One-pack aqueous paint composition

Abstract

This one-pack aqueous paint composition contains: an aqueous (meth)acrylic resin (A) having structural units derived from a versatic acid vinyl ester; an aqueous (meth)acrylic resin (B) free of structural units derived from a versatic acid vinyl ester; and water.

Description

One-component water-based paint composition

[0001] The present disclosure relates to a one-component water-based coating composition.

[0002] Steel structures such as ships, bridges, and tanks are coated with multilayer coatings of various specifications to fulfill various functions according to their intended purpose. For example, an anticorrosion coating film made of an anticorrosion coating composition (e.g., an epoxy resin-based anticorrosion coating composition) is applied as an undercoat paint to the surface of a substrate such as a steel structure, and a topcoat coating film made of a topcoat coating composition is applied on the anticorrosion coating film to enhance design, weather resistance, etc. Known topcoat coating compositions include, for example, two-component reactive curing compositions such as urethane resin-based coating compositions and one-component compositions such as (meth)acrylic resin-based coating compositions.

[0003] In order to protect the natural environment and the painting work environment, regulations on organic solvent emissions have been tightened in recent years, and in the field of paint compositions, development of aqueous paint compositions with low volatile organic compounds (VOC) content has been promoted (see, for example, Patent Documents 1 to 3).

[0004] JP 2016-222901 A JP 2022-157093 A International Publication No. 2020-022073

[0005] For example, it may be required to apply a coating composition such as an anticorrosive coating composition (e.g., an epoxy resin-based anticorrosive coating composition) to the surface of a substrate to form a resin coating film, and then apply an aqueous coating composition as a topcoat coating to the resin coating film to form a topcoat coating film.

[0006] Typically, after a coating composition is applied to a substrate to form a resin coating film, a topcoat coating composition is applied after a predetermined coating interval. When the steel structure is a ship, this interval tends to be long. Therefore, even if the interval is long, it is desirable that the topcoat coating film has high adhesion (adhesion) to the resin coating film. It is also desirable that such a topcoat coating film has excellent coating film condition. The present disclosure aims to provide an aqueous coating composition that is capable of forming a topcoat coating film that has excellent adhesion to the resin coating film and excellent coating film condition, even if an interval is long.

[0007] The present inventors have found that the above problems can be solved by an aqueous coating composition having the following composition: The aqueous coating composition of the present disclosure is a one-component aqueous coating composition containing an aqueous (meth)acrylic resin (A) having structural units derived from a versatate vinyl ester, an aqueous (meth)acrylic resin (B) not having structural units derived from a versatate vinyl ester, and water.

[0008] According to the present disclosure, it is possible to provide an aqueous coating composition that can form a topcoat coating film that has excellent adhesion to resin coating films and excellent coating film condition, even when an interval is left (for example, when the interval is long).

[0009] Fig. 1 is a schematic cross-sectional view of a multilayer coating film according to one embodiment. Fig. 2 is a schematic cross-sectional view of a coated product according to one embodiment. Fig. 3 is a table showing the evaluation criteria for a cross-cut tape peel test.

[0010] An embodiment of the present disclosure will be described in detail below. Each component described in this specification can be used singly or in combination. The term "polymer" is used to encompass both homopolymers and copolymers. That is, the term "polymer" can refer to either a homopolymer or a copolymer. "(Meth)acrylate" is a general term for acrylate and methacrylate. "(Meth)acrylic" is a general term for acrylic and methacrylic. "(Meth)acrylic acid" is a general term for acrylic acid and methacrylic acid. The same applies to other examples.

[0011] In this disclosure, the numerical range n1 to n2 means n1 or more and n2 or less. Here, n1 and n2 are any numbers that satisfy n1 < n2. In this disclosure, when multiple lower limit values ​​and multiple upper limit values ​​are listed for a certain element, 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.

[0012] "Constituent units derived from XX" means XX is A 1 A 2 C=CA 3 A4 (C═C is a polymerizable carbon-carbon double bond, A 1 ~A 4 are atoms or groups bonded to carbon atoms), the structural unit is, for example, represented by the following formula:

[0013]

[0014] [One-component aqueous coating composition] The one-component aqueous coating composition of the present disclosure (hereinafter also referred to as "the composition of the present disclosure") contains an aqueous (meth)acrylic resin (A) having a constituent unit derived from a vinyl ester of versatate, an aqueous (meth)acrylic resin (B) not having a constituent unit derived from a vinyl ester of versatate, and water.

[0015] In this specification, the term "aqueous (meth)acrylic resin" refers to a highly hydrophilic (meth)acrylic resin, and means a "water-soluble" (meth)acrylic resin that can be dissolved in water, or a "water-dispersible" (meth)acrylic resin that can be dispersed in water. Examples of such (meth)acrylic resins include water-soluble resins that have hydrophilic groups such as carboxyl groups and hydroxyl 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.

[0016] The effects of the composition of the present disclosure will be described below. Although water-based paint compositions have become more common in recent years, most steel structures require high corrosion protection performance over a long period of time. Therefore, organic solvent-based anticorrosion paint compositions containing an organic solvent as a solvent are still primarily used. For example, on steel structures, a topcoat paint composition may be applied to an anticorrosion coating film formed from an anticorrosion coating composition for the purpose of improving design and weather resistance. Traditionally, topcoat paint compositions have predominantly been organic solvent-based, similar to anticorrosion coating compositions, but demand for water-based paint compositions has increased in recent years. However, coatings formed from conventional water-based paint compositions tend to have lower adhesion (adhesion) to resin coatings compared to coatings formed from organic solvent-based paint compositions. In particular, when an aqueous paint composition is applied as a topcoat to a resin coating film formed from an organic solvent-based paint composition (e.g., an organic solvent-based epoxy resin paint composition), a significant decrease in adhesion is observed. This is presumably because the aqueous coating composition does not contain any organic solvent or contains only a small amount of organic solvent, so it cannot dissolve or swell the surface of the underlying resin coating film, and if the surface of the underlying resin coating film is hydrophobic, it is difficult to wet with water.Therefore, when a topcoat coating film is formed on a resin coating film using a composition that contains aqueous (meth)acrylic resin (B) but does not contain aqueous (meth)acrylic resin (A), the adhesion of the topcoat coating film to the resin coating film tends to be insufficient.

[0017] The composition of the present disclosure contains an aqueous (meth)acrylic resin (A) in addition to an aqueous (meth)acrylic resin (B). A topcoat coating film formed from the composition of the present disclosure has excellent adhesion and interval adhesion to a resin coating film, particularly a resin coating film formed from an organic solvent-based paint composition (e.g., an organic solvent-based epoxy resin paint composition). Herein, the adhesion of a topcoat coating film to a resin coating film formed on the surface of a substrate after a predetermined period of time has been determined and is also referred to as "interval adhesion" in this specification.

[0018] The topcoat coating film formed from the composition of the present disclosure has low tack and excellent coating film condition. The topcoat coating film formed from the composition of the present disclosure can exhibit gloss equal to or greater than that of topcoat coating films formed from conventional organic solvent-based (meth)acrylic resin-based topcoat coating compositions, and has excellent appearance.

[0019] <Aqueous (meth)acrylic resin (A)> The aqueous (meth)acrylic resin (A) has a structural unit derived from versatic acid vinyl ester (hereinafter also referred to as "Veova"). The structural unit derived from versatic acid vinyl ester is presumed to be able to impart appropriate hydrophobicity and appropriate flexibility to the coating film. In one embodiment, the aqueous (meth)acrylic resin (A) is a versatic acid vinyl ester copolymer. The versatic acid vinyl ester copolymer may be, for example, a random copolymer or a block copolymer.

[0020] The versatate vinyl ester copolymer may have a constituent unit derived from versatate vinyl ester and a constituent unit derived from a (meth)acrylic monomer, and may further have a constituent unit derived from another ethylenically unsaturated monomer copolymerizable with versatate vinyl ester and / or the (meth)acrylic monomer. The versatate vinyl ester copolymer may have two or more constituent units derived from versatate vinyl ester. The versatate vinyl ester copolymer may have two or more constituent units derived from a (meth)acrylic monomer. The versatate vinyl ester copolymer may have two or more constituent units derived from another ethylenically unsaturated monomer.

