JP4685651B2 - Method for producing iron oxide powder for red pigment - Google Patents

Description

The present invention relates to an iron oxide powder for a red pigment, and more particularly to a method for producing an iron chloride powder for an iron chloride red pigment exhibiting a bright red color.

  Iron oxide (hematite) has long been used as a red inorganic pigment because of its high safety to the human body and excellent weather resistance and chemical resistance. Even today, concrete, asphalt, rubber, and plastic are used. It is used as a colorant in various fields such as ceramics.

  Conventionally, iron sulfate powders for iron pigments that use bright red iron sulfate as a raw material have been mainly used as iron oxide powders for red pigments (hereinafter, iron oxide powders are also abbreviated as “iron oxide”). It was. This iron sulfate-based iron oxide is manufactured by using a ferrous sulfate solution and an alkaline solution as raw materials, synthesizing magnetite, goethite, and the like by a wet method and then heat-treating them. However, the production method using the wet method requires that the synthesis be batch processing, an alkali solution for neutralizing the ferrous sulfate solution, and a step of heat-treating the obtained magnetite or goethite. In addition, there are problems such as complicated processes and long manufacturing costs.

  As iron oxide for red pigments, iron chloride-based iron oxide is also used. This iron chloride-based iron oxide is produced by using a pickling waste solution (iron chloride solution) generated in the production process of steel as a raw material, spray roasting and pyrolyzing it. As a method for thermally decomposing iron chloride, the Rusner method, the Lurgi method, the chemilite method, and the like are known, and these methods can produce iron oxide continuously in large quantities. Therefore, iron chloride-based iron oxide is advantageous in terms of cost compared to iron sulfate-based iron oxide.

  However, iron oxide produced by thermally decomposing an iron chloride solution has a brown or purple color, which is far from being used for a bright red pigment and is not suitable for a pigment. Therefore, even if it is used as a pigment, it is used only for a very limited color, and its use is extremely limited.

  Factors affecting the color tone of iron oxide include particle size and particle size distribution (aggregation state). The smaller the particle size, the brighter the red color, and vice versa. However, it is known that the broader the particles are, the darker the color is red, and the sharper the particle size distribution is, the brighter the color is.

  However, the amount of Mn contained in iron oxide has a great influence on the color tone of iron oxide along with the particle size and particle size distribution. The larger the amount of Mn, the darker the color tone of iron oxide, and the more unsuitable for vivid red pigments. The color tone of iron chloride-based iron oxide is inferior because of the large amount of Mn, and when it contains a large amount of Mn, even if the particle size is reduced or the particle size distribution is improved, a bright red color Can't get. The reason why a large amount of Mn is contained in the chlorinated iron oxide produced by spray roasting is that the pickling waste liquid used as a raw material contains Mn originating from a steel plate, and it is directly taken into the iron oxide. It is because it ends.

Conventionally, various techniques have been developed in order to reduce the amount of Mn in iron oxide and to obtain colorful iron oxide for red pigments. For example, in the wet method which is the main production method of iron oxide for iron sulfate-based red pigment, Patent Document 1 discloses Fe (obtained by adding an equivalent amount or more of alkali to a ferrous sulfate solution containing Mn ions as impurities. An oxidizing gas is blown into an alkaline white suspension containing OH) ₂ and Mn (OH) ₂ while being heated to 60 to 90 ° C., and the amount of Fe (OH) _{2 in} the liquid is Mn (OH). _The oxidation reaction is stopped until the amount reaches at least twice the amount of _2, and Fe (OH) ₂ and Mn (OH) ₂ remaining in the solution are dissolved by acid treatment, and then remain in the solution. There has been proposed a method of obtaining a raw material powder with a small amount of Mn by filtering and collecting a precipitate of Fe ₃ O ₄ particles.

  Further, in Patent Document 2, when an oxidizing gas is blown into a ferrous sulfate solution containing Mn as an impurity to generate an iron oxide precipitate, the iron ion concentration in the solution is the manganese ion concentration. Methods have been proposed to stop the reaction without lowering. Further, Patent Document 3 proposes a method of obtaining red iron oxide by producing low-Mn yellow iron oxide or black iron oxide in a wet synthesis method using a ferrous chloride solution and heat-treating it. ing. However, since these techniques all use the wet method, there is a problem that the cost is higher than that in the case of using the spray roasting method.

