ANTI-SOILING NANO-COATING SYSTEMS WITH: ENHANCED ANTIMICROBIAL ACTIVITY.

FIELD OF THE INVENTION

This invention refers to a method of development of a new nano-coating system for solid surfaces. The method involves the preparation of the substrate and the application of an ultra-thin coating, in order for the surface to acquire anti-contamination properties. The system can be applied on any glass, metal, plastic, mineral or composite surface, in order for that to acquire easy-to-clean properties, soiling adsorption deterrence properties and strong antimicrobial activity for long periods of time.

BACKGROUND OF THE INVENTION

The pollution of a surface does not only degrade its aesthetic, but it is a persistent problem with significant impact. Its impact can be economic, (e.g., reduction of the energy generated by photovoltaic / solar thermal systems, due to dust accumulation at the panels), functional, (e.g., increase of friction in engines due to deposits on moving parts), or even at public health level, as, usually, the spread of diseases and dangerous infections is due to the frequent contact of human with surfaces, contaminated with bacteria, microbes and viruses. At this point, distinction should be made between the pollution due to non-pathogenic substances, and the one that contains pathogenic microorganisms. However, its development mechanism on a surface is common, and it is based on the manifestation of weak forces, mainly Van der Waals, which trigger adsorption processes, of either pollutants or micro-organisms.

As we know, the adsorption of foreign substances is enhanced in porous materials and in materials with intense nano-roughness, due to increase of the specific surface. This phenomenon is not always directly perceptible, because ordinary surfaces (e.g., glass), macroscopically appear smooth. In fact, however, they are composed of minute mountains and valleys, which form a pronounced topography, which is visible only through a microscope. Various contaminants (e.g., salts) and micro-organisms arc trapped in these points. Standard cleaning/disinfecting agents contain surfactants that remove the contaminants or kill the micro-organisms; but they are often harmful for human health and for the environment. Furthermore, their use does not act as a deterrent to the recurrence of soiling.

Anti-pollution or anti-contamination nano-coatings, namely extremely thin films, invisible to the human eye, which exhibit soiling and microorganism adsorption deterrence properties, are an efficient alternative to the above problem, as they do not alter the optical (or even tactile) characteristics of the surfaces where they are applied and, under conditions, they can have increased functionality at a low application cost.

The development, in recent years, of easy-to-clean or self-cleaning coatings, which repel pollution, due to hydrophobic and/or lipophobic characteristics, was based on this rationale. Many attempts have been recorded in the past [1-10, 23] relating to the development of hydrophobic coatings on a series of substrates (e.g., glass, ceramic, wood, plastic, metal, etc.). For that purpose, alkyl silanes are typically used.

The majority of the above systems is based on sol-gel technology. The latter exploits hydrolysis and condensation reactions of organosilanes to produce polymerized networks of nano dimensions. The same mechanism is also commonly found in antibacterial coatings [11 -16], which base their activity on typical antimicrobial agents (e.g., quaternary ammonium salts, titanium dioxide, silver, copper, etc.).

Sol-gel technology can have extensive application in an industrial environment, because it offers flexibility and a wide range of possibilities in the design of functional coatings. On the other hand, techniques such as chemical vapor deposition, or ion implantation, have not been widely accepted yet, due to high cost and complexity in application. The main disadvantage of sol-gel anti-contamination systems is the reduced durability and, in some cases, limited functionality. For example, the antimicrobial activity coatings, based on silver ions, is rapidly degenerating after some months. Moreover, hydrophilic coatings that are based on photocatalytic materials (e.g., titanium dioxide) work best in laboratory conditions and for the removal of mainly organic pollutants. The durability can be improved in some cases with increase in the thickness of the coating, e.g., through the use of resins, a practice, however, that adversely affects transparency. However, it should be noted that the nature of the substrate plays a key role, on both the durability and the functionality of a coating. Each substrate has different structure, and, therefore, requires different processing, in order to be appropriately activated before its coating. And in the case that anchoring of the coating is carried out through surface hydroxyl groups, the nature of the substrate assumes key importance. For example, on glass/ceramic glass surfaces good mechanical strength is easily achieved, due to abundance of silanols. However, this is not the case on metal surfaces with low hydroxyl concentration or on plastic substrates, where the development of hydroxyl groups is feasible only with the use of plasma, a fact that automatically imposes technical restrictions on the surface modification capabilities of large surfaces. At the same time, surface roughening methods, in order to improve the mechanical adhesion of the coating, are not an acceptable solution, because they usually adversely affect transparency.

