Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
1997-06-12
2001-11-06
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of polyamidoester
C524S507000
Reexamination Certificate
active
06312815
ABSTRACT:
TECHNICAL FIELD
This invention relates to means for facilitating removal of unwanted substances, such as graffiti, from walls or similar surfaces. Specifically, this invention relates to the pre-treatment of surfaces with environmentally safe coatings which allow removal of contaminants and graffiti from the surface without degradation of the underlying coating.
BACKGROUND
The application of graffiti to walls, vehicles and other surfaces has been a concern to society and individuals for decades. Graffiti is not only unsightly, but destructive, and leads to the expenditure of millions of dollars each year to obliterate or remove the graffiti and to restore the underlying surface. In some cities, for example, graffiti is such a pervasive problem that special booths are constructed through which municipal buses are driven to clean and restore the paint on the body of the vehicle.
Traditionally, graffiti has been removed by sandblasting the painted surface, but sandblasting obviously damages the surface over time and reduces its longevity. Graffiti has also been removed by simply repainting or recoating the graffitied surface. Repainting or recoating, however, is time-consuming and expensive. Therefore, a variety of systems have been developed for preventing, removing or obliterating graffiti. Examples of such systems are disclosed in U.S. Pat. No. 5,039,745 to Riddle, issued Aug. 13, 1991 (system providing a non-stick surface); U.S. Pat. No. 4,478,975 to Dessaint, issued Oct. 23, 1984 (disclosing a fluorinated copolymer for water- and oil-proofing surfaces); U.S. Pat. No. 4,716,056 to Fox, et al., issued Dec. 29, 1987 (disclosing a pre-reacted water-based epoxy color coating for obliterating graffiti); U.S. Pat. No. 5,024,780 to Leys, issued Jun. 18, 1991 (disclosing a substance for removing graffiti as well as paint and other coatings); U.S. Pat. No. 5,017,237 to Svensson, issued May 21, 1991 (disclosing a polysaccharide coating which hardens on a surface and which is thereafter removed when soiled); U.S. Pat. No. 4,353,745 to Ebbeler, issued Oct. 12, 1982 (disclosing a clear protective coating for a surface which is thereafter removed when soiled); and U.S. Pat. No. 4,600,522 to Grzeskowiak, et al., issued Jul. 15, 1986 (disclosing a biodegradable cleaner for removing graffiti from anodized aluminum, stainless steel and glass).
One of the most commonly used graffiti removal systems at present comprises coating a surface with a substance which is thereafter removed when soiled by graffiti or other material. Such systems are commonly referred to as “sacrificial coatings” since the coating is removed after soiling and must be replaced to provide further protection from graffiti and other contaminants.
Other graffiti removal systems provide obliterative coatings for covering graffiti already applied to a surface. A system of that type is described in U.S. Pat. No. 4,716,056 (referenced previously) in which a colored water-based epoxy coating is applied over a graffitied surface followed by an aliphatic urethane top coating. Because both the water-based epoxy and urethane coatings described therein are pre-reacted (i.e., cross-linked prior to mixing or application) and are able to be applied only after addition of a solvent and a hardener, the coatings are susceptible to degradation from application of solvent during cleaning. That is, integrity of the polymers is compromised upon subsequent application of solvent.
A number of polymer coatings presently on the market which purport to be formulated for the easy removal of graffiti therefrom are cured by solvent evaporation. While such coatings have some advantages over older formulations, they are susceptible to degradation from the solvents in spray paints used for making graffiti. That is, the solvents in spray paints weaken the polymeric integrity of the coating and a portion of the spray paint becomes imbedded in the coating as it cures. This is particularly prevalent when the graffiti is not removed within thirty-six hours after application. When cleaned, a residual amount of graffiti remains on the coating.
Solvent evaporation-cured coatings, as well as chemically cross-linked polymeric coatings currently on the market may be sufficiently cleanable to remove an acceptable amount of graffiti therefrom, but repeated cleanings tend to weaken the polymeric bonds of these coatings so that the coating becomes ineffective or permanently stained after a relatively few number of cleanings.
Additionally, many graffiti systems require removal of graffiti from the coating surface with volatile chemical substances which are potentially harmful to the user and particularly harmful to the environment. Even with sacrificial coatings, the protective coating and the chemicals used to remove the coating are potentially unsafe for the environment.
Therefore, it would be advantageous to provide a graffiti removal system comprising a non-sacrificed polymeric protective coating which is not susceptible to degradation when solvents and cleaners are applied, and which has a low volatile organics content thereby rendering the coating safe for the environment and users, and a non-toxic, biodegradable cleaner for removing graffiti from the protective coating which does not affect or degrade the coating.
DISCLOSURE OF THE INVENTION
In accordance with the present invention, a graffiti-removal system is provided which includes a protective coating for application to an underlying surface, the coating being either a water-based epoxy or an aliphatic urethane material having a low volatile organics content, and a non-toxic, biodegradable cleaner. The coatings of the present invention provide a strong and impenetrable surface which is neither degraded nor compromised by the application of solvents or cleaners and which is particularly unaffected by application of the biodegradable cleaner of the invention. That is, the cleaner, when applied to the coating, will not compromise the integrity of the protective coating, but will effectively remove graffiti therefrom. The protective coatings of the invention are suitable for application to many surfaces for the easy removal of unwanted contaminants therefrom, such as industrial byproducts and wastes. However, this disclosure focusses on removal of graffiti as an exemplar.
The protective coating of the invention is applicable to a variety of surfaces, including but not limited to stone, masonry, brick, wood and metal, which have been properly prepared. The protective coating is generally a nonpre-reacted polymer material which cures by chemical cross-linking producing a high bond density. The coating bonds effectively to any surface.
After being contaminated by graffiti, or some other unwanted substance, the protective coating is contacted with cleaner to remove the graffiti. The protective coating is neither affected by the cleaner nor by the contaminants placed thereon, such as solvent-based paints. The coating is particularly formulated to be unaffected by prolonged application (longer than fifteen minutes) of one hundred percent concentrated N-methyl pyrrolidone. All other known coatings will degrade (i.e. soften and become permeable to entry of the unwanted substances, loss of adhesion, blistering, etc.) after a few minutes of being contacted with such a high concentration of N-methyl pyrrolidone. The protective coating may be cleaned continuously (more than one hundred times) without any need for reapplication of the coating. The protective coating of the present invention also has excellent weatherability and is resistant to chalking, flaking and yellowing (i.e., no chalking, flaking or yellowing is observed after the coating has been subjected to environmental forces for over three months).
The protective coating may be a water-based epoxy which is water soluble and has a low volatile organics content (about 0.05 to about 2.0 pounds per gallon [about 0.059 kg to about 0.24 kg per liter]). The water-based epoxy coating generally comprises a two component system which provides mixture of the polymeri
Dobney David
Macris Michael N.
American Polymer Corporation
Aylward D.
Dawson Robert
Workman & Nydegger & Seeley
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