JP7241632B2 - Photocatalyst composition - Google Patents

Description

The present invention relates to photocatalyst compositions.

When the photocatalyst is irradiated with light, the photocatalyst exhibits photocatalytic activity. Various coating agents containing photocatalysts have been studied. In order to suppress the generation of agglomerated particles, the photocatalytic hydrophilic coating agent described in Patent Document 1 contains water, photocatalytic metal oxide, alkylsilicate, and alkali silicate. This photocatalytic hydrophilic coating agent may further contain a polymeric thickener such as, for example, carboxymethylcellulose.

Japanese Patent Application Laid-Open No. 2001-089706

However, the present inventors' investigation revealed that the photocatalytic activity of the photocatalyst is lowered when a polymer thickener such as carboxymethylcellulose is contained.

The present invention has been made in view of the above problems, and an object thereof is to provide a photocatalyst composition that improves the dispersion stability of the photocatalyst without lowering the photocatalytic activity.

The photocatalyst composition of the present invention contains a photocatalyst containing tungsten oxide particles, a thickening agent, and a dispersion medium. The thickening agent includes an inorganic thickening agent or cellulose nanofibers.

ADVANTAGE OF THE INVENTION The photocatalyst composition of this invention can improve the dispersion stability of a photocatalyst, without reducing photocatalyst activity.

FIG. 4 is a graph showing the ratio of the concentration of the supernatant after a predetermined time has passed since the end of stirring to the concentration of the supernatant immediately after stirring of the sedimentation test sample of Reference Example. FIG. 4 is a graph showing the ratio of the concentration of the photocatalyst composition (C-1) in the supernatant immediately after stirring to the concentration in the supernatant after a predetermined time has passed since the end of stirring. FIG. 3 is a diagram showing a volume-based particle size distribution curve of secondary particles of tungsten oxide particles. FIG. 4 is a diagram showing a volume-based particle size distribution curve of secondary particles of titanium oxide particles. FIG. 4 is a graph showing the ratio of the concentration of the supernatant of the photocatalyst composition (A-1) after a predetermined time has passed since the end of stirring to the concentration of the supernatant immediately after stirring. FIG. 4 is a graph showing the ratio of the concentration of the photocatalyst composition (A-2) in the supernatant after a predetermined time has passed from the end of stirring to the concentration in the supernatant immediately after stirring. FIG. 4 is a graph showing the ratio of the concentration of a photocatalyst composition (A-3) in a supernatant after a predetermined time has elapsed from the end of stirring to the concentration in the supernatant immediately after stirring. FIG. 4 is a graph showing the ratio of the concentration of a photocatalyst composition (B-1) in a supernatant after a predetermined time has passed from the end of stirring to the concentration in the supernatant immediately after stirring. FIG. 4 is a graph showing the ratio of the concentration of the photocatalyst composition (B-2) in the supernatant after a predetermined time has elapsed from the end of stirring to the concentration in the supernatant immediately after stirring. FIG. 4 is a graph showing the ratio of the concentration of the photocatalyst composition (B-3) in the supernatant after a predetermined time has passed from the end of stirring to the concentration in the supernatant immediately after stirring. FIG. 4 is a graph showing temporal changes in acetaldehyde concentration and carbon dioxide concentration in an atmosphere in which a photocatalyst composition (A-1) is placed. FIG. 4 is a graph showing temporal changes in acetaldehyde concentration and carbon dioxide concentration in an atmosphere in which a photocatalyst composition (A-2) is placed. FIG. 4 is a graph showing changes over time in acetaldehyde concentration and carbon dioxide concentration in an atmosphere in which a photocatalyst composition (A-3) is placed. FIG. 4 is a graph showing temporal changes in acetaldehyde concentration and carbon dioxide concentration in an atmosphere in which a photocatalyst composition (B-1) is placed. FIG. 4 is a graph showing changes over time in acetaldehyde concentration and carbon dioxide concentration in an atmosphere in which a photocatalyst composition (B-2) is placed. FIG. 4 is a graph showing changes over time in acetaldehyde concentration and carbon dioxide concentration in an atmosphere in which a photocatalyst composition (B-3) is placed. FIG. 4 is a graph showing temporal changes in acetaldehyde concentration and carbon dioxide concentration in an atmosphere in which a single photocatalyst is placed.

Embodiments of the present invention will be described below. However, the present invention is by no means limited to the embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present invention. The photocatalyst composition of the present embodiment (hereinafter sometimes simply referred to as "composition") contains a photocatalyst, a thickener, and a dispersion medium. The photocatalyst contains tungsten oxide particles. Thickeners include inorganic thickeners or cellulose nanofibers. The composition of the present embodiment is a visible-light-responsive composition that exhibits photocatalytic activity by absorbing visible light. The composition of this embodiment can improve the dispersion stability of the photocatalyst without lowering the photocatalytic activity. The reason is presumed as follows.

The composition contains tungsten oxide particles as photocatalyst particles. Among metals having photocatalytic activity, tungsten oxide has a large specific gravity. Therefore, the tungsten oxide particles tend to settle in the composition due to their own weight. Here, in this embodiment, the composition contains a thickening agent. By containing the thickener, sedimentation of the photocatalyst containing the tungsten oxide particles can be suppressed, and the dispersion stability of the photocatalyst can be improved.

However, studies by the present inventors have revealed that photocatalytic activity decreases when compositions containing specific thickeners such as carboxymethylcellulose, hydroxyethylcellulose, and hydroxypropylmethylcellulose are used. bottom. This is believed to be because the photocatalyst contained in the composition preferentially decomposes the specific thickener over the decomposition target (e.g., formaldehyde) when the composition is irradiated with light. . Therefore, the present inventors have made extensive studies on thickeners that are not or hardly decomposed by photocatalysts. They have also found that the decrease in photocatalytic activity of the composition can be suppressed by including an inorganic thickener or cellulose nanofibers in the composition as a thickener.

Examples of decomposition targets to be decomposed by photocatalysts include volatile organic compounds (VOCs), more specifically formaldehyde, acetaldehyde, and ammonia.

<Photocatalyst>
The photocatalyst contains tungsten oxide particles. Tungsten oxide contained in tungsten oxide particles includes, for _example , _{WO3 (} tungsten trioxide) _{, WO2} , WO _{, W2O3} , _W4O5 , _W4O11 , _W25O73 , _{W20O 58} , and _{W24O68 ,} and mixtures thereof. _WO3 is preferred as the tungsten oxide in order to improve the photocatalytic activity.

The crystal structure of tungsten oxide contained in the tungsten oxide particles is not particularly limited. Crystal structures of tungsten oxide include, for example, monoclinic, triclinic, orthorhombic, and mixed crystals of at least two of these.

