Protective Coating Composition and Method of Using Such Composition

The present invention relates to surface protective coatings and more specifically to coatings effective for protecting the exposed surfaces of vehicles.

The surface paint finishes of new vehicles are subject to a variety of injuries both during the assembly process and during transportation from the assembly plant to retail locations. These finishes are especially prone to damage in the first months following manufacture because the paint has not had sufficient time to cure. Typical sources of damage include acid rain, bird droppings, and "rail dust", a cloud of hard, abrasive particles which rises from a rail bed as a train passes over the rails. Rail dust is an especially difficult problem for car manufacturers as many cars are transported from assembly plants or dockyards to retail markets by rail. The damage inflicted on the vehicle's surface finish during transit can be quite severe, even requiring shipment back to the assembly plant for complete repainting.

In addition to new vehicles, other products are also subjected to abrasive and deleterious conditions during transit. For instance, storm windows and other glass products must be specially protected to avoid scratching and marring during road and rail transit. Deck cargo is also susceptible to surface damage caused by salt water and other factors. Further, vehicle surfaces are often damaged by environmental factors during normal driving. For example, train locomotive exteriors can be damaged by the same factors that impact on the vehicles they are transporting. Even typical city and country driving can quickly damage car, bus, truck, etc. finishes.

Various solutions have been attempted to protect the exposed surfaces of vehicles during the manufacturing and transportation. Physical protection (e.g., covering the vehicle with plastic or canvas) is effective, but it is labor intensive and therefore prohibitively expensive for mass shipments or typical driving. Further, the materials used for physical protection also create solid waste problems as they are not readily reusable. Chemical methods have also been proposed, but to-date these methods have found limited use because of their difficult application to, and removal from, the vehicle's surface. Also, traditional chemical methods suffer from high cost and the health and environmental dangers posed by solvent-based solutions and coatings. Especially important in chemical protective techniques is the ability to remove the chemical protective coating with water in view of the ever increasing regulation of solvent use in the workplace and the dangers solvent may pose to the vehicle's surface.

It is therefore clear that a method of protecting surfaces is needed which allows for easy, inexpensive, and safe application and removal.

The present invention includes a surface protective coating composition and a method of protecting surfaces. The coating composition includes a water solubilized acrylic acid copolymer, a ph-neutral acrylic copolymer, an alkyl alcohol having between one and four carbon atoms, a surfactant and water. As used herein, "pH neutral acrylic copolymer" refers to acrylic copolymers that can not be solubilized at an alkaline pH. Typically, those copolymers will have few if any free acidic or basic functions. In a preferred embodiment, the composition includes between about 1 and about 20% of a water solubilized acrylic acid copolymer, between about 0 and about 60% of an acrylic copolymer, between about 1 and about 20% of an alkyl alcohol (having four or fewer carbon atoms), between about 0.01 and about 2% of a surfactant, and water. Each of the components is provided on a per weight basis. In more preferred embodiments, the composition includes between about 1 and about 10% of a water solubilized acrylic acid copolymer, between about 1 and about 10% of an acrylic copolymer, between about 1 and about 10% of an alkyl alcohol (having four or fewer carbon atoms), between about 0.1 and about 1% of a surfactant, and water. In each of the above embodiments, the water solubilized acrylic acid copolymer preferably contains volatile ammonium or ethanol ammonium carboxylate moieties. In other preferred embodiments, the surfactant used in the above embodiments includes a fluorinated surfactant.

A preferred method of protecting surfaces according to this invention includes steps of applying the coating composition to the surface to be protected in a substantially continuous film. The composition is then dried to form a tough, yet flexible coating. Additionally, the present invention includes a method of transporting vehicles or other products in a manner that protects their exterior finishes. This method includes steps of applying the coating composition to the vehicle or product in a substantially continuous film, transporting the vehicle or product, and removing the coating by washing the coated surface with an aqueous solution having a pH substantially between 7 and 9. "Vehicle" as used herein includes such modes of transportation as cars, trucks, boats, bicycles and the like. The coating composition is easily applied and readily removed after use with relatively reduced health and environmental risk.

A further understanding of the nature and advantages of the invention herein may be realized by reference to the remaining portions of the specification.

The present invention provides an improved surface protective coating composition and method for protecting surfaces. The method and coating composition produce a film which adheres well to a surface to be protected, with few or no pinholes. Further, the coating film may be removed easily with a ph-basic water wash (i.e., an aqueous solution having a pH greater than 7).

The surface protective coating composition of the invention preferably includes a water solubilized acrylic acid copolymer, a ph-neutral acrylic copolymer, an alkyl alcohol, and one or more surfactants (e.g., a fluorinated surfactant). In preferred embodiments, the water solubilized acrylic acid copolymer contains volatile conjugate bases (e.g., the copolymer includes ammonium or ethanol ammonium carboxylate moieties). Such materials may be prepared, for example, by adding ammonia or an ethanol amine to an acrylic acid copolymer. Upon drying, coating compositions employing these volatile conjugate bases will release ammonia or ethanol amine and leave a tough, weather-resistant coating containing free acrylic acid copolymers. The coating resists discoloration and opacity resulting from exposure to sunlight, and other influences. In particular, the coating does not absorb water and thus does not form the opaque films associated with many other coatings. When it is no longer needed, the coating can be removed with an aqueous detergent solution having a basic pH.

