JPH0834617A - Black magnetic iron oxide particle-shaped powder - Google Patents

Abstract

PURPOSE:To obtain black magnetic iron oxide particle-shaped powder having a low magnetization value sigma1,000, ensuring a large amt. of negative charges and excellent in blackness. CONSTITUTION:This black magnetic iron oxide particle-shaped powder has 20-50emu/g magnetization value sigma1,000 in a magnetic field of 1kOe and contains 0.5-10.0at.% (expressed in terms of Ti) titanium compd. basing on the amt. of total Fe in this powder. This powder is preferably chargeable by -10 to -70muC/g.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a magnetization value σ ₁₀₀₀ in a magnetic field of 1 kOe (hereinafter, simply referred to as “magnetization value σ ₁₀₀₀ ”).
The present invention relates to a black magnetic iron oxide particle powder which has a small negative charge amount, a large negative charge amount, and an excellent blackness.

The main uses of the black magnetic iron oxide particle powder according to the present invention are material particle powder for magnetic toner and magnetic carrier.

[0003]

2. Description of the Related Art Black magnetic iron oxide particle powder is widely used as a black color pigment powder for paints, printing inks, rubbers and plastics because it has a black color.

Further, among the black magnetic iron oxide particle powders, the magnetite particle powder is a ferromagnetic particle. Therefore, by mixing and dispersing it in a resin to form a composite particle, a magnetic toner for electrostatic copying is used. It is used as a material particle powder and a material particle powder for magnetic carriers.

In any of the above-mentioned fields, there is no end to the demand for higher performance and higher quality, and there is a strong demand for improving the characteristics of the particle powder, in particular for its good dispersibility in the resin.

Regarding the magnetite particle powder as the material particle powder for magnetic toner, it should have good compatibility with "... VII) resin of JP-A-55-65406. Usually, the particle diameter of the toner is several tens of μm or less. Therefore, the degree of microscopic mixing in the toner is important for the characteristics of the toner.

Regarding the magnetite particle powder as the material particle powder for magnetic carrier, Japanese Patent Laid-Open No. 61-53660 is available.
According to the present invention, the dispersibility of primary particles is improved, the magnetic powder is uniformly dispersed, and the difference in charging property and magnetic property between magnetic developer particles is reduced. ".

Usually, the magnetite particle powder is produced by a so-called wet method in which it is directly produced from an aqueous solution.

The wet method is a suspension containing Fe-containing precipitate obtained by mixing an aqueous solution of ferrous salt such as ferrous sulfate with an alkaline aqueous solution such as sodium hydroxide and sodium carbonate. This is a method of ventilating an oxygen-containing gas in the temperature range of -100 ° C (Japanese Patent Publication No. 44-668).

However, the magnetite particle powder obtained by the above wet method has a magnetization value σ ₁₀₀₀ of 50 to 75 emu /
g, which is large and tends to cause magnetic aggregation, which is an obstacle to improving dispersibility.

Therefore, in order to further improve the dispersibility in the resin, a magnetite particle powder having a small magnetization value σ ₁₀₀₀ is strongly required. In particular, when magnetite particle powder is used as a material powder for magnetic toner, a magnetite particle powder having a small magnetization value σ ₁₀₀₀ is strongly required in order to achieve high image quality. This fact will be explained below.

As the electrostatic copying machine becomes smaller and faster and has higher performance, there is a strong demand for magnetic toner which is a developer and has improved characteristics, that is, high density development and high resolution.

The characteristics of the magnetic toner are closely related to the characteristics of the magnetic particle powder contained in the resin. In order to enable high density development, the content of the magnetic particle powder contained in the resin is required. However, if the content of the magnetic particle powder is increased, magnetic toner remains as agglomerates on the latent image after development due to magnetic agglomeration of the magnetic particle powder, and a fine latent image is faithfully reproduced. It is difficult to reproduce, and high resolution cannot be obtained.

