WO1994016026A1

WO1994016026A1 - Water-borne coating compositions

Info

Publication number: WO1994016026A1
Application number: PCT/US1994/000230
Authority: WO
Inventors: Thauming Kuo
Original assignee: Eastman Chemical Company
Priority date: 1993-01-15
Filing date: 1994-01-11
Publication date: 1994-07-21
Also published as: CN1094428A

Abstract

Provided are curable water-borne resin compositions having phenolic functional groups which are neutralized with an amine to yield quaternary ammonium salts. The coatings made possible by these compositions exhibit excellent properties and are useful as coating compositions for automotive, appliance, and machinery coating applications.

Description

WATER-BORNE COATING COMPOSITIONS

This invention belongs to the field of organic chemistry. More particularly, this invention relates to polyester compositions suitable for use in water-borne coating compositions.

Water-borne coatings have recently become an important area of research because of environmental concern and governmental regulation to reduce amounts of volatile organic compounds (VOCs) used in coating compositions. Compared to other new technologies developed for complying with VOC regulations such as high-solids, powder, and UV-cured coatings, water-borne coatings represent a practical alternative due to the utilization of a considerable amount of water in place of such volatile organics. However, efforts to obtain satisfactory water-borne coatings are often unsuccessful due to the hydrophilic nature of coating binders. While hydrophilic resins are required to afford water-borne coatings, it is also critical to have water-resistant cured coatings for outdoor applications. As a result, it is particularly challenging for coating scientists to achieve these two goals simultaneously. In the present invention, crosslinkable polyesters having phenolic end- groups are utilized to obtain phenolic ammonium salts which are then dispersed in water and formulated into industrial baking enamels. Thermosetting coatings thus prepared exhibit excellent water-resistance in addition to other superior properties and are useful for high performance coatings such as automotive, appliance, and machinery coatings.

A common water-borne baking enamel used in

industrial coatings is based on neutralization of carboxyl functionalized curable resins which yield water-dispersible quaternary ammonium salts. This conventional amine-neutralization method has already been described in considerable detail (see, for example, Olding and Hayward, Ed., "Resins for Surface Coatings" Volume III, SITA Technology, London, 1987, p. 171).

The above conventional water-borne composition is achieved by incorporating a polybasic acid such as trimellitic acid in the synthesis of the curable

polyester resin to produce a carboxyl enriched

composition which is then neutralized with an amine and dispersed with water. Alternatively, a hydroxyl

enriched polyester composition may be reacted with a trimellitic acid or anhydride such as trimellitic acid, trimellitic anhydride (TMA), or phthalic anhydride to produce a carboxyl enriched curable polyester which can be further neutralized with an amine, e.g. N,N-dimethyl- ethanolamine, triethylamine, or ammonia. For the preparation of satisfactory water-borne enamel compositions, it is desirable that the curable polyester resins have an acid number of about 40 to about 70. The amine used for forming the hydrophilic salts can be evaporated during the baking process for curing. However, coatings thus prepared may be water sensitive due to the presence of residual amine, unreacted TMA, and hydrophilic carboxyl end-groups in the cured films.

Crosslinkable resins end-capped with phenolic groups have been disclosed in a number of references. However, such resins have never been utilized to obtain hydrophilic phenolic ammonium salts for water-borne coatings. European Patent Application No. 419,088 discloses esterphenol-capped liquid polymer and polyol compositions in combination with an amino crosslinking agent which provides films having superior properties. U.S. Patent No. 2,993,873 discloses that drying times and coating properties of oil-modified alkyd resins can be improved by replacing part of unsaturated fatty acids with hydroxybenzoic acid in the resin formulations. The coatings are cured by air dry or baking without the presence of a crosslinking agent. U.S. Patent

Nos. 4,267,239 and 4,298,658 describe the modification of alkyd resins by reacting with p-hydroxybenzoic acid. The resulting resins can be rapidly cured at ambient temperatures with isocyanates in the presence of a tertiary amine vapor. U.S. Patent Nos. 4,343,839 and 3,836,491 disclose a coating composition which is rapidly curable at room temperature in the presence of a tertiary amine catalyst vapor. The coating compositions are phenolic terminated polyesters and multi-isocyanate curing agents. U.S. Patent No. 4,331,782 discloses the improved synthesis of a phenol-functional polyester which utilizes a preformed adduct of a hydroxybenzoic acid and an epoxy compound. Japanese Patent Nos.

