Method for inhibiting biofilm formation and the growth of mold and bacteria on solid surfaces

Abstract

This invention provides a method for suppressing biofilm formation and the growth of fungi and bacteria on solid surfaces in environments where biofilm formation is likely. [Solution] A method for suppressing the formation of biofilms and the growth of mold and bacteria on solid surfaces of various equipment such as food processing machinery and air conditioners, characterized in that, on the surface of air conditioning equipment or the surface of machinery or equipment for processing, preparing, storing, or filling food or beverages, and which is prone to water accumulation and constantly wet, an antibacterial and antifungal ultraviolet-curing or thermosetting resin coating is applied to the solid surface when the solid surface is clean and dry.

Description

[Technical Field]

[0001] The present invention relates primarily to a method for suppressing the formation of biofilms and the growth of molds and bacteria on solid surfaces such as resin surfaces. [Background technology]

[0002] A biofilm is a biological membrane formed on the surface of a solid material by microorganisms growing densely together and secreting extracellular polymer matrix (EPS). Microorganisms in a biofilm differ significantly from freely floating cells and do not exhibit the same sensitivity to antimicrobial agents. Therefore, once a biofilm is formed, antibodies thickly cover the outside of the biofilm but do not penetrate into the biofilm itself (see Non-Patent Literature 1).

[0003] Biofilms readily form on surfaces where water is present. Although the growth rate of biofilms varies depending on the environment, they are mainly formed in five stages (see Non-Patent Literature 2). Stage 1: Formation of a conditioning film on the surface of a solid material and reversible adsorption of microorganisms; Stage 2: Irreversible adsorption of microorganisms onto the conditioning film; Stage 3: High-density proliferation of microorganisms (microcolony formation); Stage 4: EPS secretion from microorganisms and further proliferation of microorganisms; and Stage 5: When the biofilm thickness reaches a certain level, it matures, and parts of it break off, allowing microorganisms to escape from within and move in search of new growth sites (solid material surfaces). Once a biofilm is formed on a solid material surface, it must be physically peeled off or chemically decomposed with cleaning agents to remove it, and even then, it is difficult to remove all of the biofilm. Therefore, it is important to modify the fixed surface to a state where biofilms are less likely to form.

[0004] Moisture is essential for biofilm formation. Therefore, in food processing, there is a high risk of biofilm formation in areas where water tends to accumulate, such as the connection points of agitators and conveyor belts, the inside of pipes, and the bottom of sinks. In air conditioners, during cooling and dehumidifying operations, moisture in the air condenses on the surface of the heat exchanger and drips down as condensate, so there is a high risk of biofilm formation in drain pans and other areas that receive the condensate.

[0005] Drain pans are made of sheet metal, resin, or a combination of sheet metal and resin. Resin drain pans are widely used because they are easy to mold, have excellent heat insulation properties, are lightweight, and inexpensive, and are molded from foamed resin materials such as polystyrene foam. For example, Patent Document 1 proposes a drain pan in which a waterproof resin sheet and an antibacterial film are laminated on the inside to receive condensed water dripping from a heat exchanger. However, after using the air conditioner for 2-3 years, the antibacterial agent is washed away by the condensed water, causing the antibacterial properties to be lost. This leads to the proliferation of bacteria and other microorganisms, which can form sludge or jelly-like substances that clog the condensed water passages and drains.

[0006] Methods using silver ions (e.g., Patent Document 2) and ultraviolet light (e.g., Patent Documents 3-5) have been explored as means of preventing the growth of mold and bacteria in drain pans, but it has been found that the effect of silver ions is insufficient. The method of preventing the growth of mold and bacteria in drain pans using ultraviolet light has the advantage of providing a stable effect over a long period of time, but in the case of resin drain pans, irradiating the drain pan with ultraviolet light causes the resin to deteriorate due to the action of ultraviolet light, making it hard and brittle, which can lead to cracks and water leakage from the drain pan.

[0007] As a means of preventing deterioration of resin drain pans due to ultraviolet light, a method has been proposed (Patent Document 4) in which a substrate coated with a photocatalyst is placed inside the drain pan, and ultraviolet light is irradiated onto the substrate so that it is not directly irradiated onto the drain pan, thereby achieving both prevention of drain pan deterioration and disinfection of drain water. However, there is a problem that ultraviolet light leaks into the surroundings, causing deterioration of parts of the drain pan that are not coated with the photocatalyst, and covering it with a shielding material to prevent deterioration results in a complex device. Therefore, there is also the problem that it is not possible to prevent the growth of mold and bacteria in areas that are not irradiated with ultraviolet light.

[0008] Furthermore, a coating agent (Patent Document 5) has been proposed that contains a metal powder with UV protection properties and an antibacterial and antifungal agent, which protects resin products from ultraviolet rays and prevents the growth of mold and bacteria in areas not irradiated with ultraviolet rays. This coating agent has the advantage of being able to handle a variety of applications regardless of whether or not an ultraviolet irradiation device is installed. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Patent No. 3663016 [Patent Document 2] Japanese Patent Application Publication No. 4-134008 [Patent Document 3] Japanese Patent Publication No. 2001-324195 [Patent Document 4] Japanese Patent Publication No. 2020-134028 [Patent Document 5] Patent No. 7493206 [Non-patent literature]

[0010] [Non-Patent Document 1] Katsunori Furuhata, Journal of the Japan Society for Environmental Biotechnology, Vol. 22, No. 1, 23-32 (2022) [Non-Patent Document 2] Akiko Ogawa, Properties of Material Surfaces and Biofilm Suppression in Biofilm Formation, Thermal Spraying, Vol. 61, No. 2 (2024) [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] Based on their long-standing experience in implementing mold prevention measures, the inventors have been investigating methods to suppress biofilm formation and the growth of mold and bacteria on solid surfaces. Furthermore, conventionally, mold and bacteria have proliferated on solid surfaces, and then antifungal and anti-mold coatings have been applied to prevent mold growth. However, this method makes it difficult to kill mold and bacteria that have penetrated into the interior of solid surfaces such as resins with micropores. Additionally, although the entire mechanism of biofilm formation has not yet been fully elucidated, it has been concluded that once a biofilm reaches a certain thickness, it matures (becomes a mature biofilm), and parts of it break off, allowing microorganisms to escape from within and move in search of new growth sites (solid surfaces). Therefore, once a biofilm forms on a solid surface, it is difficult to remove all of it, and prevention is crucial.

[0012] The present invention aims to provide a method for suppressing biofilm formation and the growth of molds and bacteria on solid surfaces in environments where biofilms are easily formed. [Means for solving the problem]

[0013] The present inventors, after diligent research to solve the above problems, have discovered that in order to suppress biofilm formation and the growth of mold and bacteria on solid surfaces, applying an antibacterial and antifungal coating to a solid surface when the surface to be coated is clean and dry, specifically when it is new and before use, or when it is clean and dry after washing, disinfection, or sterilization, can form an antibacterial and antifungal coating on a clean surface, and that this can prevent biofilm formation and the growth of mold and bacteria quickly and reliably, thus leading to the present invention.