In one preferred embodiment, the coating composition contains between about 1 and 10% of a water solubilized acrylic acid copolymer solution, between about 1 and 10% by weight of a ph-neutral acrylic copolymer, between about 1 and 10% of an alkyl alcohol containing four or fewer carbon atoms, between about 0.01 and 1% of surfactant, and water. Preferably, the surfactant component of the composition will include a fluorinated surfactant. In some preferred embodiments, the composition also includes a thickener having a concentration of between about 0.1% and 1% by weight.

Although the surface protective coating is preferably water insoluble in neutral conditions, it should be soluble in basic solutions. The acid moieties of the acrylic acid copolymer present in the coating provide water solubility upon contact with a PH-basic aqueous solution due to the formation of water-soluble carboxylate salts. One suitable acrylic acid copolymer solution is commercially available under the trade name " Acrysol.TM." (available from Rohm & Haas). The acrylic acid copolymer may also be provided as a mixture of several grades of water solubilized acrylic acid copolymers depending on the desired qualities of the coating. Further, the individual acrylic acid copolymers can contain variable percentages of acrylic acid, methacrylic acid and other monomer units. The copolymer may also be provided in a range of molecular weights. In all cases, the acrylic acid copolymer should be water solubilized with a volatile conjugate base such as ammonia or an ethanol amine as discussed above. In preferred embodiments, the water solubilized acrylic acid copolymer will be present in the composition of about 5-10% by weight.

The coating compositions also include a ph-neutral acrylic copolymer, such as are sold under the trade name "Rhoplex.TM." (Rohm & Haas) to increase the hardness or flexibility of the coating. Generally, preferred formulations of the coating composition contain between about 1 and about 5% of such copolymers by weight. The chemical composition of the acrylic copolymer may vary depending upon the intended application. For example, copolymers containing relatively large numbers of methacrylate (as opposed to acrylate) monomer units can be used to increase the modulus of the coating composition. Suitable acrylic copolymers generally include those having various alkyl carboxylate monomer units (e.g. methyl, ethyl, propyl, butyl etc. esters).

The surface protective coating composition also includes an alkyl alcohol (C.sub.n H.sub.2n+1 OH). Preferred alcohols are those where n.ltoreq.4, including methyl alcohol, ethyl alcohol, and propyl alcohol. A most preferred alcohol is ethyl alcohol. The percentage of alcohol utilized is preferably less than about 5% by weight (based on 95% alcohol), with compositions having between 1.5% and 3% alcohol most preferred. When ethyl alcohol is utilized, a preferred composition includes about 2.5% alcohol by weight. When methyl or propyl (such as isopropyl or n-propyl) alcohol is utilized, compositions with less than about 10% by weight of alcohol are preferred, and compositions of between about 1 and 5% are most preferred.

The surface protective coating composition of the invention also includes a surfactant. The surfactant is, in one embodiment, a non-ionic biodegradable surfactant such as an acetylenic diol. In preferred embodiments the invention includes an alkyl aryl surfactant (such as Triton CF-10 and CF-12), a polyethoxy adduct, or a modified (poly) ethoxylate (such as Triton DF-12 and DF-16). Other surfactants include nonylphenoxypolyethanol (such as IGEPAL CO-660 made by GAF), polyoxyalkylene glycol (such as Macol 18 and 19 made by Mazur Chemicals), acetylenic diol-based surfactants (such as Surfynol 104A made by Air Products), and the like. Preferred compositions include up to 1% surfactant. Most preferred compositions include between 0.05% and 0.15% by weight surfactant and more preferably about 0.1% surfactant.

In addition to (or in place of) the above surfactant, the protective coating compositions preferably include a defoamer or wetting agent to reduce the formation of pinholes and facilitate smooth coverage of the surface, especially when the coating composition is applied with a spray gun. Fluorinated surfactants such as "Flourad.TM." (available from 3M Corporation) are preferred defoamers. Specific fluorinated surfactants suitable for use in this invention include "Fluorad FC-171" and "Fluorad FC-431" . Generally such surfactants comprise between 0.02 and 14% of the weight of the coating composition, with about 0.1% being preferred. The fluorinated surfactant may also be a mixture of two or more grades of surfactant, depending on the qualities of the coating which are desired.

Many preferred embodiments also include a thickener which, of course, renders the composition thicker so that it can be more easily applied to a vertical work surface. Thickeners also prevent the undesirable phenomenon of "sagging" in which the coating becomes thinner near the top of a vertical work surface. Specific examples of compatible copolymer thickeners include "Acrysol I-98" and "Acrysol TT-615" available from Rohm and Haas.

