CN111566174A - Powder coating composition - Google Patents

Abstract

The present invention relates to a powder coating composition comprising epoxy resin and amine curing agent, wherein the epoxy resin comprises bisphenol A epoxy resin, isocyanate modified epoxy resin and novolac epoxy resin.

Description

Powder coating composition

technical field

The present invention relates to powder coating compositions.

Background technique

Powder coatings are different from liquid coatings in that they are coatings in the form of solid powders that do not contain diluents such as volatile organic solvents. When they are applied to the object to be coated and heated, a curing reaction occurs to form a coating film. Therefore, it has no volatile components and does not emit pollution-causing substances, and it is one of the paints that has attracted much attention as a countermeasure against environmental regulations that are being tightened around the world.

Powder coating using powder coatings has excellent physical properties of the coating film and requires less operator proficiency than solvent-based coatings, and has excellent impact resistance, etc. widely used in the field. In particular, in the coating of electrical and electronic components and busbars for construction, a large amount of powder coating compositions has recently been used.

The Republic of Korea Patent Publication No. 2003-0017873 discloses a powder coating for electrical and electronic parts comprising bisphenol A epoxy resin and rubber-modified epoxy resin, but the powder coating cannot exhibit excellent performance due to low dispersibility. Disadvantages of appearance characteristics. Japanese Laid-Open Patent Publication No. 2008-56838 discloses an epoxy resin powder coating containing epoxy resin, curing agent, inorganic filler and silane coupling agent, but the powder coating has impact resistance under high temperature and humidity environment and the disadvantage of poor adhesion.

SUMMARY OF THE INVENTION

Invention to solve problem

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

solution to the problem

The present invention provides a powder coating composition comprising an epoxy resin and an amine curing agent, wherein the epoxy resin comprises a bisphenol A type epoxy resin, an isocyanate modified epoxy resin and a novolac type epoxy resin.

Invention effect

The powder coating composition of the present invention can form a coating film excellent in heat resistance, durability, and electrical insulating properties under long-term high temperature conditions. In addition, the powder coating composition of the present invention ensures long-term fluidity, improves workability, and is excellent in fluidity and coating film flexibility, so that busbars with many angular (edge) portions can be effectively coated.

Detailed ways

The present invention will be described below. However, the present invention is not limited to the following contents, and each constituent element can be modified into various forms or selectively mixed as required. Therefore, it should be understood that the present invention includes all modifications, equivalents, and substitutes included in the spirit and technical scope of the present invention.

The powder coating composition of the present invention includes an epoxy resin and an amine curing agent. The epoxy resin includes a bisphenol A epoxy resin, an isocyanate modified epoxy resin, and a novolac epoxy resin. Contains pigments, inorganic fillers, curing accelerators and additives commonly used in the field of powder coatings. See the composition of the powder coating composition of the present invention as follows.

epoxy resin

In the powder coating composition of the present invention, the epoxy resin as the main resin includes a bisphenol A epoxy resin, an isocyanate modified epoxy resin, and a novolac epoxy resin. When the isocyanate-modified epoxy resin is used alone or in a high content, there will be differences in physical properties due to changes in the reaction rate (gel time, etc.). On the other hand, when the novolac epoxy resin is used alone or in a high content, fluidity problems and poor mechanical properties will occur. In the present invention, the three types of epoxy resins are mixed as the main resin, thereby ensuring excellent physical properties of the paint.

Bisphenol A epoxy resin is an epoxy resin obtained by 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 weight (EEW) of the bisphenol A epoxy resin is not particularly limited, but may be 900 to 1,300 g/eq, for example, 1,100 to 1,200 g/eq. In addition, the viscosity and softening point of the bisphenol A epoxy resin are not particularly limited, but the viscosity when melted at 200° C. may be 1,800 to 2,800 CPS, for example, 2,000 to 2,600 CPS, and the softening point may be 100 to 100 CPS. 120°C, for example, may be 105 to 115°C. When the physical properties of the bisphenol A epoxy resin are in the aforementioned ranges, the composition has excellent storage stability, and the appearance properties and flexibility of the coating film are improved, so that cracks in the coating film can be minimized.

