Water-based paint composition, coating film and coated article

Abstract

Provided is a water-based coating composition that can form a coating film that is excellent in appearance and corrosion resistance. [Solution] A water-based coating composition having a first agent containing a hydrophilic (meth)acrylic polyol (A), a polylactone-modified polyol (B), and water, and a second agent containing a polyisocyanate compound (C) and an epoxy group-containing silane coupling agent (D), or having a first agent containing a hydrophilic (meth)acrylic polyol (A), a polylactone-modified polyol (B), and water, a second agent containing a polyisocyanate compound (C), and a third agent containing an epoxy group-containing silane coupling agent (D).

Description

[Technical Field]

[0001] The present disclosure relates to a water-based coating composition, a coating film, and a coated article. [Background technology]

[0002] Steel structures such as ships, bridges, and tanks are coated with multilayer coating films of various specifications to provide various functions according to their purpose (see, for example, Patent Document 1). For example, an anticorrosion coating film formed from an epoxy resin-based anticorrosion coating composition is applied as an undercoat to the surface of the steel structure, and a topcoat coating film formed from a topcoat paint composition is applied on top of the anticorrosion coating film for the purpose of improving design, weather resistance, etc. Examples of topcoat paint compositions include two-component reactive curing compositions such as urethane resin-based paint compositions, and one-component compositions such as (meth)acrylic resin-based paint compositions.

[0003] In recent years, regulations on organic solvent emissions have been tightened in consideration of the natural environment and the painting work environment. Water-based paint compositions generally contain less volatile organic compounds (VOCs) than organic solvent-based paint compositions. One method for reducing VOCs is to make paint compositions water-based. For example, multi-component water-based polyurethane paint compositions containing a hydrophilic polyol as the main component and a hydrophilic polyisocyanate or low-viscosity polyisocyanate as the curing agent have been investigated (see, for example, Patent Documents 2 to 4). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-193705 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-151645 [Patent Document 3] Japanese Patent Application Publication No. 2018-178082 [Patent Document 4] Japanese Patent Application Publication No. 2022-186298 Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have investigated water-based polyurethane coating compositions and have found that coating films formed from these compositions are prone to exhibiting poor appearance such as foam marks, and that the coating films tend to have insufficient corrosion resistance.

[0006] An object of the present disclosure is to provide a water-based coating composition capable of forming a coating film that is excellent in appearance and corrosion resistance. [Means for solving the problem]

[0007] One embodiment of the aqueous coating composition of the present disclosure comprises a first agent containing a hydrophilic (meth)acrylic polyol (A), a polylactone-modified polyol (B), and water, and a second agent containing a polyisocyanate compound (C) and an epoxy group-containing silane coupling agent (D), or comprises a first agent containing a hydrophilic (meth)acrylic polyol (A), a polylactone-modified polyol (B), and water, a second agent containing a polyisocyanate compound (C), and a third agent containing an epoxy group-containing silane coupling agent (D). [Effects of the Invention]

[0008] The water-based coating composition of the present disclosure can form a coating film that is excellent in appearance and corrosion resistance. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a table showing the evaluation criteria for the cross-cut tape peeling test. DETAILED DESCRIPTION OF THE INVENTION

[0010] Each of the components described in this specification can be used alone or in combination of two or more. In this specification, the term "polymer" may be used without any particular distinction between homopolymers and copolymers. That is, the term "polymer" is used to mean both homopolymers and copolymers.

[0011] In this specification, the numerical range n1 to n2 means a numerical range from n1 to n2. When multiple lower limit values ​​and multiple upper limit values ​​are listed for a certain element in this specification, the numerical range defined by combining a value arbitrarily selected from the listed lower limit values ​​with a value arbitrarily selected from the listed upper limit values ​​is also considered to be listed.

[0012] [Water-based paint composition] One embodiment of the aqueous coating composition of the present disclosure comprises a first part containing a hydrophilic (meth)acrylic polyol (A), a polylactone-modified polyol (B), and water, and a second part containing a polyisocyanate compound (C) and an epoxy group-containing silane coupling agent (D). Another embodiment of the aqueous coating composition of the present disclosure comprises the above-mentioned first agent, a second agent containing a polyisocyanate compound (C), and a third agent containing an epoxy group-containing silane coupling agent (D). Another embodiment of the aqueous coating composition of the present disclosure contains a hydrophilic (meth)acrylic polyol (A), a polylactone-modified polyol (B), a polyisocyanate compound (C), an epoxy group-containing silane coupling agent (D), and water. Hereinafter, the water-based coating composition of the present disclosure will also be referred to simply as "the composition."

[0013] In this specification, the term "paint composition" may refer to a multi-component composition in which each component, such as a first component and a second component, is stored or preserved in a separate container, or may refer to a composition containing the above-mentioned components (A) to (D) and water. In this specification, when referring to the content ratio of each component, the mass of the solid content of the composition means, in the case of a multi-component composition, the total mass of the solid content of each component (used for mixing), such as the solid content of the first component and the solid content of the second component, that make up the composition.

[0014] <First agent> The first agent constituting one embodiment of the present composition contains a hydrophilic (meth)acrylic polyol (A), a polylactone-modified polyol (B), and water. The first agent is preferably liquid at 1 atmosphere and 23°C.

[0015] <Hydrophilic (meth)acrylic polyol (A)> As used herein, "hydrophilic (meth)acrylic polyol" refers to a (meth)acrylic polyol having hydrophilic properties, such as a "water-soluble" (meth)acrylic polyol that can be dissolved in water, or a "water-dispersible" (meth)acrylic polyol that can be dispersed in water. Examples of such (meth)acrylic polyols include water-soluble resins that have hydroxy groups (hydrophilic groups) and can be uniformly dissolved in water, and water-dispersible resins that can be uniformly dispersed in water in the form of fine particles. The (meth)acrylic polyol may further have anionic groups such as carboxy groups and sulfonic acid groups from the standpoint of hydrophilicity, etc.

[0016] As used herein, "(meth)acrylic polyol" has two or more hydroxy groups. As used herein, "(meth)acrylic" means acrylic and / or methacrylic, and expressions such as (meth)acrylate, which will be described later, have the same meaning.

[0017] Examples of the hydrophilic (meth)acrylic polyol (A) (hereinafter also referred to as "component (A)") include a copolymer of an ethylenically unsaturated monomer having a hydroxy group and another ethylenically unsaturated monomer copolymerizable therewith. Component (A) may have two or more types of structural units derived from the ethylenically unsaturated monomer having a hydroxy group. Component (A) may also have two or more types of structural units derived from the other ethylenically unsaturated monomer.

