Patent Application
20060135656
This invention relates to coating compositions and, more particularly, to waterborne epoxy coating compositions and methods for using such compositions.
Epoxy coating compositions are used to treat surfaces to protect against corrosion and other forms of wear and tear caused by use and the environment. The types of surfaces treated include concrete, metal, and other surfaces. Effective coating compositions are prized not only for the quality of protection, but also for easy and efficient transportation, storage, and application. Thus, a good coating composition will not only protect the surface, but also be easy to apply and quick to cure.
The use of epoxy compositions containing volatile organic solvents has fallen out of favor even though these compositions provide exceptional anti-corrosion protection. The organic solvent based compositions are environmentally unfriendly and their use has been curtailed. Solvent free epoxy coatings often require sophisticated, non-standard equipment for application.
Other epoxy coating compositions provide good protection if applied at the recommended thickness. This recommended thickness requires multiple coats and each coat must be cured or set before another coat may be applied. Each additional coat requires additional labor, which increases the cost of application. Other coats may be applied at greater initial thickness, but require more time to set up. Coatings applied at greater initial thicknesses may also introduce flaws caused by voids from evaporation of volatile components during the curing process.
The combination of an epoxy resin and cement in a coating composition has been used previously to create cement compositions suitable for overlaying concrete. For example, prior products include cement based compositions with an epoxy used as “mortars,” “toppings,” or “overlays” to coat Portland cement concrete or metal surfaces. These compositions use a small portion of epoxy to enhance the cement composition and the final compositions are thick like cement and resembles cement. These are generally two-component compositions having a dry-mix component and a wet-mix component which are combined to form the final composition for application to surfaces in thick films, typically greater than about 20 mils. Other compositions have used an epoxy to bind a cement composition.
There is, therefore, provided in the practice of the invention a novel waterborne fluid coating composition, which is epoxy based and includes hydraulic cement, for reduced initial thickness application, and which provides for a quicker application at a reduced cost. The waterborne epoxy coating composition broadly includes an epoxy resin, a hydraulic cement powder, a curing agent and water.
In one embodiment, the coating composition is prepared by mixing two pre-blended liquid components; one component containing a liquid epoxy resin and hydraulic cement powder; and the other component containing an amine-based curing agent and water. The first part may also include additives, such as a non-reactive diluent, a reactive diluent, a silicone adhesion promoter, a pigment, hollow spheres, or other materials. The second part may also include additives, such as a cement plasticizer, a non-reactive diluent, a water-based latex resin, a defoamer, a corrosion inhibitor, or other materials.
Accordingly, it is an object of the present invention to provide an improved two-part waterborne epoxy coating providing anti-corrosion protection.
The waterborne epoxy composition broadly includes an epoxy resin, cement powder, an amine-based curing agent, and water. The composition may be enhanced with additives, including a non-reactive diluent, a reactive diluent, a silicone adhesion promoter, a pigment, hollow spheres, a cement plasticizer, a water-based latex resin, a defoamer, a corrosion inhibitor, or other materials Each element of the general formula will be discussed in detail below, followed by several embodiments of the composition and the method of production and application.
The epoxy resin may be liquid, solid or semi-solid. The epoxy resin functions as the curable component of one part of the two-part epoxy coating composition. In one embodiment, the epoxy resin may consist of any one of bisphenol A, bisphenol F, epoxy phenol novolac, epoxy cresol novolac, naphthalene epoxy, or tertiary butyl cathecol epoxy. Another epoxy may be used besides those listed here, although these are preferred. In exemplary embodiments, the epoxy resin is a liquid bisphenol A epoxy resin, including for example, liquid bisphenol A epoxy resin such as Huntsman GY6010, or a water-dispersed bisphenol A epoxy resin such as Resolution EPI-REZ 3510-W-60.
The hydraulic cement powder may be any type of Portland cement and may also be any color. Portland cement comes in Types I, II, III, IV, and V. The possible colors include white, grey, etc. In another embodiment, the hydraulic cement powder is a mixture of 0.50 to 0.95 weight parts of Portland Cement and 0.05 to 0.50 weight parts pozzolan powder derived from a group comprising fly ash, steel slag, silica fume, or calcined kaolin clay.
