FR2996853A1 - Sacrificial and aqueous anti-graffiti coating composition, used in to-be protected surface e.g. painted or unpainted nonporous solid surface of walls and doors of public buildings, comprises film-forming acrylic resin and thickening agent - Google Patents

Abstract

Sacrificial and aqueous anti-graffiti coating composition comprises a film-forming acrylic resin and a thickening agent with the weight ratio of 10-80. An independent claim is included for temporarily protecting a surface against a graffiti including: applying a layer of an aqueous coating composition on a to-be protected surface; drying to form a sacrificial anti-graffiti coating; and totally or partially removing the coating with warm water under pressure.

Description

- 1 - SACRIFICIAL ANTI-GRAFFITI COATING IN THE FORM OF AQUEOUS COMPOSITION COMPRISING AT LEAST ONE FILMOGENIC ACRYLIC RESIN, AND AT LEAST ONE THICKENING AGENT Description Technical Field of the Invention The subject of the invention is an anti-graffiti sacrificial coating and its use. It also relates to a method for temporarily protecting a surface against graffiti. The invention relates to the technical field of protection of porous or non-porous surfaces, painted or not, against graffiti, with the aid of a coating that can be removed. 20 State of the art. Graffiti (unauthorized) is generally considered to be an act of vandalism and incivility resulting in the degradation of public or private property and places and increasing feelings of discomfort and insecurity. The damage caused by such an act is not only visual, 10 - 2 - but, they are for the most part irreparable or at the very least very expensive. Graffiti consists of inscriptions, drawings, symbols or messages painted, drawn, scribbled or scratched on all kinds of exposed and unprotected surfaces such as fences, walls, doors and windows of public or private buildings but also on the walls of furniture urban and public or private transport vehicles (eg buses, metro trains or cars of trains, cars, trucks, or other). The vast majority of graffiti are applied with aerosol paints (eg epoxies, lacquers, urethanes, etc.), felt pens, ink markers, or other writing fluids. Whatever their means of application, graffiti are often very difficult to remove. Indeed, damaged surfaces often have to be repainted to cover graffiti marks or treated with organic solvents and / or very caustic solutions then cleaned with hot water under pressure and sometimes even stripped / sanded with risk to lose their original hue and / or aesthetic appearance. These traditional techniques of graffiti removal are inefficient, require the intervention of cleaning staff and the use of heavy and expensive equipment that uses large amounts of water. In addition, they do not prevent recurrence, because graffiti is a quasi-random phenomenon that is impossible to predict, and may in some cases alter the physicochemical characteristics of the surfaces attacked. An alternative solution is to cover the surface to be protected with a sacrificial coating that can be removed and replaced when it is soiled by graffiti or other contaminations. Such coatings are for example described in the following patent documents: US5719221 (SWIDLER, R.), US20070184200 (BELL, Otis F.), US6011107 (MAXWELL, J. et al.), EPO750949 (KANSAI PAINT), EP402085 (Nippon OIL), EP0115694 (Imperial Chemical Industries), EP0911375 (HONDA) WO9724407 (Eastman Chemical Company), WO2008157670 (CELLULAR BIOENGINEERING), WO200372270 (BAF INDUSTRIES). These coatings are generally in the form of an aqueous composition intended to be applied to a surface to be protected, said composition comprising at least one film-forming acrylic resin and at least one thickening agent. These known coatings of the prior art have a certain number of drawbacks among which: low chemical resistance: the coatings can be removed before the surface is tagged simply with the aid of a basic aqueous detergent solution; low mechanical strength: the coatings are resistant to mechanical aggression such as shocks, scratches, scratches, or other; toxicity and increased costs: coatings typically contain solvents and surfactants which, in addition to their high price, lead to releases of volatile organic compounds into the atmosphere and / or have an adverse effect on the environment and the health of the environment. users, professionals or not; low service life: generally less than 1 year; - Delicate removal: need for any pretreatment of the coatings with a corrosive basic aqueous solution.

The main objective of the invention is to remedy this state of affairs. The invention particularly aims to provide a sacrificial anti-graffiti coating having a better resistance to chemical attack. Another object of the invention is to provide an anti-graffiti sacrificial coating having a better resistance to mechanical aggression. Yet another object of the invention is to provide a sacrificial anti-graffiti coating of low toxicity. Yet another object of the invention is to provide an anti-graffiti sacrificial coating whose production costs are reduced.

