Paint compositions for metal plates and painted articles

Abstract

The present disclosure aims to provide a coating composition for metal plates that uses raw materials that can be manufactured from biomass raw materials, has good coating properties, good appearance, hardness, chemical resistance and processability of the coating film, and can produce a coating film with better hardness and chemical resistance compared to that obtained when using conventional curing agents, even under lower curing conditions. [Solution] The solution comprises a coating-forming resin (A) and a curing agent (B), wherein the coating-forming resin (A) has active hydrogen groups and a hydrogen bonding term δ that constitutes the Hansen solubility parameter. h However, 3.5 MPa 0.5 Above 15.0 MPa 0.5 A coating composition for metal plates comprising the following resin (A1), wherein the curing agent (B) comprises a blocked isocyanate compound (B1) in which the isocyanate groups of pentamethylene diisocyanate and / or a pentamethylene diisocyanate derivative are blocked by a sealant.

Description

[Technical Field]

[0001] This disclosure relates to coating compositions for metal plates and coated articles. [Background technology]

[0002] Examples of painted articles having a coating on a metal plate include building materials, automobile parts, construction machinery, agricultural machinery, electrical equipment, kitchen appliances, and office equipment. Known methods for coating such articles include post-coating, in which the article is painted after processing such as cutting and bending, and pre-coating, in which the above processing is performed after the article is painted on the metal plate.

[0003] Patent Document 1 describes a pre-coat metal coating composition comprising a main component and a latent curing agent, in which the latent curing agent is a blocked isocyanate obtained by encapsulating the isocyanate groups of a polyisocyanate mixture (A) with a mass ratio of (a) / (b) = 50 / 50 to 95 / 5, consisting of an isocyanate-terminated prepolymer (a) obtained by reacting toluene diisocyanate (a) with a polyester polyol (b) having a number average molecular weight of 500 to 5,000, and an isocyanate-terminated prepolymer (b) obtained by reacting toluene diisocyanate (a) with a low molecular weight polyol (c) having a number average molecular weight of less than 500, with a blocking agent (B). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2005-290025 [Overview of the project] [Problems that the invention aims to solve]

[0005] When conventional paint compositions were used to form coatings for metal plates, the physical properties of the coating film after curing at low temperatures were sometimes not entirely satisfactory.

[0006] On the other hand, in various fields, there is a growing movement to use biomass-derived raw materials (biomass raw materials) that can replace petroleum in consideration of the environment, and the paint industry is no exception. However, it is still often difficult to achieve both the use of biomass raw materials and the securing of the desired physical properties of paints and coatings.

[0007] The present disclosure aims to provide a coating composition for metal plates that uses raw materials that can be manufactured from biomass raw materials, has good coating properties, good appearance, hardness, chemical resistance and processability of the coating film, and can produce a coating film that is superior in hardness and chemical resistance compared to when using conventional curing agents, even under lower curing conditions. [Means for solving the problem]

[0008] This disclosure provides the following aspects: <1> The material comprises a film-forming resin (A) and a curing agent (B), wherein the film-forming resin (A) has active hydrogen groups and a hydrogen bonding term δ that constitutes the Hansen solubility parameter. h However, 3.5 MPa 0.5 Above 15.0 MPa 0.5 A coating composition for metal plates comprising the following resin (A1), wherein the curing agent (B) comprises a blocked isocyanate compound (B1) in which the isocyanate groups of pentamethylene diisocyanate and / or a pentamethylene diisocyanate derivative are blocked by a sealant. <2> The distance R of the Hansen solubility parameter between the resin (A1) and the blocked isocyanate compound (B1) a However, 1.6 MPa 0.5 The above is 16.3 MPa. 0.5 The following is: <1> The metal plate coating composition described above. <3> The ratio (NCO / H ratio) of isocyanate groups contained in the curing agent (B) to active hydrogen groups contained in the coating resin (A) is 0.9 or more and 3.0 or less. <1> or <2> The metal plate coating composition described above. <4> The distance R of the Hansen solubility parameter between the resin (A1) and the blocked isocyanate compound (B1) a is 1.8 MPa 0.5 or more and 13.5 MPa 0.5 or less. The coating composition for a metal plate according to any one of <1> to <3>. <5> The hydrogen bonding term δ that constitutes the Hansen solubility parameter of the resin (A1) h is 6.0 MPa 0.5 or more and 11.0 MPa 0.5 or less. The coating composition for a metal plate according to any one of <1> to <4>. <6> The coating composition for a metal plate according to any one of <1> to <5>, wherein the pentamethylene diisocyanate derivative contains one or more selected from the group consisting of an isocyanurate group and a urethane bond. <7> The coating composition for a metal plate according to any one of <1> to <6>, wherein the resin (A1) contains one or more selected from the group consisting of a polyester polyol, an alkyd resin, and an acrylic polyol. <8> A coated article comprising a metal plate and a coating film disposed on the surface of the metal plate and formed from the coating composition for a metal plate according to any one of <1> to <7>.

Advantages of the Invention

[0009] The coating composition of the present invention uses raw materials that can be produced from biomass raw materials, has good coating properties, has good appearance, hardness, chemical resistance, and processability of the coating film, and can obtain a coating film that is excellent in hardness and chemical resistance compared to the case of using a conventional curing agent even under lower temperature curing conditions.

Embodiments for Carrying Out the Invention

[0010] The coating composition of the present disclosure includes a coating film-forming resin (A) and a curing agent (B). The coating film-forming resin (A) has an active hydrogen group and a hydrogen bonding term δ that constitutes the Hansen solubility parameter h is 3.5 MPa0.5 Above 15.0 MPa 0.5 The coating composition comprises the following resin (A1), wherein the curing agent (B) comprises a blocked isocyanate compound in which the isocyanate groups of pentamethylene diisocyanate are blocked with a encapsulant, and / or a blocked isocyanate compound (B1) in which the isocyanate groups of a pentamethylene diisocyanate derivative are blocked with a encapsulant (hereinafter also referred to as "a blocked isocyanate compound derived from pentamethylene diisocyanate"). The coating composition of this disclosure is used for metal sheets.

[0011] Despite using a blocked isocyanate compound (B1) derived from or produced from biomass raw materials, the coating composition exhibits good paint properties, good appearance, hardness, chemical resistance, and processability of the coating film, and even under lower curing conditions, it yields a coating film with superior hardness and chemical resistance compared to that obtained when using conventional curing agents (e.g., blocked isocyanates derived from hexamethylene diisocyanate). This disclosure should not be construed as limiting to any particular theory, but the reasons why the coating composition of this disclosure may achieve such effects are thought to be as follows.

[0012] In other words, the paint composition of this disclosure uses a blocked isocyanate compound derived from pentamethylene diisocyanate as the curing agent (B), and uses a hydrogen bonding term δ as the film-forming resin (A). h The present invention uses a resin (A1) that is within a predetermined range. By using such a paint composition, the properties during storage are stabilized, and during film formation, the reactivity between the active hydrogen groups in resin (A1) and the isocyanate groups in the blocked isocyanate compound (B1) is improved, which may lead to more uniform hardening of the paint film and contribute to improvements in the appearance, hardness, chemical resistance, and processability of the paint film.

[0013] [Coating film forming resin (A)] The coating-forming resin (A) refers to a resin that reacts with the hardening agent (B) to form a coating film.

[0014] The coating resin (A) has active hydrogen groups and the hydrogen bonding term δ that constitutes the Hansen solubility parameter h However, 3.5 MPa 0.5 Above 15.0 MPa 0.5 The following resin (A1) is included. Resin (A1) has active hydrogen groups, which react with the curing agent (B) to form a coating film.

[0015] The above-mentioned active hydrogen group may be any group having an active hydrogen atom, and examples include hydroxyl groups, mercapto groups, carboxyl groups, phosphate groups, sulfonic acid groups, amino groups, imino groups, urethane groups, urea groups, etc. Preferably, the active hydrogen group contains at least one selected from hydroxyl groups and carboxyl groups.

[0016] Hydrogen bond term δ of resin (A1) h 3.5 MPa 0.5 Above 15.0 MPa 0.5 The following is preferred, preferably 6.0 MPa 0.5 Above 11.0 MPa 0.5 Below, fuffer 6.2 MPa 0.5 The above is 10.7 MPa. 0.5 The following is the hydrogen bonding term δ of resin (A1). h Because it is within the range in which this occurs, the reactivity between the active hydrogen groups in resin (A1) and the isocyanate groups in curing agent (B1) is improved, and as a result, even when cured at lower temperatures, it is easier to obtain a coating film with better physical properties compared to when using conventional curing agents (for example, blocked isocyanates derived from hexamethylene diisocyanate). In particular, the hydrogen bonding term δ of resin (A1) h 3.5 MPa 0.5 As the amount increases, the uniform dispersibility of the paint composition improves, and the hardness, processability, and chemical resistance of the coating film improve. Also, the hydrogen bonding term δ of resin (A1) h 15.0 MPa 0.5 As the concentration decreases, the uniform dispersibility of the paint composition improves, and the hardness, processability, and chemical resistance of the coating film improve.

