Thermosetting powder coating composition

Abstract

A powder coating composition comprising: (A.) a carboxyl functionalized polyester, the carboxyl functionalized polyester being the reaction product of: a polyol component comprising: (i.) 2, 2, 4, 4-tetramethyl-1, 3-cyclobutanediol; (ii.) at least one diol other than 2, 2, 4, 4-tetramethyl-1, 3-cyclobutanediol; (iii.) trimethylolpropane; and a dicarboxylic acid component, the dicarboxylic acid component comprising: (iv.) hexahydrophthalic anhydride; (v) 1, 4-cyclohexanedicarboxylic acid or 1, 3-cyclohexanedicarboxylic acid, or a mixture thereof; and optionally, (vi.) an acyclic diacid; wherein the carboxyl-functionalized polyester has a glass transition temperature of from 45 DEG C to 90 DEG C, an acid number of from 35 mg KOH / g to 90 mg KOH / g, a number average molecular weight of from 2,000 g / mol to 10,000 g / mol, and a weight average molecular weight of from 5,000 g / mol to 80,000 g / mol; and B. one or more compounds that react with the carboxyl functionalized polyesters.

Description

Technical Field

[0001] Embodiments of this disclosure generally relate to powder coating compositions comprising carboxyl-functionalized polyesters, and more specifically, to powder coating compositions comprising carboxyl-functionalized polyesters for use in automotive bodies and components, such as automotive wheels. Background Technology

[0002] Thermosetting powder coatings are environmentally friendly coatings with extremely low emissions of volatile organic compounds (VOCs) into the atmosphere. Thermosetting powder coatings can be broadly classified into four categories—polyester-based, epoxy-based, polyester / epoxy hybrid, and acrylic-based. Based on their price and performance, the market for these coatings has developed for different applications. Due to their excellent corrosion resistance and outdoor durability, the industrial demand for powder coatings is increasing.

[0003] Thermosetting powder coatings can be used for coating the substrates of automotive bodies and components such as aluminum wheels, windshield wipers, pillars, door handles, fenders, hoods, spoilers, stabilizer bars, and grilles. Exposed parts of automotive components are subjected to impacts from gravel, stone chips, and climatic factors (such as UV radiation, temperature, humidity, and / or corrosive environmental conditions) during normal use, which can wear down the protective coatings on the surface of these components. Furthermore, polyester-based clear coats are prone to cracking when directly sprayed onto metal surfaces.

[0004] Therefore, there is an urgent need to develop a polyester-based powder coating composition with improved crack resistance, as crack resistance is directly related to flexibility. Summary of the Invention

[0005] The embodiments herein disclose powder coating compositions. The compositions comprise: A. a carboxyl-functionalized polyester, said carboxyl-functionalized polyester being a reaction product of: a polyol component comprising: i. 2,2,4,4-tetramethyl-1,3-cyclobutanediol, at 55 mol% to 84 mol% based on the total molar percentage of i., ii. and iii.; ii. at least one diol other than 2,2,4,4-tetramethyl-1,3-cyclobutanediol, at 6 mol% to 43 mol% based on the total molar percentage of i., ii. and iii.; iii. at 2 mol% to 20 mol% based on the total molar percentage of i., ii. and iii. A. A percentage of trimethylolpropane; and a dicarboxylic acid component comprising: iv. 60 to 95 mol percent of hexahydrophthalic anhydride based on the total moles of iv., v., and vi.; v. 5 to 35 mol percent of 1,4-cyclohexanedicarboxylic acid or 1,3-cyclohexanedicarboxylic acid or mixtures thereof based on the total moles of iv., v., and vi.; vi. 0 to 20 mol percent of acyclic dicarboxylic acid based on the total moles of iv., v., and vi.; wherein the carboxyl-functionalized polyester has a glass transition temperature of 45°C to 90°C, an acid value of 35 mg KOH / g to 90 mg KOH / g, a number-average molecular weight of 2,000 g / mol to 10,000 g / mol, and a weight-average molecular weight of 5,000 g / mol to 80,000 g / mol; and B. one or more compounds that react with the carboxyl-functionalized polyester.

