WO2024247107A1 - Coating composition, coating method, and mold treatment method - Google Patents

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

Coating composition, coating method, and mold treatment method

The present disclosure relates to a coating composition for producing a film that inhibits contamination of a substrate, a method for coating a substrate, and a method for treating mold on a substrate.

Various types of dirt, such as dust, oily smoke, and mold, adhere to the surfaces of various items used indoors or outdoors. In particular, mold adheres to the surface of items and grows on dust and oily smoke as nutrients, causing dirt. Therefore, in order to achieve a high level of dirt prevention, it is necessary to inhibit the growth of mold, and there is a demand for technology that inhibits the adhesion and growth of mold.

Patent Document 1 describes a coating composition that contains an antifungal agent and forms a film that coats a substrate, thereby inhibiting the adhesion and growth of mold on the substrate.

JP 2011-57855 A

However, Patent Document 1 does not mention any technology for preventing the adhesion of dust, oily smoke, mold, etc. to the surface of the coating film obtained from the coating composition. When dust or oily smoke, which serve as nutrients for mold, accumulates on the surface of the coating film, mold can easily grow as it adheres to the accumulated dirt.

Patent Document 1 also discloses sodium hypochlorite as an antibacterial agent contained in the coating composition, and an organic compound as the antibacterial agent or the above-mentioned antifungal agent, but when an organic compound and sodium hypochlorite are contained in a coating composition, there is a possibility that the organic compound will be decomposed by the sodium hypochlorite. As a result, there is a risk that the stability of the coating composition will decrease.

The present disclosure has been 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 to inhibit adhesion of dirt such as dust and mold, and antifungal performance to inhibit the growth of mold, a method for coating a substrate, and a method for treating mold on a substrate.

The coating composition according to the present disclosure contains 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.

The coating method according to the present disclosure is a method for coating a substrate, in which a coating composition containing 5% or less by mass of silica particles, fluororesin particles, 0.001% or more by mass and 5% or less by mass of a chlorine bleaching agent, and water is applied to the substrate to form a coating film on the surface of the substrate.

The mold treatment method disclosed herein involves applying to a substrate a coating composition that contains 5% or less silica particles, fluororesin particles, 0.001% or more and 5% or less chlorine bleach, and water.

The coating composition, coating method, and mold treatment method disclosed herein can ensure the stability of the coating composition, and can also produce a coating film with improved stain-proofing and mold-proofing properties, thereby suppressing the adhesion and proliferation of mold on the substrate.

1 is a schematic cross-sectional view of a coating film obtained from a coating composition according to embodiment 1. FIG. FIG. 2 is a top view schematic diagram illustrating a coating film obtained from the coating composition according to the first embodiment. FIG. 4 is a schematic top view showing a coating film in a comparative example. FIG. 11 is a schematic cross-sectional view illustrating a coating film formed on a substrate having water absorbency or porosity by the coating composition according to the second embodiment. FIG. 2 is a diagram showing several examples of the proportions of components in a coating composition according to the first embodiment. FIG. 1 is a diagram showing evaluation results of coating compositions according to Examples 1 to 9 and Comparative Examples 1 to 3. FIG. 13 shows several examples of the proportions of components in a coating composition according to embodiment 2. FIG. 1 is a diagram showing evaluation results of coating compositions according to Examples 10 to 11 and Comparative Example 4. FIG. 2 is a diagram showing several examples of the ratio of components in a coating composition according to the first and second embodiments. FIG. 1 is a diagram showing evaluation results of coating compositions according to Examples 12 to 14 and Comparative Examples 5 to 7.

The coating composition according to the embodiment will be described below with reference to the drawings. Note that in the drawings, the relative dimensional relationships and shapes of the components may differ from the actual ones. In the drawings, components with the same reference numerals are the same or correspond to each other. The components in the embodiment are merely examples and are not limited to these.

Embodiment 1.
1 is a schematic cross-sectional view of a coating film 1 obtained from a 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 contains a plurality of silica particles 2, a plurality of fluororesin particles 3, and 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 scattered in the silica film.

Chlorine bleach breaks down mold and organic contaminants. The organic contaminants are oily soot, sebum, keratin, etc., which serve as nutrients for mold. In the coating composition applied to the surface of the substrate 4, the chlorine bleach breaks down mold and organic contaminants attached to the surface of the substrate 4, and also breaks down mold and organic contaminants that have diffused from the surface of the substrate 4 into the coating composition. The chlorine bleach also breaks down mold and organic contaminants that have attached to the coating composition from the surrounding environment, such as the atmosphere. This provides a disinfecting effect on the surface of the substrate 4, a blocking effect on the supply of organic contaminants that serve as nutrients to the mold, and an inhibitory effect on the growth of mold on the surface of the substrate 4 and within the coating film 1. The chlorine bleach also breaks down mold and other substances on the surface of the substrate 4, thereby maintaining or improving the adhesion of the coating film 1 to the surface of the substrate 4 and maintaining the design of the substrate 4. The chlorine bleach breaks down mold and organic contaminants in the coating composition as well as mold and organic contaminants from the surrounding environment, thereby maintaining or improving the strength of the coating film 1.

The chlorine bleach becomes concentrated as the water contained in the coating composition applied to the surface of the substrate 4 evaporates, and the concentration of the chlorine bleach increases. As a result, the chlorine bleach naturally decomposes and is no longer contained in the coating film 1.

The content of the chlorine bleach in the coating composition is 0.001 to 5.0% by mass, preferably 0.01 to 3.0% by mass. A content in this range can decompose mold and organic contaminants, and can provide a stable coating composition. If the content of the chlorine bleach is less than 0.001% by mass, there is a risk that mold and organic contaminants on the surface of the substrate 4 and on the surface and inside of the coating composition cannot be decomposed. On the other hand, if the content of the chlorine bleach is 5.0% by mass or more, the dispersibility of the silica particles 2 and fluororesin particles 3 in the coating composition may decrease, which may cause the silica particles 2 and fluororesin particles 3 to aggregate and precipitate, and the stability of the coating composition may not be ensured.

Chlorine bleaches include hypochlorous acid, sodium hypochlorite, lithium hypochlorite, potassium hypochlorite, calcium hypochlorite, sodium dichloroisocyanurate, or potassium dichloroisocyanurate. The chlorine bleach may be any mixture of two or more of these.

