JP2004082114A - Photocatalyst composite powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photocatalyst composite powder which has no pollution without containing chromium or lead and is capable of suppressing the formation of secondary particles with excellent dispersibility and restraining the deterioration of supports themselves even if the photocatalyst composite powder adheres to the supports such as a coating film or a fiber. <P>SOLUTION: A photocatalyst composite powder is formed by supporting a photocatalyst in a porous inorganic powder primarily composed of iron oxide. Preferably, the average particle size of the porous inorganic powder is bigger than the average particle size of the photocatalyst and the ratio of iron to all metals is more than 5 mol% in the porous inorganic powder. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a photocatalyst composite powder in which a photocatalyst is supported on a porous inorganic powder. The photocatalyst composite powder of the present invention can be used in various fields requiring water treatment, deodorizing effect, air pollution purifying effect, antibacterial effect, self-cleaning effect, and the like.

(4) Since photocatalysts generate strong oxidation-reduction power (photocatalytic reaction) when irradiated with light, they have recently been attracting attention in many industrial fields, and their applications are constantly expanding. For example, photocatalysts can decompose pollutants using clean light energy, have high redox ability, and remove harmful gas phase substances (NOx, SOx, formaldehyde, etc.), fungi, bacteria, etc. Since it can be decomposed, it is applied to many products such as antibacterial tiles, air purifiers, purification of domestic wastewater and industrial wastewater. At present, environmental issues on a global scale, such as an increase in carbon dioxide and global warming, air pollution by NOx and SOx, and water pollution of rivers by harmful substances, are seriously questioned. Is attracting attention.

Recently, in order to improve the photocatalytic function of the photocatalyst powder, a photocatalyst powder in which a photocatalyst powder and an iron compound are combined has been reported.
For example, Patent Literature 1 discloses a method for obtaining a titanium oxide having an excellent photocatalytic function by supporting an iron compound on the inside or the surface of fine titanium oxide particles.

JP-A-7-303835

However, when the composite powder of Patent Document 1 is used by being fixed to a support such as a coating film or a fiber, there is a problem that the composite powders easily aggregate to form secondary particles.
Further, the support itself may be decomposed and deteriorated by the photocatalytic reaction. Increasing the amount of the iron compound supported on the titanium oxide tends to alleviate the problem of decomposing and degrading the support itself, but since the titanium compound is coated with the iron compound, the composite powder The surface area having photocatalytic activity in the body is reduced, and the photocatalytic activity is reduced.

In order to solve the above-mentioned problems, the present invention has conducted intensive studies and found that the photocatalyst is supported on an inexpensive, non-polluting porous inorganic powder containing iron oxide as a main component, thereby fixing the photocatalyst to a support. It has been found that even in this case, a photocatalyst composite powder having excellent dispersibility, suppressing formation of secondary particles, suppressing deterioration of the support itself, and having excellent photocatalytic ability can be obtained.

That is, the present invention has the following features.
1. A photocatalyst composite powder comprising a photocatalyst supported on a porous inorganic powder containing iron oxide as a main component.
2. A photocatalyst composite powder comprising a photocatalyst and a metal supported on a porous inorganic powder containing iron oxide as a main component.
3. The average particle diameter of the porous inorganic powder is larger than the average particle diameter of the photocatalyst. Or 2. 2. The photocatalyst composite powder according to item 1.
4. The ratio of Fe to all metal elements in the porous inorganic powder is 5 mol% or more. From 3. The photocatalyst composite powder according to any one of the above.
5. The photocatalyst is supported by 0.1 to 30 wt% with respect to the porous inorganic powder. From 4. The photocatalyst composite powder according to any one of the above.
6. 1. The metal is at least one metal selected from palladium, platinum, rhodium, ruthenium, nickel, iron, copper, silver, gold, and zinc. To 5. The photocatalyst composite powder according to any one of the above.
7. 1. characterized in that the metal is supported in an amount of 0.01 to 10% by weight with respect to the porous inorganic powder. To 6. The photocatalyst composite powder according to any one of the above.
8. The specific surface area is 40 m ² / g or more. To 7. The photocatalyst composite powder according to any one of the above.
9. The average particle size is 0.01 to 100 μm. From 8. The photocatalyst composite powder according to any one of the above.