This fact is described in Japanese Unexamined Patent Publication No. 4-184354, "... In this way, a toner faithful to a signal, an original, that is, a latent image and a high density developing toner is required. However, it is difficult to satisfy the above high requirements by using a toner containing a magnetic substance, for example, by increasing the coloring power of the magnetic toner to obtain a high density, the content of the magnetic substance is simply increased. If it is increased, the image quality becomes poor and the high resolution cannot be satisfied.
Because the size of the ears is related to the magnetic force of the toner. As the amount of magnetic material increases, the ears grow larger. Such ears tend to remain as agglomerates due to the aggregating force even on the latent image after the toner is developed, and it becomes difficult to faithfully reproduce a fine latent image. On the contrary, in order to satisfy high resolution, it may be possible to reduce the magnetic substance content to reduce the magnetic cohesive force, but in addition to the decrease in coloring power, the decrease in developability due to the increase in the charge amount and the toner production efficiency. Decrease. In that case, it may be improved by using a colorant such as carbon black in combination, but it may be difficult to put it into practical use because it may cause deterioration of environmental dependency. ...
Therefore, it has been proposed to adjust the magnetic force to obtain high-performance toner. "..." and "..." By containing an appropriate amount of a magnetic material having an appropriately small magnetic force, fine line reproducibility is improved, and an image quality can be obtained by developing a latent image or a signal with high fidelity. Is the street.

Therefore, in order to obtain a magnetic toner capable of high-concentration development and high resolution, even if the content of the magnetic particle powder contained in the resin is increased, magnetic cohesive force does not occur, so that the magnetic property is improved. It is required that the magnetization value σ ₁₀₀₀ of the particle powder be as small as possible and that it be black.

Regarding the charging property of the magnetic toner material particle powder, "... Toner of Japanese Patent Application Laid-Open No. 60-117259 needs to be adjusted so as to be charged positively or negatively depending on the type of the photoreceptor. From this point of view, when magnetic particles such as magnetite are considered, they have the property of being negatively charged.The characteristics of such magnetic particles are that when they are used in a magnetic toner having a positive charging property, the magnetic particles exposed on the toner surface are Due to the presence of body particles, a phenomenon in which positively charged portions and negatively charged portions coexist on the surface of one toner particle, or different charging characteristics for each toner particle is presumed, and in the one-component development method using magnetic toner, It is assumed that this is one of the causes of remarkably abnormal copy image characteristics due to environmental conditions, and it is desired to make the magnetic particles in the toner positively charged.
As described above, it is preferable that the magnetic particles used for the positively charged toner are positively charged and the magnetic particles used for the negatively charged toner are negatively charged. Furthermore, the charge amount of each toner is adapted to the developing device. Therefore, it is necessary to adjust to an appropriate range.

Regarding the charge amount of the toner, the above-mentioned Japanese Patent Laid-Open No.
No. 184354, “... A good image cannot be obtained unless the toner charge amount is appropriate.
An absolute value of 5 to 50 μc / g is good. Preferably 5 to
It is 40 μc / g, and more preferably 5 to 30 μc / g. When it is less than 5 μc / g, the sharpness of the image is deteriorated and the background is stained. Further, in a high temperature and high humidity environment, a decrease in image density becomes a problem. If it is larger than 50 μc / g, the electrostatic cohesive force becomes large, the image quality is deteriorated, and the fine line reproducibility becomes insufficient. In particular,
In a low-temperature and low-humidity environment, the mirroring power with respect to the toner carrying member becomes larger than necessary, so that the image density is lowered. ...
... ", the charge amount of the toner is 5 to 40 μc /
g is required.

Then, as described in the above publication, "... Stabilize the chargeability of the toner by using a magnetic material whose surface is hydrophobized, ...", the particle surface is hydrophobized. In addition to using a magnetic material, that is, zinc ferrite or zinc-manganese ferrite particles whose surface is hydrophobized, negatively chargeable colloidal silica or positively chargeable colloidal silica is used as shown in each Example of the publication. In addition, the charge amount of the toner is adjusted.

The amount of charge of the magnetite particles obtained by the above-mentioned wet method is about 0 to -10 μC / g, and as described above, the magnetite particles are dispersed in a resin to achieve high density development and high resolution magnetic properties. It is difficult to realize the toner. Therefore, in order to obtain a magnetic toner capable of high-concentration development and high resolution without increasing the content of the magnetic particle powder contained in the resin or using a colorant such as carbon black in combination, It is required that the magnetic particle powder has a large charge amount and that it be black.

Conventionally, as magnetic particle powders having a small magnetization value σ ₁₀₀₀ , zinc ferrite particles or zinc-containing spinel type crystal structure described in the above-mentioned JP-A-4-184354 can be used.
Examples include manganese ferrite particles. Also, the magnetization value σ
₁₀₀₀ is very small, as a black particle powder,
The black pigment particle powder described in JP-A-3-2276 can be used.

[0021]

[Problems to be Solved by the Invention] However, the magnetization value σ ₁₀₀₀
Of black magnetic iron oxide particles having a large negative charge amount and a large negative charge amount have not yet been obtained.

