Coating composition, coating method, and mold treatment method

Abstract

This coating composition comprises 5% by mass or less of silica particles, fluororesin particles, 0.001%-5% by mass of a chlorine-based bleaching agent, and water.

Description

Technical Field

[0001] The present disclosure relates to a coating composition for forming a film that suppresses contamination of a substrate, a method for coating a substrate, and a method for treating mold on a substrate.

Background Art

[0002] Various contaminants such as dust, fumes, and mold adhere to the surfaces of various articles used indoors or outdoors. In particular, mold adheres to the surface of an article and induces contamination by growing using dust and fumes as nutrients. Therefore, in order to obtain a high antifouling effect, it is necessary to inhibit the growth of mold, and a technique for inhibiting the adhesion and growth of mold is required.

[0003] Here, Patent Document 1 discloses a coating composition that contains an antifungal agent, forms a film that coats a substrate, and suppresses the adhesion and growth of mold on the substrate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, Patent Document 1 does not mention a technique for inhibiting the adhesion of dust, fumes, mold, etc. to the surface of the coating film obtained from the coating composition. When dust or fumes, which serve as nutrients for mold, accumulate on the surface of the coating film, mold can easily grow by adhering to the accumulated dirt.

[0006] Furthermore, Patent Document 1 shows sodium hypochlorite as an antibacterial agent contained in a coating composition, and an organic compound is shown as the antibacterial agent or antifungal agent. However, when an organic compound and sodium hypochlorite are contained in a coating composition, the organic compound may be decomposed by the sodium hypochlorite. As a result, the stability of the coating composition may decrease.

[0007] This disclosure was made to solve the above problems and aims to provide a coating composition that produces a coating film that is stable and has improved antifouling performance that suppresses the adhesion of dirt such as dust and mold, and antifungal performance that suppresses the growth of mold, as well as a method for coating a substrate and a method for treating mold on a substrate. [Means for solving the problem]

[0008] The coating composition relating to this disclosure comprises 5% by mass or less of silica particles, fluororesin particles, 0.001% by mass or more and 5% by mass or less of a chlorine-based bleaching agent, and water.

[0009] The coating method according to this disclosure is a method for coating a substrate, comprising applying a coating composition containing 5% by mass or less of silica particles, fluororesin particles, 0.001% by mass or more and 5% by mass or less of a chlorine-based bleaching agent, and water to the substrate to form a coating film on the surface of the substrate.

[0010] The mold treatment method according to this disclosure involves applying a coating composition containing 5% by mass or less of silica particles, fluororesin particles, 0.001% by mass or more and 5% by mass or less of a chlorine-based bleaching agent, and water to a substrate. [Effects of the Invention]

[0011] According to the coating composition, coating method, and mold treatment method of this disclosure, it is possible to ensure the stability of the coating composition and to obtain a coating film with improved antifouling and antifungal properties, thereby suppressing the adhesion and growth of mold on the substrate. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic cross-sectional view of a coating film obtained from the coating composition according to Embodiment 1. [Figure 2] This is a schematic top view illustrating a coating film obtained from the coating composition according to Embodiment 1. [Figure 3] This is a schematic top view diagram showing the coating film in the comparative example. [Figure 4] This is a schematic cross-sectional view illustrating a coating film formed on a substrate having water absorption or porous properties, etc., using the coating composition according to Embodiment 2. [Figure 5] This figure shows multiple examples of the proportion of constituent elements in the coating composition according to Embodiment 1. [Figure 6] This figure shows the evaluation results of the coating compositions for Examples 1 to 9 and Comparative Examples 1 to 3. [Figure 7] This figure shows multiple examples of the proportion of constituent elements in the coating composition according to Embodiment 2. [Figure 8] This figure shows the evaluation results of the coating compositions related to Examples 10 to 11 and Comparative Example 4. [Figure 9] This figure shows multiple examples of the proportion of constituent elements in the coating compositions according to Embodiments 1 and 2. [Figure 10] This figure shows the evaluation results of the coating compositions for Examples 12 to 14 and Comparative Examples 5 to 7. [Modes for carrying out the invention]

[0013] Hereinafter, referring to the drawings, a coating composition according to an embodiment will be described. In the following drawings, the relative dimensional relationships and shapes of each component may be different from the actual ones. Also, in the following drawings, components with the same reference numerals are the same or corresponding ones. The components in the embodiment are merely examples and are not limited thereto.

[0014] Embodiment 1. FIG. 1 is a schematic cross-sectional view of a coating film 1 obtained from the coating composition according to Embodiment 1. The coating composition is applied onto a substrate 4 to form the coating film 1. The coating composition according to the embodiment includes a plurality of silica particles 2, a plurality of fluororesin particles 3, water and a chlorine-based bleaching agent (not shown). In the coating film 1, the plurality of silica particles 2 aggregate to form a silica film, and the plurality of fluororesin particles 3 are dispersed in the silica film.

[0015] The chlorine-based bleaching agent decomposes mold and organic contaminants, etc. The organic contaminants are oil fumes, sebum, or keratin, etc., which serve as nutrients for mold. In the coating composition applied to the surface of the substrate 4, the chlorine-based bleaching agent decomposes mold and organic contaminants, etc. adhering to the surface of the substrate 4, and also decomposes mold and organic contaminants, etc. diffused from the surface of the substrate 4 into the coating composition. Further, the chlorine-based bleaching agent also decomposes mold and organic contaminants, etc. adhering to the coating composition from the surrounding environment such as the atmosphere. Thereby, a sterilization effect on the surface of the substrate 4, a blocking effect on the supply of organic contaminants, etc. serving as nutrients to mold, and an inhibitory effect on the growth of mold on the surface of the substrate 4 and within the coating film 1 can be obtained. Also, by the chlorine-based bleaching agent decomposing mold, etc. on the surface of the substrate 4, the adhesion of the coating film 1 to the surface of the substrate 4 can be maintained or improved, and the design property of the substrate 4 can be maintained. By the chlorine-based bleaching agent decomposing mold and organic contaminants, etc. within the coating composition and mold and organic contaminants, etc. from the surrounding environment, the strength of the coating film 1 can be maintained or improved.

[0016] As the moisture contained in the coating composition applied to the surface of the substrate 4 volatilizes, the chlorine-based bleaching agent is concentrated and its concentration increases. As a result, the chlorine-based bleaching agent decomposes naturally and disappears from the coating film 1.

[0017] The content of the chlorine-based bleaching agent in the coating composition is 0.001 to 5.0% by mass, preferably 0.01 to 3.0% by mass. If the content is within this range, it can decompose mold, organic contaminants, etc., and a coating composition with stability can be obtained. If the content of the chlorine-based bleaching agent is less than 0.001% by mass, there is a possibility that the mold and organic contaminants on the surface of the substrate 4, as well as the surface and inside of the coating composition, cannot be decomposed. On the other hand, if the content of the chlorine-based bleaching agent is 5.0% by mass or more, the dispersibility of the silica particles 2 and fluororesin particles 3 in the coating composition may decrease. As a result, the silica particles 2 and fluororesin particles 3 may aggregate and precipitate, and there is a possibility that the stability as a coating composition cannot be ensured.

[0018] Examples of the chlorine-based bleaching agent include hypochlorous acid, sodium hypochlorite, lithium hypochlorite, potassium hypochlorite, calcium hypochlorite, sodium dichloroisocyanurate, or potassium dichloroisocyanurate. The chlorine-based bleaching agent may be a mixture of any two or more of these.

[0019] The substrate 4, before the coating composition is applied, is contaminated with mold and organic pollutants. The mold adheres to the surface of the substrate 4 as spores or hyphae. The mold and organic pollutants adhering to the surface of the substrate 4 not only impair the hygiene and cleanliness of the article, but also discolor the article due to the pigments it contains, impairing its aesthetic appeal. Mold proliferates in soil and plants worldwide, releasing spores into the air. Therefore, articles placed outdoors are exposed to spores floating in the air. On the other hand, articles indoors are exposed to spores and other contaminants as humans, pets and other living things enter and exit the room. Mold reproduces when spores attached to the surface of the substrate 4 germinate and hyphae grow. Mold also reproduces when hyphae grow from mold-containing dirt attached to the substrate 4. Organic pollutants, which serve as nutrients for mold, also adhere to the surface of the substrate 4. The organic pollutants attached to the substrate 4 provide nutrients for mold to grow. Therefore, in order to inhibit mold growth, it is necessary to remove mold and organic contaminants.

