Powder coating composition

Abstract

The present invention relates to a powder coating composition having excellent heat resistance, water resistance, and long-term corrosion resistance while securing a high glass transition temperature.

Description

Technology Field

[0001] The present invention relates to a powder coating composition having excellent heat resistance, water resistance, and long-term corrosion resistance while securing a high glass transition temperature. Background Technology

[0002] Pipes used for oil extraction and transportation are coated on their inner and outer surfaces to prevent corrosion caused by microcurrents, moisture, and other harsh conditions in buried environments, such as above ground, underground, and underwater. However, standards for managing the long-term physical properties of coating materials required by the industry are becoming increasingly stringent. In particular, as mining in harsh environments becomes more frequent due to the depletion of underground resources, and as mining depths increase and buried environments become harsher, there is a continuous demand for improvements in the thermal, chemical, and mechanical properties of pipe coating paints to protect pipes from corrosion under high-temperature conditions. Consequently, research on paints that satisfy these properties is also ongoing. For example, U.S. Patent No. 5,407,978 discloses a powder coating for pipes comprising an aromatic bisphenol diglycidyl ether, an aliphatic polyol trifunctional polyglycidyl ether, a co-reactant, and a curing accelerator.

[0003] Conventional powder coatings have a glass transition temperature of 100°C or lower, which is insufficient for application to pipes transporting high-temperature fluids, and also has problems with water resistance and long-term corrosion resistance, which are insufficient for application in harsh environments. Accordingly, there is a need to develop a powder coating composition that has excellent heat resistance, water resistance, and long-term corrosion resistance while securing a high glass transition temperature. The problem to be solved

[0004] The present invention provides a powder coating composition that has excellent heat resistance, water resistance, and long-term corrosion resistance while securing a high glass transition temperature. means of solving the problem

[0005] The present invention provides a powder coating composition comprising an isocyanate-modified epoxy resin, a bisphenol A epoxy resin, a silicone resin, and a curing agent. Effects of the invention

[0006] The present invention provides a powder coating composition having excellent heat resistance, water resistance, and long-term corrosion resistance while securing a high glass transition temperature (e.g., 120°C or higher). The powder coating composition of the present invention is applicable to pipe coating for high-temperature fluid transfer. Specific details for implementing the invention

[0007] The present invention will be described below. However, it is not limited to the following description, and each component may be modified in various ways or selectively combined as needed. Accordingly, it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0008] As used herein, the “glass transition temperature” is measured by conventional methods known in the art, for example, by thermomechanical analysis (TMA) or differential scanning calorimetry (DSC). The “viscosity” is measured by conventional methods known in the art, for example, by using a Brookfield viscometer at room temperature (25 °C). The “softening point” is measured by conventional methods known in the art, for example, by using a dropping point system calorimetry DP70 from Mettler Toledo.

[0009] The powder coating composition according to the present invention comprises an isocyanate-modified epoxy resin, a bisphenol A epoxy resin, a silicone resin, and a curing agent.

[0010] The above-mentioned isocyanate-modified epoxy resin and bisphenol A-type epoxy resin are main resins that form a paint film and can affect basic physical properties, and can affect the glass transition temperature of the cured film. The above-mentioned isocyanate-modified epoxy resin has the advantage of a robust crosslinking density due to its network structure, but has the disadvantage of reduced mechanical properties. The above-mentioned bisphenol A-type epoxy resin has the advantage of excellent mechanical properties because it has a symmetrical structure and is stable against external stimuli, but has the disadvantage of limiting the increase in crosslinking density due to its linear shape. In the present invention, by mixing the above-mentioned isocyanate-modified epoxy resin and the above-mentioned bisphenol A-type epoxy resin, a paint composition having high crosslinking density and excellent mechanical properties is provided.

