KR102173752B1 - Powder coating composition - Google Patents

Abstract

The present invention is a polyimide compound comprising a polyimide compound, a polyfunctional benzoxazine compound, and an amino alcohol-modified epoxy resin, and a polyamic acid resin obtained by polymerizing the diamine and acid anhydride is imidized, and the polyfunctional benzoxazine compound is a benzoic acid It relates to a powder coating composition, a compound containing two or more photo (Benzoxazine) groups.

Description

Powder coating composition {Powder coating composition}

The present invention relates to a powder coating composition excellent in high temperature heat resistance and adhesion, flexibility, corrosion resistance, and the like.

The pipeline for petroleum mining and transport buried underground or under the sea is coated with paint to prevent corrosion and improve durability. In order to prevent corrosion of pipes due to harsh conditions other than microcurrent and moisture in buried environments such as above, underground, and underwater, long-term physical property management standards for coating materials are being reinforced in the industry. In addition to corrosion resistance to prevent corrosion of the body in a buried environment, the coating material inside and outside the pipe must have flexibility to protect the body from impacts and scratches and heat resistance at high temperature conditions at the same time. In particular, as mining in poor environments due to depletion of underground resources becomes frequent, the depth of mining becomes deeper and the buried environment becomes harsh.In order to protect the pipe from corrosion under high temperature conditions, thermal, chemical, mechanical coatings for pipe coatings are also used. There is a continuous demand for improvement of properties, and studies on paints that satisfy these properties are also ongoing.

For example, U.S. Patent No. 5,407,978 discloses the use of an aliphatic polyol-modified epoxy resin and a phenol curing agent as the main composition of a powder coating for pipes. On the other hand, U.S. Patent No. 5,112,932 discloses dicyandiamide and dicyandiamide, characterized in that polyisocyanate is added to form oxazolidone and isocyanurate rings in the process of polymerizing a low equivalent epoxy resin. Reacting or reacting with a phenolic resin is disclosed. However, in the case of using such a method, polyisocyanate is consumed by reacting with the secondary hydroxyl group of the epoxy base material, and there is a possibility that the functional group capable of hydrogen bonding with the hydroxyl group of the iron material decreases, as a result, impairing the adhesion of boiling water.

In addition, a technology to improve the adhesion between the substrate and the coating film by including 1 to 50% by weight of an amino alcohol-modified epoxy resin in the powder coating composition for pipe coating is also used, but a powder coating system that satisfies the long-term, high-temperature test required by the industry. In order to implement it, it is necessary to further improve high temperature heat resistance.

The present invention provides a powder coating composition excellent in high temperature heat resistance and adhesion, flexibility, and corrosion resistance.

The present invention includes a polyimide compound, a polyfunctional benzoxazine compound, and an amino alcohol-modified epoxy resin, the polyimide compound is a polyamic acid resin obtained by polymerizing diamine and an acid anhydride is an imidized compound, and the polyfunctional benzoxazine compound Provides a powder coating composition which is a compound containing two or more benzoxazine groups.

The present invention provides a powder coating composition excellent in high temperature heat resistance and adhesion, flexibility, and corrosion resistance. The powder coating composition according to the present invention can be used for pipe coating.

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.

It includes the powder coating polyimide compound, a polyfunctional benzoxazine compound, and an amino alcohol-modified epoxy resin according to the present invention. The powder coating composition may further include one or more epoxy resins.

In addition, the powder coating composition of the present invention may further include additives commonly used in the fields of a curing agent, a curing aid, an inorganic filler, a metal filler, a pigment, and a paint, if necessary. Hereinafter, looking at the composition of the powder coating composition of the present invention is as follows.

Polyimide compound

The powder coating composition according to the present invention includes a polyimide compound. The polyimide compound is a compound in which a polyamic acid resin obtained by polymerizing diamine and acid anhydride is imidized.

The diamine may be a compound represented by Formula 1 below.

[Formula 1]

In the above formula,

,

,

또는

이며,A is oxygen, an alkyl group having 1 to 3 carbon atoms,

,

,

or

Is,

R ¹ is hydrogen, an alkyl group having 1 to 3 carbon atoms, -OH or -COOR ² ,

R ² is hydrogen or an alkyl group having 1 to 5 carbon atoms,

R ³ is hydrogen, an alkyl group having 1 to 5 carbon atoms or -OH,

n is an integer between 0 and 4.

The acid anhydride may be a compound represented by Formula 2 below.