To enhance the durability of sol-gel systems, an attractive solution is the creation of an ultra-thin matrix, capable of functioning as “primer”, namely as a durable interlayer, which will be strongly bound with both the coating and the substrate, regardless of its nature.

It should be pointed out that the terms “easy -to-c lean” or “anti-pollution” are usually understood as the property of the coating to repel atmospheric pollutants, dust and other organic or inorganic deposits (e.g., salts). Therefore, its ability to deter the accumulation of micro-organisms (bacteria, microbes and viruses) is disregarded, which is probably due to the perception that the phenomenon can be effectively addressed only through the use of antimicrobial technologies, e.g., disinfectants.

In common antimicrobial technologies, the protection mechanism is usually “active”, namely it is not based on the repulsion of microbes, but on their natural elimination through the release of substances that penetrate their cell wall, poisoning them on the inside, as they interfere with the metabolic chain and alter their DNA. For example, the activity of disinfectants, which are applied periodically, is based on this rationale. This practice, however, leads to mutations and to the development of adaptive micro-organisms. Moreover, the above substances are often unstable to light or high temperatures, and, in some cases, toxic or harmful to the environment.

As a result, in recent years, the idea of using antibacterial coatings has been significantly reinforced [11-22, 24-28]. In terms of cost and environmental friendliness, the latter have an advantage over traditional technologies, as they do not produce hazardous waste. On the other hand, they lag behind in terms of the range of protection they provide against different types of micro-organisms and viruses. Also, the functionality of the coatings is often limited in time (e.g., some days or a few months), so the advantage they have over periodically used disinfectants fades.

It is apparent, therefore, that a coating of hybrid nature, namely that combines both “anti-adhesive” properties, therefore providing passive antimicrobial protection, and properties of natural killing of microbes (active antimicrobial protection), can be infinitively more effective in reducing pollution, whether it relates to pathogenic microorganisms or not.

In conclusion, in modem anti-pollution systems, the range of efficiency, the durability and the user-friendliness remain challenges, while, at the same time, there is no method that could be universally applied on multiple substrates. Finally, the potential toxicity of some raw materials (e.g., fluoropolymers) is often a side problem. An ideal system should have the following characteristics: i) Ability to deter the accumulation of both pollutants and micro-organisms and viruses, ii) Bacteriostatic and microbiostatic properties, iii) Increased lifespan and resistance to abrasion, chemicals, UV, high temperatures and temperature changes, iv) Universal substrate preparation process, v) High adhesion and functionality of the coating on any substrate, vi) Curing of the coating at standard temperature and humidity conditions, vii) Full transparency, viii) Increased shelf life of the coating solution, ix) Environmentally-friendly chemical composition and x) Easy application.

Moreover, ideally, the coating should be breathable, exhibit excellent step coverage, have minimum roughness and not absorb solar radiation.

