Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2000-09-25
2002-12-31
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S077000, C522S079000, C522S080000, C522S081000, C522S090000, C522S097000, C522S109000, C522S110000, C522S111000, C522S182000, C522S120000, C522S121000, C522S134000, C522S135000, C522S142000, C522S144000, C522S007000, C522S011000, C522S015000, C522S016000, C522S024000, C522S025000, C522S026000
Reexamination Certificate
active
06500877
ABSTRACT:
TECHNICAL FIELD
The present invention relates to ultraviolet light (UV) curable paint compositions capable of producing coating with enhanced corrosion and weathering resistance.
BACKGROUND OF THE INVENTION
UV radiation curable paint compositions are applied to a substrate through spraying, screen printing, dipping or brushing for the protection or decoration of the substrate. In the usual application, a substrate such as metal, glass, or plastic is coated with the paint composition and then UV light is introduced to compete the curing process. The UV curable paint compositions offer many advantages over typical heat curable compositions.
Heat curable compositions require the use of organic solvents that contain a significant amount of volatile organic compounds (VOCs). These VOCs escape into the atmosphere while the heat curable composition dries. Such solvent based systems are undesirable because of the hazards and expenses associated with VOCs. The hazards include water and air pollution and the expenses include the cost of complying with strict government regulation on solvent emission levels. In contrast, UV curable compositions contain reactive monomers instead of solvents; thus eliminating the detrimental effects of the VOCs.
The use of heat curable compositions not only raises environmental concerns but other disadvantages exist with their use as well. Heat curable compositions suffer from slow cure times which lead to decreased productivity. These compositions require high energy for curing due to energy loss as well as the energy required to heat the substrate. Additionally, many heat curable compositions yield poor film properties that result in decreased value of the end product.
Although UV curable compositions exhibit superior properties and performance over their heat curable counterparts, UV curable compositions themselves suffer from certain disadvantages. Generally, UV compositions have high molecular weights and a substantial degree of cross linkage due to the highly reactive nature of the composition. As a result, many of these compositions suffer from low durability and resin shrinkage. With the use of many such compositions, an inordinately high amount of UV light is required to cure. New formulations that lessen these problems typically suffer from diminished abrasion, chemical, and scratch resistance as well as low thermal stability and adhesion.
An additional disadvantage of typical UV compositions is their lack of stability which results in dispersion. With some compositions, suspended solids fall out of solution after a period of one to two days. Dispersion adversely affects the gloss and clarity of the finished product. To combat this problem, new compositions have been formulated with higher viscosities which often lessen the flowability of the composition. These viscous formulations rule out spray application and provide for an unsuitably high dipping thickness.
Accordingly, there exists a need to provide environmentally safe UV curable paint compositions which exhibit improved appearance, weatherability, corrosion resistance and workability. Additionally, there is a need to provide a method of applying an improved composition which furthers the goal of improved performance.
SUMMARY OF INVENTION
It is an object of the present invention to provide an improved paint composition that is curable by ultraviolet light.
It is another object of the present invention to provide an improved paint composition that can be applied by spraying, screen printing, dipping, and brushing.
It is yet another object of the present invention to provide an improved paint composition that is capable of protecting metal surfaces from chemical corrosion and weathering.
It is still another object of the present invention to provide an improved paint composition that can be used to coat the metal parts in the undercarriage of an automobile.
It is still another object of the present invention to provide an improved paint composition that comprises at least one aliphatic acrylated oligomer that can be used to coat a metallic substrate such that no significant amount of volatile organic solvents do not become incorporated in the coating after the composition is cured.
The present invention discloses an ultraviolet light curable paint composition and method for making such a composition that may be used to produce a paint coating on a substrate. The disclosed composition does not contain any significant amount of volatile organic solvents that do not become incorporated in the coating after curing. Specifically, the paint composition contains 5% or less volatile organic solvents by weight. The disclosed invention provides a paint composition that is capable of protecting metal parts from chemical corrosion and weathering. In particular, automobile undercarriage components that are coated with the disclosed paint composition and then cured with ultraviolet light experience improved protection from the harmful effects of salt and adverse weather conditions. Further, the cured paint composition produces a coating with improved appearance and with improved resistance to rubbing off. Automobile undercarriage components include, but are not limited, to suspension swing arms, coil spring brackets, suspension stabilizers, frames, axles, and brake arms. The disclosed invention allows these automobile components to be coated more economically than the standard electronic primer coat basecoat and powder coat that is traditionally used in coating automobile undercarriage components.
In accordance with one aspect of the invention, an ultraviolet light curable paint composition is provided. The paint composition comprises a mixture of one or more aliphatic acrylated oligomers, wherein the aliphatic acrylated oligomer mixture is present in an amount of about 8% to 60% of the paint composition. All percentages of the paint composition as expressed in this document refer to the weight percentage of the stated component to the total weight of the paint composition.
The paint composition preferably comprises an isobornyl acrylate monomer in an amount of about 20% to 60% of the paint composition, optionally an adhesion promoter in an amount of 1% to 12%, a photoinitiator in an amount of about 1% to 16% of the paint composition, optionally, a flow promoting agent in an amount of about 0.1% to 6% of the paint composition, and a pigmented composition in an amount of 0% to 50%.
In accordance with yet another aspect of the invention, a method is provided for depositing or applying a paint coating on a substrate. The method comprises a first step of applying to the substrate a paint-containing fluid-phase composition (“paint composition”). Suitable methods of applying the paint composition to the substrate include spraying, screen-printing, dipping, and brushing. The paint composition comprises a mixture of aliphatic acrylated oligomers, wherein the aliphatic acrylated oligomer is present in an amount of about 8% to 60% of the paint composition. The paint composition also includes an isobornyl acrylate monomer in an amount of about 20% to 60% of the paint composition, a photoinitiator in an amount of about 1% to 16% of the paint composition, a flow promoting agent in an amount of about 0.1% to 6% of the paint composition, a pigmented composition in an amount of 0% to 50% of the paint composition, and optionally an adhesion promoter in an amount of 1% to 12%.
The method also includes a second step of illuminating the paint composition on the substrate with an ultraviolet light to cause the paint composition to cure into the paint coating.
In accordance with this method, the paint composition can be selectively deposited on the substrate at specific locations where paint plating is desired. The paint composition need not be applied to the entire substrate.
BEST MODE FOR CARRYING OUT THE INVENTION
Paint Compositions
Reference will now be made in detail to presently preferred compositions or embodiments and methods of the invention, which constitute the best modes of practicing the invention presently known
Brooks & Kushman P.C.
Krohn Industries, Inc.
McClendon Sanza
Nutter Nathan M.
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