KR102244453B1 - Powder coating composition - Google Patents

Abstract

The present invention relates to a powder coating composition comprising an epoxy resin including a bisphenol A type epoxy resin, an isocyanate-modified epoxy resin, and a novolak type epoxy resin, and an amine-based curing agent.

Description

Powder coating composition {POWDER COATING COMPOSITION}

The present invention relates to a powder coating composition.

Powder coatings, unlike liquid coatings, are solid powdery coatings that do not contain diluents such as volatile organic solvents, and are cured when heated to form a coating film. Therefore, it is one of the paints that are in the spotlight as a countermeasure to cope with the globally reinforced environmental regulations, as they do not emit polluting substances because they do not contain volatile components.

Powder coating using powder coatings is widely used in various fields such as architecture, home appliances, and automobile industries due to its excellent properties of the coating film, does not require much skill of the operator compared to solvent type coatings, and has excellent impact resistance. Particularly, powder coating compositions have been widely used recently for painting electric and electronic parts or building busbars.

Korean Patent Application Publication No. 2003-0017873 discloses a powder coating for electric and electronic parts including a bisphenol A type epoxy resin and a rubber-modified epoxy resin, but the powder coating has a disadvantage in that it does not exhibit excellent appearance characteristics due to low dispersibility. have. Japanese Patent Application Laid-Open No. 2008-56838 discloses an epoxy resin powder coating containing an epoxy resin, a curing agent, an inorganic filler, and a silane coupling agent, but the powder coating has a disadvantage of poor impact resistance and adhesion in a high temperature and humidity environment. .

The present invention provides a powder coating composition excellent in durability, heat resistance and electrical insulation.

The present invention provides a powder coating composition comprising an epoxy resin including a bisphenol A type epoxy resin, an isocyanate-modified epoxy resin, and a novolak type epoxy resin, and an amine-based curing agent.

The powder coating composition of the present invention can form a coating film having excellent heat resistance, durability, and electrical insulation properties under long-term high temperature conditions. In addition, since the powder coating composition of the present invention secures long-term fluidity, improves workability, and has excellent flowability and flexibility of the coating film, it is possible to effectively coat busbars having many angled corners (edges).

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 used as necessary. Therefore, it should be understood to include all changes, 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 resin and an amine-based curing agent including a bisphenol A type epoxy resin, an isocyanate-modified epoxy resin, and a novolak type epoxy resin, and if necessary, a pigment, an inorganic filler, a curing accelerator and a powder It may further include additives commonly used in the paint field. Hereinafter, looking at the composition of the powder coating composition of the present invention is as follows.

(a) epoxy resin

In the powder coating composition according to the present invention, the epoxy resin is a main resin, and includes a bisphenol A type epoxy resin, an isocyanate-modified epoxy resin, and a novolac type epoxy resin. When the isocyanate-modified epoxy resin is used alone or in a high content, a difference in physical properties may occur due to a change in reaction rate (Gel time, etc.). On the other hand, when the novolac-type epoxy resin is used alone or in a high content, flow problems and mechanical properties may deteriorate. In the present invention, excellent paint properties were secured by mixing the three types of epoxy resins and using them as the main resin.

Bisphenol A type epoxy resin is an epoxy resin obtained from the reaction of bisphenol A (BPA) and epichlorohydrin. The bisphenol A type epoxy resin is not particularly limited as long as it is a conventional epoxy resin known in the art.

The epoxy equivalent (EEW) of the bisphenol A type epoxy resin is not particularly limited, but may be about 900 to 1,300 g/eq, for example, about 1,100 to 1,200 g/eq. In addition, the viscosity and softening point of the bisphenol A type epoxy resin is not particularly limited, but the viscosity (based on 200°C melting) may be 1,800 to 2,800 CPS, for example, 2,000 to 2,600 CPS, and the softening point is about 100 to 120°C, For example, it may be 105 to 115 ℃. When the physical properties of the bisphenol A-type epoxy resin are within the above-described range, the composition has excellent storage stability, and the appearance characteristics and flexibility of the coating film are improved, thereby minimizing the occurrence of cracks in the coating film.