Yet another object of the invention is to provide an anti-graffiti sacrificial coating whose lifetime is greater than 1 year. Yet another object of the invention is to provide an anti-graffiti sacrificial coating which has the capacity to be cleaned partially or totally, when graffiti, polluted or soiled while offering the possibility of restoring the temporary protection of surfaces cleaned. Yet another object of the invention is to provide an anti-graffiti sacrificial coating having a matt or satin surface appearance. Yet another object of the invention is to provide an anti-graffiti sacrificial coating whose removal does not require pretreatment with corrosive basic solutions. Disclosure of the invention.

The solution proposed by the invention is an anti-graffiti (or more generally antifouling) sacrificial coating, in the form of an aqueous composition intended to be applied to a surface to be protected, said composition comprising at least one resin film-forming acrylic, and at least one thickening agent. This coating is remarkable in that the ratio by weight of said at least one film-forming acrylic resin and said at least one thickening agent is between 10 and 80. Unexpectedly, the applicant discovered during its research that by associating a film-forming acrylic resin with a thickening agent in a ratio by weight between the film-forming acrylic resin and the thickening agent of between 10 and 80, it was possible to obtain a coating against graffiti having properties of resistance to mechanical and chemical aggression. improved over known coatings of the prior art, in particular a coating against graffiti having a better resistance to attacks by alkaline solutions while having the ability to be removed or cleaned with a simple jet of hot water under pressure . In addition, it has been found that the coating effectively withstands mechanical aggression such as shocks, scratches, scratches, abrasions or other. In addition, such a coating is of low cost. It can be prepared with products that are readily available commercially and by methods that are easy to implement.

