COATING COMPONENTS, COATINGS, AND COATING METHODS

Abstract

The invention relates to a coating composition consisting of irregularly shaped silica particles (2) of medium size from 12 nm to 250 nm, hydrophobic resin particles (3) of medium size from 50 nm to 500 nm, and water-sparing antifungal particles (4) of rod, needle, or filamentous crystalline form of crystal length from 1 µm to 10 mm and crystal thickness from 0.1 µm to 15 µm; a mixed liquid in which the irregularly shaped silica particles (2), hydrophobic resin particles (3), water, and antifungal particles (4) are mixed having an alkaline pH from 9 to 11.

Description

Coating composition, coating film, and method for producing coating film

[0001] The present disclosure relates to a coating composition, a coating film, and a method for producing a coating film formed on a substrate or the like.

[0002] In indoor spaces, for example, cold radiation from a freezer or refrigerator can cool the ceiling or walls around the freezer or refrigerator, which, combined with warm air flowing in from outside, can easily cause condensation. It is also common to see condensation or dirt on the ceiling or wall near the air conditioner vent. In such places, mold is likely to grow, using the moisture or dirt from the condensation as nutrients. Given the increasing demand for cleanliness in recent years, measures to prevent mold growth are needed.

[0003] As a measure to suppress mold growth, technologies have been developed to optimize air conditioning capacity to prevent condensation, dirt, and mold caused by these factors, thereby preventing a condensation environment. Patent Document 1 discloses a method of incorporating a water-insoluble antifungal agent into gypsum board, which is a ceiling material. Patent Document 2 discloses a technology for imparting antifouling and antibacterial properties by using an aqueous coating agent consisting of a photocatalytic oxide, a hydrophobic resin emulsion, and silica particles.

[0004] Japanese Patent No. 5520603 Japanese Patent Laid-Open No. 2005-105053

[0005] However, optimizing the air conditioning capacity for each indoor space requires time and cost for design, and environmental and equipment constraints may prevent reliable results. Furthermore, using anti-fungal gypsum board as a ceiling material, as in Patent Document 1, requires extensive construction work on the existing ceiling, which increases costs. Furthermore, as in Patent Document 2, functional coating agents using photocatalysts are limited to their effectiveness in dark areas. There is a need to suppress condensation, dirt, and the resulting mold growth on existing ceilings, walls, and other objects.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a coating composition, a coating film, and a method for producing a coating film that suppress condensation, stains, and the resulting mold growth on existing ceilings, walls, or other articles.

[0007] The coating composition according to the present disclosure comprises irregularly shaped silica particles having an average particle size of 12 nm to 250 nm, hydrophobic resin particles having an average particle size of 50 nm to 500 nm, and poorly water-soluble antifungal particles having rod-like, needle-like, or fibrous crystallinity with a crystal length of 1 μm to 10 mm and a crystal thickness of 0.1 μm to 15 μm, and a mixture of the irregularly shaped silica particles, the hydrophobic resin particles, water, and the antifungal particles has an alkaline pH of 9 to 11.

[0008] According to the present disclosure, it is possible to suppress condensation, dirt, and the resulting mold growth on existing ceilings, walls, and other objects, thereby maintaining cleanliness.

[0009] It is a cross-sectional schematic diagram showing a coating film according to embodiment 1. It is a schematic diagram showing chain-like irregular shaped silica particles according to embodiment 1. It is a schematic diagram showing bead-like irregular shaped silica particles according to embodiment 1.

[0010] Hereinafter, embodiments of the coating composition, coating film, and method for producing a coating film according to the present disclosure will be described with reference to the drawings. Note that the present disclosure is not limited to the embodiments described below. Furthermore, the dimensional relationships between the components in the drawings may differ from those in reality. Furthermore, in the following description, terms indicating directions will be used as appropriate to facilitate understanding of the present disclosure, but these terms are for the purpose of explaining the present disclosure and do not limit the present disclosure. Examples of terms indicating directions include "up," "down," "right," "left," "front," and "rear."

[0011] Embodiment 1. Fig. 1 is a cross-sectional schematic diagram showing a coating film 5 according to embodiment 1. As shown in Fig. 1, the coating film 5 is formed by applying a coating composition, which is an aqueous mixture containing irregularly shaped silica particles 2, hydrophobic resin particles 3, and antifungal particles 4, to a substrate 1.

