Photocatalytic coating liquid and photocatalytic spray can

Abstract

The present invention provides a photocatalyst coating liquid capable of forming a photocatalyst layer having excellent contact resistance and high photocatalytic activity. [Solution] The photocatalyst coating liquid of the present invention comprises 1.0 wt% to 5.0 wt% photocatalyst particles, 0.05 wt% to 0.5 wt% binder, metal ions, and an aqueous dispersion medium, wherein the photocatalyst particles include tungsten oxide particles, and the average particle diameter of the primary particles, calculated from the BET specific surface area of ​​the photocatalyst particles using a spherical model, is 10 nm to 50 nm, and the average particle diameter D50 of the secondary particles of the photocatalyst particles is 600 μm to 1000 μm.

Description

[Technical Field]

[0001] The present invention relates to a photocatalytic coating liquid and a photocatalytic spray can. [Background technology]

[0002] A method for forming a photocatalyst layer by applying a photocatalyst coating liquid containing photocatalyst particles and a binder onto a substrate is known (see, for example, Patent Document 1). The photocatalyst particles contained in the photocatalyst layer produced by this method are fixed by the binder and are unlikely to detach from the photocatalyst layer. This allows the photocatalyst layer to have contact resistance and maintain photocatalytic activity for a long period of time. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-75802 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a photocatalyst layer containing photocatalyst particles and a binder, the photocatalyst particles may become buried in the binder, and the organic gas decomposition performance may not be exhibited. Furthermore, if photocatalyst particles with a large particle size are used to prevent the photocatalyst particles from being buried in the binder, the surface area of ​​the photocatalyst particles becomes small, and the organic gas decomposition performance decreases. The present invention has been made in view of the above circumstances, and provides a photocatalyst coating liquid that can form a photocatalyst layer having excellent contact resistance and high photocatalytic activity. [Means for solving the problem]

[0005] The present invention provides a photocatalyst coating liquid comprising 1.0 wt% to 5.0 wt% of photocatalyst particles, 0.05 wt% to 0.5 wt% of a binder, metal ions, and an aqueous dispersion medium, wherein the photocatalyst particles contain tungsten oxide particles, and the average particle diameter of the primary particles, calculated from the BET specific surface area of ​​the photocatalyst particles using a spherical model, is 10 nm to 50 nm, and the average particle diameter D50 of the secondary particles of the photocatalyst particles is 600 μm to 1000 μm. [Effects of the Invention]

[0006] The photocatalyst layer formed using the photocatalyst coating liquid of the present invention has excellent contact resistance and high photocatalytic activity, which has been demonstrated by experiments conducted by the present inventors. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is an explanatory diagram of a method for forming a photocatalyst layer using a photocatalyst coating liquid according to one embodiment of the present invention. [Figure 2] 1 is a graph showing the change in secondary particle size of photocatalyst particles relative to the concentration of copper ions contained in a photocatalyst coating solution. [Figure 3] 1 is a graph showing the change in gas removal rate relative to the concentration of copper ions contained in the photocatalyst coating liquid. DETAILED DESCRIPTION OF THE INVENTION

[0008] The photocatalyst coating liquid of the present invention comprises 1.0 wt% to 5.0 wt% photocatalyst particles, 0.05 wt% to 0.5 wt% binder, metal ions, and an aqueous dispersion medium, wherein the photocatalyst particles contain tungsten oxide particles, and the average particle diameter of the primary particles, calculated from the BET specific surface area of ​​the photocatalyst particles using a spherical model, is 10 nm to 50 nm, and the average particle diameter D50 of the secondary particles of the photocatalyst particles is 600 μm to 1000 μm.

[0009] The concentration of the metal ions in the photocatalyst coating liquid is preferably 100 ppm or more and 300 ppm or less. The binder preferably has an inorganic skeleton formed of siloxane bonds or a silanol group. The metal ions preferably include at least one of copper ions, silver ions, iron ions, and zinc ions.

[0010] The present invention also provides a photocatalyst spray can comprising the photocatalyst coating liquid of the present invention, a propellant, and a spray container that contains the photocatalyst coating liquid and the propellant, wherein the spray container has an injection hole that is arranged to inject the photocatalyst coating liquid together with the propellant. Preferably, the propellant contains dimethyl ether, the diameter of the injection hole is 0.3 mm or less, and the internal pressure of the spray container is 0.4 MPa or more at a temperature of 25°C.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The configurations shown in the drawings and the following description are merely examples, and the scope of the present invention is not limited to those shown in the drawings and the following description.