[0021] Versatic acid vinyl ester is a compound represented by the following formula (1):

[0022] In formula (1), R 1 and R 2 are each independently an alkyl group having 1 to 7 carbon atoms, and R 1 and R 2 may be bonded to each other to form a ring. 1 and R 2The total number of carbon atoms in formula (1) is preferably 6 to 10, more preferably 6 to 8. The total number of carbon atoms in formula (1) is preferably 11 to 15, more preferably 11 to 13.

[0023] Examples of the alkyl group include methyl, ethyl, propyl groups such as n-propyl and isopropyl, butyl groups such as n-butyl, tert-butyl, sec-butyl and isobutyl, pentyl groups such as n-pentyl, tert-pentyl, isopentyl and sec-pentyl, hexyl, heptyl, 1,1-dimethylbutyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1-ethylbutyl, 2-ethylbutyl, 3-ethylbutyl, and 1-methyl-1-ethylpropyl. The alkyl group may be linear or branched. R 1 and R 2 At least one of R is preferably a branched alkyl group. 1 and R 2 Both may be branched alkyl groups.

[0024] In one embodiment, R 1 is a propyl group, and R 2 is a propyl group, a butyl group, or a pentyl group. 1 is an n-butyl group, and R 2 is an isobutyl group.

[0025] 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 such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate; aryl (meth)acrylates such as phenyl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and the like. hydroxyalkyl (meth)acrylates such as butyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate; aminoalkyl (meth)acrylates such as aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and butylaminoethyl (meth)acrylate; and alkoxysilyl group-containing (meth)acrylates such as trimethoxysilylpropyl (meth)acrylate, triethoxysilylpropyl (meth)acrylate, tributoxysilylpropyl (meth)acrylate, dimethoxymethylsilylpropyl (meth)acrylate, and methoxydimethylsilylpropyl (meth)acrylate.Examples of (meth)acrylic acid amides include (meth)acrylic acid aminoalkylamides such as aminoethyl(meth)acrylamide, dimethylaminomethyl(meth)acrylamide, and methylaminopropyl(meth)acrylamide; and other amide group-containing (meth)acrylic monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-methylol(meth)acrylamide, methoxybutyl(meth)acrylamide, and diacetone(meth)acrylamide.

[0026] Examples of other ethylenically unsaturated monomers copolymerizable with versatic acid vinyl ester and / or (meth)acrylic monomers include α-olefins such as ethylene, propylene, and 1-butene; conjugated dienes such as 1,3-butadiene, isoprene, and chloroprene; styrene monomers such as styrene, α-methylstyrene, and halogenated styrene; vinyl esters (excluding versatic acid vinyl ester) such as vinyl acetate and vinyl propionate; vinyl cyanide compounds such as (meth)acrylonitrile; unsaturated monocarboxylic acids such as crotonic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; monoesters of unsaturated dicarboxylic acids such as ethyl maleate and butyl maleate; diesters of unsaturated dicarboxylic acids such as diethyl maleate and dibutyl maleate; and alkoxysilyl group-containing ethylenically unsaturated monomers such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyldimethoxymethylsilane, vinylmethoxydimethylsilane, and vinyltris(β-methoxyethoxy)silane.

[0027] Examples of the aqueous (meth)acrylic resin (A) include a versatic acid vinyl ester-(meth)acrylic monomer copolymer, a versatic acid vinyl ester-(meth)acrylic monomer-styrene monomer copolymer, and a versatic acid vinyl ester-vinyl ester copolymer.

[0028] The aqueous (meth)acrylic resin (A) may be a silicon-modified (meth)acrylic resin having a structural unit derived from a versatate vinyl ester.

[0029] Examples of the silicon-modified (meth)acrylic resin include resins in which a (meth)acrylic resin skeleton and a polysiloxane resin skeleton are bonded by a covalent bond, such as a block copolymer in which the ends of a (meth)acrylic resin and a polysiloxane resin are bonded together, a copolymer having a polysiloxane resin as the main skeleton and a (meth)acrylic resin bonded to the main skeleton as a side chain, and a copolymer having a (meth)acrylic resin as the main skeleton and a polysiloxane resin bonded to the main skeleton as a side chain. The (meth)acrylic resin in these examples has a structural unit derived from versatate vinyl ester.

[0030] The content ratio of the (meth)acrylic resin skeleton and the polysiloxane resin skeleton constituting the silicon-modified (meth)acrylic resin ((meth)acrylic resin skeleton / polysiloxane resin skeleton) on a mass basis is, for example, 1 / 10 to 50 / 1.

[0031] The silicon-modified (meth)acrylic resin may also be a versatic acid vinyl ester copolymer having a constituent unit derived from a versatic acid vinyl ester, a constituent unit derived from a (meth)acrylic monomer (excluding a constituent unit derived from a silyl group-containing unsaturated monomer), and a constituent unit derived from a silyl group-containing unsaturated monomer. Examples of the silyl group-containing unsaturated monomer include the above-mentioned alkoxysilyl group-containing (meth)acrylate and alkoxysilyl group-containing ethylenically unsaturated monomer. The versatic acid vinyl ester copolymer may have two or more constituent units derived from the silyl group-containing unsaturated monomer.

[0032] As the aqueous (meth)acrylic resin (A), from the viewpoint of being able to form a coating film having excellent weather resistance, a versatate vinyl ester-(meth)acrylic monomer copolymer and a silicon-modified (meth)acrylic resin having a constituent unit derived from a versatate vinyl ester are preferred.

[0033] In the aqueous (meth)acrylic resin (A), the content of the constituent units derived from versatate vinyl ester, based on 100% by mass of all constituent units, is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, even more preferably 35% by mass or more, and particularly preferably 40% by mass or more, 45% by mass or more, 50% by mass or more, or 55% by mass or more. A composition containing such an aqueous (meth)acrylic resin (A) can impart appropriate hydrophobicity and flexibility to a coating film, thereby forming a coating film that is excellent in water resistance and adhesion to resin coatings, particularly interval adhesion. In particular, when the content of the constituent units derived from versatate vinyl ester is 30% by mass or more, interval adhesion tends to be even better. In this specification, the content of each constituent unit is measured by nuclear magnetic resonance spectroscopy (NMR).

[0034] In the aqueous (meth)acrylic resin (A), the content of structural units derived from a versatate vinyl ester relative to 100% by mass of all structural units is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, even more preferably 75% by mass or less, and particularly preferably 70% by mass or less. Such an aqueous (meth)acrylic resin (A) tends to have excellent compatibility with the aqueous (meth)acrylic resin (B). In the aqueous (meth)acrylic resin (A), the content of structural units derived from a versatate vinyl ester relative to 100% by mass of all structural units is, for example, 20 to 90% by mass.

[0035] In the aqueous (meth)acrylic resin (A), the content of structural units derived from (meth)acrylic monomers in 100% by mass of all structural units is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, still more preferably 25% by mass or more, and particularly preferably 30% by mass or more, and is preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 70% by mass or less, still more preferably 65% ​​by mass or less, particularly preferably 60% by mass or less, 55% by mass or less, 50% by mass or less, or 45% by mass or less, for example, 10 to 80% by mass.

[0036] The glass transition temperature (Tg) of the aqueous (meth)acrylic resin (A) is preferably 0°C or higher, more preferably 5°C or higher, even more preferably 10°C or higher, and preferably 100°C or lower, more preferably 60°C or lower, even more preferably 50°C or lower, even more preferably 40°C or lower, and particularly preferably 30°C or lower, for example, 0 to 100°C. In this specification, Tg refers to the midpoint glass transition temperature obtained by differential scanning calorimetry (DSC) in accordance with JIS K7121:2012. A composition containing a resin (A) having a Tg equal to or higher than the lower limit can form a coating film that is excellent in strength and water resistance, and that is suppressed from softening or blistering even when exposed to high temperatures. A composition containing a resin (A) having a Tg equal to or lower than the upper limit can form a coating film that is excellent in adhesion to the substrate, and that is excellent in film-forming properties and suppressed from cracking, even when applied in low-temperature environments such as winter.