[0014] That is, the present invention provides a method for inhibiting biofilm formation and fungal / bacterial growth on solid surfaces, the method being characterized by applying an antibacterial and antifungal thermosetting or ultraviolet-curable resin coating to a solid surface that is prone to water accumulation and constantly in a wet state, which is a surface of an air conditioning facility or a surface of a machine or facility for processing, preparing, storing or filling food or beverages, when the solid surface is in a clean and dry state. Effects of the Invention

[0015] According to the present invention, an antibacterial and antifungal coating film is formed on a solid surface of an air conditioning facility or the like where fungi and bacteria are notably prone to generate, when the solid surface is in a clean and dry state, whereby it is possible to inhibit biofilm formation and the propagation of fungi and bacteria on the solid surface. Even if biofilm formation or fungal / bacterial propagation occurs on the coating film thereafter, they can be easily removed by alcohol cleaning or the like. Among them, the ultraviolet-curable resin coating has a fast curing speed and does not contain an aqueous solvent, so no drying step is required and a coating film can be formed rapidly, which enables application on a production line (in-line), and application during the installation of air conditioning facilities and the like can also be completed in a short time. For air conditioning facilities or the like equipped with an ultraviolet lamp on the solid surface, the ultraviolet-curable coating can be cured using the built-in equipment. By using the ultraviolet-curable or thermosetting resin coating in combination with an emulsion-type resin coating, the former is separately applied to the ultraviolet irradiation region or the heating region, and the latter is applied to the other surfaces, whereby biofilm formation and the generation of fungi and bacteria can be inhibited over a long period of time in air conditioners, food processing machines and the like. Brief Description of the Drawings

[0016] [Figure 1] (1) An explanatory view illustrating the structure of an exemplary ceiling cassette-type air conditioner, the installation of an ultraviolet lamp, and the coating application portion, and (2) An explanatory view of an example of the coating application portion of the ceiling cassette-type air conditioner. [Figure 2](1) An external view of an example air handling unit and (2) an explanatory diagram of an example of the internal structure and paint application section of the air handling unit. [Figure 3] (1) An external view of an example floor-standing packaged air conditioner and (2) an explanatory diagram of an example of a paint-coated section of the floor-standing packaged air conditioner. [Figure 4] (1) An external view of an example of a ceiling-mounted, concealed-type air conditioner, and (2) an explanatory diagram of an example of the internal structure and paint application area of ​​the said ceiling-mounted, concealed-type air conditioner. [Figure 5] (1) An external view of an example wall-mounted air conditioner and (2) an explanatory diagram of an example of the internal structure and paint application area of ​​the wall-mounted air conditioner. [Modes for carrying out the invention]

[0017] Biofilms are thought to be a state of symbiosis in which microscopic organisms (bacteria, fungi, protozoa, diatoms, etc.) that are extremely common on Earth coexist. Biofilms that form in the environment can be found on the surfaces of natural rocks and artificial objects submerged in lakes, rivers, brackish waters, and the sea; on the surfaces of bridge piers and artificial structures built along the coast that are submerged in water; on the surfaces of ship hulls; on the inner walls of sewer pipes, pipelines and drain pipes that transport crude oil; on the inner surfaces of plastic containers and structures; on kitchen sinks, bathroom floors, corners, drains, drain pipes; inside air conditioners and drain ducts; around outdoor water taps; inside aquariums where goldfish and tropical fish are kept; and inside vases where flowers are placed.

[0018] When biofilms form on the surfaces of pipelines and ships, they increase turbulence in liquids such as crude oil and water, leading to reduced transport efficiency and thrust. Furthermore, when biofilms form on the metal surfaces of artificial structures, the metal material directly beneath them can corrode. Additionally, if biofilms form on the inner walls of water supply lines or pipelines carrying food products from food factories, the biofilms can detach due to water flow and contaminate water or food, potentially causing health problems if ingested by consumers. Pseudomonas aeruginosa, which is widely distributed in aquatic environments such as water systems, readily forms biofilms.

[0019] To investigate the microstructure of biofilms, optical microscopes, confocal laser microscopes, electron microscopes, fluorescence microscopes, atomic force microscopes, and other instruments are used.

[0020] The main components of basic biofilms are water-soluble polymers (polysaccharides, proteins, extracellular DNA) and poorly soluble polymers (cellulose, chitin, lipids, bio-derived surfactants). These extracellular polymers are used to create multilayered biofilms, which are like collective housing for microorganisms. Biofilms can be undulating and uneven, or flat, with a thickness of about 10-60 μm. For example, in Pseudomonas aeruginosa that have formed biofilms, antibiotic resistance increases several hundred times compared to suspended cells, making drug treatment difficult. Extracellular matrix isolated and identified from Staphylococcus aureus biofilms contains polysaccharides, DNA, proteins, etc., as well as approximately 130 types of proteins, of which 64% are cytoplasmic proteins, 12% are secretory proteins, and 6% are membrane proteins (see Katsunori Furuhata, Journal of Environmental Biotechnology, Vol. 22 No. 1 23-32 2022).

[0021] Since biofilm formation begins with bacteria attaching to a carrier, preventing this is crucial. Even if attachment is tolerated, preventing proliferation is essential. Physically removing (cleaning) the biofilm before it matures and forms a strong membrane, and then using disinfectants after cleaning, can delay the formation of subsequent microcolonies as much as possible.

[0022] <<Solid surface>> In the present invention, examples of solid surfaces include resin surfaces (including foamed resins), painted surfaces, metal surfaces, ceramic surfaces, and the like. The resin may be either a thermoplastic resin or a thermosetting resin. The type of resin is not particularly limited, but examples of thermoplastic resins include polyvinyl chloride resin, polyethylene resin, polypropylene resin, polystyrene resin, acrylic resin, ABS resin, and silicone resin, while examples of thermosetting resins include epoxy resin. The application and location of the resin are not limited.

[0023] Specific examples of solid surfaces will be discussed later, but examples include the surfaces of air conditioning equipment and food manufacturing equipment, as well as residential equipment, machinery, bridges, and vehicles (trains, freight cars, trucks, passenger cars, etc.).

[0024] In this invention, there are no limitations on the types of molds and bacteria to be suppressed. Pseudomonas aeruginosa, which is widely distributed in aquatic environments such as bathrooms, rivers, and the sea, easily forms biofilms.

[0025] <<Antibacterial and antifungal paint>> In the suppression method of the present invention, an antibacterial and antifungal coating (hereinafter referred to as antibacterial and antifungal coating) is applied to a solid surface on which a biofilm can be formed and a solid surface on which mold and bacteria can grow, either in-line application (application during the manufacturing process of equipment having the above-mentioned solid surface) or offline application (application outside the manufacturing process, for example, in a factory, office, or general household) when the solid surface is clean and dry, thereby forming a coating film on the solid surface. Hereafter, "antibacterial and antifungal paint" may be referred to simply as "paint."

[0026] In the antibacterial and antifungal coating of the present invention, the film-forming resin includes a base resin that is excellent in film-forming properties (film-forming rate), adhesion of the coating film to solid surfaces where mold and bacteria easily proliferate, and the ability to support antibacterial and antifungal components within the coating film. Poor film-forming properties can be a hindrance, especially in in-line application, and poor adhesion can create a breeding ground for mold and bacteria.

[0027] <Thermosetting resin paint> In this invention, a thermosetting resin coating refers to a coating that can be cured by heat. Thermosetting resin coatings are suitable for the applications of this invention because they are used for coating interior materials in rooms with high humidity, such as bathrooms and kitchens, and for coating the exterior panels of equipment that handles water, such as electric washing machines. As the thermosetting resin coating, known commercially available products can be used. The base resin that forms the coating film of the thermosetting resin coating can be selected from known resins, such as phenolic resins, urea / melamine resins, polyester resins, epoxy resins, polystyrene resins, vinyl resins, polyamide resins, polyolefin resins, polycarbonate resins, acetal resins, acrylic resins, fluororesins, and polyurethane resins. Emulsion-type resin coatings are preferred because they have excellent environmental friendliness. Among these, acrylic silicone resins, fluororesins, and polyurethane resins are preferred. These resins are preferred because they have excellent water resistance, chemical resistance, stain resistance, and weather resistance, and they can form coatings with high adhesion to solid surfaces where mold and bacteria tend to grow.

[0028] For example, in the case of an air conditioner, it is typically used for cooling in the summer and heating in the winter, so each component of the air conditioner is subjected to large temperature changes between operation and shutdown. Therefore, the paint coating must be able to adapt to temperature changes.

[0029] Acrylic silicone resin coatings are preferable because they have a high elongation at break of the coating film and excellent elasticity. The coating film is also preferable because it exhibits excellent recoatability, hardness, water resistance, chemical resistance, oil resistance, stain resistance, and weather resistance. Furthermore, emulsion-type acrylic silicone resin emulsion coatings are particularly preferable because they are easy to prepare, have excellent drying and workability of the coating film (fast coating film formation speed), and have excellent elasticity, hardness, water resistance, adhesion to materials, and are non-polluting. The method for producing acrylic silicone resin emulsions is not particularly limited. For example, they can be produced by emulsion copolymerization of a silicone compound containing polymerizable double bonds and a (meth)acrylic acid ester.