[0012] Photocatalytic coating liquid and photocatalytic layer FIG. 1 is an explanatory diagram of a method for forming a photocatalyst layer using the photocatalyst coating liquid of this embodiment. The photocatalyst coating liquid 2 of this embodiment comprises photocatalyst particles of 1.0 wt% or more and 5.0 wt% or less, a binder of 0.05 wt% or more and 0.5 wt% or less, metal ions, and an aqueous dispersion medium, and the photocatalyst particles include tungsten oxide particles, and the average particle diameter of the primary particles converted from the BET specific surface area of ​​the photocatalyst particles using a spherical model is 10 nm or more and 50 nm or less, and the average particle diameter D50 of the secondary particles of the photocatalyst particles is 600 μm or more and 1000 μm or less.

[0013] The photocatalyst coating liquid 2 is a dispersion liquid for forming a photocatalyst layer 16 on the surface of an object (for example, a substrate 14) by a coating method, and is a suspension in which photocatalyst particles are dispersed in an aqueous dispersion medium in which a metal salt (metal ion) and a binder are dissolved. The photocatalyst coating liquid may contain a dispersant, porous particles, etc. The photocatalyst coating liquid may be a photocatalyst spray liquid. The photocatalyst coating liquid 2 may be acidic.

[0014] The photocatalyst coating liquid 2 can be prepared, for example, as follows: (1) Photocatalyst particles (powder or slurry) are dispersed in water to prepare a dispersion (if necessary, a dispersant is also added). (2) A binder is mixed into the dispersion. (3) Metal salts that are the source of metal ions are mixed into the dispersion and dissolved. The photocatalyst particles can generally be dispersed in water using a wet disperser, and examples of the disperser include an ultrasonic disperser, a colloid mill, and a bead mill. A general liquid mixer can be used for mixing. If the mixer is equipped with a stirring blade or the like, the composition of the photocatalyst coating liquid 2 can be made more uniform.

[0015] The method for applying the photocatalyst coating liquid 2 to the object is not particularly limited, and examples thereof include spray coating, dip coating, spin coating, bar coating, brush coating, roller brush coating, roll coater coating, curtain flow coater coating, etc. In the example shown in Fig. 1, the photocatalyst coating liquid 2 is spray-applied onto a substrate 14 using a spray container 3 (aerosol container) to form a coating film 15, and the coating film 15 is dried to form a photocatalyst layer 16.

[0016] The aqueous dispersion medium is water or an aqueous solution in which the photocatalyst particles are dispersed. Examples of the aqueous dispersion medium include an aqueous solution in which a metal salt, a binder, etc. are dissolved, and an ethanol aqueous solution. The photocatalyst particles contained in the photocatalyst coating liquid 2 are particles or powder that exhibit photocatalytic activity upon exposure to light. The photocatalyst particles include tungsten oxide particles (WO3 particles). The tungsten oxide particles may have a composition that deviates from the stoichiometric composition, as long as they have photocatalytic activity. The tungsten oxide particles may also contain impurity atoms or additive atoms to the extent that they do not lose their photocatalytic activity. The photocatalyst fine particles may also have a co-catalyst on their surface. The co-catalyst includes, for example, platinum group metals such as Pt, Pd, Rh, Ru, Os, and Ir.

[0017] The ratio of photocatalyst particles in the photocatalyst coating liquid 2 is 1.0 wt% or more and 5.0 wt% or less, and preferably 1.5 wt% or more and 5.0 wt% or less. The average particle diameter of the primary particles, calculated using a spherical model from the BET specific surface area of ​​the photocatalyst particles contained in the photocatalyst coating solution 2, is 10 nm or more and 50 nm or less. This allows the surface area of ​​the photocatalyst particles in the photocatalyst layer 16 to be increased, allowing the photocatalyst layer 16 to have high photocatalytic activity. The average particle diameter of the primary particles of the photocatalyst particles can be calculated, for example, by drying the photocatalyst coating solution 2 to produce a photocatalyst particle powder, measuring the specific surface area of ​​this powder using the BET method, and then calculating the average particle diameter from the measurement results. A common measuring device can be used, such as the NOVA series all-in-one BET specific surface area / pore size analyzer manufactured by Anton Paar.

