JPH11116851A - Epoxidized polyester-based powder coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject coating composition capable of giving coating film of high UV durability and good gloss retainability at 60 deg.C, and useful for the outdoor durability of automobiles or the like, by including a specific solid epoxidized polyester and a solid carboxylic acid component. SOLUTION: This coating composition comprises (A) a solid epoxidized polyester prepared by epoxidizing a polyester >=90 deg.C in melting point and <=50 p in viscosity at 200 deg.C and (B) a solid carboxylic acid component in such a weight as to correspond to an acid equivalent of 100-1,500. The polyester for the component A is prepared by reaction of a mixture composed of (1) tetrahydrophthalic acid (anhydride), (2) an alicyclic polyol, (3) a saturated polycarboxylic acid and (4) a 5-50C polyhydric alcohol in the molar ratio (l)/(2)/(3)/(4) so as to be (0.8:1) to (0.96:1) in the equivalent ratio for the carboxyl and hydroxyl groups, i.e., in the equivalent ratios (l)/((3) and (2)/(4) of (100:1) to (1:4) and (100:0) to (4:1) until the acid value of the above reaction mixture comes to <=5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a powder coating composition and a method for producing the same. In particular, the present invention relates to an epoxidized solid resin composition useful for powder coatings.

[0002]

BACKGROUND OF THE INVENTION Thermosetting powder coatings having some degree of outdoor durability can be prepared from combinations of polyesters and acrylic resins with suitable co-reactants. Triglycidyl isocyanurate (TGI) is a currently available outdoor grade epoxy group-containing material.
C) and an acrylic resin containing glycidyl methacrylate (GMA). However, TG
IC powder coatings lose gloss and discolor,
Does not have sufficient weather resistance. Acrylic materials generally have excellent weather resistance, but have physical properties (eg,
(Flexibility and impact resistance) are known to be inferior, and when present as contaminants in other powder coating materials, the coating film is known to have defects. EPON ™ resin 200
Other solid epoxy resins such as 2, 2003 and 2004 can be applied, but since they are composed of aromatic subunits, they have no outdoor durability. Accordingly, there is a need for improved low aromatic or non-aromatic solid epoxy resins that can be reacted with low aromatic or non-aromatic acrylic resins and polyesters to produce weather resistant powder coatings. .

[0003]

According to the present invention, (a)
A solid epoxidized polyester made by epoxidizing a polyester having a melting point of at least 90 ° C. and a viscosity of at most 50 poise at 200 ° C., said polyester comprising the following components (i) to (iv): In the reaction mixture, the equivalent ratio of acid to hydroxyl is 0.1.
(I) :( ii) :( iii): 8: 1 to 0.96: 1
(iv) molar ratio, and the equivalent ratio of (i) :( iii) is 100: 1.
１ ： 1: 4 and the equivalent ratio of (ii) :( iv) is 100: 0０〜
4: 1 and a polyester produced by reacting until the acid value of the reaction mixture is 5 or less: (i) tetrahydrophthalic acid or its anhydride, (ii) at least one alicyclic Polyols, (iii) optionally at least one saturated polycarboxylic acid, and (iv) optionally at least one polyhydric alcohol having from 5 to 50 carbon atoms; and (b) a range from 100 to 1500. Curable powder coating composition comprising: a solid carboxylic acid component having an acid equivalent weight within the above range.

[0004]

BEST MODE FOR CARRYING OUT THE INVENTION

1. Solid Epoxidized Compositions Epoxidized polyesters must be brittle and non-semi-fusible to be useful in powder coating applications. Polyesters agglomerate (with viscous) within one week at room temperature and semi-melt if they cannot be easily redispersed. The solid epoxidized polyester preferably has a melting point of at least 100 ° C. for good performance.