[0006] The embodiments herein also disclose powder coating compositions. The compositions comprise: A. a carboxyl-functionalized polyester, said carboxyl-functionalized polyester being a reaction product of: a polyol component comprising: i. 60 to 80 mol percent of 2,2,4,4-tetramethyl-1,3-cyclobutanediol based on the total molar percentage of i., ii. and iii.; ii. at least one diol other than 2,2,4,4-tetramethyl-1,3-cyclobutanediol based on the total molar percentage of i., ii. and iii.; iii. 5 to 17 mol percent based on the total molar percentage of i., ii. and iii. The product comprises: B. trimethylolpropane; and C. a dicarboxylic acid component comprising: iv. 65 to 85 mol percent of hexahydrophthalic anhydride based on the total moles of iv., v., and vi.; v. 10 to 30 mol percent of 1,4-cyclohexanedicarboxylic acid or 1,3-cyclohexanedicarboxylic acid, or mixtures thereof, based on the total moles of iv., v., and vi.; vi. 5 to 15 mol percent of acyclic dicarboxylic acid based on the total moles of iv., v., and vi.; wherein the carboxyl-functionalized polyester has a glass transition temperature of 45°C to 90°C, an acid value of 35 mg KOH / g to 90 mg KOH / g, a number-average molecular weight of 2,000 g / mol to 10,000 g / mol, and a weight-average molecular weight of 5,000 g / mol to 80,000 g / mol; and B. a crosslinking agent selected from β-hydroxyalkylamides, glycidyl-functionalized compounds, and mixtures thereof.

[0007] The embodiments herein also disclose articles at least partially coated with the powder coating composition described herein.

[0008] Further features and advantages of the embodiments will be described in the following detailed description, and some of these features and advantages will become apparent to those skilled in the art from the description or by practicing the embodiments described herein. It should be understood that the above and following detailed descriptions depict various embodiments and are intended to provide an overview or framework for understanding the nature and characteristics of the claimed subject matter. Detailed Implementation

[0009] Detailed reference will now be made to embodiments of the thermosetting powder coating compositions, their manufacturing methods, and articles coated with the cured thermosetting powder coating compositions described herein. These thermosetting powder coating compositions can be used to manufacture automotive parts, particularly automotive wheel parts. However, it should be noted that these are merely illustrative embodiments of the disclosed embodiments. These embodiments are applicable to other automotive parts susceptible to similar problems, such as windshield wipers, pillars, door handles, fenders, hoods, air spoilers, stabilizers, and grilles, as well as automotive bodies.

[0010] In embodiments described herein, the powder coating composition comprises a carboxyl-functionalized polyester and one or more compounds that react with the carboxyl-functionalized polyester. In one or more embodiments described herein, the powder coating composition may comprise 60% to 90% by weight of a carboxyl-functionalized polyester and 10% to 40% by weight of one or more compounds that react with the carboxyl-functionalized polyester. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, based on the total amount of the carboxyl-functionalized polyester and one or more compounds that react with the carboxyl-functionalized polyester, the powder coating composition may comprise 70% to 80% by weight of a carboxyl-functionalized polyester and 20% to 30% by weight of one or more compounds that react with the carboxyl-functionalized polyester.

[0011] Carboxyl-functionalized polyesters are reaction products of a polyol component and a dicarboxylic acid component. In one or more embodiments herein, the equivalence ratio of the polyol component to the dicarboxylic acid component is 0.8 to 0.99, or 0.85 to 0.97, or 0.9 to 0.95.

[0012] In embodiments herein, the polyol component comprises 2,2,4,4-tetramethyl-1,3-cyclobutanediol (TMCD), at least one diol other than TMCD, and trimethylolpropane (TMP). In one or more embodiments herein, the polyol component may comprise: i. 55 mol% to 84 mol% of TMCD based on (i-iii) total moles; ii. at least one diol other than TMCD based on (i-iii) total moles; and iii. 2 mol% to 20 mol% of trimethylolpropane (TMP) based on (i-iii) total moles. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, based on the total molar amount of (i-iii), the amount of TMCD monomer may be 55 mol%-84 mol%, 57 mol%-82 mol%, or 60 mol%-80 mol%; based on the total molar amount of (i-iii), the amount of at least one diol other than TMCD may be 6 mol%-43 mol%, 6 mol%-40 mol%, 8 mol%-33 mol%, 8 to 28 mol%, 10 to 25 mol% or 5 to 25 mol%; based on the total molar amount of (i-iii), the amount of trimethylolpropane (TMP) may be 2 mol%-20 mol%, 5 mol%-20 mol%, 2 mol%-18 mol%, 5 mol%-17 mol%, 10 mol%-17 mol% or 12 mol%-17 mol%.