[0018] Examples of ethylenically unsaturated monomers having a hydroxy group include hydroxyalkyl (meth)acrylates, (meth)acrylic acid polyalkylene glycol monoesters, and lactone-modified products of these compounds. Examples of other ethylenically unsaturated monomers include (meth)acrylic monomers and other ethylenically unsaturated monomers other than (meth)acrylic monomers.

[0019] Examples of hydroxyalkyl(meth)acrylates include hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxybutyl(meth)acrylate, and hydroxymethylcyclohexyl(meth)acrylate. Examples of (meth)acrylic acid polyalkylene glycol monoesters include polyethylene glycol mono(meth)acrylate and polypropylene glycol mono(meth)acrylate.

[0020] Examples of (meth)acrylic monomers include (meth)acrylic acid esters, (meth)acrylic acid amides, and (meth)acrylic acid. Examples of (meth)acrylic acid esters include alkyl (meth)acrylates, alicyclic (meth)acrylates, aryl (meth)acrylates, aralkyl (meth)acrylates, epoxy group-containing (meth)acrylates, aminoalkyl (meth)acrylates, and alkoxysilyl group-containing (meth)acrylates. Examples of ethylenically unsaturated monomers other than (meth)acrylic monomers include α-olefins, conjugated dienes, styrene-based monomers, vinyl esters, vinyl cyanide compounds, unsaturated monocarboxylic acids, unsaturated dicarboxylic acids and their monoesters or diesters, and alkoxysilyl group-containing ethylenically unsaturated monomers.

[0021] The hydroxyl value of component (A) is preferably 20 to 300 mgKOH / g, more preferably 30 to 250 mgKOH / g, and even more preferably 40 to 200 mgKOH / g, calculated as resin, from the viewpoints of improving the storage stability of the first agent, the curing reactivity of the composition, and improving the mechanical strength and water resistance of the coating film obtained from the composition. The hydroxyl value is measured in accordance with the neutralization titration method of JIS K0070:1992.

[0022] Component (A) may have an acid value of more than 0 mgKOH / g. From the viewpoint of achieving better storage stability of the first agent, the acid value of component (A) is preferably 1 to 30 mgKOH / g, more preferably 3 to 25 mgKOH / g, and even more preferably 5 to 20 mgKOH / g, calculated as resin. The acid value is measured in accordance with the neutralization titration method of JIS K0070:1992.

[0023] The weight average molecular weight (Mw) of component (A) is preferably 1,000 to 100,000, more preferably 2,000 to 80,000, and even more preferably 3,000 to 50,000, from the viewpoints of improving the drying properties of the composition and the crosslink density and weather resistance of the resulting coating film.

[0024] Mw is a value calculated in terms of polystyrene measured by gel permeation chromatography (GPC) under the following conditions. (GPC measurement conditions) Device: "HLC-8320GPC" (Tosoh Corporation) Column: "TSKgel guardcolumn SuperMP(HZ)-M + TSKgel SuperMultiporeHZ-M + TSKgel SuperMultiporeHZ-M" (all manufactured by Tosoh Corporation) Eluent: tetrahydrofuran (THF) Flow rate: 0.35ml / min Detector: Refractive index (RI) detector Column thermostat temperature: 40℃ Calibration curve: Standard polystyrene Sample preparation method: The polymer solution is diluted with THF, and then filtered through a membrane filter to obtain a filtrate, which is used as a GPC measurement sample.

[0025] Component (A) may be present in the composition or the first pack in the form of particles. For example, when the composition is applied and dried, water evaporates, causing the particles to bond together and form a film. In this case, the median diameter of the particles of component (A) is preferably 10 nm to 1 μm, more preferably 20 to 500 nm, and even more preferably 30 to 300 nm. Component (A) with a median diameter within this range tends to be stable in the composition or the first pack and tends to form a coating film with uniform coating properties. The median diameter is the 50% diameter in the volume-based particle size distribution measured by laser diffraction at 25°C.

[0026] When producing the present composition or the first agent, it is preferable to use an aqueous dispersion in which component (A) is dispersed in a dispersion medium containing water (hereinafter also referred to as "aqueous medium") and mix the aqueous dispersion with other constituents. This makes it easier for component (A) to be stably and uniformly present in the present composition or the first agent, and tends to enable the formation of a coating film with uniform coating properties. The aqueous dispersion is preferably an emulsion. The content of component (A) in the above aqueous dispersion is, for example, 20 to 60 mass%.

[0027] The aqueous medium is not particularly limited as long as it contains water. The water content in the aqueous medium is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. The aqueous medium may contain a medium other than water. Examples of the medium other than water include acetone, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-butoxy-2-propanol, diacetone alcohol, dioxane, ethylene glycol, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, ethylene glycol monopropyl ether, and ethylene glycol monohexyl ether.

[0028] Methods for synthesizing component (A) include known methods, such as polymerizing a monomer in the presence of a radical polymerization initiator by solution polymerization, suspension polymerization, bulk polymerization, or emulsion polymerization.

[0029] The component (A) may be used alone or in combination of two or more. The content of component (A) in the composition is preferably 5 to 40 mass%, more preferably 6 to 35 mass%, and even more preferably 8 to 30 mass%, based on the mass of the solid content of the composition, from the viewpoints of improving the curing reactivity of the composition and improving the mechanical strength and water resistance of the coating film obtained from the composition. The content of component (A) in the first pack is not particularly limited, as long as the content of component (A) in the solid content of the composition is set within the above range, and is, for example, 5 to 50 mass%, based on the mass of the solid content of the first pack.

[0030] The solid content of a substance (e.g., this composition or each component) refers to the heating residue (non-volatile content) when the substance is dried in an incubator at 108°C for 3 hours. Specifically, the heating residue is the residue of the sample (including the residue adhering to the wire) obtained by weighing out a 1.0 g sample of the substance in question onto a flat-bottomed dish, spreading it evenly using a wire of known mass, and drying it in an incubator at 1 atmosphere and 108°C for 3 hours. The solid content percentage (solid concentration) (mass %) of the substance is calculated from the amount of heating residue.

[0031] <Polylactone-modified polyol (B)> The first agent contains polylactone-modified polyol (B) (hereinafter also referred to as "component (B)," excluding compounds corresponding to component (A)). By using component (B) together with the above and below components, it is possible to form a coating film that is excellent in appearance, corrosion resistance, and adhesion to the substrate, although the reason is unclear. In addition, component (B) can increase the solid content of the composition.