[0020] When the coating composition is applied to the substrate 4, the chlorine bleach acts as an oxidizing agent, decomposing and removing mold and organic contaminants. The chlorine bleach is dispersed in the liquid within the coating composition applied to the substrate 4. When the chlorine bleach reaches the mold, it decomposes and removes the mold by altering and breaking down the cell wall, cell membrane, cytoplasm, and enzymes. The chlorine bleach also decomposes and removes organic contaminants by altering and breaking down the organic components that make up the organic contaminants. In decomposing and removing mold and organic contaminants, the chlorine bleach also decomposes the pigments contained in the mold and organic contaminants. This results in a bleaching effect. As the water contained in the coating composition evaporates, the concentration of the chlorine bleach increases, further enhancing its performance as an oxidizing agent that decomposes mold and organic contaminants. Furthermore, as the concentration of the chlorine bleach increases, the rate of natural decomposition also increases, causing it to disappear from the coating film 1.

[0021] In the coating film 1 of this embodiment, the silica film is a dense film with fine voids because the silica particles 2 are fine particles with a large surface area per unit volume. The silica film suppresses the adhesion and adhesion of dirt such as dust due to static electricity. In particular, since the silica particles 2 are hydrophilic, hydrophobic dirt can be made to adhere and adhere to it. In the coating film 1 of this embodiment, the fluororesin particles 3 scattered on the silica film are hydrophobic, so hydrophilic dirt can be made to adhere and adhere to it.

[0022] The coating film 1 is obtained by the evaporation of water contained in the coating composition applied to the surface of the substrate 4. The coating film 1, through the silica particles 2 and fluororesin particles 3, can obtain antifouling properties that make it difficult for mold and organic contaminants to adhere and fix to it. In addition to this antifouling property, the coating film 1 can also obtain antifungal properties through the decomposition effect of chlorine-based bleach on mold and organic contaminants.

[0023] Since silica particles 2 are stable inorganic components, they are not decomposed by chlorine-based bleaches. Furthermore, since fluororesin particles 3 are stable organic components with chemical resistance, they are not decomposed by chlorine-based bleaches. Therefore, the coating composition according to Embodiment 1 exhibits excellent stability.

[0024] As shown in Figure 1, the shape of the silica particles 2 in Embodiment 1 is spherical. Furthermore, the average particle size of the silica particles 2 in Embodiment 1, when measured by light scattering, is 4 nm or more and 25 nm or less. Preferably, the average particle size of the silica particles 2 is 4 nm to 15 nm. By including silica particles 2 having an average particle size in this range in the coating composition, the silica particles tend to aggregate when dried, making it easier for the coating composition to solidify. In addition, since the number of silica particles 2 dissolved in equilibrium in the coating composition increases, a relatively high-strength coating film 1 can be obtained without the need to add a special binder. Furthermore, since the light scattering of the silica particles 2 is reduced, the transparency of the coating film 1 is improved, and changes in the color tone and texture of the surface of the article on which the coating film 1 is formed can be suppressed. Note that if the average particle size of the silica particles 2 is greater than 25 nm, the coating film 1 may not have sufficient strength. Also, if the average particle size of the silica particles 2 is less than 4 nm, the stability of the coating composition may decrease, and the strength and antifouling properties of the coating film 1 may decrease.

[0025] The mass of silica particles 2 contained in the coating composition according to Embodiment 1 is 0.1 to 5.0% of the total mass of the coating composition. Preferably, the mass of silica particles 2 contained in the coating composition is 0.3 to 2.5% of the total mass of the coating composition. When the silica particle content is 0.1 to 5.0%, a uniform and thin coating film can be formed without impairing the color tone and texture of the surface of the article. If the silica particle content is less than 0.1% by mass, the resulting coating film becomes too thin, making it difficult to obtain the desired antifouling properties. On the other hand, if the silica particle content exceeds 5% by mass, the coating film becomes an uneven, cloudy film, prone to cracking and peeling.

[0026] Examples of the fluororesin particles 3 in Embodiment 1 include PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene hexafluoropropylene copolymer), PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer), ETFE (ethylene tetrafluoroethylene copolymer), ECTFE (ethylene chlorotrifluoroethylene copolymer), PVDF (polyvinylidene fluoride), PCTFE (polychlorotrifluoroethylene), or PVF (polyvinyl fluoride). The fluororesin particles 3 may be copolymers or mixtures of these, or they may be fluororesins mixed with other resins. Among the above, PTFE and FEP are preferred as the fluororesin particles 3 because they have excellent stability and high hydrophobicity.

[0027] The average particle size of the fluororesin particles 3 is not particularly limited, but is preferably 50 nm to 10,000 nm, and more preferably 100 nm to 5,000 nm, when measured by light scattering. By including fluororesin particles 3 having an average particle size within this range in the coating composition, the fluororesin particles 3 are appropriately dispersed inside the coating film 1 and are easily exposed on the surface of the coating film 1, thereby obtaining good antifouling performance. If the average particle size of the fluororesin particles 3 is less than 50 nm, the stability of the coating composition may not be obtained, and the fluororesin particles 3 may not be easily exposed on the surface of the coating film 1, potentially resulting in a failure to obtain the desired antifouling performance. On the other hand, if the average particle size of the fluororesin particles 3 exceeds 10,000 nm, the hydrophobic region in the resulting coating film 1 becomes larger, and the surface irregularities of the coating film 1 become too large, potentially resulting in a failure to obtain the desired antifouling performance.

[0028] The mass ratio of silica particles 2 to fluororesin particles 3 in the coating composition according to Embodiment 1 is 40:60 to 95:5, more preferably 50:50 to 90:10. When the mass ratio of silica particles 22 to fluororesin particles 3 is 40:60 to 95:5, a coating film 1 is obtained by drying at room temperature in which hydrophilic portions due to silica particles 2 and hydrophobic portions due to fluororesin particles 3 are well mixed, and the coating film 1 has good antifouling performance.

[0029] Figure 2 is a schematic top view illustrating a coating film 1 obtained from the coating composition according to Embodiment 1. The mass ratio of silica particles 2 to fluororesin particles 3 in the coating film 1 in Figure 2 is 75:25. As shown in Figure 2, the fluororesin particles 3 are scattered in a silica film formed by the aggregation of multiple silica particles 2. On the surface of the coating film 1 shown in Figure 2, the area of ​​the silica film, which is the hydrophilic portion, is sufficiently larger than the area of ​​the fluororesin particles 3, which are the hydrophobic portion; therefore, the film as a whole is hydrophilic. The hydrophilic portion on the surface of the coating film 1 plays an important role in improving its antifungal performance. The antifungal performance due to the hydrophilic portion on the surface of the coating film 1 will be described in detail below.

[0030] On the surface of the coating film 1, the hydrophilic portion is continuous without being interrupted by the hydrophobic portion. Therefore, when water droplets such as condensation adhere to the surface of the coating film 1, the water droplets flow out through the hydrophilic portion as a channel and are easily discharged from the surface of the coating film 1. In addition, water droplets adhering to the surface of the coating film 1 tend to spread thinly across the entire coating film 1, thereby allowing the water droplets to evaporate easily. Generally, the surface of an object in a state where water droplets remain attached is an environment where mold easily grows. However, the coating film 1 of Embodiment 1 has the characteristics that water droplets adhering to the surface are easily discharged and easily evaporate, thus improving its mold-resistant performance. Furthermore, due to the characteristic that liquid droplets tend to spread across the entire coating film 1, hydrophilic or hydrophobic dirt adhering to the surface of the coating film 1 is removed by the flow of water droplets or becomes less likely to adhere. In particular, dirt on the surface of the coating film 1 is easily removed during condensation, rainfall, or cleaning. Furthermore, since the coating film 1 of Embodiment 1 is mainly composed of a continuous silica film, it can also suppress static charge on the film surface, which causes dirt to adhere. Moreover, since both the silica film and the fluororesin particles 3 of the coating film 1 are oil-repellent, oil droplets are less likely to adhere to it.