75 40,629, 76 56,839, 76 44,130, and 7773,929 disclose powder coating compositions containing phenolic hydroxy end groups. These resins have high softening points and are applied to the surface as powders.

The present invention provides curable resin compositions having phenolic functional groups which are neutralized with an amine to yield quaternary ammonium salts. These resin salts are hydrophilic, and thus can be dispersed in water and further formulated into industrial baking enamels. The end groups of the resins described herein are hydroxyl enriched and the resins have a low acid number of about 5 to about 39. The acid number stated herein is defined as the number of

milligrams of potassium hydroxide required to neutralize the carboxyl end-groups of the resin in 1 g of the sample. The analysis is carried out according to ASTM Method D 1639 except that the end point is determined by a potentiometric titration method in order to

distinguish it from the end point of phenolic functional groups. These resins having an acid number of about 5 to about 39 can be directly neutralized with an amine such as N,N-dimethylethanolamine or triethylamine.

There is thus no need to use water-sensitive, highly toxic trimellitic anhydride as a component in resin compositions. The amine can be easily removed from the phenolic ammonium salts when coatings are cured, and the phenolic groups readily react with a suitable cross- linking agent. As a result, coatings prepared from the enamel compositions of the present invention exhibit excellent water-resistance. The coatings made possible by the application of the compositions of the present invention are useful as automotive, appliance, and machinery coatings.

The present invention provides a water-borne enamel composition, comprising

(I) an amine salt of a curable polymer having at least one aromatic hydroxyl functional group and an acid number of about 5 to about 39, said polymer having the following structure: Z- [-Ar-O^-+N(R')₃H]_n wherein Z is a curable polymer residue; Ar is an aromatic moiety attached to said polymer residue chain-end, backbone, or side-chain; R' is hydrogen, C₁-C₆ alkyl, or substituted C₁-C₆ alkyl; and n is an integer equal to or greater than one; (II) a water-dispersible crosslinking agent having suitable functional groups which can react with component (I) and form a coating film; and

(III) an amount of water sufficient to disperse

components (I) and (II).

In a preferred embodiment of the present invention, there is provided the above composition wherein

component (I) is present in a range of about 25 to about 65 weight percent; component (II) is present in a range of about 5 to about 20 weight percent; and component (III) is present in a range of about 30 to about 70 weight percent, the total of (I), (II), and (III) being 100%.

The above enamel composition may further comprise a suitable amount of an organic co-solvent. Such solvents include ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, isobutanol, ethylene glycol monobutyl ether, propylene glycol n-butyl ether, propylene glycol methyl ether, propylene glycol monopropyl ether,

dipropylene glycol methyl ether, diacetone alcohol, and other water-miscible solvents.

Examples of polymer of component (I) include polyesters, alkyds, epoxys, and acrylic polymers.

The amine salt of component (I) is prepared by reacting a phenolic-functional polymer, e.g., a

polyester, with an amine at ambient temperatures under agitation. In the case where the polymer is a

polyester, it may be an oil-free polyester or an alkyd. In the preparation of the phenolic-functional polyester, it is preferred that the reactants, i.e., the diol, triol/polyol, diacid, and an aromatic hydroxyacid, be combined neat in the presence of a condensation catalyst and heated to a temperature of about 175°C to about 230°C. Typical reaction times range from about 5 hours to about 20 hours. The reaction generally requires the use of a steam heated partial-condenser to remove the condensate, water and/or alcohol, and at the same time condense back the volatile reactants. The reaction is preferably carried out under the constant flow of nitrogen gas.

In the above polyester synthesis, it is further preferred that the triol/polyol be combined with the aromatic hydroxyacid in the first stage of the reaction in order to produce a diol adduct, followed by the addition of diol and diacid.

In such curable polyesters, suitable diol residues are preferably selected from residues of ethylene glycol; propylene glycol; 1,3-propanediol; 2,4-dimethyl- 2-ethylhexane-1,3-diol; 2,2-dimethyl-1, 3-propanediol; 2-ethyl-2-butyl-1,3-propanediol; 2-ethyl-2-isobutyl-1,3- propanediol; 1,3-butanediol; 1,4-butanediol; 1,5- pentanediol, 1,6-hexanediol; 2,2,4-trimethyl-1,3- pentanediol; thiodiethanol; 1,2-cyclohexanedimethanol; 1,3-cyclohexanedimethanol; 1,4-cyclohexanedimethanol; 2,2,4,4-tetramethyl-1, 3-cyclobutanediol; p-xylylenediol; diethylene glycol, triethylene glycol; tetraethylene glycol; and pentaethylene, hexaethylene, heptaethylene, octaethylene, nonaethylene, and decaethylene glycols; suitable triol and/or polyol residues are selected from residues of trimethylolpropane; trimethylolethane;

glycerol; 2,2-bis(hydroxymethyl)-1, 3-propanediol;

1,2,3,4,5,6-hexahydroxyhexane, and bis(2,2-bis(hydroxy- methyl)-3-propanol ether.

