TW202134358A - Aqueous resin composition, coating film, and method for forming coating film - Google Patents

Abstract

An aqueous resin composition which comprises a specific aqueous resin emulsion ([alpha]), a curing agent ([beta]), and a curing accelerator ([gamma]), wherein the aqueous resin emulsion ([alpha]) comprises a copolymer (X), a polyepoxy compound (Y) having no ethylenically unsaturated bond and having two or more epoxy groups in the molecule, and an aqueous medium (Z), the curing agent ([beta]) comprises a compound having, in the molecule, a functional group (F) having reactivity with epoxy groups, and the curing accelerator ([gamma]) comprises a tertiary amine not having the functional group (F) in the molecule.

Description

Aqueous resin composition, film, and film forming method

The present invention relates to an aqueous resin composition, a coating film, and a method for forming the coating film. This case is based on Special Application No. 2019-218183 filed in Japan on December 2, 2019. Priority is claimed, and its content is cited here.

Generally speaking, surface treatment is applied to the surface of metal products. In particular, metal products used outdoors and metal products that are supposed to be exposed to moisture are often coated to prevent rust.

In the past, coatings containing organic solvents were used in the surface coating of metal products. However, when coating a paint containing an organic solvent on the surface of a metal product, there must be a countermeasure against volatile organic compounds (VOC) for the operator and the surrounding environment. Therefore, instead of coatings containing organic solvents in coatings used for surface coating of metal products, the trend of using water-based coatings has become active.

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

Patent Document 2 describes a composition containing an aqueous dispersion of thermoplastic polymer particles, which absorbs a thermosetting compound having an ethylene oxide group. In addition, Patent Document 2 describes that the polymer particles have a sufficient concentration of anti-aggregation functional groups in order to stabilize the latex against aggregation.

Patent Document 3 describes that by mixing an epoxy emulsion with an emulsion of an acrylate resin, an acrylate resin (acrylic/epoxy latex) absorbing an epoxy compound is formed. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] JP 2011-89092 A [Patent Document 2] JP 2014-65914 A [Patent Document 3] International Publication No. 2017/112018

[The problem to be solved by the invention]

However, the film formed from the cured product of the conventional water-based resin composition has insufficient yield strength of the film. Therefore, in the conventional aqueous resin composition, it is required to increase the yield strength of the film obtained by curing the composition.

The present invention was completed in view of the above circumstances, and its object is to provide an aqueous resin composition that can obtain a cured product having good adhesion to metal materials and high film yield strength. In addition, the object of the present invention is to provide a film having a high yield strength of the film, which includes a cured product of the aqueous resin composition of the present invention. In addition, an object of the present invention is to provide a method for forming a film, which forms a film containing a cured product of the aqueous resin composition of the present invention. [Means to solve the problem]

The constitution of the present invention for achieving the above-mentioned object is as follows [1] to [15]. The first aspect of the present invention is the following water-based resin composition.

[1] An aqueous resin composition comprising an aqueous resin emulsion (α), a hardening agent (β) and a hardening accelerator (γ), The aforementioned aqueous resin emulsion (α) includes: copolymer (X), a polyepoxy compound (Y) having two or more epoxy groups in one molecule without ethylenically unsaturated bonds, and an aqueous medium (Z), The content rate of the polyepoxy compound (Y) is 1-40% by mass relative to the total amount of the copolymer (X) and the polyepoxy compound (Y), The aforementioned copolymer (X) contains a structural unit derived from (meth)acrylate (A) and a structural unit derived from ethylenically unsaturated carboxylic acid (B), The content of the structural unit derived from the (meth)acrylate (A) is 20 to 98% by mass relative to the total amount of the copolymer (X) and the polyepoxy compound (Y), The content of the structural unit derived from the ethylenically unsaturated carboxylic acid (B) is 0.1-10% by mass relative to the total amount of the copolymer (X) and the polyepoxy compound (Y), The aforementioned structural unit derived from (meth)acrylate (A) includes a structural unit derived from hydrophilic (meth)acrylate (A1) with a carbon number of 2 or less in the alcohol-derived part, The content of the structural unit derived from the hydrophilic (meth)acrylate (A1) is 15 to 98% by mass relative to the total amount of the copolymer (X) and the polyepoxy compound (Y), One or both of the aforementioned copolymer (X) and the aforementioned polyepoxy compound (Y) contain a carboxyl group, The aforementioned curing agent (β) contains a compound having a functional group (F) reactive with epoxy groups, The content of the functional group (F) contained in the curing agent (β) is 0.010 equivalent or more and 3.0 equivalent or less with respect to 1 equivalent of epoxy group contained in the aqueous resin emulsion (α), The aforementioned hardening accelerator (γ) contains tertiary amines that do not have functional groups reactive with epoxy groups, The content of the hardening accelerator (γ) is 0.0070 mol or more and 1.5 mol or less with respect to 1 equivalent of epoxy groups contained in the aqueous resin emulsion (α).

The water-based resin composition of the first aspect of the present invention preferably includes the characteristics described in the following [2] to [12]. It is also preferable to combine two or more of these features. [2] The aqueous resin composition according to [1], wherein the (meth)acrylate (A) contains an alkyl (meth)acrylate. [3] The aqueous resin composition as described in [1] or [2], wherein the ethylenically unsaturated carboxylic acid (B) is composed of α, β-unsaturated monocarboxylic acid and α, β-unsaturated dicarboxylic acid And at least one of the group of vinyl compounds containing carboxyl groups.

[4] The aqueous resin composition according to any one of [1] to [3], wherein the polyepoxy compound (Y) is composed of a bisphenol type epoxy compound, a hydrogenated bisphenol type epoxy compound, and a bicyclic epoxy compound. At least one selected from oxypropyl ether, triglycidyl ether, tetraglycidyl ether, diglycidyl ester, triglycidyl ester, and tetraglycidyl ester.

[5] The aqueous resin composition according to any one of [1] to [4], wherein the copolymer (X) comprises the structural unit derived from the (meth)acrylate (A) and the ethylene derived The structural unit of an unsaturated carboxylic acid (B). [6] The aqueous resin composition according to any one of [1] to [4], wherein the copolymer (X) contains an ethylenically unsaturated aromatic compound derived from a benzene ring and an ethylenically unsaturated bond ( C) The structural unit. [7] The aqueous resin composition according to [6], wherein the ethylenically unsaturated aromatic compound (C) is an aromatic vinyl compound.

[8] The water-based resin composition according to any one of [1] to [7], wherein the curing agent (β) comprises an amino group, a carboxyl group, and a mercapto group selected from unsubstituted or having only one substituent. At least any one of the groups. [9] The aqueous resin composition according to any one of [1] to [8], wherein the hardening accelerator (γ) is selected from the group consisting of tertiary aliphatic amines, tertiary alicyclic amines, and tertiary heteroaromatics At least one compound in the group of amines.

[10] The aqueous resin composition according to any one of [1] to [9], wherein the aqueous resin emulsion (α) is in the aqueous medium (Z) and becomes a structural unit of the copolymer (X) The monomer is an emulsion that is emulsified and polymerized in the presence of the aforementioned polyepoxy compound (Y). [11] The aqueous resin composition according to any one of [1] to [10], wherein the content of the carboxyl group in the total amount of the copolymer (X) and the polyepoxy compound (Y) is 0.10× 10 ^-4 mol/g or more. [12] The aqueous resin composition according to any one of [1] to [11], wherein the epoxy group content in the total amount of the copolymer (X) and the polyepoxy compound (Y) is 0.50×10 ^-4 mol/g or more.

The second aspect of the present invention is the following cured product. [13] A coating film comprising a cured product of the aqueous resin composition as described in any one of [1] to [12]. The third aspect of the present invention is the method of forming the film described below. [14] A method for forming a coating film, which comprises a coating step of applying the aqueous resin composition as described in any one of [1] to [12] to a surface to be coated, and applying the above-mentioned coated aqueous resin composition The hardening step of the hardening of the resin composition. [Effects of the invention]

According to the present invention, it is possible to provide an aqueous resin composition which can obtain a cured product having good adhesion to metal materials and high film yield strength. Furthermore, according to the present invention, it is possible to provide a film having a high yield strength of the film, which includes a cured product of the aqueous resin composition of the present invention. In addition, according to the present invention, it is possible to provide a method for forming a film, which forms a film including a cured product of the aqueous resin composition of the present invention.

[The form of implementing the invention]

Hereinafter, the aqueous resin composition, film, and film forming method of the present invention will be described in detail. In addition, the present invention is not limited only by the embodiments shown below. For example, the present invention may be added, omitted, replaced, changed, etc., in terms of number, type, position, amount, ratio, material, structure, etc., within the scope not departing from the spirit of the present invention.

