KR102175053B1 - Powder coating composition - Google Patents

Abstract

The present invention relates to a powder coating composition comprising a fluorine-containing epoxy resin, a rubber-modified epoxy resin, and a curing agent.

Description

Powder coating composition {Powder coating composition}

The present invention relates to an epoxy resin powder coating composition with improved heat resistance, chemical resistance and mechanical properties.

Epoxy resin paints have been used as coating paints to prevent corrosion of steel pipes or pipelines buried underground or in the sea floor, and to secure heat resistance and durability. However, due to the gradual depletion of oil fields and technology development in recent years, crude oil drilling and transportation under severe environmental conditions are being actively carried out, and improvement of the thermal, chemical, and physical properties of the epoxy coating film to protect the pipe from corrosion under harsher environments Is required. In particular, the fluid is heated to a high temperature of 120° C. or higher for smooth transfer of crude oil, and there is an increasing demand for a paint that satisfies sufficient heat resistance and chemical resistance in such a high temperature environment.

U.S. Patent No. 9,315,664 discloses a composition related to a coating composition implementing a high glass transition temperature using a cycloaliphatic epoxy resin and a cycloaliphatic anhydride curing agent. However, the paint has a problem in that mechanical properties such as flexibility and storage are not sufficient.

The present invention provides a powder coating composition excellent in heat resistance, chemical resistance and mechanical properties.

The present invention provides a powder coating composition comprising a fluorine-containing epoxy resin, a rubber-modified epoxy resin, and a curing agent.

The present invention provides a powder coating composition excellent in heat resistance, chemical resistance and mechanical properties. In particular, the present invention provides a powder coating composition for coating inside a steel pipe having a high glass transition temperature and excellent in high temperature/high pressure heat resistance and transport efficiency, which can be used for high temperature gas and fluid transport.

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 is to be understood as including 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 a fluorine-containing epoxy resin, a rubber-modified epoxy resin, and a curing agent. The powder coating composition of the present invention may further include additives commonly used in the field of pigments, extenders, catalysts, and powder coatings, if necessary. Hereinafter, looking at the composition of the powder coating composition of the present invention is as follows.

Fluorine-containing epoxy resin

The powder coating composition according to the present invention includes a fluorine-containing epoxy resin. By including the fluorine-containing epoxy resin as the main resin, a high glass transition temperature and excellent heat resistance of the paint can be secured.

The epoxy resin is not particularly limited as long as it is a conventional epoxy resin known in the art. Non-limiting examples of usable epoxy resins include bisphenol A type epoxy resin, cresol novolak type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, naphthalene type epoxy resin, anthracene epoxy resin, biphenyl type epoxy resin, Tetramethyl biphenyl-type epoxy resin, phenol novolac-type epoxy resin, bisphenol A novolac-type epoxy resin, bisphenol S novolac-type epoxy resin, biphenyl novolac-type epoxy resin, naphthol novolac-type epoxy resin, naphthol phenol co-condensation furnace Rock type epoxy resin, naphthol cresol co-condensed novolak type epoxy resin, aromatic hydrocarbon formaldehyde resin modified phenol resin type epoxy resin, triphenyl methane type epoxy resin, tetraphenyl ethane type epoxy resin, dicyclopentadiene type epoxy resin, dicyclo At least one of a pentadiene phenol addition reaction type epoxy resin, a phenol aralkyl type epoxy resin, a polyfunctional phenolic epoxy resin, and a naphthol aralkyl type epoxy resin may be mentioned, but is not limited thereto.

The fluorine-containing compound contained in the fluorine-containing epoxy resin is not particularly limited as long as it can generate fluorine ions in the solution. For example, the fluorine-containing compound is ammonium fluoride (NH ₄ F), sodium fluoride (NaF), potassium fluoride (KF), ammonium bifluoride (NH ₄ F·HF). ), sodium bifluoride (NaF·HF), and potassium bifluoride (KF·HF).