DETAILED DESCRIPTION OF THE INVENTION

In this invention the development of an innovative anti-soiling nanocoating system with enhanced antimicrobial properties is described. This system involves two application stages:

1) The stage of mechanochemical activation of the substrate, which prepares the latter for the development of stable chemical bonds with the antimicrobial coating. During this stage, disinfection of the substrate is carried out and its simultaneous coating with a hydrophilic thin film that contains functional groups able to covalently bond with the antimicrobial coating, thus ensuring stable anchoring of the latter to any surface. For this purpose, a solution is used, consisting of: a) a mixture of A and B organosilanes with a total amount of 0.02-10% w/w, preferably 0.2-1% w/w and with a relative weight ratio (weight A:weight B) from 1 : 1 to 1 :100 and, in particular, a mixture comprising: i) one organosilane A with up to 4 hydrolyzable groups, as a three- dimensional silica matrix growth medium, of the formula (I):

R'aSifX),-. (I) or, of the formula (II):

R ^l _a Si(X)3-a-R ² "Si(X) ₃ (II) where R ¹ is independently an alkyl, alkenyl or aryl radical having up to 12 carbon atoms, R ² is a divalent saturated hydrocarbon radical having up to 12 carbon atoms and X is an alkoxy radical having up to 12 carbon atoms or chlorine, and a is 0 or 1 ; and ii) one organosilane B with up to 3 hydrolyzable groups, as coupling agent, of the formula (III):

G-R ³ “Si(R ⁴ ) _b (Y) ₃ -b (HI) where G is a glycidol, amine or thiol functional group, R ³ is a divalent saturated hydrocarbon radical having up to 12 carbon atoms, R ⁴ is an alkyl radical having up to 12 carbon atoms and Y is an alkoxy radical having up to 8 carbon atoms or chlorine, and b is 0 or 1; b) an oxidizing agent, the dissociation of which yields hyperoxide anions of concentration between 0.1 and 10 gr-ion/L, preferably between 1 and 3 gr- ion/L; c) an acidifying agent or pH adjustment chelate; d) a mixture of surfactants, consisting of one alkoxylated fatty alcohol (AA) and one alkyl polyglycoside (APG), with a total amount of 0.02-5% w/w, preferably 0.03-1% w/w and a relative molar ratio (moles AA:moles APG) in dry active basis from 1:1 to 100:1 and in particular, a mixture of: i) an alkoxylated fatty alcohol (AA), of the formula (IV):

R ⁵ (OR ⁶ )COH (IV) where R ⁵ is an alkyl radical having from 4 to about 26 carbon atoms, R ⁶ is a divalent saturated hydrocarbon radical having from 2 to about 4 carbon atoms and c takes values from 1 to about 18; and of ii) one alkyl polyglycoside (APG), of the formula (V):

C _d H _2d+2 O ₆ (V) where d takes values from 11 to about 26; and e) solvent, in particular deionized water of conductivity less than 10 pS/cm, preferably less than 5 pS/cm, or a mixture of water and appropriate organic solvent, e.g., alcohol. The silane mixture consists of silane A which aims at the development of a compact silicate network and from silane B which bears a functional group capable of being chemically combined with hydroxyl groups of the coating. It was found that hydrolysis and polycondensation reactions that take place at the same time between silanes A and B lead to the development of a three-dimensional silicate structure, which promotes the adhesion of the coating. This structure is developed after aging of the solution of silanes for at least 24 hours at ambient temperature.

It was also found unexpectedly that when the mixture of organosilanes has a total concentration between about 0.2% and about 1% and the relative weight ratio of the two organosilanes (weight A:weight B) is from 1 :1 to 1 :100, the resulting structure is hydrophilic with satisfactory mechanical strength, thus enhancing adhesion of the coating, even on surfaces that lack surface hydroxyl groups.

The above finding is possibly due to two phenomena that compete against each other. On the one hand, the polymerization reactions between Si-OH groups lead to the curing of the silicate network and the emergence of nonpolar terminal groups. This phenomenon is reinforced, with either the addition in the solution of a volatile organic solvent (e.g., alcohol), the rapid evaporation of which helps the formation of durable, hydrophobic structures, or with increase in the concentration of silane A, which results in higher thickness of the silicate network. Simultaneously, the functional group of silane B seems to accelerate the rate of cross-linking under normal conditions, resulting in the formation of a modified compact structure of high interconnection degree.