The isocyanate-modified epoxy resin is a polymer obtained by modifying an epoxy resin with an isocyanate compound, and the epoxy resin contains an oxazolidone ring in the main chain and a glycidyl group at the terminal. This 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 epoxy resin may have a weight average molecular weight of 350 to 400 g/mol and an epoxy equivalent weight of 170 to 200 g/eq.

As the isocyanate compound, for example, monoisocyanate or diisocyanate can be used. As non-limiting examples of such monoisocyanates, there are p-toluenesulfonyl isocyanate, 4-phenoxybenzene isocyanate, 4-cyanobenzene isocyanate, and the like. As non-limiting examples of such diisocyanates, there are methane diisocyanate, butane-1,1-diisocyanate, ethane-1,2-diisocyanate, butane-1,2-diisocyanate, transvinyl 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. These can be used individually or in mixture of 2 or more types. The content of the isocyanate compound may be 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, and the like can be used, but are not limited thereto. These can be used individually or in mixture of 2 or more types. The content of the catalyst may be 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 200 to 600 g/eq, for example, 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 when melted at 150°C may be 10,000 to 30,000 CPS, for example, 15,000 to 25,000 CPS, and the softening point may be 100 to 125 °C, for example, may be 105 to 115 °C. When the physical properties of the isocyanate-modified epoxy resin are within the aforementioned ranges, the appearance properties and corrosion resistance of the coating film can be improved.

As a multifunctional epoxy resin, novolac epoxy resin has more epoxy rings than other types of epoxy resins, so when forming a coating film, it can increase the crosslinking density, thereby improving the durability of the coating film. properties, corrosion resistance and chemical resistance. The novolac epoxy resin is not particularly limited as long as it is a conventional epoxy resin known in the art. As non-limiting examples of novolac epoxy resins that can be used in the present invention, there are phenol novolac epoxy resins, cresol novolac epoxy resins, bisphenol A novolac epoxy resins, bisphenol S novolac epoxy resins Resin, biphenyl novolac epoxy resin, naphthol novolac epoxy resin, etc. As an 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 650 to 950 g/eq, for example, 750 to 850 g/eq. In addition, the viscosity and softening point of the novolac epoxy resin are not particularly limited, but the viscosity when melted at 150°C may be 20,000 to 50,000 CPS, for example, 30,000 to 40,000 CPS, and the softening point may be 100 to 125° C. , for example, may be 110 to 125°C. When the physical properties of the novolak-type epoxy resin are within the aforementioned ranges, workability and mechanical properties of the coating film can be improved.

In the present invention, the mixing ratio of the bisphenol A epoxy resin, the isocyanate modified epoxy resin and the novolac epoxy resin may be 1 to 4:0.5 to 2.5:1 to 4 by weight. When the mixing ratio is within the above-mentioned range, a coating material excellent in reactivity and mechanical properties (impact properties, adhesion, flexibility, etc.) can be secured.

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

Amine curing agent

The powder coating composition of the present invention contains an amine curing agent. Amine curing agents can react with bisphenol A epoxy resin, isocyanate modified epoxy resin and phenolic epoxy resin, thereby improving the curing degree of the coating film. bendability.

The amine-based curing agent is not particularly limited as long as it is an amine-based curing agent that can undergo a curing reaction with bisphenol A epoxy resin, novolac epoxy resin, and isocyanate-modified epoxy resin. For example, there are aliphatic amine-based curing agents, alicyclic amine-based curing agents, aromatic amine-based curing agents, and the like, and these can be used alone or in combination of two or more. As non-limiting examples of amine-based curing agents that can be used, there are 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylmethane, dicyandiamide, and the like. As an example, the amine curing agent may be dicyandiamide.

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

pigment

The powder coating composition of the present invention may optionally include pigments conventionally used in the powder coating field within the range that the inherent properties of the composition are not impaired.

