in the first-stage reaction of the present invention is 70 to 100 ° C. When the temperature is lower than 70 ° C., acicular goethite particles are mixed. When the temperature exceeds 100 ° C., magnetite particles are generated, but it is not industrially easy because an apparatus such as an autoclave is required.
[0061]
The oxidizing means in the first-stage reaction of the present invention is performed by passing an oxygen-containing gas (for example, air) through the liquid.
[0062]
As the water-soluble silicate used in the first-stage reaction of the present invention, sodium silicate, potassium silicate and the like can be used.
The addition amount of the water-soluble silicate is 1.0 to 8.0 at%, preferably 1.5 to 6.5 at% in terms of Si with respect to Fe. If the content is less than 1.0 atomic%, the particles become hexahedral particles, and the effect of preventing the particles from falling off the toner surface is inferior. On the other hand, if it exceeds 8.0 atomic%, acicular goethite particles are mixed. Further, since the amount of silicon contained increases, the amount of adsorbed moisture increases, and when the toner is used, the environmental stability of the toner may be affected. In addition, Si precipitated separately from the magnetic iron oxide particle powder hinders uniform charging, resulting in poor charging stability.
[0063]
The time of addition of the water-soluble silicate in the first-stage reaction is as follows. During the first-stage reaction, an oxygen-containing gas is passed through a ferrous-salt-reaction aqueous solution containing ferrous hydroxide colloid to magnetite nucleus crystals. It is necessary to be in the process of generating particles.
The addition can be carried out by dividing the addition into two or more, preferably five or more times, or by continuously dropping. The rate of dropping in the case of continuous dropping is 0.5 to 5.0% per minute, preferably 1.0 to 3.0% per minute, based on the total amount of the water-soluble silicate added.
When added all at once, it is not preferable because Si is hardly contained in the generated magnetic iron oxide particles and precipitates alone.
[0064]
In the first stage reaction of the present invention, ferrous Fe²⁺Degree of oxidation (Fe³⁺/ Total Fe) is in the range of 20% or more, the pH of the suspension is in the range of 7.5 to 9.5, and the oxidation degree (Fe³⁺The pH of the suspension is in the range of 8.0 to 9.5 when the ratio of (/ total Fe) is 30% or more. When the pH of the suspension is not in this range, the pH of the suspension is adjusted to a range of 7.5 to 9.5 with an acid such as sulfuric acid or an alkali such as an aqueous alkali hydroxide solution. When the pH of the suspension is less than 7.5, the surface of the particles has less irregularities and becomes nearly spherical, and the effect of preventing the particles from falling off the toner surface is not sufficient. When the pH of the suspension exceeds 9.5, Si becomes difficult to be contained on the surface of the particles, and in the case of a toner, the fluidity is poor.
[0065]
The amount of the aqueous alkali hydroxide used in the second-stage reaction of the present invention depends on the amount of Fe remaining at the start of the second-stage reaction.²⁺1.00 equivalent or more. If it is less than 1.00 equivalent, the remaining Fe²⁺Does not precipitate. Practically, an amount considering industrial properties of 1.00 equivalent or more is preferable.
[0066]
The reaction temperature in the second stage reaction of the present invention can be selected from the same conditions as in the first stage reaction. Also, the oxidizing means can be selected from the same conditions as in the first stage reaction.
[0067]
In addition, between the first-stage reaction and after the addition of the raw materials, and between the first-stage reaction and the second-stage reaction, if necessary, sufficient stirring may be performed for a required time.
[0068]
Oxides, hydroxides, and hydrates of specific elements (one or more elements selected from Al, Ti, Mg, Si, Co, Zr, Mn, and Zn) on the surface of the magnetic iron oxide particles in the present invention. The deposition of either the oxide or a mixture thereof may be performed by adding the inorganic compound of the selected element or an aqueous solution thereof to an aqueous suspension of magnetic iron oxide particles or an aqueous suspension after the completion of the second-stage reaction. The addition can be carried out by adjusting the pH to a known pH range in which the specific element precipitates as an oxide, hydroxide, or hydrated oxide.
[0069]
As the aqueous suspension of the magnetic iron oxide particle powder, when using the magnetic iron oxide particle powder once dried, in order to obtain a more uniform coating layer to be a sufficiently dispersed aqueous suspension. is necessary. When the aqueous suspension of magnetic iron oxide particles after the completion of the second-stage reaction is used as it is, it is more industrial because the above-mentioned dispersion step is not required.
