KR20200063918A - Powder coating composition - Google Patents

Abstract

The present invention relates to a powder paint composition having improved corrosion resistance and recoatability. The powder paint composition comprises: 60 to 90 wt% of an epoxy functional (meth)acrylic resin; 5 to 25 wt% of a polyester resin; and 5 to 25 wt% of a curing agent based on the total weight of the powder paint composition.

Description

Powder coating composition {Powder coating composition}

The present invention relates to a powder coating composition having improved corrosion resistance and recoatability.

Metals such as aluminum, titanium, and copper are used as main materials for automobile or aircraft parts, and the surface of the metal is coated with a coating composition to protect it from harsh external environments. Various properties such as corrosion resistance, acid resistance, alkali resistance, and weather resistance are required in the coating composition, and when used as an automobile part such as an aluminum wheel, fillform corrosion resistance is important.

Various additives have been used to prevent such corrosion. As an example, Korean Patent Application Publication No. 10-2009-0083267 discloses a coating composition containing one or more hydrophobic submicron particle additives as a powder coating composition for preventing filament corrosion. The hydrophobic submicron particle additive comprises a submicron inorganic oxide and one or more organosilicon compounds. However, when the hydrophobic submicron particles are included as in the coating composition, there is a problem in that the paintability of the composition, in particular, the recoatability is lowered, and thus cannot be applied to various coating specifications.

The present invention provides a powder coating composition excellent in corrosion resistance and recoatability.

The present invention provides a powder coating composition comprising an epoxy functional (meth)acrylic resin, a polyester resin and a curing agent.

The present invention provides a powder coating composition excellent in corrosion resistance and paintability. In particular, the powder coating composition according to the present invention is excellent in recoatability and can be applied to various coating specifications, and is suitable for application to automobile parts (for example, automobile wheels).

The molecular weight used in the present invention is measured by a conventional method known in the art, for example, it can be measured by a gel permeation chromatograph (GPC) method. In addition, the glass transition temperature is measured by a conventional method known in the art, and can be measured, for example, by differential scanning calorimetry (DSC).

Hereinafter, the present invention will be described. However, it is not limited only by the following contents, and each component may be variously modified or selectively mixed as necessary. Therefore, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

The powder coating composition according to the present invention includes an epoxy functional (meth)acrylic resin, a polyester resin and a curing agent. The powder coating composition of the present invention may further include additives commonly used in the powder coating field, if necessary. Hereinafter, the composition of the powder coating composition of the present invention will be described.

Epoxy functional (meth)acrylic resin

The powder coating composition according to the present invention includes an epoxy functional (meth)acrylic resin as a main resin. The epoxy-functional (meth)acrylic resin serves to secure water resistance, corrosion resistance and glossiness when the coating is applied.

As an example, the epoxy functional (meth)acrylic resin may be prepared by synthesizing an epoxy functional group-containing monomer and a (meth)acrylic monomer.

The type of the monomer containing the epoxy functional group is not particularly limited, for example, one selected from glycidyl (meth)acrylate, glycidyl (meth) allyl ether and 3,4-epoxycyclohexyl (meth)acrylate. The above can be used.

Examples of the (meth)acrylic monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, and t-butyl (meth)acrylic. Aliphatic (meth)acrylics such as acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, and stearyl (meth)acrylate Rate-based monomers; aromatic (meth)acrylate-based monomers such as phenoxy (meth)acrylate; and (meth) acrylic acid trifluoroethyl.

The epoxy equivalent of the epoxy functional (meth)acrylic resin is not particularly limited, and may be about 200 to 1,500 g/eq, for example, about 300 to 800 g/eq. When the epoxy equivalent satisfies the above-described range, a coating film having excellent corrosion resistance and appearance may be formed. When the epoxy equivalent is less than 200 g/eq, the gel time becomes faster, and the glass transition temperature of the coating film increases, so that recoatability may be deteriorated. In addition, when the epoxy equivalent exceeds 1,500 g/eq, it is difficult to secure a crosslinking density, and adhesion, water resistance, and salt spray resistance may be deteriorated.

