A long-lasting antibacterial coating agent composed of food-grade materials that can be removed by hot water treatment.

Abstract

We provide an antibacterial coating agent that combines antibacterial effect with safety. [Solution] An antimicrobial coating agent comprising an aqueous film-forming agent, one or more antimicrobial agents, and a stable solvent, wherein the aqueous film-forming agent is polyvinyl alcohol whose safety is guaranteed, the antimicrobial agents are one or more combinations of food additives or food materials with a history of consumption, and the stable solvent is water.

Description

[Technical Field]

[0001] This invention relates to an antimicrobial coating agent that is safe for humans, effectively inhibits the growth of microorganisms on structures, and has mild peeling conditions for the coating layer. More specifically, it is an antimicrobial coating agent composed of an antimicrobial component which is a food additive or food material extract, a polymer with high water resistance and unique temperature sensitivity which has a history of being used in food, and a stable solvent. In other words, this coating agent has the property of maintaining adhesion for a long period of time even on structures in high humidity environments, while peeling can be adjusted under mild conditions with warm water, and furthermore, it has a high non-toxicity value and is safe for living organisms. [Background technology]

[0002] Traditionally, in humid environments both inside and outside buildings, such as bathrooms, swimming pools, and the walls and ceilings of various factories and warehouses, the growth of mold and other microorganisms has posed sanitary and aesthetic problems. Mold, in particular, not only spoils the appearance but also causes structural damage, releases spores, odors, and toxins into the air, degrading indoor air quality, and can even contribute to allergies and respiratory problems, increasing health risks. Especially in places where a high level of cleanliness is required, such as hospitals and food processing facilities, the removal and inhibition of growth of bacteria and viruses in addition to mold is considered important. In nurseries, kindergartens, children's centers, nursing homes, and hospitals, where infants and the elderly with weakened immune systems gather, there is a growing demand for safe and effective antibacterial and antimicrobial growth inhibitory coatings to prevent infectious diseases.

[0003] Traditionally, chlorine-based removers have been widely used for bacterial removal. While they are highly effective and fast-acting, their removal capabilities are limited to the surface of structures. Therefore, maintaining a clean environment requires continuous and frequent removal using chlorine-based removers.

[0004] Chlorine-based bacterial removal agents rely on harmful chemicals such as hypochlorous acid and chlorine, and frequent removal operations have been criticized for potential environmental burdens, safety concerns for humans, and accelerated deterioration of treated structures.

[0005] Furthermore, chlorine-based disinfectants do not prevent the re-growth of bacteria and are not an effective means of maintaining a clean environment.

[0006] For the reasons stated above, selecting chlorine-based disinfectants as a measure against bacteria such as mold in large-scale facilities requires significant costs to maintain a clean environment, sometimes leading to situations where maintaining a clean environment in parts of it has to be abandoned.

[0007] In particular, in food processing plants, which are constantly at risk of food poisoning and other problems, bacterial growth, especially mold, is a very serious issue. However, the use of removal agents containing harmful chemicals creates a risk of food contamination separate from bacterial contamination. As a result, reducing bacterial removal operations can lead to a decline in food safety. Therefore, bacterial control in food processing plants is particularly constrained, and there is a strong demand for the development of safe, proven antimicrobial coating agents composed of ingredients with a proven track record of safety in food consumption.

[0008] Furthermore, regarding the use of disinfectants and antibacterial agents in public and medical facilities, there is a demand for antibacterial coating agents that are harmless to the human body while maintaining a high disinfecting effect over a long period. Most conventional disinfectants and antibacterial agents rely on chemically synthesized substances, and due to concerns about their impact on the environment and human health, there is a need for highly safe solutions that give due consideration to animals, including humans, and the environment. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2023-004163 (Antibacterial Film) [Patent Document 2] Japanese Patent Publication No. 2014-167011, Japanese Patent Publication No. 2009-527357 (Removable antimicrobial coating composition and method of use thereof) [Patent Document 3] Japanese Patent Publication No. 2015-514758 (Long-lasting surface antibacterial agent and application method) [Patent Document 4] JP-A-08-092878 (Antibacterial wall covering material) [Patent Document 5] JP-A-08-113898 (Antibacterial wall covering material) [Patent Document 6] JP 08-113899 (Antibacterial wall covering material) [Patent Document 7] JP 08-144472 (Composite building materials) [Patent Document 8] Japanese Patent Publication No. 09-100205 (Antibacterial Coating Composition) [Patent Document 9] Japanese Patent Publication No. 09-132735 (Antibacterial coating film using antibacterial paint) [Patent Document 10] Japanese Patent Publication No. 2000-511887 (Method of using water-stabilized organosilane) [Patent Document 11] Japanese Patent Publication No. 11-228908 (Antibacterial Coating Resin Composition) [Patent Document 12] Japanese Patent Publication No. 2001-081409 (Antibacterial coating agent, antibacterial agent, and method for preventing hospital-acquired infections) [Patent Document 13] Japanese Patent Publication No. 2006-213709 (Water-stabilized organosilane and method of use) [Patent Document 14] Japanese Patent Publication No. 2008-308437 (Antibacterial coating agent for toilet bowls and antibacterial method for toilet bowls) [Patent Document 15] Japanese Patent Publication No. 2009-067849 (Antibacterial coating film, cooking container having the same, and antibacterial coating agent) [Patent Document 16] Japanese Patent Publication No. 2009-138288 (Antibacterial agent and antibacterial coating agent) [Patent Document 17] Japanese Patent Publication No. 2015-190033 (Laminate and method for manufacturing the same, as well as reflector, mirror film, antibacterial coating, conductive film, and thermal conductor) [Patent Document 18] Japanese Patent Publication No. 2015-191180 (Laminate and method for manufacturing the same, as well as reflector, mirror film, antibacterial coating, conductive film, and thermal conductor) [Patent Document 19] Re-Publication No. 2016 / 047568 (Antibacterial Sheet, Antibacterial Coat, Laminate, Antibacterial Liquid) [Patent Document 20] Japanese Unexamined Patent Application Publication No. 2017-030823 (Packaging Bag) [Patent Document 21] Japanese Unexamined Patent Application Publication No. 2022-018206 (Antibacterial Agent Composition) [Patent Document 22] Japanese Unexamined Patent Application Publication No. 2022-080334 (Antibacterial Coating Agent and Printed Matter Using the Same) [Patent Document 23] Japanese Patent No. 7126642 (Antibacterial Coating Agent, Printed Matter Using the Same) [Non-Patent Document]