[0013] In some embodiments, based on the total molar number of i., ii. and iii., the polyol component comprises 57 to 82 mol percent of 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 8 to 33 or 8 to 28 mol percent of at least one diol other than 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and 5 to 20 mol percent of trimethylolpropane. In other embodiments, based on the total molar amounts of i., ii., and iii., the polyol component comprises 60 to 80 mol percent of 2,2,4,4-tetramethyl-1,3-cyclobutanediol; 8 to 33 mol percent, 8 to 28 mol percent, or 10 to 25 mol percent of at least one diol other than 2,2,4,4-tetramethyl-1,3-cyclobutanediol; and 5 to 20 mol percent, 10 to 17 mol percent, or 5 to 17 mol percent of trimethylolpropane.

[0014] In one or more embodiments herein, suitable examples of diols other than TMCD may include, but are not limited to, C3-C19 straight-chain or branched aliphatic diols. Specific examples of suitable diols other than TMCD may include neopentyl glycol, propylene glycol, 1,6-hexanediol, 1,4-butanediol, 2,2-dimethylpropane-1,3-diol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-cyclohexanediethanol, 1,3-cyclohexanediethanol, cis-1,2-cyclohexanediethanol, 1,4-cyclohexanediol, 1,3-cyclohexanediol, 1,2-cyclohexanediol, 4-methyl-1,2-cyclohexanediethanol, 4-cyclopenten-1,3-diol, 4,4'-isopropylidene dicyclohexanol, hydroxypentyl hydroxypentanoate, etc. In some embodiments, at least one diol, other than 2,2,4,4-tetramethyl-1,3-cyclobutanediol, is selected from neopentyl glycol, cyclohexanediol, hydroxyneopentyl hydroxypentanoate, 1,6-hexanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, and mixtures thereof. In other embodiments, at least one diol, other than 2,2,4,4-tetramethyl-1,3-cyclobutanediol, is selected from neopentyl glycol, cyclohexanediol, hydroxyneopentyl hydroxypentanoate, 2-butyl-2-ethyl-1,3-propanediol, and mixtures thereof.

[0015] In some embodiments, based on the total molar amounts of iv., v., and vi., the dicarboxylic acid component comprises: iv. 60 mol percent to 95 mol percent of hexahydrophthalic anhydride, v. 5 mol percent to 35 mol percent of an aliphatic cyclic dicarboxylic acid selected from 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and mixtures thereof, and vi. 0 mol percent to 20 mol percent of an acyclic dicarboxylic acid. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, based on the total molar number of iv., v. and vi., the dicarboxylic acid component comprises iv. 65 mol%-95 mol%, 65 mol%-90 mol% or 65 mol%-85 mol% of hexahydrophthalic anhydride, v. 5 mol% to 35 mol%, 5 mol% to 30 mol%, 10 mol% to 30 mol% or 10 mol% to 25 mol% of aliphatic cyclic diacid, and vi. 5 mol% to 20 mol% or 5 mol% to 15 mol% of acyclic diacid.

[0016] In one or more embodiments herein, examples of suitable aliphatic cyclic diacids may include, but are not limited to, aliphatic cyclic diacids having 6 to 12 carbon atoms in the cyclic ring. In some embodiments, the aliphatic cyclic diacid is selected from 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and mixtures thereof. In other embodiments, the aliphatic cyclic diacid is selected from 1,4-cyclohexanedicarboxylic acid.

[0017] In one or more embodiments herein, the dicarboxylic acid component may further comprise 5 to 20 mol percent of an acyclic diacid, based on the total molar amounts of iv., v., and vi. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the dicarboxylic acid component may further comprise 5 to 20 mol percent or 5 to 15 mol percent of an acyclic diacid, based on the total molar amounts of iv., v., and vi.