On the other hand, in the spray roasting method, for example, Patent Document 4 proposes a method of obtaining red iron oxide by spraying an aqueous solution mainly composed of ferrous chloride at a temperature of 500 ° C. or lower. However, this method is not vivid because unreacted compounds remain in the iron oxide, and cannot suppress the effect of blackening the color tone due to Mn. Patent Document 5 proposes a method of spray roasting an iron chloride solution to which SiO ₂ or Al is added. However, although it has been described that iron oxide is atomized and color tone is improved by adding SiO ₂ or Al, there is no mention of suppressing the effect of Mn.
Japanese Patent Laid-Open No. 54-064099 JP 63-117915 A JP-A-11-228144 JP 2004-175596 A JP 60-215530 A

  As described above, in the manufacturing method of spraying and roasting iron chloride solution, the technology to obtain the vivid iron oxide for red pigment by suppressing the effect of darkening the color tone by Mn has not been established so far. . In recent years, reduction in manufacturing cost has been required for iron sulfate-based iron oxide for red pigments, and accordingly, iron chloride produced by spray roasting, which is cheaper than wet methods. Application of iron oxide to red pigments is beginning to be studied.

  On the other hand, iron chloride-based iron oxide has been used mainly as a raw material for hard ferrites and soft ferrites, but with the overseas transfer of the ferrite industry, development of applications in fields other than ferrite is desired. became.

Then, the objective of this invention is suppressing the influence of Mn contained in iron oxide, and is proposing the advantageous manufacturing method of the iron oxide powder for iron chloride type | system | group red pigments which show bright red.

  Inventors repeated earnest examination about the technique for suppressing the influence of Mn contained in iron oxide. As a result, it was found that by adding an appropriate amount of Al to iron oxide containing Mn as an impurity, the above-mentioned problems can be solved and a bright iron oxide powder for a red pigment can be obtained, and the present invention has been completed. It was.

That is , the present invention contains 0.1 to 3 mass% of Mn and 0.03 to 3 mass% of Al in terms of iron oxide, and the mass ratio of Al to Mn (Al / Mn) is 0.3 to 25. An iron chloride powder for red pigments, characterized in that a certain iron chloride solution is spray roasted at a temperature of 550 to 800 ° C. and then pulverized to obtain an iron oxide powder having a specific surface area of 6 to 14 m ² / g. It is a manufacturing method.
Further, the production method of the present invention, D ₅₀ was measured with a laser diffraction type particle size distribution measuring apparatus with 0.7μm or less, 2 [mu] m or more aggregated particles and obtaining the iron oxide powder is less than 5 vol% .

  According to the present invention, it is possible to obtain an iron oxide powder for a red pigment exhibiting a vivid red color, which suppresses the influence of iron oxide color tone blackening by Mn in a manufacturing method of spray roasting an iron chloride solution. Compared with the iron sulfate-based red pigment, the cost can be greatly reduced.

  The iron oxide powder for red pigment of the present invention is produced by spray roasting and pyrolyzing an iron chloride solution. This manufacturing method is suitable for continuous mass production, and is superior in cost compared to a manufacturing method of iron sulfate-based iron oxide powder. As the iron chloride solution as a raw material, a ferrous chloride solution, a ferric chloride solution, or a mixed solution of a ferrous solution and a ferric solution can be used. Usually, ferrous chloride solution is often used.

