Aqueous emulsion, method for producing aqueous emulsion, aqueous resin composition, aqueous resin composition set, and method for producing coating film

Abstract

This aqueous emulsion contains a copolymer (X), a polyepoxy compound (Y) which does not have an ethylenically unsaturated bond, while having two or more epoxy groups in each molecule, and an aqueous medium (Z). The copolymer (X) contains structural units derived from (meth)acrylate esters (A) and structural units (b) derived from ethylenically unsaturated monomers (B) that each have a carboxy group. At least one of the ethylenically unsaturated monomers (B) is an ethylenically unsaturated monomer (B1) that has two or more carboxy groups. The content ratio of carboxy groups in the structural units (b1) derived from the ethylenically unsaturated monomer (B1) in all carboxy groups in the structural units (b) is 5 mol% to 75 mol%. The content of the polyepoxy compound (Y) relative to a total of 100 parts by mass of the copolymer (X) is 1.0 part by mass to 67 parts by mass.

Description

Aqueous emulsion, method for producing aqueous emulsion, aqueous resin composition, aqueous resin composition set, and method for producing coating film

[0001] The present invention relates to an aqueous emulsion, a method for producing an aqueous emulsion, an aqueous resin composition, an aqueous resin composition set, and a method for producing a coating film. This application claims priority based on Japanese Patent Application No. 2022-208301, filed on December 26, 2022, the contents of which are incorporated herein by reference.

[0002] Generally, the surfaces of metal products are subjected to surface treatment. In particular, metal products that are used outdoors or that are expected to be exposed to moisture are often surface-painted to prevent rust.

[0003] Conventionally, paints containing organic solvents have been used to coat the surfaces of metal products. However, when applying paints containing organic solvents to the surface of metal products, it is necessary to take measures against volatile organic compounds (VOCs) that are harmful to workers and the surrounding environment. Therefore, there has been a growing trend to use water-based paints instead of paints containing organic solvents for coating the surfaces of metal products.

[0004] Patent Document 1 describes a coating composition for thick coating, which contains an emulsion composition in which polymer particles are dispersed in an aqueous medium, and an aggregate. The polymer particles described in Patent Document 1 are produced by emulsion polymerization of a structural unit formed by polymerizing an alkyl (meth)acrylate monomer having an alkyl group with 4 to 14 carbon atoms, a structural unit formed by polymerizing an ethylenically unsaturated carboxylic acid monomer, and a structural unit formed by polymerizing other monomers, in the presence of a compound having at least two epoxy groups per molecule and a basic catalyst.

[0005] Patent Document 2 describes a composition containing an aqueous dispersion of thermoplastic polymer particles imbibed with a thermosetting compound having an oxirane group, and also describes that the polymer particles have a sufficient concentration of anti-agglomerating functional groups to stabilize the latex against agglomeration.

[0006] Patent Document 3 describes a method of mixing an emulsion of an acrylate resin with an epoxy emulsion to form an acrylate resin that has absorbed an epoxy compound (acrylic / epoxy latex).

[0007] JP 2011-89092 A JP 2014-65914 A International Publication No. 2017 / 112018

[0008] However, conventional aqueous resin compositions sometimes fail to provide sufficient rust prevention when applied to the surface of a metal product and cured without heating. This has been particularly problematic because coatings formed on the surface of metal products installed outdoors are often formed by applying the composition outdoors and curing without heating, yet still require sufficient rust prevention. Furthermore, when applying an aqueous resin composition to the surface of large metal products used outdoors, such as steel towers, bridges, ships, and port facilities, to form a coating, the application process tends to take a long time. As a result, the aqueous resin composition may gel during application, reducing workability or even making application impossible. For this reason, conventional aqueous resin compositions are required to have improved formulation stability and extend the application time (use life).

[0009] The present invention has been made in view of the above circumstances, and aims to provide an aqueous emulsion that can be used as a material for an aqueous resin composition that has excellent formulation stability and can form a coating film that exhibits good rust prevention properties even when cured at room temperature, and a method for producing the same. Another aim of the present invention is to provide an aqueous resin composition containing the aqueous emulsion of the present invention, an aqueous resin composition set containing the aqueous emulsion of the present invention, and a method for producing a coating film using the same.

[0010] The present invention to achieve the above object is configured as follows [1] to

[16] .

[0011] [1] A copolymer (X), a polyepoxy compound (Y) having no ethylenically unsaturated bond and having two or more epoxy groups in one molecule, and an aqueous medium (Z), wherein the copolymer (X) comprises a structural unit (a) derived from a (meth)acrylic acid ester (A) and a structural unit (b) derived from an ethylenically unsaturated monomer (B) having a carboxy group, wherein the content of the structural unit (a) derived from the (meth)acrylic acid ester (A) in the copolymer (X) is 10 mol % or more and 99.9 mol % or less, wherein the content of the structural unit (b) derived from the ethylenically unsaturated monomer (B) having a carboxy group in the copolymer (X) is 0.1 mol % or more and 20 mol % or less, and at least one of the ethylenically unsaturated monomers (B) having a carboxy group is an ethylenically unsaturated monomer (B1) having two or more carboxy groups, an aqueous emulsion in which the content of carboxy groups in the structural units (b1) derived from the ethylenically unsaturated monomer (B1) having two or more carboxy groups is 5 mol % or more and 75 mol % or less of the total number of carboxy groups in the structural units (b) derived from the ethylenically unsaturated monomer (B) having a carboxy group; and an amount of the polyepoxy compound (Y) relative to 100 parts by mass of the total amount of the copolymer (X) is 1.0 part by mass or more and 67 parts by mass or less.

[0012] [2] The aqueous emulsion according to [1], which contains emulsified particles containing the copolymer (X) and the polyepoxy compound (Y). [3] The aqueous emulsion according to [1], which contains emulsified particles containing the copolymer (X) and emulsified particles containing the polyepoxy compound (Y).

[0013] [4] The aqueous emulsion according to any one of [1] to [3], wherein the copolymer (X) contains a structural unit (c) derived from an ethylenically unsaturated aromatic compound (C) having a benzene ring and an ethylenically unsaturated bond. [5] The aqueous emulsion according to [4], wherein the content of the structural unit (a) derived from the (meth)acrylic acid ester (A) in the copolymer (X) is 10 mol % or more and 89.9 mol % or less, and the content of the structural unit (c) derived from the ethylenically unsaturated aromatic compound (C) is 10 mol % or more and 89.9 mol % or less.

[0014] [6] The aqueous emulsion according to any one of [1] to [3], wherein at least one of the ethylenically unsaturated monomers (B1) having two or more carboxy groups is maleic acid, itaconic acid, fumaric acid, mesaconic acid, citraconic acid, glutaconic acid, cis-4-cyclohexene-1,2-dicarboxylic acid, 3-butene-1,2,3-tricarboxylic acid, or ethylene tetracarboxylic acid. [7] The aqueous emulsion according to any one of [1] to [3], wherein at least one of the ethylenically unsaturated monomers (B1) having two or more carboxy groups is an ethylenically unsaturated monomer having two carboxy groups. [8] The aqueous emulsion according to any one of [1] to [3], wherein at least one of the ethylenically unsaturated monomers (B1) having two or more carboxy groups is maleic acid.

[0015] [9] The aqueous emulsion according to any one of [1] to [3], wherein at least one of the polyepoxy compounds (Y) is a bisphenol epoxy compound, a hydrogenated bisphenol epoxy compound, a diglycidyl ether, a triglycidyl ether, a tetraglycidyl ether, a diglycidyl ester, a triglycidyl ester, or a tetraglycidyl ester.

[0016]

[10] The method includes an emulsion polymerization step of emulsion-polymerizing a monomer raw material including a (meth)acrylic acid ester (A) and an ethylenically unsaturated monomer having a carboxy group (B) in an aqueous medium (Z) in the presence of a polyepoxy compound (Y) having no ethylenically unsaturated bond and having two or more epoxy groups in one molecule, wherein the content of the (meth)acrylic acid ester (A) in the monomer raw material is 10 mol% or more and 99.9 mol% or less, the content of the ethylenically unsaturated monomer having a carboxy group (B) in the monomer raw material is 0.1 mol% or more and 20 mol% or less, and at least one of the ethylenically unsaturated monomers having a carboxy group (B) is an ethylenically unsaturated monomer (B1) having two or more carboxy groups, a content of carboxy groups of the ethylenically unsaturated monomer (B1) having two or more carboxy groups in the total number of carboxy groups of the ethylenically unsaturated monomer (B) having a carboxy group is 5 mol % or more and 75 mol % or less, and a content of the polyepoxy compound (Y) relative to 100 parts by mass of the monomer raw material is 1.0 part by mass or more and 67 parts by mass or less.

[0017]

[11] An aqueous resin composition comprising the aqueous emulsion (α) according to any one of [1] to [3], a curing agent (β), and a curing accelerator (γ).

[12] The aqueous resin composition according to

[11] , wherein at least one of the curing agents (β) is a polyamine (F) having an active hydrogen reactive with an epoxy group.

[13] The aqueous resin composition according to

[11] , wherein at least one of the curing accelerators (γ) is a tertiary aliphatic amine, a tertiary alicyclic amine, or a tertiary heteroaromatic amine.

[0018]

[14] An aqueous resin composition set, which is stored separately as a first part containing the aqueous emulsion (α) according to any one of [1] to [3], and a second part containing a curing agent (β) and a curing accelerator (γ).

[0019]

[15] A method for producing a coating film, comprising: a mixing step of preparing an aqueous resin composition by mixing the first part and the second part of the aqueous resin composition set described in

[14] ; and an application step of applying the aqueous resin composition to a surface to be coated.

[16] A method for producing a coating film according to

[15] , comprising a curing step of curing the aqueous resin composition applied to the surface to be coated at a temperature of 20°C to 40°C.

[0020] According to the present invention, it is possible to provide an aqueous emulsion that can be used as a material for an aqueous resin composition that has excellent compounding stability and can form a coating film that exhibits good rust prevention properties even when cured at room temperature, an aqueous resin composition set, and a method for producing the aqueous emulsion. Furthermore, because the aqueous resin composition of the present invention contains the aqueous emulsion of the present invention, it has excellent compounding stability and can form a coating film that exhibits good rust prevention properties even when cured at room temperature.

[0021] Furthermore, in the coating film forming method of the present invention, the aqueous resin composition is prepared by mixing the first and second parts of the aqueous resin composition set containing the aqueous emulsion of the present invention, thereby achieving excellent blend stability. Therefore, the time during which the coating work can be performed (pot life) can be sufficiently secured. Furthermore, even when the prepared aqueous resin composition is applied to a surface to be coated and then cured at room temperature, a coating film exhibiting excellent rust prevention properties can be formed.

[0022] The aqueous emulsion, its manufacturing method, aqueous resin composition, aqueous resin composition set, and coating film manufacturing method of the present invention are described in detail below. Note that the present invention is not limited to the following embodiments. For example, the present invention allows addition, omission, substitution, and modification of the number, type, position, amount, ratio, material, and configuration, etc., within the scope of the present invention.

[0023] Here, the following terms used in this specification will be explained. "(Meth)acrylic" is a general term for acrylic and methacrylic. "(Meth)acrylate" is a general term for acrylate and methacrylate. "Ethylenically unsaturated bond" refers to an ethylenically unsaturated bond having radical polymerizability, unless otherwise specified. "Weight average molecular weight" is a value calculated in terms of standard polystyrene measured by gel permeation chromatography (GPC).

[0024] In a polymer using a compound having an ethylenically unsaturated bond, a structural unit derived from the compound having an ethylenically unsaturated bond means a structural unit in which the chemical structure of the portion other than the ethylenically unsaturated bond in the compound having an ethylenically unsaturated bond is the same as the chemical structure of the portion in the polymer other than the portion corresponding to the ethylenically unsaturated bond of the structural unit. The ethylenically unsaturated bond of the compound is converted into a single bond when forming a polymer. For example, in a polymer of methyl methacrylate, the structural unit derived from methyl methacrylate is -CH ２ -C(CH ３ ) (COOCH ３ )- is represented by

[0025] In the case of a polymer of a compound having an ionic functional group and an ethylenically unsaturated bond, for example, a structural unit having an ionic functional group such as a carboxy group is considered to be a structural unit derived from the same ionic compound, regardless of whether a part of the functional group has been ion-exchanged or not. For example, -CH ２ -C(CH ３ The structural unit represented by (COONa)- may also be considered to be a structural unit derived from methacrylic acid.

