Thermosetting powder coating compositions

Abstract

Powder coating compositions that comprise: (A.) a carboxyl-functional polyester, which is 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 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-functional polyester has a glass transition temperature of 45 to 90°C, an acid number of 35 to 90 mg KOH / g, a number average molecular weight of 2,000 to 10,000 g / mole, and a weight average molecular weight of 5,000 to 80,000 g / mole; and B. one or more compounds reactive with the carboxyl-functional polyester.

Description

THERMOSETTING POWDER COATING COMPOSITIONS TECHNICALFIELD

[0001] Embodiments of the present disclosure generally relate to powder coating compositions comprising carboxyl-functional polyesters, and more particularly, relate to powder coating compositions comprising carboxyl-functional polyesters for use with automotive bodies and parts, such as, automotive wheels. BACKGROUND

[0002] Thermosetting powder coatings can be environmentally friendly paints having very low volatile organic compound (VOC) emission into the atmosphere. Thermosetting powder coatings may be broadly classified into four groups -- polyester, epoxy, polyester / epoxy hybrid and acrylic, and their markets have been developed for various uses according to their prices and performance. There have been increasing demands for powder coatings in the industry due to their good corrosion protection and outdoor durability.

[0003] Thermosetting powder coatings can be used for coating of substrate surfaces of automotive bodies and automotive parts, such as, aluminum wheels, wipers, pillars, door handles, fenders, bonnets, air spoilers, stabilizers and grilles. Exposed portions of automotive parts can be subjected to a fury of grit, stone chips damage, as well as weather elements (e.g., UV-exposure, temperature, humidity and / or corrosive environment conditions) during normal use, which can abrade a protective coating on the surface of these automotive parts. Further, polyester-based clearcoats tend to show crazing issues when sprayed direct to metal.

[0004] Accordingly, it would be highly desirable to develop a polyester-based powder coating composition having improved crazing resistance, which is directly related to flexibility. SUMMARY

[0005] Disclosed in embodiments herein are powder coating compositions. The compositions comprise: A. a carboxyl-functional polyester, which is the reaction product of: a polyol component comprising: i. 55 to 84 mole percent of 2,2,4,4-tetramethyl-1,3- cyclobutanediol, based on the total moles of i., ii., and iii.; ii. 6 to 43 mole percent of at leastone diol other than 2,2,4,4-tetramethyl-1,3-cyclobutanediol, based on the total moles of i., ii., and iii.; iii. 2 to 20 mole percent of trimethylolpropane, based on the total moles of i., ii., and iii.; and a dicarboxylic acid component comprising: iv. 60 to 95 mole percent of hexahydrophthalic anhydride, based on the total moles of iv., v., and vi.; and v. 5 to 35 mole percent of 1,4-cyclohexanedicarboxylic acid or 1,3-cyclohexanedicarboxylic acid, or a mixture thereof, based on the total moles of iv., v., and vi.; vi 0 to 20 mole percent of an acyclic diacid, based on the total moles of iv., v., and vi; wherein the carboxyl-functional polyester has a glass transition temperature of 45 to 90°C, an acid number of 35 to 90 mg KOH / g, a number average molecular weight of 2,000 to 10,000 g / mole, and a weight average molecular weight of 5,000 to 80,000 g / mole; and B. one or more compounds reactive with the carboxyl-functional polyester.

[0006] Further disclosed in embodiments herein are powder coating compositions. The compositions comprise: A. a carboxyl-functional polyester, which is the reaction product of: a polyol component comprising: i. 60 to 80 mole percent of 2,2,4,4-tetramethyl-1,3- cyclobutanediol, based on the total moles of i., ii., and iii.; ii. 8 to 33 mole percent of at least one diol other than 2,2,4,4-tetramethyl-1,3-cyclobutanediol, based on the total moles of i., ii., and iii.; iii. 5 to 17 mole percent of trimethylolpropane, based on the total moles of i., ii., and iii.; and a dicarboxylic acid component comprising: iv. 65 to 85 mole percent of hexahydrophthalic anhydride, based on the total moles of iv., v., and vi.; and v. 10 to 30 mole percent of 1,4-cyclohexanedicarboxylic acid or 1,3-cyclohexanedicarboxylic acid, or a mixture thereof, based on the total moles of iv., v., and vi.; vi.5 to 15 mole percent of an acyclic diacid, based on the total moles of iv., v., and vi; wherein the carboxyl-functional polyester has a glass transition temperature of 45 to 90°C, an acid number of 35 to 90 mg KOH / g, a number average molecular weight of 2,000 to 10,000 g / mole, and a weight average molecular weight of 5,000 to 80,000 g / mole; and B. a crosslinker selected from the group consisting of β- hydroxyalkylamides, glycidyl-functional compounds, and mixtures thereof.