The tungsten oxide particles may carry a promoter. By supporting the co-catalyst, the photocatalytic activity of the composition can be improved. Only one cocatalyst may be supported, or two or more cocatalysts may be supported.

Examples of metals contained in the promoter include platinum (Pt), gold (Au), silver (Ag), copper (Cu), zinc (Zn), palladium, iron, nickel, ruthenium, iridium, niobium, and zirconium. , and molybdenum. These metals are contained in the promoter in the form of complexes, chlorides, bromides, iodides, oxides, hydroxides, sulfates, nitrates, carbonates, acetates, phosphates, or organic acid salts, for example. may have been A suitable example of the co-catalyst is platinum. The tungsten oxide particles are preferably tungsten oxide particles supporting platinum as a co-catalyst.

The content of the cocatalyst with respect to the mass of the photocatalyst (hereinafter sometimes referred to as cocatalyst loading ratio) is preferably 0.01% by mass or more and 3% by mass or less. The photocatalytic activity of the composition can be further improved when the cocatalyst loading rate is within such a range.

The volume median diameter (hereinafter sometimes referred to as “D ₅₀ ”) of the tungsten oxide particles is preferably 0.5 μm or more and 10.0 μm or less, more preferably 1.0 μm or more and 10.0 μm or less. More preferably, it is 3.0 μm or more and 10.0 μm or less. _D50 is a volume-based 50% cumulative diameter measured based on a laser diffraction scattering method using a laser diffraction scattering particle size distribution analyzer. The _D50 of tungsten oxide is the _D50 of secondary particles of tungsten oxide. When the tungsten oxide particles carry a cocatalyst, it is the _D50 of the tungsten oxide particles carrying a cocatalyst. By agglomerating tungsten oxide, tungsten oxide particles with D ₅₀ in such ranges are obtained.

Tungsten oxide particles with a _D50 between 0.5 μm and 10.0 μm have the following advantages. When the composition is applied to the substrate, the thickener and dispersion medium flow down from the tops of the tungsten oxide particles under their own weight. The flow down exposes the tungsten oxide particles from the thickener and dispersion medium to form exposed areas in the tungsten oxide particles. The higher the _D50 of the tungsten oxide particles, the easier it is for the tungsten oxide particles to form exposed regions. The exposed areas of the tungsten oxide particles are directly exposed to ambient air and light. The exposed regions of the tungsten oxide particles allow the tungsten oxide particles to come into contact with the decomposition target, and the tungsten oxide particles favorably decompose the decomposition target. Therefore, the photocatalytic activity of the composition is improved.

However, while having the above advantages, when the D ₅₀ of the tungsten oxide particles increases, the mass of the tungsten oxide particles increases and the tungsten oxide particles tend to settle out within the composition. However, in this embodiment, the composition contains inorganic thickeners or cellulose nanofibers as thickeners. By containing such a thickener, even when the _D50 of the tungsten oxide particles is large, sedimentation of the photocatalyst containing the tungsten oxide particles is suppressed, and the dispersion stability of the photocatalyst can be improved.

In order to improve the dispersion stability of the photocatalyst without lowering the photocatalytic activity, the content of the tungsten oxide particles should be 0.5% by mass or more with respect to the mass of the mixture of the thickener and the dispersion medium. 0% by mass or less, and more preferably 20.0% by mass or more and 30.0% by mass or less.

The composition may contain only one type of tungsten oxide particles, or may contain two or more types of tungsten oxide particles as photocatalyst particles. The photocatalyst contained in the composition is mainly composed of tungsten oxide particles. However, the composition may further contain photocatalyst particles other than tungsten oxide particles in addition to tungsten oxide particles as photocatalyst particles.

<Thickener>
Thickeners include inorganic thickeners or cellulose nanofibers. The inorganic thickener and cellulose nanofibers are not or hardly decomposed by the photocatalyst contained in the composition when the composition is irradiated with light. Therefore, the photocatalyst contained in the composition preferentially decomposes the substance to be decomposed rather than the thickener, thereby suppressing a decrease in the photocatalytic activity of the composition. In addition, the inorganic thickener and cellulose nanofibers are less likely to inhibit the contact between the photocatalyst and the decomposition target.

Inorganic thickeners include, for example, clay thickeners. An advantage of the clay thickener is that the clay particles contained in the clay thickener are extremely small, so when the composition is irradiated with light, the clay thickener hardly inhibits the penetration of light. be done. Clay thickeners contain clay minerals. The clay thickener may be a natural clay thickener or a synthetic clay thickener. Clay thickeners include layered silicate minerals. A layered silicate mineral has multiple (for example, many) layers. Each of the plurality of layers contains at least silicon atoms and oxygen atoms. Layered silicate minerals include, for example, bentonite, smectite, mica, kaolin mineral, and talc. Bentonite contains montmorillonite. Hectorite, saponite, montmorillonite, beidellite, nontronite, sauconite, and stevensite are collectively referred to as smectite. Montmorillonite is a clay mineral common to each of bentonite and smectite.

In order to improve the dispersion stability of the photocatalyst without lowering the photocatalytic activity, the thickener is preferably an inorganic thickener, more preferably a clay thickener, and still more preferably a layered silicate mineral.

As the layered silicate mineral, smectite or bentonite is more preferable, smectite is still more preferable, and montmorillonite is particularly preferable. Smectite and bentonite have high swelling properties with respect to a dispersion medium (especially water), and therefore can impart thickening properties to a composition containing a dispersion medium. In the composition to which the thickening property is imparted, sedimentation of the photocatalyst containing tungsten oxide particles is suppressed, so that the dispersion stability of the photocatalyst can be improved.

As the layered silicate mineral, mica (especially swelling mica) is also preferable. Swellable mica is mica that swells with respect to a dispersion medium (especially water). Since swelling mica has a high swelling property with respect to a dispersion medium (especially water), it can impart thickening properties to a composition containing a dispersion medium. In the composition to which the thickening property is imparted, sedimentation of the photocatalyst containing tungsten oxide particles is suppressed, so that the dispersion stability of the photocatalyst can be improved.

The layered silicate mineral preferably has interlayer ions between layers of the layered silicate mineral. The interlayer ions are preferably alkali metal ions, more preferably sodium ions (Na ⁺ ), potassium ions (K ⁺ ), or lithium ions (Li ⁺ ), and still more preferably sodium ions or lithium ions. Compared to the case where the interlayer ions are potassium ions, when the interlayer ions are sodium ions or lithium ions, the swelling property of the layered silicate mineral with respect to the dispersion medium (especially water) is increased.

