BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a system for treating a surface which system makes the surface substantially resistant to markings of graffiti, makes the surface resistance to corrosion and acid rain, and provides a high degree of dielectric resistance. The present invention also relates to a clear top coat system alone which is effective to improve the surface resistance to corrosion, acid rain attack and graffiti on certain surfaces.

More particularly, the present invention relates to such a system which includes a composition and method to treat such surface to render the surface substantially resistant to the permanent adhesion of subsequent markings of graffiti and to permit it to be readily, inexpensively and repeatedly cleaned using a certain cleaning composition without altering the surface or causing damage to any area in close proximity thereto. The system also makes the surface resistant to salt and chemical corrosion and acid

rain, and provides the surface with a high degree of dielectric resistance. In particular cases, the top coat is used by itself. It is a transparent coat designed for use on traffic signs, marble, granite, limestone, sandstone and certain aggregates where transparency is required to make the surface resistant to salt and chemical corrosion, acid rain and graffiti.

Concerning graffiti, there has been an increased concern in recent years over this rapidly growing problem, particularly in urban areas. In modern times, the term graffiti has come to acquire a meaning which differs substantially from it's historical meaning. The modern observer views graffiti not as an art form, but rather, as a form of destruction and vandalism.

The application of graffiti has become most prevalent in institutions, such as, schools, public and private buildings, automobiles, trucks, train; cars and rest rooms which are available to the public at large. Graffiti is even more problematic in open areas, such as, support walls and piles for bridges, retaining walls, sound barriers, exterior walls of buildings, various structures in parks, which incidentally were put there in the first place to cosmetically improve the parks, and the like. The vast majority of such graffiti is spray paint and color markers having pigmented dyes with fast drying solvents and oil

based paints including enamels, epoxies, lacquers and urethanes. The graffiti is applied in a majority of instances by spray cans or color markers to various types of surfaces.

The methods for the removal of graffiti, which are for the most part economically cost prohibitive, have heretofore included sandblasting, hydrosanding and hydroblasting the surfaces bearing the graffiti. These methods often require or mandate a subsequent re-coating of the surface in order to protect the surface from further decay and to restore its aesthetically pleasing appearance since sandblasting, hydrosanding and hydroblasting will etch, score and make the surface porous and rough and, therefore, more susceptable to weathering, deterioration and permanent unremovable staining by subsequently applied graffiti. Depending on the nature of the surface, such methods often have a potentially deleterious effect to the surface and any area in close proximity thereto. Further, sandblasting emits potentially carcinogenic and siliceous particles into the air. Moreover, the use of such methods, as has been proved over and over, are extremely costly, disruptive and do not provide for any long-term solution. This is particularly true where the surface will have had its porosity greatly increased thereby leaving it increasingly more susceptable to deterioration, weathering, and likely to become permanently damaged by new graffiti.

Another method which has been used for graffiti removal includes chemically treating the surface on which the graffiti appears. This method has also proven costly and most often unsuccessful. It has been found that repetitive chemical cleaning treatments quickly destroy the painted surface, necessitating frequent repainting. The application of such strong chemical cleaners also has a deleterious effect to the surrounding environment and can have dangerous side effects on the person applying the chemicals, as well as to the substrate upon which the strong chemical cleaners are used.

Perhaps the most common way of removing graffiti is to repaint the surface and hope that the repainting is not taken as a new invitation to one to refine and redisplay his or her art skills. As can be appreciated, this approach is perhaps the least effective. It requires the use of a paint which is capable of covering the graffiti and which will prevent the graffiti from bleeding through the overcoat usually not possible with other solvent based paint.

Besides graffiti, there has been a need to protect a surface against corrosion, which is principally due to salt and chemical oxidation, and from acid rain. Further, there has been a need to increase the dielectric resistance properties of coatings used in protective insulation

applications. This is achieved by the use of the system of the present application. Heretofore, there has not been a system or composition which can achieve all of the above.