The isocyanate-modified epoxy resin is a polymer obtained by modifying an epoxy resin with an isocyanate compound, and contains an oxazolidone ring in the main chain skeleton of the epoxy resin and a glycidyl group at the terminal. Such an isocyanate-modified epoxy resin can be prepared by reacting an epoxy resin with an isocyanate compound in the presence of a catalyst. The isocyanate modification rate is not particularly limited, but may be, for example, 20 to 30% by weight. The isocyanate-modified epoxy resin is not particularly limited as long as it is a conventional epoxy resin known in the art.

The weight average molecular weight of the epoxy resin may be about 350 to 400 g/mol, and the epoxy equivalent may be about 170 to 200 g/eq.

As the isocyanate compound, for example, monoisocyanate or diisocyanate may be used. Non-limiting examples of the monoisocyanate include p-toluenesulfonyl isocyanate, 4-phenoxyphenyl isocyanate, and 4-cyanophenyl isocyanate. Non-limiting examples of the diisocyanate include methane diisocyanate, butane-1,1-diisocyanate, ethane-1,2-diisocyanate, butane-1,2-diisocyanate, transvinyline diisocyanate, heptane-1 ,7-diisocyanate, 2,2-dimethyl-pentane-1,5-diisocyanate, hexane-1,6-diisocyanate, octane-1,8-diisocyanate, nonane-1,9-diisocyanate, dimethylsilane Diisocyanate, diphenylsilane diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4-diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,6-toluene diisocyanate, 2,4-toluene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, trans-1,4-cyclohexane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, and the like. These may be used alone or in combination of two or more. The content of the isocyanate compound may be about 1 to 40 parts by weight based on 100 parts by weight of the epoxy resin.

As the catalyst, bases, amines, hydrogen compounds, imidazoles, phosphonium salts and derivatives thereof may be used, but are not limited thereto. These may be used alone or in combination of two or more. The content of the catalyst may be about 0.01 to 0.5 parts by weight based on 100 parts by weight of the isocyanate compound.

The epoxy equivalent of the isocyanate-modified epoxy resin of the present invention is not particularly limited, but may be about 200 to 600 g/eq, for example, about 400 to 500 g/eq. In addition, the viscosity and softening point of the isocyanate-modified epoxy resin are not particularly limited, but the viscosity (based on 150° C. Melting) may be 10,000 to 30,000 CPS, for example, 15,000 to 25,000 CPS, and the softening point is 100 to 125° C., for example. For example, it may be 105 to 115 ℃. When the physical properties of the isocyanate-modified epoxy resin are within the above-described range, appearance characteristics and corrosion resistance of the coating film may be improved.

Novolac-type epoxy resin is a multifunctional epoxy resin and has more epoxide rings compared to other types of epoxy resins, so it can improve the durability, corrosion resistance, and chemical properties of the coating film by increasing the crosslinking density when forming a coating film. have. The novolak-type epoxy resin is not particularly limited as long as it is a conventional epoxy resin known in the art. Non-limiting examples of the novolac-type epoxy resin usable in the present invention include phenol novolac-type epoxy resin, cresol novolac-type epoxy resin, bisphenol A novolac-type epoxy resin, bisphenol S novolac-type epoxy resin, biphenyl no Rock-type epoxy resins, naphthol novolac-type epoxy resins, and the like. For example, the novolac-type epoxy resin is a phenol novolac-type epoxy resin.

The epoxy equivalent of the novolak-type epoxy resin is not particularly limited, but may be about 650 to 950 g/eq, for example, about 750 to 850 g/eq. In addition, the viscosity and softening point of the novolak type epoxy resin are not particularly limited, but the viscosity (based on 150°C melting) may be 20,000 to 50,000 CPS, for example, 30,000 to 40,000 CPS, and the softening point is 100 to 125°C, eg For example, it may be 110 to 125 ℃. When the physical properties of the novolac-type epoxy resin are within the above-described range, workability and mechanical properties of the coating film may be improved.