[0030] Commercially available acrylic silicone resin emulsions can be used, such as Cymac US-380, US-450, US-480 (manufactured by Toagosei Co., Ltd.), IE-7170, SE1980CLEAR, BY22-826EX, POLON-MF-40 (manufactured by Toray Dow Corning Co., Ltd.), Movinyl (manufactured by Japan Coating Resin Co., Ltd.), Kotax (manufactured by Toray Corporation), and Daitozol 5000SJ (manufactured by Daito Chemical Industries Co., Ltd.).

[0031] The content of acrylic silicone resin (base resin) in the paint affects the film formation, film thickness, durability, and ease of application (especially ease of application to drain pipes and drain pumps). For this reason, the base resin content is preferably 20-50% by mass (hereinafter abbreviated as "%") in terms of solid content relative to the total mass of the paint, and more preferably 30-45%. If the content is 20% or more, a paint film supporting UV absorbers and antibacterial / antifungal agents can be formed, and if it is 50% or less, the viscosity of the paint does not become too high, and the UV absorbers and antibacterial / antifungal agents can be uniformly dispersed, so that the application work does not become difficult and the drying time of the paint film does not decrease work efficiency.

[0032] Emulsion-type fluororesins and polyurethane resins are also preferred. Polytetrafluoroethylene (PTFE) resin emulsion is preferably used as the fluororesin emulsion. The PTFE resin constituting the PTFE resin emulsion can be not only a homopolymer of tetrafluoroethylene (TFE), but also a copolymer of TFE with a small amount of perfluoroalkyl vinyl ether, hexafluoropropylene, or ethylene. Commercially available PTFE resin emulsions can be used, such as 31-JR (manufactured by Mitsui Chemours Fluoroproducts Co., Ltd.), Polyflon PTFE D series (manufactured by Daikin Industries, Ltd.), and Fluon PTFE AD911E (manufactured by AGC Inc.).

[0033] The polyurethane resin constituting the polyurethane resin emulsion is manufactured by known methods, for example, by reacting a polyisocyanate compound, a polyol compound, and, if necessary, a chain extender. The polyisocyanate compound and polyol compound are not particularly limited; examples of polyisocyanate compounds include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates, while examples of polyol compounds include polyether polyols, polyester polyols, and polycarbonate polyols. Commercially available polyurethane resin emulsions can be used, such as the ETERNACOLL UW series (manufactured by Ube Industries, Ltd.), U-Coat UWS-145 (manufactured by Sanyo Chemical Industries, Ltd.), Superflex 700 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and AQ Urethane (manufactured by Dainippon Paint Co., Ltd.).

[0034] <Ultraviolet curable resin paint> UV-curing resin coatings are suitable for the applications of the present invention because they have a fast curing speed (the resin hardens in a few seconds due to the light energy of ultraviolet rays) and excellent UV resistance. As UV-curable resin coatings, known coatings are used, specifically those containing components such as photopolymerizable oligomers, photopolymerizable monomers (reactive diluents), photoinitiators, other fillers, adhesion promoters, and colorants (pigments). They may be solvent-based or solvent-free. By using monomers as a solvent and washing or removing uncured monomers, a resin film can be formed on surfaces with complex shapes. In other words, UV-curable resin coatings offer excellent adhesion and drying properties to complex surfaces.

[0035] Examples of the photopolymerizable oligomers include polyurethane acrylate, polyester acrylate, polyether acrylate, epoxy acrylate, and others that have an ethylenic double bond, and any of these may be used. Among these, (meth)acrylate-based UV-curable resin coatings are preferable in terms of curing film formation, and a cured coating film can be formed by UV irradiation using a commonly used mercury lamp.

[0036] For example, polyurethane acrylates are polymers obtained by reacting diisocyanates, polyols, and hydroxyacrylates, and have acryloyl groups (CH2=CHCO-) ​​and urethane bonds (-NH·COO-) as functional groups in their molecules. Examples of diisocyanates include hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), methylenebis(4-cyclohexyl isocyanate) (HMDI), trimethylhexamethylene diisocyanate (TMHMDI), tolylene diisocyanate (TDI), 4,4-diphenylmethane diisocyanate (MDI), and xylylene diisocyanate (XDI). Examples of polyols include poly(propylene oxide)diol, poly(propylene oxide)triol, poly(tetramethylene oxide)diol, and ethoxylated bisphenol A. Examples of hydroxyacrylates include 2-hydroxyethyl acrylate (HEA), 2-hydroxyethyl methacrylate (HEMA), 2-hydroxypropyl acrylate (HPA), glycidol dimethacrylate (GDMA), and pentaerythritol triacrylate (PETA). Examples of photopolymerization initiators include benzoin-based photoinitiators, acetophenone-based photoinitiators, thioxanthone-based photoinitiators, oxyphenyl acetate-based photoinitiators, α-hydroxyketone-based photoinitiators, alkylphenone-based photoinitiators, intramolecular hydrogen abstraction-type photoinitiators, and aminoalkylphenone-based photoinitiators. Furthermore, the coating may be an ultraviolet-curable resin coating containing a photopolymerizable oligomer, a polyfunctional (meth)acrylate, a photopolymerization initiator, a light stabilizer, etc. The coating may also contain an ultraviolet absorber.

[0037] Commercially available UV-curing resin coatings can be used, for example, solvent-free UV-curing resin coatings such as "Forseed" (manufactured by Chugoku Marine Paints Co., Ltd.), and water-based or water-soluble UV-curing resin coatings such as "UCECOAT" (manufactured by Daicel Ornex Co., Ltd.).

[0038] <<Antibacterial and antifungal agent>> In the present invention, the component in question imparts antibacterial and antifungal properties to the coating film and has the function of causing airborne mold and bacteria to adhere to the coating film. Antimicrobial and antifungal agents can be arbitrarily selected from known organic, inorganic, and organic-inorganic hybrid antimicrobial and antifungal agents, and two or more, or even three or more, can be used in combination. This is because using antimicrobial and antifungal agents with different antimicrobial spectra allows for application to a wide variety of molds and bacteria. Next, we will explain in detail the combinations of antibacterial and antifungal agents.

[0039] <Anti-mold agent> Synthetic organic fungicides are used as antifungal agents. Organic antifungal agents include isothiazolinoline, benzimidazole, phthalimide, bromine, and iodine-based antifungal agents. Among these antifungal agents, it is best to select those that exhibit very high activity against mold, can be used on textiles and plastics, have a high melting point, and are poorly soluble in water and organic solvents as essential components.

[0040] Examples of benzimidazole-based antifungal agents include 2-(4-thiazolyl)benzimidazole (TBZ) and methylbenzimidazole-2-ylcarbamate. TBZ and similar agents exhibit very high activity and a broad spectrum against mold, are poorly soluble in water and organic solvents, have a high melting point (approximately 300°C), do not volatilize even when exposed to hot air, and have excellent support properties in coating films.

[0041] As an isothiazoline-based antifungal agent, it exhibits high activity against bacteria and fungi, showing a broad spectrum of activity, and is also superior in that it poses almost no risk of adverse effects such as corrosion on resin materials such as polyethylene and polystyrene. Because it has bactericidal and corrosion-preventive properties, there is no risk of corrosion of aluminum materials such as aluminum fins. Isothiazoline-based antifungal agents can be used individually or in combination of two or more types, but using two or more types together results in high activity against various bacteria and fungi.

[0042] Examples of isothiazolin-based fungicides include compounds represented by the following formulas (1) or (2). In the formulas, R 11 R represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. 12 ~R 17 Each of these independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0043] [ka] [ka]

[0044] R 11 Examples of C1-C10 alkyl groups in R include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl groups. 12 ~R 17 Examples of C1-C6 alkyl groups in this context include methyl, ethyl, propyl, butyl, pentyl, and hexyl groups.

