JP2003286030A - Mg-CONTAINING BLACK IRON OXIDE PARTICLE AND METHOD FOR MANUFACTURING THE SAME - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide black multicomponent oxide particles which are small in environmental load, are excellent in the degree of black color and are low in magnetization and a method for making the same. <P>SOLUTION: The Mg-containing black iron oxide particles contain the composition expressed by Mg<SB>x</SB>Fe<SB>y</SB>O(Fe<SB>2</SB>O<SB>3</SB>)<SB>1+z</SB>(where, 0.3<x<1, 0<y<0.7, x+y=1, 0<z<0.5), and have an average grain size of 0.01 to 0.5 μm. The method for making the Mg-containing black iron oxide particles comprises subjecting a ferrous hydroxide slurry containing magnesium hydroxide to an oxidation reaction within a liquid temperature ranging from 20 to 50°C while maintaining the pH of the slurry at ≥7, then subjecting the resultant multicomponent oxide particles to a heat treatment at 1,000 to 1,300°C under an inert gaseous atmosphere. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to black iron oxide particles and a method for producing the same, and more specifically, it has a specific elemental composition and is mainly used as a black pigment for paints, inks, toners, rubbers and plastics. The present invention relates to Mg-containing iron oxide particles having excellent blackness, which are suitable for non-magnetic toner as a substitute for carbon black and for coloring engineering plastics that require high-temperature kneading, and a method for producing the same.

[0002]

2. Description of the Related Art Black pigments used for paints, inks, toners, rubbers and plastics, etc. are required to be excellent in properties such as blackness, hue, coloring power and hiding power, and inexpensive. Therefore, iron oxide pigments such as carbon black and magnetite, and other complex oxide pigments are used depending on the application.

Recently, in any of the above fields, not only the demand for higher performance and higher quality, but for example, the carbon black has been withheld from use due to environmental problems and effects on the human body. On the other hand, iron oxide pigments obtained by a wet oxidation reaction, represented by magnetite, have few problems such as carbon black, but their blackness is dependent on the FeO quality contained and deteriorates over time due to oxidation. In addition, since it has relatively high magnetization, it is unsuitable for applications requiring low magnetization or non-magnetism.

As a technique relating to a black pigment for improving the above-mentioned problems, a composite oxide pigment containing various inorganic components has recently been attracting attention. As a typical example thereof, Japanese Patent Laid-Open No. 9-
No. 124972 and Japanese Patent Application Laid-Open No. 9-237570 are listed. This publication discloses a composite oxide black pigment whose main component is two or more metal oxides selected from a specific group consisting of copper, chromium, iron, manganese and the like.

[0005]

However, even in the above-mentioned composite oxide pigment, the technology is one in which a material whose main metal component is still positioned as an environmentally hazardous substance such as copper, chromium and manganese. This fact is clear from the fact that these main metals themselves or their compounds have been designated as specific chemical substances with the establishment of domestic laws of the Environmentally Hazardous Substances Release and Transfer Registration System (PRTR). However, it is difficult to obtain an excellent black pigment even if it takes one of the important properties of black pigment, that is, the blackness, and it is difficult to obtain an excellent black pigment, and a satisfactory material has not yet been found. The reality is not.

Therefore, the object of the present invention is mainly suitable as a black pigment for paints, inks, toners, rubbers and plastics, has a small environmental load, is excellent in blackness, and has a low magnetization black composite. An object is to provide iron oxide particles and a method for producing the same.

[0007]

Means for Solving the Problems As a result of careful examination of a raw material having a low environmental load, and the inventors of the present invention, as a result of a thorough examination of a material having excellent blackness as a composite oxide black pigment, a specific composite iron oxide containing Mg was found. The present invention was completed by finding composite iron oxide particles containing a composition.

That is, the Mg-containing black iron oxide particles of the present invention have a composition of Mg _x Fe _y O (Fe ₂ O ₃ ) _{1 + z} (where
0.3 <x <1, 0 <y <0.7, x + y = 1, 0 <z
It is characterized by containing a composition represented by <0.5) and having an average particle diameter of 0.01 to 0.5 μm.