On the other hand, as the silicate network develops, side-chains with terminal hydrophilic Si-OH groups are simultaneously formed, as well as Si-OOH groups, due to the presence of the hydroperoxide anions. In the case where the concentration of the silanes is low and water is used as solvent, the above groups prevail, but at the expense of the mechanical strength of the matrix. At the same time, the functional groups G of organosilane B bond to the siliconized frame of the latter through siloxane groups Si-O-Si, thus enhancing the hydrophilic nature of the resulting structure.

It is evident that at a specific range of values of relative weight ratio and total concentration of the two silanes in the solution, the silicate matrix can exhibit both hydrophilic attributes and satisfactory mechanical strength, even at non-hydroxylated substrates.

The above finding exceeds existing knowledge on the mechanism of action of silane-based adhesion promoters. The reason is that anchoring of such silanes to non-hydroxylated substrates, without prior proper processing (e.g., with plasma), was considered, to this day, impossible. It should be noted that silane A can be a bipolar silane of the formula (II), which, due to high hydrolytic stability, provides the silicate background with even greater mechanical strength.

The oxidizing agent, mainly hydrogen peroxide or peracetic acid, has a multifunctional role. First, it serves as a detergent and disinfectant of the substrate before the application of the coating, which is crucial for the antimicrobial/antiviral efficacy of the latter. Moreover, at some substrates (e.g., T1O2) it accelerates the development of terminal hydroxyls, thus offering more anchorage points. Finally, at sufficiently hydroxylated surfaces, it contributes to greater durability of the coating. Particularly, when the latter contains cationic groups, the stability of the final structure increases even more, due to the development of strong bonds with the hydroperoxide groups of the substrate.

The desired pH value is achieved with the addition of an appropriate acidifying medium (e.g., organic acid). Chelates, e.g., chelate acids, are particularly advantageous, because they prevent the catalytic disproportionation of the oxidizing agent from metal ions and, at the same time, they contribute to the binding of contaminants.

The mixture of surfactants aims at, on the one hand, cleaning and disinfecting the substrate; on the other hand, reducing the surface tension of the solution, especially in the case it is aqueous, in order to maximize the adhesion of the developing siloxane network. Mixtures of alkoxylated fatty alcohols and alkyl polyglycosides especially significantly improve the wetting of low surface energy substrates (e.g. plastic surfaces), at low concentrations, typically less than 0.5 mmol/1, and, therefore, they do not hinder the development of the silicate matrix. The above surfactants are derived from renewable sources, they are biodegradable and they exhibit excellent detergent action against lipophilic pollutants. But they mainly act as deterrents, even at room temperature, to the formation of microorganism communities (biofilm), which allows to maintain the surface after its activation and before its coating at a, to the extent possible, sterile condition.

The activation solution is water based. The addition of a small quantity of organic solvent, which is chemically compatible with the substrate, generally improves weting and accelerates the formation of the modified silicate background.

The preparation of the activation solution is carried out in HDPE plastic tanks. The constituents are successively added to the solvent with continuous stirring at 300 rpm. After the addition of the last constituent the mixture is still being stirred for another 5-10 min. Subsequently it should be left to age at room temperature for at least 24 hours before use. The solution is applied on the substrate, either manually by wiping, or mechanically with a polisher, or even with spraying techniques (e.g., HVLP). The surface should then be left to dry for at least 1-2 minutes, in order to achieve partial curing.

2) The stage of coating. After preparation of the substrate, application of the coating solution takes place. The latter dries in air, ultimately leading to the formation of an anti-contamination coating having a thickness ranging between 50 and 500 nm, preferably between 100 and 300 nm. The dry coating combines both anti-soiling and antimicrobial properties, exhibits high mechanical and chemical resistance, and is resistant to temperatures close to 250 °C. It is also resistant to sudden temperature changes.