[0011] Meanwhile, epoxy resin can form a hard film due to its inherent properties, such as its ability to form a dense network structure with a curing agent and its high glass transition temperature; however, organic resins containing carbon-carbon bonds can have these bonds easily broken when heat is applied. To compensate for this, the present invention incorporates silicone resin. Since the silicone resin contains Si-O bonds with higher bonding energy compared to organic resins, decomposition occurs at higher temperatures, thereby increasing resistance to heat.

[0012] The powder coating composition of the present invention may further include a novolak-type epoxy resin and, if necessary, may further include additives commonly used in the relevant technical field, such as extender pigments, color pigments, anti-corrosion pigments, catalysts, surface modifiers, and adhesion promoters.

[0014] Isocyanate-modified epoxy resin

[0015] The powder coating composition according to the present invention comprises an isocyanate-modified epoxy resin. The isocyanate-modified epoxy resin serves as the main resin and provides a high glass transition temperature and heat resistance.

[0016] Isocyanate-modified epoxy resin is a polymer in which epoxy resin is modified with an isocyanate compound, containing an oxazolidone ring in the main chain backbone of the epoxy resin and a glycidyl group at the end. Such isocyanate-modified epoxy resin can be prepared by reacting an epoxy resin with an isocyanate compound in the presence of a catalyst.

[0017] As the above epoxy resin, any epoxy resin known in the relevant technical field may be used without special restrictions.

[0018] Monoisocyanate or diisocyanate may be used as the above isocyanate compound. Non-limiting examples of the above monoisocyanate include p-toluenesulfonyl isocyanate, 4-phenoxyphenyl isocyanate, 4-cyanophenyl isocyanate, etc. Non-limiting examples of the above diisocyanates include methane diisocyanate, butane-1,1-diisocyanate, ethane-1,2-diisocyanate, butane-1,2-diisocyanate, transvinyline diisocyanate, heptane-1,7-diisocyanate, 2,2-dimethyl-pentane-1,5-diisocyanate, hexane-1,6-diisocyanate, octane-1,8-diisocyanate, nonane-1,9-diisocyanate, dimethylsilane diisocyanate, diphenylsilane diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4-diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,6-toluene diisocyanate, and 2,4-toluene diisocyanate. Examples include 4,4'-dicyclohexylmethane diisocyanate, trans-1,4-cyclohexane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, etc. These may be used alone or in a mixture of two or more. The content of the isocyanate compound may be about 1 to 40 parts by weight per 100 parts by weight of epoxy resin.

[0019] The above catalyst may include, but is not limited to, bases, amines, hydrogen compounds, imidazoles, phosphonium salts, and derivatives thereof. These may be used alone or in a mixture of two or more types. The content of the above catalyst may be about 0.01 to 0.5 parts by weight per 100 parts by weight of the isocyanate compound.

[0020] The epoxy equivalent of the above isocyanate-modified epoxy resin may be 200 to 600 g / eq, for example, 400 to 500 g / eq. If the epoxy equivalent of the above isocyanate-modified epoxy resin is less than the aforementioned range, the reactivity with the curing agent is fast, so the coating film is cured before it is formed, which may result in a decrease in overall physical properties; if it exceeds the aforementioned range, the viscosity is high, making it difficult to coat, which may result in a decrease in appearance.

[0021] Additionally, the viscosity (150 °C) of the isocyanate-modified epoxy resin may be 10,000 to 30,000 CPS, for example, 15,000 to 25,000 CPS, the softening point may be 100 to 125 °C, for example, 105 to 115 °C, and the isocyanate modification rate may be 20 to 30 weight%. If the viscosity of the isocyanate-modified epoxy resin is below the aforementioned range, mechanical properties may be reduced, and if it exceeds the aforementioned range, a suitable crosslinking density may not be formed. If the softening point of the isocyanate-modified epoxy resin is below the aforementioned range, storage stability and dispersibility may be reduced, and if it exceeds the aforementioned range, crosslinking density and dispersibility may be reduced. If the isocyanate modification rate of the above isocyanate-modified epoxy resin is less than the aforementioned range, the crosslinking density of the coating film may be reduced, and if it exceeds the aforementioned range, the mechanical properties may be reduced.

