Aqueous coating composition

Abstract

Disclosed is an aqueous coating composition which contains synthetic resin particles (A), an organic solvent (B) that has a water solubility of 1.0 (g / 100 g of water) or more and a boiling point of 200°C or more, and water. The content ratio of the organic solvent (B) in the composition is 1-16 mass%. The composition is used for the purpose of coating the surface of a (meth)acrylic resin-based coating film.

Description

water-based paint composition

[0001] The present disclosure relates to water-based coating compositions.

[0002] In natural environments, surfaces of substrates that are in contact with water for extended periods of time are prone to attracting a wide variety of aquatic organisms, including animals such as oysters, mussels, and barnacles, plants such as seaweed and sea lettuce, and bacteria.

[0003] When aquatic organisms attach to the surface of a substrate, various problems can occur. If the substrate is the outer hull of a ship, the attachment of aquatic organisms increases resistance to water flow, which can slow the ship's speed and reduce fuel efficiency. If the substrate is an underwater structure, the corrosion-resistant coating formed on the surface of the substrate can be damaged by aquatic organisms, reducing the strength and functionality of the substrate and shortening its lifespan. If the substrate is a seawater supply and drainage pipe in various facilities, aquatic organisms can clog the pipes and reduce the flow rate. If the substrate is a fishing net, aquatic organisms can clog the mesh, causing problems such as the death of farmed and caught organisms due to oxygen deprivation.

[0004] In order to prevent aquatic organisms from adhering to the surface of a substrate, a (meth)acrylic resin-based antifouling coating film has been formed on the substrate (see, for example, Patent Document 1). The (meth)acrylic resin-based antifouling coating film contains a (meth)acrylic resin and, optionally, an antifouling agent. For example, in some antifouling coating films, the (meth)acrylic resin in the antifouling coating film gradually dissolves in water, causing an appropriate renewal of the coating surface and thereby exhibiting antifouling properties. For example, the antifouling agent in the antifouling coating film gradually dissolves in water, thereby exhibiting antifouling properties. When the (meth)acrylic resin-based antifouling coating film present on the substrate becomes worn, abraded, peeled, or the like, the antifouling coating film may be repaired in order to continuously prevent aquatic organisms from adhering to the surface of the substrate for a long period of time.

[0005] Furthermore, (meth)acrylic resin-based topcoat coating films are formed on substrates such as the outer hulls, decks, and superstructures of ships, and bridges (see, for example, Patent Document 2). However, such (meth)acrylic resin-based topcoat coating films have the problem of being prone to coating film deterioration (coating film defects) such as blisters and cracks. Therefore, when deterioration occurs in the (meth)acrylic resin-based topcoat coating film present on the substrate, it is required to repair the topcoat coating film.

[0006] JP-A-56-73578 JP-A-52-3631

[0007] In repairing a (meth)acrylic resin coating film on a substrate, the removal of the coating film is costly. Therefore, it is desirable to apply a new coating (e.g., an antifouling paint or a topcoat) to the surface of the coating film (repair coating) and form a new coating film on the coating film. However, the adhesion (adhesion) between the coating films may be insufficient.

[0008] The present inventors have investigated the provision of a binder layer between the coating films in order to improve the adhesion between the coating films. Furthermore, in order to consider the natural environment and the coating work environment, regulations on organic solvent emissions have been tightened in recent years. For this reason, in the field of coating compositions, there is a demand for water-based coating compositions with a low content of organic compounds that are highly volatile at room temperature. However, the present inventors have found that when a binder layer is formed by applying a water-based coating composition to the surface of the coating film, the adhesion between the coating film and the binder layer may be insufficient.

[0009] One object of the present disclosure is to provide a water-based coating composition capable of forming a binder layer that has excellent adhesion to a (meth)acrylic resin coating film.

[0010] One embodiment of the aqueous coating composition of the present disclosure contains synthetic resin particles (A), an organic solvent (B) having a water solubility of 1.0 (g / 100 g of water) or more and a boiling point of 200°C or more, and water, wherein the content of the organic solvent (B) in the composition is 1 to 16 mass%, and the composition is a composition for application to the surface of a (meth)acrylic resin coating film.

[0011] According to the present disclosure, it is possible to provide a water-based coating composition capable of forming a binder layer that has excellent adhesion to a (meth)acrylic resin coating film.

[0012] 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 substrate with a multilayer coating film according to one embodiment.

[0013] Embodiments of the present disclosure will be described in detail below. Each component described in this specification can be used singly or in combination. In this specification, the term "polymer" may be used without any particular distinction between homopolymers and copolymers. That is, the term "polymer" is used to mean either a homopolymer or a copolymer. "(Meth)acrylate" is a general term for acrylate and methacrylate, and may be either acrylate or methacrylate. "(Meth)acrylic" is a general term for acrylic and methacrylic, and may be either acrylic or methacrylic. "(Meth)acrylic acid" is a general term for acrylic acid and methacrylic acid, and may be either acrylic acid or methacrylic acid. The same applies to other examples.

[0014] As used herein, the term "old coating film" encompasses not only a coating film formed on a substrate that has deteriorated (e.g., worn, abraded, peeled, blistered, cracked) due to aging or use since its formation, but also a coating film that has not deteriorated. The old coating film may be, for example, an old antifouling coating film or an old topcoat coating film. The old coating film may have, for example, a single-layer structure or a laminate structure of two or more layers. As used herein, the term "old antifouling coating film" encompasses not only an antifouling coating film formed on a substrate that has been in contact with water such as seawater or freshwater for a certain period of time (e.g., an antifouling coating film that has been immersed in water such as the ocean, river, or lake for a certain period of time), but also an antifouling coating film prior to such contact or that has not been immersed. In this specification, the term "old topcoat coating film" includes not only a topcoat coating film formed on a substrate that has deteriorated due to aging or use since the coating film was formed, but also a topcoat coating film that has not deteriorated.

[0015] As used herein, the term "new coating film" refers to a coating film newly formed on an old coating film (e.g., via a binder layer, as described below). Examples of cases in which a new coating film is formed on an old coating film include cases in which a new coating film is formed on a deteriorated coating film, and cases in which a new coating film is formed on an undeteriorated coating film after a coating film has been formed by mistake or a coating film that differs from the design. The new coating film may be, for example, a new antifouling coating film or a new topcoat coating film. The new coating film may have, for example, a single-layer structure or a laminated structure of two or more layers.

[0016] In this specification, the numerical range n1 to n2 means n1 or more and n2 or less if n1<n2, and n1>n2 means n2 or more and n1 or less if n1>n2. In this specification, 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.

[0017] [Water-based coating composition] The water-based coating composition of the present disclosure (hereinafter also referred to as "the composition of the present disclosure") contains synthetic resin particles (A), an organic solvent (B) having a water solubility of 1.0 (g / 100 g of water) or more and a boiling point of 200°C or more, and water.

[0018] <Synthetic Resin Particles (A)> The composition of the present disclosure contains synthetic resin particles (A). The synthetic resin particles (A) may be any synthetic resin particles other than the rubber component (C) described below, and examples thereof include (meth)acrylic resin particles, epoxy resin particles, polyester resin particles, polyurethane resin particles, polyamide resin particles, polyether resin particles, polyolefin resin particles, polystyrene resin particles, vinyl acetate resin particles, vinyl chloride resin particles, polyvinyl alcohol resin particles, polyvinyl ester resin particles, and fluororesin particles. Among these, (meth)acrylic resin particles and epoxy resin particles are preferred, and (meth)acrylic resin particles are more preferred. A composition containing at least one type of particle selected from (meth)acrylic resin particles and epoxy resin particles tends to be able to form a coating film that has high adhesion to the old coating film.

[0019] The (meth)acrylic resin particles are composed of a (meth)acrylic resin. The (meth)acrylic resin has a structural unit derived from a (meth)acrylic monomer and may further have a structural unit derived from another ethylenically unsaturated monomer copolymerizable with the (meth)acrylic monomer. The (meth)acrylic resin 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 the other ethylenically unsaturated monomer. The copolymer may be, for example, a random copolymer or a block copolymer. The (meth)acrylic resin may have two or more types of structural units derived from a (meth)acrylic monomer. The (meth)acrylic resin may have one type or two or more types of structural units derived from the other ethylenically unsaturated monomer.

[0020] Examples of (meth)acrylic monomers include (meth)acrylic acid esters, (meth)acrylic acid amides, (meth)acrylonitrile, 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, 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. hydroxyalkyl (meth)acrylates such as glycidyl (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.

[0021] Examples of other ethylenically unsaturated monomers copolymerizable with the (meth)acrylic monomer include α-olefins such as ethylene, propylene, and 1-butene; conjugated dienes such as 1,3-butadiene, isoprene, and chloroprene; styrenic monomers such as styrene, α-methylstyrene, and halogenated styrene; vinyl esters such as vinyl acetate and vinyl propionate; 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.

