Coating composition and use of the coating composition

Abstract

A coating composition containing silver ions and an isothiazolinone derivative as antimicrobial agents, wherein the silver ions and the isothiazolinone derivative are homogeneously dispersed in a liquid matrix and their total concentration is not more than 10% by weight of the matrix, and further the weight ratio of silver ions, calculated as elemental silver, to isothiazolinone derivative is 1:50 to 50:1, wherein the isothiazolinone derivative is selected from the group consisting of 2-n-octyl-4-isothiazolin-3-one and 2-octyl-2H-isothiazolin-3-one and / or salts thereof, and further wherein the silver ions are contained as a silver salt, wherein the silver salt is selected from silver carboxylates, silver fluoride, silver bromide, silver phosphate, silver phosphate glass, silver iodide, silver carbonate, and any combination of the aforementioned silver salts.

Description

BRIEF DESCRIPTION OF THE INVENTIONThe present invention provides a liquid coating composition which is characterized by antimicrobial and antiviral properties. The biocidal activity is provided by a biocidally effective and cost-effective amount of a silver compound, the antimicrobial and antiviral activity of which is unexpectedly synergistically further enhanced by addition of a minimum and cost-effective amount of an isothiazolinone derivative.The coating composition also provides scratch resistant properties once applied to the substrate.Moreover, after application of the biocidal components, this coating composition does not significantly leach into the environment over time. The coating composition may contain TiO2-anatase to further improve (activate) the properties of biocides in the event of exposure to UV light.Moreover, the coating composition contains, inter alia, a component which has a fluorescence emission in the range between 400 nm and 760 nm in order to be able to check the homogeneous application of the coating on the treated surfaces with a simple UV lamp.BACKGROUND OF THE INVENTIONThe demand for antimicrobial coatings is constantly increasing. Triggers are the increasing strengthening of the population and the persistent genetic mutations that are experienced by disease viruses and bacteria.The increase of antibiotic resistant strains of, for example, Salmonella, Escherichia coli, Staphylococcus aureus and Listeria is a serious global problem, especially in clinical medicine. Moreover, the recent pandemia caused by Covid-19 has demonstrated how important it is to have efficient methods and tools to prevent the transmission of viruses.Moreover, it is known that paints and lacquers often have insufficient resistance to the action of microorganisms.Some of these coating compositions, such as lacquers and house paints, contain as resinous binders drying oils, fatty lacquers or alkyd resins which are attacked by fungi and bacteria which can then proliferate and thus increase the risk of infection.Moreover, the pandemia unfolding at onset 2020 has forced the clinician to respond in a manner that could result in an increase in super bug infections. Indeed, it is reported that in the first half of the last year during pandemia more than half of the patients who were fed to hospitals with Covid-19 were given antibiotics. Moreover, recent research results [1] show that 52% of hospital prescriptions associated with coronavirus resulted in at least one antibiotic prescription, and even several prescriptions in 36% of the cases.This causes new concern about the spread of drug resistance, so-called super bugs, in connection with an overwriting. This is only one of the reasons why there is now more than one need for efficient and easy-to-use antimicrobial coatings for surfaces which are exposed to possible contact with viruses and bacteria, thus reducing human-to-human transfer.Another problem is the fact that the process of treating a surface with an antimicrobial coating can leave sites of the substrate uncoated and thus exposed to contamination. This could also be due to the wear effect associated with ambient conditions or mechanical abrasion. The challenge is to identify in time the uncoated sites, which are therefore subject to bacterial or viral contamination.It is important to note at this point that the coating industry is under extreme pressure to reduce the formulation costs as much as possible to obtain the economic viability that previously marked the entire industry.In other words, the market and science are constantly in the search for coating solutions that are simple to use, more effective and with a better cost structure than the options currently available on the market.Coatings from the maritime sector are described in CN 112662299A and US 2009 / 185867 A1 and have antifouling properties.US 2020 / 0377738 A1 describes a dry film preservative composition which acts against fungi and / or algae. The composition is used for the protection of house walls.The composition contains two components: a) at least one bactericide comprising an immobilized isothiazolin-3-one derivative / zinc oxide complex; b) at least one dry film preservative effective against fungi or against algae or against fungi and algae.In the examples, only one immobilized BIT / zinc oxide complex is used.CN 105131772 A describes a self-cleaning antifouling inner wall paint. The color comprises:40-60 parts of a modified fluorocarbon emulsion,1-6 parts of a pure acrylic emulsion,6-16 parts of light calcium carbonate,10-15 parts of calcined kaolin,3-6 parts diatomaceous earth powder,2-4 parts forsterite powder,2-4 parts of nanotin oxide,4-6 parts of magnesium sulfate,0.1-0.3 parts of hydroxyethyl cellulose,5-0.7 parts of dispersant SN-50400,1-0.3 parts of multifunctional auxiliary AMP-950,0.5-0.8 parts of alcohol ester,160.2-0.4 parts of antifoam CF,0.7-1.0 part of an anionic antibacterial additive,0.2 to 0.5 part of sodium hexametaphosphate,3-0.5 parts of levelling agent L-1500,10.5-1.0 part of stainproof agent JZM,0.5-1.8 parts of ethylene glycol,0.3-1.2 parts of mildew-proofing agent,0.3-0.5 parts of wetting agent,50-70 parts of water.CN 104365668 A describes an antifouling material having a long action time. The agent is intended to prevent algae fouling on surfaces in maritime environment, i.e. for example hulls of ships. The antifouling material contains a silver component, which is preferably "charged sustained release silver" using zirconium phosphate as a support material.US 2019 / 0071575 A1 describes a method for reducing microbial attack on a product, which comprises the following steps. First, the product is provided and then 1 to 100 ppm of 5-chloro-2-methyl-4-isothiazolin-3-one having a content of 2-methyl-4-isothiazolin-3-one in the range from 0 to 2% by weight, based on the total proportion of 5-chloro-2-methyl-4-isothiazolin-3-one, is added. The 5-chloro-2-methyl-4-isothiazolin-3-one is decomposed using at least one compound that decomposes 5-chloro-2-methyl-4-isothiazolone. Furthermore, at least one biocide selected from the group consisting of 1,2-benzisothiazolin-3-one in an amount of 1 to 1,000 ppm; 2,2-dibromo-3-nitrilopropionamide in an amount of 1 to 2,500 ppm; 2,2-dibromoomalonamide, tetramethylolacetylene diurea, formaldehyde, glutaraldehyde, phenoxyethanol, 2-bromo-2-nitropropane-1,3-diol in an amount of 1 to 2,000 ppm; zinc pyrithione in an amount of 1 to 2,500 ppm; sodium pyrithione, benzyl alcohol, 3-iodopropargyl-N-butylcarbamate, 2-n-octyl-4-isothiazolin-3-one, 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one, a silver source in an amount