JP2007297491A - Curable aqueous resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a curable aqueous resin composition having extremely good curability which excels in water resistance and finishing properties even under normal temperature drying conditions and can maintain the external appearance of the initial coating state even in a severe environment. <P>SOLUTION: The curable aqueous resin composition comprises: (A) an aqueous fatty acid modified resin dispersion which is produced by finely dispersing a monomer mixture (I) comprising a fatty acid modified polymerizable unsaturated monomer (a), a carboxyl group-containing polymerizable unsaturated monomer (b), and other polymerizable monomers (c) in an aqueous medium so as for the average particle diameter to be not greater than 500 nm, and polymerized the resulting monomer emulsion; and (B) a compound having two or more functional groups capable of reacting with carboxyl groups in the molecule; wherein the functional group capable of reacting with the carboxyl group in the compound (B) per mole of the carboxyl group in (A) is in the range of 0.1-3.0 mole. An aqueous coating composition comprises the curable aqueous resin composition, and a coating method is also disclosed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a curable aqueous resin composition which is very good in curability even under normal temperature drying conditions and is suitable for forming a coating film having good finish and water resistance.

  In recent years, in the field of paints, attempts have been made to make it water-based in order to cope with environmental problems and to improve the working environment. In general, water-based paints tend to be inferior to solvent-based paints in terms of finish and coating film performance.Particularly, in the case of water-based paints that are dried at room temperature or forcedly dried, the leveling properties and coating properties of the paint film surface in the drying stage are difficult. Since the crosslinking reaction in the film is insufficient as compared with the case of the thermosetting type, it is difficult to bring the finish property and the physical properties of the coating film closer to the solvent-based paint.

  On the other hand, in the market, a one-pack type paint is desired from the viewpoint of versatility, and it is desired to develop a one-pack type water-based paint that has good finish and coating performance even under normal temperature drying or forced drying conditions.

  For example, Patent Document 1 discloses a composition containing emulsion particles containing a crosslinkable carbonyl group and a dihydrazide compound as a normally dry water-based paint. The composition can form a coating film having excellent storage properties and excellent physical properties such as water resistance, but the glossiness of the coating film may not be sufficient.

  As a one-pack type water-based paint capable of forming a crosslinked coating film having excellent gloss even under conditions of room temperature drying, an aqueous paint containing a fatty acid-modified acrylic resin as a film-forming component is known.

  For example, Patent Document 2 discloses an emulsion obtained by finely dispersing a monomer mixture containing a fatty acid-modified polymerizable unsaturated monomer and another polymerizable unsaturated monomer in an aqueous medium so that the average particle size is 500 nm or less. An aqueous coating composition containing an aqueous resin dispersion having an average particle diameter of 500 nm or less is described.

  According to the water-based paint, it can be cross-linked even at room temperature, and can form a finished paint film having water resistance and a feeling of meatiness. However, in a severe environment where water and oil frequently contact, the paint film peels off. It has a problem that it may occur.

Japanese Patent Laid-Open No. 4-249487 WO2004 / 074327

  An object of the present invention is to provide a curable aqueous resin composition having excellent water resistance and finish even under conditions of room temperature drying and having very good curability capable of maintaining the initial appearance of coating even in harsh environments. There is.

As a result of intensive studies on the above-mentioned problems, the inventors of the present invention have added a functional group capable of reacting with a carboxyl group in the molecule to the aqueous fatty acid-modified resin dispersion having a carboxyl group produced by a specific production method. The inventors have found that a curable aqueous resin composition characterized by containing a specific amount of a compound having two or more compounds can solve the above-mentioned problems, and has completed the present invention. That is, the present invention
1. (A) Average particle size of monomer mixture (I) containing fatty acid-modified polymerizable unsaturated monomer (a), carboxyl group-containing polymerizable unsaturated monomer (b) and other polymerizable unsaturated monomer (c) in an aqueous medium Aqueous fatty acid-modified resin dispersion produced by fine dispersion so that the diameter is 500 nm or less and polymerizing the resulting monomer emulsion, and (B) two functional groups capable of reacting with carboxyl groups in one molecule The functional group which contains the compound which has the above and can react with the carboxyl group in the compound (B) with respect to 1 mol of the carboxyl group in (A) is in the range of 0.1 to 3.0 mol. A curable aqueous resin composition,
2. The proportion of monomer (a), monomer (b) and monomer (c) used is 5 to 70 masses of monomer (a) based on the total amount of monomer (a), monomer (b) and monomer (c). %, The monomer (b) is in the range of 0.1 to 30% by mass, and the monomer (c) is in the range of more than 0 to ˜94.9% by mass.
3. Item 3. The curable aqueous resin composition according to Item 1 or 2, wherein the compound (B) having two or more functional groups capable of reacting with a carboxyl group is a polycarbodiimide compound and / or a polyoxazoline compound.
4). An aqueous coating composition comprising the curable aqueous resin composition according to any one of items 1 to 3,
5). A method for forming a coating film, characterized by applying the aqueous coating composition described in item 4 to a surface to be coated,
About.

  According to the curable aqueous resin composition of the present invention, the specific fatty acid-modified resin dispersion is used as a coating film-forming component, and contains a compound having a functional group that has good compatibility with the resin dispersion and can be reacted. Therefore, in the coating film forming process, the unsaturated fatty acid group in the resin composition undergoes a cross-linking reaction, and the cross-linking reaction between the carboxyl group and the functional group capable of reacting with the carboxyl group proceeds to be tough and meaty. It is possible to form a crosslinked coating film having a feeling and excellent finishing properties even under conditions of room temperature drying. In addition, as the crosslinking reaction proceeds in the coating film formation process, the carboxyl group, which is a hydrophilic group, can be reduced from the coating film, and the water resistance of the coating film can be significantly improved. is there.