The curing agent may be a substantially solvent free, or a water dilutable polyamine having a plurality of N—H linkages capable of reacting with the epoxy resin. The amine-based curing agent may be a polyoxyalkylene polyamine, arylene polyamine, cyclo-aliphatic polyamine, Mannich base, or a blend of two or more of these polyamines. An example of a solvent free amine curing agent used in an embodiment is a polyoxypropylene polyamine such as Huntsman JEFFAMINE D-400. Examples of commercially available water-based amine curing agents useful in the invention include, for example, Cognis WATERPOXY 751, UCB BECKOPOX 613, Huntsman ARADUR 39, Bakelite RUETADUR VE-51, and Air Products ANQUAMINE 287.
The coating compositions of the invention are prepared from a desired amount of epoxy resin such that the weight ratio of epoxy resin to hydraulic cement is in the range of about 0.1:1 to about 1.2:1; the compositions further provide a ratio of about 0.8 to 1.3 equivalents of total epoxy groups to 1.0 equivalent of reactive curing agent amine groups; and 0.2 to 0.9 parts water to 1.0 part hydraulic cement.
A non-reactive diluent may be added to decrease the viscosity of the mixture. Any diluent that does not react with the other elements of the composition and decreases viscosity may be used. In one embodiment, the non-reactive diluent is benzyl alcohol, which not only reduces viscosity, but also speeds the epoxy/amine reaction and helps prevent freezing or crystallization of the coating composition. In another embodiment, the non-reactive diluent is an aromatic hydrocarbon resin, such as Rutgers NOVARES LS 500 for example, which not only reduces viscosity, but also has lower volatility. The non-reactive diluent may be included in either or both components of the composition.
The composition may further include a reactive diluent. The reactive diluent may be an aliphatic, cycloaliphatic, or aromatic epoxy functional diluent. The reactive diluent may be either monofunctional or multifunctional. In one embodiment, the reactive diluent is a C6 to C18 alkyl mono glycidyl ether, and is included at a ratio of about 8 to 26 parts per 100 parts of epoxy resin. One example of a commercial reactive diluent suitable for this composition is Air Products EPODIL 748.
The composition may further include a silicone adhesion promoter to enhance the adhesion of the cured composition to the surface being coated. The silicone adhesion promoter is included in a ratio of about 0.5 to 2 parts to 100 parts of epoxy resin. In one embodiment, the silicone adhesion promoter is γ-glycidoxypropyl-trimethoxy silane.
The composition may further include a water-based latex resin in a ratio of up to about 1.2 parts water-based latex resin to 1.0 part of hydraulic cement. Examples of useful water-based latex resins include, acrylic, styrene-acrylic, styrene butadiene rubber (SBR), polyvinyl acetate(PVA), and ethylene vinyl acetate (EVA) latexes. In one embodiment, the latex resin is an acrylic, styrene-acrylic, or styrene butadiene rubber (SBR) latex. Examples include Rohm & Haas RHOPLEX MC-1834, SYNTHOMER 29Y46 SBR, and Resolution IC-780.
The composition may further include a desired amount of pigment up to about 24.0% in order to achieve the desired coating color. In one embodiment the pigment is titanium dioxide. The pigment may be dispersed in either component of the two-part composition of the invention.
The composition may further include up to about 8.0% hollow spheres as an inert filler. In one embodiment the hollow spheres are hollow micro-spheres having a particle diameter in the range of about 5 to 90 microns and are included in the hydraulic cement containing component of the two-part composition in a ratio of about 1 part hollow spheres to about 3 to 50 parts of hydraulic cement. Examples include 3M SCOTCHLITE K37 Glass Bubbles and CHL A-90 Hollow Ceramic Microspheres.
The composition may further include up to about 0.4% of a cement plasticizer, such as a lignosulfonate salt, for example Lignotech Norlig 24C; up to about 0.55% of a defoamer, such as a non-silicone defoamer, for example BYK-Chemie BYK-011, and/or a silicone defoamer, for example Tego FOAMEX 805; and up to about 2.4% of a corrosion inhibitor, such as Cortec MCI-2000 or W. R. Grace DCI S; all as set forth in the following examples and claims.