of 1 to 500 ppm; is added; 2-Methyl-1,2-benzisothiazolin-3-one, ethylhexylglycerol, 1,2-octanediol, 1,2-hexanediol, 1,2-pentanediol, 1,2-decanediol, propyl p-hydroxybenzoate, sorbic acid, benzoic acid, ascorbic acid, benzalkonium chloride, dimethyldidodecylammonium chloride, terbutryn, diuron, carbendazim, tebuconazole and o-phenylphenol.The present invention addresses, but is not limited to, the biocidal properties of silver ions. The antimicrobial properties of silver and some silver derivatives have been known for centuries [2]. Indeed, it has been used in medicine since the 19th century until the discovery and development of the first modern antibiotics in the 1940s for the treatment of bacterial infections.Silver nitrate was used in eye drops to treat eye infections in newborn infants. In rod form, silver nitrate and silver chloride were used to treat warts and in lotions to treat lesions. Moreover, silver nitrate was used in combination with ammonia as an antimicrobial dental guard. Several other silver salts such as acetate, citrate, lactate, picrate and methylenebisnaphthalenesulfonate have found use in various therapeutic compositions, such as ocular lotions, dust powders for wounds, in astringents and antiseptics, in the treatment of vaginal trichomoniasis and candidiasis and in the treatment of burns, varicose ulcers and pressure ulcers.Silver protein complexes have also been frequently used in preparations such as creams, lotions and ointments. A sulfonamide derivative, silver sulfadiazine, has successfully treated burns as well as acute and chronic wounds in creams and lotions. However, there are reports on microbes in hospitals which develop resistance to silver sulfadiazine, which limits its broad application.Although the exact mode of action of silver salts in killing microbes has not yet been clarified--and remains an active research topic, it is known that silver ions react with cellular components (proteins, membranes, DNA) and react particularly rapidly with the DNA and RNA portion of a cell with deleterious effects on the integrity of the microorganism and biochemical functions, with comparatively minimal toxicity to mammalian cells.It is scientifically proven that silver ions can damage the cell indirectly by generating singlet reactive oxygen species leading to the formation of hydrogen peroxide [3]. Moreover, it has also been confirmed that metallic silver is an effective antimicrobial agent, whether in the form of thin films, nanoparticles or colloidal silver.Chemical compounds such as silver phosphate, silver norfloxazinate, and silver nitrate are, in some circumstances, the most familiar and effective antimicrobial agents are silver based.Despite the plethora of studies and scientific treatises on the biocidal properties of silver ions, studies show that silver is not effective under certain conditions. The relevant literature reports three main conditions which can negatively impair an antimicrobial effect.Thus silver salts of particular strength bind to a variety of organic molecules such as carboxylic acids, thiols, phenols, amines, phosphates and halogenated compounds [4]. After binding, however, the silver ions are no longer available for biocidal activity.Silver resistance [5] developed by certain bacteria has also been reported associated with the presence of a binding protein, flagellum protein [6], which binds the silver ions.In this case, silver resistance develops without genetic alterations; only a phenotypic alteration is required to reduce the colloidal stability of the nanoparticles and thus eliminate their antibacterial activity by preventing free radical damage to bacterial DNA.In this case, the resistance mechanism cannot be overcome by additional stabilization of the silver nanoparticles by surfactants or polymers, as has been proposed in the past.Moreover, a third, almost obvious reason exists why silver ions cannot be effective in concentration; indeed, a strongly infected environment requires a high concentration of ions, and in some cases the solutions available on the market have too low a concentration to be biocidally active. Researchers have found ways to avoid the ineffectiveness of silver ions; for example, an antimicrobial composition is reported in the patent application of Jampani, Hanuman, B. [7] which controls or prevents resistance to antimicrobial activity. The compositions comprise an antimicrobial agent in combination with antioxidant agents that block intrinsic or acquired bacterial resistance.The problem of silver ion resistance has also been considered and addressed by some other authors [8] using certain substances acting as resistance inhibitors. Without wishing to be bound by theory, it is believed that these substances are capable of promoting the transport of silver ions through the cell wall and of disrupting the ion pumping mechanism essential for the cells. More specifically, the resistance inhibitors act by altering the permeability of the membrane of the microorganism, for example, by physical disruption or by altering the nature and nature of the phospholipids present in the membrane.Among the most commonly used resistance inhibitors are the ionophore monensin and other carboxyl ionophores (e.g. salinomycin and lasalocid). In addition, calcium channel activators such as dihydropyridine, bezoilpyrrole and matiotoxin may also be effective. In addition, the enzymes phospholipase A2 and triacylglycerol hydrolases and the cationic peptides CAP18 can control the resistance of the cells to silver ions [9].As already mentioned, many coating formulations with biocidal activity due to the presence of silver ions are described in the scientific literature. However, very little has been written about the possible leaching of silver ions by the applied coating. One method of preventing the leaching of biocidal agents into the environment is to embed the silver ions into a vitreous matrix using sol-gel technology. An example of this is the patent application of De Xian Wang et al.

[10] which discloses dispersion of metal ions in a silica sol also containing TiO2; the sol is then coated and sintered to obtain a vitreous transparent coating having antibacterial properties.The disadvantage of the proposed solution is, however, that it requires a cumbersome heating treatment in an oven. This in turn prevents the application of the sol-gel coating in many areas where it is impossible to sinter the coating on the substrate or generally apply some heat.One skilled in the art to which the invention relates knows that another important problem with which formulations for coatings are mostly faced is the need to reduce the cost of the formulation. In this regard, a possibility would be to remain economically viable by reducing the silver content, which is very often the most expensive component in the coating formulation, as far as possible to the lower biocidal limit and adding a molecule that acts as a booster for silver performance.To the authors of this patent, there are very few examples of boosters for biocidal activity against bacteria and fungi and none that describes a synergistic effect of biocides against the virus. An interesting example is the patent application of Thomas Zahn

[11] , which describes a synergistic effect of isothiazolinone derivatives and a quaternary ammonium salt.In addition, I. Sok Hwang

[12] describes in a scientific article the synergistic effect of antibiotics on the biocidal effect of silver nanoparticles. Another interesting patent application to be mentioned is that of Downey Angela Bridgeget et al.