Fatty acid-modified polymerizable unsaturated monomer (a)
The fatty acid-modified polymerizable unsaturated monomer (a) used in the present invention can stably produce the aqueous fatty acid-modified resin dispersion (A), and uses the finally obtained curable aqueous resin composition. The coating film to be formed has a feeling of richness and can introduce an oxidative curing group into the aqueous fatty acid-modified resin dispersion (A) particles, and is polymerizable unsaturated at the terminal of the fatty acid-derived hydrocarbon chain. Polymerizable unsaturated monomers having groups are included. Here, examples of the polymerizable unsaturated group include a vinyl group and a (meth) acryloyl group, and a (meth) acryloyl group is particularly preferable.

  Examples of the fatty acid-modified polymerizable unsaturated monomer (a) are those obtained by reacting a fatty acid (a1) with an epoxy group-containing polymerizable unsaturated monomer (a2) or a hydroxyl group-containing polymerizable unsaturated monomer (a3). Can be mentioned.

  Examples of the fatty acid (a1) include those having a structure in which a carboxyl group is bonded to the end of a hydrocarbon chain, and examples thereof include a dry oil fatty acid, a semi-dry oil fatty acid, and a non-dry oil fatty acid. Dry oil fatty acids and semi-dry oil fatty acids are not strictly distinguishable, but usually dry oil fatty acids are unsaturated fatty acids that are iodinated 130 or more, and semi-dry oil fatty acids are iodinated 100 or more and less than 130. Of unsaturated fatty acids. On the other hand, non-drying oil fatty acids are usually fatty acids having an iodine value of less than 100.

  Examples of the dry oil fatty acid and the semidry oil fatty acid include fish oil fatty acid, dehydrated castor oil fatty acid, safflower oil fatty acid, linseed oil fatty acid, soybean oil fatty acid, sesame oil fatty acid, poppy oil fatty acid, eno oil fatty acid, hemp oil fatty acid, grape Nuclear oil fatty acid, corn oil fatty acid, tall oil fatty acid, sunflower oil fatty acid, cottonseed oil fatty acid, walnut oil fatty acid, rubber seed oil fatty acid, hydienoic acid fatty acid, etc., and non-drying oil fatty acid include, for example, coconut oil fatty acid , Hydrogenated coconut oil fatty acid, palm oil fatty acid and the like. These can be used alone or in combination of two or more. Furthermore, these fatty acids can be used in combination with caproic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid and the like.

  In the present invention, a dry oil fatty acid and / or a semi-dry oil fatty acid is preferred as the fatty acid (a1) from the viewpoint of the initial water resistance of the formed coating film.

  The epoxy group-containing polymerizable unsaturated monomer (a2) that can be reacted with the fatty acid (a1) to produce the fatty acid-modified polymerizable unsaturated monomer (a) is one epoxy group and one in one molecule. The compound which has the following polymerizable unsaturated group is included, for example, glycidyl (meth) acrylate, (beta) -methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4- Examples thereof include epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, and allyl glycidyl ether. These can be used alone or in combination of two or more.

  The fatty acid (a1) and the epoxy group-containing polymerizable unsaturated monomer (a2) have an equivalent ratio of a carboxyl group in the fatty acid (a1) and an epoxy group in the epoxy group-containing monomer (a2) of 0.75: 1 to 1. The reaction can be carried out in such a ratio that it is in the range of 1.25: 1, preferably 0.8: 1 to 1.2: 1.

  The reaction between the fatty acid (a1) and the epoxy group-containing polymerizable unsaturated monomer (a2) is usually carried out in the presence of a polymerization inhibitor without causing a problem such as gelation in the fatty acid component. The reaction can be carried out under conditions that allow the group and the epoxy group in the epoxy group-containing polymerizable unsaturated monomer to react smoothly, and is usually heated at a temperature of about 100 to about 180 ° C. for about 0.5 to about 10 hours. Is suitable.

  In this reaction, an esterification reaction catalyst such as a tertiary amine such as N, N-dimethylaminoethanol, a quaternary ammonium salt such as tetraethylammonium bromide or tetrabutylammonium bromide can be used. An inert organic solvent may be used.

  Examples of the polymerization inhibitor include hydroxy compounds such as hydroquinone, hydroquinone monomethyl ether, pyrocatechol and p-tert-butylcatechol; nitrobenzene, nitrobenzoic acid, o-, m- or p-dinitrobenzene, 2,4- Nitro compounds such as dinitrotoluene, 2,4-dinitrophenol, trinitrobenzene, picric acid; quinone compounds such as p-benzoquinone, dichlorobenzoquinone, chloranil, anthraquinone, phenanthroquinone; nitrosobenzene, nitroso-β-naphthol, etc. Examples thereof include radical polymerization inhibitors known per se such as nitroso compounds, and these can be used alone or in combination of two or more.

  The fatty acid-modified polymerizable monomer (a) can also be obtained by esterifying the fatty acid (a1) with the hydroxyl group-containing polymerizable unsaturated monomer (a3). Examples of the hydroxyl group-containing polymerizable unsaturated monomer (a3) include a compound having one hydroxyl group and one polymerizable unsaturated group in one molecule. Specifically, for example, 2-hydroxyethyl (meta C2-C8 hydroxyalkyl (meth) acrylate of (meth) acrylic acid such as acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, allyl alcohol -(Meth) acrylate having a hydroxyl group, such as an ε-caprolactone modified product of the above C2-C8 hydroxyalkyl (meth) acrylate; (meth) acrylate having a polyoxyethylene chain having a hydroxyl group at the molecular end, and the like. These can be used alone or in combination of two or more. .

Carboxyl group-containing polymerizable unsaturated monomer (b)
In the present invention, the carboxyl group-containing polymerizable unsaturated monomer (b) is a functional group that can be a reaction partner of the compound (B) described later, and the aqueous medium of the resulting aqueous fatty acid-modified resin dispersion (A) particles It is possible to ensure the stability and mechanical stability in the interior, and to improve the toning property of the paint when the curable aqueous resin composition containing it is applied to the enamel paint. .