[0012] In indoor spaces, for example, cold radiation from a freezer or refrigerator can cool the ceiling or walls around the freezer or refrigerator, which, combined with warm air flowing in from outside, can easily cause condensation. It is also common to see darkened ceilings or walls near air conditioner vents due to condensation or dirt. This is because mold is more likely to grow in such locations, using the moisture or dirt from condensation as nutrients. It is known that mold growth requires spores, water, nutrients, oxygen, and temperature. In typical indoor spaces, oxygen and temperature provide an environment sufficient for mold growth. Furthermore, mold spores grow in typical soil and plants, and are released into the air. Mold spores enter indoor spaces as people or objects enter and exit, so they are airborne in all spaces. Therefore, to suppress mold growth, it is necessary to reduce both water and nutrients, as well as suppress the adhesion of mold spores and the growth of mold mycelia.

[0013] (Substrate 1) The substrate 1 is, for example, a water-absorbent ceiling material or wall material.

[0014] (Irregular Silica Particles 2) FIG. 2 is a schematic diagram showing chain-like irregular silica particles 2 according to embodiment 1, and FIG. 3 is a schematic diagram showing beaded irregular silica particles 2 according to embodiment 1. The irregular silica particles 2 have an irregular shape such as needle-like, scale-like, chain-like, or beaded shape. The irregular silica particles 2 are formed by bonding roughly spherical particles having a particle size of 5 nm to 20 nm. Preferably, the irregular silica particles 2 are bonded in a chain-like or beaded shape and have an average particle size of 12 nm to 250 nm. The chain-like irregular silica particles 2 shown in FIG. 2 and the beaded irregular silica particles 2 shown in FIG. 3 are examples, and some may be bonded in a chain-like or beaded shape. Furthermore, the irregular silica particles 2 may be mixed with roughly spherical particles, or may be mixed with chain-like, bead-like, or scale-like particles.

[0015] The average particle size is measured by dynamic light scattering or laser diffraction of an aqueous dispersion of silica particles before mixing into the coating composition, but may also be measured by other methods. In the coating composition, the silica particles may aggregate to increase the average particle size.

[0016] The irregular silica particles 2 are the main component of the coating film 5 and also function as a binder to fix the hydrophobic resin particles 3 and antifungal particles 4. The use of chain-like or bead-like irregular silica particles 2 allows for favorable control of the fluidity of the coating composition during application and drying. When applying to an uneven surface, if the coating composition is based on spherical silica, the coating film 5 obtained after application and drying will not form a sufficient coating on the protrusions because the liquid will accumulate only in the recesses. Furthermore, when using a coating composition based on spherical silica on a water-absorbent or porous substrate 1, the spherical silica particles will migrate into the substrate 1 along with the water in the coating composition due to capillary action, preventing the formation of a satisfactory coating film 5. In contrast, the irregular silica particles 2 of the present embodiment 1 have difficulty passing through the pores of the substrate 1 due to their size, making it possible to form a coating on the surface of the substrate 1.

[0017] In a coating composition containing irregularly shaped silica particles 2 bonded in a chain-like or beaded shape, a coating film 5 obtained by application to a substrate 1 and drying has fine voids within the film. The irregularly shaped silica particles 2 are the main component that makes the coating film 5 hydrophilic, and the formation of fine voids makes it more hydrophilic than when spherical silica is used. Furthermore, the irregularly shaped silica particles 2 are less likely to lose their hydrophilicity even when contaminants are present due to the adsorption of water-repellent substances. Furthermore, the irregularly shaped silica particles 2 also have the effect of preventing dust contamination, as the voids reduce intermolecular forces (adhesion forces), making it more difficult for dust to adhere.

[0018] The use of irregularly shaped silica particles 2 has the advantage that film defects such as cracks are less likely to form in the coating film 5 than when spherical silica is used. This makes the coating film 5 less likely to peel off, suppresses deterioration due to friction or environmental changes, and provides a long life and high durability. Furthermore, since there are no cracks to which dust can adhere, there is also the effect of less dust contamination.