Other preferred features of the invention are listed below, each of these characteristics being able to be considered alone or in combination with the remarkable characteristics defined above: the film-forming acrylic resin is an acrylic copolymer in aqueous dispersion (without solvent and stabilized by surfactant). the content of film-forming acrylic resin is between 30% and 80% (»composition, preferably approximately 50% of the composition) In the remainder of the description, the" p / composition "ratio represents a content expressed by weight calculated on the total composition. ready-to-use, the thickening agent comprises one or more HASE emulsions, the content of thickening agent is between 1% and 5% by weight, and preferably about 3% by weight. The pH of the aqueous composition is from 7 to 10. The aqueous composition further comprises one or more additives from the following list taken alone or in combination: anti-foam agent, corrosion inhibitor, coalescing agent. the aqueous composition preferably comprises: from 30% to 80% of the composition, preferably about 50% of the composition of an aqueous dispersion of a film-forming polymer, from 1% to 5% by weight, preferably 3% P / Pcomposition a thickening agent, o 0.1% to 1% P / composition, preferably 0.3% P / P composition of an antifoam agent, o 1% at 5 ° AP / composition, preferably 4% w / w composition of a corrosion inhibitor, o 0.3% at 1 ° AP / composition, preferably between 0.3% and 0.8% P / composition of a pH adjuster, o demineralized water QSP 100% P / Pcomposition. Another aspect of the invention relates to a method of temporarily protecting a surface against graffiti, characterized in that it comprises the following steps: i) applying, on the surface to be protected, at least one layer of the aqueous composition of the sacrificial coating object of the invention, ii) drying to form the anti-graffiti sacrificial coating, iii) total or partial removal of said coating with hot water under pressure, when it is stained by graffiti. The composition may be applied so that the coating has, after drying, a total thickness of between 1 μm and 1 mm, preferably between 10 μm and 100 μm. Yet another aspect of the invention relates to the use of a coating according to one of the preceding characteristics, for the protection against graffiti of a porous or non-porous solid surface, preferably non-porous painted or unpainted. Other objects and advantages of the present invention will become apparent from the following description, which is for illustrative purposes only and is not intended to limit its scope. Embodiments of the Invention The coating object of the invention is well suited to the production of sacrificial films or coatings on solid surfaces requiring temporary protection against graffiti. The surfaces to be protected can be of any kind and in particular porous (bricks, cement, concrete or wood) or non-porous. In particular, nonporous solid surfaces, painted or unpainted, made of glass, or of organic polymers or of metal, are intended, in particular metal surfaces, painted or unpainted, of public transport vehicles such as the train, metro, tram, bus, etc. By "sacrificial" is meant that the coating may be removed wholly or partially from the surface to which it is applied. For the purpose of the present invention, the term "graffiti" designates undesirable marks (for example: inscriptions, drawings, messages, tags or others) made in ink, in paint, or in chalk, to which may be added, in an expanded definition, posters, stickers, and contaminations such as soiling due to atmospheric or biological pollution, bird droppings, insect carcasses. The coating is in the form of an aqueous composition ready for use, intended to be applied to the surface to be protected. The coating object of the invention can thus be in the form of pots or any other tank containing the aqueous composition and can be used directly. In practice, the aqueous composition has a content of volatile compounds (CV) of at most 50% by weight, and at least 80% w / pcv is represented by water, ensuring that the content of the compound volatile organic (s) (VOC) is the lowest possible. Preferably, the VOC content is from 0% w / wt to 20% w / wt, preferably from 0% w / wt to 10% w / wt, more preferably 0% w / wt. at 5 ° to p / pcv and more preferably 0% p / pcv. The aqueous composition comprises at least one film-forming acrylic resin mixed with at least one thickening agent. In practice, the film-forming acrylic resin used is an acrylic copolymer in dispersion (without solvent, and stabilized by surfactant) capable of forming, on its own or in the presence of auxiliary film-forming agent, a film or continuous and adherent coating. on the surface to be protected, at a temperature between 5 ° C and 40 ° C, preferably at room temperature. Advantageously used is a film-forming acrylic resin, or a mixture of film-forming acrylic resins, containing an acrylic copolymer in aqueous dispersion, with a very low VOC content, preferably between 30% and 80% by weight, preferably about 50%. w / pcompositinn. This type of resin has the advantage of being free of volatile organic solvents, or where appropriate, of having a very low VOC content, of being compatible with the other constituents of the aqueous composition and of conferring on the The coating according to the invention has excellent adhesion properties to solid supports and good mechanical properties, in particular the chemical resistance to graffiti (the latter being unable to pass through the coating to reach the surface to be protected), resistance to moisture and to other chemical, mechanical and atmospheric aggression. Various aqueous dispersions of acrylic copolymers (known to those skilled in the art) can be used. A preferred example of a film-forming acrylic resin which can be employed in the aqueous composition according to the invention is an aqueous acrylic copolymer dispersion sold under the name Revacryl DP 5467® by the company Synthomer®. This resin has a dry weight content of between 20% by weight / presine and 40% by weight / presine, a pH between 7 and 8, a Brookfield RVT viscosity of between 10 and 500 mPa.s at 23 ° C. (RVT 1/20 rpm) and a minimum film-forming temperature (TMF) of about 0 ° C. The TMF is the lowest temperature at which the particles of the dispersion form a continuous film after evaporation of the water. The function of the thickening agent is to allow an adequate thickening of the aqueous composition according to the invention without impairing its ease of application (that is to say, its good pot life, without sedimentation or phase separation). excessive, a good loading of the application tool (roller, brush) and a good quality of application). Advantageously, the thickening agent, or a mixture of thickening agents, contains one or more HASE emulsions preferentially dosed between 1 ° A and 5% p / pcomposition. The thickening agent content is preferably limited because, because of its solubility in water, too high a content may increase the sensitivity of the dry sacrificial coating to water and attacks by alkaline solutions. Therefore, it is advantageously between 1% and 5% P / composition, preferably 3% p / composition. The Applicant has found that such a thickening agent conferred on the aqueous composition according to the invention an optimum fluidity and / or viscosity to be applied with excellent tension without risk of sagging on a solid surface, in particular a metallic surface. vertical. The HASE type emulsions are hydrophobically modified and thickening emulsions in an alkaline medium, the term HASE being an acronym for "Hydrophobically Alkali Swellable Emulsion". The HASE emulsions preferentially used contain at least one copolymer of (meth) acrylic acid, of a non-water-soluble monomer which is preferably a (meth) acrylic ester chosen very preferably from ethyl acrylate, acrylate butyl, methyl methacrylate and mixtures thereof, and a monomer containing at least one hydrophobic group. Said monomer containing at least one hydrophobic group has the following general formula: in which: m, n, p and q are integers and m, n, p are less than 150, R comprises a polymerizable vinyl function, R1 and R2 are the same or different and represent hydrogen atoms or alkyl groups, R 'is a hydrophobic group comprising at least 6, preferably at least 10, most preferably at least 12 carbon atoms. Representative examples of the thickening agent include THIXOLO thickeners, and / or RHEOTECH® series, which are marketed by COATEXO. A particularly preferred thickening agent according to the present invention is selected from THIXOLO 53L, RHEOTECH® 3000, and mixtures thereof. In the context of its research, the applicant has demonstrated that the use of a thickening agent comprising THIXOLO 53L and RHEOTECH® 3000, preferably in a THIXOLO 53L / RHEOTECH® 3000 weight ratio of between 0.3 and 1, preferably about 0.6 gave the best results. The thickening agent that is preferably used has an acidic pH, generally a pH of about 3. The aqueous composition according to the invention generally has a basic pH of between 7 and 10, preferably between 8 and 9.5, but can reach higher values. In practice, the basic pH of the composition according to the invention is achieved using a water-soluble base selected from the group comprising ammonia, sodium hydroxide, ethanolamine and mixtures thereof. A mixture comprising ammonia and sodium hydroxide is preferably used. In general, from 0.3% to 1% by weight of the pH adjuster is used and preferably from 0.3% to 0.8% by weight.