The epoxy equivalent (EEW) of the fluorine-containing epoxy resin is not particularly limited, but may be about 200 to 1,000 g/eq, for example, about 200 to 600 g/eq, and the viscosity is about 1,000 to 5,000 mPa·s (180 ℃ melting basis). The viscosity of the fluorine-containing epoxy resin can be measured using a Cone & Plate viscometer. When the epoxy equivalent and viscosity of the fluorine-containing epoxy resin are less than the above range, there is a problem that dispersibility and mechanical properties are deteriorated, and when it exceeds the above range, the wettability of the paint may be poor.

The fluorine content of the fluorine-containing epoxy resin is not particularly limited, but may be about 10 to 10,000 ppm. When the fluorine content of the fluorine-containing epoxy resin is out of the above range, the heat resistance of the coating film may be poor.

The fluorine-containing epoxy resin may be used in an amount of about 40 to 70% by weight, for example, about 40 to 60% by weight based on the total amount of the powder coating composition. When the content of the fluorine-containing epoxy resin is less than 40% by weight, sufficient heat resistance may not be secured due to a decrease in the glass transition temperature of the coating film, and when the content is more than 70% by weight, mechanical properties may be poor.

When the fluorine-containing epoxy resin is used in the above-described physical property range and content range, heat resistance is secured, and storage stability, appearance characteristics, and flexibility of the coating film may be improved.

Rubber modified epoxy resin

The powder coating composition according to the present invention includes a rubber-modified epoxy resin.

The rubber-modified epoxy resin is a synthesis of an epoxy resin and a rubber-modified polymer. For example, a resin synthesized by mixing an epoxy resin and a rubber-modified polymer in a weight ratio of 95:5 to 40:60 may be used. By using the rubber-modified epoxy resin as the main resin, the mechanical properties of the powder coating composition can be improved.

The epoxy resin is not particularly limited as long as it is a conventional epoxy resin known in the art. For example, a bisphenol A type epoxy resin or a bisphenol F type epoxy resin can be used. 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.

The rubber-modified polymer may be a butadiene polymer or a butadiene-acrylonitrile copolymer, and the butadiene polymer or butadiene-acrylonitrile may have a terminal functional group. For example, carboxyl-terminated butadiene acrylonitrile (CTBN: Carboxyl Terminated Butadiene Acrylonitrile), amine-terminated butadiene acrylonitrile (ATBN: Amine Terminated Butadiene Acrylonitrile), in addition to methacrylate, may be a rubber modified polymer having epoxy functional groups. have. At this time, the rubber-modified polymer may contain about 20 to 40% by weight of a rubber raw material.

The rubber-modified polymer may be, for example, carboxyl-terminated butadiene acrylonitrile (CTBN) or amine-terminated butadiene acrylonitrile (ATBN: Amine Terminated Butadiene Acrylonitrile), and is represented by the following Formula 1 or Formula 2. I can.

[Formula 1]

[Formula 2]

In the case of the rubber-modified epoxy resin, it not only maintains excellent mechanical properties (adhesion strength, oxidation stability, chemical stability, etc.) of the epoxy resin itself, but also has excellent elasticity after performing the curing step by being modified with an epoxy resin having rubber properties. In addition, it can exhibit more flexible physical properties at low temperatures.

The epoxy equivalent of the rubber-modified epoxy resin is not particularly limited, but may be about 800 to 1,500 g/eq, for example, about 925 to 1,375 g/eq. When the epoxy equivalent of the rubber-modified epoxy resin is less than 800 g/eq, mechanical properties may be deteriorated, and when the epoxy equivalent is more than 1,500 g/eq, dispersibility and wettability may decrease.

The softening point of the rubber-modified epoxy resin may be about 50 to 100°C, for example about 60 to 90°C. When the softening point of the rubber-modified epoxy resin is less than 50°C, storage may be poor, and when the softening point is more than 100°C, dispersibility may be poor.