Here, the following words and phrases used in this manual are explained. "(Meth)acrylate" means acrylate or methacrylate. In addition, "(meth)acrylic acid" means acrylic acid or methacrylic acid. "Ethylene unsaturated bond" means a double bond between carbon atoms other than carbon atoms forming an aromatic ring. The "weight average molecular weight" is a standard polystyrene conversion value measured by gel permeation chromatography (GPC: gel permeation chromatography).

In a polymer using a compound having an ethylenically unsaturated bond, the so-called structural unit derived from the aforementioned compound having an ethylenically unsaturated bond is the chemical structure of the part other than the ethylenically unsaturated bond in the compound and the aforementioned The chemical structure of the part other than the part corresponding to the ethylenically unsaturated bond of the aforementioned structural unit may mean the same unit. The ethylenically unsaturated bond of the aforementioned compound can be changed to a single bond when forming a polymer. For example, in the polymer of methyl methacrylate, the structural unit derived from methyl methacrylate is represented by -CH ₂ -C(CH ₃ )(COOCH ₃ )-.

Furthermore, in the case of a polymer of a compound having an ionic functional group and an ethylenically unsaturated bond, for example, the structural unit (b) derived from an ethylenically unsaturated carboxylic acid (B) described later, regarding the polymer having a carboxyl group The structural unit of the ionic functional group may be ion-exchanged with a part of the aforementioned functional group, or may not be ion-exchanged, and may be a structural unit derived from the same ionic compound. For example, _{the structural unit represented by -CH 2} -C(CH ₃ )(COONa)- can also be considered as a structural unit derived from methacrylic acid.

In addition, with regard to a compound having a plurality of independent ethylenically unsaturated bonds, as a structural unit of the polymer of the aforementioned compound, one or more ethylenic unsaturated bonds may remain in the structural unit. The plural independent ethylenically unsaturated bonds can mean plural ethylenically unsaturated bonds that do not form a conjugated diene with each other. For example, in the case of a polymer of divinylbenzene, the structural unit derived from divinylbenzene may be a structure that does not have ethylenically unsaturated bonds (corresponding to the part of the two ethylenically unsaturated bonds of divinylbenzene) Both are incorporated into the polymer chain), or may have a structure with one ethylenically unsaturated bond (only one of the ethylenically unsaturated bonds is incorporated into the polymer chain) .

The so-called "hardening" means that the molecules contained in the raw material are bonded to each other through a chemical reaction to form a polymer with a network structure. The "coating film", unless otherwise specified, means a coating film formed by applying the aqueous resin composition of the present embodiment, drying the medium, and curing the resin component at the same time.

＜1. Water-based resin composition＞ The aqueous resin composition of this embodiment includes an aqueous resin emulsion (α), a curing agent (β), and a curing accelerator (γ). The aqueous resin composition system of this embodiment is manufactured by mixing an aqueous resin emulsion (α), a hardening agent (β), and a hardening accelerator (γ) as described later.

[1-1. Water-based resin emulsion (α)] The aqueous resin emulsion (α) contains a copolymer (X), a polyepoxy compound (Y) having two or more epoxy groups in one molecule without an ethylenically unsaturated bond, and an aqueous medium (Z). The aqueous resin emulsion (α) is an emulsion formed by emulsifying and polymerizing the monomer that becomes the structural unit of the copolymer (X) in the presence of the polyepoxy compound (Y) in the aqueous medium (Z). This is to obtain a coating film with high strength and high elongation when it is mixed with a curing agent (β) described later and cured.

＜1-1-1. Copolymer (X)＞ The copolymer (X) has a structural unit (a) derived from a (meth)acrylate (A) and a structural unit (b) derived from an ethylenically unsaturated carboxylic acid (B). Furthermore, the structural unit (a) derived from the (meth)acrylate (A) contains the structural unit (a1) derived from the hydrophilic (meth)acrylate (A1).

The copolymer (X) may be composed only of the structural unit (a) and the structural unit (b) (as the copolymer (X1)). The copolymer (X) may also be a structural unit (c) having a structural unit (a), a structural unit (b), and a structural unit (c) derived from an ethylenically unsaturated aromatic compound (C) having a benzene ring and an ethylenically unsaturated bond (As a copolymer (X2)). The copolymer (X2) may be composed of only the structural units (a) to (c). The copolymer (X) may have a structural unit (d) (a structural unit derived from another monomer (D)) other than the aforementioned structural units (a) to (c).

The amount of the copolymer (X) contained in the aqueous resin emulsion (α) can be arbitrarily selected, but it is preferably 10% by mass or more, and more preferably 20% by mass or more relative to the total amount of the aqueous resin emulsion (α). More preferably, it is 25% by mass or more. The amount of the copolymer (X) contained in the aqueous resin emulsion (α) can be arbitrarily selected, but relative to the total amount of the aqueous resin emulsion (α), it is preferably 60% by mass or less, more preferably 50% by mass or less , Particularly preferably 40% by mass or less. However, it is not limited by these examples.

With respect to the total amount of the copolymer (X) and the polyepoxy compound (Y) described later, the content of the copolymer (X) is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 65% by mass above. The content of the copolymer (X) is preferably 99% by mass or less, more preferably 94% by mass or less, and particularly preferably 88% by mass relative to the total amount of the copolymer (X) and the polyepoxy compound (Y) described later. the following.

[(Meth)acrylate (A)] As the (meth)acrylate (A), one or more types can be arbitrarily selected, but it is preferably composed of an alkyl (meth)acrylate. As an example of (meth)acrylic acid alkyl ester, it is more preferable that it is a (meth)acrylic acid alkyl ester which has a C1-C18 linear, branched, or cyclic alkyl group. Specific examples include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and tertiary butyl (meth)acrylate. , Cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate and isobornyl (meth)acrylate, etc. These systems can be used singly or in combination of two or more types.

In the example of (meth)acrylate (A), the example of the hydrophilic (meth)acrylate (A1) mentioned later may also be included. Furthermore, the (meth)acrylate system which has a carboxyl group is not contained in (meth)acrylate (A), but is contained in the ethylenically unsaturated carboxylic acid (B) mentioned later.

The (meth)acrylate (A) preferably contains a compound with low hydrophilicity. This is to improve the rust resistance of the coating film. For the same reason, as the (meth)acrylate (A), (meth)acrylate having an epoxy group may be included.

Examples of the (meth)acrylate having an epoxy group include glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, and 4-hydroxy (meth)acrylate Butyl glycidyl ether, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate and 3,4 (meth)acrylate -Epoxy cyclohexyl propyl ester and the like. The structural unit (a) may include structural units derived from only one type of these compounds, or may include structural units derived from two or more types. Furthermore, among these compounds, the structural unit (a) preferably includes a structural unit derived from glycidyl (meth)acrylate.

In addition, the (meth)acrylate (A) may be a (meth)acrylate which is not any one of the alkyl (meth)acrylate and the compound having an epoxy group. As such (meth)acrylate, (meth)acrylate etc. which have a hydroxyl group are mentioned.

Examples of the (meth)acrylate having a hydroxyl 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, (meth)acrylate 8 -Hydroxyoctyl ester, 12-hydroxylauryl (meth)acrylate. Moreover, the mono(meth)acrylate of polyalkylene glycols, such as the mono(meth)acrylate of polyethyleneglycol and the mono(meth)acrylate of polypropylene glycol, etc. can also be mentioned. These (meth)acrylates which have a hydroxyl group may use only 1 type, and may use 2 or more types together.

The content rate of the structural unit (a) derived from (meth)acrylate (A) with respect to the total amount of the copolymer (X) and the polyepoxy compound (Y) is 20% by mass or more. This is to improve the dispersion stability of the monomer of the copolymer (X) and the polyepoxy compound (Y) in the method for producing the aqueous resin emulsion described later. From this viewpoint, the content of the structural unit (a) derived from (meth)acrylate (A) is preferably 35% by mass or more relative to the total amount of the copolymer (X) and the polyepoxy compound (Y) , More preferably 45% by mass or more, particularly preferably 60% by mass or more.

Relative to the total amount of the copolymer (X), the content of the structural unit (a) derived from the (meth)acrylate (A) is preferably 40% by mass or more, more preferably 60% by mass or more, and particularly preferably 75% by mass or more, particularly preferably 90% by mass or more. This is because if it is in the aforementioned range, the water swelling resistance rate of the film produced using the aqueous resin composition can be further reduced. The content of the structural unit (a) derived from the (meth)acrylate (A) relative to the total amount of the copolymer (X) is preferably 99% by mass or less.

Moreover, in this embodiment, the content rate of the structural unit derived from a compound can mean the ratio (mass %) of the said compound used. For example, relative to the total amount of the copolymer (X) and the polyepoxy compound (Y), the content rate of the structural unit (a) derived from the (meth)acrylate (A) can mean relative to the aforementioned total amount In other words, the ratio (mass%) of the (meth)acrylate (A) used in the production of the copolymer (X).