[0005] Solid epoxidized polyesters useful for powder coatings preferably have a Tg of about 50 ° C. or higher, a melting point of at least about 90 ° C. and a viscosity at 200 ° C. of at most 50 poise (ICI cone and plate viscosity). It has been found that it can be produced by epoxidizing polyester. Such polyesters include (i) tetrahydrophthalic acid or anhydride thereof, (ii) at least one cycloaliphatic polyol, (iii) optionally at least one
It can be prepared by epoxidizing at least the following saturated polycarboxylic acids and (iv) optionally at least one polyhydric alcohol having from 5 to 50 carbon atoms. That is, the equivalent ratio of acid to hydroxyl is from about 0.8: 1 to about 0.96: 1, preferably about 0.8: 1.
(I) :( ii) :( ii) such that 5: 1 to about 0.95: 1.
i): (iv) molar ratio, and the equivalent ratio of (i) :( iii) is about 10
0: 1, preferably about 4: 1 to about 1: 4, preferably about 2: 1 to about 1: 2 and the equivalent ratio of (ii) :( iv) is about 1
00: 0 to about 4: 1, preferably about 12.5: 1. In a preferred embodiment, it is desirable that the equivalent ratio of components (i) :( iii) be from about 2: 1 to about 1: 2 to obtain a good weatherable formulation. The reaction is typically conducted at a temperature of about 150 ° C., preferably about 170 ° C. to about 240 ° C., preferably about 230 ° C., such that the acid value of the reaction mixture is about 5 or less, preferably about 2 or less. Until the mixture is heated. It is preferred that other condensation products and / or water produced during the reaction are continuously removed. The reaction mixture can also contain inert solvents, for example, ketones such as 2-butanone, 4-methyl-2-pentanone and hydrocarbons such as xylene and toluene. A catalyst can be added to promote the completion of the reaction. Such catalysts include, for example, those made from titanium, zirconium, tin and antimony, and conventional catalysts used in polyesterification reactions. The produced polyester can be recovered by a conventional method.

As the alcohol, a polyhydric alcohol having 2 to 4 hydroxyl groups and 5 to 50 carbon atoms per molecule is preferred. The total hydroxyl content of polyhydric alcohols or monoalcohols having 4 or less carbon atoms is small,
At most 15 equivalent percent, preferably no more than 10 equivalent percent, can be present in the reaction mixture.

[0007] Examples of tetraphthalic acid or anhydrides useful in the production of solid polyesters include cyclohexe-4.
-Ene-1,2-dicarboxylic anhydride, 3-methylcyclohex-4-ene-1,2-dicarboxylic anhydride, 4
-Methylcyclohex-4-ene-1,2-dicarboxylic anhydride, cyclohex-4-ene-1,2-dicarboxylic acid, 3-methyl-cyclohex-4-ene-1,2-
There are dicarboxylic acids, 4-methyl-cyclohex-4-ene-1,2-dicarboxylic acids and mixtures thereof. Examples of cycloaliphatic polyols useful for making solid polyesters include cyclohexane dimethanol and hydrogenated bisphenol A, and mixtures thereof. Examples of saturated polycarboxylic acids useful for producing solid polyesters include:
Hexahydrophthalic anhydride, hexahydrophthalic acid,
There are 1,4-cyclohexanedicarboxylic acid, dimethyl ester of 1,4-cyclohexanedicarboxylic acid, and mixtures thereof. Examples of the polyhydric alcohol of the component (iv) include trimethylolpropane, neopentyl glycol, trimethylolethane, pentaerythritol,
And their mixtures. Examples of polyhydric alcohols having 4 or less carbon atoms include ethylene glycol, 1,3-propanediol, 1,4-butanediol. Examples of monoalcohols include butanol,
There are 2-ethyl-hexanol and cyclohexanol.

[0008] Solid polyesters are disclosed in US Patent No. 5,244,985.
No. 3,493,631 and No. 2,928,805. For example, the solid polyester can be obtained from formic acid and hydrogen peroxide in the presence of a strong acid or acidic resin at a temperature of about 0 ° C., preferably in the range of about 20 ° C. to about 70 ° C., preferably 40 ° C., or sodium carbonate, Treated with a mixture of molybdic acid and hydrogen peroxide in the presence of a sufficient amount of a salt such as sodium bicarbonate or disodium hydrogen phosphate, separately or in situ with an acid solution such as peracetic acid or formic acid By neutralizing the strong acid contained, epoxidation can be performed. The resulting epoxidized solid polyester preferably has a WPE (weight per epoxy functional equivalent) in the range of about 350 to about 1500. The solid brittle epoxidized polyester is recovered in a conventional manner.

[0009] 2. Solid Carboxylic Acids Solid carboxylic acids must also be solid and brittle to be useful in powder coatings. Such carboxylic acid components useful as curing agents for powder coatings include about 100,
It should preferably have an acid equivalent weight in the range of about 110 to about 1500, preferably about 900. Such carboxylic acids preferably have from 10 to 100 carbon atoms and an average of from 2 to 4, preferably about 2 carboxyl groups per molecule if they have an acid equivalent weight in the range of about 100 to about 1500. .