[0010] [Non-Patent Document 1] Presentato A, Piacenza E, Scurria A, Albanese L, Zabini F, Meneguzzo F, Nuzzo D, Pagliaro M, Martino DC, Alduina R, Ciriminna R., A New Water-Soluble Bactericidal Agent for the Treatment of Infections Caused by Gram-Positive and Gram-Negative Bacterial Strains., September 8, 2020, Antibiotics (Basel), Vol. 9, No. 9, pp. 586 - 600 [Non-Patent Document 2] Presentato A, Scurria A, Albanese L, Lino C, Sciortino M, Pagliaro M, Zabini F, Meneguzzo F, Alduina R, Nuzzo D, Ciriminna R. Superior Antibacterial Activity of Integral Lemon Pectin Extracted via Hydrodynamic Cavitation. ChemistryOpen, May 28, 2020, Vol. 9, No. 5, pp. 628 - 630

Non - Patent Document 3

Non - Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0011] The antibacterial coating agent disclosed in Patent Document 1, like the present invention, uses polyvinyl alcohol as a coating substrate and contains sorbates, dehydroacetates, propions, acetates, and benzoates as antibacterial components. Some of the described antibacterial agents are registered as food additives, but for example, sorbic acid has an upper limit on the amount that can be used and cannot be said to be completely safe. Also, propionic acid is a compound that has an unpleasant odor. The film composed of polyvinyl alcohol did not show blocking properties when dried with water at 80°C for 30 minutes, and showed water resistance and heat resistance, but it did not exhibit the property of being able to peel off the antibacterial coating layer of the present invention under specific mild conditions. The antibacterial coating agent disclosed in Patent Document 2 is an antibacterial coating agent based on an organic polymer, and it is stated that the peeling conditions can be changed by adding additives. However, although the coating agent does not dissolve in water at 20°C, it is easily removed mechanically, and in cold water, the addition of iron chloride is required to maintain stability. Therefore, it does not have sufficient strength to maintain the antibacterial coating layer in a living environment. The disinfecting effect of the surface disinfectant disclosed in Patent Document 3 lasts for a maximum of 24 hours and is not suitable as a method for maintaining a continuously disinfected environment. The antibacterial coating agent disclosed in Patent Document 11 is a coating agent based on an alkyd-modified acrylic polyol resin that contains heavy metal ions such as silver, copper, zinc, tin, lead, bismuth, mercury, cadmium, or chromium as antibacterial agents. Because it requires the use of organic solvents for application and baking the coated surface at 50-100°C, it is virtually impossible to apply it to large areas such as walls and ceilings in living areas or facilities in operation. The antibacterial coating agent disclosed in Patent Document 12 uses nano-sized silver or copper particles as the antibacterial agent and an acrylic resin as the coating film substrate forming component. This antibacterial agent is characterized by surface treatment by spraying, durability of the coating layer, and water resistance, but removal requires wiping with alcohol. Therefore, it is not suitable for situations where removal and repainting are anticipated on fabrics or large areas of walls and ceilings. The antibacterial coating agent disclosed in Patent Document 16 is an antibacterial coating agent consisting of a chitosan derivative using silver ions as the main antibacterial active component and a fatty acid. Although it is highly safe for the human body, its range of applications is limited to textiles. The antibacterial coating agents disclosed in Patent Documents 4 to 6 have an antibacterial coating layer formed on their surface, but the antibacterial component is an inorganic antibacterial agent whose safety for humans has not been demonstrated. Furthermore, they are laminated structures composed of vinyl chloride, polyethylene terephthalate, etc., which limits their ability to be applied to large areas with uneven surfaces, and they are not designed to withstand peeling of the coating layer. In the composite building material with an antibacterial agent coated on the interior side disclosed in Patent Document 7, the antibacterial active component is heavy metal ions such as copper ions and silver ions mixed into the resin to form an antibacterial coating layer, which limits the application location and is constrained by the fact that it is a building material. The antibacterial coating composition disclosed in Patent Document 8 is based on silver zeolite as the antibacterial component and is an antibacterial coating agent using heat or ultraviolet curing resin. In particular, application by in-mold coating has low versatility due to the specific requirements of the equipment, and is unsuitable for antibacterial coating over large areas in terms of reapplication after the antibacterial effect has diminished. In the antibacterial coating film disclosed in Patent Document 9, the antibacterial agent is a particle of synthetic butylosulfate silver complex, which may alter the appearance of the applied surface. Furthermore, the antibacterial coating film requires the object to be applied to be immersed in a solvent containing suspended antibacterial particles, which limits the size of the object to be applied. The antibacterial coating agents disclosed in Patent Documents 10 and 13 are organosilane agents having antibacterial quaternary ammonium groups, and their safety for humans is unknown. Furthermore, because these coating agents are based on polymerization reactions involving silanol groups, hydroxyl groups are required on the coating surface, thus limiting the types of substances that can be coated. The antibacterial coating agent disclosed in Patent Document 14 has a silane compound as the antibacterial coating layer forming agent, and the materials to which it can be applied are limited. In fact, Patent Document 14 is specifically for application to toilets. The antibacterial coating agent disclosed in Patent Document 15 is preferably composed of a fluororesin containing fine silver particles as an antibacterial agent and a polyether ether ketone resin. Its application requires a baking process at 400°C, limits the materials it can be applied to, and makes reapplication to the entire residential area impossible. The antibacterial coating agents disclosed in Patent Documents 17 to 19 are films in which a silver complex or surfactant is laminated as an antibacterial agent on a resin substrate, and do not directly form an antibacterial coating layer on the surface to be applied, such as the walls of buildings. The packaging bag containing an antimicrobial agent disclosed in Patent Document 20 is a technology aimed at maintaining a sterile state inside the bag, and the antimicrobial active ingredient is allyl isothiocyanate, which is a volatile substance. It is not a technology that forms an antimicrobial coating layer on a structure afterward, as in the present invention. The antimicrobial agent composition disclosed in Patent Document 21 consists of an iodine-based antimicrobial agent and a metal ion, but it does not have any features related to an antimicrobial coating. The antibacterial agents made of binder resins containing metal particles as antibacterial agents, as disclosed in Patent Documents 22 and 23, are said to have substrate adhesion, blocking resistance, and weather resistance, but their properties in high-temperature, high-humidity environments such as bathrooms and food processing plants have not been shown, and their use is limited to printed materials. The above-mentioned antibacterial coating agents have problems with either the application method, the antibacterial effect, or the duration of their effect. The objective of this invention is to provide an antibacterial coating agent that combines all three of these qualities.