The coating solution can be easily applied by wiping, therefore glass, ceramic, plastic, metal, mineral and composite surfaces, of all shapes and sizes can be coated. Typical examples are: sanitary fixtures, knobs, screens of electronic devices, kitchen and bathroom worktops, squares, tiles and roofing materials, concrete structures, boat decks, railings, furniture, banisters, tanks, hospital equipment, medical implants, photovoltaics and solar collectors, painted surfaces, etc. The coating solution consists of: a) a mixture of organosilanes C and D, with a total amount of 0.02-20% w/w, preferably 0.04-12% w/w and with a relative weight ratio (weight C:weight D) from 1:100 to 100:1 and in particular, a mixture comprising: i) one organosilane C with up to 4 hydrolyzable groups, as a three- dimensional silica matrix growth medium, of the formula (I):

R ^l _a Si(XXa (I) where R ¹ is independently an alkyl, alkenyl or aryl radical having up to 12 carbon atoms and X is an alkoxy having up to 12 carbon atoms or chlorine, and a is 0 or 1 ; and ii) one organosilane D with 3 hydrolyzable groups, as anti-contamination agent, in particular of one cationic derivative of organosilanes with quaternary ammonium salts, of the formula (VI): where Z is an alkoxy radical having up to 8 carbon atoms, R ⁷ is a divalent saturated hydrocarbon radical having up to 12 carbon atoms, R ⁸ and R ⁹ are independently a hydrogen or an alkyl radical having up to 12 carbon atoms, R ¹⁰ is a saturated or unsaturated hydrocarbon radical having from 8 to about 24 carbon atoms and H is a halogen or carboxyl, or hydroxide, or phosphate or sulfate or nitrate radical; b) an inorganic or organic acid as catalyst; c) a mixture of surfactants, consisting of an amphoteric polymer (AP) and an alkoxylated fatty alcohol (AA), with a total amount of 0.002-0.4% w/w, preferably 0.003-0.1% w/w and a relative weight ratio (weight AP:weight AA) from 1 :100 to 100:1, and, in particular, a mixture of: i) an amphoteric polymer (AP), which has been formed by at least one quaternary ammonium monomer, of the formula (VII):

T\R ^{1 :} LNAR ¹² R ¹³ R ¹⁴ a (vii) where T is an acrylamide group, R ⁿ is a divalent saturated hydrocarbon radical with up to 4 carbon atoms, R ¹² and R ¹³ are independently a hydrogen or alkyl radical having up to 3 carbon atoms, R ¹⁴ is a hydrogen or alkyl radical with up to 8 carbon atoms and Q is a halogen or carboxyl, or hydroxide, or phosphate or sulfate or nitrate radical; and of ii) one alkoxylated fatty alcohol, of the formula (IV):

R ⁵ (OR ⁶ ) _C OH (IV) where R ⁵ is an alkyl radical having from 4 to about 26 carbon atoms, R ⁶ is a divalent saturated hydrocarbon radical having from 2 to about 4 carbon atoms and c takes values from 1 to about 18; d) solvent, in particular deionized water of conductivity less than 10 pS/cm, preferably less than 5 pS/cm, or mixture of water and appropriate organic solvent, e.g., alcohol.

In order to achieve satisfactory coupling between the silanes C and D, the coating solution should be left to age at room temperature for at least 24 hours before use. The catalyst accelerates hydrolysis and polycondensation reactions between the two silanes, especially at pH values between about 3 and about 5.5. The resulting structure is anchored to the primer with covalent bonds, which are developed during the simultaneous curing of the two layers. Anchoring is carried out either through free silanols of the silicate primer, or through functional groups of silane B, which serve as a bridge between substrate and coating, contributing in enhancing the mechanical strength of the latter. In fact, at substrates with high surface concentration of hydroxyls, it is reasonable to expect even higher adhesion of the coating with the substrate, due to multiple points of interconnection.