The photocatalyst composite powder of the present invention is inexpensive and non-polluting, and has photocatalytic effects such as water purification, deodorization, environmental purification effects such as purification of air pollution, antibacterial effects, and self-cleaning effects. Further, when it is fixed to a support such as a coating film or a fiber, it has excellent dispersibility, can suppress the formation of secondary particles, suppresses deterioration of the support itself, and has excellent photocatalytic activity. Further, it is also effective as a pigment having a new color used for paints and the like.

Hereinafter, the present invention will be described in detail based on the best mode for carrying out the invention.

(Porous inorganic powder)
The porous inorganic powder of the present invention (hereinafter also referred to as “porous iron oxide powder”) is not particularly limited as long as it contains iron oxide as a main component, and a known powder may be used.
Examples of iron oxide include α-Fe ₂ O ₃ (hemite), γ-Fe ₂ O ₃ (maghemite), and Fe ₃ O ₄ . In particular, when α-Fe ₂ O ₃ (hemite) and γ-Fe ₂ O ₃ (maghemite) are used, they are chemically stable and are preferable. Further, at least one or more metal elements selected from Al, Si, Zn, Ca, Sr, Ba, Co, Ni, Bi, Y, and lanthanoids can be partially substituted for these iron oxides before use. By changing the content of such a metal element, color, magnetic characteristics, and the like can be controlled.

比率 The ratio of Fe to all metal elements in the porous inorganic powder is preferably 5 mol% or more, more preferably 10 mol% or more, further preferably 20 mol% or more, and most preferably 50 mol% or more. When the ratio of Fe to all metal elements is 5 mol% or more, the photocatalytic ability can be sufficiently exhibited.

The inorganic powder of the present invention is essential to be porous, and preferably has a specific surface area of 40 m ² / g or more, more preferably 60 m ² / g or more. Since the inorganic powder is porous, it is possible to obtain a composite powder having an excellent gas adsorption ability, an increased amount of a photocatalyst carried, and an excellent photocatalytic ability.
The average particle size of the porous inorganic powder is not particularly limited, but is preferably 0.01 to 100 μm, and more preferably 0.1 to 50 μm. The particle size distribution, particle shape, and the like of the porous inorganic powder can be appropriately set.

As a method for obtaining a porous iron oxide powder, a method of heating and dehydrating iron oxide hydroxide, a method of heat-treating an iron oxide powder supporting amorphous silica (for example, JP-A-2000-290018) and the like are available. No.
In the method of heating and dehydrating iron oxide hydroxide, by subjecting the iron oxide hydroxide to a heat treatment in the air or in a reducing atmosphere, a dehydration reaction occurs and a target porous iron oxide powder can be obtained. The heat treatment temperature is preferably in the range of 150C to 500C. At a temperature lower than this range, the desired dehydration reaction does not easily occur. If the temperature is higher than this range, the aggregation between the particles greatly proceeds, so that it is not possible to obtain a porous powder having good dispersibility and a large specific surface area.

As the above iron oxide hydroxide, α-FeOOH (goethite), β-FeOOH (akaganeite), γ-FeOOH (lepidocrotite), δ-FeOOH and the like can be used. α-FeOOH, β-FeOOH, and γ-FeOOH can be more preferably used. A composite oxide hydroxide in which at least one metal element selected from Al, Si, Zn, Ca, Sr, Ba, Co, Ni, Y, and lanthanoid is partially substituted for these iron oxide hydroxides can also be used. By changing the content of the substitution element, it is possible to control the color, magnetic properties, and the like of the composite oxide generated by the thermal dehydration reaction.
Incidentally, by appropriately setting the particle diameter, particle diameter distribution, particle shape, and the like of these oxidized hydroxides, it is possible to control the particle diameter, particle diameter distribution, particle shape, and the like of the composite oxide generated by the heat dehydration reaction. it can.