Before the coating composition is applied, the substrate 4 is contaminated with mold and organic contaminants. Mold adheres to the substrate 4 surface as spores or hyphae. Mold and organic contaminants adhered to the substrate 4 surface not only impair the hygiene and cleanliness of the item, but also discolor the item due to the pigments they contain, impairing the design of the item. Mold grows in soil and plants around the world and releases spores into the air. Therefore, items placed outdoors are exposed to spores floating in the air. On the other hand, items inside the room are exposed to spores and the like due to living things such as humans and pets, as well as the entrance and exit of items. Mold grows when spores attached to the substrate 4 surface germinate and hyphae grow. Mold also grows when hyphae grow from dirt containing mold attached to the substrate 4. Organic contaminants that serve as nutrients for mold also adhere to the substrate 4 surface. Organic contaminants attached to the base material 4 serve as nutrients for mold to grow. Therefore, to prevent mold growth, it is necessary to remove the mold and organic contaminants.

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 in the coating composition applied to the substrate 4. When the chlorine bleach reaches the mold, it alters and decomposes the cell walls, cell membranes, cytoplasm, and enzymes, thereby removing and decomposing the mold. The chlorine bleach also alters and decomposes the organic components that make up the organic contaminants, thereby removing and decomposing the organic contaminants. The chlorine bleach decomposes the pigments contained in the mold and organic contaminants while decomposing and removing them. This provides a bleaching effect. As the moisture contained in the coating composition evaporates, the concentration of the chlorine bleach increases, and the performance as an oxidizing agent that decomposes mold and organic contaminants is further improved. Furthermore, as the concentration of the chlorine bleach increases, the natural decomposition rate also increases, so that the chlorine bleach disappears from the coating film 1.

The silica film in the coating film 1 of the embodiment is a dense film with fine voids because the silica particles 2 are fine particles and have a large surface area per unit volume. The silica film suppresses the adhesion and fixation of dirt such as dust caused by static electricity. In particular, the silica particles 2 are hydrophilic, making it difficult for hydrophobic dirt to adhere and fix. In the coating film 1 of the embodiment, the fluororesin particles 3 scattered throughout the silica film are hydrophobic, making it difficult for hydrophilic dirt to adhere and fix.

The coating film 1 is obtained by evaporating the water contained in the coating composition applied to the surface of the substrate 4. The coating film 1 can obtain anti-fouling properties that make it difficult for mold, organic contaminants, etc. to adhere and adhere due to the silica particles 2 and fluororesin particles 3. In addition to the anti-fouling properties, the coating film 1 can also obtain anti-mold properties due to the decomposition effect of the chlorine bleach on mold, organic contaminants, etc.

The silica particles 2 are a stable inorganic component and are therefore not decomposed by chlorine bleach. The fluororesin particles 3 are a stable organic component with chemical resistance and are therefore not decomposed by chlorine bleach. Therefore, the coating composition according to the first embodiment has excellent stability.

As shown in FIG. 1, the shape of the silica particles 2 in the first embodiment is spherical. In addition, the average particle size of the silica particles 2 in the first embodiment is 4 nm or more and 25 nm or less when measured by a light scattering method. 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, and the coating composition is easily solidified. In addition, since the number of silica particles 2 dissolved in equilibrium in the coating composition increases, a coating film 1 with relatively high strength can be obtained without blending 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. In addition, 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.

The mass of the silica particles 2 contained in the coating composition according to the first embodiment is 0.1 to 5.0% of the total mass of the coating composition. Preferably, the mass of the silica particles 2 contained in the coating composition is 0.3 to 2.5% of the total mass of the coating composition. When the content of the silica particles 2 is 0.1 to 5.0%, a uniform and thin coating film can be formed without impairing the color tone and texture of the article surface. When the content of the silica particles 2 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, when the content of the silica particles 2 exceeds 5% by mass, the coating film becomes an uneven, cloudy film, cracks occur, and it becomes easy to peel off.

The fluororesin particles 3 in the first embodiment 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), and PVF (polyvinyl fluoride). The fluororesin particles 3 may be a copolymer or mixture of these, or may be a mixture of these fluororesins with other resins. Of the above, PTFE and FEP are preferred as the fluororesin particles 3 because of their excellent stability and high hydrophobicity.

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 a light scattering method. By including fluororesin particles 3 having an average particle size in this range in the coating composition, the fluororesin particles 3 are appropriately dispersed inside the coating film 1 and are easily exposed to the surface of the coating film 1, so that good antifouling performance can be obtained. 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 be difficult to expose to the surface of the coating film 1, so that the desired antifouling performance may not be obtained. On the other hand, if the average particle size of the fluororesin particles 3 exceeds 10,000 nm, the hydrophobic area in the resulting coating film 1 becomes large, and the unevenness of the coating film 1 becomes too large, so that the desired antifouling performance may not be obtained.

The mass ratio of the silica particles 2 to the fluororesin particles 3 contained in the coating composition according to the first embodiment is 40:60 to 95:5, and more preferably 50:50 to 90:10. If the mass ratio of the silica particles 22 to the fluororesin particles 3 is 40:60 to 95:5, a coating film 1 having a well-balanced mixture of hydrophilic portions originating from the silica particles 2 and hydrophobic portions originating from the fluororesin particles 3 can be obtained by drying at room temperature, and the coating film 1 has good antifouling performance.

FIG. 2 is a schematic top view illustrating a coating film 1 obtained from the coating composition according to the first embodiment. The mass ratio of the silica particles 2 to the fluororesin particles 3 contained in the coating film 1 in FIG. 2 is 75:25. As shown in FIG. 2, the fluororesin particles 3 are scattered in a silica film in which a plurality of silica particles 2 are aggregated. On the surface of the coating film 1 shown in FIG. 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, so that the film as a whole is hydrophilic. The hydrophilic portion on the surface of the coating film 1 plays an important role in improving the antifungal performance. The antifungal performance due to the hydrophilic portion on the surface of the coating film 1 will be described in detail below.