More preferably, the layered silicate mineral has sodium ions between each layer of the layered silicate mineral. A layered silicate mineral having sodium ions as interlayer ions has a higher swelling property with respect to a dispersion medium (especially water). The dispersion medium is attracted to sodium ions, which are interlayer ions, and enters between the layers of the layered silicate mineral. When the dispersion medium enters, the layers of the layered silicate mineral are peeled off from each other, the surface area of the layered silicate mineral is greatly increased, and the composition is imparted with thickening properties. In the composition to which the thickening property is imparted, sedimentation of the photocatalyst containing tungsten oxide particles is suppressed, so that the dispersion stability of the photocatalyst can be improved.

Since it has a high swelling property with respect to a dispersion medium (especially water) and can impart a thickening property to a composition containing a dispersion medium, the layered silicate minerals include smectites having sodium as interlayer ions, or smectites having sodium as interlayer ions. Swellable mica is preferred.

Cellulose nanofibers have a fiber diameter in nano units. The fiber diameter of the cellulose nanofibers is preferably 500 nm or less, more preferably 100 nm or less, and even more preferably 20 nm or more and 50 nm or less. The fiber diameter of cellulose nanofibers can be measured, for example, by observing the cellulose nanofibers using an electron microscope.

The content of the thickener is preferably 0.5% by mass or more and 1000.0% by mass or less, and is 0.5% by mass or more and 50.0% by mass or less with respect to the mass of the tungsten oxide particles. is more preferable, more preferably 0.5% by mass or more and 35.0% by mass or less, and particularly preferably 0.5% by mass or more and 20.0% by mass or less. When the content of the thickener is within this range with respect to the mass of the tungsten oxide particles, sedimentation of the photocatalyst containing the tungsten oxide particles is suppressed, and the dispersion stability of the photocatalyst can be improved.

The content of the thickener is preferably 0.5% by mass or more and 10.0% by mass or less, and preferably 0.5% by mass or more and 5.0% by mass or less, relative to the mass of the dispersion medium. more preferred. When the content of the thickener is within this range with respect to the mass of the dispersion medium, sedimentation of the photocatalyst containing tungsten oxide particles is suppressed, and the dispersion stability of the photocatalyst can be improved.

The viscosity of the mixture of the thickener and the dispersion medium is preferably 10.0 mPa s or more and 2000.0 mPa s or less, more preferably 10.0 mPa s or more and 100.0 mPa s or less, It is more preferably 10.0 mPa·s or more and 80.0 mPa·s or less, further preferably 55.0 mPa·s or more and 70.0 mPa·s or less, and 55.0 mPa·s or more and 65.0 mPa·s. The following are particularly preferred. When the viscosity of the mixture of the thickener and the dispersion medium is within such a range, sedimentation of the photocatalyst containing the tungsten oxide particles is suppressed, and the dispersion stability of the photocatalyst can be improved. Further, when the viscosity of the mixture of the thickener and the dispersion medium is 2000.0 mPa·s or less, the viscosity of the composition does not become too high, and the composition can be suitably applied to the substrate.

<Dispersion medium>
Examples of the dispersion medium include polar solvents. Polar solvents include, for example, water, methanol, ethanol, and isopropanol.

In addition, the composition may further contain a binder as needed. Moreover, the composition may further contain an additive as needed.

<Change Rate of Photocatalyst Concentration>
The photocatalyst concentration change rates C _A , C _B , and C _C of the composition of the present embodiment are preferably within the following ranges. The photocatalyst concentration change rates C _A , C _B , and C _C will be described in order.

The rate of change C _A of the concentration of the photocatalyst is represented by Equation (1A). The photocatalyst concentration change rate C _A is preferably 0.0% or more and 2.5% or less, more preferably 0.0% or more and 2.0% or less, and 0.0% or more and 1.0% or more. 0% or less is even more preferable.
C _A =|100×(C ₀ −C ₂₁ )/C ₀ | (1A)

In formula (1A), C ₀ represents the mass percent concentration (unit: mass %) of the photocatalyst in the composition measured at a predetermined position immediately after stirring the composition (immediately after the end of stirring). C ₂₁ indicates the mass percent concentration (unit: mass %) of the photocatalyst in the composition measured at a predetermined position 21 hours after the composition was stirred (21 hours after the end of stirring). The predetermined position is a position at a depth of 1 cm from the surface of the composition when the composition is put into the container. When the composition is liquid, the surface of the composition is the liquid surface. "|100×(C ₀ -C ₂₁ )/C ₀ |" in the formula (1A) indicates the absolute value of 100×(C ₀ -C ₂₁ )/C ₀ . Hereinafter, "mass percent concentration of the photocatalyst in the composition measured at a predetermined position" may be referred to as "supernatant concentration". The stirring conditions for the composition will be described later in Examples.

The photocatalyst concentration change rate C _A indicates the ease with which the photocatalyst settles in the composition. The smaller the rate of change _CA of the photocatalyst concentration, the smaller the amount of photocatalyst that settles in the composition. The greater the rate of change _CA of the photocatalyst concentration, the lower the concentration of the photocatalyst in the supernatant of the composition, and the greater the amount of photocatalyst that settles in the composition. When the photocatalyst concentration change rate C _A is 0.0% or more and 2.5% or less, sedimentation of the photocatalyst in the composition over time is preferably suppressed. By suppressing sedimentation of the photocatalyst over time, the concentration of the composition can be kept uniform over a long period of time.

The rate of change C _B of the concentration of the photocatalyst is shown by Equation (1B). The rate of change C _B of the concentration of the photocatalyst is preferably 0.0% or more and 10.0% or less, more preferably 0.0% or more and 5.0% or less.
C _B =|100×(C ₀ −C ₃₃₆ )/C ₀ | (1B)

C ₀ in formula (1B) has the same meaning as C ₀ in formula (1A). In formula (1B), C ₃₃₆ is the mass percent concentration (unit: mass %) of the photocatalyst in the composition measured at a predetermined position 336 hours after stirring the composition (336 hours after the end of stirring). indicates "|100×(C ₀ -C ₃₃₆ )/C ₀ |" in formula (1B) indicates the absolute value of 100×(C ₀ -C ₃₃₆ )/C ₀ . When the photocatalyst concentration change rate C _B is 0.0% or more and 10.0% or less, sedimentation of the photocatalyst in the composition over time can be more preferably suppressed.

The rate of change C _C of the concentration of the photocatalyst is shown by Equation (1C). The rate of change C _C of the concentration of the photocatalyst is preferably 0.0% or more and 10.0% or less, more preferably 0.0% or more and 5.0% or less.
C _C =|100×(C ₀ −C ₆₇₂ )/C ₀ | (1C)

C ₀ in formula (1C) has the same meaning as C ₀ in formula (1A). In formula (1C), C ₆₇₂ is the mass percent concentration (unit: mass %) of the photocatalyst in the composition measured at a predetermined position 672 hours after stirring the composition (672 hours after the end of stirring). indicates "|100×(C ₀ -C ₆₇₂ )/C ₀ |" in formula (1C) indicates the absolute value of 100×(C ₀ -C ₆₇₂ )/C ₀ . When the photocatalyst concentration change rate C _C is 0.0% or more and 10.0% or less, sedimentation of the photocatalyst in the composition over time can be particularly preferably suppressed.