[0026] Furthermore, after polymerization, when a portion other than the chain structure corresponding to the ethylenically unsaturated bond in the polymer, for example, a functional group such as a carboxy group, no longer corresponds to the chemical structure of the monomer due to a chemical reaction, the structural unit of the polymer is made to be a structural unit derived from a compound having an ethylenically unsaturated bond in the polymer. For example, when vinyl acetate is polymerized and then saponified, the structural unit of the polymer is made to be a structural unit derived from vinyl alcohol, not a structural unit derived from vinyl acetate, based on the chemical structure of the polymer.

[0027] "Curing" refers to the process in which molecules contained in the raw materials bond together through a chemical reaction to form a polymer with a network structure. The "coating film" is a cured product formed by curing the resin component contained in the aqueous resin composition of this embodiment, and is integrated with the surface to be coated, obtained by applying the aqueous resin composition to the surface to be coated and drying the medium, for example.

[0028] [1. Aqueous Emulsion (α)] The aqueous emulsion (α) contains a copolymer (X), a polyepoxy compound (Y) having no ethylenically unsaturated bonds and having two or more epoxy groups per molecule, and an aqueous medium (Z). The aqueous emulsion (α) can be mixed with a curing agent (β) and a curing accelerator (γ) described below, applied to a surface to be coated, and then cured at room temperature (20°C to 40°C) to form a coating film that exhibits good rust prevention properties.

[0029] The aqueous emulsion (α) may contain emulsified particles containing the copolymer (X) and the polyepoxy compound (Y). The emulsified particles containing the copolymer (X) and the polyepoxy compound (Y) are emulsions obtained by emulsion polymerization of monomer raw materials that will become structural units of the copolymer (X) in the presence of the polyepoxy compound (Y) in an aqueous medium (Z).

[0030] The aqueous emulsion (α) may contain emulsified particles containing the copolymer (X) and emulsified particles containing the polyepoxy compound (Y). In such an aqueous emulsion (α), the emulsified particles containing the copolymer (X) dispersed in the aqueous medium (Z) and the emulsified particles containing the polyepoxy compound (Y) are electrically repelled. For this reason, it is presumed that the emulsified particles containing the copolymer (X) and the emulsified particles containing the polyepoxy compound (Y) dispersed in the aqueous medium (Z) do not aggregate and are uniformly dispersed.

[0031] When the aqueous emulsion (α) contains emulsified particles containing copolymer (X) and polyepoxy compound (Y), it has superior blending stability compared to when it contains both emulsified particles containing copolymer (X) and emulsified particles containing polyepoxy compound (Y), and can be used as a material for aqueous resin compositions that can form coating films with good rust prevention properties. This is presumably because when the aqueous emulsion (α) contains emulsified particles containing copolymer (X) and polyepoxy compound (Y), the concentration of polyepoxy compound (Y) in the emulsified particles is lower than when it contains emulsified particles containing polyepoxy compound (Y), so the reaction rate between the curing agent that has penetrated the emulsified particles and the polyepoxy compound (Y) is slower, resulting in superior blending stability. Furthermore, coating films obtained by curing an aqueous resin composition containing emulsified particles containing copolymer (X) and polyepoxy compound (Y) have smaller and more densely distributed domains derived from the copolymer (X) and polyepoxy compound (Y). As a result, it is presumed that the poor water resistance of the domains derived from copolymer (X) is alleviated, and good rust prevention properties are exhibited.

[0032] <1-1. Copolymer (X)> The copolymer (X) contains a structural unit (a) derived from a (meth)acrylic acid ester (A) and a structural unit (b) derived from an ethylenically unsaturated monomer (B) having a carboxy group. At least one of the ethylenically unsaturated monomers (B) having a carboxy group is an ethylenically unsaturated monomer (B1) having two or more carboxy groups.

[0033] The copolymer (X) may be one consisting of the structural unit (a) and the structural unit (b) (referred to as copolymer (X1)). The copolymer (X) may be one containing the structural unit (a), the structural unit (b), and further a structural unit (c) derived from an ethylenically unsaturated aromatic compound (C) having a benzene ring and an ethylenically unsaturated bond (referred to as copolymer (X2)). The copolymer (X2) may be one consisting only of the structural units (a) to (c). The copolymer (X) may also have a structural unit (d) (referred to as a structural unit derived from another monomer (D)) other than the structural units (a) to (c).

[0034] [(Meth)acrylic acid ester (A)] The (meth)acrylic acid ester (A) preferably contains an alkyl (meth)acrylate ester, and more preferably consists of an alkyl (meth)acrylate ester. The alkyl group of the alkyl (meth)acrylate ester is more preferably a linear, branched, or cyclic alkyl group having 1 to 18 carbon atoms. Specific examples include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and isobornyl (meth)acrylate. These may be used alone or in combination of two or more.

[0035] The (meth)acrylic acid ester (A) may also include a (meth)acrylic acid ester (A1) having two or less carbon atoms in the portion derived from alcohol. The (meth)acrylic acid ester (A1) is a (meth)acrylic acid ester having a (meth)acryloyloxy group (CH ２ =CR-COO-, where R represents hydrogen or a methyl group), and the portion derived from an alcohol, i.e., the portion other than the (meth)acryloyloxy group, has 2 or less carbon atoms. The number of carbon atoms in the portion other than the acryloyloxy group may be, for example, 1 or 2.

[0036] Examples of the (meth)acrylic acid ester (A1) include methyl (meth)acrylate, ethyl (meth)acrylate, etc. The (meth)acrylic acid ester (A1) is preferably a (meth)acrylic acid alkyl ester having two or less carbon atoms in the alcohol-derived moiety, and more preferably methyl methacrylate.

[0037] The (meth)acrylic acid ester (A) may contain a (meth)acrylic acid ester having an epoxy group, because this improves the rust prevention properties of a coating film made of a cured product of the aqueous resin composition containing the aqueous emulsion (α) of this embodiment.

[0038] Examples of the (meth)acrylic acid ester having an epoxy group include glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, and 3,4-epoxycyclohexylpropyl (meth)acrylate. These (meth)acrylic acid esters having an epoxy group may be used alone or in combination of two or more. Among these (meth)acrylic acid esters having an epoxy group, glycidyl (meth)acrylate is preferred.

[0039] Furthermore, the (meth)acrylic acid ester (A) may be neither a (meth)acrylic acid alkyl ester nor a (meth)acrylic acid ester having an epoxy group, but may be any other (meth)acrylic acid ester, such as a (meth)acrylic acid ester having a hydroxy group or a (meth)acrylic acid ester having a benzene ring.

[0040] Examples of the (meth)acrylic acid ester having a hydroxy group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, mono(meth)acrylic acid esters of polyalkylene glycols such as mono(meth)acrylic acid esters of polyethylene glycol and mono(meth)acrylic acid esters of polypropylene glycol. These (meth)acrylic acid esters having a hydroxy group may be used alone or in combination of two or more.

[0041] Examples of the (meth)acrylic acid ester having a benzene ring include benzyl (meth)acrylate.

[0042] In this embodiment, a compound that can be classified as both a (meth)acrylic acid ester (A) and an ethylenically unsaturated monomer (B) having a carboxy group, which will be described later, is considered to be an ethylenically unsaturated monomer (B) having a carboxy group. For example, a (meth)acrylic acid ester having a carboxy group is classified as an ethylenically unsaturated monomer (B) having a carboxy group. Furthermore, a compound that can be classified as both a (meth)acrylic acid ester (A) and an ethylenically unsaturated aromatic compound (C) having a benzene ring and an ethylenically unsaturated bond, which will be described later, is considered to be a (meth)acrylic acid ester (A). For example, benzyl (meth)acrylate is classified as a (meth)acrylic acid ester (A).

[0043] The structural unit (a) derived from the (meth)acrylic acid ester (A) may be a structural unit derived from only one type of compound selected from these compounds, or may include two or more types of structural units derived from two or more types of compounds.

[0044] In this embodiment, the content of the structural unit derived from the compound used as a monomer in the copolymer (X) is a value calculated based on the amount of the compound used as a monomer raw material for the copolymer (X). Specifically, for example, the content of the structural unit (a) derived from the (meth)acrylic acid ester (A) in the copolymer (X) means the ratio (mol %) of the amount of the (meth)acrylic acid ester (A) used as a raw material for the copolymer (X) to the total amount of the compounds used as monomer raw materials for the copolymer (X).

[0045] The content of the structural unit (a) derived from the (meth)acrylic acid ester (A) in the copolymer (X) is 10 mol% or more. This is because, in the production method of the aqueous emulsion (α) described below, the dispersibility of the monomer raw material that becomes the structural unit of the copolymer (X) and the polyepoxy compound (Y) described below can be improved. From this viewpoint, the content of the structural unit (a) derived from the (meth)acrylic acid ester (A) in the copolymer (X) is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, and particularly preferably 50 mol% or more.

[0046] The content of the structural unit (a) derived from the (meth)acrylic acid ester (A) in the copolymer (X) is 99.9 mol% or less. This is because if the content of the structural unit (a) exceeds 99.9 mol%, the dispersibility of the aqueous emulsion (α) tends to decrease. From this viewpoint, the content of the structural unit (a) derived from the (meth)acrylic acid ester (A) in the copolymer (X) is preferably 98.5 mol% or less, more preferably 98.0 mol% or less.

[0047] When the copolymer (X) is a copolymer (X1) consisting only of the structural unit (a) and the structural unit (b), the following ratios are preferred from the viewpoint of improving the dispersibility of the monomer raw materials that form the structural units of the copolymer (X1) with the polyepoxy compound (Y). That is, the content of the structural unit (a) derived from the (meth)acrylic acid ester (A) in the copolymer (X1) is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and particularly preferably 95 mol% or more. Furthermore, the content of the structural unit (a) derived from the (meth)acrylic acid ester (A) in the copolymer (X1) is preferably 98.5 mol% or less, more preferably 98.0 mol% or less.

[0048] When the copolymer (X) is a copolymer (X2) having the structural unit (a), the structural unit (b), and the structural unit (c), the dispersibility of the aqueous emulsion (α) tends to decrease, so the following ratio is preferred. The content of the structural unit (a) derived from the (meth)acrylic acid ester (A) in the copolymer (X2) is preferably 89.9 mol% or less, more preferably 80 mol% or less, even more preferably 70 mol% or less, and particularly preferably 60 mol% or less. Furthermore, the content of the structural unit (a) derived from the (meth)acrylic acid ester (A) in the copolymer (X2) is 10 mol% or more, preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, and particularly preferably 50 mol% or more.

[0049] When the structural unit (a1) derived from the (meth)acrylic acid ester (A1) having an alcohol-derived moiety with two or less carbon atoms is introduced into the copolymer (X), the content thereof is preferably 10 mol% or more, more preferably 15 mol% or more. This is because the dispersibility of the aqueous emulsion (α) is improved. The content of the structural unit (a1) may be 50 mol% or more, or may be 60 mol% or more.

[0050] The upper limit of the content of the structural unit (a1) derived from the (meth)acrylic acid ester (A1) in the copolymer (X1) is the same as the upper limit of the content of the structural unit (a) derived from the (meth)acrylic acid ester (A), i.e., 99 mol % or less, preferably 98.5 mol % or less, and more preferably 98.0 mol % or less.

[0051] [Carboxy group-containing ethylenically unsaturated monomer (B)] The carboxy group-containing ethylenically unsaturated monomer (B) includes an ethylenically unsaturated monomer (B1) having two or more carboxy groups. The ethylenically unsaturated monomer (B1) having two or more carboxy groups may be used alone or in combination of two or more.