According to the invention, the weight ratio between the film-forming acrylic resin (or a mixture of acrylic resins) and the thickening agent (or a mixture of thickening agents) is between 10 and 80. The Applicant has found that With such proportions, a sacrificial coating having improved properties of resistance to mechanical aggression (shocks, scratches, scratches, abrasion, etc.) and to chemical attacks (especially attacks by alkaline solutions, pollutions, etc.) was obtained. .).

The aqueous composition according to the invention may further comprise one or more additives from the following list taken alone or in combination: anti-foam agent, corrosion inhibitor, coalescing agent. The anti-foaming agent is, for example, an agent marketed under the trade name DAPRO® DF 7010 by the company ELEMENTISO, said anti-foaming agent being dosed in proportions of between 0.1 ° A and 1% P / composition, preferably at 0.3% per compound. The corrosion inhibitor makes it possible to prevent the phenomenon of immediate corrosion (also called "flash-rusting") and / or atmospheric corrosion, in particular when the aqueous composition according to the invention is applied to a metal surface that is particularly subject to corrosion. . Compounds with corrosion inhibiting activity are well known to those skilled in the art. For obvious reasons of respect for the environment and public health, it is recommended to avoid the use of toxic corrosion inhibitors, such as those containing nitrites, lead or hexavalent forms of chromium. By way of example, the corrosion inhibitor used is, for example, sold under the brand name Additex AFRO by the company SCOTT BADER®, said inhibitor being dosed in proportions of between 1% and 5% by weight / composition, preferably of 4%. The coalescing agent is, for example, an agent sold under the trademark Arcane 220US® by the company Arcane-Industries®, said agent being dosed in proportions of between 1% and 5%. - Composing, preferably between 1% and 3% p / composition. Other ingredients (ex: dyes, anti-UV agents, preserving agents, flame retardants, biocides, anti-fouling agents or others) commonly used in the field of surface coating and suitable for the intended application, can of course be used, provided that the properties and advantageous characteristics of the coating of the invention are not impaired.

The aqueous composition advantageously contains water in proportions of between 20 ° to 55% by weight, the water content depending on the fluidity and / or the desired viscosity and / or the nature of the surface to be protected. (the water content will be lower for the application of the aqueous composition to a smooth surface than for application to a porous surface). To avoid any deposit formation and to further improve the performance, particularly with respect to corrosion, water that is free of soluble salts, such as distilled, deionized or deionized water, may be used. However, satisfactory anti-graffiti protection and corrosion resistance performance is obtained with the water from the urban distribution network. The preparation of the aqueous composition according to the invention is carried out by mixing its constituents, by any method known per se by those skilled in the art. Generally, it will be sought to obtain compositions comprising at least 15 to 30% solids, preferably at least 20% solids.