Preferably the carboxylic acid residues of the curable polyesters are selected from residues of oxalic; malonic, dimethylmalonic; succinic; glutaric; adipic; trimethyladipic; pimelic, 2,2-dimethylglutaric; azelaic; sebacic, fumaric; maleic; itaconic; 1,3-cyclc- pentanedicarboxylic; 1,2-cyclohexanedicarboxylic; 1,3- cyclohexanedicarboxylic; 1,4-cyclohexanedicarboxylic; phthalic; terephthalic; isophthalic; 2,5-norbornane- dicarboxylic; 1,4-naphthalic; diphenic; 4,4'-oxydi- benzoic, diglycolic; thiodipropionic; 4,4'-sulfonyl- dibenzoic; and 2,6-naphthalenedicarboxylic acids or anhydrides thereof.

In such polyesters, the aromatichydroxy acid residue is preferably a residue of p-hydroxybenzoic acid, m-hydroxybenzoic acid, salicylic acid, 5- hydroxyisophthalic acid, 4-hydroxyisophthalic acid, 1-hydroxy-4-naphthoic acid, 1-hydroxy-5-naphthoic acid, 1-hydroxy-6-naphthoic acid, 1-hydroxy-7-naphthoic acid, 1-hydroxy-8-naphthoic acid, 2-hydroxy-4-naphthoic acid, 2-hydroxy-5-naphthoic acid, 2-hydroxy-6-naphthoic acid, 2-hydroxy-7-naphthoic acid, and 2-hydroxy-8-naphthoic acid.

The alkyd component (I) is a polyester described above, further incorporating unsaturated fatty acids or oils such a linseed oil, tall oil, soya bean oil, coconut oil, and the like into the polymer chains.

The epoxy component (I) is preferably a diglycidyl ether of bisphenol A prepared by condensation of

bisphenol A and epichlorohydrin, such as DER 330, 331, 332, and 337, available from Dow Chemical Company.

Phenolic-functional polymers may be obtained by reacting these epoxy polymers with a aromatic hydroxyacid such as the ones listed above.

The acrylic polymer component (I) is preferably a polymer or resin prepared by polymerization of a

hydroxyl-bearing monomer such as hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxyhexyl acrylate, hydroxyhexyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxyIbutyl methacrylate and the like, or an epoxy-bearing monomer such as glycidyl acrylate, glycidyl methacrylate; optionally polymerized with other monomers such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, isobutyl acrylate, isobutyl

methacrylate, ethylhexyl acrylate, ethylhexyl

methacrylate, styrene, vinyl acetate, acrylic acid methacyrlic acid and the like. Phenolic-functional acrylic polymers may be obtained by reacting the above hydroxy or epoxy-bearing acrylic polymers with an aromatic hydroxy acid such as those listed above.

The aromatic moiety in component (I) is preferably a phenyl or naphthyl group and may be further

substituted with one to three groups independently selected from C₁-C₄ alkyl, C₁-C₄ alkoxy, or halogen.

Examples of crosslinking agents include amino crosslinking agents such as hexamethoxymethylmelamine, mixed methoxymethyl/methylol-melamine, mixed

butoxy/roethoxy-methylmelamine, tetramethoxy- methylbenzoquanamine, tetramethoxymethylurea, and the like; isocyanate type crosslinking agents such as toluene diisocyanate, hexamethylene diisocyanate, 4,4'- dicyclohexylmethane diisocyanate, and the like; epoxy type crosslinking agent such as bisphenol A epoxy resins and the like. The cross-linking agent is preferably a melamine-formaldehyde type cross-linking agent, i.e., a cross-linking agent having a plurality of -N(CH₂OR³)₂ functional groups, wherein R³ is C₁-C₄ alkyl or

hydrogen, preferably methyl. In general, the cross-linking agent may be selected from compounds of the following formulae, wherein R³ is independently C₁-C₄ alkyl or hydrogen:

In the preparation of the amine salt of component

(I), compounds of the formula N(R')₃ are used, wherein

R' is hydrogen, C₂-C₆ alkyl, or substituted C₂-C₆ alkyl. Examples of the term "C₁-C₆ alkyl" include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl,

n-pentyl, sec-pentyl, hexyl, sec-hexyl and the like. The term "substituted C₁-C₆ alkyl" includes the above alkyl groups substituted by one to three groups selected from halo, nitro, hydroxy, C₂-C₆ alkoxy, and cyano.