As a method for producing iron oxyhydroxide, known methods can be mentioned. JP-B-6-42889, JP-B-6-42900, JP-B4-22233, JP-B4-22233, JP-B-54-7292, JP-B-59-17050, JP-A-9-165531, JP-A-1-182363, Kaihei 3-163172, JP-B-46-39681, JP-B-53-4078, H.C. Christensen and and A. N. Christensen, Acta Chemica Scandinavicica, Series A 32 (1978) 87; L. MacKay, Minerological {Magazine} and {Journal} of the {Mineralogical} Society {32} (1960) 545, and the like. In addition, commercially available products can also be used.

(photocatalyst)
The photocatalyst used in the present invention is not particularly limited, and a normal photocatalyst can be used. Examples of the photocatalyst include titanium dioxide, zinc oxide, zirconium oxide, and tungsten oxide, and one or more of these can be used. In particular, titanium dioxide and zinc oxide are preferably used.
The average particle size of the photocatalyst is not particularly limited, but is usually about 0.005 to 0.25 μm, and preferably about 0.01 to 0.2 μm.

Further, in the present invention, it is preferable that a metal is supported together with the photocatalyst on the porous inorganic powder mainly composed of iron oxide. By carrying the metal, harmful substances can be decomposed with high efficiency, and the environmental purification effect such as water purification, deodorization, and air pollution purification, and the photocatalytic effect such as antibacterial effect can be improved. This effect is considered to be due to the fact that, of the electrons and holes generated from the photocatalyst irradiated with light, the electrons move to the metal, so that the recombination of the electrons and holes hardly occurs.

Examples of the metal include palladium, platinum, rhodium, ruthenium, nickel, iron, copper, silver, gold, zinc and the like, and one or more of these can be used in combination. In the present invention, palladium, platinum, copper, silver, and gold are particularly preferable, and platinum, silver, and gold are more preferable.
The average particle diameter of the metal is preferably smaller than the average particle diameter of the porous inorganic powder. Although the average particle diameter of the metal is not particularly limited, it is usually preferably 0.005 to 0.25 μm, more preferably 0.01 to 0.2 μm.

(Production method of photocatalyst composite powder)
The method for producing the photocatalyst composite powder of the present invention includes a method of supporting a photocatalyst on a porous inorganic powder and a method of supporting a photocatalyst and a metal on a porous inorganic powder.

(Method of supporting photocatalyst on porous inorganic powder)
The method of supporting the photocatalyst on the porous inorganic powder is not particularly limited. For example, a method of heat-treating the powder obtained by fixing the photocatalyst precursor to the porous iron oxide powder, or a method of preforming the porous iron oxide powder And a method of heat-treating a powder in which a photocatalyst precursor is fixed on iron oxide hydroxide particles as a body.

Examples of a method for fixing the photocatalyst precursor to the porous iron oxide particles or iron oxide hydroxide particles include a precipitation method and a sputtering method. In the precipitation method, a metal ion is precipitated as a hydroxide by neutralization in a mixed solution of the above-described porous iron oxide particles or iron oxide hydroxide particles, or a method of hydrolyzing a metal alkoxide is used. In this method, a photocatalyst precursor is gradually generated on the surface of porous iron oxide particles or iron oxide hydroxide particles. Next, by heating the porous iron oxide powder or the iron oxide hydroxide powder to which the photocatalyst precursor obtained by removing the solvent by filtration or the like is fixed, the porous iron oxide carrying the photocatalyst is heated. A powder is obtained.
At this time, the heat treatment temperature of the iron oxide hydroxide powder to which the photocatalyst precursor is fixed varies depending on the fixed photocatalyst, but is usually preferably in the range of 150 ° C to 500 ° C.
The heat treatment temperature of the porous iron oxide powder to which the photocatalyst precursor is fixed varies depending on the fixed photocatalyst, but is usually preferably in the range of 500 ° C. or less.
In the present invention, by appropriately selecting the particle size of the porous iron oxide powder or iron oxide hydroxide particles, a uniform photocatalyst composite powder, or a photocatalyst composite powder having a certain particle size distribution, The particle size can be controlled according to the purpose.

