WO1999061506A1

WO1999061506A1 - Thermosetting coating compositions based on polyesters

Info

Publication number: WO1999061506A1
Application number: PCT/US1998/027919
Authority: WO
Inventors: Philip Conrad Heidt; Matthew Lynn Elliott
Original assignee: Eastman Chemical Company
Priority date: 1998-12-30
Filing date: 1998-12-30
Publication date: 1999-12-02

Abstract

The invention describes oil-free polyester resin compositions based on the polycondensation product of a diol and a diacid of which either or both are a decalin or tetralin derivative. Enamel coating compositions containing such polyester resin compositions are also described. Application and curing of such enamel coating compositions onto a substrate or article gave films exhibiting excellent flexibility, hardness, weatherability, acid-etch, and stain resistance.

Description

THERMOSETTING COATING COMPOSITIONS BASED ON POLYESTERS

Field of the Invention

This invention belongs to the field of polyester chemistry. In particular, the invention relates to use of various decalin- and tetralin- diols and/or dicarboxyhc acids to form polyesters. Such polyesters are useful in coating compositions.

Background of the Invention

There is a need in the coatings industry for highly weatherable thermosetting coatings which also exhibit high degrees of hardness, acid-etch and stain resistance while maintaining excellent flexibility. Because hardness and scratch resistance are related to the glass transition temperatures (T_g) of the coatings, it is desirable to have coatings with high T_g's. It is well-known that highly crosslinked coatings which also contribute to increasing the hardness and T_g of the coating also suffer from inadequate flexibility for many applications. U.S. Patent No. 3,271,365 describes the use of decalin derivatives to make high molecular weight linear thermoplastic polyesters which could be made into various molded articles, fibers, and films. The use of decalindimethanol is described in U.S. patent 3,361,716. U.S. Patent No. 3,505,282 describes the use of tetralin derivatives to make high molecular weight linear thermoplastic polyesters. The use of both decalin and tetralin derivatives have been extended into polyamides for applications, such as, molded articles, fibers, and films as described in U.S. Patent No. 3,534,002. Although the use of both decalin and tetralin derivatives have been used in the above mentioned applications, the use of high molecular weight linear polyesters and polyamides severely restrict their use in thermosetting applications especially for use in coatings where high performance and low volatile organic compound (VOC) coatings are required.

The use of decalin derivatives in aqueous urethane polyester polymer dispersions in thermosetting coatings have been described in U.S. Patent No. 4,758,615. Although mentioned in the broadest terms, no advantages on the use of tetralin and decalin derivatives were ever mentioned. Instead, the application was for the use of urethane dispersions and the use of the tetralin and decalin derivatives were just part of a generic polyester backbone.

In the present invention, the use of properly designed bicyclic resin intermediates in a coatings composition in place of or in combination with commonly used aromatic, acyclic and monocycloaliphatic resin intermediates provides for coatings which are highly flexible while still maintaining excellent weathering, hardness, acid-etch, and stain resistance.

Summary of the Invention The invention provides oil-free polyester resin compositions containing bicycloaliphatic (eg. decalin) and/or bicycloaromatic (eg. tetralin) groups prepared by conventional direct polycondensation processes.

The invention further provides enamel coating compositions based on oil-free polyester resin compositions containing bicycloaliphatic and/or bicycloaromatic groups. For example, resin composition of the invention may be dissolved in conventional solvents or used as powders and further formulated into thermosetting coating compositions. Upon application to a substrate and subsequent curing, such coating compositions form films which exhibit excellent flexibility, hardness, weatherability, acid-etch, and stain resistance.

Detailed Description of the Invention

The present invention provides a curable polyester resin composition having a number average molecular weight of about 800 to about 5000 and a weight average molecular weight of about 1600 to about 50,000, and containing the polycondensation product of diol and a diacid of which either or both of the diol and the diacid is a decalin or tetralin derivative, as described below. Preferably, a polyester resin composition of the invention contains about 20-100 mol percent of a decalin or tetralin derivative of the diol or diacid based on the total mol percent of decalin and/or tetralin derivative present in the composition. As used herein, "decalin" is defined as "decahydronaphthalene" and further refers to all stereoisomers thereof and "tetralin" is defined as "1,2,3,4-tetrahydronaphthalene" and all stereoisomers thereof. Thus, for example, 2,6-decalindicarboxylic acid as used in this invention refers to 2,6-decahydronaphthalenedicarboxylic acid. The structures of 2,6- decalindimethanol, 2,6-decalindicarboxylic acid (and derivatives), and 2,6- tetralindicarboxylic acid (and derivatives) are shown below as Figures 1, 2, and 3 respectively:

In the processes and curable polyesters described herein, preferred diols are chosen from ethylene glycol; propylene glycol; 1,3-propanediol; 2-methyl-l,3- propanediol; 2,2-dimethyl-l,3-propanediol; 2-butyl-2-ethyl-l,3-propanediol; 2-ethyl-2- isobutyl-l,3-propanediol; 1,3-butanediol; 1 ,4-butanediol; 1,5-pentanediol; 2,2,4- trimethyl-l,3-pentanediol; 1,6-hexanediol; 2,4-dimethyl-2-ethyl-l,3-hexanediol; thiodiethanol; hydrogenated bisphenol A; 1,2-cyclohexanedimethanol; 1,3- cyclohexanedimethanol; 1 ,4-cyclohexanedimethanol; 2,2,4,4-tetramethyl-l,3- cyclobutanediol; diethylene glycol; triethylene glycol; tetraethylene glycol; pentaethylene glycol; hexaethylene glycol; heptaethylene glycol; octaethylene glycol; nonaethylene glycol; decaethylene glycol; 1,1-decalindimethanol; 1,2-decalindimethanol; 1,3-decalindimethanol; 1,4-decalindimethanol; 1,5-decalindimethanol; 1,6- decalindimethanol; 1,7-decalindimethanol; 1,8-decalindimethanol; 2,2- decalindimethanol; 2,3-decalindimethanol; 2,6-decalindimethanol; 2,7- decalindimethanol; and 3-hydroxy-2,2-dimethylpropyl 3-hydroxy-2,2- dimethanolpropanoate. The more preferred diols are 2,6-decalindimethanol (DDM); 2,2- dimethyl-l,3-propanediol; 2-butyl-2-ethyl-l,3-propanediol; 1,6-hexanediol; 1,4- cyclohexanedimethanol; hydrogenated bisphenol A; and 3-hydroxy-2,2-dimethylpropyl 3-hydroxy-2,2-dimethylpropanoate.

Triols and tetraols may also be used in the compositions of the invention. Preferred triols include, but not limited to, trimethanolethane, trimethanolpropane, glycerol, and the like. The most preferred triol is trimethanolpropane (TMP). A preferred tetraol is pentaerythritol.

In the processes and curable polyesters described herein, preferred acids, esters and anhydrides thereof are chosen from succinic; glutaric; adipic; pimelic; suberic; azelaic; sebacic; dodecanedioic; phthalic; isophthalic; terephthalic; 1,2- cyclohexanedicarboxylic; 1,3-cyclohexanedicarboxylic; 1,4-cyclohexanedicarboxylic; methylhexahydrophthalic; ethylhexahydrophthalic; propylhexahydrophthalic; butylhexahydrophthalic; tetrahydrophthalic; methyltetrahydrophthalic, ethyltetrahydrophthalic; propyltetrahydrophthalic; butyltetrahydrophthalic; maleic; 1,2- decalindicarboxylic; 1,3-decalindicarboxylic; 1,4-decalindicarboxylic; 1,5- decalindicarboxylic; 1,6-decalindicarboxylic; 1,7-decalindicarboxylic; 1,8- decalindicarboxylic; 2,3-decalindicarboxylic; 2,6-decalindicarboxylic; 2,7- decalindicarboxylic; 1,2-tetralindicarboxylic; 1,3-tetralindicarboxylic; 1,4- tetralindicarboxylic; 1,5-tetralindicarboxylic; 1,6-tetralindicarboxylic; 1,7- tetralindicarboxylic; 1,8-tetralindicarboxylic; 2,3-tetralindicarboxylic; 2,6- tetralindicarboxylic; and 2,7-tetralindicarboxylic. The more preferred acids, esters and anhydrides thereof include adipic; isophthalic; 1,2-cyclohexanedicarboxylic; 1,3- cyclohexanedicarboxylic; 1,4-cyclohexanedicarboxylic; 2,6-decalindicarboxylic; and 2,6-tetralindicarboxylic.

The curable polyesters provided herein preferably have an acid number of not greater than 80 and a hydroxyl number of at least 10.