In the present invention, the mixing ratio of the bisphenol A type epoxy resin, isocyanate-modified epoxy resin, and novolak type epoxy resin may be 1 to 4: 0.5 to 2.5: 1 to 4 weight ratio. When the mixing ratio is within the above-described range, physical properties of a paint having excellent reactivity and mechanical properties (impact, adhesiveness, flexibility, etc.) can be secured.

In the powder coating composition of the present invention, the content of the epoxy resin is not particularly limited, and may be, for example, about 30 to 70% by weight based on the total amount of the powder coating composition, and in another example about 40 to 60% by weight. When the content of the epoxy resin is within the above-described range, mechanical properties and workability of the coating film may be improved.

(b) amine curing agent

The powder coating composition of the present invention contains an amine-based curing agent. The amine-based curing agent can improve the curing degree of the coating film by curing reaction with a bisphenol A type epoxy resin, an isocyanate-modified epoxy resin, and a novolak type epoxy resin, thereby improving the flexibility of the coating film compared to other curing agents.

The amine-based curing agent is not particularly limited as long as it is an amine-based curing agent capable of curing reaction with a bisphenol A type epoxy resin, a novolak type epoxy resin, and an isocyanate-modified epoxy resin. For example, there are an aliphatic amine-based curing agent, an alicyclic amine-based curing agent, an aromatic amine-based curing agent, and the like, and these may be used alone or in combination of two or more. Non-limiting examples of amine-based curing agents that can be used include 4,4'-diamino diphenyl sulfone, 4,4'-diamino diphenyl methane, dicyandiamide, and the like. As an example, the amine-based curing agent may be dicyan diamide.

In the present invention, the content of the amine-based curing agent is not particularly limited, and may be, for example, about 1 to 20% by weight, and in another example, about 5 to 15% by weight based on the total amount of the powder coating composition. When the content of the amine-based curing agent is within the above-described range, the degree of curing of the coating film is high, and physical properties of the coating film may be improved.

(c) pigment

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

The pigment may be mixed with an epoxy resin to express a desired color (color) in a powder coating or used to increase the strength or gloss of the coating film. As such pigments, organic pigments, metallic pigments, aluminum-paste, pearl, and the like, which are commonly used in powder coatings, may be used without limitation, and these may be used alone or in combination of two or more. Non-limiting examples of usable pigments include azo-based, phthalocyanine-based, iron oxide-based, cobalt-based, silicate-based, chromate-based pigments, and the like, such as titanium dioxide, zinc oxide, bismuth vanadate, cyanine green, carbon black , Iron oxide, iron oxide, navy blue, cyanine blue, and mixtures of two or more thereof. As an example, the pigment may be carbon black.

In the present invention, the content of the pigment is not particularly limited, and may be, for example, about 0.1 to 10% by weight, for example, about 0.1 to 5% by weight, based on the total amount of the powder coating composition. When the content of the pigment is within the above-described range, the color expression of the coating film to which the powder coating composition of the present invention is applied is excellent, and the hiding property and mechanical properties of the coating film can be improved.

(d) inorganic filler

The powder coating composition of the present invention may optionally further include an inorganic filler commonly used in the powder coating field within a range that does not impair the intrinsic properties of the composition.

Non-limiting examples of inorganic fillers that can be used include calcium carbonate, feldspar, barium sulfate, silica, alumina hydroxide, magnesium hydroxide, titanium dioxide, magnesium carbonate, alumina, mica, montmorillonite, olastonite, talc, aluminum nitride, silicon nitride, There are boron nitride, aluminum oxide, aluminum nitride, barium sulfate, and the like, which may be used alone or in combination of two or more.