[0023] Bisphenol A epoxy resin

[0024] The powder coating composition according to the present invention includes bisphenol A epoxy resin. Bisphenol A epoxy resin has a symmetrical structure and plays a role in supplementing physical properties such as corrosion resistance.

[0025] The epoxy equivalent (EEW) of the above bisphenol A type epoxy resin may be 900 to 1,300 g / eq, for example, 1,100 to 1,200 g / eq. If the epoxy equivalent of the above bisphenol A type epoxy resin is less than the aforementioned range, mechanical properties may be reduced, and if it exceeds the aforementioned range, appearance and dispersion power may be reduced.

[0026] In addition, the viscosity (200 ℃) of the bisphenol A type epoxy resin may be 1,800 to 2,800 cps, for example, 2,000 to 2,600 cps, and the softening point may be 100 to 130 ℃, for example, 110 to 125 ℃. If the viscosity of the bisphenol A type epoxy resin is below the aforementioned range, low-temperature flexibility may be reduced, and if it exceeds the aforementioned range, appearance and dispersion power may be reduced. If the softening point of the bisphenol A type epoxy resin is below the aforementioned range, storage stability and mechanical properties may be reduced, and if it exceeds the aforementioned range, dispersion power may be reduced.

[0027] The above isocyanate-modified epoxy resin and the above bisphenol A-type epoxy resin may be mixed in a weight ratio of 0.8 to 1.8:1. The isocyanate-modified epoxy resin has a structure favorable for forming crosslinks, and the bisphenol A-type epoxy resin has a structure favorable for improving mechanical properties; when these are mixed in the aforementioned weight ratio, excellent properties can be imparted to the paint composition. If the content of the isocyanate-modified epoxy resin relative to the bisphenol A-type epoxy resin is below the aforementioned range, the crosslinking density decreases, resulting in a lower glass transition temperature than required, which may reduce the heat resistance of the coating film; if it exceeds the aforementioned range, mechanical properties such as water resistance may decrease.

[0029] silicone resin

[0030] The powder coating composition according to the present invention includes a silicone resin. The silicone resin is a resin manufactured by synthesizing silicon, and due to the inherent properties of silicone, it has excellent heat resistance and water repellency, thereby playing a role in improving the heat resistance and water repellency of the coating composition.

[0031] Because the bonding energy between silicon and oxygen (Si-O) in silicone resin is higher than that between carbon and carbon (CC) in organic synthetic resin, silicone resin is resistant to heat and does not easily decompose due to heat, thus exhibiting excellent heat resistance. The above silicone resin includes a polyalkylphenylsiloxane-based resin. In the above polyalkylphenylsiloxane-based resin, the alkyl group (R) may be an alkyl group having 1 to 3 carbon atoms. For example, the above polyalkylphenylsiloxane-based resin may include silanol at the terminal end.

[0032] The above-mentioned polyalkylphenylsiloxane resin is a siloxane resin containing both alkyl and phenyl groups. The phenyl group is a stable form of aromatic hydrocarbon in which double bonds of sigma and pi bonds coexist. Since its bond energy is higher than that of a molecular structure consisting only of single bonds, it does not easily undergo chemical decomposition even when exposed to heat, thereby improving the heat resistance of the coating film. As the content of the phenyl group increases, the molecular weight of the silicone resin increases, and a silicone resin with a higher molecular weight can improve the hardness and mechanical strength of the formed coating film. Furthermore, the phenyl group is a type of hydrocarbon derivative that can affect compatibility with other organic components constituting the paint, such as epoxy resin; compatibility can be improved as its content increases. Meanwhile, the alkyl group has a structure capable of forming crosslinks, allowing it to form smooth crosslinks with its surroundings to impart stable adhesion to the paint.