Furthermore, when the copolymer (X) is composed of only the structural unit (a) and the structural unit (b), that is, the copolymer (X1), based on the same viewpoint of improving dispersion stability, the following ratio is preferred . That is, with respect to the total amount of the copolymer (X1) and the polyepoxy compound (Y), the content of the structural unit (a) derived from the (meth)acrylate (A) is more preferably 50% by mass or more, Particularly preferred is 60% by mass or more. The preferable upper limit of this content rate is the same as that of copolymer (X).

The content rate of the structural unit (a) derived from the (meth)acrylate (A) with respect to the total amount of the copolymer (X) and the polyepoxy compound (Y) is 98% by mass or less. This is because if it does not exceed 98% by mass, the dispersion stability of the aqueous resin emulsion does not decrease. From this viewpoint, the content of the structural unit (a) derived from (meth)acrylate (A) is preferably 92% by mass or less relative to the total amount of the copolymer (X) and the polyepoxy compound (Y) , More preferably 87% by mass or less.

Furthermore, the copolymer (X) has a structural unit (a), a structural unit (b), and a structural unit (c). When the copolymer (X) is the copolymer (X2), from the same viewpoint, the following ratio is preferable. Relative to the total amount of the copolymer (X) and the polyepoxy compound (Y), the content of the structural unit (a) derived from the (meth)acrylate (A) is more preferably 75% by mass or less, particularly preferably 65% by mass or less. The preferable lower limit of this content rate is the same as that of copolymer (X).

[Hydrophilic (meth)acrylate (A1)] The aforementioned structural unit derived from (meth)acrylate (A) includes a structural unit derived from hydrophilic (meth)acrylate (A1).

Hydrophilic (meth)acrylate (A1) has a (meth)acryloyloxy group (CH ₂ =CR-COO-, R represents hydrogen or methyl), and the part derived from alcohol is (meth)acrylic acid (Meth)acrylates in which the number of carbon atoms in the part other than the oxy group is 2 or less. The number of carbon atoms in the portion other than the propyleneoxy group may be 1 or 2, for example.

Examples of the hydrophilic (meth)acrylate (A1) include methyl (meth)acrylate, ethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and the like. The hydrophilic (meth)acrylate (A1) is an alkyl (meth)acrylate whose carbon number of the alcohol-derived part is preferably 2 or less, more preferably methyl methacrylate.

The content rate of the structural unit (a1) derived from the hydrophilic (meth)acrylate (A1) relative to the total amount of the copolymer (X) and the polyepoxy compound (Y) is 15% by mass or more. This is because, as described above, if the content of the hydrophilic (meth)acrylate is small, when the aqueous resin emulsion (α) is mixed with the polyamine-containing hardener, the gelation will progress quickly.

The content of the structural unit (a1) derived from the hydrophilic (meth)acrylate (A1) relative to the total amount of the copolymer (X) and the polyepoxy compound (Y) is 15% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, and particularly preferably 40% by mass or more. This is to improve the water resistance and rust resistance of the cured coating film. The aforementioned content rate may be 45% by mass or more or 50% by mass or more.

With respect to the total amount of the copolymer (X) and the polyepoxy compound (Y), the upper limit of the content rate of the structural unit (a1) derived from the hydrophilic (meth)acrylate (A1) is the same as that derived from the (methyl) ) The upper limit of the content rate described in the structural unit (a) of the acrylate (A) is the same. That is, the aforementioned upper limit is 98% by mass or less, preferably 92% by mass or less, and more preferably 87% by mass or less. However, when the below-mentioned polyepoxy compound (Y) is a hydrophobic compound such as a bisphenol type epoxy compound, a hydrogenated bisphenol type epoxy compound, a phenol novolak type epoxy compound, etc., the structure occupied by the structural unit (a) The ratio of the unit (a1) is preferably 90% by mass or less, more preferably 80% by mass or less, and particularly preferably 70% by mass or less. This is to increase the affinity between the copolymer (X) and the polyepoxy compound (Y).

[Ethylene Unsaturated Carboxylic Acid (B)] The ethylenically unsaturated carboxylic acid (B) is a compound having an ethylenically unsaturated bond and a carboxyl group. The ethylenically unsaturated carboxylic acid (B) preferably contains a monoalkyl ester of α, β-unsaturated monocarboxylic acid, α, β-unsaturated dicarboxylic acid, α, β-unsaturated dicarboxylic acid, and a carboxyl group. At least one of the group consisting of vinyl compounds, more preferably the group consisting of α,β-unsaturated monocarboxylic acids, α,β-unsaturated dicarboxylic acids and vinyl compounds containing carboxyl groups At least one of them. Examples of α,β-unsaturated mono- or dicarboxylic acids include acrylic acid, methacrylic acid, crotonic acid, citraconic acid, itaconic acid, maleic acid, maleic anhydride, and fumaric acid. Examples of the carboxyl group-containing vinyl compound include (meth)acrylate monohydroxyethyl phthalate, (meth)acrylate monohydroxypropyl oxalate, and the like.

The structural unit (b) may be a structural unit derived from only one type of these compounds, or may include a structural unit derived from two or more types. Among these compounds, the ethylenically unsaturated carboxylic acid (B) preferably contains a compound having a (meth)acryloyl group and a carboxyl group, or is composed only of a compound having a (meth)acryloyl group and a carboxyl group. become. As the ethylenically unsaturated carboxylic acid (B), it is also preferable to include (meth)acrylic acid or to be composed of (meth)acrylic acid only. The structural unit (b) is preferably composed only of a structural unit derived from a compound having a (meth)acryloyl group and a carboxyl group, and more preferably contains a structural unit derived from (meth)acrylic acid.

The content rate of the structural unit (b) derived from the ethylenically unsaturated carboxylic acid (B) with respect to the total amount of the copolymer (X) and the polyepoxy compound (Y) is 0.1% by mass or more. This is to improve the dispersion stability of the aqueous resin emulsion (α). From this viewpoint, the content of the structural unit (b) derived from the ethylenically unsaturated carboxylic acid (B) is preferably 0.3% by mass or more relative to the total amount of the copolymer (X) and the polyepoxy compound (Y) , More preferably 0.5% by mass or more. The aforementioned content rate may be 0.8% by mass or more or 1.0% by mass or more. The content rate of the structural unit (b) derived from the ethylenically unsaturated carboxylic acid (B) with respect to the total amount of the copolymer (X) and the polyepoxy compound (Y) is 10% by mass or less. This is to prevent the copolymer (X) from turning into a gel state in a high temperature environment, and to improve the high temperature stability of the aqueous resin emulsion (α). From this viewpoint, the content of the structural unit (b) derived from the ethylenically unsaturated carboxylic acid (B) is preferably 7 mass% or less relative to the total amount of the copolymer (X) and the polyepoxy compound (Y) , More preferably 5% by mass or less. The aforementioned content rate may be 4% by mass or less or 3% by mass or less.

Furthermore, relative to the total amount of the copolymer (X), the content of the structural unit (b) derived from the ethylenically unsaturated carboxylic acid (B) is preferably 0.2% by mass or more, more preferably 0.5% by mass or more, especially Preferably, it is 0.8% by mass or more. The content of the structural unit (b) derived from the ethylenically unsaturated carboxylic acid (B) relative to the total amount of the copolymer (X) is preferably 12% by mass or less, more preferably 8% by mass or less, and particularly preferably 5% by mass or less, particularly preferably 3% by mass or less.

[Ethylene Unsaturated Aromatic Compound (C)] The ethylenically unsaturated aromatic compound (C) is not equivalent to any of (meth)acrylate (A) and ethylenically unsaturated carboxylic acid (B), and is a compound having a benzene ring and an ethylenically unsaturated bond . The ethylenically unsaturated aromatic compound (C) is preferably an aromatic vinyl compound.

Examples of the aromatic vinyl compound of the ethylenically unsaturated aromatic compound (C) include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, and α-methyl Styrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tertiary butylstyrene, tertiary butoxystyrene, vinyl toluene, divinyl toluene, Vinyl naphthalene, monochlorostyrene, dichlorostyrene, monobromostyrene, dibromostyrene, tribromostyrene, fluorostyrene, styrene sulfonic acid and its salts, α-methylstyrene sulfonic acid and Its salt, p-hydroxystyrene, m-hydroxystyrene, o-hydroxystyrene, p-isopropenyl phenol, m-isopropenyl phenol and o-isopropenyl phenol, etc. The structural unit (c) may be only one type derived from these compounds, or may include a structural unit derived from two or more types. Among these, the structural unit (c) preferably includes a structural unit derived from a hydrocarbon, and particularly preferably a structural unit derived from styrene.