光 The weight of the photocatalyst supported on the porous iron oxide powder is preferably 0.1 to 30 wt%, more preferably 0.5 to 20 wt%, based on the porous inorganic powder. When the weight of the photocatalyst is smaller than this range, the effect as the photocatalytic ability is reduced. Further, if the weight of the photocatalyst is larger than this range, there is a possibility that photocatalyst particles not supported by the porous iron oxide powder may be generated. Therefore, it is necessary to prepare only the photocatalyst composite powder supporting the photocatalyst intended for the present invention. Becomes difficult.

光 The photocatalyst composite powder of the present invention has a photocatalyst supported on porous iron oxide powder, and the photocatalytic activity is improved by the iron oxide composite. Furthermore, when the photocatalyst composite powder is fixed to the support, the photocatalysts are hardly in contact with each other, are excellent in dispersibility, can suppress the formation of secondary particles, and are hardly in contact with the photocatalyst and the support. Body deterioration can be suppressed. Further, since porous particles are used, they are excellent in gas adsorption and the like. Although a large amount of the photocatalyst is present in the pores of the porous iron oxide powder, it may be present on the surface of the porous iron oxide powder to the extent that the effects of the present invention are not impaired.

The present invention is a photocatalyst composite powder obtained by supporting a photocatalyst on a porous inorganic powder mainly composed of iron oxide, wherein the average particle diameter of the porous inorganic powder is larger than the average particle diameter of the photocatalyst. Is preferred. Since the average particle diameter of the porous inorganic powder is larger than the average particle diameter of the photocatalyst, the photocatalyst supported on the porous inorganic powder is less likely to come into contact with the coating film or the fiber support, and the support is deteriorated. And has excellent photocatalytic performance.

The photocatalyst composite powder preferably has a specific surface area measured by the BET method of 40 m ² / g or more, and more preferably 60 m ² / g or more. When the specific surface area is 40 m ² / g or more, adsorption and decomposition as a photocatalyst can be advanced more efficiently.
The particle diameter of the photocatalyst composite powder is preferably from 0.01 to 100 μm, more preferably from 0.1 to 50 μm. When used for a support such as a coating film or a fiber, the particle size is in such a range, the dispersibility is excellent, the concealing property is excellent, and the ultraviolet ray shielding ability is also excellent, the support of the ultraviolet ray It also has the effect of protecting against deterioration.

In addition, the photocatalyst composite powder of the present invention is a colored powder containing at least an Fe component and a photocatalyst component. Can be obtained. Such a photocatalyst composite powder can also be used as a colored pigment such as a paint.

(Method of supporting photocatalyst and metal on porous inorganic powder)
Examples of the method of supporting the photocatalyst and the metal on the porous inorganic powder include a method of supporting the metal after supporting the photocatalyst on the porous inorganic powder, and a method of simultaneously supporting the photocatalyst and the metal on the porous inorganic powder. In the present invention, a method of supporting the metal after supporting the photocatalyst on the porous inorganic powder is preferably used.

The method described above may be used as a method for supporting the photocatalyst on the porous inorganic powder.
Further, as a method of supporting a metal, for example, there are methods such as an electroless plating method, a physical vapor deposition method, and a mechanical alloying method. In particular, the mechanical alloying method is preferable because a small amount of waste liquid is discharged and a relatively inexpensive apparatus can be used.

As a method of supporting a metal by the mechanical alloying method, a photocatalyst composite powder in which a photocatalyst is supported on a porous inorganic powder and a method of mixing a metal, or a photocatalyst composite powder in which a photocatalyst is supported on a porous inorganic powder And a method of mixing a body, a metal salt solution and a reducing agent. In the present invention, a method of mixing a photocatalyst composite powder in which a photocatalyst is supported on a porous inorganic powder, a metal salt solution and a reducing agent is preferable. According to this method, the metal can be more uniformly supported on the surface of the porous inorganic powder.

