Ceramic materials have long been used in a wide variety of applications, including as roofing material and, more commonly today, as floor and wall coverings in homes. Innumerable formulations have been devised to produce kiln-fired ceramic materials having the appropriate properties for the desired end use. Traditional examples of those ceramic formulations include those which contain either shale or clay as the primary component.
Recently, however, formulations have been developed, in conjunction with the recycling movement, in which glass, e.g., waste glass, is included as a component of the ceramic formulation. The inclusion of glass in such formulations, however, was not achieved by simply substituting glass for another component in an existing clay or shale formulation. On the contrary, it was found that the introduction of glass into a ceramic formulation, due to its particular physical characteristics, influenced the properties of the formulation, the manner in which the formulation may be processed, and the characteristics of the final ceramic product prepared from the formulation. Accordingly, the preparation of ceramic products using glass, where glass had not been previously included as a component, was determined to require careful evaluation to insure that the resulting glass-based formulation is capable of being made into a tile and, further, that the characteristics of the resulting tile are not adversely affected due to the incompatibility of glass with the other formulation components.
One commercially significant property of ceramic tile products prepared using glass is the appearance of the finished product. Specifically, glass-based ceramic tiles, when a colorant such as a stain is added to the formulation, provide a tile which exhibits the color of the stain in a very vibrant manner. Due to the commercial significance of this color vibrancy, it is therefore essential that any new glass-based formulation provide a tile that has the desirable physical properties and staining characteristics of known glass-based tiles.
The vibrancy and depth of color associated with glass-based tiles may be further attributable to the ability of the color of the tile itself to be refracted through the body of the tile. Glass-based tile is an ideal medium for accepting a variety of colored stains, these stains imparting the desired color to the entire tile body. In contrast, conventional clay- and shale-based tiles, when fired, provide a tile that has a generally flat red color throughout. This is due to the colorants which are inherently present in the components used to prepare those tiles. Due to that inherent coloration, a minimal effect on the coloration of such tile bodies will be observed when a stain or other colorant is added to the formulation. Coloration is therefore typically added to those clay- and shale-based tiles only to the outer surface of the tiles. This is accomplished by means of a glaze which is applied to the outside of the tile body.
One example of a glass-containing ceramic formulation and product is provided by U.S. Pat. No. 5,028,569. The ceramic article disclosed therein is prepared from a raw batch formulation comprising virgin soda-lime glass, preferably in an amount greater than 60 to about 85 wt. %, clay, preferably in an amount from about 15 to about 40 wt. %, and, optionally, flint in an amount ranging from about 0 to about 10 wt. %.
U.S. Pat. No. 4,120,735 provides another example of a glass-based ceramic composition. This patent discloses a brick or other fired construction material prepared from a raw batch which comprises: the nonferrous, inorganic portion of municipal refuse, i.e., principally glass, as well as metals, slag, charred and unburned paper, and ash; coal fly ash; and a binder such as sodium silicate. Other binders said to be suitable substitutes for the sodium silicate are liquid extract, lignin sulfonate, lignin ammonium sulfonate, paraffin, starch, cellulosegum, methyl cellulose, and polyvinyl alcohol. No clay is included in the raw batch. In fact, conventional clay bricks were distinguished from the products disclosed in the patent in view of the clay brick's relatively low compressive strength and relatively high firing temperatures.
One disadvantage of tile formulations which include glass and clay, however, is the relatively high cost of these components. In particular, and depending upon the quality desired in the final ceramic product, the purity of the glass will impact the physical properties of the final product. One of the purest recycled glasses available is recycled soda lime silicate glass which, unfortunately, is quite expensive.
One glass-based ceramic product presently available which uses recycled soda lime silicate glass is Traffic Tile, manufactured by Stoneware Tile Company of Arlington Heights, Ill. This product comprises recycled soda lime silicate glass, clay, sand, and feldspar.
Moreover, glazing such glass-based ceramic tiles has also been problematic. Among other problems, those in the art have experienced difficulties in making the glazing formulation adhere to the glass-based green tile substrate. Adding to these problems is that there are no glazing formulations which are universal to every type of tile. Each type of tile formulation must be mated with a particular glazing formulation.
Thus, a need exists for a ceramic tile, and related method for its preparation, which exhibits the commercially-desirable characteristics of glass-based ceramic tiles, but at a lower cost. Moreover, it is particularly desirable that a new ceramic tile be able to meet established industry standards for conventional ceramic tiles, e.g., ANSI A 137.1. A need further exists for a glazing formulation that will adhere to such tiles and provide a uniformly glazed tile product after firing.
In view of those needs, one object of the present invention to provide a ceramic tile, and related method for its preparation, which exhibits the commercially-desirable characteristics of glass-based ceramic tiles, but at a lower cost.
A further object of the present invention is to provide a ceramic tile that is able to meet established industry standards, e.g., ANSI A 137.1.
Yet another object of the present invention is to provide a glazing formulation that will adhere to the new ceramic tiles and provide a uniformly glazed tile product after firing.
These and other objects and advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.