[0037] The aqueous (meth)acrylic resin (A) may have an acid value of more than 0 mgKOH / g. The acid value (unit: mgKOH / g) of the aqueous (meth)acrylic resin (A) is preferably 1 or more, more preferably 5 or more, even more preferably 10 or more, and preferably 35 or less, more preferably 30 or less, even more preferably 25 or less, for example, 1 to 35. An aqueous (meth)acrylic resin (A) having an acid value within this range has appropriate hydrophilicity and can exist stably in an aqueous paint composition. A resin (A) having an acid value equal to or greater than the lower limit has excellent stability in an aqueous paint composition. A composition containing a resin (A) having an acid value equal to or less than the upper limit can form a coating film with excellent water resistance, and the coating film is less likely to develop coating defects such as whitening or blisters when exposed to water, for example, from rain. In this specification, the acid value is the amount (mg) of potassium hydroxide required to neutralize acid groups such as carboxy groups per gram of nonvolatile matter in a sample, and is measured in accordance with JIS K0070:1992.

[0038] The aqueous (meth)acrylic resin (A) may be present in the composition in particulate form. For example, during application and drying of the composition, water evaporates, causing the particles to bond together and form a film. In this case, the average particle size of the aqueous (meth)acrylic resin (A) is not particularly limited, but is preferably 10 nm or more, more preferably 20 nm or more, even more preferably 30 nm or more, and particularly preferably 50 nm or more, and is preferably 2 μm or less, more preferably 1 μm or less, even more preferably 500 nm or less, even more preferably 300 nm or less, and particularly preferably 200 nm or less, for example, 10 nm to 2 μm. An aqueous (meth)acrylic resin (A) having an average particle size within this range tends to be able to exist stably in the aqueous coating composition and tends to be able to form a coating film with uniform coating film properties. In this specification, the average particle size refers to the volume-based average particle size measured by laser diffraction at 25°C.

[0039] When producing the composition of the present disclosure, it is preferable to use an aqueous dispersion in which the aqueous (meth)acrylic resin (A) is dispersed in a dispersion medium containing water (hereinafter also referred to as "aqueous medium"), and mix the aqueous dispersion with other components. This makes it easier for the aqueous (meth)acrylic resin (A) to be stably and uniformly present in the composition of the present disclosure, and tends to enable the formation of a coating film with uniform coating film properties. The aqueous dispersion is preferably an emulsion. The content of the aqueous (meth)acrylic resin (A) in the aqueous dispersion is, for example, 20 to 60 mass%.

[0040] The aqueous medium is not particularly limited as long as it contains water, but the water content in the aqueous medium is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, even more preferably 70 to 100% by mass, still more preferably 80 to 100% by mass, and particularly preferably 90 to 100% by mass. The aqueous medium may contain a medium other than water, and examples of such a medium 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, diacetone alcohol, dioxane, ethylene glycol, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol monopropyl ether, and ethylene glycol monohexyl ether.

[0041] The aqueous (meth)acrylic resin (A) may be a self-crosslinking type. Examples of a method for synthesizing the aqueous (meth)acrylic resin (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.

[0042] The content of the aqueous (meth)acrylic resin (A) per 100 parts by mass of the total content of the aqueous (meth)acrylic resin (A), the aqueous (meth)acrylic resin (B), and the optionally contained (meth)acrylic polyol (C) is preferably 30 parts by mass or more, more preferably 35 parts by mass or more, even more preferably 38 parts by mass or more, and is preferably 80 parts by mass or less, more preferably 75 parts by mass or less, even more preferably 70 parts by mass or less, still more preferably 65 parts by mass or less, and particularly preferably 60 parts by mass or less, for example, 30 to 80 parts by mass. Coating films formed from compositions having a content of the aqueous (meth)acrylic resin (A) within this range have low tack and excellent adhesion and interval adhesion to resin coating films such as organic solvent-based resin coating films, making them suitable as topcoat coating films.

[0043] <Aqueous (meth)acrylic resin (B)> The aqueous (meth)acrylic resin (B) has a structural unit derived from a (meth)acrylic monomer, but does not have a structural unit derived from a versatate vinyl ester. However, in the present disclosure, the aqueous (meth)acrylic resin (B) does not include the (meth)acrylic polyol (C) described later.

[0044] The aqueous (meth)acrylic resin (B) may be a homopolymer of a (meth)acrylic monomer, a copolymer of two or more (meth)acrylic monomers, or a copolymer of a (meth)acrylic monomer and another ethylenically unsaturated monomer copolymerizable with the (meth)acrylic monomer. The copolymer may be, for example, a random copolymer or a block copolymer. The aqueous (meth)acrylic resin (B) may have two or more types of structural units derived from the (meth)acrylic monomer. The aqueous (meth)acrylic resin (B) may have two or more types of structural units derived from the other ethylenically unsaturated monomer.

[0045] Examples of (meth)acrylic monomers include (meth)acrylic acid esters, (meth)acrylic acid amides, and (meth)acrylic acid. Specific examples of (meth)acrylic acid esters and (meth)acrylic acid amides are as described above. Specific examples of other ethylenically unsaturated monomers are as described above.

[0046] In the aqueous (meth)acrylic resin (B), the content of structural units derived from (meth)acrylic monomers in 100% by mass of all structural units is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, still more preferably 40% by mass or more, and particularly preferably 50% by mass or more.

[0047] Examples of the aqueous (meth)acrylic resin (B) include nonionic (meth)acrylic resins, anionic (meth)acrylic resins, and cationic (meth)acrylic resins. Examples of the aqueous (meth)acrylic resin (B) include (meth)acrylic monomer polymers which are homopolymers or copolymers of (meth)acrylic monomers, (meth)acrylic monomer-styrene monomer copolymers, (meth)acrylic monomer-vinyl ester copolymers, silicone-modified (meth)acrylic resins, and urethane-modified (meth)acrylic resins.

[0048] Examples of the silicon-modified (meth)acrylic resin include a resin in which a (meth)acrylic resin skeleton and a polysiloxane resin skeleton are bonded by a covalent bond, such as a block copolymer in which the ends of a (meth)acrylic resin and a polysiloxane resin are bonded together, a copolymer having a polysiloxane resin as a main skeleton to which a (meth)acrylic resin is bonded as a side chain, and a copolymer having a (meth)acrylic resin as a main skeleton to which a polysiloxane resin is bonded as a side chain. The mass ratio of the (meth)acrylic resin skeleton to the polysiloxane resin skeleton constituting the silicon-modified (meth)acrylic resin ((meth)acrylic resin skeleton / polysiloxane resin skeleton) is, for example, 1 / 10 to 50 / 1.

[0049] The silicon-modified (meth)acrylic resin may also be a copolymer having a structural unit derived from a (meth)acrylic monomer (excluding a structural unit derived from a silyl group-containing unsaturated monomer) and a structural unit derived from a silyl group-containing unsaturated monomer. Examples of the silyl group-containing unsaturated monomer include the above-mentioned alkoxysilyl group-containing (meth)acrylate and alkoxysilyl group-containing ethylenically unsaturated monomer. The silicon-modified (meth)acrylic resin may have two or more structural units derived from the silyl group-containing unsaturated monomer.

[0050] As the aqueous (meth)acrylic resin (B), from the viewpoint of being able to form a coating film having excellent weather resistance, a (meth)acrylic monomer polymer, a (meth)acrylic monomer-vinyl ester copolymer, a silicon-modified (meth)acrylic resin, and a urethane-modified (meth)acrylic resin are preferred.

[0051] The glass transition temperature (Tg) of the aqueous (meth)acrylic resin (B) is preferably 0°C or higher, more preferably 5°C or higher, even more preferably 8°C or higher, and preferably 70°C or lower, more preferably 60°C or lower, even more preferably 50°C or lower, for example, 0 to 70°C. A composition containing a resin (B) having a Tg within this range can form a coating film that has a good appearance and is excellent in water resistance and adhesion to the substrate. A composition containing a resin (B) having a Tg equal to or higher than the lower limit can form a coating film that is suppressed from softening or blistering even when exposed to a high-temperature environment. A composition containing a resin (B) having a Tg equal to or lower than the upper limit can form a coating film that has excellent film-forming properties and is suppressed from cracking, even when applied in a low-temperature environment such as winter.

