JP2005225711A - Iron oxide-based yellow pigment and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an iron oxide-based yellow pigment containing no harmful material to human body/ environment and having excellent weather resistance/heat resistance and a method of manufacturing the same. <P>SOLUTION: The iron oxide-based yellow pigment is manufactured by firing Al-substituted Zn ferrite having a structure of Zn(Fe<SB>(1-x)</SB>Al<SB>x</SB>)<SB>2</SB>O<SB>4</SB>(where 0<x<1) at 500-1,400 °C. When (x) is ≥0.075 and ≤0.8, clear yellow color is exhibited particularly. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an iron oxide yellow pigment and a method for producing the same. More specifically, the present invention relates to an iron oxide-based yellow pigment excellent in weather resistance and heat resistance without containing any harmful substances such as chrome lead and the human body and the environment, and a method for producing the same.

  Inorganic pigments are superior in heat resistance, weather resistance, and chemical resistance compared to organic pigments, and are less likely to cause discoloration. Therefore, they are often used in harsh environments such as outdoors and underwater. Among inorganic pigments, yellow inorganic pigments are widely used for traffic paint, construction vehicles, construction machines, etc. to call attention, and the demand for them is very high, second only to red pigments among colored pigments.

Conventionally known yellow inorganic pigments include yellow lead (PbCrO _{4 and the} like), cadmium yellow, and iron oxide yellow (γ-FeOOH). However, yellow lead and cadmium yellow are not preferable because they contain substances harmful to the human body and the environment such as lead (Pb), chromium (Cr), and cadmium (Cd). In particular, yellow lead is a harmful substance specified in the lead poisoning prevention regulations. On the other hand, iron oxide yellow is preferable in that it does not contain the above-mentioned harmful substances, but has a disadvantage that it has low heat resistance and undergoes phase transformation to γ-Fe ₂ O ₃ at about 300 ° C. and discolors to black brown. Therefore, there is a demand for the development of yellow inorganic pigments that do not contain such substances harmful to the human body and the environment, and are rich in heat resistance and weather resistance.

  As this yellow inorganic pigment (a method for producing the pigment), a pigment obtained by depositing zinc hydroxide on a yellow iron oxide pigment and baking it is disclosed (see Patent Document 1). Moreover, aluminum solid solution yellow iron oxide in which Al is dissolved in α-FeOOH is disclosed (see Patent Document 2). In addition, a yellow inorganic pigment made of a composite oxide (ferrite) made of iron (Fe) / zinc (Zn) or the like having a spinel structure is disclosed (see, for example, Patent Documents 3 to 8).

By the way, a method for producing a compound in which a part of Fe of ZnFe ₂ O ₄ (zinc ferrite) is replaced with aluminum (Al) by a solid phase reaction method or a hydrothermal reaction method is already known (non-patent). Reference 1 and 2).
Japanese Examined Patent Publication No. 3-57055 (Public Notice: August 30, 1991, Publication: Japanese Patent Laid-Open No. 63-8221, Publication: January 14, 1988) JP 11-209645 A (publication date: August 3, 1999 (1999)) JP 56-95955 A (publication date: August 3, 1981) JP 58-60622 A (publication date: April 11, 1983) JP 51-35700 A (publication date: March 26, 1976) Japanese Laid-Open Patent Publication No. 57-11829 (Publication date: January 21, 1982) Japanese Examined Patent Publication No. 7-17384 (Public Notice: March 1, 1995, Publication: JP-A-2-32169, Publication: February 1, 1990) JP-A-4-224115 (Publication date: August 13, 1992) JC Waerenborgh, MO Figueiredo, JMP Cabral and LCJ Pereira. “Temperature and Composition Dependence of the Cation Distribution in Synthetic ZnFeyAl2-yO4 (0 ≦ y ≦ 1) Spinels” Journal of Solid State Chemistory, Volume 111, Issue 2, August 1994, Pages 300-309. JA Toledo, MA Valenzuela, P. Bosch, H. Armendariz, A. Montoya, N. Nava and A. Vazquez. “Effect of Al3 + introduction into hydrothermally prepared ZnFe2O4” Applied Catalysis A: Genaral, Volume 198, Issues 1-2 , 15 May 2000, Pages 235-245.

  However, although the above-mentioned alternative yellow inorganic pigments such as chrome lead are excellent in that they do not contain harmful substances, they have problems of heat resistance and weather resistance, problems in the manufacturing process, problems in color tone, etc. .

Specifically, the yellow inorganic pigment described in Patent Document 1 is a dispersion of a plurality of compounds (Fe ₂ O ₃ , ZnO, ZnFe ₂ O _4, etc.), and the composition ratio of each compound can be controlled during production. As a result, the produced pigment tends to vary in color tone.

  The yellow inorganic pigment described in Patent Document 2 has improved heat resistance as compared with α-FeOOH, but when used in traffic paints and the like because it undergoes phase transformation at about 330 ° C. or higher, its baking temperature. At about 800 ° C, the color changes to blackish brown.

  Therefore, as described above, the above conventional methods have not been sufficiently satisfactory as alternative yellow inorganic pigments such as chrome lead and cadmium yellow.

  Therefore, the present invention has been made in view of the above problems, and its object is to provide an iron oxide-based yellow pigment excellent in weather resistance and heat resistance without containing a substance harmful to the human body and the environment, and a method for producing the same. It is to provide.

In order to solve the above-mentioned problems, the present inventors are a spinel type compound (for example, MgAl ₂ O ₄ ) known as a compound having excellent heat resistance, acid resistance, and base resistance, particularly a harmless and safe brown pigment. Focusing on Zn ferrite (ZnFe ₂ O ₄ ) and white pigment ZnAl ₂ O ₄ , so-called Zn (Fe _(1-x) Al _x ) ₂ O ₄ (where 0 <x <1) The possibility of producing a yellow inorganic pigment made of Al-substituted Zn ferrite was investigated. More specifically, Al substituted Zn ferrite having various composition ratios of Fe and Al is produced by various firing temperatures and various production methods (complex polymerization method, wet coprecipitation method, solid phase reaction method), The color tone was determined.