The iron oxide powder for red pigment according to the present invention will be described.
Mn: 0.1-3 mass%
In general, iron chloride-based iron oxide powder produced by spray roasting uses an iron chloride solution obtained from a waste solution obtained by pickling steel as a raw material, so that Mn derived from steel is inevitably included. The amount of Mn contained in the iron oxide of the present invention needs to be 0.1 to 3 mass%. If the amount of Mn contained in the iron oxide is less than 0.1 mass%, the influence of Mn is small and a bright red color is exhibited as it is, so that it is not necessary to apply the present invention. On the other hand, when the amount of Mn exceeds 0.1 mass%, the color tone of iron oxide becomes dark due to the influence of Mn. As will be described later, the adverse effect of Mn is suppressed by the addition of Al, and a bright red color can be obtained. However, if the amount of Mn contained in iron oxide exceeds 3 mass%, it is difficult to obtain a bright red color even if Al is added. Therefore, the amount of Mn in the iron oxide is in the range of 0.1 to 3 mass%.

Al: 0.03 to 3 mass%
As described above, Al is an effective component for suppressing the influence of darkening of the color tone due to Mn and obtaining a bright red color. When the Al content is less than 0.03 mass%, the effect of suppressing the adverse effect of Mn is not sufficient, and a bright red color cannot be obtained. On the other hand, when Al exceeds 3 mass%, since the solid solubility limit of Al is exceeded, problems such as generation of phases other than iron oxide (hematite) such as AlFeO ₃ and α-Al ₂ O ₃ occur. Therefore, the Al content is in the range of 0.03 to 3 mass%. A preferable Al content is 0.1 to 2.5 mass%, more preferably 0.15 to 2 mass%.

Mass ratio of Al and Mn (Al / Mn): 0.3-25
The mass ratio (Al / Mn) of Al and Mn contained in the iron oxide is preferably 0.3 to 25. This is because it is desirable to contain a certain amount or more of Al with respect to Mn in order to suppress the adverse effect of blackening the color tone due to Mn. If Al / Mn is less than 0.3, it is not sufficient to suppress the influence of Mn. On the other hand, if it exceeds 25, the color tone of the pigment becomes yellow or exceeds the solid solubility limit of Al, so that AlFeO ₃ This is because a problem occurs in that a phase other than iron oxide (hematite) such as α-Al ₂ O ₃ is formed.

The iron oxide powder of the present invention may contain general impurities contained in iron oxide, such as SiO ₂ , Ca, Ni, Co, Mg, P, Cl, and S, in addition to Mn and Al. The effect is not lost.

Specific surface area: 6 to 14 m ² / g
The iron oxide powder for red pigment of the present invention preferably has a specific surface area of 6 to 14 m ² / g. It is known that the color tone of red iron oxide depends on the particle size. When the particle size is large, the color tone is purple or brown, but as the particle size decreases, dark red → red → yellow It changes in the order of red. The specific surface area of iron oxide produced by spray roasting is generally about 3 to 4 m ² / g, and even iron oxide with a small particle size is about 5 m ² / g. That is, since the particle size is larger than that of bright red iron oxide for pigments, it has a brown or purple color and is far from a bright red pigment.

However, by optimizing the conditions for spray roasting, the primary particles can be made small and the specific surface area can be made 6 to 14 m ² / g, and a bright red color can be obtained. When the specific surface area is less than 6 m ² / g, it cannot be used for a bright red pigment for the above-described reason. On the other hand, when the specific surface area exceeds 14 m ² / g, the reddishness becomes weak and the yellowishness becomes strong. Moreover, intensified agglomeration by finer, be a 0.7μm or less becomes difficult to be D ₅₀ and pulverized. Moreover, even if it grind | pulverizes, since the coarse particle amount of 2 micrometers or more mentioned later does not become 5 vol% or less, a color tone deteriorates and it is unpreferable. A more preferable specific surface area is 6 to 12 m ² / g, and further preferably 7 to 10 m ² / g.