[0033] By adjusting the ratio of phenyl groups to alkyl groups in the above-mentioned polyalkylphenylsiloxane resin to a specific range, excellent physical properties can be imparted to the paint composition. For example, the ratio of phenyl groups to alkyl groups (P / R ratio) in the above-mentioned polyalkylphenylsiloxane resin may be 0.5 to 1.5. If the ratio of phenyl groups to alkyl groups is less than the aforementioned range, the content of phenyl groups is low, which may reduce the heat resistance of the coating film and reduce compatibility with the organic resin, such as epoxy resin. On the other hand, if the ratio of phenyl groups to alkyl groups exceeds the aforementioned range, the content of phenyl groups is high, resulting in excellent heat resistance, but the adhesion may be reduced due to a decrease in the content of alkyl groups participating in crosslinking.

[0034] The hydroxyl group content in the above polyalkylphenylsiloxane resin may be greater than 0 weight% and less than or equal to 7 weight%. If the hydroxyl group content exceeds the aforementioned range, a deterioration in appearance due to bubble formation may occur.

[0035] The weight-average molecular weight of the above polyalkylphenylsiloxane resin may be 1,000 to 4,500 g / mol, for example, 1,000 to 4,000 g / mol. If the weight-average molecular weight of the above polyalkylphenylsiloxane resin is less than the aforementioned range, the gloss may be reduced, and if it exceeds the aforementioned range, the appearance may be reduced due to the generation of bubbles.

[0036] The degree of substitution of the above-mentioned polyalkylphenylsiloxane resin, that is, the average number of organic substituents per silicon atom (R / Si), may be 1 to 2, for example, 1 to 1.5. The degree of substitution of the above-mentioned polyalkylphenylsiloxane resin affects the degree of crosslinking, and if the degree of substitution is below the aforementioned range, adhesion may be reduced, and if it exceeds the aforementioned range, flexibility may be reduced due to a decrease in the degree of crosslinking.

[0037] The silicone resin may be included in an amount of 0.1 to 1 part by weight for every 100 parts by weight of the total isocyanate-modified epoxy resin and the bisphenol A epoxy resin. If the content of the silicone resin is less than the aforementioned range, water resistance may be reduced, and if it exceeds the aforementioned range, corrosion resistance may be reduced and compatibility with the epoxy resin may be reduced.

[0038] The aforementioned isocyanate-modified epoxy resin and bisphenol A-type epoxy resin have a strong crosslinking density, but water resistance may be reduced when the epoxy resin is applied alone. On the other hand, the silicone resin has excellent water resistance, but high-temperature corrosion resistance may be inferior when applied alone. In the present invention, by mixing the isocyanate-modified epoxy resin, bisphenol A-type epoxy resin, and the silicone resin, it is possible to achieve a suitable crosslinking density while simultaneously providing excellent water resistance.

[0040] Novolak-type epoxy resin

[0041] The powder coating composition according to the present invention may further include a novolak-type epoxy resin. The novolak-type epoxy resin is a polyfunctional epoxy resin that has more epoxide rings compared to other types of epoxy resins, and thus can increase the crosslinking density during film formation, thereby improving the durability, corrosion resistance, and chemical resistance properties of the film. The novolak-type epoxy resin may include phenol novolak-type epoxy resin, cresol novolak-type epoxy resin, bisphenol A novolak-type epoxy resin, bisphenol S novolak-type epoxy resin, biphenyl novolak-type epoxy resin, naphthol novolak-type epoxy resin, etc. Preferably, the novolak-type epoxy resin may include a cresol-type novolak-type resin.