That is, as for general-purpose magnetite particles, so-called granular magnetite particles having an octahedral or hexahedral shape have a magnetization value σ ₁₀₀₀ of 50 to 70 emu /
The charge amount is about −5 to −10 μC / g at about g, and the magnetic value σ _{1000 of} the spherical magnetite particles is 60 to 75.
The charge amount is about 0 to −7 μC / g at about emu / g.

The zinc ferrite particles and zinc-manganese ferrite particles described in JP-A-4-184354 have a small magnetization value σ _{1000 of 10} to 40 emu / g and a charge amount of about 0 to -15 μC / g. However, as shown in Comparative Example 1 below, since the hue is not black but dark brown, the blackness is insufficient as a material for the magnetic toner.

In the black pigment particle powder described in JP-A-3-2276, the titanium compound is 15.0 to 50.0 in terms of Ti based on the total Fe in the magnetite particles.
Atomic% is included, and the magnetization value σ ₁₀₀₀ is 0.5-
Since it is 5.0 emu / g, it has almost no magnetism and is not suitable as a material particle powder for a magnetic toner or a magnetic carrier. In this publication, the charge amount is suggested.
There is no description to teach.

Therefore, a technical object of the present invention is to obtain a black magnetic iron oxide particle powder having a small magnetization value σ ₁₀₀₀ , a large negative charge amount, and an excellent blackness.

[0026]

The above technical problems can be achieved by the present invention as follows.

That is, in the present invention, the magnetization value σ ₁₀₀₀ is 20 to 5
It is 0 emu / g, and is a black magnetic iron oxide particle powder containing a titanium compound in an amount of 0.5 to 10.0 atomic% in terms of Ti based on the total Fe in the black magnetic iron oxide particle powder.

In the present invention, the charge amount is -10 to -70.
The black magnetic iron oxide particle powder is μC / g.

The structure of the present invention will be described in more detail as follows.

The content of the titanium compound in the black magnetic iron oxide particle powder in the present invention is 0.5 to 10.0 atom% in terms of Ti based on the total Fe in the black magnetic iron oxide particle powder. When the content of the titanium compound is less than 0.5 atom%, the magnetization value σ ₁₀₀₀ does not become 50 emu / g or less and the negative charge amount is small. If it exceeds 10.0 atomic%,
The magnetization value σ ₁₀₀₀ is less than 20 emu / g, which is not preferable as a magnetic toner material powder. The preferred content is 0.5 to 8.0 atomic%, more preferably 1.0 to
It is 8.0 atomic%.

The magnetization value σ ₁₀₀₀ of the black magnetic iron oxide particle powder according to the present invention is 20 to 50 emu / g. When the magnetization value σ ₁₀₀₀ is less than 20 emu / g, the magnetization value becomes too small, which is not preferable as the magnetic toner material powder. When it exceeds 50 emu / g, the cohesive force by magnetism becomes large, and the dispersibility in the resin decreases. It is preferably 25 to 50 emu / g, more preferably 25 to 48 emu / g.

When the use of the black magnetic iron oxide particle powder in the present invention is for a magnetic toner or magnetic carrier, the charge amount of the particle powder is -10 to -70 μC / g. When the charge amount is less than −10 μC / g, the content of the magnetic iron oxide particle powder contained in a normal magnetic toner is 3 or less.
When the magnetic toner is set to 0 to 50 wt%, the charge amount becomes lower than the proper range, which is not preferable. -70 μC /
If it exceeds g, the amount of charge of the magnetic toner becomes high and electrostatic aggregation may occur. Preferably-
10 to -60 μC / g, more preferably -15 to
-60 μC / g.

The blackness of the black magnetic iron oxide particles according to the present invention has a lightness L ^* value of 0 to 25 and an a ^* value of −.
1.0 to +1.0 (L ^* value and a ^* value are CIE
1976 (L ^* , a ^* , b ^* ) is a value displayed in the uniform perceptual color space. ). If the lightness L ^* value exceeds 25,
Blackness is insufficient. It is preferably 0 to 20. When the a ^* value is negatively larger than -1.0, the greenness is increased and the blackness is lowered. When it exceeds +1.0, the redness is increased and the blackness is lowered. Preferably -1.0 to +
It is 0.8.

Next, a method for producing the black magnetic iron oxide particle powder according to the present invention will be described.

As the starting material powder to be treated,
Examples thereof include magnetite particle powder and hematite particle powder.

