Antibacterial coating agent

Abstract

The purpose of the present invention is to provide an antibacterial coating agent having both antibacterial effect and a high degree of safety.　The antibacterial coating agent according to the present invention contains an aqueous film-forming agent, one or more antibacterial agents, and a stable solvent, and is characterized in that: the aqueous film-forming agent is a polyvinyl alcohol of which safety has been ensured; the antibacterial agent is one, or a combination of food additives or food materials with a history of food safety; and the stable solvent is water.

Description

Antibacterial coating agent

[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.

[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.

[0009] Japanese Patent Publication No. 2023-004163 (Antibacterial Film), Japanese Patent Publication No. 2014-167011, Japanese Patent Publication No. 2009-527357 (Removable Antibacterial Coating Composition and Method of Use Thereof), Japanese Patent Publication No. 2015-514758 (Long-lasting Surface Antibacterial Agent and Method of Application), Japanese Patent Publication No. 08-092878 (Antibacterial Wall Covering), Japanese Patent Publication No. 08-113898 (Antibacterial Wall Covering), Japanese Patent Publication No. 08-113899 (Antibacterial Wall Covering), Japanese Patent Publication No. 0 8-144472 (Composite building materials) JP-A-09-100205 (Antibacterial coating composition) JP-A-09-132735 (Antibacterial coating film by antibacterial paint) JP-A-2000-511887 (Method of using water-stabilized organosilane) JP-A-11-228908 (Antibacterial coating agent resin composition) JP-A-2001-081409 (Antibacterial coating agent, antibacterial agent, and method for preventing hospital-acquired infections) JP-A-2006-213709 (Water-stabilized organosilane) (Nosilane and method of use) JP 2008-308437 (Antibacterial coating agent for toilet bowl application and antibacterial method for toilet bowl) JP 2009-067849 (Antibacterial coating film and cooking container having the same and antibacterial coating agent) JP 2009-138288 (Antibacterial agent and antibacterial coating agent) JP 2015-190033 (Laminate and method of manufacturing the same, and reflector, mirror film, antibacterial coating, conductive film, heat conductor) JP 2015-19118 Publication No. 0 (Laminate and method for manufacturing the same, as well as reflector, mirror film, antibacterial coating, conductive film, thermal conductor) Re-listed 2016 / 047568 (Antibacterial sheet, antibacterial coating, laminate, antibacterial liquid) JP 2017-030823 (Packaging bag) JP 2022-018206 (Antibacterial agent composition) JP 2022-080334 (Antibacterial coating agent, and printed matter using the same) Patent No. 7126642 (Antibacterial coating agent, printed matter using the same)

[0010] Presented by 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), Volume 9, Issue 9, pp. 586 - 600 Presented by 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, Volume 9, Issue 5, pp. 628 - 630 Scurria A, Sciortino M, Albanese L, Nuzzo D, Zabini F, Meneguzzo F, Alduina R, Presentato A, Pagliaro M, Avellone G, Ciriminna R. Flavonoids in Lemon and Grapefruit IntegroPectin. ChemistryOpen, October 2021, Volume 10, Issue 10, pp. 1055 - 1058 Scurria A, Sciortino M, Garcia AR, Pagliaro M, Avellone G, Fidalgo A, Albanese L, Meneguzzo F, Ciriminna R, Ilharco LM. Red Orange and Bitter Orange IntegroPectin: Structure and Main Functional Compounds.Molecules, May 19, 2022, Volume 27, Issue 10, Page 3243.

