Aqueous coating composition, coating film, coated article and method for producing same

Abstract

Provided is an aqueous coating composition including: a first agent containing a hydrophilic (meth)acrylic polyol (A), at least one component (B) selected from the group consisting of polyaspartic acid esters (B1) and polylactone-modified polyols (B2), and water, and a second agent containing a polyisocyanate compound (C) and an epoxy group-containing silane coupling agent (D); or the abovementioned first agent, a second agent containing the polyisocyanate compound (C), and a third agent containing the epoxy group-containing silane coupling agent (D).

Description

Water-based coating composition, coating film, coated product and method for producing the same CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority based on Japanese Patent Application Nos. 2024-149009 and 2024-149010, filed on August 30, 2024, and incorporates by reference all the contents of those Japanese applications.

[0002] The present disclosure relates to a water-based paint composition, a coating film, a coated article, and a method for producing the same.

[0003] 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 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.

[0004] In order to protect the natural environment and the coating work environment, regulations on organic solvent emissions have been tightened in recent years. Water-based coating compositions generally contain less volatile organic compounds (VOCs) than organic solvent-based coating compositions. One method for reducing VOCs is to convert coating compositions to water-based compositions. For example, multi-component water-based polyurethane coating compositions containing a hydrophilic polyol as the base component and a hydrophilic polyisocyanate or low-viscosity polyisocyanate as the curing agent have been investigated (see, for example, Patent Documents 2 to 4).

[0005] JP 2017-193705 A JP 2013-151645 A JP 2018-178082 A JP 2022-186298 A

[0006] 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.

[0007] 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.

[0008] One aspect of the aqueous coating composition of the present disclosure comprises: a first agent containing a hydrophilic (meth)acrylic polyol (A), at least one component (B) selected from the group consisting of a polyaspartic acid ester (B1) and a polylactone-modified polyol (B2), 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), at least one component (B) selected from the group consisting of a polyaspartic acid ester (B1) and a polylactone-modified polyol (B2), and water; a second agent containing a polyisocyanate compound (C), and a third agent containing an epoxy group-containing silane coupling agent (D).

[0009] The water-based coating composition of the present disclosure can form a coating film that is excellent in appearance and corrosion resistance.

[0010] FIG. 1 is a table showing the evaluation criteria for the cross-cut tape peel test.

[0011] Each component described in this specification may be used singly or in combination of two or more types. 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.

[0012] 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, a numerical range formed by combining a value arbitrarily selected from the listed lower limit value and a value arbitrarily selected from the listed upper limit value is also considered to be listed.

[0013] [Water-based Coating Composition] One aspect of the water-based coating composition of the present disclosure comprises a first agent containing a hydrophilic (meth)acrylic polyol (A), at least one component (B) selected from the group consisting of a polyaspartic acid ester (B1) and a polylactone-modified polyol (B2), water, and a second agent containing a polyisocyanate compound (C) and an epoxy group-containing silane coupling agent (D). Another aspect of the water-based coating composition of the present disclosure comprises the first agent, a second agent containing the polyisocyanate compound (C), and a third agent containing the epoxy group-containing silane coupling agent (D). Another aspect of the water-based coating composition of the present disclosure comprises a hydrophilic (meth)acrylic polyol (A), at least one component (B) selected from the group consisting of a polyaspartic acid ester (B1) and a polylactone-modified polyol (B2), 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."

[0014] 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 preserved or stored 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.

[0015] <First Agent> The first agent, which constitutes one embodiment of the present composition, contains a hydrophilic (meth)acrylic polyol (A), at least one component (B) selected from the group consisting of a polyaspartic acid ester (B1) and a polylactone-modified polyol (B2), and water. In the following description, a first agent containing the hydrophilic (meth)acrylic polyol (A), the polyaspartic acid ester (B1), and water is also referred to as the "first agent of the first embodiment," and a composition containing the first agent of the first embodiment or a composition obtained using the first agent is also referred to as the "composition of the first embodiment." Furthermore, a first agent containing the hydrophilic (meth)acrylic polyol (A), the polylactone-modified polyol (B2), and water is also referred to as the "first agent of the second embodiment," and a composition containing the first agent of the second embodiment or a composition obtained using the first agent is also referred to as the "composition of the second embodiment." The first agent is preferably liquid at 1 atmosphere and 23°C.

[0016] <Hydrophilic (meth)acrylic polyol (A)> In this specification, "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 viewpoint of hydrophilicity, etc.

[0017] As used herein, "(meth)acrylic polyol" refers to a polyol having two or more hydroxy groups. As used herein, "(meth)acrylic" refers to acrylic and / or methacrylic, and expressions such as (meth)acrylate, which will be described later, have the same meaning.

[0018] 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 have two or more types of structural units derived from the other ethylenically unsaturated monomer.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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 achieving superior mechanical strength and water resistance of a coating film obtained from the composition. The hydroxyl value is measured in accordance with the neutralization titration method of JIS K0070:1992.

[0023] 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.

[0024] 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 achieving better drying properties of the composition and better crosslink density and weather resistance of the resulting coating film.

[0025] Mw is a polystyrene-equivalent value measured by gel permeation chromatography (GPC) under the following conditions. (GPC Measurement Conditions) Apparatus: "HLC-8320GPC" (manufactured by Tosoh Corporation) Column: "TSKgel guard column Super MP (HZ)-M + TSKgel Super Multipore HZ-M + TSKgel Super Multipore HZ-M" (both manufactured by Tosoh Corporation) Eluent: tetrahydrofuran (THF) Flow rate: 0.35 ml / min Detector: refractive index (RI) detector Column thermostat temperature: 40°C Calibration curve: standard polystyrene Sample preparation method: The polymer solution was diluted with THF and then filtered through a membrane filter, and the filtrate obtained was used as the GPC measurement sample.

[0026] Component (A) may be present in the composition or the first part in particulate form. 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 part, 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.