<Acetaldehyde decomposition rate>
The acetaldehyde decomposition rate D _A of the composition and the acetaldehyde decomposition rate D _B of only the photocatalyst preferably satisfy the formula (4).
85≦100×D _A /D _B ≦100 (4)

The acetaldehyde decomposition rate D _A of the composition is calculated from Equation (2).
D _A =100×(D _A0 −D _A2 )/D _A0 (2)

In formula (2), D _A0 and D _A2 are as follows. Prepare an amount of composition containing 1.3 g of photocatalyst. After removing the dispersion medium from the composition, the composition from which the dispersion medium has been removed (for example, a composition containing a photocatalyst and a thickener but not containing a dispersion medium) is placed in a predetermined atmosphere. D _A0 is the acetaldehyde concentration in a given atmosphere before irradiation with a given light. D _A2 is the acetaldehyde concentration in a given atmosphere after irradiation with given light for 2.0 hours. In this embodiment, the predetermined atmosphere is an atmosphere containing acetaldehyde at a concentration of 300 ppm. The predetermined light has a central wavelength of 450 nm and an illuminance of 2500 lux.

The acetaldehyde decomposition rate D _B of only the photocatalyst is calculated from Equation (3).
D _B =100×(D _B0 −D _B2 )/D _B0 (3)

In formula (3), D _B0 and D _B2 are as follows. Place only 1.3 g of photocatalyst in a predetermined atmosphere. D _B0 is the acetaldehyde concentration in a given atmosphere before irradiation with a given light. D _B2 is the acetaldehyde concentration in a given atmosphere after being irradiated with a given light for 2.0 hours.

“100×D _A /D _B ” in the formula (4) is how much the acetaldehyde decomposition rate D _A of the composition from which the dispersion medium is removed is maintained relative to the acetaldehyde decomposition rate D _B of the photocatalyst alone. indicates The state in which the dispersion medium is removed from the composition corresponds to the state in which the composition is applied to the substrate and dried. A higher value of “100×D _A /D _B ” indicates that the acetaldehyde decomposition rate D _A of the composition from which the dispersion medium has been removed is less likely to decrease relative to the acetaldehyde decomposition rate D _B of the photocatalyst alone. This indicates that the thickener does not cause or hardly causes a decrease in photocatalytic activity. In order to suppress the decrease in photocatalytic activity, it is preferable that 90 ≤ 100 × D _A /D _B ≤ 100, more preferably 95 ≤ 100 × D _A /D _B ≤ 100, and 100 × D _A /D _B =100 is particularly preferred.

<Method for producing composition>
Next, a method for producing the composition will be described. The method for producing the composition includes a photocatalyst forming step and a mixing step. In addition, when using a commercially available photocatalyst, the photocatalyst forming step can be omitted.

(Photocatalyst forming step)
The photocatalyst forming step includes a primary pulverization step and a secondary pulverization step. The photocatalyst forming step may further include a cocatalyst supporting step, if necessary.

The primary pulverization process will be explained. In the primary pulverization step, the photocatalyst containing tungsten oxide particles is primarily pulverized in a liquid. Thereafter, at least part of the liquid is removed to obtain a photocatalyst mass. Primary pulverization is wet pulverization using a liquid. The primary pulverization can reduce the number average primary particle size of the photocatalyst. Hereinafter, "number average primary particle size" may be referred to as "primary particle size". The smaller the primary particle size, the larger the surface area of the photocatalyst, which can improve the photocatalytic activity of the photocatalyst. The primary particle size of the photocatalyst is more preferably 500 nm or less, even more preferably 200 nm or less, and even more preferably 100 nm or less. Although the lower limit of the primary particle size of the photocatalyst is not particularly limited, it can be, for example, 10 nm or more.

Liquids used for primary pulverization include, for example, water and ethanol. Pulverizers for primary pulverization include, for example, homogenizers, ultrasonic dispersers, and bead mills. The primary particle size of the photocatalyst becomes smaller as the peripheral speed of the pulverizer for primary pulverization increases. The longer the primary pulverization time, the smaller the primary particle size of the photocatalyst. Methods for removing at least part of the liquid include, for example, air drying and heat drying.

The photocatalyst mass obtained in the primary pulverization step is used in the secondary pulverization step. However, when performing the cocatalyst loading step described below, after the photocatalyst is primarily pulverized in the liquid, the liquid containing the photocatalyst may be used in the cocatalyst loading step without removing at least part of the liquid. .

The co-catalyst supporting step will be explained. In the co-catalyst carrying step, the co-catalyst is carried on the tungsten oxide particles. Examples of the method for supporting the co-catalyst include a method of heat treatment, a method of photoprecipitation with ultraviolet light, and a method of photoprecipitation with visible light.

In the cocatalyst supporting step, a cocatalyst precursor may be added instead of the cocatalyst. When the precursor of the co-catalyst is heated, it changes into the co-catalyst, and the co-catalyst is supported on the tungsten oxide particles. When the cocatalyst is platinum, the precursor of the cocatalyst may be, for example, platinum(II) oxide, platinum(IV) oxide, platinum(II) chloride, platinum(IV) chloride, chloroplatinic acid, hexachloroplatinic acid, or Tetrachloroplatinic acid or complexes thereof can be added.

The secondary pulverization process will be explained. In the secondary pulverization step, the photocatalyst mass obtained in the primary pulverization step is secondary pulverized in gas. When the cocatalyst supporting step is performed, the photocatalyst obtained in the cocatalyst supporting step (specifically, the tungsten oxide particles supporting the cocatalyst) is subjected to secondary pulverization in gas. The secondary pulverization adjusts the _D50 of the secondary particles of the photocatalyst. Secondary pulverization is dry pulverization performed in gas. The secondary pulverization aggregates the photocatalyst primary particles to form photocatalyst secondary particles.

Specific examples of secondary pulverization in gas include secondary pulverization in air or in an inert gas atmosphere. Secondary pulverization can be performed using a pulverizer. Examples of pulverizers that perform secondary pulverization include impact plate pulverizers (e.g., impingement plate jet mills), fluidized bed pulverizers (e.g., fluidized bed jet mills), and mechanical pulverizers (e.g., hammer mills). , and ball mills. Secondary grinding can also be done using a mortar and pestle. The shorter the secondary pulverization time, the larger the _D50 of the photocatalyst secondary particles.