[0018] The average particle diameter D50 of the secondary particles of the photocatalyst particles contained in the photocatalyst coating liquid 2 is 600 μm or more and 1000 μm or less. By making the average particle diameter of the secondary particles of the photocatalyst particles 600 μm or more, it is possible to prevent the photocatalyst particles from being buried in the binder in the photocatalyst layer 16, and the photocatalyst layer 16 can have high photocatalytic activity. Furthermore, by making the average particle diameter of the secondary particles of the photocatalyst particles 1000 μm or less, it is possible to cause photocatalytic activity in many of the primary particles that make up the secondary particles, and the photocatalyst layer 16 can have high photocatalytic activity. The average particle diameter D50 of the secondary particles of the photocatalyst particles contained in the photocatalyst coating solution 2 can be obtained by measuring the photocatalyst coating solution 2 with a laser diffraction / scattering particle size distribution measuring device. A general measuring device can be used, such as the Microtrac MT3000II series manufactured by Microtrac Bell.

[0019] The binder contained in the photocatalyst coating liquid 2 is not particularly limited, and examples thereof include hydrolysates of silane coupling agents, dehydration condensates of hydrolysates of silane coupling agents, hydrolysates of tetraalkoxysilanes, dehydration condensates of hydrolysates of tetraalkoxysilanes, silicone resins, epoxy resins, urethane resins, phenolic resins, acrylic resins, styrene resins, polyamides, polyesters, acetal resins, polycarbonates, vinyl chloride resins, vinyl acetate resins, cellulose resins, polyolefins, copolymer resins thereof, and blended resins. The binder contained in the photocatalyst coating liquid 2 preferably has an inorganic skeleton formed from siloxane bonds or a silanol group. Such a binder is resistant to light and heat, and is not easily decomposed by photocatalytic activity.

[0020] Examples of binders having an inorganic skeleton formed from siloxane bonds include silicone resins, dehydration condensates of hydrolyzates of silane coupling agents, and dehydration condensates of hydrolyzates of tetraalkoxysilanes. The dehydration condensate can be produced, for example, by mixing a silane coupling agent or a tetraalkoxysilane with water to cause a hydrolysis reaction, and then allowing a dehydration reaction to occur between two silanol groups produced by the hydrolysis reaction. Such a dehydration condensate is a compound having an inorganic skeleton formed of siloxane bonds. The dehydration condensate may be produced by using a silane coupling agent or a tetraalkoxysilane as a raw material for the photocatalyst coating liquid 2 and causing a hydrolysis reaction and a dehydration reaction to occur in the preparation of the photocatalyst coating liquid 2. The alcohol produced by the hydrolysis reaction may be contained in the photocatalyst coating liquid 2.

[0021] Examples of binders having silanol groups include hydrolysates of silane coupling agents and hydrolysates of tetraalkoxysilanes. The hydrolyzate can be produced by mixing a silane coupling agent or a tetraalkoxysilane with water to allow a hydrolysis reaction to proceed. Such a hydrolyzate is a compound having a silanol group. The hydrolyzate may be produced by using a silane coupling agent or a tetraalkoxysilane as a raw material for the photocatalyst coating liquid 2 and allowing a hydrolysis reaction to proceed in the preparation of the photocatalyst coating liquid 2. The alcohol produced by the hydrolysis reaction may be contained in the photocatalyst coating liquid 2.

[0022] The organic functional group possessed by the silane coupling agent serving as a raw material for the dehydrated condensate or the hydrolyzate is not particularly limited, and examples thereof include an epoxy group, a methacryl group, etc. Examples of commercially available silane coupling agents that can be used as raw materials include those manufactured by Shin-Etsu Chemical Co., Ltd. under the product names: KBE-403, KBM-403, KBM-303, KBE-503, KBM-4803, X-12-981S, KBM-1003, KBM-1083, KBM-5103, KBE-903, KBE-603, KBE-573, KBM-803, KBE-9007N, and X-12-967C. Examples of commercially available silicone resins that can be used as a raw material include those manufactured by Toray Dow Corning Co., Ltd. under the product names BA2400, BA2410, BA2411, BA2510, BA2405, 840RESIN, and 804RESIN, and those manufactured by Shin-Etsu Chemical Co., Ltd. under the product names KR350, KR271, KR272, KR274, KR216, KR280, KR282, KR261, KR260, KR255, KR266, KR251, KR155, KR152, KR214, KR220, X-4040-171, KR201, KR5202, and KR3093.