As a result, an Al-substituted Zn ferrite solid solution having a structure of Zn (Fe _(1-x) Al _x ) ₂ O ₄ (where 0 <x <1) is obtained in the firing temperature range of 500 ° C. to 1400 ° C. In addition, the present inventors have found that the compound powder exhibiting a clear yellowish color tone can be obtained at a composition ratio of x not less than 0.075 and not more than 0.8, thereby completing the present invention.

That is, the iron oxide yellow pigment according to the present invention is an iron oxide pigment composed of Zn, Fe, and Al in order to solve the above problems, and has the formula Zn (Fe _(1-x) Al _x ) ₂ O _4. However, it is characterized by containing Al-substituted Zn ferrite represented by the formula (0 <x <1) and exhibiting yellow.

  According to the said structure, it becomes possible to provide the iron oxide type | system | group yellow pigment excellent in the weather resistance and heat resistance, without including harmful substances, such as chrome lead, to human bodies and the environment.

  The iron oxide yellow pigment according to the present invention is characterized in that, in addition to the above configuration, x in the above formula is 0.075 or more and 0.8 or less in order to solve the above problems.

  According to the said structure, it becomes possible to provide the iron oxide type | system | group yellow pigment which exhibits a clear yellowish color tone by making a calcination temperature range over 500 degreeC and less than 1400 degreeC.

  Moreover, in order to solve the said subject, the iron oxide type yellow pigment concerning this invention is further characterized by x being 0.4-0.8 in addition to the said structure.

  According to the said structure, it will become possible to provide the iron oxide type | system | group yellow pigment which exhibits a clear yellowish color tone if a calcination temperature shall be the range which exceeds 500 degreeC and less than 900 degreeC.

  Moreover, in order to solve the said subject, the iron oxide type yellow pigment concerning this invention is further characterized by x being 0.15-0.6 in addition to the said structure.

  According to the said structure, it becomes possible to provide the iron oxide type | system | group yellow pigment which exhibits a clear yellow color tone by making a calcination temperature range into 800 degreeC or more and less than 1400 degreeC.

  Moreover, in order to solve the said subject, the iron oxide type yellow pigment concerning this invention is characterized by exhibiting yellow in 1200 degrees C or less further in addition to the said structure.

  According to the above configuration, an iron oxide yellow pigment having excellent heat resistance can be provided, and it can be suitably used for the application without discoloration even at a baking temperature (about 800 ° C.) when used for traffic paint or the like. It is.

On the other hand, the method for producing an iron oxide yellow pigment according to the present invention, in order to solve the above problems,
An iron oxide pigment comprising Zn, Fe, Al,
When producing an iron oxide-based yellow pigment containing Al-substituted Zn ferrite represented by the formula Zn (Fe _(1-x) Al _x ) ₂ O ₄ (where 0 <x <1) and exhibiting a yellow color ,
It is characterized by using a complex polymerization method, a wet coprecipitation method or a solid phase reaction method.

  By using any of the above methods, it is possible to produce an iron oxide yellow pigment having excellent weather resistance and heat resistance without containing substances harmful to the human body and the environment such as yellow lead.

  Moreover, in addition to the said structure, in addition to the said structure, the manufacturing method of the iron oxide type yellow pigment concerning this invention WHEREIN: When x is 0.075 or more and 0.8 or less in said formula, calcination temperature is It is characterized by being over 500 ° C and below 1400 ° C.

  According to the said structure, it becomes possible to manufacture the iron oxide type yellow pigment which exhibits a clear yellowish color tone.

  Moreover, in order to solve the said subject, in addition to the said structure, the manufacturing method of the iron oxide type yellow pigment concerning this invention further, when x is 0.4 or more and 0.8 or less in said formula, a calcination temperature is It is characterized by being over 500 ° C and below 900 ° C.

  According to the said structure, it becomes possible to manufacture the iron oxide type yellow pigment which exhibits a clear yellowish color tone.

  Moreover, in order to solve the said subject, in addition to the said structure, the manufacturing method of the iron oxide type yellow pigment concerning this invention has a calcination temperature in the case where x is 0.15 or more and 0.6 or less further in the said formula. It is characterized by being 800 ° C. or higher and lower than 1400 ° C.

  According to the said structure, it becomes possible to manufacture the iron oxide type yellow pigment which exhibits a clear yellowish color tone.

  The method for producing an iron oxide-based yellow pigment according to the present invention is characterized in that coprecipitation is performed under a condition of pH 7.5 or higher when the wet coprecipitation method is used in order to solve the above problems. .

  According to the said structure, it becomes possible to manufacture the iron oxide type yellow pigment which exhibits a clear yellowish color tone.

  According to the iron oxide yellow pigment and the method for producing the same according to the present invention, there are provided an iron oxide yellow pigment having excellent weather resistance and heat resistance without containing a substance harmful to the human body and the environment, and a method for producing the same. It becomes possible. In other words, it is possible to provide an iron oxide yellow pigment that stably exhibits a yellow color even under severe use conditions such as traffic paint and is safe.

  An embodiment of the present invention will be described as follows. Note that the present invention is not limited to this.

The iron oxide yellow pigment according to the present invention (hereinafter referred to as the present yellow pigment as appropriate) is an iron oxide pigment composed of Zn, Fe, and Al, and includes Zn (Fe _(1-x) Al _x ) ₂ O ₄ ( However, it contains Al-substituted Zn ferrite represented by 0 <x <1) and exhibits a yellow color. Hereinafter, the structural formula of the Al-substituted ferrite is simply referred to as “the above formula”.