[0017] The Hansen solubility parameter (HSP) is an index that indicates the degree of affinity (mismatch) between a substance (X) and another substance (Y). The Hansen solubility parameter (HSP) is calculated by dividing the solubility parameter by the dispersion term δ. d , polarity term δ p , hydrogen bond term δ h It is divided into three components and quantified using a vector in three-dimensional space (Hansen solubility parameter: δ=(δd 2 +δp 2 +δh 2 ) 1 / 2 ). Dispersion term δ d This shows the effect due to dispersion forces, and the polar term δ p This shows the effect due to the inter-dipole force, and the hydrogen bond term δ h This demonstrates the effect of hydrogen bonding. It shows that the closer the distance (HSP distance (Ra)) between the vector of substance (X) and the vector of another substance (Y) in three-dimensional space, the easier it is for substance (X) and substance (Y) to dissolve in each other (higher compatibility). The HSP distance (Ra) is defined by the following formula. Ra=[4(δd X -δd Y ) 2 +(δp X -δp Y ) 2 +(δh X -δh Y ) 2 ] 1 / 2 δd i Dispersion force term of substance i δp i : Polarity term of substance i δh i : Hydrogen bonding term of substance i

[0018] The definition and calculation method of Hansen solubility parameters are described in "Hansen Solubility Parameters: A Users Handbook (CRC Press, 2007)" by Charles M. Hansen.

[0019] In this disclosure, the Hansen solubility parameter can be calculated using computer software (Hansen Solubility Parameters in Practice (HSPiP) version 5.3.05).

[0020] Specifically, 4 mL of each solvent listed in Table 1 is added to 4 mL of the sample to be measured. The sample to be measured may be a solvent-free resin or a solvent-containing varnish. From the viewpoint of minimizing or eliminating the influence of the properties of the sample to the measurement value, if the sample to be measured is a solvent-containing varnish, its kinematic viscosity at 25°C should be 100 to 15,000 mm². 2 The range is preferably / s. After adding the solvent, if it is dispersed or dissolved after standing for 30 minutes, it is judged to be a good solvent, and if it precipitates or is insoluble, it is judged to be a poor solvent. Based on these affinity evaluation results, Hansen solubility spheres are prepared using HSPiP (version 5.3.05) and the Hansen solubility parameter is calculated.

[0021] [Table 1]

[0022] The resin (A1) preferably contains one or more selected from the group consisting of polyester polyols, alkyd resins, and acrylic polyols.

[0023] The above-mentioned polyester polyol refers to a polymer having ester bonds within its molecule and two or more hydroxyl groups. Polyester polyols can be produced by conventional methods, for example, by condensing desired monomer components such as polybasic acids, polyhydric alcohols, hydroxycarboxylic acids, and their derivatives.

[0024] In this disclosure, the polyhydric alcohol refers to a compound having two or more hydroxyl groups in one molecule. Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol or 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, hydrogenated bisphenol A, hydroxyalkylated bisphenol A, 1,4-cyclohexanedimethanol, N,N-bis-(2-hydroxyethyl)dimethylhydantoin, 2 Examples include diols such as 2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate, neopentyl glycol hydroxypivalate, and lactone adducts thereof; and polyols having 3 or more hydroxyl groups per molecule, such as glycerin, sorbitol, annitol, trimethylolethane, trimethylolpropane, trimethylolbutane, hexanetriol, pentaerythritol, dipentaerythritol, tris-(hydroxyethyl)isocyanate, xylitol, and lactone adducts thereof. One polyhydric alcohol may be used alone, or two or more may be used in combination.

[0025] In this disclosure, a polybasic acid means a compound having two or more carboxyl groups in one molecule. Examples of the above polybasic acids include phthalic acid, phthalic anhydride, 3-methylphthalic acid, 3-methylphthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, methyltetraphthalic acid, methyltetrahydrophthalic anhydride, hymicic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, isophthalic acid, terephthalic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, adipic acid, azelaic acid, sebacic acid, succinic acid, succinic anhydride, lactic acid, dodecenyl succinic acid, dodecenyl succinic anhydride, cyclohexane-1,4-dicarboxylic acid, endoic anhydride, and the like. The above polybasic acids may be used individually or in combination of two or more.

[0026] Examples of the above-mentioned hydroxycarboxylic acids and / or derivatives include monohydroxycarboxylic acids such as glycolic acid, lactic acid, hydroxybutanoic acid, and hydroxypivalic acid; dihydroxycarboxylic acids such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylolbutyric acid, and 2,2-dimethylolvaleric acid; and lactones such as β-butyrolactone, β-propiolactone, β-dimethylpropiolactone, γ-butyrolactone, γ-dimethylbutyrolactone, δ-valerolactone, and ε-caprolactone. The above-mentioned hydroxycarboxylic acids and / or derivatives may be used individually or in combination of two or more.

[0027] When producing the above-mentioned polyester polyol, other monomers may be used in combination. Examples of other monomers include epoxy compounds, specifically glycidyl ester compounds such as glycidyl benzoate, t-butyl-glycidyl benzoate, p-glycidyl tolylate, glycidyl cyclohexanecarboxylic acid, glycidyl pelargonic acid, glycidyl neodecanoate, glycidyl stearate, glycidyl laurate, glycidyl palmitate, glycidyl behenate, glycidyl versatate, glycidyl oleate, glycidyl linoleate, glycidyl linolenic acid, glycidyl behenolate, and glycidyl stearolate; and glycidyl ether compounds. The above-mentioned other monomers may be used individually or in combination of two or more.

[0028] As the above-mentioned polyester polyol, modified polyester polyols can also be used, such as urethane-modified polyester polyol, epoxy-modified polyester polyol, acrylic-modified polyester polyol, and silicone-modified polyester polyol.

[0029] The hydroxyl value of the polyester polyol is preferably 1 mg KOH / g to 300 mg KOH / g, more preferably 4 mg KOH / g to 290 mg KOH / g. The higher the hydroxyl value of the polyester polyol, the easier it is to crosslink with isocyanate groups, and the higher the crosslinking density can be. As a result, it is easier to improve the hardness and durability of the coating film (especially chemical resistance and solvent rubbing resistance). Also, the lower the hydroxyl value, the less the coating film hardens, and the more flexible and processable the resulting coating film can be.

[0030] The acid value of the polyester polyol is preferably 0 mg KOH / g to 30 mg KOH / g, more preferably 0.1 mg KOH / g to 20 mg KOH / g. Having the acid value of the polyester polyol within this range ensures good storage stability of the coating composition (good coating properties, preferably less prone to precipitation during storage) and good hydrolysis resistance of the resulting coating film. In this disclosure, hydroxyl value and acid value refer to the hydroxyl value and acid value of the solids, and can be measured in accordance with JIS K 0070:1999.

[0031] The weight-average molecular weight of the polyester polyol is preferably 300 to 80,000, more preferably 400 to 50,000. The number-average molecular weight of the polyester polyol is preferably 200 to 50,000, more preferably 300 to 40,000. By having the weight-average molecular weight and / or number-average molecular weight of the polyester polyol within this range, the paint viscosity is optimized, resulting in good paint workability, and the reactivity with the isocyanate group is optimized, allowing for a balance between hardness and flexibility of the coating film. For example, the smaller the weight-average molecular weight and / or number-average molecular weight, the lower the paint viscosity can be, resulting in good paint workability and increased flexibility of the coating film. The larger the weight-average molecular weight and / or number-average molecular weight, the higher the hardness of the coating film can be. In this disclosure, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) are standard polystyrene equivalent values ​​measured by gel permeation chromatography.

[0032] The glass transition temperature of the polyester polyol is preferably between -50°C and 100°C, more preferably between -40°C and 90°C. Having the glass transition temperature of the polyester polyol within this range increases the hardness of the resulting coating film, improving durability, particularly scratch resistance. In this disclosure, the glass transition temperature can be measured by differential thermal scanning calorimetry.

[0033] In one embodiment, the polyester polyol content in the coating resin (A) is preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less. In another embodiment, the polyester polyol content in the coating resin (A) may be 0% by mass or more and 20% by mass or less, even more preferably 0% by mass or more and 10% by mass or less, or 0% by mass or more and 5% by mass or less.

[0034] The alkyd resins described above are typically polymers obtained by polycondensation of polyhydric alcohols, polybasic acids, and other acidic components.

[0035] Polyhydric alcohols used in the production of alkyd resins include compounds similar to those used in the production of polyester polyols.

[0036] Examples of polybasic acids used in the production of alkyd resins include compounds similar to those used in the production of polyester polyols.

[0037] Other acidic components mentioned above include unsaturated fatty acids and saturated fatty acids. Unsaturated fatty acids include fatty acids from drying and semi-drying oils such as linseed oil, safflower oil, soybean oil, sesame oil, poppy oil, oat oil, corn oil, tall oil, sunflower oil, cottonseed oil, tung oil, dehydrated castor oil, and rice bran oil; and synthetic unsaturated fatty acids such as hydene fatty acids. Saturated fatty acids include saturated fatty acids such as isononanoic acid, neodecanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, and linolenic acid.

[0038] The hydroxyl value of the alkyd resin is preferably 1 mg KOH / g to 300 mg KOH / g, more preferably 4 mg KOH / g to 290 mg KOH / g. The higher the hydroxyl value of the alkyd resin, the easier it is to crosslink with isocyanate groups, and the higher the crosslinking density can be. As a result, it is easier to improve the hardness and durability of the coating film (especially chemical resistance and solvent rubbing resistance). Furthermore, the lower the hydroxyl value, the less the coating film hardens, and the more flexible and processable the resulting coating film can be.