One embodiment of the waterborne epoxy coating composition is divided into two parts for easy storage and transportation. Part A of this formula is non-aqueous and includes liquid Bisphenol A epoxy resin, reactive diluent, silicone adhesion promoter, hydraulic cement, and hollow spheres. Part B is aqueous and includes water-based amine curing agent, water-based latex resin, and defoamer. The two parts are combined in a sprayer to mix the two parts together and then apply the coating composition to a surface, wherein the composition has a weight ratio of epoxy resin to hydraulic cement in the range of about 0.19:1 to about 0.6:1; a ratio of about 0.9 to 1.15 equivalents of total epoxy groups to 1.0 equivalent of reactive curing agent amine groups; and 0.3 to 0.6 parts total water to 1.0 part hydraulic cement.
Another embodiment comprises a non-aqueous Part A including liquid Bisphenol A epoxy resin, reactive diluent, silicone adhesion promoter, hydraulic cement, and hollow spheres; and an aqueous Part B including a water-based amine curing agent, water-based latex resin, and defoamer. The two parts are combined in a sprayer to mix the two parts together and then apply the coating composition to a surface, wherein the final composition has a weight ration of epoxy resin to hydraulic cement is in the range of about 0.25:1 to about 0.5:1; a ration of about 0.95 to 1.1 equivalents of total epoxy groups to 1.0 equivalent of reactive curing agent amine groups; and 0.4 to 0.6 parts total water to 1.0 part hydraulic cement. Each part is approximately equal in volume and additional water may be added after the two parts are mixed.
In an alternative embodiment the non-aqueous Part A includes a solvent-free amine curing agent, hydraulic cement and hollow spheres. Part B is aqueous and includes a water-dispersed epoxy resin, and may further contain a water-based latex resin, and defoamer. The two parts are combined in a sprayer to mix the two parts together and then apply the coating composition to a surface, wherein the composition has a weight ratio of epoxy resin to hydraulic cement in the range of about 0.1:1 to about 1.2:1; a ratio of about 0.8 to 1.3 equivalents of total epoxy groups to 1.0 equivalent of reactive curing agent amine groups; and 0.2 to 0.9 parts total water to 1.0 part hydraulic cement.
The embodiments of the waterborne epoxy coating composition may be applied with a brush, roller, or airless sprayer to produce cured coatings with a thickness from about 78% to about 95% of the single coat wet thickness. Exemplary embodiments of the composition applied by airless sprayer produce cured coatings with a thickness from about 90% to about 95% of the single coat wet thickness. The embodiments of the composition exhibit gel times from about 60 minutes to about 120 minutes and are dry to touch in less than 24 hours.
The embodiments of the composition are more specifically shown in the following examples.
Further embodiments of the composition are described by the following untested examples. The following examples are provide by way of illustration not limitation, and the changes reflected are equally applicable to each of the compositions specifically described in Examples 1 through 59.
Any of the disclosed embodiments of the claimed composition may be used in a process to protectively coat a surface. The process involves preparing the composition according to the present invention, mixing the two parts with an appropriate amount of water, and applying the coating to the surface. The formula may be applied with a brush, roller or airless sprayer and will achieve a high build film in a single application, although multiple coats may be applied at the discretion of the user.
Thus, a waterborne epoxy composition is disclosed which utilizes hydraulic cement powder as an element of the epoxy composition to provide a desired initial application coat thickness with good fluidity and enhanced cure time while still providing protection against corrosion and other environmental threats. The coating composition also provides corrosion resistance equal to organic solvent based and solvent free coatings.
While preferred embodiments and particular applications of this invention have been shown and described, it is apparent to those skilled in the art that many other modifications and applications of this invention are possible, including using the teaching to develop coating compositions having three or more components, without departing from the inventive concepts herein. It is, therefore, to be understood that, within the scope of the appended claims, this invention may be practiced otherwise than as specifically described, and the invention is not to be restricted except in the spirit of the appended claims. Though some of the features of the invention may be claimed in dependency, each feature has merit if used independently.