  Specific examples thereof include (meth) acrylic acid, fumaric acid, itaconic acid, maleic acid, crotonic acid, β-carboxyethyl acrylate, maleic anhydride, itaconic anhydride and the like. It can be used in combination of more than one species.

Other polymerizable unsaturated monomer (c)
In the aqueous fatty acid-modified resin dispersion (A) in the present invention, the other polymerizable unsaturated monomer (c) can be copolymerized with the fatty acid-modified polymerizable unsaturated monomer (a) and the carboxyl group-containing polymerizable unsaturated monomer. Examples of the polymerizable unsaturated monomer include compounds having one or more, preferably one polymerizable unsaturated group in the molecule. Examples of the polymerizable unsaturated group include a vinyl group and a (meth) acryloyl group. Specific examples of the other polymerizable unsaturated monomer (b) include methyl (meth) acrylate, ethyl (meth) acrylate, n -Propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, octyl (meta ) Acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, “isostearyl acrylate” (manufactured by Osaka Organic Chemical Co., Ltd.), cyclohexyl ( (Meta) acrylate Alkyl or cycloalkyl (meth) acrylate such as methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, etc .; having isobornyl group such as isobornyl (meth) acrylate Polymerizable unsaturated monomer; polymerizable unsaturated monomer having an adamantyl group such as adamantyl (meth) acrylate; glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, Epoxy group-containing polymerizable unsaturated monomers such as 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, and allyl glycidyl ether; styrene, α-methyl Aromatic vinyl monomers such as styrene and vinyltoluene; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyl Alkoxysilyl group-containing polymerizable unsaturated monomer such as triethoxysilane; siloxane macromonomer such as polydimethylsiloxane macromonomer; perfluoroalkyl such as perfluorobutylethyl (meth) acrylate and perfluorooctylethyl (meth) acrylate (meta ) Acrylate; polymerizable unsaturated monomer containing alkyl fluorine group such as fluoroolefin; polymerizable unsaturated monomer having photopolymerizable functional group such as maleimide group; N-vinylpyrrolidone; Vinyl compounds such as tylene, butadiene, chloroprene, vinyl propionate, vinyl acetate; (meth) acrylonitrile, (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, dimethylaminoethyl (meth) acrylate, and glycidyl (meth) acrylate Nitrogen-containing polymerizable unsaturated monomers such as adducts with amines; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, hydroxybutyl ( Alkyl (meth) acrylates and allyl alcohols containing hydroxyl groups of 2 to 8 carbon atoms of (meth) acrylic acid such as (meth) acrylates, and ε-caprolactone modified products of the above hydroxy (meth) acrylates of 2 to 8 carbon atoms Hydroxyl groups such as (Meth) acrylate having a hydroxyl group-containing polymerizable unsaturated monomer such as (meth) acrylate having a polyoxyethylene chain having a hydroxyl group at the molecular end: (meth) acrylate having a polyoxyethylene chain having an alkoxy group at the molecular end Sulfonic acid group-containing polymerizable unsaturated monomers such as 2-acrylamido-2-methylpropane sulfonic acid, allyl sulfonic acid, sodium styrene sulfonate, sulfoethyl methacrylate and its sodium salt and ammonium salt; 2-hydroxy-4- (3-Methacryloyloxy-2-hydroxypropoxy) benzophenone, 2-hydroxy-4- (3-acryloyloxy-2-hydroxypropoxy) benzophenone, 2,2′-dihydroxy-4- (3-methacryloyloxy-2-hydroxy The (Roxy) benzophenone, 2,2'-dihydroxy-4- (3-acryloxy-2-hydroxypropoxy) benzophenone, 2,4-dihydroxybenzophenone, 2,2 ', 4-trihydroxybenzophenone and other hydroxybenzophenones and glycidyl An addition reaction product with (meth) acrylate, or a polymerizable unsaturated monomer having an ultraviolet-absorbing functional group such as 2- (2′-hydroxy-5′-methacryloyloxyethylphenyl) -2H-benzotriazole; (Meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-cyano-4- (meth) acryloyl Amino-2,2,6,6-tetramethylpiperidine, 1- (me T) Acryloyl-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4-cyano-4- (meth) acryloylamino-2,2,6,6 -Tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 4-crotonoylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy Polymerizable unsaturated monomers having UV-stable functional groups such as 2,2,6,6-tetramethylpiperidine; acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formylstyrene, 4 to 7 Vinyl alkyl ketones having a number of carbon atoms (eg vinyl methyl ketone, vinyl Carbonyl group-containing polymerizable unsaturated monomers such as ruethylketone and vinylbutylketone; allyl (meth) acrylate, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene Glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, 1,4-butanediol di (meth) acrylate, neo Pentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tetra (meth) acrylate, glycero -Ludi (meth) acrylate, 1,1,1-trishydroxymethylethane di (meth) acrylate -1,1,1-trishydroxymethylethane tri (meth) acrylate, 1,1,1-trishydroxymethylpropane tri (meth) acrylate, triallyl isocyanurate, diallyl terephthalate And polyvinyl compounds having at least two polymerizable unsaturated groups in one molecule such as divinylbenzene, etc., and the like. These may be used alone or in combination of two or more according to the desired performance. .

The use ratio of the monomer (a), the monomer (b) and the monomer (c) is not particularly limited. From the viewpoint of compatibility with the compound (B) described later, and the curable aqueous resin of the present invention. From the viewpoint of the finish and curability of the coating film formed using the composition, in general, based on the total amount of monomer (a), monomer (b) and monomer (c),
The monomer (a) is 5 to 70% by mass, preferably 10 to 70% by mass.
The monomer (b) is 0.1 to 30% by mass, preferably 0.5 to 29.5% by mass.
Monomer (c) is more than 0 and 94.9% by mass, preferably 0.5 to 89.5% by mass.
Can be within the range.