[0007] Further disclosed in embodiments herein are articles at least partially coated with the powder coating compositions described herein.

[0008] Additional features and advantages of the embodiments will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein. It is to be understood that both the foregoing and the following description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. DETAILED DESCRIPTION

[0009] Reference will now be made in detail to embodiments of thermosetting powder coating compositions and methods of manufacturing thereof, as well as articles coated with cured thermosetting powder coating compositions described herein. The thermosetting powder coating compositions may be used in the manufacture of automotive parts, and particularly, in automotive wheel parts. It is noted, however, that this is merely an illustrative implementation of the embodiments disclosed herein. The embodiments are applicable to other automotive parts that are susceptible to similar problems as those discussed above, such as wipers, pillars, door handles, fenders, bonnets, air spoilers, stabilizers and grilles, as well as, automotive bodies.

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

[0011] The carboxyl-functional polyester is the reaction product of a polyol component and a dicarboxylic acid component. In one or more embodiments herein, the equivalent ratio of the polyol component and the diacid 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. TMCD in an amount of 55-84 mole %, based on the total moles of (i-iii); ii. at least one diol other than TMCD in an amount of 6-43 mole %, based on the total moles of (i-iii); iii. trimethylolpropane (TMP) in an amount of 2-20 mole %, based on the total moles of (i-iii). All individual values and subranges are included and disclosed herein. For example, in some embodiments, the TMCD monomer may be in an amount of 55-84 mole%, 57-82 mole % or 60-80 mole %, based on the total moles of (i-iii); the at least one diol other than TMCD may be in an amount of 6-43 mole %, 6-40 mole %, 8-33 mole %, 8 to 28 mole %, 10 to 25 mole %, or 5 to 25 mole %, based on the total moles of ((i-iii); the trimethylolpropane (TMP) may be in an amount of 2-20 mole %, 5-20 mole %, 2-18 mole %, 5-17 mole %, 10-17 mole %, or 12-17 mole %, based on the total moles of (i-iii).

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

[0014] In one or more embodiments herein, examples of suitable diols other than TMCD may include, but are not limited to, C3-C19 linear 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-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, cis- 1,2-cyclohexanedimethanol, 1,4-cyclohexanediol, 1,3-cyclohexanediol, 1,2-cyclohexanediol, 4-methyl-1,2-cyclohexanedimethanol, 4-cyclopentene-1,3-diol, 4,4'- isopropylidenedicyclohexanol, hydroxypivalyl hydroxypivalate, and the like. In some embodiments herein, the at least one diol other than 2,2,4,4-tetramethyl-1,3-cyclobutanediol isselected from the group consisting of neopentyl glycol, cyclohexanedimethanol, hydroxypivalyl hydroxypivalate, 1,6-hexanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 2- butyl-2-ethyl-1,3-propanediol, and mixtures thereof. In other embodiments, the at least one diol other than 2,2,4,4-tetramethyl-1,3-cyclobutanediol is selected from the group consisting of neopentyl glycol, cyclohexanedimethanol, hydroxypivalyl hydroxypivalate, 2-butyl-2-ethyl- 1,3-propanediol, and mixtures thereof.

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

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

[0017] In one or more embodiments herein, the dicarboxylic acid component may further comprise from 5 to 20 mole percent of an acyclic diacid, based on the total moles 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 from 5 to 20 mole percent or 5 to 15 mole percent of an acyclic diacid, based on the total moles of iv., v., and vi.

[0018] In one or more embodiments herein, examples of suitable acyclic diacids may include, but are not limited to, C4-C14acyclic diacids. Specific examples of acyclic diacids mayinclude succinic acid, adipic acid, pimelic acid, suberic acid, sebacic acid, dodecanedioic acid, and mixtures thereof. In some embodiments, the acyclic diacid is selected from the group consisting of succinic acid, adipic acid, sebacic acid, dodecanedioic acid, and mixtures thereof. In other embodiments, the acyclic diacid is adipic acid, dodecanedioic acid, and mixtures thereof. In further embodiments, the acyclic diacid is adipic acid.