Examples of polycarboxylic acids are linear or branched solid, preferably crystalline, alkonic acids such as dodecanedienoic acid and sebacic acid. Another preferred polycarboxylic acid is a mixture comprising at least one cycloaliphatic dicarboxylic acid or anhydride and at least one polyhydric alcohol having 5 to 50 carbon atoms, having an acid to hydroxyl equivalent ratio of 2 or less. : 1, preferably about 1.2:
It can be produced by reacting from 1 to 2: 1, preferably up to 1.4: 1. Mixtures of more than one polyhydric alcohol are preferred because they provide the best performance and are easy to handle. Examples of the alicyclic dicarboxylic acid or its anhydride and the polyhydric alcohol are described above.

3. Powder Coating The curable powder coating composition contains (a) a solid epoxidized polyester and (b) an acid functional component. The amounts of (a) and (b) are generally within ± about 35% of the theoretical amount. This ratio can be adjusted according to the type of catalyst, curing conditions, and desired coating properties. Out of range proportions reduce the molecular weight and give poor crosslinked products with less than the best properties. Conventional powder coating additives such as flow control agents, anti-popping agents, powder flow materials, fillers and pigments can be included. The curable powder coating composition may further comprise a phosphate (eg, ethyltriphenylphosphine iodide), an imidazole and a tin salt (eg, dibutyltin oxide) to increase the rate of crosslinking of the coating composition depending on the desired application. A few percent of the catalyst.

Thermosetting powder coating compositions can be prepared by various methods known in the powder coating industry; dry blending, melt compounding with a twin screw mill or extruder and spray drying. A typically used method is the melt compounding process; dry blending the components in a planetary mixer and then mixing the mixture in an extruder for about 8 hours.
Blend at temperatures ranging from 0 ° C to 130 ° C. Then
The extrudate is cooled and ground to a granular blend.

[0013] The thermosetting powder coating composition then comprises a substrate,
For example, it can be applied directly to a metal such as steel or aluminum. Non-metallic substrates such as plastics and composites can also be used. The application of the paint can be carried out by using electrostatic spraying or fluid immersion.
Electrostatic spraying is the preferred method. The powder coating can be applied in one or several coats so that the cured thickness is from about 2.0 to about 15.0 mils.

The substrate can optionally be preheated before applying the powder coating composition to promote uniform and thick powder coating. After application of the powder coating, the powder-coated substrate is typically at about 120 ° C, preferably 1 ° C.
At a temperature from 50 ° C. to about 205 ° C., for a time sufficient to cure the powder coating composition, typically from about 1 minute to 60 minutes;
Preferably, it is baked for about 10 to 30 minutes.

The thermosetting powder coating composition can be applied directly to the substrate metal or plastic or composite (eg, to untreated, unprimed steel) or to a pre-treated surface. The powder coating composition may also be applied to a phosphate coated steel as a thin layer (0.8-2 mil) of an electrodeposited primer or to a top coat layer prior to application of the cured or uncured powder coating composition. As a coating on the chip-resistant coating layer. For examples of chip-resistant layers:
For example, it is described in U.S. Patent Nos. 5,115,029 and 5,264,503. The electrodeposition primer coating on the metal substrate is, for example, a cationic electrodeposition primer composition. In one aspect of the present invention, the powder coating composition can be applied over the uncured electrodeposited primer coater, and the powder coating is applied at a temperature of about 150 ° C to about 180 ° C for about 10 minutes to about 30 minutes. Co-curing can be performed by heating.

The powder coating composition of the present invention has good UV durability, good gloss retention at 60 ° C., good chemical resistance,
It exhibits good flowability under curing conditions and is useful for outdoor durability for automobiles, common metal surfaces such as wheel covers and building components such as window frames. Since the powder coating composition of the present invention contains essentially no volatile organic substances, it is desirable that the composition be of a general liquid type or higher.

[0017]

The following illustrative embodiments describe the novel epoxy resins of the present invention and are provided for illustrative purposes, and are not meant to limit the present invention.