[0045] Preferred examples of isothiazolin-based antifungal agents include, for example, 2-n-octyl-4-isothiazolin-3-one (OIT), 2-methyl-4-isothiazolin-3-one (MIT), 2-methyl-4,5-trimethylene-4-isothiazolin-3-one (MTI), 1,2-benzisothiazolin-3-one (BIT), and Nn-butyl-1,2-benzisothiazolin-3-one (Bu-BIT). One or more of these can be used. The isothiazolin-based compounds have antimicrobial properties and are easy to handle as they do not volatilize even when exposed to high temperatures.

[0046] Among the isothiazolinone-based antifungal agents mentioned above, OIT is preferred as a compound to be used in combination with TBZ due to its broad antimicrobial spectrum complementarity and synergistic combination effect. In other words, by using TBZ and an isothiazolinone-based antifungal agent in combination, excellent antibacterial and antifungal effects are achieved against various molds and bacteria.

[0047] The ratio of benzimidazole-based antifungal agents to isothiazoline-based antifungal agents is preferably in the range of 1:1 to 10 by mass ratio. More preferably, it is in the range of 1:1 to 3 by mass ratio, even more preferably in the range of 1:1 to 2 by mass ratio, and particularly preferably in the range of 1:1.1 to 1.5 by mass ratio. By setting the ratio of isothiazoline-based antifungal agents to 1 or more, antibacterial and antifungal functions can be effectively imparted to the coating film. While the antifungal effect of the coating film tends to increase with a higher ratio of isothiazoline-based antifungal agents, the effect plateaus when the ratio of isothiazoline-based antifungal agents exceeds 10, so keeping it at 10 or less avoids wasting isothiazoline-based antifungal agents.

[0048] <Antibacterial agent> When antibacterial agents are combined with antifungal agents, a broad antibacterial spectrum complementing and synergistic effects can be expected. Examples of antibacterial agents include inorganic antibacterial agents such as silver-based and photocatalytic antibacterial agents, synthetic and natural organic antibacterial agents, and organic-inorganic hybrid antibacterial agents. One or more of these can be used. A preferred antibacterial agent is, for example, zinc pyrithione (ZPT).

[0049] <Antibacterial and antifungal agent composition> A preferred antibacterial and antifungal agent composition in the present invention includes the combined use of TBZ, OIT, and an isothiazoline-based antifungal agent other than OIT. Alternatively, a combined use of TBZ, OIT, and an antibacterial agent (ZPT) is also possible, with ZPT being superior in terms of complementing a broad antibacterial spectrum and synergistic combination effects. Among the isothiazoline-based antifungal agents other than OIT, Nn-butyl-1,2-benzisothiazolin-3-one (Bu-BIT) is preferred in terms of complementing a broad antibacterial spectrum and synergistic combination effects.

[0050] In the above composition, it is preferable to use 0.5 to 2 parts, and more preferably 1 to 1.5 parts, of the benzimidazole-based antifungal agent and antibacterial agent per 1 part by mass of TBZ (hereinafter abbreviated as "parts"). In total, it is preferable to use 1 to 10 parts, and more preferably 2 to 8 parts, of the benzimidazole-based antifungal agent per 100 parts of the film-forming resin (solid content). If the amount is 1 part or more, sufficient antifungal properties can be imparted to the coating film, and if it is 10 parts or less, it will not bleed out and fall off from the coating film, so it will not be wasted.

[0051] Furthermore, by using MIT in combination with isothiazolin compounds such as BIT and OIT, or zinc pyrithione (ZPT), it is possible to impart an effect that suppresses the formation of biofilms by the paint. MIT is effective against Pseudomonas aeruginosa. Typically, MIT should be used at a ratio of 0.25 to 1.0 part per 100 parts of the film-forming resin.

[0052] <Other antibacterial agents> In addition to the above-mentioned antibacterial and antifungal agents, other known antibacterial agents, such as benzoic acids, chlorhexidine, sorbic acids, organic iodine compounds, alcohol compounds, phenolic compounds, quaternary ammonium salts, sulfur compounds, and organic acid esters, may be used in combination, provided they do not inhibit the effects of the present invention. Among these antibacterial agents, compounds that do not volatilize in high-temperature rooms are preferred.

[0053] <Amount of antibacterial and antifungal agents> The total amount of antibacterial and antifungal agents in the paint of the present invention is preferably 1 to 20 parts per 100 parts by mass (hereinafter abbreviated as "parts") of the film-forming resin. If the amount is less than 1 part, it becomes difficult to impart sufficient antibacterial and antifungal properties to the film formed by the paint, and if it exceeds 20 parts, there is a risk that the antibacterial and antifungal agents will bleed out and fall off from the film. The total amount of antibacterial and antifungal agents is preferably 2 to 20 parts, more preferably 3 to 15 parts, even more preferably 5 to 15 parts, and particularly preferably 8 to 13 parts.

[0054] As an example, when the paint of the present invention is used as a paint for air conditioners (including air conditioners equipped with ultraviolet irradiation devices), food manufacturing equipment, housing equipment, etc. (for example, as an ultraviolet-resistant antibacterial and antifungal paint), preferred combinations of antibacterial and antifungal agents include TBZ, OIT, Bu-BIT and / or ZPT.

[0055] As another example, when the paint of the present invention is used as a paint for food manufacturing equipment, preferred combinations of antibacterial and antifungal agents include TBZ, OIT, Bu-BIT and / or ZPT. In addition, paints containing at least one antibacterial agent approved as a food additive, such as polylysine, protamine histone, sorbic acid, potassium sorbate, propionic acid, sodium propionate, benzoic acid, and sodium benzoate, are preferred. Among these, the combined use of polylysine and protamine histone is preferred. Antimicrobial agents approved as food additives are typically added in an amount of 0.05 to 0.2 parts per 100 parts of the coating resin.

[0056] <Inorganic antibacterial agents> Examples of inorganic antibacterial agents include at least one metal powder selected from zinc powder, aluminum powder, and stainless steel powder. These metal powders are highly safe, inexpensive, and readily available, and have the function of imparting antibacterial and UV-protective properties to the paint. Among these, zinc powder and stainless steel powder are preferred due to their excellent UV resistance, and zinc powder is even more preferred because it is relatively inexpensive, has high affinity with acrylic silicone resins, and is less likely to detach from the coating film. Zinc powder is also preferred because the coating film retains its antibacterial and antifungal properties even after UV irradiation. Zinc powder may be used in combination with stainless steel powder or aluminum powder. As a measure to prevent deterioration of the coating film due to ultraviolet rays, a method is known in which fine particles are incorporated into the paint and the fine particles in the coating film reflect ultraviolet rays. However, unlike photocatalytic oxides such as titanium dioxide and zinc oxide, the above-mentioned metal powders do not pose a risk of decomposing the coating film-forming resin.

[0057] The metal powder described above preferably has an average particle size in the range of 1 to 50 μm. If the average particle size is 1 μm or larger, problems such as clumping during paint preparation and uneven dispersion in the coating film are avoided, making it easier to form a coating film with excellent surface smoothness. If the average particle size is 50 μm or smaller, the surface area of ​​the metal powder decreases, reducing the area covered by the powder, thus making it less likely for ultraviolet rays to penetrate the coating film. The average particle size of the metal powder is more preferably 2 to 30 μm, and even more preferably 5 to 20 μm. The average particle size is measured by laser diffraction or the like.

[0058] The amount of inorganic antibacterial agent added to the coating of the present invention is preferably 90 to 400 parts per 100 parts of the film-forming resin. If the amount added is less than 90 parts, it becomes difficult to impart ultraviolet protection function to the coating film, while if it exceeds 400 parts, it becomes difficult to retain the inorganic antibacterial agent powder in the coating film, resulting in problems such as the powder falling off the coating film. The amount of inorganic antibacterial agent added is preferably 90 to 300 parts per 100 parts of the film-forming resin, more preferably 90 to 250 parts, and particularly preferably 100 to 200 parts.