[13] , which describes the synergistic effect of 2-methyl-3-isothiazolinone on the biocidal effect of 2-n-octyl-3-isothiazolinone and vice versa. However, this patent application does not relate to a specific coating formulation.David Oppong, in U.S. Patent Application

[14] , describes synergistic biocidal compositions which are combinations of 1,2-benzoisothiazol-in-3-one (BIT) and an iodopropargyl compound (iodopropynyl compound). As such a compound, there is mentioned, for example, 3-iodopro-pargyl-N-butylcarbamate.Elsewhere, Dagmar Antoni-Zimmermann

[15] has reported a synergistic biocidal composition in which the biocidal effect of 2-methylisothiazolinone-3-one is enhanced by the addition of a relatively small amount of a biocide such as polyhexamethylene biguanide, N-hydroxymethyl-1,2-benzoisothiazolin-3-one, benzalkonium chloride, pyridione. However, this patent application does not describe the combination of one of the biocides mentioned above with silver ions or silver nanoparticles.Moreover, this patent application also relates to a coating composition containing TiO2to improve the effect of biocides. Several studies report the use of TiO2in anti-bacterial coatings, although none of these coatings have been claimed to be effective against viruses to the best knowledge of the authors.It has been known since 1985

[16] that TiO2with the crystalline form anatase--with rutile not being active--is activated upon photoexcitation, as a result of which in turn electrons migrate from the valence band into the conduction band and electron deficiency (which may also be referred to as holes) arises in the valence band. This produces singlet reactive oxygen species, including hydroxyl radicals, hydrogen peroxide, and superoxide ions.Such ions attack bacteria and other microbes by peroxidation and disruption of phospholipids and lipopolysaccharides within the bacterial cell membranes.This patent also relates to a coating composition containing a fluorescent molecule. The use of fluorescent molecules in coatings is already known and has been reported. The patent application of Dainippon Toryo KK

[17] describes a varnish with a fluorescent component which gives the treated substrate a brilliant color even if the white undercoat layer is not completely formed. However, the authors of this patent application have not found a description of the prior art describing the use of a fluorescent molecule specifically contained in an antibacterial coating.A coating may wear over time due to friction, harsh environmental conditions, or weather conditions. Therefore, accurate and easy monitoring of the quality of the antimicrobial coating is extremely important when the coating is transparent, particularly in a medical environment.The present application proposes the use of fluorescent molecules, the presence of which could be detected by a simple lamp with an emission spectrum in the range 340 nm - 440 nm. In this case, the appearance of fluorescent spots in the visible part of the electromagnetic spectrum (380-760 nm) is a confirmation that the coating is still on the substrate; the treated surface is thus still antimicrobially active.DETAILED DESCRIPTION OF THE INVENTIONThe present inventors recognize that there are a great number of patent applications describing coating formulations having biocidal properties and containing silver ions. However, the coating composition proposed here has silver ions whose antimicrobial properties are enhanced by adding a further component, namely an isothiazolinone derivative.In detail, it has been surprisingly found that isothiazolinone derivatives enhance the biocidal effect of silver ions against fungi, bacteria and viruses even when the silver concentration in the matrix is extremely low and below a reasonable and sufficient biocidal activity.Moreover, the authors have surprisingly discovered that the combination of the microbial components also improves the anti-scratch properties of the coating. Without wishing to be bound by theory, the authors believe that the unexpected advantages in terms of mechanical properties are due to the combination of the cross-linking properties of the two biocides, which lead to the formation of a stable and robust network. The formation of the network is also responsible for the low leaching of silver ions, even under harsh conditions, which results in better durability of the coating.In the context of the present invention, silver in a higher oxidation state than silver ions, i.e. Ag 1+, is incorporated into the coating composition and provided in silver solutions. The particles of the silver compound have a particle size which is between 150 nanometers and 6000 nanometers, preferably from 500 to 3000 nanometers, and particularly preferably from about 1500 to 2500 nanometers, with D90<5 μm.Suitable silver compounds are silver carboxylates such as silver formate, silver acetate, silver oxalate, silver malonate, silver benzoate and silver phthalate; silver fluoride, silver bromide, silver phosphate, silver iodide, silver carbonate and any combination of any of the foregoing. Commercially available silver compounds include Sanitized AG silver phosphate glass sold under the tradename Sanitized, Silvadur.RTM. 900, Silvadur 930, Silvadur 961, and Silvadur ET from The Dow Chemical Company, and BASF silver derivatives sold under the tradename Irgaguard.The silver content in the coating composition is in the range of from 0.01 % by weight to 10.0 % by weight, preferably from 0.05 % to 8 % by weight, and more preferably from about 0.1 % to 4 % by weight.As already mentioned, the silver performance improvers are the isothiazolinone derivatives from the group of 2-n-octyl-4-isothiazolinon-3-one and 2-octyl-isothiazonolin-3-one, or salts thereof.The isothiazolinone derivative can contain stabilizing amounts of copper(II) ions as stabilizer. The content of isothiazolinone in the coating formulation is between 0.01% and 2% by weight, preferably 0.1% to 0.4% by weight, particularly preferably from 0.2% to 0.35% by weight.The coating formulation may also contain TiO2-anatase to improve the biocidal properties of the coating. Examples of the TiO2 anatase include VLP 7000, CristalACTiV™ PC500 manufactured by Crystal Global, and Aeroxide ® P25 manufactured by EVONIK Degussa Industries.The content of TiO2in the coating composition is in the range of from 0.01 % by weight to 5.0 % by weight, preferably from 0.05 % to 2 % by weight, and more preferably from about 0.10 % to 1.5 % by weight.The coating composition may be non-aqueous or aqueous and may be water-like or viscous. Viscosity may be required to avoid settling of the silver particles during storage and to facilitate application of the solution to the substrate.The aqueous coating composition has a viscosity of more than 80 mPas, preferably more than 200 mPas. Viscosity was measured with a Brookfield RTV, spindle 20 or spindle 15 at 25°C.The non-aqueous formulation, solvent-based, is suitable for aerosol and