[0052] The hydroxyl value (unit: mgKOH / g) of the aqueous (meth)acrylic resin (B) is preferably less than 30. In this specification, the hydroxyl value is the amount (mg) of potassium hydroxide required to neutralize acetic acid bonded to hydroxyl groups when 1 g of the nonvolatile content of a sample is acetylated, and is measured in accordance with JIS K0070:1992.

[0053] The aqueous (meth)acrylic resin (B) may be present in the composition 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 average particle size of the aqueous (meth)acrylic resin (B) is not particularly limited, but is preferably 10 nm or more, more preferably 20 nm or more, even more preferably 30 nm or more, and particularly preferably 50 nm or more, and is preferably 2 μm or less, more preferably 1 μm or less, even more preferably 500 nm or less, even more preferably 300 nm or less, and particularly preferably 200 nm or less, for example, 10 nm to 2 μm. An aqueous (meth)acrylic resin (B) having an average particle size within this range tends to be able to exist stably in the aqueous coating composition and tends to be able to form a coating film with uniform coating film properties.

[0054] When producing the composition of the present disclosure, it is preferable to use an aqueous dispersion in which the aqueous (meth)acrylic resin (B) is dispersed in an aqueous medium and mix the aqueous dispersion with other components. This makes it easier for the aqueous (meth)acrylic resin (B) to be stably and uniformly present in the composition of the present disclosure, and tends to enable the formation of a coating film with uniform coating properties. The aqueous dispersion is preferably an emulsion. The content of the aqueous (meth)acrylic resin (B) in the aqueous dispersion is, for example, 20 to 60 mass%.

[0055] The aqueous (meth)acrylic resin (B) may be a self-crosslinking type. Examples of a method for synthesizing the aqueous (meth)acrylic resin (B) 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.

[0056] The content of the aqueous (meth)acrylic resin (B) in 100 parts by mass of the total content of the aqueous (meth)acrylic resin (A), the aqueous (meth)acrylic resin (B), and the optionally contained (meth)acrylic polyol (C) is preferably 20 parts by mass or more, more preferably 25 parts by mass or more, even more preferably 30 parts by mass or more, and is preferably 65 parts by mass or less, more preferably 60 parts by mass or less, even more preferably 55 parts by mass or less, for example, 20 to 65 parts by mass. A composition having a content of the aqueous (meth)acrylic resin (B) within this range can form a coating film that has good appearance and is excellent in water resistance, adhesion to the substrate, and interval adhesion.

[0057] <(Meth)acrylic polyol (C)> The composition of the present disclosure may further contain a (meth)acrylic polyol (C). The (meth)acrylic polyol (C) is a relatively low-molecular-weight aqueous (meth)acrylic resin having multiple hydroxy groups. Coating films formed from such compositions tend to have excellent initial gloss and leveling, in addition to the above-mentioned adhesion and long-term interval adhesion.

[0058] Examples of the (meth)acrylic polyol (C) include a copolymer of an ethylenically unsaturated monomer having a hydroxy group and another ethylenically unsaturated monomer copolymerizable therewith. The (meth)acrylic polyol (C) may have two or more structural units derived from the ethylenically unsaturated monomer having a hydroxy group. The (meth)acrylic polyol (C) may have two or more structural units derived from the other ethylenically unsaturated monomer.

[0059] Examples of the ethylenically unsaturated monomer having a hydroxy group include the above-mentioned hydroxyalkyl (meth)acrylates. Examples of the other ethylenically unsaturated monomer include the above-mentioned (meth)acrylic monomers (excluding the above-mentioned hydroxyalkyl (meth)acrylates) and the above-mentioned other ethylenically unsaturated monomers other than the (meth)acrylic monomers.

[0060] The hydroxyl value (unit: mgKOH / g) of the (meth)acrylic polyol (C) is preferably 30 or more, more preferably 50 or more, even more preferably 70 or more, and is preferably 300 or less, more preferably 250 or less, even more preferably 200 or less, for example, 30 to 300. When the hydroxyl value of the (meth)acrylic polyol (C) is within this range, the compatibility between the aqueous (meth)acrylic resin (A) and the aqueous (meth)acrylic resin (B) can be improved, and the storage stability of the composition of the present disclosure can be further improved.

[0061] The (meth)acrylic polyol (C) may have an acid value of more than 0 mgKOH / g. The acid value (unit: mgKOH / g) of the (meth)acrylic polyol (C) is preferably 1 or more, more preferably 3 or more, even more preferably 5 or more, and is preferably 30 or less, more preferably 25 or less, even more preferably 20 or less, for example, 1 to 30.

[0062] The weight average molecular weight (Mw) of the (meth)acrylic polyol (C) is preferably 1,000 or more, more preferably 2,000 or more, even more preferably 5,000 or more, and is preferably 100,000 or less, more preferably 50,000 or less, even more preferably 30,000 or less, for example, 1,000 to 100,000. A composition containing such a relatively low molecular weight (meth)acrylic polyol (C) can form a coating film that is excellent in initial gloss and leveling properties.

[0063] 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.

[0064] The (meth)acrylic polyol (C) may be present in the composition 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 average particle size of the (meth)acrylic polyol (C) is not particularly limited, but is preferably 10 nm or more, more preferably 20 nm or more, even more preferably 30 nm or more, and particularly preferably 50 nm or more, and is preferably 2 μm or less, more preferably 1 μm or less, even more preferably 500 nm or less, even more preferably 300 nm or less, and particularly preferably 200 nm or less, for example, 10 nm to 2 μm. A (meth)acrylic polyol (C) having an average particle size within this range tends to be able to exist stably in the aqueous coating composition and tends to be able to form a coating film with uniform coating film properties.

[0065] When producing the composition of the present disclosure, it is preferable to use an aqueous dispersion in which the (meth)acrylic polyol (C) is dispersed in an aqueous medium and mix the aqueous dispersion with other components. This makes it easier for the (meth)acrylic polyol (C) to be stably and uniformly present in the composition of the present disclosure, and tends to enable the formation of a coating film with uniform coating properties. The aqueous dispersion is preferably an emulsion. The content of the (meth)acrylic polyol (C) in the aqueous dispersion is, for example, 20 to 60 mass%.

[0066] When the composition of the present disclosure contains a (meth)acrylic polyol (C), the content of the (meth)acrylic polyol (C) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, and preferably 40 parts by mass or less, more preferably 35 parts by mass or less, even more preferably 30 parts by mass or less, for example, 5 to 40 parts by mass, per 100 parts by mass of the total content of the aqueous (meth)acrylic resin (A), the aqueous (meth)acrylic resin (B), and the (meth)acrylic polyol (C). A composition having a (meth)acrylic polyol (C) content within this range can form a coating film with excellent gloss and leveling properties. Furthermore, a composition having a (meth)acrylic polyol (C) content equal to or less than the upper limit can form a coating film that is less susceptible to cracking and has excellent adhesion.

[0067] In the composition of the present disclosure, the total proportion of the aqueous (meth)acrylic resin (A), the aqueous (meth)acrylic resin (B), and the (meth)acrylic polyol (C) relative to the total amount of solids in the composition is preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, for example, 40 to 90% by mass.

[0068] <Other Components> The composition of the present disclosure may contain other components such as pigments, rust inhibitors, and additives, as long as the effects of the present invention are not impaired. Examples of additives include dispersants, wetting agents, anti-sagging agents (anti-settling agents, thixotropic agents, rheology control agents), antifoaming agents, film-forming aids, leveling agents, surfactants, thickeners, mildew inhibitors, preservatives, UV absorbers, pH adjusters, antioxidants, and flash rust inhibitors. These may be used alone or in combination of two or more.