[0022] In the (meth)acrylic resin, the content of structural units derived from (meth)acrylic monomers in 100% by mass of all structural units derived from polymerizable monomers is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, still more preferably 50% by mass or more, and particularly preferably 60% by mass or more. In this specification, the content of each structural unit is measured by nuclear magnetic resonance spectroscopy (NMR).

[0023] In the (meth)acrylic resin, the content of the structural units derived from the other ethylenically unsaturated monomers in 100% by mass of all structural units derived from polymerizable monomers is preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 60% by mass or less, still more preferably 50% by mass or less, and particularly preferably 40% by mass or less.

[0024] Examples of the (meth)acrylic resin include a (meth)acrylic monomer polymer, which is a homopolymer or copolymer of a (meth)acrylic monomer, a (meth)acrylic monomer-styrene monomer copolymer, and a (meth)acrylic monomer-vinyl ester copolymer. The (meth)acrylic resin may be, for example, a silicone-modified resin or a urethane-modified resin.

[0025] The (meth)acrylic resin may be self-crosslinking or non-self-crosslinking.

[0026] The glass transition temperature (Tg) of the (meth)acrylic resin is preferably 0°C or higher, more preferably 5°C or higher, even more preferably 10°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. Compositions containing (meth)acrylic resins having a Tg equal to or higher than the lower limit tend to be able to form coating films that are excellent in strength and water resistance. Compositions containing (meth)acrylic resins having a Tg equal to or lower than the upper limit tend to be able to form coating films that are excellent in adhesion to the substrate. In this specification, Tg refers to the midpoint glass transition temperature obtained by differential scanning calorimetry (DSC) in accordance with JIS K7121:2012.

[0027] The (meth)acrylic resin may have an acid value of more than 0 mgKOH / g. The acid value (unit: mgKOH / g) of the (meth)acrylic resin 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. A (meth)acrylic resin having an acid value equal to or greater than the lower limit tends to have excellent stability in an aqueous paint composition. A composition containing a (meth)acrylic resin having an acid value equal to or less than the upper limit tends to be able to form a coating film with excellent water resistance. 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 content of a sample, and is measured in accordance with JIS K0070:1992.

[0028] Examples of a method for synthesizing the (meth)acrylic resin include known methods, such as a method of polymerizing a polymerizable monomer in the presence of a radical polymerization initiator by solution polymerization, suspension polymerization, bulk polymerization, or emulsion polymerization.

[0029] When preparing a water-based coating composition containing (meth)acrylic resin particles, for example, an emulsion containing (meth)acrylic resin particles, as described below, may be used. The emulsion containing (meth)acrylic resin particles may be one obtained by emulsifying a (meth)acrylic resin prepared by a polymerization method other than emulsion polymerization (for example, solution polymerization) using an emulsifier as necessary, or may be an emulsion prepared by emulsion polymerization. The emulsifier used in emulsion polymerization may be a reactive emulsifier having a group capable of copolymerizing with a (meth)acrylic monomer, or a non-reactive emulsifier not having such a group.

[0030] The epoxy resin particles are made of an epoxy resin, such as bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin (e.g., phenol novolac epoxy resin, cresol novolac epoxy resin), alicyclic epoxy resin, and aliphatic-modified epoxy resin.

[0031] An epoxy resin is a resin having at least two epoxy groups per molecule. The epoxy equivalent of the epoxy resin, calculated per nonvolatile content, is preferably 50 g / mol or more, more preferably 75 g / mol or more, even more preferably 100 g / mol or more, and is preferably 5,000 g / mol or less, more preferably 2,500 g / mol or less, even more preferably 1,000 g / mol or less, for example, 50 to 5,000 g / mol. In this specification, the epoxy equivalent is calculated by the method described in JIS K7236:2009.

[0032] When the aqueous coating composition contains epoxy resin particles as the synthetic resin particles (A), the composition preferably further contains a curing agent for the epoxy resin, preferably a polyamine.

[0033] Polyamines are water-soluble or water-dispersible compounds having at least two amino groups per molecule. Polyamines can be used, for example, in the form of an aqueous solution containing the polyamine or an aqueous dispersion containing the polyamine. Examples of polyamines include aliphatic polyamines such as ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, triaminopropane, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, isophoronediamine, and 1,3-bisaminomethylcyclohexane; aromatic polyamines such as phenylenediamine, metaxylylenediamine, paraxylylenediamine, and diaminodiphenylmethane; other polyamines such as polyoxyethylenediamine, polyoxypropylenediamine, triethyleneglycoldiamine, and tripropyleneglycoldiamine; and modified polyamines obtained by modifying these polyamines using known methods. Examples of modifications include amidation, Mannich reaction, and epoxy adduct formation.

[0034] The amount of polyamine used is, for example, such that the amount of active hydrogen in the polyamine is preferably 0.1 to 1.5 equivalents, more preferably 0.2 to 1.3 equivalents, and even more preferably 0.3 to 1.0 equivalents per equivalent of epoxy groups in the epoxy resin.

[0035] When epoxy resin particles and a curing agent thereof are used, the composition may be stored, for example, in the form of a two-component composition having a base component containing epoxy resin particles and a curing agent component containing a curing agent such as polyamine.

[0036] The synthetic resin particles (A) are preferably water-dispersible particles that can be dispersed in water. When the synthetic resin particles (A) are (meth)acrylic resin particles, the (meth)acrylic resin constituting the particles may have a hydrophilic group such as a carboxy group or a hydroxy group.

[0037] The synthetic resin particles (A) are usually 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. The Z-average particle size of the synthetic resin particles (A) 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, and particularly preferably 300 nm or less, for example, 10 nm to 2 μm. Synthetic resin particles (A) having a Z-average particle size within the above range tend to be able to exist stably in aqueous paint compositions, and such compositions tend to be able to form coatings with uniform coating properties. In this specification, the Z-average particle size is measured at 23°C by dynamic light scattering (DLS) using a particle size measurement device (e.g., Malvern Zetasizer Nano-ZS).

[0038] When producing the composition of the present disclosure, it is preferable to use an aqueous dispersion in which synthetic resin particles (A) are 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 synthetic resin particles (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 properties. The aqueous dispersion is preferably an emulsion. The content of the synthetic resin particles (A) in the aqueous dispersion is preferably 20% by mass or more, more preferably 30% by mass or more, and preferably 70% by mass or less, more preferably 60% by mass or less, for example 20 to 70% by mass.

[0039] The aqueous medium is not particularly limited as long as it contains water, but from the viewpoint of reducing the environmental load, the water content in the aqueous medium is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. 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, and ethylene glycol monopropyl ether.

[0040] The composition of the present disclosure may contain two or more types of synthetic resin particles (A). The content of the synthetic resin particles (A) in 100% by mass of the nonvolatile content of the aqueous coating composition of the present disclosure is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and is preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less, for example, 10 to 70% by mass.

[0041] <Organic Solvent (B)> The composition of the present disclosure contains an organic solvent (B). The organic solvent (B) has a water solubility of 1.0 (g / 100 g of water) or more and a boiling point of 200°C or more. The organic solvent (B) is a compound that is liquid at 23°C under 1 atmosphere.

[0042] The effects of the composition of the present disclosure will be explained below. By providing a coating film formed from the composition of the present disclosure as a binder layer between an old coating film and a new coating film, it is possible to obtain a multilayer coating film having the old coating film, binder layer, and new coating film in that order, and which has excellent adhesion between the old coating film and the binder layer. The reason for this is unclear, but the inventors speculate as follows.

[0043] The (meth)acrylic resin coating film present on the substrate as the old coating film is formed from a paint containing a (meth)acrylic resin or the like, and has a certain degree of hydrophilicity. When the composition of the present disclosure containing an organic solvent (B) having a certain level of water solubility is applied to the surface of such an old coating film, the composition blends well with the surface of the old coating film, and the organic solvent (B) can dissolve the surface of the old coating film, thereby forming a binder layer that has excellent adhesion to the old coating film. Because the organic solvent (B) has a high boiling point, it is prevented from immediately volatilizing upon application of the composition, and therefore the above-mentioned effects can be fully achieved.

[0044] Thus, the composition of the present disclosure is suitable as a coating composition for application to the surface of a (meth)acrylic resin coating film, for example, as a coating composition for forming a binder layer for repairing an old coating film, specifically as a coating composition for forming a binder layer to be provided between an old coating film and a new coating film when repairing the old coating film. The (meth)acrylic resin coating film is, for example, an antifouling coating film or a topcoat coating film.

[0045] As used herein, the term "(meth)acrylic resin coating film" refers to a coating film formed from a paint containing a (meth)acrylic resin. The (meth)acrylic resin content in the (meth)acrylic resin coating film is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more, relative to 100% by mass of the resin components contained in the (meth)acrylic resin coating film. The (meth)acrylic resin coating film may have a single-layer structure or a laminate structure of two or more layers.