The melt viscosity of the epoxy functional (meth)acrylic resin (200° C., I.C.I viscometer) is not particularly limited, and may be, for example, about 1,000 to 2,500 cps, and another example, about 1,100 to 2,200 cps. When the melt viscosity of the epoxy functional (meth)acrylic resin is within the above-described range, a coating film having excellent leveling properties and workability and excellent appearance characteristics can be secured. When the melt viscosity of the resin is less than 1,000 cps, the leveling property may be good, but the edge area cover may be weak. On the other hand, when the melt viscosity is 2,500 cps or more, it is difficult to secure a beautiful appearance of the paint.

The glass transition temperature of the epoxy functional (meth)acrylic resin is not particularly limited, and may be, for example, about 25 to 100°C, and about 35 to 85°C as another example. When the glass transition temperature of the epoxy-functional (meth)acrylic resin is in the above-described range, the workability and leveling property of the paint are excellent, and the hardness and impact resistance of the coating film can also be improved. When the glass transition temperature of the resin is less than 25°C, the storage property of the coating material is poor, so that the coating may occur, and when it exceeds 100°C, the glass transition temperature of the coating film may be high, resulting in poor recoatability.

The epoxy-functional (meth)acrylic resin may be included in about 60 to 90% by weight, for example, 70 to 80% by weight, based on the total weight of the powder coating composition. When the content of the epoxy functional (meth)acrylic resin satisfies the above-described range, not only can a transparent coating film be formed, but also the leveling property, flexibility, adhesion, etc. of the coating film can be improved.

Polyester resin

The powder coating composition of the present invention includes a polyester resin. As the polyester resin, a conventional resin known in the art may be used, and for example, a polyester resin containing a carboxyl group in the molecule may be used.

The acid value of the polyester resin may be about 10 to 80 mgKOH/g, for example, about 20 to 70 mgKOH/g. When the acid value of the polyester resin is less than 10 mgKOH/g, the reactivity and crosslinking density of the coating film may drop, so that the desired coating film properties may not be sufficiently exhibited, and when it exceeds 80 mgKOH/g, the reaction rate during curing increases, thereby causing pinholes. It may occur, and a rapid deterioration of leveling may result, and the appearance may be deteriorated.

The polyester resin may have a melt viscosity of 500 to 3,500 cps (200°C, I.C.I viscometer), for example, 1,500 to 3,000 cps (200°C, I.C.I viscometer). When the melt viscosity of the polyester resin is less than 500 cps, the appearance may be lowered, and when it exceeds 3,500 cps, the leveling is lowered and a problem in storage properties may occur.

The polyester resin may have a glass transition temperature (Tg) of 30 to 120°C, for example, 45 to 100°C. If the glass transition temperature of the polyester resin is less than 30 °C, storage may be poor, and if it exceeds 120 °C, dispersibility may be lowered.

The polyester resin may have a number average molecular weight (Mn) of 1,500 to 3,000 g/mol, for example, 1,700 to 2,800 g/mol. If the number average molecular weight of the polyester resin is less than 1,500 g/mol, the appearance of the coating film may be poor, and if it exceeds 3,000 g/mol, the mechanical properties of the coating film may be deteriorated.

In the present invention, at least one type of the polyester resin may be used, for example, two types may be used in combination. At this time, the mixing ratio between the two types of polyester resin is not particularly limited and can be appropriately adjusted.

The polyester resin may be included in about 5 to 25% by weight, for example, about 5 to 15% by weight, based on the total weight of the powder coating composition. When the content of the polyester resin is less than the above-mentioned range, the mechanical properties of the coating film may be deteriorated, and when the content of the above-mentioned content range is exceeded, the workability of the coating may be deteriorated.

Hardener

The powder coating composition according to the present invention includes an epoxy functional (meth)acrylic resin and a curing agent that causes a curing reaction. The curing agent is not particularly limited as long as it is a curing agent in the art that can undergo a curing reaction with an epoxy functional (meth)acrylic resin, for example, one or more selected from (meth)acrylic acid polymers, acid curing agents, and acid anhydride curing agents. Can be used.

The (meth)acrylic acid polymer refers to a polymer-type compound obtained by reacting a (meth)acrylic acid monomer. The (meth)acrylic acid polymer has a double bond in the polymer structure, and causes a curing reaction with the epoxy functional (meth)acrylic resin to control the curing density.