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

[0020] In embodiments herein, the powder coating composition also comprises one or more compounds reactive with the carboxyl-functional polyester. In one or more embodiments herein, the one or more compounds reactive with the carboxyl-functional polyester are crosslinkers. Exemplary crosslinkers may include β-hydroxyalkylamides, glycidyl-functional compounds, and mixtures thereof. Examples of β-hydroxyalkylamide crosslinkers may include bis(N,N'-dihydroxyethyl)adipamide, bis(N,N'-dihydroxypropyl)adipamide, or a mixture thereof. Exemplary glycidyl-functional compounds described herein may include epoxy- functional compounds. Commercially available glycidyl-functional compounds may include triglycidyl isocyanurate-based crosslinkers available from Huntsman as ARALDITE™ PT 810, PT910, and PT 912. Also suitable are glycidyl acrylates and glycidyl methacrylates such as those commercially available as GMA 300G, 400G and 500 from Estron Chemical. Exemplary epoxy-functional compounds may include those having a molecular weight of about 300 to about 4000 g / mole, and may have approximately 0.05 to about 0.99 epoxy groups per 100 grams of resin (i.e., 100-2000 weight per epoxy (WPE)). Such resins are widely known andcommercially available under the EPON™ mark (Hexion), and the ARALDITE™ mark (Huntsman).

[0021] In some embodiments herein, the compound reactive with the carboxyl-functional polyester is a crosslinker selected from the group consisting of β-hydroxyalkylamides, glycidyl- functional compounds, and mixtures thereof. In other embodiments herein, the compound reactive with the carboxyl-functional polyester is a crosslinker, wherein the crosslinker is an epoxy-functional compound. In further embodiments herein, the compound reactive with the carboxyl-functional polyester is a crosslinker, wherein the crosslinker is an β- hydroxyalkylamide selected from the group consisting of bis(N,N'-dihydroxyethyl)adipamide, bis(N,N'-dihydroxypropyl)adipamide, or a mixture thereof. In even further embodiments herein, the compound reactive with the carboxyl-functional polyester is a crosslinker, wherein the crosslinker is a mixture of β-hydroxyalkylamides and glycidyl-functional compounds. In one or more embodiments herein, the mixture may comprise from 3 wt.% to 50 wt.%, alternatively, 5 wt.% to 40 wt.%, 8 to 30 wt.% or 10 to 20 wt.% of the β-hydroxyalkylamides and from 50 wt.% to 97 wt.%, alternatively, 60 to 95 wt.%, or 70 to 92 wt.%, or 80 to 90 wt.% of the glycidyl-functional compounds, based on the total amount of β-hydroxyalkylamides and glycidyl-functional compounds.

[0022] In one or more embodiments herein, the carboxyl-functional polyester may be present in an amount of 60 to 90 percent, by weight, and the compound reactive with the carboxyl-functional polyester is a cross-linker that may be present in an amount of 10 to 40 percent, by weight. All individual values and subranges are included and disclosed herein. For example, in some embodiments, the carboxyl-functional polyester may be present in an amount of 70 to 80 percent, by weight, and the compound reactive with the carboxyl-functional polyester is a cross-linker that may be present in an amount of 20 to 30 percent, by weight, based on the total amount of carboxyl-functional polyester and cross-linker.

[0023] In one or more embodiments herein, the powder coating compositions may further comprise waxes, pigments, fillers, degassing agents, flow 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 weathering stabilizers include hindered amine light stabilizers and UV absorbers. Examples of degassing agents include cyclohexane dimethanol dibenzoate, benzoin, and benzoin derivatives. Examples of flow control agents include BYK™ 361 N (BYK) and RESIFLOW™ PV-5 (Estron). Further examples of typical additives for powder coating compositions can be found in U.S. Patent No. 10,916,539, incorporated herein by reference.