[0052] At least one of the ethylenically unsaturated monomers (B1) having two or more carboxy groups is preferably an ethylenically unsaturated monomer having two carboxy groups. Specifically, at least one of the ethylenically unsaturated monomers having two carboxy groups is preferably maleic acid, itaconic acid, fumaric acid, mesaconic acid, citraconic acid, glutaconic acid, or cis-4-cyclohexene-1,2-dicarboxylic acid. As the ethylenically unsaturated monomer having three or more carboxy groups, 3-butene-1,2,3-tricarboxylic acid or ethylene tetracarboxylic acid is preferred. In order to improve the rust prevention properties of a coating film formed from a cured product of the aqueous resin composition containing the aqueous emulsion (α) of this embodiment, at least one of the ethylenically unsaturated monomers (B1) having two or more carboxy groups is preferably maleic acid.

[0053] The ethylenically unsaturated monomer (B) having a carboxy group may consist solely of an ethylenically unsaturated monomer (B1) having two or more carboxy groups, or may contain an ethylenically unsaturated monomer (B2) having one carboxy group. Therefore, the structural unit (b) derived from the ethylenically unsaturated monomer (B) having a carboxy group may be a structural unit (b1) derived solely from an ethylenically unsaturated monomer (B1) having two or more carboxy groups, or may contain a structural unit (b2) derived from an ethylenically unsaturated monomer (B2) having one carboxy group.

[0054] Examples of the ethylenically unsaturated monomer (B2) having one carboxy group include acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, and alkyl esters of the ethylenically unsaturated monomer (B1) having two or more carboxy groups, each having only one carboxy group. Among these ethylenically unsaturated monomers (B2) having one carboxy group, methacrylic acid is preferred. This is because the aqueous resin composition containing the aqueous emulsion (α) of this embodiment has good pigment compatibility and blend stability. The ethylenically unsaturated monomer (B2) having one carboxy group may be used alone or in combination of two or more.

[0055] The structural unit (b) derived from the ethylenically unsaturated aromatic compound (B) may be a structural unit derived from only one type of compound selected from these compounds, or may contain two or more types of structural units derived from two or more types of compounds.

[0056] The content of the structural unit (b) derived from the ethylenically unsaturated monomer (B) having a carboxy group in the copolymer (X) is 0.1 mol% or more. This is because the dispersibility of the copolymer (X) in the aqueous emulsion (α) is improved. From this viewpoint, the content of the structural unit (b) derived from the ethylenically unsaturated monomer (B) having a carboxy group in the copolymer (X) is preferably 1.0 mol% or more, more preferably 2.0 mol% or more. The content of the structural unit (b) derived from the ethylenically unsaturated monomer (B) having a carboxy group in the copolymer (X) may be 2.5 mol% or more, or may be 3.0 mol% or more.

[0057] The content of the structural unit (b) derived from the ethylenically unsaturated monomer (B) having a carboxy group in the copolymer (X) is 20 mol% or less. This is to prevent the copolymer (X) from gelling in a high-temperature environment and improve the high-temperature stability of the aqueous emulsion (α). From this viewpoint, the content of the structural unit (b) derived from the ethylenically unsaturated monomer (B) having a carboxy group in the copolymer (X) is preferably 17 mol% or less, more preferably 15 mol% or less, even more preferably 10 mol% or less, and particularly preferably 5 mol% or less.

[0058] Next, the content of carboxy groups in the structural unit (b1) derived from the ethylenically unsaturated monomer (B1) having two or more carboxy groups relative to the total number of carboxy groups in the structural unit (b) derived from the ethylenically unsaturated monomer (B) having a carboxy group will be described using an example. For example, when the ethylenically unsaturated monomer (B) having a carboxy group is composed of maleic acid, which is the ethylenically unsaturated monomer (B1) having two carboxy groups, and methacrylic acid, which is the ethylenically unsaturated monomer (B2) having one carboxy group, and contains 3 mol of maleic acid and 4 mol of methacrylic acid, the content is calculated using the following formula: (B1) * 2 / [(B1) * 2 + (B2)] = {3 * 2 / (3 * 2 + 4)} x 100 = 60 mol%

[0059] The content of carboxy groups in the structural units (b1) derived from the ethylenically unsaturated monomer (B1) having two or more carboxy groups in the total number of carboxy groups in the structural units (b) derived from the ethylenically unsaturated monomer (B) having a carboxy group is 5 mol% or more, preferably 15 mol% or more, more preferably 30 mol% or more, more preferably 40 mol% or more, and even more preferably 50 mol% or more, because this improves the adhesion of a coating film made of a cured product of the aqueous resin composition containing the aqueous emulsion (α) of this embodiment to a metal surface.

[0060] The content of carboxy groups in the structural units (b1) derived from the ethylenically unsaturated monomer (B1) having two or more carboxy groups in the total number of carboxy groups in the structural units (b) derived from the ethylenically unsaturated monomer (B) having a carboxy group is 75 mol % or less, preferably 70 mol % or less, and more preferably 65 mol % or less, because this improves the pigment compatibility and blend stability of the aqueous resin composition containing the aqueous emulsion (α) of this embodiment.

[0061] [Ethylenically unsaturated aromatic compound (C)] The ethylenically unsaturated aromatic compound (C) is a compound that does not fall under either the (meth)acrylic acid ester (A) or the ethylenically unsaturated monomer having a carboxy group (B) and has a benzene ring and an ethylenically unsaturated bond, provided that the ethylenically unsaturated aromatic compound (C) does not include a maleimide compound described below.

[0062] The ethylenically unsaturated aromatic compound (C) is preferably an aromatic vinyl compound. Examples of aromatic vinyl compounds include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, tert-butoxystyrene, vinyltoluene, divinyltoluene, vinylnaphthalene, monochlorostyrene, dichlorostyrene, monobromostyrene, dibromostyrene, tribromostyrene, fluorostyrene, styrene sulfonic acid and its salts, α-methylstyrene sulfonic acid and its salts, p-hydroxystyrene, m-hydroxystyrene, o-hydroxystyrene, p-isopropenylphenol, m-isopropenylphenol, and o-isopropenylphenol. Among these ethylenically unsaturated aromatic compounds (C), styrene is particularly preferred because it improves the blending stability of the aqueous resin composition containing the aqueous emulsion (α) of this embodiment.

[0063] The structural unit (c) derived from the ethylenically unsaturated aromatic compound (C) may be a structural unit derived from only one type of compound selected from these compounds, or may contain two or more types of structural units derived from two or more types of compounds.

[0064] When the copolymer (X) contains a structural unit (c) derived from the ethylenically unsaturated aromatic compound (C), i.e., when the copolymer (X) is the copolymer (X2), the content of the structural unit (c) in the copolymer (X2) is preferably 10 mol% or more. This is because the water resistance of the coating film made of the cured product of the aqueous resin composition containing the aqueous emulsion (α) of this embodiment is improved, and better rust prevention properties are obtained. From this viewpoint, the content of the structural unit (c) in the copolymer (X2) is more preferably 20 mol% or more, and even more preferably 30 mol% or more.

[0065] When the copolymer (X) is the copolymer (X2), the content of the structural unit (c) in the copolymer (X2) is preferably 89.9 mol% or less. This is because the aqueous resin composition containing the aqueous emulsion (α) of this embodiment has better pigment miscibility and blend stability. From this viewpoint, the content of the structural unit (c) in the copolymer (X2) is more preferably 80 mol% or less, and even more preferably 70 mol% or less.

[0066] [Other Monomer (D)] The other monomer (D) is a compound having an ethylenically unsaturated bond that does not fall under any of the (meth)acrylic acid ester (A), the ethylenically unsaturated monomer having a carboxy group (B), and the ethylenically unsaturated aromatic compound having a benzene ring and an ethylenically unsaturated bond (C), and that is copolymerizable with the compound used in the synthesis of the copolymer (X). Examples of the other monomer (D) include conjugated diene compounds, maleimide compounds, and vinyl compounds having a cyano group.

[0067] Examples of the conjugated diene compound include 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, chloroprene (2-chloro-1,3-butadiene), etc. These conjugated diene compounds may be used alone or in combination of two or more.

[0068] Examples of the maleimide compound include maleimide, N-methylmaleimide, N-isopropylmaleimide, N-butylmaleimide, N-dodecylmaleimide, N-phenylmaleimide, N-(2-methylphenyl)maleimide, N-(4-methylphenyl)maleimide, N-(2,6-dimethylphenyl)maleimide, N-(2,6-diethylphenyl)maleimide, N-(2-methoxyphenyl)maleimide, N-benzylmaleimide, N-(4-hydroxyphenyl)maleimide, N-naphthylmaleimide, N-cyclohexylmaleimide, etc. These maleimide compounds may be used alone or in combination of two or more.

[0069] Examples of the vinyl compound having a cyano group include acrylonitrile, methacrylonitrile, α-ethylacrylonitrile, α-isopropylacrylonitrile, α-chloroacrylonitrile, and α-fluoroacrylonitrile. These vinyl compounds having a cyano group may be used alone or in combination of two or more.

[0070] The amount of copolymer (X) contained in aqueous emulsion (α) can be selected arbitrarily, but is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more, based on the total amount of aqueous emulsion (α). The amount of copolymer (X) contained in aqueous emulsion (α) is preferably 60% by mass or less, more preferably 57% by mass or less, based on the total amount of aqueous emulsion (α). However, it is not limited to these examples.

[0071] <1-2. Polyepoxy compound (Y)> The polyepoxy compound (Y) is a compound that does not have an ethylenically unsaturated bond and has two or more epoxy groups in one molecule. Only one type of polyepoxy compound (Y) may be used, or two or more types may be used.

[0072] Specific examples of the polyepoxy compound (Y) include diglycidyl ether of bisphenol A, diglycidyl ether of hydrogenated bisphenol A, diglycidyl ether of bisphenol F, diglycidyl ether of hydrogenated bisphenol F, glycerin polyglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, diglycidyl ester of phthalic acid, 1,4-cyclohexanedimethanol diglycidyl ether, 1,3-cyclohexanedimethanol diglycidyl ether, and diglycidyl ester of hexahydrophthalic acid.

[0073] At least one of the polyepoxy compounds (Y) is preferably a bisphenol-type epoxy compound, a hydrogenated bisphenol-type epoxy compound, a diglycidyl ether, a triglycidyl ether, a tetraglycidyl ether, a diglycidyl ester, a triglycidyl ester, or a tetraglycidyl ester. The polyepoxy compound (Y) is more preferably a bisphenol-type epoxy compound and / or a hydrogenated bisphenol-type epoxy compound, even more preferably a bisphenol A-type epoxy compound and / or a hydrogenated bisphenol A-type epoxy compound, and even more preferably a bisphenol A-type epoxy compound. This is because the water resistance and rust prevention of a coating film made of a cured product of the aqueous resin composition containing the aqueous emulsion (α) of this embodiment are further improved.

[0074] The weight-average molecular weight of the polyepoxy compound (Y) is not particularly limited, but is preferably 1,000 or less, more preferably 800 or less, and even more preferably 500 or less. This is because the compatibility of the polyepoxy compound (Y) with the copolymer (X) is improved, resulting in an aqueous emulsion (α) with excellent dispersibility and storage stability. The lower limit of the weight-average molecular weight of the polyepoxy compound (Y) can be selected arbitrarily and may be, for example, 200 or 300, but is not limited thereto.

[0075] The epoxy equivalent of the polyepoxy compound (Y) (mass of the polyepoxy compound (Y) per mol of epoxy groups) is preferably 500 g / mol or less, more preferably 350 g / mol or less, even more preferably 250 g / mol or less, and particularly preferably 200 g / mol or less. This is because the coating film made of the cured product of the aqueous resin composition containing the aqueous emulsion (α) of this embodiment will have high strength. The lower limit of the epoxy equivalent can be selected arbitrarily and may be, for example, 70 g / mol or more or 120 g / mol or more, but is not limited to these examples.