On the surface of the coating film 1, the hydrophilic parts are continuous without being divided by the hydrophobic parts. Therefore, when water droplets such as condensation water adhere to the surface of the coating film 1, the water droplets flow out through the hydrophilic parts as a flow path, and are easily discharged from the surface of the coating film 1. In addition, water droplets that adhere to the surface of the coating film 1 tend to spread thinly over the entire coating film 1, which allows the water droplets to volatilize easily. In general, the surface of an object on which water droplets continue to adhere is an environment in which mold is likely to grow. However, the coating film 1 of embodiment 1 has the property that water droplets that adhere to the surface are easily discharged and easily volatilized, and therefore the mold prevention performance can be improved. Furthermore, due to the property that droplets easily spread over the entire coating film 1, hydrophilic or hydrophobic dirt that adheres to the surface of the coating film 1 is removed by the flow of water droplets, or is difficult to adhere. In particular, dirt on the surface of the coating film 1 is easily removed during condensation, rainfall, cleaning, etc. In addition, since the coating film 1 of embodiment 1 is mainly composed of a continuous silica film, it is also possible to suppress electrostatic charging of the film surface, which causes dirt to be attracted. Furthermore, 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 the coating film 1.

On the other hand, if the ratio of silica particles 2 is greater than the above-mentioned range, the coating film 1 can effectively prevent the adhesion of hydrophobic dirt such as oily soot or carbon, but is prone to adhesion of hydrophilic dirt such as 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 dirt such as dust or dirt, but is prone to adhesion of hydrophobic dirt such as oily soot or carbon. Mold and organic contaminants contained in oily soot, carbon, dust, or dust adhere to the coating film 1, creating a habitat for mold, which results in a decrease in anti-mold performance.

Here, an example in which the mass ratio of the silica particles 2 and the fluororesin particles 3 contained in the coating film 1 is outside the above-mentioned range will be described with reference to FIG. 3. FIG. 3 is a schematic top view of the coating film 1 in a comparative example. In FIG. 3, the mass ratio of the silica particles 2 and the fluororesin particles 3 contained in the coating film 1 is 25:75. In the coating film 1 shown in FIG. 3, the ratio of the fluororesin particles 3 to the silica particles 2 is high, so there are many hydrophobic parts, and the hydrophilic parts are divided by the hydrophobic parts. Therefore, when water droplets adhere to the coating film 1, the flow of the water droplets is hindered by the hydrophobic parts, and the water droplets cannot flow out using the hydrophilic parts as a flow path, but remain on the surface of the coating film 1. In addition, the water droplets adhered to the surface of the coating film 1 are difficult to spread thinly over the entire coating film 1, so the time required for evaporation is long. Therefore, the coating film 1 as exemplified in FIG. 3 does not provide high antifungal performance and does not provide good antifouling performance.

Mold that flies into the coating film 1 from the surrounding environment includes mold that floats in the air as a single spore, 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 bridges with water, or intermolecular forces. Mold spores are minute particles with a particle size of 2 μm to 10 μm. In order 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, mold hyphae generally have a length of several tens of μm to several mm. Therefore, hydrophilic or hydrophobic dirt mixed with mold is a particle with a size of several tens of μm to several mm. In order 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, including mold, it is necessary to form a coating film 1 that does not have hydrophobic parts large enough for hydrophobic dirt to adhere.

Hydrophilic dirt such as sand and dust generally adheres to objects due to electrostatic bonding between hydrophilic groups, liquid bridges with water or the like, or intermolecular forces. Sand and dust are minute particles with diameters of several μm to several tens of μm, while dust is much larger than sand and dust. In order to prevent the adhesion of hydrophilic dirt due to electrostatic bonding between hydrophilic groups, it is necessary to form a coating film 1 that does not have hydrophilic portions large enough for hydrophilic dirt to adhere to.

Furthermore, hydrophobic dirt such as oil soot, carbon, sebum, or keratin generally adheres to objects by intermolecular forces or, in the presence of water, by hydrophobic bonds. Hydrophobic dirt is generally made up of minute particles with a diameter of 1 μm or less, and most of these particles have a diameter of 0.3 μm or less. If the surface of the coating film 1 is hydrophobic, hydrophobic dirt will adhere more easily. Furthermore, if the hydrophobic surface is covered with condensed water or the like and is in contact with hydrophobic dirt, the cohesive force of the water will create a hydrophobic bond between the surface and the hydrophobic dirt, and the hydrophobic dirt may adhere to the surface of the coating film 1.

In the first embodiment, by setting the mass ratio of the silica particles 2 and the fluororesin particles 3 contained in the coating composition to the above-mentioned range, it is possible to obtain a coating film 1 in which hydrophobic portions are appropriately dispersed in the hydrophilic portions, as shown in FIG. 2. As a result, the hydrophilic and hydrophobic portions in the coating film 1 of the first embodiment are of a size that makes it difficult for mold spores and mold-mixed dirt to adhere to them. Therefore, the coating film 1 of the first embodiment can suppress the adhesion of mold spores and mold-mixed dirt due to electrostatic bonding between hydrophilic groups or between hydrophobic groups. Therefore, it is possible to suppress the growth of mold on the surface of the coating film 1, and excellent mold prevention performance can be obtained.

In addition, in the first embodiment, by setting the mass ratio of the silica particles 2 and the fluororesin particles 3 contained in the coating composition to the above range, the hydrophobic parts are appropriately dispersed in the hydrophilic parts, and a coating film 1 is formed in which there are almost no hydrophilic parts of a size to which hydrophilic dirt can stably adhere, so that 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 the first embodiment, even if hydrophilic dirt adheres to the hydrophilic parts, the hydrophilic dirt cannot sufficiently adhere to the hydrophilic parts due to physical obstruction by the surface of the hydrophobic part adjacent to the hydrophilic part or the protrusions of the hydrophobic part. Therefore, the hydrophilic dirt is difficult to fix on the surface of the coating film 1. Furthermore, since the coating film 1 of the first embodiment is a porous coating film 1 composed of the silica particles 2 and the fluororesin particles 3, even if liquid bridges due to water or the like occur, the water between the silica particles 2 is easily removed quickly from the surface of the silica film in the drying process.

In addition, since the coating composition according to embodiment 1 does not contain binders or organic polymers as constituents, the state of the surface of the coating film 1 is not changed by, for example, precipitating the binders or organic polymers on the surface of the coating film 1 after the liquid bridge is eliminated. Furthermore, since the coating film 1 of embodiment 1 has extremely small voids and is a film with a low density, it is possible to suppress the adhesion of hydrophilic dirt due to intermolecular forces. Furthermore, by suppressing the adhesion of hydrophilic dirt, the coating film 1 of embodiment 1 suppresses the adhesion of nutrients necessary for mold growth, thereby inhibiting mold growth.

