Coating composition

Abstract

To provide a coating composition capable of securing a sufficient pot life.SOLUTION: The coating composition contains an aqueous resin dispersion, an isocyanate curing agent, and a glycol ether-based solvent. The glycol ether-based solvent is one or more selected from ethylene glycol mono-n-butyl ether, 3-methoxy-3-methylbutanol, ethylene glycol mono-2-ethylhexyl ether, and 2,2,4-trimethylpentane-1,3-diol monoisobutyrate.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a coating composition. [Background technology]

[0002] As coating compositions for building materials, coating compositions containing aqueous resin dispersions which have little odor problems are generally used. However, since it may be difficult to ensure the necessary physical properties by simply fusing the aqueous resin dispersion to form a coating film, a crosslinked coating film may be formed by blending a curing agent into the coating composition.

[0003] As the curing agent, an isocyanate curing agent is used since it reacts with the hydroxyl groups of the resin in the coating film to form urethane bonds which have excellent physical properties. For example, Patent Document 1 discloses a coating composition containing a hydroxyl group-containing resin and a polyisocyanate curing agent. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-130812 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, as described in Patent Document 1, simply mixing a hydroxyl-containing resin with an isocyanate curing agent results in a short usable time (pot life) from when the resin and the curing agent are mixed until the composition can be used as a coating composition. An object of the present invention is to provide a coating composition which can ensure a sufficient pot life. [Means for solving the problem]

[0006] The present invention has the following aspects. [1] A coating composition comprising an aqueous resin dispersion, an isocyanate curing agent, and a glycol ether solvent, A coating composition, wherein the glycol ether solvent is at least one selected from the group consisting of ethylene glycol mono-n-butyl ether, 3-methoxy-3-methylbutanol, ethylene glycol mono-2-ethylhexyl ether, and 2,2,4-trimethylpentane-1,3-diol monoisobutyrate. Effect of the Invention

[0007] According to the present invention, it is possible to provide a coating composition which ensures a sufficient pot life. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The following definitions of terms apply throughout the specification and claims. "(Meth)acrylate" is a general term for methacrylate and acrylate. "(Meth)acrylic acid" is a general term for methacrylic acid and acrylic acid. The term "(meth)acryloyl group" is a general term for a methacryloyl group and an acryloyl group. The "coating film" refers to a coating film formed from the coating composition of the present invention, and is also called a "cured coating film" or a "crosslinked coating film." The symbol "~" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0009] [Paint composition] The coating composition of the present invention is a water-based coating composition containing the aqueous resin dispersion shown below, an isocyanate curing agent, and a glycol ether solvent. The coating composition may further contain components other than the aqueous resin dispersion, the isocyanate curing agent, and the glycol ether solvent (hereinafter also referred to as "optional components") as necessary, so long as the effects of the present invention are not impaired.

[0010] <Aqueous resin dispersion> The aqueous resin dispersion is one in which an aqueous resin is dispersed in an aqueous medium, and may be an emulsion (aqueous resin emulsion) or a dispersion (aqueous resin dispersion). Examples of the aqueous resin include acrylic resin, urethane resin, vinyl acetate resin, silicone resin, fluorine resin, acrylic urethane resin, acrylic silicone resin, acrylic fluorine resin, acrylic polyol resin, acrylic styrene resin, acrylonitrile resin, epoxy resin, and vinyl chloride resin. Among these, acrylic resin, urethane resin, acrylic urethane resin, acrylic silicone resin, acrylic fluorine resin, acrylic polyol resin, acrylic styrene resin, acrylonitrile resin, and epoxy resin are preferred, acrylic resin and urethane resin are more preferred, and acrylic resin is particularly preferred. That is, preferred examples of the aqueous resin dispersion include acrylic resin dispersion and urethane resin dispersion, and among these, acrylic resin emulsion, acrylic resin dispersion, and urethane resin dispersion are more preferred, and acrylic resin emulsion is particularly preferred. Moreover, the aqueous resin is preferably an aqueous resin having a hydroxyl group. That is, the aqueous resin dispersion is preferably an aqueous resin dispersion having a hydroxyl group (hereinafter also referred to as a "hydroxyl-containing aqueous resin dispersion"), among which an acrylic resin dispersion having a hydroxyl group (hereinafter also referred to as a "hydroxyl-containing acrylic resin dispersion") is particularly preferred, and a hydroxyl-containing acrylic resin emulsion is more preferred. The aqueous resin may be used alone or in combination of two or more kinds.