[0069] 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 pigments. When the composition of the present disclosure contains a pigment, the pigment may be used alone or in combination of two or more types.

[0070] 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.

[0071] When the composition of the present disclosure contains an extender pigment, the content of the extender pigment is preferably 1% by mass or more, more preferably 5% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, for example, 1 to 50% by mass, relative to 100% by mass of the total solid content of the composition.

[0072] 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, cyanine blue, and cyanine green; and gloss pigments such as aluminum flakes, flaky iron oxide, and stainless steel flakes.

[0073] When the composition of the present disclosure contains a color pigment, the content of the color pigment is, relative to 100% by mass of the total solid content in the composition, preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, for example, 1 to 50% by mass.

[0074] 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.

[0075] When the composition of the present disclosure contains an anti-rust pigment, the content of the anti-rust pigment is preferably 1% by mass or more, more preferably 3% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, for example, 1 to 20% by mass, relative to 100% by mass of the total solid content of the composition.

[0076] 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 of the present disclosure is not particularly limited.

[0077] The composition of the present disclosure preferably contains a dispersant from the viewpoints of improving the dispersibility of pigments and the like in the composition, facilitating the formation of a coating film with good appearance and excellent crack resistance, etc. Examples of dispersants include polymers having a pigment-adsorbing group (pigment-affinity group) and a compatible chain such as fatty acid, polyamino, polyether, polyester, polyurethane, and polyacrylate. Examples of pigment-adsorbing groups include a carboxy group, a phosphate group, an amino group, salt groups thereof, and an ammonium salt group.

[0078] When the composition of the present disclosure contains a dispersant, the content of the dispersant is, relative to 100% by mass of the total solid content in the composition, preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and preferably 3% by mass or less, more preferably 2% by mass or less, for example, 0.1 to 3% by mass.

[0079] The composition of the present disclosure preferably contains an anti-sagging agent from the viewpoints of improving thick coating properties and anti-sagging properties during application and suppressing the settling of insoluble components such as pigments in water. Examples of the anti-sagging agent 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.

[0080] When the composition of the present disclosure contains an anti-sagging agent, the content of the anti-sagging agent is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and preferably 3% by mass or less, more preferably 2% by mass or less, for example, 0.01 to 3% by mass, relative to 100% by mass of the total solid content in the composition.

[0081] The defoaming agent is preferably a material that can suppress the generation of bubbles during the production and application of the coating composition, or a material that can break down bubbles that have formed in the coating composition. The use of a defoaming agent can, for example, suppress the generation of bubble marks or pinholes in the coating film, thereby improving the film-forming properties and crack resistance of the coating film. Examples of defoaming agents include silicone-based defoaming agents, polymer-based (non-silicone-based) defoaming agents, and mineral oil-based defoaming agents.

[0082] When the composition of the present disclosure contains an antifoaming agent, the content of the antifoaming agent is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and preferably 5% by mass or less, more preferably 3% by mass or less, for example, 0.05 to 5% by mass, relative to 100% by mass of the total solid content in the composition.

[0083] The composition of the present disclosure preferably contains a coalescing aid, since the composition may freeze in winter due to the inclusion of water, and from the viewpoint of improving film-forming properties at low temperatures and the finished appearance of the resulting coating film. Examples of coalescing aids include alcohols, glycol ethers, and esters, and specific examples include alcohols having 1 to 3 carbon atoms such as isopropyl alcohol, 2,2,4-trimethylpentanediol, benzyl alcohol, and other alcohols; 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.

[0084] When the composition of the present disclosure contains a coalescing agent, the content of the coalescing agent is preferably 0.5 parts by mass or more, more preferably 2 parts by mass or more, and preferably 30 parts by mass or less, more preferably 25 parts by mass or less, for example, 0.5 to 30 parts by mass, relative to 100 parts by mass of the total content of the aqueous (meth)acrylic resin (A), the aqueous (meth)acrylic resin (B), and the (meth)acrylic polyol (C) that is optionally contained in the composition.

[0085] The composition of the present disclosure preferably contains a leveling agent from the viewpoints of improving cissing of the coating film when the composition is applied, improving wettability to the surface of the object to be coated, and easily obtaining a coating film of uniform thickness, etc. Examples of the leveling agent include various leveling agents such as fluorine-based, acrylic-based, and silicone-based leveling agents.

[0086] When the composition of the present disclosure contains a leveling agent, the content of the leveling agent is, relative to 100% by mass of the total solid content in the composition, preferably 0.005% by mass or more, more preferably 0.01% by mass or more, and preferably 2% by mass or less, more preferably 1.5% by mass or less, for example, 0.005 to 2% by mass.

[0087] The thickener may be, for example, a commercially available product generally sold as a thickener, such as an alkali thickener, a nonionic association thickener, an acrylic thickener, a urethane thickener, a water-soluble polymer thickener, a polyamide thickener, or a hydroxyethyl cellulose thickener.

[0088] When the composition of the present disclosure contains a thickener, the content of the thickener is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and preferably 5% by mass or less, more preferably 1% by mass or less, for example, 0.01 to 5% by mass, relative to 100% by mass of the total solid content in the composition.

[0089] When an aqueous coating composition is applied to an active steel surface or the like, immediately after application and during the drying process, rust may occur due to the elution of iron ions from the steel surface, and the rust may appear on the surface of the coating film, causing flash rust. In order to suppress such flash rust, the composition of the present disclosure preferably contains a flash rust inhibitor.

[0090] Examples of flash rust inhibitors include nitrites such as sodium nitrite, potassium nitrite, calcium nitrite, strontium nitrite, barium nitrite, and ammonium nitrite; benzoates such as sodium benzoate, potassium benzoate, calcium benzoate, and ammonium benzoate; phytates such as sodium phytate and potassium phytate; organic carboxylates such as sebacic acid and dodecanoic acid; phosphoric acid derivatives such as alkyl phosphates and polyphosphoric acids; tannates; metal sulfonates; N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA), ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid ( Examples of suitable chelating agents include amine-based chelating agents such as propylenediaminetetraacetic acid (DTPA), propylenediaminetetraacetic acid (PDTA), iminodiacetic acid, nitrilotriacetic acid (NTA), diethylenetriaminepentamethylenephosphonic acid (DTPMP), and alkali metal salts thereof; addition reaction products of 4-methyl-γ-oxo-benzenebutanoic acid and N-ethylmorpholine; intercalation compounds obtained by intercalating monoalkylamines, polyamines, quaternary ammonium ions, etc., into layered phosphates such as aluminum dihydrogen tripolyphosphate; hydrazine derivatives such as hydrazide compounds, semicarbazide compounds, and hydrazone compounds; and azole compounds such as benzotriazole, its derivatives, and salts thereof. Among these, nitrites (e.g., metal salts such as sodium, potassium, calcium, etc., and ammonium salts) and benzoates (e.g., metal salts such as sodium, potassium, calcium, etc., and ammonium salts) are preferred from the viewpoints of excellent flash rust resistance and low cost. Nitrite is more preferred, and sodium nitrite is particularly preferred from the viewpoint of easily obtaining a composition that exhibits high flash rust resistance even when used in small amounts.

[0091] When the composition of the present disclosure contains a flash rust inhibitor, the content of the flash rust inhibitor is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and is preferably 5% by mass or less, more preferably 3% by mass or less, for example, 0.05 to 5% by mass, relative to 100% by mass of the total solids content in the composition.

[0092] <Water> The composition of the present disclosure is an aqueous coating composition. In this disclosure, an "aqueous" coating composition refers to a coating composition containing water. The water is not particularly limited, and examples include tap water, ion-exchanged water, and deionized water, with ion-exchanged water and deionized water being preferred. The water includes water that serves as a dispersion medium when the aqueous (meth)acrylic resin (A), the aqueous (meth)acrylic resin (B), and the optional (meth)acrylic polyol (C) are dispersed in an aqueous medium, as well as water contained in additives. The water content in the composition of the present disclosure is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more, and preferably 70% by mass or less, more preferably 65% ​​by mass or less, and even more preferably 60% by mass or less, for example, 20 to 70% by mass.