[0042] The epoxy equivalent of the above-mentioned novolak-type epoxy resin may be 100 to 400 g / eq, for example, 200 to 210 g / eq. If the epoxy equivalent of the above-mentioned novolak-type epoxy resin is less than the aforementioned range, mechanical properties may be reduced, and if it exceeds the aforementioned range, the crosslinking density may be reduced. In addition, the viscosity (150 °C) of the above-mentioned novolak-type epoxy resin may be 2,000 to 5,000 cps, for example, 3,000 to 4,500 cps, and the softening point may be 100 to 125 °C, for example, 110 to 125 °C. If the viscosity of the above-mentioned novolak-type epoxy resin is less than the aforementioned range, mechanical properties may be reduced, and if it exceeds the aforementioned range, the crosslinking density may be reduced. If the softening point of the above-mentioned novolak-type epoxy resin is below the aforementioned range, the mechanical properties may be reduced, and if it exceeds the aforementioned range, the crosslinking density may be reduced.

[0043] For every 100 parts by weight of the total isocyanate-modified epoxy resin and the bisphenol A epoxy resin, 0.5 to 2 parts by weight of the novolak-type epoxy resin may be included. If the content of the novolak-type epoxy resin is less than the aforementioned range, heat resistance may be inferior, and if it exceeds the aforementioned range, mechanical properties may be degraded.

[0045] hardener

[0046] The powder coating composition of the present invention includes a curing agent. The curing agent is not particularly limited as long as it is a curing agent capable of curing with an epoxy resin, and may use aliphatic amine-based curing agents, alicyclic amine-based curing agents, aromatic amine-based curing agents, etc. These may be used alone or in a mixture of two or more types. For example, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylmethane, dicyandiamide, etc. may be used.

[0047] The amine value of the curing agent may be 10 to 40 mgKOH / g, for example, 15 to 25 mgKOH / g. If the amine value of the curing agent is below the aforementioned range, mechanical properties may be reduced, and if it exceeds the aforementioned range, water resistance may be reduced.

[0048] The curing agent may be included in an amount of 1.6 to 3.3 parts by weight per 100 parts by weight of the total isocyanate-modified epoxy resin and the bisphenol A epoxy resin. When the content of the curing agent satisfies the aforementioned range, the degree of curing of the coating film is increased, and the physical properties of the coating film can be improved.

[0050] pigment

[0051] The powder coating composition of the present invention may further include one or more of extender pigments, color pigments, and anti-corrosion pigments commonly used in the field of powder coatings, within a range that does not impair the inherent characteristics of the coating composition.

[0052] Extender pigments play a role in supplementing water resistance and corrosion resistance. As extender pigments, materials such as olastonite, calcium carbonate, feldspar, barium sulfate, silica, alumina hydroxide, magnesium hydroxide, titanium dioxide, magnesium carbonate, alumina, mica, montmorillonite, talc, aluminum nitride, silicon nitride, boron nitride, aluminum oxide, aluminum nitride, and barium sulfate may be used, and these may be used individually or mixed in a combination of two or more types. The composition may include 20 to 50 parts by weight of the extender pigment per 100 parts by weight of the total isocyanate-modified epoxy resin and the bisphenol A epoxy resin. When the content of the extender pigment satisfies the aforementioned range, the mechanical properties, impact resistance, adhesion, etc., of the coating film may be improved.

[0053] Color pigments are used to achieve a desired color in powder coatings. Organic pigments, metallic pigments, aluminum paste (Al-paste), pearls, etc., may be used as color pigments without limitation, and these may be used individually or in combination of two or more types. Non-limiting examples of usable color pigments include azo-based, phthalocyanine-based, iron oxide-based, cobalt-based, silicate-based, and chromate-based pigments, such as titanium dioxide, zinc oxide, bismuth vanadate, cyanine green, carbon black, iron oxide red, iron oxide yellow, navy blue, cyanine blue, and mixtures of two or more of these. The color pigment may be included in an amount of 1 to 5 parts by weight per 100 parts by weight of the total isocyanate-modified epoxy resin and the bisphenol A epoxy resin. When the content of the color pigment satisfies the aforementioned range, the color expression of the coating film is excellent, and the opacity of the coating film can be improved.