[0046] The paint for forming the (meth)acrylic resin coating film is not particularly limited, and may be, for example, a paint composition prepared based on the descriptions in JP-A-2016-180051, JP-A-2018-44162, JP-A-2019-56064, etc., or a commercially available product. The paint may be a non-reactive curing paint or a reactive curing paint.

[0047] The composition of the present disclosure is particularly suitable as a coating composition to be applied to the surface of an old antifouling coating film, for example, as a coating composition for forming a binder layer for repairing an old antifouling coating film, specifically as a coating composition for forming a binder layer to be provided between an old antifouling coating film and a new antifouling coating film when repairing an old antifouling coating film. Below, the case where the old coating film is an old antifouling coating film will be further explained.

[0048]

[0003] Antifouling coating films are typically provided on substrates to prevent aquatic organisms from adhering to the surface of the substrate. As described above, for example, a new antifouling coating film is typically provided on the old antifouling coating film to repair the old one. When a new antifouling coating film is directly formed on the surface of the old antifouling coating film, the adhesion between the old and new antifouling coating films may be insufficient. Antifouling coating films provided on ship bottom shell plates are exposed to a submerged environment for long periods of time, and therefore tend to require particularly high adhesion. When a binder layer formed from a conventional water-based paint composition is provided between the old and new antifouling coating films to improve adhesion, the adhesion between the old and new antifouling coating films is insufficient, and in a laminated coating film consisting of the old antifouling coating film and the binder layer, the upper binder layer tends to peel off easily from the lower old antifouling coating film.

[0049] By providing a coating film formed from the composition of the present disclosure as a binder layer between an old antifouling coating film and a new antifouling coating film, it is possible to obtain a multilayer coating film having the old antifouling coating film, the binder layer, and the new antifouling coating film in that order, which has excellent adhesion between the old antifouling coating film and the binder layer. The reason for this is unclear, but the inventors speculate as follows.

[0050] The old antifouling coating film is formed from an antifouling paint containing a (meth)acrylic resin and, optionally, an antifouling agent, and has a certain degree of hydrophilicity. After contact with water, such as seawater or freshwater, the old antifouling coating film has a fragile surface layer (weak layer) with fine cavities, formed by the (meth)acrylic resin or antifouling agent dissolving in the water. When a composition of the present disclosure, containing an organic solvent (B) with a certain level of water solubility or higher, is applied to the surface of such an old antifouling coating film, the composition adheres well to the surface of the old antifouling coating film, and the organic solvent (B) dissolves the surface of the old antifouling coating film (the fragile layer), preventing binder layer peeling due to cohesive failure in the fragile layer. Therefore, a binder layer with excellent adhesion to the old antifouling coating film can be formed. The high boiling point of the organic solvent (B) prevents the composition from immediately volatilizing upon application, thereby achieving the above-mentioned effects. The above reasons are speculation and do not limit the composition of the present disclosure in any way.

[0051] The water solubility of the organic solvent (B) (unit: g / 100 g of water) is 1.0 or more, preferably 1.5 or more, more preferably 2.0 or more, and even more preferably 2.5 or more. The upper limit of the water solubility of the organic solvent (B) is not particularly limited. The organic solvent (B) may be, for example, a water-miscible organic solvent that can be miscible with water in any amount. Organic solvents with a water solubility of less than 1.0 (g / 100 g of water) tend not to fully exhibit the above-mentioned effects. The water solubility of the organic solvent (B) represents the maximum amount (g) of the organic solvent that dissolves in 100 g of water. The water solubility is measured by the EPA 830.7840 flask shaker method under conditions of 1 atmosphere and 23°C.

[0052] The boiling point of the organic solvent (B) is 200°C or higher, preferably 205°C or higher, more preferably 210°C or higher, even more preferably 220°C or higher, and preferably 300°C or lower, more preferably 290°C or lower, even more preferably 280°C or lower, for example, 200 to 300°C. Organic solvents having a boiling point of less than 200°C tend to volatilize easily when the composition is applied, and therefore tend not to fully exhibit the above-mentioned effects. The boiling point of the organic solvent (B) is measured under 1 atmosphere.

[0053] Examples of the organic solvent (B) include glycol ethers, glycol acetates, glycols, alcohols, and esters, each of which has a water solubility and boiling point within the above ranges. Among these, glycol ethers are preferred. Examples of glycol ethers include alkylene glycol monoalkyl ethers, alkylene glycol monoaryl ethers, dialkylene glycol monoalkyl ethers, dialkylene glycol monoaryl ethers, trialkylene glycol monoalkyl ethers, and trialkylene glycol monoaryl ethers. The "alkylene" in these compounds includes, for example, alkylene groups having 2 or 3 carbon atoms. The "alkyl" in these compounds includes, for example, alkyl groups having 1 to 10 carbon atoms, such as methyl, ethyl, propyl, butyl, and hexyl, preferably alkyl groups having 3 to 10 carbon atoms, more preferably alkyl groups having 3 to 6 carbon atoms, and even more preferably alkyl groups having 3 to 4 carbon atoms, with linear alkyl groups being preferred. The "aryl" in these compounds includes, for example, aryl groups having 6 to 10 carbon atoms, such as phenyl.

[0054] The molecular weight of the organic solvent (B) is preferably 350 or less, more preferably 300 or less, even more preferably 250 or less, and is preferably 100 or more, for example, 100 to 350. A composition containing an organic solvent (B) having a molecular weight equal to or less than the upper limit tends to be able to exhibit the above-mentioned effects more effectively.

[0055] The organic solvent (B) preferably has a linear alkoxy group having 3 or more carbon atoms at the molecular terminal. A composition containing an organic solvent (B) having such an alkoxy group tends to be able to more effectively exhibit the above-mentioned effects. The number of carbon atoms in the linear alkoxy group is preferably 3 to 10, more preferably 3 to 6, and even more preferably 3 to 4. The organic solvent (B) preferably does not have a phenyl group, as this tends to be able to more effectively exhibit the above-mentioned effects.

[0056] Examples of organic solvents (B) include ethylene glycol monophenyl ether (2.3 g, 245°C), diethylene glycol monobutyl ether (miscible, 230°C), diethylene glycol monohexyl ether (1.7 g, 260°C), propylene glycol monophenyl ether (1.1 g, 242°C), dipropylene glycol monopropyl ether (18 g, 210°C), dipropylene glycol monobutyl ether (3 g, 222°C), tripropylene glycol monomethyl ether (miscible, 241°C), tripropylene glycol monobutyl ether (3 g, 276°C), and benzyl alcohol (4 g, 205°C). The value on the left side of the parentheses indicates the amount of the organic solvent dissolved in 100 g of water, and organic solvents that can be dissolved and miscible in any amount in water are described as "miscible." The value on the right side of the parentheses indicates the boiling point of the organic solvent.

[0057] The content of organic solvent (B) in the composition of the present disclosure is 1 to 16% by mass. Coating films (e.g., binder layers) formed from compositions containing less than 1% by mass of organic solvent (B) tend to be unable to fully exhibit the above-mentioned effects. Due to its low volatility, organic solvent (B) tends to remain in coating films formed from the above-mentioned compositions. Coating films formed from compositions containing more than 16% by mass of organic solvent (B) tend to have a relatively reduced amount of resin components in the coating film, resulting in insufficient adhesion to the underlying (meth)acrylic resin coating film.

[0058] From the viewpoint of better exerting the above-described effects, the content of the organic solvent (B) in the composition of the present disclosure is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, and is preferably 16% by mass or less, more preferably 14% by mass or less, even more preferably 13% by mass or less.

[0059] The boiling point of the organic solvent (B) is 200° C. or higher, and therefore the organic solvent (B) has low volatility at room temperature (23° C.). Therefore, the composition of the present disclosure, which contains the organic solvent (B) and is aqueous, is a composition with a low environmental impact.

[0060] The composition of the present disclosure may contain two or more organic solvents (B). The composition of the present disclosure contains water and the organic solvent (B). From the viewpoint of better exhibiting the above-mentioned effects, the content of the organic solvent (B) in the composition is preferably 2 parts by mass or more, more preferably 6 parts by mass or more, and even more preferably 8 parts by mass or more, and is preferably 55 parts by mass or less, more preferably 45 parts by mass or less, and even more preferably 40 parts by mass or less, for example, 2 to 55 parts by mass, relative to 100 parts by mass of water.

[0061] <Rubber Component (C)> The composition of the present disclosure may further contain a rubber component (C). Compositions further containing a rubber component (C) tend to be able to form a coating film that has better adhesion to, for example, an old coating film or a substrate.

[0062] Examples of the rubber component (C) include synthetic rubbers such as styrene-butadiene synthetic rubbers, (meth)acrylonitrile-butadiene synthetic rubbers, and isobutylene synthetic rubbers; and natural rubbers.