[0093] From the viewpoint of providing a composition with excellent coating workability, the content ratio of the total solids in the composition of the present disclosure is preferably 30% by mass or more, more preferably 35% by mass or more, even more preferably 40% by mass or more, and is preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 70% by mass or less, for example, 30 to 80% by mass.

[0094] <VOC> The content of volatile organic compounds (VOCs) in the composition of the present disclosure 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 of the present disclosure, the more preferable it is, 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.

[0095] Examples of VOCs include organic solvents, such as aromatic hydrocarbon solvents such as toluene, o-xylene, m-xylene, p-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.

[0096] In the present disclosure, the content of VOCs in the composition is calculated based on the following formula (1) using the specific gravity of the composition, the solid concentration, and the water concentration: VOC content (g / L) = specific gravity of the composition × 1000 × (100 - solid concentration - water concentration) / 100 (1)

[0097] The specific gravity (g / mL) of a composition is a value calculated by filling a 100 mL volumetric density cup with the composition at a temperature of 23°C and measuring the mass of the composition. The solid content concentration (mass%) is a value calculated by the method described in the Examples section below. In the present disclosure, the solid content in a composition refers to the heating residue (non-volatile content) when the composition is dried in an incubator at 108°C for 3 hours, as described in the Examples section below. Similarly, the solid content in each component (e.g., aqueous dispersion) refers to the heating residue (non-volatile content) when each component is dried in an incubator at 108°C for 3 hours, as described in the Examples section below. The water concentration (mass%) is the amount of water (mass%) contained in 100% by mass of a composition, and is measured using a water content measuring device (e.g., CA-310, manufactured by Nitto Seiko Analytech Co., Ltd.) according to the Karl Fischer method.

[0098] <Method for Producing Composition> The composition of the present disclosure can be produced by appropriately utilizing a known method. For example, the aqueous (meth)acrylic resin (A), the aqueous (meth)acrylic resin (B), optionally the (meth)acrylic polyol (C), and optionally other components are added to a stirring vessel all at once or in any order, and the components are mixed by known stirring and mixing means to be dispersed or dissolved in water to produce the composition. In the above mixing, an aqueous dispersion in which the aqueous (meth)acrylic resin (A) is dispersed in an aqueous medium may be used, or an aqueous dispersion in which the aqueous (meth)acrylic resin (B) is dispersed in an aqueous medium may be used, or an aqueous dispersion in which the (meth)acrylic polyol (C) is dispersed in an aqueous medium may be used.

[0099] For mixing (kneading), conventionally known devices such as mixers, dispersers, and stirrers can be used. Examples of such devices include dispersers, mixing and dispersion mills, mortar mixers, rolls, paint shakers, and homogenizers. Mixing (kneading) may be performed while heating or cooling depending on the season, environment, and the like.

[0100] The composition of the present disclosure is an aqueous coating composition, and therefore has minimal adverse effects on the environment and human body, and also has excellent storage stability. Even when the composition of the present disclosure is applied over a wide range of applications, the coating film formed has excellent adhesion (tightness) to the base coating film, and is less likely to crack or peel off, making the composition suitable for topcoat application or repair application.

[0101] [Uses of Coating Composition, Laminated Coating Film, and Coated Article] The composition of the present disclosure is applied to, for example, a substrate. The substrate refers to an article to which the composition of the present disclosure is applied. Examples of the surface material of the substrate to which the composition is applied include resin coatings, metal materials, wood, plastic, rubber, stone, concrete, mortar, glass, porcelain, ceramics, and composites thereof. Examples of resin coatings include primer coatings, intermediate coatings, and resin coatings (old coatings) to be repaired. Examples of metal materials include steel (iron, steel, ferroalloy, carbon steel, mild steel, alloy steel, etc.), non-ferrous metals (zinc, aluminum, copper, brass, zinc plating, zinc spraying, etc.), and stainless steel (SUS304, SUS410, etc.).

[0102] The object to be coated may have, for example, a substrate and a resin coating film provided on the surface of the substrate. Examples of the material of the substrate where the resin coating film is provided include metal materials, wood, plastic, rubber, stone, concrete, mortar, glass, porcelain, pottery, and composites thereof, with metal materials being preferred. Specific examples of the substrate include ships, vehicles, aircraft, buildings, bridges, plants, tanks, containers, pipes, steel pipes, and cast iron pipes, such as structures such as steel structures. The substrate may be a land structure or a marine structure.

[0103] In order to remove rust, oil, moisture, dust, salt, old coatings, etc. from the substrate and to improve adhesion between the substrate and coating, the substrate surface may be treated as needed (for example, blast treatment (ISO8501-1 Sa2 1 / 2), degreasing to remove oil and dust, etc.). The surface of the substrate may be coated with a shop primer or the like for the purpose of primary rust prevention.

[0104] The coating film of the present disclosure is formed from the composition of the present disclosure. The coating film of the present disclosure is excellent in appearance, coating film condition, weather resistance, and the like, and is therefore suitable as a topcoat coating film to be laminated on a resin coating film. The thickness (dry film thickness) of the coating film of the present disclosure is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, and preferably 1,000 μm or less, more preferably 500 μm or less, even more preferably 300 μm or less, for example, 10 to 1,000 μm. The composition may be applied multiple times to form a coating film having a desired thickness. A coating film having a desired thickness may be formed by a single application (single application), or by two or more applications (two or more applications).

[0105] The coating film of the present disclosure can be formed by applying the composition of the present disclosure to an object to be coated and drying it. Application methods include, for example, spray coating, such as airless spray coating and air spray coating, brush coating, and roller coating. The composition of the present disclosure can be dried by natural drying or by heat drying. In the case of natural drying, the drying time to obtain a dried coating film is preferably 1 hour or more, more preferably 1 day or more, and even more preferably 5 days or more. In the case of heat drying, a hot air dryer may be used. In the case of heat drying, the drying time to obtain a dried coating film is, for example, 5 to 60 minutes, and the drying temperature is preferably 30°C or more and less than 100°C, more preferably 40 to 80°C.

[0106] The multilayer coating film of the present disclosure has a resin coating film and a coating film of the present disclosure provided on the surface of the resin coating film. Figure 1 shows a schematic cross-sectional view of one embodiment of the multilayer coating film of the present disclosure. The multilayer coating film 1 of Figure 1 has a resin coating film 10 and a coating film 20 of the present disclosure provided on the surface of the resin coating film 10. In one embodiment, the resin coating film includes an epoxy resin coating film such as an epoxy resin-based corrosion-protective coating film.

[0107] The resin coating film may be, for example, an undercoat coating film intended to improve adhesion to a substrate or corrosion resistance, or may have an undercoat coating film and an intermediate coating film provided on the undercoat coating film. That is, the resin coating film may have a laminated structure. The laminated coating film of the present disclosure may have, for example, an undercoat coating film and a coating film of the present disclosure as a topcoat coating film, in this order in the thickness direction, or may have an undercoat coating film, an intermediate coating film, and a coating film of the present disclosure as a topcoat coating, in this order in the thickness direction.

[0108] The undercoat film may be, for example, a film formed from various anticorrosion coating compositions such as an epoxy resin-based anticorrosion coating composition. The thickness of the undercoat film is preferably 20 to 300 μm, more preferably 20 to 250 μm.

[0109] Examples of intermediate coating films include coating films formed from various intermediate coating compositions such as (meth)acrylic resin coating compositions, epoxy resin coating compositions, and urethane resin coating compositions. The thickness of the intermediate coating film is preferably 10 to 300 μm, more preferably 10 to 250 μm.

[0110] As described above, the coating film of the present disclosure has excellent adhesion and interval adhesion to resin coating films such as epoxy resin coating films (e.g., epoxy resin-based corrosion-protective coating films), particularly to resin coating films formed from organic solvent-based paint compositions (e.g., organic solvent-based epoxy resin paint compositions).