[0012] In this application, "antibacterial" means a killing effect or an inhibitory effect on the growth of viruses, bacteria, yeasts, and fungi, and refers to one or both of these effects. [Means for solving the problem]

[0013] The present invention provides an antimicrobial coating agent comprising (1) an aqueous film-forming agent, (2) one or more antimicrobial agents, and (3) a stable solvent, and also discloses a method for controlling microorganisms using this agent. The antimicrobial coating agent of the present invention is a simple combination. [Effects of the Invention]

[0014] The antibacterial coating agent of the present invention exhibits a strong antibacterial effect against a wide range of bacteria and viruses while being safe for humans and minimizing environmental impact.

[0015] In the antibacterial coating agent of the present invention, the antibacterial agents contained in grapefruit seed extract and citrus peel extracts such as grapefruit, orange, and lemon directly act on fungi such as mold, efficiently inhibiting their growth. As a result, a single application provides long-lasting antibacterial effects. Consequently, frequent antibacterial application becomes unnecessary, significantly reducing the time and cost required for antibacterial treatment.

[0016] By using a special polyvinyl alcohol with water and heat resistance as the aqueous film-forming agent for the antibacterial coating, the antibacterial coating can be maintained on treated structures for extended periods even in environments exposed to water, hot water, and steam (e.g., factories, warehouses, baths, swimming pools). This, in turn, helps to suppress contamination of food processing with antibacterial coating components and unintentional ingestion by humans.

[0017] Presentato et al. reported in 2020 that aqueous extracts of grapefruit, orange, and lemon peel contain integropectin, a novel antimicrobial substance that exhibits strong antimicrobial activity against both Gram-positive and Gram-negative bacteria ([Non-Patent Document 1] to [Non-Patent Document 4]).

[0018] In order to designate polyvinyl alcohol as a food additive and to establish standards, the Food Safety Commission was asked to give its opinion on June 22, 2022, under Article 24, Paragraph 1, Item 1 of the Basic Food Safety Act (Act No. 48 of 2003), by Ministry of Health, Labour and Welfare, Food Safety Commission Notification No. 0622-1. Regarding the food health impact assessment of polyvinyl alcohol, the evaluation result was notified on June 7, 2023, in Food Safety Commission Notification No. 379, stating that "when polyvinyl alcohol is used appropriately as a food additive, there are no safety concerns, and it is not necessary to specify an acceptable daily intake." The following is an excerpt of the main parts of the description regarding the food health impact assessment in the additive evaluation report.