The coating formulation also includes a substantial amount of water, such as 18 megaohm/cm deionized water (D. I. water). In one embodiment of the invention, the balance of the composition is composed of water, although a variety of other materials may also be included such as dyes, odorants, and the like.

The coating composition is made by conventional means, typically including steps of simply admixing the components (or aqueous solutions, dispersions, etc. thereof) at substantially atmospheric pressure so as to form a substantially homogeneous mixture. In preferred embodiments ammonia or an ethanol amine is added until the thickener dissolves (typically at a pH of between about 7 and about 9). It has been found that the mechanical and thermal properties of the coating of the invention can be controlled by appropriate combination of neutral and acidic acrylic polymer solutions. Acidic polyacrylics allow for the removal of the coating with a basic-ph water wash, but if used alone they can impart brittleness to the dried coating. This will cause the coating to crack with changes in temperature or upon physical contact and thus impair the protection afforded by the coating. Neutral polyacrylics act to make the coating more flexible or hard depending the specific type and amount added. But if neutral polyacrylics are used alone, the coating generally can not be removed by an aqueous PH-basic detergent solution. Thus, the solubility, mechanical, and thermal properties of the coating will depend, in part, on the ratio of acrylic acid copolymer to neutral polyacrylics. However, care should be taken when mixing polyacrylics to produce a clear film (i.e., the polyacrylics should be miscible) so that the coating's mechanical properties are uniform.

The present invention also includes a method of protecting surfaces wherein a substantially continuous film of the above-described surface protective coating composition is applied to the surface to be protected. Such surfaces may include the exterior painted portions of an automobile or other vehicle. The coating composition is applied by one of a variety of techniques. Preferred techniques include brushing and spraying of the surface with the coating composition. In some cases, additional water may be added for easier application, such as a 10% dilution. Thereafter, the coating composition may be applied with a pressure pot sprayer, preferably first in a thin mist and, thereafter, in a flow coat or thicker substantially continuous film. The coating composition is sprayed primarily on the surface to be protected, although overspray will not pose significant problems since any overspray may be readily removed with, for example, a wet towel or sponge. The resulting masking coating composition is from about 0.1 to about 10 mils thick, preferably about 0.5 to about 2 mils thick, with a preferred thickness of about 1 mil.

The coating composition is then permitted to dry, normally at atmospheric temperatures and pressures. Such drying will take about 5 to 10 minutes in typical applications (at room temperature and 30% humidity). Significantly longer drying times are needed at 50.degree. F. For such lower temperatures, additional ethanol may be provided in a separate container to increase the ethanol content by about 10% by weight.

The invention further includes a method of transporting vehicles which protects the exterior painted portions of the vehicle from scratches. Generally, the above-described surface protective coating composition is applied to the surface to be protected, the vehicle is transported, and the protective coating is then removed by washing the coated surfaces with an aqueous detergent solution having a pH of greater than 7 and preferably between 7 and 9 (e.g., a solution of aqueous ammonia, sodium carbonate, potassium carbonate, ethanol amines, etc.). For example, cars to be loaded onto auto-carriers (either road or rail) are first cleaned of surface debris and dust and then coated with the surface protective coating composition of the invention as described above. The cars are then transported to their destination where the surface protective coating is removed by washing with an alkaline aqueous detergent solution. Ammonia and ethanol amines are preferred for use in the detergent solution because they form soluble salts with acrylic acid copolymers and because they act fast.

In addition, the coatings of the present invention may be applied to protect sensitive finishes on most any item exposed to deleterious environmental factors. For example, the composition of this invention can be used to coat glass and chrome products being transported, boats being stored outdoors (particularly during winter), chrome tanks on tank trucks, and vehicles generally. It has been found that coatings prepared according to the present invention can be used to protect against graffiti. The paint from graffiti is simply washed away together with the protective coating by wiping with an alkaline aqueous detergent solution.

The following examples are intended to illustrate the present invention and are not intended to limit the scope of the invention in any way.

The following components were combined at room temperature and at atmospheric pressure by slow stirring to form a suitable surface protective coating composition of the invention:

The following components were combined at room temperature and at atmosphere pressure by slow stirring to form a suitable surface protective coating composition of the invention:

Two sets of tests have been conducted on finished surfaces protected with the above coating compositions. Protected and unprotected surfaces were subjected to, for example, ultraviolet radiation, salt water, acid rain, and abrasion. The finishes on the unprotected surfaces were damaged, while the finishes on the protected surfaces were unaffected by the above factors.

The advantages of the invention will now be apparent. The invention provides a surface protective coating composition and method of protecting surfaces which is easy and cost effective to use and at a relatively reduced health and environmental risk. Using the method of the invention, large surface areas or many surfaces may be protected from damage quickly, easily, cheaply, and safely. Although certain embodiments and examples have been used to describe the invention, it will be apparent to those skilled in the art that various changes may be made to those embodiments and/or examples without departing from the scope of the invention.