In the first embodiment, a coating film 1 is obtained in which hydrophobic portions are appropriately dispersed among hydrophilic portions, and therefore the hydrophilic groups on the surface of the coating film 1 or the presence of water adsorbed to the surface can suppress adhesion of hydrophobic dirt. Furthermore, the coating film 1 of the first embodiment can inhibit the adhesion of nutrients necessary for mold growth by suppressing the adhesion of hydrophobic dirt, thereby inhibiting mold growth.

Furthermore, since the coating film 1 of the first embodiment is composed of chemically stable silica particles 2 and fluororesin particles 3, it is possible to maintain antifouling performance for a long period of time, and therefore obtain sustained antifungal performance.

The coating composition according to the first embodiment contains water as a solvent, which is a volatile component. Here, if the amount of minerals contained in the water is large, it may become impossible to control the aggregation of the silica particles 2. In particular, if the concentration of ionic impurities in the water exceeds 200 ppm, the silica particles 2 may aggregate and precipitate. This may result in a decrease in the strength or transparency of the coating film 1. Therefore, from the viewpoint of the dispersion stability of the silica particles 2, it is preferable that the water in the coating composition contains a small amount of divalent or higher ionic impurities such as calcium ions or magnesium ions. Specifically, the water contained in the coating composition according to the first embodiment is preferably deionized water, but may also contain ionic impurities. In this case, the concentration of the ionic impurities is preferably 200 ppm or less, and more preferably 50 ppm or less.

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 contain an organic solvent or the like to adjust the stability, coatability, and drying properties of the coating composition.

In the first embodiment, when obtaining a coating composition by mixing chlorine bleach, silica particles 2, fluororesin particles 3, etc., the solution or dispersion of chlorine bleach, silica particles 2, fluororesin particles 3, etc. before mixing may be prevented from being a combination of a basic liquid with a pH of 8 or more and an acidic liquid with a pH of 6 or less. This can suppress aggregation or precipitation in the coating composition. Therefore, the coating film 1 obtained after drying of the coating composition applied to the substrate 4 becomes homogeneous. In addition, decomposition of the chlorine bleach before application of the coating composition can be suppressed.

The coating composition according to the first embodiment may contain various known components in the technical field of coatings, provided that the above-mentioned effects are not impaired. Examples of such components include surfactants, coupling agents, silane compounds, and antifungal agents. The amounts of these components are not particularly limited as long as they do not impair the above-mentioned effects, and may be adjusted appropriately depending on the types of components.

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

The method for producing a coating composition according to the first embodiment may include a method for adjusting the coating composition by redispersing the aggregates or precipitates using a homogenizer or a high-pressure dispersion processing device when aggregation or precipitation of components occurs due to mixing of multiple liquids. In addition, in order 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 initial mixing or re-dispersion. By mixing the materials in multiple stages in this way, a wide range of material combinations can be used when producing the coating composition, and by achieving an appropriate state of aggregation, the fluidity of the coating composition can be improved, or the density of the coating film 1 formed can be optimized, or the smoothness can be improved.

The coating composition may be obtained by mixing all the components at once, in which case it is stored in a container until use and applied to the substrate 4 without the need for processing. Alternatively, the coating composition may be obtained by mixing two or more pre-prepared liquids immediately before use. In the latter case, there is a method in which only the chlorine bleach, which is particularly susceptible to decomposition, is mixed with the other components of the coating composition immediately before use. This allows the effects of the chlorine bleach and other agents in the coating composition to be maintained even after long-term storage.

　Examples of the method of applying the coating composition of the first embodiment to the substrate 4 include a spray application method, a brush or roller bucket application method, and a dipping application method. Spray application methods include a method in which an already prepared 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. Brush or roller bucket application methods include a method in which two or more liquids are layered using separate application tools. Dipping application methods include a method in which two or more liquids are dipped in multiple stages.

In the method of applying the coating composition to the substrate 4 according to the first embodiment, the silica particles 2 are solidified by drying alone, so that heating or the like is not required, and it is possible to fix the fluororesin particles 3 to the silica film. Here, when drying the coating composition, excess coating composition may be removed from the substrate 4 by an airflow. In particular, by removing excess coating composition by an airflow, a thin coating film 1 in which the fluororesin particles 3 are uniformly dispersed in the silica film can be rapidly obtained.

As a method of applying the coating composition to the substrate 4, it is preferable to mix two or more kinds of 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 kinds of liquids for obtaining the coating composition to the surface of the substrate 4, mix the two or more kinds of liquids on the surface of the substrate 4, and generate the coating composition on the surface of the substrate 4. In this way, according to the method of forming a liquid film of the coating composition on the surface of the substrate 4 and drying the liquid film to obtain the coating film 1, it is possible to suppress the decomposition of chlorine-based bleach, which is easily decomposed. It is also possible to form the coating film 1 using a combination of coating compositions that cannot exist stably as a liquid, such as by coagulating when mixed. It is also possible to reduce the labor of the work. The coating film 1 obtained in this way can have little organic contamination and an appropriate porosity.

The formation of the coating film 1 containing the silica particles 2 and the fluororesin particles 3 and the decomposition of mold and organic matter by the chlorine bleach may be carried out separately. In other words, the chlorine bleach may be applied to the surface of the substrate 4 before or after the coating composition or two or more liquids constituting the coating composition are applied to the substrate 4.

The article serving as the substrate 4 to which the coating composition is applied is not particularly limited, but examples include various articles used indoors or outdoors that are subject to various hydrophilic or hydrophobic stains such as dust, oily smoke, mold, or organic contaminants. Depending on the article to which the coating film 1 is applied, the surface of the article may be pretreated with a detergent or alcohol, corona treatment, UV treatment, or other pretreatment, 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 contaminants, a pretreatment such as disinfection with a chlorine bleach may be applied.

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, and the coating composition may be applied to the side or back surface of the substrate 4, or to multiple surfaces.

Embodiment 2.
Hereinafter, a coating composition according to embodiment 2 will be described. In embodiment 2, the same components as those in embodiment 1 are denoted by the same reference numerals. In embodiment 2, the same configurations as those in embodiment 1 and the same functions as those in embodiment 1 will not be described unless there are special circumstances.