[0019] Polyvinyl alcohol contains methyl acetate and methanol as impurities, and of these, methyl acetate decomposes into methanol and acetic acid. Therefore, a comprehensive safety assessment (health impact assessment) of "polyvinyl alcohol" was conducted, taking into account knowledge regarding methanol and acetic acid in addition to polyvinyl alcohol itself.

[0020] 1. Polyvinyl alcohol Regarding pharmacokinetics, the absorption of polyvinyl alcohol after oral administration was very small, and the main excretion route was considered to be feces. Furthermore, based on the results of tests on excretion after intravenous administration, it was considered that when polyvinyl alcohol is absorbed into the body, low molecular weight polyvinyl alcohol is rapidly excreted in the urine, but excretion slows down as the molecular weight increases. We determined that polyvinyl alcohol does not have genotoxicity. Based on repeated-dose toxicity and reproductive / developmental toxicity studies, and considering the results of a 90-day repeated oral administration study in rats and a rat reproductive toxicity study, the NOAEL of polyvinyl alcohol was determined to be the maximum dose of 5,000 mg / kg body weight / day. The estimated daily intake of polyvinyl alcohol was 590 mg / person / day (11 mg / kg body weight / day) for the general population and 370 mg / person / day (23 mg / kg body weight / day) for children. Since polyvinyl alcohol is hardly absorbed in the gastrointestinal tract, and no toxic findings were observed up to the maximum dose of 5,000 mg / kg body weight / day in a 90-day repeated oral administration study in rats and in a rat reproductive toxicity study, it was determined that there are no safety concerns regarding polyvinyl alcohol when used appropriately as an additive, and therefore, it was not necessary to specify an ADI (Acceptable Daily Intake).

[0021] 2. methanol An evaluation was conducted by the Food Safety Commission in 2019. Since no new findings have been recognized since then, no further studies on pharmacokinetics and toxicity have been conducted. The estimated daily intake of methanol derived from "polyvinyl alcohol" is 0.15 mg / kg body weight / day for the average population and 0.32 mg / kg body weight / day for children. It is thought to be absorbed, metabolized, and excreted in the body in the same way as methanol from a normal diet. Considering human findings, the amount of methanol consumed in a normal diet (2.0 mg / kg body weight / day for the average population and 0.81 mg / kg body weight / day for children), and the ADI set by the FDA (7.1-8.4 mg / kg body weight / day), it was determined that methanol derived from "polyvinyl alcohol" poses no safety concerns when "polyvinyl alcohol" is used appropriately as a food additive.

[0022] 3. Acetic acid An evaluation was conducted by the Food Safety Commission in 2017. Since no new findings have been recognized since then, no further studies on pharmacokinetics and toxicity have been conducted. Based on an evaluation that the intake from "polyvinyl alcohol" (average of 5.0 mg / person / day for the general population, 3.6 mg / person / day for children) is low compared to the intake from diet (130-520 mg / person / day), it was determined that there are no safety concerns regarding acetic acid derived from "polyvinyl alcohol" when it is used appropriately as a food additive.

[0023] Based on paragraphs

[0017] to

[0021] , it was determined that there are no safety concerns when "polyvinyl alcohol" is used appropriately, and therefore it is not necessary to specify an ADI.

[0024] Even if the antibacterial coating components were to be ingested by the human body, the antibacterial coating agent of the present invention is extremely safe because its main components are an aqueous film-forming agent consisting of an antibacterial agent such as grapefruit seed extract or citrus peel extract such as grapefruit, orange, and lemon, which are natural ingredients, and polyvinyl alcohol, whose safety has been ensured. Therefore, concerns about contamination with bacterial removal agents or antibacterial coating materials are extremely low, even in places such as food processing plants. In other words, even in places and situations where disinfection work has been avoided due to concerns about the toxicity of cleaning detergents and antibacterial coating agents, the antibacterial coating agent of the present invention can be used with peace of mind.

[0025] Furthermore, the antibacterial coating layer formed by the present invention does not require any harmful special chemicals, can be easily removed with warm water and slight friction, and can be easily reapplied. This reduces the burden on the environment and contributes to protecting the health of workers. [Brief explanation of the drawing]

[0026] [Figure 1] This figure shows the experimental results in Example 1. [Modes for carrying out the invention]

[0027] (Antibacterial coating agent) The present invention relates to an antimicrobial coating agent comprising an aqueous film-forming agent, one or more antimicrobial agents, and a stable solvent.

[0028] The aqueous film-forming agent constituting the antibacterial coating agent of the present invention is polyvinyl alcohol with guaranteed safety. The antibacterial agent is one or more combinations of food additives or food materials with a history of consumption. The stable solvent is water.

[0029] Examples of antibacterial agents include grapefruit seed extract or citrus peel extracts such as grapefruit, orange, and lemon. A specific example of grapefruit seed extract is "Desfan-10" (distributed by Adept Co., Ltd.). "Desfan-10" is a natural disinfectant and antibacterial agent (grapefruit seed extract) extracted from grapefruit seeds and is approved as a food additive. Other options include citrus peel extracts from grapefruit, lemon, and orange, which have a history of being consumed. These extracts contain integropectin, a type of pectin that encapsulates polyphenols, flavonoids, and terpenes that exhibit antibacterial activity. Antibacterial agents may consist of such food additives or food ingredient extracts with a history of being consumed, either alone or in combination.