D ₅₀ : 0.7 μm or less Agglomerated particles of 2 μm or more: 5 vol% or less Further, the iron oxide of the present invention has a D ₅₀ (particle size distribution in powder particle size distribution) measured with a laser diffraction type particle size distribution analyzer. The particle diameter when the mass of particles larger than the diameter occupies 50% of the total powder is also referred to as a median diameter) is 0.7 μm or less, and the amount of aggregated particles of 2 μm or more is 5 vol% or less. It is preferable. As described above, when the particle size is large, the color tone becomes dark and is not suitable for use as a bright red pigment. However, iron oxide produced by spray pyrolysis of an iron chloride solution is produced by roasting at a high temperature, and therefore generally tends to agglomerate due to heat during production. Therefore, there is a problem that it contains a large amount of aggregated particles and has a large D ₅₀ compared to iron sulfate pigment iron oxide. Accordingly, in order to obtain a red pigment having a vivid color tone, it is necessary to reduce large agglomerated particles and make D ₅₀ small. Particularly, when D ₅₀ exceeds 0.7 μm, the color becomes dark. ₅₀ is preferably 0.7 μm or less. D ₅₀ is more preferably 0.6 μm or less, and even more preferably 0.5 μm or less.

  Further, since the aggregated particles behave in the same manner as primary particles having a large particle size, when there are many aggregated particles, the color tone becomes dark and is not suitable for use as a brightly colored red pigment. Aggregated particles having a size of 2 μm or more greatly affect the color tone. In particular, when the amount of aggregated particles is more than 5 vol%, the color tone becomes dark, which is not preferable. Therefore, the aggregated particle size of 2 μm or more is preferably 5 vol% or less. More preferably, it is 3% or less, more preferably 1% or less, and ideally 0% is desirable. As the above-described laser diffraction type particle size distribution measuring apparatus, commercially available ones can be used.

Next, the manufacturing method of the iron oxide which concerns on this invention is demonstrated.
The method for producing iron oxide of the present invention contains Mn inevitably contained in an amount of 0.1 to 3 mass% in terms of iron oxide, and further contains Al in an amount of 0.03 to 3 mass% in terms of iron oxide. An iron chloride solution having a Mn content ratio (Al / Mn) in the range of 0.3 to 25 is spray roasted at a temperature of 550 to 800 ° C. and then pulverized.

  If the amount of Mn contained in the iron chloride solution as a raw material is less than 0.1 mass% in terms of iron oxide, the resulting iron oxide has little adverse effect on the color tone due to Mn, and vivid red iron oxide can be used as it is. Obtainable. However, if the amount of Mn exceeds 0.1 mass%, the color tone of iron oxide becomes dark due to the influence of Mn, but if the amount of Mn is 0.1 to 3 mass%, the addition of Al will affect the influence of Mn. It can be suppressed to obtain a bright red color. On the other hand, if the amount of Mn contained in the iron chloride solution exceeds 3 mass%, it is difficult to obtain a bright red color even if Al is added.

  In addition to Mn, the iron chloride solution as a raw material must contain 0.03 to 3 mass% of Al in terms of iron oxide. This is because the inclusion of Al suppresses the effect of darkening the color tone due to Mn, and a bright red color can be obtained. When Al is less than 0.03 mass%, the effect of suppressing the influence of Mn is not sufficient, and a bright red color cannot be obtained. On the other hand, when Al exceeds 3 mass%, the solid solubility limit of Al is exceeded, and thus problems such as generation of phases other than iron oxide occur. The preferable Al content in the iron chloride solution is 0.1 to 2.5 mass%, more preferably 0.15 to 2 mass%, in terms of iron oxide.

Moreover, the mass ratio (Al / Mn) of Al and Mn contained in the raw iron chloride solution is 0.3 to 25. This is because it is necessary to contain a certain amount or more of Al in order to suppress the effect of darkening the color tone due to Mn. If the mass ratio Al / Mn is less than 0.3, it is not sufficient to suppress the influence of Mn. If it exceeds 25, the solid solubility limit of Al is exceeded, so iron oxides such as AlFeO ₃ and α-Al ₂ O ₃ Problems such as generation of phases other than (hematite) occur. As a method for adding Al, aluminum chloride, aluminum hydroxide, or the like may be added to the iron chloride solution.