[0024] The powder coating compositions described herein may be prepared by any method known in the art. In one embodiment, the powders of the carboxyl-functional polyester and the crosslinker are mixed along with any desired additives at room temperature to obtain a premix. The premix is then extruded at an elevated temperature such as, for example, 80° to 130°, 90° to 125°, or 100° to 120 °C, to yield an extrudate, which is then cooled to solidify the mixture. The resulting solid is then made into powder by milling and subsequently sieved to classify the size of the particles. The powder coating may desirably have particle sizes of less than about 120 µm, less than 110 µm, or less than 100 µm. In one or more embodiments described herein are methods of manufacturing powder coating compositions, the method comprising mixing the carboxyl-functional polyester and crosslinker together to form a premix, heating the obtained premix in an extruder to form an extrudate; cooling the extrudate to obtain a solidified extrudate and breaking the obtained solidified extrudate into smaller particles to obtain the thermosetting powder coating composition.

[0025] The powder coating composition may be applied to a substrate or article by a common method, such as electrostatic spray deposition (ESD) or fluidized bed application, at a thickness of about 1 to about 10 mils (1 mil = 25 µm). The coating may be cured at 140° to 230°C, 140° to 200°C, 140° to 180°C, or 140° to 160°C for 10 minutes to one hour, or other suitable conditions, and allowed to cool. See also: User’s Guide to Powder Coating, 4th Ed., Nicholas Liberto, editor, Society of Manufacturing Engineers (2003).

[0026] Also disclosed in embodiments herein are that the powder coating compositions of the invention can be applied to a substrate or shaped or article. Thus, in one or more embodiments herein, an article (e.g., a shaped or formed article) is at least partially coated withthe coating compositions described herein. The substrate can be any common substrate such as aluminum, tin, steel or galvanized sheeting, and the like. The coating composition can be coated onto a substrate using techniques known in the art, for example, by electrostatic spray deposition (ESD) or fluidized bed application at a thickness of about 1 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 time period that ranges from about 10 minutes to about 60 minutes and allowed to cool. In one or more embodiments herein, an article (e.g., a shaped or formed article) is at least partially coated with the cured coating compositions described herein. TESTMETHODSAcid Number (AN)

[0027] Acid number is measured according to ASTM D7253-1 entitled “Standard Test Method for Polyurethane Raw Materials: Determination of Acidity as Acid Number for Polyether Polyols. The acid number is reported in mg KOH / g. Molecular Weight

[0028] The number average molecular weight (Mn), the weight average molecular weight (Mw), and the z-average molecular weight (Mz) are determined by gel permeation chromatography using a refractive index detector with polystyrene standards. The results are reported in g / mole. Glass Transition Temperature (Tg)

[0029] Glass transition temperature (Tg) is determined by placing about 0.3g of the resin is placed into a small aluminum weighing pan and heated for one hour at 110°C. A sample is then transferred to a differential scanning calorimeter (TA Instruments DSC Q2000 V24.9 Build 121). On the first heating cycle, the sample is heated under nitrogen atmosphere from -50°C to 140°C at a rate of 20°C / min. The sample is then quench cooled to -50°C. For the second heating cycle, the sample is heated under the same conditions as those used in the first heating cycle. The midpoint of the second heating cycle is reported as the Tg of the sample. The results are reported in ºC.Viscosity

[0030] Viscosity is measured using a CAP 2000 viscometer at 200°C with a 45 sec hold, 30 sec run time, 600 rpm and spindle number 5. The results are reported in poise (P). Coating Flexibility

[0031] Coating flexibility is evaluated using conical mandrel bends (ASTM D522). Panels are placed at the end of the conical mandrel jig corresponding to the smallest bend diameter and are bent at a constant speed over the course of one second. Coatings are then visually compared to one another on a scale of 1-8. Better appearances (less crazing) are assigned higher scores per the following ratings shown in the table, wherein cracking represents a more severe form of crazingEXAMPLES

[0032] The following specific examples are given to illustrate the process and performance properties associated with powder coating compositions and its components. The inventive and comparative examples are provided below with the details of the formulations and results are provided in Tables 2-5. Table 1 – Raw Materials

[0033] The carboxyl-functional polyesters are prepared as follows: the resin is prepared in a two-liter reaction kettle equipped with a heating mantle, mechanical stirrer, thermocouple, nitrogen blanket (1.0 standard cubic feet per hour), oil-heated partial condenser (103°C - 105°C), condensate trap, and water-cooled total condenser (15°C). The condensate trap, kettle top and adapter from the kettle to the column are wrapped in aluminum foil and fiberglass tape to facilitate water removal.