contains organic solvents, resin, pigments (in the case of a colored coating), film-forming solvents, drying agents, thickeners, surfactants, anti-skin agents, plasticizers, martensitic agents, anticorrosives, anti-flooding, silver compounds, isothiazolinone and propellant gas. Most commercial solvent-based aerosol formulations contain mixtures of low molecular weight hydrocarbons as propellant gas which have also been used for the present invention. Most commonly, a mixture of propane and isobutane is used.Examples of liquid aerosol propellants are ethylene glycol monopropyl ether, isobutyl acetate, methyl acetate, cellulose acetate butyrate, dipropylene glycol methyl ether, ethylene glycol ether, butyl acetate and dimethyl ether (DME). The latter two are preferred because they have a lower toxicity profile for humans and have the same performance as the former. The formulation typically comprises from about 20% to about 50%, and preferably from about 20% to about 30%, by weight of the propellant added to the formulation.The method of adding the blowing agent to the mixture may be as follows. After the mixture is placed in the can, the container is vacuumed and the propellant is simply injected and the can is then sealed. The coating composition may also contain an adhesion promoter to improve adhesion to surfaces such as TPO and PP characterized by low polarity. It is advisable to use a coupling agent such as AP-550 from Eastman (25% by weight xylene).It is important to note that solvent-based coatings tend to sink or sink when the coating is applied to inclined and particularly vertical surfaces. This is especially true for high solids coating formulations which become more and more important with the need to reduce the content of volatile organic compounds (VOCs) in the coatings.Thus, there is a highly specific need for rheology modifiers that reduce the tendency of coatings to sink.Ideally, such rheology modifiers should impart structural properties to the coating, such as high viscosity at low shear to prevent sag after application of the coating and low viscosity at high shear to allow flow and leveling of the coating during application.The resins suitable for use range from silicone-modified alkyd, acrylate and epoxy resins via nitrocellulose to polyesters and vinyl esters, to name a few. Some examples of resins are acrylates, diacrylates, triacrylates or multifunctional acrylates which form the crosslinkable group and are polymerized via free radical polymerization. Examples of silicone modified resins are those from Reichhold Chemicals and from The Dow Chemical. The range of products is from the pure acrylate products such as Elvacite from Dupont, Acronal from BASF.Other suitable polymeric rheology modifiers include hydroxypropyl cellulose, hydroxypropyl methylcellulose, fumed silica, precipitated silica, and any combination of the foregoing. Preferred rheology modifiers are polyacrylates and hydroxypropyl cellulose. The composition typically contains from about 0.05% to about 5%, and preferably from about 0.1% to about 1% by weight of polymeric rheology modifier.For formulations with a high organic solvent content, the coating formulation may include evaporation retarders such as silicone fluid, water-based wax emulsion, paraffin oil, paraffin wax, and any combination of the foregoing.A surfactant or a surfactant mixture is usually required as a solubilizers emulsifier and also for preventing phase separation during storage of finished products. The surfactants contemplated in this patent are nonionic surfactants such as Triton X-15 (octylphenoxy polyethoxy ethanol) from The Dow Chemical, Novelusion 333 from Sasol, Capstone FS-31 from Chemours.Other emulsifiers include, but are not limited to, fluorinated alkyl esters, polyethoxylated sorbitan monooleate, trioleate polysorbates, and any combination of any of the foregoing components. The composition typically comprises about 0.1% to about 7% by weight, and preferably about 0.1% to about 2% by weight, of surfactant or emulsifier.The coating formulation may contain organic solvents. A list of suitable solvents includes hexane, heptane, THF, tetrahydrofuran, mineral oil, xylene, toluene, acetone, diethylene glycol, butanone, esters of acrylic and / or methacrylic acid with alkanols containing 1 to 12 carbon atoms, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl propionate, vinyl esters of versatic acid, vinyl esters of long-chain fatty acids.The coating composition may also contain an aromatic hydrocarbon cosolvent to improve the stability of the mixture and thereby increase the shelf life of the composition. The aromatic hydrocarbon cosolvent may be a mixture of one or more aromatic hydrocarbon solvents.Suitable aromatic hydrocarbon cosolvents include, but are not limited to, Aromatic 200Nd from Exxon, metaphenoxybenzyl alcohol, xylene, and any combination of any of the foregoing. The composition typically comprises from about 0.5% to about 40% by weight, preferably from about 1% to about 20% by weight, and more preferably from 1% to 5% by weight, of aromatic hydrocarbon cosolvent.The coating composition has a solids content between 0.3% by weight and 60% by weight.In the case of an aqueous formulation, the coating formulation has been thickened with customary thickeners such as polyacrylates or derivatives or thickeners based on polysaccharides, e.g. xanthan, or cellulose derivatives. The aqueous coating formulation may contain an associative thickener modified with a hydrophobic oligomer. In this case, the coating formulation is suitable for industrial applications requiring a high shear thinning rheology profile and high sag resistance, such as sprayed metal coatings on vertical surfaces.Among associative thickeners suitable for the present invention, the authors tested associative thickeners based on polyethylene oxide-urethane (HEURs) that have imparted good flowability and leveling to the paint, along with acceptable sag resistance.The present invention also contemplates the use of other associative thickeners which function as the basic polymers:• Hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, polyethylene oxide, ethyl hydroxyethyl cellulose, carboxymethyl cellulose, guar gum, starch, starch ethers, in particular hydroxyethyl starch, locust bean gum, pectin, xanthan gum, methyl hydroxyethyl cellulose, polyvinyl pyrolidone, polyvinyl alcohol, methyl hydroxypropyl cellulose, mixed ethers of the above cellulose derivatives and mixtures thereof.Particular preference is given to hydrophobically modified hydroxyethyl cellulose, hydrophobically modified methyl hydroxyethyl cellulose, hydrophobically modified hydroxypropyl cellulose, hydrophobically modified polyethylene glycol, in particular hydrophobic end-capped polyethylene glycols. Dodecyl- and cetyl-modified polymers, for example polyethylene oxides, are preferred. Preferred thickeners are set out, for example, in patent applications from Acqualon [13, 14]. Starch and derivatives