[0070]
The inorganic compound of the selected element may be a water-soluble one.
As the Al compound, aluminum sulfate, aluminum chloride, aluminum nitrate, sodium aluminate and the like can be used.
As the Ti compound, titanyl sulfate, titanium chloride and the like can be used.
As the Mg compound, magnesium sulfate, magnesium chloride and the like can be used.
As the Si compound, No. 3 water glass, sodium silicate, potassium silicate and the like can be used.
As the Co compound, cobalt sulfate, cobalt chloride and the like can be used.
As the Zr compound, zirconium sulfate, zirconium chloride and the like can be used.
As the Mn compound, manganese sulfate, manganese chloride and the like can be used.
As the Zn compound, zinc sulfate, zinc chloride and the like can be used.
[0071]
The addition amount of the inorganic compound of the selected element is preferably 0.02 to 10% by weight. If it is less than 0.02% by weight, sufficient heat resistance cannot be obtained. If it exceeds 10% by weight, it may precipitate alone on the surface other than the particle surface, which is not preferable.
[0072]
The prepared pH after adding the inorganic compound of the selected element is in the range of pH 4 to 12 for Al, pH 3 or more for Ti, and pH 9.5 or more for Mg, It is pH 9.5 or less for Si, pH 7.5 or more for Co, pH 2 or more for Zr, pH 8.5 or more for Mn, and Zn for Zn. Is in the range of pH 6.5-14.
[0073]
The application of the hydrophobizing agent in the present invention may be performed by either a dry process or a wet process, but is preferably performed by a dry process. In this case, a wheel-type kneader, a grinder, a Henschel mixer, etc. Can be used.
[0074]
The added amount of the hydrophobizing agent is preferably 0.1 to 10.0% by weight, more preferably 0.2 to 5.0% by weight. If the amount is less than 0.1% by weight, the effect of hydrophobization is not sufficient, and if it exceeds 10.0% by weight, the entire amount of the hydrophobizing agent is not adhered to the particle surface, and the hydrophobizing agent alone is used. Is undesirably present.
[0075]
The magnetic toner according to the present invention will be described.
[0076]
The magnetic toner according to the present invention has a volume average particle size of 3 to 20 μm, preferably 5 to 15 μm.
[0077]
The magnetic toner according to the present invention comprises the magnetic iron oxide particles for a magnetic toner and a binder resin, and may optionally contain a release agent, a colorant, a charge control agent, and other additives. Good.
The ratio of the binder resin and the magnetic iron oxide particles for magnetic toner is 20 to 150 parts by weight, preferably 30 to 120 parts by weight, based on 100 parts by weight of the binder resin. .
[0078]
In the magnetic toner according to the present invention, the magnetic iron oxide particles hardly fall off from the toner surface.
[0079]
The magnetic toner according to the present invention is capable of obtaining high-resolution image quality due to good fluidity.
[0080]
As the binder resin used for the magnetic toner, a vinyl polymer obtained by polymerizing or copolymerizing vinyl monomers such as styrene, alkyl acrylate and alkyl methacrylate can be used. Examples of the styrene as a monomer constituting the binder resin include styrene such as styrene, α-methylstyrene, and p-chlorostyrene and a substituted product thereof. Examples of the alkyl acrylate include acrylic acid and methyl acrylate. Ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, isobutyl acrylate and hexyl acrylate. Examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, ethyl methacrylate, butyl methacrylate, and methacrylic acid. Monocarboxylic acids having a double bond, such as octyl acid, isobutyl methacrylate, dodecyl methacrylate, and hexyl methacrylate, and substituted products thereof.
The copolymer preferably contains 50 to 95% by weight of a styrene component.
[0081]
For the production of the copolymer, known polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization are used.
As the binder resin, a known polymer or copolymer such as a polyester-based resin, an epoxy-based resin, or a polyurethane-based resin can be used, if necessary, in addition to the above components.
[0082]
As the release agent, a paraffin having 8 or more carbon atoms, polyolefin, or the like is preferable. For example, polyethylene, polypropylene, paraffin wax, paraffin latex, microcrystalline wax, carnauba wax, or the like can be used. It is generally preferred that the compounding amount of these polyolefins is in the range of 1 to 10% by weight.
[0083]
As the colorant, any appropriate pigment or dye can be used as needed. For example, carbon black, chrome yellow, aniline blue, phthalocyanine blue, ultramarine, quinacridone, benzidine yellow and the like can be used.