The secondary pulverized photocatalyst may be directly used in the mixing step. Alternatively, the secondary pulverized photocatalyst may be classified and the classified photocatalyst may be used in the mixing step. By classifying the secondary pulverized photocatalyst, the _D50 of the secondary particles of the photocatalyst is further adjusted. Classifiers include, for example, air classifiers and vibrating screens. By changing the classification conditions, the _D50 of the secondary particles of the photocatalyst can be adjusted. For example, when classifying with a vibrating sieve, the larger the mesh diameter of the sieve, the larger the _D50 of the secondary particles of the photocatalyst.

(Mixing process)
A mixing process WHEREIN: A thickener, a dispersion medium, and a photocatalyst are mixed. A composition is obtained by mixing. In order to improve the dispersibility of the photocatalyst, it is preferable to first stir the thickener and the dispersion medium to obtain a mixture of the thickener and the dispersion medium, and then second stir the mixture and the photocatalyst. . Mixing and stirring can be performed using, for example, a stirrer.

A photocatalyst layer is formed on the substrate by applying the composition to the substrate and drying the dispersion medium. A photocatalytic layer is provided on the substrate. The photocatalyst layer contains a photocatalyst containing tungsten oxide particles and a thickening agent. The tungsten oxide particles preferably have contact points that make contact with the back surface of the photocatalytic layer. The back surface of the photocatalyst layer is the substrate-side surface of the photocatalyst layer. Among metals having photocatalytic activity, tungsten oxide has a large specific gravity. Therefore, when the composition is applied to a substrate, the tungsten oxide particles settle in the composition due to their own weight, and the tungsten oxide particles come into contact with the substrate. In this way contact points can be efficiently formed on the tungsten oxide particles.

The tungsten oxide particles contained in the photocatalyst layer preferably have exposed regions in addition to the contact points. The exposed regions of the tungsten oxide particles protrude without being coated with the thickening agent, and constitute at least part of the convex surface of the surface of the photocatalyst layer. The exposed areas of the tungsten oxide particles are directly exposed to ambient air and light. The exposed regions of the tungsten oxide particles allow the tungsten oxide particles to come into contact with the decomposition target, and the tungsten oxide particles favorably decompose the decomposition target. For example, a single tungsten oxide particle preferably has both contact points and exposed areas.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the examples.

[Sedimentation test (reference example)]
First, a sedimentation test was carried out as a reference example to examine whether or not a problem of sedimentation of the photocatalyst would occur.

47.1 parts by mass of titanium oxide particles (“STS-01” manufactured by Ishihara Sangyo Co., Ltd., D ₅₀ : 0.13 μm) and 100.0 parts by mass of water were placed in a container and stirred with a magnetic stirrer (AS ONE Corporation). The mixture was stirred at 1500 rpm for 10 minutes using a commercially available "REXIM"). Thus, a sedimentation test sample containing titanium oxide particles but not containing a thickener was obtained. The height of the sedimentation test sample in the container was 3 cm. Immediately after the end of stirring (after 0 hours), 0.5 mL of the liquid at a depth of 1 cm was removed from the surface (liquid surface) of the sedimentation test sample in the container using a pipette. Using an infrared moisture meter (“FD-720” manufactured by Ketto Kagaku Kenkyusho Co., Ltd.), the concentration of titanium oxide particles in the liquid taken out was measured. The measured concentration of the titanium oxide particles was taken as the supernatant concentration of the titanium oxide particles. Then, after a predetermined time had elapsed from the end of stirring, the concentration of titanium oxide particles in the supernatant was measured by the same method. Predetermined times were 240 hours and 384 hours in the measurement of the concentration of the titanium oxide particles in the supernatant.

Next, except that 47.1 parts by mass of titanium oxide particles were changed to 25.0 parts by mass of tungsten oxide particles (D ₅₀ : 3.1 μm), and the predetermined time was set to 21 hours, the supernatant concentration of titanium oxide particles was The supernatant concentration of tungsten oxide particles was measured in the same manner as in the measurement of . The sample for which the supernatant concentration of the tungsten oxide particles was measured corresponds to composition (C-1) described later.

Table 1 shows the measurement results of the concentration of the titanium oxide particles in the supernatant. Table 1 and FIG. 1 show the concentration ratio of titanium oxide particles. Table 2 shows the measurement results of the concentration of the tungsten oxide particles in the supernatant. Table 2 and FIG. 2 show the concentration ratio of the tungsten oxide particles. The concentration ratio is the ratio of the concentration of the supernatant after a predetermined time has passed since the end of stirring to the concentration of the supernatant after 0 hours have passed since the end of stirring (that is, immediately after stirring).

As shown in Table 1 and FIG. 1, the concentration of the titanium oxide particles in the supernatant did not decrease even after 384 hours had elapsed since the end of stirring, and the titanium oxide particles were difficult to settle. On the other hand, the concentration of the tungsten oxide particles in the supernatant decreased to 0.1% by mass after 21 hours from the end of stirring, which caused sedimentation of the tungsten oxide particles. A possible reason for this is that the specific gravity of the tungsten oxide particles is higher than that of the titanium oxide particles, and the tungsten oxide particles settle more easily than the titanium oxide particles. Tungsten oxide tends to agglomerate more easily than titanium oxide, and it is conceivable that _D50 of secondary particles of tungsten oxide particles is larger than _D50 of secondary particles of titanium oxide particles. From the above, it was found that the composition containing titanium oxide particles is less prone to the problem of photocatalyst sedimentation. On the other hand, it has been found that the composition containing tungsten oxide particles has a remarkable problem of photocatalyst sedimentation. Therefore, the compositions that can suppress the sedimentation of the photocatalyst and have excellent dispersion stability even when they contain tungsten oxide were examined in the following examples.

[Compositions according to Examples and Comparative Examples]
Table 3 shows the configurations of compositions (A-1) to (A-3), (B-1) to (B-3), and (C-1) according to Examples or Comparative Examples.

Each term in Table 3 has the following meaning. "Parts" means "mass parts". "Thickener/water mixture viscosity" indicates "viscosity of a mixture of a thickener and a dispersion medium (specifically, water)". "WO ₃ " indicates "tungsten oxide particles (WA)". A method for preparing the tungsten oxide particles (WA) will be described later. The terms shown below in Table 3 and Tables 4 and 5, which will be described later, have the following meanings.

As the "smectite", "Knipia F" manufactured by Kunimine Industries Co., Ltd. was used. The content of montmorillonite in Kunipia F was 98.5% or more. The chemical formula of _the main component _of Kunipia F was _Si8 ( _Al3.34Mg0.66 ) _Na0.66O20 (OH) ₄ . Kunipia F had sodium ions as interlayer ions.