[0032] Component (B) is, for example, a ring-opening adduct of a lactone compound to a polyhydric alcohol. From the viewpoint of the crosslink density and corrosion resistance of the coating film, component (B) has two or more, preferably three or more, more preferably three to six, and even more preferably three to four hydroxy groups per molecule. Component (B) can be obtained, for example, by ring-opening addition polymerization of a lactone compound to a polyhydric alcohol.

[0033] Examples of polyhydric alcohols include aliphatic polyhydric alcohols, specifically ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl Examples of the polyhydric alcohol include dihydric alcohols (preferably having 2 to 12 carbon atoms) such as 1,3-hexanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,10-decanediol, and 1,12-octadecanediol; and tri- to hexahydric, preferably tri- to tetrahydric, alcohols (preferably having 3 to 12 carbon atoms) such as glycerin, trimethylolethane, trimethylolpropane, trimethyloloctane, 1,2,6-hexanetriol, pentaerythritol, diglycerin, and ditrimethylolpropane. Among polyhydric alcohols, tri- and tetrahydric alcohols are preferred.

[0034] Examples of lactone compounds include caprolactones such as ε-caprolactone, methyl-ε-caprolactone, dimethyl-ε-caprolactone, and trimethyl-ε-caprolactone; valerolactones such as δ-valerolactone and β-methyl-δ-valerolactone; butyrolactones; and propiolactones. Among these, caprolactones are preferred, and ε-caprolactone is more preferred.

[0035] As component (B), polycaprolactone-modified polyols are preferred, and polyε-caprolactone-modified polyols are more preferred. As component (B), from the viewpoint of crosslinking density of the coating film and corrosion resistance, ring-opening adducts of caprolactones to 3- to 4-valent alcohols are preferred.

[0036] The hydroxyl value of component (B) is preferably 50 to 1000 mgKOH / g, more preferably 100 to 800 mgKOH / g, and even more preferably 130 to 600 mgKOH / g. Component (B) having a hydroxyl value equal to or greater than the lower limit is preferred as a component of an aqueous coating composition. Component (B) having a hydroxyl value equal to or less than the upper limit is preferred from the viewpoint of the water resistance of the coating film, etc. The hydroxyl value of component (B) is even more preferably 500 mgKOH / g or less, particularly preferably 400 mgKOH / g or less, from the viewpoint of the water resistance of the coating film, and superior adhesion (adhesion) and corrosion prevention to substrates such as metal substrates in corrosive environments or high-temperature, high-humidity environments. The hydroxyl value is measured in accordance with the neutralization titration method of JIS K0070:1992.

[0037] The weight-average molecular weight (Mw) of component (B) is preferably 200 to 3,000, more preferably 250 to 2,000, and even more preferably 280 to 1,500, from the viewpoints of improving the corrosion resistance of the coating film and increasing the solid content of the composition. The weight-average molecular weight (Mw) is a polystyrene-equivalent value measured by gel permeation chromatography (GPC). The detailed measurement conditions for the GPC method are as described above.

[0038] The first agent in this composition has excellent storage stability because it contains both the polylactone-modified polyol (B) and the hydrophilic (meth)acrylic polyol (A). Although the reason for this is unclear, it is presumed that component (A) stabilizes component (B) in water, and particularly when an aqueous dispersion of component (A) is used, the aqueous dispersion stabilizes component (B). However, the contents of the present disclosure are not bound by this presumption.

[0039] The component (B) may be used alone or in combination of two or more. The content of component (B) in the composition is preferably 1 to 30 mass%, more preferably 2 to 20 mass%, and even more preferably 3 to 10 mass%, based on the mass of the solid content of the composition, from the viewpoints of corrosion resistance, adhesion, gloss, weather resistance, etc. The content of component (B) in the first pack may be set so that the content of component (B) in the solid content of the composition falls within the above range. When component (B) having a hydroxyl value of more than 500 mg KOH / g is used, the content of component (B) in the composition is particularly preferably 6 mass% or less based on the mass of the solid content of the composition, from the viewpoints of water resistance, etc.

[0040] The content of component (B) in the composition or the first pack is preferably 10 to 200 parts by mass, more preferably 15 to 120 parts by mass, and even more preferably 15 to 60 parts by mass per 100 parts by mass of component (A) from the viewpoints of corrosion resistance, adhesion, gloss, weather resistance, etc. When component (B) having a hydroxyl value of more than 500 mgKOH / g is used, the content of component (B) in the composition or the first pack is particularly preferably 30 parts by mass or less per 100 parts by mass of component (A) from the viewpoints of water resistance, etc.

[0041] ≪Water≫ The present composition is a water-based coating composition. In this disclosure, a "water-based" coating composition refers to a coating composition containing water. The water is not particularly limited, and examples thereof include tap water, ion-exchanged water, and deionized water, with ion-exchanged water and deionized water being preferred. The above-mentioned water includes, for example, water that is the dispersion medium when an aqueous dispersion of component (A) is used, and water that may be contained in additives.

[0042] The content of water in the first agent is preferably 20 to 70 mass %, more preferably 25 to 65 mass %, and even more preferably 30 to 60 mass %. The content of water in the present composition is preferably 20 to 70 mass %, more preferably 25 to 65 mass %, and even more preferably 30 to 60 mass %. The water content is measured according to the Karl Fischer method using a moisture measuring device (for example, CA-310, manufactured by Nitto Seiko Analytech Co., Ltd.).

[0043] Other ingredients The composition and / or the first agent may further contain components other than the above-mentioned components (hereinafter also referred to as "other components"). Examples of other components include pigments, rust inhibitors, and additives. Examples of additives include dispersants, wetting agents, anti-sagging agents (thixotropic agents), antifoaming agents, film-forming aids, leveling agents, flash rust inhibitors, thickeners, surfactants, mildew inhibitors, preservatives, UV absorbers, pH adjusters, and antioxidants. The other components may be used alone or in combination of two or more.

[0044] Pigments can be used to impart strength, corrosion resistance, hue, etc. to the coating film. Examples of pigments include extender pigments, color pigments, and anti-rust pigments, and may be either organic or inorganic. When the composition contains a pigment, one type of pigment may be used, or two or more types may be used.

[0045] Examples of extender pigments include talc, mica, (precipitated) barium sulfate, (potassium) feldspar, kaolin, alumina white, bentonite, wollastonite, clay, glass flake, aluminum flake, magnesium carbonate, barium carbonate, calcium carbonate, dolomite, and silica.