[0084]
Examples of the charge control agent include a fluorine-based surfactant, an azo-based metal complex, a chromium salicylate complex, a metal complex of dialkylsalicylic acid and naphthoic acid, an azine-based dye such as nigrosine, a quaternary ammonium salt, and carbon black.
[0085]
Further, as other additives, tin oxide, strontium titanate, barium titanate, tungsten carbide, etc. can be used as abrasives. You may add resin fine particles and inorganic fine particles which perform the above.
[0086]
The method for preparing the magnetic toner according to the present invention can be performed by a known method such as mixing, kneading, and pulverization. Specifically, the magnetic iron oxide particles for magnetic toner and the binder resin, Accordingly, a colorant, a release agent, a charge control agent, other additives, and the like are mixed sufficiently by a mixer first, and then a resin and the like are melted and kneaded by a heating kneader to compatibilize the magnetic iron oxide. After the particles and the like are dispersed and solidified by cooling, the obtained resin kneaded material is pulverized and classified to obtain a magnetic toner.
[0087]
As the mixer, a mixer such as a Henschel mixer or a ball mill can be used. As the heating kneader, a heating kneader such as a roll mill, a kneader, a twin-screw type, an extruder and the like can be used. The pulverization can be performed by a pulverizer such as a cutter mill or a jet mill, and the classification can also be performed by a known method.
[0088]
Other methods for obtaining the magnetic toner according to the present invention include a suspension polymerization method and an emulsion polymerization method. In the suspension polymerization method, a polymerizable monomer and magnetic iron oxide particles for a magnetic toner, a colorant, A polymerization initiator, a cross-linking agent, a charge control agent, and a monomer composition in which other additives are dissolved or dispersed according to the above are added to an aqueous phase containing a suspension stabilizer while stirring to granulate. Can be polymerized to form toner particles.
[0089]
In the emulsion polymerization method, toner particles having an appropriate particle size are obtained by adding an emulsifier to a process in which a monomer, a magnetic iron oxide particle powder for a magnetic toner, a colorant, and a polymerization initiator are dispersed in water and polymerization is performed. Can be formed.
[0090]
BEST MODE FOR CARRYING OUT THE INVENTION
A typical embodiment of the present invention is as follows.
[0091]
The average particle diameter of the magnetic iron oxide particles was indicated by an average value of numerical values measured from an electron micrograph, and the specific surface area was indicated by a value measured by a BET method. The magnetic characteristics were measured using an external magnetic field using a "vibrating sample magnetometer VSM-3S-15" (manufactured by Toei Kogyo Co., Ltd.)795.8 kA / m (10 KOe)The measurements were taken over
[0092]
The particle shape of the magnetic iron oxide particles was observed with a scanning electron microscope (Hitachi S-800).
Further, with respect to the protrusions on the particle surfaces of the magnetic iron oxide particles, those satisfying the following conditions were recognized as convex protrusions.
That is, on the projection view (transmission electron micrograph) of the magnetic iron oxide particles,
(1) Both ends of the projection are concave.
(2) When two or more protruding portions are overlapped, only the tip portion is used as a protruding object.
(3) The length (a) and height (b) of the base of the protrusion and the particle diameter (c) of the particle satisfy the following formula.
i) 10 ≦ a / c × 100 ≦ 40
ii) 5 ≦ b / c × 100 ≦ 30
[0093]
(1) and (2) are visually determined on the projection view (transmission electron micrograph).
Regarding (3), the length (a), height (b) and length of the base of each of the protrusions on the particle surface of the magnetic iron oxide particles in the projection view (transmission electron micrograph) are shown. With respect to the particle diameter (c), a / c and b / c were calculated by measuring with a digitizer (HP-85B (manufactured by Hewlett-Packard)), and it was determined whether or not the conditions i) and ii) were satisfied. .
[0094]
It is determined whether or not the magnetic iron oxide particles according to the present invention are based on whether or not the projections satisfying the conditions (1) to (3) in the projection view are in the range of 2 to 30 on the particle surface. And calculating the ratio of the number of particles having the number of convex protrusions on the particle surface in the range of 2 to 30 in the projections to the total number of particles, and calculating the magnetic iron oxide for magnetic toner according to the present invention. It was determined whether or not the particles were powder.
[0095]
The amount of Si in the magnetic iron oxide particles before the surface treatment was measured using a “fluorescent X-ray analyzer 3063M” (manufactured by Rigaku Corporation) according to JIS K0119 “General rules for fluorescent X-ray analysis”. Indicated by.