[0031] On the other hand, if the ratio of silica particles 2 exceeds the above-mentioned range, the coating film 1 can effectively prevent the adhesion of hydrophobic contaminants such as oil fumes or carbon, but it becomes more susceptible to the adhesion of hydrophilic contaminants such as sand dust or dirt. Also, if the ratio of silica particles 2 does not reach the above-mentioned range, the coating film 1 can effectively prevent the adhesion of hydrophilic contaminants such as sand dust or dirt, but it becomes more susceptible to the adhesion of hydrophobic contaminants such as oil fumes or carbon. Mold and organic pollutants contained in oil fumes, carbon, sand dust, or dirt adhere to the coating film 1, creating a habitat for mold, and as a result, the antifungal performance deteriorates.

[0032] Here, an example of a case where the mass ratio of silica particles 2 to fluororesin particles 3 contained in the coating film 1 is outside the range described above will be explained with reference to Figure 3. Figure 3 is a schematic top view showing the coating film 1 in a comparative example. In Figure 3, the mass ratio of silica particles 2 to fluororesin particles 3 contained in the coating film 1 is 25:75. In the coating film 1 shown in Figure 3, because the ratio of fluororesin particles 3 to silica particles 2 is high, there are many hydrophobic parts, and the hydrophilic parts are separated by the hydrophobic parts. Therefore, when water droplets adhere to the coating film 1, the flow of the water droplets is inhibited by the hydrophobic parts, and the water droplets cannot flow out through the hydrophilic parts as a channel, remaining on the surface of the coating film 1. In addition, water droplets adhering to the surface of the coating film 1 do not easily spread thinly over the entire coating film 1, so the time required for evaporation is long. Therefore, in a coating film 1 as exemplified in Figure 3, high antifungal performance cannot be obtained, and good antifouling performance cannot be obtained.

[0033] Mold that flies onto the coating film 1 from the surrounding environment includes mold that floats in the air as individual spores and mold that is mixed in hydrophilic or hydrophobic dirt as spores and hyphae. Generally, mold spores have a hydrophilic surface and adhere to objects by electrostatic bonding between hydrophilic groups, liquid crosslinking by water, or intermolecular forces. Mold spores are minute particles with a particle size of 2 μm to 10 μm. To prevent the adhesion of mold spores, it is necessary to form a coating film 1 that does not have hydrophilic parts of a size to which hydrophilic dirt can adhere. On the other hand, generally, mold hyphae have a length of tens of μm to several mm. Therefore, hydrophilic or hydrophobic dirt mixed with mold consists of particles of a size of tens of μm to several mm. To prevent the adhesion of hydrophilic dirt mixed with mold, it is necessary to form a coating film 1 that does not have hydrophilic parts of a size to which hydrophilic dirt can adhere. In order to prevent the adhesion of hydrophobic dirt containing mold, it is necessary to form a coating film 1 that does not have hydrophobic areas large enough for hydrophobic dirt to adhere to.

[0034] Furthermore, hydrophilic contaminants such as sand and dust generally adhere to objects through electrostatic bonding between hydrophilic groups, liquid crosslinking by water, or intermolecular forces. Sand and dust are minute particles with a diameter of several micrometers to tens of micrometers, while dust particles are much larger than sand and dust. To prevent the adhesion of hydrophilic contaminants through electrostatic bonding between hydrophilic groups, it is necessary to form a coating film 1 that does not have hydrophilic portions of a size to which hydrophilic contaminants can adhere.

[0035] Furthermore, hydrophobic contaminants such as oil fumes, carbon, sebum, or dead skin cells generally adhere to objects through intermolecular forces or, in the case of water, hydrophobic bonds. Hydrophobic contaminants are generally minute particles with a diameter of 1 μm or less, and most of them have a diameter of 0.3 μm or less. If the surface of coating film 1 is hydrophobic, hydrophobic contaminants will adhere more easily. Also, if the hydrophobic surface is covered with condensation water or the like, and the surface is in contact with hydrophobic contaminants, the cohesive force of water can create a hydrophobic bonding force between the surface and the hydrophobic contaminants, causing the hydrophobic contaminants to adhere to the surface of coating film 1.

[0036] In Embodiment 1, by setting the mass ratio of silica particles 2 to fluororesin particles 3 in the coating composition to the range described above, a coating film 1 can be obtained in which hydrophobic portions are appropriately dispersed in the hydrophilic portions, as shown in Figure 2. As a result, the hydrophilic and hydrophobic portions of the coating film 1 in Embodiment 1 are of a size that makes it difficult for mold spores and dirt containing mold to adhere to them. Therefore, the coating film 1 in Embodiment 1 can suppress the adhesion of mold spores and dirt containing mold through electrostatic bonding between hydrophilic groups or between hydrophobic groups. Consequently, the growth of mold on the surface of the coating film 1 can be suppressed, and excellent mold-resistant performance can be obtained.

[0037] Furthermore, in Embodiment 1, by setting the mass ratio of silica particles 2 to fluororesin particles 3 in the coating composition to the above-mentioned range, hydrophobic portions are appropriately dispersed in the hydrophilic portions, and a coating film 1 is formed in which there are almost no hydrophilic portions of a size to which hydrophilic dirt can stably adhere. Therefore, the adhesion of hydrophilic dirt due to electrostatic bonding between hydrophilic groups on the surface of the coating film 1 can be suppressed. In addition, in the coating film 1 of Embodiment 1, even if hydrophilic dirt adheres to the hydrophilic portion, physical obstruction by the surface of the hydrophobic portion adjacent to the hydrophilic portion or the protrusions of the hydrophobic portion prevents the hydrophilic dirt from adhering sufficiently to the hydrophilic portion. Therefore, hydrophilic dirt is less likely to adhere to the surface of the coating film 1. Moreover, since the coating film 1 of Embodiment 1 is a porous coating film 1 composed of silica particles 2 and fluororesin particles 3, even if liquid crosslinking occurs due to water, etc., the water between the silica particles 2 is easily and quickly removed from the silica film surface during the drying process.

[0038] Furthermore, since the coating composition according to Embodiment 1 does not contain binders or organic polymers as constituent components, after liquid crosslinking is resolved, the binders or organic polymers do not precipitate on the surface of the coating film 1, thereby changing the state of the surface of the coating film 1. Moreover, since the coating film 1 of Embodiment 1 has extremely small voids and is a low-density film, it can suppress the adhesion of hydrophilic dirt due to intermolecular forces. In addition, by suppressing the adhesion of hydrophilic dirt, the coating film 1 of Embodiment 1 can suppress the adhesion of nutrients necessary for mold growth, thereby inhibiting mold growth.

[0039] In Embodiment 1, a coating film 1 is obtained in which hydrophobic portions are appropriately dispersed in hydrophilic portions. Therefore, the presence of hydrophilic groups on the surface of the coating film 1, or water adsorbed on the surface, can suppress the adhesion of hydrophobic dirt. Furthermore, by suppressing the adhesion of hydrophobic dirt, the coating film 1 of Embodiment 1 suppresses the adhesion of nutrients necessary for mold growth, thus inhibiting mold growth.

[0040] Furthermore, since the coating film 1 of Embodiment 1 is composed of chemically stable silica particles 2 and fluororesin particles 3, it can maintain its antifouling performance over a long period of time, thus providing sustained antifungal performance.

[0041] The coating composition according to Embodiment 1 contains water as a solvent, which is a volatile component. However, if the amount of minerals in the water is high, it may become impossible to control the aggregation of silica particles 2. Specifically, if the concentration of ionic impurities in the water exceeds 200 ppm, the silica particles 2 may aggregate and precipitate. This may reduce the strength or transparency of the coating film 1. Therefore, from the viewpoint of the dispersion stability of silica particles 2, it is preferable that the water in the coating composition contains few ionic impurities of divalent or higher, such as calcium ions or magnesium ions. Specifically, deionized water is preferred as the water contained in the coating composition of Embodiment 1, but water containing ionic impurities may also be used. In this case, the concentration of ionic impurities is preferably 200 ppm or less, and more preferably 50 ppm or less.