[0027] 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%.

[0028] 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.

[0029] Methods for synthesizing component (A) include known methods, such as a method of polymerizing a monomer in the presence of a radical polymerization initiator by solution polymerization, suspension polymerization, bulk polymerization, or emulsion polymerization.

[0030] One type of component (A) may be used, or two or more types may be used. From the viewpoints of improving the curing reactivity of the composition and improving the mechanical strength and water resistance of a coating film obtained from the composition, 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. 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.

[0031] The solid content of a substance (e.g., the present 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 1.0 g of the substance sample 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 (solid concentration) (mass%) of the substance is calculated from the amount of heating residue.

[0032] <Polyaspartic acid ester (B1)> In this specification, polyaspartic acid ester (B1) (hereinafter also referred to as "component (B1)") refers to a compound having two or more aspartic acid ester structures. The aspartic acid ester structure refers to a structure represented by formula (1). The number of aspartic acid ester structures in component (B1) is preferably 2 to 6, more preferably 2 to 4, and even more preferably 2.

[0033]

[0034] R in formula (1) 1 and R 2 R is each independently a monovalent organic group. 1 and R 2 The monovalent organic group in is preferably an organic group that is inactive to an isocyanate group under the drying conditions (curing reaction conditions) described below. Such an inactive organic group is preferably an organic group that does not have an active hydrogen-containing group such as a hydroxy group, an amino group, or a thiol group.

[0035] R 1 and R 2 The monovalent organic group in the formula (I) is preferably a monovalent hydrocarbon group. The number of carbon atoms in the monovalent hydrocarbon group is preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less.

[0036] Examples of the monovalent hydrocarbon group include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and a group formed by combining two or more groups selected from an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group.

[0037] The aliphatic hydrocarbon group may be linear or branched. The number of carbon atoms in the aliphatic hydrocarbon group is preferably 1 to 20, more preferably 1 to 15, even more preferably 1 to 10, and particularly preferably 1 to 4. The aliphatic hydrocarbon group is preferably an alkyl group or an alkenyl group, more preferably an alkyl group. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group.

[0038] The alicyclic hydrocarbon group may be, for example, monocyclic or polycyclic. The number of carbon atoms in the alicyclic hydrocarbon group is preferably 3 to 20, more preferably 3 to 15, and even more preferably 4 to 10. The alicyclic hydrocarbon group is preferably a cycloalkyl group or a cycloalkenyl group, and more preferably a cycloalkyl group. Examples of cycloalkyl groups include a cyclohexyl group and a methylcyclohexyl group.

[0039] The aromatic hydrocarbon group may be, for example, monocyclic or polycyclic. In the case of a polycyclic group, two or more rings may form a fused ring. The number of carbon atoms in the aromatic hydrocarbon group is preferably 6 to 20, more preferably 6 to 15, and even more preferably 6 to 10. The aromatic hydrocarbon group is preferably an aryl group. Examples of aryl groups include a phenyl group, a tolyl group, a xylyl group, and a naphthyl group.

[0040] Examples of groups that combine two or more groups selected from the group consisting of aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups include groups that consist of an alicyclic hydrocarbon group and an aliphatic hydrocarbon group, such as a cyclohexylmethyl group and a methylcyclohexylmethyl group; and groups that consist of an aromatic hydrocarbon group and an aliphatic hydrocarbon group, such as a benzyl group and a phenylethyl group.

[0041] R 1 and R 2As the monovalent organic group in the above formula (I), from the viewpoint of excellent pot life and the like, an aliphatic hydrocarbon group is preferred, an alkyl group is more preferred, an alkyl group having 1 to 20 carbon atoms is even more preferred, an alkyl group having 1 to 15 carbon atoms is still more preferred, an alkyl group having 1 to 10 carbon atoms is particularly preferred, and an alkyl group having 1 to 4 carbon atoms is most preferred.

[0042] As the component (B1), a compound represented by formula (2) is preferred.

[0043] The meanings of the symbols in formula (2) are as follows. X in formula (2) is an n-valent organic group. The n-valent organic group is preferably an n-valent hydrocarbon group or substituted hydrocarbon group. The n-valent hydrocarbon group or substituted hydrocarbon group preferably has 1 to 50 carbon atoms, more preferably 3 to 40 carbon atoms, even more preferably 5 to 30 carbon atoms, still more preferably 5 to 20 carbon atoms, and particularly preferably 10 to 16 carbon atoms.

[0044] Examples of the n-valent hydrocarbon group include an n-valent aliphatic hydrocarbon group, an n-valent alicyclic hydrocarbon group, an n-valent aromatic hydrocarbon group, and an n-valent group formed by combining two or more groups selected from the group consisting of aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. Among these groups, a divalent hydrocarbon group is preferred.

[0045] The n-valent aliphatic hydrocarbon group may be, for example, linear or branched. The number of carbon atoms in the n-valent aliphatic hydrocarbon group is preferably 1 to 30, more preferably 1 to 20, and even more preferably 1 to 10. Examples of the n-valent aliphatic hydrocarbon group include groups derived from alkanes (in the case of divalent groups, alkanediyl groups) and groups derived from alkenes (in the case of divalent groups, alkenediyl groups), with groups derived from alkanes being preferred. Examples of the alkanediyl group include methanediyl, ethanediyl, propanediyl, butanediyl, pentanediyl, and hexanediyl groups.

[0046] The n-valent alicyclic hydrocarbon group may be, for example, monocyclic or polycyclic. The number of carbon atoms in the n-valent alicyclic hydrocarbon group is preferably 3 to 30, more preferably 4 to 20, and even more preferably 5 to 10. Examples of the n-valent alicyclic hydrocarbon group include groups derived from cycloalkanes (cycloalkanediyl groups in the case of divalent groups) and groups derived from cycloalkenes (cycloalkenediyl groups in the case of divalent groups), with groups derived from cycloalkanes being preferred. Examples of cycloalkanediyl groups include cyclohexanediyl groups and methylcyclohexanediyl groups.