  In the fatty acid-modified resin dispersion (A), the carboxyl group-containing polymerizable unsaturated monomer (b) and the other polymerizable unsaturated monomer (c) include (co) monomer (b) and monomer (c). It is desirable to select the polymer so that the theoretical glass transition temperature is in the range of 0 to 100 ° C, preferably 10 to 80 ° C.

In the present invention, the glass transition temperature (absolute temperature) is a value calculated by the following formula.
1 / Tg = W1 / T1 + W2 / T2 + ... Wn / Tn
In the formula, W1, W2... Wn are mass% of each monomer [= (blending amount of each monomer / total monomer mass) × 100], and T1, T2... Tn are glass transition temperatures (absolutely) of the homopolymer of each monomer. Temperature). The glass transition temperature of the homopolymer of each monomer is a value according to Polymer Hand Book (Second Edition, edited by J. Brandrup / EHImmergut), and the glass transition temperature of a monomer not described in this document is the homopolymer of the monomer. The polymer is synthesized so that the weight average molecular weight is about 50,000, and the value when the glass transition temperature is measured by differential scanning thermal analysis is used.

  By making the theoretical glass transition temperature of the monomer (b) and the (co) polymer of the monomer (c) to be within the above range, a coating film formed using the curable aqueous resin composition is prepared. Both film properties such as film properties and water resistance can be achieved.

  In addition, the other polymerizable unsaturated monomer (c) is at least a part of the polymerizable unsaturated monomer containing a linear, branched or cyclic, saturated or unsaturated hydrocarbon group having 4 or more carbon atoms. Monomer (c1) is 30 to 90% by mass, preferably 35 to 85% by mass, more preferably 45 to 80% by mass, based on the total mass of monomer (a), monomer (b) and monomer (c). It is desirable to comprise within the range.

  Examples of the polymerizable unsaturated monomer (c1) containing a linear, branched or cyclic, saturated or unsaturated hydrocarbon group having 4 or more carbon atoms include n-butyl (meth) acrylate and i-butyl. (Meth) acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (meth) ) Acrylate, stearyl (meth) acrylate, “isostearyl acrylate” (manufactured by Osaka Organic Chemical Co., Ltd.), cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, Cyclododecyl (meth) acrylate, etc. Alkyl or cycloalkyl (meth) acrylate; polymerizable unsaturated compound having an isobornyl group such as isobornyl (meth) acrylate; polymerizable unsaturated compound having an adamantyl group such as adamantyl (meth) acrylate; styrene, α-methylstyrene, And vinyl aromatic compounds such as vinyl toluene. By using the polymerizable unsaturated monomer (c1) having a hydrocarbon group having 4 or more carbon atoms, the water resistance of the coating film formed using the curable aqueous resin composition can be improved.

  In addition, the other polymerizable unsaturated monomer (c) includes, as at least a part thereof, a polymerizable unsaturated monomer (c2) containing a linear or branched hydrocarbon group having 6 or more carbon atoms. It is desirable to contain 1 to 30% by mass, preferably 5 to 20% by mass, and more preferably 6 to 18% by mass based on the total mass of (a), monomer (b) and monomer (c).

  Examples of the polymerizable unsaturated monomer (c2) containing a linear or branched hydrocarbon group having 6 or more carbon atoms include n-hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl ( And (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, “isostearyl acrylate” (manufactured by Osaka Organic Chemical Co., Ltd.), etc. Or in combination of two or more.

  By using the polymerizable unsaturated monomer (c2) containing a linear or branched hydrocarbon group having 6 or more carbon atoms as at least a part of the other polymerizable unsaturated monomer (c), aqueous When the carboxyl group-containing polymerizable unsaturated monomer (b) and other polymerizable unsaturated monomer (c) are atomized together with the fatty acid-modified polymerizable unsaturated monomer (a) in the production of the fatty acid-modified resin dispersion (A) The polymerization stability of the monomer emulsion in can be maintained, and the water resistance of the coating film formed using the curable aqueous resin composition can be improved.

  In addition, the other polymerizable unsaturated monomer (c) preferably includes the cycloalkyl group-containing polymerizable unsaturated monomer (c3) as at least a part thereof. As the cycloalkyl group-containing polymerizable unsaturated monomer (c3), a compound having one cycloalkyl group having 6 or more carbon atoms and one polymerizable unsaturated bond in one molecule is suitable. Examples thereof include cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, and the like. These can be used in combination. Of these, cyclohexyl (meth) acrylate is preferred.

  It is formed by using a curable aqueous resin composition by using one comprising a cycloalkyl group-containing polymerizable unsaturated monomer (c3) as at least a part of the other polymerizable unsaturated monomer (c). The weather resistance of the coating film can be improved. The content is 1 to 70% by mass, preferably 10 to 60% by mass, more preferably 25 to 45% by mass, based on the total mass of the monomer (a), the monomer (b) and the monomer (c). Within the range is preferred.

  Further, the other polymerizable unsaturated monomer (c) desirably contains an aromatic vinyl monomer (c4) as at least a part thereof. Examples of the aromatic vinyl monomer (c5) include vinyl aromatic compounds such as styrene, α-methylstyrene and vinyltoluene, and these can be used alone or in combination of two or more. By using such aromatic vinyl monomer (c4), the copolymerizability of monomer (a), monomer (b) and monomer (c) can be increased, unreacted monomer can be minimized, and The physical properties of the formed coating film such as water resistance can be improved.

  The aromatic vinyl monomer (c4) is generally 1 to 50% by mass, preferably 5 to 45% by mass, more preferably based on the total mass of the monomer (a), the monomer (b) and the monomer (c). Is preferably used within the range of 12 to 35% by mass.

  In addition, the other polymerizable unsaturated monomer (c) contains a hydroxyl group-containing (meth) acrylate (c5) in order to ensure the stability of the particles in the polymerization stage or storage stage in the aqueous fatty acid-modified resin dispersion (A). It can also comprise. Examples of the hydroxyl group-containing (meth) acrylate include those exemplified above, and the use ratio thereof is generally 1 to 50 based on the total amount of the monomer (a), the monomer (b) and the monomer (c). It can be in the range of 1 mass%, preferably 1-30 mass%, more preferably 1-10 mass%.