[0018] In one or more embodiments herein, suitable examples of acyclic dicarboxylic acids may include, but are not limited to, C4-C 14 Acyclic diacids. Specific examples of acyclic diacids may include succinic acid, adipic acid, pimelic acid, octanoic acid, sebacic acid, dodecanoic acid, and mixtures thereof. In some embodiments, the acyclic diacid is selected from succinic acid, adipic acid, sebacic acid, dodecanoic acid, and mixtures thereof. In other embodiments, the acyclic diacid is adipic acid, dodecanoic acid, and mixtures thereof. In still other embodiments, the acyclic diacid is adipic acid.

[0019] In one or more embodiments herein, the carboxyl-functionalized polyester has a glass transition temperature (Tg) of 45°C to 90°C, an acid value (AN) of 35 mg KOH / g to 90 mg KOH / g, a number-average molecular weight (Mn) of 2,000 g / mol to 10,000 g / mol, and a weight-average molecular weight (Mw) of 5,000 g / mol to 80,000 g / mol. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the carboxyl-functionalized polyester may have a glass transition temperature (Tg) of 45.0°C to 90.0°C, 45.0°C to 80.0°C, or 45.0°C to 77.0°C; an acid value (AN) of 35 mg KOH / g to 90 mg KOH / g, 40 mg KOH / g to 60 mg KOH / g, or 44 mg KOH / g to 55 mg KOH / g; a number-average molecular weight (Mn) of 2,000 g / mol to 10,000 g / mol, 2,000 g / mol to 6,000 g / mol, or 2,500 g / mol to 5,000 g / mol; and a weight-average molecular weight (Mw) of 5,000 g / mol to 80,000 g / mol, 10,000 g / mol to 80,000 g / mol, or 15,000 g / mol to 50,000 g / mol.

[0020] In embodiments described herein, the powder coating composition further comprises one or more compounds that react with a carboxyl-functionalized polyester. In one or more embodiments described herein, one or more compounds that react with a carboxyl-functionalized polyester are crosslinking agents. Exemplary crosslinking agents may include β-hydroxyalkylamides, glycidyl functionalized compounds, and mixtures thereof. Examples of β-hydroxyalkylamide crosslinking agents may include bis(N,N'-dihydroxyethyl)hexamethylenediamide, bis(N,N'-dihydroxypropyl)hexamethylenediamide, or mixtures thereof. Exemplary glycidyl functionalized compounds described herein may include epoxy functionalized compounds. Commercially available glycidyl functionalized compounds may include triglycidyl isocyanurate crosslinking agents sold by Huntsman as ARALDITE™ PT 810, PT 910, and PT 912. Glycidyl acrylates and glycidyl methacrylates, such as Estron Chemical's commercially available GMA 300G, 400G, and 500, are also suitable. Exemplary epoxy functionalized compounds may include those with a molecular weight of about 300 g / mol to about 4000 g / mol, and may have about 0.05 to about 0.99 epoxy groups per 100 grams of resin (i.e., epoxy equivalent 100-2000 (WPE)). Such resins are well known and commercially available under the trademarks EPON™ (Hexion) and ARALDITE™ (Huntsman).

[0021] The compound reacting with the carboxyl-functionalized polyester is a crosslinking agent selected from β-hydroxyalkylamides, glycidyl functionalized compounds, and mixtures thereof. In other embodiments herein, the compound reacting with the carboxyl-functionalized polyester is a crosslinking agent, wherein the crosslinking agent is an epoxy functionalized compound. In a further embodiment herein, the compound reacting with the carboxyl-functionalized polyester is a crosslinking agent, wherein the crosslinking agent is a β-hydroxyalkylamide selected from bis(N,N'-dihydroxyethyl)hexamethylenediamide, bis(N,N'-dihydroxypropyl)hexamethylenediamide, or mixtures thereof. In an even further embodiment herein, the compound reacting with the carboxyl-functionalized polyester is a crosslinking agent, wherein the crosslinking agent is a mixture of β-hydroxyalkylamide and glycidyl functionalized compounds. In one or more embodiments herein, the mixture may comprise, based on the total amount of β-hydroxyalkylamide and glycidyl functionalized compound, 3% to 50% by weight, or 5% to 40% by weight, or 8% to 30% by weight, or 10% to 20% by weight of β-hydroxyalkylamide, and 50% to 97% by weight, or 60% to 95% by weight, or 70% to 92% by weight, or 80% to 90% by weight of glycidyl functionalized compound.