2. Description of the Prior Art

U.S. Patent No. 4,716,056 to Frank Fox and Cassius Leys, the latter being the inventor of the present invention, issued on December 29, 1987. This patent, which is directed to a System for Treating a Surface, provides a system having a composition which treats a surface to render it substantially resistant to subsequent markings and to permit it to be readily and inexpensively cleaned using a particular cleaning composition without altering the surface or causing damage to any area in close proximity thereto. The present system has markedly improved the graffiti resistant properties over the system of this patent in that the present system is much faster curing and provides substantially more effective protection. In addition, the present system effectively protects a surface against acid rain attack and corrosion and, still further, provides the surface with desired enhanced dielectric resistance properties.

SUMMARY OF THE INVENTION

Against the foregoing background, it is a primary object of the present invention to provide a system for treating a surface to render it substantially resistant to subsequent permanent adhesion of graffiti and facilitate the repetitive removal thereof.

It is another object of the present invention to provide such a system which includes a method and composition for treating the surface to cover and mask over any graffiti previously applied thereto and to facilitate repetitive cleaning of subsequently applied graffiti thereof.

It is still another object of the present invention to provide such a system which includes a cleaning composition to remove subsequent applications of graffiti from the surface protected by the coating (previously applied) numerous times without damage to the protective coating and without the need for recoating the surface.

It is yet another object of the present invention to provide such a system which acts to protect the surface from corrosion and the adverse continuing effects of acid rain.

It is still yet another object of the present invention to provide such a system which provides a high degree of dielectric resistance properties to the surface coated with this system.

It is yet still another object of the present invention to provide that the top coat alone is effective in improving the resistance to corrosion, acid rain and graffiti on certain substrates.

It is yet still another object of the present invention to provide such a top coat which provides a transparent or clear coat so that the color and the texture of the surface is visible after application of the clear protective coating.

To the accomplishments of the foregoing objects and advantages, the present invention, in brief summary, includes a system for treating a surface which system makes the surface substantially resistant to the subsequent adhesion of markings of graffiti, corrosion and acid rain attack, and provides a high degree of dielectric resistance properties. The complete system includes the use of a water based epoxy mixture as an undercoat which is initially applied to the surface to act as a bonding water proof and masking vehicle to cover any existing graffiti or

rust protection coating thereon. After drying thereof, a modified polyurethane mixture is applied to the surface and permitted to cure. Subsequent applications of graffiti can be removed using non-chlorinated, non-toxic, non-flammable cleaners, such as the AGP cleaner from AGP Systems, Inc. , the assignee of the present application, which is the subject of a co-pending application filed August 30, 1989 titled Cleaner for Treating a Surface to Cassius Leys, the inventor of the present application. This application is incorporated herein by reference. •

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The system of the present invention is particularly adapted for use on most surfaces generally susceptible to the application of graffiti and degradation by corrosion including, for example, masonry, wood and steel surfaces. Such masonry surfaces may include cement, cement blocks, concrete, brick, mortar and the like. The present system is particularly adaptable for use on steel structures such as bridges and piers for same, buildings, highway underpasses and overpasses, statues, walls and the like for protection against both graffiti and corrosion (both natural and chemically induced corrosion) . Further, the present system is particularly adapted for use on steel structures and electric conduit mediums to provide greatly enhanced dielectric resistance properties to the metal substrates as well as long term corrosion resistance.

Depending on the condition of the surface to be treated, scraping, degreasing, brushing down, and/or light sanding may be required to enhance the adhesion or bonding of the undercoat or base coat to the surface. Thus, if splinters, rust, scale or loose pieces of debris such as, for instance, paint chips or the like, are present on the surface to be treated, it is preferable to remove them prior to application of the compositions of the present system. Additionally, if the surface has previously been

painted several times, it is preferable to "roughen up" the surface to make sure the previous coating has firm adhesion and provides adhesion for the present system. Finally, even if the surface is in relatively good condition, the surface should be washed with water or a mild solvent to remove any deposited dirt, grease and surface film which might affect bonding.