The amount of Si on the particle surface before the surface treatment was measured by the following method.
That is, after mixing the magnetic iron oxide particles before surface treatment and ion-exchanged water, disperse the suspension into a suspension, mix with an aqueous alkali hydroxide solution, stir for 30 minutes or more, and then suspend the suspension. The Si amount of the magnetic iron oxide particles obtained by filtration and drying was measured, and the difference from the total Si amount before the treatment with the alkali was defined as the Si amount on the surface of the magnetic iron oxide particles before the surface treatment.
[0096]
Fe²⁺The content was indicated by a value determined by the following chemical analysis method. That is, in an inert gas atmosphere, 25 cc of a mixed solution containing phosphoric acid and sulfuric acid at a ratio of 2: 1 to 0.5 g of the magnetic iron oxide particles is added to dissolve the magnetic iron oxide particles. After adding a few drops of diphenylamine sulfonic acid as an indicator to this diluted solution of the aqueous solution, redox titration was performed using an aqueous solution of potassium dichromate. The end point was defined as the time when the diluting solution turned purple, and it was calculated from the amount of the aqueous potassium dichromate solution used up to the end point.
[0097]
The amounts of Al, Ti, Mg, Si, Co, Zr, Mn, and Zn deposited on the particle surface by the surface treatment were measured using a fluorescent X-ray analyzer 3063M (manufactured by Rigaku Corporation). It is measured by performing X-ray fluorescence analysis in accordance with "General rules of X-ray fluorescence analysis" of JIS-K-0119, and the content of each element measured in advance before the deposition is subtracted, whereby the deposition on the particle surface is performed. The amount was calculated. When the amount of deposition was very small, it was measured using "Inductively Coupled Plasma Emission Spectroscopy Analyzer SPS4000" (manufactured by Seiko Instruments Inc.).
[0098]
The amount of the hydrophobizing agent to be applied is determined based on the amount of carbon measured using "Horiba Metal Carbon Sulfur Analyzer EMIA-2200" (manufactured by Horiba, Ltd.). Was estimated and converted.
[0099]
The charge amount of the magnetic iron oxide particles was measured using a blow-off charge amount measuring device TB-200 (manufactured by Toshiba Chemical Co., Ltd.), and the carrier was manufactured using TFV-200 / 300 (manufactured by Powder Tech). Was mixed at a concentration of 5% and measured after shaking for 30 minutes.
[0100]
The degree of compression of the magnetic iron oxide particles was indicated by a value calculated by measuring the bulk density (ρa) and the tap density (ρt), and substituting these values into the following equation.
Compression degree = [(ρt−ρa) / ρt] × 100
The smaller the degree of compression, the better the fluidity.
[0101]
The bulk density (ρa) is measured by the pigment test method of JIS-5101, and the tap density (ρt) is 10 g of the magnetic iron oxide particle powder after the bulk density measurement is gently placed in a 20 cc measuring cylinder using a funnel. After filling and then dropping naturally from a height of 25 mm 600 times, the amount (cc) of the filled magnetic iron oxide particles was read from the scale of the measuring cylinder, and this value was substituted into the following equation. The calculated value was shown.
Tap density (g / cc) = 10 (g) / capacity (cc)
[0102]
The oil absorption of the magnetic iron oxide particles was measured by the pigment test method of JIS-K-5101.
[0103]
The heat resistance of the magnetic iron oxide particles was indicated by a heat generation starting temperature (° C.) by differential thermal analysis measured using a “differential scanning calorimeter DSC-200” (manufactured by Seiko Instruments Inc.).
[0104]
The volume average diameter of the toner was measured using a Coulter Counter TA-II (Coulter Electronics Co.).
[0105]
The evaluation of the detachability of the magnetic iron oxide particles from the surface of the toner particles was performed by the following method.
That is, a resin kneaded product obtained by kneading a magnetic iron oxide particle powder and a styrene acrylic resin is pulverized to prepare a resin kneaded material particle powder, and the resin kneaded material particle powder is shaken with a paint shaker for 60 minutes to be produced. The amount of the fine magnetic iron oxide particles was observed by an electron microscope, and evaluated by comparison with the case where conventional spherical magnetite particles were used.