Tetrahydrophthalic anhydride is obtained from Janssen.
Hexahydrophthalic anhydride and hydrogenated bisphenol A from Chemical Company
-Cyclohexanedimethanol was obtained from Aldrich Chemical or Eastman Chemical. 1,4-Cyclohexanedicarboxylic acid was provided by Eastman Chemical.
The trimethylolpropane described in the following Examples is Aldrich
Obtained from Chemical Company. Elf A for tin catalyst (Fascat 4100)
Obtained from tochem. Equilibrium peracetic acid (35%) is from Aldrich Che
purchased from mical.

Examples 1 to 8 Preparation of solid hydroxyl-functional polyesters Solid polyesters having a plurality of olefinically unsaturated groups were prepared by reacting various amounts of the reactants (CHDA: cyclohexanedicarboxylic acid, THPA: tetrahydrophthalic anhydride) shown in Table 1. , HHPA: hexahydrophthalic anhydride, CH
DM: 1,4-cyclohexanedimethanol, HBP
A: hydrogenated bisphenol A, TMP: trimethylolpropane). Two techniques were used to add the reactants. In one approach, the acid-functional reactant, HBPA and toluene were placed in a 5.0 liter flask equipped with a Dean-Stark trap and condenser, thermocouple and overhead stirrer. The flask and its contents were briefly purged with nitrogen and then maintained under nitrogen pressure until the beginning of the sparge. The components were heated to reflux and maintained for one hour. Then, 2-butanone (8
00g) and the remaining hydroxyl components were added and the solvent was continuously removed. In another approach, cyclohexanedimethanol was added along with the other reactants before heating.

The reaction mixture was slowly warmed to 200 ° C. to remove solvent and by-product water. The reflux of the reaction mixture was maintained to facilitate water removal until water evolution was reduced. Fascat 4100 (butylated tin oxide) was added all at once, at the beginning of the reaction or after the initial generation of water of slow condensation. After maintaining at 200 ° C. for 1-2 hours, the reaction mixture was further warmed to 220 ° C. and sparged with nitrogen. This was maintained until the acid value of the resin became 1 or less. The acid value was measured by titration of a 50:50 (W / W) toluene / isopropanol solution of the resin with 0.1N ethanolic potassium hydroxide. The produced polyester resin was taken out by transferring the contents of the flask to an aluminum pan.

The properties of the obtained solid polyester are shown in Table 2. Viscosity is measured at 200 ° C. by ICI Cone & Plate unless otherwise specified. Mettler melting point (M.
P. ° C) and the final acid number.

[0022]

[Table 1]

[0023]

[Table 2]

As can be seen from the above table, the polyesters of Examples 1-2 and 5-8 have a melting point of about 90 ° C. and a viscosity at 200 ° C. of less than 50 poise. Example 4 is a comparative example whose melting point is too low. Example 3 is a comparative example where the viscosity is too high.
The acid to OH ratio of Example 7 appears to give low viscosity values suitable for powder coating applications.

Examples 9-13 Preparation of Solid Epoxidized Polyester The polyester obtained above was dissolved in toluene or methylene chloride (25 / 75-40 / 60 w / w) and equilibrated at 25-40 ° C. for 2-3 hours, 35 hours. % Peracetic acid. The reaction mixture was treated with sufficient sodium carbonate to neutralize the sulfuric acid contained in peracetic acid. Following the reaction, the epoxidized polyester was isolated in one of two ways. One method (Method A)
In, the reaction mixture was concentrated under reduced pressure to remove water and unreacted hydrogen peroxide, peracetic acid and acetic acid, and solvents. Residue 25% with toluene or methylene chloride
Dilute to a solid and filter or wash 4-5 times with water to remove solid impurities. The resin solution was then concentrated by distilling volatiles under reduced pressure and heating (up to 200 ° C.). The residue was optionally sparged with nitrogen to remove trace volatiles to make the product more acceptable as a powder coating vehicle. In another method (Method B),
After completion of the epoxidation reaction, the reaction mixture is
% Solids, then filtered, after which the mixture was washed 4-5 times with water, concentrated by distillation and sparged as above.

WPE (weight per equivalent of epoxy functionality), Mettler melting point (MP ° C.) and ICI at 200 ° C.
Cone & Plate viscosity is shown in Table 3. WPE was measured at the endpoint with crystal violet by titration of the resin with standard 0.1 N peracetic acid in acetic acid and a dichloromethane / acetic acid solution of tetraethylammonium bromide.