After surface preparation and removal of any loose rust, scale, effluorescence, cement dust, grease and grime, a base coat is applied to either a wet or dry, but clean, surface to mask over and cover any existing graffiti and rust to prevent any such graffiti from bleeding through. Further, the base coat will abate corrosion, in particular salt and chemical corrosion, and acid rain attack. Still further, the base coat provides a solid undercoat for the subsequent application of a protective top coat to any surface that is treated to prevent subsequently applied graffiti from permanently adhering and stop and prevent, salt and chemical corrosion, and acid rain or chemical attack, and to enhance dielectric resistance properties of the coated surface. With this system, it is not necessary to take metal down to the "white metal" which is usual to stop rust.

It has been found that a preferred base coat is a water based epoxy paint. Water based epoxy paint has been

known to be particularly effective in covering (masking) any existing graffiti and preventing bleed through. It is now appreciated that it is particularly effective in covering any rust residue and preventing the coating system from being raised or buffered off by any such underlying rust. In virtually all instances, such water based epoxy paints neither chemically attack the surfaces to which they are applied nor the graffiti which may be found thereon. This is due to the fact that a water based epoxy paint is incapable of reacting with or softening any underlying graffiti which is typically a solvent based paint. What has been found is that the water based epoxy paints tend to effectively seal the graffiti and residual surface rust on the surface. This is in direct contrast with a solvent based epoxy paint which may tend to react with, raise, remove, partially dissolve and absorb the underlying graffiti and otherwise incompletely bond with the underlying substrate. Any moisture remaining on the surface of metal or the underlying substrate is commingled with and utilized in curing the water based epoxy.

The preferred water based epoxy paint of the present invention is a water based epoxy paint mixture consisting of three basic parts. The system includes an amine emulsion as the epoxy coating hardener, a diglycidyl ether of disphenol A emulsion as the epoxy resin coating and catalyst, and proprietary additives. One example of a

viable water based epoxy paint formula having two parts of the system is the product Dur-A-Poxy 200, which is manufactured and distributed by Dur-A-Flex, Inc. This paint formula has the amine emulsion and the diglycidyl ether of disphenol A emulsion, but not the proprietary additives.

Dur-A-Poxy 200 is a catalyzed, true epoxy which will not alter 20 the surface to which it is applied, but rather, will seal the graffiti and/or corrosion on the surface. It has been found that the use of a catalyzed epoxy provides a good coating with strong adhesion properties. The amine emulsion mixed with a catalyst and the proprietary additives serve to set up a permanent bond with the underlying surface.

The properties of the water based epoxy paint employed should be such that the graffiti it covers will not "bleed through". That is to say, the underlying graffiti will not react with, lift off, or penetrate through the undercoat. It simply becomes encapsulated under the epoxy coating.

The proprietary additives discussed above comprise an accelerator and an ingredient selected form the group consisting of 2, butoxy ethanol (butyl celusolve) and N-methylpyrrolidone. The proprietary additives may also include lavender oil and distilled water.

The accelerator is a tertiary amine which accelerates the reaction between the undercoat and the surface to be treated. The tertiary amine should be combined with distilled water. It is preferred that the accelerator be present in an amount between about 1 to about 3 ounces, with the preferred amount being about 2 ounces.

Distilled water is used since it does not contain chlorine or fluorine. In the batch of undercoat or base coat of about 264 ounces, the proprietary additives should constitute between about 8 to 12 ounces, but preferably about 8 ounces of the base coat. The distilled water should be present in an amount between about 2 1/2 to 7 ounces depending on the temperature at which the undercoat will be used and the total amount of the proprietary additives is about 8 to about 12 ounces. Specifically, the hotter or higher the temperature, the greater the amount of distilled water to be used. Preferably, the distilled water is present in an amount about 2 1/2 ounces.

In that batch of base coat, the lavender oil should be present in an amount of about 1/2 of an ounce. Further, either 2, butoxy ethanol, which is sold under the mark

Butyl Celusolve by Sherwin Williams, or

N-methylpyrrolidone, which is sold under the mark M-pyrol by G.A.F., should be present in an amount between about 2 to about 4 ounces, preferably about 3 ounces.