Examples of preferred amines of the formula N(R')₃ include N,N-dimethylethanolamine, triethylamine,

diethylamine, ammonium hydroxide, triethanolamine, diethanolamine, ethanolamine, isopropanolamine, N,N- diethylethanolamine, 2-N,N-dimethylamino-2-methylpropanol, 2-amino-2-methylpropanol, N-ethylmorpholine and the like. Tertiary amines are especially preferred.

As noted above, n is an integer which is greater than or equal to 1, preferably from 1 to about 10.

In another embodiment of this invention, there is provided a water-borne enamel composition, comprising

(I) about 25 to about 65 weight percent of an

amine salt of a curable polyester containing phenolic functional groups; wherein said polyester has an acid number of about 5 to 39, a number average molecular weight of about 800 to 3,500 and a weight average molecular weight of about 3,000 to 70,000, comprising

(a) about 20 to 45 mole percent of diol

residues, based on the total moles of

(a), (b), (c), (d), and (e);

(b) about 4 to 21 mole percent of triol

residues, based on the total moles of (a), (b), (c), (d), and (e);

(c) about 5 to 20 mole percent, based on the total moles of (a), (b), (c), (d), and (e), of residues of an aliphatic diacid; (d) about 20 to 35 mole percent, based on the total moles of (a), (b), (c), (d), and (e), of residues of aromatic diacids; (e) about 12 to 20 mole percent based on the total moles of (a), (b), (c), (d), and (e), of residues of an aromatic hydroxy acid; (II) about 5 to about 20 weight percent of an amino crosslinking agent;

(III) about 0 to about 10 weight percent of a

water-miscible organic solvent; and

(IV) about 30 to about 70 weight percent of water; the total weight percent of (I), (II), (III), and (IV) being 100. As a further aspect of the present invention, thereis rovided a water-borne enamel composition, comprising

(I) about 25 to about 65 weight percent of an

amine salt of a curable polyester containing phenolic functional groups; wherein said polyester having an acid number of about 5 to 39, a number average molecular weight of about 800 to 3,500 and a weight average molecular weight of about 3,000 to 70,000, comprising

(a) about 20 to 45 mole percent of diol

residues, based on the total moles of (a), (b), (c), (d), and (e); (b) about 4 to 21 mole percent of triol residues, based on the total moles of (a), (b), (c), (d), and (e); (c) about 0 to 20 mole percent, based on the total moles of (a), (b), (c), (d), and (e), of residues of an acyclic aliphatic diacid; (d) about 20 to 35 mole percent, based on the total moles of (a), (b), (c), (d), and (e), of residues of cycloaliphatic diacids; (e) about 12 to 20 mole percent based on the total moles of (a), (b), (c), (d), and (e), of residues of an aromatic hydroxy acid; (II) about 5 to about 20 weight percent of an amino crosslinking agent;

(III) about 0 to about 10 weight percent of a

water-miscible organic solvent; and

(IV) about 30 to about 70 weight percent of water; the total weight percent of (I), (II), (III), and (IV) being 100. The most preferred acid number range of the

polyesters of this invention is about 10 to about 25.

Examples of cycloaliphatic diacid components include 1,2-cyclohexanedicarboxylic acid, 1,3- cyclohexanedicarboxylic acid, 1,4-cyclohexane- dicarboxylic acid, and 1,3-cyclopentanedicarboxylic acid and anhydrides thereof. 1,4-Cyclohexanedicarboxylic acid is highly preferred.

The enamel of this invention may be prepared by dissolving the neat polyester resin in an organic cosolvent at an elevated temperature, followed by

dispersing the resin solution with amine and water, followed by adding a crosslinking agent. The enamel can also be prepared from a 70-80 % resin by weight in an organic solvent. This viscous, pourable resin is prepared by adding a suitable organic solvent to the reaction mixture after the completion of resin synthesis and is being stored. Amine, water, and crosslinking agent are added to this resin under agitation to yield an aqueous dispersion; heating is not required.