Aqueous fatty acid-modified resin dispersion (A)
In the present invention, the monomer mixture (I) contains a fatty acid-modified polymerizable unsaturated monomer (a), a carboxyl group-containing polymerizable unsaturated monomer (b), and other polymerizable unsaturated monomers (c) as essential components. Furthermore, the compound which does not contain a polymerizable unsaturated group substantially can also be contained, and, thereby, the aqueous | water-based fatty acid modified resin dispersion (A) particle | grains can also include this compound.

  Examples of such a compound that does not substantially contain a polymerizable unsaturated group include, for example, UV absorbers, UV stabilizers and additives for coating materials such as metal dryers; curing agents such as isocyanate compounds, blocked isocyanate compounds, and melamines; acrylic resins And resins such as polyester resins, polyurethane resins, alkyd resins, polyorganosiloxanes; colorants such as pigments and dyes.

  When the monomer mixture (I) is finely dispersed in an aqueous medium, an emulsifier may be used in combination as necessary. As the emulsifier, an anionic emulsifier and a nonionic emulsifier are suitable. Examples of the anionic emulsifier include sodium salts and ammonium salts such as alkylsulfonic acid, alkylbenzenesulfonic acid, and alkylphosphoric acid. Nonionic emulsifiers include, for example, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene phenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene octyl Phenyl ether, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, sorbitan monolaurate, sorbitan monos Areto, sorbitan monostearate, sorbitan trioleate, polyoxyethylene sorbitan monolaurate, and the like.

  Also, a polyoxyalkylene group-containing anionic emulsifier having an anionic group and a polyoxyalkylene group such as a polyoxyethylene group or a polyoxypropylene group in one molecule, A reactive anionic emulsifier having a group may be used.

  The emulsifier can be used in the range of 0.1 to 15% by mass, preferably 0.5 to 12% by mass, based on the total amount of all monomers used.

  The monomer mixture (I) may contain a chain transfer agent for the purpose of adjusting the molecular weight of the resulting aqueous fatty acid-modified resin dispersion (A). Examples of the chain transfer agent include compounds having a mercapto group. Specifically, for example, lauryl mercaptan, t-dodecyl mercaptan, octyl mercaptan, 2-ethylhexyl thioglycolate, 2-methyl-5-tert- Examples thereof include butylthiophenol, mercaptoethanol, thioglycerol, mercaptoacetic acid (thioglycolic acid), mercaptopropionate, and n-octyl-3-mercaptopropionate. In general, the chain transfer agent is preferably used in an amount of 0.05 to 10% by mass, particularly 0.1 to 5% by mass, based on the total amount of all monomers.

  The aqueous fatty acid-modified resin dispersion (A) in the present invention suppresses diffusion of the monomer (b) and the monomer (c) into the aqueous medium in the polymerization stage by the fatty acid-modified polymerizable unsaturated monomer (a) and the like. In general, a mini-emulsion such as a long-chain saturated hydrocarbon solvent such as hexadecane or a long-chain alcohol solvent such as hexadecanol is added to the monomer mixture (I) as needed. You may mix | blend the hydrophobic organic solvent used by superposition | polymerization.

  The monomer mixture (I) described above is finely dispersed in an aqueous medium, whereby a fatty acid-modified polymerizable unsaturated monomer (a), a carboxyl group-containing polymerizable unsaturated monomer (b) and other polymerizable unsaturated monomers ( A monomer emulsion (hereinafter, may be abbreviated as “monomer emulsion”) which is a particle dispersion containing c) is formed.

  The concentration of the monomer mixture (I) in the aqueous medium is generally 10 to 70 from the viewpoint of atomization suitability of the monomer emulsion to be formed, stability in the polymerization stage, practicality when applied to an aqueous paint, and the like. The mass is preferably in the range of 20 to 60% by mass.

  Examples of the aqueous medium include water or a water-organic solvent mixed solution obtained by mixing water with an organic solvent such as a water-soluble organic solvent.

  The fine dispersion of the monomer mixture (I) in the aqueous medium can be usually performed using a disperser having high energy shearing ability. Examples of the disperser that can be used in this case include a high-pressure emulsifier, an ultrasonic emulsifier, a high-pressure colloid mill, and a high-pressure homogenizer. These dispersers can usually be operated under a high pressure of about 10 to 1000 MPa, preferably about 50 to 300 MPa. In addition, the monomer mixture (I) may be pre-emulsified with a disper or the like in advance before being dispersed by the machine.

  The average particle diameter of the dispersed particles in the monomer emulsion obtained by finely dispersing the monomer mixture (I) in the aqueous medium by the above method is 500 nm or less from the viewpoint of the transparency of the formed coating film, water resistance, and the like. The range of 80 to 400 nm is preferable, and the range of 100 to 300 nm is more preferable. When the average particle diameter exceeds 500 nm, the finish and storage stability of the coating film formed using the curable aqueous resin composition of the present invention are inferior, and the practicality is lowered, which is not preferable.

  In this specification, the average particle size is “SALD-3100” (trade name, manufactured by Shimadzu Corporation, laser diffraction particle size distribution analyzer), and the sample is diluted with deionized water to 20 ° C. The average particle size of the emulsion or resin dispersion of the atomized monomer mixture (I) is measured at 30 minutes after the production, respectively.

  In the polymerization of the monomer emulsion thus obtained, for example, in accordance with the mini-emulsion polymerization method, all the monomer emulsion after fine dispersion is charged into a reactor equipped with a stirrer, a polymerization initiator is added, and the mixture is heated while stirring. Can be performed.