[0059] Furthermore, the optimal amount of inorganic antibacterial agent added to the paint of the present invention varies depending on the application, but it is preferably 25 to 65% by mass of the total mass of the paint, and more preferably 30 to 60% by mass. Including 25% by mass or more provides UV protection, and including 65% by mass or less prevents detachment from the paint film.

[0060] When adding inorganic antibacterial agents to UV-curing resin paints, unlike general paints, if there is a large amount of inorganic matter in the paint, the ultraviolet rays may be blocked by the inorganic matter, potentially leaving the resin in an uncured state. This phenomenon is particularly noticeable when applying large amounts of paint. Therefore, it is preferable not to add the aforementioned inorganic antibacterial agents to UV-curing resin paints. When adding inorganic antibacterial agents to thermosetting resin paints, the inorganic matter in the paint may settle before the paint film is baked and cured, and may not be present on the surface of the paint film, thus preventing the antibacterial and antifungal effects from being exerted. Therefore, when adding the aforementioned inorganic antibacterial agents, it is preferable to use those with a small average particle size.

[0061] (Water-soluble polymer) The paint used in this invention may contain a water-soluble polymer. This component has the function of imparting water retention to the coating film formed by the antibacterial and antifungal paint, and the function of supporting the ultraviolet absorber and light stabilizer described later on the coating film. By imparting water retention to the coating film, the antibacterial and antifungal agents supported on the coating film are protected from drying out, and the antibacterial and antifungal functions can be maintained for a long period of time.

[0062] As for water-soluble polymers, nonionic polymers, cationic polymers, or amphoteric polymers are preferred, with nonionic polymers and cationic polymers being more preferred, because they have good compatibility with acrylic silicone resins, facilitate the preparation of paint compositions, and do not easily inhibit the action of antibacterial and antifungal agents.

[0063] Examples of nonionic polymers include gums such as guar gum, locust bean gum, and xanthan gum; cellulose derivatives such as methylcellulose, hydroxyethylcellulose, and hydroxyethylpropylcellulose; polyethylene glycol (for example, with an average molecular weight of 200-400); and polyethylene polypropylene block copolymers.

[0064] Examples of cationic polymers include 2-methacryloyloxyethyl phosphorylcholine (MPC) / butyl acrylate copolymer (LIPIDURE, manufactured by NOF Corporation), vinylimidazolium chloride / vinylpyrrolidone copolymer (Rubicat, manufactured by BASF), polyvinylpyrrolidone / alkylaminoacrylate copolymer (Rubiflex, manufactured by BASF), hydroxyethylcellulose / dimethyldiallylammonium chloride graft polymer (Cellcut, manufactured by National Starch), and dimethyldiallylammonium chloride / acrylamide copolymer (Marquardt, manufactured by Nalco).

[0065] Examples of amphoteric polymers include carboxybetaine polymers (Yukahomer, manufactured by Mitsubishi Chemical Corporation) and copolymers of diallylamine salts and maleic acid (PAS, manufactured by Nitto Boseki Co., Ltd.).

[0066] One or more of these water-soluble polymers can be used, but it is preferable to use one or more selected from polyethylene glycol, methylcellulose, 2-methacryloyloxyethyl phosphorylcholine (MPC) / butyl acrylate copolymer, vinylimidazolium chloride / vinylpyrrolidone copolymer, and dimethyldiallylammonium chloride / acrylamide copolymer.

[0067] The water-soluble polymer content is preferably 0.05 to 3% of the total mass of the paint, and more preferably 0.1 to 1.5%. If the content is 0.05% or more, it can effectively impart water retention to the coating film and maintain antibacterial and antifungal effects. On the other hand, if the content is 3% or less, the compatibility with acrylic silicone resins and the like will not be impaired.

[0068] (UV absorbers, stabilizers) The paint used in this invention may contain an ultraviolet absorber and a stabilizer. The ultraviolet absorber provides the paint film with an ultraviolet protective function, and the stabilizer provides durability to the aforementioned function.

[0069] The ultraviolet absorber is not particularly limited as long as it can prevent deterioration of the coating film, and one or more organic or inorganic ultraviolet absorbers can be used in combination. Organic UV absorbers include salicylic acid derivatives such as pt-butylphenyl salicylate and p-octylphenyl salicylate; benzophenone compounds such as 2-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, and 2-hydroxy-4-n-octoxybenzophenone; benzotriazole compounds such as 2-(2'-hydroxyphenyl)benzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, and 2-(2'-hydroxy-3',5'-di-t-amylphenyl)benzotriazole; and 2-[4-[(2-hydroxy-3-(2'-ethyl)hexyl)o Examples include triazine compounds such as 1-xyl-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-[4-[(2-hydroxy-3-dodecyloxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, and 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine; coumarin compounds such as 3-phenyl-7-(4'-methyl-5'-n-butoxybenzotriazolyl-2-)coumarin, and cyanoacrylate compounds such as 2'-ethyl-2-cyano-3,3'-diphenyl acrylate and 2'-ethylhexyl-2-cyano-3,3'-diphenyl acrylate.

[0070] Among the above UV absorbers, dihydroxybenzophenone-based UV absorbers are preferred from the viewpoint of preventing deterioration of the coating film as much as possible, as they have a UV-cutting effect up to 400 nm and absorb deep ultraviolet light with a wavelength of 280 nm or less. These UV absorbers also have excellent compatibility with acrylic resins and the like.

[0071] Examples of dihydroxybenzophenone-based UV absorbers include 2-hydroxy-4-methoxybenzophenone (Uvinul(R)3049, manufactured by BASF) and 2,4-dihydroxybenzophenone (Uvinul(R)3050, manufactured by BASF).

[0072] The amount of UV absorber used is preferably 5 parts or less, more preferably 0.01 to 3 parts, and even more preferably 0.05 to 2 parts, per 100 parts of the coating resin (solid content). If the amount is 0.1 parts or more, a good UV protection effect can be imparted to the coating film formed by the resin, while if the amount is 5 parts or less, there is no risk of the UV absorber being not sufficiently supported on the resin and bleeding out and falling off, thus the effect is sustained.

[0073] Hindered amine-based light stabilizers are preferred. Examples include bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis(1-octanoxy-2,2,6,6-tetramethylpiperidine-4-yl) sebacate, bis(1-undecanoxy-2,2,6,6-tetramethylpiperidine-4-yl) carbonate, and N,N-bis(2,2,6,6-tetramethylpiperidine-4-yl)hexane-1,6-diamine. Light stabilizers can be used individually or in combination of two or more. More preferably, one or more selected from bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, and bis(1-octanoxy-2,2,6,6-tetramethylpiperidine-4-yl) sebacate are used.

[0074] The amount of light stabilizer used is preferably 0.5 to 3 parts, and more preferably 1 to 2 parts, per 100 parts of the coating resin (solid content). If it is 0.5 parts or more, the durability of the UV protection function can be effectively improved. On the other hand, if it is 3 parts or less, it will not bleed out and fall off without being sufficiently supported on the resin, so it will not be wasted.

[0075] (Other ingredients) To ensure good coatability and prevent sagging during application, the viscosity of the paint should be adjusted as appropriate. If the viscosity is too high, it can be diluted with water; if the viscosity is too low, a thickening agent can be used to adjust the viscosity. As a thickening agent, alkali-soluble or alkali-swelling acrylic acid polymers are preferred because they have good compatibility with resins and provide a thickening effect in small amounts, and can be used in a state containing alkaline components such as amines.

[0076] In addition to the components described above, the paint of the present invention may contain optional components such as fillers, plasticizers, pigments, colorants, defoamers, antistatic agents, and flame retardants, within the limits commonly used by those skilled in the art, as long as they do not impede the effects of the present invention. For example, a defoamer can be used to suppress foam generated when preparing the paint of the present invention. Also, if the paint film is hard and prone to cracking, a plasticizer can be used to adjust the hardness of the paint film.