[0022] In one or more embodiments, the carboxyl-functionalized polyester may be present in an amount of 60% to 90% by weight, and the compound reacting with the carboxyl-functionalized polyester is a crosslinking agent, which may be present in an amount of 10% to 40% by weight. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the carboxyl-functionalized polyester may be present in an amount of 70% to 80% by weight based on the total amount of the carboxyl-functionalized polyester and the crosslinking agent, and the compound reacting with the carboxyl-functionalized polyester is a crosslinking agent, which may be present in an amount of 20% to 30% by weight.

[0023] In one or more embodiments herein, the powder coating composition may further comprise waxes, pigments, fillers, degassing agents, flow control agents, and / or other additives. Examples of pigments include inorganic and organic pigments such as titanium dioxide, iron oxide, chromium oxide, zinc sulfide, zinc phosphate, mica, azo compounds, and the like. Exemplary fillers include silicates, sulfates, and carbonates. Examples of additives include degassing agents, antioxidants, and UV stabilizers. Exemplary weather stabilizers include hindered amine light stabilizers and UV absorbers. Examples of degassing agents include cyclohexanediol dibenzoate, benzoin, and benzoin derivatives. Examples of flow control agents include BYK™ 361 N (BYK) and RESIFLOW™ PV-5 (Estron). Other examples of typical additives for powder coating compositions can be found in U.S. Patent 10,916,539, which is incorporated herein by reference.

[0024] The powder coating compositions described herein can be prepared by any method known in the art. In one embodiment, a carboxyl-functionalized polyester powder is mixed with a crosslinking agent powder along with any desired additives at room temperature to obtain a premix. The premix is ​​then extruded at a high temperature, for example, 80°C to 130°C, 90°C to 125°C, or 100°C to 120°C, to produce an extrudate, which is then cooled to cure the mixture. The resulting solid is then milled into a powder and sieved to classify it according to particle size. The powder coating preferably has a particle size of less than about 120 µm, less than 110 µm, or less than 100 µm. One or more embodiments described herein provide a method for manufacturing a powder coating composition, the method comprising mixing a carboxyl-functionalized polyester with a crosslinking agent to form a premix, heating the resulting premix in an extruder to form an extrudate; cooling the extrudate to obtain a cured extrudate, and breaking the cured extrudate into smaller particles to obtain a thermosetting powder coating composition.

[0025] Powder coating compositions can be applied to substrates or articles using conventional methods such as electrostatic deposition (ESD) or fluidized bed coating to a thickness of approximately 1 to 10 mils (1 mil = 25 µm). The coating can be cured at 140°C to 230°C, 140°C to 200°C, 140°C to 180°C, or 140°C to 160°C for 10 minutes to one hour, or under other suitable conditions, allowing the coating to cool. See also: User's Guide to Powder Coating, 4th Edition, edited by Nicholas Liberto, Society of Manufacturing Engineers (2003).

[0026] The embodiments herein also disclose that the powder coating composition of the present invention can be applied to a substrate, a molded part, or an article. Therefore, in one or more embodiments herein, an article (e.g., a molded article) is at least partially coated with the coating composition described herein. The substrate can be any common substrate, such as aluminum, tin, steel, or galvanized sheet, etc. The coating composition can be applied to the substrate using techniques known in the art (e.g., by electrostatic spray deposition (ESD) or fluidized bed application) at a thickness of about 1 mil to about 10 mils (1 mil = 25 μm). The coating can be cured at a temperature of about 140°C to about 230°C for a period of about 10 minutes to about 60 minutes, allowing the coating to cool. In one or more embodiments herein, an article (e.g., a molded or cast article) is at least partially coated with the cured coating composition described herein.

[0027] Test methods Acid value (AN) Acid value was determined according to ASTM D7253-1 (titled "Standard Test Method for Polyurethane Raw Materials: Determination of Acidity as Acid Number for Polyether Polyols"). Acid value is reported in mg KOH / g.

[0028] molecular weight Number-average molecular weight (Mn), weight-average molecular weight (Mw), and z-average molecular weight (Mz) were determined by gel permeation chromatography using a differential refractive index detector with polystyrene standards. Results are reported in g / mol.