In the first embodiment, the silica particles 2 contained in the coating composition are spherical, but in the second embodiment, the silica particles 2 contained in the coating composition have irregular shapes such as needles, scales, chains, beads, or pearl necklaces. This makes it easier to form a coating film 1 with excellent antifouling properties even on the surface of a substrate 4 that is absorbent or porous, making it difficult to form a coating film 1.

FIG. 4 is a schematic cross-sectional view illustrating a coating film 1 formed on a substrate 4 having water absorption or porosity, etc., by the coating composition according to embodiment 2. As shown in FIG. 4, the coating film 1 formed from the coating composition according to embodiment 2 includes a silica film to which silica particles 2 are adhered, and fluororesin particles 3 dispersed in the silica film.

When the coating composition of the second embodiment is applied to a substrate 4 having water absorption or porosity, a part of the water and a part of the chlorine bleaching agent in the coating composition flow from the surface to the inside of the substrate 4 due to the capillary phenomenon 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 the silica particles 2 have a particle size that can block the pores 5 of the substrate 4, and are difficult to penetrate into the substrate 4. Therefore, the ratio of the silica particles 2 and the fluororesin particles 3 in the coating film 1 is maintained almost the same as the ratio of the silica particles 2 and the fluororesin particles 3 in the coating composition before application. Therefore, by adjusting the ratio of the silica particles 2 and the fluororesin particles 3 in the coating composition, excellent antifouling performance can be obtained. Note that the blocking of the pores 5 by the fluororesin particles 3 and the silica particles 2 means that the fluororesin particles 3 and the silica particles 2 cannot pass through the pores 5, and water, the chlorine bleaching agent, or the air can pass through the fine gaps in the silica film.

In addition, the silica particles 2 in the coating film 1 formed from the coating composition of embodiment 2 are irregularly shaped particles, and therefore have a large surface area per unit volume. Therefore, the silica film formed by the silica particles 2 has very small voids and a low density, which reduces adhesion of dirt to the coating film 1 due to intermolecular forces.

The silica particles 2 in the second embodiment may be particles of irregular shapes such as needles, scales, chains, beads, or pearl necklaces, or a mixture of particles of two or more shapes selected from the needles, scales, chains, beads, and pearl necklaces. The average particle size of the silica particles 2 in the second embodiment is 50 nm or more and 500 nm or less, preferably 50 nm to 300 nm, when measured by a light scattering method. By including irregular silica particles 2 having an average particle size of 500 nm or less in the coating composition, the silica particles 2 tend to remain on the surface of the substrate 4, which has water absorption or porosity, and the like, so that the coating film 1 is easily formed. In addition, the silica film made of irregular silica particles 2 having an average particle size of 500 nm or less has very small voids and is a film with a low density, so that adhesion of dirt due to intermolecular forces is also reduced. Furthermore, since 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 in which the silica particles 2 adhere to each other in the silica film becomes 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 fold and entangle and adhere to each other, resulting in a coating film 1 with sufficient strength.

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 porosity, the silica particles 2 will easily penetrate into the substrate 4 due to capillary action. Therefore, the ratio of the silica particles 2 to the fluororesin particles 3 in the coating film 1 on the surface of the substrate 4 may not be controllable, and there is a risk that it may be 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 will not easily entangle with each other in the silica film, and the voids in the silica film will become coarse, which may reduce the strength of the coating film 1. In addition, the unevenness of the coating film 1 will become too large, making it easier for hydrophilic dirt to adhere, and there is a risk that the desired antifouling performance will not be obtained.

If the coating composition contains spherical silica particles 2 with an average particle size longer than 50 nm, there is a risk that the coating film 1 will not have sufficient strength. In addition, 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, which increases the density of the silica film and can increase the adhesion of dirt due to intermolecular forces.

Before the coating composition is applied to the substrate 4, which is water-absorbent or porous, it is contaminated with mold or organic contaminants. Mold adheres to the surface of the substrate 4 and the walls of the pores 5 as spores or hyphae. The humidity inside the substrate 4 is easily kept constant in the substrate 4, which is an environment in which mold is easily propagated. Furthermore, in a substrate 4 in which mold has propagated, the mold inside the substrate 4 remains if only the surface of the substrate 4 is sterilized, and mold propagation reoccurs. 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 serve as nutrients for mold propagation. For these reasons, in order to inhibit mold propagation, 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.

When the coating composition of embodiment 2 is applied to the substrate 4, the chlorine bleach decomposes and removes mold and organic contaminants adhering to the surface of the substrate 4 and the walls of the pores 5. That is, the chlorine bleach that penetrates into the substrate 4 due to capillary action in the pores 5 of the substrate 4 decomposes and removes mold and organic contaminants adhering to the substrate 4. In addition, the chlorine bleach that does not penetrate into the substrate 4 remains on the surface of the substrate 4 together with the silica particles 2 and the fluororesin particles 3, thereby decomposing and removing mold and organic contaminants adhering to the surface of the substrate 4.

The water contained in the coating composition gradually evaporates when it comes into contact with air. The coating composition comes into contact with air at the surface of the substrate 4 to which it is applied, and at the pores 5 inside the substrate 4 into which the coating composition has permeated. Here, the chlorine 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 become more cohesive, forming a coating film 1. Meanwhile, the water that has permeated the pores 5 evaporates on the surface of the coating film 1 through the fine gaps in the coating film 1.

In addition, air flow is restricted in the pores 5 inside the substrate 4 compared to the surface of the substrate 4. Furthermore, the contact area between the liquid that has penetrated into the pores 5 and the air is often smaller than the contact area between the liquid and the air on the surface of the substrate 4. Therefore, the volatilization rate of the liquid in the pores 5 may be slower than the volatilization 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 aqueous solution of chlorine bleach for a long period of time. This allows excellent mold prevention performance to be exhibited not only on the surface of the substrate 4 but also inside.

Below, examples of the coating composition according to the first and second embodiments are described. Figure 5 is a diagram showing several examples of the proportions of the components in the coating composition according to the first embodiment. Note that Figure 5 shows the several examples in a table format. Figure 5 also shows the proportions of the components in each of the coating compositions according to several comparative examples.