[0019] In the coating composition, silica particles are used as the base composition. Silica particles have a lower refractive index than other hydrophilic inorganic particles such as titania particles or alumina particles, and therefore are less likely to cause cloudiness due to light scattering at the interface or surface. In the present embodiment 1, irregularly shaped silica particles 2 are used as the silica particles, and the coating film 5 has fine voids. This further lowers the refractive index. In addition, the formation of cracks that cause light scattering is suppressed, thereby reducing cloudiness.

[0020] If the average particle size of the irregularly shaped silica particles 2 is less than 12 nm, the effects of coatability to uneven or water-absorbent surfaces, low turbidity, low contamination, etc. cannot be sufficiently obtained. If the average particle size exceeds 250 nm, the coating film 5 formed becomes brittle, or the microvoids in the film become excessively large, making it prone to turbidity, which is undesirable.

[0021] The content of the irregular silica particles 2 in the coating composition is not particularly limited, but is preferably 0.1 wt % or more and 15 wt % or less, and more preferably 0.5 wt % or more and 10 wt % or less. If the content of the irregular silica particles 2 is too low, the substrate 1 cannot be sufficiently covered with the coating film 5. On the other hand, if the content of the irregular silica particles 2 is too high, the formed film becomes too thick, and becomes cloudy or is prone to peeling.

[0022] Generally, when silica particles are stably dispersed in water, their stability is affected by pH. Silica particles exhibit high stability in the acidic range of pH 2 to 4 and in the alkaline range of pH 8 to 11. In the case of an alkaline range of pH above 9, the dissolved silica component acts as a binder between the silica particles when dried, which is preferable because it makes it easier to obtain a strong film. In the coating composition of the first embodiment, the pH is also preferably 8 to 12, and more preferably 9 to 11.

[0023] To obtain an alkaline coating composition, it is preferable to use an alkaline aqueous silica dispersion as the silica particles. If necessary, a water-soluble alkaline component is added to adjust the pH. Examples of the water-soluble alkaline component that can be used include sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium silicate, and lithium silicate. When an alkaline component is added, it is preferably added in an amount of 2% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 25% by mass or less, based on the silica particles. If the amount of the water-soluble alkaline component added is too large, the effects of low cloudiness and low contamination obtained by adding the irregularly shaped silica particles 2 may not be fully achieved.

[0024] When adding a water-soluble alkaline component, sodium silicate and lithium silicate in particular function as binders for silica particles. This is preferable because it provides the effect of increasing the strength of the coating film 5 and also the effect of improving water resistance. In addition, in this case, for sodium silicate, n is preferably 2 or more and 4 or less in Na2O·nSiO2. For lithium silicate, n is preferably 5 or more and 8 or less in Li2O·nSiO2. When n is small, i.e., when SiO2 is low, the effect of adjusting the alkalinity is obtained, but the effect of increasing the strength of the coating film 5 is not obtained. When n is large, i.e., when SiO2 is high, the effects of low cloudiness and low contamination obtained by adding the irregularly shaped silica particles 2 may not be fully obtained.

[0025] pH is also related to the mold-inhibiting effect. Mold grows easily at a pH of 2 to 8.5, but only a limited number of molds can grow in alkaline environments above pH 9. The coating film 5 obtained with a coating composition having a pH of 8 to 12 contains alkaline components. When conditions favorable for mold growth arise due to condensation or the like, the alkaline components are eluted, alkalizing the surface and providing the effect of inhibiting mold growth.

[0026] (Hydrophobic Resin Particles 3) The hydrophobic resin particles 3 are particles of a resin that has low affinity for water and is difficult to dissolve in water. The hydrophobic resin particles 3 include, for example, silicone resin particles or fluororesin particles, but are not limited thereto and may be other resins. Note that fluororesin particles are preferred as those that disperse in an aqueous medium. Specific examples of fluororesin particles 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), PVF (polyvinyl fluoride), copolymers and mixtures thereof, and mixtures of these fluororesins with other resins. Of these, PTFE (polytetrafluoroethylene) and FEP (tetrafluoroethylene-hexafluoropropylene copolymer) are preferred as the hydrophobic resin particles 3 because they have excellent stability and high hydrophobicity.