[0076] The content of polyepoxy compound (Y) per 100 parts by mass of the total amount of copolymer (X) is 1.0 part by mass or more. This is because a coating film made of a cured product of an aqueous resin composition containing the aqueous emulsion (α) of this embodiment and a curing agent (β) described later will have excellent rust prevention properties even when cured at room temperature. From this perspective, the content of polyepoxy compound (Y) per 100 parts by mass of the total amount of copolymer (X) is preferably 11 parts by mass or more, more preferably 25 parts by mass or more, and even more preferably 33 parts by mass or more.

[0077] The content of polyepoxy compound (Y) per 100 parts by mass of the total amount of copolymer (X) is 67 parts by mass or less. This is because the aqueous emulsion (α) of this embodiment has excellent dispersibility in an aqueous resin composition containing the aqueous emulsion (α), a curing agent (β) described later, and a curing accelerator (γ) described later. From this viewpoint, the content of polyepoxy compound (Y) per 100 parts by mass of the total amount of copolymer (X) is preferably 50 parts by mass or less, and more preferably 47 parts by mass or less. In this embodiment, 100 parts by mass of the total amount of copolymer (X) is considered to be 100 parts by mass of the total amount of the monomer raw materials used in the polymerization of copolymer (X).

[0078] <1-3. Aqueous Medium (Z)> The aqueous medium (Z) can be selected arbitrarily, and it is preferable to use water. However, as long as the dispersibility of the aqueous emulsion (α) of this embodiment is not impaired, for example, a medium obtained by adding a water-soluble solvent to water may be used as the aqueous medium (Z). The hydrophilic (water-soluble) solvent to be added to water can be selected arbitrarily, and examples thereof include methanol, ethanol, and N-methylpyrrolidone.

[0079] <1-4. Method for producing aqueous emulsion (α)> (First production method) When the aqueous emulsion (α) contains emulsified particles containing the copolymer (X) and the polyepoxy compound (Y), it can be produced, for example, by the method shown below.

[0080] The aqueous emulsion (α) containing emulsified particles containing the copolymer (X) and the polyepoxy compound (Y) can be produced by an emulsion polymerization method. Specifically, the aqueous emulsion (α) can be produced by emulsion polymerization of a monomer raw material containing the (meth)acrylic acid ester (A), the ethylenically unsaturated monomer (B) having a carboxy group, and an optional ethylenically unsaturated aromatic compound (C) and / or other monomer (D) (i.e., all monomers that will become structural units of the copolymer (X)) in an aqueous medium (Z) in the presence of the polyepoxy compound (Y).

[0081] When an aqueous emulsion (α) containing emulsified particles containing the copolymer (X) and the polyepoxy compound (Y) is produced by emulsion polymerization, the solution to be emulsion polymerized, which contains the monomer raw materials, the polyepoxy compound (Y), and the aqueous medium (Z), may contain an emulsifier, a polymerization initiator, a basic substance, a chain transfer agent, etc. The emulsifier and / or the basic substance may be added to the aqueous emulsion (α) obtained after emulsion polymerization.

[0082] The content of each raw material in the total raw materials used to produce the aqueous emulsion (α) of this embodiment is the same as the content of the component derived from each raw material in the aqueous emulsion (α) obtained after emulsion polymerization. Therefore, the content of each monomer component in the monomer raw materials used to produce the aqueous emulsion (α) is the same as the content of the structural unit derived from each monomer in the structural unit of copolymer (X) contained in the emulsion particles containing copolymer (X) and polyepoxy compound (Y) contained in the aqueous emulsion (α).

[0083] (Emulsifier) ​​The emulsifier improves the dispersion stability of the solution during emulsion polymerization and / or the aqueous emulsion (α) obtained after emulsion polymerization. The emulsifier that may be used in the emulsion polymerization step is preferably a non-polymerizable surfactant. The non-polymerizable surfactant is a surfactant that does not have a polymerizable unsaturated bond in its chemical structure. The surfactant that may be used in the emulsion polymerization step is preferably an anionic surfactant and / or a nonionic surfactant.

[0084] Examples of anionic surfactants include alkyl sulfates, alkylbenzene sulfonates, alkyl sulfosuccinates, alkyl diphenyl ether disulfonates, polyoxyalkylene alkyl sulfates, polyoxyalkylene alkyl phosphates, etc. Examples of nonionic surfactants include polyoxyalkylene alkyl ethers, polyoxyalkylene alkylphenol ethers, polyoxyalkylene fatty acid esters, polyoxyalkylene sorbitan fatty acid esters, etc.

[0085] These emulsifiers may be used alone or in combination of two or more. Among these emulsifiers, it is preferable to use a combination of an alkylbenzene sulfonate and a polyoxyalkylene alkyl ether. As the alkylbenzene sulfonate, it is preferable to use sodium dodecylbenzene sulfonate, and as the polyoxyalkylene alkyl ether, it is preferable to use a polyoxyethylene alkyl ether. This is because the dispersion stability of the aqueous emulsion (α) becomes good.

[0086] (Polymerization initiator) The polymerization initiator used in the emulsion polymerization step may be, for example, a peroxide, or a combination of a peroxide and a reducing agent. Examples of peroxides include persulfates such as potassium persulfate and ammonium persulfate, and hydrogen peroxide. Examples of reducing agents include sodium hydrogen sulfite, sodium sulfoxylate formaldehyde, ascorbic acid, sulfites, tartaric acid or its salts, etc.

[0087] (Chain Transfer Agent) In the emulsion polymerization step, a chain transfer agent is used to adjust the molecular weight of the copolymer (X) obtained by emulsion polymerization. Examples of the chain transfer agent that can be used include alcohols such as methyl alcohol, n-propyl alcohol, isopropyl alcohol, t-butyl alcohol, and benzyl alcohol, and mercaptans such as n-dodecyl mercaptan, tert-dodecyl mercaptan, and n-butyl mercaptan.

[0088] (Basic Substance) In the emulsion polymerization step, the acidic components contained in the raw materials used to produce the aqueous emulsion (α) are neutralized by adding a basic substance. As a result, the pH of the solution during emulsion polymerization and / or the aqueous emulsion (α) after emulsion polymerization is kept within an appropriate range. Therefore, the stability of the solution during emulsion polymerization and / or the aqueous emulsion (α) after emulsion polymerization is improved.

[0089] Examples of basic substances include ammonia, triethylamine, ethanolamine, sodium hydroxide, lithium hydroxide, etc. These basic substances may be used alone or in combination of two or more.

[0090] The emulsion polymerization step for producing the aqueous emulsion (α) containing emulsified particles containing the copolymer (X) and the polyepoxy compound (Y) may be a step in which the components, including the monomer raw materials, used to produce the aqueous emulsion (α) are charged into a reaction vessel all at once and emulsion polymerized, or a step in which the components, including the monomer raw materials, are continuously fed into the reaction vessel and emulsion polymerized. The emulsion polymerization is preferably carried out while stirring the solution in the reaction vessel during emulsion polymerization.

[0091] In the first production method, emulsion polymerization for producing an aqueous emulsion (α) containing emulsion particles comprising a copolymer (X) and a polyepoxy compound (Y) can be carried out at any temperature. The emulsion polymerization temperature can be, for example, 30°C to 90°C, preferably 40°C to 85°C, and more preferably 40°C to 70°C. When the emulsion polymerization temperature is 30°C or higher, the emulsion polymerization reaction is accelerated. Therefore, emulsion particles containing a copolymer (X) and a polyepoxy compound (Y) can be efficiently produced. Furthermore, when the emulsion polymerization temperature is 90°C or lower, the emulsion polymerization step can suppress reaction between carboxy groups in compounds contained in the monomer raw materials and epoxy groups contained in the polyepoxy compound (Y).

[0092] According to the first production method, an aqueous emulsion (α) is obtained in which emulsified particles, each of which has a polyepoxy compound (Y) dispersed in particles of copolymer (X), are dispersed in an aqueous medium (Z). In this embodiment, the state in which "polyepoxy compound (Y) is dispersed in particles of copolymer (X)" does not necessarily require that copolymer (X) and polyepoxy compound (Y) are compatible with each other, but rather requires that domains of polyepoxy compound (Y) are present evenly both at the center and on the surface of the particles of copolymer (X).

[0093] (Second Production Method) When the aqueous emulsion (α) contains emulsified particles containing the copolymer (X) and emulsified particles containing the polyepoxy compound (Y), it can be produced, for example, by the method shown below. In the second production method, an emulsion containing emulsified particles containing the copolymer (X) and an emulsion containing emulsified particles containing the polyepoxy compound (Y) are produced separately.

[0094] The emulsion containing emulsified particles containing the copolymer (X) can be produced by emulsion polymerization of a monomer raw material (i.e., all monomers that will become structural units of the copolymer (X)) containing the (meth)acrylic acid ester (A), the ethylenically unsaturated monomer (B) having a carboxy group, and an optional ethylenically unsaturated aromatic compound (C) and / or other monomer (D) in an aqueous medium (Z).

[0095] In this case, an emulsifier, a polymerization initiator, a basic substance, a chain transfer agent, etc. may be added to the solution to be emulsion polymerized, which contains the monomer raw materials and the aqueous medium (Z). The emulsifier and / or the basic substance may be added to the emulsion containing emulsified particles containing the copolymer (X) obtained after the emulsion polymerization. The emulsifier, polymerization initiator, basic substance, and chain transfer agent may be the same as those that can be used in producing the aqueous emulsion (α) containing emulsified particles containing the copolymer (X) and the polyepoxy compound (Y) in the first production method.

[0096] In the emulsion polymerization for producing an emulsion containing emulsion particles containing copolymer (X), the components including the monomer raw materials may be charged into a reaction vessel all at once and the emulsion polymerization may be carried out, or the components including the monomer raw materials may be continuously fed into the reaction vessel and the emulsion polymerization may be carried out. The emulsion polymerization is preferably carried out while stirring the reaction solution in the reaction vessel.

[0097] Emulsion polymerization for producing an emulsion containing emulsion particles containing copolymer (X) can be carried out at any temperature. The emulsion polymerization temperature can be, for example, 30°C to 90°C, preferably 40°C to 85°C, and more preferably 40°C to 80°C. When the emulsion polymerization temperature is 30°C or higher, the emulsion polymerization reaction is promoted. Therefore, emulsion particles containing copolymer (X) can be produced efficiently. Furthermore, when the aqueous medium (Z) is water, an emulsion polymerization temperature of 90°C or lower is preferable because it allows the emulsion to be produced without boiling the aqueous medium (Z).

[0098] The emulsion containing emulsified particles containing the polyepoxy compound (Y) can be produced by dispersing the polyepoxy compound (Y) in the aqueous medium (Z) by a known method. When dispersing the polyepoxy compound (Y) in the aqueous medium (Z), an emulsifier may be used as needed. The emulsifier may be the same as that which can be used in producing the aqueous emulsion (α) containing emulsified particles containing the copolymer (X) and the polyepoxy compound (Y) in the first production method.

[0099] The emulsion containing emulsified particles containing polyepoxy compound (Y) may be commercially available. Examples include an emulsion containing emulsified particles containing bisphenol A type epoxy as the polyepoxy compound (Y) (solid content 47%; content of polyepoxy compound (Y) in the emulsion 45 to 49% by mass; manufactured by ADEKA Corporation; product name: ADEKA RESIN EM-101-50), an emulsion containing emulsified particles containing bisphenol A type epoxy (solid content 53%; epoxy equivalent of polyepoxy compound (Y): 990; product name: BECKOPOX EP386w / 52WA, manufactured by Daicel-Allnex Corporation), and an emulsion containing emulsified particles containing bisphenol A type epoxy (solid content 46%; epoxy equivalent of polyepoxy compound (Y): 4200; product name: BECKOPOX EP2307w / 45WAMP, manufactured by Daicel-Allnex Corporation).

[0100] Next, the emulsion containing the emulsion particles containing the copolymer (X) and the emulsion containing the emulsion particles containing the polyepoxy compound (Y) are mixed by a known method, thereby obtaining an aqueous emulsion (α) in which the emulsion particles containing the copolymer (X) and the emulsion particles containing the polyepoxy compound (Y) are dispersed in the aqueous medium (Z).