First, the magnetite particle powder as the particles to be treated has a pH value obtained by reacting an aqueous ferrous salt solution and an aqueous alkali hydroxide solution in an amount equal to or more than Fe ²⁺ in the aqueous ferrous salt solution. A method of obtaining octahedral magnetite particle powder by an oxidation reaction in which an oxygen-containing gas is passed through a suspension containing a ferrous hydroxide colloid having a ratio of 10 or more (JP-B-44).
-668 gazette), the pH value obtained by reacting an aqueous solution of ferrous salt and an aqueous solution of alkali hydroxide in an equivalent amount or less to Fe ^{2+ in the} aqueous solution of ferrous salt is in the range of 6 to 7.5. The suspension containing ferrous hydroxide colloid is aerated with oxygen-containing gas to partially oxidize the suspension to generate magnetite core particles, and then the suspension containing the magnetite core particles and ferrous hydroxide colloid. A method of obtaining a magnetite particle powder exhibiting a hexahedron by carrying out a growth reaction of the magnetite nucleus particles by aerating an oxygen-containing gas in the suspension in the range of pH value of 8 to 9.5 (JP-A-3-201509). ) And a ferrous hydroxide colloid obtained by reacting an aqueous solution of ferrous salt with 0.80 to 0.99 equivalents of alkali hydroxide with respect to Fe ²⁺ in the aqueous solution of ferrous salt. Oxygen-containing gas should be passed through the suspension. Accordingly, a first stage to produce spherical magnetite particles, one stage after the completion of the reaction said residual Fe
^A method of obtaining spherical magnetite particle powder by adding 1.00 equivalent or more of alkali hydroxide to ²⁺ and performing an oxidation reaction at a pH value of 10 or more (JP-B-62-51).
No. 208) and the like.

Next, the hematite particle powder of the particles to be treated is obtained by, for example, heating each of the magnetite particle powders obtained by the above-mentioned methods in the air in the temperature range of 500 to 900 ° C. to oxidize them.

When the hematite particle powder is produced directly from the aqueous solution, for example, Japanese Patent Publication No. 38-985.
No. 2, JP-B No. 60-3012, JP-A No. 51-
The methods described in JP-A-8193, JP-A-62-128927 and JP-A-62-128930 can be adopted.

The magnetite particle powder and the hematite particle powder as the particles to be treated may be particles in the form of particles or spheres, and particles having a size of about 0.05 to 0.35 μm can be used. There is a correlation between the size of the particles to be treated and the size of the product particles, and when the particles to be treated having a small size have a small product particle size, when the particles to be treated having a large size have a large size product particles. Tends to be obtained.

The black magnetic iron oxide particle powder according to the present invention is
For example, a magnetite particle powder whose particle surface is coated with a titanium compound, or a reduced powder obtained by reducing a hematite particle powder whose particle surface is coated with a titanium compound, is treated at 650 to 850 ° C. under a non-oxidizing atmosphere. It can be manufactured by a method of calcination after heating at temperature.

It is preferable to use the magnetite particle powder having the particle surface coated with the titanium compound, since particles having a small magnetization value σ ₁₀₀₀ are easily obtained.

When using a hematite particle powder whose particle surface is coated with a titanium compound, the hematite particle powder coated in advance is reduced at 350 to 500 ° C. in a reducing atmosphere (for example, hydrogen gas). To form magnetite particles whose surface is coated with a titanium compound, and the particles are heated and fired at a temperature of 650 to 850 ° C. in a non-oxidizing atmosphere.

As the titanium compound, titanyl sulfate (T
iOSO ₄ ), titanium tetrachloride, titanium trichloride and the like.

The amount of the titanium compound added is 0.5 to 10.0 atomic% in terms of Ti based on the total Fe in the particles to be treated.
Is. When the addition amount of the titanium compound is less than 0.5 atom%, the magnetization value σ ₁₀₀₀ does not become 50 emu / g or less and the charge amount is small. If it exceeds 10.0 atomic%, the magnetization value σ ₁₀₀₀ becomes less than 20 emu / g, which is not preferable as a magnetic toner material powder. The preferable content is 0.5 to 8.0 atom%, and more preferably 1.0 to 8.0 atom%.

N ₂ gas or the like can be used as the non-oxidizing atmosphere. When the atmosphere is an oxidizing or reducing atmosphere, the target black magnetic iron oxide particle powder cannot be obtained.