[0023] The proportion of the binder in the photocatalyst coating liquid 2 is 0.05 wt% or more and 0.5 wt% or less, and preferably 0.1 wt% or more and 0.5 wt% or less. By setting the proportion of the binder to 0.05 wt% or more, it is possible to increase the adhesive strength between the photocatalyst particles in the photocatalyst layer 16 and between the photocatalyst particles and the substrate 14, and to form a photocatalyst layer 16 with excellent contact resistance. Furthermore, by setting the proportion of the binder to 0.5 wt% or less, it is possible to prevent the photocatalyst particles in the photocatalyst layer 16 from being buried in the binder, which would otherwise reduce the photocatalytic activity.

[0024] The metal ions contained in the photocatalyst coating liquid 2 are, for example, copper ions, silver ions, iron ions, zinc ions, etc. The metal ions contained in the photocatalyst coating liquid 2 may also be cationic ions. The metal ions contained in the photocatalyst coating liquid 2 may be generated by dissolving the raw material metal salt in an aqueous dispersion medium. By including metal ions in the photocatalyst coating liquid 2, the secondary particle size of the photocatalyst particles can be increased, and it is possible to prevent the photocatalyst particles from being buried in the binder in the photocatalyst layer 16 and reducing their photocatalytic activity. Although the mechanism by which metal ions promote the aggregation of primary particles of the photocatalyst particles is not clear, it is thought that electrostatic interaction occurs among multiple tungsten oxide particles (photocatalyst particles), which tend to be negatively charged due to the action of the cationic metal ions.

[0025] The metal salts that are the raw materials for the metal ions contained in the photocatalyst coating liquid 2 are not particularly limited as long as they are soluble in the aqueous dispersion medium of the photocatalyst coating liquid 2, and examples thereof include copper nitrate, copper acetate, copper chloride, copper gluconate, copper sulfide, silver nitrate, silver chloride, iron chloride, iron sulfate, iron nitrate, iron sulfide, and zinc gluconate.

[0026] The concentration (mass ratio) of metal ions in the photocatalyst coating solution 2 is 100 ppm or more and 300 ppm or less. By setting the metal ion concentration to 100 ppm or more, the secondary particle diameter of the photocatalyst particles can be increased, and it is possible to prevent the photocatalyst particles from being buried in the binder in the photocatalyst layer 16, resulting in a decrease in photocatalytic activity. Furthermore, by setting the metal ion concentration to 300 ppm or less, it is possible to prevent the secondary particle diameter of the photocatalyst particles from becoming too large, and it is possible to generate photocatalytic activity in many of the primary particles that make up the secondary particles.

[0027] Photocatalytic spray can The photocatalyst spray can 20 of this embodiment comprises a photocatalyst coating liquid 2, a propellant, and a spray container 3 that contains the photocatalyst coating liquid 2 and the propellant, and the spray container 3 is characterized by having an injection hole 7 that is provided so as to inject the photocatalyst coating liquid 2 together with the propellant. The photocatalyst spray can 20 may also be an aerosol spray. The photocatalyst spray can 20 is provided so that the photocatalyst coating liquid 2 inside the spray container 3 (aerosol container) is discharged to the outside of the spray container 3 by the pressure of the propellant. When the photocatalyst coating liquid 2 is discharged toward an object (for example, a substrate 14) using the photocatalyst spray can 20, a photocatalyst layer 16 containing photocatalyst fine particles is formed on the surface of the object, and the object can be evenly coated with the photocatalyst layer 16.

[0028] The spray container 3 is a container for a photocatalyst spray can 20, and includes a pressure-resistant container 9 that contains the photocatalyst coating liquid 2 and a propellant, a valve member 5, an actuator 4, a tube 6, etc. The valve member 5 can include a stem, a stem hole, a stem gasket, etc. When the head of the actuator 4 is not pressed, the stem gasket closes the stem hole, and the inside of the spray container 3 is sealed. When the head of the actuator 4 is pressed, the stem and stem gasket move down, opening the stem hole and connecting the flow path of the photocatalyst coating liquid 2 to the injection hole 7. The inside of the spray container 3 is under high pressure due to the propellant, and this pressure causes the photocatalyst coating liquid 2 to flow through the flow path of the tube 6, valve member 5 and actuator 4 and be sprayed out from the injection hole 7. The diameter of the injection hole 7 is preferably 0.3 mm or less.

[0029] The propellant is a component for creating high pressure inside the spray container 3, and contains dimethyl ether. The boiling point of dimethyl ether is -24.8°C, and since dimethyl ether is placed in the spray container 3 as a liquefied gas, inside the spray container 3, some of the dimethyl ether is dissolved in the photocatalyst coating liquid 2 or exists as a liquid, and some of the dimethyl ether exists as a gas in the gas phase 8. In addition, an amount of propellant is placed in the spray container 3 such that the internal pressure of the spray container 3 is 0.40 MPa or more at 25°C.

