Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2002-01-30
2003-09-23
Zitomer, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C428S423100, C428S425800, C428S474400, C428S500000, C524S501000, C524S589000
Reexamination Certificate
active
06624241
ABSTRACT:
FIELD OF THE INVENTION
This invention concerns aqueous coating compositions containing polymers dispersed by water-soluble materials, especially curable coating compositions.
BACKGROUND OF THE INVENTION
Carbamate-functional materials have found particular utility in coating compositions as crosslinkable resins. Curable coating compositions utilizing carbamate-functional resins are described, for example, in U.S. Pat. Nos. 5,693,724, 5,693,723, 5,639,828, 5,512,639, 5,508,379, 5,451,656, 5,356,669, 5,336,566, and 5,532,061, each of which is incorporated herein by reference. These coating compositions can provide significant advantages over other coating compositions, such as hydroxy-functional acrylic/melamine coating compositions. For example, the coatings produced using carbamate-functional resins typically have excellent resistance to environmental etch (also called acid etch). Environmental etch results in spots or marks on or in the coating that often cannot be rubbed out.
One drawback of coatings with carbamate-functional resins is that they tend to require more organic solvent to achieve acceptable viscosity and for application. Carbamate-functional materials prepared from an isocyanurate of a diisocyanate, for example, are generally advantageous as an additive resin or principal resin in a coating composition, but these materials increase the viscosity of the coating composition so that more solvent is required. Coatings with higher amounts of organic solvent are undesirable because they produce more regulated emissions during application.
Aqueous coating compositions have gained prominence due to the regulations on organic emissions. Such coatings have tended to be water-sensitive, however, because of the presence of the hydrophilic groups used to disperse the binder resins or the surfactants, such as polyether-based surfactants, that remain in the coating film as low molecular weight, hydrophilic materials.
It would be advantageous to use a water-soluble, carbamate-functional material to emulsify, disperse, or aid in dissolving binder resins or polymers in an aqueous coating composition because the carbamate-functional material, in particular the carbamate group that accounts for its water solubility, could become part of the cured coating and would then not cause water-sensitivity in the cured coating.
SUMMARY OF THE INVENTION
The invention provides an aqueous coating composition containing a dispersed, emulsified, or dissolved resin or polymer, in which the dispersant for, emulsifier for, or aid for dissolving the resin or polymer is a water-soluble, carbamate-functional material. The invention further provides a coating prepared from the coating composition and a coated substrate, especially an automotive substrate, having the coating thereon.
The water-soluble, carbamate-functional materials of the invention have a sufficient number of &bgr;-hydroxy carbamate groups to be soluble in water. The water-soluble, carbamate-functional materials may be dissolved in water at ambient temperature or in warm water, with the water being heated up to perhaps about 50° C. The &bgr;-hydroxy carbamate groups have the isomeric structures
wherein each R is independently hydrogen, methyl, or ethyl and x is an integer of 1 to 3. Preferably, R is in each case a hydrogen and x is 1.
In one embodiment, the water-soluble, carbamate-functional materials may be represented by a structure
in which B represents &bgr;-hydroxy carbamate groups having the above structures; L represents a linking group formed with a hydrogen acceptor group; C represents an n-functional central moiety; and n is a positive integer. The carbamate groups are primary carbamate groups, i.e. there are two nitrogen hydrogens.
The central moiety C has up to about 6 carbon atoms per &bgr;-hydroxy carbamate group, preferably up to about 4.5 carbons per &bgr;-hydroxy carbamate group, more preferably up to about 4.0 carbons per &bgr;-hydroxy carbamate group, and still more preferably up to about 3.0 carbons per &bgr;-hydroxy carbamate group. In terms of the structure, the number of carbons of the C group may be represented by up to 6·n, preferably up to 4.5·n, more preferably up to 4.0·n, and still more preferably up to 3.0·n. For some applications, such as automotive topcoats, particularly automotive clearcoats, the C group is preferably aliphatic. In some preferred embodiments the C group includes an aliphatic ring.
The aqueous coating composition also includes at least a second component, which may be an organic compound, resin, and/or polymer, that is brought into the aqueous coating composition using the &bgr;-hydroxy carbamate material. The second component may be dispersed, emulsified, or form a homogenous aqueous phase. For purposes of this invention, no distinction will be made between “dispersions” and “emulsions,” and those terms may be used herein as synonyms. The second component may have some water solubility, but is not completely water soluble and is less water soluble than the &bgr;-hydroxy carbamate material. Thus, in one embodiment, the second component may partially dissolve in water without using the &bgr;-hydroxy carbamate material, but the &bgr;-hydroxy carbamate material can be used to bring the second component into the aqueous medium to form a stable, clear medium that does not phase separate over time. The second component may be, for example, any organic compound, resin, or polymer suitable for coating compositions, including especially film-forming materials such as crosslinking agents which may cure the water-soluble, carbamate-functional material under appropriate curing conditions, curable polymers, curable oligomers, and curable compounds, especially curable materials having active hydrogen functionality.
Preferably, the coating composition is curable, and preferably both the second component and the &bgr;-hydroxy carbamate material crosslink during curing of the coating composition.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
In one embodiment, the water-soluble, carbamate-functional materials used to disperse the component may be represented by a structure
in which B represents &bgr;-hydroxy carbamate groups having the structures
wherein each R is independently hydrogen, methyl, or ethyl, preferably hydrogen and x is an integer of 1 to 3, preferably 1; L represents a linking group formed by a hydrogen acceptor group; C represents an n-functional central moiety; and n is a positive integer, preferably from 1 to about 8, more preferably at least two, even more preferably from 2 to about 4.
Suitable examples of the linking group L include, without limitation,
with one free bond of each group connected to B and the other free bond connected to C.
In one embodiment of the invention, the water-soluble, carbamate-functional material may be a homopolymer having a monomer unit represented by the structure
in which each R
2
is independently H or methyl and B is as defined above, or a monomer unit
in which B is as defined above.
The water-soluble, carbamate-functional material may also be a copolymer having the monomer unit just described and having a fraction of different monomer units, particularly hydrophilic monomer units, in an amount so that the copolymer is water-soluble.
The water-soluble, &bgr;-hydroxy carbamate polymer may be the polymerization product of a monomer prepared by reacting a glycidyl-group containing polymerizable monomer first with carbon dioxide to convert the oxirane group to a cyclic carbonate group, and then with ammonia or a primary amine to convert the cyclic carbonate group to a &bgr;-hydroxy carbamate group. Examples of suitable oxirane group-containing polymerizable monomers include, without limitation, glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, and allyl glycidyl ether. Oxirane groups can be converted to carbamate groups by first converting to a cyclic carbonate group by rea
Herrel Patricia A.
Law David J.
Ohrbom Walter H.
Weise Robert D.
BASF Corporation
Budde Anna M.
Zitomer Fred
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