[0027] The average particle size of the hydrophobic resin particles 3 is not particularly limited, but is preferably 50 nm to 500 nm, and more preferably 100 nm to 250 nm, as measured by a light scattering method. By incorporating hydrophobic resin particles 3 having an average particle size within this range into the coating composition, the hydrophobic resin particles 3 are adequately dispersed in the coating film 5 and are easily exposed on the surface of the coating film 5, thereby achieving good antifouling performance. If the average particle size of the hydrophobic resin particles 3 is less than 50 nm, the hydrophobic resin particles 3 are less likely to be exposed on the surface of the coating film 5, and the desired antifouling performance may not be achieved. On the other hand, if the average particle size of the hydrophobic resin particles 3 exceeds 500 nm, the hydrophobic regions in the resulting coating film 5 may become large, or the coating film 5 may have large irregularities, resulting in the desired antifouling performance not being achieved.

[0028] The weight ratio of the irregularly shaped silica particles 2 to the hydrophobic resin particles 3 in the coating composition is 70:30 to 95:5, preferably 75:25 to 90:10. A mass ratio within this range results in a coating film 5 with a well-balanced mixture of hydrophilic portions originating from the irregularly shaped silica particles 2 and hydrophobic portions originating from the hydrophobic resin particles 3. The coating film 5 obtained by drying at room temperature exhibits excellent antifouling performance. The hydrophilic portions on the surface of the coating film 5 play an important role in improving the antifouling performance. Furthermore, with a mass ratio within this range, the hydrophilic portions on the surface of the coating film 5 are continuous without being interrupted by hydrophobic portions. Therefore, when water droplets or the like adhere to the surface of the coating film 5, the water easily spreads throughout the entire coating film 5.

[0029] Water also has the effect of lifting and removing hydrophilic and hydrophobic contaminants adhering to the surface of the coating film 5, or making them less likely to adhere. Adhered contaminants are particularly easily removed from the surface of the coating film 5 during condensation, rainfall, cleaning, and other processes. Furthermore, because the coating film 5 is primarily composed of a continuous silica film, it is also possible to suppress electrostatic charge on the film surface, which can cause contaminant adsorption. Furthermore, the coating film 5 has the property of easily spreading water. Therefore, even if condensation occurs, the condensed water spreads across the coating film 5 and therefore dries easily. Because the coating film 5 is less susceptible to contamination and the condensed water easily spreads and dries easily, an environment is created that is less conducive to the growth of mold, which feeds on dust and water.

[0030] Mold floating in the air exists as either mold spores alone or as mold spores or mold mycelia mixed with hydrophilic and hydrophobic soils. Generally, mold spores have a hydrophilic surface and adhere by electrostatic bonding between hydrophilic groups, liquid bridging with 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 sufficient to form a coating film 5 that does not have hydrophilic portions large enough to allow hydrophilic soils to adhere.

[0031] Generally, mold hyphae are several tens of micrometers to several millimeters long. Therefore, both hydrophilic and hydrophobic stains containing mold are several tens of micrometers to several millimeters in size. To prevent the adhesion of hydrophilic stains containing mold, it is necessary to form a coating film 5 with antifouling properties that does not have hydrophilic portions large enough to accommodate hydrophilic stains. Similarly, to prevent the adhesion of hydrophobic stains containing mold, it is necessary to form a coating film 5 with antifouling properties that does not have hydrophobic portions large enough to accommodate hydrophobic stains. In this embodiment, by setting the mass ratio of the irregularly shaped silica particles 2 to the hydrophobic resin particles 3 to the aforementioned mass ratio, the hydrophobic resin particles 3 are appropriately dispersed in the hydrophilic silica film. As a result, even if hydrophilic stains adhere to the hydrophilic portions, they are less likely to adhere due to physical isolation by the surfaces of the hydrophobic portions or protrusions of the hydrophobic portions adjacent to the hydrophilic portions. Similarly, the hydrophilic portions of the coating film 5 can suppress the adhesion of hydrophobic stains.

[0032] Commercially available hydrophobic resin particles that are dispersed in water in advance may be used as the hydrophobic resin particles 3. In this case, it is preferable to use a neutral or alkaline dispersion liquid in order to make the coating composition alkaline.