The acid curing agent is a curing agent containing an acid functional group, and for example, a polybasic acid curing agent or the like can be used. Non-limiting examples of acid curing agents include sebasic acid, succinic acid, glutaric acid, adipic acid, pimeric acid, and azelaic acid , Nonanoic acid, decanoic acid, dodecanoic acid, dodecandionic acid, hexadecanoic acid, itaconic acid , Maleic acid, and the like. These may be used alone or in combination of two or more.

Although the acid value of the acid curing agent is not particularly limited, for example, in the case of 400 to 600 mgKOH/g, not only is it excellent in reactivity, but adhesion of the coating film, appearance characteristics, and the like can be improved.

The acid anhydride curing agent is a latent curing agent, and is used to improve the curing density or to impart flow or flexibility of the coating film. Non-limiting examples of such acid anhydride curing agents include phthalic anhydride, p-chlorophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, hexahydrophthalic anhydride, pyromellitic anhydride, tetrabromophthalic anhydride , Cyclohexane-1,2-dicarboxylic anhydride, cyclopentane-1,2-dicarboxylic anhydride, dodecylsuccinic anhydride, succinic anhydride, maleic anhydride, methylsuccinic anhydride, azelaic anhydride, And polyadipic anhydride, polyazelaic anhydride, polyseva type anhydride, polydodetanoic anhydride, and polyeic acid noic anhydride. These may be used alone or in combination of two or more.

The acid anhydride equivalent of the acid anhydride curing agent is not particularly limited, and may be, for example, about 100 to 200 g/eq. When the acid anhydride equivalent of the acid anhydride curing agent is in the above-described range, long-term corrosion resistance, adhesion, etc. may be improved due to high crosslinking degree.

The curing agent may be included in about 5 to 25% by weight, for example, 10 to 20% by weight based on the total weight of the powder coating composition. When the content of the curing agent is within the above-mentioned range, crosslinking density is improved without deteriorating the water resistance of the coating film, so that long-term corrosion resistance, adhesion, leveling property, etc. of the coating film may be improved, and yellowing may be minimized.

additive

The powder coating composition of the present invention may further include additives commonly used in the powder coating field, within a range that does not impair the inherent properties of the composition.

Non-limiting examples of additives usable in the present invention include leveling agents, pinhole inhibitors, waxes, ultraviolet absorbers, heat stabilizers, antioxidants, coupling agents, etc., which may be used alone or in combination of two or more. have.

The leveling agent is intended to improve the appearance properties of the coating film while enhancing the adhesion in the composition by leveling the coating composition so that it is coated flat and smooth. The leveling agent may be at least one selected from acrylic, silicone, polyester and amine leveling agents, for example, an acrylic leveling agent. Non-limiting examples of such an acrylic leveling agent include polyacrylate polymers, polymethacrylate polymers, polyethylacrylate, polybutylacrylate, and ethylhexyl poly-2-acrylate.

The pinhole preventing agent may release volatile substances from the coating film during the curing process, thereby preventing pinhole generation in the coating film and improving appearance characteristics. Non-limiting examples of pinhole inhibitors include amide-based (eg, ceraflour 960 (BYK)), polypropylene-based, and stearic acid-based pinhole inhibitors. In one example, the pinhole inhibitor may be benzoin or a mixture of benzoin and an amide pinhole inhibitor.

As the wax, paraffin wax, natural wax, synthetic wax or a mixture thereof can be used. Natural waxes include carnauba wax, and synthetic waxes include polyamide wax and polyethylene wax.

UV absorbers can improve external durability after painting. Non-limiting examples of ultraviolet absorbers include benzotriazole-based, benzylidene-hydant-based, benzophenone-based, and benzoguanine-based, which may be used alone or in combination of two or more.

The heat-resistant stabilizer can improve the long-term heat stability of the coating film while preventing deterioration in physical properties or deterioration in appearance when exposed to high temperatures. The heat stabilizer usable in the present invention is not particularly limited as long as it is a heat stabilizer commonly known in the art. Non-limiting examples include sulfur-based heat stabilizers, phenol-based heat stabilizers, and phosphorus-based heat stabilizers, such as pentaerythryl tetrakis(3-laurylthiopropionate, tetrakis(methylene (3,5-di-t- Butyl-4-hydroxy)hydrosilylnate), 1,3,5-trimethyl-tris(3,5-di-t-butyl-4-hydroxybenzene), tris(2,4-di-t-butyl Phenol) phosphite, etc. These may be used alone or in combination of two or more.