The heating and firing temperature is in the range of 650 to 850 ° C. When the temperature is lower than 650 ° C., the solid phase reaction between the magnetite particles and the titanium compound does not sufficiently occur, and the desired black magnetic iron oxide particle powder cannot be obtained. When the temperature exceeds 850 ° C., sintering between particles of the black magnetic particle powder is remarkable and it becomes difficult to obtain the effect of preventing sintering. Preferably 65
It is 0-750 degreeC.

If desired, the particles to be treated may be coated with a known sintering inhibitor before heating and firing. In this case, it is possible to prevent the particles and the sintering between the particles during heating and firing, and it is possible to obtain black magnetic iron oxide particle powder having excellent dispersibility.

Further, as a sintering inhibitor which does not impair the various properties of the target black magnetic iron oxide particle powder, Al, S
A compound consisting of one or more elements selected from i, Zr and P can be used. The chargeability can be improved by using an appropriate sintering inhibitor.

The amount of the sintering inhibitor is 0.1 to 15.0 atomic% with respect to the total Fe in the black magnetic iron oxide particle powder.
In order to obtain a sufficient effect of preventing sintering, the content is preferably 0.1 atom% or more, and when it exceeds 15.0 atom%,
Since the solid-phase reaction between the particles to be treated and the titanium compound does not sufficiently occur, it is difficult to obtain the black magnetic iron oxide particle powder which is the object of the present invention.

The crushing is carried out using a commonly used crusher such as a ball mill, an attritor, a vibration mill, a Simpson mix muller, a multi-mill, a Stuts mill, a reverse flow kneader, an Eyrich mill, a wet pan mill, a melanger, a whirl mix, and a wheel of a quick kneader. It can be carried out using a kneading machine such as a mold kneader, a blade type kneader, or a kneader.

The black magnetic iron oxide particle powder according to the present invention is
The coating treatment may be performed with a known hydrophobizing agent such as a coupling agent, silicone, or higher fatty acid. The coating amount of the hydrophobizing agent is 0.05 to 2.0% by weight in terms of carbon element with respect to the black magnetic particle powder. If it is less than 0.01% by weight, the hydrophobicity is insufficient and the dispersibility is insufficiently improved. If it exceeds 2.0% by weight, the total amount of the hydrophobizing agent is not covered on the surface of the black magnetic iron oxide particles, and the hydrophobizing agent is present alone, which is not preferable.

The coupling agent is a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, etc., the silicone is silicon oil, etc., and the higher fatty acid is stearic acid, isostearic acid, palmitic acid, isopalmitin. Acid, oleic acid and the like.

In order to improve the charging property, it is preferable to treat the particle surface of the magnetic iron oxide particle powder with a monomolecular weight calculated from the coating area per molecule of the hydrophobizing agent. When γ-chloropropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, etc. or silicon oil among the silane coupling agents is subjected to hydrophobic treatment on the black magnetic iron oxide particle powder obtained in the present invention, It is preferable because the negative charge amount of the black magnetic iron oxide particle powder can be further increased.

The hydrophobizing treatment may be carried out by either a dry treatment or a wet treatment, but preferably it is carried out by a dry treatment. In this case, a wheel type kneader, a raider, a Henschel mixer or the like can be used. . The addition amount is preferably 0.25 to 5.0% by weight with respect to the black magnetic iron oxide particles, and if less than 0.25% by weight, the hydrophobization is insufficient and exceeds 5.0% by weight. In this case, the hydrophobizing agent is not entirely adsorbed on the particle surface, and the non-adsorbing hydrophobizing agent is solely present.

[0055]

The operation of the present invention having the above-described structure is as follows.

The zinc ferrite particle powder shown in Comparative Example 1 below obtained by the same method as described in JP-A-4-184354 has a magnetization value σ ₁₀₀₀ of 31.5.
It has an emu / g, a charge amount of −10 μC / g, an L ^* value of 20, but an a ^* value of +1.2, which is dark brown.

The black pigment particle powder described in JP-A-3-2276 is black Fe ₂ TiO ₅ and Fe.
_Although it is a polycrystalline particle powder having a mixed composition with a ₂ O ₃ —FeTiO ₃ solid solution, the magnetization value σ ₁₀₀₀ is 0.5 to 5.0 e.
It is about mu / g, and is a black pigment particle powder having almost no magnetism.

The present inventor has paid attention to the black pigment particle powder described in JP-A-3-2276, and by improving this pigment particle powder, an excellent black magnetic iron oxide particle powder for magnetic toner is obtained. I thought it would be possible to obtain more and studied further.