[0046] When the composition contains an extender pigment, the content of the extender pigment in the composition is preferably 1 to 50 mass %, more preferably 5 to 40 mass %, based on the mass of the solid content of the composition. The content of the pigment in the first pack may be set so that the content of the pigment in the solid content of the composition falls within the above range. The same applies to the content of each component in the following explanation.

[0047] As the color pigment, any conventionally known color pigment can be used, and examples thereof include inorganic pigments such as titanium oxide, yellow iron oxide, red iron oxide, and carbon black, organic pigments such as naphthol red, phthalocyanine blue, and phthalocyanine green, and gloss pigments such as aluminum flakes, flaky iron oxide, and stainless steel flakes. When the composition contains a color pigment, the content of the color pigment in the composition is preferably 1 to 50 mass%, more preferably 5 to 45 mass%, and even more preferably 10 to 40 mass%, based on the mass of the solid content of the composition.

[0048] Examples of anti-rust pigments include zinc phosphate compounds, calcium phosphate compounds, aluminum phosphate compounds, magnesium phosphate compounds, zinc phosphite compounds, calcium phosphite compounds, aluminum phosphite compounds, strontium phosphite compounds, aluminum tripolyphosphate compounds, molybdate compounds, zinc cyanamide compounds, borate compounds, nitro compounds, and composite oxides. When the composition contains an anti-rust pigment, the content of the anti-rust pigment in the composition is preferably 1 to 20 mass %, more preferably 3 to 15 mass %, based on the mass of the solids content of the composition.

[0049] When the present composition contains a pigment, the pigment volume concentration (hereinafter also referred to as "PVC") of the present composition is preferably 5 to 35% by volume, more preferably 10 to 25% by volume, from the viewpoint of easily obtaining a coating film that has a good balance between flexibility and adhesion.

[0050] PVC refers to the ratio of the total volume of pigments in a paint composition to the volume of the solid content of the paint composition. Specifically, PVC can be calculated using the following formula: PVC [%] = Total volume of all pigments in the paint composition × 100 / Volume of solids in the coating composition

[0051] The volume of the solid content of the coating composition can be calculated from the mass and true density of the solid content of the coating composition. The mass and true density of the solid content may be measured values ​​or may be values ​​calculated from the raw materials used. The volume of the pigment can be calculated from the mass and true density of the pigment used. The mass and true density of the pigment may be measured values ​​or may be values ​​calculated from the raw materials used. For example, the pigment and other components may be separated from the solid content of the coating composition, and the mass and true density of the separated pigment may be measured.

[0052] The rust inhibitor is a compound other than the rust-preventive pigment that has rust-preventing properties. Conventionally known compounds can be used as the rust inhibitor. The content of the rust inhibitor in the composition is not particularly limited.

[0053] Examples of dispersants include polymers having a pigment-adsorbing group (pigment-affinity group) and a compatible chain. Examples of pigment-adsorbing groups include carboxyl groups, acid anhydride groups, phosphate groups, amino groups, salt groups thereof, and ammonium salt groups. Examples of compatible chains include fatty acids, polyaminos, polyethers, polyesters, polyurethanes, and poly(meth)acrylates. When the composition contains a dispersant, the content of the dispersant in the composition is preferably 0.1 to 3 mass %, more preferably 0.2 to 2 mass %, based on the mass of the solids content of the composition.

[0054] Examples of anti-slip agents include organic slipogenators such as hydrogenated castor oil-based slipogenators, amide wax-based slipogenators, polyethylene oxide-based slipogenators, and urethane-based slipogenators; as well as inorganic slipogenators such as clay minerals (e.g., bentonite, smectite, and hectorite) and synthetic fine silica. When the composition contains an anti-slip agent, the content of the anti-slip agent in the composition is preferably 0.01 to 3% by mass, more preferably 0.05 to 2% by mass, based on the mass of the solid content of the composition.

[0055] Examples of antifoaming agents include silicone-based antifoaming agents, polymer-based (non-silicone-based) antifoaming agents, and mineral oil-based antifoaming agents. When the composition contains an antifoaming agent, the content of the antifoaming agent in the composition is preferably 0.05 to 5 mass %, more preferably 0.1 to 3 mass %, based on the mass of the solid content of the composition.

[0056] Examples of film-forming aids include alcohols, glycol ethers, and esters. Specifically, examples include alcohols such as isopropyl alcohol, 2,2,4-trimethylpentanediol, and benzyl alcohol; glycol ethers such as ethylene glycol monobutyl ether, ethylene glycol diethyl ether, diethylene glycol monobutyl ether, diethylene glycol diethyl ether, propylene glycol diethyl ether, dipropylene glycol diethyl ether, dipropylene glycol n-butyl ether, ethylene glycol monobenzyl ether, and ethylene glycol monophenyl ether; and esters such as 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate. When the composition contains a film-forming aid, the content of the film-forming aid is preferably 0.5 to 30 parts by mass, more preferably 2 to 25 parts by mass, based on 100 parts by mass of the total content of component (A) and component (B).

[0057] Examples of the leveling agent include various leveling agents such as fluorine-based, (meth)acrylic, silicone-based, etc. When the present composition contains a leveling agent, the content of the leveling agent in the present composition is preferably 0.005 to 2 mass %, more preferably 0.01 to 1.5 mass %, based on the mass of the solid content of the present composition.

[0058] Examples of flash rust inhibitors include nitrites such as sodium nitrite, potassium nitrite, calcium nitrite, strontium nitrite, barium nitrite, and ammonium nitrite, benzoates, phytates, organic carboxylates, phosphoric acid derivatives, tannates, metal sulfonates, amine chelating agents, hydrazine derivatives, azole compounds, the addition reaction product of 4-methyl-γ-oxo-benzenebutanoic acid and N-ethylmorpholine, and intercalation compounds obtained by intercalating monoalkylamines, polyamines, quaternary ammonium ions, etc. into layered phosphates such as aluminum dihydrogen triphosphate. Among these, nitrites are preferred, and sodium nitrite is more preferred.

[0059] When the present composition contains a flash rust inhibitor, the content of the flash rust inhibitor in the present composition is preferably 0.05 to 5 mass %, more preferably 0.1 to 3 mass %, based on the mass of the solid content of the present composition.

[0060] <Second and third agents> The second part constituting one embodiment of the present composition contains a polyisocyanate compound (C) and may further contain an epoxy group-containing silane coupling agent (D). The third agent, which constitutes one embodiment of the present composition, contains the above-mentioned silane coupling agent (D). The form of the second and third agents is not particularly limited, but it is preferable that each be liquid at 1 atmosphere and 23°C.