When the copolymer (X) contains the structural unit (c) derived from the ethylenically unsaturated aromatic compound (C), that is, the copolymer (X) is the copolymer (X2), as opposed to the copolymer (X2) and the polycyclic The content of the structural unit (c) of the total amount of the oxygen compound (Y) is preferably 5% by mass or more. This is to improve the water resistance of the coating film. From this viewpoint, the content rate of the structural unit (c) is preferably 10% by mass or more, and more preferably 15% by mass or more with respect to the total amount of the copolymer (X2) and the polyepoxy compound (Y). The aforementioned content rate may be 18% by mass or more, 20% by mass or more, or 23% by mass or more.

When the copolymer (X) is the copolymer (X2), the content of the structural unit (c) is preferably 50% by mass or less with respect to the total amount of the copolymer (X2) and the polyepoxy compound (Y). This is to improve the weather resistance of the coating film. From this viewpoint, the content of the structural unit (c) is more preferably 40% by mass or less, and particularly preferably 35% by mass or less relative to the total amount of the copolymer (X2) and the polyepoxy compound (Y). The aforementioned content rate may be 33% by mass or less, 30% by mass or less, or 28% by mass or less.

Relative to the total amount of the copolymer (X2), the content of the structural unit (c) is preferably 5% by mass or more, more preferably 15% by mass or more, and particularly preferably 25% by mass or more. Relative to the total amount of the copolymer (X2), the content of the structural unit (c) is preferably 55% by mass or less, more preferably 45% by mass or less, and particularly preferably 35% by mass or less.

[Other monomers (D)] Other monomers (D) are not equivalent to (meth)acrylate (A), ethylenically unsaturated carboxylic acid (B), and ethylenically unsaturated aromatic compound (C), and are The compound used in the synthesis of the copolymer (X) is a compound with an ethylenically unsaturated bond that can be copolymerized. Examples of other monomers (D) include conjugated diene compounds, maleimide compounds, vinyl ether compounds, allyl ether compounds, dialkyl esters of unsaturated dicarboxylic acids, and cyano groups. The vinyl compound and so on.

As the aforementioned conjugated diene compound, for example, 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3 Butadiene, chloroprene (2-chloro-1,3-butadiene), etc. Only one type of these conjugated diene compounds may be used, or two or more types may be used in combination.

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 Amine, N-(2,6-dimethylphenyl)maleimide, N-(2,6-diethylphenyl)maleimide, N-(2-methoxyphenyl) )Maleimide, N-benzylmaleimide, N-(4-hydroxyphenyl)maleimide, N-naphthylmaleimide, N-cyclohexylmaleimide Amine etc. These maleimine compounds may be used alone or in combination of two or more kinds.

Examples of the aforementioned vinyl ether compounds include alkyl vinyl ethers such as methyl vinyl ether and ethyl vinyl ether, and hydroxyl-containing alkyl vinyl ethers in which a part of hydrogen atoms are substituted with hydroxyl groups.

Examples of the aforementioned allyl ether compounds include allyl alkyl ethers such as allyl methyl ether or allyl ethyl ether, and hydroxyl-containing allyl alkane in which a part of hydrogen atoms are substituted with hydroxyl groups. Base ether, allyl glycidyl ether, etc.

Examples of dialkyl esters of the aforementioned unsaturated dicarboxylic acids include maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, maleic anhydride, itaconic anhydride, citraconic anhydride, and tetrahydro Dialkyl esters of unsaturated dicarboxylic acids such as phthalic anhydride. Only one type of these dialkyl esters may be used, or two or more types may be used in combination. Only one type of these unsaturated compounds may be used, or two or more types may be used in combination.

Examples of the vinyl compound having a cyano group include acrylonitrile, methacrylonitrile, α-ethacrylonitrile, α-isopropylacrylonitrile, α-chloroacrylonitrile, and α-fluoroacrylonitrile. Only one type of these cyano group-containing vinyl monomers may be used, or two or more types may be used in combination.

＜1-1-2. Polyepoxy compound (Y)＞ The polyepoxy compound (Y) is a compound having two or more epoxy groups in one molecule that does not have an ethylenically unsaturated bond.

The polyepoxy compound (Y) is preferably composed of a bisphenol type epoxy compound, a hydrogenated bisphenol type epoxy compound, a diglycidyl ether, a triglycidyl ether, a tetraglycidyl ether, and a diepoxide. At least one selected from propyl ester, triglycidyl ester, and tetraglycidyl ester.

Examples of compounds having two or more epoxy groups in one molecule include diepoxypropyl ether of bisphenol A, diepoxypropyl ether of hydrogenated bisphenol A, and diepoxy of bisphenol F Propyl ether, diglycidyl ether of hydrogenated bisphenol F, glycerin polyglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether Ether, diglycidyl ester of phthalic acid, 1,4-cyclohexane dimethanol diglycidyl ether, 1,3-cyclohexane dimethanol diglycidyl ether and hexahydro o-benzene Diglycidyl dicarboxylic acid etc. One type of these compounds may be included, or two or more types may be included.

The aforementioned polyepoxy compound (Y) is more preferably a bisphenol type epoxy compound or a hydrogenated bisphenol type epoxy compound, particularly preferably a bisphenol A type epoxy compound, a hydrogenated bisphenol A type epoxy compound, and more preferably Bisphenol A type epoxy compound. This is to further improve the water resistance and rust resistance of the cured coating film.

The weight average molecular weight of the polyepoxy compound (Y) is not particularly limited, but is preferably 1000 or less, more preferably 800 or less, and particularly preferably 500 or less. It can be an emulsion with improved compatibility of the polyepoxy compound (Y) with the copolymer (X), and excellent dispersion stability and storage stability. The aforementioned lower limit of molecular weight can be arbitrarily selected, for example, it can be 200 or 300, but is not limited by these.

The epoxy equivalent of the polyepoxy compound (Y) (the mass of the polyepoxy compound (Y) per 1 mol of epoxy groups) is preferably 500 g/mol or less, more preferably 350 g/mol or less, and particularly preferably 250 g/mol Below, it is especially preferable that it is 200 g/mol or less. This is to increase the strength of the coating film formed by curing the aqueous resin composition described later. The lower limit of the epoxy equivalent weight can be arbitrarily selected. For example, it can be 70 g/mol or more, or 120 g/mol or more, but it is not limited by these examples.

The content rate of the polyepoxy compound (Y) is 1% by mass or more with respect to the total amount of the copolymer (X) and the polyepoxy compound (Y). This is to harden the water-based resin composition to obtain a coating film with excellent rust resistance. Based on this point of view, the content of the polyepoxy compound (Y) is preferably 5% by mass or more, more preferably 8% by mass or more relative to the total amount of the copolymer (X) and the polyepoxy compound (Y), especially Preferably, it is 10% by mass or more. If necessary, it may be 12% by mass or more or 20% by mass or more. The content rate of the polyepoxy compound (Y) is 40% by mass or less with respect to the total amount of the copolymer (X) and the polyepoxy compound (Y). This is to obtain an aqueous resin emulsion (α) with high dispersion stability. From this viewpoint, the content of the polyepoxy compound (Y) is preferably 35% by mass or less, and more preferably 30% by mass or less relative to the total amount of the copolymer (X) and the polyepoxy compound (Y).

The amount of the polyepoxy compound (Y) contained in the aqueous resin emulsion (α) is preferably 1% by mass or more, more preferably 3% by mass or more, with respect to the total amount of the aqueous resin emulsion (α) 4% by mass or more. The amount of the polyepoxy compound (Y) contained in the aqueous resin emulsion (α) is preferably 30% by mass or less, more preferably 20% by mass or less, with respect to the total amount of the aqueous resin emulsion (α) 15% by mass or less.

＜1-1-3. Aqueous medium (Z)＞ As the aqueous medium (Z), it can be arbitrarily selected, and water is preferably used. However, as long as the dispersion stability of the copolymer (X) and the polyepoxy compound (Y) is not impaired, for example, a water-soluble solvent added to water can be used as the aqueous medium (Z). As a hydrophilic solvent added to water, it can select arbitrarily, methanol, ethanol, N-methylpyrrolidone, etc. are mentioned.

The amount of the aqueous medium (Z) in the aqueous resin emulsion (α) can be selected as needed, but is preferably 20% by mass or more, more preferably 30% by mass or more, and particularly preferably 40% by mass or more. The amount of the aqueous medium (Z) in the aqueous resin emulsion (α) can be selected as needed, but is preferably 80% by mass or more, and more preferably 70% by mass or more. The aforementioned concentration may also be 50 to 70% by mass or 55 to 65% by mass.