Further, in the method for producing Mg-containing black iron oxide particles of the present invention, the pH of the ferrous hydroxide slurry containing magnesium hydroxide is maintained at 7 or more while the liquid temperature is 20 to 50 ° C. Oxidation reaction is performed in the range, and the obtained composite oxide particles are treated under an inert gas atmosphere at 1000 to 1300.
It is characterized in that the heat treatment is performed at ° C.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. Mg-containing black complex iron oxide particles of the present invention, Mg _x
Fe _y O (Fe ₂ O ₃ ) _{1+ z} (provided that 0.3 <x <
1, 0 <y <0.7, x + y = 1, 0 <z <0.5) and having an average particle size of 0.01 to
It is characterized by being 0.5 μm.

As described in the prior art, in conventional iron oxide pigments represented by magnetite, although there are few problems such as carbon black, its blackness depends on the FeO quality contained and oxidation This causes deterioration over time and has a drawback that the magnetization is relatively high. On the other hand, Mg, which is the focus of the present invention, does not show black as an oxide alone, but when it is compounded with iron oxide, for example, MgOFe ₂ O ₃ is known to exhibit a yellowish brown color. Has been.

The inventors of the present invention and Fe ₂ O ₃ are not a compound in which they are simply mixed, but Fe-- which has the characteristics of a spinel system.
It was considered that the Mg-containing composite iron oxide having a Mg solid solution type composition could exhibit low blackness or non-magnetism and exhibit the blackness required for the black pigment. An example of the results of X-ray diffraction measurement performed on the Mg-containing black composite iron oxide particles of the present invention is shown in FIG. 1. According to these results, the Mg-containing black composite iron oxide particles of the present invention show that FeOFe ₂ O ₃ And M
Although it deviates from the peak value peculiar to gOFe ₂ O ₃ ,
It can be seen that the particles are spinel-based composite iron oxide particles.

Originally, in the case of a Fe-Mg solid solution having a spinel structure based on the stoichiometric ratio, FeOFe ₂ O ₃ and Mg
It is considered that the peak of the composite iron oxide particles appears between the peaks specific to OFe ₂ O ₃ . On the other hand, the peaks of the Mg-containing black composite iron oxide particles of the present invention do not exist between the peaks and do not match the peaks of Fe ₂ O ₃ , so that they are merely FeOFe ₂ O ₃ or MgOFe ₂ O. ₃ or a mixture of Fe ₂ O ₃ and not Mg _x Fe for convenience.
_y O (Fe ₂ O ₃ ) _{1 + z} (where 0.3 <x <1,
0 <y <0.7, x + y = 1, 0 <z <0.5).

When 0 <z <0.5, the mechanism of suppressing the magnetization has not been clarified, but FeOFe
_By substituting a part of the spinel structure represented by ₂ O ₃ with Fe ₂ O ₃ , magnetization is suppressed, and chemically stable and less F
It is possible to secure blackness with the amount of eO.

When z = 0, the iron oxide particles have a spinel structure based on the stoichiometric ratio and have a well-defined crystal structure, so that the effect of increasing or decreasing FeO or MgO is large.
Stability of blackness may not be obtained, or it may be difficult to suppress magnetization. When z <0, the iron oxide particles have high blackness, but are chemically unstable because they become oxygen-defective Fe—Mg solid solution, and the surface of the particles is oxidized over time, resulting in a blackness. It may deteriorate. Further, since the magnetization is high, it is not suitable for applications requiring low magnetization or non-magnetism. If z> 0.5,
Oxygen is sufficiently present in the crystal, so stability over time is good,
Although it has low magnetization, it contains a large amount of Fe ₂ O ₃ , resulting in poor blackness and hue.

On the other hand, when x ≦ 0.3 (y ≧ 0.7),
Since FeO is high relative to MgO, blackness is high, but it lacks stability and becomes particles with relatively high magnetization, which is unsuitable for applications requiring low magnetization or non-magnetism. is there. When x = 1 (y = 0),
Since the composition is similar to that of MgOFe ₂ O ₃ , the blackness and hue are poor although the magnetization is low.

From the above, in order to balance blackness and suppression of magnetization, 0.3 <x <1, 0 <y <0.
It is important that 7, x + y = 1, 0 <z <0.5. If 0.5 <x <1 and 0 <y <0.5,
Further, it becomes a composite iron oxide particle having excellent blackness and low magnetization and excellent in stability over time, which is preferable.

The Mg-containing black composite iron oxide particles of the present invention have an average particle size of 0.01 to 0.5 μm. If the average particle size is less than 0.01 μm, the powder color may be reddish and the blackness may be poor. If the average particle size exceeds 0.5 μm, fine particles for toner and the like are required. It is not suitable for the application field.

