WO2024257716A1 - One-pack aqueous paint composition - Google Patents

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

This disclosure relates to a one-component water-based paint composition.

Steel structures such as ships, bridges, and tanks are coated with laminated coatings of various specifications to perform various functions according to purpose. For example, an anticorrosive coating made of an anticorrosive coating composition (e.g., an epoxy resin-based anticorrosive coating composition) is applied as an undercoat paint to the surface of a substrate such as a steel structure, and a topcoat coating made of a topcoat paint composition is applied on the anticorrosive coating to improve design or weather resistance. Known topcoat paint compositions include, for example, two-component reactive curing compositions such as urethane resin-based paint compositions, and one-component compositions such as (meth)acrylic resin-based paint compositions.

In order to take into consideration the natural environment and the painting work environment, regulations on organic solvent emissions have been strengthened in recent years. For this reason, in the field of paint compositions, efforts are being made to develop water-based paint compositions with low volatile organic compounds (VOCs) content (see, for example, Patent Documents 1 to 3).

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

For example, it may be necessary 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 to the resin coating film to form a topcoat coating film.

Usually, after a paint composition is applied to a substrate to form a resin coating, a topcoat paint composition is applied after a specified 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 for the topcoat paint film to have high adhesion (adhesion) to the resin coating film. It is also desirable for such a topcoat paint film to have excellent coating film condition. The present disclosure aims to provide an aqueous paint composition that is capable of forming a topcoat paint film that has excellent adhesion to the resin coating film and excellent coating film condition, even when an interval is used.

The present inventors have found that the above problems can be solved by an aqueous coating composition having the following composition. That is, the aqueous coating composition of the present disclosure is a one-component aqueous coating composition that contains an aqueous (meth)acrylic resin (A) having a constituent unit derived from a vinyl ester of versatic acid, an aqueous (meth)acrylic resin (B) not having a constituent unit derived from a vinyl ester of versatic acid, and water.

According to the present disclosure, it is possible to provide an aqueous paint composition that is capable of forming a topcoat film that has excellent adhesion to resin coating films and excellent coating film condition, even when an interval is provided (e.g., when the interval is long).

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 article according to one embodiment. FIG. 3 is a table showing the evaluation criteria for the cross-cut tape peel test.

An embodiment of the present disclosure will be described in detail below.
Each of the components described in this specification may be used alone or in combination of two or more.
The term "polymer" is used to include homopolymers and copolymers, i.e., the term "polymer" may mean either a homopolymer or a copolymer.
"(Meth)acrylate" is a term that collectively refers to acrylate and methacrylate. "(Meth)acrylic" is a term that collectively refers to acrylic and methacrylic. "(Meth)acrylic acid" is a term that collectively refers to acrylic acid and methacrylic acid. The same applies to other examples.

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.

A "structural unit derived from XX" is, for example, a structural unit represented by the ^following formula, where XX is represented as ^A1A2C = ^CA3A4 (C= ^C is a polymerizable carbon-carbon double bond, and ^A1 to ^A4 are each an atom or group bonded to a carbon atom).

[One-component water-based paint composition]
The one-pack water-based coating composition of the present disclosure (hereinafter also referred to as the "composition of the present disclosure") comprises a water-based (meth)acrylic resin (A) having a constituent unit derived from a vinyl ester of versatic acid, and a water-based (meth)acrylic resin (B) having a constituent unit derived from a vinyl ester of versatic acid. The composition contains an aqueous (meth)acrylic resin (B) that does not have any of the structural units of the above formula (1) and water.

In this specification, "aqueous (meth)acrylic resin" refers to a highly hydrophilic (meth)acrylic resin, meaning 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 carboxy groups and hydroxy groups and can be dissolved uniformly in water, and water-dispersible resins that can be dispersed uniformly in water in the form of fine particles.