Here, the Al-substituted Zn ferrite is a compound in which Fe in Zn ferrite (ZnFe ₂ O ₄ ) excellent in heat resistance, acid resistance, and base resistance is substituted with Al. The present inventors have examined whether such Al-substituted Zn ferrite can be a yellow pigment. More specifically, pigment samples comprising a plurality of Al-substituted Zn ferrites each having different Al substitution ratios in the Al-substituted Zn ferrite (hereinafter sometimes referred to as “x” in the above formula) and firing temperature conditions at the time of production are different. Manufactured and evaluated the color and tone of each of the pigment samples to examine the conditions for producing a yellow color. That is, the preferred conditions for the substitution ratio of Al in which the pigment sample exhibits a yellow color, and the same suitable firing temperature were studied. In addition, the production method of this yellow pigment was also examined.

<1. Method for producing the present yellow pigment>
The method for producing the yellow pigment is not particularly limited. For example, a complex polymerization method, a wet coprecipitation method or a solid phase reaction method known per se can be suitably used.

(1-1. Complex polymerization method)
The “complex polymerization method” is simply a method in which metal ions are uniformly dispersed through complexation (chelation) of metal ions with citric acid and a three-dimensional network with ethylene glycol. To explain further with reference to FIG. 2, a plurality of metal ions (Fe ³⁺ , Al ³⁺ ) and citric acid are dissolved in water to form a stable chelate complex, and ethylene glycol is added to this to heat polymerize. In this method, esterification is performed, and finally a polymer gel having a three-dimensional network structure, that is, complex polymerization is formed through an oligomer. According to this method, metal ions can be uniformly dispersed, and expansion of the solid solution region can be expected. In addition, the raw material cost is low.

In producing the yellow pigment, the yellow pigment may be produced, for example, by the process shown in FIG. Specifically, iron nitrate (Fe (NO ₃ ) ₃ · 9H ₂ O), aluminum nitrate (Al (NO ₃ ) ₃ · 9H ₂ O), and zinc nitrate (Zn (NO ₃ ) ₂ · 6H ₂ O) Weigh and mix. At this time, aluminum nitrate and iron nitrate are mixed at a ratio corresponding to the target Al substitution ratio (x in the above formula). For example, when x is set to 0.4 in the above formula, mixing is performed so that the molar ratio of aluminum (Al) to iron (Fe) is 0.4: 0.6. Next, a 5-fold amount of citric acid, a 15-fold amount of ethylene glycol, and a 50-fold amount of water are added to form a complex and gel by the molar ratio with respect to the total of the above raw materials. Next, polymerization is performed in the atmosphere at 180 ° C. for 12 hours, and then thermal decomposition is performed at 450 ° C. for 24 hours. This is fired at 500 to 1400 ° C. for 2 hours, and then cooled and pulverized to produce a pigment sample.

  In one example of the above production method, iron nitrate hydrate is used as a raw material for Fe, but the Fe raw material is not particularly limited to this. For example, iron (II) acetate / iron bromide (II) And its hydrate, iron (III) bromide, iron (II) chloride and its hydrate, iron (III) chloride and its hydrate, iron (III) citrate and its hydrate, iron lactate ( II) and its hydrate, iron nitrate (III) and its hydrate, iron (II) perchlorate and its hydrate, iron (II) sulfate and its hydrate, iron (III) sulfate and its Hydrate, iron (III) ammonium citrate, iron iron (II) sulfate and its hydrate, iron iron (III) sulfate and its hydrate, and iron (II) oxalate dihydrate, iron phosphate ( II) and hydrates thereof, iron (III) phosphate and hydrates thereof Iron oxide, iron fluoride (II) and its hydrates, iron (III) oxalate ammonium and hydrates thereof or the like can be used.

  Further, in the above example of the production method, aluminum nitrate hydrate is used as the Al raw material, but the Al raw material is not particularly limited thereto. For example, aluminum acetate and its hydrate, ammonium aluminum sulfate and Its hydrate, Aluminum bromide, Aluminum lactate, Aluminum nitrate and its hydrate, Aluminum perchlorate and its hydrate, Aluminum sulfate and its hydrate, Aluminum oxalate and its hydrate, Diphosphate Hydrogen aluminum or the like can be used.

  In the above manufacturing method, zinc nitrate hydrate is used as the Zn raw material, but the Zn raw material is not particularly limited to this, and for example, zinc acetate, zinc chloride, etc. can be used. .

  On the other hand, in one example of the production method, the amount of citric acid added is 5 times the molar ratio with respect to the total of the above raw materials, but this is not particularly limited and is based on the total of the raw materials. Thus, it may be added in a molar ratio of 1 to 10 times. Further, it is preferable to add 3 times to 8 times. In addition, as for the amount of ethylene glycol added, in the example of the production method, 15 times the molar ratio of the raw materials is added, but this is not particularly limited, and the total amount of raw materials is not limited. What is necessary is just to add 5-30 times amount by molar ratio. Further, it is preferable to add 10 times to 20 times. In addition, the amount of water added is 50 times the molar ratio with respect to the total of the raw materials in one example of the above production method, but this is not particularly limited, and the molar amount relative to the total of the raw materials is not limited. What is necessary is just to add 5 to 70 times amount by ratio. Further, it is preferable to add 30 times to 60 times.

  Iron (II) oxalate dihydrate, iron (II) phosphate and its hydrate, iron (III) phosphate and its hydrate, iron oxide, iron (II) fluoride and its hydrate In addition, when complex polymerization is performed using iron (III) ammonium oxalate and its hydrate as an Fe raw material, citric acid and ethylene glycol are added after each raw material is dissolved in an acid such as nitric acid, hydrochloric acid, and acetic acid. Therefore, it is necessary to perform a complex polymerization method. This is because the solubility of the Fe raw material itself is low.