[0047] The n-valent aromatic hydrocarbon group may be, for example, monocyclic or polycyclic. In the case of a polycyclic group, two or more rings may form a fused ring. The number of carbon atoms in the n-valent aromatic hydrocarbon group is preferably 6 to 30, more preferably 6 to 20, and even more preferably 6 to 10. Examples of the n-valent aromatic hydrocarbon group include groups derived from aromatic hydrocarbons (arylene groups in the case of divalent groups). Examples of arylene groups include phenylene groups, toluenediyl groups, xylenediyl groups, and naphthylene groups.

[0048] Examples of the n-valent group formed by combining two or more groups selected from the group consisting of aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups include an n-valent group formed by combining an aliphatic hydrocarbon group with an alicyclic hydrocarbon group, and an n-valent group formed by combining an aliphatic hydrocarbon group with an aromatic hydrocarbon group.

[0049] Examples of n-valent groups combining an aliphatic hydrocarbon group and an alicyclic hydrocarbon group include dicyclohexylmethane-4,4'-diyl and bis(methylcyclohexyl)methane-4,4'-diyl. Examples of n-valent groups combining an aliphatic hydrocarbon group and an aromatic hydrocarbon group include diphenylmethane-4,4'-diyl and 2,2-diphenylpropane-4,4'-diyl.

[0050] Examples of the n-valent substituted hydrocarbon group include groups in which an ether bond is introduced into the above-mentioned aliphatic hydrocarbon group, and specifically, -A-(O-A) mIn the formula, each A is independently an alkanediyl group having 1 to 6 carbon atoms, preferably 2 to 4 carbon atoms, such as an ethanediyl group or a propanediyl group, and m is an integer of 1 or more, preferably 2 to 10, more preferably 2 to 6, and even more preferably 2 to 4.

[0051] As the n-valent organic group for X, from the viewpoint of, for example, providing a composition having an excellent pot life, an n-valent alicyclic hydrocarbon group, an n-valent group formed by combining an aliphatic hydrocarbon group with an alicyclic hydrocarbon group, or a group having an ether bond introduced into the above-mentioned aliphatic hydrocarbon group is more preferable, and an n-valent group formed by combining an aliphatic hydrocarbon group with an alicyclic hydrocarbon group is particularly preferable.

[0052] X in formula (2) is preferably an n-valent organic group obtained by removing amino groups (—NH) from a polyamine having n amino groups (hereinafter also referred to as an “organic group derived from a polyamine”).

[0053] The polyamine in the organic group of X is preferably an aliphatic and / or alicyclic polyamine from the viewpoint of providing a composition with an excellent pot life. That is, the organic group of X is preferably an organic group derived from an aliphatic and / or alicyclic polyamine. Examples of the polyamine include ethylenediamine, 1,2-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,5-diamino-2-methylpentane, 1,6-diaminohexane, 2,5-diamino-2,5-dimethylhexane, 2,2,4-trimethyl-1,6-diaminohexane, 2,4,4-trimethyl-1,6-diaminohexane, 1,11-diaminoundecane, 1,12-diamino-2, ... Nododecane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane, 2,4-hexahydrotolylenediamine, 2,6-hexahydrotolylenediamine, 2,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexylmethane, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, and 2,4,4'-triamino-5-methyldicyclohexylmethane.

[0054] The polyamine in the organic group of X may be, for example, a polyalkylene glycol diamine such as polyethylene glycol diamine or polypropylene glycol diamine, where "poly" includes "di," "tri," or "tetra."

[0055] R in formula (2) 1 and R 2 are R in formula (1), respectively. 1 and R 2 is synonymous with.

[0056] n in formula (2) and n in the n-valent group are integers of 2 or greater. From the viewpoint of ease of synthesis or availability of the polyaspartic acid ester, n is preferably an integer of 2 to 6, more preferably an integer of 2 to 4, and even more preferably 2.

[0057] Specific examples of component (B1) include compounds represented by formulas (2-1) to (2-4). Among these, from the viewpoints of the storage stability and usable life of the first agent, the physical properties of the coating film (e.g., adhesion to substrates, corrosion resistance), and the appearance of the coating film, compounds represented by formulas (2-2) to (2-4) are preferred, and compounds represented by formula (2-3) or (2-4) are more preferred, and from the viewpoint of the weather resistance of the coating film, compounds represented by formula (2-3) are particularly preferred.

[0058] In formula (2-4), m is the number of repeating propylene oxide groups.

[0059] In one embodiment, component (B1) is liquid and tends to have a low viscosity compared to, for example, polyol compounds.

[0060] The molecular weight of component (B1) is preferably 2000 or less, more preferably 1500 or less, even more preferably 1000 or less, still more preferably 800 or less, and particularly preferably 600 or less. From the viewpoint of reaction rate, the amine equivalent of component (B1) is preferably 100 to 500 g / mol, more preferably 150 to 400 g / mol, and even more preferably 200 to 350 g / mol. The amine equivalent is calculated from the molecular weight and number of amino groups of component (B1).

[0061] Component (B1) may be a commercially available product. Component (B1) can be produced, for example, by reacting a primary polyamine represented by formula (3) with a maleic acid ester or fumaric acid ester represented by formula (4). X-[NH2] n …(3) R 1 OOC-CH=CH-COOR 2 ...(4) X and n in formula (3) are defined the same as X and n in formula (2), respectively. R in formula (4) 1 and R 2 are R in formula (1), respectively. 1 and R 2 The primary polyamines include, for example, the polyamines described above in the description of the organic group of X. The maleic acid esters or fumaric acid esters include, for example, dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate, dimethyl fumarate, diethyl fumarate, dipropyl fumarate, and dibutyl fumarate.