The effects of the composition of the present disclosure will be described below.
In recent years, although the coating composition has been increasingly water-based, most steel structures require high anticorrosive performance over a long period of time, and therefore, organic solvent-based coating compositions containing organic solvents as a solvent are still mainly used for anticorrosive coating compositions. For example, in steel structures, a topcoat coating composition may be applied on an anticorrosive coating film formed from an anticorrosive coating composition for the purpose of improving design and weather resistance. Conventionally, as with anticorrosive coating compositions, organic solvent-based topcoat coating compositions containing organic solvents as a solvent have been mainstream, but in recent years, the demand for water-based coating compositions has been increasing. However, coating films formed from conventional water-based coating compositions tend to have lower adhesion (adhesion) to resin coating films compared to coating films formed from organic solvent-based coating compositions. In particular, when an aqueous coating composition is applied as a topcoat on a resin coating film formed from an organic solvent-based coating composition (e.g., an organic solvent-based epoxy resin coating composition), a significant decrease in adhesion is observed. This is presumably because the aqueous coating composition does not contain organic solvent or contains only a small amount of organic solvent, so it cannot dissolve or swell the surface of the lower resin coating film, and if the surface of the lower resin coating film is hydrophobic, it is difficult to get 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.

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). Here, the adhesion of a topcoat coating film to a resin coating film when a resin coating film is formed on the surface of a substrate and then a topcoat coating film is formed on the resin coating film after a predetermined period of time is also referred to as "interval adhesion" in this specification.

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

<Water-based (meth)acrylic resin (A)>
The aqueous (meth)acrylic resin (A) has a constituent unit derived from a versatic acid vinyl ester (hereinafter also referred to as "Veova"). It is presumed that the constituent unit derived from a versatic acid vinyl ester can impart moderate hydrophobicity and moderate 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.

The versatic acid vinyl ester copolymer may have a constituent unit derived from versatic acid vinyl ester and a constituent unit derived from a (meth)acrylic monomer, and may further have a constituent unit derived from other ethylenically unsaturated monomers copolymerizable with versatic acid vinyl ester and/or (meth)acrylic monomer. The versatic acid vinyl ester copolymer may have two or more constituent units derived from versatic acid vinyl ester. The versatic acid vinyl ester copolymer may have two or more constituent units derived from (meth)acrylic monomer. The versatic acid vinyl ester copolymer may have two or more constituent units derived from other ethylenically unsaturated monomer.

Versatic acid vinyl ester is a compound represented by the following formula (1).

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. The total number of carbon atoms in R ¹ and R ² is preferably 6 to 10, more preferably 6 to 8. The total number of carbon atoms in the entire formula (1) is preferably 11 to 15, more preferably 11 to 13.

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. At least one of ^{R 1} and R ² is preferably a branched alkyl group, and both R ¹ and R ² may be branched alkyl groups.

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

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 2-hydroxypropyl (meth)acrylate. 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.

Other ethylenically unsaturated monomers copolymerizable with versatic acid vinyl ester and/or (meth)acrylic monomers include, for example, 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 such as vinyl acetate and vinyl propionate (excluding versatic acid vinyl ester); cyanide vinyl 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-containing ethylenically unsaturated monomers such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyldimethoxymethylsilane, vinylmethoxydimethylsilane, and vinyltris(β-methoxyethoxy)silane.

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

The aqueous (meth)acrylic resin (A) may be a silicone-modified (meth)acrylic resin having a structural unit derived from a vinyl ester of versatic acid.

Examples of silicon-modified (meth)acrylic resins 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 resins in these examples have constituent units derived from versatic acid vinyl ester.

The mass ratio of the (meth)acrylic resin skeleton and the polysiloxane resin skeleton that make up the silicon-modified (meth)acrylic resin ((meth)acrylic resin skeleton/polysiloxane resin skeleton) is, for example, 1/10 to 50/1.

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 alkoxysilyl group-containing (meth)acrylate and alkoxysilyl group-containing ethylenically unsaturated monomer described above. The versatic acid vinyl ester copolymer may have two or more constituent units derived from a silyl group-containing unsaturated monomer.

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

In the aqueous (meth)acrylic resin (A), the content of the constituent units derived from the versatic acid vinyl ester in 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, 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 moderate hydrophobicity and moderate flexibility to a coating film, and therefore can form a coating film that is excellent in water resistance and adhesion to resin coating films, particularly interval adhesion. In particular, when the content of the constituent units derived from the versatic acid vinyl ester is 30% by mass or more, the interval adhesion tends to be more excellent. In this specification, the content of each constituent unit is measured by nuclear magnetic resonance spectroscopy (NMR).

In the aqueous (meth)acrylic resin (A), the content of constituent units derived from versatic acid vinyl ester in 100% by mass of all constituent 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 constituent units derived from versatic acid vinyl ester in 100% by mass of all constituent units is, for example, 20 to 90% by mass.