"CNF" indicates "cellulose nanofibers". As “CNF”, cellulose nanofiber (“BiNFi-s (registered trademark)” manufactured by Sugino Machine Co., Ltd., fiber diameter: 20 nm or more and 50 nm or less) was used.

As "mica", hydrophilic swelling mica ("Somasif ME-100" manufactured by Katakura Co-op Aguri Co., Ltd.) was used. Somasif ME-100 had sodium ions as interlayer ions.

"CMC" stands for "carboxymethyl cellulose". As "CMC", carboxymethyl cellulose ("FINNFIX" manufactured by Sansho Co., Ltd.) was used.

"HEC" stands for "hydroxyethyl cellulose". As "HEC", hydroxyethyl cellulose ("SANHEC" manufactured by Sansho Co., Ltd.) was used.

"HPMC" stands for "hydroxypropyl methylcellulose". As "HPMC", hydroxypropyl methylcellulose ("NEOVISCO-MC" manufactured by Sansho Co., Ltd.) was used.

Next, the preparation method, measurement method and measurement results of compositions (A-1) to (A-3), (B-1) to (B-3), and (C-1) shown in Table 3, and The evaluation method and evaluation results will be explained.

[Manufacturing method]
<Preparation of tungsten oxide particles (WA)>
Tungsten oxide particles (WA) were produced by the following method. The tungsten oxide particles (WA) are used for producing compositions (A-1) to (A-3), (B-1) to (B-3), and (C-1).

(Primary pulverization process)
Using a bead mill (media stirring type wet ultra-fine grinding/dispersing machine "MSC50" manufactured by Nippon Coke Kogyo Co., Ltd.), 135 g of tungsten oxide (specifically, WO ₃ , manufactured by Kishida Chemical Co., Ltd.) and 1215 g of ion-exchanged water, A dispersion of tungsten oxide was obtained by primary pulverization. Beads (manufactured by Nikkato Co., Ltd., diameter: 0.1 mm) were used for the bead mill. The bead mill conditions were a peripheral speed of 10 m/sec and a processing time of 360 minutes. The primary particle size of tungsten oxide contained in the dispersion after the primary pulverization was about 50 nm. The dispersion liquid after the primary pulverization was used in the cocatalyst supporting step without being dried.

(Promoter supporting step)
Hexachloroplatinum (VI) hexahydrate (manufactured by Kishida Chemical Co., Ltd., solid concentration: 98.5%) was dissolved in the dispersion of tungsten oxide obtained in the primary pulverization step. The amount of hexachloroplatinum (VI) hexahydrate added is such that the content of simple platinum is 0.025% by mass with respect to the mass of tungsten oxide particles (WA) to be produced. rice field. The dispersion was then heated at 100° C. to evaporate water. As a result, lumps of tungsten oxide supporting platinum were obtained.

(Secondary crushing process)
The mass obtained in the co-catalyst supporting step was pulverized using a mortar and pestle to obtain pulverized tungsten oxide supporting platinum. The pulverized material was sieved using a vibrating sieve to obtain tungsten oxide particles that passed through a sieve with an opening of 63 μm. The obtained tungsten oxide particles were mixed with pure water to prepare a slurry of tungsten oxide particles. The tungsten oxide particles (WA) having the desired particle size (ie, D ₅₀ of 3.1 μm) were obtained by spray-drying the prepared slurry of tungsten oxide particles. The obtained tungsten oxide particles (WA) carried platinum as a promoter.

<Preparation of composition>
(Preparation of composition (A-1))
Using a magnetic stirrer ("REXIM" sold by AS ONE Co., Ltd.), 5.0 parts by mass of smectite ("Kunipia F" manufactured by Kunimine Industries Co., Ltd.), which is a thickener, and 95.0 parts by mass of water, which is a dispersion medium. was first stirred at 1500 rpm for 180 minutes. A mixture of the thickener and the dispersion medium was thus obtained. 25.0 parts by mass of tungsten oxide particles (WA) as a photocatalyst were added to the mixture, and the mixture was secondly stirred at 1500 rpm for 30 minutes using a magnetic stirrer (“REXIM” sold by AS ONE Co., Ltd.). Thus, composition (A-1) was obtained.

(Production of compositions (A-2) to (A-3) and (B-1) to (B-3))
Composition (A- Compositions (A-2) to (A-3) and (B-1) to (B-3) were prepared in the same manner as in 1).

(Preparation of composition (C-1))
To 100.0 parts by mass of water, 25.0 parts by mass of photocatalyst tungsten oxide particles (WA) were added and stirred at 1500 rpm for 10 minutes using a magnetic stirrer ("REXIM" sold by AS ONE Co., Ltd.). . Thus, composition (C-1) was obtained.

[Measurement method and measurement results]
<Viscosity>
The viscosity of the mixture of the thickener and the dispersion medium obtained in <Preparation of the composition> was measured by a method according to JISZ 8803:2011. Specifically, the viscosity of the mixture was measured using a vibrating viscometer ("Viscomate VM-10A-L" manufactured by Sekonic Co., Ltd.). The viscosity of the mixture was measured immediately after completion of the first stirring in the above <Preparation of composition> and before addition of the tungsten oxide particles (WA). The measurement results were as shown in Table 3 above. As for the composition (C-1), since no thickening agent was added, the viscosity of the mixture was not measured.

<Particle size of tungsten oxide particles (WA)>
The particle size of the secondary particles of the tungsten oxide particles (WA) produced in the above <Preparation of tungsten oxide particles (WA)> was measured by a laser diffraction/scattering particle size distribution analyzer (manufactured by Microtrac Bell). It was measured using “Microtrac (registered trademark) MT3000II”). FIG. 3 shows a volume-based particle size distribution curve of secondary particles of tungsten oxide particles (WA). The secondary particles of tungsten oxide particles (WA) had D ₁₀ of 0.9 μm, D ₅₀ of 3.1 μm, and D ₉₀ of 7.5 μm.

<Particle size of titanium oxide particles>
Except that the tungsten oxide particles (WA) were changed to titanium oxide particles ("STS-01" manufactured by Ishihara Sangyo Co., Ltd.), oxidation was performed in the same manner as the particle size measurement of the tungsten oxide particles (WA). The particle size of secondary particles of titanium particles was measured. The titanium oxide particles are used in the above reference examples. FIG. 4 shows a volume-based particle size distribution curve of secondary particles of titanium oxide particles. The secondary particles of the titanium oxide particles had a _D10 of 0.08 μm, a _D50 of 0.13 μm, and a _D90 of 0.19 μm.