Thus, it is preferred that the base coat mixture comprise about one gallon of amine emulsion, about one gallon of diglycidyl ether of disphenol A emulsion and 8 to 12 ounces of the proprietary additives. To prepare the base coat it is recommended that the amine emulsion and the proprietary additive (either 2butoxy ethanol or N-methylpyrrolidone) be mixed together first and stirred well until the mixture is smooth. Then, the diglycidyl ether of disphenol A emulsion be mixed in by mechanical agitation for about three to no more than five minutes.

After five minutes, it has been found that continued mixing would simply reduce the pot life. Thereafter, the remaining proprietary additives should be added and mixed for approximately one minute. After one minute, it has been found that continued mixing simply has no effect and, therefore, is a waste of time. Once the proprietary additives are incorporated into the mixture it will take approximately one hour and then the mixture becomes useless. Specifically, the components immediately start an irreversible chemical reaction which unless the mixture has already been applied onto the surface to be treated, the mixture solidifies, thereby becoming useless. Therefore, one has approximately one hour from when the proprietary additives are added to the mixture to apply the base coat.

The base coat may be applied to the surface by conventional methods of application, i.e., by the use of a

roller or brush or spray. A particularly preferred means of application is by the use of airless sprayer since it permits a faster and more even application.

The base coat, which is preferably applied to a dried film thickness of between about 0.002 and about 0.003 inches, may, in certain instances, be diluted at the beginning of the mixing only by the addition of up to about 10% water for ease of application. At such thickness, one gallon of the base coat will typically cover between about 150 to about 200 square feet of surface area although this will vary greatly as a function of the porosity of the surface being covered. For example, more porous surfaces, such as for example concrete and the like, will tend to absorb greater amounts of the base coat than less porous surfaces such as for example steel and other metals.

As used in this application, wet coat or film thickness is the thickness of the layer when the layer is first applied. The wet film thickness will shrink to between about 40 to about 50 percent when it dries and the thickness when the coat is dried is called the dry film thickness. Thus, wet film thickness is about 40 to about 50 percent greater than the dry film thickness. The thickness used in the present application is the dry film thickness unless indicated to the contrary.

Whether or not the base coat is actually diluted depends in large measure upon the vehicle used for application. One advantage of diluting the base coat is that is has been found to increase its pot life.

After application, the base coat is permitted to dry for a period of at least about two (2) to about three (3) hours depending on relative humidity to permit release of any moisture which may be contained in the base coat. This is an improvement over the undercoat system of U.S. Patent No. 4,716,056, which took approximately four to eight hours. The improvement is attributed to the use of the proprietary additives.

After drying, a top coat of the present application is then applied to the surface over the base coat. A preferred top coat includes a mixture of a modified polyurethane resin, a catalyst, a reduction agent and certain proprietary additives. These proprietary additives are admixed together immediately prior to application of the top coat to the substrate.

A particularly preferred polyurethane resin is a fully cross-linked polyurethane resin such as, for example, the polyurethane resin marketed by PPG Industries, Inc. under the mark "Durethane". It should be understood that the polyurethane resin coat can be either clear or a color

resin coat. The polyurethane, however, has been modified to remove the organotin and dibutyltin laurate which are film softeners known as DXU 790 available through PPG Industries, Inc. and may also be modified to remove any DXU 789.

A particularly preferred polyurethane catalyst is the catalyst marketed by PPG Industries, Inc. under the trademark "DU-5".

The above recited components are admixed immediately prior to 5 application and then thinned or otherwise reduced using a reducing agent or thinner. A preferred reducing agent is one marketed by PPG under the "Durethane" mark.

The purpose of the reducing agent or thinner is to facilitate the ease of application of the top coat. The amount of thinner added will vary between about one-quarter to three-quarters of a gallon depending upon which instrument is used to apply the top coat and also depending on the degree of porosity of the substrate or surface to which the top coat is applied. Specifically, there are four common methods or instruments for applying the coat to the substrate. They are brush, roller, air spray and airless spray. With either the brush or roller, about one-quarter of a gallon of thinner is needed. In the

airless spray about one-half gallon of thinner is needed, while in the air spray about three-quarters of a gallon of thinner is needed. Further, the more porous the surface to be treated, the lesser the amount of thinner that is needed.