Suitable solvents for the curable enamel composition include xylenes, cyclohexanone, ketones (for example, methyl amyl ketone), 2-butoxyethanol, ethyl 3- ethoxypropionate, toluene, n-butanol, and other volatile inert solvents typically used in industrial baking (i.e. thermosetting) enamels. Suitable crosslinking agents includes amino-resins, isocyanates, and epoxies. The "amino crosslinking agent" is preferably a melamine type crosslinking agent, i.e., a crosslinking agent having a plurality of -N(CH₂OR³)₂ functional groups, wherein R³ is C,-C₄ alkyl, preferably methyl. In general, the crosslinking agent may be selected from compounds of the following formulae, wherein R³ is independently C,-C alkyl:

In this regard, preferred amino-crosslinking agents include hexamethoxymethylmelamine, tetramethoxy-methylbenzoguanamine, tetramethoxymethylurea, mixed butoxy/methoxy substituted melamines, and the like. The most preferred amino-crosslinking agent is hexamethoxymethylmelamine. Suitable polyisocyanate crosslinkers include aliphatic, cycloaliphatic, and aromatic polyisocyanates, such as, 1,6-hexamethylene diisocyanate; isophorone diisocyanate; toluene diisocyanate; 4,4'-biphenylene diisocyanate; bis cyclohexyl diisocyanate; 4,4'-biscyclohexyl dimethylmethane diisocyanate; 1,4-cyclohexylene diisocyanate; 1,3-cyclopentylene diisocyanate; 1, 3 -phenylene diisocyanate; 1,5- naphthalene diisocyanate; triphenylmethane triisocyanate; 1,3,5-benzene triisocyanate; 2,4,6-toluene triisocyanate; trimer of hexamethylene diisocyanate (DESMODUR N- 3390); an adduct of trimethylolpropane and tetramethylxylene diisocyanate (CYTHANE 3160); and the like. The polyisocyanates may further be blocked with caprolactams, ketoximes, and the like.

As a further aspect of this present invention there is provided a crosslinkable enamel composition as described above, further comprising one or more leveling, rheology, and flow control agents, such as, silicones, fluorocarbons, or cellulosics; flatting agents; pigment wetting and dispersing agents; surfactants; ultraviolet absorbers; antioxidants; hindered amine 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 mildewcides; 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 dihexylsulfo- succinnate, sodium dicyclohexyl sulfosuccinnate, diamyl sodium sulfosuccinnate, sodium diisobutyl sulfosuccinnate, disodium iso-decyl sulfosuccinnate, disodium ethoxylated alcohol half ester of sulfosuccinnic acid, disodium alkyl amido polyethoxy sulfosuccinnate, tetrasodium N-(l,2-dicarboxy-ethyl)-N-oxtadecyl sulfosuccinnamate, disodium N-octasulfosuccinnamate, sulfated ethoxylated nonylphenol, 2-amino-2- methyl-1-propanol, 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 B YK 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, mildewcides, and biocides include 4,4- dimethyloxazolidine, 3,4,4-trimethyloxazolidine, midified barium metaborate, potassium N-hydroxy-methyl-N-methyldithiocarbamate, 2-(thiocyanomethylthio) benzothiazole, potassium dimethyl dithiocarbamate, 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 140 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

Polyester resin prepared from 1.565 equivalents NPG glycol (Eastman Chemical Company), 0.470 equivalents TMP (Hoechst Celanese), and 1.55 equivalents DDA (2,6- decalindicarboxylic acid, Eastman Chemical Company). To the monomers was added 0.1 percent Fascat 4100 (Elf Atochem) based on resin yield and 0.5 moles of deionized water. Polycondensation materialized using a single-stage reaction whereby the temperature was increased approximately 10 °C every 35 minutes (once a temperature of 140 °C was reached) until a maximum of 230 °C was obtained and remain there until a final acid number of approximately 5 was obtained. The resin had a final acid number of

3.8, Mn=3209, Mw=9614, and a T_g of 46.8 °C.

Example 2

Polyester resin prepared from 7.792 equivalents NPG glycol, 0.913 equivalents TMP, 6.228 equivalents IPA (Amoco purified isophthalic acid), and 1.557 equivalents

DDA. To the monomers was added 0.1 percent Fascat 4100 and 1.67 moles of deionized water. The temperature was raised 10 °C every 30 minutes once 150 °C was obtained to a maximum of 230 °C. A final acid number of 7.0, Mn=1812, Mw=6756, T_g of 54.6 °C, and a corrected hydroxyl number of 45 was obtained.

Example 3

Polyester resin prepared similarly to resin in Example 2 using 0.736 equivalents of NPG glycol, 0.184 equivalents of DDM (2,6-decalindimethanol, Eastman Chemical Company), 0.136 equivalents of TMP, 0.918 equivalents of DDA, 0.1 percent Fascat 4100, and 0.83 moles of deionized water. A final acid number of 8.8, Mn=3790,

Mw=13054, T_g of 66.6 °C, and a corrected hydroxyl number of 35 was obtained.