[0061] <Polyisocyanate compound (C)> The polyisocyanate compound (C) (hereinafter also referred to as "component (C)") has two or more isocyanate groups in one molecule. The number of isocyanate groups in component (C) is preferably 2 to 6, and more preferably 2 to 4.

[0062] Component (C) is preferably a water-dispersible polyisocyanate compound. The term "water-dispersible polyisocyanate compound" refers to a polyisocyanate compound that has water dispersibility and can be dispersed without phase separation when added to an aqueous medium.

[0063] Examples of component (C) include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates, as well as derivatives of aliphatic polyisocyanates, alicyclic polyisocyanates, or aromatic polyisocyanates, such as biuret derivatives, uretdione derivatives, isocyanurate derivatives, allophanate derivatives, and adducts (e.g., adducts to polyhydric alcohols such as trimethylolpropane).

[0064] Examples of aliphatic polyisocyanates include aliphatic diisocyanates, and specific examples include linear aliphatic diisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, and hexamethylene diisocyanate (HDI); and branched aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate. Examples of alicyclic polyisocyanates include alicyclic diisocyanates such as cyclopentane diisocyanate, cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, and hydrogenated toluene diisocyanate. Examples of aromatic polyisocyanates include aromatic diisocyanates such as phenylene diisocyanate, xylylene diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, dianisidine diisocyanate, tetramethylxylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and 3,3'-dimethyldiphenyl-4,4'-diisocyanate.

[0065] As component (C), a hydrophilized polyisocyanate compound obtained by introducing a hydrophilic group into the above polyisocyanate compound may be used. Examples of the hydrophilic group include an ether bond and an anionic group.

[0066] Examples of hydrophilized polyisocyanate compounds include polyether-modified polyisocyanate compounds and anionic group-containing polyisocyanate compounds. Examples of polyether-modified polyisocyanate compounds include compounds obtained by reacting a polyisocyanate compound with a hydrophilic polyether alcohol such as a polyoxyethylene monoalcohol. Examples of anionic group-containing polyisocyanate compounds include compounds obtained by reacting an active hydrogen-containing group of an active hydrogen-containing compound having an anionic group with an isocyanate group of a polyisocyanate compound.

[0067] Examples of active hydrogen-containing compounds having an anionic group include compounds having one anionic group and at least one active hydrogen-containing group. Examples of anionic groups include carboxyl groups, sulfonic acid groups, phosphate groups, and betaine structure-containing groups. The active hydrogen-containing group is a functional group that can react with an isocyanate group. Examples of active hydrogen-containing groups include hydroxyl groups and amino groups. By reacting the active hydrogen-containing compound with a polyisocyanate compound, hydrophilicity can be imparted to the polyisocyanate compound.

[0068] Of the components (C), at least one selected from the group consisting of HDI-based polyisocyanates such as HDI and its derivatives (e.g., isocyanurates), and IPDI-based polyisocyanates such as IPDI and its derivatives (e.g., isocyanurates) is preferred. From the viewpoints of the weather resistance of the resulting coating film and the usable life, it is preferred that component (C) contains at least an IPDI-based polyisocyanate.

[0069] The mass ratio of isocyanate groups to the entire component (C) (hereinafter also referred to as "NCO group content") is preferably 3 to 40%, more preferably 5 to 30%, and even more preferably 10 to 20%.

[0070] The component (C) may be used alone or in combination of two or more. The content of component (C) in the composition is preferably 5 to 40 mass%, more preferably 10 to 35 mass%, and even more preferably 15 to 30 mass%, based on the mass of the solid content of the composition. The content of component (C) in the second pack is not particularly limited, as long as the content of component (C) in the solid content of the composition is set within the above range, and is, for example, 50 mass% or more based on the mass of the solid content of the second pack.

[0071] In this composition, the equivalent ratio (NCO / OH) of the number of equivalents of isocyanate groups (NCO) in the polyisocyanate compound (C) to the total number of equivalents (OH) of hydroxy groups in the hydrophilic (meth)acrylic polyol (A) and the polylactone-modified polyol (B) is preferably 0.5 to 2.0, more preferably 0.7 to 1.5, and even more preferably 0.8 to 1.3. A composition having this ratio exhibits, for example, an excellent balance between dry curing properties and usable life. The number of equivalents of each component is calculated as follows: Isocyanate group equivalent number = (amount of polyisocyanate compound blended × NCO group content (%) / 100) / molecular weight of NCO Polyol hydroxyl group equivalent number = Polyol hydroxyl value (mg KOH / g) × Polyol blend amount / KOH molecular weight The unit of the amount of each component is mass (g), the molecular weight of NCO is 42, the NCO group content is the proportion of NCO groups in the polyisocyanate compound expressed as mass%, and for convenience of unit conversion, the molecular weight of KOH is converted to mg and set to 56,100.

[0072] <Epoxy group-containing silane coupling agent (D)> The composition contains an epoxy group-containing silane coupling agent (D) (hereinafter also referred to as "component (D)"). The second part of the composition may contain component (D). The composition may further contain a third part containing component (D) in addition to the second part containing component (C).

[0073] Conventional water-based polyurethane coating compositions are prone to the generation of carbon dioxide gas resulting from the reaction between the polyisocyanate compound and the water contained in the coating, which can lead to the formation of foaming marks and poor appearance in the coating film. The use of an epoxy group-containing silane coupling agent (D) along with the above components in this composition, for reasons that are unclear, can suppress the formation of foaming carbon dioxide gas and other gases when forming a coating film using this composition, resulting in the formation of a coating film with excellent appearance, even when the film is thick. Furthermore, coating films formed from this composition exhibit excellent adhesion (tightness) and corrosion resistance to substrates such as metal substrates in corrosive environments or high-temperature, high-humidity environments.

[0074] Examples of component (D) include compounds having a reactive silyl group and an epoxy group in one molecule. The reactive silyl group is not particularly limited as long as it generates a silanol group upon hydrolysis.

[0075] As the component (D), a compound represented by the following formula (1) is preferred. R 3 -Si(R 4 ) p (OR 5 ) 3-p …(1) Each symbol in formula (1) is explained below. R 3 is an organic group containing an epoxy group, such as a glycidoxyalkyl group or a (3,4-epoxycyclohexyl)alkyl group. The "alkyl" (specifically, an alkanediyl group) in these groups is an alkanediyl group having 1 to 8 carbon atoms, such as a methylene group, an ethylene group, or a propylene group, and is preferably an ethylene group or a propylene group. R 4 and R 5are each independently an alkyl group having 1 to 10 carbon atoms, preferably 1 to 3 carbon atoms, such as a methyl group or an ethyl group, or an aryl group having 6 to 10 carbon atoms, such as a phenyl group. p is an integer of 0 to 2, and is preferably 0 or 1.