First, as a result of measuring the charge amount of the black pigment particle powder, the charge amount was about -15 to -30 μC / g. From this, the charge amount was increased by incorporating the titanium compound into the magnetite particle powder.

Next, as a result of various studies on the relationship between the content of the titanium compound contained in the magnetite particle powder and the magnetization value σ ₁₀₀₀ , as shown in FIG. 1, Ti was calculated for all Fe in the magnetic iron oxide particle powder. When 0.5 to 10.0 atomic% of the titanium compound is included, the magnetization value σ ₁₀₀₀
It was found that a magnetic iron oxide particle powder having a viscosity of 20 to 50 emu / g was obtained.

Further, as shown in FIG. 2, when a titanium compound exceeding 0.5 atom% in terms of Ti is contained with respect to all Fe in the magnetic iron oxide particle powder, the magnetic iron oxide particle powder is charged. It was found that a magnetic iron oxide particle powder having an amount exceeding -10 μC / g was obtained.

Further, the blackness of the magnetic iron oxide particle powder when the titanium compound is contained in an amount of 0.5 to 10.0 atom% in terms of Ti based on the total Fe in the magnetic iron oxide particle powder has a lightness L. ^* Value is in the range of 0 to 25, and a ^* value is from -1.0 to
From the range of +1.0, it was found that the blackness was also excellent.

From the above results, the magnetization value σ ₁₀₀₀ of the granular magnetite particle powder is 50 to 70 emu / g and the charge amount is −
What was about 5 to -10 μC / g, the magnetization value σ ₁₀₀₀
Is 20 to 45 emu / g and the charge amount is -20 to -40 μC
/ G.

The spherical magnetite particles have a magnetization value σ ₁₀₀₀ of 60 to 75 emu / g and a charge amount of 0 to -7 μC.
/ G was about, but the magnetization value σ ₁₀₀₀ was 20 to 45e
The charge amount was about −15 to −35 μC / g at mu / g.

As described above, the magnetization value σ ₁₀₀₀ could be reduced by about 30 emu / g, and the negative charge amount could be doubled or more, as compared with the magnetite particle powder as the particles to be treated.

That is, the black magnetic iron oxide particle powder according to the present invention is a particle powder having a small magnetization value σ ₁₀₀₀ , a large negative charge amount, and an excellent blackness. Therefore,
Since the content of the magnetic iron oxide particle powder contained in the magnetic toner when dispersed and mixed in a resin to form a magnetic toner can be increased, a high-concentration development and high-resolution negatively charged material for magnetic toner It is also excellent as a particle powder.

Incidentally, "...
The magnetite particle powder and hematite particle powder may be particles of any shape such as granular, spherical, needle-like,
Can be used. "..." and "...
A magnetite particle powder whose particle surface is coated with a titanium compound, a mixed powder of a magnetite particle powder and a titanium compound, or a reduced powder obtained by reducing a hematite particle powder whose particle surface is coated with a titanium compound is used in a non-oxidizing atmosphere. It is obtained by a method of calcination after heating and baking at a temperature of 700 ° C. or lower. Needle-shaped particles can be used as described above, and a mixed powder of magnetite particle powder and a titanium compound can be used in a non-oxidizing atmosphere at 700
It is said that it can be obtained by heating and firing at a temperature of ℃ or more.

However, as shown in Comparative Example 4 below, when the particles to be treated were magnetite particles in the form of needles, the magnetization value σ ₁₀₀₀ was 36.0 emu / g and the charge amount was −15 μC.
/ G and the a ^* value is +0.8, but the L ^* value is 27.
Therefore, since the lightness L ^* value is large and the blackness is problematic, the black magnetic iron oxide particle powder intended by the present invention cannot be obtained. In addition, since the remanent magnetization value σr of the obtained black magnetic iron oxide particle powder in a magnetic field of 1 kOe is as large as 25 emu / g, magnetic aggregation is likely to occur, resulting in poor dispersion, which is not preferable.

As shown in Comparative Example 5 below, when a mixed powder of magnetite particle powder and a titanium compound was heated and fired at a temperature of 700 ° C. in a non-oxidizing atmosphere, the magnetization value σ ₁₀₀₀ was 45. 0 emu / g, charge amount -12 μC /
g, L ^* value is 23, a ^* value is +1.2, and there is a problem with blackness due to a strong reddish color. Therefore, the black magnetic iron oxide particle powder of the present invention is obtained. I can't.