  The polymerization initiator may be any of oil-soluble and water-soluble types. For example, benzoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, cumene hydroperoxide, tert- Organic peroxides such as butyl peroxide, tert-butyl peroxylaurate, tert-butyl peroxyisopropyl carbonate, tert-butyl peroxyacetate, diisopropylbenzene hydroperoxide; azobisisobutyronitrile, azobis (2, 4-dimethylvaleronitrile), azobis (2-methylpropiononitrile), azobis (2-methylbutyronitrile), 4,4′-azobis (4-cyanobutanoic acid), dimethylazobis (2-methylpropionate) Azo compounds such as azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], azobis {2-methyl-N- [2- (1-hydroxybutyl)]-propionamide}; potassium persulfate And persulfates such as ammonium persulfate and sodium persulfate. These can be used alone or in combination of two or more. Further, if necessary, a reducing agent such as sugar, sodium formaldehyde sulfoxylate, or iron complex may be used in combination with the polymerization initiator to form a redox polymerization system.

  The amount of the polymerization initiator used is generally 0.1 to 5% by mass, particularly 0.2 to 3% by mass, based on the total mass of the monomer (a), the monomer (b) and the monomer (c). Within the range is preferable. The method for adding the polymerization initiator is not particularly limited, and can be appropriately selected depending on the type and amount thereof. For example, it may be previously contained in the monomer mixture (I) or the aqueous medium, or may be added all at once during the polymerization, or may be added dropwise.

  In the present invention, in order to improve the mechanical stability of the particles of the obtained aqueous fatty acid-modified resin dispersion (A), the carboxyl group of the aqueous fatty acid-modified resin dispersion (A) is neutralized with a neutralizing agent. It is desirable. The neutralizing agent is not particularly limited as long as it can neutralize the carboxyl group. For example, sodium hydroxide, potassium hydroxide, trimethylamine, dimethylaminoethanol, 2-methyl-2-amino-1-propanol, Examples thereof include triethylamine and aqueous ammonia, and these neutralizing agents are desirably used in such an amount that the pH of the aqueous resin dispersion after neutralization is about 6.5 to 9.0.

  The aqueous fatty acid-modified resin dispersion (A) is generally 10,000 to 500,000, particularly 30,000 to 20 from the viewpoint of the weather resistance, water resistance and finish of the coating film formed using the aqueous resin composition. It is desirable to have a weight average molecular weight in the range of 10,000. Here, the weight average molecular weight is a value obtained by converting the molecular weight measured by gel permeation chromatography based on the molecular weight of polystyrene using tetrahydrofuran as a solvent. Columns used in the gel permeation chromatography are “TSKgel G-4000H × L”, “TSKgel G-3000H × L”, “TSKgel G-2500H × L”, “TSKgel G-2000H × L” (all Tosoh Corporation).

  In the aqueous fatty acid-modified resin dispersion (A), the average particle size of the dispersed resin can be within the range of 500 nm or less, particularly 100 to 300 nm, as the average particle size of the dispersed resin.

  The aqueous fatty acid-modified resin dispersion (A) obtained by the above production method can be stably produced, and the cured coating film formed by combining the resin dispersion (A) with the compound (B) described later has a film-forming property. Excellent finish and good coating properties.

Compound (B) having two or more functional groups capable of reacting with a carboxyl group in one molecule
In the present invention, specific examples of the compound (B) having two or more functional groups capable of reacting with a carboxyl group in one molecule include polycarbodiimide compounds and polyoxazoline compounds.

  The polycarbodiimide compound is preferably a compound having two or more carbodiimide groups in the molecule, and is not particularly limited, but is preferably water-soluble or water-dispersible, and has a carbodiimide equivalent of 100 to 800. It is desirable that the compound be in the range of 200 to 600.

  Specific examples thereof include “Carbodilite V-02”, “Carbodilite V-04”, “Carbodilite V-06”, “Carbodilite E-01”, “Carbodilite E-04” (trade name, manufactured by Nisshinbo Co., Ltd.) And other commercial products. These can be used alone or in a mixture of two or more.

  As the polyoxazoline compound, a compound having two or more oxazoline groups in the molecule is suitable. For example, 2,2′-p-phenylene-bis- (1,3-oxazoline), 2,2′-tetra Low molecular weight poly (1,3-oxazoline) compounds such as methylene-bis- (1,3-oxazoline), 2,2′-octamethylene-bis- (2-oxazoline); and further, 2-isopropenyl- A 1,3-oxazoline group-containing vinyl monomer such as 1,3-oxazoline is obtained by copolymerizing a homopolymer or various vinyl monomers copolymerizable therewith. A vinyl polymer containing an oxazoline group can be mentioned, and it is desirable that the oxazoline group equivalent is a compound having a range of 100 to 800, preferably 200 to 600.

  Commercially available products of such polyoxazoline compounds include “Epocross K-1000”, “Epocross K-1020E”, “Epocross K-1030E”, “Epocross K-2010E”, “Epocross K” manufactured by Nippon Shokubai Chemical Industry Co., Ltd. -2020E "," Epocross K-2030E "," WS-500 "," WS-700 ", and the like.

Curable aqueous resin composition The curable aqueous resin composition of the present invention comprises the aqueous fatty acid-modified resin dispersion (A) and a compound (B) having two or more functional groups capable of reacting with a carboxyl group in one molecule. Although it is contained as an essential component and the blending ratio is not strictly limited, the functional group capable of reacting with the carboxyl group in the compound (B) with respect to 1 mol of the carboxyl group in (A) Is in the range of 0.1 to 3.0, preferably 0.2 to 2.0 mol.

  When the functional group in the compound (B) with respect to 1 mol of the carboxyl group is less than 0.1 mol, the effect of improving curability and water resistance is insufficient, while when it exceeds 3.0 mol, the curable aqueous resin of the present invention. The storage stability of the composition, the finish of the formed coating film, and the water resistance are insufficient, which is not preferable.