[0063] As the rubber component (C), a rubber component having butadiene-derived structural units is preferred, with styrene-butadiene synthetic rubber and (meth)acrylonitrile-butadiene synthetic rubber being more preferred, and styrene-butadiene synthetic rubber being even more preferred. Styrene-butadiene synthetic rubber is a copolymer rubber having styrene-derived structural units and butadiene (1,3-butadiene)-derived structural units as the main components, i.e., having a total of more than 50 mass% of these structural units. (Meth)acrylonitrile-butadiene synthetic rubber is a copolymer rubber having (meth)acrylonitrile-derived structural units and butadiene (1,3-butadiene)-derived structural units as the main components, i.e., having a total of more than 50 mass% of these structural units.

[0064] The rubber component may further contain, for example, structural units derived from other polymerizable monomers. Examples of other polymerizable monomers include (meth)acrylic acid; alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, and lauryl (meth)acrylate; hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate; alkoxyalkyl (meth)acrylates such as 2-methoxyethyl (meth)acrylate; epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate; cyanide vinyl compounds such as (meth)acrylonitrile; (meth)acrylic acid amides such as N-methylol (meth)acrylic acid amide; and aromatic vinyl compounds such as α-methylstyrene. The rubber component may contain one structural unit derived from the other polymerizable monomer, or two or more structural units.

[0065] In a rubber component having butadiene-derived structural units, the content of butadiene-derived structural units in 100% by mass of all structural units derived from polymerizable monomers is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, particularly preferably 25% by mass or more, and is preferably 95% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, particularly preferably 60% by mass or less, for example, 10 to 95% by mass.

[0066] In styrene-butadiene synthetic rubbers, the content of styrene-derived structural units in 100% by mass of all structural units derived from polymerizable monomers is preferably 5% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, particularly preferably 40% by mass or more, and is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, particularly preferably 75% by mass or less, for example, 5 to 90% by mass.

[0067] In the styrene-butadiene synthetic rubber, the content of structural units derived from other polymerizable monomers in 100% by mass of all structural units derived from polymerizable monomers is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less.

[0068] The glass transition temperature (Tg) of the rubber component (C) is preferably −40°C or higher, more preferably −30°C or higher, even more preferably −20°C or higher, and preferably 50°C or lower, more preferably 40°C or lower, even more preferably 30°C or lower, for example, −40 to 50°C. A composition containing a rubber component (C) having a Tg equal to or higher than the lower limit tends to be able to form a coating film having excellent strength and water resistance. A composition containing a rubber component (C) having a Tg equal to or lower than the upper limit tends to be able to form a coating film having excellent adhesion to the substrate. When a coating film formed from the composition of the present disclosure is laminated on an old coating film as a binder layer, the Tg of the rubber component (C) is preferably −30 to 30°C. A composition containing a rubber component (C) having a Tg within the above range tends to be able to form a coating film having even better adhesion to the old coating film. From the viewpoint of adhesion, the old coating film is preferably an old antifouling coating film, and more preferably an old hydration-decomposable antifouling coating film.

[0069] The rubber component (C) may be present in the composition in the form of particles. The Z-average particle size of the rubber component (C) particles 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, and particularly preferably 300 nm or less, for example, 10 nm to 2 μm. The rubber component (C) particles having a Z-average particle size within the above range tend to be able to exist stably in the water-based coating composition, and such a composition tends to be able to form a coating film with uniform coating film properties.

[0070] When producing the composition of the present disclosure, it is preferable to use an aqueous dispersion in which the rubber component (C) is dispersed in an aqueous medium and mix the aqueous dispersion with other constituents. This makes it easier for the rubber component (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 rubber component (C) in the aqueous dispersion is preferably 20% by mass or more, more preferably 30% by mass or more, and preferably 70% by mass or less, more preferably 60% by mass or less, for example, 20 to 70% by mass.

[0071] The composition of the present disclosure may contain one or more types of rubber component (C). A case where the composition of the present disclosure contains the rubber component (C) will be described. From the viewpoint of the above-mentioned adhesion, when the total content of the synthetic resin particles (A) and the rubber component (C) is taken as 100 parts by mass, the content of the synthetic resin particles (A) is preferably 60 to 95 parts by mass, more preferably 70 to 95 parts by mass, and even more preferably 70 to 90 parts by mass, and the content of the rubber component (C) is preferably 5 to 40 parts by mass, more preferably 5 to 30 parts by mass, and even more preferably 10 to 30 parts by mass.

[0072] <Other Components> The composition of the present disclosure may contain other components such as pigments and additives, as long as the above-described effects are not impaired. Examples of additives include dispersants, wetting agents, anti-sagging agents (anti-settling agents, thixotropic agents, rheology control agents), antifoaming agents, leveling agents, surfactants, thickeners, anti-mold agents, preservatives, pH adjusters, UV absorbers, and antioxidants. The composition of the present disclosure may contain one or more of the other components.

[0073] Examples of pigments include extender pigments and color pigments, and may be either organic or inorganic pigments. The composition of the present disclosure may contain one or more pigments.

[0074] Examples of extender pigments include talc, silica, mica, clay, potassium feldspar, calcium carbonate, kaolin, alumina white, white carbon, aluminum hydroxide, magnesium carbonate, barium carbonate, barium sulfate, zinc oxide, and zinc sulfide. When the composition of the present disclosure contains a body pigment, the content of the body pigment is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 5% by mass or more, and is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less, for example, 0.1 to 80% by mass, based on 100% by mass of the nonvolatile content of the composition.

[0075] Examples of color pigments include inorganic pigments and organic pigments. Examples of inorganic pigments include carbon black, red iron oxide, titanium white (titanium oxide), yellow iron oxide, and red iron oxide. Examples of organic pigments include naphthol red and phthalocyanine blue. When the composition of the present disclosure contains a color pigment, the content of the color pigment is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.5% by mass or more, and is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less, for example, 0.01 to 40% by mass, based on 100% by mass of the nonvolatile content of the composition.

[0076] The composition of the present disclosure may contain a dispersant from the viewpoint of improving the dispersibility of insoluble components such as pigments, facilitating the formation of a coating film with a good appearance, and facilitating the formation of a coating film with excellent crack resistance. Examples of dispersants include polymers having a pigment-adsorbing group (pigment-affinity group) and a compatible chain, such as fatty acids, polyaminos, polyethers, polyesters, polyurethanes, and polyacrylates. Examples of pigment-adsorbing groups include carboxy groups, acid anhydride groups, phosphate groups, amino groups, salt groups thereof, and ammonium salt groups. 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 nonvolatile content of the composition.

[0077] The composition of the present disclosure may contain a wetting agent from the viewpoint of spreading the composition more easily over the surface of the substrate. Examples of wetting agents include acetylene diol wetting agents, silicone wetting agents, (meth)acrylic wetting agents, vinyl wetting agents, and fluorine-based wetting agents. When the composition of the present disclosure contains a wetting agent, the content of the wetting agent 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, 0.01 to 3% by mass, based on 100% by mass of the nonvolatile content of the composition.

[0078] The composition of the present disclosure may contain 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 anti-sagging agents include organic thixotropes such as hydrogenated castor oil-based thixotropes, amide wax-based thixotropes, polyethylene oxide-based thixotropes, and urethane-based thixotropes; and inorganic thixotropes such as clay minerals (e.g., bentonite, smectite, and hectorite) and synthetic finely powdered silica. When the composition 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, based on 100% by mass of the nonvolatile content of the composition.

[0079] The defoaming agent is preferably a material capable of suppressing the generation of bubbles during the preparation and application of the composition, or a material capable of breaking down bubbles generated in the 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. When the composition of the present disclosure contains a defoaming agent, the content of the defoaming 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, based on 100% by mass of the nonvolatile content of the composition.

[0080] As the thickener, for example, commercially available products generally sold as thickeners can be used. Examples of thickeners include alkali thickeners, nonionic association types, acrylic types, urethane types, water-soluble polymer types, and polyamide types, as well as cellulose-based thickeners such as 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 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 nonvolatile content of the composition.

[0081] In the composition of the present disclosure, the content of organic solvents other than the organic solvent (B) having a water solubility of 1.0 (g / 100 g of water) or more and a boiling point of 200°C or more is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less.

[0082] <Water> The composition of the present disclosure is a water-based coating composition. In the present disclosure, a "water-based" coating composition refers to a coating composition containing water. Examples of water include tap water, ion-exchanged water, and deionized water, with ion-exchanged water and deionized water being preferred. Examples of the water include water contained in an aqueous dispersion of synthetic resin particles (A), water contained in an aqueous dispersion of the rubber component (C), and water contained in additives.

[0083] The water content in the composition of the present disclosure is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, and is preferably 60% by mass or less, more preferably 55% by mass or less, even more preferably 50% by mass or less, for example, 20 to 60% by mass. The water content is measured according to the Karl Fischer method using a moisture meter (e.g., CA-310, manufactured by Nitto Seiko Analytech).

[0084] From the viewpoint of providing a composition with excellent coating workability, the nonvolatile content in the composition of the present disclosure is preferably 25% by mass or more, more preferably 30% by mass or more, even more preferably 35% by mass or more, and is preferably 75% by mass or less, more preferably 70% by mass or less, even more preferably 65% ​​by mass or less, for example, 25 to 75% by mass. The nonvolatile content is measured by the method described in the Examples section.

