Compositions: coating or plastic – Coating or plastic compositions – Alkali metal silicate containing
Reexamination Certificate
1997-12-31
2001-09-11
Marcantoni, Paul (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Alkali metal silicate containing
C106S601000, C106S796000, C106S800000, C501S133000
Reexamination Certificate
active
06287378
ABSTRACT:
FIELD OF INVENTION
The present invention relates to glass making compositions and methods. More particularly, the present invention relates to an alkali metal precursor material made from calcium oxides and magnesium oxides, water and sodium silicates, such as silica sand. Such material is particularly useful in glass making and affords using lower energy with less volatiles associated with conventional production batches.
BACKGROUND OF THE INVENTION
Glass can be produced from glass formers, which can be theorized under the random-network theory of glass as material having heavy cation - oxygen bond strengths greater than about 335 kilo Joules per mole. Typical formers are oxides such as B
2
O
3
, SiO
2
, GeO
2
, P
2
O
5
, As
2
O
5
, P
2
O
3
, As
2
O
3
, Sb
2
O
3
, V
2
O
5
, Sb
2
O
5
, Nb
2
O
5
, and Ta
2
O
5
. The fluoride BeF
2
also qualifies. Additional components can be mixed with glass formers to provide various effects. These components include glass intermediates, having bond strengths of about 250-350 kilo-Joules/mole, and which may or may not become part of the network; and glass modifiers, having bond strengths of less than about 250 kilo Joules per mole, and which do not become part of the network. Typical modifiers are oxides of gallium, magnesium, lithium, zinc, calcium, sodium and potassium. Other formers, intermediates and modifiers are known, as illustrated in “GLASS”,
Kirk-Othmer Encyclopedia of Chemical Technology
, vol. 12, pp 555+(
1994).
One form of glass is a silicate system containing modifiers and intermediates. Such silicates have a network of silicon to oxygen to silicon bonds. Use of a modifier, such as sodium oxide, can cleave these bonds by forming a silicon to oxygen to terminal sodium linkage. Other modifiers can be used. Such modifiers can make the glass more fluid, decrease resistivity, increase thermal expansion, lower chemical durability or increase flux.
Soda-lime glass is perhaps the most ubiquitous glass product. Such soda-lime glasses involve mixtures of alkali and alkali earths. These glasses can be produced using oxides of sodium, calcium, silicon, magnesium, aluminum, barium and potassium.
Most glass is manufactured by a process in which raw materials are converted at high temperatures to a homogeneous melt that is then formed. The raw materials used are typically sand, as the source of silicon; limestone or dolomitic lime, as the source of calcium and/or magnesium; and soda ash or caustic soda, as the source of sodium. The limestone is typically a high calcium limestone (95% calcite, CaCO
3
), aragonite mineral, or a dolomitic limestone (mixture of dolomite, CaMg(CO
3
)
2
, and calcite). The soda ash (sodium carbonate, Na
2
CO
3
) can be a Solvay process product or mineral deposit. Typical manufacturing processes involve the batch mixing of sand, soda ash, limestone and other materials at elevated temperatures above 1000° C.
There is a continued need for new processes and materials which facilitate the production of glass and which provide energy savings and increased production through-put.
RELATED ART
U.S. Pat. No. 5,004,706 discloses a method of making molten glass wherein silica is heated with a batch component comprising a sodium alkaline earth silicate which includes a major portion of the sodium in the resultant molten glass. The patent also discloses a batch component for use in glass manufacture, comprising sodium calcium silicate, and, optionally, sodium magnesium silicate. A method for producing a batch component comprising sodium calcium silicate is also disclosed, comprising heating a mixture of a source of sodium oxide, a source of silica, and either a source of calcium silicate or a source of calcium oxide at a temperature of greater than about 800° C., with a Na
2
O, CaO, and SiO
2
molar ratio of 1:1:1. The resulting batch components can be preheated without melting prior to mixing and feeding the furnace.
U.S. Pat. No. 4,920,080 discloses a method of making glass in which silica is reacted with sodium carbonate to form sodium silicate as a preliminary step. The resulting sodium silicate is combined with a calcium carbonate - containing batch material which has been preferably calcined to release carbon dioxide prior to contacting with the sodium silicate. The patent suggests that the process maximizes the recovery of waste heat from glass melting and that the resulting batch materials are substantially free of carbon dioxide which minimizes gaseous inclusions in the glass.
U.S. Pat. No. 4,023,976 discloses an improved process for making glass in which a glass batch is mixed with a binder, aged, compacted, and compressed into briquettes, which are heated to partially react the contents of the batch in a prereaction stage. This process minimizes segregation and non-uniformity in the glass batch, and reduces the operating temperature of the glass furnace.
U.S. Pat. No. 3,883,364 discloses a dust-free granular alkaline earth carbonate material particularly suited for feed stock for glass furnaces. The process for preparing the granular material involves combining a freshly prepared aqueous slurry of alkaline earth carbonate with a solution of alkali silicate, drying the slurry and sintering at temperature of about 700-900° C., thereby converting the aqueous slurry solids to a dense material which can be ground to a dust-free, free flowing form suitable for use as a feed stock in glass furnaces.
U.S. Pat. No. 3,967,943 discloses a method of improving glass batch melting by using sodium silicate water solution as a batch ingredient to supply from about 1% to about 10% of the total Na
2
O content, with conventional sodium-containing batch materials supplying the bulk of the Na
2
O content. The patent suggests that the addition of sodium silicate water solution enables a lower temperature and/or less fuel to be used in melting, results in lower dusting, and reduces the incidence of glass inhomogeneities or defects.
SUMMARY
The present invention is a method of producing a molten ceramic by use of a synthetic silicate, wherein the synthetic silicate is produced by mixing a slaked source of calcium and/or magnesium and a source of silicon dioxide. Preferably, the synthetic silicate can be made by a soluble silicate route or a silica sand route. Advantageously, the synthetic silicate can be formed into a cylindrical pellet.
In accord with one or more aspects, the invention provides energy savings and other benefits, including, but not limited to, reduced levels of evolved carbon dioxide and reduced foam formation in glass making processes, reduced impurities in formed glass, increased furnace pull rates, and customized elemental ratios in the produced glass and improved batch uniformity.
EMBODIMENTS OF THE PRESENT INVENTION
One embodiment of the present invention is a method of producing a molten ceramic comprising the step of admixing a slaked source of calcium and/or magnesium with a source of silicon dioxide to produce a silicate material (hereinafter “synthetic silicate”) comprising one or more compounds selected from the group consisting of calcium silicates, magnesium silicates and calcium magnesium silicates. This synthetic silicate can be a precursor material in the production of glass or other ceramic products. The synthetic silicate optionally contains free water which can be residual water from the slaking process producing the slaked source of calcium and/or magnesium. The method further comprises admixing under appropriate production conditions the synthetic silicate and a second source of silicon dioxide to produce a molten ceramic material. The second source of silicon dioxide can be the same as the source used to produce the synthetic silicate or can be a different source.
The molten ceramic produced is dependent upon the selection of materials and the corresponding ceramic production conditions. The molten ceramic is preferably a glass precursor suitable for making glass products including, but not limited to, glassware, glass bottles, glass windows (e.g. building, vehicular and the like), fiberglass, o
Fairchild George Henry
Hockman John Albert
Marcantoni Paul
Minerals Technologies Inc.
Morris Terry B.
Powell Marvin J.
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