[0062] The composition of the first aspect contains a polyaspartic acid ester (B1) in addition to a hydrophilic (meth)acrylic polyol (A) and a polyisocyanate compound (C). Such a composition has a well-balanced drying property, curing reactivity, and pot life, and is excellent in workability, and can form a coating film that is excellent in appearance and corrosion resistance in a corrosive environment or a high-temperature, high-humidity environment.

[0063] Polyaspartic acid ester (B1) has low solubility in water, making it difficult to stably disperse it in water. Furthermore, it tends to be incompatible with water, as it hydrolyzes over time in water. For this reason, aqueous coating compositions containing polyaspartic acid ester (B1) may not have high storage stability. However, the first agent of the first aspect of the present composition contains both polyaspartic acid ester (B1) and hydrophilic (meth)acrylic polyol (A), and therefore has excellent storage stability. While the reason for this is unclear, it is presumed that the hydrophilic (meth)acrylic polyol (A) stabilizes the polyaspartic acid ester (B1) in water, and particularly when an aqueous dispersion of hydrophilic (meth)acrylic polyol (A) is used, the aqueous dispersion emulsifies and stabilizes the polyaspartic acid ester (B1). However, the contents of the present disclosure are in no way bound by this presumption.

[0064] One type of component (B1) may be used, or two or more types may be used. The content of component (B1) in the composition of the first embodiment is preferably 3 to 40 mass%, more preferably 5 to 30 mass%, and even more preferably 8 to 20 mass%, based on the mass of the solid content of the composition, from the viewpoint of the balance between drying and curing properties and usable life. The content of component (B1) in the first agent of the first embodiment may be set so that the content of component (B1) in the solid content of the composition falls within the above range.

[0065] The content of component (B1) in the present composition of the first aspect or the first agent of the first aspect is preferably 20 to 250 parts by mass, more preferably 25 to 200 parts by mass, and even more preferably 30 to 150 parts by mass, per 100 parts by mass of component (A), from the viewpoints of the balance between the drying and curing properties and the pot life, the stability of component (B1), and the like.

[0066] <Polylactone-Modified Polyol (B2)> The first agent of the first aspect may further contain a polylactone-modified polyol (B2) (hereinafter also referred to as "component (B2)," excluding compounds corresponding to component (A)). The present composition of the first aspect may further contain component (B2). By using component (B2) together with the above components, it is likely that a coating film with even better corrosion resistance, adhesion to substrates, and weather resistance can be formed, although the reason is unclear. In addition, component (B2) can increase the solid content of the present composition. The first agent of the second aspect contains a polylactone-modified polyol (B2) (component (B2); excluding compounds corresponding to component (A)). By using component (B2) together with the above and following components, it is possible to form a coating film with excellent appearance, corrosion resistance, and adhesion to substrates, although the reason is unclear. In addition, component (B2) can increase the solid content of the present composition.

[0067] Component (B2) 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 (B2) 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 (B2) can be obtained, for example, by ring-opening addition polymerization of a lactone compound to a polyhydric alcohol.

[0068] 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 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.

[0069] 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.

[0070] As component (B2), polycaprolactone-modified polyols are preferred, and poly-ε-caprolactone-modified polyols are more preferred. As component (B2), from the viewpoints of the crosslink density and corrosion resistance of the coating film, ring-opening adducts of caprolactones to tri- or tetrahydric alcohols are preferred.

[0071] The hydroxyl value of component (B2) is preferably 50 to 1,000 mgKOH / g, more preferably 100 to 800 mgKOH / g, and even more preferably 130 to 600 mgKOH / g. Component (B2) having a hydroxyl value equal to or greater than the lower limit is preferred as a component of an aqueous coating composition. Component (B2) 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 is measured in accordance with the neutralization titration method of JIS K0070:1992. In the second embodiment, the hydroxyl value of component (B2) 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 properties to substrates such as metal substrates in corrosive environments or high-temperature, high-humidity environments.

[0072] The weight average molecular weight (Mw) of component (B2) 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). Details of the measurement conditions for the GPC method are as described above.

[0073] The first agent of the second aspect of the composition contains the hydrophilic (meth)acrylic polyol (A) as well as the polylactone-modified polyol (B2), and therefore has excellent storage stability. Although the reason for this is unclear, it is presumed that component (A) stabilizes component (B2) in water, and particularly when an aqueous dispersion of component (A) is used, the aqueous dispersion stabilizes component (B2). However, the contents of the present disclosure are not bound by this presumption in any way.

[0074] One type of component (B2) may be used, or two or more types may be used. When the composition of the first embodiment further contains component (B2), the content of component (B2) 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 prevention, adhesion, weather resistance, etc. The content of component (B2) in the first agent of the first embodiment may be set so that the content of component (B2) in the solid content of the composition falls within the above range.

[0075] The content of component (B2) in the composition of the second embodiment 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 (B2) in the first agent of the second embodiment may be set so that the content of component (B2) in the solid content of the composition falls within the above range. When component (B2) having a hydroxyl value of more than 500 mg KOH / g is used, the content of component (B2) in the composition of the second embodiment 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.

[0076] When the composition of the first aspect or the first agent of the first aspect further contains component (B2), the content of component (B2) in the composition or the first agent is preferably 10 to 200 parts by mass, more preferably 15 to 120 parts by mass, and even more preferably 20 to 60 parts by mass per 100 parts by mass of component (A), from the viewpoints of corrosion prevention, adhesion, weather resistance, etc.

[0077] The content of component (B2) in the composition of the second embodiment or the first pack of the second embodiment 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 (B2) having a hydroxyl value of more than 500 mg KOH / g is used, the content of component (B2) in the composition of the second embodiment or the first pack of the second embodiment is particularly preferably 30 parts by mass or less per 100 parts by mass of component (A) from the viewpoints of water resistance, etc.

[0078] <Water> The present composition is a water-based coating composition. In the present 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.