[0085] <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 viewpoint of consideration for the natural environment and the coating work environment. The lower the VOC content in the composition of the present disclosure, the better, but the content may be, for example, 1 g / L or more, 5 g / L or more, 10 g / L or more, 20 g / L or more, or 30 g / L or more. The VOC content in the composition of the present disclosure may be, for example, 1 to 150 g / L.

[0086] The VOC content in the composition of the present disclosure is calculated based on the following formula (1) using the values ​​of the composition specific gravity, nonvolatile content concentration, and water concentration, each of which will be described below: VOC content (g / L) = composition specific gravity × 1000 × (100 - nonvolatile content concentration - water concentration) / 100 (1)

[0087] The specific gravity (g / mL) of a composition is a value calculated by filling a 100 mL volume specific gravity cup with the composition at a temperature of 23°C and measuring the mass of the composition. The non-volatile content (mass%) is a value calculated by the method described in the Examples section. The non-volatile content of a composition refers to the heating residue when the composition is dried in an incubator at 108°C for 3 hours, as described in the Examples section. The moisture concentration (mass%) is the amount of water (mass%) contained in 100% by mass of the composition, and is measured using a moisture measuring device (e.g., CA-310, manufactured by Nitto Seiko Analytech) according to the Karl Fischer method.

[0088] <Method for Producing Composition> The composition of the present disclosure can be produced by appropriately utilizing a known method. For example, the above-mentioned components can be charged into a stirring vessel all at once or in any order, and the components are mixed using known stirring and mixing means, and dispersed or dissolved in water to produce the composition. In the above mixing, an aqueous dispersion in which the synthetic resin particles (A) are dispersed in an aqueous medium may be used, or an aqueous dispersion in which the rubber component (C) is dispersed in an aqueous medium may be used.

[0089] Examples of stirring / mixing means include a paint shaker, a high-speed disperser, a sand grind mill, a basket mill, a ball mill, a three-roll mill, a Ross mixer, or a planetary mixer. Mixing (kneading) may be performed with heating or cooling depending on the season, environment, etc.

[0090] The composition of the present disclosure is a water-based coating composition, which has minimal adverse effects on the environment and the human body and also has excellent storage stability. A coating film formed from the composition of the present disclosure has excellent adhesion to the old coating film and the substrate to be coated, as well as to the new coating film formed on the old coating film, and is resistant to peeling.

[0091] The composition of the present disclosure may be a one-component composition containing the above-mentioned components, or a multi-component composition such as a two-component composition. For example, when the synthetic resin particles (A) are (meth)acrylic resin particles, a one-component composition is preferred. For example, when the synthetic resin particles (A) are epoxy resin particles, a two-component composition is preferred. In the case of a multi-component composition, each component is usually stored, preserved, transported, etc. in a separate container, and mixed together immediately before use.

[0092] [Uses of the Composition, Multilayer Coating Film, Substrate with Multilayer Coating Film, and Manufacturing Method Thereof] 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, fiber-reinforced plastic (FRP), rubber, stone, concrete, mortar, glass, porcelain, ceramics, and composites thereof. Examples of resin coatings include antifouling coatings, primer coatings, intermediate coatings, topcoat coatings, and resin coatings to be repaired (e.g., old antifouling coatings and old topcoat coatings). 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 spray coating, etc.), and stainless steel (SUS304, SUS410, etc.).

[0093] The object to be coated is, for example, a substrate. The object to be coated may have, for example, a substrate and a resin coating film provided on the substrate. The resin coating film may be, for example, a former antifouling coating film or a former topcoat coating film. The resin coating film may be, for example, a (meth)acrylic resin-based coating film. Examples of the material of the substrate at the location where the resin coating film is provided include metal materials, wood, plastic, fiber-reinforced plastic (FRP), rubber, stone, concrete, mortar, glass, porcelain, pottery, and composites thereof, with metal materials being preferred.

[0094] Substrates include, for example, ship hull shells, decks and superstructures, underwater structures, seawater or freshwater supply and drainage pipes in various facilities, fishing equipment, and other marine materials, as well as land structures. Examples of ships include large steel ships such as container ships and tankers, fishing boats, FRP boats, wooden boats, yachts, motorboats, and personal watercraft. Examples of ship hull shells include bottom shells and outer hulls. Examples of underwater structures include oil pipelines, water supply and drainage pipes, circulating water pipes, water supply and drainage outlets in various facilities, submarine cables, seawater utilization equipment (seawater pumps, etc.), megafloats, coastal roads, undersea tunnels, port facilities, offshore wind power generation facilities, and various underwater civil engineering structures in canals and waterways. Examples of such facilities include factories, thermal power plants, and nuclear power plants. Examples of fishing equipment include ropes, fishing gear, fishing nets, floats, and buoys. Other marine materials include, for example, swimsuits, diver suits, goggles, oxygen tanks, and torpedoes. Land structures include, for example, bridges, steel towers, and chimneys in waste incinerators, power plants, factories, and the like.

[0095] When the composition of the present disclosure is applied to the surface of an antifouling coating film, the substrate is preferably a ship bottom shell, an underwater structure, or a fishing material, more preferably a ship bottom shell.When the composition of the present disclosure is applied to the surface of a topcoat coating film, the substrate is preferably a ship's outer side, deck, and superstructure, an underwater structure, or a land structure.

[0096] In order to remove rust, oil, moisture, dust, salt, and the like from the substrate and to improve adhesion between the substrate and the coating, the substrate surface may be treated as needed (for example, blast treatment (ISO8501-1 Sa2 1 / 2), degreasing to remove oil and dust). A primer such as an anti-rust paint may be applied to the surface of the substrate for the purpose of primary rust prevention. Examples of anti-rust paints include zinc-based shop primers, epoxy resin-based zinc-rich primers, and epoxy resin-based anti-corrosion paints.

[0097] The thickness (dry film thickness) of a coating film or binder layer formed from the composition of the present disclosure is preferably 10 μm or more, more preferably 15 μm or more, even more preferably 20 μm or more, and is preferably 500 μm or less, more preferably 400 μm or less, even more preferably 300 μm or less, for example, 10 to 500 μm. A coating film having a desired thickness may be formed by applying the composition multiple times. A coating film having a desired thickness may be formed by applying it once (single coating), or by applying it twice or more times (two or more coatings).

[0098] A coating film (e.g., a binder layer) 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.

[0099] The composition of the present disclosure can be used, for example, as an aqueous coating composition for forming a binder layer for an antifouling coating film or a topcoat coating film, i.e., a binder paint for an antifouling coating film or a topcoat coating film. The binder layer for an antifouling coating film or a topcoat coating film is a layer for improving the adhesion of the newly formed antifouling coating film or a topcoat coating film to the substrate. The binder paint for an antifouling coating film or a topcoat coating film is a paint applied to the substrate before applying the antifouling paint or a topcoat coating. In one embodiment, the antifouling substrate has, in this order, a substrate, a coating film (binder layer) formed from the composition of the present disclosure, and an antifouling coating film. Other layers, such as an anticorrosion coating film, may be provided between the substrate and the coating film (binder layer). In one embodiment, the substrate with a topcoat coating film has, in this order, a substrate, an undercoat coating film, an intermediate coating film if necessary, a coating film (binder layer) formed from the composition of the present disclosure, and a topcoat coating film.

[0100] A multilayer coating film, which is an example of an application of the composition of the present disclosure, will be described. In one embodiment, the multilayer coating film has, in this order, a first (meth)acrylic resin coating film, a binder layer formed from the composition of the present disclosure, and a second (meth)acrylic resin coating film. In one embodiment, the substrate with the multilayer coating film has, in this order, a substrate, a first (meth)acrylic resin coating film, a binder layer formed from the composition of the present disclosure, and a second (meth)acrylic resin coating film.

[0101] The binder layer is provided between the first (meth)acrylic resin coating film and the second (meth)acrylic resin coating film. A binder layer formed from the composition of the present disclosure or a conventionally known coating composition, or other layers such as a corrosion-resistant coating film may be provided between the substrate and the first (meth)acrylic resin coating film.

[0102] In one embodiment, the substrate with a multilayer coating film is an antifouling substrate, and the first (meth)acrylic resin-based coating film is a first antifouling coating film (old antifouling coating film), and the second (meth)acrylic resin-based coating film is a second antifouling coating film (new antifouling coating film). For example, the first (meth)acrylic resin-based coating film may be an antifouling coating film that may have deteriorated, and the second (meth)acrylic resin-based coating film may be an antifouling coating film for repair. In one embodiment, the substrate with a multilayer coating film is a substrate with a topcoat coating film, and the first (meth)acrylic resin-based coating film is a first topcoat coating film (old topcoat coating film), and the second (meth)acrylic resin-based coating film is a second topcoat coating film (new topcoat coating film). For example, the first (meth)acrylic resin-based coating film may be a topcoat coating film that may have deteriorated, and the second (meth)acrylic resin-based coating film may be a topcoat coating film for repair. A substrate with a topcoat coating film comprises, for example, a substrate, an undercoat coating film, an intermediate coating film if necessary, a first topcoat coating film, a binder layer formed from the composition of the present disclosure, and a second topcoat coating film, in this order.