[0030] The photocatalyst spray can 20 can be manufactured by a normal aerosol spray manufacturing method. The spray can 3 is a cylindrical container with a bottom made of aluminum or tinplate, and after filling it with the photocatalyst coating liquid 2, an aerosol bubble is clinched to the opening at the top via a gasket, and the propellant is filled up to a predetermined liquid volume. In addition, to adjust the internal pressure of the spray can 3, compressed gases such as carbon dioxide gas, nitrogen gas, compressed air, and oxygen gas can be used as a pressurizing agent. The internal pressure of the photocatalyst spray can 20 is preferably 0.40 MPa or more at a temperature of 25°C.

[0031] Preparation of photocatalyst coating solution Photocatalyst coating solutions were prepared for Examples 1 to 14 and Comparative Examples 1 to 8. Table 1 shows the primary particle size of the photocatalyst particles, the proportion of photocatalyst particles, the silane coupling agent, the proportion of silane coupling agent (addition proportion), and the proportions of metal salt and metal ions for Examples 1 to 11 and Comparative Examples 1 to 4. Table 2 also shows the proportion of silane coupling agent (addition proportion), the proportion of photocatalyst particles, the proportion of copper gluconate, and the copper ion concentration for Examples 12 to 14 and Comparative Examples 5 to 8.

[0032] [Table 1]

[0033] [Table 2]

[0034] [Example 1] A slurry (dispersion medium: water) containing dispersed tungsten oxide photocatalyst particles (WO3 particles) with an average primary particle size of 30 nm, a silane coupling agent with an epoxy group (KBE-403 manufactured by Shin-Etsu Chemical Co., Ltd.), copper gluconate, and water were mixed to prepare a photocatalyst coating solution containing 2.0 wt% photocatalyst particles, 0.3 wt% silane coupling agent (addition ratio), and 140 ppm copper ions. The silane coupling agent was hydrolyzed during preparation to produce a binder. The average particle size of the primary particles of the photocatalyst particles was calculated by measuring the specific surface area of ​​the photocatalyst particles obtained by drying the slurry using the BET method and converting this specific surface area using a spherical model. The copper ions are produced by dissolving copper gluconate in water.

[0035] [Example 2] A photocatalyst coating solution was prepared in the same manner as in Example 1, except that tungsten oxide photocatalyst particles having an average primary particle size of 10 nm were used.

[0036] [Example 3] A photocatalyst coating solution was prepared in the same manner as in Example 1, except that tungsten oxide photocatalyst particles having an average primary particle size of 50 nm were used.

[0037] [Example 4] A photocatalyst coating liquid was prepared in the same manner as in Example 1, except that the ratio of photocatalyst particles contained in the photocatalyst coating liquid was set to 5.0 wt %.

[0038] [Example 5] A photocatalyst coating liquid was prepared in the same manner as in Example 1, except that the ratio of photocatalyst particles contained in the photocatalyst coating liquid was 1.0 wt %.

[0039] [Example 6] A photocatalyst coating liquid was prepared in the same manner as in Example 1, except that the proportion (addition proportion) of the silane coupling agent was set to 0.5 wt %.

[0040] [Example 7] A photocatalyst coating liquid was prepared in the same manner as in Example 1, except that the proportion (addition proportion) of the silane coupling agent was set to 0.1 wt %.

[0041] [Example 8] A photocatalyst coating liquid was prepared in the same manner as in Example 1, except that the concentration of copper ions contained in the photocatalyst coating liquid was set to 300 ppm.

[0042] [Example 9] A photocatalyst coating liquid was prepared in the same manner as in Example 1, except that the concentration of copper ions contained in the photocatalyst coating liquid was set to 100 ppm.

[0043] [Example 10] A photocatalyst coating liquid was prepared in the same manner as in Example 1, except that a silane coupling agent having a methacryl group (KBE-503 manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of the silane coupling agent having an epoxy group.

[0044] [Example 11] A photocatalyst coating solution was prepared in the same manner as in Example 1, except that iron II chloride tetrahydrate was used instead of copper gluconate, and the photocatalyst coating solution contained iron ions instead of copper ions.

[0045] [Example 12] A photocatalyst coating liquid was prepared in the same manner as in Example 1, except that the proportion (addition proportion) of the silane coupling agent was set to 0.2 wt % and the concentration of copper ions contained in the photocatalyst coating liquid was set to 126 ppm.

