Amine cured epoxies are widely used. Amines and amine functional amides are common curing agents for high performance epoxy coatings. Epoxy resins which are cured, hardened, or crosslinked with multifunctional amines, i.e., amine compounds having three or more active amine hydrogens, are well known in the industry. These materials are widely used in applications such as coatings, adhesives, composites, and civil engineering applications such as formulations for flooring, In coating applications, amine cured epoxy formulations generally can be cured at room temperature to yield films with high mechanical strength, good water, chemical, and corrosion resistance, and excellent adhesion properties. Thus, they are often employed as primers and topcoats for large structures such as ships, bridges, and industrial plants and equipment,
Many amine cured epoxy coatings if polymerized or cured using non-prescribed conditions such as cool ambient temperature or high humidity can develop problems referred to in the industry as amine blush . With primary amines, the amine that has migrated to the surface can react with CO2 present in the air, ultimately resulting in the formation of carbamates on the surface of the epoxy coating. The presence of carbamates can lead to intercoat adhesion failures if the film is re-coated. This is a serious problem because many epoxy coatings are over coated. The additional coatings are not limited to epoxy-based systems and can include other chemical coating systems (e.g., polyurethanes) in order to provide particular end-use properties, such as corrosion resistance, weatherability, etc.
When determining if an epoxy coating can be over coated, it is important to determine if the coating exhibits the phenomenon of amine blush. Similarly when analyzing why an epoxy coating could not be successfully overcoated, it is important to determine whether the cause was amine blush. When blush is visible to the naked eye, it can appear as a thin spotty or greasy layer ranging in color from white to amber. Previous quick field tests relied on pH to determine the presence of amine blush as a result of the presence of carbamates; however in many cases the raised pH was not caused by the presence of carbamates. The present invention identifies that carbamates are present and does not rely on raised pH for that purpose. It can be done as field test—at the location where the epoxy surface was created—or in the laboratory.
USPTO Backgrounds
USPTO Backgrounds