[0042] The water content in the coating composition is not particularly limited, but is, for example, 30 to 99.8% by mass. However, the water content is preferably 50% by mass or more and 99.5% by mass or less, and more preferably 60% by mass or more and 99% by mass or less. The coating composition may also contain organic solvents or the like to adjust the stability, applicability, and drying properties of the coating composition.

[0043] In Embodiment 1, when obtaining a coating composition by blending a chlorine-based bleach, silica particles 2, and fluororesin particles 3, the solution or dispersion of the chlorine-based bleach, silica particles 2, and fluororesin particles 3 before blending may be configured so that it is not a combination of a basic liquid with a pH of 8 or higher and an acidic liquid with a pH of 6 or lower. This can suppress aggregation or precipitation in the coating composition. As a result, the coating film 1 obtained after drying the coating composition applied to the substrate 4 becomes homogeneous. Furthermore, the decomposition of the chlorine-based bleach before application of the coating composition can be suppressed.

[0044] The coating composition according to Embodiment 1 may contain various known components in the field of coatings, as long as they do not impair the effects described above. Examples of such components include surfactants, coupling agents, silane compounds, or antifungal agents. The amounts of these components are not particularly limited as long as they do not impair the effects described above, and may be adjusted as appropriate depending on the type of component.

[0045] The method for producing the coating composition according to Embodiment 1 is not particularly limited and may be based on methods known in the field of coatings. For example, the coating composition according to Embodiment 1 can be produced by mixing a dispersion of silica particles 2, a dispersion of fluororesin particles 3, and a chlorine-based bleaching agent.

[0046] The method for producing the coating composition according to Embodiment 1 may include a method for adjusting the coating composition by redispersing the aggregated or precipitated material using a homogenizer or high-pressure dispersion apparatus when aggregation or precipitation of components occurs due to the mixing of multiple liquids. In addition, to suppress re-aggregation, a surfactant, an inorganic dispersant, or a high-viscosity solvent such as ethylene glycol may be added to the mixed liquid during the initial mixing or redispersion. By mixing the materials in multiple stages in this way, a wide range of material combinations become possible when producing the coating composition, and improvements in the fluidity of the coating composition, optimization of the density of the formed coating film 1, or improvement of smoothness can be achieved by realizing an appropriate aggregation state.

[0047] The coating composition may be obtained by mixing all components at once, in which case it is stored in the container until use and applied to the substrate 4 without requiring any processing at the time of use. Alternatively, the coating composition may be obtained by mixing two or more pre-formulated liquids immediately before use. In the latter case, a method is used in which only a chlorine-based bleach, which is particularly easily decomposed, is mixed with the other components of the coating composition immediately before use. This ensures that the effects of the chlorine-based bleach and other components in the coating composition are maintained even after long-term storage.

[0048] Methods for applying the coating composition according to Embodiment 1 to the substrate 4 include, for example, a spray application method, a brush or roller application method, or a dipping application method. The spray application method includes a method in which a pre-mixed coating composition is sprayed from a spray nozzle, and a method in which two or more liquids for obtaining the coating composition are sprayed from separate spray nozzles and mixed on the surface of the substrate 4, or just before reaching the substrate 4. The brush or roller application method includes a method in which two or more liquids are applied in layers using separate application tools. The dipping application method includes a method in which two or more liquids are dipped in multiple stages.

[0049] According to the method of applying the coating composition to the substrate 4 in Embodiment 1, the silica particles 2 solidify by drying alone, eliminating the need for heating, and making it possible to fix the fluororesin particles 3 to the silica film. Here, during the drying of the coating composition, excess coating composition may be removed from the substrate 4 by airflow. In particular, by removing excess coating composition by airflow, a thin coating film 1 in which fluororesin particles 3 are uniformly dispersed in the silica film can be obtained quickly.

[0050] Furthermore, as a method for applying the coating composition to the substrate 4, it is preferable to mix two or more liquids for obtaining the coating composition during the application process and prepare the coating composition on the surface of the substrate 4. That is, it is preferable to apply each of the two or more liquids for obtaining the coating composition to the surface of the substrate 4, mix the two or more liquids on the surface of the substrate 4, and generate the coating composition on the surface of the substrate 4. By forming a liquid film of the coating composition on the surface of the substrate 4 in this way and drying the liquid film to obtain the coating film 1, it is possible to suppress the decomposition of easily decomposable chlorine-based bleaches. In addition, it becomes possible to form a coating film 1 with a combination of coating compositions that cannot exist stably as a liquid due to agglomeration when mixed. Furthermore, it is possible to reduce the amount of work required. The coating film 1 obtained in this way may have less organic contamination and an appropriate porosity.

[0051] The formation of the coating film 1 containing silica particles 2 and fluororesin particles 3 and the decomposition of mold and organic matter by a chlorine-based bleach may be carried out separately. That is, a chlorine-based bleach may be applied to the surface of the substrate 4 before or after applying the coating composition, or two or more liquids constituting the coating composition, to the substrate 4.

[0052] The articles that are the substrates 4 to which the coating composition is applied are not particularly limited, but include various articles used indoors or outdoors that are subject to various hydrophilic or hydrophobic contaminants such as dust, oil fumes, mold, or organic pollutants. Depending on the article to which the coating film 1 is applied, pretreatment such as washing with detergent or alcohol, corona treatment, or UV treatment may be applied to the surface of the article from the viewpoint of improving the wettability of the coating composition and the adhesion of the coating film 1. Furthermore, for articles that are significantly contaminated with mold or organic pollutants, pretreatment such as disinfection with a chlorine-based bleach may be applied.

[0053] The surface of the substrate 4 to which the coating composition is applied is not limited to a specific surface such as the top surface of the substrate 4; the coating composition may be applied to the side or back surface of the substrate 4, or to multiple surfaces.

[0054] Embodiment 2. The coating composition according to Embodiment 2 will be described below. In Embodiment 2, the same reference numerals will be used for components that are the same as those in Embodiment 1. In Embodiment 2, the same components as those in Embodiment 1, and the same functions as those in Embodiment 1, will not be described unless there are special circumstances.

[0055] In Embodiment 1, the silica particles 2 contained in the coating composition were spherical, but in Embodiment 2, the silica particles 2 contained in the coating composition are made to have irregular shapes such as needle-shaped, flake-shaped, chain-shaped, bead-shaped, or pearl necklace-shaped. This makes it easier to form a coating film 1 with excellent antifouling properties even on the surface of a substrate 4 that is difficult to form a coating film 1 on, such as having water absorption or porous properties.

[0056] Figure 4 is a schematic cross-sectional view illustrating a coating film 1 formed on a substrate 4 having water absorption or porous properties, etc., by the coating composition according to Embodiment 2. As shown in Figure 4, the coating film 1 formed from the coating composition of Embodiment 2 includes a silica film to which silica particles 2 are adhered and fluororesin particles 3 dispersed in the silica film.

[0057] When the coating composition of Embodiment 2 is applied to a substrate 4 having water absorption or porous properties, some of the water and some of the chlorine bleach components of the coating composition flow from the surface to the interior of the substrate 4 due to capillary action in the pores 5 of the substrate 4. On the other hand, among the components contained in the coating composition, the fluororesin particles 3 and silica particles 2 have a particle size that can block the pores 5 of the substrate 4 and do not easily penetrate into the interior of the substrate 4. Therefore, the ratio of silica particles 2 to fluororesin particles 3 in the coating film 1 is maintained to be approximately the same as the ratio of silica particles 2 to fluororesin particles 3 in the coating composition before application. Thus, by adjusting the ratio of silica particles 2 to fluororesin particles 3 in the coating composition, excellent antifouling performance can be obtained. Note that the blockage of the pores 5 by the fluororesin particles 3 and silica particles 2 means that the fluororesin particles 3 and silica particles 2 cannot pass through the pores 5, while water, chlorine bleach, or air can pass through the fine voids in the silica film.

[0058] Furthermore, the silica particles 2 in the coating film 1 formed from the coating composition of Embodiment 2 are irregularly shaped particles, resulting in a large surface area per unit volume. Therefore, the silica film formed by the silica particles 2 has very small voids and low density, which reduces the adhesion of dirt due to intermolecular forces on the coating film 1.