[0106]
<Production of magnetic iron oxide particles>
Fe²⁺21.0 l of an aqueous ferrous sulfate solution containing 1.6 mol / l was added to 20.7 l of a 3.1 N aqueous sodium hydroxide solution prepared in a reactor in advance (Fe²⁺0.95 equivalents. ), A ferrous salt suspension containing a ferrous hydroxide salt colloid was produced at a pH of 6.7 and a temperature of 90 ° C., after which 80 l of air was blown per minute to start the first-stage reaction, At the same time, No. 3 water glass (SiO₂196.3 g (28.8 wt%) of 196.3 g (corresponding to 4.5 atomic% in terms of Si with respect to Fe) diluted with water to 0.3 l was dropped at a rate of 5 ml per minute. After completion of the dropping of the water glass solution, the oxidation reaction was continued while stirring for 30 minutes, and the first-stage reaction was terminated to obtain a ferrous iron suspension containing magnetite nucleus particles.
At this time, after the oxidation reaction starts, Fe²⁺After the oxidation degree exceeded 20%, the pH was within the range of 7.5 to 9.5, and after 30%, the pH was within the range of 8.0 to 9.5. .
[0107]
After the completion of the first-stage reaction, 0.4 L of a 9N aqueous sodium hydroxide solution was added to the ferrous salt suspension containing the magnetite nucleus particles to adjust the pH of the suspension to 9.5. At 90 ° C., 100 l / min of air was passed through for 30 minutes to carry out a second-stage reaction to generate magnetite particles.
The produced particles were washed with water, separated by filtration, dried and pulverized by a conventional method.
[0108]
As is clear from the transmission electron micrograph (× 50000) shown in FIG. 1, the obtained magnetite particles have a rounded confetti with rounded corners based on a granular shape and a uniform particle size. Yes, average particle diameter 0.20 μm, BET specific surface area 10.4 m²/ G.
[0109]
As a result of inspecting the projection methods (1) to (3) for the projections on the surface of the particles, the particles having 2 to 30 projections per particle with respect to the total number of particles were found. It was 76 number%.
[0110]
Further, as a result of X-ray fluorescence analysis, this magnetite particle powder contained 3.7 atom% of Si with respect to Fe, and the amount of Si on the particle surface was 0.19 atom%. In addition, as a result of the oxidation-reduction titration, Fe²⁺The amount was 18.4% by weight and had sufficient blackness. The magnetic characteristics are such that the saturation magnetization value is 88.7.Am ² / KgMet. The results of measurement of the degree of compression indicated that the composition had excellent fluidity. The charge amount was −18.0 μC / g. The oil absorption was 20 ml / 100 g, and the heat generation starting temperature was 131 ° C.
[0111]
A resin kneaded product particle powder, which is a crushed product of a resin kneaded product obtained by kneading the obtained magnetite particle powder and a styrene acrylic resin, is prepared, and the dropout property of the magnetic iron oxide particle powder is evaluated by the above evaluation method. As a result, it had a sufficient effect of preventing falling off.
[0112]
<Deposition processing>
After 1 kg of the magnetite particle powder was dispersed in water at 80 ° C., an aqueous solution of sodium hydroxide was added dropwise with stirring to adjust the pH to 11. Next, an aqueous solution containing 12.7 g of aluminum sulfate of 0.20% by weight in terms of Al was dropped to the particles, and 3.6N sulfuric acid was dropped to adjust the pH to 5, followed by stirring for 5 minutes. Subsequently, the pH was adjusted to pH 7 by dropwise addition of an aqueous sodium hydroxide solution, and the mixture was stirred for 30 minutes. Then, after filtration and washing with water, drying was performed at 60 ° C. to obtain magnetite particle powder in which aluminum hydroxide was adhered to the particle surface.
[0113]
The obtained magnetite particle powder having aluminum hydroxide adhered to the particle surface has a BET specific surface area of 10.6 m.^Two/ G, saturation magnetization of 88.2Am ² / KgThe Al content on the particle surface was 0.18% by weight, the oil absorption was 20 ml / 100 ml, and the heat generation starting temperature was 158 ° C.
[0114]
The magnetite particle powder in which aluminum hydroxide is adhered to the surface of the obtained particles is one that maintains a particle shape of a rounded confetti-like particle having a rounded corner based on a granular shape before the adhesion, and a resin kneaded material. The magnetic iron oxide particle powder was evaluated for the falling off property from the particle powder by the above-mentioned evaluation method. As a result, the powder had a sufficient effect of preventing falling off. In addition, it also maintained characteristics excellent in fluidity.
[0115]
<Manufacture of magnetic toner>
100 parts by weight of styrene-n-butyl acrylate copolymer
(Copolymerization ratio = 85: 15, Mw = 250,000, Tg = 62 ° C.)