[0029] Glass transition temperature (Tg) The glass transition temperature (Tg) was determined as follows: Approximately 0.3 g of resin was placed in a small aluminum weighing pan and heated at 110 °C for one hour. The sample was then transferred to a differential scanning calorimeter (TA Instruments DSC Q2000V24.9 Build 121). During the first heating cycle, the sample was heated from -50 °C to 140 °C at a rate of 20 °C / min under a nitrogen atmosphere. The sample was then quenched to -50 °C. For the second heating cycle, the sample was heated under the same conditions as in the first heating cycle. The midpoint of the second heating cycle was reported as the Tg of the sample. The results were reported in °C.

[0030] Viscosity Viscosities were measured using a CAP 2000 viscometer at 200°C, with a holding time of 45 seconds, a running time of 30 seconds, a rotation speed of 600 rpm, and a No. 5 rotor. Results are reported in poise (P).

[0031] Coating flexibility Coating flexibility was evaluated using a conical mandrel bending test (ASTM D522). The test plate was placed on the end of the conical mandrel clamp corresponding to the minimum bending diameter and bent at a constant speed for one second. The coatings were then visually compared to each other on a scale of 1-8. Coatings with better appearance (fewer cracks) were assigned higher scores according to the rating criteria shown in the table below, where cracking represents a more severe form of crack. Example The following specific examples illustrate the process and performance characteristics related to powder coating compositions and their components. Details of the embodiments and comparative examples of the invention, as well as the formulations, are provided below, with results provided in Tables 2-5.

[0032] Table 1 - Raw Materials The preparation method of carboxyl-functionalized polyester is as follows: The resin is prepared in a two-liter reactor equipped with a heating mantle, mechanical stirrer, thermocouple, nitrogen layer (1.0 standard cubic feet per hour), oil-heated partial condenser (103℃-105℃), condensate trap, and water-cooled total condenser (15℃). The condensate trap, reactor lid, and connection from the reactor to the column are all wrapped with aluminum foil and fiberglass tape to facilitate water removal.

[0033] In the first stage of the reaction, TMCD was added to the reactor in the amounts (in grams) listed in Table 2, along with a diacid component selected from HHPA, adipic acid, CHDA, and DDDA. The reactor was then heated from room temperature to 100°C at a rate of 1°C / min to obtain a homogeneous melt. Stirring was then initiated at 300 rpm, and the temperature was increased to 165°C at a rate of 1°C / min. Exothermic reactions were observed from 140°C to 180°C. After the exothermic reaction was complete, the acid value (AN) was measured to ensure complete reaction of TMCD, and the reactor was then cooled to 150°C for the second stage reaction as described below.

[0034] Under stirring conditions and at 150°C, the catalyst FASCAT™ 4100 and the polyol components (selected from TMP, NPG, CHDM, BEPD, and HPHP, excluding TMCD) were added in the amounts listed in Table 2. The temperature was then set to 165°C. Once the temperature stabilized at 165°C, it was increased to 235°C at a rate of 0.1°C / min. The reaction was maintained at 235°C until the target acid value was reached.

[0035] Table 2 - Resin synthesized by weight of raw materials, in grams Table 3 - Resin Synthesis by Mole % The measurement characteristics of each resin are shown in Table 4 below.

[0036] Table 4 - Resin Properties Coating composition Each coating composition was weighed and placed into a container. The compositions were then milled using a Vitamix mill. The resulting milled compositions were extruded on a twin-screw extruder at 320 RPM and 60%-70% torque. Zone 1 was heated to 100°C, while Zone 2 was heated to 110°C. The compositions were cooled on a twin-roll cooler at 2°C to 5°C and collected in plastic bags. The compositions were allowed to cool completely to room temperature overnight. They were then ground into powder using a Strand mill. The resulting powder compositions were sieved through a 106-micron sieve. The sieved powder coating compositions were ready for immediate spraying.

[0037] Application of coating composition The coating composition was applied to a metal substrate using a Parker Ionics GX700C powder coating system with electrostatic powder coating. The composition was applied to an AQT-36 aluminum plate purchased from Q-Panel Inc. The composition was cured in a 200°C oven for 20 minutes (5 minutes to reach this temperature, 15 minutes to maintain the metal temperature). The target film thickness of the resulting coating was between 45 and 75 micrometers. The actual range is wider.

[0038] Table 5 - Coating compositions by weight, grams Coating testing The flexibility of the coating composition was tested according to the test method provided above. The results are shown in Table 6 below.