The average particle diameter of the inorganic filler is not particularly limited, and may be, for example, about 1 to 20 μm. In addition, the shape of the inorganic filler may be spherical or amorphous, and is not particularly limited thereto.

In the present invention, the content of the inorganic filler may be, for example, about 1 to 60% by weight based on the total amount of the powder coating composition, and in another example, about 1 to 50% by weight. When the content of the inorganic filler is within the above-described range, mechanical properties, impact resistance, and adhesion of the coating film may be improved.

(e) hardening accelerator

The powder coating composition of the present invention may optionally further include a curing accelerator commonly used in the powder coating field within a range that does not impair the intrinsic properties of the composition.

The curing accelerator is a material that accelerates the reaction between the epoxy resin as the main resin and the curing agent (especially, amine curing agent), such as imidazole curing accelerator, phosphonium curing accelerator, amine curing accelerator, metal curing accelerator And the like, but these may be used alone or in combination of two or more.

Non-limiting examples of the imidazole-based curing accelerator, imidazole, 2-methylimidazole, 2-ethylimidazole, 2-decylimidazole, 2-hectylimidazole, 2-isopropyl Midazole, 2-undecyl imidazole, 2-heptanedecyl imidazole, 2-ethyl-4-methyl imidazole, 2-phenylimidazole, 2-phenyl-4-methyl imidazole, 1-benzyl-2- Methyl imidazole, 1-benzyl-2-phenyl imidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl- 2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecyl-imidazole trimellitate, 1-cyanoethyl-2-phenyl imidazole tri Melitate, 2,4-diamino-6-(2'-methylimidazole-(1')-ethyl-s-triazine, 2-fesyl-4,5-dihydroxymethylimidazole, 2 -Pesyl-4-methyl-5-hydroxymethylimidazole, 2-fesyl-4-benzyl-5-hydroxymethylimidazole, 4,4'-methylene-bis-(2-ethyl-5-methyl Imidazole), 2-aminoethyl-2-methyl imidazole, 1-cyanoethyl-2-phenyl-4,5-di (cyanoethoxy methyl) imidazole, 1-dodecyl-2-methyl- 3-benzylimidazolinium chloride, imidazole-containing polyamide, and the like.

Non-limiting examples of the phosphonium-based curing accelerator include benzyltriphenyl phosphonium chloride, butyltriphenyl phosphonium chloride, butyltriphenyl phosphonium bromide, ethyltriphenyl phosphonium acetate, ethyltriphenyl phosphonium bromide, ethyltriphenyl Phosphonium iodide, tetraphenyl phosphonium bromide, tetraphenyl phosphonium chloride or tetraphenyl phosphonium iodide.

Non-limiting examples of the amine-based curing accelerator include triethylamine, triethylenediamine, tetramethyl-1,3-butanediamine, ethylmorpholine, diazabicycloundecene, diazabicyclononene, and the like.

Examples of the metal-based curing accelerator include organic metal complexes or organic metal salts such as cobalt, copper, zinc, iron, nickel, manganese, and tin. Examples of the organometallic complex include organic cobalt complexes such as cobalt(II) acetylacetonate, cobalt(III) acetylacetonate, organic copper complexes such as copper(II) acetylacetonate, zinc(II) acetylacetonate, and the like. Organic zinc complexes, organic iron complexes such as iron(III) acetylacetonate, organic nickel complexes such as nickel(II) acetylacetonate, and organic manganese complexes such as manganese(II)acetylacetonate. It is not limited. Examples of the organometallic salt include, but are not limited to, zinc octylate, tin octylate, zinc naphthenate, cobalt naphthenate, tin stearate, zinc stearate, and the like.

In the present invention, the content of the curing accelerator may be appropriately adjusted according to the reactivity of the binder resin and the curing agent. For example, the content of the curing accelerator may be about 0.1 to 5% by weight, in another example, about 0.1 to 3% by weight, based on the total amount of the powder coating composition. When the content of the curing accelerator is out of the above-described range, mechanical properties of the coating film may be deteriorated.