Magnetic iron oxide particles (80% by weight according to the embodiment of the present invention)
1.5 parts by weight of positive charge control agent
2 parts by weight of low molecular weight ethylene-propylene copolymer
The mixture was hot-kneaded in a two-roll mill set at 140 ° C. for about 15 minutes, cooled, coarsely ground and finely ground. Further, fine powder and coarse powder were cut out by classification to obtain a magnetic toner having a volume average diameter of 10.4 μm.
[0116]
A one-component developer composed of the obtained magnetic toner was prepared, and the image density, fog, and the durability of the magnetic iron oxide particles from the magnetic toner were determined by a shaking test using a paint shaker. Inspection revealed that the image quality was higher than that of the conventional one-component developer made of magnetic toner using spherical magnetic iron oxide particles, and that there was almost no generation of fine powder. Was good.
[0117]
[Action]
Conventionally, in order to suppress the pulverization due to the falling off of the magnetic particle powder from the surface of the toner particles, a surface treatment has been performed to more firmly bind the bonding between the particle surface of the magnetic particles and the resin. I have been. However, when the present inventor considered the binding property between the particle surface and the resin, it was thought that increasing the contact area would be effective in preventing falling off from the toner surface, As a result of intensive studies on whether or not a shape having irregularities can be obtained, the present invention has been achieved.
[0118]
In a method for producing magnetite particle powder comprising a two-step reaction, the present inventor has disclosed that a water-soluble silicate aqueous solution of 1.0 to 8.0 atomic% in terms of Si is fed at least twice with respect to Fe during the first step reaction. It is added in divided portions as described above, or is added dropwise at a rate in the range of 0.5 to 5.0% per minute with respect to the total amount of Si added.²⁺Degree of oxidation (Fe³⁺By setting the pH in the range of 7.5 to 9.5 in the range of (total Fe) of 20% or more, rounded confetti-like magnetite particles having rounded corners based on granularity can be obtained. It does not fall off from the surface and has excellent durability. Since Si is contained on the particle surface, it has good fluidity when used as a toner, and uniform chargeability is obtained. It has been found that a magnetic iron oxide particle powder for a magnetic toner capable of obtaining a resolution image quality can be obtained.
[0119]
A magnetic iron oxide for a magnetic toner containing at least 60% by number of magnetic iron oxide particles having any one of oxides, hydroxides, hydrated oxides or a mixture of the specific elements adhered to the particle surface. The particle powder can have excellent heat resistance.
[0120]
Further, the oil absorption of the magnetic iron oxide particles for magnetic toner containing 60% or more by number of magnetic iron oxide particles having a hydrophobizing agent adhered to the particle surface can be reduced, and the dispersion in the resin can be reduced. Performance can be improved.
[0121]
【Example】
Next, examples and comparative examples will be described.
[0122]
Examples 1 to 22, Comparative Examples 1 to 11;
<Production of magnetic iron oxide particles>
Example 1
Fe²⁺21.0 l of an aqueous ferrous sulfate solution containing 1.6 mol / l was added to 20.7 l of a 3.1 N aqueous sodium hydroxide solution prepared in a reactor in advance (Fe²⁺0.95 equivalents. ), A ferrous salt suspension containing a ferrous hydroxide salt colloid was produced at a pH of 6.7 and a temperature of 90 ° C., after which 80 l of air was blown per minute to start the first-stage reaction, At the same time, No. 3 water glass (SiO₂(28.8 wt%) 196.3 g (corresponding to 4.5 atomic% in terms of Si with respect to Fe) diluted with water to 0.3 l is divided into 5 portions of 0.06 l every 10 minutes. And added. After completion of the dropping of the water glass solution, the oxidation reaction was continued while stirring for 30 minutes, and the first-stage reaction was terminated to obtain a ferrous iron suspension containing magnetite nucleus particles.
At this time, after the oxidation reaction starts, Fe²⁺After the oxidation degree exceeded 20%, the pH was within the range of 7.5 to 9.5, and after 30%, the pH was within the range of 8.0 to 9.5. .
[0123]
After the completion of the first-stage reaction, 0.4 L of a 9N aqueous sodium hydroxide solution was added to the ferrous salt suspension containing the magnetite nucleus particles to adjust the pH of the suspension to 9.5. At 90 ° C., 100 l / min of air was passed through for 30 minutes to carry out a second-stage reaction to generate magnetite particles.
The produced particles were washed with water, separated by filtration, dried and pulverized by a conventional method.