The top coat is modified to include additives. The additives comprise a resin hardener and film former which is known as DXU 789, also available through PPG Industries, Inc., an accelerator, and an ultraviolet absorber (UV absorber) . The total amount of these proprietary additives in the preferred formula set forth above is between about 6 to about 8 ounces.

The polyurethane resin after modification does not contain any DXU 789 or DXU 790. However, DXU 789 should be added to the top coat to provide a hardener and film former. The total amount of DXU 789 in the top coat should be between about 5 to about 10 ounces, with the preferred range between about 4 to about 6 ounces. The actual amount of DXU 789 in the top coat depends upon the temperature. In particular, the amount of DXU 789 decreases as the temperature increases. Specifically, about six ounces is added when the temperature is about fifty degrees, about five ounces is added when the temperature is about sixty-five degrees, and about four ounces is added when the temperature is about eighty degrees.

DXU 789, as set forth in the material safety data sheet of PPG Industries, Inc. is comprised in percentage by weight of 25 to 30 percent N-butyl acetate, 20-25 percent toluene, 2-5 percent isopropyl alcohol (anhydrous) , 15-20 percent tertiary amine and 30-35 percent film formers, resins and additives.

The modification of the polyurethane resin, especially by the addition of the DXU 789 resin, results a reduction in the ability of the film to soften and increases the hardness and creates a non-microporous effect in the coating system. This creates a relatively hard, but flexible, impervious surface which may be readily cleaned after application and which prevents the penetration of solvents and free radical ions into the coat or film.

An accelerator, such as for example, toluene blended with dibutyltin laurate is used to accelerate or otherwise increase the cure time. This accelerator, which is sold under the mark DXR-81, is marketed by PPG Industries, Inc. and consists between about ninety-five percent to about one hundred percent toluene and between about one percent to about two percent dibutyltin laurate.

It appears that the UV absorber needs to be a hindered amine light stabilizer (HALS) . This type of UV absorber provides significant levels of stabilization, extended life

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and durability to the top coat by inhibiting the degradation of the binder amongst chemicals of the top coat. The UV absorber used stabilizes coatings without absorbing UV radiation making it uniquely suitable for stabilizing ultraviolet cured coatings. A particularly preferred hindered amine light stabilizer UV absorber is Tinuven 292 which is sold by Ciba Geigy.

The ratio of the four proprietary additives is about 5 to about 10 parts hardener and film former, one part accelerator, and one part UV absorber.

The top coat may be applied to the surface over the base coat by conventional application means, i.e., by the use of a squeegee roller, brush, air assisted airless spray gun or an airless spray gun. A particularly preferred means of application is by the use of an airless spray gun since it permits a faster and more even application.

It will be appreciated that the amount of each component portion of the top coat system will vary depending upon the particular application. In a preferred embodiment, however, the top coat includes the following components in the following amounts:

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Component Amount

Modified Polyurethane Coat 1 gallon

Catalyst 1 gallon

Thinner or reducing agent 1/4 to 3/4 gallon

Additives 6 to 8 ounces

The top coat, which is preferably applied to a thickness of between about 0.002" and about 0.004" dry film thickness may not be diluted. At such a dry film thickness, one gallon of top coat will typically cover about 400 square feet of surface area. It has been found that that application of the base coat provides a strong and even surface for accepting the subsequent application of the top coat which bonds (fuses) with the base coat.

In a preferred embodiment, two relatively thin coats of the top coat is applied in serium, i.e., the second coat of the top coat is applied over the first coat before the first coat is permitted to cure. The first coat is a light or tack or mist coat, while the second coat is a normal coat which is between about 0.001" to 0.002" in wet coat thickness. The total thickness of the top coat should be between about 0.002" and about 0.004" in dry coat thickness. A preferred dry coat thickness is about 0.002".

After application and drying of the top coat, the surface is now ready to be used in normal fashion. In those instances where subsequent cleaning of fresh graffiti is required, it has been found that the surface provided by

the top coat may be easily cleaned with the cleaner formula in co-pending application filed August 30, 1989 titled Cleaner for Treating a Surface to the inventor of the present application.