  In one example of the above production method, the polymerization is carried out at 180 ° C. for 12 hours, but is not particularly limited thereto. That is, the temperature condition is preferably in the range of 120 ° C. to 350 ° C., more preferably in the range of 150 ° C. to 250 ° C., and in the range of 150 ° C. to 200 ° C. in view of reaction efficiency, production cost, and the like. Most preferably, The reaction time largely depends on the reaction temperature, and the reaction may be performed until gelation occurs at each reaction temperature. Moreover, what is necessary is just to carry out under atmospheric pressure about the pressure conditions in the atmosphere in the case of superposition | polymerization.

  In one example of the above production method, thermal decomposition is performed in the atmosphere at 450 ° C. for 24 hours, but is not particularly limited thereto. That is, the temperature condition is preferably 400 ° C. or higher, more preferably 400 ° C. or higher and 500 ° C. or lower, considering thermal decomposition efficiency, production cost, and the like. The reaction time is preferably 1 hour to 48 hours, more preferably 8 hours to 24 hours. The pressure conditions in the atmosphere during the thermal decomposition may be performed under atmospheric pressure in consideration of the manufacturing cost.

  In one example of the production method, the firing temperature is in the range of more than 500 ° C. and less than 1400 ° C. This is because a solid solution of Al-substituted Zn ferrite is difficult to be generated at 500 ° C. or lower, and the energy cost is increased at 1400 ° C. or higher, and color reproduction is difficult. Therefore, when the preferable condition of x in the above formula is 0.075 or more and 0.8 or less, a yellow pigment exhibiting a yellow color can be produced if firing is performed in the range of more than 500 ° C. and less than 1400 ° C. In particular, the firing temperature when x in the above formula is 0.4 or more and 0.8 or less is preferably more than 500 ° C and less than 900 ° C, and more preferably 500 ° C or more and 750 ° C or less. It is because the yellow pigment which exhibits yellow excellent in color tone can be manufactured by setting it as the said calcination temperature conditions. On the other hand, the firing temperature when x in the above formula is 0.15 or more and 0.6 or less is preferably 800 ° C. or more and less than 1400 ° C., and more preferably 850 ° C. or more and 1150 ° C. or less. It is because the yellow pigment which exhibits yellow excellent in color tone can be manufactured by setting it as the said calcination temperature conditions. Moreover, what is necessary is just to carry out under atmospheric pressure about the pressure conditions in the atmosphere in the case of thermal decomposition. Also, the firing time is not particularly limited, preferably 1 to 24 hours, more preferably 1 to 8 hours, and most preferably 1 to 4 hours. By setting it as the said preferable conditions, the yellow pigment which exhibits yellow excellent in color tone can be manufactured.

As for the cooling conditions after firing, either rapid cooling or slow cooling may be performed. The rapid cooling means cooling from the heating temperature to room temperature at a rate of 10 ° C./min or more, and the slow cooling means gradually cooling at a rate of 10 ° C./min or less. FIG. 7 shows a pigment sample having an Al substitution ratio (x in the above formula) of 0.4, 0.5, and 0.6, fired at 1100 ° C. for 2 hours and then rapidly cooled, and conditions of 10 ° C./min or less. The result of having compared the color tone of the pigment sample which performed the slow cooling by is shown. According to FIG. 7, the lightly cooled pigment sample increased in brightness and saturation, and became more yellow (the L ^* a ^* b ^* value increased. About the L ^* a ^* b ^* value) Will be described later). Therefore, it can be said that it is more preferable to perform slow cooling after firing. The cooling means / conditions may be those normally used.

  Also, the means for pulverizing the sample after cooling may be any means or conditions that are usually used. For example, a ball mill, a stamp mill, an automatic mortar or the like can be preferably used. In order to produce a pigment having excellent coloring power and dispersibility, it is preferable to grind until the average particle diameter of the pigment sample is as fine as possible.

  In Examples to be described later, the present inventors have succeeded in producing pigment samples made of various Al-substituted Zn ferrites by such complex polymerization method, and producing the yellow pigments exhibiting yellow color from them.

(1-2. Wet coprecipitation method)
The “wet coprecipitation method” is a method in which a mixed aqueous solution of each raw material is coprecipitated by adding sodium hydroxide (NaOH) or the like as a precipitating agent, and the resulting precipitate is filtered, baked and pulverized to produce a pigment sample is there. FIG. 4 shows an example of producing a pigment sample using the wet coprecipitation method. First, iron nitrate (Fe (NO ₃ ) ₃ · 9H ₂ O), aluminum nitrate (Al (NO ₃ ) ₃ · 9H ₂ O) and zinc nitrate (Zn (NO ₃ ) ₂ · 6H ₂ O) are weighed. Mix to prepare an aqueous raw material solution. At this time, aluminum nitrate and iron nitrate are mixed at a ratio corresponding to the target Al substitution ratio (x in the above formula). For example, when x is set to 0.4 in the above formula, mixing is performed so that the molar ratio of aluminum (Al) to iron (Fe) is 0.4: 0.6. Further, the concentration of each metal salt aqueous solution at this time is preferably in the range of about 1M at maximum, although it varies depending on the solubility of the metal salt. Next, 2M NaOH is added dropwise to the raw material aqueous solution until the pH reaches 7.5 or 8.0 to coprecipitate a mixture of zinc hydroxide, iron hydroxide, and aluminum hydroxide (synthesis / reaction). Next, the mixture of zinc hydroxide / iron hydroxide / aluminum hydroxide generated by filtration or the like is separated from the solvent (solid-liquid separation). Next, the filtered mixture of zinc hydroxide, iron hydroxide, and aluminum hydroxide is washed with water to completely remove NaNO ₃ . Next, the mixture of zinc hydroxide, iron hydroxide and aluminum hydroxide is dried and then calcined at 500 ° C. to 1400 ° C. for 2 hours to obtain Al-substituted Zn ferrite. The Al-substituted Zn ferrite obtained by firing is cooled and then pulverized to finally produce a pigment sample.

