KR20190097602A - Powder coating composition - Google Patents

Abstract

The present invention relates to a powder paint composition, which comprises: an epoxy resin including a bisphenol A type epoxy resin, an isocyanate modified epoxy resin, and a novolac type epoxy resin; and an amine-based curing agent. The powder paint composition is excellent in durability, heat resistance, and electrical insulating properties.

Description

Powder coating composition {POWDER COATING COMPOSITION}

The present invention relates to a powder coating composition.

Powder coatings, unlike liquid coatings, do not contain diluents such as volatile organic solvents, and are paints in the form of a solid powder. Therefore, it does not emit pollutants due to the absence of volatile components, and is one of the paints that is in the limelight as a countermeasure against environmental regulations that are being strengthened around the world.

Powder coating using the powder coating is excellent in physical properties of the coating film and does not require much skill of the operator compared to the solvent type paint, and excellent in impact resistance, and is widely used in various fields such as construction, home appliances, automobile industry, and the like. In particular, powder coating compositions have recently been used for the coating of electrical and electronic parts and architectural busbars.

Korean Patent Laid-Open Publication No. 2003-0017873 discloses a powder coating material for an electric and electronic component 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 its low dispersibility. have. Japanese Patent 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 in that impact and adhesion are inferior 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 comprising an bisphenol A type epoxy resin, an isocyanate modified epoxy resin and a novolak type epoxy resin and an amine curing agent.

The powder coating composition of this invention can form the coating film excellent in heat resistance, durability, and electrical insulation under long-term high temperature conditions. In addition, since the powder coating composition of the present invention ensures long-term fluidity, improves workability, and is excellent in flowability and flexibility of the coating film, it is possible to effectively paint a busbar having many angled edges.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated. However, the present invention is not limited only to the following contents, and each component may be variously modified or optionally mixed as necessary. Therefore, it is to be understood that all changes, equivalents, and substitutes included in the spirit and scope of the present invention are included.

The powder coating composition according to the present invention comprises an epoxy resin and an amine curing agent including a bisphenol A type epoxy resin, an isocyanate modified epoxy resin and a novolak type epoxy resin, and, if necessary, pigments, inorganic fillers, curing accelerators and powders. It may further include an additive commonly used in the paint field. Hereinafter, looking at the composition of the powder coating composition of the present invention.

(a) epoxy resin

In the powder coating composition according to the present invention, the epoxy resin includes, as main resins, a bisphenol A type epoxy resin, an isocyanate modified epoxy resin and a novolac type epoxy resin. When isocyanate-modified epoxy resins are used alone or in high amounts, physical property differences may occur due to changes in reaction rates (Gel time, etc.). On the other hand, when the novolak-type epoxy resin is used alone or used in a high content, flow problems and mechanical properties can be reduced. In the present invention, the three kinds of epoxy resins are mixed and used as main resins to secure excellent paint properties.

Bisphenol A type epoxy resin is an epoxy resin obtained from the reaction of bisphenol A (BPA) and epichlorohydrin. The bisphenol A 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 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 epoxy resin is not particularly limited, the viscosity (based on 200 ℃ Melting) may be 1,800 to 2,800 CPS, for example 2,000 to 2,600 CPS, softening point is about 100 to 120 ℃, For example, it may be 105 to 115 ℃. When the physical properties of the bisphenol A-type epoxy resin is in the above-described range, the storage stability of the composition is excellent, and the appearance property and the bendability of the coating film may be improved to minimize cracking of 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 its terminal. Such isocyanate-modified epoxy resin can be prepared by reacting an epoxy resin with an isocyanate compound in the presence of a catalyst. 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, the epoxy equivalent may be about 170 to 200 g / eq.

As said isocyanate compound, monoisocyanate or diisocyanate can be used, for example. Non-limiting examples of such monoisocyanates include p-toluenesulfonyl isocyanate, 4-phenoxyphenyl isocyanate, 4-cyanophenyl isocyanate and the like. 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, etc. are mentioned. These may be used alone or in combination of two or more thereof. 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.

Examples of the catalyst may include bases, amines, hydrogen compounds, imidazoles, phosphonium salts and derivatives thereof, but are not limited thereto. These may be used alone or in combination of two or more thereof. 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 is not particularly limited, but the viscosity (150 ℃ Melting basis) may be 10,000 to 30,000 CPS, for example 15,000 to 25,000 CPS, softening point is 100 to 125 ℃, for example For example, it may be 105 to 115 ℃. When the physical properties of the isocyanate-modified epoxy resin are in the above-described range, the appearance characteristics and the corrosion resistance of the coating film may be improved.