[0111] The coated article of the present disclosure has a substrate and a coating film of the present disclosure. The coated article of the present disclosure preferably has a substrate and a laminate coating film of the present disclosure, specifically, a substrate, a resin coating film, and a coating film of the present disclosure, in that order in the thickness direction. Figure 2 shows a schematic cross-sectional view of one embodiment of the coated article of the present disclosure. The coated article 2 of Figure 2 has a substrate 30 and a laminate coating film 1 of the present disclosure provided on the substrate 30. Details of the resin coating film are as described above. The coated article of the present disclosure can be produced, for example, by a production method comprising the steps of applying a composition of the present disclosure to an object to be coated and drying the applied composition to form a coating film.

[0112] [Aspects of the Present Disclosure] The present disclosure relates to, for example, the following [1] to

[15] . [1] A one-component aqueous coating composition containing an aqueous (meth)acrylic resin (A) having structural units derived from a versatate vinyl ester, an aqueous (meth)acrylic resin (B) not having structural units derived from a versatate vinyl ester, and water. [2] The one-component aqueous coating composition according to [1] above, wherein the content of structural units derived from a versatate vinyl ester in the aqueous (meth)acrylic resin (A) relative to 100% by mass of all structural units is 20% by mass or more. [3] The one-component aqueous coating composition according to [1] or [2] above, wherein the content of structural units derived from a versatate vinyl ester in the aqueous (meth)acrylic resin (A) relative to 100% by mass of all structural units is 30% by mass or more. [4] The one-component aqueous coating composition according to any one of [1] to [3] above, wherein the aqueous (meth)acrylic resin (A) has a glass transition temperature (Tg) of 0°C or higher. [5] The one-component aqueous coating composition according to any one of [1] to [4] above, further containing a (meth)acrylic polyol (C). [6] The one-component aqueous coating composition according to [5] above, wherein the content of the (meth)acrylic polyol (C) is 5 to 40 parts by mass per 100 parts by mass of the total content of the aqueous (meth)acrylic resin (A), the aqueous (meth)acrylic resin (B), and the (meth)acrylic polyol (C). [7] The one-component aqueous coating composition according to any one of [1] to [6] above, wherein the aqueous coating composition optionally further contains a (meth)acrylic polyol (C), and the content of the aqueous (meth)acrylic resin (A) per 100 parts by mass of the total content of the aqueous (meth)acrylic resin (A), the aqueous (meth)acrylic resin (B), and the (meth)acrylic polyol (C) is 30 to 80 parts by mass. [8] The one-component aqueous coating composition according to any one of [1] to [7] above, wherein the water content in the one-component aqueous coating composition is 20 to 70 mass %. [9] The one-component aqueous coating composition according to any one of [1] to [8] above, which is used to form a topcoat coating film on the surface of a resin coating film.

[10] A coating film formed from the one-component aqueous coating composition according to any one of [1] to [9] above.

[11] A laminated coating film having a resin coating film and the coating film described in

[10] above provided on the surface of the resin coating film.

[12] The laminated coating film described in

[11] above, wherein the resin coating film comprises an epoxy resin coating film.

[13] A coated article having a substrate and the coating film described in

[10] above.

[14] The coated article described in

[13] above, further comprising a resin coating film between the substrate and the coating film.

[15] The coated article described in

[14] above, wherein the resin coating film comprises an epoxy resin coating film.

[0113] The one-component aqueous coating composition of the present disclosure will be explained in more detail below based on examples, but the one-component aqueous coating composition of the present disclosure is not limited to the following examples. In the following examples and comparative examples, "parts" means "parts by mass."

[0114] [Components] The components used in the examples and comparative examples are listed below. Flash rust inhibitor: sodium nitrite (molecular weight 69), manufactured by Kanto Chemical Co., Inc. Dispersant (wetting dispersant): DISPERBYK-190, non-volatile content: 40% by mass, manufactured by BYK-Chemie GmbH Anti-sagging agent (thixotropic agent): Primal RM-12W, non-volatile content: 19% by mass, manufactured by Dow Chemical Company Defoamer A: BYK-024, non-volatile content: 100% by mass, manufactured by BYK-Chemie GmbH Defoamer B: BYK-1770, non-volatile content: 100% by mass, manufactured by BYK-Chemie GmbH Titanium oxide: Tipaque R-930, manufactured by Ishihara Sangyo Kaisha, Ltd. Film-forming aid: Dowanol DPnB, dipropylene glycol n-butyl ether, manufactured by Dow Chemical Company. Leveling agent: TEGO Glide A 116, non-volatile content: 100% by mass, manufactured by Evonik. Resin emulsion (A-1): DSV-4116, emulsion of versatate vinyl ester (Veova) modified (meth)acrylic resin (composition ratio (meth)acrylic: 40% by mass, Veova: 60% by mass), non-volatile content: 45% by mass, Tg: 22°C, acid value: 19.5 mg KOH / g, average particle size: 100 nm, self-crosslinking, manufactured by VANORA. Resin emulsion (A-2): DXV-4051, emulsion of versatate vinyl ester (Veova) modified (meth)acrylic resin (composition ratio Emulsion of (meth)acrylic: 40% by mass, Veova: 60% by mass), non-volatile content: 50% by mass, Tg: 10°C, acid value: 15.5 mg KOH / g, average particle size: 100 nm, non-self-crosslinking, manufactured by VANORA. Resin emulsion (A-3): DSV-4176, emulsion of versatate vinyl ester (Veova)-modified (meth)acrylic resin (composition ratio: (meth)acrylic: 72% by mass, Veova: 25% by mass, SiO2: 3% by mass), non-volatile content: 45% by mass, Tg: 10°C, acid value: 17 mg KOH / g, average particle size: 120 nm, self-crosslinking, manufactured by VANORA.Resin emulsion (A-4): M. 1630. AV, emulsion of versatate vinyl ester (VEOVA) modified acrylic resin (composition ratio (meth)acrylic: 40% by mass, VEOVA: 60% by mass), non-volatile content: 45% by mass, Tg: 19°C, acid value: 16 mg KOH / g, average particle size: 100 nm, non-self-crosslinking, manufactured by VANORA. Resin emulsion (B-1): Polysol AP-3900, (meth)acrylic resin emulsion, non-volatile content: 50% by mass, Tg: 10°C, manufactured by Resonac Corporation. Resin emulsion (B-2): Polysol AP-3720N, (meth)acrylic resin emulsion, non-volatile content: 50% by mass, Tg: 8°C, manufactured by Resonac Corporation. Resin emulsion (B-3): Polysol AP-3770, styrene-(meth)acrylic resin emulsion, non-volatile content: 50% by mass, Tg: 10°C, manufactured by Resonac Corporation. Resin emulsion (B-4): U-DOUBLE E-135, (meth)acrylic resin emulsion, non-volatile content: 50% by mass, Tg: 10°C, manufactured by Nippon Shokubai Co., Ltd. Resin emulsion (B-5): U-DOUBLE E-015, (meth)acrylic resin emulsion, non-volatile content: 50% by mass, Tg: 15°C, manufactured by Nippon Shokubai Co., Ltd. Resin emulsion (B-6): VONCOAT SA-6340, silicone-modified (meth)acrylic resin emulsion, non-volatile content: 50% by mass, Tg: 20°C, manufactured by DIC Corporation. Resin emulsion (B-7): VONCOAT YG-651, (meth)acrylic resin emulsion, non-volatile content: 47% by mass, Tg: 47°C, manufactured by DIC Corporation. Resin emulsion (B-8): VONCOAT CC-6180, (meth)acrylic resin emulsion, non-volatile content: 50% by mass, Tg: 34°C, manufactured by DIC Corporation. (meth)acrylic polyol emulsion (C-1): SETAQUA6515, acrylic polyol emulsion, hydroxyl value: 108.9 mgKOH / g, acid value: 9.9 mgKOH / g, non-volatile content: 45% by mass, manufactured by Allnex.

[0115] [Solid Content Concentration] The solid content or nonvolatile content of the composition and each component refers to the heating residue when the composition and each component are dried in an incubator at 108°C for 3 hours. Specifically, the heating residue is the residue of a sample obtained by weighing 1.0 g of sample onto a flat-bottom 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 content concentration) (mass%) of the composition and each component was calculated from the amount of heating residue.