[0046] [Example 13] A photocatalyst coating liquid was prepared in the same manner as in Example 1, except that the proportion (addition proportion) of the silane coupling agent was set to 0.2 wt % and the concentration of copper ions contained in the photocatalyst coating liquid was set to 182 ppm.

[0047] [Example 14] A photocatalyst coating liquid was prepared in the same manner as in Example 1, except that the proportion (addition proportion) of the silane coupling agent was set to 0.2 wt % and the concentration of copper ions contained in the photocatalyst coating liquid was set to 280 ppm.

[0048] [Comparative Example 1] A photocatalyst coating solution was prepared in the same manner as in Example 1, except that tungsten oxide photocatalyst particles having an average primary particle size of 100 nm were used.

[0049] Comparative Example 2 A silane coupling agent with an epoxy group (KBE-403 manufactured by Shin-Etsu Chemical Co., Ltd.), copper gluconate, and water were mixed to prepare a coating solution containing 0.3 wt% of the silane coupling agent (addition ratio) and 140 ppm of copper ions (no photocatalytic particles were added). The silane coupling agent was hydrolyzed during preparation, producing a binder.

[0050] Comparative Example 3 A slurry (dispersion medium: water) in which tungsten oxide photocatalyst particles with an average primary particle size of 30 nm were dispersed was mixed with copper gluconate and water to prepare a photocatalyst coating solution containing 2.0 wt% photocatalyst particles and 140 ppm copper ions (no silane coupling agent was added).

[0051] Comparative Example 4 A slurry (dispersion medium: water) in which tungsten oxide photocatalyst particles with an average primary particle size of 30 nm are dispersed, a silane coupling agent with an epoxy group (KBE-403 manufactured by Shin-Etsu Chemical Co., Ltd.), and water were mixed to prepare a photocatalyst coating solution containing 2.0 wt% of photocatalyst particles and 0.3 wt% of silane coupling agent (addition ratio) (no metal salt added). The silane coupling agent is hydrolyzed during preparation to produce a binder.

[0052] Comparative Example 5 A slurry (dispersion medium: water) in which tungsten oxide photocatalyst particles with an average primary particle size of 30 nm are dispersed, a silane coupling agent with an epoxy group (KBE-403 manufactured by Shin-Etsu Chemical Co., Ltd.), and water were mixed to prepare a photocatalyst coating solution containing 2.0 wt% of photocatalyst particles and 0.2 wt% of silane coupling agent (addition ratio) (no metal salt added). The silane coupling agent is hydrolyzed during preparation to produce a binder.

[0053] Comparative Example 6 A photocatalyst coating liquid was prepared in the same manner as in Example 1, except that the concentration (addition rate) of the silane coupling agent was set to 0.2 wt % and the concentration of copper ions contained in the photocatalyst coating liquid was set to 70 ppm.

[0054] Comparative Example 7 A photocatalyst coating liquid was prepared in the same manner as in Example 1, except that the concentration (addition rate) of the silane coupling agent was set to 0.2 wt % and the concentration of copper ions contained in the photocatalyst coating liquid was set to 350 ppm.

[0055] [Comparative Example 8] The photocatalyst coating liquid was prepared in the same manner as in Example 1, except that the concentration (addition ratio) of the silane coupling agent contained in the photocatalyst coating liquid was 0.2 wt % and the concentration of copper ions contained in the photocatalyst coating liquid was 420 ppm.

[0056] Measurement of secondary particle size of photocatalyst particles The secondary particle diameters of the photocatalyst particles contained in the photocatalyst coating liquids of Examples 1 to 14 and Comparative Examples 1 to 8 were measured using a laser diffraction / scattering particle size distribution analyzer. The measurement results are shown in Tables 2 and 3. FIG. 2 is a graph showing the change in secondary particle diameter of the photocatalyst particles versus the concentration of copper ions contained in the photocatalyst coating liquids of Examples 12 to 14 and Comparative Examples 5 to 8. As can be seen from FIG. 2, the higher the concentration of copper ions contained in the photocatalyst coating liquid, the larger the secondary particle diameter of the photocatalyst particles contained in the photocatalyst coating liquid. The reason for this is not clear, but it is thought that copper ions, which are cations, promote the aggregation of photocatalyst particles, including tungsten oxide particles, whose surfaces tend to be negatively charged.

