Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Nitrogen-containing reactant
Reexamination Certificate
2002-04-23
2003-11-18
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Nitrogen-containing reactant
C528S486000, C528S493000, C525S278000, C525S326100, C525S363000, C428S423100
Reexamination Certificate
active
06649734
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to curable coating compositions having improved scratch and mar resistance, especially to automotive clearcoat coating compositions having improved scratch and mar resistance.
BACKGROUND OF THE INVENTION
Composite color-plus-clear coatings are widely utilized in the coatings art. They are particularly desirable where exceptional gloss, depth of color, distinctness of image, and/or special metallic effects are required.
As used herein, the term “composite color-plus-clear” relates to composite coating systems requiring the application of a first coating, typically a colored basecoat coating, followed by the application of a second coating, generally a clearcoat, over the noncured or “wet” first coating. The applied first and second coatings are then cured. Thus, such systems are often described as “wet on wet” or “two-coat/one bake”. Drying processes which fall short of complete cure may be used between the application of the coatings.
Color-plus-clear systems are often selected when an exterior coating must possess an optimum visual appearance as well as superior durability and weatherability. As a result, the automotive industry has made extensive use of color-plus-clear composite coatings, especially for automotive body panels.
Minimum performance requirements for coating compositions intended for use on automotive body panels include high levels of etch resistance, intercoat adhesion, repair adhesion, substrate adhesion, scratch and mar resistance, chip resistance, humidity resistance, weatherability as measured by QUV and the like. Color-plus-clear composite coatings and/or the individual components thereof must also be capable of providing a visual appearance characterized by a high degree of gloss, distinctness of image (DOI), and smoothness. The latter requirements are particularly important for clearcoat compositions.
Scratch and mar resistance has proven to be a particularly difficult performance property to achieve relative to the balance of the other required performance and appearance properties. Scratch and mar resistance typically refers to a coating's ability to resist scratching from mechanical abrasions caused by car wash brushes, tree limbs, keys, fingernails, and the like. As stated by one researcher, “[i]ncreased scratch resistance of coatings has been a long sought-after goal in the automotive industry . . . . The ability to quantify what the variances in coating attributes contribute to increased scratch resistance, however remains a subject of controversy.” Ryntz, R. A., Abell, B. D., Pollano, G. M., Nguyen, L. H., and Shen., W. C., “Scratch Resistance Behavior of Model Coating Systems” JOURNAL OF COATINGS TECHNOLOGY, 72, No.904, 47(2000). As the exterior most coating in the color-plus-clear composite system, it is particularly important that clearcoat compositions possess advantageous scratch and mar resistance.
In addition to providing the foregoing performance and appearance parameters, the various coating components must be easy to apply in a manufacturing environment. All components of a composite color-plus-clear coating will preferably be resistant to application defects resulting from variations in application and/or curing environments.
Finally, any coating composition that is intended for use in a composite color-plus-clear system must be compatible with a wide variety of other coating compositions. For example, a coatings manufacturer may not formulate a basecoat composition for use solely with one particular primer or clearcoat composition. Furthermore, in many automotive paint shops, the clearcoat supplier may not supply all of the basecoats that are used in the wet on wet application process. In such cases where the clearcoat supplier has no control over the basecoat formula, it is particularly desirable to have compatibility with a wide range of basecoat types. Compatibility and ease of use with many commercially available coating compositions is thus a necessity for the individual components of a composite color-plus-clear coating system. A successful clearcoat composition will be compatible with both waterborne and solventborne basecoat compositions, as well as medium and high solids versions thereof. This compatibility must exist regardless of the differences in film-forming technology. “Compatible” as used herein refers to a combination of two or more individual coating components which provides acceptable levels of the previously discussed performance, appearance and application requirements of composite color-plus-clear systems.
However, certain basecoat formulations present particular compatibility challenges for the clearcoat coating manufacturer. For example, waterborne basecoats, particularly those containing tertiary amines, often appear to cause unacceptable wrinkling in subsequently applied and cured clearcoat formulations. Similarly, it has been found that basecoats containing high imino aminoplast resins present challenges for subsequently applied clearcoat compositions, especially with regard to intercoat adhesion.
Thus, the challenge for the coatings manufacturer is to provide coating compositions, especially clearcoat compositions, which provide all of the necessary performance, appearance and application properties discussed above but which are further compatible with a wide array of commercially available coating compositions, including but not limited to, waterborne basecoat formulations and basecoat formulations containing high imino aminoplasts. More particularly, it would be advantageous to retain or improve the performance, appearance and application parameters of prior art clearcoats but without the basecoat compatibility issues discussed above.
However, the prior art has been unable to achieve these advantages.
Japanese Patent Nos. 3006400 and 3006408 disclose water-based acrylic resin coating compositions having aminoplast resin crosslinking agents and amine-blocked acid catalysts. The compositions are used to coat polyester-coated deep drawn cans and teach that a combination of amine-blocked acid catalysts having different dissociation temperatures must be used to provide improvements and/or desirable performance in adhesion, retort resistance, scratch resistance, fabricability and glossiness. In particular, the compositions must have an amine-blocked acid catalyst (A) having a dissociation temperature of 45 to 65° C. and two or more of amine-blocked acid catalysts (B/2a), (C/2b), (D)/2c) respectively having dissociation temperatures of 100 to 120° C., 120 to 140° C., and/or 150 to 170° C.
Japanese Unexamined Patent Publication 7-62269 discloses powder paint coating compositions for use in a method for obtaining decorative honeycomb or turtle shell patterns. The compositions require the use of a toluene sulphonamide-modified melamine resin having a specific glass transition temperature and a sulphonic acid blocked with an amino compound having secondary or tertiary amino groups.
Japanese Patent Publication 2645494 discloses a paint composition having a hydroxyl containing polyester or acrylic resin, a crosslinking resin of at least one methylated melamine or butylated melamine, and a sulphonic acid blocked with a tertiary amine having a boiling point of 80-115° C.
U.S. Pat. No. 5,115,083, Piedrahita et al., discloses curable compositions having a least one aminoplast (A) and a catalyst (B) selected from the acid, anhydride, ester, ammonium salt or metal salt of three specific phosphorus and sulfur containing compound, and aminoplast coreactants (C) which may be any agent which is reactive with the aminoplast resin. Examples of suitable coreactants (C) include polyfunctional amines such as those having at least one tertiary amino group.
U.S. Pat. No. 5,175,227, Gardon et al., discloses a high solids coating composition intended to be a one package isocyanate free coating. The coating requires a particular hydroxyl functional polyurethane polyol and a hydroxyl reactive crosslinking agent. The patent further teaches that well-known acid catalysts may be
Bearyman William
Campbell Donald
Cook Vincent
Oermann Bruce
BASF Corporation
Golota Mary E.
Truong Duc
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