Pigments can be mixed with epoxy resins to render the desired color (pigmented) in powder coatings or to increase the strength or gloss of the coating film. As such pigments, organic pigments, metallic pigments, aluminum pastes, pearls, etc. conventionally used in powder coatings can be used without limitation, and these can be used alone or in combination of two or more. As non-limiting examples of pigments that can be used, there are 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 , phthalocyanine green, carbon black, iron oxide red, iron oxide yellow, navy blue, phthalocyanine blue and mixtures of two or more of them. As an example, the pigment may be carbon black.

In the present invention, the content of the pigment is not particularly limited, for example, based on the total amount of the powder coating composition, it may be 0.1 to 10 wt %, and as another example, 0.1 to 5 wt %. When the content of the pigment is in the aforementioned range, the color development of the coating film to which the powder coating composition of the present invention is applied is excellent, and the hiding properties and mechanical properties of the coating film can be improved.

Inorganic filler

The powder coating composition of the present invention may optionally contain inorganic fillers conventionally used in the field of powder coatings within the range not impairing the inherent properties of the composition.

As non-limiting examples of inorganic fillers that can be used, there are calcium carbonate, feldspar, barium sulfate, silica, aluminum hydroxide, magnesium hydroxide, titanium dioxide, magnesium carbonate, alumina, mica, montmorillonite, silica fume Stone, talc, aluminum nitride, silicon nitride, boron nitride, aluminum oxide, aluminum nitride, barium sulfate, etc., can 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, 1 to 20 μm. In addition, the shape of the inorganic filler may be spherical or amorphous, which is not particularly limited.

In the present invention, the content of the inorganic filler may be 1 to 60 wt %, for example, based on the total amount of the powder coating composition, and may be 1 to 50 wt % as another example. When the content of the inorganic filler is within the aforementioned range, the mechanical properties, impact resistance, adhesion, and the like of the coating film can be improved.

curing accelerator

The powder coating composition of the present invention may optionally contain a curing accelerator commonly used in the powder coating field within the range that the inherent properties of the composition are not impaired.

The curing accelerator is a substance that promotes the reaction between the epoxy resin as the main resin and the curing agent (especially the amine curing agent), such as imidazole curing accelerators, phosphonium curing accelerators, amine curing accelerators, metal curing accelerators. Such as curing accelerators and the like, these can be used alone or in combination of two or more.

As non-limiting examples of the imidazole-based curing accelerator, there are imidazole, 2-methylimidazole, 2-ethylimidazole, 2-decylimidazole, 2-hexylimidazole, 2-isopropylimidazole, 2-decylimidazole Monoalkylimidazole, 2-heptadecylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methyl Imidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2- Undecyl imidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecyl-imidazole trimellitate, 1-cyanoethyl-2-phenylimidazole trimellitate, 2,4-diamino-6-(2'-methylimidazole-(1')-ethyl-s-triazine, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4-benzyl-5-hydroxymethylimidazole, 4,4'-methylene-bis-(2-ethyl -5-methylimidazole), 2-aminoethyl-2-methylimidazole, 1-cyanoethyl-2-phenyl-4,5-bis(cyanoethoxymethyl)imidazole, 1-deca Dialkyl-2-methyl-3-benzyl imidazoline chloride, imidazole-containing polyamide, etc.

As non-limiting examples of the phosphonium-based curing accelerator, there are benzyl triphenyl phosphine chloride, butyl triphenyl phosphine chloride, butyl triphenyl phosphine bromide, ethyl triphenyl phosphine acetate, Ethyltriphenylphosphine bromide, ethyltriphenylphosphine iodide, tetraphenylphosphine bromide, tetraphenylphosphine chloride, tetraphenylphosphine iodide, etc.

As non-limiting examples of the amine curing accelerator, there are triethylamine, triethylenediamine, tetramethyl-1,3-butanediamine, ethylmorpholine, diazabicycloundecene, diazabicycloundecene Azabicyclononene, etc.