[0077] <Preparation of antibacterial and antifungal paints> The paint of the present invention can be prepared by blending each of the above-mentioned active ingredients with a balanced amount of water. The water may be deionized water, pure water, or tap water. For example, it can be prepared by first dissolving a water-soluble polymer in water, adding an antibacterial and antifungal agent and other components to the solution and dissolving or dispersing them, then adding the solution to a film-forming resin (solution, emulsion) while stirring, and then adding the antibacterial and antifungal agent while stirring and dispersing it. Alternatively, it can be prepared by first dissolving a water-soluble polymer in water, and separately dissolving or dispersing an antibacterial and antifungal agent and other components in water, then adding the dissolved solution or dispersion and the water-soluble polymer aqueous solution to a film-forming resin (solution, emulsion) while stirring, and finally adding the antibacterial and antifungal agent while stirring and dispersing it.

[0078] The paint of the present invention may contain at least one water-soluble thickener to ensure good coatability and prevent sagging during application. As the thickener, an alkali-soluble or alkali-swelling acrylic acid polymer (e.g., a carboxyl polymer) is preferred because it has good compatibility with the film-forming resin and provides a thickening effect in small amounts. It can be used in a state containing an alkaline component such as an amine. The content of the water-soluble thickener is preferably 0.05 to 3% by mass, and more preferably 0.1 to 1.5% by mass, relative to the total mass of the paint. In addition to the above components, one or more optional components such as fillers, plasticizers, pigments, colorants, defoamers, preservatives, antistatic agents, and surfactants can be added. For example, an defoamer can be used to suppress foam generated during paint preparation, and a plasticizer can be used to adjust the hardness of the paint film if it is too hard and prone to cracking. UV absorbers and light stabilizers can be added in amounts typically used, but it is preferable not to add them due to their low economic efficiency and low effectiveness in improving UV resistance.

[0079] <Coating film formation method> In the present invention's suppression method, a solid surface on which a biofilm can form and a solid surface on which mold and bacteria can grow is coated with a paint having antibacterial and antifungal properties. A clean state refers to a state in which no foreign matter such as dust is attached and the surface is not dirty. A dry state refers to a state in which the surface is dry to a level that is not visible to the human eye. This is because surfaces where water constantly accumulates (especially the surfaces of resin parts; so-called resin surfaces) are prone to the growth of biofilms, mold, and bacteria. The present invention's method for suppressing biofilm formation, which involves forming an antibacterial and antifungal coating on a solid surface before use, either in-line or offline, is particularly effective for materials constituting air conditioners, food processing machinery, etc., before use (new), especially for solid surfaces that are prone to biofilm formation.

[0080] For example, in the case of air conditioners, this includes commercial, residential, and automotive air conditioners. Specifically, it covers at least one solid surface among the components that make up an air conditioner, such as the intake, outlet, air passage wall, fan, air deflector, damper, drain pan, drain pump, and drain piping. It also covers solid surfaces of total heat exchangers, ducts, branch chambers, humidifiers, etc., which require mold prevention measures similar to those for air conditioners. Figures 1 to 5 show an example of the basic structure of an air conditioner.

[0081] The present invention's suppression method is suitably applied to the drain pan, drain pump, and drain piping, which are components of air conditioners where biofilm is likely to form. In air conditioners having solid surfaces to be coated, it is desirable that the drain pan be configured to be irradiated with ultraviolet light by an ultraviolet irradiation device equipped with an ultraviolet lamp, and that an ultraviolet-curing resin coating be applied. If an ultraviolet irradiation device is not provided, it is preferable to apply an acrylic silicone resin coating containing an antibacterial and antifungal agent. While ultraviolet-curing resin coatings or acrylic silicone resin coatings can be applied to the sirocco fan, fan cover, interior of the unit, and air outlet other than the drain pan, it is preferable to apply an acrylic silicone resin coating considering appearance (aesthetics), economy, and the configuration of the device, and from the viewpoint of productivity, it is preferable to apply it offline (at the installation site).

[0082] The aforementioned ultraviolet irradiation device is not particularly limited and can be installed in an air conditioner; it may be any known device capable of irradiating light including ultraviolet light. In the case of ceiling cassette type air conditioners, UVC-LEDs are preferred because they consume relatively little power and therefore provide energy-saving benefits. It is desirable to install the ultraviolet irradiation device so that ultraviolet light is irradiated onto the drain pan, drain water storage section, etc. In the case of air handling units and floor-standing package type air conditioners (large air conditioners), a large ultraviolet irradiation device is required, so a mercury UVC device is preferable. In the case of ceiling-suspended, ceiling-concealed, and wall-mounted air conditioners (small air conditioners), an ultraviolet irradiation device (UVC-LED) is not mandatory, but it may be installed.

[0083] The wavelength range of the ultraviolet light to be irradiated is preferably the deep ultraviolet (UV-C) wavelength range (100-280 nm).

[0084] Furthermore, the paint of the present invention, which is configured to contain an inorganic antibacterial agent, can be suitably applied to solid surfaces in food manufacturing facilities or residential facilities equipped with ultraviolet irradiation devices. For example, it can be applied to the parts and surrounding areas of food manufacturing equipment components that have a function to prevent the growth of bacteria and mold by irradiating ultraviolet light onto slicer blades, parts called "bridges" that connect conveyors, or the air outlets of packaging machines that open the tare bag with air to seal the product. The types and materials of the equipment components mentioned above are not particularly limited, and examples include rubber, plastic, and metal components. Specifically, the paint of the present invention is applied to resin components such as slicer blades, packings and tubes installed around the "transfer" sections of conveyors or air outlets of packaging machines, and control panel covers. This prevents deterioration of components exposed to ultraviolet light and surrounding components due to ultraviolet light, and also prevents the growth of bacteria and mold on these components even when ultraviolet light irradiation is stopped. Suppression of ultraviolet light in food manufacturing equipment can be carried out in the same manner as described for suppression of ultraviolet light in air conditioners.

[0085] Furthermore, the present invention can be applied to residential equipment components that have a function to prevent the growth of bacteria and mold through ultraviolet irradiation, such as the back of a bathtub, the inside of a toilet water tank or toilet shower nozzle, kitchen products such as storage cabinets under sinks and range hoods, specifically to the parts and surrounding areas that are irradiated with ultraviolet light. Specifically, the paint of the present invention is applied to the back of a bathtub, the floor under the bathtub, the wall members of the storage cabinet under the sink, the inside of a toilet water tank, and the resin components around the shower nozzle. This prevents deterioration of the irradiated components and surrounding components due to ultraviolet light, and also prevents the growth of bacteria and mold on the components even when ultraviolet irradiation is stopped. The treatment method for residential equipment can be the same as the treatment method for air conditioners described above.

[0086] The paint of the present invention can be applied to solid surfaces on which biofilm may form or mold and bacteria may grow, even in applications other than the aforementioned air conditioners and food manufacturing equipment, and regardless of whether or not an ultraviolet irradiation device is installed. Examples of such surfaces include various heat exchangers, floors, walls, and ceilings of medical facilities such as hospitals and nursing care facilities, food storage areas, tanks, conveyors, floors, industrial machinery, storage tanks, medical equipment, floating equipment, marine equipment, and solid surfaces of buildings. Considering that mold growth increases after air conditioning is turned off in the summer, the cumulative irradiation dose can be reduced by operating the ultraviolet lamp intermittently for a predetermined period of time after the air conditioner has been turned off.

[0087] In this invention, the paint can be applied to areas that are not exposed to ultraviolet light, and preferably to the entire surface of the drain pan. By doing so, antibacterial and antifungal properties can be imparted to surfaces that are not exposed to ultraviolet light, thereby preventing the growth of bacteria and mold on the drain pan even when ultraviolet light irradiation is stopped. This allows for comprehensive prevention of the growth of bacteria and mold in air conditioners. Furthermore, by applying the paint to parts other than the drain pan (drain piping, drain pump, etc.), antibacterial and antifungal functions can be imparted without irradiation with ultraviolet light. As a result, it becomes possible to concentrate the ultraviolet irradiation on the drain water in the drain pan near the drain pump installation site, where bacteria and mold are likely to proliferate, thereby minimizing photodegradation of resin parts other than the drain pan due to ultraviolet light leakage to areas other than the irradiation site.