thereof are also associative thickeners which can be used advantageously--according to the invention.The thickener content should be 0.05% to 5.0% by weight, preferably 0.075% to 3.5% by weight and particularly preferably 0.1% to 3.0% by weight. The coating formulation may contain suitable mineral fillers such as alkaline earth metal oxides. Carbonate fillers such as calcium carbonate, dolomite and / or aragonite are also preferred in the water-based coating composition of the present invention. The function of such fillers is to reduce the formulation costs or to increase the viscosity and to ensure deflection resistance.Generally, the coating formulation may be colorless or colored; in the latter case, suitable pigments may be present.Suitable pigments are titanium dioxide (rutile), iron oxide, zinc oxide, chromium oxide, cobalt oxides, mixed oxides of cobalt and aluminum, for example cobalt blue, phthalocyanine pigments, spinel pigments, for example spinels of cobalt with nickel and zinc, and iron- and chromium-based spinels with copper, zinc and manganese, nickel and chromium titanate, manganese titanium rutil, rutile mixed phases, bismuth vanadate, ultramarine blue and sulfides of the rare earths. Preferred pigments are, for example, titanium dioxide, zinc sulfide, zinc oxide, carbon black, iron oxide, chromium oxide, cobalt blue, barite, nickel titanate, phthalocyanine pigment, spinel pigment and / or chromium titanate.The content of inorganic pigments should be from 0.005 % to 3.0 % by weight, preferably from 0.075 % to 1.5 % by weight.Organic pigments are also suitable, and the list comprises monoazo pigments, diazo pigments, diazo condensation pigments, anthraquinone pigments, anthrapyrimidine pigments, quinacridone pigments, diketopyrrolopyrrole pigments, dioxazine pigments, flavanthrone pigments, indanthrone pigments, isoindoline pigments, isoindolinone pigments, isoviolanthrone pigments, perinone pigments, perylene pigments, phthalocyanine pigments, pyranthrone pigments, pyrazoloquinolone pigments, thioindigo pigments, triarylcarbonium pigments, and mixtures thereof.Among the organic color pigments, there can be mentioned, for example, C.I. Pigment Blue 15, C.I. Pigment Blue 15:1, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 15:4, C.I. Pigment Blue 15:6, C.I. Pigment Blue 16, C.I. Pigment Green 7, C.I. Pigment Green 36, C.I. Pigment Orange 36, C.I. Pigment Orange 43, C.I. Pigment Orange 73, C.I. Pigment Red 122, C.I. Pigment Red 168, C.I. Pigment Red 179, C.I. Pigment Red 188, C.I. Pigment Red 254, C.I. Pigment Red 264, C.I. Pigment Red 282, C.I. Pigment Violet 19, C.I. Pigment Violet 23, C.I. Pigment Yellow 74, C.I. Pigment Yellow 83, C.I. Pigment Yellow 97, C.I. Pigment Yellow 110, C.I. Pigment Yellow 138, C.I. Pigment Yellow 154, or any mixtures of these pigments.The content of organic pigments should be from 0.005 % to 3.0 % by weight, preferably from 0.075 % to 1.5 % by weight.The present invention also relates to a coating composition containing at least one fluorescent additive which absorbs light having a wavelength of less than about 500 nanometers and fluoresces the light in the visible part (range: 400 nm - 760 nm) of the spectrum.Molecules, but not limited to, are fluorol green gold, 2-Duil ASP, 4-dimethylamino 4-nitrostilbene, 9-cyanoanthracene, Carboxynaphtofluorescina zinc tetramesityl prophyrin, QpyMe2, magnesium tetraphenylporphyrin, and coumarin 6.In order to check the homogeneity of the coating on the substrate, suitable lamps are used for the listed fluorescent molecules. Thus, the authors have identified the following lamps: Phoseon FJ100 365, Phoseon FJ100 385, Phoseon FJ100 395, and Phoseon FJ100 405.BIOCIDAL ACTIVITY ON BACTERIA AND FUNGITo quantify the synergistic effect of isothiazolinone on the biocidal effect of silver particles, the authors have developed the following test.Six simple coating formulations and one control formulation were developed and then applied to aluminum metal plates. The coating solutions were prepared by first dispersing the carboxymethylcellulose in water using a high shear mixer (TDS Conti mixer type). Isothiazolinone and silver phosphate are then added and the dispersion is kept under stirring for 20 minutes.The coating solution is applied by the dipping process (dipping speed 0.3 cm / s) to rectangular aluminum plates (5 cm length, 5 cm width and 0.1 cm thickness). The plates were then dried at room temperature for 8 hours.The plates were then tested for antimicrobial properties according to ISO Test Method 22196 with the following bacterial species:Staphylococcus aureusATCC 6538P, CIP 53.156, DSM 346,NBRC 12732, NCIB 8625ANDEscherichia coliATCC 8739, CIP 53.126, DSM 1576,NBRC 3972, NCIB 8545The procedure for the test was as follows.First, a thin liquid film containing the bacteria (1.25×104 KB / cm 2) was directly applied to the test pattern (5 cm×105cm). A film (4 cm×4 cm, stomacher bags) is then placed on it to avoid drying. Immediately after inoculation, the bacteria of the reference sample are separated from the sample and the enveloping film surface by means of ultrasonic and vortex devices and the number of viable germs (CFU-colony-forming unit) is determined (t0 value). Subsequently, a further set of antimicrobially treated reference samples is incubated with bacteria in the liquid film and the enveloping film in a moist environment at 37° C. After at least 24 hours, the bacteria are separated from the sample surfaces with the aid of ultrasonic and vortex devices and the number of viable germs is determined (t24 value).Formulations A and D are formulations with only silver, while formulations B and E contain only isothiazolinone and formulations C and F both contain biocides. In the case of formulation F, the content of isothiazolinone and silver is significantly below the biocidal activity threshold. Table 1 Table 1Tap water98,50%98,5%98,50%98,50%98,5%98,50%98,50%2-Octyl-2H-isothiazol-3-ones0,0%0,05%0,05%0,0%0,025%0,025%0,0%Silver-phosphate glass1,0%0,0%1,0%0,5%0,0%0,5%0,0%Sodium Carboxymethyl Cellulose0,5%0,5%0,5%0,5%0,5%0,5%0,5%Test results:Table 2 Table 2Formulation A90%87%20%Formulation B40%32%65%Formulation C99,7%99, 6%90%Formulation D80%71%12%Formulation E30%28%48%Formulation F99,8%98, 9%84%Control Formulation G2%6 %1%The results clearly show that the combination of the two components, silver phosphate and 2-octyl-2H-isothiazol-3-one, synergistically and surprisingly enhance the antibacterial and antifungal activity of the coated panels. In detail, the table shows that a silver concentration in the range of 0.5 % by weight is below the threshold of biocidal activity, but the effect is greatly raised to a biocidal level by the addition of a minute amount of the isothiazolinone derivative.It will be apparent to those skilled in the art that the synergistic adequate amounts required will vary depending upon the particular organisms and application and can be readily ascertained by routine experimentation. Moreover, the use