(f) additive

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

Non-limiting examples of additives that can be used in the present invention, pinhole inhibitors, leveling agents, waxes, low stress agents, dispersants, flow improvers, cratering inhibitors, coupling agents, gloss modifiers, adhesion improvers, flame retardants, matting agents, There are light absorbers and the like, and these may be used alone or in combination of two or more.

The powder coating composition of the present invention may further include at least one selected from the group consisting of a leveling agent, a pinhole inhibitor, a dispersant, an adhesion promoter, a flowability additive, and a flowability improver.

The leveling agent is for improving the appearance characteristics of the coating film while improving the adhesion in the composition by leveling the coating composition so that it is coated smoothly and smoothly. For example, there are acrylic-based, silicone-based, polyester-based, amine-based leveling agents, and the like, but is not particularly limited thereto.

The pinhole inhibitor allows volatile substances to be released from the coating film during the curing process, thereby preventing the occurrence of pinholes in the coating film and improving appearance characteristics. Non-limiting examples of the pinhole inhibitor include amide-based (eg, ceraflour 960 (BYK)), polypropylene-based, stearic acid-based pinhole inhibitor, and the like. For example, the pinhole inhibitor may be benzoin or a mixture of benzoin and an amide pinhole inhibitor.

As the dispersant, conventional ones known in the art may be used without limitation, and as an example, a polyacrylic dispersant may be used that is adsorbed on the surface of a colored pigment to maximize a degassing effect.

The adhesion promoter is a material for enhancing the adhesion of the coating film, and a silane adhesion promoter or the like may be used. Non-limiting examples of the adhesion promoter include mercaptoalkylakoxysilane, gammaglydoxypropyltrimethoxysilane, and the like, and as an example, the adhesion promoter may be a mercaptoalkylalkoxysilane having a molecular weight of 150 to 300. .

The flowability additive is used to maximize the flowability effect, and can secure long-term flowability while improving the adhesion of the paint. As the flowable additive, waxes, silica, and the like may be used. Non-limiting examples of flowable additives that can be used include paraffin wax, natural wax (e.g., carnauba wax, etc.), synthetic wax (e.g., polyethylene wax, etc.), silica, etc. These are used alone or in combination of two or more. Can be used. In addition, waxes may be mixed with silica and used. The flowable additive may be used as an additive component after adding it after making a chip.

The flow improving agent is used to lower the surface tension of the coating film and realize a flexible appearance, and a conventional one known in the art may be used. Non-limiting examples include acrylic or silicone flow improvers.

Such additives may be appropriately added within a content range known in the art, and for example, may be about 0.1 to 20% by weight, for example, about 0.1 to 10% by weight, based on the total weight of the powder coating composition. When the content of the additive is within the above-described range, the appearance and hardness of the coating film may be improved.

In addition to the above-described epoxy resin, amine-based curing agent, pigment, and inorganic filler, the powder coating composition of the present invention comprises about 0.1 to 2% by weight of adhesion promoter, about 0.4 to 2% by weight of flow additive, 0.1 To 3% by weight of a leveling agent, about 0.1 to 3% by weight of a pinhole inhibitor, and about 0.2 to 2% by weight of a dispersant may be further included.

The powder coating composition according to the present invention may be prepared by a method known in the art, and for example, may be prepared through processes such as metering, premixing, melt dispersion, and pulverization.

For example, a mixture of raw materials containing bisphenol A type epoxy resin, novolac type epoxy resin, isocyanate-modified epoxy resin, amine-based curing agent, pigment, inorganic filler, and optionally a curing accelerator and additive is added to a container mixer and uniformly mixed. And, after melt-mixing the mixed composition, it can be prepared by pulverizing it. As an 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 prepared chips may be pulverized in 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, 40 to 80 mesh. Accordingly, a powder coating material 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, coating workability and appearance characteristics of the coating film may be improved.