The rubber-modified epoxy resin may be used in an amount of about 15 to 40% by weight, for example, about 20 to 35% by weight based on the total amount of the powder coating composition. When the content of the rubber-modified epoxy resin is less than 15% by weight, there is a problem of deterioration of mechanical properties, and when the content is more than 40% by weight, the glass transition temperature and wettability of the coating film may be lowered.

When the rubber-modified epoxy resin is used in the above-described physical property range and content range, it is possible to effectively improve the abrasion resistance and flexibility of the paint.

Hardener

The powder coating composition of the present invention contains at least one of an amine-based curing agent and a phenolic curing agent as a curing agent.

The amine-based curing agent can react with the epoxy resin to improve the degree of curing of the coating film, 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 fluorine-containing epoxy resin rubber-modified epoxy resin. For example, there are an aliphatic amine-based curing agent, an alicyclic amine-based curing agent, and an aromatic amine-based curing agent, and these may be used alone or in combination of two or more. The amine value of the amine-based curing agent is not particularly limited, and may be, for example, 15 to 30 mgKOH/g.

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. For example, the amine-based curing agent may be dicyandiamide.

As the phenolic curing agent, those commonly used in the powder coating field may be used without limitation. For example, the phenolic curing agent may be a polyfunctional phenolic resin having two or more functional groups. Since the polyfunctional phenolic resin has high heat resistance and a high concentration of hydrophobic groups in a molecule, it has the advantage of exhibiting low hygroscopicity, and thus has excellent solder crack resistance. The hydroxyl group equivalent of the phenolic curing agent is not particularly limited, and may be, for example, 200 to 300 g/eq.

Non-limiting examples of the phenolic curing agent that can be used include resol-type phenolic resins, novolac-type phenolic resins, and polyhydroxystyrene resins. Examples of the resol-type phenolic resin include aniline-modified resol resin and melamine-modified resol resin. Examples of the novolak-type phenolic resin include phenol novolac resin, cresol novolac resin, tert-butylphenol novolac resin, nonylphenol novolac resin, naphthol novolac resin, dicyclopentadiene-modified phenol resin, terpene-modified phenol. Type resin, triphenol-methane type resin, naphthol aralkyl resin, and the like. Examples of the polyhydroxystyrene resin include poly(p-hydroxystyrene).

In the present invention, the content of the curing agent is not particularly limited, and may be, for example, about 0.1 to 20% by weight, for example about 0.5 to 10% by weight, based on the total amount of the powder coating composition. When the content of the curing agent is within the above-described range, the degree of curing of the coating film is increased, and thus physical properties of the coating film may be improved.

Extender pigment

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

Non-limiting examples of extender pigments that can be used include calcium carbonate, feldspar, barium sulfate, silica, alumina hydroxide, magnesium hydroxide, titanium dioxide, magnesium carbonate, alumina, mica, montmorolonite, olastonite, talc, aluminum nitride, There are silicon nitride, boron nitride, aluminum oxide, barium sulfate, and the like, and these may be used alone or in combination of two or more. For example, the extender pigment may be barium sulfate.

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

In the present invention, the content of the extender pigment may be, for example, about 5 to 30% by weight based on the total amount of the powder coating composition, and in another example, about 5 to 15% by weight. When the content of the extender pigment is in the above-described range, mechanical properties, impact resistance, and adhesion of the coating film may be improved.

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 inherent 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, inorganic pigments, metallic pigments, aluminum-paste, pearl, etc., which are commonly used in powder coatings, can be used without limitation, and these may be used alone or in combination of two or more. I can. Non-limiting examples of pigments that can be used include azo-based, phthalocyanine-based, iron oxide-based, cobalt-based, carbonate-based, sulfate-based, silicate-based, chromate-based pigments, and the like, such as titanium dioxide, zinc oxide, bismuth vanadate. , Cyanine green, carbon black, iron oxide, sulfur iron oxide, navy blue, cyanine blue, and mixtures of two or more thereof. As an example, the pigment may be an iron oxide pigment.