[0039] The acid value of the alkyd resin is preferably 0 mg KOH / g to 30 mg KOH / g, more preferably 0.1 mg KOH / g to 20 mg KOH / g. Having the alkyd resin's acid value within this range ensures good storage stability of the coating composition and good hydrolysis resistance of the resulting coating film.

[0040] The weight-average molecular weight of the alkyd resin is preferably 300 to 80,000, more preferably 400 to 50,000. The number-average molecular weight of the alkyd resin is preferably 200 to 50,000, more preferably 300 to 40,000. By having the weight-average molecular weight and / or number-average molecular weight of the alkyd resin within this range, the paint viscosity is optimized, resulting in good paint workability, and the reactivity with isocyanate is optimized, allowing for a balance of hardness and flexibility in the coating film. For example, the smaller the weight-average molecular weight and / or number-average molecular weight, the lower the paint viscosity can be, resulting in good paint workability and increased flexibility of the coating film. The larger the weight-average molecular weight and / or number-average molecular weight, the higher the hardness of the coating film can be.

[0041] The glass transition temperature of the alkyd resin is preferably between -50°C and 100°C, more preferably between -40°C and 90°C. By having the glass transition temperature of the alkyd resin within this range, the hardness of the resulting coating film can be increased, improving durability, particularly scratch resistance.

[0042] In one embodiment, the alkyd resin content in the coating resin (A) is preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less. In another embodiment, the alkyd resin content in the coating resin (A) may be 0% by mass or more and 20% by mass or less, even more preferably 0% by mass or more and 10% by mass or less, or 0% by mass or more and 5% by mass or less.

[0043] The above-mentioned acrylic polyol means a polymer having units derived from monomers having (meth)acryloyl groups and having two or more hydroxyl groups. Acrylic polyols can be prepared by polymerizing a monomer mixture containing monomers having ethylenically unsaturated bonds. In this disclosure, "(meth)acrylic" means acrylic and / or methacrylic.

[0044] The monomers having the ethylenically unsaturated bond include unsaturated carboxylic acids such as (meth)acrylic acid, crotonic acid, isocrotonic acid, 2-propenoic acid, ethacrylic acid, propylacrylic acid, and isopropylacrylic acid; unsaturated polycarboxylic acids such as maleic acid, fumaric acid, and itaconic acid (including their anhydrides); monoalkyl esters of unsaturated polycarboxylic acids such as ethyl maleate, butyl maleate, ethyl fumarate, butyl fumarate, ethyl itaconate, and butyl itaconate; methyl (meth)acrylate, ethyl (meth)acrylate, (methyl (Meth)Propyl acrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-pentyl methacrylate, neopentyl methacrylate, isopentyl methacrylate, sec-pentyl methacrylate, 3-pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, undecyl methacrylate Alkyl (meth)acrylate esters such as syl, dodecyl (meth)acrylate, and stearyl (meth)acrylate; (meth)acrylate esters having alicyclic hydrocarbon groups such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, tricyclodecyl (meth)acrylate, and adamantyl (meth)acrylate; hydroxy (meth)acrylate esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Lukil; (meth)acrylic acid esters having hydroxyl groups, such as these lactone adducts (e.g., ε-caprolactone); monomers having organosilyl groups, such as γ-(meth)acryloxypropyltrimethoxysilane, γ-(meth)acryloxypropylmethyldimethoxysilane, γ-(meth)acryloxypropyltriethoxysilane, γ-(meth)acryloxypropylmethyldiethoxysilane, vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane, and vinylmethyldithoxysilane;Monomers having sulfonic acid groups such as α-vinylbenzenesulfonic acid, p-(meth)acrylamidepropanesulfonic acid, t-butyl(meth)acrylamidesulfonic acid; monomers having phosphate groups such as (meth)acrylic acid ester nophosphate monoesters having the hydroxyl group; (meth)acrylamide monomers such as (meth)acrylamide, N-methylol(meth)acrylamide, methoxybutyl(meth)acrylamide, diacetone(meth)acrylamide; aminoethyl(meth)acrylamide, dimethylaminoethyl(meth)acrylamide, methylaminopropyl(meth) Examples include (meth)acrylamide monomers having an amino group such as acrylamide; (meth)acrylic acid esters having an epoxy group (oxyranyl group) such as glycidyl (meth)acrylate; (meth)acrylonitrile monomers such as (meth)acrylonitrile and α-chloro(meth)acrylonitrile; vinyl carboxylate esters such as vinyl acetate and vinyl propionate; styrene monomers such as styrene, α-methylstyrene, α-methylstyrene dimer, vinyltoluene, and divinylbenzene; carbonyl group monomers; and crosslinkable monomers such as polyfunctional vinyl monomers other than those mentioned above. The monomer having an ethylenically unsaturated bond may be used alone or in combination of two or more types.

[0045] The hydroxyl value of the acrylic polyol is preferably 1 mg KOH / g to 300 mg KOH / g, more preferably 4 mg KOH / g to 290 mg KOH / g. The higher the hydroxyl value of the acrylic polyol, the easier it is to crosslink with isocyanate groups, and the higher the crosslinking density can be. As a result, it is easier to improve the hardness and durability of the coating film (especially chemical resistance and solvent rubbing resistance). Also, the lower the hydroxyl value, the less the coating film hardens, and the more flexible and processable the resulting coating film can be.

[0046] The acid value of the acrylic polyol is preferably 0 mg KOH / g to 30 mg KOH / g, more preferably 0.1 mg KOH / g to 20 mg KOH / g. Having the acid value of the acrylic polyol within this range ensures good storage stability of the coating composition and good hydrolysis resistance of the resulting coating film.

[0047] The weight-average molecular weight of the acrylic polyol is preferably 300 to 80,000, more preferably 400 to 50,000. The number-average molecular weight of the acrylic polyol is preferably 200 to 50,000, more preferably 300 to 40,000. By having the weight-average molecular weight and / or number-average molecular weight of the acrylic polyol within this range, the paint viscosity is optimized, resulting in good paint workability, and the reactivity with isocyanate is optimized, allowing for a balance between hardness and flexibility of the coating film. For example, the smaller the weight-average molecular weight and / or number-average molecular weight, the lower the paint viscosity can be, resulting in good paint workability and increased flexibility of the coating film. The larger the weight-average molecular weight and / or number-average molecular weight, the higher the hardness of the coating film can be.

[0048] The glass transition temperature of the acrylic polyol is preferably between -50°C and 100°C, more preferably between -40°C and 90°C. Having the glass transition temperature of the acrylic polyol within this range increases the hardness of the resulting coating film, improving durability, particularly scratch resistance.

[0049] In one embodiment, the acrylic polyol content in the coating resin (A) is preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less. In another embodiment, the acrylic polyol content in the coating resin (A) may be 0% by mass or more and 20% by mass or less, even more preferably 0% by mass or more and 10% by mass or less, or 0% by mass or more and 5% by mass or less.

[0050] The total content of polyester polyol, alkyd resin, and acrylic polyol in resin (A1) is preferably 80% to 100% by mass, more preferably 90% to 100% by mass, and even more preferably 95% to 100% by mass, based on 100% by mass of the total amount of resin (A1).

[0051] The hydroxyl value of resin (A1) is preferably 1 mg KOH / g or more and 300 mg KOH / g or less, more preferably 4 mg KOH / g or more and 290 mg KOH / g or less. The higher the hydroxyl value of resin (A1), the easier it is to crosslink with isocyanate groups, and the higher the crosslinking density can be. As a result, it is easier to improve the hardness and durability of the coating film (especially chemical resistance and solvent rubbing resistance). Also, the lower the hydroxyl value, the less the coating film hardness will be, and the flexibility and processability of the resulting coating film can be improved.

[0052] The acid value of resin (A1) is preferably 0 mg KOH / g or more and 30 mg KOH / g or less, more preferably 0.1 mg KOH / g or more and 20 mg KOH / g or less. Having the acid value of resin (A1) within this range ensures good storage stability of the coating composition and good hydrolysis resistance of the resulting coating film.

[0053] The weight-average molecular weight of resin (A1) is preferably 300 to 80,000, more preferably 400 to 50,000. Having the weight-average molecular weight of resin (A1) within this range optimizes the paint viscosity, resulting in good paint workability, and also optimizes the reactivity with isocyanate, allowing for a balance of hardness and flexibility in the coating film. For example, a smaller weight-average molecular weight allows for lower paint viscosity, better paint workability, and increased flexibility of the coating film. A larger weight-average molecular weight allows for increased hardness of the coating film.

[0054] The glass transition temperature of resin (A1) is preferably between -50°C and 100°C, more preferably between -40°C and 90°C. Having the glass transition temperature of resin (A1) within this range increases the hardness of the resulting coating, improving durability, particularly scratch resistance.

[0055] The content of resin (A1) is preferably 80% to 100% by mass, more preferably 90% to 100% by mass, and even more preferably 95% to 100% by mass, out of 100% by mass of the total amount of coating resin (A).

[0056] The coating-forming resin (A) may contain other resins (A2) in addition to resin (A1). Examples of other resins (A2) include urethane resin, polyether resin, polystyrene resin, polyamide resin, polyimide resin, and polycarbonate resin.

[0057] [Hardening agent (B)] The curing agent (B) refers to a compound that contains at least two compounds in one molecule that can react with the active hydrogen groups contained in the resin (A1), and which reacts with the film-forming resin (A) to form a coating film.