An acid catalyst is not required provided that the coating is cured at a temperature higher than 150°C. An acid catalyst may be added to obtain optimal coating properties or for curing at lower temperatures. Suitable acid catalysts include p-toluenesulfonic acid; NACURE

5076, 155, 1051 from King Industries; and amine blocked acid catalysts such as BYK-catalyst 450, 460, 470 from BYK-Chemie USA.

As a further aspect of the present invention there is provided a cross-linkable enamel composition as described above, further comprising one or more

leveling, rheology, and flow control agents such as siliconeε, fluorocarbons or cellulosics; flatting agents; pigment wetting and dispersing agents;

surfactants; ultraviolet (UV) absorbers; UV light stabilizers; tinting pigments; defoaming and antifoaming agents; anti-settling, anti-sag and bodying agents;

anti-skinning agents; anti-flooding and anti-floating agents; fungicides and mildewicides; corrosion

inhibitors; thickening agents; or coalescing agents.

Specific examples of such additives can be found in Raw Materials Index, published by the National Paint & Coatings Association, 1500 Rhode Island Avenue, N.W., Washington, D.C. 20005.

Examples of flatting agents include synthetic silica, available from the Davison Chemical Division of W.R. Grace & Company under the trademark SYLOID^®;

polypropylene, available from Hercules Inc., under the trademark HERCOFLAT^®; synthetic silicate, available from J.M. Huber Corporation under the trademark ZEOLEX^®.

Examples of dispersing agents and surfactants include sodium bis(tridecyl) sulfosuccinnate, di(2-ethyl hexyl) sodium sulfosuccinnate, sodium dihexylsulfc- succinnate, sodium dicyclohexyl sulfosuccinnate, diamyl sodium sulfosuccinnate, sodium diisobutyl sulfosuccinnate, disodium isodecyl sulfosuccinnate, disodium ethoxylated alcohol half ester of sulfosuccinnic acid, disodium alkyl amido polyethoxy sulfosuccinnate, tetra- sodium N-(1,2-dicarboxy-ethyl)-N-octadecyl sulfc- succinnamate, disodium N-octasulfosuccinnamate, sulfated ethoxylated nonylphenol, 2-amino-2-methyl-1-propanol, and products available from BYK-Chemie, U.S.A., under the marks BYKUMEN^®, DISPERBYK^®, LACTIMON^®, and the like.

Examples of viscosity, suspension, and flow control agents include polyaminoamide phosphate, high molecular weight carboxylic acid salts of polyamine amides, and alkyl amine salt of an unsaturated fatty acid, all available from BYK Chemie U.S.A. under the trademark ANTI TERRA^®. Further examples include polysiloxane copolymers, polyacrylate solution, cellulose esters, hydroxyethyl cellulose, hydrophobically-modified

hydroxyethyl cellulose, hydroxypropyl cellulose. polyamide wax, polyolefin wax, carboxymethyl cellulose, ammonium polyacrylate, sodium polyacrylate, and

polyethylene oxide.

Several proprietary antifoaming agents are

commercially available, for example, under the trademark BRUBREAK of Buckman Laboratories Inc., under the BYK^® trademark of BYK Chemie, U.S.A., under the FOAMASTER^® and NOPCO^® trademarks of Henkel Corp./Coating Chemicals, under the DREWPLUS^® trademark of the Drew Industrial Division of Ashland Chemical Company, under the TROYSOL^® and TROYKYD^® trademarks of Troy Chemical Corporation, and under the SAG^® trademark of Union Carbide

Corporation.

Examples of fungicides, mildewicides, and biocides include 4,4-dimethyloxazolidine, 3,4,4-trimethyl- oxazolidine, modified barium metaborate, potassium

N-hydroxy-methyl-N-methyldithiocarbamate, 2-(thiocyano- methylthio) benzothiazole, potassium dimethyl dithio- carbamate, adamantane, N-(trichloromethylthio)

phthalimide, 2,4,5,6-tetrachloroisophthalonitrile, orthophenyl phenol, 2,4,5-trichlorophenol, dehydroacetic acid, copper naphthenate, copper octoate, organic arsenic, tributyl tin oxide, zinc naphthenate, and copper 8-quinolinate.