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

In the present invention, the content of the curing accelerator can 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 0.1 to 5 wt % based on the total amount of the powder coating composition, and as another example, 0.1 to 3 wt %. When the content of the curing accelerator exceeds the aforementioned range, the mechanical properties of the coating film will be deteriorated.

additive

The powder coating composition of the present invention may optionally contain additives conventionally used in the powder coating field within a range not impairing the inherent properties of the composition.

As non-limiting examples of additives that can be used in the present invention, there are anti-pinhole agents, leveling agents, waxes, low stress agents, dispersants, fluidity enhancers, anti-lockhole agents, coupling agents, gloss modifiers , adhesion improver, flame retardant, matting agent, light absorber, etc., these can be used alone or in combination of two or more.

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

Leveling agents are used for leveling so that the coating composition is applied evenly and smoothly, thereby improving adhesion within the composition and improving the appearance characteristics of the coating film. For example, there are acrylic-based, silicone-based, polyester-based, amine-based leveling agents, and the like, which are not particularly limited.

The anti-pinhole agent can release volatile substances from the coating film during the curing process, thereby preventing the generation of pinholes in the coating film and improving the appearance characteristics. As non-limiting examples of anti-pinhole agents, there are amides [eg ceraflour 960, BYK], polypropylene-based, stearic acid-based anti-pinhole agents, and the like. As an example, the anti-pinhole agent may be benzoin or a mixture of benzoin and an amide anti-pinhole agent.

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

Adhesion Promoter As a substance for improving the adhesion of the coating film, a silane-based adhesion promoter or the like can be used. As non-limiting examples of the adhesion promoter, there are mercaptoalkylakoxysilane, γ-glycidyloxypropyltrimethoxysilane, and the like. As an example, the adhesion promoter may be a mercaptoalkylalkoxysilane having a molecular weight of 150 to 300.

The flow additive is used to maximize the flow effect, can improve the adhesion of the paint, and ensure long-term flow. As the fluidity additive, waxes, silica, or the like can be used. As non-limiting examples of flowability additives that can be used, there are paraffin wax, natural wax (eg, carnauba wax, etc.), synthetic wax (eg, polyethylene wax, etc.), silica, etc., which may be used alone or in combination of two or more use. In addition, waxes may be used in combination with silica. The flow additive can be used as a post-add ingredient added after the tablet is made.

The fluidity enhancer is used to reduce the surface tension of the coating film to achieve a soft appearance, and conventional products known in the art can be used. As non-limiting examples, there are acrylic or silicone-based fluidity enhancers and the like.

Such additives may be appropriately added in a content range known in the art, for example, 0.1 to 20 wt %, and as another example, 0.1 to 10 wt %, based on the total weight of the powder coating composition. When the content of the additive is within the aforementioned range, the appearance and hardness of the coating film can be improved.

In addition to the aforementioned epoxy resin, amine curing agent, pigment, and inorganic filler, the powder coating composition of the present invention may further comprise, based on the total amount of the composition, 0.1 to 2% by weight of an adhesion promoter, 0.4 to 2 wt % flow additive, 0.1 to 3 wt % leveling agent, 0.1 to 3 wt % anti-pinhole agent, and 0.2 to 2 wt % dispersant.

The powder coating composition of the present invention can be prepared according to a method known in the art, and as an example, it can be prepared by processes such as weighing, premixing, melt dispersion, and pulverization.

For example, a raw material mixture containing bisphenol A-type epoxy resin, novolac-type epoxy resin, isocyanate-modified epoxy resin, amine-based curing agent, pigment, inorganic filler, and optionally curing accelerator and additives is put into a container and mixed The mixture is uniformly mixed with a machine, and the mixed composition is melt-mixed and then pulverized to prepare. As an example, the raw material mixture may be melt-dispersed at 70 to 130° C. by means of a melt-kneading device such as a kneader or an extruder to prepare a tablet of a predetermined thickness (for example, 1 to 5 mm). , the prepared tablet is pulverized to a range of 40 to 80 μm using a pulverizing device such as a high-speed mixer, and then sieved to prepare a powder coating composition.