The novolak type epoxy resin is a polyfunctional epoxy resin, which has more epoxide rings compared to other types of epoxy resins, thereby increasing the crosslinking density when forming the coating film, thereby improving the durability, corrosion resistance, and chemical resistance of the coating film. have. The novolac 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 novolak-type epoxy resin that can be used in the present invention include phenol novolak-type epoxy resin, cresol novolak-type epoxy resin, bisphenol A novolak-type epoxy resin, bisphenol S novolak-type epoxy resin, biphenyl furnace And a naphthol novolac epoxy resin. In one example, the novolac epoxy resin is a phenol novolac epoxy resin.

The epoxy equivalent of the novolac 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 is not particularly limited, the viscosity (150 ℃ Melting basis) may be 20,000 to 50,000 CPS, for example 30,000 to 40,000 CPS, softening point is 100 to 125 ℃, For example, it may be 110 to 125 ℃. When the physical properties of the novolac-type epoxy resin is in 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 in the above-described range, it is possible to secure the physical properties of the paint excellent in reactivity, mechanical properties (impact, adhesion and flexibility).

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, and in another example, about 40 to 60% by weight based on the total amount of the powder coating composition. When the content of the epoxy resin is in the above range, the mechanical properties and workability of the coating film can be improved.

(b) amine curing agent

The powder coating composition of the present invention contains an amine curing agent. An amine curing agent can harden and react with bisphenol-A epoxy resin, an isocyanate modified epoxy resin, and a novolak-type epoxy resin, and can improve the hardening degree of a coating film, and can improve the flexibility of a coating film compared with other hardening agents.

The amine curing agent is not particularly limited as long as it is an amine 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 curing agent, an alicyclic amine curing agent, an aromatic amine curing agent, and the like, which may be used alone or in combination of two or more thereof. 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. In one example, the amine-based curing agent may be dicyane diamide.

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

(c) pigments

The powder coating composition of the present invention may optionally further include pigments commonly used in the field of powder coating, within the scope of not impairing the inherent properties of the composition.

Pigments may be used in admixture with epoxy resins to express the desired color (colour) in the powder coating or to increase the strength or gloss of the coating. As such pigments, organic pigments, metallic pigments, aluminum-pastes, pearls, 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 thereof. Non-limiting examples of pigments that can be used include azo, phthalocyanine, iron oxide, cobalt, silicate, chromate pigments, and the like, for example, 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. In one example, the pigment may be carbon black.

In the present invention, the content of the pigment is not particularly limited, and for example, may be about 0.1 to 10% by weight, in another 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 in 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) weapon filler

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

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

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, but is not particularly limited thereto.

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

(e) Curing accelerator

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

The curing accelerator is a substance that promotes a reaction between an epoxy resin, which is a main resin, and a curing agent (particularly, an amine curing agent), such as an imidazole curing accelerator, a phosphonium curing accelerator, an amine curing accelerator, or a metallic curing accelerator. Etc., but these may be used alone or in combination of two or more thereof.

Non-limiting examples of the imidazole-based curing accelerators include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-decylimidazole, 2-heptimidazole, and 2-isopropyl. Midazole, 2-undecyl imidazole, 2-heptanedyl 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 tree Mellitate, 2,4-diamino-6- (2'-methylimidazole- (1 ')-ethyl-s-triazine, 2-pesy-4,5-dihydroxymethylimidazole, 2 -Pesyl-4-methyl-5-hydroxymethylimidazole, 2-pesy-4-benzyl-5-hydroxymethylimidazole, 4,4'-methylene-bis- (2-ethyl-5-methyl Imidazole), 2- Minoethyl-2-methyl imidazole, 1-cyanoethyl-2-phenyl-4,5-di (cyanoethoxy methyl) imidazole, 1-dodecyl-2-methyl-3-benzylimidazolinium Chlorides, imidazole-containing polyamides, and the like.

Non-limiting examples of the phosphonium-based curing accelerators 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 and the like.

Non-limiting examples of the amine curing accelerator include triethylamine, triethylenediamine, tetramethyl-1,3-butanediamine, ethyl morpholine, diazabicyclo undecene, diazabicyclononene and the like.