The horizontal axis in FIGS. 3 and 4 indicates the particle diameter (unit: μm) of the measurement object measured on a volume basis. The vertical axis in FIGS. 3 and 4 indicates the frequency (unit: %) of the measurement object having each particle size measured on a volume basis. In the particle size distribution curves shown in FIGS. 3 and 4, D ₁₀ was defined as the particle size at which the existence frequency integrated from the small particle size side (0.01 μm side) was 10%. In the particle size distribution curves shown in FIGS. 3 and 4, _D50 was defined as the particle size at which the existence frequency integrated from the smaller particle size side (0.01 μm side) was 50%. In the particle size distribution curves shown in FIGS. 3 and 4, _D90 was defined as the particle size at which the existence frequency integrated from the small particle size side (0.01 μm side) was 90%.

[Evaluation method and evaluation result]
<Evaluation of dispersion stability of photocatalyst>
For each of the compositions (A-1) to (A-3), (B-1) to (B-3), and (C-1) shown in Table 3 above, the dispersion stability of the photocatalyst was evaluated. The composition was introduced into a container. The composition was stirred using a magnetic stirrer (“REXIM” sold by AS ONE Co., Ltd.). Stirring conditions were 1500 rpm for 10 minutes. The height of the composition in the container was 3 cm. Immediately after the end of the stirring (after 0 hours), 0.5 mL of the liquid at a depth of 1 cm from the surface (liquid surface) of the composition in the container was taken out using a pipette. Using an infrared moisture meter ("FD-720" manufactured by Kett Scientific Laboratory Co., Ltd.), the concentration of tungsten oxide particles in the liquid taken out was measured. The measured concentration of the tungsten oxide particles was taken as the supernatant concentration of the tungsten oxide particles. Then, after a predetermined time had elapsed from the end of stirring, the concentration of the tungsten oxide particles in the supernatant was measured by the same method. In this measurement, the predetermined times were 21 hours, 336 hours, and 672 hours.

Table 4 shows the measurement results of the supernatant concentration of the tungsten oxide particles in the composition and the concentration ratio. The measurement results of the supernatant concentration and the concentration ratio of composition (C-1) have already been shown in Table 2, but are shown again in Table 4 for better understanding. Also, the concentration ratios of compositions (A-1), (A-2), (A-3), (B-1), (B-2), and (B-3) are shown in FIGS. 6, 7, 8, 9 and 10. FIG. The concentration ratio of composition (C-1) is already shown in FIG.

The "concentration ratio" in Table 4 indicates the ratio of the concentration of the supernatant after a predetermined time has passed since the end of stirring to the concentration of the supernatant after 0 hours have passed since the end of stirring (that is, immediately after stirring). "C _A " in Table 4 indicates the rate of change C _A of the concentration of the photocatalyst represented by the formula (1A). “C ₀ ” in formula (1A) is the supernatant concentration when “time” in Table 4 is 0 hours. “C ₂₁ ” in formula (1A) is the supernatant concentration when “time” in Table 4 is 21 hours. "C _B " in Table 4 indicates the rate of change C _B of the concentration of the photocatalyst represented by the formula (1B). “C ₀ ” in formula (1B) is the supernatant concentration when “time” in Table 4 is 0 hours. “C ₃₃₆ ” in formula (1B) is the supernatant concentration when “time” in Table 4 is 336 hours. “C _C ” in Table 4 indicates the rate of change C _C of the concentration of the photocatalyst represented by formula (1C). “C ₀ ” in formula (1C) is the supernatant concentration when “time” in Table 4 is 0 hours. “C ₆₇₂ ” in formula (1C) is the supernatant concentration when “time” in Table 4 is 672 hours. Composition (A-3) "not measured" in Table 4 has a photocatalyst sedimentation rate similar to composition (A-1), and it was confirmed that the photocatalyst is difficult to settle, so measurement was performed. Indicates an interruption. For compositions (B-1) to (B-3) and (C-1) "not measured" in Table 4, most of the photocatalyst settled, so the concentration of the supernatant in the next predetermined time was not measured. indicates that

As shown in Table 3, compositions (A-1) to (A-3) contained a photocatalyst containing tungsten oxide particles, a thickener, and a dispersion medium. Thickeners were inorganic thickeners (specifically smectites or swellable mica) or cellulose nanofibers. As shown in Table 4 and FIGS. 5 to 6, even after 672 hours from the end of stirring, the supernatant concentration of compositions (A-1) and (A-2) was 20.3% by mass or more. rice field. As shown in Table 4 and FIG. 7, the supernatant concentration of composition (A-3) was 21.5% by mass even after 336 hours from the end of stirring. On the other hand, as shown in Table 3, the thickening agents contained in compositions (B-1) to (B-3) were neither inorganic thickening agents nor cellulose nanofibers. As shown in Table 4 and FIGS. 8 to 10, the supernatant concentrations of compositions (B-1) to (B-3) after 336 hours from the end of stirring were 6.7% by mass or less. As shown in Table 3, composition (C-1) contained no thickening agent. As shown in Table 4 and FIG. 2, the supernatant concentration of composition (C-1) after 21 hours from the end of stirring was 0.1% by mass. As shown above, compositions (A-1) to (A-3) compare to compositions (B-1) to (B-3) and (C-1), the supernatant concentration was difficult to decrease, and the dispersion stability of the photocatalyst was excellent.

<Evaluation of photocatalytic activity>
Each of the compositions (A-1) to (A-3) and (B-1) to (B-3) was evaluated for photocatalytic activity. As the photocatalytic activity, the decomposition activity from acetaldehyde to carbon dioxide caused by the photocatalyst irradiated with visible light was evaluated. Specifically, the composition was placed in a petri dish (60 mm in diameter) in such an amount that the mass of the photocatalyst contained in the composition was 1.3 g, and the composition was dried at 80°C for 30 minutes. In this way the water in the composition was evaporated. A petri dish containing the dried composition was placed in a 5 L gas bag. The gas bag was filled with acetaldehyde having a concentration of 300 ppm. Then, the gas bag was irradiated with light (center wavelength: 450 nm, illuminance: 2500 lux). Before light irradiation (0.0 hour) and after 0.5 hours, 1.0 hours, 1.5 hours, and 2.0 hours from the start of light irradiation, the concentration of acetaldehyde and dioxide in the gas bag Carbon concentration was measured. A gas detector tube for acetaldehyde (“92” manufactured by GASTEC Co., Ltd.) was used to measure the acetaldehyde concentration. A gas detector tube for carbon dioxide (“2LC” manufactured by GASTEC Co., Ltd.) was used to measure the carbon dioxide concentration. Note that the higher the photocatalytic activity, the higher the activity of decomposing acetaldehyde into carbon dioxide caused by the photocatalyst. The higher the decomposition activity, the lower the acetaldehyde concentration and the higher the carbon dioxide concentration.

Next, the photocatalytic activity of the photocatalyst alone (tungsten oxide particles (WA) only) was evaluated instead of the composition. Instead of placing the petri dish containing the composition after drying in the gas bag, the photocatalytic activity of the composition was The photocatalytic activity of the single photocatalyst was evaluated in the same manner as in the evaluation of .