金属 The metal salt solution of the present invention is used for reacting with a reducing agent to precipitate a metal. The solute of such a metal salt solution is not particularly limited, and includes, for example, at least one metal element selected from palladium, platinum, rhodium, ruthenium, nickel, iron, copper, silver, gold, zinc, and the like. Are preferably used, and those containing palladium, platinum, copper, silver, and gold, and those containing platinum, silver, and gold are particularly preferable because they are stable. In the present invention, metal salts such as nitrates, chlorides, acetates, sulfates, acetylacetonates and ammine complexes of such metal elements can also be used.

The solvent for the metal salt solution is not limited as long as it can stably dissolve the metal salt. Water, methanol, ethanol, n-propanol, alcohols such as isopropanol, ethylene glycol, ethylene glycol monomethyl ether, propylene glycol, propylene In addition to glycol derivatives such as glycol monomethyl ether, diethylene glycol monoethyl ether, and ethylene glycol monoethyl ether acetate, esters, ketones, ethers, n-hexane, n-pentane, n-octane, n-nonane, and n-decane , N-undecane, n-dodecane, terpin oil, aliphatic hydrocarbons such as mineral spirits, aromatic hydrocarbons such as toluene, xylene and solvent naphtha, and others, ethyl acetate, butyl acetate, methyl ethyl Tons, and methyl isobutyl ketone.
Further, the pH of the metal salt solution may be appropriately adjusted in the range of 0 to 14 using a known base or acid. By adjusting the pH, a stable metal salt solution can be prepared. Examples of the base include sodium hydroxide, potassium hydroxide, calcium hydroxide, potassium hydroxide, ammonia, urea, amines and the like. Examples of the acid include hydrochloric acid, sulfuric acid, acetic acid, nitric acid, citric acid, and formic acid.

The reducing agent functions to precipitate a metal by reacting with the metal salt solution. Examples of the reducing agent include hydrazine, formaldehyde, and polysaccharides such as glucose. Particularly, polysaccharides such as glucose, which are safe and inexpensive, are preferable.
The mixing amount of the reducing agent may be generally about 25 to 400 wt% with respect to the metal element.

金属 The weight of the metal supported on the porous inorganic powder is preferably 0.01 to 10 wt%, more preferably 0.1 to 9.0 wt%, based on the porous inorganic powder. If the weight of the metal is less than this range, it is difficult to further improve the photocatalytic effect. On the other hand, if the weight of the metal is larger than this range, the photocatalyst effect may be reduced because the supported metal inhibits light irradiation on the photocatalyst.

実 施 Examples and comparative examples are shown below to further clarify the features of the present invention, but the present invention is not limited to these examples.