[0124]
The obtained magnetite particles have a particle shape of rounded confetti with rounded corners based on a granular shape, uniform particle sizes, an average particle size of 0.19 μm, and a BET specific surface area of 11. .3m²/ G.
[0125]
As a result of the inspection methods (1) to (3) for the projections on the surface of the particles, the particles having 2 to 30 projections per one particle with respect to the total number of particles were determined. It was 81% by number.
[0126]
Further, as a result of X-ray fluorescence analysis, this magnetite particle powder contained 3.7 atom% of Si with respect to Fe, and the amount of Si on the particle surface was 0.21 atom%. In addition, as a result of the oxidation-reduction titration, Fe²⁺The amount was 18.2% by weight, and it had sufficient blackness. The magnetic characteristics are such that the saturation magnetization value is 88.0.Am ² / KgMet. The results of measurement of the degree of compression indicated that the composition had excellent fluidity. The charge amount was -20.0 µC / g. The oil absorption was 21 ml / 100 g, and the heat generation starting temperature was 134 ° C.
[0127]
A resin kneaded product particle powder, which is a crushed product of a resin kneaded product obtained by kneading the obtained magnetite particle powder and a styrene acrylic resin, is prepared, and the dropout property of the magnetic iron oxide particle powder is evaluated by the above evaluation method. As a result, it had a sufficient effect of preventing falling off.
[0128]
Examples 2-3, Comparative Examples 1-7
The type, concentration and amount of the aqueous ferrous salt solution in the first-stage reaction, the type and concentration of the aqueous alkali hydroxide solution, the addition method and amount of the water glass, the adjusted pH during the first-stage reaction, the second-stage reaction Magnetite particle powder was obtained in the same manner as in the embodiment or Example 1 of the present invention, except that the kind of the alkali hydroxide aqueous solution and the reaction temperature in the second stage reaction were variously changed.
Table 1 shows the main production conditions at this time, and Table 2 shows various properties of the obtained magnetic iron oxide particles.
[0129]
[Table 1]

[0130]
[Table 2]

[0131]
The magnetite particle powder obtained in Comparative Example 1 has a hexahedral shape, as is clear from the electron micrograph (× 50000) shown in FIG. 3, and is more resin-kneaded than the magnetite particle powder of Example 1. The effect of preventing the particles from falling off the surface of the particles is not sufficient, and the amount of Si contained in the particle surface is small, so that the fluidity is poor.
[0132]
<Deposition processing>
Example 4
After 1 kg of the magnetite particle powder obtained in Example 1 was dispersed in water at 80 ° C., an aqueous solution of sodium hydroxide was added dropwise with stirring to adjust the pH to 11. Next, an aqueous solution containing 63.4 g of aluminum sulfate of 1.00% by weight in terms of Al was added dropwise to the particles, 3.6N sulfuric acid was added dropwise, and the mixture was adjusted to pH 7 and stirred for 30 minutes. Then, after filtration and washing with water, drying was performed at 60 ° C. to obtain magnetite particle powder in which aluminum hydroxide was adhered to the particle surface.
[0133]
Examples 5 to 8, Comparative Examples 8 to 9
The deposition treatment was performed in the same manner as in Example 4, except that the type of the particles to be processed, the type of the processed product, and the amount added were changed. Table 3 shows the conditions of the deposition treatment and various properties of the obtained magnetic iron oxide particles.
[0134]
[Table 3]

[0135]
<Hydrophobic treatment>
Example 9
10 kg of the magnetite particle powder obtained in the above embodiment and 15 g of the silane coupling agent A-143 (manufactured by Nippon Yunika Co., Ltd.) were put into a wheel-type kneader (trade name: Sandmill Co., Ltd., manufactured by Matsumoto Cast Iron Works). After charging and operating for one hour, magnetite particle powder having a silane coupling agent adhered to the particle surface was obtained.
[0136]
Examples 10 to 15 and Comparative Examples 10 to 11
The hydrophobic treatment was carried out in the same manner as in Example 9 except that the type of the particles to be treated and the type of the hydrophobizing agent and the amount thereof were changed. Table 4 shows the conditions of the hydrophobizing treatment and various properties of the obtained magnetic iron oxide particles.
In addition, as a hydrophobizing agent other than the above, a titanate coupling agent Blenact TTS (manufactured by Ajinomoto Co., Inc.) and isopalmitic acid (manufactured by Nissan Chemical Co., Ltd.) were used.