Examples of U.V. absorbers and U.V. light

stabilizers include substituted benzophenone,

substituted benzotriazole, hindered amine, and hindered benzoate, available from American Cyanamide Company under the tradename Cyasorb UV, and available from Ciba Geigy under the tradename Tinuvin, and diethyl-3-acetyl- 4-hydroxy-benzyl-phosphonate, 4-dodecyloxy-2-hydroxy benzophenone, and resorcinol monobenzoate.

Such paint or coating additives as described above form a relatively minor proportion of the enamel composition, preferably about 0.05 weight % to about 5.00 weight %.

As a further aspect of the present invention, there is provided a curable enamel composition optionally containing one or more of the above-described additives, further comprising one or more pigments.

Pigments suitable for use in the enamel compositions envisioned by the present invention are the typical organic and inorganic pigments, well-known to one of ordinary skill in the art of surface coatings, especially those set forth by the Colour Index, 3d Ed., 2d Rev., 1982, published by the Society of Dyers and Colourists in association with the American Association of Textile Chemists and Colorists. Examples include but are not limited to the following: CI Pigment White 6

(titanium dioxide); CI Pigment Red 101 (red iron oxide); CI Pigment Yellow 42, CI Pigment Blue 15, 15:1, 15:2, 15:3, 15:4 (copper phthalocyanines); CI Pigment Red 49:1, and CI Pigment Red 57:1.

Upon formulation above, the curable enamel composition is then applied to the desired substrate or

article, e.g., steel, aluminum, or galvanized sheeting (either primed or unprimed), heated (i.e., cured) to a temperature of about 130°C to about 175°C, for a time period of 5-60 minutes and subsequently allowed to cool. Thus, as a further aspect of the present invention, there is provided a shaped or formed article which has been coated with the thermosetting coating compositions of the present invention and cured.

Further examples of typical application and curing methods can be found in U.S. Patent Nos. 4,737,551 and 4,698,391, incorporated herein by reference.

As a further aspect of the present invention, there is provided a coating which results from the application and curing of the curable enamel composition as set forth above.

Experimental Section

Example 1 - Preparation of Resin 1

To a three-neck round bottom flask equipped with a mechanical stirrer, a steam partial-condenser, a Dean- Stark trap, and a water condenser were charged the following reactants: trimethylolpropane (TMP) 121.1 g (0.90 mole), p-hydroxybenzoic acid (PHBA) 146.5 g (1.06 mole), the catalyst, FASCAT 4100 0.5 g, and the color stabilizer, WESTON 618, 1 g. The mixture was heated to 150°C and stirred under a nitrogen atmosphere. The temperature was then gradually increased to 220°C in a period of one hour and the distillate collected in the Dean-Stark trap. When the collection of the distillate stopped (1.5 more hours), indicating the first stage reaction was almost complete, neopentyl glycol (NPG)

222.0 g (2.13 mole) and isophthalic acid (IPA) 358.6 g (2.16 mole) were then added. After stirring for eight more hours, adipic acid (AD) 81.8 g (0.56 mole) was added. The reaction was complete after stirring for four more hours to give a resin with an ICI Cone and Plate viscosity of 59 poises at 175°C. The resin was

collected in a metal container and allowed to cool to room temperature (rt). Example 2 - Preparation of Water-borne Enamel 1

Resin 1 (40 g) was heated to 125°C and stirred in a round-bottom flask equipped with a water condenser. To the resin was added ethylene glycol monobutyl ether (10 g), EKTASOLVE ethylene glycol monobutyl ether (EB) available from the Eastman Chemical Company division of Eastman Kodak Company, followed by the addition of N,N- dimethylethanolamine DMEA (1.25 g). The mixture was stirred for 20 minutes and cooled to 50°C. Distilled water (60 g) was then gradually added to the mixture to give a milky aqueous dispersion. A water-borne enamel was prepared by adding CYMEL 303 (American Cyanamid) (10 g) and additional water (10 g) to the above aqueous dispersion.

Example 3 - Preparation of Resin 2 as 70 % Solid

To a three-neck round bottom flask equipped with a mechanical stirrer, a steam partial-condenser, a Dean- Stark trap, and a water condenser were charged the following reactants: TMP 70.19 g (0.52 mole), PHBA 84.90 g (0.62 mole), the catalyst, FASCAT 4100 0.45 g, and the color stabilizer, WESTON 618, 0.92 g. The mixture was heated to 150°C and stirred under a nitrogen atmosphere. The temperature was then gradually increased to 200°C and the distillate collected in the Dean-Stark trap.

