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
1993-07-09
2001-05-22
Sellers, Robert E. L. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S108000, C525S113000, C525S117000, C525S123000, C525S125000, C525S127000, C525S166000, C525S167500, C525S176000
Reexamination Certificate
active
06235846
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to novel reactive coatings which can be cured at room temperature or force dried at temperatures ranging up to about 350° F. The coatings may be utilized as primers, topcoats or as clearcoats and/or basecoats in clearcoat/basecoat compositions. The combination of hydroxy-functional compounds, anhydride-functional compounds, and epoxy-functional compounds, especially cycloaliphatic epoxy compounds, provides fast reacting, durable coatings which minimize the toxicity problems which may be associated with other low temperature curing systems.
2. Description of the Prior Art
One approach to high performance low temperature curing coatings has involved two component coatings comprising reactive isocyanates and active hydrogen containing compounds such as hydroxyl containing polymers or amine containing polymers to produce urethane or urea coatings. Although these materials have excellent performance and cure at low temperatures, the isocyanates may, under some conditions, be relatively hazardous to handle.
Coating compositions comprising reactive combinations of epoxy containing compounds and compounds having acid or amine functionality are known in the art. Similarly, coating compositions comprising cyclic anhydrides and hydroxy-functional compounds are also known in the art. The prior art has not, however, taught the combination of anhydride-functional compounds, epoxy-functional compounds, and hydroxy-functional compounds to provide low temperature curing coatings having excellent durability and performance.
BRIEF SUMMARY OF THE INVENTION
This invention involves a curable composition which comprises: (i) a hydroxy-functional compound having an average of at least two hydroxyl groups per molecule; (ii) an anhydride-functional compound having an average of at least two cyclic carboxylic acid anhydride groups per molecule; and (iii) an epoxy-functional compound having an average of at least one and, preferably, at least two epoxy groups per molecule. At least one of the compounds (i), (ii), or (iii) should comprise a film forming polymer. The term “compound” is used in its broadest sense to include monomers, oligomers, and polymers. The term “film forming polymer” means any polymeric material that can form a film from evaporation of any carrier or solvent.
It its most preferred formulation, this invention relates to curable compositions wherein the hydroxy-functional compound is a polymer prepared by the free radical addition polymerization of one or more monomers, at least one of which contains or can be reacted to produce a reactive hydroxyl group; and wherein the anhydride-functional compound is the addition polymerization product of at least one unsaturated monomer having anhydride functionality, especially maleic anhydride, and at least one other ethylenically unsaturated monomer; and wherein the epoxy-functional compound is a cycloaliphatic epoxy compound.
It is especially preferred to utilize the curable composition of this invention in combination with from about 5 to about 80%, and especially 5 to about 50%, by weight of an inert solvent, such as ketones, esters, and aromatic or aliphatic hydro-carbons. It is convenient to provide the coating composition as a two-component system wherein the anhydride-functional compound provides one package and the hydroxy-functional compound and the epoxy-functional compound provide a second package. The two components can be fixed prior to application to provide the curable coatings.
In one preferred application, this invention relates to coated substrates having a multi-layer decorative and/or protective coating which comprises:
(a) a basecoat comprising a pigmented film-forming polymer; and
(b) a transparent clearcoat comprising a film-forming polymer applied to the surface of the basecoat composition;
wherein the clearcoat and/or the basecoat comprises the curable compositions of this invention.
Accordingly, it is an object of this invention to provide improved curable compositions having excellent reactivity at low temperatures. It is a further object of this invention to provide coating compositions which may be utilized as primers, topcoats or clearcoats and/or basecoats in clearcoat/basecoat compositions. Another object of this invention is to provide an improved two-component coating composition wherein one component comprises an anhydride-functional compound and the other component comprises a hydroxy-functional compound and an epoxy-functional compound. Another object of this invention is to provide coatings having excellent exterior durability and corrosion resistance. A further object of this invention is to provide improved coating compositions which can be cured at room temperature or force dried at elevated temperatures. These and other objects of the invention will become apparent from the following discussions.
DETAILED DESCRIPTION OF THE INVENTION
1. Hydroxy-Functional Compounds
The hydroxy-functional compounds which are useful in the practice of this invention have an average of at least two hydroxyl groups per molecule. Although low molecular weight diols and polyols such as propylene glycol, 1,6-hexanediol triethanol amine, and pentaerythritol can be utilized in the practice of this invention, it is especially preferred to utilize polymeric hydroxy-functional compounds such as polyethers, polyesters, acrylics, polyurethanes, polycaprolactones, etc.
Preferably the hydroxy-functional polymer will have a number average molecular weight of at least about 400. Typical number average molecular weights will range from about 400 to about 30,000, and especially 500 to about 7,000. In order to provide the fastest rate of reaction during cure it is preferred in the practice of this invention to utilize hydroxy-functional compounds having predominantly, and preferably all, primary hydroxyl functionality.
Representative hydroxy-functional polymers include those described in Sections 1.1 through 1.5 below:
1.1. Polyether polyols are well known in the art and are conveniently prepared by the reaction of a diol or polyol with the corresponding alkylene oxide. These materials are commercially available and may be prepared by a known process such as, for example, the processes described in
Encyclopedia of Chemical Technology,
Volume 7, pages 257-262, published by Interscience Publishers, Inc., 1951. Representative examples include the polypropylene ether glycols and polyethylene ether glycols such as those marketed as Niax® Polyols from Union Carbide Corporation.
1.2. Another useful class of hydroxy-functional polymers are those prepared by condensation polymerization reaction techniques as are well known in the art. Representative condensation polymerization reactions include polyesters prepared by the condensation of polyhydric alcohols and polycarboxylic acids or anhydrides, with or without the inclusion of drying oil, semi-drying oil, or non-drying oil fatty acids. By adjusting the stoichiometry of the alcohols and the acids while maintaining an excess of hydroxyl groups, hydroxy-functional polyesters can be readily produced to provide a wide range of desired molecular weights and performance characteristics.
The polyester polyols are derived from one or more aromatic and/or aliphatic polycarboxylic acids, the anhydrides thereof, and one or more aliphatic andlor aromatic polyols. The carboxylic acids include the saturated and unsaturated polycarboxylic acids and the derivatives thereof, such as maleic acid, fumaric acid, succinic acid, adipic acid, azelaic acid, and dicyclopentadiene dicarboxylic acid. The carboxylic acids also include the aromatic polycarboxylic acids, such as phthalic acid, isophthalic acid, terephthalic acid, etc. Anhydrides such as maleic anhydride, phthalic anhydride, trimellitic anhydride, or Nadic Methyl Anhydride (brand name for methylbicyclo[2.2.]heptene-2,3-dicarboxylic anhydride isomers) can also be used.
Representative saturated and unsaturated polyols which can be reacted in stoichiometric excess with the carbox
Babjak John R.
Harris Rodney M.
Marquart James A.
Shalati Mohamad D.
Katterle Paul R.
McDonald Robert E.
Sellers Robert E. L.
The Sherwin-Williams Company
Tsang Vivien Y.
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