[0011] An acrylic resin is a resin that contains (meth)acrylate units. Examples of acrylic resins include homopolymers of (meth)acrylate monomers, copolymers of two or more types of (meth)acrylate monomers, and copolymers of (meth)acrylate monomers and monomers other than (meth)acrylate monomers (hereinafter also referred to as "other monomers"). The proportion of the (meth)acrylate monomer unit to the total mass of all monomer units constituting the acrylic resin is preferably from 50 to 100% by mass, and more preferably from 70 to 100% by mass.

[0012] Examples of the (meth)acrylate monomer include a monomer having one (meth)acryloyl group in the molecule, a monomer having two (meth)acryloyl groups in the molecule, and a monomer having three or more (meth)acryloyl groups in the molecule. These (meth)acrylate monomers may be used alone or in combination of two or more.

[0013] Examples of monomers having one (meth)acryloyl group in the molecule include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-hexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; and alkoxyalkyl (meth)acrylates such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-(n-propoxy)ethyl (meth)acrylate, 2-(n-butoxy)ethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 2-(n-propoxy)propyl (meth)acrylate, and 2-(n-butoxy)propyl (meth)acrylate. cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, dicyclohexylpentanyl (meth)acrylate, and isobornyl (meth)acrylate; hydroxyl-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate; aryl-containing (meth)acrylates such as phenyl (meth)acrylate; and aralkyl-containing (meth)acrylates such as benzyl (meth)acrylate and phenethyl (meth)acrylate. Among these, alkyl (meth)acrylates and hydroxyl-containing (meth)acrylates are preferred. These monomers may be used alone or in combination of two or more.

[0014] Examples of monomers having two (meth)acryloyl groups in the molecule include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,3 butanediol di(meth)acrylate, 1,4 butanediol di(meth)acrylate, 1,6 hexanediol di(meth)acrylate, 1,9 nonanediol di(meth)acrylate, glycerin di(meth)acrylate, and neopentyl glycol di(meth)acrylate. acrylate, 3-methyl-1,5 pentanediol di(meth)acrylate, 2-butyl-2-ethyl-1,3 propane di(meth)acrylate, dimethylol tricyclodecane di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetrapropylene glycol di(meth)acrylate, neopentyl glycol hydroxypivalate di(meth)acrylate, dimethylol dicyclopentane di(meth)acrylate, and the like. These monomers may be used alone or in combination of two or more.

[0015] Examples of monomers having three or more (meth)acryloyl groups in the molecule include tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, dimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, propoxylated pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. These monomers may be used alone or in combination of two or more.

[0016] The other monomer is not particularly limited as long as it is copolymerizable with the (meth)acrylate monomer, and examples thereof include (meth)acrylic acid; aromatic vinyl monomers such as styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and divinylbenzene; and monomers having an amide group such as (meth)acrylamide, hydroxyethyl(meth)acrylamide, dimethyl(meth)acrylamide, diethyl(meth)acrylamide, isopropyl(meth)acrylamide, and dimethylaminopropyl(meth)acrylamide. These other monomers may be used alone or in combination of two or more.

[0017] The acrylic resin is preferably an acrylic resin having a hydroxyl group-containing (meth)acrylate unit.

[0018] The hydroxyl value of the aqueous resin is preferably 30 to 200 mgKOH / g, more preferably 50 to 200 mgKOH / g, and even more preferably 100 to 200 mgKOH / g. If the hydroxyl value of the aqueous resin is equal to or higher than the lower limit, sufficient performance as a crosslinked coating film can be obtained. If the hydroxyl value of the aqueous resin is equal to or lower than the upper limit, sufficient pot life can be more easily ensured. The hydroxyl value of the aqueous resin is measured according to JIS K 0070:1992 "Testing methods for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponifiable matter of chemical products". For those with catalog values, the catalog values ​​may be used as a simplified measurement value for the hydroxyl value of the aqueous resin.