[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 made of polyvinyl alcohol did not show blocking properties under the drying conditions of water at 80°C for 30 minutes and showed water resistance and heat resistance, but it did not show 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 additives, but the coating agent does not dissolve in water at 20°C but is easily removed mechanically, and in cold water the addition of iron chloride is required to maintain stability, and 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 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 of the coated surface at 50 to 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 an antibacterial agent and an acrylic resin as a coating film substrate forming component. This antibacterial agent is characterized by surface treatment by spraying and the durability and water resistance of the coating layer, but it requires wiping with alcohol to remove it. Therefore, it is not suitable when considering removal and repainting of 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 the 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 polyvinyl chloride, polyethylene terephthalate, etc., which limits their ability to be applied to large areas with uneven surfaces, and 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 an antibacterial coating agent based on silver zeolite as the antibacterial component and is cured by heat or ultraviolet resin. In particular, application by in-mold coating has low versatility due to the special nature of the equipment, and is unsuitable for antibacterial coating over large areas in terms of reapplication after the antibacterial effect has decreased. The antibacterial coating film disclosed in Patent Document 9 uses synthetic butylosulfate silver complex particles as the antibacterial agent, which may alter the appearance of the application surface. Furthermore, the antibacterial coating film requires the application object to be immersed in a solvent containing suspended antibacterial particles, limiting the size of the application object. The antibacterial coating agents disclosed in Patent Documents 10 and 13 are organosilane agents having antibacterial quaternary ammonium groups, and their safety for human use is unknown. Moreover, because they are coating agents based on polymerization reactions using silanol groups, hydroxyl groups are required on the application surface, thus limiting the materials that can be applied. The antibacterial coating agent disclosed in Patent Document 14 uses a silane compound as the antibacterial coating layer forming agent, limiting the materials that can be applied. In fact, Patent Document 14 is specifically designed 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, limiting the materials that can be applied, and making reapplication to an 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 component is the volatile substance allyl isothiocyanate, and 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 is an antimicrobial agent consisting of an iodine-based antimicrobial agent and a metal ion, but it does not have any features related to an antimicrobial coating. The antimicrobial agent consisting of a binder resin with metal particles as an antimicrobial agent disclosed in Patent Documents 22 and 23 is said to have substrate adhesion, blocking resistance and weather resistance, but its properties in high-temperature, high-humidity environments such as bathrooms and food processing plants have not been shown, and it is limited to printed materials. The above antimicrobial coating agents have problems with either the application method, antimicrobial effect, or duration. The object of the present invention is to provide an antimicrobial coating agent that combines all three of these.

[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.

[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 the same. The antimicrobial coating agent of the present invention is a simple combination.

[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 Documents 1 to 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), as stipulated in Ministry of Health, Labour and Welfare Notification No. 0622-1. Regarding the food health impact assessment of polyvinyl alcohol, the evaluation result was notified on June 7, 2023, under Document No. 379 of the Prefectural Food Safety Commission, 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. Regarding the pharmacokinetics of polyvinyl alcohol, the absorption of polyvinyl alcohol after oral administration was considered to be very small, and the main excretion route was thought 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 with increasing molecular weight. It was determined that polyvinyl alcohol does not have genotoxicity. After examining repeated-dose toxicity and reproductive and developmental toxicity tests, the NOAEL of polyvinyl alcohol was determined to be the maximum dose of 5,000 mg / kg body weight / day based on the results of a 90-day repeated oral administration test in rats and a rat reproductive toxicity test. The estimated daily intake of polyvinyl alcohol was 590 mg / person / day (11 mg / kg body weight / day) for the national average 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. The Food Safety Commission for Methanol conducted an evaluation in 2019. Since no new findings have been recognized since then, no further studies on its 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 assumed that it is absorbed, metabolized, and excreted in the body in the same way as methanol from a normal diet. Considering the findings in humans, 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. The Acetic Acid Food Safety Commission conducted an evaluation in 2017. Since no new findings have been recognized since then, no further studies on its 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 lower than 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 "polyvinyl alcohol" 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.

[0026] This figure shows the experimental results in Example 1.

[0027] (Antibacterial coating agent) The present invention is an antibacterial coating agent comprising an aqueous film-forming agent, one or more antibacterial 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 to 98% by mass, grapefruit seed extract or citrus peel extract such as grapefruit, orange, or lemon: 1 to 20% by mass, and polyvinyl alcohol: 0.5 to 30%. Alternatively, a composition ratio of water: 88 to 96% by mass, grapefruit seed extract or citrus peel extract: 3 to 8% by mass, and polyvinyl alcohol: 1 to 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 (for example, factories, warehouses, baths, 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, and more preferably, polyvinyl alcohol with a saponification degree of 98 mol% or higher and a polymerization degree of 200 to 3500. By using such special polyvinyl alcohol as a component of an antibacterial coating agent, a water-resistant 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-resistant 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 for 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 agent) As an example of a microbial control method, we will explain mold prevention treatment using the antimicrobial coating agent mentioned above. In mold prevention treatment, an antimicrobial coating agent consisting of polyvinyl alcohol, grapefruit seed extract, and water is used as an example of an antimicrobial 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, an antibacterial coating agent is applied to the dried construction surface (surface to be mold-proofed). When applying using a hand spray, put the antibacterial coating agent in a spray bottle and spray it evenly on the construction surface, and then spread it thinly with a cloth, sponge, roller, brush, etc. that has been soaked with the antibacterial coating agent. As a result, a film of the antibacterial coating agent is formed on the construction surface.

[0038] The thickness of this film is not particularly limited. For example, when the thickness is several μm to several hundred μm that can sufficiently exhibit the intended effect, it is colorless and transparent, so the natural appearance of the construction surface can be maintained even after construction, and the aesthetics will not be impaired.