[0058] The curing agent (B) contains a blocked isocyanate compound (B1). A blocked isocyanate compound refers to an isocyanate compound in which the isocyanate group is blocked with a encapsulant. By blocking the isocyanate group with a encapsulant, it is easy to ensure that the isocyanate compound is stably present in the composition.

[0059] The blocked isocyanate compound (B1) includes a blocked isocyanate compound in which the isocyanate group of pentamethylene diisocyanate is blocked with a encapsulant, and / or a blocked isocyanate compound in which the isocyanate group of a pentamethylene diisocyanate derivative is blocked with a encapsulant, preferably including a blocked isocyanate compound in which the isocyanate group of a pentamethylene diisocyanate derivative is blocked with a encapsulant.

[0060] By including a blocked isocyanate compound derived from pentamethylene diisocyanate, a highly hard coating can be obtained even under lower curing conditions. For example, when comparing the use of a blocked isocyanate compound derived from pentamethylene diisocyanate with the use of only blocked compounds of other polyisocyanate compounds (e.g., hexamethylene diisocyanate derivatives) for the same resin, if only blocked compounds of other diisocyanate compounds are used, the hardness of the coating may decrease when the curing temperature is lowered, even if the hardness of the coating is good when cured at high temperatures. In contrast, when a blocked isocyanate compound derived from pentamethylene diisocyanate is used, a coating with good hardness can be obtained even when the curing temperature is lowered.

[0061] In a blocked isocyanate compound, the encapsulant blocking the isocyanate group is released, generating the isocyanate group, which reacts with the active hydrogen group contained in the resin (A1) to form a coating film. In this disclosure, the number or amount of substance of isocyanate groups in the curing agent (B) refers to the total number or amount of substance of isocyanate groups present in the curing agent (B) and isocyanate groups blocked by the encapsulant (i.e., latent isocyanate groups).

[0062] In this disclosure, a pentamethylene diisocyanate derivative means a compound obtained by modifying pentamethylene diisocyanate and having an isocyanate group. A pentamethylene diisocyanate derivative preferably has one or more selected from the group consisting of a uretdione group, an isocyanurate group, an allophanate group, a biuret group, an iminooxadiazinedione group, an oxadiazinetrione group, a urethane bond, a urea bond, a carbodiimide bond, and a uretonimine bond, and more preferably has one or more selected from the group consisting of an isocyanurate group and a urethane bond.

[0063] Derivatives having a uretdione group, an allophanate group, a biuret group, an iminooxadiadindione group, or an oxadiadintrione group are also referred to as uretdione derivatives, allophanate derivatives, biuret derivatives, iminooxadiadindione derivatives, or oxadiadintrione derivatives, respectively, and are each produced by conventionally known methods.

[0064] Derivatives containing urethane bonds are typically obtained by reacting pentamethylene isocyanate with a polyol of trivalent or higher valentity, such as trimethylolpropane.

[0065] Derivatives containing an isocyanurate group are also called isocyanurates, and are typically obtained by isocyanurating pentamethylene diisocyanate in the presence of an isocyanuration catalyst.

[0066] Derivatives containing a urea bond are typically obtained by reacting pentamethylene diisocyanate with water and / or a polyamine.

[0067] Derivatives having a carbodiimide bond are typically obtained by dimerization of pentamethylene diisocyanate, while derivatives having a uretonimine bond are obtained by further reacting a derivative having a carbodiimide bond with pentamethylene diisocyanate.

[0068] In one embodiment, the number of isocyanate groups contained in the pentamethylene diisocyanate derivative is, on average, preferably 2 or more, more preferably 2.0 to 4.0, even more preferably 2.5 to 4.0, even more preferably 2.6 to less than 3, and even more preferably 2.7 to 2.9 per molecule. Having the number of isocyanate groups within this range is advantageous for improving compatibility with other components and the flexibility of the coating film.

[0069] In another embodiment, the number of isocyanate groups contained in the pentamethylene diisocyanate derivative is, on average, preferably 2 or more, more preferably 2.5 to 4.0, even more preferably 3.0 to 3.9, and even more preferably 3.1 to 3.8 per molecule. Having the number of isocyanate groups within this range results in good light resistance and durability of the resulting coating film.

[0070] The number of isocyanate groups in a pentamethylene diisocyanate derivative can be calculated based on the number-average molecular weight of the pentamethylene diisocyanate derivative, the isocyanate group content of the pentamethylene isocyanate derivative, and the formula weight of the isocyanate groups. Specifically, the following formula: Number of isocyanate groups in a pentamethylene diisocyanate derivative = Number-average molecular weight of pentamethylene diisocyanate derivative (g / mol) × Isocyanate group content of pentamethylene diisocyanate derivative (mass%) / 42 (g / mol) It can be calculated based on this. Furthermore, in this disclosure, the isocyanate group content (mass%) can be measured in accordance with Method A or Method B of JIS K 1603-1 (2007).

[0071] The number-average molecular weight of the above pentamethylene diisocyanate derivative is preferably 450 to 1,000, more preferably 460 to 900, even more preferably 470 to 800, and even more preferably 480 to 700.

[0072] The above-mentioned encapsulants include monohydric alkyl (or aromatic) alcohols such as n-butanol, n-hexyl alcohol, 2-ethylhexanol, lauryl alcohol, phenolcarbinol, and methylphenylcarbinol; cellosolves such as ethylene glycol monohexyl ether and ethylene glycol mono-2-ethylhexyl ether; polyether-type terminal diols such as polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycolphenol; polyester-type terminal polyols obtained from diols such as ethylene glycol, propylene glycol, and 1,4-butanediol, and dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, suberic acid, and sebacic acid; phenols such as para-t-butylphenol and cresol; dimethyl ketoxime, methyl ethyl ketoxime, methyl isobutyl ketoxime, and methyl Oximes such as lucetoxime and cyclohexanone oxime; lactams represented by ε-caprolactam and γ-butyrolactam; pyrazoles such as pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 3-methyl-5-phenylpyrazole; imidazoles or imidazoles such as imidazole, benzimidazole, 2-methylimidazole, 2-ethylimidazole, and 2-phenylimidazole; imidazolines such as 2-methylimidazoline and 2-phenylimidazoline; and amines such as diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, diisopropylamine, butylamine, dibutylamine, and butylphenylamine. The aforementioned sealing agent may be used alone or in combination of two or more types.

[0073] The blocking rate in the above-mentioned blocked isocyanate compound (B1) is preferably 80% to 100%, more preferably 90% to 100%, and even more preferably 95% to 100%.

[0074] The above-mentioned blocked isocyanate compound (B1) preferably has good affinity with the resin (A1). For example, the distance R of the Hansen solubility parameter between the resin (A1) and the blocked isocyanate compound. a Preferably 1.6 MPa 0.5 The above is 16.3 MPa. 0.5 Below is a comfortable 1.7 MPa. 0.5 Above 14.0 MPa 0.5 More preferably, 1.8 MPa 0.5 The above is 13.5 MPa. 0.5 More preferably, 2.0 MPa 0.5 The above is 13.0 MPa. 0.5 The following applies:

[0075] The content of the blocked isocyanate compound (B1) in the curing agent (B) is preferably 80% to 100% by mass, more preferably 90% to 100% by mass, and even more preferably 95% to 100% by mass, based on 100% by mass of the total amount of the curing agent (B).

[0076] The curing agent (B) may contain other curing agents (B2) in addition to the blocked isocyanate compound (B1). Examples of other curing agents (B2) include melamine resin, phenol resin, silane coupling agent, and metal curing agent.

[0077] As the pentamethylene diisocyanate used as a raw material for the blocked isocyanate compound (B1), a product manufactured or derived from biomass raw materials may be used. Commercial products of this type include the "Stavio" series. The paint composition of this disclosure contains a resin (A1) having active hydrogen groups and in which the hydrogen bonding terms constituting the Hansen solubility parameter are within a specific range. Therefore, even when biomass-derived pentamethylene diisocyanate is used as a raw material, a coating film with good physical properties can be obtained.

[0078] The biomass content of the hardening agent (B) is preferably greater than 0%, 1% or more, 5% or more, 15% or more, or 20% or more, and preferably greater than 0% and 70% or less, 1% or more and 60% or less, 5% or more and 50% or less, 15% or more and 40% or less, or 20% or more and 40% or less. In this disclosure, the biomass content can be measured in accordance with ASTM D6866.

[0079] The ratio (NCO / H ratio) of isocyanate groups contained in the curing agent (B) to active hydrogen groups contained in the film-forming resin (A) is preferably 0.9 to 3.0, more preferably 1.0 to 2.8, and even more preferably 1.4 to 2.5. Having this ratio (NCO / H ratio) within this range allows for the generation of a sufficient amount of isocyanate groups (isocyanate groups generated by the dissociation of the encapsulant) even with a short heating time during coating. This facilitates the crosslinking reaction with the active hydrogen groups contained in the resin (A1), resulting in a coating with good performance (e.g., water resistance) and durability (especially solvent rubbing resistance and scratch resistance).

[0080] In the coating composition for metal plates of this disclosure, the solid content is preferably 20% by mass or more and 80% by mass or less, more preferably 25% by mass or more and 75% by mass or less, and even more preferably 30% by mass or more and 72% by mass or less. In this disclosure, the solid content of a component means the residue after heating the component at 150°C for 1 hour.