of a synergistically effective amount allows the use of a substantially lesser amount of each biocide. Indeed, 2-octyl-2H-isothiazol-3-one, even at a very low concentration (0.025% wt%), increases the effect of silver phosphate.BIOCIDAL ACTIVITY AGAINST VIRUSESFormulations A - G (Table 1) were further tested on aluminium substrate against coronaviruses. The assays were performed according to the test method ISO 21702 and using bovine coronavirus and Vero E6 cells. The samples were run as described above on rectangular aluminum plates (5 cm long, 5 cm wide and 0.1 cm thick) coated by a dip coater. The plates were then dried at room temperature for 24 hours.4 samples per each coated and uncoated control. Inoculation consists of 400 μl of virus suspension applied to the test and control areas. After a contact time of 24 hours at room temperature, the virus suspension is recovered from the coated and uncoated specimens; testing against Bovine Coronavirus was carried out under BSL-2 conditions.The antiviral activity of the specimens is calculated in comparison with the G formulation (coated specimen without biocides) and carried out in duplicates and two independent experiments.Test results:Table 3 Table 3Formulation: G (reference)0 minute minute minute minute minute minute minute-0%24 Std.-4%Formulation: A24 Std.0,16131% Reduction: ReductionFormulation: B24 Std.0,12525% Reduction: ReductionFormulation: C24 Std.0,56973% Reduction: ReductionFormulation: D24 Std.0,12525% Reduction: ReductionFormulation: E24 Std.0,10221% Reduction: ReductionFormulation: F24 Std.0,40961% Reduction: ReductionThe results show that the combination of isothiazolinone and silver phosphate acts synergistically against viruses and the biocidal effect is already present at a very low concentration, as in the case of formulation F.The invention will now be illustrated by the following non-limiting examples.EXAMPLESExample 1Water-based with silver and isothiazolinone opaque table 4 Table 4Tap water76,80%Anti-foaming agent (silicone-based)0,30%Surfactant (Surfynol 104A)0,65%Mineral Oil1,85%Isothiazolinone0,30%Silver phosphate glass2,00%Sodium carboxymethylcellulose was neutralized (Walocel CRT 20000 Dow Chemical)0,50%Kaolins9,60%Calcium carbonates8,00%The coating solution was prepared by first dispersing the carboxymethylcellulose in water using a high shear mixer (TDS Conti Laboratory Mixer Type). Isothiazolinone, defoamer, nonionic surfactant and mineral oil are then added and the dispersion is maintained with vigorous stirring. After 5 minutes, the solid ingredients are dispersed in the solution which is then kept under stirring for an additional 20 minutes.The coating solution is applied by the dipping process (dipping speed 0.3 cm / s) to rectangular polycarbonate sheets (10 cm length, 15 cm width and 0.5 cm thickness). The plates were then dried at room temperature for 7 hoursThe coating adhesion was evaluated by evaluating the adhesion of the coating films to the substrate by applying and removing pressure-sensitive adhesive tape over a one-hundred-part screen incorporated in the film.The test was carried out according to the test method of JIS K5400. Regarding the test results, "pass" means that no damage to the coating was observed; conversely, "fail" means that at least a portion was damaged.The hardness of the substrate treated with the coating formulation was determined using pencil lead using the method ASTM D3363-20.The results show that the coating formulation provides unexpected structural mechanical resistance to the substrate and excellent adhesion to the support material. Table 5 Table 5Hardness Test according to ASTM D3363-20Grid Adhesion TestPolycarbonate untreatedF. FNAPolycarbonate coated with formulation according to Example 1HBPASSExample 2Water-based with isothiazolinone and silver Transparent Table 6 Table 6Tap water94,50%Anti-foaming agent (silicone-based)0,30%Surfactants (Surfynol 104A)0,65%Mineral Oil1,85%Isothiazolinone0,30%Silver phosphate glass2,00%Carboxymethyl cellulose was neutralized (Walocel CRT 20000 Dow Chemical)0,50%The coating solution was prepared by first dispersing the carboxymethylcellulose in water using a high shear mixer (TDS Conti Laboratory Mixer Type). Isothiazolinone, defoamer, nonionic surfactant, and mineral oil are then added and the dispersion was maintained with vigorous stirring. After 5 minutes, silver phosphate glass is dispersed in the solution which is then kept under stirring for an additional 20 minutes.The coating solution is applied by the dipping process (dipping speed 0.3 cm / s) to rectangular polycarbonate sheets (10 cm length, 15 cm width and 0.5 cm thickness). The plates were then dried at room temperature for 7 hours.The coating adhesion was evaluated by evaluating the adhesion of coating films to the substrate by applying and removing pressure-sensitive adhesive tape through a one hundred part mesh incorporated in the film.The test was carried out according to the test method of JIS K5400. Regarding the test results, "pass" means that no damage was observed on the coating; conversely, "fail" means that at least a portion was damaged.The hardness of the substrate treated with the coating formulation was determined using pencil lead using the method ASTM D3363-20.The results show that the coating formulation provides unexpected structural, mechanical resistance to the substrate and excellent adhesion to the support material. Table 7 Table 7Hardness Test according to ASTM D3363-20Grid Adhesion TestUntreated polycarbonateF. FNAPolycarbonate coated with formulation according to Example 2HBPASSAnother embodiment of the present invention relates to the determination of a low leaching characteristic with respect to biocides, particularly with respect to silver ions, from the substrate treated with a coating formulation described in this patent.Critical input parameters required for the estimation are the leaching rates, which in some countries are part of the required data set for the admission of active substances and biocide products. However, despite the importance of the leaching rate as a parameter for characterizing a coated surface, there is no harmonised set of leaching tests or suitable methods for calculating the leaching rates for most applications of biocide products in materials during their useful life.The authors of this patent decided on the following method.An aluminum plate (10 cm in length, 15 cm in width and 0.5 cm in thickness) was coated with the coating formulation of Example 3 by dip coating according to the method described above. The plates (5) were dried at room temperature for 2 days and then stored in boiling brine (50 g NaCl per 1 1 water) for 5 hours.The saline solution was cooled and titrated to determine the presence of silver ions which would be evidence of leaching. In particular, the silver content is determined by precipitation titration with potassium thiocyanate KSCN as titration agent. Titration is monitored with a combined silver ring