  In one example of the above production method, iron nitrate hydrate is used as a raw material for Fe, but the Fe raw material is not particularly limited to this, and any water-soluble metal salt can be suitably used. It is. For example, iron (II) acetate, iron bromide (II) and its hydrate, iron (III) bromide, iron (II) chloride and its hydrate, iron chloride (III) and its hydrate, Iron (III) acid and its hydrates ・ Iron lactate (II) and its hydrate ・ Iron nitrate (III) and its hydrate ・ Iron (II) perchlorate and its hydrate ・ Iron sulfate (II) ) And its hydrates ・ Iron sulfate (III) and its hydrate ・ Ammonium iron citrate (III) ・ Ammonium iron (II) sulfate and its hydrate ・ Iron sulfate (III) and its hydrate Is possible.

  In the above production method, aluminum nitrate hydrate is used as the Al raw material. However, the Al raw material is not particularly limited to this, and any water-soluble metal salt is preferably used. Is possible. For example, aluminum acetate and its hydrate, ammonium sulfate and its hydrate, aluminum bromide, aluminum lactate, aluminum nitrate and its hydrate, aluminum perchlorate and its hydrate, aluminum sulfate and its hydrate -Aluminum oxalate and its hydrates, aluminum dihydrogen phosphate, etc. can be used.

  Moreover, although zinc nitrate hydrate is used as a Zn raw material in one example of the above production method, the Zn raw material is not particularly limited to this, and any water-soluble metal salt is preferably used. Is possible. For example, zinc acetate and zinc chloride can be used.

  In one example of the above production method, 2M NaOH is used as the precipitating agent. However, the present invention is not particularly limited to this, and ammonia, potassium hydroxide (KOH), and the like can be used. Further, the concentration is not particularly limited, and is preferably 1M or more and 10M or less, more preferably 1M or more and 5M or less.

In addition, when coprecipitation is performed in an example of the above production method, 2M NaOH is added to the raw material aqueous solution so that the pH is 7.5 or 8.0. This is because a pigment sample produced by adding NaOH so as to have a pH of 7.0 or less exhibits a reddish brown color and does not become a target yellow pigment. This is because the produced pigment sample coexists in two phases of an α-Fe ₂ O ₃ solid solution and a ZnAl ₂ O ₄ solid solution, and the α-Fe ₂ O ₃ solid solution of these exhibits a reddish brown color. FIG. 8 shows the results of comparing the color tones of pigment samples produced by coprecipitation under conditions of pH 7.0, 7.5, and 8.0. The pigment sample shows the results when the Al substitution ratio (x in the above formula) is 0.5. The firing conditions are shown for a pigment sample fired at 1100 ° C. for 2 hours and then rapidly cooled, and a pigment sample subjected to slow cooling at 10 ° C./min or less. According to FIG. 8, it can be seen that the sample co-precipitated under the conditions of pH 7.5 and 8.0 exhibits a yellow color, and the sample co-precipitated under the condition of pH 7.0 exhibits a reddish brown color (FIG. 8). The medium L ^* a ^* b ^* value will be described later). Therefore, when manufacturing this yellow pigment using a wet coprecipitation method, it is preferable that the pH conditions at the time of coprecipitation are 7.5 or more.

  In one example of the production method described above, solid-liquid separation is performed by filtration, but as means for solid-liquid separation, means such as filtration using ordinary filter paper, nylon membrane filter, etc., and centrifugation may be used. In Examples described later, filtration is performed using filter paper having a pore size of 3 μm.

In one example of the above production method, washing with water is performed. In washing with water, for example, the precipitate separated by filtration is resuspended in water, and solid-liquid separation is performed again by means such as filtration. This is repeated until there is no NaNO ₃ .

  The means and conditions for firing and pulverization are the same as those explained in the above section “Complex polymerization method”.

  In Examples to be described later, the inventors have succeeded in producing pigment samples made of various Al-substituted Zn ferrites by the wet coprecipitation method, and producing the yellow pigment having a yellow color from them.

(1-3. Solid-phase reaction method)
The “solid phase reaction method” is a method for producing a pigment sample by mixing a metal compound as a raw material in a solid state, firing at a high temperature, pulverizing after cooling.

  Among the metal raw material compounds used in the production of the present yellow pigment, for example, iron oxide, iron hydroxide, and iron oxyhydroxide are suitable as the Fe raw material, and aluminum oxide, aluminum hydroxide, for example, are suitable as the Al raw material. For example, zinc oxide and zinc hydroxide are preferably used as the Zn raw material. At this time, aluminum oxide and iron oxide are mixed at a ratio corresponding to the target Al substitution ratio (x in the above formula). For example, when x is set to 0.4 in the above formula, mixing is performed so that the molar ratio of aluminum (Al) to iron (Fe) is 0.4: 0.6.

  The means and conditions for firing and pulverization are the same as those explained in the above section “Complex polymerization method”.

<2. Method for evaluating pigment sample>
(2-1. Confirmation of Al substitution ratio (x in the above formula) and confirmation of solid solution formation)
About the various pigment samples manufactured by the said manufacturing method, Al substitution ratio (x in the said formula) is confirmed by X-ray diffraction. An example of the result is shown in FIG. FIG. 5 shows the results of X-ray diffraction performed on pigment samples having respective Al substitution ratios obtained by baking at 1,000 ° C. for 2 hours. According to the result of FIG. 5, it can be confirmed that Fe in the above formula is replaced by Al. Although the said confirmation was performed about the pigment sample manufactured on the baking conditions of 600 to 1400 degreeC, the production | generation of Al substituted Zn ferrite has been confirmed on all the conditions. The X-ray diffraction was performed by a powder X-ray diffraction method using RINT-2000 manufactured by Rigaku Corporation.