  Moreover, the said curable aqueous resin composition can also contain a metal dryer as a catalyst for promoting oxidation hardening. Examples of such metal dryers include salts of at least one metal selected from the group consisting of aluminum, calcium, cerium, cobalt, iron, lithium, magnesium, manganese, zinc, and zirconium with an acid. Examples include capric acid, caprylic acid, isodecanoic acid, linolenic acid, naphthenic acid, neodecanoic acid, octenoic acid, oleic acid, palmitic acid, resin acid, ricinoleic acid, soybean oil fatty acid, stearic acid, tall oil fatty acid and the like. It is done.

  The blending amount of the metal dryer is desirably in the range of 0.001 to 10 mass%, particularly 0.02 to 5 mass%, based on the solid content of the aqueous fatty acid-modified resin dispersion (A).

  The curable aqueous resin composition may be a water-soluble or emulsion-type acrylic resin, urethane resin, alkyd resin, silicone resin, fluororesin, epoxy resin, polyester resin, amino resin, or the like, if necessary; polyethylene glycol, Water-soluble polymers such as polyvinyl alcohol; Natural resins such as shellac and rosin; Modified resins such as; Curing agents such as isocyanate compounds, block polyisocyanate compounds and melamine resins; Wetting agents, antifoaming agents, plasticizers, and film-forming Auxiliaries, organic solvents, thickeners, preservatives, fungicides, pH adjusters, curing catalysts, surface adjusters, and the like can be appropriately selected and combined.

  Thus, the curable water-based resin composition is used for coatings such as for building, automobile outer panels, automobile parts, automobile repair, PCM, coating materials such as printing inks, paint additives, nonwoven fabrics, etc. It can be used for various applications such as a bonding agent, an adhesive, a filler, a molding material, and a resist. Moreover, it has the advantage that it can be liquefied as a curable resin composition.

Aqueous paint composition The aqueous paint composition of the present invention comprises the curable aqueous resin composition described above.

  When the curable aqueous resin composition is applied to an aqueous coating composition, it can be applied to either a clear coating or an enamel coating.

  When applied as an enamel paint, conventionally known color pigments, glitter pigments, extender pigments, rust preventive pigments, and the like can be blended as the pigment component.

  In the above aqueous coating composition, in addition to the above components, pigment dispersant, surfactant, surface conditioner, plasticizer, anti-settling agent, antistatic agent, antibacterial agent, fragrance, ultraviolet absorber, ultraviolet stabilizer, curing Catalysts, dispersants, antifoaming agents, thickeners, film-forming aids, antiseptics, antifungal agents, antifreezing agents, pH adjusters, flash last deterrents, aldehyde scavengers, lamellar viscosity minerals, powders or fine particles Additives such as activated carbon and photocatalytic titanium oxide can be appropriately selected and combined.

  The present invention is a coating method for coating the above-mentioned aqueous coating composition on a surface to be coated.

  Examples of coated surfaces include gypsum board, concrete surface, mortar surface, slate plate, PC plate, ALC plate, cemented calcium silicate plate, wood, stone and other inorganic substrates; plastic and other organic substrates; iron, aluminum Metal base materials such as stainless steel; surface materials such as acrylic resins, acrylic urethane resins, polyurethane resins, fluororesins, silicon acrylic resins, vinyl acetate resins, epoxies provided on these substrates Examples of the resin coating surface can be listed.

  The aqueous coating composition can be applied using a method such as roller, air spray, airless spray, lysine gun, universal gun, brush, electrostatic coating, and the like. Moreover, as a drying method, any of heat drying, forced drying, and normal temperature drying may be sufficient.

  Hereinafter, the present invention will be described more specifically with reference to examples. “Parts” and “%” are “parts by mass” and “% by mass”.

Production of fatty acid-modified polymerizable unsaturated monomer Production Example 1
The following components were put into a reaction vessel and reacted at a reaction temperature of 140 ° C. for 5 hours while stirring to obtain a fatty acid-modified polymerizable unsaturated monomer (a-1).
Safflower oil fatty acid 280 parts Glycidyl methacrylate 142 parts.

Production Example 2
A fatty acid-modified polymerizable unsaturated monomer (a-2) was obtained in the same manner as in Production Example 1 except that the components to be reacted were changed to the following.
Flaxseed oil fatty acid 280 parts Glycidyl methacrylate 142 parts.

Production and production example 3 of aqueous fatty acid-modified resin dispersion 3
The following components are put into a glass beaker and stirred at 2000 rpm for 15 minutes with a disper to produce a pre-emulsified liquid. Then, the pre-emulsified liquid is pressurized at 100 MPa with a high-pressure emulsifier that applies high-pressure energy to collide the fluids. By processing, a monomer emulsion having an average particle size of dispersed particles of 190 nm was obtained.
Monomer emulsion composition Fatty acid-modified polymerizable unsaturated monomer (a-1) 30.15 parts Styrene 15 parts 2-hydroxyethyl methacrylate 4.5 parts i-butyl methacrylate 20.35 parts t-butyl methacrylate 20 parts 2-ethylhexyl acrylate 8 parts methacrylic acid 2 parts n-octyl-3-mercaptopropionate 0.3 part “Newcol 707SF” (Note 1) 10 parts deionized water 85 parts The above monomer emulsion is then transferred to a flask and deionized. Dilute with water to a solids concentration of 45%. Thereafter, the temperature was raised to 85 ° C., and an initiator aqueous solution in which 2 parts of “VA-086” (Note 2) was dissolved in 10 parts of deionized water was added to the flask, and stirred for 3 hours while maintaining the temperature. Thereafter, an initiator aqueous solution in which 0.5 part of “VA-086” (Note 2) was dissolved in 10 parts of deionized water was added to the flask, stirred for 1 hour while maintaining the temperature, and then cooled to 40 ° C. The pH was adjusted to 8.0 with dimethylaminoethanol to obtain an aqueous fatty acid-modified resin dispersion (I-1) having a solid content concentration of 40% and an average particle diameter of the dispersion resin of 165 nm.
(Note 1) “Newcol 707SF”: trade name, manufactured by Nippon Emulsifier Co., Ltd., an anionic emulsifier having a polyoxyethylene chain, 30% active ingredient,
(Note 2) “VA-086”: trade name, manufactured by Wako Pure Chemical Industries, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide].