In the aqueous (meth)acrylic resin (A), the content of constituent units derived from (meth)acrylic monomers in 100% by mass of all constituent units is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 25% by mass or more, 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, even 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.

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 is 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 is the midpoint glass transition temperature obtained by differential scanning calorimetry (DSC) in accordance with JIS K7121:2012. A composition containing a resin (A) whose Tg is equal to or higher than the lower limit can form a coating film that is excellent in strength and water resistance, and can form a coating film that is suppressed from softening or blisters even when exposed to a high temperature environment. A composition containing a resin (A) whose Tg is equal to or lower than the upper limit can form a coating film that is excellent in adhesion to the substrate, and can form a coating film that is excellent in film formation and suppresses cracking even when applied in a low temperature environment such as winter.

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 is 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 moderate 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 film defects such as whitening or blisters when it comes into contact with water, for example, rainfall. In this specification, the acid value is the amount (mg) of potassium hydroxide required to neutralize acid groups such as carboxyl groups per gram of nonvolatile matter in the sample, and is measured in accordance with JIS K0070:1992.

The aqueous (meth)acrylic resin (A) may be present in the composition in the form of particles. For example, when the composition is applied and dried, water evaporates and the particles bond together to 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. The aqueous (meth)acrylic resin (A) having an average particle size within this range tends to be able to exist stably in the aqueous paint composition and tends to be able to form a coating film with uniform coating film properties. In this specification, the average particle size is the volume-based average particle size measured by a laser diffraction method at a temperature of 25°C.

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 present stably and uniformly in the composition of the present disclosure, and tends to form a coating film with uniform coating 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%.

The aqueous medium is not particularly limited as long as it contains water, but the content of water 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, even 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.

The aqueous (meth)acrylic resin (A) may be of 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 a solution polymerization method, a suspension polymerization method, a bulk polymerization method, or an emulsion polymerization method.

The content of the aqueous (meth)acrylic resin (A) in 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 included 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. A coating film formed from a composition having a content of the aqueous (meth)acrylic resin (A) within this range has low adhesion, and is excellent in adhesion and interval adhesion to resin coating films such as organic solvent-based resin coating films, and is suitable as a topcoat coating film.

<Water-based (meth)acrylic resin (B)>
The aqueous (meth)acrylic resin (B) has a constituent unit derived from a (meth)acrylic monomer and does not have a constituent unit derived from a vinyl ester of versatic acid, provided that in the present disclosure, the aqueous (meth)acrylic resin (B) does not include the (meth)acrylic polyol (C) described below.

The aqueous (meth)acrylic resin (B) may be a homopolymer of a (meth)acrylic monomer, a copolymer of two or more kinds of (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 kinds of constituent units derived from a (meth)acrylic monomer. The aqueous (meth)acrylic resin (B) may have two or more kinds of constituent units derived from another ethylenically unsaturated monomer.

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.

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

Examples of the aqueous (meth)acrylic resin (B) include nonionic (meth)acrylic resin, anionic (meth)acrylic resin, and cationic (meth)acrylic resin. 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.

Examples of silicone-modified (meth)acrylic resins include resins in which a (meth)acrylic resin skeleton and a polysiloxane resin skeleton are bonded by a covalent bond, such as block copolymers in which the ends of a (meth)acrylic resin and a polysiloxane resin are bonded together, copolymers having a polysiloxane resin as the main skeleton and a (meth)acrylic resin bonded to the main skeleton as a side chain, and copolymers having a (meth)acrylic resin as the main skeleton and a polysiloxane resin bonded to the main skeleton as a side chain. The content ratio of the (meth)acrylic resin skeleton and the polysiloxane resin skeleton that constitute the silicone-modified (meth)acrylic resin ((meth)acrylic resin skeleton/polysiloxane resin skeleton) on a mass basis is, for example, 1/10 to 50/1.

The silicon-modified (meth)acrylic resin may also be a copolymer having 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 alkoxysilyl group-containing (meth)acrylate and alkoxysilyl group-containing ethylenically unsaturated monomer described above. The silicon-modified (meth)acrylic resin may have two or more kinds of constituent units derived from a silyl group-containing unsaturated monomer.

As the aqueous (meth)acrylic resin (B), from the viewpoint of being able to form a coating film with 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.