[0081] The paint compositions of this disclosure may contain solvents. Examples of solvents include: water; glycol-based solvents such as ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monobutyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, and propylene glycol monomethyl ether acetate; alcohol-based solvents such as methanol, ethanol, isopropyl alcohol, isobutanol, and benzyl alcohol; ether-based solvents such as dioxane and tetrahydrofuran; ester-based solvents such as 3-methoxybutyl acetate, ethyl acetate, isopropyl acetate, and butyl acetate; ketone-based solvents such as methyl ethyl ketone, acetone, methyl isobutyl ketone, cyclohexanone, and isophorone; N-methyl-2-pyrrolidone, toluene, pentane, iso-pentane, hexane, iso-hexane, cyclohexane, solvent naphtha, mineral spirits, T-SOL 100 (manufactured by ENEOS Corporation), and T-SOL Examples include 150 (manufactured by ENEOS Corporation). Among these, cyclohexanone, butyl acetate, and T-SOL 100 are preferred. These solvents may be used individually or in combination of two or more.

[0082] The paint compositions disclosed herein may contain coloring pigments, extender pigments, and other additives as needed, depending on the purpose and application. However, other additives may be added in a manner that does not impair the various physical properties of the paint compositions disclosed herein.

[0083] When a coloring pigment is included, the pigment mass concentration of the coloring pigment is preferably 10% to 70% by mass, and more preferably 15% to 60% by mass, of 100% by mass of the solid content of the paint composition.

[0084] Other additives include, for example, curing catalysts such as p-toluenesulfonic acid, tin octoate, dibutyltin dilaurate, and lead 2-ethylhexoate; pigments such as calcium carbonate, kaolin, clay, titanium dioxide, talc, barium sulfate, mica, red iron oxide, manganese blue, carbon black, aluminum powder, and pearl mica; dispersants; waxes; defoamers; leveling agents; thickeners; plasticizers; antioxidants; UV absorbers; anti-repellent agents; and anti-leaching agents.

[0085] The coating composition for metal plates of this disclosure can be manufactured by methods commonly used by those skilled in the art, such as kneading and dispersing a film-forming resin (A) and a curing agent (B) with other components as needed using a disperser, homogenizer, kneader, etc.

[0086] The biomass content of the solids in the coating composition of this disclosure is preferably greater than 0%, 0.1% or more, or 0.5% or more, and there is no upper limit, but it is preferably greater than 0% and 80% or less, 0.1% or more and 60% or less, or 0.5% or more and 50% or less.

[0087] (subject to be coated) The substrates to be coated with the coating compositions for metal sheets of this disclosure are not limited to metal sheets (for example, metal sheets that require corrosion resistance). Examples include steel sheets that serve as base materials for pre-coated metal (painted steel sheets) and / or post-coated metal. Examples of steel sheets include galvanized steel sheets, cold-rolled steel sheets, stainless steel sheets, and aluminum sheets (including aluminum alloy sheets). Examples of zinc-plated steel sheets include zinc-containing plated steel sheets that utilize zinc sacrificial corrosion protection, specifically hot-dip galvanized steel sheets, electro-galvanized steel sheets, alloyed hot-dip galvanized steel sheets, aluminum-zinc plated steel sheets, nickel-zinc plated steel sheets, magnesium-aluminum-zinc plated steel sheets, and magnesium-aluminum-silica-zinc plated steel sheets.

[0088] The metal sheet relating to this disclosure is preferably surface-treated. Specifically, the metal sheet relating to this disclosure is preferably subjected to a chemical conversion treatment after undergoing a pretreatment such as alkaline degreasing, hot water washing, or water washing. The chemical conversion treatment may be carried out by known methods, and examples include chromate treatment, zinc phosphate treatment, and other non-chromate treatments.

[0089] The technical scope of this disclosure also includes painted articles comprising a metal plate and a coating film disposed on the surface of the metal plate and formed from the metal plate coating composition of this disclosure.

[0090] If the above-mentioned painted article has a coating film formed from the paint composition of this disclosure on one surface, the other surface may have a coating film formed from a known paint composition. For example, the other surface may have a film formed from a known paint composition, such as a paint composition containing epoxy resin and / or polyester resin.

[0091] The above-mentioned painted article may further have an undercoat between the metal plate and the coating film formed from the paint composition of this disclosure. Having an undercoat enhances the adhesion and corrosion resistance of the coating film formed from the paint composition of this disclosure. Furthermore, it can more strongly reinforce the properties of the coating film formed from the paint composition of this disclosure, thereby increasing the durability of the metal plate.

[0092] In one embodiment, the undercoat film preferably contains epoxy resin, polyester resin, or urethane resin. In another embodiment, the thickness of the undercoat film is 3 μm to 15 μm, for example, 5 μm to 10 μm.

[0093] (Coating film formation method) The coating of the coating composition disclosed herein can be carried out using a roll coater, airless sprayer, electrostatic sprayer, curtain flow coater, etc., and preferably using a roll coater or curtain flow coater. After coating, the coating film is baked by heating means such as hot air heating, infrared heating, or induction heating to crosslink the resin and obtain a coating film.

[0094] The painted articles of this disclosure can be manufactured by a manufacturing method that includes applying the paint composition of this disclosure to at least one surface of a metal plate to be painted, such that the thickness after curing is, for example, 2 μm or more and 200 μm or less, to obtain a painted film, and drying and curing the painted film under conditions where the maximum temperature attainable by the material (metal plate) is 50°C or more and 270°C or less, and the drying and curing time is 10 seconds or more and 60 minutes or less, to obtain a painted film.

[0095] The maximum temperature reached by the material is preferably between 50°C and 270°C. The drying and curing time is preferably between 10 seconds and 60 minutes.

[0096] The coating compositions of this disclosure are also preferably used for coated articles having two or more coating layers. In one embodiment, the coating compositions of this disclosure can be used as a topcoat in a two-coat, two-bake or three-coat, three-bake system. When used in a three-coat, three-bake system, it is preferable to provide an intermediate coating layer, as is typically done in a three-coat, three-bake system, between the coating layer of the coating composition for metal plates of this disclosure and the primer coating layer (undercoat).

[0097] When forming a coating film by post-coating, methods such as roll coaters, airless sprayers, electrostatic sprayers, and curtain flow coaters can be used to apply the coating composition to the substrate.

[0098] A coating film formed by post-coating can be created by applying the paint composition to a metal plate, which is the object to be coated, and then performing a baking treatment (drying and curing) by heating the metal, or by curing by drying at room temperature. The baking temperature (the highest temperature reached by the metal plate, i.e., the highest temperature the material can reach) is, for example, 50°C to 180°C. By curing the paint composition of this disclosure at such a temperature, a coating film with sufficient strength can be formed. By forming a coating film with sufficient strength, it is possible to further demonstrate excellent rust prevention over a long period of time and to form a coating film that exhibits excellent moisture resistance.

[0099] When forming a coating film by post-coating, the baking time (drying and curing time) is, for example, 10 to 60 minutes. For example, when forming a multi-layer coating film consisting of two layers, a primer coating film and a topcoat coating film, the coating composition of this disclosure can be used as at least one (preferably the topcoat coating composition) or both of the primer coating composition and the topcoat coating composition. Such a multi-layer coating film may be formed by applying the primer coating composition, baking it, then applying the topcoat coating composition, and baking or drying the topcoat coating film at room temperature, or by applying the primer coating composition, then applying the topcoat coating composition wet-on-wet without baking, and simultaneously baking or drying at room temperature. In addition, when only the topcoat coating composition is applied without applying the primer coating composition, the topcoat coating film may be baked or dried at room temperature.

[0100] When forming a coating film by pre-coating, methods such as roll coaters, airless sprayers, electrostatic sprayers, and curtain flow coaters can be used to apply the coating composition to the object to be coated.

[0101] A coating film formed by pre-coating can be created by applying the paint composition to a workpiece such as a steel plate, and then performing a baking treatment by heating the workpiece. The baking temperature (the maximum temperature reached by the workpiece such as a steel plate) is, for example, 150°C to 270°C. By curing the paint composition of this disclosure at such a temperature, a coating film with sufficient strength can be formed. By forming a coating film with sufficient strength, it is possible to further demonstrate excellent rust prevention over a long period of time and to form a coating film that exhibits excellent moisture resistance.

[0102] When forming a coating film by pre-coating, the baking time (curing time) is, for example, 10 to 200 seconds. For example, when forming a multi-layer coating film consisting of two layers, a primer coating film and a topcoat coating film, the primer coating composition may be applied and then baked, and then the topcoat coating composition may be applied and the topcoat coating film baked, or the primer coating composition may be applied, and then the topcoat coating composition may be applied wet-on-wet without baking, and baked simultaneously.

[0103] After the baking process, the painted product can be obtained by cooling it to room temperature. For cooling after the baking process, it is preferable to rapidly cool the plate temperature to room temperature using water.

[0104] The film thickness of the coating on painted articles can be, for example, 2 μm to 200 μm. For example, when the coating is formed by pre-coating, it is preferably 5 μm to 80 μm, and in one embodiment, it may be, for example, 10 μm to 25 μm, or even 15 μm to 23 μm. When the coating is formed by post-coating, it is preferably 50 μm to 150 μm. When the film thickness of the coating is within this range, the processability, aesthetics, and weather resistance of the resulting coating are better.