[0076] Specific examples of component (D) include glycidoxymethyltrimethoxysilane, glycidoxymethyltriethoxysilane, 2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 8-glycidoxyoctyltrimethoxysilane, 8-glycidoxyoctyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylethyldimethoxysilane silane, 3-glycidoxypropylethyldiethoxysilane, 8-glycidoxyoctylmethyldimethoxysilane, 8-glycidoxyoctylmethyldiethoxysilane, 3-glycidoxypropyldimethylmethoxysilane, 3-glycidoxypropyldiethylethoxysilane, (3,4-epoxycyclohexyl)methyltrimethoxysilane, (3,4-epoxycyclohexyl)methyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane.

[0077] The component (D) may be used alone or in combination of two or more. The content of component (D) in the composition is preferably 0.5 to 20 mass%, more preferably 1 to 15 mass%, even more preferably 1.5 to 10 mass%, and particularly preferably 2 to 5 mass%, based on the mass of the solid content of the composition. The content of component (D) in the second or third part may be set so that the content of component (D) in the solid content of the composition falls within the above range. Such a composition can form a coating film that is excellent in appearance, corrosion resistance, and adhesion to substrates.

[0078] Other ingredients The second and / or third agents may further contain other ingredients as described above. The other components may be used alone or in combination of two or more. The second agent may further contain an organic solvent that does not have an active hydrogen-containing group such as a hydroxy group or an amino group. Examples of such organic solvents include glycol dialkyl ether organic solvents, glycol monoalkyl ether acetate organic solvents, ketone organic solvents, ester organic solvents, and aromatic hydrocarbon solvents. One or more of the above organic solvents may be used.

[0079] <Agents other than those listed above> In one embodiment, the present composition is a multi-component composition having a first component and a second component, or a first component, a second component, and a third component, preferably a multi-component composition, such as a two-component composition consisting of a first component and a second component, or a three-component composition consisting of a first component, a second component, and a third component. In one embodiment, the first component may be a so-called base component, and the second component may be a so-called curing agent. The present composition may further contain agents other than the above-mentioned agents (hereinafter also referred to as "other agents") depending on the components used.

[0080] <voc> The content of volatile organic compounds (VOCs) in the composition is preferably 150 g / L or less, more preferably 100 g / L or less, from the viewpoints of environmental conservation and working environment safety, etc. The lower the VOC content in the composition, the better, but the content may be, for example, 1 g / L or more, 5 g / L or more, 10 g / L or more, 20 g / L or more, or 30 g / L or more.

[0081] Examples of VOCs include organic solvents, such as aromatic hydrocarbon solvents such as toluene, xylene, ethylbenzene, and mesitylene; alcohol solvents such as ethanol, propanol, isopropyl alcohol, butanol, and isobutanol; ether solvents such as propylene glycol monomethyl ether and dipropylene glycol monomethyl ether; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, and cyclohexanone; and ester solvents such as ethyl acetate, butyl acetate, and propylene glycol monomethyl ether acetate.

[0082] The VOC content in the composition is calculated based on the following formula using the specific gravity, solids concentration, and water concentration of the composition. VOC content (g / L) = Composition specific gravity x 1000 x (100 - solid content concentration - water concentration) / 100

[0083] The specific gravity (g / mL) of the composition is a value calculated by filling a 100 mL specific gravity cup with the composition (the mixture immediately after mixing the respective agents) at a temperature of 23° C. and measuring the mass of the composition. The solid concentration is the content of the above-mentioned solids in the composition, and the water concentration is the content of the above-mentioned water in the composition, and the methods for measuring each are as described above.

[0084] <Method for preparing water-based coating composition> When each of the first to third agents and other agents is a mixture, it can be prepared by mixing the respective components to be blended. In preparing the first agent, an aqueous dispersion in which the hydrophilic (meth)acrylic polyol (A) is dispersed in an aqueous medium may be used.

[0085] Each agent, such as the first to third agents and other agents, is usually preserved, stored, or transported in a separate container. At the time of use (e.g., immediately before painting), the first agent, the second agent, and other agents used as needed, or the first agent, the second agent, the third agent, and other agents used as needed, are mixed to prepare a paint (mixture). In other words, the above-mentioned agents can be said to be components of a kit for preparing a paint (mixture). After or during this preparation, the composition may be diluted before use depending on the painting method, etc. The descriptions in this specification, except for those related to such dilution, are descriptions of the composition before dilution.

[0086] The mixing can be performed using conventionally known devices such as mixers, dispersers, and stirrers. Examples of such devices include dispersers, mixing / dispersion mills, mortar mixers, rolls, paint shakers, and homogenizers. Mixing can be performed while heating or cooling, depending on the season or environment.

[0087] Since this composition is a water-based coating composition, it has little adverse effect on the environment and human body and also has excellent storage stability. By using this composition, even thick coatings can be formed with suppressed foaming, and coatings that have excellent appearance such as high gloss, excellent weather resistance, corrosion resistance, and excellent adhesion to substrates such as metal substrates. Therefore, this composition is suitable for applications such as topcoat coating or repair coating, and direct coating on metal substrates. Because the present composition exhibits such excellent effects, it can be used as a primer paint, a top coat paint, or a paint that can be used as both a primer paint and a top coat. By using the present composition, a coating film that satisfies the physical properties required for both the primer paint film and the top coat paint film can be formed with a single paint, and the efficiency of the coating work can be improved, for example, by shortening the number of days and man-hours required for the coating process.

[0088] [Coatings and painted products] The coating of the present disclosure is formed using the present composition. The coating film is believed to contain a polyurethane compound formed by the reaction of the hydrophilic (meth)acrylic polyol (A) and / or the polylactone-modified polyol (B) with the polyisocyanate compound (C). Therefore, the coating film has, for example, excellent mechanical strength. In one embodiment, the coating film has a polyurethane structure.