[0101] In the second production method, the content of each raw material in the total raw materials used to produce the aqueous emulsion (α) (the sum of the raw materials for the emulsion containing emulsified particles containing the copolymer (X) and the raw materials for the emulsion containing emulsified particles containing the polyepoxy compound (Y)) is the same as the content of the components derived from each raw material in the aqueous emulsion (α) obtained after production.

[0102] <1-5. Properties of aqueous emulsion (α)> [pH of aqueous emulsion (α)] The pH of the aqueous emulsion (α) is preferably 2 to 10, and more preferably 5 to 9. When the pH is within this range, the mechanical stability and chemical stability of the aqueous emulsion (α) are improved. The pH is a value measured at a liquid temperature of 23°C using a pH meter with a hydrogen ion concentration indicator that uses a glass electrode as the standard electrode.

[0103] The pH can be adjusted, for example, by adding a basic substance to the solution during or after emulsion polymerization for producing the aqueous emulsion (α) containing emulsified particles comprising the copolymer (X) and the polyepoxy compound (Y) in the first production method, or to the solution during or after emulsion polymerization for producing the emulsion containing emulsified particles comprising the copolymer (X) in the second production method.

[0104] [Nonvolatile content concentration of aqueous emulsion (α)] The nonvolatile content concentration of the aqueous emulsion (α) is preferably 10 to 65 mass%, more preferably 20 to 60 mass%, and even more preferably 30 to 55 mass%. The nonvolatile content concentration in the aqueous emulsion (α) can be appropriately determined taking into consideration the workability in the mixing step for preparing the aqueous resin composition described below or the application step for applying the aqueous resin composition to the surface to be coated. The nonvolatile content concentration in the aqueous emulsion (α) can be appropriately adjusted by adjusting the amount of aqueous medium (Z) added.

[0105] The nonvolatile content of the aqueous emulsion (α) can be determined by the following method. 1 g of the aqueous emulsion (α) is weighed into an aluminum dish with a diameter of 5 cm, and dried at 105°C for 1 hour in a dryer at atmospheric pressure while circulating air. The mass of the resulting residue is then measured. The ratio (mass %) of the measured mass of the residue to the mass of the aqueous emulsion (α) before drying is then determined as the nonvolatile content of the aqueous emulsion (α).

[0106] [Viscosity of Aqueous Emulsion (α)] In this embodiment, the viscosity of the aqueous emulsion (α) is measured at 23°C. The viscosity of the aqueous emulsion (α) is measured using a Brookfield viscometer at a rotation speed of 60 rpm, with a rotor selected according to the viscosity of the aqueous emulsion (α). For example, when the viscosity of the aqueous emulsion (α) is on the order of several mPa·s to several hundred mPa·s, the measurement is performed using rotor No. 1. When the aqueous emulsion (α) contains emulsified particles containing copolymer (X) and emulsified particles containing polyepoxy compound (Y), the viscosity of the aqueous emulsion (α) refers to the viscosity measured immediately after mixing the emulsified particles containing copolymer (X) and the emulsified particles containing polyepoxy compound (Y) (in other words, immediately after producing the aqueous emulsion (α)).

[0107] The viscosity of the aqueous emulsion (α) may be, for example, 0.1 to 1000 mPa·s, 1 to 100 mPa·s, 3 to 50 mPa·s, or 5 to 25 mPa·s. When the viscosity of the aqueous emulsion (α) is 0.1 to 1000 mPa·s, an aqueous resin composition containing the aqueous emulsion (α) is easy to apply, and the components are uniformly mixed.

[0108] [2. Aqueous Resin Composition] The aqueous resin composition of this embodiment contains the aqueous emulsion (α) of the above-described embodiment, a curing agent (β), and a curing accelerator (γ). The aqueous resin composition of this embodiment is produced by mixing the aqueous emulsion (α), the curing agent (β), and the curing accelerator (γ), as described below.

[0109] <2-1. Curing Agent (β)> At least one of the curing agents (β) is preferably a polyamine (F) having active hydrogen that is reactive with epoxy groups. In this embodiment, "polyamine (F)" is a compound having two or more amino groups in one molecule. At least one of the polyamines (F) is preferably a compound having an amino group that is unsubstituted or has only one substituent. At least two of the amino groups of the polyamine (F) having active hydrogen are primary amino groups (—NH ２It is more preferable that the polyamine (F) having an active hydrogen atom for an epoxy group contained in the curing agent (β) is either a primary amino group (—NHR (where R is a substituent)) or a secondary amino group (—NHR (where R is a substituent)). The type of polyamine (F) having an active hydrogen atom for an epoxy group contained in the curing agent (β) may be one type or two or more types.

[0110] Examples of the polyamine (F) include aliphatic polyamines, alicyclic polyamines, and aromatic polyamines. Examples of the aliphatic polyamines include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and modified products thereof. Examples of the aromatic polyamines include m-xylylenediamine, diaminodiphenylmethane, m-phenylenediamine, diaminodiphenylsulfone, and modified products thereof.

[0111] The curing agent (β) may be a commercially available product. Examples of commercially available curing agents include ADEKA HARDNER EH-8051 (polyamine) (manufactured by ADEKA Corporation), FUJICURE FXI-919, TOMAID TXH-674-B, and TXS-53-C (manufactured by T&K TOKA Corporation), Gaskamine 328 (Mitsubishi Gas Chemical Company, Inc.), Jeffamine D-230, and Jeffamine ED-600 (Huntsman Japan Co., Ltd.).

[0112] The amount of curing agent (β) used in the aqueous resin composition is preferably such that the chemical equivalent of the active hydrogen in the polyamine (F) contained in the curing agent (β) relative to the epoxy groups in the aqueous emulsion (α) is 0.10 equivalents or more, more preferably 0.20 equivalents or more, even more preferably 0.50 equivalents or more, and particularly preferably 0.60 equivalents or more. This is because the crosslinking reaction between the polyepoxy compound (Y) and the curing agent (β) in the aqueous resin composition proceeds sufficiently, resulting in a coating film with better suppressed penetration of water and ions. Furthermore, the increased reaction rate of the epoxy groups results in a coating film with better adhesion to metal materials. For these reasons, by using an amount of curing agent (β) such that the active hydrogen in the polyamine (F) is 0.10 equivalents or more, the coating film made of the cured product of the aqueous resin composition exhibits long-term rust prevention properties.

[0113] The amount of curing agent (β) used in the aqueous resin composition is preferably such that the chemical equivalent of the active hydrogen in the polyamine (F) contained in the curing agent (β) relative to the epoxy groups contained in the aqueous emulsion (α) is 1.5 equivalents or less, more preferably 1.3 equivalents or less, and even more preferably 1.2 equivalents or less, because this suppresses excessive cure shrinkage of the epoxy resin and improves the adhesion of the coating film to the substrate.

[0114] <2-2. Curing Accelerator (γ)> The curing accelerator (γ) has the function of accelerating the curing of the aqueous resin composition and forming a coating film with high hardness and water resistance. The curing accelerator (γ) is preferably a tertiary amine that does not have an active hydrogen atom on the nitrogen atom that is reactive with an epoxy group. The tertiary amine in this embodiment is NR １１ R ２２ R ３３ (In the formula, R １１ R ２２ R ３３ are substituents, and may be different from each other, or two or more of the same may be included. １１ R ２２ R ３３ may be bonded to each other to form a ring.

[0115] At least one of the curing accelerators (γ) is preferably a tertiary aliphatic amine, a tertiary alicyclic amine, or a tertiary heteroaromatic amine, in order to enhance the nucleophilicity of the curing accelerator (γ) and efficiently promote the curing reaction of the aqueous resin composition.

[0116] Examples of tertiary aliphatic amines include triethylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, tri-sec-butylamine, and tri-n-hexylamine. Examples of tertiary alicyclic amines include 1,4-diazabicyclo[2.2.2]octane (DABCO), 1,5-diazabicyclo[4.3.0]non-5-ene, and 1,8-diazabicyclo[5.4.0]undec-7-ene. As the tertiary heteroaromatic amine, it is preferable to use a compound having an imidazole skeleton, and specific examples include imidazole, 2-methylimidazole, and 2-ethyl-4-methylimidazole.

[0117] The curing accelerator (γ) is a tertiary amine (NR １１ R ２２ R ３３ ) may be a tertiary aromatic amine having a phenyl group that is not directly bonded to the nitrogen atom of the tertiary aromatic amine. Examples of such tertiary aromatic amines include dimethylbenzylamine, diethylbenzylamine, tribenzylamine, 2,4,6-trisdimethylaminomethylphenol, and 2-phenylimidazole.

[0118] Among these curing accelerators (γ), it is particularly preferable to use the following compounds (i) and / or (ii): (i) a tertiary alicyclic amine having a saturated ring structure in which two nitrogen atoms are bonded together by three amino group substituents and no active hydrogen atom reactive with epoxy groups on the nitrogen atom; (ii) a tertiary heteroaromatic amine having a heteroaromatic ring structure containing two or more nitrogen atoms and no active hydrogen atom reactive with epoxy groups.

[0119] (i) Examples of tertiary alicyclic amines include 1,4-diazabicyclo[2.2.2]octane (DABCO). (ii) Examples of tertiary heteroaromatic amines include imidazole. The curing accelerator (γ) may be used alone or in combination of two or more.

[0120] The amount of curing accelerator (γ) used in the aqueous resin composition is preferably 0.0070 equivalents or more, more preferably 0.010 equivalents or more, even more preferably 0.05 equivalents or more, and particularly preferably 0.10 equivalents or more, in terms of chemical equivalent relative to the epoxy groups contained in the aqueous emulsion (α). This is because a coating film made of a cured product of the aqueous resin composition of this embodiment will have a high crosslink density, high adhesion to substrates, and exhibit long-term rust prevention properties.

[0121] The amount of the curing accelerator (γ) is preferably 1.5 equivalents or less, more preferably 0.70 equivalents or less, even more preferably 0.44 equivalents or less, and particularly preferably 0.38 equivalents or less, relative to the epoxy groups contained in the aqueous emulsion (α). This is because the cured product of the aqueous resin composition of this embodiment becomes a coating film with good adhesion to metal materials. Furthermore, when the content of the curing accelerator (γ) is 1.5 equivalents or less, gelation of the aqueous resin composition in a short period of time can be suppressed, and a coating film made of a cured product with good rust prevention properties can be obtained.

[0122] <2-3. Other Components> In addition to the aqueous emulsion (α), the curing agent (β), and the curing accelerator (γ), the aqueous resin composition according to this embodiment may contain other components as necessary depending on the intended use of the aqueous resin composition. These other components may include additives such as pigments, thickeners, primary rust inhibitors, coupling agents, fillers, organic or inorganic hollow balloons, pigment dispersants, surfactants, defoamers, preservatives (e.g., biocides, mildewcides, fungicides, algicides, and combinations thereof), flow agents, leveling agents, and neutralizers (e.g., hydroxides, amines, ammonia, carbonates, etc.).

[0123] Examples of pigments that may be contained in the aqueous resin composition include titanium oxide, talc, barium sulfate, carbon black, red iron oxide, calcium carbonate, silicon oxide, talc, mica, kaolin, clay, ferrite, and silica sand. The pigment may contain only one type of compound, or may contain two or more types of compounds. The pigment is preferably contained in the aqueous resin composition in an amount of 0.1 to 50% by mass, and more preferably 1 to 40% by mass. This is to improve the hiding power of the coating film.

[0124] Examples of pigment dispersants that can be used include amino alcohols and polycarboxylic acid surfactants such as polycarboxylates. Examples of thickeners that can be used include hydroxyethyl cellulose and polyether polyol urethane polymers. Examples of primary rust inhibitors that can be used include sodium nitrite and benzotriazole. Examples of surfactants that can be used include the same emulsifiers that can be used when producing the aqueous emulsion (α).