The top coat prevents penetration of solvents and fluorine, chlorine and oxygen as they appear in nature and will withstand acids having a concentration level of five (5) percent or less. Further, the top coat provides a better, harder and more impervious system than the heretofore known systems.

The total thickness of both coats of the present system should be between about 3 to about 6 ml in dry film thickness if the system is to enhance its anti-corrosion and dielectric protective properties.

It has been found that the present system has a dielectric breakdown voltage of 12.8 KV for the top coat and 14.1 KV for the system. This measurement was determined in accordance with ASTM standard D-149.

The above system has been found particularly effective for treating a many types of surfaces, such as masonry, namely cement, cement blocks, concrete, brick, mortar and the like, wood and steel. The system makes such surfaces substantially resistant to markings of graffiti and

improves the surface resistance to corrosion and acid rain. Further, the system provides greatly enhanced dielectric resistance properties to the surface, especially a steel surface. Specifically, the system renders the surface substantially resistant to subsequent markings of graffiti and to permit it to be readily and inexpensively cleaned using a particular cleaning composition without altering the surface or causing damage to any area in close proximity thereto. The system also makes the surface resistant to salt and chemical corrosion, especially caused by free radical ions of oxygen and chlorine, and acid rain attack, and provides the surface with enhanced dielectric resistance properties.

The top coat of the system alone should be used in certain surfaces to improve those surfaces' resistance to corrosion, acid rain attack and graffiti and to maintain the color and texture of those surfaces. Specifically, certain surfaces, such as for example, traffic sign surfaces, marble, sandstone, limestone, granite and certain aggregates, i.e. surfaces composed on a combination of stone, rocks and bricks, have a texture and color which must be maintained, yet those surfaces require protection against corrosion, acid rain and graffiti. For these certain surfaces, the top coat alone is applied. The top coat is a transparent coat which will not effect the color or damage the texture of the surface. It should be

understood that the entire system can be used and, in fact, should be used if enhanced dielectric properties are desired. However, use of the entire system, i.e. with the base coat, would color the surface to be treated.

The top coat can be applied by an air assisted, airless spray, an airless spray and a squeegee roller. A brush, however, should not be used since it will cause bubbles on the surface. The air assisted, airless spray is the most preferred method of application of the top coat. The airless spray alone is preferred over the squeegee roller as alternative methods of application of the top coat.

The top coat is applied on several mist or tack coating layers when applied to traffic signs. Specifically, at least two and preferably four coating layers of the top coat are applied to the surface. The coating layers are applied in a cross hatch pattern. In particular, the first coating layer is applied either a vertical or horizontal direction, and the second coating layer is applied in the other of the vertical or horizontal directions. It is preferred to properly treat or coat a surface that this be repeated, thus four coating layers will be applied to the surface. Each coating layer is applied less than 0.0025" in wet film thickness. The time between the application of each coating layer will vary

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between about ten to about fifteen minutes, depending on the surface. For example, the time between coatings for a non-porous surface, such as a traffic sign, while the time between coatings will be about ten minutes for a porous surface. This prevents sagging or running of the base and the top coats.

The total thickness of the top coat will be about one-quarter to about one-half mil in dry film thickness per tack coat.

A preferred system has been tested by United States Training Company and produced the following results:

Cast Sysiεm -Fsπarmsπcs ΩsiΞ (c rnalie by United S ares Testing Company)

SUBSTITUTE SHEET

The system tested is one preferred embodiment of the present system and comprises a base coat system of a water based epoxy mixture including an epoxy coating hardener, an epoxy resin coating and first group of proprietary additives which includes a tertiary amine and 2 butoxy ethanol; and, a top coat system including a modified polyurethane resin (without organotin) , a catalyst, a reducing agent, and second group of proprietary additives which includes a hardener and film former, toluene blended with dibutyltin laurate and a hindered amine light stabilizer UV absorber.

Having thus described the invention with particular reference to the preferred forms thereof, it will be obvious that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

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