Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2000-05-19
2002-02-26
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C525S100000, C525S124000, C525S192000, C525S222000, C525S223000, C525S330500, C526S279000, C528S032000, C528S045000, C252S389310, C427S387000
Reexamination Certificate
active
06350526
ABSTRACT:
TECHNICAL FIELD
This invention relates to high solids solvent based coating compositions and in particular to a clear coating composition for clear coat/color coat finishes for automobiles and trucks having improved resistance to etching from acid rain and other environmental pollutants.
BACKGROUND OF THE INVENTION
WO 96/34904 published Nov. 7, 1996 shows a curable coating composition having improved mar and abrasion resistance of polyepoxide and polyacid crosslinking agent, an acrylosilane polymer and an acrylic polyol polymer and a tricarbamoyl triazine compound as a crosslinking agent. The composition can be used as a monocoat over a primer or as a clear coat over a conventional base coat in a base coat clear coat finish. Mauer et at U.S. Pat. No. 5,565,243 issued Oct. 15, 1996 shows a process for applying a base coat plus clear coat finish to substrates such as conventionally used for automobiles and trucks in which the base coat which is pigmented and contains a tricarbamoyl triazine as a crosslinking agent.
There is a need for a coating composition that has improved acid etch resistance and mar and abrasion resistance.
SUMMARY OF THE INVENTION
A coating composition containing about 40-90% by weight of film forming binder and 10-60% by weight of an organic liquid carrier;
wherein the binder contains about
(a) about 50-90% by weight of an acrylosilane polymer containing about 30-95% by weight, based on the weight of the acrylosilane polymer, of polymerized monomers of the group of styrene, alkyl (meth)acrylates having 1-12 carbon atoms in the alkyl group, hydroxy alkyl (meth)acrylates having 1-4 carbon atoms in the alkyl group and any mixtures thereof, and 5-70% by weight, based on the weight of the polymer, of polymerized ethylenically unsaturated monomers containing reactive silane groups and the polymer has a weight average molecular weight of about 1,000-30,000;
(b) about 5-25% by weight of a non-aqueous dispersed polymer having
(i) a macromolecular core having a weight average molecular weight of about 50,000-500,000, and
(ii) attached to the macromolecular core, a plurality of macromonomer chains having a weight average molecular weight of about 1,000-30,000 of 5-30% by weight, based on the weight of the macromonomer, of polymerized ethylenically unsaturated monomers which having functional groups selected from the following epoxide, anhydride, isocyanate, silane, acid hydroxy, amide or any combination of these groups; and about 70-95% by weight, based on the weight of the macromonomer, of at least one other polymerized ethylenically unsaturated monomer without a crosslinking functionality; and
(c) about 5-25% by weight, of a crosslinking agent of tris(alkoxy carbonyl amino) triazine.
DETAILED DESCRIPTION OF THE INVENTION
The novel coating composition of this invention contains a combination of film forming components of an acrylosilane polymer, a non-aqueous dispersed polymer, referred to as a (NAD) polymer, and the crosslinking agent of tris(alkoxy carbonyl amino) triazine that provides improved resistance to acid etching from environmental air pollution and improved mar and abrasion resistance in comparison to conventional coating compositions containing acrylic polymers and melamine crosslinking agents.
Molecular weights are determined by GPC (gel permeation chromatography) using polystyrene as a standard.
The term (meth)acrylate refers to esters of both acrylic and methacrylic acids.
The coating composition of this invention is useful for finishing the exterior of automobile and truck bodies. Depending on its use, the present composition is capable of providing a coating which is durable, has excellent adhesion to basecoats, does not crack, does not deteriorate in terms of transparency under prolonged exposure to weather conditions, and imparts a superior glossy appearance for an extended period. Also, the coating composition offers a significant improvement over conventionally used coating compositions in terms of resistance to etching caused by environmental chemical attack.
A typical steel auto or truck body has several layers of coatings. The steel is typically first coated with an inorganic rust-proofing zinc or iron phosphate layer over which a primer coating is applied which typically is an electrocoated primer or can be a repair primer. A typical electrocoated primer comprises a cathodically deposited epoxy modified resin that is crosslinked with a polyisocyanate. A typical repair primer comprises an alkyd resin. Optionally, a primer surfacer can be applied over the primer coating to provide for better appearance and/or improved adhesion of the basecoat to the primer coat. A pigmented basecoat or colorcoat is next applied over the primer surfacer. A typical basecoat comprises a pigment, which may include metallic flakes in the case of a metallic finish, and polyester or acrylourethane as a film-forming binder. A clear topcoat (clearcoat) is then applied to the pigmented basecoat (colorcoat). The colorcoat and clearcoat are preferably applied to have thickness of about 0.1-3 mils and 1.0-5.0 mils, respectively. A composition of this invention, depending on the presence of pigments or other conventional components, may be used as a basecoat, clearcoat, or primer. However, a particularly preferred composition is useful as a clear topcoat to prevent environmental chemical attack to the entire finish. A clearcoat composition of the present invention may be applied over a basecoat composition of the present invention.
The film-forming portion of the coating composition of this invention, comprising polymeric components, is referred to as the “binder” or “binder solids” and is dissolved, emulsified or otherwise dispersed in an organic solvent or liquid carrier. The binder solids generally include all the normally solid polymeric non-liquid components of the total composition. Generally, catalysts, pigments, and non-polymeric chemical additives such as stabilizers are not considered part of the binder solids. Non-binder solids other than pigments usually do not amount to more than about 5% by weight of the composition. In this disclosure, the term binder includes the acrylosilane polymer, the NAD polymer, tris(alkoxycarbonyl amino) triazine and other crosslinking agents and all other optional film-forming polymers.
The coating composition contains about 40-90% by weight of the binder and about 10-60% by weight of an organic solvent or another liquid carrier. The binder of the coating composition contains about 50-90%, preferably 60-80%, by weight of a film-forming acrylosilane polymer.
The acrylosilane polymer portion of the binder has a weight average molecular weight of about 1,000-30,000, a number average molecular weight of about 500-10,000.
The acrylosilane polymer is the polymerization product of about 30-95%, preferably 50-90%, by weight ethylenically unsaturated non-silane containing monomers and about 5-70%, preferably 10-50% by weight ethylenically unsaturated silane containing monomers, based on the weight of the acrylosilane polymer. Suitable ethylenically unsaturated non-silane containing monomers are alkyl (meth)acrylates, styrene and any mixtures thereof, where the alkyl groups have 1-12 carbon atoms, preferably 3-8 carbon atoms.
Suitable alkyl (meth)acrylate monomers used to form the acrylosilane polymer are methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, isobutyl methacrylate, pentyl methacrylate, hexyl methacrylate, octyl methacrylate, nonyl methacrylate, lauryl methacrylate and the like; methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, pentyl acrylate, hexyl acrylate, octyl acrylate, nonyl acrylate, lauryl acrylate and the like. Cycloaliphatic (meth)acrylates also can be used, for example, such as trimethylcyclohlexyl methacrylate, trimethylcyclohexyl acrylate, iso-butyl methacrylate, t-butyl cyclohexyl acrylate, or t-butyl cyclohexyl methacrylate. Aryl (meth)acrylate and also can be used, for example, such as benzyl acrylate and benzyl methacrylate. Mixtures of the two or
Fox Michael D.
Johnson Jeffrey W.
Benjamin Steven C.
Dawson Robert
E. I. du Pont de Nemours and Company
Zimmer Marc S.
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