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
2002-01-09
2003-09-23
Zitomer, Fred (Department: 1713)
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...
C428S423100, C428S474400, C428S500000, C525S452000, C525S456000, C525S509000
Reexamination Certificate
active
06624279
ABSTRACT:
FIELD OF THE INVENTION
This invention concerns water-soluble carbamate-functional materials and curable coating compositions containing such materials, especially waterborne coating compositions containing such materials.
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 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 surfactants, such as polyether-based surfactants, that remain in the coating film as low molecular weight, hydrophilic materials.
It would be advantageous to provide a water-soluble, carbamate-functional material for a coating composition that would not have water-sensitivity in a cured coating.
SUMMARY OF THE INVENTION
The invention provides a water-soluble, carbamate-functional materials and coating compositions, especially waterborne coating compositions, containing the carbamate-functional materials. The invention further provides a coating prepared from the coating composition and a coated substrate, especially an automotive substrate, having the coating thereon. The carbamate-functional materials of the invention have a sufficient number of &bgr;-hydroxy carbamate groups to be soluble in water. The carbamate materials may be dissolved in water at ambient temperature or 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
(B—L&Parenclosest;
n
C
in which B represents &bgr;-hydroxy carbamate groups having the above structures; L represents a linking group formed by 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 5 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 5·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.
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 may be represented by a structure
(B—L&Parenclosest;
n
C
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 at least two.
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 &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 reaction with CO
2
. This can be done at any pressure from atmospheric up to supercritical CO
2
pressures, but is preferably under elevated pressure (e.g., 60-150 psi). The temperature for this reaction is preferably 60-150° C. Useful catalysts include any that activate an oxirane ring, such as tertiary amine or quaternary salts (e.g., tetramethyl ammonium bromide), combinations of complex organotin halides and alkyl phosphonium halides (e.g., (CH
3
)
3
SnI, Bu
4
Snl, Bu
4
PI, and (CH
3
)
4
PI), potassium salts (e.g., K
2
CO
3
, KI) preferably in combination with crown ethers, tin octoate, calcium octoate, and the like.
The cyclic carbonate group is reacted with ammonia or a primary amine. The primary amine preferably has up to four carbons, e.g. methyl amine. Preferably, the cyclic carbonate is reacted with ammonia. The ammonia may be aqueous ammonia (i.e., NH
4
OH). The reaction ring-opens the cyclic carbonate to form a &bgr;-hydroxy carbamate monomer.
The polymerization of the monomer preferably is carried out in water or in an a mixture that includes water. The &bgr;-hydroxy carbamate monomer may be polymerized in the presence of free-radical initiators or with a redox initiator system. Useful initiators and redox initiator systems are well-known. The polymerization may be carried out without solvent or in an organic or aqueous medium. In a preferred embodiment, the &bgr;-hydroxy carbamate monomer is polymerized in an aqueous medium, preferably without any organic solvent or with a minor amount (up to about 10% by weight of the aqueous medium) of a polar solvent such as methanol, tetrahydrofuran, propylene glycol monomethyl ether, or other water-soluble or water-miscible solvents. The &bgr;-hydroxy carbamate monomer may be dissolved in water along with the initiating system and polymerized at a suitable temperature for the initiating system.
In an alternative embodiment, a homopolymer or copolymer includ
Herrel Patricia A.
Law David J.
Ohrbom Walter H.
BASF Corporation
Budde Anna M.
Zitomer Fred
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