Further, in the Mg-containing black composite iron oxide particles of the present invention, the Mg content is preferably 5 to 14 mass% with respect to the entire iron oxide particles. When the Mg content is less than 5% by mass, the iron oxide particles are similar to iron-based iron oxide particles alone, and therefore, even if the blackness is high, the magnetization is high, and thus it is inconvenient for use in a field where magnetism is not required and for substitution. Is.
Further, when the Mg content exceeds 14 mass%, the MgOF
There is concern about precipitation of the e ₂ O ₃ crystal phase, which may lead to a decrease in blackness.

In the Mg-containing black composite iron oxide particles of the present invention, the Mg / Fe molar ratio is preferably 0.1 to 0.5. This Mg / Fe molar ratio is 0.1
If it is less than the above, the iron oxide particles are similar to iron-based iron oxide particles alone. Therefore, even if the blackness is high, the magnetization is high, so that it is inconvenient to use or substitute in the field where magnetism is not required. Also, Mg
When the molar ratio of / Fe exceeds 0.5, MgOFe ₂ O
There is concern about precipitation of the _three crystal phases, which may lead to a decrease in blackness.

The Mg-containing black composite iron oxide particles of the present invention preferably have a saturation magnetization value of 40 Am ² / kg or less at a load magnetic field of 79.6 kA / m.
When the saturation magnetization value exceeds 40 Am ² / kg, it is inconvenient for use and substitution in fields that do not require magnetism such as non-magnetic toner applications.

In addition, in the Mg-containing black composite iron oxide particles of the present invention, in measuring the blackness and hue of the powder in accordance with JIS K5101-1991, L by a color difference meter is measured.
It is preferable that the value is 22 or less, the a value is 0.5 or less, and the b value is 0.5 or less. If these numerical values do not satisfy the above conditions, the blackness is low and the hue is also strongly reddish or yellowish, which is a problem as a black pigment.

Further, in the Mg-containing black composite iron oxide particles of the present invention, it is more preferable to contain one kind or two or more kinds of Al, Ti and Ca. When these substances are contained, composite iron oxide particles having a lower magnetization can be obtained. Therefore, for the purpose of field applications where magnetism is not required, it is said that the total amount of these substances is 12% by mass or less. Therefore, the above characteristics can be exhibited without lowering the blackness.

Further, in the Mg-containing black composite iron oxide particles of the present invention, it is preferable that the total content of Cr, Mn, Co, Ni, Cu and Zn is 1% by mass or less. Since the substance has a high environmental load, it is industrially contained in the iron oxide particles as an unavoidable component in the raw material in many cases, but needless to say, the lower amount is preferable.

Further, in the Mg-containing black composite iron oxide particles of the present invention, the elution amount of Mg when suspended in a 0.01N potassium hydrogen phthalate solution adjusted to pH 4 is equivalent to that of the entire particles. It is preferably 1% or less with respect to the amount of magnesium. This is because the amount of elution into the potassium hydrogen phthalate solution is large when Mg is not incorporated in the iron oxide particles in the form of complex iron oxide.

The shape of the Mg-containing black composite iron oxide particles of the present invention is not particularly limited as long as it is granular (spherical, hexahedral, octahedral, etc.).

Next, a method for producing the Mg-containing black composite iron oxide particles of the present invention will be described. In the method for producing Mg-containing black composite iron oxide particles of the present invention, the oxidation reaction is performed at a liquid temperature in the range of 20 to 50 ° C. while maintaining the pH of the ferrous hydroxide slurry containing magnesium hydroxide at 7 or higher. And then
The composite oxide fine particles, which have been subjected to solid-liquid separation and water removal, are heat-treated at 1000 to 1300 ° C. in an inert gas atmosphere.

The iron and magnesium raw materials used in the present invention may be soluble salts, or those prepared by dissolving a metal or metal oxide with an acid. First, the iron and magnesium raw materials are neutralized with a basic aqueous solution. A ferrous hydroxide slurry containing magnesium hydroxide is produced. The basic aqueous solution used at this time is not particularly limited as long as it has a neutralizing action, regardless of whether it is a strong base or a weak base, such as sodium hydroxide, potassium hydroxide, aqueous ammonia, sodium carbonate.

First, the above metal salt aqueous solution and basic aqueous solution are mixed to neutralize and form a hydroxide, and then at a temperature of 20 to 5
The oxidation reaction is performed while maintaining the pH at 0 ° C. and 7 or higher.
This oxidation reaction may be carried out with an oxygen-containing gas, or various oxidizing agents such as hydrogen peroxide solution may be used.

