Coating processes – Restoring or repairing
Reexamination Certificate
1998-09-02
2001-02-13
Dawson, Robert (Department: 1712)
Coating processes
Restoring or repairing
C156S094000
Reexamination Certificate
active
06187374
ABSTRACT:
FIELD OF THE INVENTION
The invention is directed to a coating composition for bonding to substrates having low surface tension including porcelain, glazed ceramic and fiberglass.
BACKGROUND OF THE INVENTION
The ability to paint substrates that have low surface tension and are in need of refinishing, such as porcelain sinks and ceramic tile, offers a major cost savings compared to replacing the substrates. Many types of coatings and paints have been tried in the past for this purpose. Most air-dry, ambient curing coatings and paints do not bond well to porcelain or ceramic surfaces. The problem of maintaining adhesion to these surfaces is further complicated by a soapy, hot water environment in which these substrates are often used.
Ambient curing, two-component epoxy and polyurethane paints and coatings have had the best results in the past for this application. Some of these coatings may last for months or even years without failure when there is minimum use of the tub or sink. Their effectiveness is limited, however, when the coating is subjected to the soapy, hot water environment. These coatings fail rapidly and delaminate from the surface in a matter of hours once damaged or cut through ordinary use of the shower, tub or sink. The coating or paint fails when the film is undercut and loses its adhesive bond.
Thus, there is a need for a coating composition that provides a high quality, long-lasting finish that bonds to tough-to-coat substrates having low surface tension including porcelain and glazed ceramic surfaces such as those used in sinks, tubs, and showers.
SUMMARY OF THE INVENTION
The invention relates to a coating composition that not only bonds extremely well to substrates having low surface tension, such as glazed ceramic tile and porcelain surfaces, but also withstands the hot, soapy water environment of tubs, sinks and shower areas. This invention is also more advantageous than coatings that have been used in the past to paint porcelain and ceramic tubs, sinks and shower areas, because it maintains a strong bond to the surface that is capable of resisting peeling and delamination from the surface even if the coating is cut or damaged.
In general, the composition comprises:
a. epoxy resin in an amount ranging from about 25.0 to about 60.0 parts by weight;
b. acrylic resin in an amount ranging from about 5.00 to about 50.0 parts by weight;
c. amine in an amount ranging from about 30.0 to about 45.0 parts by weight; and
d. silane in an amount ranging from greater than 0 to about 10.0 parts by weight.
Solvent may optionally be used, the amount of solvent ranging from 0 to 70.0% by weight based upon the total weight of the composition.
In particular, the invention is directed to a two component coating. That is, some of the compounds of the coating composition are kept separate from others until application at which time the compounds of each component are mixed. The coating composition comprises a mixture of binder, solvent and pigment. The binder (after mixing the components) includes the following:
a. epoxy resin in an amount ranging from about 25.0 to about 60.0 parts by weight based upon the total weight of the binder, one suitable example being epichlorohydrin-bisphenol polymer;
b. acrylic resin in an amount ranging from about 5 to about 50.0 parts by weight based upon the total weight of the binder;
c. cycloaliphatic amine in an amount ranging from about 30.0 to about 45.0 parts by weight (from 0.85 to 1.15 amine equivalents per epoxy equivalent), preferred amines being selected from the group consisting of isophorone diamine, diamino cyclohexane, and 4,4 bis(para aminocyclohexyl)methane; and
d. organosilane in an amount ranging from greater than 0.0 to about 10.0 parts by weight, a preferred organosilane being an epoxy silane. The sum of the weights of the compounds of the binder preferably totals 100 parts by weight. Of course, other compounds (such as pigment) may be added to or omitted from a calculated formulation of the binder that has amounts of compounds that total 100 parts by weight, in which case the relative amounts of each of the compounds would be adjusted accordingly to total 100 parts by weight, as would be apparent to one skilled in the art in view of this disclosure.
The pigment is present in an amount ranging from 0.0 to 50.0 percent (%) Pigment Volume Concentration (PVC), where PVC is defined as the percentage of: the total volume of pigment to the sum of the total volume of the pigment and the total volume of binder, as follows:
PVC
=
Vp
Vp
+
Vb
where:
Vp is the total volume of pigment, and
Vb is the total volume of binder.
The coating composition comprises a mixture of volatile components (solvents) and non-volatile components (binder, pigment, non-volatile additives). Organic solvent carrier is preferably used in an amount ranging from about 30.0 to about 70.0% by weight based on the total weight of the coating composition. Other additives, including but not limited to surfactants and wetting agents, thickeners and viscosity builders, flow and leveling agents, and UV absorbers, may also be used in an amount up to about 5.0% by weight based upon the total weight of the coating composition.
Another form of the invention is directed to a coated substrate comprising a substrate and a protective coating on the substrate. The protective coating is formed of the inventive coating composition. At least a portion of the coated substrate is subjected to an environment of hot water and soap, and that portion is characterized by adhesion to the substrate despite exposure to the environment. The substrate may include or be fastened to a building material that is disposed in a tub, sink or shower area. The substrate may be ceramic tile and, in the case of glazed ceramic tile, the coating is adhered to the glaze. The substrate may also be porcelain whereby the coating adheres to the porcelain. Other substrates, selected from the grouping consisting of glass, formica, fiberglass, acrylic and plastic materials, may also be used.
A method of refinishing substrates comprises selecting at least one substrate in a tub, sink or shower area for refinishing. A coating having the inventive composition is applied to the substrate. The coating on at least a portion of the substrate is subjected to an environment comprising hot water and soap. The coating is characterized by adherence to the portion of the substrate despite exposure to the environment. The coating may be applied by troweling or skim-coating, but is preferably applied by spraying or painting onto the substrate.
The inventive coating is advantageous in that it can adhere to a substrate even when it is exposed to a hot, soapy water environment in sink, tub and shower areas. The coating may also be used in other wet, high temperature, high humidity environments, including those that subject the coating to soaps. The inventive coating is specially formulated to adhere exceptionally well to difficult-to-coat substrates having low surface tension such as glazed ceramic tile and porcelain. The inventive coating has such good adhesion it even adheres well in the hot soapy water environment when it is cut. The inventive coating is expected to last as much as five to ten times as long as conventional coatings in the hot, soapy water environment.
Other objects and a fuller understanding of the invention will be had from the following description of preferred embodiments.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention is an ambient curing, two-component epoxy composition including a binder comprising: epoxy resin in an amount ranging from 25.0 to about 60.0 parts by weight, even more preferably, from about 45.0 to about 55.0 parts by weight, based upon the total weight of the binder; acrylic resin in an amount ranging from about 5.00 to about 50.0 parts by weight, even more preferably, from about 7.00 to about 14.0 parts by weight, based upon the total weight of the binder; cycloaliphatic amine in an amount ranging from about 30.0 to about 45.0 parts by weight based upon the total weight
Hardy Richard D.
Jarufe Juan E.
Aylward D.
Dawson Robert
Watts Hoffman Fisher & Heinke
XIM Products, Inc.
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