The aqueous composition preferably comprises: from 30% to 80% by weight, preferably about 50% by composition of an aqueous dispersion of a film-forming polymer, from 1% to 5% by weight, preferably 3% by weight of a thickening agent, 0.1% to 1% by weight, preferably 0.3% by weight, an anti-foaming agent composition, 1% to 5% P / composition, preferably 4% by composition of a corrosion inhibitor, 0.3% to 1% P / composition, preferably 0.3% to 0.8% by composition of a pH adjuster , demineralized water QSP 100% p / pcomposition. In practice, at least one layer of the aqueous composition of the sacrificial coating object of the invention is applied to the surface to be protected. The aqueous composition is advantageously applied in several passes, for example two or four passes. The number of layers depends on one hand on the porosity and roughness of the solid surface to be protected and on the other hand on the desired thickness of the coating after drying. However, a single pass may suffice for smooth, painted or unpainted metal surfaces. In practice, the aqueous composition is applied so that the coating has, before drying, a wet thickness of between 100 μm and 200 μm, and after drying, a dry thickness of between 1 μm and 1 mm, preferably between 10 μm and 1 μm. pm and 100 μm, more preferably between 15 μm and 80 μm. The application of the aqueous composition is without sagging and with excellent tension. The aqueous composition may be applied by any means known to those skilled in the art, for example by spreading by brush, brush, roller, or squeegee or by spraying / spraying. The aqueous composition is then dried, for example by evaporation. Drying time will vary depending on temperature, humidity and air circulation. In wet and cold periods, the drying will be longer. In general, coating formation is rapid (usually from a few minutes to a few hours), when the aqueous composition is applied at a temperature of between 5 ° C and 35 ° C, preferably between 10 ° C and 25 ° C. The drying operation can be carried out at a temperature between 5 ° C and 35 ° C and preferably at room temperature (about 25 ° C). In general, the coating is dry to the touch in less than 60 minutes, under normal temperature and humidity conditions, preferably in less than 30 minutes. Advantageously, the coating of the invention has a matt or satin surface appearance. The Applicant has found that the sacrificial coating object of the invention has a good resistance to cold water, that is to say a water having a temperature of less than or equal to 30 ° C and good resistance to attack by alkaline solutions, while offering the possibility of removing it partially or totally from hot water under pressure, when it is soiled by graffiti, and without deterioration of the underlying surfaces. When the coating of the invention is graffiti, polluted or soiled, it can be removed partially or completely in hot water under pressure without deterioration of the underlying surface. In practice, the coating is removed by means of a pressurized hot water cleaner (for example of the Karcher® type), preferably at a temperature of between 30 ° C. and 80 ° C. and under a pressure comprised between between 106 Pa and 18 x 106 Pa. The time required to remove the soiled coating is very short, generally between 0.5 min / m2 and 5 min / m2, better still in a time of less than 2 min / m2, thus providing an optimal response to the management of the time and manpower of the cleaning sites. In order to restore the temporary protection against graffiti, the aqueous composition can be applied again to the portion of the coating thus cleaned. A further advantage of the present invention is that the waste produced by the removal of the sacrificial coating from hot water under pressure can be recovered, for example on a filter mat, and destroyed, for example in an incinerator furnace without supplying toxic products. The invention will now be described with reference to the following examples given for illustrative and non-limiting.