[0079] The water content in the first agent is preferably 20 to 70% by mass, more preferably 25 to 65% by mass, and even more preferably 30 to 60% by mass. The water content in the present composition is preferably 20 to 70% by mass, more preferably 25 to 65% by mass, and even more preferably 30 to 60% by mass. The water content is measured according to the Karl Fischer method using a water content measuring device (e.g., CA-310, manufactured by Nitto Seiko Analytech Co., Ltd.).

[0080] <<Other Components>> The present 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 above-mentioned other components may be used singly or in combination of two or more.

[0081] 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.

[0082] 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.

[0083] When the present composition contains an extender pigment, the content of the extender pigment in the present composition is preferably 1 to 50 mass %, more preferably 5 to 40 mass %, based on the mass of the solid content of the present 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 present composition falls within the above range. The same applies to the content of each component in the following explanation.

[0084] 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 solids content of the composition.

[0085] 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.

[0086] 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 being able to easily obtain a coating film that is excellent in balance between flexibility and adhesion.

[0087] 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 solid content of the paint composition

[0088] 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.

[0089] 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.

[0090] 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.

[0091] Examples of anti-sagging agents include organic thixotropes such as hydrogenated castor oil-based thixotropes, amide wax-based thixotropes, polyethylene oxide-based thixotropes, and urethane-based thixotropes; and inorganic thixotropes such as clay minerals (e.g., bentonite, smectite, and hectorite) and synthetic finely powdered silica. When the composition contains an anti-sagging agent, the content of the anti-sagging agent in the composition is preferably 0.01 to 3 mass %, more preferably 0.05 to 2 mass %, based on the mass of the solids content of the composition.

[0092] 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.

[0093] Examples of coalescents include alcohols, glycol ethers, and esters, and specific 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 of the first aspect contains a coalescent, the content of the coalescent is preferably 0.5 to 30 parts by mass, and more preferably 2 to 25 parts by mass, per 100 parts by mass of the total content of component (A), component (B1), and optional component (B2). When the composition of the second aspect contains a coalescing agent, the content of the coalescing agent is preferably 0.5 to 30 parts by mass, more preferably 2 to 25 parts by mass, per 100 parts by mass of the total content of component (A) and component (B2).

[0094] 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.

[0095] 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, addition reaction products 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.

[0096] 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 solids content of the present composition.

[0097] <Second Agent, Third Agent> The second agent, which constitutes one embodiment of the present composition, contains a polyisocyanate compound (C). The second agent 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 forms of the second agent and the third agent are not particularly limited, but it is preferable that each be liquid at 1 atmosphere and 23°C.

[0098] <Polyisocyanate Compound (C)> The polyisocyanate compound (C) (hereinafter also referred to as "component (C)") has two or more isocyanate groups per molecule. The number of isocyanate groups in component (C) is preferably 2 to 6, and more preferably 2 to 4.

[0099] As component (C), a water-dispersible polyisocyanate compound is preferred. 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.

[0100] 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).

[0101] Examples of aliphatic polyisocyanates include aliphatic diisocyanates, specifically 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.

[0102] As component (C), a hydrophilized polyisocyanate compound may be used, in which a hydrophilic group has been introduced into the above polyisocyanate compound. Examples of the hydrophilic group include an ether bond and an anionic group.

[0103] 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.

[0104] 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.

[0105] Of the component (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.

[0106] The mass ratio of isocyanate groups to the total mass of 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%.

[0107] One type of component (C) may be used, or two or more types may be used. The content of component (C) in the present 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 part 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 part.

[0108] In the composition of the first aspect, the equivalent ratio (NCO / (OH+NH)) of the number of equivalents of isocyanate groups (NCO) in the polyisocyanate compound (C) to the total number of equivalents (OH+NH) of the hydroxy groups in the hydrophilic (meth)acrylic polyol (A), the amino groups in the polyaspartic acid ester (B1), and the hydroxy groups in the optional polylactone-modified polyol (B2) is preferably 0.5 to 2.0, more preferably 0.7 to 1.5, and even more preferably 0.8 to 1.3. Compositions having this ratio exhibit, for example, an excellent balance between dry curing properties and pot life.

[0109] In the composition of the second aspect, the equivalent ratio (NCO / OH) of the number of equivalents of isocyanate groups (NCO) of the polyisocyanate compound (C) to the total number of equivalents (OH) of hydroxy groups of the hydrophilic (meth)acrylic polyol (A) and the polylactone-modified polyol (B2) is preferably 0.5 to 2.0, more preferably 0.7 to 1.5, and even more preferably 0.8 to 1.3. Compositions having this ratio exhibit, for example, an excellent balance between dry curing properties and usable life.

[0110] The equivalent number of each component is calculated as follows: Isocyanate group equivalent number = (amount of polyisocyanate compound × NCO group content (%) / 100) / molecular weight of NCO, Hydroxy group equivalent number of polyol = Hydroxyl value of polyol (mg KOH / g) × amount of polyol / molecular weight of KOH, Amino group equivalent number of polyaspartic acid ester = amount of polyaspartic acid ester / amine equivalent, 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 % by mass, and for convenience of unit conversion, the molecular weight of KOH is converted to mg and set to 56,100.

[0111] <Epoxy Group-Containing Silane Coupling Agent (D)> The present composition contains an epoxy group-containing silane coupling agent (D) (hereinafter also referred to as "component (D)"). The second part in the present composition may contain component (D). The present composition may further contain a third part containing component (D) in addition to the second part containing component (C).

[0112] In conventional water-based polyurethane coating compositions, carbon dioxide gas is easily generated due to the reaction between the polyisocyanate compound and the water contained in the coating, and therefore foam marks are easily observed in the coating film formed, resulting in poor appearance. By using the epoxy group-containing silane coupling agent (D) together with the above components in the present composition, foaming of carbon dioxide gas and the like can be suppressed when forming a coating film using the present composition, and for example, even if the coating film is thick, a coating film with excellent appearance can be formed. In addition, the coating film formed from the present composition has excellent adhesion (adhesion) and corrosion resistance to substrates such as metal substrates in corrosive environments or high-temperature, high-humidity environments.