(Measuring method)
1. The crystal structure of the composite powder was analyzed with an X-ray diffractometer (RINT-1100, manufactured by Rigaku Corporation).
2. The particle shape and particle diameter of the composite powder were observed with an electron microscope (JSM-5310, manufactured by JEOL Ltd.).
3. The specific surface area of the composite powder was measured by a BET method using a surface area measuring device P-700 manufactured by Shibata Scientific Instruments Co., Ltd. with dead volume measurement gas: helium and adsorption gas: nitrogen.
4. Evaluation test of photocatalytic activity 5 g of the composite powder was placed on a glass dish, uniformly dispersed using 12.5 g of ethanol, dried at 110 ° C for 2 hours, and the glass dish was placed on a glass top plate (5 mm thick). It was hung and fixed in the reaction vessel. Next, a commercially available ammonia gas was passed, and when the ammonia concentration in the reaction vessel became stable at 1%, the ventilation was stopped, UV irradiation was started, and the decomposition rate of ammonia was measured after 40 minutes. Note that a 6 W UV lamp was used as a light source, and irradiation was performed from above the test specimen by 5 cm.
5. Hue test In advance, the composite powder is dispersed in acrylic silicone resin (solid content 50%) and red-down with the same resin, whereby 72 parts by weight of acrylic silicone resin (solid content 50%), 10 parts by weight of composite powder, A base paint of 18 parts by weight of thinner was obtained. To 100 parts by weight of the base paint, 10 parts by weight of a curing agent was mixed, applied to a standard white paper with a coating thickness of 0.25 mm, and dried for 24 hours to obtain a test specimen. The obtained test body was measured with a color difference meter (SPECTROPHOTOMETER CM-3700d, manufactured by Minolta Co., Ltd.).
6. Concealment Ratio Test A coating prepared in the same manner as in the hue test was applied to a cover ratio test paper at a coating thickness of 0.25 mm and dried for 24 hours to obtain a test specimen. The concealment rate of the obtained test body was measured with a color difference meter (SPECTROPHOTOMETER CM-3700d, manufactured by Minolta Co., Ltd.).
7. Deterioration test of paint film A paint prepared in the same manner as in the hue test was applied to an aluminum plate (70 mm x 150 mm x 0.8 mm) (JIS H 4000) previously coated with a white acrylic resin paint with a thickness of 0.25 mm. And cured for 24 hours to obtain a test body. The specular gloss (measurement angle: 60 degrees) (initial gloss) of the obtained specimen was measured with a gloss meter (Microtrigloss, manufactured by BYK Japan KK). The results are shown in FIG. Further, the test specimen was attached to a sunshine weather meter (manufactured by Suga Test Instruments Co., Ltd.), the glossiness after exposure for 500 hours was measured, and the gloss retention was calculated from the initial glossiness and the glossiness after exposure for 500 hours. The results are shown in FIG. The gloss retention is a value calculated by the following equation.
Gloss retention (%) = gloss after exposure for 500 hours / initial gloss × 100

(Example 1)
20 g of needle-like α-FeOOH (major axis length 1 μm) was suspended in 400 ml of ethanol, and 2 g of titanium butoxide was added. After stirring and mixing for 60 minutes, 28 ml of 30% aqueous hydrogen peroxide was added, and the mixture was stirred at 75 ° C. for 6 hours. The ethanol-water solvent was removed by filtration and then dried to obtain titania sol composite α-FeOOH. Next, the titania sol composite α-FeOOH was heat-treated in air at 300 ° C. for 2 hours to obtain a mahogany titanium dioxide-α-Fe ₂ O ₃ composite powder.
As a result of analyzing the X-ray diffraction pattern of the obtained composite powder, as shown in FIG. 1, it was confirmed that anatase type titanium dioxide was generated together with α-Fe ₂ O ₃ . When observed with an electron microscope, a titanium oxide-α-Fe ₂ O ₃ composite powder having a needle-like shape with a major axis length of about 1 μm was observed. The specific surface area was 97.0 m ² / g.
The ammonia decomposition rate was 80%, indicating that the decomposition of ammonia was remarkable, indicating that the composition had excellent photocatalytic activity. The initial glossiness was 84.1 as shown in FIG. 7, and the dispersibility was excellent. The gloss retention was maintained at 100% as shown in FIG. 8, and the weather resistance was excellent. Further, when the film coating, hue, ^{L *} value, respectively 41.72, ^{a *} value is 28.93, ^{b *} values are 23.65, contrast ratio was 99.6%.

(Example 2)
An amber-colored titanium dioxide having an average particle size of 0.5 μm was prepared in the same manner as in Example 1, except that needle-like γ-FeOOH (major axis length 0.5 μm) was used instead of α-FeOOH. An Fe ₂ O ₃ composite powder was obtained.
As a result of analyzing the X-ray diffraction pattern of the obtained composite powder, as shown in FIG. 2, it was confirmed that anatase type titanium dioxide was generated together with γ-Fe ₂ O ₃ . When observed with an electron microscope, a titanium oxide-γ-Fe ₂ O ₃ composite powder having a needle-like shape with a long axis length of about 0.5 μm was observed. The specific surface area was 106.3 m ² / g.
The ammonia decomposition rate was 82%, indicating that the decomposition of ammonia had occurred remarkably, indicating that it had excellent photocatalytic activity. The initial glossiness was 84.9 as shown in FIG. 7, and the dispersibility was excellent. The gloss retention was maintained at 100% as shown in FIG. 8, and the weather resistance was excellent. The hue at the time of forming the coating film was L ^* value of 37.50, a ^* value of 21.87, b ^* value of 19.11, and hiding ratio of 98.9%.