The coating compositions of Examples 1 to 9 in FIG. 5 contain sodium hypochlorite as a chlorine bleaching agent. The coating compositions of Examples 1 to 3 contain 1.0 mass% silica particles 2 and 0.8 mass% fluororesin particles 3. The coating composition of Example 1 contains 1.000 mass% sodium hypochlorite, the coating composition of Example 2 contains 0.001 mass% sodium hypochlorite, and the coating composition of Example 3 contains 4.000 mass% 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 according to Examples 1 to 3 are prepared by stirring and mixing pure water, colloidal silica containing the silica particles 2, and a PTFE dispersion containing the PTFE particles, and then adding an aqueous sodium hypochlorite solution containing sodium hypochlorite and stirring and mixing.

The coating composition of Example 4 contains 1.0 mass% silica particles 2, 0.8 mass% fluororesin particles 3, and 0.500 mass% sodium hypochlorite. The coating composition of Example 5 contains 0.2 mass% silica particles 2, 0.1 mass% fluororesin particles 3, and 0.500 mass% sodium hypochlorite. The coating composition of Example 6 contains 4.0 mass% silica particles 2, 3.2 mass% fluororesin particles 3, and 2.000 mass% 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 of Examples 4 to 6 are prepared by stirring and mixing pure water, colloidal silica containing the silica particles 2, and a PTFE dispersion containing the PTFE particles, and then adding an aqueous sodium hypochlorite solution containing sodium hypochlorite and stirring and mixing.

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 of Examples 7 to 9 are prepared by stirring and mixing pure water, colloidal silica containing the silica particles 2, and a PTFE dispersion containing the PTFE particles, and then adding an aqueous sodium hypochlorite solution containing sodium hypochlorite and stirring and mixing.

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

The coating composition according to Comparative Example 2 shown in the table of FIG. 5 contains PTFE particles with an average particle size of 250 nm as the fluororesin particles 3, and sodium hypochlorite as the chlorine 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 a PTFE dispersion containing the PTFE particles, and then further adding and stirring an aqueous sodium hypochlorite solution containing sodium hypochlorite. The coating composition according to 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.

The coating composition according to Comparative Example 3 shown in the table of FIG. 5 contains sodium hypochlorite as a chlorine 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 an aqueous sodium hypochlorite solution containing sodium hypochlorite and stirring and mixing. The coating composition of Comparative Example 3 contains 10.0% by mass of silica particles 2 and 1.000% by mass of sodium hypochlorite.

An experiment was conducted to evaluate the liquid stability of the coating compositions of Examples 1 to 9 and Comparative Examples 1 to 3. After the coating compositions of Examples 1 to 9 and Comparative Examples 1 to 3 were applied to a substrate 4 by dipping, the substrate 4 after application of the coating composition was placed on a sample stand and allowed to dry naturally at room temperature for approximately 10 minutes, forming a coating film 1 on the substrate 4. In this experiment, a polypropylene substrate was used as the substrate 4.

Below, with reference to Figure 6, the evaluation results of the liquid stability of the coating compositions of Examples 1 to 9 and Comparative Examples 1 to 3, and the evaluation results of the properties, antifouling performance, weather resistance, and antifungal performance of the coating film 1 obtained from the coating compositions will be described. Figure 6 is a diagram illustrating the evaluation results of the coating compositions of Examples 1 to 9 and Comparative Examples 1 to 3. Figure 6 shows the evaluation results of Examples 1 to 9 and Comparative Examples 1 to 3 in a table format.

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

In Figure 6, the anti-fouling performance is shown by sand 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 the coating film 1 with air, and the coloring caused by the adhesion of the Kanto loam dust was evaluated on a 5-point scale by visual observation. In this 5-point scale evaluation, the greater the amount of Kanto loam dust that adhered, the higher the value, with 1 indicating almost no adhesion of Kanto loam dust and 5 indicating a large amount of adhesion of Kanto loam dust.

Dust adhesion corresponds to the adhesion of hydrophobic dirt. Dust adhesion was evaluated as follows. A predetermined amount of carbon black was sprayed onto the surface of the coating film 1 with air, and the coloring due to the adhesion of the carbon black was evaluated on a 5-point scale by visual observation. In this 5-point scale evaluation, the greater the amount of carbon black adhesion, the higher the number, with 1 indicating almost no carbon black adhesion and 5 indicating a large amount of carbon black adhesion.

Weather resistance was evaluated as follows. Using an existing highly accelerated weather resistance 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 rated on a 5-point scale. In this 5-point scale, the greater the degree of discoloration, the higher the number. Using the color of the substrate 4 on which the coating film 1 is not formed as the standard, a score of 1 indicates that there is almost no difference in color from the standard, and a score of 5 indicates that there has been significant discoloration and that the color is significantly different from the standard.

The evaluation of antifungal performance was carried out as follows. The coating compositions of Examples 1 to 9 and Comparative Examples 1 to 3 were applied to the substrate 4 by dipping, and the substrate 4 after application of the coating composition was then placed on a sample stand and naturally dried at room temperature for about 10 minutes to form the coating film 1 on the substrate 4. The coating film 1 was then exposed to soil containing mold such as Aspergillus niger, Penicillium niger, and Trichoderma, and the mold was cultivated for 168 hours at a temperature of 35°C and a humidity of 90%. The state of mold growth on the surface of the coating film 1 was then evaluated on a five-point scale by visual observation and by observation using an existing optical microscope (DSX1000, manufactured by Olympus Corporation). In the five-point evaluation, the greater the degree of mold growth, the higher the value, with 1 indicating the minimum degree of mold growth and 5 indicating the maximum degree of mold growth.

As shown in Figure 6, it was confirmed that the coating compositions of Examples 1 to 9 and Comparative Examples 1 and 3 did not undergo aggregation or precipitation and were highly stable as liquids. In contrast, the coating composition of Comparative Example 2 contained an excessive amount of sodium hypochlorite, which caused aggregation and precipitation, making it impossible to ensure stability as a liquid.

In each of the coating compositions of Examples 1 to 9 and Comparative Example 1, a uniform coating film 1 could be formed on the substrate 4. In contrast, the coating composition of Comparative Example 2 was unable to form a film on the substrate 4 due to aggregation and precipitation in the liquid. In addition, in the coating composition of Comparative Example 3, the silica particles 2 were coarse spherical particles with an average particle size exceeding 25 nm, so a non-uniform coating film 1 was formed on the substrate 4. As a result, the resulting coating film 1 was prone to cracking and peeling.