[0116] Example 1 A container was charged with 7 parts of ion-exchanged water, 0.1 parts of a flash rust inhibitor, 1 part of a dispersant, 0.4 parts of an anti-sagging agent, 0.3 parts of an antifoaming agent A, and 24 parts of titanium oxide, and using a paint shaker, each component was dispersed in the ion-exchanged water until the particle gauge reached 30 μm or less according to the method of JIS K5600-2-5: 1999. In this way, a pigment dispersion was prepared.

[0117] To the pigment dispersion, 40 parts of resin emulsion (A-1), 36 parts of resin emulsion (B-1), and 5.4 parts of film-forming aid were added, and the contents in the container were stirred for 15 minutes using a high-speed disperser. Next, 0.4 parts of defoamer B and 0.4 parts of leveling agent were added to the container, and the contents in the container were stirred for an additional minute using the high-speed disperser. In this way, a coating composition was prepared.

[0118] Examples 2 to 22 and Comparative Examples 1 to 12 Coating compositions were prepared in the same manner as in Example 1, except that the components shown in Tables 1 to 3 were used in the amounts shown in the respective tables.

[0119] [Appearance, Adhesion, and Gloss Value of Coating Film] SS400 sandblasted steel plates measuring 150 mm in length, 70 mm in width, and 1.6 mm in thickness were prepared. The arithmetic mean roughness (Ra, in accordance with JIS B0601:2013) of the surface of the sandblasted steel plate was in the range of 30 to 75 μm. An organic solvent-based epoxy resin paint (Banno 1500 Light Gray, manufactured by Chugoku Toryo Co., Ltd.) was applied to the surface of the sandblasted steel plate using an air spray painter (W-77, manufactured by Anest Iwata Corporation) to a dry film thickness of approximately 200 μm, and the paint was dried for one day at a temperature of 23°C and a humidity of 50% to form a primer coating film. Each of the coating compositions of the Examples and Comparative Examples was applied to the surface of the primer coating film using an applicator to a dry film thickness of approximately 60 μm, and the paint was dried for seven days at a temperature of 23°C and a humidity of 50% to form a topcoat coating film. In this way, a test piece I was prepared, which had a sandblasted steel plate, an undercoat coating film, and a topcoat coating film in this order.

[0120] The appearance and adhesion of the topcoat coating film on Test Piece I were evaluated according to the following evaluation criteria. The gloss value of the topcoat coating film on Test Piece I was measured in accordance with JIS K5600-4-7:1999 using a surface gloss meter (model: Microtrigloss 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).

[0121] (Evaluation criteria for visual inspection of coating appearance) 3: No abnormalities such as pinholes or craters were observed, and leveling was also good. 2: A few abnormalities such as pinholes or craters were observed, and / or leveling was slightly poor. 1: Many abnormalities such as pinholes or craters were observed, and / or leveling was poor.

[0122] (Evaluation criteria for adhesion of coating film) 3: When a finger was pressed against the coating film, no sticking was observed. 1: When a finger was pressed against the coating film, sticking was observed.

[0123] [Weathering Test] Test Piece I was placed in a QUV accelerated weathering tester (model: QUV / SE 200V, UVA-340 lamp, manufactured by Q-Lab) and subjected to weathering tests for 200 hours, 400 hours, 600 hours, and 1,200 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 film 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.

[0124] [Interval Adhesion Test] SS400 sandblasted steel plates measuring 150 mm in length, 70 mm in width, and 1.6 mm in thickness were prepared. The arithmetic mean roughness (Ra) of the surface of the sandblasted steel plate was in the range of 30 to 75 μm. An organic solvent-based epoxy resin paint (Banno 1500 Light Gray, manufactured by Chugoku Toryo Co., Ltd.) was applied to the surface of the sandblasted steel plate using an air spray painter (W-77, manufactured by Anest Iwata Corporation) to a dry film thickness of approximately 200 μm. The paint was then dried for one day at a temperature of 23°C and a humidity of 50% to form a primer coating. In this way, painted specimens were obtained. The painted specimens were exposed outdoors for 1 day, 7 days, 14 days, 21 days, 30 days, and 60 days. The outdoor-exposed painted specimens were lightly rinsed with water and thoroughly dried. Next, each of the coating compositions of the Examples and Comparative Examples was applied to the surface of the undercoat film using an applicator to a dry film thickness of approximately 60 μm, and the applied coating was dried for 7 days under conditions of a temperature of 23° C. and a humidity of 50% to form a topcoat film. In this way, test pieces II for interval adhesion tests were prepared, each having a sandblasted steel plate, an undercoat film, and a topcoat film in that order, and each having different outdoor exposure days.

[0125] (Evaluation Method) Initial Adhesion Test: A cross-cut tape peel test (2 mm x 2 mm, 25 squares, cross-cut method) was performed on Test Piece II. Using a cutter guide, 6 vertical and 6 horizontal cuts were made on the coating surface of Test Piece II to a depth reaching the steel substrate, forming a 25-square grid pattern. The cuts were spaced 2 mm apart. Next, cellophane tape was firmly pressed onto the grid-like areas of Test Piece II, and the edge of the cellophane tape was quickly peeled off at a 90° angle relative to the coating surface. The number of remaining and adhered squares out of the 25 squares was evaluated using the evaluation criteria (out of 10) shown in Figure 3. A score of 6 or higher was considered good (passed). Secondary Adhesion Test: Test Piece II was exposed outdoors for 30 days. After 30 days, the coating surface was lightly rinsed with water and thoroughly dried, and then the same test as the cross-cut tape peel test performed in the initial adhesion test was performed.

[0126]

[0127]

[0128]

[0129] 1: Multilayer coating film 2: Coated product 10: Resin coating film 20: Coating film 30: Substrate

Claims

1. A one-component aqueous coating composition comprising an aqueous (meth)acrylic resin (A) having a structural unit derived from a vinyl ester of versatic acid, an aqueous (meth)acrylic resin (B) not having a structural unit derived from a vinyl ester of versatic acid, and water.

2. A one-component aqueous coating composition as described in claim 1, wherein the content of the constituent units derived from the vinyl ester of versatate in 100% by mass of all constituent units in the aqueous (meth)acrylic resin (A) is 20% by mass or more.

3. A one-component aqueous coating composition as described in claim 1, wherein the content of the constituent units derived from the vinyl ester of versatate in 100% by mass of all constituent units in the aqueous (meth)acrylic resin (A) is 30% by mass or more.

4. The one-pack water-based coating composition according to claim 1, wherein the water-based (meth)acrylic resin (A) has a glass transition temperature (Tg) of 0°C or higher.

5. A one-component water-based coating composition according to claim 1, further comprising a (meth)acrylic polyol (C).

6. A one-component aqueous coating composition according to claim 5, wherein the content of the (meth)acrylic polyol (C) is 5 to 40 parts by mass per 100 parts by mass of the total content of the aqueous (meth)acrylic resin (A), the aqueous (meth)acrylic resin (B) and the (meth)acrylic polyol (C).

7. The one-component aqueous coating composition according to claim 1, wherein the aqueous coating composition optionally further contains a (meth)acrylic polyol (C), and the content of the aqueous (meth)acrylic resin (A) is 30 to 80 parts by mass per 100 parts by mass of the total content of the aqueous (meth)acrylic resin (A), the aqueous (meth)acrylic resin (B) and the (meth)acrylic polyol (C).

8. A one-component water-based paint composition according to claim 1, wherein the content of said water in said one-component water-based paint composition is 20 to 70 mass %.

9. The one-pack water-based coating composition according to claim 1, which is used to form a topcoat film on the surface of a resin coating film.

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

11. A laminated coating film comprising: a resin coating film; and the coating film according to claim 10 provided on a surface of the resin coating film.

12. The laminate coating according to claim 11, wherein the resin coating comprises an epoxy resin coating.

13. A coated article comprising a substrate and the coating film according to claim 10.

14. The coated article according to claim 13, further comprising a resin coating film between the substrate and the coating film.

15. The coated article according to claim 14, wherein the resin coating comprises an epoxy resin coating.

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