Further, when a titanium compound within the predetermined range in the present invention is mixed with magnetite particles, it is difficult to uniformly mix the titanium compound and magnetite particles, and the obtained magnetic iron oxide particle powder is used. When the magnetic toner is used, it is difficult to uniformly disperse it, and therefore it is difficult to reduce the difference in charging property and magnetic property between the magnetic developer particles.

[0071]

The present invention will be described below with reference to examples and comparative examples.

The shapes of the particles in the following examples and comparative examples were observed with a transmission electron microscope and a scanning electron microscope.

The Ti amount is a value measured by an inductively coupled plasma emission spectroscopic analyzer (ICAP-575, manufactured by Nippon Jarrell Ash Co., Ltd.).

The magnetic property of the magnetic particle powder is a value measured under a magnetic field of 1 kOe using a "vibrating sample magnetometer VSM-3S-15" (manufactured by Toei Industry Co., Ltd.).

The charge amount was determined by the blow-off measuring method. TB-200 (manufactured by Toshiba Chemical Co., Ltd.) was used as a measuring machine, TEFV200 / 300 (manufactured by Powder Tech Co.) was used as a carrier, and the concentration of the magnetic iron oxide particles was set to 5%, and the mixing time was 30 minutes.

Blackness is indicated by L ^* (brightness) and a ^* values, which are obtained by measuring a colorimetric test piece with a light source spectrocolorimeter MSC-
Hunte using IS-2D (Suga Test Instruments Co., Ltd.)
The L ^* value and the a ^* value are measured by the Lab space of r respectively, and CIE (International Commission on Illumination: Commission)
International de 1'Eclai
rage) 1976 (L ^* , a ^* , b ^* ) shown by the value displayed according to the uniform perceptual color space.

A sample piece for measuring blackness was prepared by kneading 0.5 g of black magnetic iron oxide particle powder containing a titanium compound and 0.5 cc of castor oil with a Hoover type muller to form a paste. 5 g was added and kneaded to form a paint, which was obtained by applying it onto cast-coated paper using a 6-mil applicator.

<Production of Black Magnetic Iron Oxide Particles> Examples 1 to 11 and Comparative Examples 1 to 6;

Example 1 The average diameter was 0.2 μm and the magnetization value σ ₁₀₀₀ was 66.0 em.
u / g, 10 kg of spherical magnetite particle powder having a charge amount of -4 μC / g in an aqueous solution containing 0.065 mol of TiOSO ₄ (5.0 atomic% in terms of Ti with respect to all Fe in the magnetic iron oxide particle powder) Equivalent to.),
Then, NaOH was added to the mixed solution and neutralized to adjust the pH value to 9.0, and after titanium hydroxide was deposited on the surface of the particles, diluted sulfuric acid was added to adjust the pH value to 7.0. It was filtered, washed with water, and dried to obtain spherical black magnetic iron oxide particle powder whose particle surface is coated with titanium hydroxide.

10 kg of spherical black magnetic iron oxide particles whose surfaces were coated with titanium hydroxide were heated and calcined at 700 ° C. for 60 minutes under N ₂ gas flow, and then Simpson Mix Mahler (Sandmill MPUV-2 :( Manufactured by Matsumoto Foundry Co., Ltd.) with a linear load of 30 kg / cm for 60 minutes to obtain a black magnetic iron oxide particle powder.

The amount of Ti in this black magnetic iron oxide particle powder is
It was 5.2 atom% with respect to the total Fe in the particle powder. Further, the magnetization value σ ₁₀₀₀ is 35.0 emu / g, and the charge amount is -2.
1 ^* C / g, L ^* value was 18, and a ^* value was +0.4.

Comparative Example 1 In a bubble oxidation type reaction column having an internal volume of 180 l, a NaOH concentration of 1 was added.
40 l of 83 g / l solution was added, and then 36 l of Fe ²⁺ concentration 135 g / l solution was added to the NaOH solution with stirring to neutralize (residual NaOH was about 4.
It was 7 g / l. ). P in which zinc hydroxide was dissolved
50l of solution with H value 11.3 (Zn concentration 40g / l
Is. ) In addition, a reaction liquid having an Fe ²⁺ concentration of about 39 g / l was prepared.

While maintaining the temperature of the reaction solution at 80 ° C., air was blown at a rate of 10 l / min to carry out the oxidation reaction. The reaction was completed in 7 hours. Then, the reaction precipitate was filtered, washed with water, and dried to obtain zinc ferrite particle powder.