Examples of the metal curing accelerator include organometallic complexes or organometallic 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 and 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, organic manganese complexes such as manganese (II) acetylacetonate, and the like. It is not limited. Examples of the organometallic salt include zinc octylate, tin octylate, zinc naphthenate, cobalt naphthenate, tin stearate, zinc stearate, and the like, but are not limited thereto.

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 amount of the curing accelerator may be about 0.1 to 5% by weight, and in another example, about 0.1 to 3% by weight based on the total amount of the powder coating composition. If the content of the curing accelerator is out of the above range, the mechanical properties of the coating film may be lowered.

(f) additives

The powder coating composition of the present invention may optionally further include additives which are commonly used in the field of powder coating, within the scope of not impairing the inherent properties of the composition.

Non-limiting examples of the additives usable in the present invention include, but are not limited to, pinhole inhibitors, leveling agents, waxes, low stress agents, dispersants, flow improvers, anti-crattering agents, coupling agents, gloss regulators, adhesion improvers, flame retardants, matting agents, There are light absorbing agents and the like, which may be used alone or in combination of two or more thereof.

The powder coating composition of the present invention may further include one or more selected from the group consisting of leveling agents, pinhole inhibitors, dispersants, adhesion promoters, flow additives, and flow enhancers.

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

The pinhole inhibitor may allow volatiles to be released from the coating during the curing process, thereby preventing the occurrence of pinholes in the coating and improving appearance characteristics. Non-limiting examples of pinhole inhibitors include amides (eg, ceraflour 960 (BYK)), polypropylenes, stearic acid-based pinholes, and the like. In one example, the pinhole inhibitor may be benzoin or a mixture of benzoin and an amide-based pinhole inhibitor.

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

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

The fluid additive is used to maximize the fluidity effect, it is possible to secure long-term fluidity with the adhesion of the paint. Waxes, silica, and the like may be used as the fluid additive. Non-limiting examples of flowable additives that can be used include paraffin wax, natural wax (e.g. carnauba wax, etc.), synthetic waxes (e.g., polyethylene wax, etc.), silica, etc., which are used alone or in combination of two or more. Can be used. Waxes can also be used in admixture with silica. The flowable additive may be used as a post-addition component added after making chips.

Flow improver is used to lower the surface tension of the coating film and to implement a flexible appearance, it can be used a conventional one known in the art. Non-limiting examples include acrylic or silicone flow improvers.

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

The powder coating composition of the present invention, in addition to the above-described epoxy resins, amine-based curing agents, pigments, inorganic fillers, based on the total amount of the composition, about 0.1 to 2% by weight of adhesion promoter, about 0.4 to 2% by weight of flow additive, 0.1 To about 3% by weight leveling agent, about 0.1 to 3% by weight pinhole inhibitor and about 0.2 to 2% by weight dispersant.

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

For example, a bisphenol A type epoxy resin, a novolak type epoxy resin, an isocyanate-modified epoxy resin, an amine curing agent, a pigment, an inorganic filler, and optionally a raw material mixture containing a curing accelerator and an additive are added to a container mixer and mixed uniformly. And it may be prepared by melting and mixing the mixed composition and then grinding it. For example, the raw material mixture is melt-dispersed at 70 to 130 ° C. by a melt kneading apparatus such as a kneader or an extruder to prepare chips having a predetermined thickness (eg, 1 to 5 mm). Thereafter, the prepared chip may be pulverized in a range of 40 to 80 μm using a grinder 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, for example, from 40 to 80 mesh. Accordingly, it is possible to obtain a powder coating material having an average particle size in the range of 40 to 80 μm. The average particle diameter of the powder is not particularly limited, but when the aforementioned range is satisfied, coating workability and appearance characteristics of the coating film may be enhanced.

In order to improve the fluidity of the powder coating, a fine powder such as silica may be used to coat the surface of the powder coating particles according to the present invention. As a method of performing such treatment, a pulverized mixing method of mixing while adding a fine powder at the time of pulverization, or a dry mixing method using a Henschel mixer or the like can be used.

The powder coating composition of this invention is excellent in long-term heat resistance and durability, and can form the coating film excellent in electrical insulation under long-term high temperature conditions. In particular, it satisfies the internationally recognized UL 1446 Class F class (155 ° C) with regard to electrical insulation. Therefore, the powder coating composition of the present invention can be applied to paint electrical and insulating parts.