EXAMPLE 1 Preparation of an aqueous composition in accordance with the invention An aqueous composition according to the invention is prepared according to the following procedure: In a reactor, kept under mechanical stirring, 50% of the quantity of water is introduced and the aqueous dispersion of acrylic copolymer (Revacryl DP 5467), then 50% of the amount of anti-foaming agent DAPRO® DF 7010 is added. To this mixture is added, with stirring, a solution of ammonia at 10% in water. 'water. The two thickeners (RHEOTEC 3000 and TIXOL 53L) are then gradually incorporated, increasing the stirring speed to allow the two thickeners to develop well. 30% diluted sodium hydroxide is then added to adjust the pH to about 8.5. After stirring for 30 minutes, the corrosion inhibitor (Additex AFR) is added, followed by the remaining amount of antifoam while controlling the stirring speed in order to optimize the effectiveness of the anti-blocking agent. -foam. Finally, the amount of water remaining is added. Thus, a temporary anti-graffiti protection composition 30 is obtained which has the following formula: Ingredients Content in% P / Composition Revacryl DP 5467 50 THIXOL® 53L 1.1 Rheotec® 3000 1.9 Ammonia 10% 3.8 NaOH at 30% 0.48 antifoam 0.2 to 0.5 Additex AFR® 4 Water (QSP) 100 This composition has the following characteristics: Dry extract: 20 +/- 2% Brookfield DVII viscosity at 20 ° C: 3500 +/- 500 cp (20 revolutions per minute, axis 10 3) Density at 20 ° C: 1.055 +/- 0.01 pH: 8.5 -F / -1 The application and adhesion tests of this composition were carried out in accordance with the requirements of the NF F 19-201 standard. They were made on train vehicles (stainless steel bottom, painted background, glass, old background). The composition is easily applied to the brush and the lacquer roller in one pass and with excellent tension (tests carried out on surfaces of 4 to 5 m2). The resulting coating has a satin appearance. It also gives back the old funds, including logos.

Evaluation of the adhesion is performed by a grid by making parallel and perpendicular incisions in the coating. The grid was found to be completely clean without any loss of coating. Tearing in the coating (monolayer) showed a breaking strength of about 1.2 MPa +/- 0.1 MPa. The coating therefore has good adhesion. The graffiti was applied with aerosol bombs from the Acryl Rai® series. 5 - 17 - The coating and the graffiti can be removed easily in less than 5 minutes for graffiti surfaces of about 5 m2. The washing equipment used is a simple High Pressure pump without rotary nozzle and supplied with water having a temperature of 35 ° C to 40 ° C.5

Claims (11)

REVENDICATIONS1. Anti-graffiti sacrificial coating, in the form of an aqueous composition intended to be applied to a surface to be protected, said composition comprising at least one film-forming acrylic resin, and at least one thickening agent, characterized in that the ratio of weight between said at least one film-forming acrylic resin and said at least one thickening agent is between 10 and 80. 2. Coating according to one of the preceding claims, characterized in that the film-forming acrylic resin is an acrylic copolymer in aqueous dispersion. Coating according to claim 2, characterized in that the content of film-forming acrylic resin is between 30% and 80% by weight, preferably about 50% by weight. 4. Coating according to one of the preceding claims, characterized in that the thickening agent comprises one or more emulsions of HASE type. 5. The coating of claim 4, characterized in that the thickener content is between 1% and 5% p / composition. 6. Coating according to one of the preceding claims, characterized in that the pH of the aqueous composition is between 7 and 10. 7. The coating according to one of the preceding claims, characterized in that the aqueous composition further comprises one or more additives from the following list taken alone or in combination: anti-foaming agent, corrosion inhibitor, agent of coalescence. 8. The coating according to one of the preceding claims, characterized in that the aqueous composition comprises: from 30% to 80% by weight, preferably about 50%, of the composition of an aqueous dispersion of a film-forming polymer, 1 to 100% by weight, preferably 3% by weight, thickener composition, 0.1% to 1% by weight, preferably 0.3% by weight. composition of an antifoaming agent, 1% to 5% P / composition, preferably 4% by composition of a corrosion inhibitor, 0.3% to 1% P / composition, preferably 0.3% and 0.8% p / composition of a pH adjuster, demineralized QSP 100% water p / composition. 9. A method of temporary protection of a surface against graffiti, characterized in that it comprises the following steps: i) application, on the surface to be protected, of at least one layer of the aqueous composition of the sacrificial coating conforming in claim 1, ii) drying to form the anti-graffiti sacrificial coating, iii) total or partial removal of said coating with hot water under pressure, when it is stained by graffiti. 10. Process according to claim 9, characterized in that the composition is applied so that the coating has, after drying, a total thickness of between 1 μm and 1 mm, preferably between 10 μm and 100 μm. 20 - 11. Use of a coating according to claim 1, for the protection against graffiti of a porous or non-porous solid surface, preferably non-porous painted or unpainted.