＜1-1-4. Production method of water-based resin emulsion (α)＞ The method for producing the aqueous resin emulsion (α) of this embodiment can be achieved by including (meth)acrylate (A) and ethylenically unsaturated carboxylic acid (B) in the presence of polyepoxy compound (Y) The monomer (that is, the monomer constituting the copolymer (X)) is emulsified and polymerized in the aqueous medium (Z). By the above-mentioned production method of this embodiment using this method, it is considered that an aqueous resin emulsion (α) in which the polyepoxy compound (Y) is uniformly dispersed in the particles of the produced copolymer (X) can be obtained. Here, the so-called "homogeneous existence" does not necessarily require that the copolymer (X) and the polyepoxy compound (Y) are compatible, as long as the copolymer (X) particles are on either the center side or the surface side, the polycyclic ring The domain of the oxygen compound (Y) only needs to be present in an unbiased manner. As a specific emulsification polymerization method, a method of adding each component including a monomer in a batch, a method of polymerizing each component while continuously feeding, etc. can be used. Stirring is preferably performed during the polymerization reaction.

The content of each raw material in the total raw materials used in the production of the aqueous resin emulsion (α) is the same as the content of the raw material-derived structural unit or compound in the aqueous resin emulsion (α).

The aforementioned polymerization is preferably carried out at an arbitrarily selected temperature, for example, at a temperature of 30 to 90°C, more preferably at a temperature of 40 to 80°C, and particularly preferably at a temperature of 40 to 70°C. This is to prevent the carboxyl group contained in the monomer from reacting with the epoxy group contained in the polyepoxy compound (Y).

The emulsifier used in the emulsion polymerization can be arbitrarily selected, for example, polyoxyalkylene alkyl ether, polyoxyalkylene alkyl phenol ether, polyoxyalkylene fatty acid ester, polyoxyalkylene sorbitan fatty acid ester, etc. Nonionic surfactants, alkyl sulfate ester salts, alkyl benzene sulfonate, alkyl sulfosuccinate, alkyl diphenyl ether disulfonate, polyoxyalkylene alkyl sulfate, polyoxyalkylene Anionic surfactants such as alkyl phosphates. These can be used individually by 1 type, and can also be used in combination of 2 or more types. As these emulsifiers, alkylbenzene sulfonate is preferred, and sodium dodecylbenzene sulfonate is more preferred.

In the emulsion polymerization, a polymerization initiator is preferably used. As the polymerization initiator, for example, peroxide is preferably used. The peroxide used as the polymerization initiator includes, for example, persulfates such as potassium persulfate and ammonium persulfate, and hydrogen peroxide. In addition, a redox initiator in which a peroxide and a reducing agent are used in combination can also be used. As a reducing agent, sodium formaldehyde sulfonate, ascorbic acid, sulfite, tartaric acid or its salt, etc. are mentioned. In addition, alcohols and mercaptans can also be used as chain transfer agents if necessary.

＜1-1-5. Characteristics of water-based resin emulsion (α)＞ [PH of water-based resin emulsion (α)] The pH of the aqueous resin emulsion (α) is preferably 2-10, more preferably 5-9. If the pH is within this range, the mechanical stability and chemical stability of the aqueous resin emulsion (α) can be improved. The pH is a value measured at a liquid temperature of 25°C using a pH meter with a hydrogen ion concentration indicator using a glass electrode as the standard electrode. For example, during or after the emulsion polymerization, the pH can be adjusted by adding an alkaline substance to the aqueous resin emulsion (α). Examples of alkaline substances used for pH adjustment include ammonia, triethylamine, ethanolamine, and caustic soda. These can be used individually by 1 type, and can also be used in combination of 2 or more types.

[Non-volatile content concentration of water-based resin emulsion (α)] The non-volatile content concentration of the aqueous resin emulsion (α) is preferably 10 to 65% by mass, more preferably 15 to 60% by mass, and particularly preferably 20 to 55% by mass. The aforementioned concentration may also be 30-50% by mass or 35-45% by mass. The concentration of non-volatile matter in the water-based resin emulsion (α) can be considered after the mixing step of the water-based resin emulsion (α), hardener (β), hardening accelerator (γ), etc., or the work in the coating step of the water-based resin composition. Sex, and appropriate decision. The concentration of non-volatile matter in the aqueous resin emulsion (α) can be appropriately adjusted by adjusting the addition amount of the aqueous medium (Z).

In addition, the non-volatile content concentration of the aqueous resin emulsion (α) is obtained by the method shown below. In an aluminum dish with a diameter of 5 cm, 1 g of the aqueous resin emulsion (α) was weighed and dried at 105°C for 1 hour in a desiccator under atmospheric pressure while circulating air, and then the mass of the resulting residue was measured. The ratio (mass %) of the measured residual mass relative to the mass of the aqueous resin emulsion (α) before drying was determined as the nonvolatile content concentration of the aqueous resin emulsion (α).

[Viscosity of water-based resin emulsion (α)] In this embodiment, the viscosity of the aqueous resin emulsion (α) is measured at 23°C. The viscosity of the water-based resin emulsion (α) was measured using a B-type viscometer at a rotation speed of 60 rpm, and the measured value was measured by selecting a rotor that meets the viscosity of the water-based resin emulsion. For example, when the viscosity of the aqueous resin emulsion (α) is about several mPa･s to several hundreds of mPa･s, use rotor No.1 for measurement. The viscosity can be, for example, 0.1 to 300 mPa･s, 1 to 100 mPa･s, 3 to 50 mPa･s, or 5 to 25 mPa･s.

[Glass transition point of copolymer (X)] The glass transition point Tg of the copolymer (X) is calculated based on the glass transition point of the homopolymer of each monomer used in the synthesis of the copolymer (X). The specific method of calculating the glass transition point Tg of the copolymer (X) is from _{the glass transition point Tg i of the homopolymer of the monomer M i} (i=1,2,3...,) used as the raw material and all the monomers The mass fraction X _i of the monomer i (ΣX _i (all monomers) = 1) is calculated by the following formula (1). In formula (1), Tg and Tg _i are calculated by absolute temperature (K).

The glass transition point Tg of the copolymer (X) is preferably -30°C (243K) or higher. This is to increase the strength of the coating film. From this point of view, the glass transition point Tg of the copolymer (X) is more preferably -10°C (263K) or higher, and particularly preferably 0°C (273K) or higher. This is because in such a range, the strength of the coating film after curing increases. The glass transition point Tg of the copolymer (X) may also be 5°C or higher or 10°C or higher. The glass transition point Tg of the copolymer (X) is preferably 100°C (373K) or lower, more preferably 80°C (353K) or lower. This is to improve the adhesion of the coating film to the substrate. From this viewpoint, the glass transition point Tg of the copolymer (X) is particularly preferably 60°C (333K) or less, and particularly preferably 50°C (323K) or less. This is because in such a range, the flexibility of the cured coating film can be improved. The glass transition point Tg of the copolymer (X) may also be 40°C or lower or 30°C or lower.

[The content of epoxy groups in the water-based resin emulsion (α)] The content of epoxy groups in the water-based resin emulsion (α) is the ratio of the number of moles of epoxy groups contained in 1 g of the water-based resin emulsion (α) . _{The method for determining the amount N 1} [mol/g] of the epoxy group contained in 1 g of the aqueous resin emulsion (α) is as described in the following Examples.

[The epoxy group content rate in the total amount of the copolymer (X) and the polyepoxy compound (Y)] As described above, the polyepoxy compound (Y) contained in the aqueous resin emulsion (α) of this embodiment , Contains epoxy groups. The epoxy group content in the total amount of the copolymer (X) and the polyepoxy compound (Y) is preferably 0.50×10 ^-4 mol/g or more, more preferably 1.0×10 ^-4 mol/g or more, It is particularly preferably 4.0×10 ^-4 mol/g or more, and even more preferably 6.0×10 ^-4 mol/g or more. This is to improve the water resistance, rust resistance, and adhesion of the cured coating film to the substrate.

The epoxy group content in the total amount of the copolymer (X) and the polyepoxy compound (Y) is preferably 50×10 ^-4 mol/g or less, more preferably 30×10 ^-4 mol/g or less, Particularly preferably, it is 20×10 ^-4 mol/g or less. The epoxy group content in the total amount of the copolymer (X) and the polyepoxy compound (Y) may be 15×10 ^-4 mol/g or less or 10×10 ^-4 mol/g or less.

[The epoxy group content in the non-volatile matter of the aqueous resin emulsion (α)] The epoxy group content in the non-volatile matter of the aqueous resin emulsion (α) is preferably 0.50×10 ^-4 mol/g or more , More preferably 3.0×10 ^-4 mol/g or more, particularly ^{preferably 5.0×10 -4} mol/g or more. This is to improve the water resistance, rust resistance, and adhesion of the cured coating film to the substrate. The epoxy group content in the non-volatile matter of the aqueous resin emulsion (α) may also be 1.0×10 ^-4 mol/g or more or 6.0×10 ^-4 mol/g or more.