[0059] In Embodiment 2, the silica particles 2 may be irregularly shaped particles such as needle-shaped, flake-shaped, chain-shaped, bead-shaped, or pearl necklace-shaped, or a mixture of two or more shapes of particles from among needle-shaped, flake-shaped, chain-shaped, bead-shaped, and pearl necklace-shaped. The average particle size of the silica particles 2 in Embodiment 2, when measured by light scattering, is 50 nm or more and 500 nm or less, preferably 50 nm to 300 nm. By including irregularly shaped silica particles 2 having an average particle size of 500 nm or less in the coating composition, the silica particles 2 are more likely to remain on the surface of the substrate 4 having water absorption or porous properties, making it easier to form the coating film 1. Furthermore, since the silica film made of irregularly shaped silica particles 2 having an average particle size of 500 nm or less has very small voids and is a low-density film, the adhesion of dirt due to intermolecular forces is also reduced. Furthermore, because the irregularly shaped silica particles 2 having an average particle size of 500 nm or less have a large surface area per unit volume, the area on which the silica particles 2 adhere to each other in the silica film is large, resulting in a coating film 1 with sufficient strength. In addition, in a silica film made of irregularly shaped silica particles 2 having an average particle size of 500 nm or less, the irregularly shaped silica particles 2 overlap, intertwine, and adhere to each other, resulting in a coating film 1 with sufficient strength.

[0060] Here, if the average particle size of the silica particles 2 in the coating composition is less than 50 nm, when the coating composition is applied to a substrate 4 having water absorption or porous properties, the silica particles 2 tend to penetrate into the substrate 4 due to capillary action. As a result, the ratio of silica particles 2 to fluororesin particles 3 in the coating film 1 on the surface of the substrate 4 may become uncontrollable, and it may become difficult to maintain high antifouling performance. On the other hand, if the average particle size of the irregularly shaped silica particles 2 is longer than 500 nm, the silica particles 2 do not intertwine with each other in the silica film, and the voids in the silica film become coarser, which may reduce the strength of the coating film 1. In addition, the unevenness of the coating film 1 may become too large, making it easier for hydrophilic dirt to adhere, and the desired antifouling performance may not be obtained.

[0061] If the coating composition contains spherical silica particles 2 with an average particle size longer than 50 nm, the coating film 1 may not have sufficient strength. Furthermore, because spherical silica particles 2 with an average particle size longer than 50 nm have a smaller surface area per unit volume compared to irregularly shaped silica particles 2 with a similar average particle size, the density of the silica film increases, which may increase the adhesion of dirt due to intermolecular forces.

[0062] Furthermore, the substrate 4, which has properties such as water absorption or porousness, is contaminated with mold or organic contaminants before the coating composition is applied. The mold adheres to the surface of the substrate 4 and the walls of the pores 5 as spores or hyphae. The substrate 4, which has properties such as water absorption or porousness, tends to maintain a constant humidity level inside the substrate 4, creating an environment where mold can easily grow. Moreover, in substrate 4 where mold has grown inside, disinfecting only the surface of the substrate 4 is insufficient because the mold inside the substrate 4 remains, leading to a recurrence of mold growth. In addition, organic contaminants, which serve as nutrients for mold, also adhere to the surface of the substrate 4 and the walls of the pores 5. The organic contaminants attached to the substrate 4 provide nutrients for mold growth. For these reasons, in order to inhibit mold growth, it is necessary to remove the mold and organic contaminants attached to the surface of the substrate 4 and the walls of the pores 5 inside the substrate 4.

[0063] The coating composition of Embodiment 2, when applied to the substrate 4, uses a chlorine-based bleach to decompose and remove mold and organic contaminants attached to the surface of the substrate 4 and the walls of the pores 5. Specifically, the chlorine-based bleach that penetrates into the substrate 4 through capillary action in the pores 5 decomposes and removes mold and organic contaminants attached to the inside of the substrate 4. In addition, the chlorine-based bleach that does not penetrate into the inside of the substrate 4 remains on the surface of the substrate 4 together with the silica particles 2 and fluororesin particles 3, thereby decomposing and removing mold and organic contaminants attached to the surface of the substrate 4.

[0064] The water contained in the coating composition gradually evaporates upon contact with air. The coating composition comes into contact with air on the surface of the substrate 4 to which the coating composition is applied, and in the pores 5 inside the substrate 4 into which the coating composition has permeated. Here, the chlorine-based bleach on the surface of the substrate 4 decomposes along with mold and organic contaminants as the water on the surface of the substrate 4 evaporates. As the water on the surface of the substrate 4 evaporates, the silica particles 2 and fluororesin particles 3 on the surface of the substrate 4 adhere to each other, forming a coating film 1. Meanwhile, the water that has permeated into the pores 5 evaporates from the surface of the coating film 1 through the fine voids in the coating film 1.

[0065] Furthermore, airflow is restricted in the pores 5 inside the substrate 4 compared to the surface of the substrate 4. Also, the contact area between the liquid that penetrates the pores 5 and the air is often smaller than the contact area between the liquid and air on the surface of the substrate 4. Therefore, the evaporation rate of the liquid in the pores 5 may be slower than the evaporation rate of the liquid on the surface of the substrate 4. As a result, mold and organic contaminants in the pores 5 inside the substrate 4 are exposed to the chlorine bleach solution for a long time. This results in excellent mold prevention performance not only on the surface of the substrate 4 but also inside it. [Examples]

[0066] The following describes examples of coating compositions according to Embodiments 1 and 2. Figure 5 is a diagram showing multiple examples of the proportion of constituent elements in the coating composition according to Embodiment 1. In Figure 5, these multiple examples are shown in a table format. Figure 5 also shows the proportion of constituent elements in each of the coating compositions according to several comparative examples.

[0067] The coating compositions according to Examples 1 to 9 in Figure 5 contain sodium hypochlorite as a chlorine-based bleaching agent. The coating compositions of Examples 1 to 3 contain 1.0% by mass of silica particles 2 and 0.8% by mass of fluororesin particles 3. The coating composition of Example 1 contains 1.000% by mass of sodium hypochlorite, the coating composition of Example 2 contains 0.001% by mass of sodium hypochlorite, and the coating composition of Example 3 contains 4.000% by mass of sodium hypochlorite. The silica particles 2 contained in the coating compositions of Examples 1 to 3 are spherical and have an average particle size of 6 nm. The fluororesin particles 3 contained in the coating compositions of Examples 1 to 3 are PTFE particles with an average particle size of 250 nm. The coating compositions of Examples 1 to 3 are prepared by stirring and mixing pure water, colloidal silica containing the silica particles 2, and PTFE dispersion containing the PTFE particles, and then further adding and stirring an aqueous sodium hypochlorite solution containing sodium hypochlorite.

[0068] The coating composition of Example 4 contains 1.0% by mass of silica particles 2, 0.8% by mass of fluororesin particles 3, and 0.500% by mass of sodium hypochlorite. The coating composition of Example 5 contains 0.2% by mass of silica particles 2, 0.1% by mass of fluororesin particles 3, and 0.500% by mass of sodium hypochlorite. The coating composition of Example 6 contains 4.0% by mass of silica particles 2, 3.2% by mass of fluororesin particles 3, and 2.000% by mass of sodium hypochlorite. The silica particles 2 contained in the coating compositions of Examples 4 to 6 are spherical and have an average particle size of 20 nm. The fluororesin particles 3 contained in the coating compositions of Examples 4 to 6 are PTFE particles with an average particle size of 1000 nm. The coating compositions according to Examples 4 to 6 are prepared by stirring and mixing pure water, colloidal silica containing the silica particles 2, and PTFE dispersion containing the PTFE particles, and then further adding an aqueous sodium hypochlorite solution containing sodium hypochlorite and stirring and mixing.

[0069] The coating composition of Example 7 contains 2.0% by mass of silica particles 2, 2.0% by mass of fluororesin particles 3, and 1.000% by mass of sodium hypochlorite. The coating composition of Example 8 contains 1.0% by mass of silica particles 2, 1.5% by mass of fluororesin particles 3, and 1.000% by mass of sodium hypochlorite. The coating composition of Example 9 contains 1.0% by mass of silica particles 2, 0.3% by mass of fluororesin particles 3, and 1.000% by mass of sodium hypochlorite. The silica particles 2 contained in the coating compositions of Examples 7 to 9 are spherical and have an average particle size of 6 nm. The fluororesin particles 3 contained in the coating compositions of Examples 7 to 9 are PTFE particles with an average particle size of 8000 nm. The coating compositions according to Examples 7 to 9 are prepared by stirring and mixing pure water, colloidal silica containing the silica particles 2, and PTFE dispersion containing the PTFE particles, and then further adding an aqueous sodium hypochlorite solution containing sodium hypochlorite and stirring and mixing.