  Similarly, it is evaluated whether or not a solid solution can be obtained by examining the relationship with the lattice constant of various pigment samples produced by the above production method. An example is shown in FIG. FIG. 6 shows the results of examining the relationship between the lattice constant and the Al substitution ratio for pigment samples having respective Al substitution ratios obtained by baking at 1,000 ° C. for 2 hours. According to the result of FIG. 6, it can be seen that the Al substitution ratio and the lattice constant show a linear relationship, and it can be confirmed that a solid solution is formed for all the pigment samples manufactured under the above-mentioned firing conditions. Although the said confirmation was performed about the pigment sample manufactured on the baking conditions of 600 to 1400 degreeC, the production | generation of the solid solution of Al substituted Zn ferrite was confirmed on all the conditions.

(2-2. Evaluation of color and tone)
Various pigment samples manufactured by the above manufacturing method are evaluated for color and tone. The evaluation method is not particularly limited, but the present inventors have performed using the L ^* a ^* b ^* display system. As other evaluation methods, an xyz color system, Munsell color system, L ^* c ^* h ^* color system, Hunter color system, and the like can be used.

The L ^* a ^* b ^* display system is a global standard indicating the color of an object standardized by the International Commission on Illumination (CIE) in 1976 and adopted in JIS in Japan. Here, L ^* indicates lightness, and a ^* and b ^* indicate hue and saturation. That is, the L ^* value is higher on the positive side, in other words, the L ^* value is positive and the absolute value is larger, indicating that the brightness is brighter and closer to white, and conversely higher on the negative side, in other words L ^{* The} value is negative and the larger the absolute value, the closer it is to black. The a ^* value is higher on the positive side, in other words a ^* value is a positive value close to red as the larger absolute value, higher on the minus side to the opposite, in other words a ^* value is negative. The larger the absolute value is, the closer it is to green. In addition, the b ^* value is higher on the positive side, in other words, the b ^* value is positive and the absolute value is larger, the closer to yellow, the higher the negative side, in other words, the b ^* value is negative. The larger the absolute value is, the closer it is to blue. Evaluation is made by comprehensively judging the above three values, but b ^* value alone is also possible for simple yellow evaluation. At this time, a b ^* value of 30 or more is suitable as a yellow pigment (in other words, a yellow pigment). Furthermore, the L ^* value and the b ^* value (30 or more) are high on the plus side, in other words, the L ^* value and the b ^* value are positive values, the absolute values thereof are large, and the a ^* value is close to 0. It is an ideal L ^* a ^* b ^* value as a yellow pigment (in other words, a pigment exhibiting a yellow color). In addition, an example of the measurement result of L ^* a ^* b ^* value of a chrome lead pigment is (L ^* = 82.16, a ^* = 18.32, b ^* = 88.32).

FIG. 1 shows the results of measuring L ^* a ^* b ^* values for various pigment samples having different Al substitution ratios (x in the above formula) and different firing temperature conditions (600 ° C. to 1200 ° C.). A spectrocolorimeter (CM-2600d manufactured by Minolta) was used for the measurement. In the horizontal axis direction in FIG. 1, each Al substitution ratio (x in the above formula) is shown. Specifically, the Al substitution ratio (x in the above formula) is 0.000, 0.075, 0.100, 0.150, 0.200, 0.225, 0.300, 0.375, from the right. 0.400, 0.450, 0.500, 0.525, 0.600, 0.675, 0.700, 0.750, 0.800, 0.875, 0.900, 1.000 Results are shown. Moreover, the result in the case of each calcination temperature condition is shown to the vertical axis | shaft direction in the same figure. More specifically, the results are shown when the firing temperatures are 1200 ° C., 1100 ° C., 1000 ° C., 900 ° C., 800 ° C., 700 ° C., and 600 ° C. from the top.

The preferred conditions for the Al substitution ratio (x in the above formula) for the various pigment samples produced to be yellow and the preferred conditions for the firing temperature are as follows. The b ^* value in FIG. If judged based on the fact that it can be judged that yellow is exhibited, all firing temperature conditions (over 500 ° C. and below 1400 ° C., 1200 ° C. · 1100 in FIG. It was possible to judge that the preferred temperature was 1000 ° C / 900 ° C / 900 ° C / 800 ° C / 700 ° C / 600 ° C. In particular, when the Al substitution ratio is 0.4 or more and 0.8 or less, it is judged that the firing temperature condition of more than 500 ° C. and less than 900 ° C. (800 ° C., 700 ° C., 600 ° C. in FIG. 1) is more preferable. did it. When the Al substitution ratio is 0.15 or more and 0.6 or less, the firing temperature condition of 800 ° C. or more and less than 1400 ° C. (1200 ° C., 1100 ° C., 1000 ° C., 900 ° C., 800 ° C. in FIG. 1) is further added. It was judged that it was suitable. Furthermore, when the Al substitution ratio is 0.4 or more and 0.6 or less, it exceeds 500 ° C. and is less than 1400 ° C. (in FIG. 1, 1200 ° C., 1100 ° C., 1000 ° C., 900 ° C., 800 ° C., 700 ° C., In the range of 600 ° C., all pigment samples exhibit a yellow color with excellent color tone.

  Therefore, if a pigment sample containing Al-substituted Zn ferrite is produced so as to satisfy the above conditions, a yellow pigment can be obtained. In addition, when the pigment sample containing Al-substituted Zn ferrite satisfying the above conditions, that is, the thermal stability of this yellow pigment was tested, no fading or discoloration occurred in the temperature range from room temperature (for example, 25 ° C.) to 1200 ° C. It was found to be a stable yellow pigment, in other words, a pigment having excellent heat resistance.

The yellow pigment may be composed of only an Al-substituted Zn ferrite having a single x in the above formula, or a mixture of Al-substituted Zn ferrite having different x in the above formula. The yellow pigment may be a mixture of other pigments, for example, a red pigment made of α-Fe ₂ O ₃ , a white pigment made of ZnO, a white pigment made of α-Al ₂ O _3, and the like. Further, the yellow pigment may contain a substance other than the Al-substituted Zn ferrite.

  Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited thereto.