(Example 3)
20 g of α-FeOOH having a needle shape (major axis length: 1.0 μm) was suspended in 1,000 ml of ion-exchanged water, and 2 g of zinc nitrate hexahydrate was added. After stirring and mixing for 60 minutes, 500 ml of 2N sodium hydroxide was added, and the mixture was stirred at 100 ° C. for 6 hours. The solvent was removed by filtration and then dried to obtain a zinc oxide composite α-FeOOH. Next, the zinc oxide composite α-FeOOH was heat-treated in air at 300 ° C. for 2 hours to obtain a mahogany zinc oxide-α-Fe ₂ O ₃ composite powder.
As a result of analyzing the X-ray diffraction pattern of the obtained composite powder, as shown in FIG. 3, it was confirmed that anatase type titanium dioxide was generated together with α-Fe ₂ O ₃ . When observed with an electron microscope, a zinc oxide-α-Fe ₂ O ₃ composite powder having a needle-like shape with a major axis length of about 1.0 μm was observed. The specific surface area was 47.8 m ² / g.
The decomposition rate of ammonia was 60%, indicating that the decomposition of ammonia had occurred to some extent, and that it had photocatalytic activity. The initial glossiness was 83.9, as shown in FIG. 7, indicating excellent dispersibility. The gloss retention was maintained at 100% as shown in FIG. 8, and the weather resistance was excellent. The hue of the resulting film was 41.50 for L ^* , 28.30 for a ^* , 23.77 for b ^* , and 98.8% for hiding ratio.

(Example 4)
10.0 g of the titanium dioxide-α-Fe ₂ O ₃ composite powder obtained in Example 1, 0.025 g of silver nitrate, 20.0 g of distilled water, 10.0 g of 25% ammonia water, and 2.0 g of glucose were mixed. Using zirconia beads (diameter 3 mm) and a planetary ball mill (Fritsch), the mixture was mixed and pulverized at a rotation speed of 450 rpm and a temperature of 25 ° C. for 150 minutes. Thereafter, solid-liquid separation was performed, followed by washing and drying at 100 ° C. for 2 hours to obtain a slightly dark brownish mahogany silver-titanium dioxide-αFe ₂ O ₃ composite powder.
As a result of analyzing the obtained X-ray diffraction pattern, it was confirmed that silver was generated together with the α-Fe ₂ O ₃ composite powder and the anatase type titanium dioxide. Further, when observed with an electron microscope, a silver-titanium dioxide-αFe ₂ O ₃ composite powder having a needle-like shape having a major axis length of about 1.0 μm was observed. The specific surface area was 103.2 m ² / g.
The ammonia decomposition rate was 89%, indicating that ammonia decomposition was remarkable, indicating that the composition had excellent photocatalytic activity. The initial glossiness was 83.1 as shown in FIG. 7, and the dispersibility was excellent. The gloss retention was maintained at 100% as shown in FIG. 8, and the light resistance was excellent. Further, when the film coating, each hue is ^{L *} value 40.62, a ^* value is 27.53, a ^{b *} value is 21.54, contrast ratio was 99.8%.

(Comparative Example 1)
Using iron oxide having no porosity (average particle diameter: 0.16 μm), the surface was coated with titania sol and dried at 70 ° C. in the air to obtain a red-brown anatase-type titanium dioxide composite powder.
As a result of analyzing the X-ray diffraction pattern of the obtained composite powder, as shown in FIG. 4, it was confirmed that anatase type titanium dioxide was generated together with α-Fe ₂ O ₃ . The specific surface area was 12 m ² / g.
The decomposition rate of ammonia was 70%, indicating that the decomposition of ammonia had occurred to some extent, and that it had photocatalytic activity. However, the initial glossiness was 70.1 as shown in FIG. The gloss retention was 86.8% as shown in FIG. 8, resulting in poor weather resistance. In addition, the hue at the time of forming a coating film was L ^* value of 37.12, a ^* of 28.40, b ^* value of 13.35, and hiding ratio of 99.0%.