[0070] The coating composition according to Comparative Example 1, shown in the table in Figure 5, contains PTFE particles with an average particle size of 20,000 nm as fluororesin particles 3. The coating composition according to Comparative Example 1 was prepared by stirring and mixing pure water with a PTFE dispersion containing the PTFE particles. The coating composition of Comparative Example 1 contains 0.8% by mass of fluororesin particles 3.

[0071] The coating composition according to Comparative Example 2, shown in the table in Figure 5, contains PTFE particles with an average particle size of 250 nm as fluororesin particles 3, and sodium hypochlorite as a chlorine-based bleaching agent. The silica particles 2 contained in the coating composition according to Comparative Example 2 are spherical and have an average particle size of 10 nm. The coating composition according to Comparative Example 2 is prepared by stirring and mixing pure water, colloidal silica containing the silica particles, and PTFE dispersion containing the PTFE particles, and then further adding and stirring an aqueous sodium hypochlorite solution containing sodium hypochlorite. The coating composition of Comparative Example 2 contains 1.0% by mass of silica particles 2, 1.0% by mass of fluororesin particles 3, and 10.000% by mass of sodium hypochlorite.

[0072] The coating composition according to Comparative Example 3, shown in the table in Figure 5, contains sodium hypochlorite as a chlorine-based bleaching agent. The silica particles 2 contained in the coating composition according to Comparative Example 3 are spherical and have an average particle size of 30 nm. The coating composition according to Comparative Example 3 is prepared by stirring and mixing pure water and colloidal silica containing the silica particles 2, and then further adding and stirring an aqueous sodium hypochlorite solution containing sodium hypochlorite. The coating composition of Comparative Example 3 contains 10.0% by mass of silica particles 2 and 1.000% by mass of sodium hypochlorite.

[0073] Liquid stability evaluation experiments were conducted for the coating compositions of Examples 1 to 9 and Comparative Examples 1 to 3. Furthermore, after applying the coating compositions of Examples 1 to 9 and Comparative Examples 1 to 3 to a substrate 4 by dipping, the substrate 4 was placed in a sample stand and air-dried at room temperature for approximately 10 minutes to form a coating film 1 on the substrate 4. In this experiment, a polypropylene substrate was used as the substrate 4.

[0074] The evaluation results for the liquid stability of the coating compositions of Examples 1 to 9 and Comparative Examples 1 to 3, and the evaluation results for the properties, antifouling performance, weather resistance, and antifungal performance of the coating film 1 obtained from these coating compositions will be described below with reference to Figure 6. Figure 6 is a diagram illustrating the evaluation results for the coating compositions of Examples 1 to 9 and Comparative Examples 1 to 3. In Figure 6, the evaluation results for Examples 1 to 9 and Comparative Examples 1 to 3 are shown in table format.

[0075] Here, the liquid stability of the coating composition was evaluated by visual observation. Furthermore, the properties of the coating film 1 were evaluated by visual observation and observation using an existing scanning electron microscope (Hitachi High-Tech Corporation; SU3800).

[0076] Figure 6 shows the antifouling performance in terms of sand and dust adhesion and dust adhesion. Sand and dust adhesion corresponds to the adhesion of hydrophilic dirt. Sand and dust adhesion was evaluated as follows: A predetermined amount of Kanto loam dust was blown onto the surface of coating film 1 with air, and the discoloration caused by the adhesion of the Kanto loam dust was visually observed and evaluated on a 5-point scale. In this 5-point scale, a higher number indicates a greater amount of Kanto loam dust adhesion, with 1 indicating almost no Kanto loam dust adhesion and 5 indicating a large amount of Kanto loam dust adhesion.

[0077] Dust adhesion refers to the adhesion of hydrophobic dirt. The dust adhesion was evaluated as follows: A predetermined amount of carbon black was sprayed onto the surface of coating film 1 using compressed air, and the coloring due to carbon black adhesion was visually observed and evaluated on a 5-point scale. In this 5-point scale, a higher number indicates a greater amount of carbon black adhesion, with 1 indicating almost no carbon black adhesion and 5 indicating a large amount of carbon black adhesion.

[0078] The weather resistance was evaluated as follows: Using an existing accelerated weathering tester (Iwasaki Electric Co., Ltd.; XER-W83), the coating film 1 was exposed to a light source for 100 hours, and discoloration was visually observed and evaluated on a 5-point scale. In this 5-point scale, a higher number was used to indicate a greater degree of discoloration. Using the color of the substrate 4 on which the coating film 1 was not formed as a reference, a score of 1 indicated that there was almost no difference in color from the reference, and a score of 5 indicated that there was significant discoloration and a large difference in color from the reference.

[0079] The antifungal performance was evaluated as follows. The coating compositions of Examples 1 to 9 and Comparative Examples 1 to 3 were applied to the substrate 4 by dipping. After the coating composition was applied, the substrate 4 was placed in a sample stand and air-dried at room temperature for about 10 minutes to form a coating film 1 on the substrate 4. Then, the coating film 1 was exposed to dust containing molds such as Aspergillus oryzae, Penicillium fuciformis, and Trichoderma, and the molds were cultured at a temperature of 35°C and a humidity of 90% for 168 hours. Subsequently, the growth status of the molds on the surface of the coating film 1 was evaluated on a 5-point scale by visual observation and observation using an existing optical microscope (Olympus Corporation; DSX1000). In this 5-point scale evaluation, a higher number indicates a greater degree of mold growth, with 1 representing the minimum degree of mold growth and 5 representing the maximum degree of mold growth.

[0080] As shown in Figure 6, the coating compositions of Examples 1 to 9 and Comparative Examples 1 and 3 were confirmed to have high stability as liquids without the occurrence of aggregation or precipitation. In contrast, the coating composition of Comparative Example 2 contained an excessive amount of sodium hypochlorite, resulting in aggregation and precipitation, and thus the stability as a liquid could not be ensured.

[0081] In each of the coating compositions in Examples 1 to 9 and Comparative Example 1, a uniform coating film 1 was formed on the substrate 4. In contrast, the coating composition of Comparative Example 2 failed to form a film on the substrate 4 because aggregation and precipitation occurred in the liquid. Furthermore, in the coating composition of Comparative Example 3, since the silica particles 2 were coarse spherical particles with an average particle size exceeding 25 nm, an uneven coating film 1 was formed on the substrate 4. As a result, the obtained coating film 1 was prone to cracking and peeling.

[0082] The coating films 1 obtained from the coating compositions of Examples 1 to 9 showed lower values ​​in evaluations of sand and dust adhesion, dust adhesion, and mold resistance compared to the coating films 1 obtained from the coating compositions of Comparative Examples 1 and 3. In other words, the coating films 1 obtained from the coating compositions of Examples 1 to 9 had better antifouling and mold resistance than the coating films 1 obtained from the coating compositions of Comparative Examples 1 and 3. In particular, the coating film 1 obtained from the coating composition of Example 1 showed the best sand and dust adhesion, dust adhesion, and mold resistance.

[0083] The weather resistance of the coating film 1 obtained from the coating compositions of Examples 1 to 9 was evaluated to be 1, which was good.

[0084] Next, examples of the coating composition according to Embodiment 2 will be described with reference to Figure 7. Figure 7 is a diagram showing multiple examples of the proportion of constituent elements in the coating composition according to Embodiment 2. In addition, these multiple examples are shown in a table format in Figure 7. Figure 7 also shows the proportion of constituent elements in the coating composition according to Embodiment 1 for comparison with Embodiment 2. Furthermore, Figure 7 also shows the proportion of constituent elements in the coating composition according to Comparative Example 4.

