Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-10-26
2002-05-21
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S444000, C524S445000, C524S448000, C428S703000
Reexamination Certificate
active
06391958
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to new “drywall” compositions and methods for making the same that are useful in the manufacture of wallboard for covering walls and ceilings in construction applications. More particularly, this invention is directed to a novel wallboard composition comprising a unique combination of synthetic binders selected for their ability to establish a strengthened permanent bond in the final dry state, in combination with an expanded mineral such as Perlite which largely reduces the amount of gypsum present in the wallboard product from what has been required by previous gypsum wallboard formulations. This reduction in the amount of gypsum present in the wallboard formulation in turn reduces the weight of the wallboard structure while maintaining its strength. Moreover, the synthetic binders uniquely cross-link with the expanded mineral to form a much stronger bond between the constituent components of the wallboard core material than that which has been available in previously utilized or known wallboard products. In a preferred embodiment, the lightweight, strengthened wallboard of the present invention also comprises a covering veneer that is applied to the top ply of the face paper to provide increased strength, moisture resistance, and fire retardency, and the back paper top ply is treated to provide increased flexural strength. Additionally, this invention relates to the unique manufacturing process to produce the wallboard composition of the present invention in order to create a lightweight, strengthened, moisture resistant, and fire retardant wallboard used to cover walls and ceilings in construction applications. Still further, this invention relates to the apparatus for manufacturing the wallboard composition of the present invention, including a method and apparatus for economically converting a standard gypsum wallboard manufacturing facility into a facility for manufacturing wallboard of the present invention.
2. Description of the Background
Conventional gypsum drywall has been utilized for approximately the past fifty years in the construction industry with gypsum comprising the primary core ingredient The manufacture of gypsum drywall is presently an expensive, complex, difficult, and tightly controlled manufacturing process. The gypsum wallboard manufacturing process today entails several elaborate steps with significant environmental concerns, both internally and externally, regarding the product itself and the manufacture thereof. An increasingly shortened supply of domestic gypsum rock remains available today, which has necessitated the development and usage of synthetic gypsum as a substitute. However, the production of synthetic gypsum requires an extremely complex synthetic gypsum production facility. Such facilities include FGD (flu gas desulferization) gypsum production plants which are required by the nature of the manufacturing process to be located next to power plant facilities. These power plants utilize high sulfur coal, which is predominate in the Eastern United States, to generate power. The waste produced by these power plants is classified and desulferized into synthetic gypsum. This synthetic gypsum is then calcined and used as a substitute for natural gypsum for use in the wallboard manufacturing process. Given the significant risk of detrimental long-term health effects of a waste slag and coal product, the processing and use of such synthetic gypsum has also fueled environmental concerns. It is an object of the present invention to provide a new and distinctly different environmentally safe class of wallboard for use in the construction industry that utilizes environmentally friendly synthetic adhesives.
The continuously depleting supply of gypsum coupled with the rising demand for wallboard products has caused the price of gypsum and gypsum-based products to rise substantially over recent years. In the field of gypsum wallboard composition, relatively low prices of materials have kept the core of gypsum wallboard unchanged for the better part of the 20th century. However, given the booming construction industry and the increasing demand for housing, the demand for wallboard products has significantly exceeded the available manufactured supply of wallboard. This increased demand has dramatically driven the costs of wallboard products upward. Likewise, the need to supplement the natural gypsum wallboard products with the more costly synthetic gypsum products have also driven up the costs of wallboard products. These increasing cost factors have established a need for a lightweight, strengthened, and re-engineered wallboard product that minimizes the amount of gypsum present in the wallboard formulation.
Attempts have been made in the past to both strengthen and lighten traditional wallboard products, but such efforts have evidenced the addition of substantial costs to the finished product. For example, attempts have been made in the past to use a very low percentage of an inorganic or synthetic binder in wallboard formulations, typically 1% to 2%, in an effort to slightly effect the strength of the wallboard product. However, the amount of binder required to substantially increase strength and remain cost effective has not been realized. As disclosed herein and as a part of the present invention, it has been found that by placing the equipment needed to polymerize the base components of the synthetic binder on-site at the wallboard manufacturing facility, manufacturing costs may be greatly reduced.
Modern gypsum wallboard manufacturing facilities are very expensive in and of themselves, comprising numerous pieces of complex manufacturing and material handling equipment. Traditionally, the removal of the gypsum rock from gypsum mines or quarries is more difficult than strip or surface mining the softer Perlite ore from the mountain or ranges. After mining, the harder and larger gypsum rocks are crushed and reduced to smaller sizes and conveyed to where these smaller rocks are crushed into tiny particles. Next, the crushed gypsum is processed through a complex Calcining system involving a roller mill, a Calcining kettle, an imp mill and/or GC mill to reduce the gypsum fines into a chalk-like gypsum aqueous slurry. This Calcining system and process is expensive as it involves flash-drying and heating the gypsum land plaster or gypsum slurry in order to remove much of the water from the material. Following this dehydration process, the gypsum stucco is stored in holding bins and fed into equipment such as a pin mixer and a screw type conveyer. Water is again added along with other ingredients such as foams, starches, cementious materials and other chemicals to form the final prepared gypsum slurry. The gypsum paste is then spread onto and compressed between facing and backing paper and is cut further down the line. Next, a complex high temperature kiln dries the green gypsum board for approximately one hour or more, which is begun at lower temperatures (approximately 250° F.), then to a higher temperature (approximately 600° F.), and down again to exit from the kiln at lower temperatures (approximately 200° F.), leaving the gypsum board virtually moisture-free. This complex system of processing and material handling equipment is extremely expensive, such that the start-up of a new facility to manufacture a new type of wallboard has in the past been cost prohibitive. It would therefore be advantageous to provide a means by which an existing manufacturing facility could be modified at little expense to produce a strengthened and lighter weight wallboard product.
Perlite and other minerals have previously been used in wallboard construction as a filler, and has likewise been used in a variety of other industrial uses, including abrasives, acoustical plaster and tile, charcoal barbecue base, cleanser base, concrete construction aggregates, filter aid, fertilizer extender, foundry ladle covering and sand additive, inert carrier, insulation board filler, loose-fill insulation, mo
Advanced Construction Materials Corp.
Cain Edward J.
Stone, Esq. Gregory M.
Whiteford Taylor & Preston L.L.P.
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