electrode and monitored with a Mettler Toledo Excellence T5 17 titration apparatus.The silver concentration determined was just above the detection limit of the apparatus, i.e. above 1 ppm, which means that the coating leaches practically no biocides even under very harsh conditions.Example 3Solvent Based with Isothiazolinone and Silver Phosphate Transparent Table 8 Table 8Acrylic-Vinyltoluene-Modified Alkyd (Polychem 7060; EPS 2580)22,96%Dispersing agent (Dysperbyk 163)1,54%Defoamer (BYK 028)0,25%n-Butyl acetate24,00%Acetone Acetone24,00%2-Methoxy-1-methylacetates4,00%Xylene Xylene Xylene4,00%Butanone butanone4,50%diethylene glycol10,00%2-octyl-2h-isothiazol-3-one0,25%Silver-phosphate glass4,00%The coating solution was prepared by first mixing the binder (acrylic-vinyl binder) with the dispersant and then adding N-butyl acetate, acetone, 2-methoxyethoxy-1-methylethyl acetate, xylene and butanone with moderate stirring in the reactor. Finally, diethylene glycol and 2-octyl-2H-isothiazol-3-one are added slowly to the solution, and the silver phosphate is added with vigorous stirring.The coating solution is applied by the dipping process (dipping speed 0.3 cm / s) to rectangular polycarbonate sheets (10 cm length, 15 cm width and 0.5 cm thickness). The plates were then dried at room temperature for 7 hours.Example 4Solvent Based with Isothiazolinone and Silver Phosphate Transparent Table 9 Table 9Acrylic resin35, 96%Dispersing agent (Dysperbyk 163)1,54%%Defoamer (BYK 028)0,25%n-Butyl acetate33,00%2-Ethyl ethoxypropionate4,00%Xylene Xylene Xylene7,00%Butanone butanone4,00%diethylene glycol10,00%2-octyl-2h-isothiazol-3-one0,25%Silver-phosphate glass4,00%The coating solution was prepared by first mixing the binder (acrylic based) with the dispersant and then adding N-butyl acetate, acetone, ethyl ethoxypropionate, xylene and butanone in the reactor with moderate stirring. Finally, diethylene glycol and 2-octyl-2H-isothiazol-3-one are added slowly to the solution, followed by addition of the silver phosphate with vigorous stirring. The coating solution is applied by the dipping process (dipping speed 0.3 cm / s) to rectangular polycarbonate sheets (10 cm length, 15 cm width and 0.5 cm thickness). The plates were then dried at room temperature for 7 hours.Example 5Solvent Based with Isothiazolinone and Silver Phosphate Transparent Table 10 Table 10Epoxy resin (Araldite GZ 7071×75)16,50%Trioleate polysorbate0,50%n-Butyl acetate30,00%Acetone Acetone12,50%2-Methoxyethoxy-1-methylethyl acetate6,00%Xylene Xylene Xylene6,00%2-Octyl-2H-isothiazol-3-one0,25%Silver-phosphate glass4,00%Butanone butanone6,00%diethylene glycol15,70%The coating solution was prepared by first mixing N-butyl acetate, acetone, 2-methoxyethoxy-1-methylethyl acetate, xylene and butanone in the reactor with moderate stirring. Finally, diethylene glycol and 2-octyl-2H-isothiazol-3-one are added slowly to the solution, and the silver phosphate is added with vigorous stirring.The coating solution is applied by the dipping process (dipping speed 0.3 cm / s) to rectangular polycarbonate sheets (10 cm length, 15 cm width and 0.5 cm thickness). The plates were then dried at room temperature for 7 hours.The coating adhesion was evaluated by evaluating the adhesion of coating films to the substrate by applying and removing pressure-sensitive adhesive tape through a one hundred part mesh incorporated in the film.The test was carried out according to the test method of JIS K5400. Regarding the test results, "pass" means that no damage to the coating was observed; conversely, "fail" means that at least a portion was damaged.The hardness of the substrate treated with the coating formulation was determined with pencil and according to the method ASTM D3363-20.The results show that the coating formulation imparts unexpected structural mechanical strength to the substrate and has excellent adhesion to the substrate. Table 11 Table 11Polycarbonate untreatedF. FNAPolycarbonate coated with formulation according to Example 5HBPASSExample 6Water-based with isothiazolinone and silver with water-resistant properties and Elastic Table 12 Table 12Tap water35,80%Defoamer (BYK 711)0,10%Thickener (Natrosol 250 MBR from Aqualon)0,30%Ammoniaabout 0.10%Isothiazolinone0,30%Silver phosphates1,00%Binder (Crillant 4706, Vynavl)60,00%Wetting agent (Cognis Disponil TL 400)0,40%Dispersing Agent0,40%Monopropylene glycol0,50%Sodium Hexametaphosphate1,10%The coating solution was prepared by first adding thickener in water and then adding ammonia dropwise. Once pH 9 is reached, all other components are added with vigorous stirring. Solid ingredients are added first and then MPG, defoamers, and wetting agents.Example 7Water-based with isothiazolinone and silver Elastic Table 13 Table 13Tap water65,40%Antifoaming agent (BYK 711)0,50%Surfactant (Gemini surfactant Evonik Environmental AD type)1,10%Mineral Oil0,50%Isothiazolinones0,30%Silver phosphate glass2,00%Cosolvent (Dowanol 255)5,00%Wetting agent (Cognis Disponil TL 400)1,30%Polyamines (Amyrez 148 / 024)23,90%The coating solution was prepared by first dispersing the polyamine in water using a high shear mixer (TDS Conti Laboratory Mixer Type). Isothiazolinone, wetting agents, cosolvents, defoamers, gemini surfactant, mineral oil are then added and the dispersion is kept with stirring. After 5 minutes, silver phosphate glass is then dispersed in the solution and is then kept under stirring for an additional 20 minutes.Example 8Water-based with isothiazolinone and silver elastic with TiO2, transparent Table 14 Table 14Tap water65,20%Defoamer (BYK 711)0,50%SurfactantMini surfactant (type Evonik Envirogem AD)1,10%Mineral Oil0,50%Isothiazolinones0,30%Silver phosphate glass2,00%Cosolvent (Dowanol 255)5,00%Wetting agent (Dysperbik 180)1,30%TiO2 anatase (Kronos Clean 7050)0,20%Polyamines (Amyrez 148 / 024)23,90%The coating solution was prepared by first dispersing the polyamide in water using a high shear mixer (TDS Conti Laboratory Mixer Type). Isothiazolinone, user agent, cosolvent, antifoam gemini surfactant, mineral oil are then added and the dispersion is kept with stirring. After 5 minutes, titanium dioxide and silver phosphate are dispersed in the solution, which is kept under stirring for 20 minutes.Example 9Water-based with isothiazolinone and silver elastic with 9-cyanoanthracene (fluorescent) Table 15 Table 15Tap water65,20%Defoamer (BYK 711)0,50%Surfactant (Gemini surfactant from Evonik type Envirochem AD)1,10%Mineral Oil0,50%Isothiazolinones0,30%Silver phosphates2,00%Cosolvent (Dowanol 255)5,00%Wetting agent (Dysperbik 180)1,30%9-Cyanoanthracene 20% solution in hexane (TCI chemicals)0,01%Polyamines (Amyrez 148 / 024)23,90%The coating solution was prepared by first dispersing the polyamine in water using a high shear mixer (TDS Conti Laboratory Mixer Type). Isothiazolinone, wetting agents, cosolvents, defoamers, gemini surfactant, mineral oil are then added and the dispersion is kept with stirring. After 5 minutes, titanium dioxide, silver