[0033] (Antifungal Particles 4) The antifungal particles 4 are preferably poorly water-soluble. This allows the antifungal particles 4 to be present on the surface of the substrate 1 even if the substrate 1 has water absorption. Therefore, a coating film 5 that is resistant to mold growth can be obtained. As the poorly water-soluble antifungal particles 4, benzimidazole-based or iodine-based antifungal agents are preferred, but are not particularly limited. Examples of antifungal particles 4 include thiabendazole (TBZ), carbendazim (BCM), 3-iodo-2-propyl-N-butylcarbamate (IPBC), and diiodomethyl-paratolyl sulfone (DMTS). The water solubility of TBZ is 0.003%, IPBC is 0.0156%, and DMTS is 0.1%, while BCM is insoluble; all of these particles are poorly soluble in water. By dispersing the antifungal particles 4 in the coating composition without dissolving them, the antifungal particles 4 can be present in the coating film 5, thereby inhibiting mold growth.

[0034] The poorly water-soluble antifungal particles 4 are antifungal agents having a crystalline form in the form of a fine powder, rod, needle, or fiber. The crystalline form of the antifungal agent is preferably rod, needle, or fiber. When the antifungal particles 4 are rod-shaped crystals, the ratio of the minor axis to the major axis is preferably 1.2 or more. In the coating composition or coating film 5, the antifungal particles 4 preferably have a crystal length of 1 μm or more and 10 mm or less, and a crystal thickness of 0.1 μm or more and 15 μm or less.

[0035] Even when a coating composition containing antifungal particles 4 is applied to a substrate 1 having a porous or uneven surface, the antifungal agent accumulates on the surface of the substrate 1 without penetrating into the interior or recesses of the substrate 1, thereby providing high antifungal properties. Furthermore, in the coating film 5, the antifungal particles 4 are arranged with their longitudinal direction aligned with the surface of the substrate 1. This makes it difficult for the antifungal particles 4 to protrude from the surface of the coating film 5, increase thickness unevenness in the coating film 5, or cause cracks. Generally, increasing the surface unevenness of the coating film 5 impairs the antifouling properties of the coating film 5. In contrast, in the present embodiment 1, the antifungal agent is added in the above-described manner, which allows for the addition of a large amount of the antifungal agent without impairing antifouling properties.

[0036] Such a coating film 5 containing antifungal particles 4 is achieved by using the aforementioned irregular silica particles as silica particles in the coating composition. By using irregular silica particles 2 as a base, the coating composition exhibits the fluidity of a pseudo-compositional fluid. Furthermore, the antifungal particles 4 are easily arranged with their longitudinal direction aligned with the surface of the substrate 1, and the presence of the antifungal particles 4 is unlikely to result in localized thickening of the film. Therefore, a highly uniform coating film 5 can be formed. Furthermore, the irregular silica particles 2 form a coating with fine voids, allowing the antifungal particles 4 to be encapsulated without cracking. Furthermore, when the coating film 5 is in a humid state, the antifungal agent can diffuse through the voids.

[0037] Even if the antifungal agent particles are in granular or powder form, they can be incorporated into the coating film 5. However, if the particles are granular and have a particle size exceeding 3 μm, the particles will be unevenly distributed during the application of the coating composition, making it difficult to form a uniform coating film 5 with antifouling properties. Furthermore, in the case of fine particles, even if a uniform coating film 5 is formed, if the amount of the antifungal agent added exceeds 5% of the total of the irregularly shaped silica particles 2 and the hydrophobic resin particles 3, a continuous silica phase will not be formed. This results in a problem of a decrease in the strength of the coating film 5, making it more susceptible to wear or peeling.

[0038] The content of the poorly water-soluble antifungal particles 4 is preferably 5 wt % or more and 500 wt % or less of the total of the irregularly shaped silica particles 2 and the hydrophobic resin particles 3. More preferably, the content of the poorly water-soluble antifungal particles 4 is 5 wt % or more and 150 wt % or less. If the content of the antifungal particles 4 is too low, it may be difficult for the coating film 5 to have sufficient antifungal properties. Furthermore, if the content of the antifungal particles 4 is too high, the antifouling properties of the coating film 5 may be impaired.