The glass transition temperature (Tg) of the aqueous (meth)acrylic resin (B) is preferably 0°C or higher, more preferably 5°C or higher, and even more preferably 8°C or higher, and is preferably 70°C or lower, more preferably 60°C or lower, and even more preferably 50°C or lower, for example, 0 to 70°C. A composition containing a resin (B) with 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) with a Tg equal to or higher than the lower limit can form a coating film that is suppressed from softening or blisters even when exposed to a high temperature environment. A composition containing a resin (B) with 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.

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 the acetic acid bonded to the hydroxyl group when 1 g of the nonvolatile content of the sample is acetylated, and is measured in accordance with JIS K0070:1992.

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 and the particles bond together to 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. The 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.

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 present stably and uniformly in the composition of the present disclosure, and tends to form 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%.

The aqueous (meth)acrylic resin (B) may be of the 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 a solution polymerization method, a suspension polymerization method, a bulk polymerization method, or an emulsion polymerization method.

The content of the aqueous (meth)acrylic resin (B) in a total of 100 parts by mass 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 with a content of the aqueous (meth)acrylic resin (B) within this range can form a coating film that has a good appearance and is excellent in water resistance, adhesion to the substrate, and interval adhesion.

<(Meth)acrylic polyol (C)>
The composition of the present disclosure may further contain (meth)acrylic polyol (C). (Meth)acrylic polyol (C) is a relatively low molecular weight aqueous (meth)acrylic resin having multiple hydroxyl groups. The coating film formed from such a composition tends to have excellent initial gloss and leveling properties in addition to the above-mentioned adhesion and long-term interval adhesion.

(Meth)acrylic polyol (C) may be, for example, a copolymer of an ethylenically unsaturated monomer having a hydroxyl group and another ethylenically unsaturated monomer copolymerizable therewith. (Meth)acrylic polyol (C) may have two or more types of structural units derived from an ethylenically unsaturated monomer having a hydroxyl group. (Meth)acrylic polyol (C) may have two or more types of structural units derived from another ethylenically unsaturated monomer.

Ethylenically unsaturated monomers having a hydroxy group include, for example, the above-mentioned hydroxyalkyl (meth)acrylates. Other ethylenically unsaturated monomers include, for example, the above-mentioned (meth)acrylic monomers (excluding the above-mentioned hydroxyalkyl (meth)acrylates) and the above-mentioned other ethylenically unsaturated monomers other than (meth)acrylic monomers.

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.

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.

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 with excellent initial gloss and leveling properties.

Mw is a value calculated in terms of polystyrene measured by gel permeation chromatography (GPC) under the following conditions.
(GPC measurement conditions)
Apparatus: "HLC-8320GPC" (manufactured by Tosoh Corporation)
Column: "TSKgel guardcolumn SuperMP(HZ)-M + TSKgel SuperMultiporeHZ-M + TSKgel SuperMultiporeHZ-M" (both manufactured by Tosoh Corporation)
Eluent: tetrahydrofuran (THF)
Flow rate: 0.35ml/min
Detector: Differential 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 to obtain a filtrate, which was used as a GPC measurement sample.

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 and the particles bond together to 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. The (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.

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 present stably and uniformly in the composition of the present disclosure, and tends to form 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%.

When the composition of the present disclosure contains (meth)acrylic polyol (C), the content of (meth)acrylic polyol (C) is, in 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), 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. A composition having a content of (meth)acrylic polyol (C) within this range can form a coating film with excellent gloss and leveling properties. Also, a composition having a content of (meth)acrylic polyol (C) equal to or less than the upper limit can form a coating film that is less susceptible to cracking and has excellent adhesion.

In the composition of the present disclosure, the total ratio of the aqueous (meth)acrylic resin (A), the aqueous (meth)acrylic resin (B) and the (meth)acrylic polyol (C) 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.

<Other ingredients>
The composition of the present disclosure may contain other components such as pigments, rust inhibitors, and additives, within the scope that does not impair the effects of the present invention.Additives include, for example, dispersants, wetting agents, anti-sagging agents (anti-settling agents, thixotropic agents, rheology control agents), defoamers, film-forming assistants, leveling agents, surfactants, thickeners, anti-mold agents, preservatives, UV absorbers, pH adjusters, antioxidants, and flash rust inhibitors.These may be used alone or in combination of two or more.

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.

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

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, based on 100% by mass of the total solid content in the composition.

　The color pigment may be any color pigment known in the art, including, for example, 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, scaly iron oxide, and stainless steel flakes.

When the composition of the present disclosure contains a coloring pigment, the content of the coloring pigment is, relative to the total solid content of the composition (100% by mass), 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.