phosphate and the 9-cyanoanthrane solution are dispersed in the solution, which is then kept under stirring for a further 20 minutes.Example 10Solvent-based with isothiazolinone and silver phosphate Transparent Table 16 Table 16Acrylic Resin28,96%Dispersing agent (Dysperbyk 163)1,54%%Defoamer (BYK 028)0,25%n-Butyl acetate20,00%Acetone Acetone20,00%2-Methoxy-1-methylethyl acetate4,00%2-Ethyl ethoxypropionate3,00%Xylene Xylene Xylene4,00%Butanone butanone4,00%Diethylene glycol10,00%2-octyl-2h-isothiazol-3-one0,25%Silver Phosphate Glass4,00%The coating solution was prepared by first mixing the binder (acrylic) with the dispersant and then adding N-butyl acetate, acetone, ethyl ethoxypropionate, 2-methoxy-1-methylethyl acetate, xylene and butanone to the reactor with moderate stirring. Finally, defoamers, diethylene glycol and 2-octyl-2H-isothiazol-3-one are slowly added to the solution, and the silver phosphate is then added with vigorous stirring.The coating solution is applied by dip coating (dip speed 0.3 cm / s) onto rectangular polycarbonate sheets (10 cm length, 15 cm width and 0.5 cm thickness). The plates were then dried at room temperature for 7 hours.Example 11Solvent based with isothiazolinone and silver phosphate transparent with fluorescent porphyrin Table 17 Table 17Epoxy resin (Araldite GZ 7071 X 75)16,50%Trioleate Polysorbates0,50%Benzotriazole0,10%n-Butyl acetate30,00%Acetones12,50%2-Methoxyethoxy-1-methylethyl acetates6,00%Xylene Xylene Xylene6,00%2-Octyl-2H-isothiazol-3-one0,30%Silver-phosphate glass6,40%Magnesium tetraphenylporphyrin (dissolved in toluene 10% by weight)0,05%Butanone butanone6,00%Diethylene Glycols15,70%The coating solution was prepared by first mixing epoxy resin, n-butyl acetate, methoxyethoxy-1-methylethyl acetate, xylene and butanone in the reactor with moderate stirring. To the solution is then slowly added diethylene glycol, magnesium tetraphenylporphyrin, 2-octyl-2H-isothiazol-3-one and, most finally, the silver phosphate with vigorous stirring. Coating formulations according to Example 6 and Example 7 were applied to aluminium plates by dip coating (dip speed 0.3 cm / s) on rectangular plates (10 cm length, 15 cm width and 0.5 cm thickness). The plates were then dried at room temperature for 4 hours.To examine the fluorescent effect, the coated substrates were irradiated with a blue lamp emitting in the range 360-430 nm (Phoseon J100), and the coated substrate showed a light color due to the emission spectrum of 9-capynoanthracene and magnesium tetraphenylporphyrin.

Claims

A coating composition containing silver ions and an isothiazolinone derivative as antimicrobial agents, wherein the silver ions and the isothiazolinone derivative are homogeneously dispersed in a liquid matrix and their total concentration is not more than 10 wt% of the matrix, and further the weight ratio of silver ions calculated as elemental silver to isothiazolinone derivative is 1:50 to 50:1, wherein the isothiazolinone derivative is selected from the group of 2-n-octyl-4-isothiazolin-3-one and 2-octyl-2H-isothiazolin-3-one and / or salts thereof, and further wherein the silver ions are contained as a silver salt, wherein the silver salt is selected from silver carboxylates, silver fluoride, silver bromide, silver phosphate, silver phosphate glass, silver iodide, silver carbonate, and any combination of the above silver salts.Coating composition according to claim 1, characterized in that the weight ratio of silver ions calculated as elemental silver to isothiazolinone derivative is 1:10 to 10:1.The coating composition according to claim 1, wherein the concentration of silver ions is 0.02 wt.% to 8.0 wt.%, preferably 0.05 wt.% to 6.0 wt.%, and more preferably 0.10 wt.% to 5.0 wt.%.The coating composition of claim 1, wherein the silver carboxylate is selected from silver formate, silver acetate, silver oxalate, silver malonate, silver benzoate and silver phthalate.The coating composition according to claim 1, wherein the concentration of the isothiazolinone derivative is 0.01 % by weight to 4.0 % by weight, preferably 0.010 % by weight to 1.0 % by weight.The coating composition of claim 1, wherein the liquid matrix contains water and the content of water is between 0.1% and 65.0%.The coating composition of claim 1, wherein the coating composition comprises copper nitrate as a stabilizer.The coating composition according to claim 7, wherein the concentration of the copper nitrate is 0.01 % by weight to 4.0 % by weight, preferably 0.010 % by weight to 2.0 % by weight.The coating composition of claim 1, comprising a fluorescent molecule.The coating composition of claim 9, wherein the fluorescent molecule is selected from the group consisting of 4-dimethylamino-4-nitrostilbene (fluorol green gold), carboxynaphthofluorescine, zinc tetramesityl porphyrin, magnesium tetraphenylporphyrin, 9-cyanoanthracene, and coumarin 6.The coating composition according to claim 9, wherein the concentration of the fluorescent molecule is 0.005 % to 1.0 %, more preferably 0.03 % to 0.5 %.Coating composition according to Claim 1, wherein the liquid matrix comprises a solvent, and the solvent is selected from hexane, heptane, THF, tetrahydrofuran, mineral oil, xylene, toluene, acetone, diethylene glycol, butanone, esters of acrylic and / or methacrylic acid with alkanols containing 1 to 12 carbon atoms, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl propionate, vinyl esters of versatic acid, vinyl esters of long-chain fatty acids.The coating composition of claim 1, wherein the coating composition comprises a thickener and the thickener is an associative thickener, preferably selected from the group of hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, polyethylene oxide, ethyl hydroxyethyl cellulose, carboxymethyl cellulose, guar gum, starch, starch ethers, hydrophobically modified hydroxyethyl cellulose, hydrophobically modified methyl hydroxyethyl cellulose, hydrophobically modified hydroxyethyl cellulose, hydrophobically modified hydroxypropyl cellulose, hydrophobically modified polyethylene glycol, hydroxyethyl starch, locust bean gum, pectin, xanthan gum, methyl hydroxyethyl cellulose, polyvinyl pyrolidone, polyvinyl alcohol, methyl hydroxypropyl cellulose, polyacrylic acid and polyacrylate derivatives, nitro-based, alkyd-based, epoxy, polyester, vinyl, silicone, or any mixture of the above polymers.The coating composition of claim 1 comprising titanium dioxide.The coating composition of claim 14, wherein the titanium dioxide is in its photocatalytically active crystalline form.The coating composition according to claim 14 or 15, wherein the concentration of titanium dioxide is 0.3% to 5.0%, more preferably 0.3% to 1.5%.The coating composition of claim 1 which exhibits a silver ion leach of less than 0.1% of the original concentration on the substrate.Use of a coating composition according to claim 1 as an aerosol paint, wherein the coating composition contains a solvent or a solvent and a propellant.