Antioxidants serve to improve external durability after painting. Non-limiting examples of antioxidants include phenol antioxidants, organic sulfur antioxidants, and phosphite antioxidants. As the phenol antioxidant, alkylphenol, monoalkylene dialkylphenol, dialkylenetrialkylphenol, tetraalkylphenol, bisphenol monosulfite, polyphenol, and the like can be used. For example, 4,4'-butyli Denbis(3-methyl-6-t-butylphenol), tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, 1, 3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tris-(3,5-di-t-butyl-4-hydroxybenzyl) )-Isocyanurate, and the like. As the organic sulfur antioxidant, 3,3'-thiodipropionic acid, pentaerythryl tetrakis (3-laurylthiopropionate), 2-mercapdobenzimidazole, etc. may be used, but are not limited thereto. Does not work. Phosphite antioxidants include triphenylphosphite, tris(nonylphenyl)phosphite, tris(2,4-di-t-butylphenyl)phosphite, cyclic neopentanetetraylbis(octadecylphosphite), etc. It can be used, but is not limited thereto. These may be used alone or in combination of two or more.

The coupling agent serves to improve the adhesion between the coating film and the material in the coating curing reaction. Non-limiting examples of coupling agents include silane-based coupling agents in which the terminal functional group is vinyl, epoxy, styryl, methacrylic, acryloxy, amino, isocyanate, isocyanurate or mercapto. As a silane coupling agent having a vinyl group at the end, vinyl trimethoxy, vinyl triethoxy, 7-octenyl triethoxy, siloxane, and the like may be used, but is not limited thereto. As the silane coupling agent having an epoxy group terminal, 2-(3, 4 epoxycyclohexyl)ethyl trimethoxy, 3-glycidoxypropyl trimethoxy, 3-glycidoxypropyl methyldimethoxy, 3-glycidoxy Propyl methyldiethoxy, 3-glycidoxypropyl triethoxy, 8-glycidoxyoctyl trimethoxy, organo, siloxane and the like can be used, but is not limited thereto. As a metacrioxy silane coupling agent, 3-methoxypropyl methyl dimethoxy, 3-methoxypropyl trimethoxy, 3-methoxypropyl methyl diethoxy, 3-methoxypropyl triethoxy, 8- Metahydroxyoctyl trimethoxy and the like can be used, but is not limited thereto. As the silane coupling agent having an amino group terminal, N-2-(aminoethyl)-3-aminopropyl methyldimethoxy, N-2-(aminoethyl)-3-aminopropyl methoxy, 3-aminopropyltriethoxy , 3-aminopropyltrimethoxy, 3-triethoxysilyl-N-(1,3 dimethyl-butylidene_propylamine, organo, N-phenyl-3-aminopropyl trimethoxy, N-2- (Aminoethyl)-8-aminooctyl trimethoxy, etc. can be used, but is not limited to this: 3-mercaptopropylmethyldimethoxy, 3-mercaptopropyltrime as a silane coupling agent having a mercapto group terminal. Toxicity, organosiloxane, etc. can be used, but are not limited to these, or may be used alone or in combination of two or more.

Such additives may be appropriately added within a content range known in the art, for example, about 0.1 to 10% by weight based on the total weight of the powder coating composition, and about 0.1 to 5% by weight as another example. When the content of the additive is within the aforementioned range, the appearance and hardness of the coating film may be improved.

The powder coating composition according to the present invention may be prepared by a method known in the art, for example, it may be prepared through processes such as raw material basis weight, dry pre-mixing, dispersion and coarse crushing, grinding and classification. For example, a raw material mixture containing an epoxy functional (meth)acrylic resin, a polyester resin, and a curing agent and optionally other additives is introduced into a container mixer to uniformly mix, and the mixed composition is melt-mixed and then pulverized. Can be manufactured. For example, the raw material mixture is melt-dispersed at 70 to 130°C by a melt-kneading device such as a kneader or an extruder to prepare chips with a predetermined thickness (eg, 1 to 5 mm). Thereafter, the produced chips may be pulverized into a range of 40 to 80 μm using a pulverizing device such as a high-speed mixer, and then classified to prepare a powder coating composition.