[0030] In this embodiment, the antibacterial coating agent is composed, for example, of water: 68.5-98% by mass, grapefruit seed extract or citrus peel extract such as grapefruit, orange, or lemon: 1-20% by mass, and polyvinyl alcohol: 0.5-30%. Alternatively, a composition ratio of water: 88-96% by mass, grapefruit seed extract or citrus peel extract: 3-8% by mass, and polyvinyl alcohol: 1-4% can also be used.

[0031] Polyvinyl alcohol (PVA), an aqueous film-forming agent, is widely used as a pharmaceutical additive in tablets, capsules, and other pharmaceuticals of similar form. Furthermore, the safety of polyvinyl alcohol for human use has already been confirmed, and its use as a food additive is currently being reviewed by the Food Safety Commission. Thus, the aqueous film-forming agent used in this invention is composed of polyvinyl alcohol, whose safety has been guaranteed.

[0032] The polyvinyl alcohol usable in this invention includes general-purpose polyvinyl alcohol and modified polyvinyl alcohol. It is preferable to use a special polyvinyl alcohol that is water-resistant and heat-resistant. By using such a special polyvinyl alcohol, it can be applied in locations exposed to water, hot water, and steam (e.g., factories, warehouses, bathrooms, swimming pools, etc.).

[0033] Specific examples of special polyvinyl alcohol with water and heat resistance include, for instance, polyvinyl alcohol with a saponification degree of 80 mol% to 99.99 mol% and a polymerization degree of 100 to 5000. More preferably, polyvinyl alcohol with a saponification degree of 98 mol% or higher and a polymerization degree of 200 to 3500 is used. By using such special polyvinyl alcohol as a component of an antibacterial coating agent, a water and heat resistant antibacterial coating can be formed. For example, if antibacterial treatment is performed in a location frequently exposed to water, hot water, or steam (factories, warehouses, baths, swimming pools, etc.) to form a water and heat resistant antibacterial coating, the antibacterial coating will be less likely to come off even when repeatedly exposed to water or hot water, making it possible to maintain the antibacterial effect over a long period of time.

[0034] Furthermore, the polyvinyl alcohol used in this embodiment possesses excellent moisture resistance, gas barrier properties, and adhesive properties, ensuring that the antibacterial coating is firmly fixed to the application surface and maintains a high antibacterial effect over a long period. This improves antibacterial performance in various environments.

[0035] (Microbial control method using antimicrobial coating agents) As an example of a microbial control method, we will describe mold prevention treatment using the antibacterial coating agent mentioned above. In mold prevention treatment, an antibacterial coating agent consisting of polyvinyl alcohol, grapefruit seed extract, and water is used as an example of an antibacterial coating agent.

[0036] When applying mold-preventive treatment, first remove any mold from the treatment surface, such as walls and ceilings. In this step, use a commercially available mold remover to remove the mold, and then thoroughly rinse off the mold remover with water. Next, allow the treatment surface to dry completely.

[0037] Next, apply the antibacterial coating agent to the dry surface (the surface to be treated for mold prevention). When applying with a hand spray, put the antibacterial coating agent into a spray bottle and spray it evenly over the surface, then spread a thin layer of the antibacterial coating agent using a cloth, sponge, roller, or brush soaked in the agent. This will form a protective film of the antibacterial coating agent on the surface.

[0038] The thickness of this coating is not particularly limited, but for example, at a thickness of a few micrometers to several hundred micrometers, which is sufficient to achieve the desired effect, it is colorless and transparent, so the natural appearance of the treated surface can be maintained after application, and the aesthetics are not compromised.

[0039] The surface and interior of the antibacterial thin film formed on the treated surface contain dispersed antibacterial agents consisting of grapefruit seed extract and citrus peel extracts, such as grapefruit, orange, and lemon, which exert a sustained effect in suppressing mold growth.

[0040] Furthermore, by covering the treated surface with an antibacterial coating containing dispersed grapefruit seed extract and citrus peel extracts such as grapefruit, orange, and lemon, it is possible to suppress the diffusion of unpleasant odors, for example, by providing an antibacterial effect against putrefactive bacteria remaining on the treated surface, as well as by suppressing the diffusion of unpleasant odors through the coating effect of polyvinyl alcohol. In other words, the antibacterial coating formed by this embodiment has not only an antifungal effect but also an anti-deodorizing effect.

[0041] The tools used when applying the antibacterial coating agent are not particularly limited; for example, one or more combinations of sprayers, hand sprayers, cloths, sponges, rollers, and brushes can be used. For example, a painting sponge can be used.

[0042] If dirt or microorganisms are found on the antibacterial thin film, the dirt and microorganisms can be easily washed away along with the antibacterial coating by scrubbing with a brush or similar tool while applying hot water at 40°C or higher. After that, the treated surface is completely dried, and the antibacterial coating agent is applied to the treated surface. Therefore, once the antibacterial coating agent of the present invention is applied, subsequent cleaning with chlorine-based liquids or the like is not required, and the antibacterial coating can be easily applied.