(Comparative Example 2)
Milky white titanium dioxide-silica gel composite by coating with a titania sol using commercially available silica gel (Silicia 370 (trade name, manufactured by Fuji Silysia Chemical Ltd.), average particle size 0.30 μm) and drying in air at 70 ° C. A powder was obtained.
As a result of analyzing the X-ray diffraction pattern of the obtained composite powder, as shown in FIG. 5, it was confirmed that anatase type titanium dioxide was generated together with silica gel. The specific surface area was 280 m ² / g.
The ammonia decomposition rate was 82%, indicating that the decomposition of ammonia had occurred remarkably, indicating that it had excellent photocatalytic activity. However, the initial glossiness was 68.1 as shown in FIG. The gloss retention was 74.9% as shown in FIG. 8, resulting in poor weather resistance. Further, when the film coating, hue, ^{L *} value, respectively 94.37, ^{a *} is -0.62, ^{b *} values are 2.47, hiding factor was 7.8%.

(Comparative Example 3)
As a result of analyzing an X-ray diffraction pattern using milky-white anatase-rutile composite titanium dioxide (manufactured by TEBSA CORPORATION, P25 (trade name), average particle diameter: 0.16 μm), as shown in FIG. Composite titanium dioxide of anatase type and rutile type was confirmed.
The ammonia decomposition rate was 70%, indicating that the decomposition of ammonia had occurred to some extent, and that it had photocatalytic activity. However, since the dispersibility was inferior to that of the examples, the initial glossiness was 68.3 as shown in FIG. The gloss retention was 73.1% as shown in FIG. 8, resulting in poor weather resistance. The hue of the resulting film was 94.02 for L ^* , -0.62 for a ^* , 2.05 for b ^* , and 52.9% for hiding.

2 is a powder X-ray diffraction pattern of the powder produced in Example 1. 5 is a powder X-ray diffraction pattern of the powder produced in Example 2. 6 is a powder X-ray diffraction pattern of the powder produced in Example 3. 6 is a powder X-ray diffraction pattern of the powder produced in Comparative Example 1. 9 is a powder X-ray diffraction pattern of the powder produced in Comparative Example 2. 9 is a powder X-ray diffraction pattern of the powder of Comparative Example 3. It is an initial gloss graph of Examples 1-4 and Comparative Examples 1-3. It is a gloss retention rate graph of Examples 1-4 and Comparative Examples 1-3.

Claims (9)

(4) A photocatalyst composite powder characterized in that a photocatalyst is supported on a porous inorganic powder containing iron oxide as a main component. (4) A photocatalyst composite powder comprising a photocatalyst and a metal supported on a porous inorganic powder containing iron oxide as a main component. The photocatalyst composite powder according to claim 1 or 2, wherein the average particle diameter of the porous inorganic powder is larger than the average particle diameter of the photocatalyst. The photocatalyst composite powder according to any one of claims 1 to 3, wherein the ratio of Fe to all metal elements in the porous inorganic powder is 5 mol% or more. The photocatalyst composite powder according to any one of claims 1 to 4, wherein the photocatalyst is supported at 0.1 to 30 wt% based on the porous inorganic powder. The metal according to any one of claims 2 to 5, wherein the metal is at least one metal selected from palladium, platinum, rhodium, ruthenium, nickel, iron, copper, silver, gold, and zinc. Photocatalyst composite powder. The photocatalyst composite powder according to any one of claims 2 to 6, wherein the metal is supported by 0.01 to 10 wt% with respect to the porous inorganic powder. The photocatalyst composite powder according to any one of claims 1 to 7, wherein the specific surface area is 40 m ² / g or more. The photocatalyst composite powder according to any one of claims 1 to 8, wherein the average particle diameter is 0.01 to 100 µm.

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