[0103] In the case of an antifouling substrate, the substrate is preferably a ship bottom shell, an underwater structure, or a fishing material, more preferably a ship bottom shell. In the case of a substrate with a topcoat coating, the substrate is preferably a ship outer side, deck, and superstructure, an underwater structure, or a land structure.

[0104] Because the composition of the present disclosure exhibits the above-described effects, it is suitable as an aqueous coating composition for forming a binder layer between an old paint film and a new paint film, i.e., as a binder coating used to form a binder layer for a new paint film when forming a new paint film on an old paint film. The binder layer improves the interlayer adhesion of a multilayer coating film having an old paint film, a binder layer, and a new paint film. The binder layer has excellent adhesion to both the old paint film and the new paint film. By using the composition of the present disclosure, when repairing an old paint film, a binder layer formed from the composition can be interposed on the old paint film to form a new paint film that has excellent adhesion to the underlying layer.

[0105] According to the present disclosure, a binder layer and a new coating film formed from the composition of the present disclosure can be formed without removing the old coating film formed on the substrate, thereby reducing the steps and costs involved in repairing the old coating film.

[0106] It may be necessary to form a coating film (hereinafter also referred to as a "different coating film") on a coating film existing on a substrate, the coating film being made of a resin system different from the resin constituting the coating film. In this case, the different coating film is prone to coating defects such as blisters and cracks, so in the past, it was necessary to remove the coating film on the substrate and then reapply a new paint. A binder layer formed from the composition of the present disclosure not only has excellent adhesion to the old coating film, but also has excellent adhesion to a new coating film formed on the binder layer, thereby suppressing the occurrence of the above-mentioned coating defects. Therefore, the type of new coating film formed on the binder layer is not particularly limited, and it is easy to form a different coating film made of a resin system different from the resin constituting the old coating film.

[0107] In one embodiment, the multilayer coating film has an old coating film, a binder layer, and a new coating film, in this order. The binder layer is provided on the surface of the old coating film. Figure 1 shows a schematic cross-sectional view of one embodiment of the multilayer coating film. The multilayer coating film 1 in Figure 1 has an old coating film 10, a binder layer 20, and a new coating film 30, in this order.

[0108] In one embodiment, the substrate with a multilayer coating film has a substrate, an old coating film, a binder layer, and a new coating film, in this order. Figure 2 shows a schematic cross-sectional view of one embodiment of a substrate with a multilayer coating film. The substrate 2 with a multilayer coating film in Figure 2 has, in this order, a substrate 40, an old coating film 10, a binder layer 20, and a new coating film 30. Other layers, such as a binder layer (not shown) formed from the composition of the present disclosure or a conventionally known coating composition, or a corrosion-resistant coating film, may be provided between the substrate 40 and the old coating film 10.

[0109] The repaired substrate with a coating film can be produced, for example, by a production method comprising the steps of applying the water-based paint composition of the present disclosure to the surface of the first (meth)acrylic resin-based coating film of the substrate with a coating film to be repaired, the substrate having a substrate and a first (meth)acrylic resin-based coating film provided on the substrate, to form a binder layer, and forming a second (meth)acrylic resin-based coating film on the binder layer.

[0110] The repaired antifouling substrate can be produced, for example, by a production method comprising the steps of applying the aqueous paint composition of the present disclosure to the surface of the first antifouling coating film of an antifouling substrate to be repaired, the antifouling substrate having a substrate and a first antifouling coating film formed on the substrate, to form a binder layer, and forming a second antifouling coating film on the binder layer.

[0111] The repaired substrate with a topcoat coating film can be produced, for example, by a production method having the steps of applying the water-based paint composition of the present disclosure to the surface of the first topcoat coating film of the substrate with a topcoat coating film to be repaired, the substrate having a substrate and a first topcoat coating film formed on the substrate, to form a binder layer, and forming a second topcoat coating film on the binder layer.

[0112] The old antifouling coating film and the new antifouling coating film are each a (meth)acrylic resin-based coating film. Examples of the old antifouling coating film and the new antifouling coating film include a hydrolysis-type antifouling coating film and a hydration-decomposition-type antifouling coating film, respectively. A hydrolysis-type antifouling coating film exhibits antifouling properties by self-dissolving the (meth)acrylic resin that constitutes the coating film through a hydrolysis reaction upon contact with water, resulting in surface renewal. A coating film formed from the composition of the present disclosure exhibits good adhesion to both a hydrolysis-type antifouling coating film and a hydration-decomposition-type antifouling coating film. A coating film formed from the composition of the present disclosure also exhibits good adhesion to an antifouling coating film formed from an organic solvent-based antifouling paint.

[0113] Examples of hydrolysis-type antifouling coating films include hydrolysis-type antifouling coating films containing (meth)acrylic resins, and specific examples include antifouling coating films formed from antifouling paints containing polymerizable unsaturated carboxylic acid silyl ester copolymers, antifouling coating films formed from antifouling paints containing organopolysiloxane block-containing copolymers, antifouling coating films formed from antifouling paints containing copolymers having (meth)acrylic acid metal salt units, and antifouling coating films containing organic tin-containing polymers. Polymerizable unsaturated carboxylic acid silyl ester copolymers, organopolysiloxane block-containing copolymers, copolymers having (meth)acrylic acid metal salt units, and organic tin-containing polymers all fall under the category of (meth)acrylic resins.

[0114] An example of the hydration decomposition type antifouling coating film is an antifouling coating film formed from an antifouling paint containing a (meth)acrylic resin and at least one selected from rosins and monocarboxylic acid compounds.

[0115] Examples of the old topcoat coating film include a (meth)acrylic resin coating film, and examples of the new topcoat coating film include synthetic resin coating films such as a (meth)acrylic resin coating film and a urethane resin coating film, with a (meth)acrylic resin coating film being preferred.

[0116] The thickness of the antifouling coating film is, for example, 30 to 1,000 μm, and the thickness of the topcoat coating film is, for example, 10 to 200 μm.

[0117] The combination of the present disclosure comprises an article having a (meth)acrylic resin-based coating film and a water-based paint composition of the present disclosure for application to the surface of the (meth)acrylic resin-based coating film. The combination of the present disclosure, for example, comprises an article having an antifouling coating film and a water-based paint composition of the present disclosure for application to the surface of the antifouling coating film. The combination of the present disclosure, for example, comprises an article having a topcoat coating film and a water-based paint composition of the present disclosure for application to the surface of the topcoat coating film. Examples of the article include a substrate with a coating film having a substrate and a (meth)acrylic resin-based coating film provided on the substrate. Specific examples include an antifouling substrate having a substrate and an antifouling coating film (e.g., an old antifouling coating film) provided on the substrate, and a substrate with a topcoat coating film having a substrate and a topcoat coating film (e.g., an old topcoat coating film) provided on the substrate. The combination of the present disclosure may further comprise a (meth)acrylic resin-based paint for forming a new (meth)acrylic resin-based coating film. The combination of the present disclosure may further comprise an antifouling paint for forming a new antifouling paint film. The combination of the present disclosure may further comprise a topcoat paint for forming a new topcoat paint film.

[0118]

[0033] In the combination of the present disclosure, the details of each element are as described above. Examples of the antifouling paint include conventionally known antifouling paints, such as antifouling paints for forming hydrolysis-type antifouling coating films and antifouling paints for forming hydration-decomposition-type antifouling coating films, and specific examples thereof include the antifouling paints described above. Examples of the topcoat paint include conventionally known topcoat paints.

[0119] [Aspects of the Present Disclosure] The present disclosure relates to, for example, the following [1] to

[15] . [1] A water-based coating composition comprising synthetic resin particles (A), an organic solvent (B) having a water solubility of 1.0 (g / 100 g of water) or more and a boiling point of 200°C or more, and water, wherein the content of the organic solvent (B) in the composition is 1 to 16 mass%, and the composition is intended for application to the surface of a (meth)acrylic resin coating film. [2] The water-based coating composition according to [1] above, further comprising a rubber component (C), the rubber component (C) having butadiene-derived structural units. [3] The water-based coating composition according to [2] above, wherein the content of the butadiene-derived structural units in the rubber component (C) is 25 mass% or more. [4] The aqueous coating composition according to any one of [1] to [3], wherein the synthetic resin particles (A) are at least one selected from (meth)acrylic resin particles and epoxy resin particles. [5] The aqueous coating composition according to any one of [2] to [4], wherein the content of the synthetic resin particles (A) is 60 to 95 parts by mass and the content of the rubber component (C) is 5 to 40 parts by mass, where the total content of the synthetic resin particles (A) and the rubber component (C) is 100 parts by mass. [6] The aqueous coating composition according to any one of [1] to [5], wherein the content of the water in the composition is 20 to 60% by mass. [7] The aqueous coating composition according to any one of [1] to [6], wherein the (meth)acrylic resin coating film is an antifouling coating film. [8] The aqueous coating composition according to [7], wherein the antifouling coating film is a hydrolysis-type antifouling coating film or a hydration-decomposition-type antifouling coating film. [9] The water-based paint composition according to [7] or [8] above, wherein the antifouling coating film is an antifouling coating film provided on at least one selected from the group consisting of ship bottom shell plating, underwater structures, and fishing equipment.