[0019] The glass transition temperature of the aqueous resin is preferably 20 to 70° C., more preferably 30 to 70° C., and even more preferably 40 to 70° C. If the glass transition temperature of the aqueous resin is within the above range, sufficient coating film performance is likely to be ensured. The glass transition temperature of the aqueous resin is a value calculated from the FOX formula shown in the following formula (1). When a catalog value is available, the catalog value may be used as a simple measured value for the glass transition temperature of the aqueous resin. 1 / (Tg+273.15)=Σ[W i / (Tg i +273.15)] ···(1) (In formula (1), Tg is the glass transition temperature of the aqueous resin (°C), and W i is the mass fraction of the monomer that constitutes the aqueous resin, and Tg i is the glass transition temperature (°C) of the homopolymer of the monomer. In addition, Tg i is widely known as a characteristic value of homopolymers, and for example, the value given in "POLYMER HANDBOOK, THIRD EDITION" or the value in the manufacturer's catalog may be used.

[0020] Examples of the aqueous medium in which the aqueous resin is dispersed include water and a mixed medium of water and an organic solvent compatible with water. The proportion of water to the total mass of the aqueous medium is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. Examples of water include ion-exchanged water and tap water. Examples of organic solvents compatible with water include alcohol-based solvents such as methanol, ethanol, and isopropyl alcohol; glycol-based solvents such as ethylene glycol, diethylene glycol, and propylene glycol; ether-based solvents such as diethyl ether, 1,2-dimethoxyethane, and diethylene glycol dimethyl ether; and other glycol ether-based solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol mono-n-butyl ether, polyethylene glycol monomethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol mono-n-butyl ether, tripropylene glycol mono-n-butyl ether, and polypropylene glycol monomethyl ether. These organic solvents may be used alone or in combination of two or more.

[0021] As the aqueous resin dispersion, a commercially available product can be used. For example, commercially available acrylic resin dispersions include the Burnock series such as Burnock WD-551 (manufactured by DIC Corporation) and the Aquanate series such as Aquanate 200 (manufactured by Tosoh Corporation). These aqueous resin dispersions may be used alone or in combination of two or more.

[0022] The content of the aqueous resin dispersion in terms of pure content is preferably from 10 to 45 mass %, more preferably from 15 to 45 mass %, and even more preferably from 20 to 45 mass %, based on the total mass of the coating composition. In this specification, the "content of the aqueous resin dispersion in terms of pure content" refers to the content of the components (non-volatile content) excluding the aqueous medium among the components contained in the aqueous resin dispersion. In other words, the content of the aqueous resin dispersion in terms of pure content is the content of the aqueous resin.

[0023] The content of the aqueous resin dispersion in terms of pure content is preferably 30 to 95 mass %, more preferably 50 to 95 mass %, and even more preferably 70 to 95 mass %, based on the total mass of the non-volatile content of the coating composition. In this specification, the "non-volatile content of the coating composition" refers to the components contained in the coating composition excluding the medium that volatilizes during coating film formation, and is the component that will ultimately form the coating film.

[0024] <Isocyanate hardener> An isocyanate curing agent is an isocyanate compound having one or more isocyanate groups. The isocyanate curing agent is not particularly limited, but is preferably one that forms a colloid having a hydrophilic segment on the outside and exists in an aqueous medium. The particle size of the colloid is preferably 100 to 200 nm. Examples of the aqueous medium include the aqueous media exemplified above in the description of the aqueous resin dispersion.

[0025] Examples of the isocyanate curing agent include aliphatic diisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate; alicyclic diisocyanates such as dicyclohexylmethane diisocyanate, isophorone diisocyanate, 1,4-cyclohexane diisocyanate, hydrogenated xylylene diisocyanate, and hydrogenated tolylene diisocyanate; aromatic diisocyanates such as tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, tolidine diisocyanate, p-phenylene diisocyanate, and naphthylene diisocyanate; dicyclohexylmethane-4,4'-diisocyanate; and biuret forms, isocyanurate forms, and adducts with trimethylolpropane of these. Of these, hexamethylene diisocyanate, lysine diisocyanate, dicyclohexyl diisocyanate, isophorone diisocyanate, tolylene diisocyanate, tolidine diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, naphthylene diisocyanate, biuret forms, isocyanurate forms, and adducts with trimethylolpropane are preferred. In addition, a blocked isocyanate compound in which a part or all of the isocyanate groups of an isocyanate hardener are blocked with a blocking agent may be used as the isocyanate hardener. These isocyanate curing agents may be used alone or in combination of two or more kinds.