The sieving process is not particularly limited, for example, 40 to 80 mesh can be filtered. Thereby, 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 it satisfies the above-mentioned range, the coating workability and the appearance characteristics of the coating film can be improved.

In order to improve the fluidity of the powder coating material, the surfaces of the powder coating material particles of the present invention may be coated with fine powders 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 is excellent in long-term heat resistance and durability, and can form a coating film excellent in electrical insulating properties under long-term high temperature conditions. In particular, the electrical insulation meets the requirements of the international certification UL 1446 Class F (155°C). Therefore, the powder coating material composition of the present invention can be used for coating electrical and insulating parts.

The present invention will be described in more detail below by way of examples. However, the following examples are only intended to help the understanding of the present invention, and the scope of the present invention is not limited to the examples in any sense.

In the present invention, the epoxy equivalent weight, viscosity, and softening point of the resin are detected by methods known in the industry. For example, the epoxy equivalent weight can be detected by dry method, the viscosity can be detected by a Brookfield viscometer, and the softening point can be detected by a dry method. Detection was performed with a Mettler FP90 and a hot plate.

[Example 1-6]

According to the composition described in Table 1 below, each component was put into a mixing tank and premixed, and then melt-dispersed at 100° C. in a disperser to prepare a chip. The prepared tablets were pulverized with a high-speed mixer to prepare the powder coating compositions of Examples 1-6 with an average particle size of 40 μm. In Table 1 below, the amount of each composition used is in % by weight and is based on the total amount of the composition.

【Table 1】

[Comparative Example 1-11]

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

【Table 2】

1) Epoxy resin 1-1: Bisphenol A type epoxy resin (epoxy equivalent: 1,150 g/eq, viscosity: 2,300 (when melted at 200°C), softening point: 110°C)

2) Epoxy resin 1-2: Bisphenol A type epoxy resin (epoxy equivalent: 950 g/eq, viscosity: 2,000 (when melted at 200°C), softening point: 105°C)

3) Epoxy resin 2-1: Isocyanate-modified epoxy resin (epoxy equivalent: 450 g/eq, viscosity: 20,000 (when melted at 150°C), softening point: 115°C)

4) Epoxy resin 2-2: Isocyanate-modified epoxy resin (epoxy equivalent: 300 g/eq, viscosity: 15,000 (when melted at 150°C), softening point: 105°C)

5) Epoxy resin 3: Phenol novolac epoxy resin (epoxy equivalent: 800 g/eq, viscosity: 35,000 (when melted at 200°C), softening point: 115°C)

6) Curing agent 1: Dicyandiamide

7) Curing agent 2: BTDA (3,3',4,4'-benzophenone tetracarboxylic dianhydride)

8) Curing agent 3: Phenol

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

10) Leveling agent: silicon dioxide

11) Anti-pinhole agent 1: benzoin (2-hydroxy-1,2-diacetophenone)

12) Anti-pinhole agent 2: CERAFLOUR 960 (polyethylene wax)

13) Dispersant: BYK-3955P (BYK)

14) Colored Pigment: Carbon Black MA-100 (Mitsubishi Chemical)

15) Inorganic filler: S-SIL 10J (quartz (SiO2))

16) Adhesion promoter: mercaptoalkylalkoxysilane (Shin-Etsu Chemical)

[Experimental Example – Physical Properties Evaluation]

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

(1) Appearance (leveling)

After preparing an iron coated test piece (size: 100 mm×100 mm×1.0 mm), the prepared test piece was preheated at 230° C. for 30 minutes. Then, after coating each powder coating composition on the preheated test piece using a coating gun, the appearance state of the coating film was visually observed. The judgment grades are divided into ◎: very good, ○: good, △: average, and ×: poor.