[0054] Anti-corrosion pigments serve to supplement corrosion resistance. Zinc phosphate, etc., may be used as anti-corrosion pigments. With respect to 100 parts by weight of the total isocyanate-modified epoxy resin and bisphenol A epoxy resin, 1 to 3 parts by weight of the anti-corrosion pigment may be included. When the content of the anti-corrosion pigment satisfies the aforementioned range, the corrosion resistance of the coating film can be improved.

[0056] additives

[0057] The powder coating composition of the present invention may further include additives commonly used in the field, such as catalysts, surface modifiers, and adhesion promoters, to the extent that the inherent characteristics of the coating composition are not compromised.

[0058] As a material that promotes the reaction between the above-mentioned catalyst epoxy resin and the curing agent, examples include imidazole-based, phosphonium-based, amine-based, and metal-based catalysts, which can be used alone or in a mixture of two or more types.

[0059] The above surface modifier is intended to improve the appearance characteristics of the coating film while enhancing adhesion within the composition by leveling the paint composition so that it is coated flat and smooth. For example, acrylic, silicone, polyester, and amine-based leveling agents may be used, but are not limited to these.

[0060] The above adhesion promoter is a substance intended to improve corrosion resistance by enhancing the adhesion of the coating film, and amino-based, silane-based adhesion promoters, etc., may be used.

[0061] The above additive may be appropriately added within a content range known in the relevant technical field, for example, 0.1 to 10 parts by weight each with respect to 100 parts by weight of the total isocyanate-modified epoxy resin and the bisphenol A epoxy resin.

[0063] The powder coating composition according to the present invention can be manufactured by methods known in the art, for example, through processes such as metering, pre-mixing, melt dispersion, and grinding. For example, a mixture of raw materials containing isocyanate-modified epoxy resin, bisphenol A epoxy resin, silicone resin, a curing agent, and, if necessary, novolak-type epoxy resin, extender pigment, color pigment, anti-corrosion pigment, catalyst, surface modifier, and adhesion promoter can be introduced into a container mixer and mixed uniformly, and the mixed composition can be manufactured by melt mixing and then grinding. For example, the mixture of raw materials can be melt-dispersed at 70 to 130°C using a melt mixing device such as a kneader or extruder to produce chips of a predetermined thickness (e.g., 1 to 5 mm), and then the produced chips can be ground to a range of 40 to 80 μm using a grinding device such as a high-speed mixer and then classified to produce the powder coating composition.

[0064] The above classification process is not particularly limited and, for example, can be filtered to a mesh of 40 to 80. Accordingly, a powder coating with an average particle size in the range of 40 to 80 μm can be obtained. The average particle size of the powder is not particularly limited, but if the above range is satisfied, the workability of the coating and the appearance characteristics of the coating film can be improved.

[0065] To improve the fluidity of the powder paint, the surface of the powder paint particles according to the present invention may be coated with fine powder such as silica. As a method for performing this treatment, a grinding and mixing method in which fine powder is added and mixed during grinding, or a dry mixing method using a Henschel mixer, etc., may be used.

[0067] The present invention will be explained in more detail below through examples. However, the following examples are intended only to aid in understanding the present invention and do not imply that the scope of the present invention is limited to these examples in any way.

[0069] [Example 1-13]

[0070] According to the compositions listed in Tables 1 and 2 below, each component was introduced into a mixing tank and pre-mixed, and then melt-dispersed at 100°C in a disperser to produce chips. The produced chips were ground with a high-speed mixer to produce powder coating compositions of each example with an average particle size of 40 μm.

[0072] [Comparative Example 1-3]

[0073] Powder coating compositions of each comparative example were prepared in the same manner as the examples, except for the compositions listed in Table 3 below.