[0034] In the first stage of the reaction, TMCD along with the diacid components selected from HHPA, Adipic Acid, CHDA, and DDDA are charged to the reactor according to the amounts (in grams) listed in Table 2. The reactor is then heated from room temperature to 100°C at 1°C / minute to obtain a homogeneous melt. Agitation is then started at 300 rpm and thetemperature is increased to 165°C at 1°C / minute. An exotherm is observed from 140°C to 180°C. After the exotherm, the acid number (AN) is taken to ensure complete reaction of the TMCD, and the reactor is allowed to cool to 150°C for the second stage of the reaction as described below.

[0035] At 150°C and under agitation, the catalyst, FASCAT™ 4100, along with the polyol components other than TMCD, selected from TMP, NPG, CHDM, BEPD, and HPHP, are added according to the amounts listed in Table 2. The temperature is then set to 165°C. Once the temperature stabilized at 165°C, the temperature is increased to 235°C at 0.1°C / min. The reaction is held at 235°C until the target acid number is reached.

[0036] Table 2 – Resin Synthesis by Weight Charges, gramsTable 3 – Resin Synthesis by Mole%

[0037] The measured properties of each resin are shown below in Table 4. Table 4 – Resin PropertiesCoating Compositions

[0038] Each coating composition is weighed into a container. The compositions are then milled using a Vitamix mill. The resulting milled compositions are extruded on a two-zone twin screw extruder at 320 RPM and 60-70% torque. Zone 1 is heated to 100oC while Zone 2 is at 110°C. The compositions are cooled on a twin roll chiller at 2-5°C and collected in a plastic bag. The compositions are allowed to fully cool to room temperature overnight. They are then powdered using a Strand mill. The resulting powder compositions are sieved using 106-micron mesh. The sieved powder coating compositions are then considered ready to spray. Coating Composition Application

[0039] Coating compositions are applied to a metal substrate using a Parker Ionics GX700C Powder Gun System electrostatic powder spray apparatus. The composition is applied to AQT- 36 aluminum panels purchased from Q-Panel Inc. The compositions are cured in an oven at 200 ºC for 20 minutes (5 minutes ramp to temp, 15 minutes at metal temperature). The resulting film thickness of the coating is targeted to be between 45-75 microns. The actual range is wider.

[0040] Table 5 – Coating Compositions by Weight, gramsCoating Testing

[0041] The coating composition flexibility is tested according to the test method provided above. The results are reported below in Table 6. Table 6 – Coating Compositions Results

[0042] As shown above in Table 6, it has been surprisingly found that the inventive coating compositions 1-20 show significantly improved flex / conical mandrel properties compared to the comparative coating compositions A-E.

[0043] The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.”

[0044] Every document cited herein, if any, including any cross- referenced or related patent or application and any patent application or patent to which this application claims priority or benefit thereof, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission thatit is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

[0045] While particular embodiments of the present invention have been illustrated and described, it would be obvious 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. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

Claims

What is claimed is:

1. A powder coating composition comprising: A. a carboxyl-functional polyester, which is the reaction product of: a polyol component comprising: i. 55 to 84 mole percent of 2,2,4,4-tetramethyl-1,3-cyclobutanediol, based on the total moles of i., ii., and iii.; ii. 6 to 43 mole percent of at least one diol other than 2,2,4,4-tetramethyl- 1,3-cyclobutanediol, based on the total moles of i., ii., and iii.; iii. 2 to 20 mole percent of trimethylolpropane, based on the total moles of i., ii., and iii.; and a dicarboxylic acid component comprising: iv. 60 to 95 mole percent of hexahydrophthalic anhydride, based on the total moles of iv., v., and vi.; and v. 5 to 35 mole percent of 1,4-cyclohexanedicarboxylic acid or 1,3- cyclohexanedicarboxylic acid, or a mixture thereof, based on the total moles of iv., v., and vi.; vi. 0 to 20 mole percent of an acyclic diacid, based on the total moles of iv., v., and vi; wherein the carboxyl-functional polyester has a glass transition temperature of 45 to 90°C, an acid number of 35 to 90 mg KOH / g, a number average molecular weight of 2,000 to 10,000 g / mole, and a weight average molecular weight of 5,000 to 80,000 g / mole; and B. one or more compounds reactive with the carboxyl-functional polyester.