[0057] [Table 3]

[0058] Acetaldehyde gas decomposition experiment 1 Using a dropper, 2 g of the photocatalyst coating solution of any one of Examples 1 to 11 and Comparative Examples 1 to 4 was evenly dripped onto an ABS resin plate (100 mm x 100 mm). The photocatalyst coating solution dripped onto the ABS resin plate was dried in a 40°C air dryer to form a photocatalyst layer, and a test sample was prepared by pre-irradiating this photocatalyst layer with 4500 lux of blue LED light for 48 hours. Next, the test sample was placed into a 1 L transparent gas bag, and then 100 ppm of acetaldehyde gas was introduced into the gas bag. After irradiating the photocatalyst layer with 4500 lux of blue LED light from outside the gas bag for 5 hours, the acetaldehyde gas concentration in the gas bag was measured using a detector tube. The gas residual rate was calculated using the formula: (gas residual rate) = (gas concentration after 5 hours) / (initial gas concentration 100 ppm). Table 3 shows the evaluation of the gas decomposition properties of each test sample (Examples 1 to 11, Comparative Examples 1 to 4) based on the gas residual rate.

[0059] In the evaluation of gas decomposition properties in Table 3, samples with a gas residual rate of less than 5% were evaluated with "◎", samples with a gas residual rate of 5% or more but less than 20% were evaluated with "○", samples with a gas residual rate of 20% or more but less than 50% were evaluated with "△", and samples with a gas residual rate of 50% or more were evaluated with "×". The gas decomposition properties of Examples 1 to 11 and Comparative Example 3 were evaluated as "◎", "◯" or "△", and it was found that they had sufficient gas decomposition properties. The gas decomposition properties of Comparative Example 1 were evaluated as "X." This is thought to be because the primary particle diameter of the photocatalyst particles contained in the photocatalyst coating liquid of Comparative Example 1 was 100 nm, which was relatively large. The gas decomposition properties of Comparative Example 2 were evaluated as "X." This is thought to be because the photocatalyst coating liquid of Comparative Example 2 did not contain photocatalyst particles. The gas decomposition characteristics of Comparative Example 4 were evaluated as "X." This is thought to be because the photocatalyst coating liquid of Comparative Example 4 did not contain metal salts and the secondary particle diameter of the photocatalyst particles was relatively small.

[0060] Rubbing fastness test 0.4g / m on ABS resin plate (30mm x 300mm) 2 A photocatalyst coating solution from any one of Examples 1 to 11 and Comparative Examples 1 to 4 was uniformly sprayed onto the ABS resin plate to form a photocatalyst layer. The photocatalyst coating solution on the ABS resin plate was dried in a 40°C air dryer for 24 hours to form a photocatalyst layer, which was then used to prepare a test sample. The test sample was attached to the horizontal test piece stand of a Gakushin-type abrasion fastness tester AB-301 manufactured by Tester Sangyo Co., Ltd., and a Bemcot M-1 manufactured by Asahi Kasei Corporation was attached to the tip of the abrasion probe. The photocatalyst layer was rubbed with the Bemcot M-1 at a load of 200 gf over a distance of 100 mm at a speed of 30 reciprocating strokes per minute for 100 reciprocating strokes (friction). After rubbing, the surfaces of the friction and non-friction areas of the sample were observed using a Keyence VHX-1000 digital microscope to confirm the condition and area of ​​the photocatalyst layer. The remaining rate of the photocatalyst layer was calculated using the following formula: (Residual rate of photocatalyst layer) = (area of ​​photocatalyst layer in friction area) / (area of ​​photocatalyst layer in non-friction area)

[0061] Table 3 shows the evaluation of the contact resistance of each test sample (Examples 1 to 11, Comparative Examples 1 to 4) based on the remaining rate of the photocatalytic layer and the like. In the evaluation of contact resistance in Table 3, samples in which the photocatalyst layer was not damaged and the boundary between the frictional and non-frictional areas could not be seen were rated with "◎", samples in which the surface of the photocatalyst layer was glossy and the boundary between the frictional and non-frictional areas could be seen but the photocatalyst layer had no clear abrasion or stretching were rated with "○", samples in which abrasion or stretching was visible but 40% or more of the photocatalyst layer remained were rated with "△", and samples in which the remaining rate of the photocatalyst layer was less than 40% were rated with "×". The contact resistance of Examples 1 to 11 and Comparative Examples 1, 2, and 4 was evaluated as "◎", "◯", or "△", and it was found that they had sufficient contact resistance. The evaluation of contact resistance for Comparative Example 3 was "X." This is thought to be because the photocatalyst coating liquid for Comparative Example 3 did not contain a binder.