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, and in another example, about 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.

catalyst

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

The catalyst is a material that accelerates the reaction between the epoxy resin and the curing agent, which is the main resin, and includes, for example, an imidazole catalyst, a phosphonium catalyst, an amine catalyst, and a metal catalyst. Can be used by mixing.

Non-limiting examples of the imidazole-based catalyst include imidazole, 2-methyl imidazole, 2-ethyl imidazole, 2-decyl imidazole, 2-hectyl imidazole, 2-isopropyl imidazole, 2-undee Silimidazole, 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-methyl imidazole, 1-cyanoethyl-2-ethyl-4-methyl imidazole, 1-cyanoethyl-2-undecyl imidazole, 1 -Cyanoethyl-2-phenyl imidazole, 1-cyanoethyl-2-undecyl imidazole trimellitate, 1-cyanoethyl-2-phenyl imidazole trimellitate, 2,4-diamino-6 -(2'-methyl imidazole-1')-ethyl-s-triazine, 2-fesyl-4,5-dihydroxymethyl imidazole, 2-fesyl-4-methyl-5-hydroxymethyl imidazole , 2-fesyl-4-benzyl-5-hydroxymethyl imidazole, 4,4'-methylene-bis-(2-ethyl-5-methyl imidazole), 2-aminoethyl-2-methyl imidazole, 1 -Cyanoethyl-2-phenyl-4,5-di(cyanoethoxymethyl)imidazole, 1-dodecyl-2-methyl-3-benzylimidazolinium chloride, imidazole-containing polyamide, etc. .

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

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

Examples of the metal catalyst may 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, etc. 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 organic metal 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 catalyst may be appropriately adjusted according to the reactivity of the main resin and the curing agent. For example, the content of the catalyst may be about 0.01 to 1% by weight, in another example about 0.1 to 1% by weight, based on the total amount of the powder coating composition. When the content of the catalyst is out of the above-described range, mechanical properties of the coating film may be deteriorated.

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 harm the intrinsic properties of the composition.

Non-limiting examples of additives that can be used in the present invention include leveling agents, pinhole inhibitors, dispersants, adhesion promoters, flow additives, flow improvers, low stress agents, cratering inhibitors, coupling agents, gloss modifiers, flame retardants, matting agents. , Light absorbers, etc., which may be used alone or in combination of two or more.

The leveling agent is intended to improve the appearance characteristics of the coating film while improving adhesion in the composition by leveling the coating composition to be coated smoothly and smoothly. For example, there are acrylic, silicone, polyester, and amine leveling agents, but are 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 substance 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 is a mercaptoalkylalkoxysilane having a molecular weight of 150 to 300 g/mol. Can be

The fluid additive is used to maximize the fluidity effect, and can secure long-term fluidity 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 enhancers.

Such additives may be appropriately added within the content range known in the art, and may be, for example, about 0.1 to 10% by weight, for example, about 0.1 to 1.0% 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.

The powder coating composition according to the present invention may be prepared by a method known in the art, and for example, it may be prepared through processes such as raw material quantification, dry premixing, dispersion and coarse pulverization, pulverization and classification. For example, a mixture of raw materials containing a fluorine-containing epoxy resin and a rubber-modified epoxy resin and optionally a curing agent, extender pigment, pigment, catalyst, and other additives is added to a container mixer and uniformly mixed, and the mixed composition is melted. After mixing it can be prepared by grinding it. For example, the raw material mixture is melt-dispersed at 70 to 130°C by a melt-kneading device such as a kneader or an extruder to prepare chips with a predetermined thickness (eg, 1 to 5 mm). Thereafter, the prepared chips are pulverized in the range of 40 to 80 μm using a pulverizing device such as a high-speed mixer, and then classified to prepare a powder coating composition.