[0125] As the coupling agent, it is preferable to use a silane coupling agent. Examples of the silane coupling agent include epoxy silane compounds. Specific examples include 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

[0126] When the aqueous resin composition contains a silane coupling agent, the content of the silane coupling agent is preferably 0.1 to 5 mol %, more preferably 0.5 to 4 mol %, based on the amount of epoxy groups contained in the polyepoxy compound (Y), because this improves the rust prevention properties and adhesion to metal materials of the cured aqueous resin composition.

[0127] [3. Aqueous Resin Composition Set] Next, the aqueous resin composition set of this embodiment will be described in detail. The aqueous resin composition of this embodiment may be stored as an aqueous resin composition set in which the constituent components of the aqueous resin composition are separated into a plurality of forms. The aqueous resin composition set of this embodiment may be, for example, a set in which the constituent components of the aqueous resin composition of this embodiment are separated and stored as two parts, a first part and a second part. Specifically, the constituent components of the aqueous resin composition of this embodiment may be separated and stored as two parts, a first liquid and a second liquid.

[0128] Examples of aqueous resin composition sets according to this embodiment include the sets shown below. That is, a set in which the first part contains an aqueous emulsion (α) but does not contain a curing agent (β) or a curing accelerator (γ), and the second part contains a curing agent (β) and a curing accelerator (γ) but does not contain an aqueous emulsion (α). The first part and / or the second part may contain other components contained in the aqueous resin composition according to this embodiment as necessary. Such aqueous resin composition sets have excellent storage stability because the aqueous emulsion (α) and the curing agent (β) do not react and cure during storage. The aqueous resin composition set may be one in which both the first part and the second part are liquid, or the first part may be liquid and the second part may be in a state other than liquid, such as solid.

[0129] The aqueous resin composition of the present embodiment contains an aqueous emulsion (α), a curing agent (β), and a curing accelerator (γ), and therefore has excellent blend stability and can form a coating film that exhibits good rust prevention properties even when cured at room temperature.

[0130] More specifically, the copolymer (X) contained in the aqueous emulsion (α) contains a structural unit (b) derived from an ethylenically unsaturated monomer (B) having a carboxy group, and the content of the structural unit (b) in the copolymer (X) is 0.1 mol% or more and 20 mol% or less. The content of carboxy groups in the structural unit (b) derived from an ethylenically unsaturated monomer (B1) having two or more carboxy groups is 5 mol% or more and 75 mol% or less. Therefore, the copolymer (X) contains a sufficient amount of carboxy groups. This improves the dispersibility of the copolymer (X) in the aqueous emulsion (α), and improves the blend stability of an aqueous resin composition containing the aqueous emulsion (α). Furthermore, the copolymer (X) contains an appropriate amount of the structural unit (b1). The two or more carboxy groups in the structural unit (b1) can interact with metal materials such as iron. Specifically, two or more carboxyl groups in the structural unit (b1) can form coordinate bonds (multidentate coordination) with metal ions such as iron ions at two or more locations. This allows a coating film formed from a cured product of the aqueous resin composition containing the aqueous emulsion (α) of this embodiment to adhere closely to the surface of a metal material. As a result, water penetration between the coating film and the metal material is suppressed, resulting in excellent rust prevention. Furthermore, since the content of the structural unit (b1) in the copolymer (X) is not too high, the blend stability of the aqueous emulsion (α) in the aqueous resin composition is not impaired.

[0131] Furthermore, the content of the polyepoxy compound (Y) having no ethylenically unsaturated bond and two or more epoxy groups per molecule is 1.0 part by mass or more and 67 parts by mass or less per 100 parts of the total amount of copolymer (X) contained in the aqueous emulsion (α), and the aqueous emulsion (α) contains an appropriate amount of epoxy groups. Therefore, the aqueous emulsion (α) in the aqueous resin composition can sufficiently crosslink with the active hydrogen reactive with the epoxy group contained in the curing agent (β). As a result, the aqueous resin composition of this embodiment can be cured at room temperature and can produce a coating film with good adhesion to metal materials and excellent rust prevention properties. Furthermore, because the epoxy groups contained in the aqueous emulsion (α) of this embodiment are not too large, the aqueous emulsion (α) is well dispersible in the aqueous resin composition containing the aqueous emulsion (α), the curing agent (β), and the curing accelerator (γ), resulting in excellent blend stability. In addition, since the amount of epoxy groups contained in the aqueous emulsion (α) is not too large, excessive cure shrinkage due to the crosslinking reaction between the aqueous emulsion (α) and the curing agent (β) in the aqueous resin composition is suppressed, the adhesion of the coating film to the substrate is good, and excellent rust prevention properties are obtained.

[0132] [4. Coating Film Manufacturing Method] Next, a method for manufacturing a coating film made of a cured product of the aqueous resin composition of this embodiment will be described in detail. In this coating film manufacturing method, the aqueous resin composition set of this embodiment is used. First, the first and second parts of the aqueous resin composition set of this embodiment are mixed to prepare the aqueous resin composition of this embodiment (mixing step). Next, the obtained aqueous resin composition is applied to a surface to be coated (application step).

[0133] In the mixing step, a first part containing the aqueous emulsion (α) and optionally containing other components contained in the aqueous resin composition of the present embodiment, and a second part containing the curing agent (β) and the curing accelerator (γ) and optionally containing other components contained in the aqueous resin composition of the present embodiment are mixed and stirred by a known method, thereby obtaining the aqueous resin composition of the present embodiment in which each component is dispersed.

[0134] The stirring in the mixing step can be performed using, for example, a Robomics (manufactured by Primix Corporation). In order to thoroughly disperse each component contained in the aqueous resin composition of this embodiment, the stirring time in the mixing step is preferably 5 minutes or more. Furthermore, in order to prevent the resin components contained in the aqueous resin composition from curing, the stirring time is preferably 1 hour or less.

[0135] In the coating step, the aqueous resin composition is applied to the surface of the substrate. Examples of materials forming the surface include metal materials such as iron. The surface may be previously subjected to a surface treatment such as a primer or undercoat. Known methods can be used to apply the aqueous resin composition. Examples of application methods include, but are not limited to, methods using a brush, roller, spray, etc. Furthermore, in order to prevent the resin components contained in the aqueous resin composition from curing before the coating step is completed, the coating step is preferably completed within 4 hours, and more preferably within 3 hours, after the end of the mixing step.

[0136] In the coating film manufacturing method of this embodiment, it is preferable to carry out a curing step after the application step, in which the resin composition applied to the surface to be coated is cured. In the curing step, for example, the surface of the substrate to be coated, to which the aqueous resin composition has been applied, is dried and cured to cure the resin component contained in the aqueous resin composition. The curing time varies depending on the temperature of the curing atmosphere. For example, the curing time can be 10 to 17 hours at 10°C, 7 to 14 hours at 20°C, 5 to 12 hours at 30°C, and 5 to 12 hours at 40°C.

[0137] The aqueous resin composition obtained in the mixing step can be cured at room temperature. In the curing step of this embodiment, the aqueous resin composition applied to the surface to be coated is preferably cured at a temperature of 20°C to 40°C, and more preferably at a temperature of 20°C to 30°C. This is because, after the aqueous resin composition is applied to the surface to be coated of an object to be coated that is installed outdoors, the aqueous resin composition can be dried and cured in the outdoor atmosphere. In this embodiment, an example has been described in which the aqueous resin composition applied to the surface to be coated is cured at a temperature of 20°C to 40°C, but the aqueous resin composition applied to the surface to be coated may be heated to shorten the curing time in the curing step.

[0138] In the coating film manufacturing method of this embodiment, a first part containing an aqueous emulsion (α) and a second part containing a curing agent (β) are mixed in the mixing step. As a result, the resulting aqueous resin composition has excellent blend stability. Therefore, a sufficient time (pot life) for coating work can be ensured in the coating step. Moreover, the aqueous resin composition obtained in the mixing step can be cured at room temperature, and a coating film with good adhesion to metal materials can be obtained. Therefore, even when cured at a temperature of 20°C to 40°C in the curing step, a coating film with excellent rust prevention properties can be obtained.

[0139] In the coating film manufacturing method of this embodiment, the mixing step has been described as an example in which the first and second parts of the aqueous resin composition set are mixed, but the aqueous resin composition may also be prepared by mixing the aqueous emulsion (α), the curing agent (β), the curing accelerator (γ), and other components that are included as needed in the mixing step. In this case, as in the case of using an aqueous resin composition set, a sufficient time for coating work (pot life) can be ensured, and a coating film that exhibits good rust prevention properties can be formed by curing at room temperature.

[0140] [5. Coating Film] The coating film of this embodiment is made of a cured product of the aqueous resin composition of this embodiment. The coating film of this embodiment can be formed by the coating film manufacturing method described above. The coating film of this embodiment may be one layer of a coating film having a multilayer structure. That is, the coating film of this embodiment may be provided by laminating, as necessary, a coating film consisting of an undercoat layer provided below the coating film made of the cured product of the aqueous resin composition of this embodiment, and / or a topcoat layer provided above the coating film. When the coating film of this embodiment is one layer of a coating film having a multilayer structure, it is preferably the layer of the coating film having a multilayer structure that comes into contact with the surface to be coated.

[0141] The coating film of this embodiment is made of a cured product of the aqueous resin composition of this embodiment. Therefore, the coating film of this embodiment can ensure a sufficient coating time (pot life) required for its formation. Therefore, the coating film of this embodiment is suitable as a coating film formed on the surface of large metal products, such as steel towers, bridges, ships, and port facilities, which tend to require long coating times. Furthermore, since the coating film of this embodiment can be cured at room temperature, it is suitable as a coating film used outdoors, such as steel towers, bridges, ships, and port facilities, and formed by a method of coating and curing outdoors. Furthermore, the coating film of this embodiment has good rust prevention properties. Therefore, it is suitable as a coating film formed on the surface of metal products.

[0142] [6. Fields of Application] The aqueous emulsion, its manufacturing method, aqueous resin composition, aqueous resin composition set, and coating film manufacturing method of the present embodiment are useful in various fields. In particular, the aqueous resin composition of the present embodiment is suitable for use as an anticorrosion coating applied to the surfaces of metal products used outdoors, such as steel towers, bridges, ships, and port facilities.

[0143] The article on which a coating film made of a cured product of the aqueous resin composition of this embodiment is formed, i.e., the object to which the aqueous resin composition of this embodiment is applied can be selected arbitrarily. Specific examples of the object to which the aqueous resin composition of this embodiment is applied include metal products used outdoors, such as steel towers, bridges, ships, and port facilities, various household items, home appliances such as refrigerators, play equipment installed in amusement parks and parks, sporting goods, buildings (interiors, exteriors, etc.), various industrial products and parts thereof, including transportation machinery and machine tools, automobile bodies and chassis, railroad car bodies and underfloor equipment, marine containers, and aircraft.

[0144] The present invention will be described in detail below using examples. Note that the following examples do not limit the entire scope of the present invention, and all implementations that do not deviate from the content of the description are included in the technical scope of the present invention.

[0145] <1. Synthesis of Aqueous Emulsion (α)> (Aqueous Emulsion (α-1)) A separable flask equipped with a condenser, a thermometer, a stirrer, and a dropping funnel was charged with 190 parts by mass of ion-exchanged water, and the temperature was raised to 60°C. Nitrogen gas was blown into the contents of the separable flask to deoxygenate them. An emulsion containing methyl methacrylate, 2-ethylhexyl acrylate, maleic acid, and methacrylic acid as monomer raw materials that would form the structural units of copolymer (X), bisphenol A-type epoxy as polyepoxy compound (Y), sodium dodecylbenzenesulfonate as an emulsifier, and polyoxyethylene alkyl ether, and 231 parts by mass of ion-exchanged water, in the amounts (parts by mass) shown in Table 1, was added dropwise to the flask over a period of 3 hours.

[0146] Simultaneously with the emulsion, a polymerization initiator prepared by dissolving 1.5 parts by mass of potassium persulfate as an oxidizing agent in 38 parts by mass of ion-exchanged water and 0.5 parts by mass of sodium hydrogen sulfite as a reducing agent in 19 parts by mass of ion-exchanged water were added dropwise at 60°C over 3.3 hours to polymerize. After completion of the dropwise addition of the emulsion and polymerization initiator, the solution was aged by continuing to stir for 1.5 hours while maintaining the temperature at 60°C. Thereafter, the solution was cooled to room temperature, and 2.7 parts by mass of 25% by mass ammonia water was added as a basic substance to obtain an aqueous emulsion (α-1) containing emulsified particles comprising copolymer (X) and polyepoxy compound (Y).

