Stock material or miscellaneous articles – Composite – Of metal
Reexamination Certificate
1999-06-10
2001-08-07
Copenheaver, Blaine (Department: 1773)
Stock material or miscellaneous articles
Composite
Of metal
C428S461000, C428S520000, C428S522000, C525S303000
Reexamination Certificate
active
06270905
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to outer coatings for substrates and, more particularly to monocoats or multi-component composite coating compositions 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 that 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. If sufficient water is not removed during drying of the basecoat, the topcoat can crack, bubble or “pop” during drying of the topcoat as water vapor from the basecoat attempts to pass through the topcoat. Another challenge to formulators of waterborne coatings is to provide good acid resistance, particularly battery acid resistance, while maintaining acceptable physical properties.
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 popping.
SUMMARY OF THE INVENTION
The present invention provides a coated substrate having on at least a portion of a surface thereof an outer coating deposited from a film-forming composition, the film-forming composition comprising: (a) a crosslinkable, non-gelled acrylic polymer which is the reaction product of the following monomers: (i) a polyoxyalkylene acrylate monomer comprising a terminal alkoxy group containing about 1 to about 6 carbon atoms; and (ii) a copolymerizable ethylenically unsaturated monomer different from the polyoxyalkylene acrylate monomer (i); and (b) a crosslinking material capable of reacting with the acrylic polymer to form a crosslinked outer coating.
Another aspect of the present invention is a multi-component composite coating composition comprising a basecoat deposited from a pigmented basecoat film-forming composition and an outer coating applied over the basecoat in which the outer coating is deposited from the above film-forming composition. A substrate coated with the multi-component composite coating composition also is provided.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The coated substrates and multi-component composite coating composition of the present invention are useful in a variety of coating applications, and are particularly useful in automotive coating applications. In one embodiment, the transparent or opaque, clear or colored outer coating is present as a monocoat. In an alternative preferred embodiment, the outer coating is applied over a pigmented or colored basecoat layer to form a multi-component composite coating composition.
The waterborne, solventborne or powder film-forming composition used to form the outer coating comprises one or more crosslinkable, non-gelled acrylic polymers and one or more crosslinking materials capable of reacting with the acrylic polymer(s) to form a crosslinked outer coating. The film-forming composition forms a self-supporting continuous film on at least a horizontal surface of the substrate upon removal of any solvents or carriers present in the aqueous coating composition or curing at ambient or elevated temperature.
As used herein, “ungelled” or “non-gelled” means that the acrylic polymer is substantially free of crosslinking (before mixing and reaction with the crosslinking materials of the aqueous coating composition) and has an intrinsic viscosity of less than about 4.0 deciliters per gram, preferably less than about 2.0 deciliters per gram, and more preferably between ranging from about 0.1 to about 1.5 deciliters per gram when dissolved in a suitable solvent without depolymerization. The intrinsic viscosity of the acrylic polymer can be determined by art-recognized methods such as are described in
Textbook of Polymer Science,
Billmeyer, lnterscience Publishers, New York (1957) at pages 79-81.
The crosslinkable, non-gelled acrylic polymer is the polymerization reaction product of one or more polyoxyalkylene acrylate monomers and one or more copolymerizable ethylenically unsaturated monomers which are chemically different from the polyoxyalkylene acrylic monomers, i.e., have at least one element or amount of an element which is different from the polyoxyalkylene acrylic monomer. The acrylic polymer can be self-crosslinking, for example by forming the acrylic polymer from acrylic monomers capable of internally crosslinking such as n-butoxymethacrylamide, or crosslinked by reaction with suitable crosslinking materials included in the film-forming composition. The acrylic polymer can be cationic, anionic or nonionic, but is preferably anionic.
Generally, the polyoxyalkylene acrylate monomer comprises a backbone of repeating alkylene glycol units. The monomer is terminated at one end with an acrylate group and at the other end with an alkoxy group containing about 1 to about 6 carbon atoms. The polyoxyalkylene acrylic monomer can further comprise one or more pendant functional groups such as hydroxy, amido, carboxy, carbamate, urea, mercapto or urethane.
Preferably, the polyoxyalkylene acrylate monomer has a structure (including isomers thereof as shown in Formula (I) below:
wherein R
1
is H or CH
3
; R
2
is a terminal alkoxy group containing about 1 to about 6 carbon atoms, such as methoxy (preferred), ethoxy, butoxy, pentoxy and hexoxy; R′ is independently selected from H or CH
3
; m is an integer which can range from about 2 to about 4; and n is an integer which can range from about 2 to about 200, preferably ranges from about 3 to about 40 and more preferably ranges from about 4 to about 20.
Non-limiting examples of suitable polyoxyalkylene acrylate monomers include alkoxy polyoxyethylene acrylates, alkoxy polyoxyethylene methacrylates, alkoxy polyoxypropylene acrylates, alkoxy polyoxypropylene methacrylates, alkoxy polyoxyethyleneyoxypropylene acrylates, alkoxy polyoxyethyleneoxypropylene methacrylates and mixtures thereof. Preferably, the polyoxyalkylene acrylate monomer is methoxy polyoxyethylene methacrylate (also known as methoxy polyethylene glycol methacrylate).
The polyoxyalkylene acrylic monomer can comprise about 0.5 to about 80 weight percent of the monomers used to produce the acrylic polymer, preferably about 0.7 to about 20 weight percent, and more preferably about 1 to about 10 weight percent.
Suitable ethylenically unsaturated monomers which can be reacted with the polyoxyalkylene acrylic monomer include ethylenically unsaturated carboxylic acid monomers, alkyl esters of ethylenically unsaturated carboxylic acid monomers, hydroxyalkyl esters of ethylenically unsaturated carboxylic acid monomers, ethylenically unsaturated carbamates, ethylenically unsaturated ureas, ethylenically unsaturated urethanes, ethylenically unsaturated mercaptans, ethylenically unsaturated silanes, vinyl aromatics such as styrene and vinyl toluene, acrylamides, acrylonitriles such as acrylonitrile and methacrylonitrile, vinyl halides and vinylidene halides such as vinyl chloride and vinylidene fluoride, vinyl acetates, vinyl ethers, allyl ethers, allyl alcohols, vinyl esters such as vinyl acetate, vinyl sulfonic acid, vinyl phosphonic acid, derivatives thereof and mixtures thereof.
Useful ethylenically unsaturated carboxylic acid monomers include acrylic acid, methacrylic acid, acryloxypropionic acid, crotonic acid, fumaric acid, monoalkyl esters of fumaric acid, maleic acid, monoalkyl esters of maleic acid, itaconic acid, monoalkyl esters of itaconic acid and mixtures thereof.
Sui
Cirani Giancarlo
Eiss Dieter
McMillan Robyn E.
Metzger Walter
Reddy James E.
Altman Deborah M.
Copenheaver Blaine
Miles Jacques B.
Paulraj Christopher
PPG Industries Ohio Inc.
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