[0043] The antibacterial coating material of the present invention can be applied to a variety of materials, such as glass for windows, pulp and synthetic fibers for wallpaper, synthetic resins for air conditioners and trash cans, wood for desks and chairs, fabrics for curtains and mattresses, leather for bags and shoes, clay for tableware, metals for watches and accessories, and ceramic materials for tiles.

[0044] The microorganisms that can be controlled using the antimicrobial coating agent of the present invention are not limited to molds, but can be used to control all kinds of microorganisms, including viruses.

[0045] In the embodiments described later, a sports gym is given as an example of a target for application, but the application of the present invention is not particularly limited and can be widely used in public facilities, hospitals and elderly care facilities, factories and home environments, etc.

[0046] Next, specific embodiments of the present invention will be described. [Examples]

[0047] (Water resistance and temperature sensitivity of polyvinyl alcohol) The water resistance of the polyvinyl alcohol used in this antibacterial coating agent was evaluated by the melting time. Films with thicknesses of 40-70 μm were prepared for three polyvinyl alcohols: polyvinyl alcohol 1 (PVA1) with a saponification degree of 99.25 mol% and a polymerization degree of 230, polyvinyl alcohol 2 (PVA2) with a saponification degree of 98.46 mol% and a polymerization degree of 250, and polyvinyl alcohol 3 (PVA3) with a saponification degree of 98.35 mol% and a polymerization degree of 300. These films were dried at 20°C and 65% relative humidity. The prepared films were cut into 1 cm squares, attached to hanging hooks, and immersed in water at 20°C and 40°C. The time it took for the film to fall from the hook was recorded as the melting time, yielding the results shown in Figure 1. At 20°C, PVA1 showed a significantly increased melting time compared to PVA2 and PVA3, with the melting time increasing with increasing film thickness. Furthermore, as shown in Table A, the melting time of a 50 μm thick film at 20°C was approximately twice that of PVA2 and PVA3. These results indicate that the coating layer formed on the surface of PVA1 has high water resistance. On the other hand, as shown in Table A, the melting time of PVA1 at 40°C was only 9 seconds different from that of PVA2 and PVA3. This result indicates that the coating layer formed with PVA1 can be easily peeled off if it is subjected to continuous contact with water at 40°C or higher.

[0048] [Table A] [Examples]

[0049] (Preparation of an antibacterial coating agent containing grapefruit seed extract) Nine antibacterial coating agents 1-9 and a comparative coating agent without antibacterial agents were prepared in 1 liter each, as shown in Table 1. Antibacterial coating agents 1-9 were prepared by mixing and stirring water, grapefruit seed extract, and polyvinyl alcohol (PVA) in the proportions shown in Table 1. The grapefruit seed extract used was "Desfan-10" (distributed by Adept Co., Ltd.). The specifications (degree of saponification, degree of polymerization) of the polyvinyl alcohol used are as shown in Table 1.

[0050] [Table 1] [Examples]

[0051] (Preparation of an antibacterial coating agent containing grapefruit peel extract) Organically grown Japanese grapefruit was thoroughly washed with water, and the peel was scraped off using a knife to a thickness of approximately 2 mm. The peel was immediately frozen at -25°C. 5 g of the freeze-dried peel was added to 15 mL of water and left to stand in the dark. After 24 hours, the supernatant was collected and freeze-dried. The solid residue was dissolved in water to prepare a 100 mg / mL grapefruit peel extract aqueous solution. Using this peel extract aqueous solution, 1 L each of the antibacterial coating agents 10-18 shown in Table 2 was prepared.

[0052] [Table 2] [Examples]

[0053] (Experiment to verify mold-preventive effect) The experiment was conducted on the bathroom ceiling of a sports gym. The bathroom at the sports gym, where the work was carried out, was exposed to hot water and steam, and mold had grown extensively on the bathroom ceiling. The moldy areas on the bathroom ceiling were divided into 20 work areas (areas 1 to 20), and the experiment was conducted according to the following procedure.

[0054] First, mold in each experimental area of ​​the bathroom ceiling was removed using a commercially available chlorine-based mold remover, and then thoroughly rinsed with water.

[0055] Next, in the first of the 20 experimental areas, antibacterial coating agent 1 was applied thinly and evenly using a sponge soaked in the agent, and then allowed to dry completely to form a film. Antibacterial coating agents 2 to 18 were applied to areas 2 to 18 using the same procedure. The comparative coating agent and negative control agent were applied to areas 19 and 20, respectively, using the same procedure.

[0056] Table 3 shows the results of observations regarding mold growth in each treated area after six months and one year under normal bathroom usage conditions, including exposure to hot water and steam.