[0147] (Aqueous Emulsions (α-2) to (α-13)) Aqueous emulsions (α-2) to (α-13), containing emulsified particles containing copolymer (X) and polyepoxy compound (Y), were synthesized in the same manner as for aqueous emulsion (α-1), except that the materials shown in Tables 1 to 3 were used in the amounts (parts by mass) shown in Tables 1 to 3.

[0148] (Aqueous Emulsion (α-14)) A separable flask equipped with a condenser, a thermometer, a stirrer, and a dropping funnel was charged with 190 parts by mass of ion-exchanged water, and the temperature was raised to 60°C. Nitrogen gas was blown into the contents of the separable flask to deoxygenate them. An emulsion containing methyl methacrylate, 2-ethylhexyl acrylate, maleic acid, and methacrylic acid as monomer raw materials that will become structural units of copolymer (X), sodium dodecylbenzenesulfonate as an emulsifier, polyoxyethylene alkyl ether, and 231 parts by mass of ion-exchanged water, in the amounts (parts by mass) shown in Table 4, was added dropwise to the flask over a period of 3 hours.

[0149] Simultaneously with the emulsion, a polymerization initiator prepared by dissolving 1.5 parts by mass of potassium persulfate as an oxidizing agent in 38 parts by mass of ion-exchanged water and 0.5 parts by mass of sodium hydrogen sulfite as a reducing agent in 19 parts by mass of ion-exchanged water were added dropwise at 60°C over 3.3 hours to polymerize. After completion of the dropwise addition of the emulsion and polymerization initiator, the solution was aged by continuing to stir for 1.5 hours while maintaining the temperature of the solution at 60°C. Thereafter, the solution was cooled to room temperature, and 4.4 parts by mass of 25% by mass ammonia water was added as a basic substance to obtain an emulsion containing emulsified particles containing copolymer (X).

[0150] Next, an emulsion containing emulsified particles containing bisphenol A epoxy in the amount (parts by mass) shown in Table 4 was prepared as an emulsion containing emulsified particles containing polyepoxy compound (Y). Thereafter, an emulsion containing emulsified particles containing copolymer (X) and an emulsion containing emulsified particles containing polyepoxy compound (Y) were mixed using a homodisper. Through the above steps, an aqueous emulsion (α-14) was obtained in which emulsified particles containing copolymer (X) and emulsified particles containing polyepoxy compound (Y) were dispersed in an aqueous medium (Z).

[0151] (Aqueous emulsion (α-15)) Aqueous emulsion (α-15) in which emulsified particles containing copolymer (X) and emulsified particles containing polyepoxy compound (Y) were dispersed in an aqueous medium (Z) was synthesized in the same manner as aqueous emulsion (α-14), except that the materials shown in Table 4 were used in the amounts (parts by mass) shown in Table 4.

[0152] The amounts of each material used in the synthesis of aqueous emulsions (α-1) to (α-15) are shown in Tables 1 to 4. The "Parts by mass" column shows the amount of each raw material used in parts by mass. The "mol % of copolymer (X)" column shows the ratio of the amount of substance of each raw material to the total amount of substance of the monomer raw materials used in copolymer (X). The "ion-exchanged water" values ​​shown in Tables 1 to 4 indicate the content of ion-exchanged water contained in the synthesized aqueous emulsions (α-1) to (α-15). The "ammonia water" values ​​shown in Tables 1 to 4 are the content of 25% ammonia water by mass, and indicate the total amount of water and ammonia contained in the ammonia water.

[0153] The polyepoxy compounds (Y) shown in Tables 1 to 4 used were as follows: "Aqueous emulsions (α-1) to (α-13)" Bisphenol A type epoxy (epoxy equivalent: 190 g / mol; manufactured by Mitsubishi Chemical Corporation; product name: JER828) "Aqueous emulsions (α-14) to (α-15)" Emulsions containing emulsified particles containing bisphenol A type epoxy (solid content: 47%; content of polyepoxy compound (Y) in the emulsion: 45 to 49% by mass; manufactured by ADEKA Corporation; product name: ADEKA RESIN EM-101-50)

[0154]

[0155]

[0156]

[0157]

[0158] For aqueous emulsions (α-1) to (α-15), the content (mol %) of carboxy groups derived from the ethylenically unsaturated monomer (B1) having two or more carboxy groups out of the total number of carboxy groups derived from the ethylenically unsaturated monomer (B) having a carboxy group, calculated based on the amount of each material used in the synthesis, is shown in Table 5. Furthermore, for aqueous emulsions (α-1) to (α-15), the content of polyepoxy compound (Y) calculated based on the amount of each material used in the synthesis, based on 100 parts of the total amount of the monomer raw materials used in copolymer (X), i.e., based on 100 parts by mass of the total amount of copolymer (X), is shown in Table 5.

[0159]

[0160] 2. Evaluation of aqueous emulsion (α) The aqueous emulsions (α-1) to (α-15) were evaluated for the following items. The results are shown in Table 6. In the following description, aqueous emulsions (α-1) to (α-15) may be collectively referred to as aqueous emulsion (α).

[0161] <2-1. Residual ratio of epoxy groups> The residual ratio of epoxy groups in the aqueous emulsion (α) is determined by the ratio N of the amount of epoxy groups contained in the aqueous emulsion (α) after synthesis. １ The total amount N of epoxy groups contained in the components (including raw materials, initiators, solvents, and other additives) used in the synthesis of the aqueous emulsion (α) [mol / g] ２ It is a ratio to [mol / g].

[0162] The amount of epoxy groups in the aqueous emulsion (α) after synthesis, N １ The measurement of [mol / g] was carried out by the following method. Excess hydrogen chloride was added to the total amount of epoxy groups contained in the components (raw materials) used in the synthesis of aqueous emulsion (α) to react with the epoxy groups. Next, the amount of remaining hydrogen chloride was confirmed by titrating the unreacted hydrogen chloride with potassium hydroxide. During this process, potassium hydroxide is consumed by reaction with acidic components, such as carboxylic acids, contained in aqueous emulsion (α). For this reason, the amount of acidic components was titrated in advance by a blank measurement without using hydrogen chloride, and the results of this measurement were corrected. The specific measurement procedures are as follows (i) to (ii).

[0163] (i) Blank measurement (confirmation of the amount of acidic component) １[g] (5 g in this example) was weighed into a 100 mL Erlenmeyer flask, 25 g of tetrahydrofuran (THF) was added, and the mixture was stirred with a magnetic stirrer to obtain a homogeneous solution. 0.15 mL of a 0.1% by mass cresol red aqueous solution was added to this solution as an indicator. The solution was titrated with a 0.1 M potassium hydroxide / ethanol solution while stirring. The point at which the purple color persisted for 30 seconds after the dropwise addition of the potassium hydroxide / ethanol solution was determined as the equivalence point. The amount of potassium hydroxide / ethanol solution used in the titration was V ＫＯＨ１ [mL]

[0164] (ii) Main measurement: The aqueous emulsion (α) was ２ [g] (5 g in this example) was weighed into a 100 mL Erlenmeyer flask, 25 g of THF was added, and the mixture was stirred with a magnetic stirrer to dissolve. 0.2 M hydrogen chloride / dioxane solution was added to the mixture, and the mixture was stirred for 1 hour to obtain a homogeneous solution. The amount of hydrogen chloride / dioxane solution added here was V ＨＣｌ [mL] (25 mL in this example). 0.15 mL of a 0.1% by mass cresol red aqueous solution was added to this solution as an indicator. The solution was titrated with a 0.1 M potassium hydroxide / ethanol solution while stirring. The point at which the purple color persisted for 30 seconds after the potassium hydroxide / ethanol solution was added was taken as the equivalence point. The amount of potassium hydroxide / ethanol solution used in the titration was V ＫＯＨ２ [mL]

[0165] From the values ​​obtained in (i) and (ii), the amount of epoxy groups per 1 g of the aqueous emulsion (α) N １ [mol / g] was calculated by the following formula (1): １ = (0.2 x V ＨＣｌ / 1000-0.1×V ＫＯＨ２ / 1000) / W ２ + (0.1 x V ＫＯＨ１ / 1000) / W １ …(1)

[0166] The total amount of epoxy groups contained in the components (raw materials) used to synthesize the aqueous emulsion (α) is N ２ [mol / g] is the mass m of each component ｉ[Parts by mass] (i = 1, 2, 3, ...) and epoxy equivalent EP ｉ The N content can be calculated from the N content [g / mol] using the following formula (2). Here, the components used in the synthesis of the aqueous emulsion (α) refer to all the components listed in Tables 1 to 4 as raw materials for the aqueous emulsion (α). ２ =Σ(m ｉ / EP ｉ ) / Σm ｉ …(2)

[0167] In addition, for compounds that do not contain epoxy groups, such as methyl methacrylate and ion-exchanged water, 1 / EP ｉ From the amount of epoxy groups thus determined, the residual rate of epoxy groups in the aqueous emulsion (α) is calculated as 100×N １ / N ２ It is expressed in [mol %].

[0168] <2-2. pH> The pH at 23°C was measured using a pH meter (glass electrode type hydrogen ion concentration indicator HM-30G manufactured by DKK-TOA Corporation).

[0169] 2-3. Non-volatile content concentration 1 g of aqueous emulsion (α) was weighed into an aluminum dish having a diameter of 5 cm and dried at 105°C for 1 hour in a dryer at atmospheric pressure while circulating air. The mass of the residue obtained after drying was measured, and the ratio (mass %) of the mass after drying to the mass of the aqueous emulsion (α) before drying was calculated and used as the non-volatile content concentration.

[0170] <2-4. Viscosity> The viscosity of the aqueous emulsion (α) was measured under the following conditions and with the following apparatus. For the aqueous emulsions (α-14) and (α-15), the viscosity was measured immediately after mixing the emulsified particles containing the copolymer (X) with the emulsified particles containing the polyepoxy compound (Y) (in other words, immediately after producing the aqueous emulsions (α-14) and (α-15)). Temperature: 23°C Measuring instrument: Brookfield viscometer Rotor: No. 1 Rotation speed: 60 rpm

[0171] <2-5. Dispersion stability> The state of the aqueous emulsion (α) immediately after synthesis was visually observed and evaluated according to the following criteria: A (Acceptable): None of aggregation, precipitation, separation, and gelation was observed. B (Unacceptable): At least one of aggregation, precipitation, separation, and gelation was observed.

[0172]

[0173] <2-6. Evaluation Results> As shown in Table 6, all of the aqueous emulsions (α-1) to (α-15) had good dispersibility stability.

[0174] 3. Preparation of Aqueous Resin Compositions Example 1 60 parts by mass of ion-exchanged water, 2.4 parts by mass of a pigment dispersant, 11.1 parts by mass of titanium oxide and 49.3 parts by mass of talc as pigments, 0.5 parts by mass of a thickener, and 1.8 parts by mass of a 10% aqueous solution of sodium nitrite as a primary rust inhibitor were placed in a polypropylene (PP) container and stirred for 10 minutes. 100 parts by mass of aqueous emulsion (α-1) shown in Table 1 was added thereto and stirred for 10 minutes to obtain a liquid first part. Furthermore, the curing agent (β) and curing accelerator (γ) shown in Table 7 were mixed in the ratio shown in Table 7 and stirred for 20 minutes to obtain a liquid second part. The entire amount of the obtained second part was then added to the polypropylene container containing the first part and stirred for 10 minutes using a homodisper to prepare the aqueous resin composition of Example 1.

[0175] (Examples 2 to 11 and Comparative Examples 1 to 5) The aqueous resin compositions of Examples 2 to 11 and Comparative Examples 1 to 5 were synthesized in the same manner as the aqueous resin composition of Example 1, except that the materials shown in Table 7 or Table 9 were used in the amounts (parts by mass) shown in Table 7 or Table 9.