[0027]

[Table 3]

Examples 14-17 Preparation of Acid Functional Component The acid functional component (polyester curing agent) was prepared using various amounts of the reactants (CHDA: cyclohexanedicarboxylic acid, HHPA: hexahydrophthalic anhydride) shown in Table 4. , CHD
M: 1,4-cyclohexanedimethanol, TMP: trimethylolpropane) in a manner analogous to that used for the preparation of the polyesters listed in Tables 1 and 2. All reactants were placed in a four-necked flask equipped with a Dean-Stark trap and condenser, thermocouple, overhead stirrer and nitrogen source. Xylene was optionally added to the reactants to use the resulting water as a carrier.
Briefly, the flask and contents were purged with nitrogen, pressurized with nitrogen, and the mixture refluxed for xylene, or heated to 150 ° C. In Examples 15 to 17, 0.1 to
0.2% by weight of Fascat 4100 catalyst was added. After 1 hour at this temperature, the mixture was warmed to 175 ° C and maintained at this temperature until approximately 75% of the water was generated. Thereafter, the mixture was warmed to 200 ° C. Again, after the generation of water slows down,
The mixture was sparged with nitrogen until the theoretical acid number was reached or exceeded. Table 4 shows the total acid / OH ratio and melting point of each product.

[0029]

[Table 4]

Examples 18-19 Preparation of powder coatings and properties of cured products

[0031]

[Table 5]

Manufacturing Method The above composition was manufactured using a typical powder coating manufacturing method. That is, vigorous premixing was performed, using a high shear melt compound (extruder), pulverized, and a 200 mesh screen.

Powder coating performance

[0034]

[Table 6]

As can be seen from the above table, the powder coating of the present invention, Example 18, has excellent weatherability, and other performance is at least equal to a typical TGIC polyester powder coating (Example 19). The 60 ° gloss retention of the invention was 30% after 1000 hours, while the TGIC polyester was after 200 hours.

Claims (23)