[0088] By selecting a paint that possesses antibacterial and antifungal properties and excellent adhesion, application to areas with complex structures becomes easy. Combined with the effects of the antibacterial and antifungal agents incorporated into the paint, it is possible to suppress the formation of biofilms and the growth of mold and bacteria on solid surfaces. It can be easily applied even to solid surfaces with many irregularities and joints and complex structures. Furthermore, by irradiating the painted surface with ultraviolet light, the formation of biofilms and the growth of mold and bacteria on solid surfaces can be further suppressed.

[0089] When applying paint, it is advisable to wipe and clean the surface to be painted before application to minimize the growth of mold and bacteria. The wiping and cleaning can be done in any way that removes mold and bacteria from the surface to be painted, and is not particularly limited. For example, one method is to wipe the surface with a cloth or paper soaked in alcohol (ethanol, isopropanol) with a concentration of 70% or higher. Next, the coating of the present invention is applied to the surface to be coated after wiping and cleaning, and dried to form a coating film. The coating can be applied by known methods such as roll coating, spray coating, dipping, flow coating, spin coating, brush coating, and trowel coating. Among these, roll coating and spray coating are preferred from the viewpoint of easily controlling the film thickness.

[0090] The paint used in this invention is usually applied without dilution. However, the product may be diluted with a solvent during application. Examples of solvents include aqueous solvents such as water, ethanol, propanol, glycol ethers, or mixtures of two or more of these. Water / ethanol mixtures and water / propanol mixtures are preferred from the viewpoint of safety, coatability, and drying properties.

[0091] The amount of paint applied in this invention is not particularly limited, but if the amount applied is too small, it will not be possible to apply it uniformly to the desired area, and the paint film will not be able to adequately inhibit the growth of mold and bacteria. On the other hand, if the amount applied is too large, it will be economically unfeasible and there is a concern that it may adversely affect the heat exchanger when applied to an air conditioner. For this reason, it is preferable that the film thickness after drying be about 60 to 1000 μm. More preferably, it is 70 to 800 μm, and even more preferably, 80 to 700 μm.

[0092] On the other hand, when applying the coating to an area irradiated with ultraviolet light from an ultraviolet irradiation device, the thickness of the coating film is not particularly limited, but to ensure the coating film exhibits sufficient ultraviolet protection, it is desirable to have a thickness of 300 to 700 μm, and more preferably 400 μm or more and 600 μm or less. When applying a coating with ultraviolet protection to an area not irradiated with ultraviolet light, the amount applied may be less than this, for example, 200 to 400 μm. Drying after application can be done by natural drying, heating (preferably 70°C or lower), or forced drying with airflow, and the drying time can be about 0.5 to 24 hours.

[0093] Furthermore, paints containing inorganic antibacterial and antifungal agents possess both UV protection and antifungal properties. Therefore, by applying them to equipment equipped with UV irradiation devices (for example, the drain pan of an air conditioner), it is possible to effectively prevent deterioration of the drain pan due to UV irradiation, the growth of bacteria and mold on the drain water and drain pan surface, and the formation of biofilm over a long period of time. Since it can prevent the growth of bacteria and mold and the formation of biofilm even when UV irradiation is stopped, the number and duration of UV irradiation can be reduced, further minimizing the impact of UV rays on the drain pan. By applying it to components other than the drain pan of an air conditioner, antifungal properties are provided, and deterioration of resin components due to leaked UV rays can be prevented, eliminating the need to install UV shielding measures inside the air conditioner. [Examples]

[0094] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited in any way to these examples.

[0095] (UV protection test) A new sheet of expanded polystyrene foam for the drain pan of a ceiling-mounted air conditioner was cut into 100mm x 100mm pieces, and the surface was disinfected by wiping it with a cloth impregnated with 70% ethanol. Next, paint was applied, and the paint film was allowed to form by natural drying for 24 hours to create the test board. Unless otherwise specified, the amount of paint applied was 500g / m². 2 That's what I decided. Place the test plate in a dark room, and irradiate deep ultraviolet light with a wavelength of 265 nm from a distance of 10 cm using an ultraviolet lamp (manufactured by Stanley Electric Co., Ltd., deep ultraviolet LED) at an irradiation intensity of 10 mW / cm 2 , observe the surface state of the test plate after a predetermined time has elapsed, and evaluate the ultraviolet protection property according to the following evaluation criteria. The general irradiation intensity of ultraviolet lamps installed in air conditioners (referred to as practical germicidal ray illuminance) is 0.12 mW / cm 2 , so the irradiation intensity in this test corresponds to an accelerated test condition of approximately 83 times.

[0096] <Ultraviolet Protection Property Evaluation Criteria> ○: No change after an irradiation time of 315 hours (equivalent to 3 years at practical germicidal ray illuminance, irradiation dose: 11,353 J / cm 2 ) (judged as having ultraviolet protection property). △: Discoloration is observed within an irradiation time of 315 hours. ×: Discoloration is observed within an irradiation time of 105 hours (equivalent to 1 year at practical germicidal ray illuminance, irradiation dose: 3,784 J / c m 2 ). ××: Discoloration is observed within an irradiation time of 36 hours (equivalent to 4 months at practical germicidal ray illuminance, irradiation dose: 1,296 J / c m 2 ).

[0097] (Mold Resistance Test) A mixed culture of three species, Aspergillus niger group, Penicillium genus, and Cladosporium genus, was used as the test bacteria, and a mold resistance test was carried out in accordance with JIS Z2911. Specifically, Test Specimen 1 and Test Specimen 2 were placed in the center of the medium smeared with the test bacteria such that the paint-coated surface faced the medium side, followed by incubation in a constant temperature bath at 26°C for 2 weeks, and then the antifungal property was judged according to the following antifungal property evaluation criteria. The medium smeared with the test bacteria was prepared by adjusting the test bacteria to a concentration of 10 5 cfu / mL using sterilized purified water to prepare a bacterial solution, and then smearing 100 μL of the bacterial solution onto a PDA medium. In addition, the mold resistance test was also carried out on each test plate (separately prepared) before starting the ultraviolet protection test, to evaluate the mold resistance.

[0098] <Criteria for evaluating mold resistance> ○: No mycelial growth was observed in the area where the test sample came into contact (fungal resistance present). △: Mycelial growth is observed in the area where the test sample came into contact, but the area of ​​mycelial growth is It must not exceed one-third of the total surface area of ​​the contact area. ×: Mycelial growth was observed in the area of ​​the test sample that came into contact with the sample, and the area of ​​the mycelial growth was... It exceeds one-third of the total surface area of ​​the contact area.

[0099] (Example 1) A dispersion was prepared by dissolving 40 parts of acrylic silicone resin emulsion (solids content: 46%, manufactured by Japan Coating Resin Co., Ltd.) and 0.4 parts of 2-methacryloyloxyethyl phosphorylcholine (MPC) / butyl acrylate copolymer (LIPIDURE, manufactured by NOF Corporation) in 7.5 parts of purified water. To this solution, 0.55 parts of TBZ, 0.7 parts of OIT, and 0.55 parts of Bu-BIT (total 1.8 parts) were added as antimicrobial and antifungal agents, and 0.3 parts of a silicone-based defoamer was added and stirred to prepare a dispersion. Next, 50 parts of zinc powder (average particle size: 10 μm, reagent) were added and stirred to prepare a paint. The resulting paint is applied to a polystyrene board (500g / m²). 2 Test panels were prepared using the following method, and ultraviolet protection tests and mold resistance tests after ultraviolet irradiation were conducted.