In order to improve the flowability of the powder coating material, the surface of the powder coating material particles according to the present invention may be coated with a fine powder such as silica. As a method of performing such a treatment, a pulverization mixing method in which fine powder is added and mixed during pulverization or a dry mixing method using a Henschel mixer or the like can be used.

The powder coating composition of the present invention has excellent long-term heat resistance and durability, and can form a coating film having excellent electrical insulation properties under long-term high temperature conditions. In particular, it satisfies the international certification UL 1446 Class F rating (155℃) for electrical insulation. Therefore, the powder coating composition of the present invention can be applied to paint electric and insulating parts.

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

[Example 1-6]

According to the composition shown in Table 1 below, each component was added to a mixing tank for premixing, and then melt-dispersed at 100°C in a disperser to prepare a chip. The prepared chips were pulverized with a high-speed mixer to prepare a powder coating composition of Example 1-3 having an average particle size of about 40 μm. In Table 1 below, the unit of use of each composition was% by weight, based on the total amount of the composition.

[Comparative Example 1-11]

Powder coating compositions of Comparative Examples 1-11 were prepared in the same manner as in Example 1, except that each component was used according to the composition shown in Table 2 below.

1) Epoxy resin 1: Bisphenol A type epoxy resin (epoxy equivalent: 1,150 g/eq, viscosity: 2,300 (200℃ melting standard), softening point: 110℃)

2) Epoxy resin 2: Isocyanate-modified epoxy resin (epoxy equivalent: 450 g/eq, viscosity: 20,000 (150°C melting standard), softening point: 115°C)

3) Epoxy resin 3: Phenol novolak type epoxy resin (epoxy equivalent: 800 g/eq, viscosity: 35,000 (200℃ melting standard), softening point: 115℃)

4) Epoxy resin 4: Bisphenol A type epoxy resin (epoxy equivalent: 950 g/eq, viscosity: 2,000 (based on 200°C melting), softening point: 105°C)

5) Epoxy resin 5: Isocyanate-modified epoxy resin (epoxy equivalent: 300 g/eq, viscosity: 15,000 (150°C melting standard), softening point: 105°C)

6) Hardener 1: BTDA (3,3',4,4'-Benzophenonetetracarboxylic dianhydride)

7) Hardener 2: dicyandiamide

8) Hardener 3: PHENOL

9) Curing accelerator: 2MI(2-METHYLIMIDAZOLE)

10) Leveling agent: Silicon dioxide

11) Pinhole inhibitor 1: Benzoin (2-Hydroxy-1,2-diphenylethanone)

12) Pinhole inhibitor 2: CERAFLOUR 960 (Polyethylene wax)

13) Dispersant: BYK-3955P (BYK company)

14) Colored pigment: CARBON BLACK MA-100 (MITUSBISHI CHEM company)

15) Inorganic filler: S-SIL 10J (Quartz(SiO ₂ ))

16) Adhesion promoter: Mercaptoalkylalkoxysilane (SHIN-ETSU CHEMICAL)

[Experimental Example-Evaluation of Physical Properties]

The physical properties of the powder coating compositions prepared in Examples 1-6 and 1-11, respectively, were measured as follows, and the results are shown in Tables 3 and 4 below.

(1) Appearance (leveling)

After preparing an iron-coated specimen (size: 100 ㎜×100 ㎜×1.0 ㎜), the prepared specimen was preheated at 230°C for 30 minutes. Thereafter, each powder coating composition was coated on the preheated specimen using a painting gun, and then the appearance state of the coating film was visually checked. The judgment grade was classified as ◎: very good, ○: good, △: normal, and x: bad.

(2) Glass transition temperature of the coating film (Tg)

After preparing an iron-coated specimen (size: 100 ㎜×100 ㎜×1.0 ㎜), the prepared specimen was preheated at 230°C for 30 minutes. Then, each powder coating composition was coated on the preheated specimen using a painting gun. Then, the glass transition temperature (℃) of the coating film was measured using DSC.