[Formula 2]

In the above formula,

이고,B is oxygen or

ego,

R ⁴ is hydrogen, a methyl group, -CH ₂ F, -CHF ₂ or -CF ₃ ,

R ⁵ is hydrogen, an alkyl group having 1 to 5 carbon atoms or -OH,

o is an integer between 0 and 3.

The mixing ratio (weight ratio) of the diamine and the acid anhydride is not particularly limited, but may be 1:0.8 to 2, for example 1:1 to 1.4. When the mixing ratio of diamine and acid anhydride satisfies the above range, mechanical properties such as adhesion and strength of the coating film and heat resistance can be improved.

The imidation rate of the polyimide compound is not particularly limited, but may be 40 to 100%, for example, 50 to 95%. When the imidation rate is out of the above-described range, moisture may be generated as the imidization proceeds during the painting operation, resulting in voids.

The polyimide compound may be used in an amount of 2 to 30% by weight, for example 3 to 25% by weight, and another example, 3 to 20% by weight based on the total amount of the powder coating composition. When the content of the polyimide compound exceeds 30% by weight, the boiling water resistance of the coating film may be deteriorated, and when the content of the polyimide compound is less than 2% by weight, a problem of lowering the heat resistance may occur.

Polyfunctional benzoxazine compounds

The powder coating composition according to the present invention includes a multifunctional benzoxazine compound. The multifunctional benzoxazine compound contains two or more, for example, 2 to 5 benzoxazine groups.

The benzoxazine group is capable of ring opening addition polymerization, a ring opening reaction with an amine compound, and the like, and a crosslinking reaction between the -OH group and the epoxy group of the phenol produced upon ring opening is also possible. Therefore, when the polyfunctional benzoxazine compound is used together with a polyimide compound and an epoxy resin, heat resistance of the coating composition may be improved.

As an example, the benzoxazine compound can be prepared by reacting a phenol compound and an amine compound under formaldehyde as shown in Scheme 1 below.

[Scheme 1]

The polyfunctional benzoxazine compound that may be included in the present invention is not particularly limited, and for example, bisphenol A-benzoxazine, bisphenol F-benzoxazine, phenolphthalein benzoxazine ), thiodiphenol benzoxazine may be used, and these may be used alone or in combination of two or more.

The multifunctional benzoxazine compound may be used in an amount of 2 to 20% by weight, for example, 3 to 15% by weight based on the total amount of the powder coating composition. When the content of the polyfunctional benzoxazine compound exceeds 20% by weight, adhesion and flexibility of the coating film may be deteriorated, and when the content is less than 2% by weight, a problem of lowering the heat resistance may occur.

Amino alcohol modified epoxy resin

The powder coating composition according to the present invention includes an amino alcohol-modified epoxy resin. The amino alcohol-modified epoxy resin is a polymer synthesized through an addition reaction of at least one general purpose epoxy resin and at least one amino alcohol. Amino alcohol can be used alone, but when used in a form reacted with an epoxy resin, better workability and long-term corrosion resistance can be secured.

As the epoxy resin used in the preparation of the amino alcohol-modified epoxy resin, any epoxy resin used in the powder coating composition may be used without particular limitation. For example, any one selected from the group consisting of bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, polyol-modified epoxy resin, novolac-modified epoxy resin, isocyanate-modified epoxy resin, cresol novolac epoxy resin, and mixtures thereof may be applied. I can.

In the case of a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, and a polyol-modified epoxy resin, an epoxy equivalent of 400 to 3,000 g/eq, for example, 400 to 1,500 g/eq may be used. In the case of a novolac-modified epoxy resin and a cresol novolac epoxy resin, an epoxy equivalent of 100 to 1,500 g/eq, for example, 200 to 800 g/eq may be used. As the isocyanate-modified epoxy resin, an epoxy equivalent of 100 to 1,500 g/eq, for example, 200 to 1,000 g/eq may be used. When each of the epoxy resins has an epoxy equivalent range of the above range, excellent flexibility, corrosion resistance, and manufacturing workability can be secured.

The amino alcohol used in the preparation of the amino alcohol-modified epoxy resin is a compound of NH ₂ R1 (wherein R1 is a linear or branched alkyl group having 1 to 12 carbon atoms containing at least one primary hydroxyl group), NHR2R3 Compound (wherein R2 is a linear or branched alkyl group having 1 to 12 carbon atoms or a linear or branched alkyl group having 1 to 12 carbon atoms containing at least one primary hydroxyl group, and R3 is It is a C1-C12 linear or branched alkyl group), and any one selected from the group consisting of a mixture thereof can be used.