The classification process is not particularly limited, and may be filtered by, for example, 80 to 120 mesh. Accordingly, a powder coating having an average particle size in the range of 40 to 80 μm can be obtained. The average particle diameter of the powder is not particularly limited, but when the above-described range is satisfied, the coating workability and the appearance characteristics of the coating film may be enhanced.

In order to improve the fluidity of the powder coating, it is also possible to coat the surface of the powder coating particles according to the present invention with fine powder such as silica. As a method of performing such treatment, a pulverization mixing method in which fine powder is added during pulverization and mixing, or a dry mixing method using a Henschel mixer can be used.

The powder coating composition of the present invention may be applied as a paint for automobile parts (for example, a coating of an automobile wheel) (eg, a clear coat), and the automobile wheel may be made of aluminum (Al) or aluminum alloy material. The powder coating composition according to the present invention may be used as a transparent coat or may be used as a colored transparent coat including colored pigments. The powder coating composition of the present invention is not only excellent in corrosion resistance, but also can be variably applied according to various coating specifications of automobile parts, and is particularly easily applicable to specifications requiring beautiful appearance and transparency.

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are only to aid the understanding of the present invention, and the scope of the present invention is not limited to the examples in any sense.

[Example 1-10]

Each component was added to a mixing tank according to the composition shown in Table 1 below, premixed, melt-dispersed at 100° C. in a disperser, and cooled to prepare a chip. The prepared chips were pulverized with a high-speed mixer to prepare powder coating compositions of Examples 1-10 having an average particle size of 40 to 80 μm. In Table 1, the unit of use of each composition is% by weight.

[Comparative Example 1-8]

Powder coating compositions of Comparative Examples 1-8 were prepared in the same manner as in Example 1-10, except that each component was used according to the composition shown in Table 2 below.

Acrylic resin 1: glycidyl methacrylate acrylic resin (epoxy equivalent: 550 g/eq, viscosity: 1,600 cps, glass transition temperature: 80°C)

Acrylic resin 2: glycidyl methacrylate acrylic resin (epoxy equivalent: 350 g/eq, viscosity: 1,200 cps, glass transition temperature: 40°C)

Acrylic resin 3: glycidyl methacrylate acrylic resin (epoxy equivalent: 750 g/eq, viscosity: 2,000 cps, glass transition temperature: 75°C)

Polyester resin 1: carboxyl polyester resin (acid value: 25 mgKOH/g, viscosity: 1,600 cps, glass transition temperature: 55°C, number average molecular weight: 2,250 g/mol)

Polyester resin 2: carboxyl polyester resin (acid value: 40 mgKOH/g, viscosity: 2,100 cps, glass transition temperature: 90°C, number average molecular weight: 2,700 g/mol)

Polyester resin 3: carboxyl polyester resin (acid value: 65 mgKOH/g, viscosity: 2,800 cps, glass transition temperature: 45°C, number average molecular weight: 1,810 g/mol)

Hardener: Dodecandionic Acid (INVISTA)

Additive 1: Acrylic Polymer (BYK)

Additive 2: Benzoin (Miwon Specialty Chemicals)

Additive 3: Micronized modified amide wax (BYK)

Additive 4: 2-Hydroxyphenyl-s-triazine (Double bond chemical company)

Additive 5: HALS (BASF)

Additive 6: IRGANOX B900 (Double bond chemical)

Additive 7: Glycidoxypropyltrimethoxysilane (ShinEtsu)

[Experimental Example-Property evaluation]

The physical properties of the powder coating compositions prepared in Examples 1-10 and Comparative Examples 1-8 were measured as follows, and the results are shown in Tables 3 and 4 below.

Specimen preparation

A specimen having a size of 75 mm×150 mm×0.4 mm was prepared by treating the aluminum with chromate.

Appearance (leveling)

After the powder coating composition was electrostatically spray-coated on the prepared specimen to form an undercoat, the visual appearance of the coating was checked visually. The evaluation grades were classified as ◎: very good, ○: good, △: normal, ×: bad.

