Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-11-02
2003-09-23
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S319000, C526S321000, C526S325000, C428S423100, C428S480000, C428S500000, C428S704000
Reexamination Certificate
active
06624275
ABSTRACT:
FIELD OF THE INVENTION
This invention concerns 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-dispersible, 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 carbamate-functional compound that is water soluble and coating compositions, especially waterborne coating compositions, containing the carbamate-functional material. The invention further provide a coating prepared from the coating composition and a coated substrate, especially an automotive substrate, having the coating thereon.
The carbamate functional compound of the invention has a structure
in which each of R
1
, R
2
, and R
3
is independently
wherein R is hydrogen, methyl, or ethyl.
The carbamate-functional compound of the invention is combined with a carbamate-reactive material to form the coating composition of the invention. The coating composition is applied to a substrate, especially to an automotive substrate, and cured to produce a coating. The coating is preferably the outermost coating on the substrate, particularly a clearcoat coating.
DETAILED DESCRIPTION OF THE INVENTION
The &bgr;-hydroxy carbamate compound of the invention may be prepared by reacting triglycidyl isocyanurate first with carbon dioxide to convert the oxirane groups to cyclic carbonate groups, and then with ammonia to convert the cyclic carbonate group to a &bgr;-hydroxy carbamate group. Triglycidyl isocyanurate is commercially available or may be prepared by reaction of isocyanuric acid with an epihalohydrin, in particular epichlorohydrin. The reaction of the triglycidyl isocyanurate 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
Snl, Bu
4
Snl, Bu
4
Pl, and (CH
3
)
4
Pl), potassium salts (e.g., K
2
CO
3
, Kl) preferably in combination with crown ethers, tin octoate, calcium octoate, and the like.
Cyclic carbonate groups can be converted to carbamate groups by reaction with ammonia, which ring-opens the cyclic carbonate to form a &bgr;-hydroxy carbamate. The ammonia may be anhydrous ammonia or aqueous ammonia (i.e., NH
4
OH). The carbonate ring can open to produce either of the two isomeric structures shown above for the R
1
, R
2
, and R
3
groups.
The &bgr;-hydroxy carbamate compound is water soluble and is also soluble in polar organic solvents, such as tetrahydrofuran, alcohols such as methanol and ethanol, and glycol ether-based compounds such as ethylene glycol monobutyl ether, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate.
The coating composition of the invention includes the &bgr;-hydroxy carbamate compound and one or more crosslinkers or curing agents reactive with the carbamate compound. The coating composition may optionally include other compounds, resins, and/or polymers reactive with the crosslinker. The combination of the &bgr;-hydroxy carbamate compound, the crosslinker, and (if present) the optional further compounds, resins, and/or polymers is referred to as the “vehicle.”
In preferred embodiments, the &bgr;-hydroxy carbamate compound is at least about 5%, more preferably at least about 10%, and still more preferably at least about 15% by weight of the nonvolatile vehicle. It is also preferred for the &bgr;-hydroxy carbamate compound to be up to about 30%, more preferably up to about 50%, and still more preferably up to about 70% by weight of the nonvolatile vehicle. The &bgr;-hydroxy carbamate compound is preferably from about 10% to about 70%, more preferably from about 15% to about 60%, and still more preferably from about 20% to about 60% by weight of the nonvolatile vehicle.
Particularly useful crosslinkers include, without limitation, materials having active methylol or methylalkoxy groups, such as aminoplast crosslinking agents or phenol/formaldehyde adducts. Examples of preferred curing agent compounds include, without limitation, melamine formaldehyde crosslinkers, including monomeric or polymeric melamine resin and partially or fully alkylated melamine resin, urea resins, and methylol ureas such as urea formaldehyde resin, alkoxy ureas such as butylated urea formaldehyde resin. Another suitable crosslinking agent is tris(alkoxy carbonylamino) triazine (available from Cytec Industries under the trademark TACT). Other useful crosslinkers include, without limitation, polyisocyanates and blocked polyisocyanates, curing agents that have epoxide groups, amine groups, acid groups, siloxane groups, cyclic carbonate groups, and anhydride groups. The curing agent may be combinations of these, particularly combinations that include aminoplast crosslinking agents. At least one crosslinker with functionality reactive with active hydrogens of the &bgr;-hydroxy carbamate compound is included. Aminoplast resins such as melamine formaldehyde resins or urea formaldehyde resins are especially preferred. Water-soluble aminoplast resins for aqueous coating compositions are known. These include high imino-content melamine formaldehyde resins and fully methoxylated melamine formaldehyde resins.
In preferred embodiments, the crosslinker is at least about 5%, more preferably at least about 10% by weight of the nonvolatile vehicle. It is also preferred for the crosslinker to be up to about 40%, more preferably up to about 30% by weight of the nonvolatile vehicle. The crosslinker is preferably from about 5% to about 40%, more preferably from about 10% to about 35%, and still more preferably from about 15% to about 35% by weight of the nonvolatile vehicle.
The coating composition may include further crosslinkable compounds, resin, and/or polymers, preferably those that have active hydrogen functionality. Examples of additional compounds, resins, and/or polymers that may optionally be included are other carbamate- or hydroxyl-functional materials,
Herrel Patricia A.
Law David J.
Ohrbom Walter H.
BASF Corporation
Budda Anna M.
Nutter Nathan M.
Ribar Travis B
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