The first stage reaction was complete after three hours; NPG 120.00 g (1.15 mole) and IPA 207.81 g (1.25 mole) were then added. After stirring for additional four hours at 220°C, AD 47.40 g (0.32 mole) was added. The reaction was complete after stirring for additional 3.5 hours to give a resin with an ICI viscosity of 43 poises at 175°C. The resin was then allowed to cooled to 145°C and 196 g of ethylene glycol monobutyl ether (EB) added to afford a 70 % solid resin. Example 4 - Preparation of Water-borne Enamel 2

To 28.6 g of Resin 2 above (70 % solid in EB) were added DMEA (0.55 g) and distilled water (30 g). The mixture was stirred to give an aqueous dispersion. To this dispersion were added CYMEL 303 (5.0 g), FLOURAD FC-430 flow control agent (3 M company) (20 % in

isopropanol, 0.3 g), and additional water (17 g) to yield a water-borne enamel.

Example 5 - Preparation of Resin 3 as 75 % Solid

The first stage reaction was complete after three hours; NPG 120.00 g (1.15 mole) and 1,4-cyclohexanedicarboxylic acid 270.94 g (1.58 mole) were then added. The reaction was complete after stirring for an additional six hours at 220°C to give a resin with an ICI viscosity of 29 poises at 175°C. The resin was then allowed to cooled to 145°C and 160 g of ethylene glycol monobutyl ether (EB) added to afford a 75 % solid resin.

Example 6 - Preparation of Water-borne Enamel 3

To 40.0 g of Resin 3 above (75 % solid in EB) were added DMEA (0.75 g) and distilled water (30 g). The mixture was stirred to give an aqueous dispersion. To this dispersion were added CYMEL 303 (American Cyanamid) (7.5 g), FLOURAD FC-430 flow control agent (3 M company) (20 % in isopropanol, 0.4 g), and additional water

(30 g) to yield a water-borne enamel.

Example 7 - Preparation of Comparative Resins

To a three-neck round bottom flask equipped with a mechanical stirrer, a steam partial-condenser, a Dean- Stark trap, and a water condenser were charged the following reactants: NPG 267.40 g (2.57 mole), TMP 38.20 g (0.29 mole), IPA 203.60 g (1.23 mole), AD 179.00 g (1.23 mole), and the catalyst, FASCAT 4100 0.8 g. The mixture was heated to 150°C and stirred under a nitrogen atmosphere. The temperature was then gradually

increased to 175°C and held for three hours; the

distillate was collected in the Dean-Stark trap. The reaction was allowed to continue at 200°C for about 2.5 hours to give a resin with an acid number of 22.

The above reaction was repeated to obtain a resin with an acid number of 14. Although these two comparative resins had similar acid numbers as resins 1, 2, and 3, it was found that stable, homogeneous aqueous enamels could not be prepared by following the same procedure as Example 2.

Example 8 - Preparation of Coatings

Coatings were prepared by applying various enamels to cold-rolled steel test panels (ACT 3x9x032 from

Advanced Coating Technologies) and baking in an oven at 175°C for 30 minutes. The thickness of the coating films was about 1.0 to 1.5 mil. The coating of Enamel 1 showed no effect after 1,000 hours of the Cleveland humidity test (ASTM Method D2247). The properties of various resins and coatings are listed in Tables I and II. Acid number and phenolic OH number were determined according to ASTM method D1639; the end points were determined by a potentiometric titration method.

Molecular weights were estimated by gel permeation chromatography. Viscosities were measured by using an ICI Cone and Plate viscometer. Acid-etch resistance of the coatings was tested by adding a few drops of 10% sulfuric acid (e.g. six drops) onto the film surface of the coated panel and baking in an oven at 50°C or 60°C for 0.5 hour. Other coating testings were carried out according to the following standard methods:

1. Film Thickness (Fisher Deltascope MP 2)

2. Solvent Resistance (MEK Double Rub, ASTM

D1308)

3. Gloss (BYK- micro-gloss, ASTM D523)

4. Pencil Hardness (ASTM D3362)

5. Impact Resistance (BYK- Gardner Impact Tester, ASTM D2794)

Mn: number average molecular weight Mw: weight average molecular weight

Claims

Claims I claim:

1. A water-borne enamel composition, comprising

(I) an amine salt of a curable polymer having at least one aromatic hydroxyl functional group and an acid number of about 5 to about 39, said polymer having the following structure: Z -[-Ar-O^-+N(R')₃H]_n wherein Z is a curable polymer residue; Ar is an aromatic moiety attached to said polymer residue chain-end, backbone, or side-chain; R' is hydrogen, C₁-C₆ alkyl, or substituted C₁-C₆ alkyl; and n is an integer equal to or greater than one;

(II) a water-dispersible crosslinking agent having suitable functional groups which can react with component (I) and form a coating film; and

(III) an amount of water sufficient to disperse

components (I) and (II).