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 complex oxides.

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, for example 1 to 20% by mass, based on 100% by mass of the total solid content in the composition.

The rust inhibitor is a compound that has rust-preventing properties, other than anti-rust pigments. Conventionally known compounds can be used as the rust inhibitor. There is no particular limit to the content of the rust inhibitor in the composition of the present disclosure.

The composition of the present disclosure preferably contains a dispersant from the viewpoints of improving the dispersibility of the pigments and the like in the composition, facilitating the formation of a coating film with a good appearance and excellent crack resistance. 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 carboxy groups, phosphate groups, amino groups, salt groups of these, and ammonium bases.

When the composition of the present disclosure contains a dispersant, the content of the dispersant is 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, based on 100% by mass of the total solid content in the composition.

The composition of the present disclosure preferably contains an anti-dripping agent from the viewpoints of improving the thick coating property and anti-dripping property during application and suppressing the settling of insoluble matters such as pigments in water. Examples of the anti-dripping agent include organic thixotropic agents such as hydrogenated castor oil-based thixotropic agents, amide wax-based thixotropic agents, polyethylene oxide-based thixotropic agents, and urethane-based thixotropic agents; and inorganic thixotropic agents such as clay minerals (e.g., bentonite, smectite, and hectorite) and synthetic fine silica powder.

When the composition of the present disclosure contains a drip-preventing agent, the content of the drip-preventing agent is, based on 100% by mass of the total solid content in the composition, 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.

The defoaming agent is preferably a material capable of suppressing the generation of bubbles during the production and application of the coating composition, or a material capable of breaking down bubbles generated in the coating composition. By using a defoaming agent, for example, the generation of bubble marks or pinholes in the coating film can be suppressed, and therefore the film-forming properties and crack resistance of the coating film can be improved. Examples of defoaming agents include silicone-based defoaming agents, polymer-based (non-silicone-based) defoaming agents, and mineral oil-based defoaming agents.

When the composition of the present disclosure contains an antifoaming agent, the content of the antifoaming agent is, based on 100% by mass of the total solid content in the composition, 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.

The composition of the present disclosure preferably contains a film-forming aid because the composition may freeze in winter due to the inclusion of water, and also from the viewpoint of improving film-forming properties at low temperatures and the finished appearance of the resulting coating film. Examples of film-forming 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.

When the composition of the present disclosure contains a film-forming aid, the content of the film-forming aid 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.

The composition of the present disclosure preferably contains a leveling agent from the viewpoints of improving repelling of the coating film when the composition is applied, improving wettability to the surface of the object to be coated, and making it easier to obtain a coating film of uniform thickness. Examples of leveling agents include various leveling agents such as fluorine-based, acrylic-based, and silicone-based leveling agents.

When the composition of the present disclosure contains a leveling agent, the content of the leveling agent is 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, based on 100% by mass of the total solid content in the composition.

As the thickener, for example, a commercially available product that is generally sold as a thickener can be used. Examples of the thickener include alkali thickeners, nonionic association types, acrylic types, urethane types, water-soluble polymer types, polyamide types, and hydroxyethyl cellulose.

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 is preferably 5% by mass or less, more preferably 1% by mass or less, for example, 0.01 to 5% by mass, based on 100% by mass of the total solid content in the composition.

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

Flash rust inhibitors include, for example, 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. amine-based chelating agents such as dimethylaminopropylamine (DTPA), propylenediaminetetraacetic acid (PDTA), iminodiacetic acid, nitrilotriacetic acid (NTA), diethylenetriaminepentamethylenephosphonic acid (DTPMP), and alkali metal salts thereof; an addition reaction product 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 its salts. 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, and nitrites are more preferred, with sodium nitrite being particularly preferred, from the viewpoints of easily obtaining a composition that exhibits high flash rust resistance even when used in small amounts.

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 preferably 5% by mass or less, more preferably 3% by mass or less, for example 0.05 to 5% by mass, based on 100% by mass of the total solid content in the composition.

<Water>
The composition of the present disclosure is an aqueous coating composition. In the present disclosure, the term "aqueous" 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 water includes water that is a dispersion medium when the aqueous (meth)acrylic resin (A), the aqueous (meth)acrylic resin (B), and the (meth)acrylic polyol (C) that is optionally included are dispersed in an aqueous medium, as well as water contained in additives. The content of water 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 is 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.

