Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
2001-07-03
2003-04-29
Seidleck, James J. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of polyamidoester
C428S423300, C428S425800, C524S591000
Reexamination Certificate
active
06555231
ABSTRACT:
FIELD OF THE INVENTION
The subject invention generally relates to an acrylic-free, waterborne coating composition for producing a waterborne paint film having improved chip resistance on a substrate. More specifically, the waterborne coating composition of the subject invention includes an aqueous polyurethane dispersion and a water-soluble cross-linker for producing the waterborne paint film to have improved chip resistance on the substrate of from 0.05 to 0.8 percent paint film loss according to a Gravel Chip Test.
BACKGROUND OF THE INVENTION
Waterborne coating compositions are known in the art. In both the refinish and original equipment manufacturer (OEM) coating industries, waterborne coating compositions are applied to a substrate, such as an automobile body, to produce a paint film on the substrate. Such paint films serve both functional and aesthetic purposes.
Many of these waterborne coating compositions incorporate polyurethane as a primary binder resin. To effectively disperse the polyurethane resin in water, the waterborne coating compositions incorporate a neutralizing agent such as an amine. Amines neutralize certain functional groups associated with the polyurethane to form salts of the polyurethane. The salts of the polyurethane promote dispersibility of the polyurethane in water. These polyurethanes are known in the art as amine dispersible polyurethane resins. Many of the prior art polyurethanes also include a third component, usually any epoxy or acrylic resin. The third component is typically utilized to increase a particular property of the waterborne coating composition such as adhesion, hardness, or appearance of the paint film.
More specifically, the waterborne coating compositions of the prior art have acrylic resin as the third component. The acrylic resin increases the hardness of the paint film produced by the waterborne coating composition upon the substrate. The disadvantage of utilizing acrylic resins is that the increased hardness of the paint film increases the amount of film loss due to chipping. If the waterborne coating composition is applied to an automotive body, the paint film will be subjected to extreme environmental chip conditions.
In sum, the waterborne coating compositions of the prior art are characterized by one or more inadequacies. Therefore, it is desirable to provide a novel waterborne coating composition that does not include acrylic resins and that produces an improved paint film having increased chip resistance.
SUMMARY OF THE INVENTION AND ADVANTAGES
An acrylic-free, waterborne coating composition is disclosed. The waterborne coating composition of the subject invention produces a waterborne paint film having improved chip resistance on a substrate. The waterborne coating composition includes an aqueous polyurethane dispersion substantially free from co-solvents. The aqueous polyurethane dispersion has carboxyl groups, and a glass transition temperature from 0° C. or less. The waterborne coating composition also includes a water-soluble cross-linker reactive with the carboxyl groups.
Together, the aqueous polyurethane dispersion and the water-soluble cross-linker form a binder component of the waterborne coating composition. The binder component includes from 60 to 90% by weight of the aqueous polyurethane dispersion based on 100% by weight of the binder component and from 10 to 40% by weight of the water-soluble cross-linker based on 100% by weight of the binder component.
The waterborne paint film produced by the waterborne coating composition of the subject invention exhibits improved resistance to chip. Furthermore, the waterborne paint film also exhibits improved resistance to chip as film build increases. Accordingly, the subject invention provides a novel acrylic-free waterborne coating composition utilizing an aqueous polyurethane dispersion and a water-soluble cross-linker. The subject invention also provides a layered paint system utilizing the novel acrylic-free waterborne coating composition.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A waterborne coating composition for producing a waterborne paint film having improved chip resistance on a substrate is disclosed. More specifically, the waterborne coating composition of the subject invention is acrylic-free and therefore does not include acrylic resins as a component of the waterborne coating composition. However, acrylic resins may be included in other layers applied to the substrate before or after the application of the waterborne coating composition. The waterborne coating composition includes an aqueous polyurethane dispersion and a water-soluble cross-linker.
The aqueous polyurethane dispersion is substantially free from co-solvents. It is to be understood that, in the context of the subject invention, substantially free of co-solvents is intended to indicate that the aqueous polyurethane dispersion has less than about 5% by weight of volatile organic solvents based on 100% by weight of the aqueous polyurethane dispersion. Preferably, the aqueous polyurethane dispersion has less than about 2.5% by weight of volatile organic solvents based on 100% by weight of the aqueous polyurethane dispersion. The waterborne coating composition is also free of polyesters in accordance with the above description of acrylic.
The aqueous polyurethane dispersion has at least one carboxyl group. The water-soluble cross-linker has at least one amine group that is reactive with the carboxyl group. As understood by those skilled in the art, the carboxyl group of the aqueous polyurethane dispersion cross-links with the amine group forming the waterborne paint film.
The aqueous polyurethane dispersion is prepared by reacting at least one polyisocyanate with at least one polyol. The reactants used to prepare the aqueous polyurethane dispersion are selected and apportioned to provide the desired glass transition temperature. Suitable polyisocyanates include, but are not limited to, aliphatic polyisocyanates, alicyclic polyisocyanates, and combinations thereof. Owing to their good resistance to ultraviolet light, aliphatic and alicyclic polyisocyanates produce paint films having a low tendency toward yellowing. This tendency is highly desirable, especially for use in automotive coatings. However, aromatic polyisocyanates may still be utilized to achieve the desired results of the subject invention.
Illustrative examples of polyisocyanates include, without limitation, isophorone diamine dissocyanate, ethylene diisocyanate, 1,2-diisocyanatopropane, 1,3-diisocyanatopropane, 1,4-butylene diisocyanate, lysine diisocyanate, 1,4-methylene bis(cyclohexyl isocyanate), toluene diisocyanates (e.g., 2,4-toluene diisocyanate and 2,6-toluene diisocyanate)diphenylmethane 4,4′-diisocyanate, methylenebis-4,4′-isocyanatocyclohexane, 1,6-hexamethylene diisocyanate, p-phenylene diisocyanate, tetramethyl xylene diisocyanate, meta-xylene diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, cyclohexane-1,3- and-1,4-diisocyanate, 1-isocyanato-2-isocyanatomethyl cyclopentane, bisphenylene diisocyanate, naphthylene diisocyanate, diphenylmethane diisocyanate, cyclobutane diisocyanate, cyclopentylene diisocyanate, cyclohexylene diisocyanate, pentamethylene diisocyanate, propylene diisocyanate, and combinations thereof. Biurets, allophonates, isocyanurates, carbodiimides, and other such modifications of these isocyanates can also be used as the polyisocyanates.
More highly functional polyisocyanates may also be used to form the polyisocyanate provided that this does not cause any gelling of the aqueous polyurethane dispersion and ultimately of the waterborne coating composition. One example of highly functional polyisocyanates are triisocyanates which are products formed by trimerization or oligomerization of diisocyanates or by reaction of diisocyanates with polyfunctional OH- or NH-containing compounds. The polyisocyanate has a functionality, which may be lowered by addition of monoisocyanates.
The polyol or polyols used to prepare the aqueous pol
Doty Robert
Kandow Timothy P.
BASF Corporation
Bissett Melanie
LaPrairie David M.
Seidleck James J.
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