Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
1999-02-16
2001-11-13
Copenheaver, Blaine (Department: 1773)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C428S474400, C428S480000, C428S423100
Reexamination Certificate
active
06316119
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to aqueous coating compositions and, more particularly, to multi-component composite coating compositions including pigmented or colored basecoats overcoated with transparent or clear topcoats which provide good smoothness and appearance in automotive coating applications.
BACKGROUND OF THE INVENTION
Over the past decade, there has been a concerted effort to reduce atmospheric pollution caused by volatile solvents which are emitted during the painting process. However, it is often difficult to achieve high quality, smooth coating finishes, such as are required in the automotive industry, without using organic solvents which contribute greatly to flow and leveling of a coating.
One of the major goals of the coatings industry is to minimize the use of organic solvents by formulating waterborne coating compositions which provide a smooth, high gloss appearance, as well as good physical properties including resistance to acid rain. Unfortunately, many waterborne coating compositions do not provide acceptable appearance. A particularly acute problem is cratering or the development of small depressions in the surface of the coating. One solution to the cratering problem is to eliminate sources of contaminates in the coatings. However, it is generally impractical to eliminate sources of contamination in an industrial setting. Other coating appearance problems can be attributed to poor flow and leveling.
Another challenge to formulators of waterborne coatings is to provide good acid resistance, particularly battery acid resistance, while maintaining acceptable physical properties. Lack of humidity resistance or blushing is another problem facing waterborne coating formulators.
Therefore, it would be desirable to provide a waterborne coating composition which is useful as an original finish for automobiles and which can be applied as a smooth, acid resistant film under a variety of conditions with minimal cratering or blushing.
SUMMARY OF THE INVENTION
The present invention provides a multi-component composite coating composition comprising a basecoat deposited from an aqueous basecoat film-forming composition and a transparent topcoat applied over the basecoat in which the transparent topcoat is deposited from a topcoat film-forming composition, the topcoat film-forming composition comprising: (a) at least one crosslinkable film-forming resin; and (b) at least one amphiphilic adjuvant comprising: a water-soluble polar end comprising at least one terminal hydrophilic group selected from the group consisting of hydroxyl groups, carbamate groups, amide groups and urea groups; and a water-insoluble hydrocarbon end comprising at least six contiguous carbon atoms, wherein the adjuvant has an acid value of less than 30 and is present in an amount ranging from about 0.01 to about 25 weight percent on a basis of total resin solids of the topcoat film-forming composition. A substrate having a surface coating of the above multi-component composite coating composition is also provided.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The multi-component composite coating composition of the present invention is useful in a variety of coating applications, and is particularly useful in automotive coating applications. The multi-component composite coating composition comprises a basecoat layer and a transparent or clear topcoat layer formed from an aqueous topcoat coating composition which is applied over the basecoat.
The aqueous topcoat coating composition of the present invention comprises one or more crosslinkable film-forming resins and one or more amphiphilic adjuvants, which will be discussed in detail below.
Useful crosslinkable film-forming resins include acrylic polymers, polyesters, including alkyds, polyurethanes, polyamides, polyethers and copolymers and mixtures thereof. These resins can be self-crosslinking or crosslinked by reaction with suitable crosslinking materials included in the topcoat composition.
Suitable crosslinkable film-forming resins include acrylic polymers such as copolymers of one or more alkyl esters of acrylic acid or methacrylic acid, optionally together with one or more other polymerizable ethylenically unsaturated monomers. Useful alkyl esters of acrylic acid or methacrylic acid include aliphatic alkyl esters containing from 1 to 30, and preferably 4 to 18 carbon atoms in the alkyl group. Non-limiting examples include methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethyl acrylate, butyl acrylate, and 2-ethyl hexyl acrylate. Suitable other copolymerizable ethylenically unsaturated monomers include vinyl aromatic compounds such as styrene and vinyl toluene; nitriles such as acrylonitrile and methacrylonitrile; vinyl and vinylidene halides such as vinyl chloride and vinylidene fluoride and vinyl esters such as vinyl acetate.
The acrylic copolymer can include hydroxyl functional groups which are often incorporated into the polymer by including one or more hydroxyl functional monomers in the reactants used to produce the copolymer. Useful hydroxyl functional monomers include hydroxyalkyl acrylates and methacrylates, preferably having 2 to 4 carbon atoms in the hydroxyalkyl group, such as hydroxyethyl acrylate, hydroxypropyl acrylate, 4-hydroxybutyl acrylate, hydroxy functional adducts of caprolactone and hydroxyalkyl acrylates, and corresponding methacrylates. The acrylic polymer can be prepared with N-(alkoxymethyl)acrylamides and N-(alkoxymethyl) methacrylamides which result in self-crosslinking acrylic polymers.
The preferred crosslinkable film-forming resin comprises an acrylic polyol polymer. Such polymers can be prepared by polymerizing one or more ethylenically unsaturated beta-hydroxy ester functional monomers, one or more polymerizable ethylenically unsaturated, hydroxyalkyl functional monomers, and optionally one or more vinyl aromatic monomers, one or more alkyl esters of acrylic or methacrylic acid and at least one other ethylenically unsaturated monomer.
The beta-hydroxy ester functional monomer can be prepared from ethylenically unsaturated, epoxy functional monomers and carboxylic acids having from about 13 to about 20 carbon atoms or ethylenically unsaturated acid functional monomers and epoxy compounds containing at least 5 carbon atoms which are not polymerizable with the ethylenically unsaturated acid functional monomer.
Useful ethylenically unsaturated, epoxy functional monomers include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, methallyl glycidyl ether, 1:1 (molar) adducts of ethylenically unsaturated monoisocyanates with hydroxy functional monoepoxides such as glycidol, and glycidyl esters of polymerizable polycarboxylic acids such as maleic acid. Glycidyl acrylate and glycidyl methacrylate are preferred. Examples of carboxylic acids include saturated monocarboxylic acids such as isostearic acid and aromatic unsaturated carboxylic acids.
Useful ethylenically unsaturated acid functional monomers include monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid; dicarboxylic acids such as itaconic acid, maleic acid and fumaric acid; and monoesters of dicarboxylic acids such as monobutyl maleate and monobutyl itaconate. The ethylenically unsaturated acid functional monomer and epoxy compound are typically reacted in a 1:1 equivalent ratio. The epoxy compound does not contain ethylenic unsaturation which would participate in free radical-initiated polymerization with the unsaturated acid functional monomer. Useful epoxy compounds include 1,2-pentene oxide, styrene oxide and glycidyl esters or ethers, preferably containing from 8 to 30 carbon atoms, such as butyl glycidyl ether, octyl glycidyl ether, phenyl glycidyl ether and para-(tertiary butyl) phenyl glycidyl ether. Preferred glycidyl esters include those of the structure:
where R is a hydrocarbon radical containing from about 4 to about 26 carbon atoms. Preferably, R is a branched hydrocarbon group having from about 8 to about 10 carbon atoms, such as neopentanoate, neoheptanoate or neodec
Glas Djurdjica
Kosto Timothy J.
McMillan Robyn E.
Metzger Walter
Olson Kurt G.
Altman Deborah M.
Copenheaver Blaine
Paulraj Christopher
PPG Industries Ohio Inc.
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