The epoxy group content in the non-volatile matter of the aqueous resin emulsion (α) is preferably 50×10 ^-4 mol/g or less, more preferably 30×10 ^-4 mol/g or less, and particularly preferably 20×10 ^-4 mol/g or less. The epoxy group content in the non-volatile matter of the aqueous resin emulsion (α) may also be 15×10 ^-4 mol/g or less or 10×10 ⁴ mol/g or less.

_{The content rate R EP} [mol/g] of the epoxy group in the non-volatile matter of (α) in the aqueous resin emulsion is the value obtained as follows. Regarding the non-volatile content concentration of the aqueous resin emulsion (α) as C _S [mass %], and the amount of epoxy groups contained in 1 g of the aqueous resin emulsion (α) as N ₁ [mol/g], the cyclic The oxygen content rate R _EP is shown in formula (2). The _{method of obtaining N 1} is described later in the examples.

[The content of carboxyl groups in the water-based resin emulsion (α)] The content rate of the carboxyl group in the aqueous resin emulsion (α) is the ratio of the number of moles of the carboxyl group contained in 1 g of the aqueous resin emulsion (α). The method for determining the number of moles of carboxyl groups contained in 1 g of the aqueous resin emulsion (α) is as described in the following Examples.

[The carboxyl group content in the total amount of the copolymer (X) and the polyepoxy compound (Y)] In this embodiment, the copolymer (X) contained in the aqueous resin emulsion (α) and the polyepoxy compound (Y) One or both of) contains a carboxyl group, and the copolymer (X) preferably contains a carboxyl group. The content of the carboxyl group in the total amount of the copolymer (X) and the polyepoxy compound (Y) is preferably 0.10×10 ^-4 mol/g or more, more preferably 0.50×10 ^-4 mol/g or more, particularly preferably It is 1.0×10 ^-4 mol/g or more. This is because it is possible to suppress aggregation of the copolymer (X) during the polymerization and during storage of the aqueous resin emulsion (α) after the polymerization.

The content of the carboxyl group in the total amount of the copolymer (X) and the polyepoxy compound (Y) is preferably 10×10 ^-4 mol/g or less, more preferably 5.0×10 ^-4 mol/g or less. It may be 3.0×10 ^-4 mol/g or less, 2.5×10 ^-4 mol/g or less or 2.0×10 ^-4 mol/g or less.

[The carboxyl group content in the non-volatile matter of the aqueous resin emulsion (α)] The carboxyl group content in the non-volatile matter of the aqueous resin emulsion (α) is preferably 0.10×10 ^-4 mol/g or more, more preferably 0.50×10 ^-4 mol/g or more, particularly preferably 1.0×10 ^-4 mol/g or more. This is because it is possible to suppress aggregation of the copolymer (X) during the polymerization and during storage of the aqueous resin emulsion (α) after the polymerization.

The content of the carboxyl group in the non-volatile matter of the aqueous resin emulsion (α) is preferably 10×10 ^-4 mol/g or less, more preferably 5.0×10 ^-4 mol/g or less. It may be 3.0×10 ^-4 mol/g or less, 2.5×10 ^-4 mol/g or less or 2.0×10 ^-4 mol/g or less.

Here, the above-mentioned carboxyl group includes not only -COOH, but also a structure in which cations other than hydrogen ions are bonded to -COO-. The content of the carboxyl group in the non-volatile matter of the aqueous resin emulsion (α) is as shown in the following formula. The value of the carboxyl group content in the raw material is subtracted from the reduction of the functional group that reacts with the carboxyl group in the raw material before and after polymerization. . The aforementioned raw materials refer to components used in the synthesis of the aqueous resin emulsion (α). In addition, the functional group that reacts with a carboxyl group is an epoxy group in the present invention, and a hydroxyl group is not considered to be a functional group that reacts with a carboxyl group.

_{Hereinafter, the method for obtaining the carboxyl group content rate R CX} [mol/g] in the non-volatile matter of the aqueous resin emulsion (α) will be described in detail. The total amount of carboxyl groups in the raw material (including the initiator, solvent, other additives, etc.) is regarded as N ₃ [mol/g], and the epoxy in the raw material (including the initiator, solvent, other additives, etc.) The total amount of the base is regarded as N ₂ [mol/g], the amount of epoxy groups contained in 1 g of the aqueous resin emulsion (α) is regarded as N ₁ [mol/g], and the content of the aqueous resin emulsion (α) The concentration of volatile matter is regarded as C _S [mass %]. At this time, the carboxyl group content rate R _CX is as shown in formula (3). The _{method of obtaining N 1} and N ₂ will be described later in the embodiment. N ₂ can be obtained by calculation.

[1-2. Hardener (β)] The hardener (β) contains a compound having a functional group reactive with an epoxy group. The functional group (F) is preferably selected from an unsubstituted amino group (-NH ₂ (no substituent), an amino group with only one substituent (-NHR (R is a substituent)), a carboxyl group, and a mercapto group. Any one of the group of. The type of the epoxy-reactive functional group (F) contained in the curing agent (β) may be only one type, or two or more types.

Examples of hardeners (β) that are unsubstituted or have an amine group having only one substituent include polyamines. Polyamine is a compound having an unsubstituted amine group (-NH ₂ ) and/or an amine group having only one substituent (-NHR (R is a substituent)). Examples include aliphatic polyamines and alicyclic Group polyamines, aromatic polyamines.

As aliphatic polyamines, for example, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, these modified products, etc. may be mentioned. As the alicyclic polyamine, for example, isophorone diamine, menthane diamine, N-amino ethyl piperidine, diamino dicyclohexyl methane, these modified products, etc. can be mentioned. Examples of aromatic polyamines include meta-xylylene diamine, diamino diphenyl methane, meta-phenylene diamine, diamino diphenyl methane, and modified products thereof.

The curing agent (β) having a carboxyl group is preferably a compound having two or more carboxyl groups in the molecule. For example, phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, methyltetrahydrophthalic acid, methylhexahydrophthalic acid, pyromellitic acid, diphenyl Ketone tetracarboxylic acid, 1,2,3,4-butane tetracarboxylic acid.

The curing agent (β) having a mercapto group is preferably a compound having two or more mercapto groups in the molecule. For example, the condensate of thioglycolic acid and polyhydric alcohol, polysulfide, etc. are mentioned.

These hardeners (β) can be used singly or in combination of two or more kinds. As the curing agent (β), a polyamine-based curing agent is preferably used.

As the hardening agent (β), a commercially available one can be used. Examples of commercially available hardeners include ADK Hardener EH-8051 (polyamine) (manufactured by ADEKA Co., Ltd.); Fujicure FXI-919; Tohide TXH-674-B and TXS-53-C (Co., Ltd.) T&K TOKA Co., Ltd.); Rikacid BTW (Nippon Rika Co., Ltd.); and Karenz MTBD-1 (Showa Denko Co., Ltd.), etc.

The content of the epoxy-reactive functional group (F) contained in the curing agent (β) is 0.010 equivalent or more, preferably 0.10, relative to 1 equivalent of epoxy group contained in the aqueous resin emulsion (α) It is more preferably 0.20 equivalent or more. This is to improve the rust resistance of the cured water-based resin composition and the adhesion to metal materials. Here, in the calculation of the equivalent of the functional group (F), when the functional group (F) has two active hydrogens without a substituted amine, the number of the functional group (F) is calculated as two.

The content of the epoxy-reactive functional group (F) contained in the hardener (β) is 3.0 equivalents or less, preferably 2.0 relative to 1 equivalent of epoxy groups contained in the aqueous resin emulsion (α) The equivalent weight or less, more preferably 1.5 equivalent weight or less, even more preferably 1.0 equivalent weight or less, even more preferably 0.80 equivalent weight or less, and particularly preferably 0.50 equivalent weight or less. This is to increase the strength of the coating film.

[1-3. Hardening accelerator (γ)] The hardening accelerator (γ) has the function of accelerating the hardening of the aqueous resin composition and forming a film with high yield strength. The hardening accelerator (γ) contains a tertiary amine that does not have a functional group reactive with epoxy groups. The tertiary amine in this embodiment is based on NR ¹ R ² R ³ (where R ¹ R ² R ³ is a substituent, and each may be different, or may include two or more identical ones; R ¹ R ² R ³ They may be bonded to each other to form a compound represented by ring).