[0074]

[0075]

[0076]

[0077] Isocyanate-modified epoxy resin 1: Epoxy equivalent 465, viscosity (150 ℃) 21,000 cps, softening point 110 ℃, NCO modification rate 25 wt%

[0078] Isocyanate-modified epoxy resin 2: Epoxy equivalent 400, viscosity (150 ℃) 15,000 cps, softening point 105 ℃, NCO modification rate 20 wt%

[0079] Isocyanate-modified epoxy resin 3: Epoxy equivalent 500, viscosity (150 ℃) 25,000 cps, softening point 115 ℃, NCO modification rate 30 wt%

[0080] Bisphenol A Epoxy Resin 1: Epoxy equivalent 1,150, viscosity (200 ℃) 2,300 cps, softening point 118.5 ℃

[0081] Bisphenol A Epoxy Resin 2: Epoxy equivalent 1,100, viscosity (200 ℃) 2,000 cps, softening point 110 ℃

[0082] Bisphenol A Epoxy Resin 3: Epoxy equivalent 1,200, viscosity (200 ℃) 2,600 cps, softening point 125 ℃

[0083] Silicone Resin 1: SILANOL FUNCTIONAL METHYLPHENYL SILICONE RESIN (Mw 2,600 g / mol, substitution rate 0.8, P / R ratio 1.3)

[0084] Silicone Resin 2: SILANOL FUNCTIONAL METHYLPHENYL SILICONE RESIN (Mw 2,000 g / mol, substitution rate 1.1, P / R ratio 1)

[0085] Silicone Resin 3: SILANOL FUNCTIONAL METHYLPHENYL SILICONE RESIN (Mw 4,000 g / mol, substitution rate 1.5, P / R ratio 1.5)

[0086] Novolak-type epoxy resin: Epoxy equivalent 205, viscosity (150 ℃) 3,750 cP, softening point 115 ℃

[0087] Hardener: Dicyandiamide (Evonik, AHEW 21)

[0088] Auxiliary Curing Agent: Amino alcohol amine-adduct

[0089] Catalyst: 2-Methyl-imidazole

[0090] Adhesion promoter: Adhesion promoter (KCC)

[0091] Coloring pigment: Iron oxide (BAYFERROX 130M)

[0092] Extender Pigment: Wollastonite (NYCO)

[0093] Anti-corrosion pigment: Zinc phosphate (Hanchang Industry)

[0095] [Physical Property Evaluation]

[0096] The physical properties of the powder coating compositions prepared in each example and comparative example were measured as follows, and the results are shown in Table 4-6 below.

[0098] Sample preparation

[0099] After preparing a shot specimen (100 mm × 100 mm × 6 mm), the specimen was preheated at a temperature of 230 ℃ for at least 30 minutes, and then each powder paint composition was applied onto the preheated specimen using a paint gun (film thickness: 562 μm).

[0101] Flexibility

[0102] Using a bending tester, the bendability (2˚ Bending) of each specimen was measured at -30 ℃.

[0103] [metewand]

[0104] Excellent (◎): No cracking, Poor (X): Cracking occurs

[0106] cathode peeling

[0107] After testing for 28 days at 65 ℃ and 95 ℃ under 1.5 V conditions, the peeling distance of the coating film was checked using a cathodic peel tester.

[0108] [Evaluation criteria at 65 ℃]

[0109] Excellent (◎): 5.0 mm or less, Good (○): Over 5.0 mm to 6.0 mm, Average (β: Over 6.0 mm to 7.0 mm, Poor (X): Over 7.0 mm

[0110] [Evaluation criteria at 95 ℃]

[0111] Excellent (◎): 6.0 mm or less, Good (○): Over 6.0 mm to 7.0 mm, Average (△): Over 7.0 mm to 8.0 mm, Poor (X): Over 7.0 mm

[0113] boiling water

[0114] After immersion in water at 75°C for 28 days, the adhesion of the coating film was checked and evaluated as a rating of 1 to 5 according to the following criteria.