[0085] The coating compositions in Examples 10 to 11 and Comparative Example 4 in Figure 7 each contain sodium hypochlorite as a chlorine-based bleaching agent. Each coating composition in Examples 10 to 11 and Comparative Example 4 contains 1.0% by mass of silica particles 2 and 0.8% by mass of fluororesin particles 3. The coating composition in Example 10 contains 1.000% by mass of sodium hypochlorite, while each coating composition in Example 11 and Comparative Example 4 contains 2.000% by mass of sodium hypochlorite.

[0086] The silica particles 2 contained in the coating composition according to Example 10 are needle-shaped and have an average particle size of 100 nm. The fluororesin particles 3 contained in the coating composition according to Example 10 are PTFE particles with an average particle size of 250 nm. The coating composition according to Example 10 is prepared by stirring and mixing pure water, colloidal silica containing the silica particles, and PTFE dispersion containing the PTFE particles, and then further adding an aqueous sodium hypochlorite solution containing sodium hypochlorite and stirring and mixing.

[0087] The silica particles 2 contained in the coating composition according to Example 11 are bead-like and have an average particle size of 400 nm. The fluororesin particles 3 contained in the coating composition according to Example 11 are PTFE particles with an average particle size of 250 nm. The coating composition according to Example 11 is prepared by stirring and mixing pure water, colloidal silica containing the silica particles, and PTFE dispersion containing the PTFE particles, and then further adding and stirring an aqueous sodium hypochlorite solution containing sodium hypochlorite.

[0088] The silica particles 2 contained in the coating composition of Comparative Example 4 are flaky and have an average particle size of 1000 nm. The fluororesin particles 3 contained in the coating composition of Comparative Example 4 are PTFE particles with an average particle size of 250 nm. The coating composition of Comparative Example 4 is prepared by stirring and mixing pure water, colloidal silica containing the silica particles, and PTFE dispersion containing the PTFE particles, and then further adding an aqueous sodium hypochlorite solution containing sodium hypochlorite and stirring and mixing.

[0089] Liquid stability evaluation experiments were conducted for the coating compositions of Examples 10-11 and Comparative Example 4. The coating compositions of Examples 10-11 and Comparative Example 4 were applied to a substrate 4 by dipping. The substrate 4 was then placed in a sample stand and air-dried at room temperature for approximately 10 minutes to form a coating film 1 on the substrate 4. In this experiment, a polypropylene substrate was used as the substrate 4.

[0090] The evaluation results for the liquid stability of the coating compositions of Examples 10 to 11 and Comparative Example 4, and the evaluation results for the properties, antifouling performance, weather resistance, and antifungal performance of the coating film 1 obtained from these coating compositions, will be described below with reference to Figure 8. Figure 8 is a diagram illustrating the evaluation results for the coating compositions of Examples 10 to 11 and Comparative Example 4. For comparison, Figure 8 also shows the evaluation results for Example 1. Figure 8 shows the evaluation results for Example 1, Examples 10 to 11, and Comparative Example 4 in table format.

[0091] As shown in Figure 8, similar to Example 1, the coating compositions of Examples 10-11 and Comparative Example 4 were confirmed to have high stability as liquids without aggregation or precipitation. Also, similar to Example 1, a uniform coating film 1 was obtained on the substrate 4 using the coating compositions of Examples 10-11. On the other hand, in Comparative Example 4, since the silica particles 2 in the coating composition were coarse and irregularly shaped particles with an average particle size exceeding 500 nm, an uneven coating film 1 was formed on the substrate 4, cracks occurred in the coating film 1, and some of the coarse particles detached from the surface.

[0092] As shown in Figure 8, the coating films 1 obtained from the coating compositions of Examples 10 to 11 showed lower values ​​in evaluations of sand and dust adhesion, dust adhesion, and antifungal performance compared to the coating film 1 obtained from the coating composition of Comparative Example 4, indicating good antifouling and antifungal performance. Furthermore, the weather resistance of the coating films obtained from the coating compositions of Examples 10 to 11 was also good.

[0093] The following describes other examples of the coating compositions according to Embodiments 1 and 2 with reference to Figure 9. Figure 9 is a diagram showing multiple examples of the proportions of constituent elements in the coating compositions according to Embodiments 1 and 2. In addition, these multiple examples are shown in a table format in Figure 9. Figure 9 also shows the proportions of constituent elements in the coating compositions according to Comparative Examples 5 to 7.

[0094] The coating compositions for Examples 12 to 14 and Comparative Examples 5 to 7 in Figure 9 each contain sodium hypochlorite as a chlorine-based bleaching agent. The coating compositions for Examples 12, 14, and Comparative Examples 5 to 7 contain 1.000% by mass of sodium hypochlorite, while the coating composition for Example 13 contains 2.000% by mass of sodium hypochlorite. The coating composition for Example 12 contains 4.0% by mass of silica particles 2 and 0.4% by mass of fluororesin particles 3. The coating compositions for Examples 13 to 14 contain 2.0% by mass of silica particles 2 and 1.6% by mass of fluororesin particles 3. The coating compositions for Comparative Examples 5 to 7 contain 1.0% by mass of silica particles 2 and 0.8% by mass of fluororesin particles 3.

[0095] The silica particles 2 contained in the coating composition according to Example 12 are spherical and have an average particle size of 20 nm. The fluororesin particles 3 contained in the coating composition according to Example 12 are PTFE particles with an average particle size of 1000 nm. The coating composition according to Example 12 is prepared by stirring and mixing pure water, colloidal silica containing the silica particles, and PTFE dispersion containing the PTFE particles, and then further adding an aqueous sodium hypochlorite solution containing sodium hypochlorite and stirring and mixing.

[0096] The silica particles 2 contained in the coating composition according to Example 13 are needle-shaped and have an average particle size of 100 nm. The fluororesin particles 3 contained in the coating composition according to Example 12 are PTFE particles with an average particle size of 250 nm. The coating composition according to Example 13 is prepared by stirring and mixing pure water, colloidal silica containing the silica particles, and PTFE dispersion containing the PTFE particles, and then further adding an aqueous sodium hypochlorite solution containing sodium hypochlorite and stirring and mixing.

[0097] The silica particles 2 contained in the coating composition according to Example 14 are bead-like and have an average particle size of 400 nm. The fluororesin particles 3 contained in the coating composition according to Example 14 are PTFE particles with an average particle size of 250 nm. The coating composition according to Example 14 is prepared by stirring and mixing pure water, colloidal silica containing the silica particles, and PTFE dispersion containing the PTFE particles, and then further adding an aqueous sodium hypochlorite solution containing sodium hypochlorite and stirring and mixing.

[0098] The silica particles 2 contained in the coating composition of Comparative Example 5 are spherical and have an average particle size of 30 nm. The fluororesin particles 3 contained in the coating composition of Comparative Example 5 are PTFE particles with an average particle size of 250 nm. The coating composition of Comparative Example 5 is prepared by stirring and mixing pure water, colloidal silica containing the silica particles, and PTFE dispersion containing the PTFE particles, and then further adding an aqueous sodium hypochlorite solution containing sodium hypochlorite and stirring and mixing.

[0099] The silica particles 2 contained in the coating composition of Comparative Example 6 are spherical and have an average particle size of 100 nm. The fluororesin particles 3 contained in the coating composition of Comparative Example 6 are PTFE particles with an average particle size of 250 nm. The coating composition of Comparative Example 6 is prepared by stirring and mixing pure water, colloidal silica containing the silica particles, and PTFE dispersion containing the PTFE particles, and then further adding an aqueous sodium hypochlorite solution containing sodium hypochlorite and stirring and mixing.

[0100] The silica particles 2 contained in the coating composition of Comparative Example 7 are needle-shaped and have an average particle size of 1000 nm. The fluororesin particles 3 contained in the coating composition of Comparative Example 7 are PTFE particles with an average particle size of 250 nm. The coating composition of Comparative Example 7 is prepared by stirring and mixing pure water, colloidal silica containing the silica particles, and PTFE dispersion containing the PTFE particles, and then further adding an aqueous sodium hypochlorite solution containing sodium hypochlorite and stirring and mixing.