The total solid content 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, from the viewpoint of providing a composition with excellent coating workability.

<VOCs>
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 safety of the working environment, etc. The lower the content of VOCs 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.

VOCs include, for example, organic solvents. Examples of organic solvents include 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.

In the present disclosure, the content of VOC in the composition is calculated based on the following formula (1) using the following values of the composition specific gravity, solid concentration, and water concentration.
VOC content (g/L)=specific gravity of composition×1000×(100−solids concentration−water concentration)/100 (1)

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 at a temperature condition 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 this disclosure, the solid content in the composition means 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) means 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 mass % of the 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.

<Production method of 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), and optionally the (meth)acrylic polyol (C), and optionally other components, are added to a stirring vessel at once or in any order, and each component is mixed by a 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, 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.

When 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 and environment.

The composition disclosed herein is an aqueous paint composition, and therefore has very little adverse effect on the environment and human body, and also has excellent storage stability. Even when the composition disclosed herein is applied in multiple coats, the coating film formed has excellent adhesion (tightness) to the base coating film, and is unlikely to crack or peel off, making the composition suitable for topcoat painting or repair painting.

[Applications of coating compositions, laminated coating films and coated products]
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, plastics, rubber, stone, concrete, mortar, glass, porcelain, pottery, and composites thereof. Examples of resin coatings include undercoat 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.).

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 at the location where the resin coating film is provided include metal materials, wood, plastic, rubber, stone, concrete, mortar, glass, porcelain, pottery, and composites of these, with metal materials being preferred. Specific examples of substrates 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.

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 necessary (for example, blast treatment (ISO8501-1 Sa2 1/2), degreasing to remove oil and dust, etc.). The substrate surface may be coated with a shop primer or the like for the purpose of primary rust prevention.

The coating film of the present disclosure is formed from the composition of the present disclosure. The coating film of the present disclosure is suitable as a topcoat coating film to be laminated on a resin coating film because it is excellent in appearance, coating film condition, weather resistance, etc. 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 one application (one application), or a coating film having a desired thickness may be formed by two or more applications (two or more applications).

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. Coating 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 dry 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 dry coating film is, for example, 5 minutes to 60 minutes, and the drying temperature is preferably 30°C or more and less than 100°C, more preferably 40 to 80°C.

The laminated 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. FIG. 1 shows a schematic cross-sectional view of one embodiment of the laminated coating film of the present disclosure. The laminated coating film 1 of FIG. 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 protection coating film.

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 that 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 that order in the thickness direction.

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

The intermediate coating film may be, for example, a coating film formed from various intermediate coating compositions such as a (meth)acrylic resin-based coating composition, an epoxy resin-based coating composition, and a urethane resin-based coating composition. The thickness of the intermediate coating film is preferably 10 to 300 μm, more preferably 10 to 250 μm.

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 protection coating films), particularly to resin coating films formed from organic solvent-based paint compositions (e.g., organic solvent-based epoxy resin paint compositions).

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. FIG. 2 shows a schematic cross-sectional view of one embodiment of the coated article of the present disclosure. The coated article 2 of FIG. 2 has a substrate 30 and a laminate coating film 1 of the present disclosure provided on the substrate 30. The details of the resin coating film are as described above. The coated article of the present disclosure can be manufactured, for example, by a manufacturing method having a step of applying a composition of the present disclosure to an object to be coated and a step of drying the applied composition to form a coating film.

Aspects of the present disclosure
The present disclosure relates to, for example, the following [1] to [15].
[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] The one-component aqueous coating composition described in [1], wherein the content of the constituent units derived from the versatic acid vinyl ester in 100% by mass of all constituent units in the aqueous (meth)acrylic resin (A) is 20% by mass or more.
[3] The one-component aqueous coating composition according to [1] or [2], wherein the content of the constituent units derived from the versatic acid vinyl ester in 100% by mass of all constituent units in the aqueous (meth)acrylic resin (A) is 30% by mass or more.
[4] The one-component aqueous coating composition according to any one of [1] to [3], 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 comprising a (meth)acrylic polyol (C).
[6] The one-component aqueous coating composition according to [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 any one of [1] to [6], further comprising a (meth)acrylic polyol (C) as desired, wherein 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] The one-component aqueous coating composition according to any one of [1] to [7], wherein the content of the water in the one-component aqueous coating composition is 20 to 70 mass %.
[9] A one-component aqueous coating composition according to any one of [1] to [8] above, which is used for forming a topcoat coating film on the surface of a resin coating film.
[10] A coating film formed from the one-component water-based 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 according to [10] provided on the surface of the resin coating film.
[12] The laminate coating film according to [11], wherein the resin coating film includes an epoxy resin coating film.
[13] A coated article having a substrate and the coating film described in [10] above.
[14] The coated article according to [13], further comprising a resin coating film between the substrate and the coating film.
[15] The coated article according to [14], wherein the resin coating film comprises an epoxy resin coating film.