(3) Flow rate

After making a tablet sample [diameter (Φ): 20 mm] by compressing the paint (2±0.05 g) in a molding mold [diameter (Φ): 20 mm] at a pressure of 1,590 kg/㎠ for 30 seconds, the tablet sample was It was placed horizontally on a steel plate (size: 150 mm×70 mm, thickness: 0.7 mm), and heated for 10 minutes at a temperature of 140° C. in a CONVECTION OVEN. After heating was completed, the sample was cooled at room temperature to measure the diameter of the sample, and the flow rate was calculated according to Equation 1 below.

(4) Flexibility

After preparing a shot specimen (size: 200 mm × 25 mm × 6 mm), preheat the specimen at a temperature of 200° C. for at least 30 minutes, and then coat each powder coating composition on the preheated specimen using a painting gun. , Flexibility (3˚ Bending) was measured using a bending tester.

(5) Insulation breakdown voltage

After preparing a coated specimen (size: 100 mm×100 mm×1.2 mm), oven aging (195° C., 72 hours) was performed, and then left at room temperature for 1 hour, and then cold chocked. ) (1 hour, external: -20°C, internal: 2°C) to check the adhesion of the aging coating film. The degree of insulation breakdown was measured at 220°C for 3 days and then the change (%) of insulation breakdown voltage.

As shown in Tables 3 and 4, the coating film formed of the powder coating composition of Example 1-6 according to the present invention was generally superior to the coating film formed of the powder coating composition of Comparative Example. In particular, the coating film formed of the powder coating composition of Example 1-6 did not deteriorate the insulation performance even when exposed to a high temperature condition for a long time, at the same time exhibited a high glass transition temperature, excellent appearance characteristics, and did not generate cracks. On the other hand, in the case of Comparative Examples 1-11 in which any one of the epoxy resins according to the present invention is not included, the amine-based curing agent according to the present invention is not used, or the mixing ratio of the epoxy resin is outside the scope of the present application, It exhibited poor physical properties in one or more of appearance characteristics, flexibility, and insulation performance.

Claims (7)

Including an epoxy resin including a bisphenol A type epoxy resin, an isocyanate-modified epoxy resin, and a novolak type epoxy resin, and an amine-based curing agent,
The mixing ratio of the bisphenol A type epoxy resin, isocyanate-modified epoxy resin, and novolak type epoxy resin is 1:0.31 to 0.59: 0.52 to 1.45 weight ratio,
The epoxy equivalent of the bisphenol A type epoxy resin is 1,100 to 1,200 g/eq, and the viscosity (based on 200° C. Melting) is 1,800 to 2,800 CPS,
The epoxy equivalent of the isocyanate-modified epoxy resin is 400 to 500 g/eq, and the viscosity (based on 150° C. Melting) is 10,000 to 30,000 CPS,
The novolak-type epoxy resin has an epoxy equivalent of 750 to 850 g/eq, and a viscosity (based on 150° C. Melting) of 20,000 to 50,000 CPS. The powder coating composition according to claim 1, wherein the bisphenol A-type epoxy resin has a softening point of 100 to 120°C. The powder coating composition of claim 1, wherein the novolak-type epoxy resin has a softening point of 100 to 125°C. The powder coating composition according to claim 1, wherein the isocyanate-modified epoxy resin has a softening point of 100 to 125°C. The powder coating composition according to claim 1, wherein the isocyanate-modified epoxy resin has a modification rate of 20 to 30% by weight. The powder coating composition according to claim 1, comprising 30 to 70% by weight of an epoxy resin and 1 to 20% by weight of an amine-based curing agent based on the total weight of the powder coating composition. The powder coating composition according to any one of claims 1 to 6, wherein the average particle diameter is 40 to 80 µm.