Production Example 4
An aqueous fatty acid-modified resin dispersion (I-2) was obtained in the same manner as in Production Example 3 except that the composition of the monomer emulsion was changed as shown in Table 1.

(*) Glass transition temperature: Calculated according to the definition in the specification.

Production Production Example 5 of Unsaturated Fatty Acid Modified Aqueous Resin Dispersion 5
A flask containing 36 parts of deionized water and 0.36 part of “Newcol 707SF” (Note 1) was heated to 80 ° C. after purging with nitrogen. While maintaining the internal solution at 80 ° C., 0.1 part of ammonium persulfate was added, and then a monomer emulsion having the following composition was added dropwise over 3 hours.
Deionized water 52.4 parts Styrene 18 parts Methyl methacrylate 40 parts n-Butyl acrylate 40 parts Methacrylic acid 2 parts "Newcol 707SF" (Note 1) 10 parts Ammonium persulfate 0.2 parts From 30 minutes after dropping, 0.1 parts An aqueous initiator solution in which 1 part of deionized water was dissolved was added dropwise over 30 minutes and maintained at 80 ° C. for 2 hours. The pH was adjusted to 8.0 with dimethylaminoethanol to obtain an aqueous resin dispersion (I-3) having a solid content concentration of 50%, a weight average molecular weight of 150,000, a glass transition temperature of 20.0 ° C. and an average particle diameter of 185 nm. It was.

Production of aqueous resin composition Examples 1-14 and Comparative Examples 1-4
An aqueous resin composition was obtained according to the composition shown in Table 2 below. Each aqueous resin composition was subjected to the following test. The results are shown in Table 2.

(Note 3) “Carbodilite V-02”: trade name, manufactured by Nisshinbo Co., Ltd., water-soluble polycarbodiimide, carbodiimide equivalent 590, active ingredient 40%,
(Note 4) “Carbodilite V-04”: trade name, manufactured by Nisshinbo Co., Ltd., water-soluble polycarbodiimide, carbodiimide equivalent 334, active ingredient 40%,
(Note 5) “Carbodilite E-01”: trade name, manufactured by Nisshinbo Co., Ltd., water-dispersible polycarbodiimide, carbodiimide equivalent 425, active ingredient 40%,
(Note 6) “Carbodilite E-04”: trade name, manufactured by Nisshinbo Co., Ltd., water-dispersible polycarbodiimide, carbodiimide equivalent 270, active ingredient 40%,
(Note 7) “Epocross K-2020E”: trade name, polyoxazoline, oxazoline group equivalent 550, active ingredient 40%,
(Note 8) “WS-500”: trade name, polyoxazoline, oxazoline group equivalent 220, active ingredient 40%,
(Note 9) “TEXANOL”: trade name, manufactured by Eastman Chemical Company, 2,2,4-trimethylpentanediol monoisobutyrate, film-forming aid,
(Note 10) “DICnate 1000W”: trade name, manufactured by Dainippon Ink & Chemicals, Ltd., metal dryer, Co content of 3.6%.

(* 1) Storage stability 70 g of each aqueous resin composition obtained above was put in a 100 cc sample bottle and kept at room temperature for 10 days. Thereafter, the state of the contents was visually evaluated.
○: No change, Δ: Slightly thickened, ×: Remarkably thickened.
(* 2) Curability Each aqueous resin composition obtained above was coated on a polypropylene plate with an applicator so that the dry film thickness was 40 μm, and was cured at 25 ° C. for 10 days. After forming the film, it was cut into a size of 4 × 4 cm to obtain a test piece. The obtained test piece was immersed in acetone at room temperature for 24 hours. The solvent extraction residue was calculated from the coating film mass before and after extraction as follows. The higher the value, the better.
Solvent extraction residue (%) = (Mass of membrane after extraction / Mass of membrane before extraction) × 100 (%)
(* 3) Compatibility Each aqueous resin composition obtained above was coated on a glass plate with an applicator so that the dry film thickness was 40 μm, and cured at 25 ° C. for 10 days to form a film. Visual evaluation was performed.
○: Transparent, Δ: Blueing, ×: Translucent.
(* 4) Water resistance After the test coating plate used in the above compatibility evaluation was immersed in clean water at 20 ° C. for 7 days, the coated surface state was observed and evaluated according to the following criteria.
A: Very good, B: Good, B: Some blisters occurred, X: Blisters occurred on the entire surface.

Claims (5)

(A) Average particle size of monomer mixture (I) containing fatty acid-modified polymerizable unsaturated monomer (a), carboxyl group-containing polymerizable unsaturated monomer (b) and other polymerizable unsaturated monomer (c) in an aqueous medium Aqueous fatty acid-modified resin dispersion produced by fine dispersion so that the diameter is 500 nm or less and polymerizing the resulting monomer emulsion, and (B) two functional groups capable of reacting with carboxyl groups in one molecule The functional group which contains the compound which has the above and can react with the carboxyl group in the compound (B) with respect to 1 mol of the carboxyl group in (A) is in the range of 0.1 to 3.0 mol. A curable aqueous resin composition. The proportion of monomer (a), monomer (b) and monomer (c) used is 5 to 70 masses of monomer (a) based on the total amount of monomer (a), monomer (b) and monomer (c). %, The monomer (b) is 0.1 to 30% by mass, and the monomer (c) is more than 0 and within the range of 94.9% by mass. The curable aqueous resin composition according to claim 1 or 2, wherein the compound (B) having two or more functional groups capable of reacting with a carboxyl group in a molecule is a polycarbodiimide compound and / or a polyoxazoline compound. An aqueous coating composition comprising the curable aqueous resin composition according to any one of claims 1 to 3. A coating film forming method, wherein the water-based coating composition according to claim 4 is applied to a surface to be coated.