[0137]
[Table 4]

[0138]
<Deposition treatment and hydrophobic treatment>
Example 16
A wheel-type kneader (10 kg) of 10 kg of magnetite particle powder having aluminum hydroxide adhered to the surface of the particles obtained in the above embodiment and 20 g of a silane coupling agent A-143 (manufactured by Nippon Yunika Co., Ltd.) Trade name: Sand Mill (manufactured by Matsumoto Cast Iron Works) and operated for one hour to obtain magnetite particle powder having a silane coupling agent adhered to the particle surface.
[0139]
Examples 17 to 22
Hydrophobizing treatment was carried out in the same manner as in Example 16 except that the type of particles to be treated in which an oxide of a specific element or the like was adhered to the particle surface, the type of the hydrophobizing agent, and the amount added were variously changed. Was. Table 5 shows the conditions of the hydrophobic treatment and various properties of the obtained magnetic iron oxide particles.
[0140]
[Table 5]

[0141]
【The invention's effect】
The magnetic iron oxide particle powder for a magnetic toner according to the present invention is a fine particle having a particle size of 0.05 to 0.50 μm, and has a particle shape of rounded confetti with rounded corners based on a granular shape, and a projection view. Since the magnetic iron oxide particles having a number of convex protrusions on the particle surface in the range of 2 to 30 are contained in the above by 60% or more by number, the particles do not fall off from the toner particles and a large amount of Si is contained on the particle surface. As a result, the fluidity of the toner is good, and the uniform chargeability is obtained. In addition, when the heat generation starting temperature is as high as 150 ° C. or more, it can be used stably even when used in a high temperature range, and when the hydrophobicity of the particle surface is sufficient and the oil absorption is small, Dispersibility It can be improved.
[Brief description of the drawings]
FIG. 1 is a conceptual explanatory view in which a form of a magnetic iron oxide particle according to the present invention is enlarged and modeled.
[Explanation of symbols]
a Length of base of protrusion
b Height of protrusion
c Particle size
FIG. 2 is an electron micrograph (× 50000) showing the particle structure of magnetite particle powder obtained in the embodiment of the present invention.
FIG. 3 is an electron micrograph (× 50000) showing the particle structure of the magnetite particle powder obtained in Comparative Example 1.
FIG. 4 is an electron micrograph (× 50000) showing the particle structure of the magnetite particle powder obtained in Comparative Example 2.
FIG. 5 is an electron micrograph (× 50000) showing the particle structure of the magnetite particle powder obtained in Comparative Example 5.

Claims (5)

A magnetite particle having a particle size of 0.05 to 0.50 μm and containing 0.9 to 6.5 atomic% of silicon with respect to Fe in terms of Si, and the particle shape of the magnetite particle is based on a granular shape. It is a round confetti, and its particle surface has an oxide, hydroxide, hydrated oxide or a mixture of one or more elements selected from Al, Ti, Mg, Si, Co, Zr, Mn, and Zn. Wherein the number of convex protrusions on the particle surface in the projected view is in the range of 2 to 30. A magnetite particle having a particle size of 0.05 to 0.50 μm and containing 0.9 to 6.5 atomic% of silicon with respect to Fe in terms of Si, and the particle shape of the magnetite particle is based on a granular shape. A magnetic particle characterized by having a round spinous sugar-like shape, a hydrophobizing agent applied to the particle surface thereof, and the number of convex projections on the particle surface being in a range of 2 to 30 on a projection view. Iron oxide particles. A magnetite particle having a particle size of 0.05 to 0.50 μm and containing 0.9 to 6.5 atomic% of silicon with respect to Fe in terms of Si, and the particle shape of the magnetite particle is based on a granular shape. It is a round confetti, and its particle surface has an oxide, hydroxide, hydrated oxide or a mixture of one or more elements selected from Al, Ti, Mg, Si, Co, Zr, Mn, and Zn. Is attached, and further, the hydrophobic treatment agent is attached, and the number of convex protrusions on the particle surface in the projection view is in the range of 2 to 30 Magnetic iron oxide particles. 4. A magnetite particle powder having an average particle size of 0.05 to 0.50 [mu] m and containing 0.9 to 6.5 atom% of silicon with respect to Fe in terms of Si, according to any one of claims 1 to 3. A magnetic iron oxide particle powder for a magnetic toner, comprising at least 60% by number of magnetic iron oxide particles. Magnetic toner comprising a fourth aspect magnetic toner magnetic iron oxide particles and a binder resin according.

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