[0026] As the isocyanate curing agent, commercially available products can be used, for example, Burnock series such as Burnock DNW-5500 (manufactured by DIC Corporation).

[0027] The content of the isocyanate curing agent is preferably 1 to 20% by mass, more preferably 2 to 10% by mass, and even more preferably 3 to 5% by mass, based on the total mass of the coating composition. If the content of the isocyanate curing agent is equal to or greater than the lower limit, sufficient performance as a crosslinked coating film can be obtained. If the content of the isocyanate curing agent is equal to or less than the upper limit, sufficient pot life can be more easily ensured. In this specification, the "content of the isocyanate curing agent" refers to the content calculated as the pure content excluding the aqueous medium when the isocyanate curing agent forms a colloid and is present in the aqueous medium.

[0028] The content of the isocyanate curing agent is preferably 2 to 30% by mass, more preferably 5 to 25% by mass, and even more preferably 10 to 20% by mass, based on the total mass of the non-volatile content of the coating composition. If the content of the isocyanate curing agent is equal to or greater than the lower limit, sufficient performance as a crosslinked coating film can be obtained. If the content of the isocyanate curing agent is equal to or less than the upper limit, sufficient pot life can be more easily ensured.

[0029] When the aqueous resin dispersion is a hydroxyl group-containing aqueous resin dispersion, the compounding ratio of the hydroxyl group-containing aqueous resin dispersion to the isocyanate curing agent is preferably in a range where the ratio of the hydroxyl group (OH-R) of the hydroxyl group-containing aqueous resin dispersion to the isocyanate group (NCO) of the isocyanate curing agent is 0.5 to 1.8, more preferably 0.8 to 1.2. If the ratio is equal to or greater than the lower limit, sufficient performance as a crosslinked coating film can be obtained. If the ratio is equal to or less than the upper limit, sufficient pot life can be more easily ensured.

[0030] <Glycol ether solvent> Examples of glycol ether solvents include ethylene glycol mono-n-butyl ether, 3-methoxy-3-methylbutanol, ethylene glycol mono-2-ethylhexyl ether, and 2,2,4-trimethylpentane-1,3-diol monoisobutyrate. Among these, ethylene glycol mono-n-butyl ether, 3-methoxy-3-methylbutanol, and ethylene glycol mono-2-ethylhexyl ether are preferred from the viewpoint of obtaining a longer pot life, and ethylene glycol mono-n-butyl ether is more preferred. In addition, in terms of improving the water resistance of the coating film, ethylene glycol mono-n-butyl ether, 3-methoxy-3-methylbutanol, and ethylene glycol mono-2-ethylhexyl ether are preferred, and 3-methoxy-3-methylbutanol and ethylene glycol mono-2-ethylhexyl ether are more preferred. These glycol ether solvents may be used alone or in combination of two or more.

[0031] The content of the glycol ether-based solvent is preferably 1 to 20 mass %, more preferably 3 to 15 mass %, and even more preferably 5 to 10 mass %, based on the total mass of the coating composition. If the content of the glycol ether-based solvent is equal to or greater than the above lower limit, a sufficient pot life can be more easily ensured. If the content of the glycol ether-based solvent is equal to or less than the above upper limit, sufficient performance as a crosslinked coating film can be obtained.

[0032] The content of the glycol ether-based solvent is preferably 3 to 45 parts by mass, more preferably 5 to 30 parts by mass, and even more preferably 10 to 25 parts by mass, based on 100 parts by mass of the total of the aqueous resin dispersion and the isocyanate curing agent in terms of pure content. If the content of the glycol ether-based solvent is equal to or more than the lower limit, a sufficient pot life can be more easily ensured. If the content of the glycol ether-based solvent is equal to or less than the upper limit, sufficient performance as a crosslinked coating film can be obtained.

[0033] <Optional ingredients> Examples of optional components include solvents other than glycol ether-based solvents (hereinafter also referred to as "other solvents"), and additives.

[0034] Examples of other solvents include water and organic solvents. Examples of the organic solvent include ester-based solvents such as ethyl acetate, butyl acetate, propyl acetate, ethyl glycol acetate, 3-methoxy-3-methylbutyl acetate, and propylene glycol monomethyl ether acetate; and organic solvents compatible with water such as those exemplified above in the description of the aqueous resin dispersion. These other solvents may be used alone or in combination of two or more.