Non-limiting examples of the amino alcohol include ethanolamine, diethanolamine, diisopropanolamine, isopropanolamine, monomethylaminoethanol, 2-amino-1-butanol, isopropylaminoethanol, 2-amino-2-methyl-1 -Propanol, 2-amino-2ethyl-1,3-propanediol, 2-amino-2-methyl-1,3-propanediol, t-butylaminoethanol, ethylaminoethanol, n-butylaminoethanol, 2- Any one selected from the group consisting of amino-2-hydroxymethyl-1,3-propanediol, tris(hydroxymethyl)aminomethane, and mixtures thereof may be mentioned. For example, one selected from the group consisting of diethanolamine, tris(hydroxymethyl)aminomethane, 2-amino-2-hydroxymethyl-1,3-propanediol, and mixtures thereof as the amino alcohol may be used. I can.

In the amino alcohol-modified epoxy resin, the equivalent ratio of the amino alcohol reactive group and the epoxy functional group capable of reacting therewith is not particularly limited, but may be 0.5 to 1.5: 1.0, for example, 0.7 to 1.2: 1.0. When the equivalent ratio of the amino alcohol reactive group and the epoxy functional group is within the above range, excellent adhesion and coating performance can be exhibited.

The amino alcohol-modified epoxy resin may be 0.1 to 10% by weight, for example, 0.5 to 5% by weight, based on the total amount of the powder coating composition. When the content of the amino alcohol-modified epoxy resin is less than 0.1% by weight, the effect of improving adhesion may not be sufficient, and when it exceeds 10% by weight, mechanical properties may be deteriorated.

Epoxy resin

The powder coating composition according to the present invention may further include at least one epoxy resin in addition to the polyimide compound, the polyfunctional benzoxazine compound, and the amino alcohol-modified epoxy resin. When an epoxy resin is additionally used as the main resin, the adhesion of the coating film to the base material may be further improved.

The epoxy resin used in the powder coating composition according to the present invention may be used without particular limitation as long as it is an epoxy resin commonly used in the powder coating composition. For example, any one selected from the group consisting of bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, polyol-modified epoxy resin, novolac-modified epoxy resin, isocyanate-modified epoxy resin, cresol novolac epoxy resin, and mixtures thereof may be applied. I can. For example, bisphenol A-type diglycidyl ether may be used as the epoxy resin.

In the case of a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, and a polyol-modified epoxy resin, an epoxy equivalent of 400 to 3,000 g/eq, for example, 400 to 1,500 g/eq may be used. In the case of a novolac-modified epoxy resin and a cresol novolac epoxy resin, an epoxy equivalent of 100 to 1,500 g/eq, for example, 200 to 800 g/eq may be used. As the isocyanate-modified epoxy resin, an epoxy equivalent of 100 to 1,500 g/eq, for example, 200 to 1,000 g/eq may be used. When each of the epoxy resins has an epoxy equivalent range of the above range, excellent flexibility, corrosion resistance, and manufacturing workability can be secured.

In the present invention, the content of the epoxy resin is not particularly limited, and as an example may be 30 to 60% by weight, for example, 45 to 60% by weight based on the total weight of the powder coating composition. When the content of the epoxy resin falls within the above-described range, the basic physical properties of the coating film are good, and excellent corrosion resistance, chemical resistance, and adhesion may be exhibited.

Hardener

The powder coating composition of the present invention may further include a curing agent. The curing agent is one selected from the group consisting of phenol curing agents, dicyandiamide curing agents, hydrazide curing agents, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, and mixtures thereof. The above can be applied, and for example, a phenol curing agent or a dicyandiamide type curing agent can be used.

Non-limiting examples of phenolic curing agents 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 may be 1 to 30% by weight based on the total weight of the powder coating composition. If it is out of the above content range, the mechanical properties of the coating film may be deteriorated.

Curing aid

The powder coating composition of the present invention may further include a curing aid. The curing aid can shorten the curing time by improving the reaction rate between the epoxy resin and the curing agent.