[0062] comprehensive evaluation Table 3 also shows the overall evaluation of Examples 1 to 11 and Comparative Examples 1 to 4. In the overall evaluation in Table 3, the evaluation of both the gas decomposition properties and the contact resistance was indicated as "◎", the evaluation of at least one gas decomposition properties and contact resistance was indicated as "○" but not as "×" or "△", the evaluation of at least one gas decomposition properties and contact resistance was indicated as "△" but not as "×", and the evaluation of at least one gas decomposition properties and contact resistance was indicated as "×".

[0063] Acetaldehyde gas decomposition experiment 2 Two grams of the photocatalyst coating solution from any one of Examples 12-14 and Comparative Examples 5-8 was evenly dripped onto a cellulose fabric (125 mm x 125 mm) using a dropper. The cellulose fabric was dried in a 40°C air dryer to form a photocatalyst layer, and a test sample was prepared by pre-irradiating this photocatalyst layer with 4500 lux of blue LED light for 48 hours. Next, the test sample was placed in a 1 L transparent gas bag, and then 50 ppm of acetaldehyde gas was introduced into the gas bag. After irradiating the photocatalyst layer with 4500 lux of blue LED light from outside the gas bag for 15 minutes, the acetaldehyde gas concentration in the gas bag was measured using a detector tube. The gas removal rate was calculated using the formula: (gas removal rate)=1-(gas concentration after 15 minutes) / (initial gas concentration 50 ppm).

[0064] Table 2 shows the acetaldehyde concentrations (concentrations after 15 minutes of light irradiation) measured in acetaldehyde gas decomposition experiment 2 for Examples 12 to 14 and Comparative Examples 5 to 8, and the calculated gas removal rates. FIG. 3 is a graph showing the change in gas removal rate versus the concentration of copper ions contained in the photocatalyst coating liquid of Examples 12 to 14 and Comparative Examples 5 to 8. As can be seen from Figure 3, the gas removal rate increases when the copper ion concentration in the photocatalyst coating solution is between 100 ppm and 300 ppm. If the copper ion concentration is too low, the secondary particle diameter of the photocatalyst particles becomes small, and it is thought that the photocatalyst particles become buried in the binder in the photocatalyst layer. This is thought to be the reason for the low gas removal rate. If the copper ion concentration is too high, it is thought that the secondary particle diameter of the photocatalyst particles becomes too large, and light does not hit the center of the secondary particle of the photocatalyst particles. This is thought to be the reason for the low gas removal rate. [Explanation of symbols]

[0065] 2: Photocatalytic coating liquid 3: Spray container 4: Actuator 5: Valve member 6: Tube 7: Spray hole 8: Gas phase 9: Pressure-resistant container 14: Substrate 15: Coating film 16: Photocatalytic layer 20: Photocatalytic spray can 25: Photocatalytic coated member

Claims

1. The composition comprises 1.0 wt % or more and 5.0 wt % or less of photocatalytic particles, 0.05 wt % or more and 0.5 wt % or less of a binder, metal ions, and an aqueous dispersion medium; the photocatalytic particles include tungsten oxide particles, The average particle diameter of the primary particles, calculated from the BET specific surface area of ​​the photocatalyst particles using a spherical model, is 10 nm or more and 50 nm or less, A photocatalyst coating solution characterized in that the average particle diameter D50 of the secondary particles of the photocatalyst particles is 600 μm or more and 1000 μm or less.

2. 2. The photocatalyst coating liquid according to claim 1, wherein the concentration of the metal ions in the photocatalyst coating liquid is 100 ppm or more and 300 ppm or less.

3. 2. The photocatalyst coating liquid according to claim 1, wherein the binder has an inorganic skeleton formed of siloxane bonds or a silanol group.

4. 2. The photocatalyst coating liquid according to claim 1, wherein the metal ions include at least one of copper ions, silver ions, iron ions, and zinc ions.

5. A spray container comprising the photocatalyst coating liquid according to any one of claims 1 to 4, a propellant, and a spray container containing the photocatalyst coating liquid and the propellant, The spray container has an injection hole provided to inject the photocatalyst coating liquid together with the propellant.

6. the propellant comprises dimethyl ether; The diameter of the injection hole is 0.3 mm or less, 6. The photocatalyst spray can according to claim 5, wherein the internal pressure of the spray container is 0.4 MPa or more at a temperature of 25°C.

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