[0039] On the surface and inside of the antibacterial thin film formed on the construction surface, an antibacterial agent composed of grapefruit seed extract or citrus peel extract typified by grapefruit, orange, and lemon is dispersed, and it exhibits the effect of continuously suppressing the generation of mold.

[0040] Further, by covering the construction surface with an antibacterial film in which grapefruit seed extract or citrus peel extract typified by grapefruit, orange, and lemon is dispersed, for example, in addition to the antibacterial action against spoilage bacteria remaining on the construction surface, the coating effect of polyvinyl alcohol can also suppress the diffusion of odors and the like. That is, the antibacterial film formed by this embodiment has not only a mold-proofing effect but also an odor-proofing effect.

[0041] The instrument used when applying the antibacterial coating agent is not particularly limited. For example, any one or a combination of two or more of a sprayer, hand spray, cloth, sponge, roller, brush, etc. can be used. For the sponge, for example, a sponge for painting can be used.

[0042] When dirt or the generation of microorganisms is observed on the antibacterial thin film, the dirt and microorganisms can be easily washed away together with the antibacterial coating by rubbing with a brush or the like while applying warm water of 40°C or higher. After that, completely dry the construction surface and apply the antibacterial coating agent to the construction surface. Therefore, once the antibacterial coating agent of the present invention is applied, cleaning work with a chlorine-based liquid or the like is not required for subsequent times, and the antibacterial film 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.

[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 to 70 μm were prepared for polyvinyl alcohol 1 (PVA1) with a degree of saponification of 99.25 mol% and a degree of polymerization of 230, polyvinyl alcohol 2 (PVA2) with a degree of saponification of 98.46 mol% and a degree of polymerization of 250, and polyvinyl alcohol 3 (PVA3) with a degree of saponification of 98.35 mol% and a degree of polymerization of 300, and dried at 20°C and 65% relative humidity. The prepared films were cut into 1 cm squares, inserted into 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, and the results shown in Figure 1 were obtained. At 20°C, PVA1 showed a significantly increased melting time compared to PVA2 and PVA3 as the film thickness increased. Furthermore, as shown in Table 1, 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 1, the melting time of PVA1 at 40°C differed from that of PVA2 and PVA3 by only 9 seconds. This result indicates that the coating layer formed with PVA1 can be easily removed if it is subjected to continuous contact with water at 40°C or higher. In addition, it was confirmed that the coating layer of this embodiment maintains its integrity (shows high resistance) to "intermittent hot water contact" such as shower splashes and steam in daily life, without the film dissolving or peeling. This is thought to be because continuous supply of thermal energy and moisture for a certain period of time or longer is necessary for the PVA film to dissolve and peel (coat hardness to decrease). In other words, the antibacterial coating agent of the present invention achieves both of the seemingly contradictory characteristics of maintaining durability during normal use (intermittent contact) and being easily removable during intentional cleaning (continuous contact).

[0048]

[0049] (Preparation of antibacterial coating agents containing grapefruit seed extract) Nine types of antibacterial coating agents 1 to 9 shown in Table 2, and a comparative coating agent without an antibacterial agent, were each prepared in 1 L. Antibacterial coating agents 1 to 9 were prepared by mixing and stirring water, grapefruit seed extract, and polyvinyl alcohol (PVA) in the proportions shown in Table 2. The grapefruit seed extract used was "Desfan-10" (distributor: Adept Co., Ltd.). The specifications (degree of saponification, degree of polymerization) of the polyvinyl alcohol used are as shown in Table 2.

[0050]

[0051] (Preparation of antibacterial coating agents containing grapefruit peel extract) Organically grown Japanese grapefruits were thoroughly washed with water, and the peel was scraped off to a thickness of approximately 2 mm using a knife. The peel was immediately frozen at -25°C. 5 g of 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 aqueous solution of grapefruit peel extract. Using this aqueous solution of peel extract, 1 L each of antibacterial coating agents 10 to 18 shown in Table 3 was prepared.

[0052]

[0053] (Verification experiment of mold prevention effect) The ceiling of a gym bathroom was used as the subject of the experiment. The environment in this example was a humid environment with a temperature of 20°C or higher and a humidity of 80% or higher, and under such conditions, the growth of mold (fungi) is greatly promoted. In fact, the bathroom of the gym where the work was carried out was exposed to hot water and steam, and mold had grown over a wide area on the bathroom ceiling. The mold-affected areas on this bathroom ceiling were divided into 20 work areas (areas 1 to 20), and the experiment was carried out 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 coating 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. A comparative coating agent and a negative control agent were applied to areas 19 and 20, respectively, using the same procedure.