[Example 1: Production of pigment sample by complex polymerization method]
(Method) Zn (NO ₃ ) ₂ .6H ₂ O (99.0%), Fe (NO ₃ ) ₃ · 9H ₂ O (99.0%), Al (NO ₃ ) which are soluble metal salts as metal raw materials _{3 · 9H 2 O (99.0%} ) was used. After mixing each metal salt so as to have an appropriate composition ratio, 50 times the amount of water was added in a molar ratio with respect to the total of each metal ion to prepare an aqueous solution. Next, 5 times the amount of citric acid is added in a molar ratio to the total of each metal salt to form a chelate complex, and similarly, 15 times the amount of ethylene glycol in the molar ratio is added to gel, and the mixture is heated at 180 ° C. for 12 hours. After the polymerization, a precursor that was pyrolyzed at 450 ° C. for 24 hours in the atmosphere was used as a precursor. Next, this precursor was calcined, cooled and pulverized at various temperatures to obtain pigment samples. The firing time was 2 hours.

The confirmation of the constituent phases of the produced pigment sample and the measurement of the lattice constant were carried out by powder X-ray diffraction using RINT-2000 manufactured by Rigaku Corporation. Moreover, the particle | grain form of the pigment sample was observed using FE-SEM (Hitachi S-4300). For the measurement of color and color tone, a spectrocolorimeter (CM-2600d manufactured by Minolta) was used, and the evaluation method was performed using an L ^* a ^* b ^* display system.

  (Results) The constituent phases of the pigment sample produced by firing at 600 ° C. to 1400 ° C. for 2 hours were confirmed by a powder X-ray diffraction method. FIG. 5 shows the results of X-ray diffraction of various pigment samples produced by firing at 1000 ° C.

5 shows that _x in the formula Zn (Fe _(1-x) Al _x ) ₂ O ₄ is 0, 0.15, 0.3, 0.45, 0.6, 0.75, 0.9, 1. Although the results in the case of 0 are shown, it was found from each X-ray diffraction pattern that single-phase Al-substituted Zn ferrite was obtained in any case. Single-phase Al-substituted Zn ferrite was obtained in pigment samples produced at all firing temperatures of 600 ° C. to 1400 ° C.

  In addition, as a result of examining the lattice constant of each pigment sample made of Al-substituted ferrite having various Al substitution ratios manufactured at different firing temperatures, the pigment sample made of Al-substituted ferrite having the same Al substitution ratio has a certain lattice constant. Had. FIG. 6 shows the results of examining the relationship between the Al substitution ratio and the lattice constant for various pigment samples produced by firing at 1000 ° C. According to FIG. 6, for the pigment sample produced by firing at 1000 ° C., the solid solution was obtained for all the pigment samples produced at the firing temperature because the Al substitution ratio and the lattice constant are in a linear relationship. It could be confirmed. In addition, as a result of investigating similarly about each pigment sample baked at 600 to 1400 degreeC, Al substitution ratio and a lattice constant had a linear relationship. Therefore, it was confirmed that a solid solution was obtained in all of these pigment samples.

The results of evaluating the color tone of variously produced pigment samples using the L ^* a ^* b ^* display system are shown in FIG. In the horizontal axis direction in FIG. 1, each Al substitution ratio (x in the above formula) is shown. Moreover, the result in the case of each calcination temperature condition is shown to the vertical axis | shaft direction in the same figure. The preferred conditions for the Al substitution ratio (x in the above formula) for the various pigment samples produced to be yellow and the preferred conditions for the firing temperature are as follows. The b ^* value in FIG. If judged based on the fact that it can be judged that yellow is exhibited, all firing temperature conditions (over 500 ° C. and below 1400 ° C., 1200 ° C. · 1100 in FIG. It was possible to judge that the preferred temperature was 1000 ° C / 900 ° C / 900 ° C / 800 ° C / 700 ° C / 600 ° C. In particular, when the Al substitution ratio is 0.4 or more and 0.8 or less, it is judged that the firing temperature condition of more than 500 ° C. and less than 900 ° C. (800 ° C., 700 ° C., 600 ° C. in FIG. 1) is more preferable. did it. When the Al substitution ratio is 0.15 or more and 0.6 or less, the firing temperature condition of 800 ° C. or more and less than 1400 ° C. (1200 ° C., 1100 ° C., 1000 ° C., 900 ° C., 800 ° C. in FIG. 1) is further added. It was judged that it was suitable.

FIG. 9 shows scanning electron microscope (SEM) photographs of pigment samples prepared from ZnFe ₂ O ₄ at calcination temperatures of 800 ° C. and 1000 ° C. From the figure, it can be seen that the particles fired at 1000 ° C. are larger than the particles fired at 800 ° C.

[Example 2: Production of pigment sample by wet coprecipitation method]
(Method) As a metal raw material, Zn (NO ₃ ) ₂ .6H ₂ O (99.0%), Fe (NO ₃ ) ₃ · 9H ₂ O (99.0%), Al (NO ₃ ) ₃ · 9H ₂ O (99.0%) was used. Each of the above reagents was adjusted to a 0.1 M aqueous solution having x = 0.4 to 0.6 in the formula Zn (Fe _(1-x) Al _x ) ₂ O ₄ . NaOH (0.1M) was added dropwise to each aqueous solution, and coprecipitation was performed under conditions of pH 7.0, 7.5, and 8.0. After solid-liquid separation, it was washed with water to completely remove NaNO ₃ . The dried sample was press-molded and fired at various temperatures for 2 hours. After cooling by rapid cooling (removing the sample from the heating furnace and cooling to room temperature) or slow cooling (cooling at a rate of 10 ° C./min), the mixture was pulverized to obtain a pigment sample. The evaluation method was performed according to the method of Example 1.

