Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
1999-02-16
2003-05-20
Seidleck, James J. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of polyamidoester
C428S423300, C428S423500, C428S423700, C428S427000, C428S427000, C428S475200, C428S480000, C428S424400, C428S475800, C428S500000
Reexamination Certificate
active
06565978
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to aqueous coating compositions and, more particularly, to their use in multi-component composite coating compositions as primers or pigmented or colored base coats overcoated with transparent 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. Achieving good appearance in popular “metallic look” coatings is particularly challenging. To achieve optimum appearance, the metallic pigment flake should be oriented such that it is parallel to the coated surface so that the visual change in brightness or lightness of the metallic flake with a change in viewing angle (flop) accentuates the lines and curves of the automobile. It is also very important that the metallic pigment be uniformly oriented across the surface of the substrate, otherwise blotchy areas of light and dark color (mottling) will be observed.
Waterborne coating compositions also are sensitive to application conditions. It is often difficult to consistently obtain smooth films free of solvent popping when the coating composition is applied over a wide range of relative humidities. At high humidity, mottling of the film is frequently observed. Wetting of the clearcoat over the basecoat and recoatability and color matching for repair of defects are other challenges in formulating waterborne coating compositions.
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 film having good flop under a variety of application conditions.
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 basecoat film-forming composition comprising: (a) at least one crosslinkable film-forming resin; and (b) at least one amphiphilic alcohol having the structural formula (I):
HO—R (I)
wherein R comprises a linear hydrocarbon segment having at least seven contiguous carbon atoms, the amphiphilic alcohol being present in an amount ranging from about 0.01 to about 50 weight percent based upon total amount of resin solids of the basecoat 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 can be used as any of the waterborne compositions useful in coating applications, and is particularly useful in automotive coating applications. The multi-component composite coating composition can be used as a colored base coat layer overcoated with a transparent topcoat layer in a “color-plus-clear” composite coating system.
The basecoat coating composition comprises one or more crosslinkable film-forming resins and one or more amphiphilic alcohols present in an aqueous medium.
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 basecoat composition.
Suitable acrylic polymers include 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 hydroxy alkyl 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.
Acrylic polymers can be prepared via aqueous emulsion polymerization techniques and used directly in the preparation of the aqueous coating composition, or via organic solution polymerization techniques with groups capable of salt formation such as acid or amine groups. Upon neutralization of these groups with a base or acid, the polymers can be dispersed into aqueous medium.
As discussed above, the crosslinkable film-forming resin can be an alkyd resin or a polyester. Such polymers can be prepared in a known manner by condensation of polyhydric alcohols and polycarboxylic acids. Suitable polyhydric alcohols include ethylene glycol, propylene glycol, butylene glycol, 1,6-hexylene glycol, neopentyl glycol, diethylene glycol, glycerol, trimethylol propane and pentaerythritol. Suitable polycarboxylic acids include succinic acid, adipic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid and trimellitic acid. Besides the polycarboxylic acids mentioned above, functional equivalents of the acids such as anhydrides where they exist or lower alkyl esters of the acids such as methyl esters can be used. Where it is desired to produce air-drying alkyd resins, suitable drying oil fatty acids can be used and include those derived from linseed oil, soya bean oil, tall oil, dehydrated castor oil, or tung oil. The polyesters and alkyd resins contain a portion of free hydroxyl and/or carboxyl groups which are available for further crosslinking reactions.
Polyurethanes can also be used as the crosslinkable film-forming resin of the basecoat coating composition. Useful polyurethanes include polymeric polyols which are prepared by reacting polyester polyols or acrylic polyols, such as those mentioned above, with a polyisocyanate such that the OH/NCO equivalent ratio is greater than 1:1 so that free hydroxyl groups are present in the product.
The organic polyisocyanate which is used to prepare the polyurethane polyol can be an aliphatic or aromatic polyisocyanate or mixtures thereof. Diisocyanates are preferred, although higher polyisocyanates can be used in place of or in combination with diisocyanates. Examples of suitable aromatic diisocyanates include 4,4′-diphenylmethane diisocyanate and toluene diisocyanate. Examples of suitable aliphatic diisocyanates include straight chain aliphatic diisocyanates such as 1,6-hexamethylene diisocyanate. Also, cycloaliphatic diisocyanates such as isophorone diisocyanate and
Pagac Edward S.
Rardon Daniel E.
Swarup Shanti
Altman Deborah M.
Bissett Melanie
PPG Industries Ohio Inc.
Seidleck James J.
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