[10] The water-based paint composition according to any one of [1] to [6] above, wherein the (meth)acrylic resin-based coating film is a topcoat coating film.

[11] A combination of an article having a (meth)acrylic resin-based coating film and the water-based paint composition according to any one of [1] to

[10] above, which is to be applied to the surface of the (meth)acrylic resin-based coating film.

[12] A substrate with a multilayer coating film comprising, in this order: a substrate; a first (meth)acrylic resin coating film provided on the substrate; a binder layer formed from the water-based paint composition described in any one of [1] to

[10] above; and a second (meth)acrylic resin coating film.

[13] The substrate with a multilayer coating film described in

[12] above, wherein the first (meth)acrylic resin coating film is an antifouling coating film and the second (meth)acrylic resin coating film is an antifouling coating film for repair.

[14] The substrate with a multilayer coating film described in

[12] above, wherein the first (meth)acrylic resin coating film is a topcoat coating film and the second (meth)acrylic resin coating film is a topcoat coating film for repair.

[15] A method for producing a repaired substrate with a coating film, comprising the steps of: applying the aqueous paint composition described in any one of [1] to

[10] above to the surface of the first (meth)acrylic resin coating film of a substrate with a coating film to be repaired, the substrate having a substrate and a first (meth)acrylic resin coating film provided on the substrate, to form a binder layer; and forming a second (meth)acrylic resin coating film on the binder layer.

[0120] The aqueous coating composition of the present disclosure will be explained in more detail below based on examples, but the 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."

[0121] [Components] The components used in the examples and comparative examples are listed below. Resin emulsion: PRIMAL TX-100, manufactured by Dow Chemical, aqueous emulsion of (meth)acrylic resin (Tg: 28°C, self-crosslinking), non-volatile content: 46.5% by mass Resin emulsion: PRIMAL AC-3001, manufactured by Dow Chemical, aqueous emulsion of (meth)acrylic resin (Tg: 32°C, non-self-crosslinking), non-volatile content: 48% by mass Resin emulsion: Beckopox EP 2384w / 57WA, manufactured by Allnex, aqueous emulsion of #1001 type epoxy resin, non-volatile content: 57% by mass, epoxy equivalent: 450 g / mol Aqueous curing agent solution: Sunmide WH-900, manufactured by Evonik Industries, aqueous solution of modified aliphatic polyamine, non-volatile content: 60% by mass

[0122] The following rubber emulsions are all emulsions of styrene-butadiene rubber components manufactured by Asahi Kasei. Rubber emulsion: SB latex DL-612, Non-volatile content: 48% by mass, Tg: -1°C Rubber emulsion: SB latex L-5702, Non-volatile content: 48% by mass, Tg: 25°C Rubber emulsion: SB latex L-2301, Non-volatile content: 50% by mass, Tg: 24°C Rubber emulsion: SB latex L-3200, Non-volatile content: 48% by mass, Tg: 8°C Rubber emulsion: SB latex A-7090, Non-volatile content: 50% by mass, Tg: 6°C Rubber emulsion: SB latex L-7063, Non-volatile content: 48% by mass, Tg: -1°C Rubber emulsion: SB latex HA-040 Non-volatile content: 52% by mass, Tg: -7°C Rubber emulsion: SB latex L-7850, Non-volatile content: 48% by mass, Tg: -27°C Rubber emulsion: SB latex A-7901, Non-volatile content: 50% by mass, Tg: -35°C

[0123] Pigment: Typeak R-930, manufactured by Ishihara Sangyo Kaisha, titanium oxide Pigment: Bengara 580R, manufactured by Toda Kogyo Co., Ltd. Pigment: Mica Powder 325mesh, manufactured by Fukuoka Talc Kogyosho, mica Pigment: Mica Powder 100mesh, manufactured by Fukuoka Talc Kogyosho, mica Pigment: F-2 talc, manufactured by Fuji Talc Kogyo Co., Ltd. Pigment: MA-100, manufactured by Mitsubishi Chemical, carbon black Dispersant: DISPERBYK-190, non-volatile content: 40% by mass, manufactured by BYK-Chemie GmbH Wetting agent: SURFYNOL SE-F, manufactured by Evonik Industries, non-volatile content: 80% by mass Anti-sagging agent (anti-settling agent): BENTONE DE Manufactured by Elementis Antifoaming agent: TEGO Airex 902W, manufactured by Evonik Industries, non-volatile content: 20% by mass Thickener: PRIMAL RM-8W, manufactured by Dow Chemical, non-volatile content: 21.3% by mass Thickener: RHEOLATE 288, manufactured by Elementis, non-volatile content: 25% by mass Mildewproofing agent: ACTICIDE MBS, non-volatile content: 5% by mass Thor Specialty Chemical

[0124] Organic solvent: an organic solvent listed in Table 1 below

[0125] [Nonvolatile content] The 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 a sample onto a flat-bottomed dish, spreading it evenly using a wire of known mass, and drying it in an incubator at 1 atmosphere and 108°C for 3 hours. The nonvolatile content (nonvolatile content concentration) (mass%) of the composition and each component was calculated from the amount of the heating residue.

[0126] Example 1: 11.4 parts of deionized water, 1.5 parts of DISPERBYK-190 (dispersant), 0.2 parts of TEGO Airex 902W (defoamer), and 0.2 parts of BENTONE DE (anti-sagging agent) were added to a container, mixed using a high-speed disperser, and dispersed for 5 minutes. Subsequently, while rotating the high-speed disperser, 4.5 parts of Typeque R-930 (pigment), 0.5 parts of Bengara 580R (pigment), 7 parts of Mica Powder 325 mesh (pigment), and 0.1 parts of PRIMAL RM-8W (thickener) were added, and the mixture was stirred for 1 hour. Subsequently, while rotating the high-speed disperser, 10 parts of PRIMAL TX-100 ((meth) acrylic resin emulsion) and 18 parts of F-2 talc (pigment) were added and dispersed, and after 30 minutes, 32.1 parts of PRIMAL TX-100 ((meth) acrylic resin emulsion), 7.1 parts of SB latex DL-612 (styrene-butadiene rubber emulsion), 4.5 parts of diethylene glycol monobutyl ether (organic solvent), 0.2 parts of TEGO Airex 902W (antifoaming agent), 0.3 parts of PRIMAL RM-8W (thickener), 2.2 parts of deionized water, and 0.2 parts of ACTICIDE MBS (mold inhibitor) were added, and the mixture was stirred for 10 minutes to obtain a binder coating composition.

[0127] [Examples 2 to 19, 21 to 27 and Comparative Examples 1 to 5] Each coating composition was prepared in the same manner as in Example 1, except that the components shown in Tables 2 to 4 were used in the amounts shown in the respective tables.

[0128] [Example 20] 15.9 parts of deionized water, 1 part of DISPERBYK-190 (dispersant), 0.4 parts of SURFYNOL SE-F (wetting agent), 0.1 parts of TEGO Airex 902W (defoaming agent), and 0.2 parts of BENTONE DE (anti-sagging agent) were added to a container, mixed using a high-speed disperser, and dispersed for 5 minutes. Subsequently, while rotating the high-speed disperser, 1.3 parts of Typek R-930 (pigment), 0.4 parts of Bengara 580R (pigment), 17 parts of F-2 talc (pigment), 6 parts of Mica Powder 100 mesh (pigment), and glass beads were added, and the mixture was stirred for 1 hour using a paint shaker to disperse these components. After dispersion, the filtrate was removed from the mixture with a filter net (opening: 80 mesh) and transferred to a container, and while rotating a high-speed disper, 10 parts of F-2 talc (pigment), 0.5 parts of benzyl alcohol (organic solvent), 2 parts of dipropylene glycol monobutyl ether (organic solvent), 38 parts of Beckopox EP 2384w / 57WA (epoxy resin emulsion), 7 parts of SB latex DL-612 (styrene-butadiene rubber emulsion), and 0.2 parts of TEGO Airex902W (defoaming agent) were added and dispersed for 30 minutes to obtain the main component of the binder coating composition. In another container, 60 parts of Sunmide WH-900 (aqueous polyamine solution), 10 parts of diethylene glycol monobutyl ether (organic solvent), and 30 parts of deionized water were added and mixed for 30 minutes using a high-speed disper, to obtain the curing agent component of the binder coating composition. 94 parts of the main component and 6 parts of the curing agent component were mixed to obtain a binder coating composition.