[0039] In addition to the poorly water-soluble antifungal particles 4, a water-soluble antifungal agent may be included. Unlike the poorly water-soluble antifungal particles 4, the water-soluble antifungal agent is less likely to remain on the surface of the water-absorbent or porous substrate 1 and penetrates into the substrate 1. Therefore, when condensation occurs on the surface of the substrate 1, the condensed water penetrates into the interior and seeps out onto the surface of the substrate 1. This makes it possible to suppress the growth of mold.

[0040] The coating composition may contain components known in the technical field from the viewpoint of imparting various properties to the coating composition, as long as the effects obtained in the present embodiment 1 are not impaired. Examples of known components include surfactants, coupling agents, and silane compounds. The amounts of these components are not particularly limited as long as the amounts are within the range that does not impair the effects obtained in the present embodiment 1, and may be adjusted appropriately depending on the types of components used.

[0041] (Method for producing coating film 5) The coating composition is prepared by mixing water, irregularly shaped silica particles 2, hydrophobic resin particles 3, and antifungal particles 4. The coating film 5 is formed using a conventionally known method without any particular limitations. Examples include spray coating, brush coating, roller coating, and dip coating. These coating methods may be combined. After application to the substrate 1, the coating composition becomes the coating film 5 simply by natural drying. Because the surfaces of the irregularly shaped silica particles 2 contained in the coating composition are partially dissolved, the silica particles adhere to each other during natural drying, forming the coating film 5. The drying can also be accelerated by using an air current, hot air, etc. to obtain the coating film 5.

[0042] The coating film 5 is primarily composed of a continuous silica film. This inhibits electrostatic charge on the film surface, which can attract dirt, and allows water to spread easily. Even if condensation occurs, the condensed water spreads across the coating film 5, making it easier to dry. Furthermore, the condensed water is alkaline, making it difficult for mold to grow. Furthermore, the presence of the water-insoluble anti-mold particles 4 inhibits mold growth. Thus, the coating film 5 of this embodiment 1 is resistant to dirt, allows condensed water to spread easily, and dries easily. This results in a film that is difficult for mold, which feeds on dust and water, to grow.

[0043] Hereinafter, the embodiment will be specifically described with reference to examples and comparative examples, but the embodiment is not limited to the following examples.

[0044] The irregularly shaped silica particles 2 were colloidal silica (Cataloid S-30L, JGC Catalysts and Chemicals Co., Ltd.), which are formed by connecting particles with particle diameters of 10 nm to 25 nm. The hydrophobic resin particles 3 were Algoflon D PTFE dispersion (Solvay Specialty Polymers Japan Co., Ltd.). A 5% ethanol solution of IPBC was used as the poorly water-soluble antifungal agent. The coating composition was formed by adding hydrophobic fine particles and the irregularly shaped silica particles 2 to deionized water while stirring. The pH was then adjusted by adding an alkaline aqueous solution. Finally, the mixture was stopped and an ethanol solution of the poorly water-soluble antifungal agent was added dropwise. The coating was applied to decorative gypsum board (Gyptone Light, Yoshino Gypsum Co., Ltd.) using a spatula and allowed to dry naturally. The coating amount was 30 g / m2.

[0045] The antifouling properties were evaluated using the following method. The substrate 1 on which the coating film 5 was formed was placed horizontally, and simulated soiling, a 1:1 mixture of Kanto loam dust and carbon black, was placed on the coating film 5 through a stainless steel sieve to cover the entire surface. The substrate 1 was then placed vertically to remove excess simulated soiling. The simulated soiling remaining on the coating film 5 was visually evaluated on a 6-point scale, with pitch-black soiling being assigned a score of 0 and almost no soiling being assigned a score of 5. The antifungal properties were evaluated using the following method. The substrate 1 on which the coating film 5 was formed was cut into 5 cm squares, and an aqueous dispersion of spores collected from indoor mold was spray-coated onto the cut pieces. The test pieces were placed in a constant temperature and high humidity environment of approximately 30°C and 80%, and the occurrence of mold was visually confirmed. The antifungal performance was compared based on the number of days until mold occurred.