It is important to keep the temperature during the oxidation reaction at 20 to 50 ° C. If the temperature is too low, the reaction does not proceed, and if the temperature is too high, the particle nucleation varies.
It adversely affects the properties of composite iron oxide particles. Especially when the temperature exceeds 50 ° C., not only is FeOFe ₂ O ₃ generated remarkably, but also magnesium hydroxide is deposited on the surface of the composite iron oxide particles, so that Mg is washed away when the slurry after reaction is washed and filtered, In addition to being difficult to obtain composite iron oxide particles uniformly incorporated into, it is likely to become particles of high magnetization even after heat treatment, which is inconvenient.

It is also important to keep the pH during the above oxidation reaction at 7 or more. If the pH is too low, the reaction will not proceed and the added metal element will not be easily incorporated into the particles. It should be noted that if the pH is too high, the effect on the properties of the composite iron oxide particles is small, but it is uneconomical in terms of cost.
It is more preferable to suppress it to about 2. Incidentally, if an operation of adding one or more water-soluble salts among Al, Ti, and Ca to the oxidation reaction slurry is performed, composite iron oxide particles having a lower magnetization can be obtained. good.

The composite iron oxide particles, which are the wet reaction products obtained by the oxidation reaction, cannot maintain a stable state or are insufficient in terms of blackness and hue, depending on the progress of oxidation. , Conventional washing, filtration, drying,
After crushing, heat treatment is performed at 1000 to 1300 ° C. By performing this heat treatment, MgOF having a spinel structure
e ₂ O ₃ and FeOFe ₂ O ₃ are composited, and Fe ₂ O ₃ excess type iron oxide particles having high stability are obtained.

If the temperature at this time is less than 1000 ° C., the spinelization does not proceed, and a large amount of hematite (α-Fe ₂ O ₃ ) remains, resulting in particles with a strong reddish hue defect. When the temperature exceeds 1300 ° C., spinelization is not a problem, but sintering of the particles progresses and agglomeration is remarkable, and it is difficult to obtain the desired particle state.

If the atmosphere during this heat treatment is carried out in a state of a large amount of oxygen, the ratio of FeO will decrease relative to MgO. Therefore, in an atmosphere of an inert gas such as nitrogen gas, argon gas or helium gas. It is important to do in. The heat treatment time is such that spinelization progresses sufficiently and
8 to 16 hours are suitable for suppressing the decrease of eO.

[0035]

EXAMPLES The present invention will be specifically described below with reference to examples.

[Example 1] The concentration was 1 mol of ferrous sulfate /
1 and 1 liter of an aqueous solution of 1 mol / l of magnesium sulfate were prepared, mixed with each other, and further mixed with 3 mol.
2 liter of a 1 / l aqueous solution of sodium hydroxide.
The temperature during this alkali mixing was adjusted to 40 ° C. To the slurry containing the hydroxide thus obtained, 140 ml of a hydrogen peroxide aqueous solution having a concentration of 34% by mass was added to adjust the pH.
8, while maintaining the liquid temperature at 40 ° C., the oxidation reaction was continued until the unreacted Fe ²⁺ in the reaction slurry became almost zero. After cooling the slurry containing the composite black oxide particles thus obtained, after washing, dehydration, drying and crushing in the usual manner,
Heat treatment was carried out at a temperature of 1050 ° C. in a nitrogen gas atmosphere for 12 hours to obtain black iron oxide particles.

The characteristics of the obtained black iron oxide particles were evaluated by the following methods. The results are shown in Table 2. [Evaluation method] Total Fe and Mg contents. Dissolve sample, I
It was measured by CP. FeO content. The sample was dissolved in sulfuric acid and measured by redox titration with a potassium permanganate standard solution. Average particle size. A SEM (scanning electron microscope) photograph was taken at a magnification of 100,000, and the Feret diameter of 200 particles was measured. Saturation magnetization. Using a vibrating sample magnetometer VSM-P7 manufactured by Toei Industry Co., Ltd., an external magnetic field of 796 kA / m was used for measurement. Blackness and hue. Blackness measurement of powder is J
It carried out based on IS K5101-1991. Sample 2.
Add 1.4 cc of castor oil to 0 g and knead with a Hoover-type Mahler. To 2.0 g of this kneaded sample, 7.5 g of lacquer was added and kneaded further.
Apply with a mil applicator, dry, and then use a color difference meter (Color Analyzer TC-1800, manufactured by Tokyo Denshoku Co., Ltd.)
At, the blackness (L value) and hue (a value, b value) were measured. In order to check the stability over time, after exposing the sample immediately after production in an environment of 60 ° C. and 90% RH for 28 days,
The same evaluation as above was performed.

