Compositions: ceramic – Ceramic compositions – Composed of waste material
Reexamination Certificate
2000-01-31
2002-01-22
Group, Karl (Department: 1755)
Compositions: ceramic
Ceramic compositions
Composed of waste material
C501S002000, C501S005000, C501S032000, C065S173000, C065S134800, C065S144000
Reexamination Certificate
active
06340650
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is directed to ceramic products made from waste glass; raw batch formulations for making ceramic products from waste glass; and a method for making ceramic products from waste glass. Examples of ceramic products that can be made by the invention are tile and brick, but other ceramic products can also be made. The invention addresses two current problems: energy usage by the ceramic industry needs to be reduced; and new recycled-glass products are needed.
The ceramic industry consumes large amounts of energy, especially during the firing process. Firing temperatures greater than 1200° C. (2200° F.) are required to sinter typical ceramic raw materials into dense products. Modifications of the raw material formulations have led to reductions in firing temperatures, but the improvements are limited because of the types of raw materials used. Most traditional ceramic products, such as tile and brick, consist mainly of clay-based raw materials, which inherently require high firing temperatures. Other ceramic manufacturing steps, such as the drying processes, are also very energy intensive. Energy costs are a major portion of the total manufacturing costs, and thus new methods to reduce the amount of energy required will be a great benefit to the ceramic industry.
New products utilizing recycled waste glass are needed to further promote glass recycling, because only a limited amount of glass can be remelted to make new containers (currently the primary use of recycled glass). New products are especially needed that are less sensitive to contaminants in the glass, and that can be made from green or mixed-color waste glass. Research has been conducted and products developed using recycled glass as a ceramic raw material. However, processing problems have limited the developments, so that only a negligible amount of waste glass is currently utilized (excluding remelting to form new glass products). These problems occur because of inherent chemical and processing incompatibilities with traditional ceramic raw materials and manufacturing methods. These incompatibilities have greatly hampered the development of ceramic products from waste glass.
Waste glass in the invention refers to any industrial or post-consumer glass that is discarded. Any form of glass, such as containers (bottles, jars, etc.), plate glass, or fiber glass, can be used. Waste glass can be obtained from recycling companies or glass manufacturers. Most waste glass consists mainly of silicon, sodium, and calcium oxides (referred to as soda-lime glass) with other minor components, such as aluminum and magnesium oxides. Soda-lime glass compositions typically soften from about 650 to about 750° C. This unique softening behavior causes articles formed from fine powders of soda lime glass to densify by viscous-phase sintering at temperatures much lower than usually required to fire ceramic products. The invention utilizes the low-temperature densification behavior of soda-lime glass to reduce manufacturing costs by conserving energy and lowering equipment and maintenance expenses.
Water, clay, and some other common ceramic raw materials are inherently incompatible with sintering of soda-lime glass powder at low temperatures. This is because chemical species resulting from reaction of glass with water, or from decomposition of clay, volatilize in the temperature range where soda-lime glass softens. The volatile species become trapped in the densifying glass, which causes foaming and porous defects in the final product. Previous waste-glass based ceramic products have been made with the addition of water and clay. The porous defects that resulted were minimized by optimizing the processing parameters, but not eliminated. The following paragraphs describe the previous processing problems that have occurred when trying to use waste glass as a ceramic raw material.
Brown and Mackenzie [J. of Materials Science, Vol. 17, pp. 2164-2193, 1982] fabricated ceramic tile from recycled glass combined with clay and water. The fired properties were found to be greatly affected by the amount of clay and water added, because of variations in the amount of porosity that occurred. Low [J. of Materials Science, Vol. 15, pp. 1509-1517, 1980] demonstrated that special foaming agents, such as calcium carbonate, were not necessary to foam glass. The volatile species from decomposition of mica, similar to that in clays, combined with the glass-water reaction was all that was necessary to produce extreme foaming.
Liu, Li, and Zhang [Glass Technology, Vol. 32, No. 1, pp. 24-27, 1991] investigated processing recycled glass powder with organic binders and water. They reported that the binder (and water) content had to be kept low to prevent bubbling in the fired samples and “inferior chemical and physical properties.” Even with low water content, the densities of the fired samples indicate that some degree of foaming occurred. This work demonstrates the adverse effects that occur from reactions between glass powder and water, even when only small amounts of water are added without the addition of clay.
Several patents involve the use of recycled glass as a ceramic raw material. Shutt and Campbell [U.S. Pat. No. 3,963,506] combined ground waste glass with clay, crushed brick, and water to produce building panels and bricks. The fired material had open porosity, and problems of warpage and bloating, indicating that adverse glass-water reactions occurred. Mackenzie [U.S. Pat. No. 3,963,503] patented a method of making glass products from ground waste glass combined with a treating agent. The work mainly concentrated on foaming glass, and is typical of how much of the research on recycled glass ended up focusing on foamed glass to take advantage of the problems that occurred.
Boyce [U.S. Pat. No. 4,271,109] received a patent for a method of manufacturing ceramic insulators for electric lamp bases from mixing 25-45% crushed scrap glass with clay and wollastonite. After firing at 1050° C., densities of 1.9 g/cc resulted, which indicates that at least 20% porosity still remained. Cihon [U.S. Pat. No. 5,028,569] patented a batch formulation and method of producing a ceramic article from 60-85% soda-lime glass cullet combined with clay, flint, and a liquid (water was used in examples). He discussed problems that occurred because of reaction of glass with water.
Dutton [U.S. Pat. No. 5,244,850] patented a building material composed of 10-50% recycled glass combined with slate particles. Two processes were described. One involved melting the recycled glass, mixing in slate particles, and then pressing the molten mixture in a mold. In the second process, slate particles with or without recycled glass were mixed with an alkali-metal silicate water solution or suspension, such as sodium silicate (water glass), pressed in a mold, dried, and fired at 920 and 1050° C. Lingart [U.S. Pat. No. 5,536,345] patented a process for manufacturing natural stone-type, panel-shaped construction and decoration materials consisting of three layers; a bottom layer of sand, middle layer of a mixture of sand and crushed glass, and a top layer of crushed glass. The glass was crushed to 2-3 mm in size and mixed with at least 5% water. The layers were deposited in a mold and fired in the mold to 600-850° C., followed by an elaborate series of holds at different temperatures and careful cooling.
Golitz et al. [U.S. Pat. No. 5,583,079] patented a ceramic tile product composed of 25-50% glass mixed with fly ash, clay, and water. This work focused on lowering the cost of the raw materials by using fly ash. The pressed green tile was glazed and then fired at 970-1025° C. Greulich [U.S. Pat. No. 5,649,987] patented a process for producing tabular building and decorative materials similar to natural stone consisting of 85-98% glass mixed with water and various other components, such as sand and inorganic pigments. The mixture was deposited in a mold
Group Karl
Lo Jack
LandOfFree
Ceramic products made from waste glass, raw batch... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ceramic products made from waste glass, raw batch..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ceramic products made from waste glass, raw batch... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2827104