Organosilane C belongs to a category of organosilanes of the same general formula as organosilane A. It was found that in the case that organosilane C has quite higher weight content compared to organosilane D, the coating exhibits hydrophobic properties, whereas when the opposite happens, its antimicrobial effectiveness is enhanced. In any case, the use of organosilane C significantly improves the durability of the final structure, compared to the case where it is not used at all. This is possibly due to the three-dimensional arrangement of the underlying modified silicate layer, which reveals active bonding cites in all directions. Organosilane C is, in turn, spatially distributed in multiple configurations, thus cross-linking density increases. As a result, the end structure becomes thicker and subsequently, its mechanical strength is improved.

On the basis of the above, it is obvious that, depending on the relative ratio of the silanes in the solution, either the antimicrobial nature of the coating or the pollutant adsorption deterrence properties are enhanced, respectively. The carbon chain of the radical R ¹⁰ , which, due to its length increases the coating hydrophobicity, and, at the same time, through its free end, is capable of rupturing the cell membrane of various micro-organisms and microbes, leading to their natural elimination, has a key role in this response. Of course, a necessary condition for the latter mechanism to exhibit, is the direct contact of the carbon chain with the microbe. This is ensured through the attraction that is exercised by the cationic charge of the coating to the cell membrane of the microbes, which is usually negatively charged.

It should also be pointed out that when the solution of the coating is acidic, the amphoteric polymer behaves as a cationic one. The synergistic action between the amphoteric polymer and the ammonium cations present in silane D, leads to extensive and strong antimicrobial activity.

Apart from the role that specifically the amphoteric polymer has in the functionality of the anti-contamination coating, the mixture of surfactants aims at the reduction of the surface tension of the coating solution, in order to ensure ease in application and maximum possible adhesion with the primer.

The coating solution is water-based. The addition of a small quantity of organic solvents (e.g., alcohol, glycol ether) improves wetting and accelerates the formation of the final structure. However, they should be sparingly used, as, usually, the underlying layer has not acquired full chemical resistance until the moment of its coating; thus, there is a possibility of removal of its surface layers, and, therefore, the risk of thinning the developed structure, which adversely affects its properties.

The preparation of the activation solution is carried out in HDPE plastic tanks. The constituents are successively added to the solvent with continuous stirring at 200 rpm. After the addition of the last constituent the mixture is still being stirred for another 60 min and then it is left to age under normal conditions.

The coating is applied with traditional techniques, e.g., manually by wiping with a micro-fiber cloth, mechanically with a polisher, with spraying techniques (e.g. HVLP), etc.

The surface is left to dry for at least 5-10 minutes. Any residues are removed with a dry micro-fiber cloth. The full curing of the coating and its maximum functionality are achieved after at least 8 hours.

The coating developed exhibits two anti-contamination mechanisms. On the first level, it repels soiling due to hydrophobic and antistatic properties. On the second level, it contributes to the elimination of pathogenic contamination, through the natural elimination of microrganisms that have not already been removed. It should be noted that the spatial arrangement of the functional groups of the coating allows for the exhibit of a “three-dimensional” antimicrobial activity. The reason is that the structure of the silicate matrix, that is developed in the stage of mechanochemical activation leaves free active centers serving as potential anchorage points for the coating in all three dimensions. Compared to the typical antimicrobial coatings, the above configuration is a significant progress, as it significantly strengthens the anti-microbial activity of the anti-pollution film. Additionally, the functionality of the latter degrades much more slowly over time.

Furthermore, the coating attains remarkable stability due to the simultaneous curing of the underlying layer and the coating. This process takes place at ambient temperature. Ideally, the application should take place between 10 and 30 °C, under relative humidity between 30 and 70%. During this time, the direct contact of the coating with chemicals and with agents that cause mechanical wear and tear should be avoided, as far as possible. Heating the coated surface at temperatures of up to about 150 °C can significantly improve the curing time.