Example 2, Comparative Examples 1 to 4 Black iron oxide particles were obtained in the same manner as in Example 1 except that the production conditions were changed as shown in Table 1. Various characteristics of the obtained black iron oxide particles were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0039]

[Table 1]

[0040]

[Table 2]

As is clear from Table 2, the composite iron oxide particles of the examples have sufficiently low L value, excellent blackness, and excellent hue. Further, it has a low saturation magnetization and is suitable for non-magnetic applications. In addition, as is clear from FIGS. 1 and 2, the composite iron oxide particles contained MgOFe ₂ O ₃
It was found that there was a peak peculiar to the spinel system although it was deviated from the peak position of FeOFe ₂ O ₃ and FeOFe ₂ O ₃ .

On the other hand, the composite iron oxide particles of Comparative Example 1 were subjected to heat treatment in the air, and as apparent from FIG. 1, α-Fe ₂ O ₃ and MgOFe ₂ O _{3 had a} peak. Was observed, and the blackness and hue were remarkably inferior.

The composite iron oxide particles of Comparative Example 2 were insufficient in spinelization because the heat treatment temperature was low.
As a result of the morphological analysis, a peak peculiar to α-Fe ₂ O ₃ was observed, and blackness and hue were remarkably inferior.

The composite iron oxide particles of Comparative Example 3 were
As a result of morphological analysis, the obtained particles showed α-Fe ₂ O ₃ and FeOFe ₂ O ₃ as peaks, and lacked stability of blackness and high saturation magnetization. It was a thing.

Further, since the composite iron oxide particles of Comparative Example 4 had a high reaction temperature during the wet oxidation reaction, FeOFe ₂ O
₃ was remarkably generated, and the yield of Mg particles was low. The obtained particles were analyzed by morphological analysis and FeOFe ₂
O ₃ and Oboshiki peak and MgOFe ₂ O ₃ is observed,
The blackness was not stable and the saturation magnetization was high.

[0046]

The black composite oxide particles according to the present invention are
It has a low environmental load, excellent blackness, and low magnetization,
It is suitable as a black pigment for paints, inks, toners, and rubber / plastics. In particular, it is suitable as a black pigment for non-magnetic toner which substitutes for carbon black or an oxide pigment containing an environmentally hazardous substance, and a black pigment for coloring engineering plastics which requires high temperature kneading.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction diagram of Example 1 and Comparative Example 1.

FIG. 2 is an enlarged view near the main peak of the X-ray diffraction diagram of Example 1.

Continued front page    F-term (reference) 2H005 AA02 AB02 CB04                 4G002 AA06 AB02 AD04 AE01 AE03                 4J037 AA15 CA11 DD05 EE19 EE25                       EE28 EE43 EE46 EE47 FF05                       FF11

Claims (6)

[Claims] 1. Mg _x Fe _y O (Fe ₂ O ₃ )
_{1 + z} (however, 0.3 <x <1, 0 <y <0.7, x
+ y = 1, 0 <z <0.5), and the Mg-containing black iron oxide particles containing the composition represented by the formula (1) and having an average particle size of 0.01 to 0.5 μm. 2. The Mg-containing black iron oxide particles according to claim 1, wherein the Mg content is 5 to 14 mass% with respect to the entire iron oxide particles. 3. The Mg-containing black iron oxide particles according to claim 1, wherein the Mg / Fe molar ratio is 0.1 to 0.5. 4. The Mg-containing black iron oxide particles according to claim 1, having a saturation magnetization value of 40 Am ² / kg or less at a load magnetic field of 79.6 kA / m. 5. In the blackness and hue measurement of powder according to JIS K5101-1991, L measured by a color difference meter
The Mg-containing black iron oxide particles according to any one of claims 1 to 4, having a value of 22 or less, an a value of 0.5 or less, and a b value of 0.5 or less. 6. Composite oxide particles obtained by carrying out an oxidation reaction in a liquid temperature range of 20 to 50 ° C. while maintaining the pH of a ferrous hydroxide slurry containing magnesium hydroxide at 7 or higher. 1000 to 130 in an inert gas atmosphere.
A method for producing Mg-containing black iron oxide particles, which comprises performing heat treatment at 0 ° C.