[Claims] (A) a melting point of at least 90 ° C. and 200
A solid epoxidized polyester produced by epoxidizing a polyester having a viscosity of at most 50 poise at a temperature of 50 ° C.
In the reaction mixture containing (iv), the equivalent ratio of acid to hydroxyl is from 0.8: 1 to 0.96: 1.
the molar ratio of (i) :( ii) :( iii) :( iv), the equivalent ratio of (i) :( iii) is 100: 1 to 1: 4, and the molar ratio of (ii) :( iv) is A polyester produced by reacting the equivalent ratio of 100: 0 to 4: 1 and reacting until the acid value of the reaction mixture becomes 5 or less: (i) tetrahydrophthalic acid or anhydride thereof, (ii) At least one cycloaliphatic polyol, (iii) optionally at least one saturated polycarboxylic acid, and (iv) optionally at least one polyhydric alcohol having 5 to 50 carbon atoms; and b) a solid carboxylic acid component having an acid equivalent weight in the range of 100 to 1500; 2. The method according to claim 1, wherein the tetrahydrophthalic acid or the anhydride thereof is cyclohex-4-ene-1,2-dicarboxylic anhydride, 3-methylcyclohex-4-ene-1,2-dicarboxylic anhydride.
Dicarboxylic anhydride, 4-methylcyclohex-4-ene-1,2-dicarboxylic anhydride, cyclohex-4-
Claims selected from the group consisting of ene-1,2-dicarboxylic acid, 3-methyl-cyclohex-4-ene-1,2-dicarboxylic acid, 4-methyl-cyclohex-4-ene-1,2-dicarboxylic acid and mixtures thereof. Item 4. The curable powder coating composition according to Item 1. 3. The curable powder coating composition according to claim 2, wherein said component (ii) is selected from the group consisting of cyclohexanedimethanol, hydrogenated bisphenol A, and mixtures thereof. 4. The group consisting of component (iii) consisting of hexahydrophthalic anhydride, hexahydrophthalic acid, 1,4-cyclohexanedicarboxylic acid, dimethyl ester of 1,4-cyclohexanedicarboxylic acid, and mixtures thereof. The curable powder coating composition according to claim 3, which is selected from the group consisting of: 5. The method according to claim 1, wherein the component (iv) is trimethylolpropane, neopentyl glycol, trimethylolethane,
The curable powder coating composition according to claim 4, which is selected from the group consisting of pentaerythritol and a mixture thereof. 6. The method according to claim 1, wherein the carboxylic acid component (b) is 10-1.
5. The curable powder coating composition according to claim 4, having 00 carbon atoms. 7. The polycarboxylic acid component (b) comprises: (v) at least one alicyclic dicarboxylic acid or an anhydride thereof; and (vi) at least one polyvalent having 5 to 50 carbon atoms. The curable powder coating composition according to claim 6, which is produced by reacting an alcohol with (v) :( vi) in a molar ratio of 1.2: 1 to 2: 1. 8. The curable powder of claim 7, wherein said component (v) is selected from the group consisting of hexahydrophthalic anhydride, hexahydrophthalic acid, 1,4-cyclohexanedicarboxylic acid, and mixtures thereof. Body paint composition. 9. The method according to claim 1, wherein the component (vi) is cyclohexanedimethanol, hydrogenated bisphenol A, trimethylolpropane, trimethylolethane, pentaerythritol,
And at least one selected from the group consisting of and mixtures thereof.
The curable powder coating composition according to the above. 10. The curable powder coating composition according to claim 6, wherein the component (ii) is hydrogenated bisphenol A. 11. The curable powder coating composition according to claim 6, wherein the component (ii) is cyclohexanedimethanol. 12. The cure according to claim 11, wherein the ratio of (i) :( ii) :( iii) :( iv) acid to hydroxyl equivalent is in the range of 0.90: 1 to 0.96: 1. Powder coating composition. 13. The cured powder coating composition according to claim 1. 14. A cured powder coating composition according to claim 3. 15. The cured powder coating composition of claim 6. 16. A cured powder coating composition according to claim 10. 17. The cured powder coating composition according to claim 11, wherein: (A) (i) tetrahydrophthalic acid or its anhydride, (ii) at least one alicyclic polyol, (ii)
i) optionally, at least one saturated polycarboxylic acid,
And (iv) optionally at least one polyhydric alcohol having from 5 to 50 carbon atoms such that the equivalent ratio of acid to hydroxyl is from 0.8: 1 to 0.96: 1.
the molar ratio of (i) :( ii) :( iii) :( iv), the equivalent ratio of (i) :( iii) is 100: 1 to 1: 4 and the ratio of (ii) :( iv) is The reaction is carried out until the equivalent ratio is from 100: 0 to 4: 1 and the acid value of the reaction mixture is 5 or less.
(B) epoxidizing the solid polyester to produce a solid epoxidized polyester; and (c) recovering the obtained solid epoxidized polyester. A method for producing a solid epoxidized polyester having a melting point of at least 100 ° C. 19. The curable powder coating composition according to claim 18, wherein said component (ii) is selected from the group consisting of cyclohexanedimethanol, hydrogenated bisphenol A, and mixtures thereof. 20. The component (iii) comprising hexahydrophthalic anhydride, hexahydrophthalic acid, 1,4-cyclohexanedicarboxylic acid, dimethyl ester of 1,4-cyclohexanedicarboxylic acid, and a mixture thereof. The curable powder coating composition according to claim 19, which is selected from the group consisting of: 21. The curable powder coating composition according to claim 20, wherein the component (iv) is selected from the group consisting of trimethylolpropane, neopentyl glycol, trimethylolethane, pentaerythritol, and a mixture thereof. 22. (a) a melting point of at least 90 ° C.
A solid epoxidized polyester produced by epoxidizing a polyester having a viscosity of at most 50 poise at 0 ° C., wherein said polyester comprises the following components:
(i) :( ii) :( iii) :( such that the equivalent ratio of acid to hydroxyl is 0.8: 1 to 0.96: 1 in the reaction mixture containing (i) to (iv). iv), wherein (i):
The equivalent ratio of (iii) is 1: 4 to 4: 1 and (ii) :( i
v) is an equivalent ratio of 100: 0 to 4: 1 and is a polyester produced by reacting them: (i) tetrahydrophthalic acid or its anhydride, (ii) cyclohexanedimethanol, hydrogenation Selected from the group consisting of bisphenol A or mixtures thereof, (iii) hexahydrophthalic anhydride or hexahydrophthalic acid, and (iv) optionally trimethylolpropane, neopentyl glycol, trimethylolethane and pentaerythritol A curable powder coating composition comprising at least one polyhydric alcohol; and (b) a solid carboxylic acid component having an acid value weight in the range of 110 to 900. 23. The cured composition of claim 22.