2. The composition of claim 1, wherein the compound reactive with the carboxyl- functional polyester is a crosslinker selected from the group consisting of β- hydroxyalkylamides, glycidyl-functional compounds, and mixtures thereof.

3. The composition of claims 1 or 2, wherein the compound reactive with the carboxyl- functional polyester is a crosslinker, wherein the crosslinker is an epoxy-functional compound.

4. The composition of claims 1 or 2, wherein the compound reactive with the carboxyl- functional polyester is a crosslinker, wherein the crosslinker is an β-hydroxyalkylamide selected from the group consisting of bis(N,N'-dihydroxyethyl)adipamide, bis(N,N'- dihydroxypropyl)adipamide, or a mixture thereof.

5. The composition of claims 1 or 2, wherein the compound reactive with the carboxyl- functional polyester is a crosslinker, wherein the crosslinker is a mixture comprising from 3 wt.% to 50 wt.% of β-hydroxyalkylamides and from 50 wt.% to 97 wt.% of glycidyl-functional compounds, based on the total amount of β-hydroxyalkylamides and glycidyl-functional compounds.

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

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

8. The composition of claims 1-7, wherein the at least one diol other than 2,2,4,4- tetramethyl-1,3-cyclobutanediol is selected from the group consisting of neopentyl glycol, cyclohexanedimethanol, hydroxypivalyl hydroxypivalate, 1,6-hexanediol, 1,4-butanediol, 2- methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, and mixtures thereof.

9. The composition of claims 1-8, wherein the at least one diol other than 2,2,4,4- tetramethyl-1,3-cyclobutanediol is selected from the group consisting of neopentyl glycol, cyclohexanedimethanol, hydroxypivalyl hydroxypivalate, 2-butyl-2-ethyl-1,3-propanediol, and mixtures thereof.

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

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

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

13. The composition of claims 1-12, wherein the acyclic diacid is selected from the group consisting of succinic acid, adipic acid, sebacic acid, dodecanedioic acid, and mixtures thereof.

14. The composition of claims 1-13, wherein the acyclic diacid is adipic acid, dodecanedioic acid, and mixtures thereof.

15. The composition of claims 1-14, wherein the carboxyl-functional polyester has an acid number of 40 to 60 mg KOH / g.

16. The composition of claims 1-15, wherein the carboxyl-functional polyester has a glass transition temperature of 45 to 80°C.

17. The composition of claims 1-16, wherein the carboxyl-functional polyester is present in an amount of 60 to 90 percent, by weight, and the compound reactive with the carboxyl- functional polyester is a crosslinker that is present in an amount of 10 to 40 percent, by weight, based on the total amount of carboxyl-functional polyester and crosslinker.

18. A powder coating composition comprising: A. a carboxyl-functional polyester, which is the reaction product of: a polyol component comprising: i. 60 to 80 mole percent of 2,2,4,4-tetramethyl-1,3-cyclobutanediol, based on the total moles of i., ii., and iii.; ii. 8 to 33 mole percent of at least one diol other than 2,2,4,4-tetramethyl- 1,3-cyclobutanediol, based on the total moles of i., ii., and iii.;iii. 5 to 17 mole percent of trimethylolpropane, based on the total moles of i., ii., and iii.; and a dicarboxylic acid component comprising: iv. 65 to 85 mole percent of hexahydrophthalic anhydride, based on the total moles of iv., v., and vi.; and v. 10 to 30 mole percent of 1,4-cyclohexanedicarboxylic acid or 1,3- cyclohexanedicarboxylic acid, or a mixture thereof, based on the total moles of iv., v., and vi.; vi. 5 to 15 mole percent of an acyclic diacid, based on the total moles of iv., v., and vi; wherein the carboxyl-functional polyester has a glass transition temperature of 45 to 90°C, an acid number of 35 to 90 mg KOH / g, a number average molecular weight of 2,000 to 10,000 g / mole, and a weight average molecular weight of 5,000 to 80,000 g / mole; and B. a crosslinker selected from the group consisting of β-hydroxyalkylamides, glycidyl- functional compounds, and mixtures thereof.

19. An article at least partially coated with the coating composition of claims 1-18.

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

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