[0101] Liquid stability evaluation experiments were conducted for the coating compositions of Examples 12 to 14 and Comparative Examples 5 to 7. Furthermore, after applying the coating compositions of Examples 12 to 14 and Comparative Examples 5 to 7 to a substrate 4 by dipping, the substrate 4 was placed in a sample stand and allowed to air dry to form a coating film 1 on the substrate 4. In this experiment, a porous substrate, gypsum board, was used as the substrate 4.

[0102] The following describes the evaluation results of the liquid stability of the coating compositions of Examples 12 to 14 and Comparative Examples 5 to 7, as well as the evaluation results of the properties, antifouling performance, weather resistance, and antifungal performance of the coating film 1 obtained from these coating compositions, with reference to Figure 10. Figure 10 is an example of the evaluation results of the coating compositions related to Examples 12 to 14 and Comparative Examples 5 to 7. In Figure 10, the evaluation results of Examples 12 to 14 and Comparative Examples 5 to 7 are shown in table format.

[0103] As shown in Figure 10, the coating compositions of Examples 12 to 14 and Comparative Examples 5 to 7 were confirmed to have high stability as liquids without aggregation or precipitation. Furthermore, a uniform coating film 1 could be formed on a gypsum board substrate from the coating compositions of Examples 12 to 14.

[0104] On the other hand, in Comparative Examples 5 to 6, since the silica particles 2 in the coating composition were coarse spherical particles with an average particle size exceeding 25 nm, an uneven coating film 1 was formed on the gypsum board substrate. This coating film 1 cracked and peeled off easily. In Comparative Example 7, since the silica particles 2 in the coating composition were coarse, irregularly shaped particles with an average particle size exceeding 500 nm, an uneven coating film 1 was formed on the gypsum board substrate. As a result, this coating film 1 cracked, and some of the coarse particles detached from the surface.

[0105] The coating films 1 obtained from the coating compositions of Examples 12 to 14 showed lower values ​​in evaluations of sand and dust adhesion, dust adhesion, and mold resistance compared to the coating films 1 obtained from the coating compositions of Comparative Examples 5 to 7, indicating better antifouling and mold resistance. In particular, the coating composition according to Example 13 showed the best sand and dust adhesion, dust adhesion, and mold resistance. Furthermore, the weather resistance of the coating films 1 obtained from the coating compositions of Examples 12 to 14 was good.

[0106] The effects of the coating composition, coating method, and mold treatment method according to Embodiments 1 and 2 are described below. The coating composition according to Embodiments 1 and 2 contains a plurality of silica particles 2 at a concentration of 5% by mass or less, a plurality of fluororesin particles 3, a chlorine-based bleach at a concentration of 0.001% by mass or more and 5% by mass or less, and water.

[0107] According to the above configuration, the multiple silica particles 2 and multiple fluororesin particles 3 contained in the coating composition are not decomposed by the chlorine-based bleach, thus ensuring the stability of the coating composition. Furthermore, since the proportion of chlorine-based bleach in the coating composition is 5% by mass or less, precipitation due to aggregation of two or more fluororesin particles 3 is less likely to occur, ensuring the stability of the coating composition. In addition, since the silica particles 2 are hydrophilic, hydrophobic dirt is less likely to adhere to the coating film 1, and since the fluororesin particles 3 are hydrophobic, hydrophilic dirt is less likely to adhere to the coating film 1. Furthermore, since the coating composition contains 0.001% by mass or more of chlorine-based bleach, decomposition of mold and organic contaminants is possible on the surface of the substrate 4 to be coated, and on the surface and interior of the coating film 1. Therefore, high antifouling performance is obtained by the multiple silica particles 2, multiple fluororesin particles 3, and chlorine-based bleach, thereby improving antifungal performance. Furthermore, since the content of multiple silica particles 2 in the coating composition is 5% by mass or less, peeling of the coating film 1 is suppressed, and antifouling and antifungal properties are maintained. Therefore, according to the coating composition and coating method of Embodiments 1 and 2, the stability of the coating composition is ensured, and it becomes possible to produce a coating film 1 having high antifouling and antifungal properties. In addition, because the coating film 1 contains silica particles 2 with low light scattering, the transparency of the coating film 1 is improved, so even when the coating film 1 is applied to the substrate 4, changes in the color tone and texture of the substrate 4 can be suppressed. Accordingly, the design quality of the substrate 4 is ensured by maintaining the color tone and texture of the substrate 4 due to the transparency of the coating film 1, suppressing pigment deposition due to the high antifungal properties mentioned above, suppressing peeling of the coating film 1, and the high weather resistance of the coating film 1.

[0108] In Embodiment 1, the average particle size of the plurality of silica particles 2 is 25 nm or less, and each of the plurality of silica particles 2 is a spherical particle. Because the average particle size of the silica particles 2 in the coating composition is 25 nm or less, the silica particles 2 tend to aggregate with each other during the formation of the coating film 1 by drying, making it easier to solidify the coating composition. In addition, compared to the case where the average particle size of the silica particles 2 is longer than 25 nm, there are more silica particles 2 dissolved in equilibrium in the coating composition, making it possible to form a uniform and high-strength coating film 1 with suppressed cracking and peeling.

[0109] In Embodiment 2, the average particle size of the multiple silica particles 2 is 50 nm or more and 1000 nm or less, and each of the multiple silica particles 2 is a non-standard particle with a needle-like, flake-like, chain-like, bead-like, or pearl necklace-like shape. Because the average particle size of the silica particles 2 is 50 nm or more, the penetration of the silica particles 2 into the substrate 4 by capillary action is suppressed in the substrate 4 which has water absorption or porous properties. Therefore, it becomes possible to control the ratio of silica particles 2 to fluororesin particles 3 on the surface of the substrate 4, and the coating film 1 can maintain high antifouling performance. In addition, the non-standard silica particles 2 overlap, intertwine, and adhere to each other in the coating film 1, resulting in a coating film 1 with sufficient strength.

[0110] The average particle size of the multiple fluororesin particles 3 in Embodiments 1 and 2 is 50 nm or more and 10,000 nm or less. As a result, the fluororesin particles 3 are appropriately dispersed within the coating composition, resulting in a stable coating composition. Furthermore, they are more easily exposed on the surface of the coating film 1, resulting in good antifouling performance.

[0111] In Embodiments 1 and 2, the mass ratio of the multiple silica particles 2 to the multiple fluororesin particles 3 is in the range of 40:60 to 95:5. As a result, a coating film 1 with good antifouling performance is obtained by drying at room temperature, in which hydrophilic portions due to the silica particles 2 and hydrophobic portions due to the fluororesin particles 3 are well mixed.

[0112] Although embodiments have been described above, the contents of this disclosure are not limited to these embodiments and include a range of equivalent embodiments. Furthermore, the configurations and their variations described in Embodiments 1 and 2 can be combined with each other to the extent that they do not impede function and operation. [Explanation of Symbols]

[0113] 1. Coating film, 2. Silica particles, 3. Fluororesin particles, 4. Substrate, 5. Pores.

Claims

1. Silica particles of 5% by mass or less, Fluororesin particles and A chlorine-based bleaching agent in an amount of 0.001% by mass or more and 5% by mass or less, Water and, A coating composition containing the following:

2. The coating composition according to claim 1, wherein the average particle size of the silica particles is 25 nm or less, and the silica particles are spherical particles.

3. The coating composition according to claim 1, wherein the average particle size of the silica particles is 50 nm or more and 1000 nm or less, and the silica particles are irregularly shaped particles such as needle-shaped, flake-shaped, chain-shaped, bead-shaped, or pearl necklace-shaped.

4. The coating composition according to any one of claims 1 to 3, wherein the average particle size of the fluororesin particles is 50 nm or more and 10,000 nm or less.

5. The coating composition according to any one of claims 1 to 3, wherein the mass ratio of the silica particles to the fluororesin particles is in the range of 40:60 to 95:

5.

6. A method for coating a substrate, A coating method comprising applying a coating composition containing 5% by mass or less of silica particles, fluororesin particles, 0.001% by mass or more and 5% by mass or less of a chlorine-based bleaching agent, and water to a substrate to form a coating film on the surface of the substrate.

7. A method for treating mold, comprising applying a coating composition containing 5% by mass or less of silica particles, fluororesin particles, 0.001% by mass or more and 5% by mass or less of a chlorine-based bleaching agent, and water to a substrate.

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