[0105] The applications of the metal plate coating composition disclosed herein are not particularly limited, but are preferably used in, for example, building materials, automobile parts, construction machinery, agricultural machinery, electrical equipment, kitchen appliances, office equipment, etc. [Examples]

[0106] The present invention will be further described in detail by the following examples, but the present invention is not limited thereto.

[0107] Manufacturing Example 1-1: Manufacturing of coating-forming resin (a10) In a reactor equipped with a stirrer, thermometer, nitrogen inlet tube, reflux tube, and water divider, 303.7 parts by mass of trimethylolpropane, 307.2 parts by mass of neopentyl glycol, 134.5 parts by mass of 1,6-hexanediol, 166.2 parts by mass of adipic acid, 263.0 parts by mass of isophthalic acid, 367.4 parts by mass of hexahydrophthalic anhydride, 133.5 parts by mass of product name "Cardura E10P" (glycidyl ester of branched synthetic fatty acid, manufactured by Hexion), and 0.33 parts by mass of dibutyltin oxide were charged. After heating and draining the initial distillate, the temperature was raised to 230°C over 3 hours and held at the same temperature for 4 hours. Then, 376.0 parts by mass of xylene were added and the mixture was uniformly stirred to obtain a polyester polyol varnish (solid content 79% by mass).

[0108] Manufacturing Example 1-2: Manufacturing of coating-forming resin (a2) In a reactor equipped with a stirrer, thermometer, nitrogen inlet tube, reflux tube, and water divider, 299.3 parts by mass of product name "Cardura E10P" (glycidyl ester of branched synthetic fatty acid, manufactured by Hexion Corporation), 147.5 parts by mass of neopentyl glycol, 201.2 parts by mass of trimethylolpropane, 177.3 parts by mass of adipic acid, 426.7 parts by mass of phthalic anhydride, and 35.5 parts by mass of xylene were charged, and heating was started. While taking care to prevent overheating, the temperature was raised to 220-225°C over 3 hours once reflux began. The mixture was held at the same temperature for 6 hours, after which 530.3 parts by mass of product name "T-SOL 150" (manufactured by ENEOS), 85.7 parts by mass of product name "Dawanol PMA" (manufactured by DOW), 36.7 parts by mass of product name "Eucalysine EEP" (manufactured by DOW), and 127.6 parts by mass of xylene were added and the mixture was uniformly stirred to obtain a polyester polyol varnish (solid content 60% by mass).

[0109] Manufacturing Example 1-3: Manufacturing of coating-forming resin (a6) In a reactor equipped with a stirrer, thermometer, nitrogen inlet tube, reflux tube, and water divider, 331.4 parts by mass of neopentyl glycol, 310.4 parts by mass of 1,6-hexanediol, 50.3 parts by mass of trimethylolpropane, 142.1 parts by mass of adipic acid, 390.0 parts by mass of isophthalic acid, 277.1 parts by mass of phthalic anhydride, and 0.28 parts by mass of dibutyltin oxide were charged and heated to dissolve. Then, after the initial distillation was discharged, the temperature was slowly raised to 220°C over 3 hours.

[0110] After confirming that the contents were clear, 42.1 parts by mass of xylene was added, and cooling was started when the desired acid value was obtained. Then, 258.5 parts by mass of xylene, 150.3 parts by mass of product name "T-SOL 150" (manufactured by ENEOS Corporation), and 150.3 parts by mass of product name "Danoir PMA" (manufactured by DOW) were added to dilute the mixture and obtain a polyester polyol varnish (solids content 70% by mass).

[0111] Manufacturing Example 1-4: Manufacturing of coating-forming resin (a7) In a reactor equipped with a stirrer, thermometer, nitrogen inlet tube, reflux tube, and water divider, 205.7 parts by mass of trimethylolpropane, 282.9 parts by mass of neopentyl glycol, 200.2 parts by mass of 1,6-hexanediol, 613.8 parts by mass of isophthalic acid, 232.2 parts by mass of adipic acid, and 0.27 parts by mass of dibutyltin oxide were added, and heating was started. After the initial distillation was discharged, the temperature was raised to 210°C over 3 hours, and at 210°C, 40.2 parts by mass of xylene were gradually added. Heating was continued, and cooling was started when the desired viscosity was obtained. 271.9 parts by mass of product name "T-SOL 150" (manufactured by ENEOS) and 348.3 parts by mass of butanol were added to dilute the mixture, and a polyester polyol varnish (solid content 67% by mass) was obtained.

[0112] Manufacturing Example 1-5: Manufacturing of coating-forming resin (a3) 576.4 parts by mass of butyl acetate was charged into a reactor equipped with a stirrer, thermometer, and nitrogen inlet tube while nitrogen gas was blown in, and the mixture was heated to 120°C. The temperature of the polymerization reaction was controlled to 120°C ± 2°C. A monomer mixture (345.8 parts by mass of styrene, 214.0 parts by mass of 2-hydroxyethyl methacrylate, 25.5 parts by mass of n-butyl acrylate, 488.8 parts by mass of n-butyl methacrylate, 71.7 parts by mass of methyl methacrylate, and 7.0 parts by mass of methacrylic acid) and an initiator solution (149.9 parts by mass of t-butyl peroxy-2-ethylhexanoate and 92.2 parts by mass of butyl acetate) were added dropwise at a constant rate over 3 hours. Next, the mixture was kept warm for 30 minutes, after which an initiator solution (5.8 parts by mass of t-butyl peroxy-2-ethylhexanoate and 23.1 parts by mass of butyl acetate) was added dropwise over 30 minutes, and then the mixture was kept warm for 60 minutes. After that, it was cooled to 60°C to obtain an acrylic polyol varnish (solids content 61% by mass).

[0113] Manufacturing Example 1-6: Manufacturing of coating-forming resin (a9) In a reactor equipped with a stirrer, thermometer, nitrogen inlet tube, reflux tube, and water divider, 466.1 parts by mass of trimethylolpropane, 41.2 parts by mass of neopentyl glycol, 258.9 parts by mass of isononanoic acid, 67.3 parts by mass of 1,6-hexanediol, 83.1 parts by mass of adipic acid, 297.2 parts by mass of hexahydrophthalic anhydride, 212.7 parts by mass of isophthalic acid, and 0.26 parts by mass of dibutyltin oxide were charged and heated to dissolve. After reaching 160°C, the mixture was heated further and slowly heated until the internal temperature reached 230-240°C. During the heating process, 13.0 parts by mass of xylene was added dropwise. Cooling was started when the desired acid value was obtained, 687.0 parts by mass of xylene was added, and the mixture was uniformly stirred to obtain an alkyd resin varnish (solid content 65% by mass).

[0114] Manufacturing Example 2-1: Manufacturing of hardener (b1) 47.4 parts by mass of product name "Stabio D-370N" (pentamethylene diisocyanate-based isocyanurate, biomass content 71%, non-volatile content 100% by mass, manufactured by Mitsui Chemicals, the same applies hereinafter), 17.0 parts by mass of product name "T-SOL 100" (manufactured by ENEOS Corporation), and 8.0 parts by mass of propylene glycol monomethyl ether acetate were charged into a reactor and heated to 60°C. While maintaining the reactor temperature at 60°C, 27.6 parts by mass of 3,5-dimethylpyrazole were added dropwise over 2 hours. After further heating at 70°C for 4 hours, the absorption corresponding to the isocyanate group was confirmed to have disappeared by IR spectroscopy, and the mixture was allowed to cool to obtain a solution containing blocked isocyanate (solid content 75% by mass).

[0115] Manufacturing Example 2-2: Manufacturing of Hardener (b2) 49.6 parts by mass of product name "Stavio D-370N" and 25.4 parts by mass of xylene were charged into a reactor and heated to 60°C. While maintaining the reactor temperature at 60°C, 25.0 parts by mass of methyl ethyl ketoxime were added dropwise over 2 hours. After further heating at 70°C for 4 hours, the absorption corresponding to the isocyanate group was confirmed to have disappeared by IR spectroscopy, and the mixture was allowed to cool to obtain a solution containing blocked isocyanate (solid content 75% by mass).

[0116] Manufacturing Example 2-3: Manufacturing of hardener (b3) 46.6 parts by mass of product name "Stavio D-370N" and 24.9 parts by mass of xylene were charged into a reactor and heated to 60°C. While maintaining the reactor temperature at 60°C, 28.4 parts by mass of diisopropylamine were added dropwise over 2 hours. After further heating at 70°C for 4 hours, the absorption corresponding to the isocyanate group was confirmed to have disappeared by IR spectroscopy, and the mixture was allowed to cool to obtain a solution containing blocked isocyanate (solid content 75% by mass).

[0117] Manufacturing Example 2-4: Manufacturing of hardener (b'1) 49.7 parts by mass of product name "Sumijool N3300" (hexamethylene diisocyanate-based isocyanurate, 0% biomass content, manufactured by Sumika Bayer Urethane, the same applies hereinafter), 17.0 parts by mass of product name "T-SOL 100" (manufactured by ENEOS Corporation), and 8.0 parts by mass of propylene glycol monomethyl ether acetate were charged into a reactor and heated to 60°C. 25.3 parts by mass of 3,5-dimethylpyrazole were added dropwise over 2 hours. After further heating at 70°C for 4 hours, the absorption based on the isocyanate group was confirmed to have disappeared by measuring the IR spectrum, and a solution containing blocked isocyanate (solid content 75% by mass) was obtained.