Example 4

Polyester resin prepared as in Example 2 using 3.351 equivalents of NPG glycol, 3.351 equivalents of DDM, 0.879 equivalents of TMP, 6.669 equivalents of HHPA (Huls, A.G., the anhydride of 1,2-CHDA), 0.1 percent Fascat 4100, and no deionized water. A final acid number of 3.0, Mn=2045, Mw=4392, T_g of 44.2 °C, and a corrected hydroxyl number of 45 was obtained.

Example 5

Polyester resin prepared as in Example 2 using 0.973 equivalents of NPG glycol, 0.973 equivalents of DDM, 0.642 equivalents of TMP, 1.220 equivalents of IP A, 0.814 equivalents of adipic acid (AD, du Pont), 0.1 percent of Fascat 4100, and 0.83 moles of deionized water. A final acid number of 2.2, Mn=1877, Mw=7928, T_g of 25.8 °C, and a corrected hydroxyl number of 79 was obtained.

Example 6

Polyester resin prepared as in Example 2 using 6.020 equivalents of NPG glycol, 1.505 equivalents of DDM, 0.891 equivalents of TMP, 4.503 equivalents of IP A, 3.002 equivalents of 1 ,4-CHDA (Eastman Chemical Company HP grade), 0.1 percent Fascat

4100, and no deionized water. A final acid number of 3.0, Mn=2199, Mw=9423, T_g of 47.0 °C, and a corrected hydroxyl number of 40 was obtained.

Example 7 Polyester resin prepared using 1.277 equivalents of NPG glycol, 1.485 equivalents of TMP, 1.738 equivalents of DMDD (dimethyl 2,6-decalindicarboxylate, Eastman Chemical Company), and 0.1 percent dibutyltin oxide (DBTO). The temperature was raised 10 °C every 30 minutes once 150 °C was obtained to a maximum of 230 °C. Methanol was removed through a partial condenser. A final Mn=2262, Mw=5057, T_g of 13.7 °C, and a corrected hydroxyl number of 198 was obtained.

Comparative Example 1

Polyester resin prepared using 10.34 equivalents NPG glycol, 2.95 equivalents TMP,

10.71 equivalents 1,4-CHDA, and 0.1 percent Fascat 4100. A final acid number of 5, Mn=2424, Mw=8521, T_g of 9.0 °C, and an uncorrected hydroxyl number of 93 was obtained.

Comparative Example 2 Polyester resin prepared as in Example 2 using 8.167 equivalents NPG glycol,

0.889 equivalents TMP, 6.516 equivalents IP A, 1.629 equivalents HHPA, 0.1 percent Fascat 4100, and no deionized water. A final acid number of 5.0, Mn=1790, Mw=6497, T_g of 48.1 °C, and a corrected hydroxyl number of 41 was obtained.

Comparative Example 3

Polyester resin prepared as in Example 2 using 5.873 equivalents NPG glycol, 0.519 equivalents TMP, 4.519 equivalents IP A, 1.130 equivalents 1,4-CHDA, 0.1 percent Fascat 4100, and 0.83 moles of deionized water. A final acid number of 2.3, T_g of 43.5 °C, and an uncorrected hydroxyl number of 40 was obtained.

Comparative Example 4

Polyester resin prepared using 4.807 equivalents NPG glycol, 1.787 equivalents TMP, 5.431 equivalents HHPA, 0.1 percent Fascat 4100, and 0.83 moles of deionized water. Once an initial temperature of 150 °C was obtained, the heating increased at such a rate as to maintain a condensate of 0.5 grams per minute to a maximum temperature of

230 °C. A final acid number of 5.5, T_g of 18.3 °C, and an uncorrected hydroxyl number of 77 was obtained.

Comparative Example 5 Polyester resin prepared using 7.86 equivalents NPG glycol, 2.11 equivalents

TMP, 4.88 equivalents IP A, 3.25 equivalents AD, 0.1 percent Fascat 4100, and 1.4 moles of deionized water. A heating rate of 0.3 °C per minute to a maximum temperature of 230 °C was used once an initial temperature of 150 °C was obtained. A final acid number of 3.0, Mn=1608, Mw=5332, T_g of 2.4 °C, and an uncorrected hydroxyl number of 86 was obtained. Comparative Example 6

Polyester resin prepared as in Comparative Example 5 using 7.33 equivalents NPG glycol, 2.10 equivalents TMP, 4.75 equivalents IP A, 3.17 equivalents 1,4-CHDA, 0.1 percent Fascat 4100, and 1.4 moles of deionized water. A final acid number of 6.7, Mn=1781, Mw=7206, T_g of 38.7 °C, and an uncorrected hydroxyl number of 64 was obtained.