10 kg of the above zinc ferrite particle powder was added to Simpson Mix Marlar (Sandmill MPUV-2:
6 with a linear load of 30 kg / cm manufactured by Matsumoto Foundry Co., Ltd.
It was processed for 0 minutes.

The obtained zinc ferrite particle powder has a magnetization value σ ₁₀₀₀ of 31.5 emu / g and a charge amount of −10 μC /
g, the L ^* value was 20, and the a ^* value was +1.2, which was a dark brown color.

Examples 2 to 11 and Comparative Examples 2 to 6 Type of powder to be treated, type of titanium compound in coating step with titanium compound, addition amount and pH at neutralization
Magnetic iron oxide particle powder was obtained in the same manner as in Example 1 except that the value, the presence or absence of the treatment with the sintering inhibitor, the type and amount, the temperature and time in the heat treatment step, and the linear load in the pulverization treatment were changed variously. . In Comparative Example 5, the spherical magnetite particle powder and the TiOSO ₄ powder were dry-mixed and then heat-treated.

The main manufacturing conditions and various characteristics at this time are shown in Tables 1 and 2.

[0088]

[Table 1]

[0089]

[Table 2]

<Hydrophobic treatment of black magnetic iron oxide particles> Examples 12 to 15;

Example 12 The magnetization value σ ₁₀₀₀ obtained in Example 1 is 35.0 emu /
g, the charge amount is −20 μC / g, and the L ^* value is 18, a
^* 10kg of black magnetic iron oxide particle powder with a value of +0.5
The Simpson Mix Mahler (Sandmill MPUV-
2: Charged to Matsumoto Foundry Iron Works Co., Ltd., and a silane coupling agent (γ-chloropropyltrimethoxysilane: A
-143: manufactured by Nippon Unicar Co., Ltd.) was added and treated with a linear load of 30 kg / cm for 60 minutes.

The resulting hydrophobically treated black magnetic iron oxide particle powder had a magnetization value σ ₁₀₀₀ of 34.5 emu / g, a charge amount of −55 μC / g, an L ^* value of 17, and an a ^* value of +
It was 0.5.

Examples 13 to 15 Hydrophobized black magnetic iron oxide particles were obtained in the same manner as in Example 12 except that the kind of the hydrophobizing agent was changed.

Table 3 shows various characteristics at this time.

[0095]

[Table 3]

[0096]

The black magnetic iron oxide particle powder according to the present invention has a small magnetization value σ ₁₀₀₀ as shown in the above Examples,
Moreover, since it is a black magnetic iron oxide particle powder that has a large amount of negative charge and is excellent in blackness, it is also excellent in dispersibility in resin, so it is a material for magnetic toner and magnetic carrier that is negatively charged. It is suitable as a particle powder.

Further, since the black magnetic iron oxide particle powder according to the present invention can increase the content of the magnetic iron oxide particle powder contained in the magnetic toner, it can be negatively charged with high density development and high resolution. It is suitable as a material particle powder for magnetic toner.

Since the black magnetic iron oxide particle powder according to the present invention is excellent in blackness, it can be used for paints, printing inks,
It can also be used as a black color pigment powder for rubber and plastics.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a content of a titanium compound in magnetic iron oxide particle powder and a magnetization value σ ₁₀₀₀ .

FIG. 2 is a diagram showing the relationship between the content of a titanium compound in the magnetic iron oxide particle powder and the charge amount.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location H01F 1/00 (72) Inventor Minoru Yoshizawa 4-1-2, Funairi Minami, Naka-ku, Hiroshima City, Hiroshima Prefecture No. Toda Kogyo Co., Ltd. Creation Center (72) Inventor Naoki Uchida 4-1-2, Funarinami, Naka-ku, Hiroshima City, Hiroshima Prefecture Toda Kogyo Co., Ltd. Creation Center (72) Inventor Tsutomu Katamoto Hiroshima City, Hiroshima Prefecture 4-1-2 Funaruinami, Naka-ku Toda Industry Co., Ltd. Creative Center

Claims (2)

[Claims] 1. A magnetization value σ _{1000 at a} magnetic field of 1 kOe is 2
0 to 50 emu / g, 0.5 to 10.0 atomic% in terms of Ti with respect to all Fe in the black magnetic iron oxide particle powder
Black magnetic iron oxide particle powder containing the titanium compound of. 2. The black magnetic iron oxide particle powder according to claim 1, which has a charge amount of −10 to −70 μC / g.