[0056] Table 4 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]

[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 to 9 were applied, no recurrence of mold was visually observed with antibacterial coating agents 1 to 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 to 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 to 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 to 18, which combined grapefruit peel extract, good results were obtained in suppressing mold recurrence with antibacterial coating agents 10 to 12, which combined polyvinyl alcohol with a saponification degree of 99.25 mol% and a polymerization degree of 230 with grapefruit seed extract. In the 19th region, where only the 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 the 20th region, 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 inhibitory 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 to 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 to 9 and 13 to 18 showed mold growth to a similar degree to that of the negative control agent. This was thought to be because the polyvinyl alcohol used had low water resistance, 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 rubbed 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 using mold removers such as chlorine-based agents as in the past.

[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.

[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) Plastic pieces measuring 5 cm x 5 cm x 1 cm were used as test specimens. The surface of the test specimens was treated with antibacterial coating agents 3 (Table 2) and 10 (Table 3) of the present invention. The treatment was carried out using the sponge method described above.

[0065] (Test Procedure) - A test specimen coated with an antibacterial agent and an untreated test specimen 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 film (5 cm x 5 cm) without antibacterial activity was placed over it, and the petri dish lid was closed. - The petri dish was incubated at 35°C and in an environment of 90% RH or higher for 24 hours. - After 24 hours, 10 ml of SCDLP medium was added to wash the test bacteria from the film and test specimens. - The number of bacteria in the wash solution was measured by the agar plate culture method. - The antibacterial activity value was calculated based on the following formula: Antibacterial activity value = log(untreated test specimen 1 cm) ２ (Number of viable bacteria per culture) - log (1 cm of antimicrobial treated test piece) ２ (Number of viable bacteria per culture)

[0066] (Experimental Results) Table 5 shows the results for antibacterial coating agents 1 and 10.

[0067]

[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.

[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 specimens 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 2) was applied to the test specimens.

[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 above 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 (weight of the formed antibacterial coating) on ​​the dried test specimens was calculated using the following formula.

[0073] Calculation formula: Adhesive amount (wt%) = (W T (W0 - 1) × 100 where, • W0: Weight of unprocessed test piece • W T Weight of processed test specimen

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

[0075] 2. Abrasion Treatment Test The abrasion treatment was carried out in accordance with JIS L 1076 Annex 3 (Normative) Method J (Modified Martindale Method) under the following conditions: • Abrasion cloth: Same fabric surface • Number of abrasion cycles: 300 • Pressing load: 4.9 N

[0076] 3. Antimicrobial Activity Evaluation Test The antimicrobial activity was evaluated in accordance with JIS L 1902:2015 (bacterial suspension absorption method) under the following conditions: • Strain: Klebsiella pneumoniae (NBRC 13277) (Klebsiella pneumoniae) • Culture conditions: 18-hour culture • Inoculum concentration: 2.3 × 10⁻⁶ 5 CFU / mL

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

[0078] Formula: Antimicrobial activity value = (log C) t - log C0) - (log T t- log T0), provided that when log C0 > log T0, log T0 was replaced by log C0 for calculation. Here, - C0: the number of viable bacteria in the negative control immediately after inoculation - C t : the number of viable bacteria in the negative control after 18-hour culture - T0: the number of viable bacteria in the test specimen immediately after inoculation - T t : the number of viable bacteria in the test specimen after 18-hour culture

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

[0080] Calculation formula: Growth value = log N t - log N0, where - N0: the number of viable bacteria immediately after inoculation - N t : the number of viable bacteria after 18-hour culture

[0081]

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

[0083] From the above experimental results, it was confirmed that when the antibacterial coating agent of the present invention was applied to the curtain, it showed high antibacterial activity and could maintain its effect even after 300 abrasion treatments. In particular, it was shown to be useful as an antibacterial measure for curtains and other fabric products used in medical facilities, nursing facilities, schools, public facilities, etc.

[0084] Since the antibacterial coating agent of the present invention has both safety and antibacterial properties, it can be suitably used in places where microbial contamination in the living area is a concern.

Claims

1. An antibacterial coating agent used to apply to an object (excluding living organisms) to form an antibacterial film on its surface, comprising an aqueous film-forming agent, one or more antibacterial agents, and a stable solvent, wherein the aqueous film-forming agent is polyvinyl alcohol whose safety is guaranteed, the antibacterial agents are food additives or food material extracts with a history of consumption, used in combination of one or more, the stable solvent is water, and the antibacterial agent is grapefruit seed extract or a fruit peel extract selected from one or more of grapefruit, orange, or lemon.

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

4. The antibacterial coating agent according to claim 1, characterized in that it can suppress the growth of microorganisms for six months or more.

5. The antibacterial coating agent according to claim 1, characterized in that the coating formed from the antibacterial coating material has reduced coating hardness and can be peeled off by friction under conditions of continuous contact with water at 40°C or higher.

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