Example A

Clear enamels were prepared using 35 parts of polyester resin of Example 1, 15 parts Resimene 745 (a hexamethoxymethylmelamine, Monsanto), 41 parts of a solvent blend (55% xylenes, 32% MAK, 6.5% Eastman EEP, 6.5% n-BuOH), 0.5 parts of a 30 percent solution of PTSA (p-toluenesulfonic acid) in t-PrOH, and 0.2 parts of a 30 percent solution of FC-430 (a flow control agent, 3M Company) in MAK. Coatings were prepared on iron phosphate treated 22 gauge polished steel panels (ACT, Advanced Coatings Technology, Inc.) using a number 50 wire- wrapped draw-down bar and cured at

150 °C for 35 minutes in a forced-air oven.

Example B

Clear enamels were prepared from 35 parts resin of Example 5, 15 parts Resimene 745, 33 parts of a solvent blend (same solvent as used in Example A), 0.5 parts of a 30 percent solution of PTSA in z-PrOH, and 0.3 parts of a 30 percent solution of FC- 430 in MAK. Coatings were prepared on iron phosphate treated 22 gauge unpolished steel panels (Q-Panel Company) using a number 50 wire- wrapped draw-down bar and cured at 160 °C for 30 minutes in a forced-air oven.

Comparative Example A

Clear enamels were prepared as in Example B using the resin of Comparative Example 1. Comparative Example B

Clear enamels were prepared as in Example A using the resin of Comparative Example 5.

1. Scale: 1-5 (5=best)

2. Cycle: 4 hours UV at 60 °C, 4 hours condensate at 50 °C

Claims

We claim:

1. A polyester resin composition comprising the polycondensation product of a diol and diacid wherein at least one of said diol or said diacid is a decalin or tetralin derivative, wherein the polyester resin composition has a number average molecular weight of about 800 to about 5000 and a weight average molecular weight of about 1600 to about 50,000.

2. A polyester resin composition of claim 1, wherein said diol is at least one of the diol residues selected from the group consisting of: 1,1-decalindimethanol, 1,2- decalindimethanol, 1,3-decalindimethanol, 1,4-decalindimethanol, 1,5- decalindimethanol, 1,6-decalindimethanol, 1 ,7-decalindimethanol, 1,8- decalindimethanol, 2,2-decalindimethanol, 2,3-decalindimethanol, 2,6- decalindimethanol, and 2,7-decalindimethanol.

3. A polyester resin composition of claim 1, wherein said diacid is selected from the group consisting of: 1,2-decalindicarboxylic acid, 1,3-decalindicarboxylic acid, 1,4- decalindicarboxylic acid, 1,5 -decalindicarboxylic acid, 1 ,6-decalindicarboxylic acid, 1,7- decalindicarboxylic acid, 1,8-decalindicarboxylic acid, 2,3-decalindicarboxylic acid, 2,6- decalindicarboxylic acid, 2,7-decalindicarboxylic acid, 1,2-tetralindicarboxylic acid, 1,3- tetralindicarboxylic acid, 1,4-tetralindicarboxylic acid, 1,5-tetralindicarboxylic acid, 1,6- tetralindicarboxylic acid, 1,7-tetralindicarboxylic acid, 1,8-tetralindicarboxylic acid, 2,3- tetralindicarboxylic acid, 2,6-tetralindicarboxylic acid, and 2,7-tetralindicarboxylic acid.

4. An enamel coating composition comprising a polyester resin composition of claim 1 ; a crosslinker or cross-linking agent; and a solvent.

5. An enamel coating composition of claim 4 further comprising at least one of the following: leveling agent, rheology agent, flow control agent, flatting agent, pigment wetting agent, dispersing agent, surfactant, ultraviolet absorber, antioxidant, hindered amine light stabilizer, tinting pigment, defoaming agent, antifoaming agent, anti-settling agent, anti-sag agent, bodying agent, anti-skinning agent, anti-flooding agent, anti- floating agent, fungicide, mildewcide, corrosion inhibitors, thickening agent, and coalescing agent.

6. A shaped or formed article or substrate coated with an enamel coating composition of claim 4.