Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
1996-08-15
2002-12-24
Gerstl, Robert (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
Reexamination Certificate
active
06498266
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to methods of preparing compounds, particularly carbamate- or urea-functional compounds, particularly compounds useful in curable compositions such as coating compositions.
BACKGROUND OF THE INVENTION
Carbamate- or urea-functional compositions have been described for uses such as curable compositions, particularly curable coating compositions. 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 aberations at the surface of the coating in order to achieve the desired visual effect such as high distinctness of image (DOI).
Such 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.
Curable coating compositions based on curable components having carbamate or urea functionality have been proposed have been described in the art to provide etch-resistant coatings, e.g., U.S. Pat. No. 5,356,669 and WO 94/10211.
In addition to resistance to environmental etch, a number of other characteristics can be desirable. For example, it may be desirable to provide a coating having a high degree of flexibility. This can be particularly advantageous if the substrate on which the coating is placed is itself flexible, as in the case of plastic, leather, or textile substrates.
It is also desirable to reduce the amount of solvent required in coating compositions in order to reduce the volatile organic content (VOC), which is better for the environment.
Finally, it is desirable to provide options of different types of carbamate- or urea-functional materials to provide coatings with a good combination of properties such as durability, hardness, and resistance to scratching, marring, solvents, and acids.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a method of preparing carbamate- or urea-functional compounds capable of providing one or more of the above-described properties. This method comprises a method of making a carbamate- or urea-functional ester-containing compound comprising the step of reacting a lactone or hydroxy carboxylic acid with a compound (A) comprising a carbamate or urea group or a group that can be converted to a carbamate or urea group, and an active hydrogen group capable of reacting with the hydroxy carboxylic acid or in a ring-opening reaction with a lactone.
Compounds prepared according to the present invention can provide coatings having a good combination of properties such as durability, hardness, and resistance to scratching, marring, solvents, and acids. Such coating compositions can also provide low VOC levels, and can be used to prepare coatings having good flexibility for use over flexible substrates.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
According to the present invention, a compound having carbamate or urea functionality is formed by reaction of a compound (A) having carbamate or urea groups or groups that can be converted to carbamate or urea, and an active hydrogen group.
Carbamate groups can generally be characterized by the formula
wherein R is H or alkyl, preferably of 1 to 4 carbon atoms. Preferably, R is H or methyl, and more preferably R is H. Urea groups can generally be characterized by the formula
wherein R′ and R″ each independently represents H or alkyl, preferably of 1 to 4 carbon atoms, or R′ and R″ may together form a heterocyclic ring structure (e.g., where R′ and R″ form an ethylene bridge).
According to the present invention, the carbamate- or urea-functional compound can be formed by reacting a lactone or hydroxy carboxylic acid with a compound (A) having an active hydrogen group capable of ring-opening the lactone or undergoing a condensation reaction with the hydroxy carboxylic acid (e.g., hydroxyl, primaryamine, acid) and a carbamate or urea group or a group that can be converted to carbamate or urea. When a compound having an active hydrogen group and a group that can be converted to carbamate or urea is used to ring-open the lactone or react with the hydroxy carboxylic acid, conversion of the group to a carbamate or urea can be accomplished during or after the ring-opening reaction.
Compounds having a carbamate or urea group and an active hydrogen group are known in the art. Hydroxypropyl carbamate and hydroxyethyl ethylene urea, for example, are well known and commercially available. Amino carbamates are described in U.S. Pat. No. 2,842,523. Hydroxyl ureas may also be prepared by reacting an oxazolidone with ammonia or a primary amine or by reacting ethylene oxide with ammonia to form an amino alcohol and then reacting the amine group of that compound or any other amino alcohol with hydrochloric acid, then urea to form a hydroxy urea. Amino ureas can be prepared, for example, by reacting a ketone with a diamine having one amine group protected from reaction (e.g., by steric hindrance), followed by reaction with HNCO (i.e., the product of the thermal decomposition of urea), and then water. Alternatively, these compounds can be prepared by starting with a compound having an active hydrogen and a group that can be converted to carbamate or urea as described below, and then converting that group to the carbamate or urea prior to commencement of the reaction with the lactone or hydroxy carboxylic acid.
Groups that can be converted to carbamate include cyclic carbonate groups, epoxy groups, and unsaturated bonds. Cyclic carbonate groups can be converted to carbamate groups by reaction with ammonia or a primary amine, which ring-opens the cyclic carbonate to form a &bgr;-hydroxy carbamate. Epoxy 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
SnI, 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 can then be converted to a carbamate group as described above. Any unsaturated bond can be converted to carbamate groups by first reacting with peroxide to convert to an epoxy group, then with CO
2
to form a cyclic carbonate, and then with ammonia or a primary amine to form the carbamate.
Other groups, such as hydroxyl groups or isocyanate groups can also be converted to carbamate groups to form a compound (A). However, if such groups were to be present on the compound (A) and then converted to carbamate after reaction with the lactone or hydroxy carboxylic acid, they would have to be blocked so that they would not react with the lactone or hydroxy carboxylic acid or with active hydrogen groups that are present. When blocking these groups is not feasible, the conversion to carbamate or urea would have to be completed prior to the reaction with the lactone or hydroxy carboxylic acid. Hydroxyl groups can be converted to carbamate groups by reaction with a monoisocyanate (e.g., methyl isocyanate) to form a secondary carbamate group or with cyanic acid (which may be formed in situ by thermal decomposition of urea) to form a primary carbamate group (i.e., unsubstitut
Bammel Brian D.
Harris Paul J.
McGee John D.
Menovcik Gregory G.
Ohrbom Walter H.
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