[0039] Table 6 - Test Results of Coating Compositions As shown in Table 6 above, it has been unexpectedly found that coating compositions 1-20 of the present invention exhibit significantly improved flexibility / conical mandrel properties compared to comparative coating composition AE.

[0040] The dimensions and values ​​disclosed herein should not be construed as strictly limited to the precise numerical values ​​stated. Rather, unless otherwise specified, each such dimension is intended to represent the stated value and a range around which it is functionally equivalent. For example, a dimension disclosed as “40 mm” is intended to represent “about 40 mm”.

[0041] Unless expressly excluded or otherwise limited, every reference cited herein (if any), including any cross-referenced or related patents or applications and any patent application or patent claiming priority or benefit to this application, is hereby incorporated in its entirety by reference. Reference to any reference does not imply that it is prior art relating to any invention disclosed or claimed herein, or that it, alone or in any combination with any other reference, teaches, suggests, or discloses any such invention. Furthermore, where any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in referenced documents, the meaning or definition given to that term in this document shall prevail.

[0042] While specific embodiments of the invention have been described and illustrated, it will be apparent to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, the appended claims are intended to cover all such changes and modifications that fall within the scope of the invention.

Claims

1. A powder coating composition comprising: A. A carboxyl-functionalized polyester, wherein the carboxyl-functionalized polyester is the product of the following reaction: The polyol component comprises: i. 55 mol percent to 84 mol percent of 2,2,4,4-tetramethyl-1,3-cyclobutanediol, based on the total molar number of i., ii. and iii; ii. Based on the total molar number of i., ii. and iii, at least one diol other than 2,2,4,4-tetramethyl-1,3-cyclobutanediol, with a molar percentage of 6 to 43; iii. Trimethylolpropane, from 2 mol percent to 20 mol percent based on the total moles of i., ii. and iii.; and The dicarboxylic acid component, wherein the dicarboxylic acid component comprises: iv. 60 mol percent to 95 mol percent of hexahydrophthalic anhydride, based on the total molar number of iv., v. and vi.; and v. 1,4-cyclohexanedicarboxylic acid or 1,3-cyclohexanedicarboxylic acid, or mixtures thereof, based on the total molar number of iv., v. and vi.; vi. Acyclic dicarboxylic acids ranging from 0 mol percent to 20 mol percent based on the total number of moles in iv., v. and vi.; The carboxyl-functionalized polyester has a glass transition temperature of 45°C to 90°C, an acid value of 35 mg KOH / g to 90 mg KOH / g, a number-average molecular weight of 2,000 g / mol to 10,000 g / mol, and a weight-average molecular weight of 5,000 g / mol to 80,000 g / mol; and B. One or more compounds that react with the carboxyl-functionalized polyester.

2. The composition according to claim 1, wherein the compound reacting with the carboxyl-functionalized polyester is a crosslinking agent selected from β-hydroxyalkylamides, glycidyl-functionalized compounds, and mixtures thereof.

3. The composition according to claim 1 or 2, wherein the compound reacting with the carboxyl-functionalized polyester is a crosslinking agent, wherein the crosslinking agent is an epoxy-functionalized compound.

4. The composition according to claim 1 or 2, wherein the compound reacting with the carboxyl-functionalized polyester is a crosslinking agent, wherein the crosslinking agent is a β-hydroxyalkylamide selected from bis(N,N'-dihydroxyethyl)hexamethylenediamide, bis(N,N'-dihydroxypropyl)hexamethylenediamide, or mixtures thereof.

5. The composition according to claim 1 or 2, wherein the compound reacting with the carboxyl-functionalized polyester is a crosslinking agent, wherein the crosslinking agent is a mixture comprising 3% to 50% by weight of β-hydroxyalkylamide and 50% to 97% by weight of glycidyl-functionalized compound, based on the total amount of β-hydroxyalkylamide and glycidyl-functionalized compound.

6. The composition according to claims 1 to 5, wherein, based on the total molar number of i., ii. and iii., the polyol component comprises 57 mol percent to 82 mol percent of 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 8 mol percent to 33 mol percent of at least one diol other than 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and 5 mol percent to 20 mol percent of trimethylolpropane; and wherein, based on the total molar number of iv. and v., the dicarboxylic acid component comprises 65 mol percent to 95 mol percent of hexahydrophthalic anhydride and 5 mol percent to 25 mol percent of cyclic diacid.