[0115] Rating 1: Almost no peeling

[0116] Rating 2: Coating peeling of less than 50%

[0117] Rating 3: Resistance to over 50% film peeling and levering action

[0118] Rating 4: The film peels off easily in pieces

[0119] Rating 5: 100% peeling

[0120] [metewand]

[0121] Excellent (◎): Rating 1, Good (○): Rating 2-3, Average (△): Rating 4, Poor (X): Rating 5

[0123] Shock

[0124] Using a DuPont impact tester, each specimen was impacted from a height of 30 cm with a 1 kg weight to check for cracks in the coating.

[0125] [metewand]

[0126] Excellent (◎): No cracking, Poor (X): Cracking occurs

[0128] Porosity

[0129] The coating of each specimen was peeled off, and the degree of porosity on the bottom and side surfaces of the coating was measured using a 40x microscope and evaluated as a Rate of 1 to 5 according to CSA Z245.20:22.

[0130] [metewand]

[0131] Excellent (◎): Rate 1, Good (○): Rate 2-3, Average (△): Rate 4, Poor (X): Rate 5

[0133] Glass transition temperature of the film

[0134] According to the CSA Z245.20 standard, 9-11 mg of paint was placed in a cell of the DSC instrument, and heat was applied according to a set cycle to determine the glass transition temperature.

[0135] [metewand]

[0136] Excellent (◎): 120 ℃ or higher, Good (○): 110 ℃ or higher but less than 120 ℃, Average (△): 100 ℃ or higher but less than 110 ℃, Poor (X): Less than 100 ℃

[0138]

[0139]

[0140]

[0141] As shown in Table 4-6, the paint compositions of the examples exhibited excellent physical properties across all measured items. On the other hand, the paint composition of Comparative Example 1, which does not contain bisphenol A type epoxy resin, showed inferior flexibility, cathodic peeling, boiling water resistance, and porosity, and a low glass transition temperature; the paint composition of Comparative Example 2, which does not contain isocyanate modified epoxy resin, showed inferior cathodic peeling, boiling water resistance, and porosity; and the paint composition of Comparative Example 3, which does not contain silicone resin, showed inferior flexibility, cathodic peeling, boiling water resistance, impact resistance, and porosity.

Claims

Claim 1 A powder coating composition comprising an isocyanate-modified epoxy resin, a bisphenol A epoxy resin, a silicone resin, and a curing agent, wherein the mixing ratio of the isocyanate-modified epoxy resin and the bisphenol A epoxy resin is a weight ratio of 0.8 to 1.8:1, the silicone resin is a polyalkylphenylsiloxane-based resin, and the ratio of phenyl groups to alkyl groups in the polyalkylphenylsiloxane-based resin (P / R ratio) is 0.5 to 1.

5. Claim 2 delete Claim 3 A powder coating composition according to claim 1, wherein the epoxy equivalent of the isocyanate-modified epoxy resin is 200 to 600 g / eq, the viscosity (150 ℃) is 10,000 to 30,000 CPS, the softening point is 100 to 125 ℃, and the isocyanate modification rate is 20 to 30 weight%. Claim 4 A powder coating composition according to claim 1, wherein the epoxy equivalent (EEW) of the bisphenol A type epoxy resin is 900 to 1,300 g / eq, the viscosity (200 ℃) is 1,800 to 2,800 CPS, and the softening point is 100 to 130 ℃. Claim 5 delete Claim 6 A powder coating composition according to claim 1, further comprising a novolak-type epoxy resin, wherein the epoxy equivalent of the novolak-type epoxy resin is 100 to 400 g / eq, the viscosity (150 ℃) is 2,000 to 5,000 cps, and the softening point is 100 to 125 ℃. Claim 7 A powder coating composition according to claim 6, comprising, with respect to 100 parts by weight of the total isocyanate-modified epoxy resin and bisphenol A epoxy resin, 0.1 to 1 part by weight of the silicone resin, 0.5 to 2 parts by weight of the novolak-type epoxy resin, and 1.6 to 3.3 parts by weight of the curing agent.

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