The hardening accelerator (γ) is preferably selected from the group consisting of tertiary aliphatic amines, tertiary alicyclic amines, tertiary heteroaromatic amines, and nitrogen ^{that is not directly bonded to tertiary amines (NR 1} R ² R ³⁾ At least one compound in the group formed by the tertiary aromatic amine of the phenyl group of atoms. This is in order to increase the nucleophilicity of the hardening accelerator (γ) and to efficiently carry out the hardening reaction.

Examples of tertiary aliphatic amines include triethylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, tri-second 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, 1,8-diazabicyclo[5.4.0]undec-7-ene and so on.

As the tertiary heteroaromatic amine, a compound having an imidazole skeleton is preferably used, and specific examples thereof include imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, and the like.

Examples of tertiary aromatic amines having a phenyl group that is not directly bonded to ^{the nitrogen atom of the tertiary amine (NR 1} R ² R ^{3) include dimethylbenzylamine, diethylbenzylamine, and tribenzylamine} Amine, 2,4,6-dimethylaminomethylphenol, 2-phenylimidazole, etc.

Among these hardening accelerators (γ), the following compounds (i) and/or (ii) are particularly preferably used. (i) A tertiary alicyclic amine that does not have a functional group (F) reactive to an epoxy group, and has a saturated ring structure in which 3 substituents of an amine group and 2 nitrogen atoms are bonded to each other. (ii) A tertiary heteroaromatic amine that does not have a functional group (F) that is reactive with an epoxy group and has a heteroaromatic ring structure containing 2 or more nitrogen atoms.

(I) Tertiary alicyclic amines include, for example, 1,4-diazabicyclo[2.2.2]octane (DABCO). The (ii) tertiary heteroaromatic amine includes imidazole, for example. The hardening accelerator (γ) can be used singly or in combination of two or more kinds.

The content of the hardening accelerator (γ) is 0.0070 mol or more, preferably 0.070 mol or more, more preferably 0.18 mol or more, and particularly preferably 0.30 mol relative to 1 equivalent of epoxy group contained in the aqueous resin emulsion (α) above. This is to obtain a cured product with a high yield strength of the film.

The content of the hardening accelerator (γ) is 1.5 mol or less, preferably 1.0 mol or less, more preferably 0.70 mol or less, and particularly preferably 0.44 mol relative to 1 equivalent of epoxy group contained in the aqueous resin emulsion (α) Below, 0.40 mol or less is more preferable, and 0.38 mol or less is especially preferable. This is to suppress the short-time gelation of the water-based resin composition. In addition, in order to obtain a cured product with good rust resistance.

[1-4. Other ingredients] The water-based resin composition of this embodiment may contain a pigment. Examples of pigments include titanium oxide, talc, barium sulfate, carbon black, iron red, calcium carbonate, silica, talc, mica, kaolin, clay, ferrite, silica sand, and the like. The pigment may include only one type of compound, or may include two or more types of compounds. The pigment is preferably contained in the aqueous resin composition at 0.1 to 50% by mass, more preferably 1 to 40% by mass. This is to improve the concealment of the coating film. The pigment may be 0.1 to 3% by mass, or 3 to 6% by mass, or 6 to 10% by mass, or 10 to 20% by mass, or 20 to 35% by mass, or 35 to 50% by mass, as needed, Contained in the water-based resin composition.

The aqueous resin composition may also include fillers, organic or inorganic hollow spheres, dispersants (for example, amino alcohols, polycarboxylates, etc.), surfactants, coupling agents (for example, silane coupling agents, etc.), and defoaming agents , Preservatives (for example, biocides, fungicides, fungicides, algaecides, and combinations thereof, etc.), flow agents, leveling agents, neutralizing agents (for example, hydroxides, amines, ammonia, Carbonate, etc.) and other additives.

As the coupling agent, a silane coupling agent is preferably used. Examples of the silane coupling agent include epoxy silane compounds. As specific examples, 3-glycidoxy propyl methyl dimethoxy silane, 3-glycidoxy propyl methyl diethoxy silane, 3-glycidoxy propyl Trimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, etc.

The addition amount of the silane coupling agent can be arbitrarily selected, but it is preferably 0.1 to 5 parts by mass, more preferably 0.3 to 3 parts by mass relative to 100 parts by mass of the aqueous resin emulsion. This is to improve the rust resistance of the cured water-based resin composition and the adhesion to metal materials.

<1-1-6. Manufacturing method of water-based resin composition> The water-based resin emulsion (α), the hardening agent (β), the hardening accelerator (γ), and other components contained as necessary are mixed. In the mixing step, for example, there are methods described later in the embodiments, but are not limited thereto.

＜2. Method of forming film＞ Next, the method of forming the film containing the cured product of the aqueous resin composition of this embodiment will be described in detail.

In the film forming method of this embodiment, first, the aqueous resin emulsion (α), the hardening agent (β), the hardening accelerator (γ), and other components contained as necessary are mixed. Thereby, the water-based resin composition of this embodiment is prepared (mixing step). Next, the aqueous resin composition obtained through the mixing step is applied to the coated surface (coating step).

In the mixing step, the aqueous resin emulsion (α), the hardener (β), the hardening accelerator (γ), and other components contained as necessary are mixed and stirred. Thereby, an aqueous resin composition in which each component is dispersed is obtained. The stirring in the mixing step can be performed by any method or device, for example, Robomix (manufactured by PRIMIX Co., Ltd.) and the like can be performed. In order to fully disperse each component, the stirring in the mixing step is preferably performed for 5 minutes or more. In addition, in order to suppress the hardening of the resin component, the stirring time is preferably set to within 1 hour.

In the coating step, the water-based resin composition is coated on the coated surface of the coated object. The material for forming the coated surface can be arbitrarily selected, but for example, a metal material can be cited. For the coated surface, surface treatment such as primer and primer can also be applied in advance. As a method of coating the aqueous resin composition, a method using a brush, a roller, etc. can be mentioned, but it is not limited thereto. Furthermore, before the completion of the coating step, in order to prevent the resin component from hardening, the coating step is preferably completed within 1 hour after the completion of the mixing step.

In the film forming method of this embodiment, after the coating step, it is preferable to perform a curing step of curing the coating film obtained on the coated surface through coating. In the curing step, for example, the resin component contained in the aqueous resin composition is cured by drying and aging the coated surface of the coated object coated with the aqueous resin composition. The curing time varies with the temperature of the curing environment. For example, it is preferably at least 5 hours at 20°C, more preferably at least 1 hour at 40°C, and particularly preferably at least 5 minutes at 60°C. Whether it has been hardened, for example, can be judged by touching it with a finger.

＜3. Film＞ The film of this embodiment contains the cured product of the water-based resin composition of this embodiment. The film of this embodiment can be formed by the above-mentioned film forming method.

The film of the present embodiment may be laminated with a film including an undercoat layer on the lower layer and/or an overcoat layer on the upper layer of the film formed from the cured product of the water-based resin composition of the present invention, if necessary. And set up.

The aqueous resin composition of this embodiment includes an aqueous resin emulsion (α), a curing agent (β), and a curing accelerator (γ). Therefore, a cured product having a high yield strength of the film is obtained.

In addition, in the film forming method of this embodiment, an aqueous resin composition is prepared by mixing an aqueous resin emulsion (α), a curing agent (β), and a curing accelerator (γ), and this is applied to the coating material. noodle. Thereby, the film of this embodiment containing the hardened|cured material which has a high film yield strength is obtained.

＜4. Application areas＞ The water-based resin composition of the present invention is used in various fields, and is particularly suitable for use as a coating on the surface of metal products. The article forming the coating film containing the cured product of the aqueous resin composition of the present invention, that is, the applicable object system of the coated article of the aqueous resin composition of the present invention, can be arbitrarily selected. Specific examples of applicable objects include various household products, household appliances such as refrigerators, game equipment installed in playgrounds, parks, etc., sporting goods, buildings (inside, exterior, etc.), Various industrial products and their parts including conveying machinery and working machinery, automobile bodies and chassis, railway vehicle bodies and underfloor machinery, ships, offshore containers, aircraft, etc. [Example]

Hereinafter, the present invention will be explained in detail using examples. In addition, the following embodiments do not limit all of the present invention, and those who implement it without departing from the content of this description are all included in the technical scope of the present invention.

＜1. Synthesis of water-based resin emulsion (α)＞ (Water-based resin emulsion (α-1)) Add 158 parts of ion-exchanged water to a separable flask with cooling tube, thermometer, stirrer, and dropping funnel, and raise the temperature to 60°C. Nitrogen gas was blown into the contents of the separable flask to deoxygenate. In it, it took 3 hours to drop the amount (parts by mass) shown in Table 1 of methyl methacrylate, 2-ethylhexyl acrylate, methacrylic acid, hydrogenated bisphenol A epoxy resin, and ten as an emulsifier. Emulsion of sodium dibenzene sulfonate and 356 parts by mass of ion-exchanged water. Simultaneously with the emulsification, it took 3.3 hours, and at 60°C, 1.2 parts by mass of potassium persulfate as an oxidizing agent were dissolved in 41 parts by mass of ion-exchange water and 0.4 parts by mass of sodium bisulfite as a reducing agent were dissolved in ions. Exchange 21 parts by mass of water for polymerization. After the dripping is over, it is matured for 1.5 hours. Then, it cooled, and 0.8 mass part of ammonia water as a basic substance was added, and the aqueous resin emulsion (α-1) was obtained.