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

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

(3) Flow rate

The paint (2±0.05 g) was compressed in a molding die [diameter (Φ): 20 mm] at a pressure of 1,590 kg/cm2 for 30 seconds to prepare a refined sample [diameter (Φ): 20 mm], and then the refined sample [diameter (Φ): 20 mm] was prepared. The material was placed horizontally on a steel plate (size: 150 mm×70 mm, thickness: 0.7 mm), and heated in a convection oven at a temperature of 140° C. for 10 minutes. After the heating was completed, the sample was cooled at normal temperature, the diameter of the sample was detected, and the flow rate was calculated according to the following formula 1.

[Mathematical formula 1]

(4) Bendability

After preparing a short test piece (size: 200mm×25mm×6mm), preheat the test piece at a temperature of 200°C for more than 30 minutes, and then use a coating gun to coat each powder coating composition on the preheated test piece. Then, the bendability (3° bending) was detected with a bending tester (Bending Tester).

(5) Dielectric breakdown voltage

After preparing the coating test piece (size: 100mm×100mm×1.2mm), after going through the oven aging (195°C, 72 hours) process, it was left at room temperature for 1 hour, and then subjected to low temperature impact (Cold chock) ( For 1 hour, external use: -20°C, internal use: 2°C), the adhesion of the aging coating film was observed. The degree of dielectric breakdown was measured as a change (%) in dielectric breakdown voltage after standing at 220°C for 3 days.

【table 3】

【Table 4】

As shown in Tables 3 and 4, the coating films formed from the powder coating compositions of Examples 1 to 6 of the present invention had overall better physical properties than the coating films formed from the powder coating compositions of Comparative Examples. . The coating films formed from the powder coating compositions of Examples 1-6, especially when exposed to high temperature conditions for a long time, have no deterioration in insulating properties, and at the same time, exhibit high glass transition temperatures, excellent appearance characteristics, and no Cracks are generated. In contrast, Comparative Examples 1 to 11 in which any epoxy resin of the present invention was not contained, or the amine curing agent of the present invention was not used, or the mixing ratio of the epoxy resin was outside the scope of the present application. , more than one of the appearance characteristics, flexibility, and insulation properties show poor physical properties.

【Industrial Applicability】

The powder coating composition of the present invention can form a coating film excellent in heat resistance, durability, and electrical insulating properties under long-term high temperature conditions. In addition, the powder coating composition of the present invention ensures long-term fluidity, improves workability, and is excellent in fluidity and coating film flexibility, so that busbars with many angular (edge) portions can be effectively coated.

Claims (8)

1. A powder coating composition comprises epoxy resin and an amine curing agent, wherein the epoxy resin comprises bisphenol A epoxy resin, isocyanate modified epoxy resin and phenolic aldehyde epoxy resin.

2. The powder coating composition according to claim 1,

the mixing ratio of the bisphenol A epoxy resin, the isocyanate modified epoxy resin and the phenolic epoxy resin is 1-4: 0.5 to 2.5: 1 to 4 by weight.

3. The powder coating composition according to claim 1,

the bisphenol A type epoxy resin has an epoxy equivalent of 900 to 1,300g/eq, a viscosity when melted at 200 ℃ of 1,800 to 2,800CPS, and a softening point of 100 to 120 ℃.

4. The powder coating composition according to claim 1,

the novolac epoxy resin has an epoxy equivalent of 650 to 950g/eq, a viscosity of 20,000 to 50,000CPS when melted at 150 ℃, and a softening point of 100 to 125 ℃.

5. The powder coating composition according to claim 1,

the isocyanate-modified epoxy resin has an epoxy equivalent of 200 to 600g/eq, a viscosity when molten at 150 ℃ of 10,000 to 30,000CPS, and a softening point of 100 to 125 ℃.

6. The powder coating composition according to claim 1,

the isocyanate-modified epoxy resin has a modification ratio of 20 to 30% by weight.

7. The powder coating composition according to claim 1,

the powder coating composition comprises 30 to 70 weight percent of epoxy resin and 1 to 20 weight percent of amine curing agent based on the total weight of the powder coating composition.

8. The powder coating composition according to any one of claims 1 to 7,

the average particle diameter is 40 to 80 μm.