Coating powder compositions and method

#The present invention is directed to coating powder compositions and to methods for preparing and using novel powder coating compositions which include admixing inorganic tinting agents, such as a mixed metal oxide or titanium dioxide, to coating powder base compositions.

#It is known in liquid paint systems to add a tinting agent to a finished base composition to achieve a final colored paint composition. This technology permits the preparation of a large array of liquid custom color paints that can be created from a small number of finished base compositions. In coating powder paint systems, the addition of a tinting agent to a coating powder base composition is more difficult and generally requires extrusion, grinding, or sieving to adequately mix the dry components. Otherwise, when a coating powder base and tinting agent are mixed, resultant coatings having poor flow are obtained. It is believed that this well-recognized difficulty for coating powder systems is caused by low wetting properties of the coating powder base composition. Thus, it is a long standing problem in the coating powder industry to be able to produce coating powders that are capable of obtaining good quality coatings using the highly advantageous technique currently used for liquid paint systems.

#The present invention may be advantageously used with a wide variety of coating powder compositions including thermosetting, thermoplastic, radiation curable, and dual systems such as thermosetting/radiation curable and fluorocarbon polymer thermosetting systems. Once a base coating powder having sufficient wetting properties, as measured by viscosity, is produced, a particulate tinting agent(s) is then mixed with such particulate base coating powder to produce a desired color. An important commercial advantage of the invention is that a base coating powder can be produced and then stored to await the final, color-producing mixing step. This procedure is not presently believed to be followed in the coating powder industry. To be able to obtain a desired colored powder by simply mixing a base and tinting agent would permit pre-production of large quantities of the base and then the use of a portion of such base to obtain a desired color rather than having a single production run capable of producing only one color. Obviously, shorter production and delivery times are possible with the invention. Moreover, if a coating powder manufacturer is in the midst of a production run of a given color, the only alternative to being able to quickly produce a different color could be to interrupt the run, clean the equipment, and then produce the other color. Then the equipment would require cleaning once more to produce the balance of the first run. This substantial problem is eliminated with the present invention, thus enabling a wide variety of colored powders to be quickly produced and shipped to customers without interruption of the base production run.

#The present invention pertains to coating powder base compositions that can be simply admixed, preferably in the dry state, with tinting agents, such as a mixed metal oxide, titanium dioxide, hybrid organic-inorganic materials, and/or organic polymer soluble dyes to prepare the final powder coating compositions. In conventional powder coating compositions, tinting agents must be added to coating powder compositions, along with other ingredients, before processing such as premixing, extrusion, cooling, grinding, classifying, and sieving. In the present invention, tinting agents are added to coating powder base compositions in a finished state, followed by a short mixing cycle. No other processing is required. Unlike organic tinting agents, which tend to decompose easily and provide off colors, the tinting agents of the present invention are compounds that can be post-mixed with coating powder base compositions to prepare the final coating powder mixture compositions. The ability to post-mix dry tinting agents and/or additives with a dry base composition enables the creation of a final coating powder of virtually any color, gloss, texture, structure, lubricity, or conductivity, thereby greatly reducing the time to produce a given color and the number of finished coating powders that need to be stored in inventory. The properties of the base compositions may vary in color, gloss, or texture but are formulated so that dry materials can be introduced by a post-addition method.

#The term “additive”, as used herein, refers to any chemical that is added to a coating powder base to alter the finish or enhance a desired property of the finished powder coating.

#The term “amorphous fumed silica”, as used herein, refers to naturally occurring or synthetically produced (SiO2) characterized by the absence of a pronounced crystalline structure.