[0035] Examples of the additives include pigments (coloring pigments, extender pigments, etc.), thickeners, defoamers, dispersants, and leveling agents. These additives may be used alone or in combination of two or more.

[0036] <Manufacturing method> The coating composition can be obtained by mixing the aqueous resin dispersion, the isocyanate curing agent, the glycol ether solvent, and, if necessary, any optional components in a predetermined ratio. For the mixing, a mixer such as a disperser, a roll mill, or a planetary mixer may be used.

[0037] <Action and effect> The coating composition of the present invention as described above contains a glycol ether solvent in addition to the aqueous resin dispersion and the isocyanate curing agent, and therefore can ensure a sufficient pot life.

[0038] <Application> The coating composition of the present invention is suitable as a coating material for coating construction materials such as the exterior and interior walls of buildings such as buildings and houses.

[0039] Since the coating composition of the present invention can ensure a sufficient pot life, it may be stored within the pot life in a state in which all components are mixed (hereinafter, the composition in this state is also referred to as a "one-component coating composition"), but the aqueous resin dispersion and isocyanate curing agent contained in the coating composition may be stored separately until immediately before the coating composition is used. In other words, the coating composition may be a kit (hereinafter, also referred to as a "coating kit" or "two-component coating composition") that independently contains the aqueous resin dispersion and the isocyanate curing agent. Here, "independently present" means that the aqueous resin dispersion and the isocyanate curing agent are present in a state where they are not mixed or in contact with each other. The aqueous resin dispersion and the isocyanate curing agent are first mixed and contacted when the paint kit is used.

[0040] The paint kit may be, for example, a collection of containers each containing an aqueous resin dispersion and an isocyanate curing agent separately. In this case, at least one of the containers containing the aqueous resin dispersion and the isocyanate curing agent may contain a glycol ether solvent and may further contain optional components as necessary. The paint kit may also contain the aqueous resin dispersion, the isocyanate curing agent, and the glycol ether solvent, each of which is independent of the other.

[0041] <Coating film> A coating film formed from the coating composition of the present invention can be obtained, for example, by applying the coating composition of the present invention onto a substrate and drying it. The laminate in which a coating film is formed on a substrate can be used as it is as a molded article (for example, an exterior wall building material, an interior wall building material, a decorative material, etc.) for various applications.

[0042] Examples of the substrate include metal substrates such as aluminum, iron, nickel, chromium, titanium, copper, silver, zinc, tin, indium, magnesium, oxides thereof, and alloys thereof; and plastic substrates such as polyester (e.g., polyethylene terephthalate, polybutylene terephthalate, etc.), polyolefin (e.g., polyethylene, polypropylene, etc.), polycarbonate, acrylonitrile-butadiene-styrene copolymer resin (ABS), acrylic resin, acrylonitrile-styrene copolymer resin, acrylic-styrene copolymer resin, polyvinyl chloride resin, etc.

[0043] The coating method is not particularly limited, but examples thereof include spray coating, brush coating, roller coating, curtain coating, flow coating, and dip coating. The drying temperature is preferably, for example, 10 to 80°C. The drying time varies depending on the drying temperature, but is preferably, for example, 5 minutes to 2 hours. EXAMPLES

[0044] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these. The materials used in each example are as follows:

[0045] [material] BURNOCK WD-551: Emulsion type hydroxyl-containing acrylic resin dispersion (manufactured by DIC Corporation, product name "BURNOCK WD-551", hydroxyl value: 100 mg KOH / g, glass transition temperature: 40°C, non-volatile content: 45% by mass, aqueous medium: diethylene glycol dimethyl ether, water). Burnock DNW-5500: Water-dispersible polyisocyanate (manufactured by DIC Corporation, product name "Burnoc DNW-5500", non-volatile content: 80 mass%, aqueous medium: propylene glycol monomethyl ether acetate, water). · Solfite: 3-Methoxy-3-methylbutanol (manufactured by Kuraray Co., Ltd., product name "Solfite"). EHG: Ethylene glycol mono-2-ethylhexyl ether (manufactured by Kanto Chemical Co., Ltd., product name "Ethylene glycol mono(2-ethylhexyl) ether"). -Butyl cellosolve: Ethylene glycol mono-n-butyl ether (manufactured by Kanto Chemical Co., Ltd., product name "2-n-butoxyethanol"). Texanol: 2,2,4-trimethylpentane-1,3-diol monoisobutyrate (manufactured by Eastman Chemical Japan, Ltd., trade name "Texanol"). DPM: Dipropylene glycol monomethyl ether (manufactured by Kanto Chemical Co., Ltd., product name "Dipropylene glycol monomethyl ether"). DPnB: Dipropylene glycol mono-n-butyl ether (manufactured by Kanto Chemical Co., Ltd., product name "Dipropylene glycol mono-n-butyl ether"). Sumack MP-40: Polypropylene glycol monomethyl ether (manufactured by Kao Corporation, product name "Sumack MP-40"). · TPnB: Tripropylene glycol mono-n-butyl ether (manufactured by Kanto Chemical Co., Ltd., product name "Tripropylene glycol mono-n-butyl ether"). SN DEFORMER 399: Silicone-based defoamer (manufactured by San Nopco Ltd., product name "SN DEFORMER 399", non-volatile content: 100% by mass). Primal RM-8W: Thickener (manufactured by Dow Chemical Japan, product name "Primal RM-8W", non-volatile content: 21.3% by mass, aqueous medium: water).

[0046] [Examples 1 to 4, Comparative Examples 1 to 4] <Preparation of Coating Composition> According to the formulations shown in Tables 1 and 2, the components were mixed using a disper to obtain coating compositions. The resulting coating compositions were subjected to a stability test as described below. In addition, for the coating compositions that were paintable after 8 hours in the stability test, the water resistance of the coating film was evaluated as described below. The results are shown in Tables 1 and 2. In addition, blanks in Tables 1 and 2 indicate that the component is not blended. Also, the "content of glycol ether-based solvent relative to the total of resin and curing agent" in Tables 1 and 2 is the amount (parts by mass) of glycol ether-based solvent relative to 100 parts by mass of the total of the aqueous resin dispersion and isocyanate curing agent in terms of pure content.

[0047] <Stability test> 500 mL of the coating composition was placed in a container, sealed, and left for 8 hours in an atmosphere at 50°C. The viscosity of the coating composition was measured every hour from the start of leaving it. If the viscosity could be measured, the coating composition was deemed usable.

[0048] <Water resistance evaluation> In the stability test, the coating composition that was still applicable after 8 hours was applied to a slate board with a coating weight of 100 g / m before drying. 2 The coating was applied with a roller so that the coating was as shown in the figure, and then dried at 50°C for 24 hours to prepare a test piece having a coating film with a thickness of 20 μm formed on the slate board. The obtained test pieces were immersed in warm water at 40°C for 72 hours and then dried at 23°C for 24 hours. The appearance of the coating film after that was visually observed and the water resistance of the coating film was evaluated according to the following evaluation criteria. (Evaluation Criteria) ◯: No whitening of the coating film was observed. △: Whitening was observed in part of the coating film. ×: Whitening was observed throughout the coating film.

[0049] [Table 1]

[0050] [Table 2]

[0051] The coating compositions obtained in each Example showed no sign of gelling even after 5 hours in the stability test, and were applicable for coating, ensuring sufficient usable time. In particular, the coating compositions obtained in Examples 1 to 3 showed no significant increase in viscosity even after 8 hours, and were applicable for coating. The coating composition obtained in Example 4 showed no sign of gelling even after 6 hours, but coating was difficult. The coating films formed from the coating compositions obtained in Examples 1 to 3 had excellent water resistance. In contrast, the coating compositions obtained in Comparative Examples 1 to 4, which did not contain the specific glycol ether solvent, gelled after 5 hours in the stability test.

Claims

[Claim 1] The composition includes an aqueous resin dispersion, an isocyanate curing agent, and a glycol ether solvent, The coating composition, wherein the glycol ether solvent is at least one selected from the group consisting of ethylene glycol mono-n-butyl ether, 3-methoxy-3-methylbutanol, ethylene glycol mono-2-ethylhexyl ether, and 2,2,4-trimethylpentane-1,3-diol monoisobutyrate.

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