[0113] 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.

[0114] Component (D) is preferably a compound represented by the following formula (5): 3 -Si(R 4 ) p (OR 5 ) 3-p ... (5) Each symbol in formula (5) will be explained below. 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 5 are 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, preferably 0 or 1.

[0115] 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.

[0116] Component (D) may be used alone or in combination with two or more other types. The content of component (D) in the present 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 present 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.

[0117] <Other Components> The second and / or third agent may further contain the other components described above. The other components may be used singly 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. The organic solvents may be used singly or in combination of two or more.

[0118] <Agents Other Than the Above-mentioned Agents> In one embodiment, the present composition is a multi-component composition having a first agent and a second agent, or a multi-component composition having a first agent, a second agent, and a third agent, preferably a multi-liquid composition, for example, a two-component composition consisting of a first agent and a second agent, or a three-component composition consisting of a first agent, a second agent, and a third agent. In one embodiment, the first agent may be a so-called main agent, and the second agent may be a so-called curing agent. Depending on the components used, the present composition may further contain agents other than the above-mentioned agents (hereinafter also referred to as "other agents").

[0119] <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.

[0120] 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.

[0121] The VOC content in the composition is calculated using the specific gravity of the composition, the solid concentration, and the water concentration according to the following formula: VOC content (g / L) = specific gravity of the composition × 1000 × (100 - solid concentration - water concentration) / 100

[0122] The specific gravity (g / mL) of the composition is a value calculated by filling a specific gravity cup having an internal volume of 100 mL with the composition (the mixture immediately after mixing the respective agents) and measuring the mass of the composition at a temperature of 23° C. The solid concentration is the content ratio of the above-mentioned solids in the composition, and the water concentration is the content ratio of the above-mentioned water in the composition, and the methods for measuring each are as described above.

[0123] <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.

[0124] Each of 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. All descriptions in this specification, except for those related to such dilution, are descriptions of the composition before dilution.

[0125] 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.

[0126] Because the composition is a water-based coating composition, it has minimal adverse effects on the environment and human body and also exhibits excellent storage stability. By using the composition, even thick coatings can be formed with suppressed foaming, excellent appearance (e.g., high gloss), excellent weather resistance, corrosion resistance, and excellent adhesion to substrates such as metal substrates. Therefore, the composition is suitable for applications such as topcoat coating, repair coating, and direct coating on metal substrates. Because of these excellent effects, the composition can be used as a primer paint, a topcoat paint, or a paint that can be used as both a primer and a topcoat. By using the composition, a coating film that meets the physical properties required for both the primer paint film and the topcoat paint film can be formed with a single paint, thereby improving the efficiency of the painting process, for example, by shortening the painting process time and reducing the number of steps.

[0127] [Coating Film and Coated Article] The coating film of the present disclosure is formed using the composition. One aspect of the coating film is believed to contain a polyurethane compound formed by the reaction of a hydrophilic (meth)acrylic polyol (A) with a polyisocyanate compound (C), and a polyurea compound formed by the reaction of a polyaspartic acid ester (B1) with a polyisocyanate compound (C), or a polyurethane-polyurea compound. Therefore, the coating film has, for example, excellent mechanical strength. In one embodiment, the coating film has a polyurethane structure and a polyurea structure. One aspect of the coating film is believed to contain a polyurethane compound formed by the reaction of a hydrophilic (meth)acrylic polyol (A) and / or a polylactone-modified polyol (B2) with a polyisocyanate compound (C). Therefore, the coating film has, for example, excellent mechanical strength. In one embodiment, the coating film has a polyurethane structure.

[0128] The coating film preferably has a dry thickness of 20 to 200 μm, more preferably 50 to 150 μm. The coating film preferably has a dry thickness of 50 μm or more. By using the present composition, even thick coatings can be formed that exhibit suppressed foaming, excellent appearance (e.g., high gloss), excellent weather resistance, corrosion resistance, and excellent adhesion to substrates such as metal substrates. The coating film can be formed, for example, by applying the present composition to a substrate and drying. Coating methods include, for example, brush coating, air spray coating, airless spray coating, roll coater coating, and immersion. However, electrocoating is not preferred. A coating film of the above thickness may be formed in a single coat or 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 less than 100°C, more preferably 5 to 40°C, even more preferably 10 to 30°C, or may be ambient temperature, for example. If the drying temperature is less than 100°C, the risk of coating defects occurring due to rapid boiling of water in the coating can be avoided.

[0129] The coated article of the present disclosure has a substrate and a coating film of the present disclosure provided on the substrate. The method for producing a coated article of the present disclosure includes a step of forming a coating film by applying the composition to a substrate and drying it. Details of the coating and drying are as described above. Examples of materials for the region of the substrate where 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, zinc plating, zinc thermal spraying), 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 a substrate that has been pretreated, such as by cleaning or blasting, to remove rust, dirt, paint (old coating), etc., adhering to the substrate.

[0130] 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.

[0131] The coated article may contain one or more layers of the coating film of the present disclosure. The coated article may further include an undercoat coating film between the substrate and the coating film of the present disclosure for the purpose of improving adhesion or corrosion resistance. The coated article may further include a topcoat coating film on the coating film of the present disclosure.

[0132] The term "undercoat coating film" encompasses not only known undercoat coating films (primer coating films) in the narrow sense, but also known coating films called "intermediate coating films." Primer coating films include, for example, coating films formed from various primer compositions such as epoxy resin-based or inorganic zinc-based. Intermediate coating films include, for example, coating films formed from various intermediate coating paint compositions such as epoxy resin-based or polyurethane resin-based. Topcoat coating films include, for example, coating films formed from two-component reactive curing compositions such as urethane resin-based paint compositions, or one-component compositions such as (meth)acrylic resin-based paint compositions.