[0176] The materials shown in Tables 7 to 9 are as follows: Pigment dispersant: polycarboxylic acid surfactant, Demol EP (Kao Corporation) Titanium oxide: Typec CR-97 (Ishihara Sangyo Kaisha, Ltd.) Talc: PKP-80 (Fuji Talc Industries Co., Ltd.) Thickener: polyether polyol urethane polymer, Adekanol UH-420 (ADEKA Corporation) Primary rust inhibitor: 10% aqueous sodium nitrite solution Curing agent (β) (polyamine (F)): EH-8051 (trade name: ADEKA Hardener EH-8051, manufactured by ADEKA Corporation). The equivalent weight of active hydrogen reactive with epoxy groups contained in ADEKA Hardener EH-8051 is 180 g / mol.

[0177] In Tables 7 to 9, the "equivalent of active hydrogen relative to epoxy group" in the curing agent (β) is a numerical value indicating the equivalent of active hydrogen contained in the polyamine (F) contained in the curing agent (β) relative to 1 equivalent of epoxy group contained in the aqueous emulsion (α), calculated based on the amount of each material used in producing the aqueous resin composition. The "equivalent of epoxy group" in the curing accelerator (γ) is a numerical value indicating the equivalent (number of moles) of the curing accelerator (γ) relative to 1 equivalent of epoxy group contained in the aqueous emulsion (α), calculated based on the amount of each material used in producing the aqueous resin composition.

[0178] 4. Evaluation of Blending Stability of Aqueous Resin Compositions The blending stability of the aqueous resin compositions was evaluated by the following method using the aqueous resin compositions of Examples 1 to 11 and Comparative Examples 1 to 5. The results are shown in Tables 7 to 9.

[0179] Immediately after preparation, 70 g of the aqueous resin composition was sealed in a 100 mL glass bottle and allowed to stand at 23°C. The glass bottle was opened every hour and a spatula was inserted to check the fluidity of the aqueous resin composition. The time until the aqueous resin composition gelled and lost its fluidity was measured. The blend stability of the aqueous resin composition was evaluated based on the results. Evaluation was performed according to the following criteria. The parenthesized values ​​in the blend stability column of Tables 7 to 9 represent the time from immediately after preparation of the aqueous resin composition until the aqueous resin composition gelled and lost its fluidity, with (>12 h) indicating that the aqueous resin composition did not gel or lose its fluidity even 12 hours after preparation. A (Acceptable): Blend stability for 4 hours or more. B (Unacceptable): Blend stability for less than 4 hours.

[0180] In evaluating the blend stability of an aqueous resin composition, a state in which fluidity has been lost means that, when the aqueous resin composition is visually observed, it is partially or completely gelled (solidified), or that no gelation is observed but the viscosity has increased and spray coating is not possible. A state in which spray coating is not possible means that the aqueous resin composition is not atomized when the aqueous resin composition is air sprayed using a gravity-type spray gun (manufactured by Anest Iwata Corporation, product name: WIDER1-10E1G, nozzle diameter: 1.0 mm) connected to a compressor under conditions of a spray air pressure of 0.3 MPa and an air consumption rate of 75 L / min.

[0181] 5. Evaluation of Rust Prevention Properties of Coating Films Using the aqueous resin compositions of Examples 1 to 11 and Comparative Examples 1 to 5, coating films were formed by the method described below, and the rust prevention properties were evaluated. The results are shown in Tables 7 to 9. The coating films of Examples 1 to 11 and Comparative Examples 1 to 5 were formed by applying the aqueous resin composition to the surface to be coated within one hour after preparing the aqueous resin composition (application was completed within one hour after the end of the mixing step).

[0182] The aqueous resin composition was applied to a cold-rolled steel plate (thickness: 800 μm) (hereinafter referred to as the “substrate”) using an air spray in a coating weight of 280 g / m ２The coating was applied so that the coating film was formed on the surface of the substrate by drying the coated substrate at 23°C for 7 days. This resulted in a rectangular test piece having a coating film on its surface and measuring 70 mm in length and 150 mm in width. The test area was a rectangular area of ​​the coating film on the test piece, measuring 45 mm in length and 125 mm in width. The thickness of the coating film on the test piece was approximately 100 µm.

[0183] An X-shaped incision was made in the coating film, forming a diagonal line of the rectangle forming the test area. The incision was made using a utility knife, extending from the coating film to the substrate. The test specimens with the incision were subjected to a neutral salt spray test (section 4.2.1) in accordance with JIS Z-2371 (2000).

[0184] For each test piece after 1000 hours of the neutral salt spray test, the area occupied by the blister of the coating film in the test area [area %] and the size of the blister [mm] were measured by the method described below, and the rust prevention properties were evaluated.

[0185] That is, the appearance of the test pieces was visually observed and evaluated by touch to check for the presence or absence of areas where swelling had occurred on the coating surface due to storage. As a result, the planar shape of all blistered areas was approximately circular. Therefore, for each blistered area, the planar shape was assumed to be a perfect circle, and the maximum linear distance connecting the outlines of the blistered areas was measured with a ruler, and this result was taken as the diameter. Then, using the diameter of each blistered area, the total area of ​​the blistered areas within the test area was calculated, and the ratio of the blistered area [%] to the area of ​​the test area (the area occupied by the blistered coating in the test area) was determined. Furthermore, the maximum diameter of each blistered area in each test piece was taken as the blister size.

[0186]

[0187]

[0188]

[0189] <6. Evaluation Results> As shown in Tables 7 and 8, the aqueous resin compositions of Examples 1 to 11 containing the aqueous emulsions (α-1) to (α-5), (α-7) to (α-9), (α-11), and (α-14) all had a blend stability evaluation of 4 hours or more, which was good. Furthermore, the coating films made of the cured products of the aqueous resin compositions of Examples 1 to 11 all had blister areas of 35% or less on the test pieces after 1000 hours, which indicated good rust prevention.

[0190] In contrast, as shown in Table 9, the aqueous resin compositions of Comparative Examples 1 and 2 lost fluidity within 3 hours and were inferior in blend stability compared to the aqueous resin compositions of Examples 1 to 11. Furthermore, the coating films made of the cured products of the aqueous resin compositions of Comparative Examples 3 to 5 all had blister areas of 40% or more on the test pieces after 1000 hours, and were inferior in rust prevention compared to the coating films made of the cured products of the aqueous resin compositions of Examples 1 to 11.

[0191] According to the present invention, it is possible to provide an aqueous emulsion that can be used as a material for an aqueous resin composition that has excellent compounding stability and can form a coating film that exhibits good rust prevention properties even when cured at room temperature, an aqueous resin composition set, and a method for producing the aqueous emulsion.

Claims

1. The composition contains a copolymer (X), a polyepoxy compound (Y) having no ethylenically unsaturated bond and having two or more epoxy groups in one molecule, and an aqueous medium (Z), The copolymer (X) contains a structural unit (a) derived from a (meth)acrylic acid ester (A) and a structural unit (b) derived from an ethylenically unsaturated monomer (B) having a carboxy group, the content of the structural unit (a) derived from the (meth)acrylic acid ester (A) in the copolymer (X) is 10 mol % or more and 99.9 mol % or less; the content of the structural unit (b) derived from the ethylenically unsaturated monomer (B) having a carboxy group in the copolymer (X) is 0.1 mol % or more and 20 mol % or less; at least one of the ethylenically unsaturated monomers (B) having a carboxy group is an ethylenically unsaturated monomer (B1) having two or more carboxy groups, a content of carboxy groups of the structural unit (b1) derived from the ethylenically unsaturated monomer (B1) having two or more carboxy groups in the total number of carboxy groups of the structural unit (b) derived from the ethylenically unsaturated monomer (B) having a carboxy group is 5 mol % or more and 75 mol % or less, the content of the polyepoxy compound (Y) is 1.0 part by mass or more and 67 parts by mass or less relative to 100 parts by mass of the total amount of the copolymer (X), An aqueous emulsion containing emulsified particles containing the copolymer (X) and the polyepoxy compound (Y).

2. The aqueous emulsion according to claim 1, comprising emulsified particles containing the copolymer (X) and emulsified particles containing the polyepoxy compound (Y).

3. 3. The aqueous emulsion according to claim 1, wherein the copolymer (X) contains a structural unit (c) derived from an ethylenically unsaturated aromatic compound (C) having a benzene ring and an ethylenically unsaturated bond.

4. In the copolymer (X), the content of the structural unit (a) derived from the (meth)acrylic acid ester (A) is 10 mol % or more and 89.9 mol % or less, The aqueous emulsion according to claim 3 , wherein the content of the structural unit (c) derived from the ethylenically unsaturated aromatic compound (C) is 10 mol % or more and 89.9 mol % or less.

5. The aqueous emulsion according to claim 1 or 2, wherein the at least one of the ethylenically unsaturated monomers (B1) having two or more carboxy groups is maleic acid, itaconic acid, fumaric acid, mesaconic acid, citraconic acid, glutaconic acid, cis-4-cyclohexene-1,2-dicarboxylic acid, 3-butene-1,2,3-tricarboxylic acid, or ethylenetetracarboxylic acid.

6. 3. The aqueous emulsion according to claim 1, wherein at least one of the ethylenically unsaturated monomers (B1) having two or more carboxy groups is an ethylenically unsaturated monomer having two carboxy groups.

7. 3. The aqueous emulsion according to claim 1, wherein at least one of the ethylenically unsaturated monomers (B1) having two or more carboxy groups is maleic acid.

8. 3. The aqueous emulsion according to claim 1, wherein at least one of the polyepoxy compounds (Y) is a bisphenol-type epoxy compound, a hydrogenated bisphenol-type epoxy compound, a diglycidyl ether, a triglycidyl ether, a tetraglycidyl ether, a diglycidyl ester, a triglycidyl ester, or a tetraglycidyl ester.

9. The method includes an emulsion polymerization step of emulsion-polymerizing a monomer raw material including a (meth)acrylic acid ester (A) and an ethylenically unsaturated monomer (B) having a carboxy group in an aqueous medium (Z) in the presence of a polyepoxy compound (Y) having no ethylenically unsaturated bond and having two or more epoxy groups in one molecule, the content of the (meth)acrylic acid ester (A) in the monomer raw material is 10 mol % or more and 99.9 mol % or less, the content of the ethylenically unsaturated monomer (B) having a carboxy group in the monomer raw material is 0.1 mol % or more and 20 mol % or less, at least one of the ethylenically unsaturated monomers (B) having a carboxy group is an ethylenically unsaturated monomer (B1) having two or more carboxy groups, a content of carboxy groups of the ethylenically unsaturated monomer (B1) having two or more carboxy groups in the total number of carboxy groups of the ethylenically unsaturated monomer (B) having a carboxy group is 5 mol % or more and 75 mol % or less, a content of the polyepoxy compound (Y) relative to 100 parts by mass of the monomer raw material of from 1.0 part by mass to 67 parts by mass,

10. 3. An aqueous resin composition comprising the aqueous emulsion (α) according to claim 1 or 2, a curing agent (β), and a curing accelerator (γ).

11. The aqueous resin composition according to claim 10, wherein at least one of the curing agents (β) is a polyamine (F) having an active hydrogen that is reactive with an epoxy group.

12. The aqueous resin composition according to claim 10, wherein at least one of the curing accelerators (γ) is a tertiary aliphatic amine, a tertiary alicyclic amine, or a tertiary heteroaromatic amine.

13. A first agent containing the aqueous emulsion (α) according to claim 1 or claim 2; The aqueous resin composition set is stored separately from a curing agent (β) and a second part containing a curing accelerator (γ).

14. a mixing step of preparing an aqueous resin composition by mixing the first part and the second part of the aqueous resin composition set according to claim 13; and a coating step of applying the aqueous resin composition to a surface to be coated.

15. The method for producing a coating film according to claim 14, further comprising a curing step of curing the aqueous resin composition applied to the surface to be coated at a temperature of 20°C to 40°C.