The one-component water-based paint composition of the present disclosure will be explained in more detail below with reference to examples, but the one-component water-based paint composition of the present disclosure is in no way limited to the following examples. In the following examples and comparative examples, "parts" refers to "parts by mass."

[component]
The components used in the examples and comparative examples are described below.
Flash rust inhibitor: sodium nitrite (molecular weight 69),
Dispersant (wetting dispersant) manufactured by Kanto Chemical Co., Ltd.: DISPERBYK-190,
Non-volatile content: 40% by weight,
BYK-Chemie GmbH: Anti-sagging agent (thixotropic agent): Primal RM-12W,
Non-volatile content: 19% by mass,
Defoamer A: BYK-024, manufactured by Dow Chemical Company; non-volatile content: 100% by weight;
Defoamer B: BYK-1770 manufactured by BYK-Chemie GmbH, non-volatile content: 100% by mass,
Titanium oxide: Tipaque R-930 manufactured by BYK-Chemie GmbH, film-forming agent: Dowanol DPnB manufactured by Ishihara Sangyo Kaisha, Ltd.
dipropylene glycol n-butyl ether,
Leveling agent manufactured by Dow Chemical Company: TEGO Glide A 116,
Non-volatile content: 100% by mass, Evonik resin emulsion (A-1): DSV-4116, emulsion of versatic acid 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 mgKOH/g, average particle size: 100 nm, self-crosslinking, VANORA resin emulsion (A-2): DXV-4051, emulsion of versatic acid 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 versatic acid vinyl ester (Veova) modified (meth)acrylic resin (composition ratio (meth)acrylic: 72% by mass, Veova: 25% by mass, SiO ₂ : 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 versatic acid 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 mgKOH/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 Co., Ltd.; resin emulsion (B-2): Polysol AP-3720N, (meth)acrylic resin emulsion, non-volatile content: 50% by mass, Tg: 8°C, manufactured by Resonac Co., Ltd.; 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, silicon-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 Corporation.

[Solid content]
The solid content or non-volatile content of the composition and each component means 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 the 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 the heating residue.

[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 a sagging agent, 0.3 parts of an antifoaming agent A, and 24 parts of titanium oxide, and each component was dispersed in the ion-exchanged water using a paint shaker until the particle gauge reached 30 μm or less according to the method of JIS K5600-2-5:1999. In this manner, a pigment dispersion was prepared.

40 parts of resin emulsion (A-1), 36 parts of resin emulsion (B-1), and 5.4 parts of film-forming agent were added to the pigment dispersion, 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 a high-speed disperser. In this way, the paint composition was prepared.

[Examples 2 to 22 and Comparative Examples 1 to 12]
Each coating composition was 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.

[Appearance, adhesion and gloss value of coating film]
A sandblasted steel plate of SS400 having dimensions of 150 mm in length, 70 mm in width, and 1.6 mm in thickness was 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 Paint Co., Ltd.) was applied to the surface of the sandblasted steel plate using an air spray painter (W-77, manufactured by Anest Iwata Corporation) so that the dry film thickness was about 200 μm, and the paint was dried for one day under conditions of a temperature of 23 ° C. and a humidity of 50% to form an undercoat coating film. Each of the coating compositions of the examples and comparative examples was applied to the surface of the undercoat coating film using an applicator so that the dry film thickness was about 60 μm, and the paint was dried for 7 days under conditions of a temperature of 23 ° C. and a humidity of 50% to form a topcoat coating film. In this manner, a test piece I having a sandblasted steel plate, an undercoat coating film and a topcoat coating film in this order was prepared.

The appearance and adhesion of the topcoat coating of test piece I were evaluated according to the following evaluation criteria. The gloss value of the topcoat coating of test piece I 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).