[0089] The coating film preferably has a dry thickness of 20 to 200 μm, more preferably 50 to 150 μm. The coating film can be formed, for example, by applying the composition to a substrate and drying it. Coating methods include, for example, brush coating, air spray coating, airless spray coating, roll coater coating, and immersion. A coating film of the above thickness may be formed by applying a single coat, or by applying two or more coats. Regarding drying conditions, for example, the drying time is preferably 1 hour to 30 days, more preferably 3 hours to 10 days, and the drying temperature is preferably 5 to 40°C, more preferably 10 to 30°C, and may be, for example, ambient temperature.

[0090] The coated article of the present disclosure has a substrate and a coating film of the present disclosure provided on the substrate. Examples of materials for the region of the substrate on which the coating film is provided include metal materials such as steel (e.g., iron, steel, ferroalloy, carbon steel, mild steel, alloy steel), non-ferrous metals (e.g., zinc, aluminum, copper, brass, galvanized, zinc sprayed), and stainless steel (e.g., SUS304, SUS410), as well as plastics, ceramics, glass, and concrete. Among these, metal materials are preferred, and steel or stainless steel is more preferred. The substrate may be one that has been pretreated by a cleaning process to remove rust, dirt, paint (old paint film), etc., adhering to the substrate, or by a blasting process.

[0091] Specific examples of the substrate include structures such as ships (e.g., decks, superstructures, or outer hulls of ships), bridges, marine structures (e.g., marine buoys, undersea pipelines), plants, tanks, containers, pipes, steel pipes, vehicles, and aircraft, with metal (e.g., steel or stainless steel) structures being preferred.

[0092] The coating film of the present disclosure contained in the coated article may be one layer or two or more layers. The coated article may further have an undercoat coating film between the substrate and the coating film of the present disclosure for the purpose of improving adhesion or corrosion resistance, etc. The coated article may further have a topcoat coating film on the coating film of the present disclosure.

[0093] The undercoat coating film includes not only the known undercoat coating film (primer coating film) in the narrow sense, but also the known coating film called the so-called intermediate coating film. Examples of the primer coating film include coating films formed from various primer compositions such as epoxy resin-based or inorganic zinc-based. Examples of the intermediate coating film include coating films formed from various intermediate coating paint compositions such as epoxy resin-based or polyurethane resin-based. Examples of topcoat coating films include coating films formed from two-component reactive curing compositions such as urethane resin-based coating compositions, or one-component compositions such as (meth)acrylic resin-based coating compositions.

[0094] The thickness of the undercoat coating film and the topcoat coating film is preferably 50 to 500 μm, more preferably 100 to 350 μm, in terms of dry film thickness, independently of each other.

[0095] The coating film of the present disclosure may be, for example, a topcoat coating film or an undercoat coating film, as described above, or may serve as both a topcoat coating film and an undercoat coating film.

[0096] [Example of situation] The present disclosure relates to, for example, the following [1] to [8]. [1] A water-based coating composition comprising a first agent containing a hydrophilic (meth)acrylic polyol (A), a polylactone-modified polyol (B), and water, and a second agent containing a polyisocyanate compound (C) and an epoxy group-containing silane coupling agent (D), or a first agent containing a hydrophilic (meth)acrylic polyol (A), a polylactone-modified polyol (B), and water, a second agent containing a polyisocyanate compound (C), and a third agent containing an epoxy group-containing silane coupling agent (D). [2] The aqueous coating composition according to [1] above, wherein the polylactone-modified polyol (B) has three or more hydroxy groups. [3] The aqueous coating composition according to [1] or [2], wherein the polylactone-modified polyol (B) has a hydroxyl value of 500 mgKOH / g or less. [4] The aqueous coating composition according to any one of [1] to [3] above, wherein the content of the hydrophilic (meth)acrylic polyol (A) is 5 to 40 mass %, the content of the polylactone-modified polyol (B) is 1 to 30 mass %, the content of the polyisocyanate compound (C) is 5 to 40 mass %, and the content of the epoxy group-containing silane coupling agent (D) is 0.5 to 20 mass %, based on the mass of the solid content of the composition. [5] The aqueous coating composition according to any one of [1] to [4] above, wherein the content of the water in the aqueous coating composition is 20 to 70 mass %. [6] A coating film formed from the water-based coating composition according to any one of [1] to [5] above. [7] A coated article having a substrate and the coating film according to [6] provided on the substrate. [8] The coated article according to [7], wherein the material of the region of the substrate where the coating film is provided is a metal material. [Example]

[0097] The present composition will be described in more detail below with reference to examples. However, the present composition is not limited to the following examples. In the following description, "parts by mass" will be simply referred to as "parts" unless otherwise specified.

[0098] [raw materials] The raw materials used to prepare the compositions of the examples or comparative examples are listed in Table 1. [Table 1]

[0099] [Example 1] A container was charged with 12.9 parts of ion-exchanged water, 0.1 parts of flash rust inhibitor (Note 1), 1 part of dispersant (Note 2), 0.4 parts of anti-sagging agent (Note 3), 0.3 parts of antifoaming agent 1 (Note 4), 16.8 parts of titanium dioxide (Note 5), 10 parts of barium sulfate (Note 6), and 4 parts of calcium carbonate (Note 7). Using a paint shaker, the mixture was dispersed according to the JIS K5600-2-5:1999 method until the particle gauge reading was 30 μm or less, preparing a pigment dispersion.

[0100] To the prepared pigment dispersion, 34 parts of hydrophilic acrylic polyol (A-1) (Note 8), 3 parts of polycaprolactone polyol (B-2) (Note 10), and 2.7 parts of coalescent (Note 11) were added, and the contents of the container were stirred for 15 minutes using a high-speed disperser. Then, 0.4 parts of defoamer 2 (Note 12) and 0.4 parts of leveling agent (Note 13) were added, and the contents of the container were stirred for another minute using a high-speed disperser to prepare the first pack.

[0101] In a separate container, 90 parts of polyisocyanate (C-1) (Note 14) and 10 parts of epoxy group-containing silane coupling agent (D-1) (Note 16) were added, and the contents of the container were stirred using a high-speed disperser until uniform, to prepare the second agent.

[0102] In this way, a two-component coating composition having a first component and a second component was obtained. 86 parts of the first component and 22 parts of the second component were mixed to prepare a coating composition.

[0103] [Examples 2 to 7 and Comparative Examples 1 to 6] The first and second agents were prepared in the same manner as in Example 1, except that the types and amounts of the components constituting the first and second agents were changed as shown in the table below. The first and second agents thus prepared were mixed to obtain the mixing ratios (mass ratios) shown in the table below to prepare the paints.