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

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

The powder coating composition of the present invention realizes a high glass transition temperature, and can form a coating film exhibiting excellent heat resistance and chemical resistance even in a high temperature/high pressure environment. Accordingly, the powder coating composition of the present invention can be used as a powder coating for coating the inside of a steel pipe required to transfer a high-temperature fluid.

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 1-7]

According to the composition shown in Table 1 below, each component was added to a mixing tank for premixing, melt-dispersed at 100°C in a disperser, and cooled to prepare a chip. The prepared chips were pulverized with a high-speed mixer to prepare a powder coating composition of Example 1-7 having an average particle size of 40 to 80 µm. In Table 1 below, the usage unit of each composition is parts by weight.

[Comparative Example 1-4]

Powder coating compositions of Comparative Example 1-4 were prepared in the same manner as in Example 1-7, except that each component was used according to the composition shown in Table 2 below.

Fluorine-containing epoxy resin 1: Epoxy equivalent: 450 g/eq, viscosity (based on 180℃ melting): 3,200 mPa·s, fluorine content: 2,500 ppm

Fluorine-containing epoxy resin 2: Epoxy equivalent: 210 g/eq, viscosity (based on 180°C melting): 3,500 mPa·s, fluorine content: 1,100 ppm

Fluorine-containing epoxy resin 3: Epoxy equivalent: 560 g/eq, viscosity (based on 180℃ melting): 2,690 mPa·s, fluorine content: 3,600 ppm

Epoxy resin: KD-214C (Kukdo Chemical Co., Ltd., epoxy equivalent: 900 to 1,000 g/eq)

Rubber Modified Epoxy Resin 1: Carboxyl Terminated Butadiene Acrylonitrile Modified Epoxy Resin (epoxy equivalent: 1,050 g/eq, softening point: 75°C)

Rubber Modified Epoxy Resin 2: Carboxyl Terminated Butadiene Acrylonitrile Modified Epoxy Resin (Epoxy equivalent: 850 g/eq, softening point 60℃)

Rubber Modified Epoxy Resin 3: Carboxyl Terminated Butadiene Acrylonitrile Modified Epoxy Resin (Epoxy equivalent: 1,400 g/eq, softening point 80℃)

Hardener: Dicyandiamide (Amine value: 21 mgKOH/g)

Extender Pigment: Barium Sulfate

Color Pigment: Iron Oxide

Catalyst: 2-Methyl Imidazole

Surface modifier: Acrilic polymer

[Experimental Example-Evaluation of Physical Properties]

The physical properties of the powder coating compositions prepared in Examples 1-7 and 1-4, respectively, were measured as follows, and the results are shown in Tables 3 and 4 below.

Flexibility

After preparing a short specimen (size: 200 mm × 25 mm × 6 mm), the specimen was preheated at a temperature of 230° C. for 40 minutes or more, and then each powder coating composition was coated on the preheated specimen using a painting gun. Thereafter, the temperature of the specimen was set to room temperature and -5°C, and the bending property (2° Bending) was measured using a bending tester.

Glass transition temperature (Tg)

Using a Differential Scanning Calorimeter, the glass transition temperature (Tg1) of the polymer before the coating was cured and the glass transition temperature (Tg2) of the coating film after the coating was cured were measured, respectively.

Cathodic peeling resistance

The specimen for the negative electrode peeling test was prepared in the same manner as in the bending resistance test, except that the steel was prepared to have a thickness of 100 mm (width) x 100 mm (length) x 6 mm (thickness). Thereafter, after a hole having a diameter of 3 mm was drilled in the center of the specimen, salt water of 3% concentration was applied to the surface of the coating film to make contact, and after preventing evaporation using a container, 1.5V voltage was applied to the substrate, respectively, at 65°C and 180°C. Was applied for 28 days to measure the peeling distance from the hole. It can be interpreted that the larger the peeling distance, the lower the adhesion of the powder coating composition to the substrate. The specimen preparation and physical property evaluation methods were performed according to CSA Z245.20, a Canadian standard for pipes.

