Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-01-04
2003-01-14
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C528S271000, C528S274000, C428S532000
Reexamination Certificate
active
06506823
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates broadly to nitrocellulose based coating compositions and is more particularly directed to such coating compositions possessed of low concentrations of Volatile Organic Compounds (hereinafter, “VOC”).
In the field of industrial finishing, particularly wood finishing, it is highly desirable that the coating compositions employed be rapidly curable to the finished state, thereby to minimize the time and expense required to produce finished coatings on the product to which the coating is applied. Industrial wood finishing involves protective coatings for such diverse products as furniture, cabinetry, joinery, millwork, flooring and miscellaneous coatings such as pencil lacquers, tool handle finishes, finishes for baseball bats and gun stocks. Traditional polymer based coating compositions are generally possessed of one or more detrimental characteristics which mitigate against their use in industrial finishing operations. Nitrocellulose lacquers are normally high in VOC and Hazardous Air Polluting Substances (hereinafter, “HAPS”) and are often slow to dry. Acid catalyzed nitrocellulose coating compositions are normally high in VOC and HAPS and, moreover, have finite pot lives requiring that the catalyzed batches thereof be entirely used within the alloted pot life. Alkyd urea compositions require heating and are generally slow to cure. Two part polyurethanes have finite pot lives and, while the coatings thereof are generally tough, they are often poor in sandability. Cellulose acetate butyrate compositions exhibit relatively low performance as protective coatings and, moreover, are high in VOC and HAPS. Oil modified polyurethanes are generally slow to cure and, in addition, often display relatively poor color properties. Moisture cured uralkyd coating compositions are slow to cure and are high in VOC. Acrylic coating compositions, which can be either solvent based or waterborne, generally provide finished coatings which, while sandable, are usually not tough and have poor resistance to scratching. When of the solvent based type, acrylic coating compositions also have high concentrations of VOC. Waterborne acrylic coatings are generally slow to dry, have limited aesthetic properties and tend to rust ferrous metal surfaces or to raise the fibers of wooden surfaces to which they are applied. Energy cured coating compositions, such as ultraviolet light or electron beam cured compositions have become more common in some industrial finishing markets. However, they, too, suffer from some limitations. For instance, urethane-acrylate compositions generally result in coatings which have relatively poor aesthetics and which have only poor to fair sandability. Epoxy coatings can display poor color characteristics and tend to yellow over time. Ultraviolet light cured acrylic coatings are not scratch resistant and have high shrinkage, thereby leading to poor adhesion to the substrate and facile crack propagation once the coated film is damaged. Acrylated urethanes can be employed to increase the toughness of acrylic coatings. However, the resulting coated films have poor sandability and hardness. Energy cured waterbased coatings must be dried prior to curing and, moreover, are possessed of the same rusting and fiber raising deficiencies mentioned above.
2. Description of Related Art
U.S. Pat. No. 5,496,589, Igarashi et al., issued Mar. 5, 1996 and assigned to Toagosei Chemical Industry Co., Ltd., discloses a radiation curable wood impregnant composition. This composition is made using long alkyloxy chains on methacrylates and is cured using ultraviolet (UV) or electron beam (EB) radiation. The cured impregnant composition is said to cure to a hardness of only about 4H.
U.S. Pat. No. 4,855,184, Klun et al., issued Aug. 8, 1989 and assigned to Minnesota Mining and Manufacturing Company, discloses a radiation curable protective coating composition which is applied in a solution of 40% butyl acetate, 20% propyl acetate and 20% n-propanol. Thus, the VOC concentration of the composition is high.
U.S. Pat. No. 4,565,857, R. J. Grant, issued Jan. 21, 1986 and assigned to Minnesota Mining and Manufacturing Company, discloses a radiation curable protective coating composition whose resinous content is comprised of cellulosic materials which are treated with isocyanatoethylmethacrylate in order to confer radiation curability thereto. The resin is coated onto a surface as a solution in organic solvents. Thus, the VOC concentration of the composition is high.
U.S. Pat. No. 6,057,033, W. L. Bilodeau, issued May 2, 2000 and assigned to Avery Dennison Corporation, discloses the use of cellulosic fibers and polyorganosilanes in the preparation of radiation curable release coating compositions. The resulting compositions are, therefore, low-surface energy coatings and their adhesion to substrates is inadequate to serve as protective coatings for the substrate.
OBJECTS OF THE INVENTION
It is a principal object of the invention to provide novel nitrocellulose based coating compositions.
It is another object of the invention to provide nitrocellulose based coating compositions having low VOC concentrations.
It is yet another object of the invention to provide nitrocellulose based coating compositions whose applied films are rapidly curable to the finished state.
It is still another object of the invention to provide nitrocellulose based coating compositions whose cured applied films have good adhesion and surface hardness properties.
It is another object of the invention to provide nitrocellulose based coating compositions whose cured applied films have good aesthetic and protective qualities.
It is another object of the invention to provide novel protective films formed from the nitrocellulose based coating compositions hereof.
Other objects and advantages of the present invention will, in part, be obvious and will, in part appear hereinafter.
BRIEF SUMMARY OF THE INVENTION
The coating compositions of the invention broadly comprise the following four components: nitrocellulose, a polymerizable reactive diluent whose homopolymers have a glass transition temperature of less than 25° C.; a polymerizable reactive diluent whose homopolymers have a glass transition temperature of greater than 25° C. and an acrylated urethane. The compositions of the invention comprise between about 3 and about 25 percent by weight of the nitrocellulose component; between about 10 and about 50 percent by weight of the polymerizable reactive diluent component whose homopolymers have a glass transition temperature of less than 25° C.; between about 25 and about 75 percent by weight of the polymerizable reactive diluent component whose homopolymers have a glass transition temperature of greater than 25° C and between about 5 and about 40 percent by weight of the acrylated urethane component. The compositions of the invention may also include between about 0.5 and about 5 percent by weight of thermal and/or photoinitiators and up to about 5 percent by weight of conventional coating composition additives. The protective films of the invention comprise the cured reaction products of the foregoing compositions.
DETAILED DESCRIPTION OF THE INVENTION
Nitrocellulose is the product of nitration of the hydroxyl groups on natural cellulose fibers. Preferably, in the practice of the present invention the nitrocellulose component utilized will be from about 10% to about 12.5% nitrated, thereby to maximize solubility of the nitrocellulose component in the reactive diluent components. The viscosity of the nitrocellulose component can reside within the range of commercially available nitrocellulose materials. The viscosity of nitrocellulose is conventionally provided in seconds and is tested in accordance with the standard method of ASTM Specification D301-50. Highly viscous nitrocellulose materials have viscosities within the range of about 30 and about 50 seconds while low viscosity materials have viscosities of less than one second. We generally prefer that the nitroce
Burns Elizabeth G.
Shearer Charles C.
Blaker Barry R.
Raffi & Swanson, Incorporated
Sanders Kriellion A.
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