[0133] The thickness of the undercoat and topcoat is preferably 50 to 500 μm, more preferably 100 to 350 μm, in terms of dry thickness, respectively.

[0134] 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.

[0135] [Examples] The present disclosure relates to the following [1] to

[16] , for example. [1] A water-based coating composition comprising a first agent containing a hydrophilic (meth)acrylic polyol (A), a polyaspartic acid ester (B1), 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 polyaspartic acid ester (B1), 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 water-based coating composition according to [1], wherein the first agent further contains a polylactone-modified polyol (B2). [3] The water-based coating composition according to [2], wherein the polylactone-modified polyol (B2) has three or more hydroxy groups. [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 polyaspartic acid ester (B1) is 3 to 40 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.

[0136] [5] A water-based coating composition comprising a first agent containing a hydrophilic (meth)acrylic polyol (A), a polylactone-modified polyol (B2), 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 (B2), and water, a second agent containing a polyisocyanate compound (C), and a third agent containing an epoxy group-containing silane coupling agent (D). [6] The water-based coating composition according to [5] above, wherein the polylactone-modified polyol (B2) has three or more hydroxy groups. [7] The water-based coating composition according to [5] or [6] above, wherein the polylactone-modified polyol (B2) has a hydroxyl value of 500 mgKOH / g or less. [8] The aqueous coating composition according to any one of [5] to [7], wherein the content of the hydrophilic (meth)acrylic polyol (A) is 5 to 40 mass%, the content of the polylactone-modified polyol (B2) 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.

[0137] [9] The aqueous coating composition according to any one of [1] to [8], wherein the water content in the aqueous coating composition is 20 to 70 mass %.

[10] The aqueous coating composition according to any one of [1] to [9], wherein the aqueous coating composition is used to form a coating film with a dry thickness of 50 μm or more.

[11] A coating film formed from the aqueous coating composition according to any one of [1] to

[10] .

[12] The coating film according to

[11] , wherein the dry thickness is 50 μm or more.

[13] A coated article comprising a substrate and the coating film according to

[11] or

[12] provided on the substrate.

[14] The coated article according to

[13] , wherein the region of the substrate where the coating film is provided is made of a metal material.

[15] A method for producing a coated article, comprising the step of applying the aqueous coating composition according to any one of [1] to

[10] to a substrate and drying the composition to form a coating film.

[16] A method for producing a coated article according to

[15] , wherein the dry thickness of the coating film is 50 μm or more.

[0138] 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.

[0139] [Raw Materials] The raw materials used to prepare the compositions of the Examples and Comparative Examples are listed in Table 1.

[0140] Example 1A A container was charged with 12.9 parts of ion-exchanged water, 0.1 parts of a flash rust inhibitor (Note 1), 1 part of a dispersant (Note 2), 0.4 parts of an anti-sagging agent (Note 3), 0.3 parts of an antifoaming agent 1 (Note 4), 16.8 parts of titanium oxide (Note 5), 10 parts of barium sulfate (Note 6), and 4 parts of calcium carbonate (Note 7), and the mixture was dispersed using a paint shaker according to the method of JIS K5600-2-5:1999 until the particle gauge reached 30 μm or less, thereby preparing a pigment dispersion.

[0141] To the prepared pigment dispersion, 42 parts of hydrophilic acrylic polyol (A-1) (Note 8), 7 parts of polyaspartic acid ester (B1-1) (Note 10), and 2.7 parts of coalescent (Note 17) 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 18), 0.4 parts of leveling agent (Note 19), and 2 parts of ion-exchanged water were added, and the contents of the container were stirred for an additional minute using a high-speed disperser to prepare the first pack.

[0142] Into a separate container, 90 parts of polyisocyanate (C-2) (Note 21) and 10 parts of epoxy group-containing silane coupling agent (D-1) (Note 22) were added, and the contents of the container were stirred using a high-speed disperser until uniform, to prepare a second part.

[0143] In this way, a two-component coating composition having a first component and a second component was obtained. 100 parts of the first component and 25 parts of the second component were mixed to prepare a coating composition.

[0144] Examples 2A to 25A and Comparative Examples 1A to 10A First and second agents were prepared in the same manner as in Example 1A, 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 paints.

[0145] Example 1B A container was charged with 12.9 parts of ion-exchanged water, 0.1 parts of a flash rust inhibitor (Note 1), 1 part of a dispersant (Note 2), 0.4 parts of an anti-sagging agent (Note 3), 0.3 parts of an antifoaming agent 1 (Note 4), 16.8 parts of titanium oxide (Note 5), 10 parts of barium sulfate (Note 6), and 4 parts of calcium carbonate (Note 7), and the mixture was dispersed using a paint shaker according to the method of JIS K5600-2-5:1999 until the particle gauge reached 30 μm or less, thereby preparing a pigment dispersion.

[0146] To the prepared pigment dispersion, 34 parts of hydrophilic acrylic polyol (A-1) (Note 8), 3 parts of polycaprolactone polyol (B2-2) (Note 14), and 2.7 parts of coalescent (Note 17) 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 18) and 0.4 parts of leveling agent (Note 19) were added, and the contents of the container were stirred for an additional minute using a high-speed disperser to prepare the first pack.

[0147] Into a separate container, 90 parts of polyisocyanate (C-1) (Note 20) and 10 parts of epoxy group-containing silane coupling agent (D-1) (Note 22) were added, and the contents of the container were stirred using a high-speed disperser until uniform, to prepare a second part.

[0148] 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.

[0149] [Examples 2B to 7B and Comparative Examples 1B to 6B] First and second agents were prepared in the same manner as in Example 1B, 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 paints.

[0150] [Storage stability of first agent] 300 g of each first agent of the Examples and Comparative Examples was weighed out immediately after preparation, placed in a sealable container, and stored 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.

