Stock material or miscellaneous articles – Composite – Of carbohydrate
Reexamination Certificate
2002-09-17
2004-01-20
Green, Anthony J. (Department: 1755)
Stock material or miscellaneous articles
Composite
Of carbohydrate
C106S015050, C106S018320, C106S018350, C106S778000, C106S780000, C106S781000, C156S039000, C156S044000, C162S160000, C162S161000, C424S413000, C424S414000, C428S070000, C428S537500, C428S907000
Reexamination Certificate
active
06680127
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates generally to gypsum board and methods for making gypsum board. More specifically, the present invention relates to gypsum board possessing antifungal properties and methods of making same.
2. Description of Related Art
Gypsum board, which is sold as wall board and drywall, is a common building material used in various applications including interior walls, partitions and ceiling construction. Commercial gypsum board products are popular for a variety of reasons. They are durable, economical and fire-retardant. In addition, these boards provide excellent compressive-strength properties and a relatively low density. Finally, they are easily decorated and are therefore attractive as surfacing materials, especially for interior construction.
One fundamental limitation of traditional gypsum board products is their susceptibility to moisture absorption in damp environments. To minimize this problem, gypsum board is normally used in interior construction where exposure to moisture is limited. Unfortunately, products used in interior construction sometimes encounter water due to seepage, leaky roofs or pipes, flooding, condensation, and the like, arising out of construction defects or other events unrelated to the manufacture of the gypsum board. Thus, a number of mechanisms result in the exposure of gypsum board products to moisture. Once exposed to moisture, traditional gypsum board products are susceptible to fungal growth.
There is an ongoing need for gypsum board products that offer reduced susceptibility to fungal growth without compromising their beneficial properties. In addition, there is an ongoing need for commercially-viable manufacturing methods for such products. The present invention solves these problems by using an antifungal agent that effectively inhibits fungal growth, is compatible with gypsum board materials, and can be incorporated into a cost-effective and commercially-viable manufacturing process.
BRIEF SUMMARY OF PREFERRED EMBODIMENTS
The preferred embodiments of the present invention include a novel gypsum board comprising an effective amount of an antifungal agent such that fungal growth on or in the board is inhibited. According to a preferred embodiment of the present invention, the antifungal agent is cetylpyridinium chloride (CPC), a quaternary ammonium compound. Preferably, the gypsum board comprises from about 0.01 to about 1.5 weight percent CPC based on the dry weight of the gypsum in the board. More preferably, the gypsum board comprises between about 0.5 and about 1.0 weight percent CPC based on the dry weight of the gypsum in the board. According to some preferred embodiments, the CPC is encapsulated in an encapsulator so that it is released over time and/or upon exposure to moisture.
The preferred embodiments of the present invention also include methods of preparing the novel gypsum board described above. According to some preferred embodiments, CPC is incorporated onto or into the gypsum core by premixing CPC with the water, premixing the CPC with the gypsum powder, admixing the CPC with both the water and gypsum powder prior to or in the slurry mixer, and/or adding CPC to a mixed gypsum slurry via a secondary or in-line mixer. According to other preferred embodiments, a CPC solution is sprayed onto the front and/or back paper facings. According to other preferred embodiments, CPC is incorporated into the front and/or back paper facings as they are manufactured with or without the use of retention aids and/or coupling agents in the paper making process.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention derives from the discovery that an effective antifungal agent exhibits compatibility with gypsum board without diminishing the qualities of the gypsum board. Preferably, the mechanical properties of the gypsum board such as density, breakstrengths, bond strength, core end and edge hardness, modulus of flexibility and the like are substantially unchanged by the addition of the antifungal agent. By substantially unchanged, a given mechanical property preferably remains within the parameters of governing standards—e.g., ASTM standards. Consequently, the novel gypsum board product achieves the structural, economic and other benefits of gypsum board while also offering significant resistance to fungal growth. The novel gypsum board product can be prepared according to methods that are cost-effective and commercially viable.
The preferred embodiments of the present invention include a novel gypsum board comprised of a gypsum core, paper surfacing bonded to both sides of the core, and an antifungal agent. Any material suitable as a gypsum core is within the scope of the present invention. Therefore, without limiting the scope of the invention, the preferred embodiments comprise a gypsum core comprised of gypsum powder, water and optionally foam, pulp, starch and/or set controlling agents. Typically, the gypsum core is sandwiched between two sheets that are commonly referred to as the front and back paper facings. The front paper facing is generally a light-colored, smoothly textured paper designed to face into the interior of the building. The back paper facing, in contrast, is typically a darker, less smoothly-textured paper designed not to be seen. Any material suitable as a front and/or back paper facing is within the scope of the present invention. Therefore, without limiting the scope of the invention, the preferred embodiments comprise front and back paper facings comprised of a cellulosic material.
The preferred embodiments of the present invention also employ an antifungal agent, as used herein meaning and including all agents, materials, and combinations thereof providing antimicrobial activity. Preferred antimicrobial agents are those of the type and in an amount effective for inhibiting the growth and/or formation of microbes such as bacteria and/or fungi. Any known antifungal agent compatible with gypsum board composition and manufacturing processes and providing the desired biocidal, antifungal, antimycogen, antibacterial, and/or like activity in the gypsum board may be employed with the present invention. As will be readily apparent to one of skill in the art, a variety of antifungal agents are known including, for example, chlorhexidine, alexidine, cetylpyridinium chloride, benzalkonium chloride, benzethonium chloride, cetalkonium chloride, cetrimide, cetrimonium bromide, glycidyl trimethylammonium chloride, stearalkonium chloride, hexetidine, triclosan and triclocarban. A preferred class of antifungal agents is quaternary ammonium compounds, including but not limited to the following compounds:
Fluoride:
Tetra-n-butylammonium Fluoride
Tetraethylammonium Fluoride
Chloride:
Acetylcholine Chloride
(3-Acrylamidopropyl)trimethylammonium Chloride
Benzalkonium Chloride
Benzethonium Chloride
Benzoylcholine Chloride
Benzylcetyldimethylammonium Chloride
N-Benzylcinchonidinium Chloride
N-Benzylcinchoninium Chloride
Benzyldimethylphenylammonium Chloride
Benzyldimethylstearylammonium Chloride
N-Benzylquinidinium Chloride
N-Benzylquininium Chloride
Benzyltri-n-butylammonium Chloride
Benzyltriethylammonium Chloride
Benzyltrimethylammonium Chloride
Carbamylcholine Chloride
DL-Carnitine Hydrochloride
Chlorocholine Chloride
(3-Chloro-2-hydroxy-n-propyl)trimethylammonium Chloride
Choline Chloride
n-Decyltrimethylammonium Chloride
Diallyldimethylammonium Chloride
Dichloromethylenedimethyliminium Chloride
Dimethyldistearylammonium Chloride
n-Dodecyltrimethylammonium Chloride
Girard's Reagent T
n-Hexadecyltrimethylammonium Chloride
Hexamethonium Chloride
Lauroylcholine Chloride
Methacholine Chloride
Methacroylcholine Chloride
(2-Methoxyethoxymethyl)triethylammonium Chloride
&bgr;-Methylcholine Chloride
Methyltriethylammonium Chloride
Myristoylcholine Chloride
n-Octyltrimethylammonium Chloride
Phenyltriethylammonium Chloride
Phenyltrimethylammonium Chloride
Phospho
Carroll Rodney B.
Conley & Rose, P.C.
Green Anthony J.
Temple-Inland Forest Products Corporation
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