2. The composition of Claim 1, wherein Ar is phenyl or naphthyl.

3. The composition of Claim 1 or 2, wherein Ar is a group in the polymer backbone having the formula

4. The composition of any one of Claims 1 to 3,

wherein n is 1 to about 10.

5. The composition of any one of Claims 1 to 4,

wherein Z is a polyester or an acrylic polymer residue.

6. The composition of any one of Claims 1 to 5,

wherein component (I) is present in a range of about 25 to about 65 weight percent; component (II) is present in a range of about 5 to about 20 weight percent; and component (III) is present in a range of about 30 to about 70 weight percent, the total of (I), (II), and (III) being 100%.

7. A water-borne enamel composition, comprising

(I) about 25 to about 65 weight percent of an

amine salt of a curable polyester having phenolic functional groups; wherein said polyester has an acid number of about 5 to 39, a number average molecular weight of about 800 to 3,500 and a weight average molecular weight of about 3,000 to 70,000, comprising

(a) about 20 to 45 mole percent of diol

residues, based on the total moles of (a), (b), (c), (d), and (e); (b) about 4 to 21 mole percent of triol residues, based on the total moles of (a), (b), (c), (d), and (e);

(c) about 5 to 20 mole percent, based on the total moles of (a), (b), (c), (d), and (e), of residues of an aliphatic diacid;

(d) about 20 to 35 mole percent, based on the total moles of (a), (b), (c), (d), and (e), of residues of aromatic diacids;

(e) about 12 to 20 mole percent based on the total moles of (a), (b), (c), (d), and (e), of residues of an aromatic hydroxy acid;

(II) about 5 to about 20 weight percent of an

amino crosslinking agent;

(III) about 0 to about 10 weight percent of a

suitable organic solvent; and

(IV) about 30 to about 70 weight percent of water; the total weight percent of (I), (II), (III), and (IV) being 100.

8. The composition of Claim 7, wherein the aromatic hydroxy acid residue is a residue of p-hydroxy benzoic acid.

9. The composition of Claim 7, wherein component (a) is neopentyl glycol; component (b) is trimethylol- propane; component (c) is adipic acid; component (d) is isophthalic acid; and component (e) is p-hydroxybenzoic acid.

10. A water-borne enamel composition, comprising

(I) about 25 to about 65 weight percent of an

(a) about 20 to 45 mole percent of diol

residues, based on the total moles of (a), (b), (c), (d), and (e);

(b) about 4 to 21 mole percent of triol

residues, based on the total moles of (a), (b), (c), (d), and (e);

(c) about 0 to 20 mole percent, based on the total moles of (a), (b), (c), (d), and (e), of residues of an acyclic aliphatic diacid;

(d) about 20 to 35 mole percent, based on the total moles of (a), (b), (c), (d), and (e), of residues of cycloaliphatic diacids;

(e) about 12 to 20 mole percent based on the total moles of (a), (b), (c), (d), and (e), of residues of an aromatic hydroxy acid; (II) about 5 to about 20 weight percent of an amino crosslinking agent;

(III) about 0 to about 10 weight percent of a

suitable organic solvent; and

(IV) about 30 to about 70 weight percent of water; the total percents of (I), (II), (III), and (IV) being 100.

11. The composition of Claim 10, wherein the cycloaliphatic diacid residues are comprised of residues of 1,4-cyclohexanedicarboxylic acid.

12. The composition of Claim 10, wherein the aromatic hydroxy acid is selected from residues of p-hydroxy benzoic acid.

13. The composition of Claim 10, wherein component (a) is neopentyl glycol; component (b) is trimethylol- propane; component (c) is adipic acid; component (d) is 1,4-cyclohexanedicarboxylic acid; and component (e) is p-hydroxybenzoic acid.

14. A shaped or formed article coated with the cured composition of Claim 1.