7. The composition according to claims 1 to 6, wherein the polyol component comprises: 60 to 80 mol percent of 2,2,4,4-tetramethyl-1,3-cyclobutanediol based on the total moles of i., ii. and iii.; at least one diol other than 2,2,4,4-tetramethyl-1,3-cyclobutane based on 10 to 25 mol percent; and trimethylolpropane based on 10 to 17 mol percent.

8. The composition according to claims 1 to 7, wherein the at least one diol other than 2,2,4,4-tetramethyl-1,3-cyclobutanediol is selected from neopentyl glycol, cyclohexanediol, hydroxypentyl hydroxypentanoate, 1,6-hexanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, and mixtures thereof.

9. The composition according to claims 1 to 8, wherein the at least one diol other than 2,2,4,4-tetramethyl-1,3-cyclobutanediol is selected from neopentyl glycol, cyclohexanediol, hydroxypentyl hydroxypentanoate, 2-butyl-2-ethyl-1,3-propanediol, and mixtures thereof.

10. The composition according to claims 1 to 9, wherein the aliphatic cyclic diacid is selected from 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and mixtures thereof.

11. The composition according to claims 1 to 10, wherein the aliphatic cyclic diacid is selected from 1,4-cyclohexanedicarboxylic acid.

12. The composition according to claims 1 to 11, wherein the dicarboxylic acid component further comprises vi. an acyclic dicarboxylic acid of 5 to 20 mol percent based on the total moles of iv., v. and vi.

13. The composition according to claims 1 to 12, wherein the acyclic diacid is selected from succinic acid, adipic acid, sebacic acid, dodecanoic acid, and mixtures thereof.

14. The composition according to claims 1 to 13, wherein the acyclic diic acid is adipic acid, dodecanoic acid, or a mixture thereof.

15. The composition according to claims 1 to 14, wherein the acid value of the carboxyl-functionalized polyester is from 40 mg KOH / g to 60 mg KOH / g.

16. The composition according to claims 1 to 15, wherein the glass transition temperature of the carboxyl-functionalized polyester is 45°C to 80°C.

17. The composition according to claims 1 to 16, wherein the carboxyl-functionalized polyester is present in an amount of 60 to 90% by weight, based on the total amount of the carboxyl-functionalized polyester and the crosslinking agent, and the compound reacting with the carboxyl-functionalized polyester is a crosslinking agent, the crosslinking agent being present in an amount of 10 to 40% by weight.

18. A powder coating composition comprising: A. A carboxyl-functionalized polyester, wherein the carboxyl-functionalized polyester is the product of the following reaction: The polyol component comprises: i. 60 to 80 mol percent of 2,2,4,4-tetramethyl-1,3-cyclobutanediol, based on the total molar number of i., ii. and iii. ii. Based on the total molar number of i., ii. and iii, at least one diol other than 2,2,4,4-tetramethyl-1,3-cyclobutanediol, with a molar percentage of 8 to 33; iii. Trimethylolpropane, from 5 mol percent to 17 mol percent based on the total moles of i., ii. and iii.; and The dicarboxylic acid component, wherein the dicarboxylic acid component comprises: iv. 65 mol% to 85 mol% of hexahydrophthalic anhydride, based on the total molar number of iv., v. and vi.; and v. 10 to 30 mol percent of 1,4-cyclohexanedicarboxylic acid or 1,3-cyclohexanedicarboxylic acid, or mixtures thereof, based on the total moles of iv., v. and vi. vi. Acyclic dicarboxylic acids, ranging from 5 mol percent to 15 mol percent based on the total number of moles in iv., v. and vi.; The carboxyl-functionalized polyester has a glass transition temperature of 45°C to 90°C, an acid value of 35 mg KOH / g to 90 mg KOH / g, a number-average molecular weight of 2,000 g / mol to 10,000 g / mol, and a weight-average molecular weight of 5,000 g / mol to 80,000 g / mol; and B. A crosslinking agent selected from β-hydroxyalkylamides, glycidyl functionalized compounds, and mixtures thereof.

19. An article having at least partially coated with the coating composition according to claims 1 to 18.

20. The article of claim 19, wherein the coating composition is a cured coating composition.

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