Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-08-07
2004-03-02
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S200000, C525S217000
Reexamination Certificate
active
06699933
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to coating compositions based on non-aqueous dispersions of solid fluoropolymer particles in an organic solution of acrylic polymers.
The coatings, referred to as “organosols,” may be clear or pigmented (opaque) coatings, which may be applied to a variety of substrates. In particular, the present invention is directed to coating compositions that have a high solids content and relatively few ingredients. The coating compositions are easily manufactured and may be applied using a number of art recognized techniques.
2. Description of the Prior Art
Fluoropolymer dispersion coatings are known in the art and are disclosed in, for example, Canadian Patent No. 756,165 to Koblitz et al., U.S. Pat. No. 4,314,004 to Stoneberg, and European Patent No. EP 0 960 918 to Lin et al.
Fluoropolymer dispersion coatings are known to exhibit outdoor durability, chemical resistance, and acceptable mechanical properties. The performance features of fluoropolymer dispersion coatings have led to their extensive use, for example, in the exterior building panel market. Fluoropolymer dispersion coatings are typically applied by spray and roll coating or coil coating of flat sheet stock techniques. The coating film is formed by thermal fusion of the fluoropolymer particles in admixture with an acrylic resin.
Historically, fluoropolymer dispersion coatings exhibit a relatively high viscosity at relatively low volume solids content. Consequently, as much as 65 percent organic solvent by volume may be required to reduce the viscosity in order to facilitate application of the fluoropolymer dispersion coatings to a substrate.
The high level of volatile organic compounds (VOCs) of fluoropolymer dispersion coatings generally requires that the solvent vapors emitted by the wet film be captured and conveyed to a gas-fired incinerator or thermal oxidizer to destroy the VOCs. For example, the large amount of VOCs produced by coil coating flat metal sheet stock can limit the line speed of the coating application, or result in blistering of the film at higher film thicknesses. The incineration of the VOCs can also produce higher amounts of nitrogen oxide pollutants, particularly for fossil fuel-fired combustion processes.
U.S. Pat. No. 6,017,639 to Higginbotham et al. discloses a high solids thermoset fluorocarbon coating. However, the composition disclosed by Higginbotham et al. relies on expensive fluorinated surfactants or “hyperdispersants” as an essential element of the coating. The coating composition is relatively complex and includes a relatively long list of ingredients.
International Application No. WO 01/00739 to Zupancic et al. discloses a high solids thermoset fluorocarbon coating, which includes a “cross-linkable” acrylic resin. An additional required ingredient in the coating composition of Zupancic et al. is a cross-linking agent for the acrylic resin. The resulting film, although flexible and solvent resistant, provides only a modest degree of film hardness, as exemplified by the reported pencil rating of “F.”
There is a clear and well defined need for a higher solids, lower VOC content liquid fluoropolymer coating composition, which would allow for higher line speed application, reduced blistering tendency of the applied coating, and a reduced impact on the environment from VOCs. Furthermore, it would be considered by those skilled in the art to be an advance and particularly economically advantageous development if such a coating composition could be achieved by the blending of relatively few ingredients while providing a simple formulation that would be easily manufactured and readily reproducible.
SUMMARY OF THE INVENTION
The present invention is directed to a simple, high solids fluoropolymer coating composition having excellent solvent resistance, hardness, and flexibility properties. The present high solids fluoropolymer coating composition does not require or include costly hyperdispersants or additional cross-linking agents.
More particularly, the fluoropolymer coating composition of the present invention includes an aminoalkyl (meth)acrylate containing acrylic polymer, a fluorocarbon polymer, and a solvent.
The acrylic polymer includes one or more (meth)acrylate monomers and one or more aminoalkyl (meth)acrylate monomers described by the structure:
where Z is a divalent linking group; R
2
and R
3
are independently selected from H or C
1
-C
6
linear or branched aliphatic; and R
4
is H or CH
3
.
The present invention is also directed to methods of coating a substrate using the present fluoropolymer coating composition. The methods include coil coating, spray coating, and extrusion coating the present fluoropolymer coating composition to a substrate.
The present invention is further directed to substrates coated with the present fluoropolymer coating composition using any of the above-mentioned methods.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Other than in the operating examples, or where otherwise indicated, all numbers or expressions referring to quantities of ingredients, reaction conditions, etc. used in the specification and claims are to be understood as modified in all instances by the term “about.”
The terms (meth)acrylic and (meth)acrylate are meant to include both acrylic and methacrylic acid derivatives, such as the corresponding alkyl esters often referred to as acrylates and (meth)acrylates, which the term (meth)acrylate is meant to encompass.
The fluoropolymer coating composition of the present invention includes a fluorocarbon polymer, an aminoalkyl (meth)acrylate containing acrylic polymer, and a solvent. The aminoalkyl (meth)acrylate containing acrylic polymer may be a thermoplastic resin. In an embodiment of the present invention, the fluorocarbon polymer is present as a dispersed phase and a solution including the acrylic polymer in the solvent is present as a continuous phase.
The acrylic polymer includes one or more (meth)acrylate monomers and one or more aminoalkyl (meth)acrylate monomers described by the structure I:
where Z is a divalent linking group; R
2
and R
3
are independently selected from H or C
1
-C
6
linear or branched aliphatic; and R
4
is H or CH
3
.
The divalent linking group Z may be described as an ester having the structure —O—R
1
— or an amide having the structure —N(R
5
)—R
1
—, where R
5
is H or C
1
-C
6
linear or branched aliphatic, and R
1
may be C
1
-C
20
linear or branched aliphatic, aryl, alkylaryl, ethoxylated alkyl, ethoxylated aryl, ethoxylated alkylaryl, propoxylated alkyl, propoxylated aryl, and propoxylated alkylaryl.
In an embodiment of the present invention, the aminoalkyl(meth)acrylate monomer may be an N-t-butyl, aminoalkyl (meth)acrylate. A non-limiting example of a suitable aminoalkyl(meth)acrylate monomer is t-butylaminoethyl methacrylate.
Any suitable (meth)acrylate monomer may be used when preparing the aminoalkyl (meth)acrylate containing acrylic polymer of the present invention. Examples of suitable (meth)acrylates include, but are not limited to, methyl(meth)acrylate, n-butyl(meth)acrylate, t-butyl(meth)acrylate, and ethyl(meth)acrylate.
In an embodiment of the present invention, the acrylic polymer contains 90 to 99.99 percent by weight, preferably 92 to 99.9 percent by weight, more preferably 95 to 99.9 percent by weight, and most preferably 98 to 99.9 percent by weight (meth)acrylic monomers based on the total weight of acrylic polymer. The acrylic polymer contains 0.01 to 10 percent by weight, preferably 0.1 to 8 percent by weight, more preferably 0.1 to 5 percent by weight, and most preferably 0.1 to 2 percent by weight aminoalkyl (meth)acrylate monomers based on the total weight of acrylic polymer. The inclusion of the aminoalkyl (meth)acrylate monomer provides for improved fluorocarbon dispersions. The dispersions contain minimal large particles and have good Hegman grind values, typically not exceeding 5 or 6. When the level of the aminoalkyl (meth)acrylate monomers is too high, the coating may develop a yellow colo
Lauer Andrew J.
Millero, Jr. Edward R.
Montague Robert A.
Nguyen Diep
Nutter Nathan M.
PPG Industries Ohio Inc.
Uhl William J.
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