[0104] [Storage stability of the first agent] Immediately after preparation, 300 g of each of the first agents of the Examples and Comparative Examples was weighed out and placed in a sealable container. After storage at 23°C for 2 months, the state of the first agent (presence or absence of separation, precipitation, and aggregates) was visually observed, and the state of the first agent when stirred with a medicine spoon was visually confirmed and evaluated according to the following evaluation criteria. The evaluation results are shown in the table below.

[0105] (Evaluation criteria) 5: No separation, sedimentation or aggregates are observed in the first formulation after storage for 2 months. 4: After 2 months of storage, slight separation was observed in the first agent. No sedimentation or agglomerates were observed, and the mixture was easily homogenized by stirring with a spoon. 3: After 2 months of storage, slight separation, sedimentation, and aggregates were observed in the first formulation. It can be easily homogenized by stirring with a spoon. 2: Separation, sedimentation, and aggregates were observed in the first formulation after storage for 2 months. Stirring with a medicine spoon will make the mixture homogenous, but it will take some time to achieve this homogenization. 1: Separation, sedimentation, and aggregates were observed in the first formulation after storage for 2 months. Even when stirred with a medicine spoon, it does not become homogenous.

[0106] [Appearance of the coating] Each of the paints from the Examples and Comparative Examples was applied to the surface of a cold-rolled steel plate measuring 150 mm in length, 70 mm in width, and 0.8 mm in thickness using an applicator so that the dry film thickness was approximately 75 μm, and the coating was dried for 7 days under conditions of a temperature of 23°C and a humidity of 50% to form a coating. In this way, test specimens were prepared. The appearance of the test piece was evaluated according to the following evaluation criteria, and the evaluation results are shown in the table below.

[0107] (Evaluation criteria) 3: No traces of foaming were observed on the coating film, and the leveling properties were good. 2: Slight traces of foaming were observed on the coating film, and leveling was slightly poor. 1: Traces of foaming were observed over the entire coating film, and the appearance was extremely poor.

[0108] The gloss value of the test piece was measured in accordance with JIS K5600-4-7:1999 using a surface gloss meter (model: Micro Trigloss 4446, manufactured by BYK-Gardner) to measure the reflectance of light incident at an angle of 60° from the normal to the coating surface (60° gloss). The measurement was performed three times, and the average value is shown in the table.

[0109] [Initial adhesion of coating] A cross-cut tape peeling test (2 mm × 2 mm, 25 squares, cross-cut method) was performed on the above test specimens. Using a cutter guide, 6 vertical and 6 horizontal cuts were made on the coating surface of the test specimen, reaching down to the steel substrate, to form a 25-square cross-cut grid. The cuts were spaced 2 mm apart. Next, cellophane tape was firmly pressed onto the cross-cut areas of the test specimen, and the edge of the cellophane tape was quickly peeled off at a 90° angle to the coating surface. The number of remaining or adhered squares out of the 25 squares was evaluated using the evaluation criteria (out of 10) shown in Figure 1.

[0110] [Salt spray test] A salt spray test was conducted in accordance with JIS K 5600-7-1:1999 by holding the test specimens in a salt spray tester under salt spray conditions of 5% by mass salt water, 35°C temperature, and 98% relative humidity for 400 hours. After the test, the adhesion of the coating film was confirmed in the same manner as in the "Initial adhesion of the coating film" above, and the corrosion resistance was evaluated according to the following evaluation criteria. The evaluation results are shown in the table below.

[0111] (Evaluation criteria) 5: No rust or blisters. 4: No blisters have occurred, but the area of ​​rust on the surface of the steel sheet beneath the paint film (hereinafter also referred to as "rusted area") is less than 0.03% of the entire surface of the steel sheet beneath the paint film. 3: A very small amount of small blisters has occurred, and the rust area is 0.03% or more but less than 0.1%. 2: Blisters have occurred and the rusted area is 0.1% or more but less than 0.3%. 1: Blisters have occurred and the rust area is 0.3% or more.

[0112] [Moisture resistance test] The moisture resistance test was carried out by holding the test pieces in a moisture resistance tester maintained at a temperature of 50°C and a relative humidity of 95% for 400 hours. After the test, the adhesion of the coating film was confirmed in the same manner as in the "Initial adhesion of the coating film" above, and the corrosion resistance was evaluated according to the evaluation criteria described above. The evaluation results are shown in the table below.

[0113] [Weather resistance test] The test specimens were placed in a QUV accelerated weathering tester (model: QUV / SE 200V, UVA-340 lamp, manufactured by Q-Lab) and subjected to weathering tests for 600, 1000, 1200, 1400, and 1600 hours according to ASTM G154 CYCLE 1. The reflectance of light incident at an angle of 60° from the normal to the coating surface after the weathering test (60° gloss) was then measured using a surface gloss meter (model: Micro Trigloss 4446, manufactured by BYK-Gardner). The gloss retention (%) of the 60° gloss after the weathering test relative to the 60° gloss value of the coating before the weathering test was calculated. Measurements were performed three times, and the average values ​​are reported in the table.

[0114] [Table 2] < / voc>

Claims

1. A first agent containing a hydrophilic (meth)acrylic polyol (A), a polylactone-modified polyol (B), and water, A second agent containing a polyisocyanate compound (C) and an epoxy group-containing silane coupling agent (D), have or A first agent containing a hydrophilic (meth)acrylic polyol (A), a polylactone-modified polyol (B), and water, A second agent containing a polyisocyanate compound (C), A third agent containing an epoxy group-containing silane coupling agent (D), A water-based coating composition comprising:

2. The aqueous coating composition according to claim 1, wherein the polylactone-modified polyol (B) has three or more hydroxyl groups.

3. The aqueous coating composition according to claim 1, wherein the polylactone-modified polyol (B) has a hydroxyl value of 500 mg KOH / g or less.

4. In the above composition, based on the mass of the solid content of the composition, The content of the hydrophilic (meth)acrylic polyol (A) is 5 to 40% by mass. The content of the polylactone-modified polyol (B) is 1 to 30% by mass. The content of the polyisocyanate compound (C) is 5 to 40% by mass. The content of the epoxy group-containing silane coupling agent (D) is 0.5 to 20% by mass. The water-based coating composition according to claim 1.

5. The water-based paint composition according to claim 1, wherein the water content in the water-based paint composition is 20 to 70% by mass.

6. A coating film formed from the water-based coating composition according to any one of claims 1 to 5.

7. A substrate; The coating film according to claim 6 provided on the substrate, A painted product having the above characteristics.

8. The painted article according to claim 7, wherein the material of the region on the substrate on which the coating film is provided is a metal material.

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