The coating film 1 obtained from the coating compositions of Examples 1 to 9 had smaller values in the evaluations of sand and dust adhesion, dust adhesion, and antifungal performance than the coating film 1 obtained from the coating compositions of Comparative Examples 1 and 3. In other words, the coating film 1 obtained from the coating compositions of Examples 1 to 9 had better antifouling and antifungal performance than the coating film 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 had the best sand and dust adhesion, dust adhesion, and antifungal performance.

The weather resistance of the coating film 1 obtained from the coating compositions of Examples 1 to 9 was evaluated to have a value of 1, which was good.

Next, examples of the coating composition according to the second embodiment will be described with reference to FIG. 7. FIG. 7 is a diagram showing several examples of the proportions of components in the coating composition according to the second embodiment. Note that FIG. 7 also shows the several examples in a table format. FIG. 7 also shows the proportions of components in the coating composition according to the first embodiment for comparison with the first embodiment. FIG. 7 also shows the proportions of components in the coating composition according to the fourth comparative example.

The coating compositions of Examples 10 to 11 and Comparative Example 4 in FIG. 7 each contain sodium hypochlorite as a chlorine bleaching agent. Each of the coating compositions of Examples 10 to 11 and Comparative Example 4 contains 1.0 mass% silica particles 2 and 0.8 mass% fluororesin particles 3. The coating composition of Example 10 contains 1.000 mass% sodium hypochlorite, and each of the coating compositions of Example 11 and Comparative Example 4 contains 2.000 mass% sodium hypochlorite.

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

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

The silica particles 2 contained in the coating composition of Comparative Example 4 are scaly 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 and colloidal silica containing the silica particles, and a PTFE dispersion containing the PTFE particles, and then further adding and stirring an aqueous sodium hypochlorite solution containing sodium hypochlorite.

An experiment was conducted to evaluate the liquid stability of the coating compositions of Examples 10 to 11 and Comparative Example 4. After the coating compositions of Examples 10 to 11 and Comparative Example 4 were applied to a substrate 4 by dipping, the substrate 4 after application of the coating composition was placed on a sample stand and allowed to dry naturally at room temperature for approximately 10 minutes, forming a coating film 1 on the substrate 4. In this experiment, a polypropylene substrate was used as the substrate 4.

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

As shown in Figure 8, similar to Example 1, the coating compositions of Examples 10 to 11 and Comparative Example 4 were confirmed to have high stability as liquid agents without aggregation or precipitation. Also, similar to Example 1, a uniform coating film 1 was obtained on the substrate 4 by the coating compositions of Examples 10 to 11. On the other hand, in Comparative Example 4, the silica particles 2 in the coating composition were coarse irregular particles with an average particle size exceeding 500 nm, so that a non-uniform coating film 1 was formed on the substrate 4, cracks occurred in the coating film 1, and some of the coarse particles fell off from the surface.

As shown in Figure 8, the coating film 1 obtained from the coating compositions of Examples 10 and 11 had smaller values in the evaluation of sand and dust adhesion, dust adhesion, and antifungal performance than the coating film 1 obtained from the coating composition of Comparative Example 4, and had better antifouling and antifungal performance. In addition, the weather resistance of the coating films obtained from the coating compositions of Examples 10 and 11 was also good.

Below, other examples of the coating compositions according to the first and second embodiments will be described with reference to FIG. 9. FIG. 9 is a diagram showing several examples of the proportions of the components in the coating compositions according to the first and second embodiments. Note that FIG. 9 also shows the several examples in table format. FIG. 9 also shows the proportions of the components in the coating compositions according to the fifth to seventh comparative examples.

The coating compositions according to Examples 12 to 14 and Comparative Examples 5 to 7 in FIG. 9 contain sodium hypochlorite as a chlorine bleaching agent. The coating compositions according to Examples 12, 14, and Comparative Examples 5 to 7 contain 1.000% by mass of sodium hypochlorite, and the coating composition according to Example 13 contains 2.000% by mass of sodium hypochlorite. The coating composition according to Example 12 contains 4.0% by mass of silica particles 2 and 0.4% by mass of fluororesin particles 3. The coating compositions according to 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 according to Comparative Examples 5 to 7 contain 1.0% by mass of silica particles 2 and 0.8% by mass of fluororesin particles 3.

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

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

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

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 and colloidal silica containing the silica particles, and a PTFE dispersion containing the PTFE particles, and then further adding and stirring an aqueous sodium hypochlorite solution containing sodium hypochlorite.

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 and colloidal silica containing the silica particles, and a PTFE dispersion containing the PTFE particles, and then further adding and stirring an aqueous sodium hypochlorite solution containing sodium hypochlorite.

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 and colloidal silica containing the silica particles, and a PTFE dispersion containing the PTFE particles, and then further adding and stirring an aqueous sodium hypochlorite solution containing sodium hypochlorite.

An experiment was conducted to evaluate the liquid stability of the coating compositions of Examples 12 to 14 and Comparative Examples 5 to 7. The coating compositions of Examples 12 to 14 and Comparative Examples 5 to 7 were applied to a substrate 4 by dipping, and the substrate 4 after application of the coating composition was then placed on a sample stand and allowed to dry naturally, forming a coating film 1 on the substrate 4. In this experiment, a gypsum board substrate, which is a porous substrate, was used as the substrate 4.

Below, with reference to Figure 10, the evaluation results of the liquid stability of the coating compositions of Examples 12 to 14 and Comparative Examples 5 to 7, and the evaluation results of the properties, antifouling performance, weather resistance, and antifungal performance of the coating film 1 obtained from the coating compositions will be described. Figure 10 is a diagram illustrating the evaluation results of the coating compositions of Examples 12 to 14 and Comparative Examples 5 to 7. Note that Figure 10 shows the evaluation results of Examples 12 to 14 and Comparative Examples 5 to 7 in a table format.

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 liquid agents without causing aggregation or precipitation. In addition, the coating compositions of Examples 12 to 14 were able to form a uniform coating film 1 on the gypsum board substrate.