[0151] (Evaluation criteria) 5: No separation, sedimentation, or agglomeration was observed in the first agent after storage for 2 months. 4: Slight separation was observed in the first agent after storage for 2 months, but no sedimentation or agglomeration was observed, and the agent was easily homogenized by stirring with a spoon. 3: Slight separation, sedimentation, and agglomeration was observed in the first agent after storage for 2 months, but the agent was easily homogenized by stirring with a spoon. 2: Separation, sedimentation, and agglomeration was observed in the first agent after storage for 2 months, and the agent was homogenized by stirring with a spoon, but it took some time to become homogenous. 1: Separation, sedimentation, and agglomeration was observed in the first agent after storage for 2 months, and the agent was not homogenized by stirring with a spoon.

[0152] [Appearance of Coating Film] Each of the coating materials of 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 to a dry film thickness of approximately 75 μm, and then dried for 7 days under conditions of a temperature of 23° C. and a humidity of 50% to form a coating film. Test specimens were prepared in this manner. The appearance of the test specimens was evaluated according to the following evaluation criteria. The evaluation results are shown in the table below.

[0153] (Evaluation criteria) 3: No traces of foaming were observed on the coating film, and leveling was good. 2: Slight traces of foaming were observed on the coating film, and leveling was slightly poor. 1: Traces of foaming were observed all over the coating film, and the appearance was extremely poor.

[0154] 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 carried out three times, and the average value is shown in the table.

[0155] [Initial Adhesion of Coating Film] A cross-cut tape peeling test (2 mm x 2 mm, 25 squares, cross-cut method) was performed on the above test specimen. Using a cutter guide, 6 vertical and 6 horizontal incisions were made on the coating surface of the test specimen, reaching down to the steel substrate, to form a 25-square cross-cut grid pattern. The incisions 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 an angle of 90° 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.

[0156] [Salt Spray Test] A salt spray test was carried out in accordance with JIS K 5600-7-1:1999 by holding the test specimens for 400 hours in a salt spray tester under salt spray conditions of 5% by mass salt water, 35°C temperature, and 98% relative humidity. After the test, the adhesion of the coating film was confirmed in the same manner as in [Initial Adhesion of Coating Film] above, and the corrosion resistance was evaluated according to the following evaluation criteria. The evaluation results are shown in the table below.

[0157] (Evaluation criteria) 5: Neither rust nor blisters have occurred. 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 number of small blisters have occurred, and the rusted 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 rusted area is 0.3% or more.

[0158] [Moisture Resistance Test] The above test pieces were placed in a moisture resistance tester maintained at a temperature of 50°C and a relative humidity of 95% for 400 hours to carry out a moisture resistance test. After the test, the adhesion of the coating film was confirmed in the same manner as in the above [Initial Adhesion of Coating Film], and the corrosion resistance was evaluated according to the above evaluation criteria. The evaluation results are shown in the table below.

[0159] [Weathering 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 hours, 1000 hours, 1200 hours, 1400 hours, and 1600 hours in accordance with ASTM G154 CYCLE 1. Thereafter, using a surface gloss meter (model: Micro Trigloss 4446, manufactured by BYK-Gardner), the reflectance of light incident at an angle of 60° from the normal to the coating surface after the weathering test (60° gloss) was measured. The gloss retention (%) of the 60° gloss after the weathering test relative to the 60° gloss value of the coating film before the weathering test was calculated. Measurements were performed three times, and the average values ​​are shown in the tables.

[0160]

[0161]

[0162]

[0163]

Claims

1. A water-based coating composition comprising: a first agent containing a hydrophilic (meth)acrylic polyol (A), at least one component (B) selected from the group consisting of a polyaspartic acid ester (B1) and a polylactone-modified polyol (B2), and water; and a second agent containing a polyisocyanate compound (C) and an epoxy group-containing silane coupling agent (D), or a water-based coating composition comprising: a first agent containing a hydrophilic (meth)acrylic polyol (A), at least one component (B) selected from the group consisting of a polyaspartic acid ester (B1) and a polylactone-modified polyol (B2), 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 water-based coating composition according to claim 1, wherein the first agent contains the polyaspartic acid ester (B1) and the polylactone-modified polyol (B2).

3. The aqueous coating composition according to claim 1, wherein the polylactone-modified polyol (B2) has three or more hydroxy groups.

4. The aqueous coating composition according to claim 1, wherein the first agent contains the polylactone-modified polyol (B2), and the polylactone-modified polyol (B2) has a hydroxyl value of 500 mg KOH / g or less.

5. The aqueous coating composition according to claim 1, wherein, in the composition, based on the mass of the solids content of the composition, the content of the hydrophilic (meth)acrylic polyol (A) is 5 to 40 mass%, the content of the polyaspartic acid ester (B1) is 3 to 40 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%.

6. The aqueous coating composition according to claim 1, wherein the content of the hydrophilic (meth)acrylic polyol (A) is 5 to 40 mass %, the content of the polylactone-modified polyol (B2) 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.

7. The aqueous coating composition according to claim 1, wherein the content of said water in said aqueous coating composition is 20 to 70 mass %.

8. The water-based coating composition according to claim 1, which is used to form a coating film having a dry thickness of 50 μm or more.

9. A coating film formed from the water-based coating composition according to any one of claims 1 to 8.

10. The coating film according to claim 9, having a dry film thickness of 50 μm or more.

11. A coated article comprising: a substrate; and a coating film according to claim 9 or 10 provided on the substrate.

12. The coated article according to claim 11, wherein the material of the region of the substrate where the coating film is provided is a metal material.

13. A method for producing a coated product, comprising the step of applying the water-based coating composition according to any one of claims 1 to 8 to a substrate and drying it to form a coating film.

14. The method for producing a coated product according to claim 13, wherein the dry thickness of the coating film is 50 μm or more.

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