[0129] [Test method 1] The following antifouling paints were used: AF1: Hydration decomposition type antifouling paint (Seajet 033, manufactured by Chugoku Paint Co., Ltd.) AF2: Zinc acrylic resin-based hydrolysis type antifouling paint (Sea Premier 1000, manufactured by Chugoku Paint Co., Ltd.) AF3: Silyl resin-based hydrolysis type antifouling paint (Sea Grand Prix 2000, manufactured by Chugoku Paint Co., Ltd.) AF4: Hydration decomposition type antifouling paint (water-based antifouling paint described in Example 1 of JP 2021-155719 A) All of the above antifouling paints contain (meth)acrylic resin.

[0130] One of the antifouling paints AF1 to AF3 was applied to the surface of an FRP substrate and dried to form a 100 μm thick antifouling coating film, yielding an FRP substrate and an antifouling substrate having an antifouling coating film. The antifouling substrate was then immersed in seawater. One year after immersion, the antifouling substrate was recovered, decontaminated with high-pressure water (100 bar, 50 cm distance), the seawater was removed, and the substrate was then dried at room temperature. The coating composition of the example or comparative example was applied to the antifouling coating film of the antifouling substrate, i.e., the immersed antifouling coating film (old antifouling coating film), using an applicator (gap 0.1 mm) and dried to form a 30 μm thick test coating film, yielding test panel (1). Test panel (1) had an FRP substrate and a laminated coating film of the old antifouling coating film and the test coating film.

[0131] The coating composition of the Example or Comparative Example was applied to the surface of an FRP substrate using an applicator (gap 0.1 mm) and dried to form a test coating film (binder layer) 30 μm thick. One of the antifouling paints AF1 to AF4 was applied to the binder layer and dried to form a 50 μm thick antifouling coating film (topcoat antifouling coating film), thereby obtaining test plate (2). Test plate (2) has an FRP substrate and a laminated coating film of a binder layer and an antifouling coating film.

[0132] The coating composition of the example or comparative example was applied to the surface of an FRP substrate using an applicator (gap 0.1 mm) and dried to form a test coating film 30 μm thick, thereby obtaining a test plate (3). The test plate (3) has an FRP substrate and a test coating film.

[0133] [Evaluation Method] <Adhesion of Old Antifouling Coating Film - Test Coating Film> In accordance with JIS K5600-5-6:1999 (cross-cut method), the laminated coating film on the test plate (1) was cut into a 5 x 5 grid (25 squares) at 2 mm intervals down to the FRP substrate, and a peel test was carried out after applying adhesive tape. The results were evaluated according to the following criteria. Evaluation criteria for adhesion (adhesion): 5... The edges of the cuts are completely smooth, and there is no peeling at any of the grid cells. 4... The area of ​​cohesive failure of the peeled / old antifouling coating film is 4% or less. 3... The peeled area is more than 4% and 12% or less. 2... The peeled area is more than 12% and 36% or less. 1... The peeled area is more than 36%.

[0134] <Adhesion of Test Coating (Binder Layer) - Topcoat Antifouling Coating> In accordance with JIS K5600-5-6:1999 (cross-cut method), the laminated coating on the test plate (2) was cut into a 5 x 5 grid (25 squares) at 2 mm intervals down to the FRP substrate, and a peel test was carried out after applying adhesive tape. The results were evaluated according to the following criteria. Evaluation criteria for adhesion (adhesion): 5... The edges of the cuts are completely smooth, and there is no peeling at any of the grid cells. 4... The peeled / cohesive failure area of ​​the topcoat antifouling coating is 4% or less. 3... The peeled area is more than 4% and 12% or less. 2... The peeled area is more than 12% and 36% or less. 1... The peeled area is more than 36%.

[0135] <Adhesion between FRP substrate and test coating> In accordance with JIS K5600-5-6:1999 (cross-cut method), the test coating on the test plate (3) was cut into a 5x5 grid (25 squares) at 2 mm intervals until it reached the FRP substrate, and a peel test was carried out after applying adhesive tape, and the results were evaluated according to the following criteria. Evaluation criteria for adhesion (adhesion): 5... The edges of the cuts are completely smooth, and there is no peeling at any of the grid cells. 4... The peeled / cohesive failure area of ​​the test coating is 4% or less. 3... The peeled area is more than 4% and 12% or less. 2... The peeled area is more than 12% and 36% or less. 1... The peeled area is more than 36%.

[0136]

[0137]

[0138]

[0139] [Test Method 2] On the surface of a sandblasted steel plate (150 mm x 70 mm x 1.6 mm), Banno 1500 (manufactured by Chugoku Toryo Co., Ltd.) was applied using an air spray to a dry film thickness of 200 μm, and the coating was dried at 23 ° C for 1 day to form a primer coating. An acrylic resin-based topcoat paint, ACRY 800 Topcoat (manufactured by Chugoku Toryo Co., Ltd.), was applied to the primer coating and dried to form a coating film with a thickness of 40 μm, thereby obtaining a topcoat coating substrate (test piece). The resulting topcoat coating substrate was exposed to water spraying. The water spray exposure test was performed using an apparatus that was kept horizontal outdoors and sprayed with tap water. The test pieces were arranged on the apparatus and exposed while the front side of the test piece was constantly wet. The coating composition of Example 1, 5, 6, 9, 12, or 16 or Comparative Example 5 was applied to the topcoat film that had been exposed to water spraying for 30 days using an applicator (gap 0.1 mm) and dried to form a test coating film 30 μm thick, to obtain a test panel. The test panel was dried at 23°C for one week, and then adhesion was evaluated. The evaluation method was the same as in <Adhesion of old antifouling coating film - test coating film>.

[0140] The results of Test Method 2 are shown in Table 5. Table 5 lists only the composition information regarding the synthetic resin particles (A), organic solvent (B), and rubber component (C) in the coating composition.

[0141]

[0142] 1: Multilayer coating film 2: Substrate with multilayer coating film 10: Old coating film 20: Binder layer 30: New coating film 40: Substrate

Claims

1. A water-based paint composition comprising: synthetic resin particles (A); an organic solvent (B) having a water solubility of 1.0 (g / 100 g water) or more and a boiling point of 200°C or more; and water, wherein the content of the organic solvent (B) in the composition is 1 to 16 mass%, and the composition is a composition for application to the surface of a (meth)acrylic resin-based coating film.

2. The aqueous coating composition according to claim 1, wherein the composition further contains a rubber component (C), and the rubber component (C) has a structural unit derived from butadiene.

3. The aqueous coating composition according to claim 2, wherein the content of the butadiene-derived structural units in the rubber component (C) is 25 mass% or more.

4. The aqueous coating composition according to claim 1, wherein the synthetic resin particles (A) are at least one type selected from the group consisting of (meth)acrylic resin particles and epoxy resin particles.

5. The aqueous coating composition according to claim 2, wherein the content of said synthetic resin particles (A) is 60 to 95 parts by mass and the content of said rubber component (C) is 5 to 40 parts by mass, when the total content of said synthetic resin particles (A) and said rubber component (C) is 100 parts by mass.

6. The aqueous coating composition according to claim 1, wherein the content of said water in said composition is 20 to 60 mass %.

7. The water-based coating composition according to claim 1, wherein the (meth)acrylic resin coating film is an antifouling coating film.

8. The aqueous coating composition according to claim 7, wherein the antifouling coating film is a hydrolysis type antifouling coating film or a hydration decomposition type antifouling coating film.

9. The aqueous coating composition according to claim 7, wherein the antifouling coating film is provided on at least one material selected from the group consisting of ship bottom shells, underwater structures, and fishing materials.

10. The water-based coating composition according to claim 1, wherein the (meth)acrylic resin coating film is a topcoat coating film.

11. A combination of an article having a (meth)acrylic resin-based coating film and the water-based coating composition according to any one of claims 1 to 10 for application to the surface of the (meth)acrylic resin-based coating film.

12. A substrate with a laminated coating film, comprising: a substrate; a first (meth)acrylic resin-based coating film provided on the substrate; a binder layer formed from the aqueous paint composition according to any one of claims 1 to 10; and a second (meth)acrylic resin-based coating film, in this order.

13. The substrate with a multilayer coating film according to claim 12, wherein the first (meth)acrylic resin coating film is an antifouling coating film, and the second (meth)acrylic resin coating film is an antifouling coating film for repair.

14. The substrate with a multilayer coating film according to claim 12, wherein the first (meth)acrylic resin coating film is a topcoat coating film, and the second (meth)acrylic resin coating film is a repair topcoat coating film.

15. A method for manufacturing a repaired substrate with a coating, comprising: a step of applying the water-based paint composition described in any one of claims 1 to 10 to a surface of a first (meth)acrylic resin-based coating film of a substrate with a coating to be repaired, the substrate having a substrate and a first (meth)acrylic resin-based coating film provided on the substrate, to form a binder layer; and a step of forming a second (meth)acrylic resin-based coating film on the binder layer.

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