On the other hand, in Comparative Examples 5 and 6, the silica particles 2 in the coating composition were coarse, spherical particles with an average particle size exceeding 25 nm, so that a non-uniform coating film 1 was formed on the gypsum board substrate. The coating film 1 cracked and peeled off easily. In Comparative Example 7, the silica particles 2 in the coating composition were coarse, irregularly shaped particles with an average particle size exceeding 500 nm, so that a non-uniform coating film 1 was formed on the gypsum board substrate. As a result, the coating film 1 cracked and some of the coarse particles fell off from the surface.

The coating film 1 obtained from the coating compositions of Examples 12 to 14 had smaller values in the evaluation of sand and dust adhesion, powder dust adhesion, and antifungal performance than the coating film 1 obtained from the coating compositions of Comparative Examples 5 to 7, and had better antifouling and antifungal performance. In particular, the coating composition of Example 13 had the best sand and dust adhesion, powder dust adhesion, and antifungal performance. In addition, the weather resistance of the coating film 1 obtained from the coating compositions of Examples 12 to 14 was good.

The effects of the coating composition, coating method, and mold treatment method according to the first and second embodiments are described below. The coating composition according to the first and second embodiments contains a plurality of silica particles 2 at 5% by mass or less, a plurality of fluororesin particles 3, 0.001% by mass or more and 5% by mass or less of a chlorine-based bleaching agent, and water.

According to the above configuration, the plurality of silica particles 2 and the plurality of fluororesin particles 3 contained in the coating composition are not decomposed by the chlorine bleach, so that the stability of the coating composition can be ensured. Furthermore, since the proportion of the chlorine bleach in the coating composition is 5 mass% or less, precipitation due to aggregation of two or more fluororesin particles 3 is unlikely to occur, and the stability of the coating composition is ensured. Furthermore, since the silica particles 2 are hydrophilic, hydrophobic dirt is unlikely to adhere to the coating film 1, and since the fluororesin particles 3 are hydrophobic, hydrophilic dirt is unlikely to adhere to the coating film 1. Furthermore, since the coating composition contains 0.001 mass% or more of chlorine bleach, it is possible to decompose mold, organic contaminants, etc. on the surface of the substrate 4 to be coated and on the surface and inside of the coating film 1. Therefore, the plurality of silica particles 2, the plurality of fluororesin particles 3, and the chlorine bleach provide high anti-fouling performance, which improves anti-fungal performance. In addition, since the content of the 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 performance is maintained. Therefore, according to the coating composition and coating method according to the first and second embodiments, the stability of the coating composition is ensured, and it is possible to produce a coating film 1 having high antifouling and antifungal performance. In addition, since the coating film 1 contains silica particles 2 with low light scattering, the transparency of the coating film 1 is improved, and even if the coating film 1 is applied to the substrate 4, changes in the color tone and texture of the substrate 4 can be suppressed. Therefore, the design of the substrate 4 is guaranteed by the maintenance of the color tone and texture of the substrate 4 due to the transparency of the coating film 1, the suppression of pigmentation due to the above-mentioned high antifungal performance, the suppression of peeling of the coating film 1, and the high weather resistance of the coating film 1.

The multiple silica particles 2 according to the first embodiment have an average particle size of 25 nm or less, and each of the multiple silica particles 2 is a spherical particle. Since 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 when the coating film 1 is formed by drying, facilitating solidification of the coating composition. In addition, since there are more silica particles 2 dissolved in equilibrium in the coating composition than when the average particle size of the silica particles 2 is longer than 25 nm, it becomes possible to form a uniform, high-strength coating film 1 that is suppressed from cracking and peeling.

In the second embodiment, the average particle size of the silica particles 2 is 50 nm or more and 1000 nm or less, and each of the silica particles 2 is an irregular particle having a needle shape, a scale shape, a chain shape, a rosary shape, or a pearl necklace shape. Since the average particle size of the silica particles 2 is 50 nm or more, the silica particles 2 in the substrate 4 having water absorption or porosity are prevented from penetrating into the substrate 4 by capillary action. Therefore, it is possible to control the ratio of the silica particles 2 and the fluororesin particles 3 on the substrate 4 surface, and the coating film 1 can maintain high antifouling performance. In addition, the irregular silica particles 2 in the coating film 1 are folded, entangled, and adhered to each other, thereby obtaining a coating film 1 having sufficient strength.

The average particle size of the multiple fluororesin particles 3 according to the first and second embodiments is 50 nm or more and 10,000 nm or less. This allows the fluororesin particles 3 to be appropriately dispersed in the coating composition, resulting in a stable coating composition. In addition, the particles are easily exposed on the surface of the coating film 1, resulting in good antifouling performance.

The mass ratio of the multiple silica particles 2 to the multiple fluororesin particles 3 in the first and second embodiments is in the range of 40:60 to 95:5. This allows a coating film 1 with good antifouling performance, in which the hydrophilic portions resulting from the silica particles 2 and the hydrophobic portions resulting from the fluororesin particles 3 are mixed in a well-balanced manner, to be obtained by drying at room temperature.

Although the embodiments have been described above, the contents of this disclosure are not limited to the embodiments and include the scope of conceivable equivalents. Furthermore, the configurations and variations thereof described in the first and second embodiments can be combined with each other to the extent that the functions and operations are not impaired.

1. Coating film, 2. Silica particles, 3. Fluorine resin particles, 4. Substrate, 5. Pores.

Claims (7)

5% by weight or less of silica particles;
Fluorine resin particles;
0.001% by mass or more and 5% by mass or less of a chlorine bleach;
Water,
1. A coating composition comprising: The coating composition according to claim 1, wherein the silica particles have an average particle size of 25 nm or less and are spherical particles. The coating composition according to claim 1, wherein the silica particles have an average particle size of 50 nm or more and 1000 nm or less, and the silica particles are irregularly shaped particles in the form of needles, scales, chains, beads, or pearl necklaces. 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. The coating composition according to any one of claims 1 to 4, wherein the mass ratio of the silica particles to the fluororesin particles is in the range of 40:60 to 95:5. 1. A method for coating a substrate, comprising the steps of:
A coating method comprising applying a coating composition containing 5 mass% or less of silica particles, fluororesin particles, 0.001 mass% or more and 5 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. A method for treating mold, comprising applying to a substrate a coating composition containing 5% or less silica particles, fluororesin particles, 0.001% or more and 5% or less chlorine bleach, and water.

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