The curing aid that can be used in the present invention is not particularly limited as long as it is known in the art. For example, any one selected from the group consisting of imidazoles, imidazole-modified epoxy resins, dibiyu, dibiyu salt, triphenylphosphine, metal chelate, and mixtures thereof can be applied. For example, 1-methylimidazole, 2-methylimidazole, 1,2-dimethylimidazole, 1,5-dimethylimidazole, 2-butyl-5-chloro-1H-imidazole-4- Carvaldehyde, Vinylimidazole, Climbazole, 1,1-carbonyldiimidazole, tert-butyl dimethylsilylchloride, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-ethyl Imidazoles such as imidazole, 1-benzyl-2-methylimidazole, and 2-butylimidazole can be used.

In the present invention, the content of the curing aid may be 0.01 to 1% by weight based on the total weight of the powder coating composition. When used in the above content range, excellent workability and mechanical properties of the coating film can be secured.

Inorganic filler

The powder coating composition according to the present invention may optionally further include an inorganic filler. Non-limiting examples of the inorganic fillers include feldspar, barium sulfate, silica, alumina hydroxide, titanium dioxide, calcium carbonate, magnesium carbonate, alumina, mica, olastonite, talc, and the like, either alone or in combination of two or more. Can be used.

The content of the inorganic filler is not particularly limited, but may be 1 to 50% by weight based on the total weight of the powder coating composition. When the content of the inorganic filler is outside the above-described range, mechanical properties of the coating film may be deteriorated.

Metal filler

The powder coating composition according to the present invention may optionally further include a metal filler. Non-limiting examples of the metal fillers include potassium, calcium, sodium, magnesium, aluminum, zinc, and oxides thereof, and these may be used alone or in combination of two or more.

The content of the metal filler is not particularly limited, but may be 1 to 30% by weight based on the total weight of the powder coating composition. When the content of the metal filler is out of the above-described range, corrosion resistance and mechanical properties of the coating film may be deteriorated.

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.

Pigments can be used to express a desired color (color) in powder coatings or 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 titanium dioxide.

In the present invention, the content of the pigment is not particularly limited, and may be, for example, 1 to 50% 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 is excellent, and the hiding property and mechanical properties of the coating film may be improved.

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

The powder coating composition of the present invention may further include a flow improving agent. The flow improver is used to prevent cratering and lower the surface tension of the coating film to realize a flexible appearance, and a conventional one known in the art may be used. Non-limiting examples of the flowability enhancer include acrylic or silicone flowability improvers. The content of the flow improving agent is not particularly limited, and may be 0.1 to 5% by weight based on the total weight of the powder coating composition. When the content of the flowability improver is out of the above-described range, flowability may decrease.

The powder coating composition of the present invention may further include a wax. Wax facilitates dispersion in the manufacture of powder coatings, and acts as a surface control agent. As the wax, for example, an amide-based, polypropylene-based, olefin-based, or Teflon-based wax may be used.

The powder coating composition according to the present invention may be prepared by a method known in the art, for example, may be prepared by the following manufacturing process.

The ingredients of the powder coating composition are blended using a container mixer and uniformly mixed. After melt-mixing the mixed composition at 80 to 120°C using a kneader or an extruder, a powder coating may be prepared using a grinder.

The average particle size of the powder coating is not particularly limited, but may be, for example, 20 to 80 μm. When the average particle size of the powder coating is within the above range, excellent coating workability and appearance characteristics can be exhibited.

The coating film using the powder coating composition according to the present invention may be formed by a method known in the art, for example, may be formed by the following process.

While preheating the base material of the steel pipe subjected to the blasting treatment in advance to 180 to 250 ℃, after coating the powder coating composition of the present invention to a thickness of 200 to 500 ㎛ with an electrostatic spray sprayer, the steel pipe body at 180 to 250 ℃ for 1 to 5 minutes After heating to form a coating film, it can be immediately immersed in cold water to form a final coating film.

The powder coating composition of the present invention can form a coating film having excellent heat resistance, adhesion, flexibility and corrosion resistance even in a high temperature/high pressure environment. Therefore, the powder coating composition of the present invention can be used as a powder coating for pipe coating required to transport 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 1-10 and Comparative Example 1-6]

The ingredients of the powder coating composition shown in Tables 1 and 2 below were blended using a container mixer and uniformly mixed. The mixed composition was melt-mixed at 100° C. using a kneader, and then powder coating compositions of Examples 1-10 and 1-6 having an average particle size of 50 μm were prepared using a grinder. In Tables 1 and 2 below, the unit of use of each composition is parts by weight.