Table 5 shows the measurement results of the acetaldehyde concentration and carbon dioxide concentration of the composition after water removal, and the measurement results of the acetaldehyde concentration and carbon dioxide concentration of the photocatalyst alone. In addition, the acetaldehyde concentration and carbon dioxide of the compositions (A-1), (A-2), (A-3), (B-1), (B-2), and (B-3) after water removal The concentration measurement results are shown in FIGS. 11, 12, 13, 14, 15 and 16, respectively. FIG. 17 shows the measurement results of the acetaldehyde concentration and carbon dioxide concentration of the photocatalyst alone. 11 to 17, diamond plots indicate acetaldehyde concentration, and round plots indicate carbon dioxide concentration.

The meanings of the terms in Table 5 are as follows. "C ₂ H ₄ O" indicates the acetaldehyde concentration (unit: ppm) in the gas bag. “CO ₂ ” indicates the carbon dioxide concentration (unit: ppm) in the gas bag. "Light irradiation time" indicates the time (unit: hour) that has elapsed since the start of light irradiation. “D _A ” indicates a value calculated from Equation (2). D _A0 in formula (2) is the value in the "C ₂ H ₄ O" column of the composition when the light irradiation time is 0.0 hour. D _A2 in formula (2) is the value in the "C ₂ H ₄ O" column of the composition when the light irradiation time is 2.0 hours. “D _B ” indicates a value calculated from Equation (3). D _B0 in the formula (3) is the value in the “C ₂ H ₄ O” column of the photocatalyst alone when the light irradiation time is 0.0 hour. D _B2 in the formula (3) is the value in the "C ₂ H ₄ O" column of the photocatalyst alone when the light irradiation time is 2.0 hours. "Formula (4) value" indicates a value calculated from Formula (4). "-" indicates not calculated because it does not correspond to the formula.

As shown in Table 3, compositions (A-1) to (A-3) contained a photocatalyst containing tungsten oxide particles, a thickener, and a dispersion medium. Thickeners were inorganic thickeners (specifically smectites or swellable mica) or cellulose nanofibers. As shown in Table 5 and FIGS. 11 and 12, when compositions (A-1) and (A-2) were used, the acetaldehyde concentration was 0 ppm two hours after the start of light irradiation. Further, as shown in Table 5 and FIG. 13, when composition (A-3) was used, the acetaldehyde concentration was 35 ppm two hours after the start of light irradiation. On the other hand, as shown in Table 3, the thickening agents contained in compositions (B-1) to (B-3) were neither inorganic thickening agents nor cellulose nanofibers. As shown in Table 5 and FIGS. 14 to 16, when compositions (B-1) to (B-3) were used, the acetaldehyde concentration was 220 ppm or more two hours after the start of light irradiation. Furthermore, as shown in Table 5 and FIG. 17, when the photocatalyst alone was used, the acetaldehyde concentration was 0 ppm two hours after the start of light irradiation. As shown above, compositions (A-1) to (A-3) have lower acetaldehyde concentration and acetaldehyde decomposition activity than compositions (B-1) to (B-3). was excellent. In addition, the acetaldehyde concentration when using the compositions (A-1) to (A-3) was comparable to the acetaldehyde concentration when using the photocatalyst alone. Compositions (A-1) to (A-3) had acetaldehyde decomposition activity comparable to that of the photocatalyst alone, even when the thickener was contained.

From the above, it was shown that the compositions (A-1) to (A-3) included in the present invention can improve the dispersion stability of the photocatalyst without lowering the photocatalytic activity.

The composition of the present invention can be used in photocatalytically active products such as building materials, automotive interior materials, home appliances and textiles.

Claims (7)

Containing a photocatalyst containing tungsten oxide particles, a thickening agent, and a dispersion medium,
The photocatalyst composition , wherein the thickener comprises cellulose nanofibers. 2. The photocatalyst composition according to claim 1, wherein the tungsten oxide particles have a volume median diameter of 0.5 [mu]m or more and 10.0 [mu]m or less. The photocatalyst composition according to claim 1 or 2, wherein the content of said thickener is 0.5% by mass or more and 1000.0% by mass or less with respect to the mass of said tungsten oxide particles. The photocatalyst composition according to any one of claims 1 to 3, wherein the viscosity of the mixture of the thickener and the dispersion medium is 10.0 mPa·s or more and 2000.0 mPa·s or less. The photocatalyst composition according to any one of claims 1 to 4 , wherein the tungsten oxide particles are platinum-supported tungsten oxide particles. The photocatalyst composition according to any one of claims 1 to 5 , wherein the photocatalyst concentration change rate C _A represented by formula (1A) is 0.0% or more and 2.5% or less.
C _A =|100×(C ₀ −C ₂₁ )/C ₀ | (1A)
(In the above formula (1A),
C ₀ represents the mass percent concentration of the photocatalyst in the photocatalyst composition measured at a predetermined position immediately after stirring the photocatalyst composition,
C ₂₁ represents the mass percent concentration of the photocatalyst in the photocatalyst composition measured at the predetermined position 21 hours after stirring the photocatalyst composition,
The predetermined position is a position at a depth of 1 cm from the surface of the photocatalyst composition. ) 2. The acetaldehyde decomposition rate D _A of the photocatalyst composition calculated from the formula (2) and the acetaldehyde decomposition rate D _B of the photocatalyst alone calculated from the formula (3) satisfy the formula (4). 7. The photocatalyst composition according to any one of 6 .
D _A =100×(D _A0 −D _A2 )/D _A0 (2)
D _B =100×(D _B0 −D _B2 )/D _B0 (3)
85≦100×D _A /D _B ≦100 (4)
(In the formula (2), D _A0 and D _A2 are each the photocatalyst composition obtained by removing the dispersion medium after removing the dispersion medium from the photocatalyst composition containing 1.3 g of the photocatalyst. An object is placed in a predetermined atmosphere, and the acetaldehyde concentration in the predetermined atmosphere before irradiation with predetermined light and the acetaldehyde concentration in the predetermined atmosphere after irradiation with the predetermined light for 2.0 hours are shown,
In the formula (3), D _B0 and D _B2 are respectively the acetaldehyde concentration in the predetermined atmosphere before irradiating the predetermined light with only 1.3 g of the photocatalyst placed in the predetermined atmosphere, and the predetermined light. 2. Shows the acetaldehyde concentration in the predetermined atmosphere after irradiation for 0 hours,
The predetermined atmosphere is an atmosphere containing acetaldehyde at a concentration of 300 ppm,
The predetermined light has a central wavelength of 450 nm and an illuminance of 2500 lux. )

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