Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-12-15
2002-03-26
Wilson, D. R. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S375000, C525S162000
Reexamination Certificate
active
06362285
ABSTRACT:
FIELD OF THE INVENTION
The instant invention relates to coating compositions comprising reactive additives. In particular, the invention provides coating compositions comprising a reactive additive comprising at least one compound having a molecular weight of from 131 to 2000 and at least one primary carbamate group and at least one alkyl group selected from the group consisting of straight chain alkyl groups of more than 10 carbons, branched alkyl group of from 5 to 30 carbons, and mixtures thereof.
BACKGROUND OF THE INVENTION
Curable coating compositions such as thermoset coatings are widely used in the coatings art. They are often used for 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.
Many curable coating compositions utilize a hydroxy-functional polymer resin such as a hydroxy-functional acrylic and a curing agent such as an aminoplast. These coating compositions suffer from environmental etch in certain topcoat applications. In spite of this, it is often desirable to use coatings based on hydroxy-functional or other active hydrogen-functional resins, as there exists a great deal of experience with these coatings, and many multilayer coating systems have incorporated this chemistry into one or more of the layers. It is also desirable to use such coatings for various applications such as basecoat and primer to provide durable coatings. It is especially desirable to utilize such coating compositions in high gloss topcoats, such as the clearcoat of a color-plus-clear composite coating, while also providing resistance to environmental etch.
U.S. Pat. Nos. 4,814,382, 5,114,015, and 5,158,808 describe the use of certain N-alkyl carbamate compounds as reactive diluents in coating compositions having OH-functional curable polymer resins. These compounds, however, may require excessively high catalyst or temperature levels in order to fully react into the crosslink matrix during cure of the film.
WO 87/00851 describes the use of certain reactive carbamate derivatives in an effort to minimize the emission of volatile organic compounds (VOC). U.S. Pat. No. 5,744,550 describes the use of primary carbamate additives. However, further reductions in VOC are desirable without loss of desirable performance properties such as etch resistance and the like.
SUMMARY OF THE INVENTION
It has been surprisingly discovered that certain primary carbamate reactive additives provide advantages over the prior art. In particular, it has been found that the incorporation of a particular reactive additive provides improved sprayability at a given nonvolatile level and advantageous resistance to environmental etch. The reactive additive comprises at least one compound having a molecular weight of from 131 to 2000 and comprising at least one &bgr;-hydroxy primary carbamate group and at least one alkyl group selected from the group consisting of straight chain alkyl groups of more than 10 carbons, branched alkyl groups of from 5 to 30 carbons, and mixtures thereof.
The invention thus provides a curable coating composition comprising (A) a polymer resin comprising active hydrogen-containing functional group other than carbamate, (B) a curing agent having groups that are reactive with said functional groups on (A), and (C) a reactive additive comprising at least one compound having a molecular weight of from 131 to 2000 and comprising at least one primary carbamate group and at least one alkyl group selected from the group consisting of straight chain alkyl groups of more than 10 carbons, branched alkyl groups of from 5 to 30 carbons, and mixtures thereof, wherein one or both of (A) and (B) comprise groups that are reactive with the primary carbamate group of (C).
The invention further provides methods of making the disclosed reactive additives.
In a first embodiment, the method comprises providing a compound comprising at least one epoxy group and at least one at least one alkyl group selected from the group consisting of straight chain alkyl groups of more than 10 carbons, branched alkyl groups of from 5 to 30 carbons and mixtures thereof, reacting said compound with carbon dioxide so as to produce a carbonate functional compound, and reacting said carbonate functional compound with ammonia so as to produce a carbamate functional reactive additive.
In a second embodiment, the method comprises providing a compound comprising at least one glycol diol and at least one alkyl group selected from the group consisting of straight chain alkyl groups of more than 10 carbons, branched alkyl groups of from 5 to 30 carbons and mixtures thereof, reacting said compound with phosgene or related materials such as triphosgene, and reacting said carbonate functional compound with ammonia or ammonium hydroxide so as to produce a carbamate functional reactive additive.
DETAILED DESCRIPTION OF THE INVENTION
The composition according to the present invention comprises a polymer resin (A) having active hydrogen-containing functional groups other than carbamate. Such polymer resins include, for example, acrylic polymers, modified acrylic polymers, polyesters, polyepoxides, polycarbonates, polyurethanes, polyamides, polyimides, and polysiloxanes, all of which are well known in the art. Preferably, the polymer is an acrylic, modified acrylic or polyester. More preferably, the polymer is an acrylic polymer. Active hydrogen-containing functional groups on polymer resins are well known in the art. Such groups include, for example, hydroxyl groups, amino groups, thiol groups, hydrazide groups, and activated methylene groups.
In one preferred embodiment of the invention, the polymer is an acrylic. The acrylic polymer preferably has a molecular weight of 500 to 1,000,000, and more preferably of 1500 to 50,000. As used herein, “molecular weight” refers to number average molecular weight, which may be determined by the GPC method using a polystyrene standard. Such polymers are well-known in the art, and can be prepared from monomers such as methyl acrylate, acrylic acid, methacrylic acid, methyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, and the like. The active hydrogen functional group, e.g., hydroxyl, can be incorporated into the ester portion of the acrylic monomer. For example, hydroxy-functional acrylic monomers that can be used to form such polymers include hyd
Harris Paul J.
Ohrbom Walter H
BASF Corporation
Golota Mary E.
Wilson D. R.
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