It is worth mentioning that the two solutions, i.e., the mechanochemical activation solution and the coating solution are usable for at least two years after their preparation. The final structure should be rather characterized as coating system and not just as coating, in the sense that the coating system implies the aforementioned sequence of processes, which must be completed in 2 stages, in order to result in a durable nano-coating with strong antimicrobial activity.

The system is suitable for any substrate, especially for smooth, nonabsorbent surfaces. Moreover, it has industrial applicability, because rapid coating of large surfaces is possible, at installations that allow movement of the substrate at constant speed and simultaneous spraying of the coating solution through nozzles, placed transversely to the substrate movement direction and at fixed distances between them.

Finally, depending on the nature of the substrate and the range of protection sought, small modifications in the chemical composition of the two solutions, i.e., primer and coating, is possible. Intervening, for example, in the composition of the coating solution, fine tuning of the hydrophobicity and disinfection efficacy of the top layer is achieved.

References

US Patents:

1. (2012/8,147,607 B2) Hydrophobic self-cleaning coating compositions. 2. (2012/8,258,206 B2) Hydrophobic coating compositions for drag reduction.

3. (2009/7,578,877 B2) Two-component coating system for equipping smooth surfaces with easy-to-clean properties.

4. (2013/0109261 A 1 ) Coating systems capable of formi ng ambiently cured highly durable hydrophobic coatings on substrates.

5. (2013/0178580 Al) Water-repellent and oil-repellent coating and formation method thereof.

6. (2007/0027232 Al) Coating compositions incorporating nanotechnology and methods for making same.

7. (2003/6,548,116 B2) Method for manufacturing a chemically adsorbed film and a chemical adsorbent solution for the method. . (2011 /7,919, 147 B2) Coating method.

9. (2012/8,338,351 B2) Coating compositions for producing transparent super-hydrophobic surfaces.

10. (1997/5,693,365 A) Method for forming water-repellent film.

11. (2015/9,011,890 B2) Antibacterial sol-gel coating solution. 2. (2015/9,210,934 B2) Surface coating. 3. (2017/0150723 Al ) Methods of preparing self-decontaminating surfaces using reactive silanes, triethanolamine and titanium anatase sol. 14. (2017/9,631,118 B2) Anti-bacterial and anti-fingerprint coating composition, film comprising the same, method of coating the same and article coated with the same.

15. (2010/0028462 Al) Stable aqueous solutions of silane quat ammonium compounds.

16. (2006/6,994,890 B2) Cleaning and multi functional coating composition containing an organosilane quaternary compound and hydrogen peroxide.

17. (2015/0225572 Al) High performance antimicrobial coating.

18. (2011/7,955,63 6B2) Antimicrobial coating.

19. (2005/0080157 Al) Antimicrobial adhesive and coating substance and method for the production thereof.

20. (2008/0138626 Al) Plasma-enhanced functionalization of substrate surfaces with quaternary ammonium and quaternary phosphonium groups.

21. (2016/0262382 Al) Surface disinfectant with residual biocidal property.

22. (2019/10,266,705 B2) Self-disinfecting surfaces.

WO Pat:

23. (2014/095299 Al) Composition for hydrophobic coating. 24. (2019/246025 A 1 ) Silver and titanium dioxide based optically transparent antimicrobial coatings and related methods.

25. (2016/043584 Al ) Method for providing a substrate with an antimicrobial coating, and coated substrates obtainable thereby. 26. (2018/231437 Al) Anti-microbial coating materials.

Eur. Pat.:

27. (2005/EP1555249 Al) Hydrophobic and/or oleophobic coating on microstructured glass surfaces providing an anti-fingerprint effect. 28. (2021/EP3170394 Bl) High quality antimicrobial paint composition.

Co-financed by Greece and the European Union

Co-financed by the European Regional Development Fund of the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH - CREATE - INNOVATE (project code: T1EDK-04949).