[0057] [Table 3]

[0058] Six months after the application of the antibacterial coating agents, the mold growth in the treated areas was checked. In the treated areas where antibacterial coating agents 1-9 were applied, no recurrence of mold was visually observed with antibacterial coating agents 1-3, which combined polyvinyl alcohol with a saponification degree of 99.25 mol% and a polymerization degree of 230 with grapefruit seed extract. On the other hand, mold growth was observed with antibacterial coating agents 4-6, which combined polyvinyl alcohol with a saponification degree of 98.46 mol% and a polymerization degree of 250 with grapefruit seed extract, and with antibacterial coating agents 7-9, which combined polyvinyl alcohol with a saponification degree of 98.35 mol% and a polymerization degree of 300 with grapefruit seed extract. Similarly, with antibacterial coating agents 10-18, which combined grapefruit peel extract, good results were obtained in suppressing mold recurrence with antibacterial coating agents 10-12, which combined polyvinyl alcohol with a saponification degree of 99.25 mol% and a polymerization degree of 230 with grapefruit seed extract. In area 19, where only polyvinyl alcohol used in antibacterial coatings 1-3 and 10-12 was applied, mold growth was observed. This result indicates that a specific combination of polyvinyl alcohol and grapefruit seed extract or grapefruit peel extract is important for achieving a sustained inhibitory effect against mold growth. In area 20, where only water was applied, mold growth was observed as before the experiment, indicating that commercially available chlorine-based mold removers cannot be expected to have a sustained mold-inhibiting effect.

[0059] The bathroom ceiling in the experimental site was left untouched for another six months (a total of one year), and the mold-inhibiting effect of antibacterial coatings 1-18 was observed. A small amount of scattered mold was found in areas treated with antibacterial coatings 1 and 10. However, the degree of mold growth was far less than in the areas treated with the comparative coating and negative control agent six months after the start of the experiment. Furthermore, no mold growth was observed in the areas treated with antibacterial coatings 2, 3, 11, and 12. The areas treated with antibacterial coatings 4-9 and 13-18 showed mold growth similar to that of the negative control agent. This was thought to be due to the low water resistance of the polyvinyl alcohol used, causing the antibacterial coating to peel off during bathroom use.

[0060] Next, when the areas treated with antibacterial coatings 1 and 10, where a small amount of mold had grown, were gently scrubbed with a brush while applying warm water at approximately 42°C, the mold was easily removed. This was thought to be because the antibacterial coating layer peeled off due to the friction from the brush in addition to the heat from the warm water. In other words, it was shown that in areas where an appropriate antibacterial coating agent was applied, mold could be removed with warm water and gentle friction, without the need to use mold removers such as chlorine-based agents as in conventional methods.

[0061] Furthermore, in the mold removal process described above, simply pouring hot water at approximately 42°C was insufficient to remove the mold. This was thought to be due to the water resistance of the polyvinyl alcohol used in antibacterial coating agents 1 and 10. In other words, this indicates that in environments frequently exposed to hot water or steam, such as walls and ceilings where physical friction does not occur on the surface where the antibacterial coating agent is applied (e.g., food processing plants, warehouses, swimming pools, bathrooms, etc.), the antibacterial coating layer will not easily peel off or dissolve, maintaining its coating state and exhibiting antibacterial effects for a long period of time.

[0062] (Summary of experimental results) The results above demonstrate that the antibacterial coating agent of the present invention forms an antibacterial coating on the applied surface, exhibiting a mold-inhibiting effect over a long period of time. Furthermore, it was confirmed that even if mold occurs on the antibacterial coating, it can be easily removed with warm water and gentle friction, without relying on mold removers that are harmful to humans and have a large environmental impact. [Examples]

[0063] Based on "JIS Z2801 Antimicrobial processed products - Antimicrobial test methods and antimicrobial effects," the antimicrobial properties of the coating layer formed by the antimicrobial coating agent of the present invention were evaluated against Staphylococcus aureus (NBRC12732), Escherichia coli (NBRC3972), and methicillin-resistant Staphylococcus aureus (MRSA IID1677).

[0064] (Preparation of test specimens) A 5 cm x 5 cm x 1 cm plastic piece was used as the test specimen. The surface of the test specimen was treated with antibacterial coating agent 3 (Table 1) and antibacterial coating agent 10 (Table 2) of the present invention. The treatment was carried out using the sponge method described above.

[0065] (Test Procedure) • Test specimens coated with an antibacterial agent and untreated test specimens were placed in a petri dish, and 0.4 ml of the test bacterial solution was dropped onto them. To prevent the test bacterial solution from drying out, a non-antimicrobial film (5cm x 5cm) was placed over it, and the lid of the petri dish was closed. The petri dishes were incubated for 24 hours at 35°C in an environment with over 90% RH. After 24 hours, 10 ml of SCDLP medium was added to wash the test bacteria from the film and test pieces. The number of bacteria in the wash solution was measured using the agar plate culture method. The antibacterial activity value was calculated based on the following formula. Antibacterial activity value = log(untreated test piece 1cm) 2 (Number of viable bacteria per culture) - log(1 cm² of antimicrobial treated test piece) 2 (Number of viable bacteria per culture)

[0066] (Experimental results) Table 4 shows the results for antibacterial coating agents 1 and 10.

[0067] [Table 4]

[0068] Based on these results, the coating layer formed using the antibacterial coating agent of the present invention showed bactericidal or bacteriostatic effects against Staphylococcus aureus, Escherichia coli, and MRSA. In other words, the antibacterial coating agent of the present invention is effective as a disinfectant for infectious disease control and can be used, for example, for infectious disease control in hospitals and nursing homes. [Examples]

[0069] The antibacterial coating agent of the present invention was applied to curtains to evaluate their antibacterial activity, and the durability of the antibacterial coating formed on the curtain surface was also evaluated.

