Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
1999-06-15
2001-05-29
Wood, Elizabeth D. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S645000, C106S646000, C106S650000, C106S651000, C106S653000, C106S654000, C106S674000, C106S675000, C106S678000, C106S680000, C106S735000, C106S736000, C106S788000, C106S792000, C106S796000, C106S799000
Reexamination Certificate
active
06238476
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to drywall joint compound and, more particularly, to a method of reducing the time required to finish drywall joints or to repair plaster walls using ready-mixed drywall joint compound.
BACKGROUND OF THE INVENTION
Gypsum board, also known as sheetrock or drywall, is widely used in the construction, remodeling and repair of residential homes, commercial buildings, and the like. Drywall is available in various sizes, such as 4×8 foot or 4×12 foot sheets that are typically ½ or ⅝ inches thick. The drywall is generally attached to the wood or steel studs of the infrastructure by nails or screws. Because joints are formed when the drywall is hung, these joints must be covered using drywall joint compound and drywall tape in order to provide an acceptable finish before paint or wallpaper is applied to the walls.
Conventional drywall joint compound is available in dry powder or “ready-mixed” form. Commonly available ready-mixed drywall joint compound products include SHEETROCK® All Purpose Joint Compound, which is available from United States Gypsum Company of Chicago, Ill., and GOLD BOND® All Purpose Ready Mix Joint Compound, which is available from National Gypsum Company of Charlotte, N.C. SHEETROCK® brand joint compound consists primarily of the following ingredients: (1) limestone, chemically known as calcium carbonate (CaCO
3
), or dolomite (CaMg(CO
3
)
2
) or gypsum (CaSO
4
.2H
2
O); (2) water; (3) mica (silicates of varying chemical composition); (4) ethylene-vinyl acetate polymer or vinyl acetate polymer; (5) attapulgite clay (hydrated aluminum silicates); and (6) trace amounts of vinyl acetate monomer, acetaldhyde and crystallized silicon dioxide (quartz). United States Gypsum SHEETROCK® may also include talc (a hydrous magnesium silicate) and pyrophyllite. National Gypsum GOLD BOND® brand joint compound consists primarily of the following ingredients: (1) calcium carbonate; (2) quartz; and (3) water. GOLD BOND® may also include mica, talc, perlite, attapulgite clay, various polymers and various monomers.
The conventional procedure for finishing drywall joints is well known in the art.
Typically, the ready-mixed joint compound already contains the proper amount of water. If not, water can be added to the drywall joint compound to produce the desired consistency for a particular application. Regardless, the joint compound should be stirred vigorously before applying it to the drywall. A 4 to 6 inch joint finishing knife is used to place a first coat of joint compound in the joint. Drywall tape is placed over the joint and pressed into the joint compound using the knife. Usually, about 24 hours must be allowed for the first coat to dry thoroughly. A second coat of joint compound is applied over the first coat that extends a few inches beyond the edges of the tape on both sides. Again, the second coat usually requires about 24 hours to dry thoroughly. A 10-inch joint finishing knife is then used to apply a third and final coat. The total width of the third coat is typically about 12-14 inches. After the final coat dries, it is sanded to a smooth finish and any dust is wiped off prior to painting or applying wallpaper. Nail holes are also filled in with the joint compound and sanded, as necessary.
A major disadvantage of the conventional method for finishing drywall joints is the extended time that is required for the drywall joint compound to dry thoroughly. Because of the 24-hour drying time required between coats, the overall time needed to finish drywall joints is significant, typically two or more days. If necessary, sanding the final coat of the drywall joint compound further increases the overall time needed to finish the drywall joints. Additionally, sanding creates a potential health hazard due to the significant amount of dust generated during the sanding process. Therefore, a method of reducing the drying, or curing, time of the drywall joint compound and of eliminating the need for sanding the final coat would be a great improvement over the art. Such a method would reduce drywall construction labor costs and reduce overall drywall construction time. The method would be especially valuable in remodeling and repairing buildings which must be occupied during the remodeling or repair process.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method for reducing the curing time of drywall joint compound in order to minimize the time required to finish drywall joints and to repair plaster walls using drywall joint compound.
It is another object of the present invention to provide a method for eliminating the need for sanding the final coat of drywall joint compound, thereby eliminating a potential health hazard.
These and other objects are provided by a method, according to the present invention, of reducing the time required to finish drywall joints using drywall joint compound which comprises the step of mixing a predetermined amount of a drying agent to ready-mixed drywall joint compound, or to drywall joint compound with the proper amount of water added, to reduce the curing time of the drywall joint compound. In a preferred embodiment, the drying agent is selected from a mixture of the group of compounds consisting of plaster of Paris, calcium carbonate, gypsum, crystallized silicon dioxide (quartz), Portland cement, perlite, lime, hydroxy ethyl ether of cellulose, polyvinyl alcohol, starch, wood fiber, potassium naphthalene sulfon, aluminum sulfate, sodium citrate, ammonium tartrate, hydrolyzed protein, monosodium phosphate, sodium naphthalene sulfonate, potassium sulfate and various trace materials.
In a preferred embodiment of the invention, plaster of Paris is selected as the drying agent to be mixed with the drywall joint compound. A small amount of water may be added to facilitate the mixing process without adversely affecting the curing time. In another preferred embodiment, the drying agent is a mixture of plaster of Paris and quartz. Again, a small amount of water may be added to facilitate the mixing process without adversely affecting the curing time. The drying agent mixture preferably comprises about 80 parts plaster of Paris and about 1 part quartz, preferably in powdered form. A commercially available example of such a drying agent mixture is GOLD BOND® Moulding Plaster sold by Gold Bond Building Products, a division of National Gypsum Company of Charlotte, N.C. The drying agent mixture may further comprise perlite or Portland cement, or both.
In another preferred embodiment, a plaster of Paris and calcium carbonate mixture in the form of a moulding plaster is selected as the drying agent for mixing with the drywall joint compound. Again, a small amount of water may be added to facilitate the mixing process without adversely affecting the curing time. In this preferred embodiment, the drying agent mixture comprises at least about 80 parts plaster of Paris and less than about 5 parts calcium carbonate. A commercially available example of such a drying agent is USG® Moulding Plaster sold by United States Gypsum Company of Chicago, Ill. The drying agent mixture may further comprise less than about 5 parts of Portland cement, less than about 3 parts lime and less than about 2 parts each of hydroxy ethyl ether of cellulose, polyvinyl alcohol, starch and wood. The drying agent mixture may further comprise less than about 1 part each of potassium naphthalene sulfon, aluminum sulfate, sodium citrate, ammonium tartrate, hydrolyzed protein, monosodium phosphate, sodium naphthalene sulfonate, potassium sulfate and methylhydroxypropyl cellulose. The drying agent mixture may further comprise trace amounts each of calcium lignosulfonate, sodium potassium tartrate, tributyl phosphate and alkyl ether sulfate.
According to one preferred embodiment of the method of the present invention, about 1 pound of the drying agent is mixed with between about 5 to about 50 pounds of drywall joint compound, and preferably with about 26 pounds of drywall
Dremann Christopher C.
Wood Elizabeth D.
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