[Table 1]

[Table 2]

, R⁴=-CHF₂, R⁵=수소, o=O인 화합물)을 중합시킨 폴리아믹산 수지가 이미드화된 폴리이미드 화합물 (디아민 및 산무수물의 배합비 1 : 1.25, 이미드화율 70%, 입자크기 100 ㎛, KCC社)Polyimide Compound 1: Diamine (in Formula 1, A = oxygen, R ³ = hydrogen, n = 0 compound) and an acid anhydride (in Formula 2, B =

, R ⁴ =-CHF ₂ , R ⁵ =Hydrogen, o=O polyimide compound in which the polyamic acid resin polymerized is imidized (mixing ratio of diamine and acid anhydride 1: 1.25, imidation ratio 70%, particles Size 100 ㎛, KCC)

, R⁴=-CF₃, R⁵=수소, o=O인 화합물)을 중합시킨 폴리아믹산 수지가 이미드화된 폴리이미드 화합물 (디아민 및 산무수물의 배합비 1 : 1.15, 이미드화율 55%, 입자크기 100 ㎛, KCC社)Polyimide compound 2: Diamine (in formula 1, A = oxygen, R ³ = hydrogen, n = 0 compound) and acid anhydride (in formula 2, B =

, R ⁴ =-CF ₃ , R ⁵ =Hydrogen, o=O polyimide compound in which the polyamic acid resin polymerized is imidized (mixing ratio of diamine and acid anhydride 1: 1.15, imidation rate 55%, particles Size 100 ㎛, KCC)

, R¹=COOR², R²=수소, R³=수소, n=0인 화합물) 및 산무수물(화학식2에서, B=

, R⁴=-CHF₂, R⁵=수소, o=O인 화합물)을 중합시킨 폴리아믹산 수지가 이미드화된 폴리이미드 화합물 (디아민 및 산무수물의 배합비 1 : 1.35, 이미드화율 85%, 입자크기 100 ㎛, KCC社)Polyimide Compound 3: Diamine (A= in Formula 1

, R ¹ =COOR ² , R ² =hydrogen, R ³ =hydrogen, n=0 compound) and an acid anhydride (in Formula 2, B=

, R ⁴ =-CHF ₂ , R ⁵ = hydrogen, o=O polyimide compound in which a polyamic acid resin polymerized is imidized (mixing ratio of diamine and acid anhydride 1: 1.35, imidation ratio 85%, particles Size 100 ㎛, KCC)

Multifunctional benzoxazine compound: bisphenol F-type benzoxazine (LMB6493, Huntsman)

Monofunctional benzoxazine compound: 3-(4-bromophenyl)-1,4-benzoxazine (3-(4-Bromophenyl)-1,4-benzoxazine, Aldrich)

Amino alcohol-modified epoxy resin 1: Polymer obtained by addition reaction of the following epoxy resin A with ethanolamine (THAM) (amine value 155.1 mgKOH/g, NV (%) 65.5%, THAM content 10% by weight, KCC)

Amino alcohol-modified epoxy resin 2: Polymer obtained by addition reaction of the following epoxy resin A with ethanolamine (DEA) (amine value 180 mgKOH/g, NV (%) 99.5%, DEA content 10% by weight, KCC)

Epoxy resin A: Bisphenol A diglycidyl ether (BADGE) (epoxy equivalent 1,200 g/eq, CNE00105, KCC)

Hardener: 1400 F (Air Products)

Curing aid: 2-MI (Shikoku)

Inorganic filler: MF200 (Buyeo Material)

Metal filler: Aluminum oxide (LK Inter)

Colored pigment: Biperox 130M (Bayer Corporation)

Flow improver: PLP-100 (KS Chemical)

[Experimental Example-Evaluation of Physical Properties]

The physical properties of the powder coating compositions prepared in Examples 1-10 and 1-6, respectively, were measured as follows, and the results are shown in Tables 3 and 4 below.

Glass Transition Temperature Test

It was measured using a Differential Scanning Calorimeter.

Bending test

A 25 mm (width) x 300 mm (length) x 6 mm (thick) steel was prepared and subjected to grit blasting surface treatment. After preheating the surface-treated steel to 230°C, the steel surface was coated with the powder coating composition according to Examples 1-10 and Comparative Example 1-6 to a thickness of 350 μm by electrostatic spraying. Was produced. Thereafter, the temperature of the specimen was set to room temperature and 0 °C, and when the specimen was bent using a mandrel adjusted to an angle of 3 ° and 2 °, it was measured whether the coating film was cracked.