[0070] (Test method) 1. Preparation of test specimens The fireproof curtain fabric was cut into circular test pieces with a diameter of 25 mm, and the antibacterial coating agent of the present invention (Example 2, corresponding to antibacterial coating agent 3 in Table 1) was applied to the test pieces.

[0071] The composition of the antibacterial coating agent used was as follows: Grapefruit seed extract: 8 wt% PVA (saponification degree 99.25 mol%, polymerization degree 230): 4 wt% ·Water: 88 wt%

[0072] The test specimens were treated by spraying the antibacterial coating agent evenly five times from a distance of 20 cm, and then drying them in the dark at room temperature for 24 hours. The amount of adhesive adhering to the test specimen after drying (weight of the formed antibacterial coating) was calculated using the following formula.

[0073] Calculation formula: Adhesive amount (wt%) = (W T / W0- 1) × 100 Here, ·W0: Weight of the unprocessed test piece ·W T : Weight of the processed test piece

[0074] The obtained amount of sizing was 0.5 wt%.

[0075] 2. Abrasion treatment test The abrasion treatment was carried out according to JIS L 1076 Annex 3 (specified) Method J (modified Martindale method) under the following conditions. · Abrasion cloth: Common cloth surface · Number of abrasion cycles: 300 cycles · Pressing load: 4.9 N

[0076] 3. Antibacterial activity evaluation test The evaluation of antibacterial activity was carried out according to JIS L 1902:2015 (bacterial liquid absorption method) under the following conditions. · Strain: Klebsiella pneumoniae (NBRC 13277) (Klebsiella pneumoniae) · Culture conditions: Cultured for 18 hours · Inoculum concentration: 2.3 × 10 5 CFU / mL

[0077] 4. Calculation of antibacterial activity value The antibacterial activity value was calculated by the following formula.

[0078] Calculation formula: Antibacterial activity value = (log C t - log C0) - (log T t - log T0) However, when log C0 > log T0, log T0 was replaced with log C0 for calculation. Here,[[]] · C0: Number of viable bacteria in the negative control immediately after inoculation · C t : Number of viable bacteria in the negative control after 18-hour culture · T0: Number of viable bacteria in the test specimen immediately after inoculation · T t : Number of viable bacteria in the test specimen after 18-hour culture

[0079] 5. Calculation of growth value The growth rate was calculated using the following formula.

[0080] Formula: Growth value = log N t - log N0 Here, • N0: Number of viable bacteria immediately after vaccination ·N t : Number of viable bacteria after 18 hours of incubation

[0081] [Table 5]

[0082] (Experimental results) In unprocessed curtain test pieces, antibacterial activity decreased after abrasion treatment, and the growth of Klebsiella pneumoniae was confirmed (growth value: 0.83, antibacterial activity value: 3.17). On the other hand, processed products coated with the antibacterial coating agent of the present invention maintained a high antibacterial effect even after abrasion treatment (antibacterial activity value: 6.25-6.28), and bacterial growth was strongly suppressed. This confirmed that the antibacterial coating agent of the present invention has abrasion resistance and can maintain sufficient antibacterial effect even under normal abrasion conditions in living environments.

[0083] Based on the experimental results described above, it was confirmed that when the antibacterial coating agent of the present invention is applied to curtains, it exhibits high antibacterial activity and maintains its effect even after 300 abrasion treatments. In particular, it has been shown to be useful as an antibacterial measure for curtains and other fabric products used in medical facilities, nursing homes, schools, and public facilities. [Industrial applicability]

[0084] Because the antibacterial coating agent of the present invention combines safety and antibacterial properties, it can be suitably used in areas where microbial contamination in living spaces is a concern.

Claims

1. An antimicrobial coating agent comprising an aqueous film-forming agent, one or more antimicrobial agents, and a stable solvent. The aqueous film-forming agent is polyvinyl alcohol, whose safety has been ensured. The aforementioned antibacterial agents are food additives or extracts of food materials with a history of consumption, and are used in combination of one or more of them. An antibacterial coating agent characterized in that the stable solvent is water.

2. The antibacterial coating agent according to claim 1, characterized in that the polyvinyl alcohol has a degree of saponification of 98 mol% or more and a degree of polymerization of 200 to 3500.

3. The antibacterial coating agent according to claim 1, characterized in that the antibacterial agent is grapefruit seed extract or grapefruit, orange, or lemon peel extract.

4. The antibacterial coating agent according to claim 1, characterized in that the no-observed-adverse-effect level is 1 g / kg body weight or more after repeated oral administration to rats for 28 days.

5. The antibacterial coating agent according to claim 1, characterized in that it can suppress the growth of microorganisms for more than six months in a humid environment where microorganisms are likely to proliferate.

6. The antibacterial coating agent according to claim 1 is characterized in that the film formed from this antibacterial coating material exhibits high resistance to intermittent contact with hot water or hot steam, while under conditions of continuous contact with water at 40°C or higher for a certain period of time or longer, the coating hardness decreases and it can be easily peeled off with weak friction.

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