The spray roasting temperature for thermal decomposition is preferably 550 to 800 ° C. When the spray roasting temperature is higher than 800 ° C., the primary particles are likely to grow and become large, and the primary particles sinter with each other due to heat to produce agglomerated particles, so the particle size is small. A bright red iron oxide having a specific surface area of 6 to 14 m ² / g cannot be obtained. On the other hand, when the spray roasting temperature is lower than 550 ° C., thermal decomposition does not occur completely, so that undecomposed iron chloride remains or unoxidized Fe ²⁺ exists in iron oxide. Therefore, it becomes iron oxide with a poor color tone. In addition to the spray roasting temperature, reducing the nozzle diameter, reducing the concentration of the iron chloride solution, and reducing the spray amount of the iron chloride solution are also effective for obtaining iron oxide with a small particle size according to the present invention. It is.

In the iron oxide production method of the present invention, it is necessary to grind after roasting. This is because the iron oxide of the present invention produces aggregated particles at the time of spray roasting because of the manufacturing method, and thus it is necessary to crush the aggregated particles to obtain a sharp particle size distribution. It is preferable that the pulverization is performed so that the D ₅₀ measured by a laser diffraction particle size distribution analyzer is 0.7 μm or less and the aggregated particles of 2 μm or more are 5 vol% or less. As a pulverization method, a known pulverization method such as a jet mill, a vibration mill, or an atomizer can be used. Also, wet grinding such as attritor, ball mill, and bead mill can be used.

Spraying ferrous chloride solutions having Fe concentrations of 120 g / l with different contents of Mn and Al in terms of iron oxide, shown as (Invention Examples 1 to 19 ) and (Comparative Examples 1 to 7 ) in Table 1 It was roasted to obtain iron chloride-based iron oxide, which was pulverized using an atomizer, a vibration mill, and a jet mill and subjected to the following evaluation. Further, as conventional examples, commercially available iron chloride-based general iron oxide (conventional example 1), commercially available iron chloride-based high purity iron oxide (conventional example 2), and commercially available iron sulfate-based iron oxide for red pigment (conventional example 3). ) Was also evaluated in the same manner.
(A) Mn and Al content in iron oxide: analyzed by ICP (b) Specific surface area: measured by BET method (c) Coarse grain size of D ₅₀ and 2 μm or more: Laser diffraction particle size distribution analyzer (HRA, (D) Color tone: Add 0.6 g of oil to 1 g of iron oxide, paste it with a Hoovermarler, add 12 g of transparent lacquer to the resulting paste, and use an applicator with a thickness of 0.2 mm. A coated film sample was prepared, and the L value, a value, and b value were measured using a color difference meter made by Nippon Denshoku for the obtained sample, and the conventional iron chloride based general iron oxide (conventional example 1) was measured. The L value, a value, and b value were used as a reference (0), and deviation values (ΔL, Δa, Δb) from this were determined.

The results of the above measurements are shown together in Table 1. From this result, spray roasting temperature is 550-800 degreeC, a specific surface area is 6-14 m < ² > / g, Mn in iron oxide is 0.1-3 mass%, Al is 0.03-3 mass%, Al and Mn The iron oxide satisfying the condition that the mass ratio (Al / Mn) is 0.3 to 25, D ₅₀ is 0.7 μm or less, and the aggregated particles of 2 μm or more are 5 vol% or less is a conventional iron chloride-based general iron oxide (conventional Compared to Example 1) and iron chloride-based high-purity iron oxide (Conventional Example 2), ΔL, Δa, and Δb are large and close to commercially available iron sulfate-based iron oxide (Conventional Example 3) and suitable as a red pigment. I understand.

  The technology of the present invention can be applied not only to general iron oxides for red pigments but also to applications that require higher heat resistance.

Claims (2)

An iron chloride solution containing 0.1 to 3 mass% of Mn and 0.03 to 3 mass% of Al in terms of iron oxide and having a mass ratio of Al to Mn (Al / Mn) of 0.3 to 25, A method for producing iron oxide powder for red pigment, characterized by obtaining iron oxide powder having a specific surface area of 6 to 14 m ² / g by spray roasting at a temperature of 550 to 800 ° C. and then further pulverizing. D measured with a laser diffraction particle size analyzer ₅₀ The method for producing an iron oxide powder for red pigment according to claim 1, wherein the iron oxide powder has a particle size of 0.7 μm or less and aggregated particles of 2 μm or more is 5 vol% or less.