Impact resistance

After the temperature of the specimen prepared by the same method as the flexural resistance test was set to 10°C, 3 J/g of impact was applied, and then damage due to impact was confirmed through a holiday tester.

Hot Water Immersion Test

A 100 mm (width) x 100 mm (length) x 6 mm (thick) steel was prepared, followed by grit blasting surface treatment. The surface-treated steel was preheated to 230°C, and then the steel surface was coated with the powder coating composition according to Examples 1-10 and Comparative Example 1-6 to a thickness of 350 μm by electrostatic spraying. Was produced. Thereafter, the specimen was immersed in a water bath at 75° C. and taken out after 28 days to evaluate adhesion. For adhesion, after cooling the pulled out specimen at room temperature for 1 hour, scrape the 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 adhesion according to the principle, the rating was calculated according to the peeling area.

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

Cathodic Disbondment

Specimens were prepared in the same manner as in the bending resistance test, but the steel was prepared in a size 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 evaporation was prevented using a container, a 1.5V voltage was applied to the substrate at 130°C for 28 days. The separation distance from the hole was measured twice. 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.

[Table 3]

Flexural resistance-○: No crack, X: Crack

Impact resistance-○: no damage, X: damage

[Table 4]

Flexural resistance-○: No crack, X: Crack

Impact resistance-○: no damage, X: damage

From the results of Tables 3 and 4, the powder coating composition of Examples 1-10 according to the present invention in which a polyimide compound, a polyfunctional benzoxazine compound, and an amino alcohol-modified epoxy resin were introduced as resin components was measured in all physical properties. It was confirmed that an excellent effect was exhibited. On the other hand, the powder coating composition of Comparative Example 1-6 showed poor bending resistance, boiling water resistance, and negative electrode peeling resistance.

Claims (8)

Based on the total amount of the powder coating composition, including 2 to 30% by weight of a polyimide compound, 2 to 20% by weight of a polyfunctional benzoxazine compound, and 0.1 to 10% by weight of an amino alcohol-modified epoxy resin,
The polyimide compound is a compound in which a polyamic acid resin obtained by polymerizing a diamine and an acid anhydride is imidized,
The acid anhydride is a compound represented by the following formula (2),
[Formula 2]

(Wherein, B is oxygen or

, R ⁴ is hydrogen, a methyl group, -CH ₂ F, -CHF ₂ or -CF ₃ , R ⁵ is hydrogen, an alkyl group having 1 to 5 carbon atoms or -OH, and o is an integer between 0 and 3)
The mixing ratio (weight ratio) of the diamine and the acid anhydride is 1: 0.8 to 2,
The multifunctional benzoxazine compound is a powder coating composition that is a compound containing two or more benzoxazine groups. The powder coating composition of claim 1, wherein the diamine is a compound represented by the following Formula 1:
[Formula 1]

In the above formula,
A is oxygen, an alkyl group having 1 to 3 carbon atoms,

,

,

or

Is,
R ¹ is hydrogen, an alkyl group having 1 to 3 carbon atoms, -OH, or -COOR ² ,
R ² is hydrogen or an alkyl group having 1 to 5 carbon atoms,
R ³ is hydrogen, an alkyl group having 1 to 5 carbon atoms or -OH,
n is an integer between 0 and 4. delete delete The method of claim 1, wherein the multifunctional benzoxazine compound is bis A-benzoxazine, bis F-benzoxazine, phenolphthalein benzoxazine, and thiodiphenol benzoxazine. Powder coating composition containing at least one of (Thiodiphenol benzoxazine). The method of claim 1, wherein the amino alcohol used in the preparation of the amino alcohol-modified epoxy resin is a compound of NH ₂ R 1 (wherein R 1 is a linear or branched alkyl group having 1 to 12 carbon atoms containing at least one primary hydroxyl group. Is a compound of NHR2R3 (wherein R2 is a linear or branched alkyl group having 1 to 12 carbon atoms or a linear or branched alkyl group having 1 to 12 carbon atoms containing one or more primary hydroxyl groups, and R3 is one or more primary hydroxyl groups. A powder coating composition which is any one selected from the group consisting of a linear or branched alkyl group having 1 to 12 carbon atoms containing a hydroxyl group) and mixtures thereof. The powder coating composition according to claim 1, wherein in the amino alcohol-modified epoxy resin, the amino alcohol reactive group is in the range of 0.5 to 1.5 equivalents based on 1.0 equivalent of an epoxy functional group capable of reacting with the amino alcohol reactive group. delete