Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2000-08-18
2001-10-23
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C428S418000, C428S423100, C428S423300, C428S520000, C428S522000, C428S450000, C525S459000, C525S450000
Reexamination Certificate
active
06306505
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to aminoplast-curable film-forming (coating) compositions, and multi-component composite coating compositions comprising a pigmented or colored base coat and a transparent (clear) coat.
BACKGROUND OF THE INVENTION
Color-plus-clear coating systems involving the application of a colored or pigmented base coat to a substrate followed by the application of a transparent or clear topcoat to the base coat have become very popular as original finishes for automobiles. The color-plus-clear systems have outstanding gloss and distinctness of image. The clear coat is particularly important for these properties.
Coating compositions based on hydroxyl functional acrylic polymers and aminoplast crosslinking agents have been particularly desirable as automotive top coats because they exhibit excellent durability, hardness, gloss and appearance. Conventional coating systems that contain hydroxyl functional film-forming resins and aminoplast crosslinking agents rely on a cure mechanism wherein hydroxyl groups on the resin react with the aminoplast to form ether linkages. See, for example, European Patent Application 0 257 848. Historically, such coating systems have been vulnerable to acid attack and hence show poor acid etch resistance.
Because many geographic areas encounter acidic precipitation, acid resistance in coatings is becoming an increasingly desirable property, particularly for automotive coatings. When acidic rain water, also known as acid rain, accumulates on a horizontal section of an automobile such as a hood or trunk deck, it spots and can actually etch away the clear coat leaving a blemish that cannot be polished out. Hydroxyl-aminoplast coating systems of the prior art are not highly effective for providing protection against etching caused by acid rain.
Alternative curing systems can be used which provide improved acid etch resistance such as hydroxyl-isocyanate, epoxy-acid and carbamate-aminoplast; however, these systems are generally more costly than the hydroxyl-aminoplast coating systems, and in certain instances, lack some beneficial properties of hydroxy-aminoplast systems such as mar resistance or hardness.
It is an object of the present invention to provide a coating composition having improved acid etch resistance, utilizing inexpensive hydroxyl-aminoplast curing for use in a color-plus-clear composite coating system.
Surprisingly, it has been found that certain addition polymers derived from beta-hydroxy ester functional monomers can be cured with aminoplast crosslinking agents to yield acid etch resistant coatings.
SUMMARY OF THE INVENTION
In accordance with the present invention, a curable film-forming composition is provided which, when cured, yields a coating which is resistant to acid etching. The curable film-forming composition comprises:
A) a polymer having a weight average molecular weight of about 5000 to about 15,000 as determined by gel permeation chromatography using g a polystyrene standard, prepared from the following ingredients:
1) about 10 to about 70 percent by weight, based on the total solid weight of monomers used to prepare the polymer, of an ethylenically unsaturated, beta-hydroxy ester functional monomer of an ethylenically unsaturated acid functional monomer and an epoxy compound which is not polymerizable with the ethylenically unsaturated acid functional monomer;
2) about 5 to about 50 percent by weight, based on the total solid weight of monomers used to prepare the polymer, of an ethylenically unsaturated, hydroxyalkyl functional monomer;
3) about 15 to about 40 percent by weight, based on the total solid weight of monomers used to prepare the polymer, of a vinyl aromatic monomer; and
4) about 10 to about 60 percent by weight, based on the total solid weight of monomers used to prepare the polymer, of an alkyl ester of acrylic or methacrylic acid having 1 to 30 carbon atoms in the alkyl group; and
B) an aminoplast crosslinking agent.
A multi-component composite coating composition is also provided by the present invention. The coating composition comprises a base coat deposited from a pigmented film-forming composition and a transparent top coat applied over the base coat in which the transparent coat, or clear coat, is deposited from the curable film-forming composition described above.
DETAILED DESCRIPTION
The polymer used in the film-forming composition of the present invention comprises the free radical initiated polymerization reaction product of:
1) about 10 to about 70 percent, preferably about 10 to about 40 percent by weight, based on the total solid weight of monomers used to prepare the polymer, of a polymerizable ethylenically unsaturated, acid functional monomer and an epoxy compound typically containing at least 5 carbon atoms which is not polymerizable with the ethylenically unsaturated acid functional monomer;
2) about 5 to about 50 percent, preferably about 20 to about 40 percent by weight, based on the total solid weight of monomers used to prepare the polymer, of a polymerizable ethylenically unsaturated, hydroxyalkyl functional monomer, typically having from 2 to 4 carbon atoms in the hydroxyalkyl group;
3) about 15 to about 40 percent, preferably about 30 to about 40 percent by weight, based on the total solid weight of monomers used to prepare the polymer, of a vinyl aromatic monomer; and
4) about 10 to about 60 percent, preferably about 10 to about 20 percent by weight, based on the total solid weight of monomers used to prepare the polymer, of an alkyl typically an aliphatic alkyl or aryl ester of acrylic or methacrylic acid having 1 to 30, preferably 4 to 30, carbon atoms in the alkyl group and 6 to 30 carbon atoms in the aryl group. Polymerization is conducted in the presence of a free radical initiator.
Examples of ethylenically unsaturated acid functional monomers include monocarboxylic acids such as acrylic acid, methacrylic acid, and 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. Acrylic acid and methacrylic acid are preferred.
The epoxy compound does not contain ethylenic unsaturation which would participate in free radical initiated polymerization with the unsaturated acid monomer. Examples of such epoxy compounds are glycidyl esters and ethers, preferably those containing from 8 to 30 carbon atoms. Examples of glycidyl ethers are glycidyl ethers of alcohols and phenols such as butyl glycidyl ether, octyl glycidyl ether, phenyl glycidyl ether and para-(tertiary-butyl) phenyl glycidyl ether.
Examples of glycidyl esters are those of the structure:
wherein R is a hydrocarbon radical containing from about 4 to about 26 carbon atoms. Preferably, R is a branched hydrocarbon radical, more preferably a tertiary aliphatic group of about 8 to about 10 carbon atoms such as neopentanoate, neoheptanoate, and neodecanoate. Glycidyl esters of commercially available mixtures of tertiary aliphatic carboxylic acids such as those available from Shell Chemical Company as VERSATIC ACID 911 are particularly preferred. The glycidyl esters themselves are also commercially available from Shell Chemical Company as CARDURA E; and from Exxon Chemical Company as GLYDEXX-10. Examples of other epoxy compounds are 1,2-pentene oxide and styrene oxide.
The ethylenically unsaturated acid functional monomer and epoxy compound are typically in an equivalent ratio (acid to epoxy) of about 1:1. Higher or lower ratios can be used as desired.
The beta-hydroxy ester functional monomer may be prepared in several ways, for example (1) the ethylenically unsaturated acid functional monomer and epoxy compound can be pre-esterified prior to polymerization and the resultant reaction product addition polymerized by free radical initiated polymerization techniques; (2) the unsaturated acid functional monomer can be addition polymerized by free radical initiated polymerization techniques, typically along with one or more hydroxyalkyl functional monomers and one or more othe
Kish Daniel D.
Mauer George W.
Rush-Batista Melissa S.
PPG Industries Ohio Inc.
Tarazano D. Lawrence
Thibodeau Paul
Uhl William J.
LandOfFree
Acid etch resistant film-forming compositions and composite... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Acid etch resistant film-forming compositions and composite..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Acid etch resistant film-forming compositions and composite... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2566124