Gel time

0.1 g of the powder coating composition was heated at 175° C. to measure the time taken to become a liquid and then harden.

Glass transition temperature of coating film (Tg)

After preparing a CR specimen of 65 mm×150 mm×0.7 mm, the glass transition temperature (° C.) of the coating film was measured using DSC. The higher the coating film Tg, the better the corrosion resistance.

Recoat

After clear coating using the powder coating composition on the prepared specimen, it was cured at 205° C.*5 min. Subsequently, the coated specimens were re-coated under the same conditions to make 10 cells at 2 mm intervals to observe whether the tape was peeled. Recoatability was evaluated by a rank of 1 to 10, and the higher the Rank, the better the physical properties.

Water resistance

After clear coating using the powder coating composition on the prepared specimen, a boiling water test (72 hours) was performed according to the NESM007 Section 29 Method, and then secondary adhesion (2 mm spacing) was evaluated. The water resistance was evaluated by a rank of 1 to 10, and the higher the Rank, the better the physical properties. Secondary adhesion must be secured at least Rank 6 or higher.

CASS

After clear coating using the powder coating composition on the prepared specimen, the CASS test (360 hours) was performed according to MS 652-18 (section 4.7), and the length (mm) at which one-sided peeling occurred was measured. The shorter the peeling length, the better the corrosion resistance.

Salt water spray resistance (SST)

After clear coating using the powder coating composition on the prepared specimen, a salt spray test (1,200 hours) was performed, and the length (mm) at which one-side peeling occurred was measured. The shorter the peeling length, the better the corrosion resistance.

Adhesion

After clear coating using the powder coating composition on the prepared specimen, the adhesion (2 mm spacing) was evaluated. The adhesiveness was evaluated by a rank of 1 to 10, and the higher the Rank, the better the physical properties. The adhesion must be secured at least Rank 6 or higher.

Heat resistance

After clear coating using the powder coating composition on the prepared specimen (average film thickness: 60 to 80㎛), cured under standard curing conditions (175℃*15min, material standard), and then the color difference value of the coating ( ΔE) value was measured. The higher the b value among the L, a, and b values, the more susceptible to yellowing.

Hardness

After clear coating using the powder coating composition on the prepared specimen, the coating film hardness was checked based on a Mitsubishi pencil. A pencil hardness of at least HB should be ensured.

Impact resistance

After clear coating using the powder coating composition on the prepared specimen, the impact resistance of the coating film was confirmed using an impact tester. The prepared weight is based on 500 g and there should be no cracking of the coating when dropped from a height of at least 30 cm.

As shown in Table 3 and Table 4, the coating film formed of the powder coating composition of Example 1-10 according to the present invention was measured excellently all properties. In particular, it was confirmed that the coating film formed of the powder coating composition of Examples 1-10 satisfies all of the water resistance and adhesiveness of Rank 6 or higher, hardness of HB or higher, and impact resistance of 500 g/30 cm or higher, which are required in the industry. On the other hand, the coating film formed of the powder coating composition of Comparative Example 1-8, which does not contain a polyester resin or the content of the components used is outside the scope of the present invention, was confirmed to have poor appearance and poor overall measured properties. .

Claims (4)

Based on the total weight of the powder coating composition
Epoxy functional (meth) acrylic resin 60 to 90% by weight,
5 to 25% by weight of polyester resin and
Powder coating composition comprising 5 to 25% by weight of a curing agent. According to claim 1, The epoxy equivalent of the epoxy functional (meth) acrylic resin is 200 to 1,500 g/eq, the melt viscosity (200 ℃, ICI viscometer) is 1,000 to 2,500 cps, the glass transition temperature is 25 to 100 ℃ powder coating composition. According to claim 1, the acid value of the polyester resin is 10 to 80 mgKOH / g, the melt viscosity is 500 to 3,500 cps (200 ℃, ICI viscometer), the glass transition temperature (Tg) is 30 to 120 ℃, Powder coating composition having a number average molecular weight (Mn) of 1,500 to 3,000 g/mol. The powder coating composition of claim 1, wherein the curing agent comprises at least one of a (meth)acrylic acid polymer, an acid curing agent, and an acid anhydride curing agent.