[0118] Manufacturing Example 2-5: Manufacturing of Hardener (b'2) 48.9 parts by mass of product "Sumijoule N3300" and 25.0 parts by mass of xylene were charged into a reactor and heated to 60°C. While maintaining the reactor temperature at 60°C, 26.1 parts by mass of diisopropylamine were added dropwise over 2 hours. After further heating at 70°C for 4 hours, the absorption based on the isocyanate group was confirmed to have disappeared by measuring the IR spectrum, and a solution containing blocked isocyanate (solid content 75% by mass) was obtained.

[0119] The components used in the examples and comparative examples were as follows: The film-forming resin (A), curing agent (B), and dispersant (C) were used as varnish, solution, or dispersion in the preparation of the paint composition. Paint film forming resin (A) (a1): Polyester polyol 1 (product name "Byron GC-63CS", manufactured by Toyobo MC Co., Ltd., solids hydroxyl value 5 mg KOH / g, solids acid value 2 mg KOH / g, Tg 7℃, Mn 23,000, solids 33% by mass, δ h = 3.6 MPa 0.5 ) (a2): Polyester polyol 2 (Polyester polyol from Production Example 1-2, solids hydroxyl value 86 mg KOH / g, solids acid value 15 mg KOH / g, Mn 3,700, solids 60% by mass, δ h = 4.4 MPa 0.5 , δ d = 17.4 MPa0.5 、 δ p = 10.6 MPa 0.5 、 HSP = 20.9 MPa 0.5 ) ·(a3): Acrylic polyol 1 (acrylic polyol of Production Example 1-5, solid content hydroxyl value 80 mgKOH / g, solid content acid value 4 mgKOH / g, Mw 6,100, Mn 3,000, solid content 61 mass%, δ h = 5.0 MPa 0.5 、 δ d = 21.8 MPa 0.5 、 δ p = 13.1 MPa 0.5 、 HSP = 25.9 MPa 0.5 ) ·(a4): Acrylic polyol 2 (product name "Dianal SE-5655", manufactured by Mitsubishi Chemical Corporation, solid content hydroxyl value 8.6 mgKOH / g, solid content acid value 10 mgKOH / g, Tg 27 °C, Mw 24,900, Mn 8,800, solid content 50 mass%, δ h = 7.0 MPa 0.5 ) ·(a5): Polyester polyol 3 (product name "Vylon GK-78CS", manufactured by Toyobo Co., Ltd., solid content hydroxyl value 11 mgKOH / g, solid content acid value 3.4 mgKOH / g, Tg 39 °C, Mw 32,100, Mn 12,300, solid content 40 mass%, δ h = 7.3 MPa 0.5 ) ·(a6): Polyester polyol 4 (polyester polyol of Production Example 1-3, solid content hydroxyl value 112 mgKOH / g, solid content acid value 15 mgKOH / g, Mn 1,000, solid content 70 mass%, δ h = 8.7 MPa 0.5 、 δ d = 17.0 MPa 0.5 、 δ p = 10.9 MPa 0.5 、 HSP = 22.0 MPa 0.5 ) ·(a7): Polyester polyol 5 (polyester polyol of Production Example 1-4, solid content hydroxyl value 126 mgKOH / g, solid content acid value 10 mgKOH / g, Mn 1,500, solid content 67 mass%, δ h = 9.0 MPa 0.5 、 δd = 15.4 MPa 0.5 and δ p = 10.5 MPa 0.5 and HSP = 20.7 MPa 0.5 ) ·(a8): Acrylic polyol 3 (Product name "Acridic BU - 955", manufactured by DIC Corporation, solid content hydroxyl value 122 mgKOH / g, solid content acid value 8 mgKOH / g, Tg 46°C, Mw 26,000, Mn 4,800, solid content 60% by mass, δ h = 9.0 MPa 0.5 and δ d = 18.9 MPa 0.5 and δ p = 14.1 MPa 0.5 and HSP = 25.2 MPa 0.5 ) ·(a9): Alkyd resin (Alkyd resin of Production Example 1 - 6, solid content hydroxyl value 148 mgKOH / g, solid content acid value 17 mgKOH / g, Mn 1,300, solid content 65% by mass, δ h = 9.5 MPa 0.5 and δ d = 18.7 MPa 0.5 and δ p = 14.0 MPa 0.5 and HSP = 25.2 MPa 0.5 ) ·(a10): Polyester polyol 6 (Polyester polyol of Production Example 1 - 1, solid content hydroxyl value 228 mgKOH / g, solid content acid value 20 mgKOH / g, Mn 700, solid content 79% by mass, δ h = 10.7 MPa 0.5 and δ d = 19.1 MPa 0.5 and δ p = 16.1 MPa 0.5 and HSP = 27.2 MPa 0.5 ) ·(a11): Acrylic polyol 4 (Product name "Hitroid 3509A", manufactured by Resonaak Corporation, solid content hydroxyl value 71 mgKOH / g, solid content acid value 8 mgKOH / g, Tg 50°C, Mw 20,000, Mn 6,400, solid content 55% by mass, δ h = 11.2 MPa 0.5 ) • (a12): Polyester polyol 7 (product name "Barnock EQD-1097", manufactured by DIC Corporation, solids hydroxyl value 290 mg KOH / g, solids acid value 8.0 mg KOH / g, solids 78% by mass, δ h = 13.0 MPa 0.5 ) • (a'1): Fluorine-containing acrylic polyol (product name "Zeffle GK-570", manufactured by Daikin Industries, Ltd., solids acid value 5.4 mg KOH / g, solids hydroxyl value 97 mg KOH / g, solids 65% by mass, δ h = 3.3 MPa 0.5 , δ d = 19.6 MPa 0.5 , δ p = 7.9 MPa 0.5 HSP = 21.4 MPa 0.5 ) Hardener (B) (b1): Blocked isocyanate from Production Example 2-1 (solution with 75% solid content by mass) • (b2): Blocked isocyanate from Production Example 2-2 (solution with 75% solid content by mass) • (b3): ​​Blocked isocyanate from manufacturing example 2-3 (solution with 75% solid content by mass) • (b'1): Blocked isocyanate from manufacturing example 2-4 (solution with 75% solid content by mass) • (b'2): Blocked isocyanate from manufacturing example 2-5 (solution with 75% solid content by mass) Pigment (C) • (c1): Typeque CR-97 (titanium dioxide, manufactured by Ishihara Sangyo Co., Ltd., solid content 100% by mass) Dispersant (D) • (d1): DISPERBYK-161 (manufactured by Bic Chemie Japan, solids content 30% by mass) Curing catalyst (E) (e1): Neostan U-100 (manufactured by Nitto Kasei Co., Ltd., dibutyltin dilaurate, 100% by mass of active ingredient) Solvent (F) (f1): Cyclohexanone • (f2): Butyl acetate (manufactured by JNC Corporation) • (f3): T-SOL 100 (manufactured by ENEOS Corporation)

[0120] The hydrogen bonding term δ that constitutes the Hansen solubility parameter (HSP) in this embodiment h , and the distance R of the Hansen solubility parameter a The values ​​were measured using the method described above (shown in Tables 2 and 3).

[0121] Example 1 A dispersion composition was prepared by mixing the film-forming resin (a1), pigment (c1), and dispersant (d1) listed in Table 1 with 23.0 parts by mass of organic solvent (f1) and 23.0 parts by mass of organic solvent (f3), and dispersing them using a sand mill (dispersion medium: glass beads) until the maximum particle size of the pigment coarse particles was 10 μm or less. A curing agent (b2) and curing catalyst (e1) were added to the obtained dispersion composition and uniformly mixed with a disperser to prepare a paint composition. The amount of curing agent (b2) was set so that the ratio of isocyanate groups (including latent isocyanate groups) contained in it to the active hydrogen groups contained in the film-forming resin (a1) (NCO / H ratio) was the value shown in Table 2, and the same was true for other examples and comparative examples.

[0122] Separately, chromate treatment is applied to both the front and back surfaces (coating amount: 150 mg / m²). 2 On the back side of a plate to be coated (zinc-aluminum alloy plated steel sheet; 300mm x 200mm x 0.35mm) that had been treated with ), Super Rack R-90 (manufactured by Nippon Paint Industrial Coatings, Inc., epoxy resin-based paint) was applied using a bar coater to a dry film thickness of 5 μm, and then baked for 40 seconds at a maximum material temperature of 210°C to form a back surface coating. On the other hand, on the front surface, Fine Tough G Primer (manufactured by Nippon Paint Industrial Coatings, Inc., epoxy resin-based primer) was applied using a bar coater to a dry film thickness of 5 μm, and then baked for 40 seconds under conditions that resulted in a maximum material temperature of 210°C to form a primer coating, thus preparing the object to be coated.

[0123] The paint composition obtained above was applied to the surface (undercoat side) of the above-mentioned workpiece using a bar coater to a dry film thickness of 15 μm. Then, the workpiece was baked for 40 seconds under conditions that the maximum temperature reached by the material (workpiece) was 230°C, thereby obtaining a paint film and a test plate (painted article) having the paint film.

[0124] Examples 2-9, Comparative Examples 1-3 A paint composition and test board were obtained in the same manner as in Example 1, except that the components and conditions were changed according to Table 2.