(Results) With each pigment sample produced by coprecipitation under the conditions of pH 7.5 and pH 8.0, single-phase Al-substituted Zn ferrite having an Al substitution ratio corresponding to the charged composition was obtained. On the other hand, the pigment sample produced at pH 7.0 was a two-phase coexistence of α-Fe ₂ O ₃ solid solution and ZnAl ₂ O ₄ solid solution. This is because 0.1M Fe ³⁺ , Al ³⁺ and Zn ²⁺ hydroxides start to precipitate at pH 1.6, ³ and 7, respectively, and Fe (OH) ₃ -Al (OH) ₃ It is considered that coprecipitation and accompanying precipitation of Al (OH) ₃ —Zn (OH) ₂ occurred respectively.

FIG. 8 shows an L ^* a ^* b ^* display system for a pigment sample having an Al substitution ratio of 0.5 produced by coprecipitation at pH 7.0, 7.5, and 8.0 and firing at 1100 ° C. for 2 hours. The result evaluated using is shown. Moreover, the result at the time of cooling after baking by rapid cooling and the result at the time of performing by slow cooling (10 degreeC / min) are shown.

Pigment samples produced by coprecipitation at pH 7.5 and pH 8.0 exhibited a yellow color. On the other hand, the pigment sample produced by coprecipitation at pH 7.0 exhibited a reddish brown color. This is because an α-Fe ₂ O ₃ solid solution was formed. Moreover, the effect by slow cooling was hardly seen. Therefore, when manufacturing this yellow pigment using a wet coprecipitation method, it can be said that it is a preferable condition that pH conditions of coprecipitation are 7.5 or more.

  Note that the present invention is not limited to the configurations described above, and various modifications are possible within the scope of the claims, and technical means disclosed in different embodiments and examples respectively. Embodiments obtained by appropriate combinations are also included in the technical scope of the present invention.

  According to the present invention, according to the iron oxide yellow pigment according to the present invention and the method for producing the same, the iron oxide yellow pigment excellent in weather resistance and heat resistance without containing a substance harmful to the human body and the environment, and The manufacturing method can be provided. In other words, it is possible to provide an iron oxide yellow pigment that stably exhibits a yellow color even under severe use conditions such as traffic paint and is safe.

  Therefore, it can be used in a wide range of industrial fields such as the machine industry (industrial use, agricultural use, etc.), construction / building industry, electrical industry, and glass industry that require yellow pigment.

It is a figure which shows the result of having measured L ^* a ^* b ^* value about the various pigment sample from which Al substitution ratio differs and baking temperature conditions (600 to 1200 degreeC) differ. It is a figure explaining the concept of complex polymerization method. It is process drawing which shows an example of the manufacturing method of the iron oxide type pigment containing Al substituted Zn ferrite by a complex polymerization method. It is process drawing which shows an example of the manufacturing method of the iron oxide pigment containing Al substituted Zn ferrite by the wet coprecipitation method. It is a figure which shows the X-ray-diffraction pattern about the various pigment samples manufactured on 1000 degreeC and the baking conditions for 2 hours. It is a figure which shows the relationship between Al substitution ratio and a lattice constant about the various pigment samples manufactured on 1000 degreeC and the baking conditions for 2 hours. For pigment samples having an Al substitution ratio (x in the above formula) of 0.4, 0.5, and 0.6, the sample was baked at 1100 ° C. for 2 hours and then rapidly cooled, and slowly cooled at 10 ° C./min or less. It is a figure which shows the result of having measured the L ^* a ^* b ^* value of the performed pigment sample. For pigment samples produced by wet coprecipitation under conditions of pH 7.0, 7.5, and 8.0, samples that were baked at 1100 ° C. for 2 hours and then cooled rapidly were gradually added under conditions of 10 ° C./min or less. It is a figure which shows the result of having measured the L ^* a ^* b ^* value of the pigment sample which cooled. (A) is a scanning electron microscope (SEM) photograph of the pigment samples prepared a ZnFe ₂ O ₄ in a firing temperature of 800 ℃, (b) the pigment samples prepared a ZnFe ₂ O ₄ in a firing temperature 1000 ° C. It is a scanning electron microscope (SEM) photograph figure.

Claims (10)

An iron oxide pigment comprising Zn, Fe, Al,
Iron oxide-based yellow pigment characterized by containing Al-substituted Zn ferrite represented by the formula Zn (Fe _(1-x) Al _x ) ₂ O ₄ (where 0 <x <1) and exhibiting yellow color .   The iron oxide yellow pigment according to claim 1, wherein x in the above formula is 0.075 or more and 0.8 or less.   The iron oxide yellow pigment according to claim 2, wherein x in the above formula is 0.4 or more and 0.8 or less.   The iron oxide yellow pigment according to claim 2, wherein x in the above formula is 0.15 or more and 0.6 or less.   The iron oxide-based yellow pigment according to any one of claims 1 to 4, which exhibits a yellow color at 1200 ° C or lower. An iron oxide pigment comprising Zn, Fe, Al,
When producing an iron oxide-based yellow pigment containing Al-substituted Zn ferrite represented by the formula Zn (Fe _(1-x) Al _x ) ₂ O ₄ (where 0 <x <1) and exhibiting a yellow color ,
A method for producing an iron oxide yellow pigment, characterized by using a complex polymerization method, a wet coprecipitation method or a solid phase reaction method. In the above formula, when x is 0.075 or more and 0.8 or less,
The method for producing an iron oxide yellow pigment according to claim 6, wherein the firing temperature is higher than 500 ° C and lower than 1400 ° C. In the case where x is 0.4 or more and 0.8 or less in the above formula,
The method for producing an iron oxide yellow pigment according to claim 7, wherein the firing temperature is higher than 500 ° C and lower than 900 ° C. In the case where x is 0.15 or more and 0.6 or less in the above formula,
The method for producing an iron oxide yellow pigment according to claim 7, wherein the firing temperature is 800 ° C or higher and lower than 1400 ° C. When using the wet coprecipitation method,
The method for producing an iron oxide yellow pigment according to any one of claims 6 to 9, wherein the coprecipitation is performed under a condition of pH 7.5 or higher.

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