Hereinafter, the present invention will be described in more detail with reference to 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  1-6]

According to the composition shown in Table 1, each component was put in a mixing tank, premixed, and then melt-dispersed at 100 ° C. in a disperser to prepare chips. The prepared chip was ground in 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, the amount of each composition used is in weight percent 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 epoxy resin (Epoxy equivalent: 1,150 g / eq, Viscosity: 2,300 (based on 200 ° C Melting), Softening point: 110 ° C)

2) Epoxy Resin 2: Isocyanate Modified Epoxy Resin (Epoxy Equivalent: 450 g / eq, Viscosity: 20,000 (based on 150 ° C Melting), Softening Point: 115 ° C)

3) Epoxy Resin 3: Phenol Novolac Epoxy Resin (Epoxy Equivalent: 800 g / eq, Viscosity: 35,000 (based on 200 ° C Melting), Softening Point: 115 ° C)

4) Epoxy Resin 4: Bisphenol A 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 (based on 150 ° C Melting), Softening Point: 105 ° C)

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

7) Hardener 2: dicyandiamide

8) Curing Agent 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 Corporation)

14) Color Pigment: CARBON BLACK MA-100 (MITUSBISHI CHEM)

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

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

[ Experimental Example  -Property evaluation]

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

(1) Appearance (leveling)

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

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

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

(3) Flow rate

The paint (2 ± 0.05 g) was compressed in a molding mold (diameter: 20 mm) at a pressure of 1,590 kg / cm 2 for 30 seconds to form a purified sample (diameter: 20 mm), and then the purified sample was The plate was placed horizontally on a steel sheet (size: 150 mm x 70 mm, thickness: 0.7 mm), and heated at a temperature of 140 ° C. for 10 minutes in a convection oven. After completion of heating, the sample was cooled at room temperature to measure the diameter of the sample, and the flow rate was calculated according to the following Equation 1.

(4) flexibility

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

(5) Breakdown voltage

After preparing the coated specimen (size: 100 mm × 100 mm × 1.2 mm), it is subjected to oven aging (195 ° C., 72 hours), left at room temperature for 1 hour, and then cold chock. ) (For 1 hour, external use: -20 ° C, internal use: 2 ° C) to confirm the adhesion of the aged coating. The degree of dielectric breakdown was measured for 3 days after the breakdown at 220 ° C.

As shown in Table 3 and Table 4, the coating film formed of the powder coating composition of Examples 1-6 according to the present invention had excellent physical properties as compared with 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 degrade the insulation performance even after long-term exposure under high temperature conditions, at the same time showed a high glass transition temperature, excellent appearance characteristics, and cracks did not occur. On the other hand, in the case of Comparative Examples 1-11 in which any one kind of epoxy resin 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. Inferior physical properties were exhibited in one or more of the appearance characteristics, flexibility and insulation performance.

Claims (8)

Powder coating composition containing an epoxy resin containing an bisphenol-A epoxy resin, an isocyanate modified epoxy resin, and a novolak-type epoxy resin, and an amine curing agent. The powder coating composition of claim 1, wherein a mixing ratio of the bisphenol A epoxy resin, the isocyanate-modified epoxy resin, and the novolak-type epoxy resin is 1 to 4: 0.5 to 2.5: 1 to 4 weight ratio. The powder coating composition of claim 1, wherein the epoxy equivalent of the bisphenol A epoxy resin is 900 to 1,300 g / eq, the viscosity (based on 200 ° C Melting) is 1,800 to 2,800 CPS, and the softening point is 100 to 120 ° C. The powder coating composition of claim 1, wherein the epoxy equivalent of the novolac epoxy resin is 650 to 950 g / eq, the viscosity (150 ° C Melting basis) is 20,000 to 50,000 CPS, and the softening point is 100 to 125 ° C. The powder coating composition of claim 1, wherein an epoxy equivalent of the isocyanate-modified epoxy resin is 200 to 600 g / eq, a viscosity (based on 150 ° C Melting) is 10,000 to 30,000 CPS, and a softening point is 100 to 125 ° C. The powder coating composition of claim 1, wherein the isocyanate-modified epoxy resin has a modification rate of 20 to 30% by weight. The powder coating composition of claim 1, comprising 30 to 70% by weight of epoxy resin and 1 to 20% by weight of an amine curing agent based on the total weight of the powder coating composition. The powder coating composition according to any one of claims 1 to 7, wherein the average particle diameter is 40 to 80 µm.