Paper making and fiber liberation – Processes and products – Multi-layer waterlaid webs or sheets
Reexamination Certificate
2002-07-23
2003-09-09
Griffin, Steven P. (Department: 1731)
Paper making and fiber liberation
Processes and products
Multi-layer waterlaid webs or sheets
C162S145000, C162S186000, C162S208000, C181S290000, C181S294000
Reexamination Certificate
active
06616804
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of mineral fiberboards. More particularly, the present invention relates to a laminate panel having a mineral fiberboard and a nodulated mineral wool overlay thereon and to a method of making the same.
BACKGROUND OF THE INVENTION
Acoustical ceiling tiles provide aesthetic appeal, acoustical modification or dampening, accessibility to space above the ceiling plane, and simple installation and removal. Yet, such ceiling tiles having these features must be produced at a low cost. To accommodate these features, ceiling tiles are constructed using strong but relatively inexpensive materials such as newsprint paper, perlite, clays, mineral wool, and binder, such as starch. Acoustical dampening, however, requires the tile to be porous, especially on the surface of the tile. Examples of porous ceiling tiles are described in U.S. Pat. Nos. 1,769,519, 4,911,788, and 5,071,511.
Presently, consumer interest is directed to the surface durability of ceiling tiles. Unfortunately, porous materials are not as durable as more dense materials. The consumer not only desires the acoustical dampening that porous materials provide, but also expects the ceiling tiles to be free of blemishes once installed. Additionally, the ceiling must remain blemish free after the panels have been removed to access the plenum space above the tiles.
Although ceiling tiles made from porous mineral fiberboard have acceptable noise reduction coefficients (NRC), porous mineral fiberboards are soft and can be damaged during installation or removal. For example, surface dents can be easily created in porous mineral fiberboard from an installer's finger pressure, and surface scratches can likewise be created from pushing a tile across a metal grid support structure. To improve the surface durability, the weight percentage of a few of the materials utilized in constructing the mineral fiberboard can be increased, especially the binder and the mineral wool. However, the resulting mineral fiberboard, and the ceiling tile formed therefrom, is heavy and expensive.
Alternatively, laminate structures have been utilized to provide the desired characteristics of acoustical dampening, surface durability, and light weight. For example, one such laminate structure is formed by placing a durable woven scrim of glass or polymer on to the porous mineral fiberboard. Although this laminate may provide the desired NRC and surface durability properties, it is expensive to manufacture. Laminate structures which do not employ a scrim are discussed in U.S. Pat. Nos. 3,283,849 and 3,444,956.
Despite existing ceiling tiles formed from mineral fiberboards, the need remains for a durable acoustical panel which provides acoustical dampening, has a durable surface, is light-weight, and is inexpensively produced. Further, there remains a need for a method of manufacturing such a panel. Accordingly, it is to the provision of a durable acoustical panel that meets these needs that the present invention is primarily directed.
SUMMARY OF THE INVENTION
This invention overcomes the disadvantages of the prior art by providing a durable, lightweight acoustical panel which has a substantially smooth, durable surface, yet provides acoustical dampening at a relatively low manufacturing cost. The acoustical panel comprises a fiberboard comprising a fibrous filler and a base binder, and a nodulated overlay disposed on the fiberboard, wherein the overlay comprises nodulated wool and an overlay binder. In one embodiment of the present invention, the fibrous filler is mineral wool and the base binder is granular starch. In an another embodiment of the present invention, the nodulated wool is nodulated mineral wool and the overlay binder is cooked pearl cornstarch.
In another aspect of the present invention, a method of making the durable acoustical panel comprises forming an aqueous slurry comprising a fibrous filler, a base binder, and water; depositing the aqueous slurry onto a moving foraminous support wire to form an aqueous felt; de-watering the aqueous felt to form a wet felt; coating the wet felt with an aqueous overlay comprising nodulated wool, overlay binder, and water; and drying the wet felt and aqueous overlay to form the panel.
Thus, a unique durable acoustical panel and a method of making the same is now provided that successfully addresses the shortcomings of existing ceiling tiles and provides distinct advantages over such ceiling tiles. Additional objects, features, and advantages of the invention will become more apparent upon review of the detailed description set forth below when taken in conjunction with the accompanying drawing figures, which are briefly described as follows.
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Buhay Barry
Chamberlain Walter W.
Felegi, Jr. John
Foster Robert E.
Ganse Robert G.
AWI Licensing Company
Griffin Steven P.
Hug Eric
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