Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
2000-09-05
2002-03-12
Yoon, Tae H. (Department: 1714)
Coating processes
With post-treatment of coating or coating material
Heating or drying
C427S372200, C428S447000, C428S522000
Reexamination Certificate
active
06355305
ABSTRACT:
TECHNICAL FIELD
The present invention is generally directed toward fluoroelastomer coating compositions and coatings and cured films therefrom. More particularly, the present invention is directed toward water-borne fluoroelastomer compositions having a technologically useful pot life, and that give rise to films having improved physical properties including adhesion and strength. Specifically, the water-borne fluoroelastomer coatings of the present invention contain a novel curative system that includes a blend of a stabilized siloxane curative with a non-stabilized silane curative.
BACKGROUND OF THE INVENTION
Fluoroelastomer coating compositions are well known. They typically comprise copolymers of vinylidene fluoride and hexafluoropropylene or terpolymers of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene.
Fluoroelastomers are well known for their heat, weather, solvent and chemical resistance. Furthermore, cured fluoroelastomer films typically exhibit good mechanical properties and adhere to a variety of surfaces. As a result of these properties, fluoroelastomer coating compositions are applied to protect a variety of surfaces including metals, plastics, rubbers, concrete, glass and the like.
Heretofore in the art, fluoroelastomer coating compositions have been applied by using organic solvent systems. Typical solvent systems employed ketones or ethers. Such solvents, however, are hazardous to use inasmuch as they are flammable, toxic, and volatile. Moreover, growing environmental concern over the use of such volatile organic compounds restricts the use of such compounds in various areas of the country. Finally, the pot life of the fluoroelastomer coating compositions employing such solvents is generally only a few hours. Pot life, as it will be used herein, refers to the time required for the fluoroelastomer coating composition to begin gelation.
Water-borne fluoroelastomer coating compositions are also known. For example, DuPont de Nemours Company, of Wilmington, Del. teaches aqueous dispersions of their fluoroelastomer, VITON®, with a polyamine curing agent. The pot life of such dispersions, however, is relatively short, generally only 2 to 5 days. Ausimont U.S.A. also teaches aqueous dispersions employing their fluoroelastomer, TECNOFLON®, with aliphatic amines as curing agents. As with the dispersions taught by DuPont, those employing aliphatic amines also have a relatively short pot life, on the order of only 3 to 5 days.
U.S. Pat. No. 4,399, 553 also teaches a water based fluoroelastomer coating composition containing partially or completely hydrolyzed aminosilane compounds, with or without additional amine compounds, as curing agents. These aqueous dispersions are taught to have a pot life of up to one month at 25° C.
Thus, although water based fluoroelastomer coating compositions are known, a need still exists for a water based fluoroelastomer coating composition having improved pot life, excellent stability, and which produces cured films with excellent adhesion to a wide variety of substrates.
SUMMARY OF INVENTION
It is therefore an object of the present invention to provide a fluoroelastomer coating composition as well as coatings and cured film therefrom.
It is another object of the present invention to provide a fluoroelastomer coating composition having a technologically useful pot life.
It is yet another object of the present invention to provide cured films of fluoroelastomer coating compositions having improved adhesion strength.
It is still another object of the present invention to provide fluoroelastomer coating compositions that are essentially devoid of volatile organic compounds.
Is another object of the present invention to provide cured films of fluoroelastomer coatings that exhibit good abrasion resistance.
It is yet another object of the present invention to provide fluoroelastomer coatings and cured films that have improved resistance against a wide variety of solvents and chemicals once cured.
It is still another object of the present invention to provide a fluoroelastomer coating composition that does not contain acid acceptors commonly used in fluoroelastomer compositions.
At least one or more of the foregoing objects, together with the advantages thereof over the known art relating to water-borne fluoroelastomer coating compositions and coatings and cured films therefrom, shall become apparent from the specification that follows, and are accomplished by the invention as hereinafter described and claimed.
In general the present invention provides a water-borne fluoroelastomer composition comprising an aqueous dispersion of a fluoroelastomer polymer, from about 2 to about 30 parts by weight per one hundred parts by weight of polymer of a curative system, said curative system having been formed by blending from about 6 to about 94 parts by weight of a stabilized siloxane and from about 94 to about 6 parts by weight of a non-stabilized silane, where said stabilized siloxane and said non-stabilized silane total about one hundred parts by weight of the curative system, from 0 to about 40 parts by weight of an additive filler per one hundred parts by weight of polymer, and sufficient water to provide a composition having a solids content of from about 10 to about 80 percent by weight of the total composition.
The present invention also includes a method for a fluoroelastomer film prepared by a process comprising the step of curing a water-borne fluoroelastomer composition of matter with a curative system that includes a mixture of a stabilized siloxane and a non-stabilized silane.
The present invention also includes a method for a fluoroelastomer film prepared by applying the composition to a substrate, wherein the fluoroelastomer composition includes an aqueous dispersion of fluoroelastomer polymer, from about 2 to about 30 parts by weight per one hundred parts by weight of polymer of a curative system, said curative system having been formed by blending from about 6 to about 94 parts by weight of a stabilized siloxane and from about 94 to about 6 parts by weight of a non-stabilized silane, where said stabilized siloxane and said non-stabilized silane total about one hundred parts by weight of the curative system, from 0 to about 40 parts by weight of an additive filler per one hundred parts by weight of polymer, and sufficient water to provide a composition having a solids content of from about 10 to about 80 percent by weight of the total composition, and curing the applied composition.
The present invention also includes a method for a water-borne fluoroelastomer composition comprising an aqueous dispersion of a fluoroelastomer polymer, from about 2 to about 30 parts by weight per one hundred parts by weight of polymer of a curative system, said curative system comprising a mixture of a stabilized siloxane and non-stabilized silane, from 0 to about 40 parts by weight of an additive filler per one hundred parts by weight of polymer, and sufficient water to provide a composition having a solids content of from about 10 to about 80 percent by weight of the total composition.
PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION
It has now been discovered that improved fluoroelastomer coating and cured fluoroelastomer films can be obtained from water-borne fluoroelastomer coating compositions containing a novel curative system. By water-borne, it is meant that the compositions are based on aqueous dispersions or latices of fluoroelastomer polymers. More specifically, it has been found that the use of the novel curative system of this invention provides for fluoroelastomer compositions having a useful pot life that yields coatings and cured films having improved properties over those coatings and films prepared from compositions that do not employ the novel curative. Accordingly, the present invention is generally directed toward water-borne fluoroelastomer compositions that include fluoroelastomer polymers, a novel curative system, and optional fillers, as well as coatings and cured films prepared from this water-borne fluoroelasto
Kirochko Pavel
Kreiner James G.
Lauren International, Inc.
Renner Kenner Greive Bobak Taylor & Weber
Yoon Tae H.
LandOfFree
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