[0125] Examples 10-17, Comparative Examples 4,5 A paint composition was obtained in the same manner as in Example 1, except that each component was changed according to Table 3, and 12.0 parts by mass of organic solvent (f2) was used instead of 23.0 parts by mass of organic solvent (f1) and 23.0 parts by mass of organic solvent (f3) in Example 1. Test plates using these paint compositions were prepared by the following method. A JIS G 3141 (SPCC-SB) cold-rolled steel sheet with a bright finish, measuring 0.8 mm x 70 mm x 150 mm, was polished and degreased with xylene. Next, as a solvent-type primer, Olga Select 30 NC Primer P-2 (urethane-modified epoxy resin undercoat paint; manufactured by Nippon Paint Industrial Coatings Co., Ltd.) was applied using an air spray to achieve a dry film thickness of 20 μm, and dried at 160°C for 20 minutes. Subsequently, the paint composition obtained above was applied to the steel sheet using an air spray to achieve a dry film thickness of 55 μm, forming an undried paint film. After being left at room temperature (23°C) for 10 minutes, it was dried for 20 minutes under heating conditions that resulted in the maximum temperature of the material being as shown in Table 3 (forced drying) to obtain a test plate (painted article) with a paint film.

[0126] The amounts listed in Tables 2 and 3 represent the amounts calculated on a solid content basis.

[0127] The following evaluations were performed on each paint composition. The results are shown in Tables 2 and 3.

[0128] (1) Paint properties The paint compositions obtained in each example and comparative example were placed in 200 mL round cans and left to stand in a 50°C constant temperature oven for 14 days. The properties of the paints thereafter were visually observed and evaluated according to the following criteria. ○ (Good): The paint composition is uniformly maintained. △ (Slightly Poor): Soft sediment (soft caking) occurs in the paint composition. × (Defective): Hard sediment (hard caking) occurs in the paint composition.

[0129] (2) Appearance of the coating The appearance of the coating film on the test plates obtained in each example and comparative example was visually observed and evaluated according to the following criteria. ○ (Good): No unevenness in the paint film. △ (Slightly Poor): Unevenness exists only in a portion of the paint film. × (Defective): Unevenness is present across the entire surface of the coating.

[0130] (3) Pencil hardness The surface of the coating obtained from each example and comparative example was measured for pencil hardness in a room at 23°C according to JIS K5600-5-4 (1999), scratch hardness (pencil method), and evaluated according to the following criteria. 〇(Good): Pencil hardness H or higher △ (Slightly poor): Pencil hardness HB or F × (defective): Pencil hardness 2B or less

[0131] (4) Processability (Examples 1-9, Comparative Examples 1-3) The test plates obtained in each example and comparative example were cut to a width of 50 mm, and a processability test was conducted in a room at 23°C. Specifically, several plates to be coated, with the same thickness (0.35 mm) as the test piece to be processed, were sandwiched inside the test piece to be processed (with the coated surface facing outwards), and then tightly folded 180 degrees. The processed area was observed and evaluated with a 10x magnifying glass. The case where three plates to be coated are sandwiched together was defined as "3T," and the minimum value at which no cracks were observed in the processed area was used as the machinability evaluation result. For example, an evaluation of "4T" indicates a case where no cracks were observed in the processed area at 4T, but cracks were observed in the processed area at 3T. Furthermore, based on the above machinability evaluation results, the machinability was evaluated according to the following criteria. ○ (Good): 1T or 2T △ (Slightly Poor): 3T or 4T × (Defective): Poor machinability compared to 5T

[0132] (5) Chemical resistance • Test plates (Examples 1-9, Comparative Examples 1-3) Each test panel was immersed in a 5% sodium hydroxide aqueous solution at 20°C for 24 hours, and the appearance of the coating was visually evaluated. The evaluation criteria were as follows: ○ (Good): Blister area is 0% to 5% △ (Slightly Poor): Blistering area is more than 5% but less than or equal to 50% × (Defective): Blistering area exceeds 50%

[0133] • Test plates (Examples 10-17, Comparative Examples 4-5) Each test panel was immersed in a 3% sodium hydroxide aqueous solution at 20°C for 72 hours, and the appearance of the coating was visually evaluated. The evaluation criteria were as follows: ○ (Good): Blister area is 0% to 5% △ (Slightly Poor): Blistering area is more than 5% but less than or equal to 50% × (Defective): Blistering area exceeds 50%

[0134] Furthermore, the hardness of the test plates obtained in Examples 10-17 and Comparative Examples 4 and 5 was measured before and after immersion in a 3% sodium hydroxide aqueous solution at 20°C for 72 hours using the scratch hardness (pencil method) according to JIS K5600-5-4 (1999), and the change in hardness before and after immersion (how many ranks it decreased) is recorded in the table. The hardness levels, from softest to hardest, are 2B, B, HB, F, H, 2H, 3H, and 4H, with a smaller decrease in hardness indicating better chemical resistance. A rank decrease of 2 or less was evaluated as ○ (good), and a rank decrease of 3 or more was evaluated as × (poor).

[0135] (6) Effect of reducing environmental impact Products containing components derived from biomass raw materials were evaluated as having an environmental impact reduction effect (○), while products not containing such components were evaluated as having no environmental impact reduction effect (×).

[0136] (7) Overall evaluation Based on the above evaluation results, an overall evaluation of the paint and coating film was conducted according to the following criteria. ◎ (Excellent): The evaluation results do not include either × (Poor) or △ (Somewhat Poor). ○ (Good): The evaluation results do not include × (Poor), but include one or more △ (Slightly Poor). × (Poor): The above evaluation results include one or more × (Poor) marks.

[0137] [Table 2]

[0138] [Table 3]

[0139] Furthermore, the hydrogen bonding term δ in the Hansen solubility parameters of the above resins (a1) to (a12) and (a'1) is... h ( MPa 0.5 The results were as shown in the table above. On the other hand, when comparing the solubility parameters (SP values) of these resins measured by the following method, for example, resin (a1) was 10.5 (cal / cm³). 3 ) 1 / 2 For resin (a2), it is 11.0 (cal / cm²). 3 ) 1 / 2 For resin (a3), it is 10.1 (cal / cm³). 3 ) 1 / 2 For resin (a6), it was 11.0 (cal / cm²). 3 ) 1 / 2 For resin (a10), it is 10.6 (cal / cm³). 3 ) 1 / 2 Therefore, no correlation was found between the properties of the paint composition and the physical properties of the paint film.

[0140] The above solubility parameters (SP values) were measured using the following method. [Method for measuring solubility parameters] For the sample, 0.5 g of the substance to be measured was weighed into a 100 mL beaker, 10 mL of a good solvent (acetone) was added using a volumetric pipette, and the substance was dissolved using a magnetic stirrer. To this sample, a poor solvent was added dropwise using a 50 mL burette at a measurement temperature of 20°C, and the point at which turbidity occurred was recorded as the volume added. Deionized water was used as the high SP poor solvent, and n-hexane was used as the low SP poor solvent, and the turbidity points of each were measured. Solubility parameter of the substance being measured (cal / cm³) 3 ) 1 / 2 This was calculated using the following formula.

[0141]

number

[0142]

number

[0143]

number

[0144] The same was true for the Hansen solubility parameter (HSP) δ of resins (a1) to (a12) and (a'1), and no correlation was found with the properties of the paint composition or the physical properties of the coating film. [Industrial applicability]

[0145] The coating compositions for metal plates disclosed herein are preferably used in, for example, building materials, automobile parts, construction machinery, agricultural machinery, electrical equipment, kitchen appliances, office equipment, and the like.

Claims

1. It comprises a film-forming resin (A) and a hardening agent (B), The coating-forming resin (A) has active hydrogen groups and the hydrogen bonding term δ that constitutes the Hansen solubility parameter. ｈ However, 3.5 MPa ０．５ Above 15.0 MPa ０．５ The following resin (A1) is included: The curing agent (B) is a metal plate coating composition comprising a blocked isocyanate compound (B1) in which the isocyanate groups of pentamethylene diisocyanate and / or a pentamethylene diisocyanate derivative are blocked by a sealing agent.

2. The distance R of the Hansen solubility parameter between the resin (A1) and the blocked isocyanate compound (B1) ａ However, 1.6 MPa ０．５ The above is 16.3 MPa. ０．５ The following is the coating composition for metal plates according to claim 1.

3. The coating composition for metal plates according to claim 1, wherein the ratio (NCO / H ratio) of isocyanate groups contained in the curing agent (B) to active hydrogen groups contained in the coating film-forming resin (A) is 0.9 or more and 3.0 or less.

4. The distance R of the Hansen solubility parameter between the resin (A1) and the blocked isocyanate compound (B1) ａ is 1.8 MPa ０．５ or more and 13.5 MPa ０．５ or less. The coating composition for a metal plate according to claim 1.

5. The hydrogen bonding term δ that constitutes the Hansen solubility parameter of the resin (A1) ｈ However, 6.0 MPa ０．５ Above 11.0 MPa ０．５ The following is the coating composition for metal plates according to claim 1.

6. The coating composition for metal plates according to claim 1, wherein the pentamethylene diisocyanate derivative comprises one or more selected from the group consisting of an isocyanurate group and a urethane bond.

7. The coating composition for metal plates according to claim 1, wherein the resin (A1) comprises one or more selected from the group consisting of polyester polyols, alkyd resins, and acrylic polyols.

8. A metal plate and A painted article comprising a coating film disposed on the surface of the metal plate and formed from a metal plate coating composition according to any one of claims 1 to 7.

Images