[0100] (Example 2) In Example 1, a paint was prepared in the same manner as in Example 1, except that aluminum powder was added instead of zinc powder. To this paint, 0.1 parts of a dihydroxybenzophenone-based UV absorber (Ubinal 3049, manufactured by BASF) and 0.1 parts of a hindered amine-based light stabilizer (HALS) (Tinuvin 765, manufactured by BASF) were added and stirred to obtain a paint. UV protection tests and mold resistance tests after UV irradiation were performed in the same manner as in Example 1.

[0101] (Example 3) In Example 1, the paint was prepared in the same manner as in Example 1, except that stainless steel powder was added instead of zinc powder. An ultraviolet protection test and a mold resistance test after ultraviolet irradiation were then performed in the same manner as in Example 1.

[0102] (Examples 4-7) Using the binder solution obtained in Example 1, zinc powder (average particle size: 10 μm, reagent) was added to the total amount of paint so that the amount of zinc powder in the total amount of paint was as shown in Table 1 to prepare the paint. An ultraviolet protection test and a mold resistance test after ultraviolet irradiation were then performed in the same manner as in Example 1.

[0103] (Example 8) Forty parts of acrylic silicone resin emulsion (solids content: 46%, manufactured by Japan Coating Resin Co., Ltd.), 0.55 parts of TBZ, 0.7 parts of OIT, 0.55 parts of Bu-BIT, and 0.2 parts of zinc pyrithione (ZPT) as antibacterial and antifungal agents (total 1.8 parts), and 0.3 parts of silicone-based defoaming agent were added and stirred to prepare the paint. Similar to Example 1, the paint was applied to the polystyrene board (200g / m²). 2 Test panels were prepared using the following method, and ultraviolet protection tests and mold resistance tests after ultraviolet irradiation were conducted.

[0104] (Example 9) Forty parts of acrylic silicone resin emulsion (solids content: 46%, manufactured by Japan Coating Resin Co., Ltd.), 0.55 parts of TBZ, 0.7 parts of OIT, and 0.55 parts of Bu-BIT (total 1.8 parts) as antibacterial and antifungal agents, and 0.3 parts of silicone-based defoaming agent were added and stirred to prepare the paint. Similar to Example 8, test boards were prepared by applying the paint to polystyrene boards, and ultraviolet protection tests and mold resistance tests after ultraviolet irradiation were conducted.

[0105] The results described above are summarized in Table 1. From Table 1, polystyrene boards coated with paint containing metal powder showed UV protection and mold resistance, but UV protection tended to be inferior when the amount of coating was small (Examples 1-8). Polystyrene boards coated with antibacterial and antifungal paint containing ZPT instead of zinc powder showed superior mold resistance after UV irradiation compared to polystyrene boards coated with paint without antibacterial agents.

[0106] [Table 1]

[0107] Next, we will specifically explain examples of how to apply antibacterial and antifungal paints.

[0108] (Example 10) Example of coating application on a ceiling cassette type air conditioner (Figure 1). A UV lamp (Stanley Electric Co., Ltd., deep ultraviolet UV-LED, peak wavelength 250-285nm) was placed in a position where ultraviolet light could be irradiated onto the drain water outlet of the drain pan. The drain pan surface, which has been wiped and disinfected with a cloth impregnated with 70% ethanol, is then exposed to ultraviolet light (deep ultraviolet) over the entire area (approximately 100 cm). 2 The antibacterial and antifungal acrylic silicone resin emulsion paint prepared in Example 1 was applied to the ) and the antibacterial and antifungal paint prepared in Example 9 was applied to the sirocco fan, the interior walls (sides and top) of the machine, and the air outlet. Deep ultraviolet light was intermittently applied during the operation of the air conditioner (7 hours) and after it stopped (3-5 hours).

[0109] (Example 11) An example of coating on an air handling unit (Figure 2). The acrylic silicone resin paint of Example 1 was applied to the drain pan, and the antibacterial and antifungal paint of Example 1 was applied to the remaining part of the casing and the entire inner wall of the motor chamber.

[0110] (Example 12) An example of coating using a floor-standing package (Figure 3). The antibacterial and antifungal paint of Example 1 was applied to the drain pan and the entire inner wall of the remaining part of the machine.

[0111] (Example 13) Examples of coating application for ceiling-mounted and concealed-type air conditioners (Figure 4). The antibacterial and antifungal paint of Example 4 was applied to the drain pan and the entire inner wall of the remaining part of the machine.

[0112] (Example 14) Example of application to a wall-mounted air conditioner (Figure 5). The antibacterial and antifungal paint of Example 6 was applied to the inside of the lower and upper drain pans and to the air outlet.

[0113] (Example 15) Example of coating application on a wall-mounted air conditioner (Figure 5). The antibacterial and antifungal paint of Example 8 was applied to the inside of the lower and upper drain pans, and the paint of Example 9 was applied to the air outlet.

[0114] In Examples 10-15, the presence or absence of biofilm formation in the drain pan of air conditioners coated with antibacterial and antifungal paint was visually confirmed (after 6 months). As a result, no biofilm formation was observed in any of the air conditioners. On the other hand, biofilm formation was confirmed in all of the same type of air conditioners that were not coated with antibacterial and antifungal paint. [Industrial applicability]

[0115] The present invention provides a method for biofilm formation and inhibition of mold and bacterial growth on solid surfaces, enabling in-line antibacterial and antifungal treatment with antibacterial and antifungal coatings. This allows for the provision of long-lasting antibacterial and antifungal functions in a relatively simple manner. Since it prevents the deterioration of resin products and other materials due to the growth of mold and bacteria, it makes a significant contribution to improving indoor environments not only in food factories, pharmaceutical factories, cosmetics factories, hospitals, schools, and offices, but also in general households.

Claims

1. A method for suppressing the formation of biofilms and the growth of molds and bacteria on a solid surface, characterized in that, on a solid surface such as the surface of air conditioning equipment or the surface of machinery or equipment used for processing, preparing, storing, or filling food or beverages, which is prone to water accumulation and is constantly wet, a thermosetting or ultraviolet-curing resin coating having antibacterial and antifungal properties is applied to the solid surface when the solid surface is clean and dry.

2. An ultraviolet lamp is provided on the aforementioned solid surface. The method according to claim 1, wherein a thermosetting or ultraviolet-curing resin coating having antibacterial and antifungal properties is applied to a solid surface corresponding to the irradiation area of ​​the ultraviolet lamp.

3. Furthermore, the method according to claim 2, wherein an emulsion-type resin coating having antibacterial and antifungal properties is applied to a solid surface that does not correspond to the irradiation area of ​​the ultraviolet lamp.

4. The solid surface is the surface of the air conditioning equipment. The method according to claim 2 or 3, wherein an ultraviolet lamp positioned on the surface is irradiated for a certain period of time while the air conditioning equipment is in operation and after it has stopped operating.

5. The method according to claim 1, wherein the air conditioning equipment comprises at least one of the following elements: a duct, an intake port, an outlet port, a ventilation wall, a fan, a wind deflector, a damper, a drain pan, a drain pump, and a drain pipe.

6. The method according to claim 1, wherein the antibacterial and antifungal thermosetting resin coating and the ultraviolet curing resin coating each contain, in total, 1 to 20 parts by mass of two or more antifungal agents selected from isothiazolin-based and benzimidazole-based agents, and at least one antibacterial agent, per 100 parts by mass of the film-forming resin.

7. The method according to claim 1, wherein the thermosetting resin coating having antibacterial and antifungal properties contains 30 to 60% by mass of at least one metal powder selected from zinc, aluminum, and stainless steel, based on the total amount of the coating.

8. The method according to claim 3, wherein the emulsion-type resin coating having antibacterial and antifungal properties contains a total of 1 to 20 parts by mass of two or more antifungal agents selected from isothiazolin-based and benzimidazole-based agents and at least one antibacterial agent per 100 parts by mass of the film-forming resin.

9. The method according to claim 1, wherein the solid surface is a foamed polystyrene resin surface.

10. The method according to claim 1, wherein the solid surface is a painted surface.

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