Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2000-12-19
2003-04-01
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C568S852000, C568S420000, C568S700000, C525S333700, C525S191000, C525S055000, C528S068000, C528S332000, C528S254000, C556S032000, C556S467000
Reexamination Certificate
active
06541594
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to coating compositions, especially thermoset coating compositions intended for use in the automotive and/or transportation industries.
BACKGROUND OF THE INVENTION
Curable coating compositions such as thermoset coatings are widely used in the coatings art. They are often used as topcoats in the automotive and industrial coatings industry. Color-plus-clear composite coatings are particularly useful as topcoats where exceptional gloss, depth of color, distinctness of image, or special metallic effects are desired. The automotive industry has made extensive use of these coatings for automotive body panels. Color-plus-clear composite coatings, however, require an extremely high degree of clarity in the clearcoat to achieve the desired visual effect. High-gloss coatings also require a low degree of visual aberrations at the surface of the coating in order to achieve the desired visual effect such as high distinctness of image (DOI).
As such, these coatings are especially susceptible to a phenomenon known as environmental etch. Environmental etch manifests itself as spots or marks on or in the finish of the coating that often cannot be rubbed out.
It is often difficult to predict the degree of resistance to environmental etch that a high gloss or color-plus-clear composite coating will exhibit. Many coating compositions known for their durability and/or weatherability when used in exterior paints, such as high-solids enamels, do not provide the desired level of resistance to environmental etch when used in high gloss coatings such as the clearcoat of a color-plus-clear composite coating.
Many compositions have been proposed for use as the clearcoat of a color-plus-clear composite coating, such as polyurethanes, acid-epoxy systems and the like. However, many prior art systems suffer from disadvantages such as coatability problems, compatibility problems with the pigmented basecoat, solubility problems. Moreover, very few one-pack coating compositions have been found that provide satisfactory resistance to environmental etch, especially in the demanding environment of automotive coatings.
It has been found that carbamate functional polymers such as those described in U.S. Pat. Nos. 5,726,246, 5,474,811, and 5,605,965 can be used to provide coating compositions which exhibit significantly improved environmental etch resistance. Carabamate functional polymers have been used to provide commercially advantageous coatings compositions, especially as clearcoats intended for use in composite color-plus-clear coatings.
However, although coating compositions containing carbamate functional polymers generally provide the performance properties currently required by the automotive industry, continuous improvement is always desired. As a result, it would be advantageous to provide improvements in solids or % nonvolatile, flexability, scratch & mar resistance, cold crack resistance, chip resistance and/or the like. At the same time, such improvements must be achieved without any decrease in environmental etch resistance or other commercially required performance property.
It would also be desireable to provide such a technology which would be applicable for use in a wide variety of coating compositions and applications, such as primers, basecoats, clearcoats, two-component systems, anti-chip coating compositions, water borne coatings, solvent borne coatings, coatings for flexible substrates, and the like.
Finally, it would be advantegous to provide improved etch resistant coating compositions which have an increased % NV (nonvolatile) or decreased VOC (volatile organic content) at a sprayable viscosity.
Accordingly, it is an object of the instant invention to provide curable coating compositions which provide all of the advantages of prior art carbamate containing coating compositions, especially good environmental etch resistance, but further exhibit improvement in one or more of the following performance parameters, i.e., flexability, scratch and mar resistance, and/or chip resistance.
It is another object of the invention to provide a technology for improving one or more of the following performance parameters, i.e., % nonvolatile solids, flexability, scratch and mar resistance, and/or chip resistance, in a wide variety of coating compositions and applications, such as primers, basecoats, clearcoats, two-component systems, anti-chip coating compositions, water borne coatings, solvent borne coatings, coatings for flexible substrates, and the like.
It is another object of the invention to provide etch resistance coating compositions which have an increased % NV (nonvolatile) or decreased VOC (volatile organic content) at a sprayable viscosity.
SUMMARY OF THE INVENTION
It has unexpectedly been found that these and other objects of the invention can be achieved with the use of a particular component (a), especially when used in conjunction with a particular crosslinking agent (b).
The invention provides curable coating compositions comprising (a) a reactive component which is substantially free of any heteroatoms and is not a crystalline solid at room temperature comprising (i) from 12 to 72 carbon atoms, and (ii) at least two functional groups, and (b) a crosslinking agent comprising a plurality of functional groups (iii) reactive with the functional groups (ii) of compound (a), wherein functional groups (ii) and (iii) are selected such that reaction of functional groups (ii) and (iii) produces a thermally irreversible chemical linkage.
In a preferred embodiment of the invention, reactive component (a) will be a liquid or a waxy solid at temperatures of less than 20 degrees C. Most preferably, reactive component (a) will comprise a mixture of reactive components selected from the group consisting of linear aliphatic reactive components, aromatic containing reactive components, and cycloaliphatic containing reactive components.
In another aspect of the invention, the claimed coating compositions will further comprise one or more polyfunctional polymeric compounds (c) and one or crosslinking agents (d). The one or more polyfunctional polymeric compounds (c) are different from (a) and have one or more hydrogen reactive functional groups (iv) and an equivalent weight of from 116 to 2000. The one or more crosslinking agents (d) comprise a plurality of functional groups (v) reactive with the functional groups (iv) of compound (c).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In its broadest embodiment, the instant invention comprises coating compositions comprising a reactive component (a) and a crosslinking agent (b). Reactive component (a) should have from 12 to 72 carbons, have at least two functional groups (ii), be substantially free of heteratoms, and not be a crystalline solid at room temperature. Crosslinking agent (b) must have a plurality of functional groups reactive with functional groups (ii) of reactive component (a). Functional groups (ii) of reactive component (a) must form a chemically irreversible linkage upon reaction with the functional groups (iii) of crosslinking agent (b).
The term “thermally irreversible linkage” refers to a linkage the reversal of which is not thermally favored under the traditional cure schedules used for automotive coating compositions. Illustrative examples of suitable thermally irreversible chemical linkages are urethanes, ureas, esters and ethers. Preferred thermally irreversible chemical linkages are urethanes, ureas and esters, with urethane linkages being most preferred. Such chemical linkages will not break and reform during the crosslinking process as is the case with the linkages formed via reaction between hydroxyl groups and aminoplast resins. The prior art has previously taught that the reversibility of crosslink bonds is both desireable and indeed critical to the success of aminoplast containing coatings. See Possible Reaction Pathways for Self-Condensation of Melamine Resins; Reversibility of Methylene Bridge Formation, Samaraweera U.,
Journal of Coatings Technology,
Vol. 64, No. 804, January
Casale Joanne
Gilbert John A.
Green Marvin L.
Herrel Patricia A.
Ohrbom Walter H.
BASF Corporation
Dawson Robert
Golota Mary E.
Peng Kuo-Liang
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