(Visual evaluation criteria for coating appearance)
3: No abnormalities such as pinholes or craters are observed, and
The leveling property was also good.
2: Slight abnormalities such as pinholes or craters are observed, and/or
The leveling was slightly poor.
1: Numerous abnormalities such as pinholes or craters are observed, and/or
The leveling property was poor.

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

[Weather resistance test]
The test piece I was placed in a QUV accelerated weathering tester (model: QUV/SE 200V, UVA-340 lamp, manufactured by Q-Lab) and weathering tests were carried out for 200 hours, 400 hours, 600 hours and 1,200 hours in accordance with ASTM G154 CYCLE1. Thereafter, the reflectance (60° gloss) of light incident at an angle of 60° from the perpendicular direction of the coating surface after the weathering test was measured using a surface gloss meter (model: Micro Trigloss 4446, manufactured by BYK-Gardner). The gloss retention (%) of the 60° gloss after the weathering test relative to the 60° gloss value of the coating film before the weathering test was calculated.

[Interval adhesion test]
A sandblasted steel plate of SS400 having dimensions of 150 mm length, 70 mm width and 1.6 mm thickness was 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 Paint Co., Ltd.) was applied to the surface of the sandblasted steel plate using an air spray painter (W-77, manufactured by Anest Iwata Co., Ltd.) so that the dry film thickness was about 200 μm, and the paint was dried for one day under conditions of a temperature of 23° C. and a humidity of 50%, to form an undercoat coating film. In this way, a coated piece was obtained. The coated piece was exposed outdoors for 1 day, 7 days, 14 days, 21 days, 30 days and 60 days. The coated piece exposed outdoors was lightly washed with water and thoroughly dried. Next, the coating compositions of the Examples and Comparative Examples were applied to the surface of the undercoat film using an applicator so that the dry film thickness was about 60 μm, and the coating was dried for 7 days under conditions of a temperature of 23° C. and a humidity of 50% to form a 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 this order, and having different outdoor exposure days.

(Evaluation Method)
Initial adhesion: A checkerboard tape peeling test (2 mm x 2 mm, 25 squares, cross-cut method) was performed on the test piece II. Using a cutter guide, 6 vertical x 6 horizontal cuts were made on the coating surface of the test piece II to a depth reaching the steel plate substrate, forming a checkerboard pattern of 25 squares with a right-angled grid pattern. The interval between the cuts was 2 mm. Next, cellophane tape was strongly pressed onto the checkerboard portion of the test piece II, and the end of the cellophane tape was peeled off at an angle of 90° to the coating surface in one go, and the number of remaining and attached squares out of the 25 squares was evaluated according to the evaluation criteria (out of 10 points) described in Figure 3. A score of 6 or more was considered good (passed).
Secondary adhesion: Test piece II was exposed outdoors for 30 days. After 30 days had passed, the coating surface was lightly washed with water and thoroughly dried, and then a test similar to the cross-cut tape peel test performed in the initial adhesion test was performed.

1: Multilayer coating film 2: Coated item 10: Resin coating film 20: Coating film 30: Substrate

Claims (15)

A one-component water-based paint composition containing an aqueous (meth)acrylic resin (A) having structural units derived from a vinyl ester of versatic acid, an aqueous (meth)acrylic resin (B) not having structural units derived from a vinyl ester of versatic acid, and water. The one-component aqueous coating composition according to 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. The one-component aqueous coating composition according to 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. The one-component aqueous coating composition according to claim 1, wherein the aqueous (meth)acrylic resin (A) has a glass transition temperature (Tg) of 0°C or higher. The one-component water-based coating composition according to claim 1, further comprising a (meth)acrylic polyol (C). The 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). The one-component aqueous coating composition according to claim 1, wherein the aqueous coating composition further contains a (meth)acrylic polyol (C) as desired, 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). The one-component water-based paint composition according to claim 1, wherein the water content in the one-component water-based paint composition is 20 to 70 mass %. The one-component water-based coating composition according to claim 1, which is used to form a topcoat coating film on the surface of a resin coating film. A coating film formed from the one-component water-based coating composition according to any one of claims 1 to 9. A resin coating and
The coating film according to claim 10 provided on a surface of the resin coating film;
A laminated coating film having the above structure. The laminate coating film according to claim 11, wherein the resin coating film includes an epoxy resin coating film. A coated article having a substrate and the coating film according to claim 10. The coated article according to claim 13, further comprising a resin coating between the substrate and the coating. The coated article according to claim 14, wherein the resin coating comprises an epoxy resin coating.

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