Boiling water resistance

In order to prepare a specimen for the boiling water resistance test, a 100 mm (width) × 100 mm (length) × 6 mm (thick) steel was prepared and subjected to grit blasting surface treatment. The surface-treated steel was preheated to 230°C, and then the powder coating composition according to Examples 1-7 and Comparative Example 1-4 was coated on the steel surface to have a coating thickness of about 350 μm by electrostatic spraying. Was produced. Thereafter, the specimen was immersed in a water bath at 95° C. and taken out after 28 days to evaluate adhesion. For adhesion, after cooling the removed specimen at room temperature for 1 hour, scrape a rectangular shape of 15 mm in width and 30 mm in length with a knife until the material is exposed, and push the knife between the coating film and the material around the exposed part of the material. After measuring the adhesiveness by the principle, the rating was calculated according to the peeling area.

It is divided into ratings 1, 2, 3, 4, 5, and Rating 1 is when the peeling of the coating film is not at all, Rating 2 is when the peeling of the coating is within 50%, and Rating 3 is when the peeling of the coating is 50% or more , Rating 4 refers to a case where the coating film is easily peeled into large pieces, and Rating 5 is a case where the coating film is easily peeled into one piece at a time.

Adhesiveness (Pull-off test)

The adhesion test was performed while maintaining the temperature at 180°C by applying heat to the coated specimen. According to ASTM D4541 standard, after bonding Dolly to the specimen, pressure was applied to measure the pressure when the coating film fell.

Chemical resistance evaluation (EIS)

The coated specimen was immersed in water at 95° C. for 28 days, and then measured using EIS (Electro Impedance Spectroscopy).

From the results of Tables 3 and 4, the powder coating composition of Examples 1-7 according to the present invention, in which a fluorine-containing epoxy resin and a rubber-modified epoxy resin were introduced as resin components, exhibited a glass transition temperature of 180°C or higher, and at the same time, bending resistance. , It was confirmed that all of the measured properties such as boiling water resistance and negative electrode peeling resistance were excellent. On the other hand, the powder coating composition of Comparative Example 1-2 containing only a fluorine-containing epoxy resin was able to achieve a high glass transition temperature of 200°C or higher, but it was found to have poor flexibility, negative electrode peeling resistance, boiling water resistance, and adhesion. The powder coating composition of Comparative Example 3 containing an epoxy resin instead of a fluorine-containing epoxy resin had good flexibility and boiling water resistance, but exhibited poor physical properties in terms of glass transition temperature, negative electrode peeling resistance, and adhesion. The powder coating composition of Comparative Example 4 containing only a rubber-modified epoxy resin instead of a fluorine-containing epoxy resin exhibited poor physical properties in all evaluation items except for flexibility.

Claims (5)

Including a fluorine-containing epoxy resin, a rubber-modified epoxy resin and a curing agent,
The fluorine-containing epoxy resin has an epoxy equivalent of 200 to 600 g/eq, and a fluorine content of 10 to 10,000 ppm. delete The powder coating composition of claim 1, wherein the rubber-modified epoxy resin has an epoxy equivalent of 800 to 1,500 g/eq. According to claim 1, The rubber-modified epoxy resin is a carboxyl-terminated butadiene acrylonitrile (Carboxyl Terminated Butadiene Acrylonitrile) modified epoxy resin, amine-terminated butadiene acrylonitrile (Amine Terminated Butadiene Acrylonitrile) modified epoxy resin or a mixture thereof powder Paint composition. The powder coating composition according to claim 1, comprising 40 to 70% by weight of a fluorine-containing epoxy resin, 15 to 40% by weight of a rubber-modified epoxy resin, and 0.1 to 20% by weight of a curing agent based on the total amount of the powder coating composition.