[0046] The results of Examples 1 to 5 and Comparative Examples 1 to 4 are summarized in Table 1. Coating compositions with different wt % of irregularly shaped silica particles 2, wt % of hydrophobic resin particles 3, wt % of poorly water-soluble antifungal particles 4, and types and amounts of water-soluble alkali were evaluated.

[0047]

[0048] All of Examples 1 to 5 exhibited high antifungal properties, with the number of days until mold development exceeding 12 days, demonstrating high antifungal properties. The higher the pH, the higher the antifungal properties. In other words, it was found that by increasing the pH through the addition of an appropriate amount of water-soluble alkali, it was possible to improve antifungal properties without impairing the antifungal properties. Comparative Example 1 did not provide antifungal properties because hydrophobic resin particles 3 were not added. Comparative Example 2 did not provide antifungal properties because irregularly shaped silica particles 2 were not added. Comparative Example 3 had low pH, resulting in low antifungal properties. Comparative Example 4 contained too much alkaline component, so although the antifungal properties were good, antifungal properties were not provided.

[0049] In this way, according to the first embodiment, it is possible to suppress condensation, dirt, and the resulting mold growth on existing ceilings, walls, and other objects, thereby maintaining cleanliness.

[0050] 1 substrate, 2 irregularly shaped silica particles, 3 hydrophobic resin particles, 4 antifungal particles, 5 coating film

Claims

1. A coating composition comprising: irregularly shaped silica particles having an average particle size of 12 nm to 250 nm; hydrophobic resin particles having an average particle size of 50 nm to 500 nm; and poorly water-soluble anti-fungal particles having rod-like, needle-like or fibrous crystallinity, with a crystal length of 1 μm or more and 10 mm or less and a crystal thickness of 0.1 μm or more and 15 μm or less, wherein a mixed liquid of the irregularly shaped silica particles, the hydrophobic resin particles, water and the anti-fungal particles has an alkaline pH of 9 to 11.

2. The coating composition according to claim 1, wherein the irregularly shaped silica particles are in the form of chains or beads.

3. The coating composition according to claim 1 or 2, wherein the weight ratio of said irregularly shaped silica particles to said hydrophobic resin particles is 70:30 to 95:

5.

4. The coating composition according to any one of claims 1 to 3, wherein the irregularly shaped silica particles are present in the mixed liquid at a concentration of 0.1 wt % to 15 wt %.

5. The coating composition according to any one of claims 1 to 4, which contains sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium silicate or lithium silicate.

6. The coating composition according to any one of claims 1 to 5, wherein the hydrophobic resin particles are fluororesin.

7. The coating composition according to any one of claims 1 to 6, wherein the antifungal particles are made of a benzimidazole or iodine-based antifungal agent having a solubility in water of 0.1% or less.

8. The coating composition according to any one of claims 1 to 6, wherein the antifungal particles are IPBC.

9. The coating composition according to any one of claims 1 to 8, further comprising a water-soluble anti-fungal agent.

10. The coating composition according to any one of claims 1 to 9, wherein the antifungal particles have rod-like crystallinity and a ratio of minor axis to major axis is 1.2 or more.

11. A coating film comprising: irregularly shaped silica particles having an average particle size of 12 nm to 250 nm; hydrophobic resin particles having an average particle size of 50 nm to 500 nm; and poorly water-soluble antifungal particles having rod-like, needle-like or fibrous crystallinity, with the crystal length being 1 μm or more and 10 mm or less, and the crystal thickness being 0.1 μm or more and 15 μm or less.

12. The coating film according to claim 11, wherein the adhering water exhibits alkaline properties.

13. A method for producing a coating film, comprising the steps of: applying a coating composition onto a substrate, the coating composition containing: irregularly shaped silica particles having an average particle size of 12 nm to 250 nm; hydrophobic resin particles having an average particle size of 50 nm to 500 nm; poorly water-soluble antifungal particles having rod-like, needle-like or fibrous crystallinity with a crystal length of 1 μm or more and 10 mm or less and a crystal thickness of 0.1 μm or more and 15 μm or less; and water; and drying the coating composition naturally or with hot air.

14. The method for producing a coating film according to claim 13, wherein the substrate is a water-absorbent ceiling or wall material.

15. The method for producing a coating film according to claim 13 or 14, further comprising the step of applying the coating composition onto the substrate using a brush or a roller.

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