Table 1 shows the amount (parts by mass) of each material used in the synthesis of the aqueous resin emulsion (α-1). The numerical value of "ion exchange water" shown in Table 1 represents the content of ion exchange water contained in the synthesized aqueous resin emulsion (α-1). In addition, the values in parentheses in the amounts of the copolymer (X) and polyepoxy compound (Y) in Table 1 represent the total amount (100%) of the copolymer (X) and polyepoxy compound (Y). ), the proportion of each material (mass%).

As the polyepoxy compound (Y) shown in Table 1, the following were used. Hydrogenated bisphenol A epoxy (epoxy equivalent 215g/mol; manufactured by Gongrong Chemical Co., Ltd.; Epolight 4000) Bisphenol A epoxy (epoxy equivalent 190g/mol; manufactured by Mitsubishi Chemical Corporation; JER828) Glycerin polyglycidyl ether (epoxy equivalent 143g/mol; manufactured by Sakamoto Pharmaceutical Co., Ltd.; SR-GLG) 1,6-Hexanediol Diglycidyl Ether (Epoxy equivalent 160g/mol; manufactured by Gongrong Chemical Co., Ltd.; Epolight 1600)

(Water-based resin emulsion (α-2)～(α-7)) Except that the materials shown in Table 1 were used in the amounts (parts by mass) shown in Table 1, the aqueous resin emulsions (α-2) to (α-7) were synthesized in the same manner as the aqueous resin emulsion (α-1). . In addition, in the water-based resin emulsion (α-2) ~ (α-7), the value of "ion exchange water" shown in Table 1 is the same as the water-based resin emulsion (α-1) synthesized, indicating the synthesized The content of ion exchange water contained in the aqueous resin emulsion (α-2) to (α-7).

＜2. Evaluation of water-based resin emulsion (α)＞ For the aqueous resin emulsions (α-1) to (α-7), the following items were evaluated respectively. Table 2 shows the results. In addition, in the aqueous resin emulsion (α-7), evaluation was not performed due to aggregation during synthesis. In the following description, when the aqueous resin emulsions (α-1) to (α-7) are collectively referred to, they may be described as the aqueous resin emulsion (α).

＜2-1. Concentration of non-volatile matter＞ In an aluminum dish with a diameter of 5 cm, 1 g of the aqueous resin emulsion (α) was weighed, and dried at 105°C for 1 hour while circulating air in a desiccator under atmospheric pressure. 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 resin emulsion (α) before drying was determined.

<2-2. Residual rate of epoxy groups> The residual rate of epoxy groups in the aqueous resin emulsion (α) is the amount of epoxy groups contained in the synthesized aqueous resin emulsion (α) N ₁ [mol/g] _{The ratio of N 2} [mol/g] to the total amount of epoxy groups contained in the components used for the synthesis of the aqueous resin emulsion (α) (including raw materials, initiators, solvents, other additives, etc.).

_{The amount of epoxy group N 1} [mol/g] of the synthesized aqueous resin emulsion (α) was measured by the method shown below. With respect to the total amount of epoxy groups contained in the components (raw materials) used for the synthesis of the aqueous resin emulsion (α), excess hydrogen chloride is added to react with the epoxy groups. Next, the unreacted hydrogen chloride was titrated with potassium hydroxide to confirm the amount of remaining hydrogen chloride. At this time, potassium hydroxide is consumed by the reaction with acidic components including the carboxylic acid contained in the aqueous resin emulsion (α). Therefore, by titrating the amount of acidic components in a blank measurement without hydrogen chloride in advance, the results of this measurement are corrected. The specific measurement procedures are as follows (i) to (ii).

(i) Blank measurement (confirmation of the amount of acidic components) W ₁ [g] (5 g in this example and comparative example) was measured in a 100 mL Erlenmeyer flask, and tetrahydrofuran (THF) was added. 25g, stirred with a magnetic stirrer to become a uniform solution. Add 0.15 mL of 0.1% by mass cresol red aqueous solution as an indicator to this solution. Titrate with 0.1M potassium hydroxide/ethanol solution while stirring the aforementioned solution. After dropping the potassium hydroxide/ethanol solution, the point where the purple color lasts for 30 seconds is regarded as the equivalent point. The amount of potassium hydroxide/ethanol solution used for the titration here is regarded as V _KOH1 [mL].

(ii) In this measurement, the amount of W ₂ [g] (5g in this example and comparative example) was used to measure the aqueous resin emulsion (α) in a 100 mL Erlenmeyer flask, add 25 g of THF, and stir with a magnetic stirrer to become uniform Solution. A 0.2M hydrogen chloride/dioxane solution was added thereto, and the mixture was stirred for 1 hour to become a uniform solution. The amount of the hydrogen chloride/dioxane solution added here is regarded as V _HCl [mL] (25 mL in this example and comparative example). Add 0.15 mL of 0.1% by mass cresol red aqueous solution as an indicator to this solution. Titrate with 0.1M potassium hydroxide/ethanol solution while stirring the aforementioned solution. After dropping the potassium hydroxide/ethanol solution, the point where the purple color lasts for 30 seconds is regarded as the equivalent point. The amount of potassium hydroxide/ethanol solution used for the titration here is regarded as V _KOH2 [mL].

_{From the values obtained in (i) and (ii), the amount N 1} [mol/g] of epoxy groups per 1 g of the aqueous resin emulsion (α) is calculated by the following formula (4).

The total amount of epoxy groups contained in the components (raw materials) used for the synthesis of the aqueous resin emulsion (α) N ₂ [mol/g] is calculated from the mass of each component m _i [mass parts] (i=1,2, 3,...) and epoxy equivalent EP _i [g/mol] can be obtained by the following formula (5). Here, the components used in the synthesis of the aqueous resin emulsion (α) mean all the components described in Table 1 as the raw materials of the aqueous resin emulsion (α).

Furthermore, with regard to epoxy-free compounds such as methyl methacrylate and ion-exchanged water, it becomes 1/EP _i =0. From the amount of epoxy groups determined in this way, the residual ratio of epoxy groups in the aqueous resin emulsion (α) is represented by 100×N ₁ /N ₂ [mol%].

<2-3. The content of epoxy groups in non-volatile matter, the content of epoxy groups in component (X)+(Y)> The concentration of non-volatile matter C _S [mass%] obtained from the above method _{], the epoxy group content N 1} in the aqueous resin emulsion (α), the total amount of epoxy groups in the raw material N ₂ , according to the formula (2) explained above, calculate the non-volatile content of the aqueous resin emulsion (α) The epoxy content in R _EP [mol/g].

In addition, the epoxy group content N ₁ in the aqueous resin emulsion (α) obtained by the above method, the total mass of all components (raw materials) used in the synthesis of the aqueous resin emulsion (α), α[g], The mass X[g] of the raw material of the copolymer (X) and the mass Y[g] of the raw material used for the polyepoxy compound (Y), according to the following formula, calculate the epoxy group in the component (X)+(Y) The content rate R _EP [mol/g].

從此處所求出的N₃ ，根據上述說明之式(3)，求出水性樹脂乳液(α)之不揮發分中的羧基之含有率R_CX [mol/g]。

<2-4. The content of carboxyl groups in non-volatile matter, the content of carboxyl groups in component (X)+(Y)> The content of carboxyl groups contained in the components (raw materials) used in the synthesis of water-based resin emulsion (α) The total amount of N ₃ [mol/g] is derived from the mass of each component m _i [parts by mass] (i= 1,2,3,...) and the carboxyl equivalent CX _i [g/mol], by the following formula (6) Find out. Here, the components used in the synthesis of the aqueous resin emulsion (α) mean all the components described in Table 1 as the raw materials of the aqueous resin emulsion (α).

From the N _{3 obtained here, the content rate R CX} [mol/g] of the carboxyl group in the non-volatile matter of the aqueous resin emulsion (α) is obtained according to the above-described formula (3).

_{Also, the epoxy group content N 1} in the aqueous resin emulsion (α) obtained by the above method, the total amount of epoxy groups N ₂ in the raw material, and the components used in the synthesis of the aqueous resin emulsion (α) (raw material ) The total amount of carboxyl groups contained in N ₃ , the total mass of all ingredients (raw materials) used in the synthesis of the aqueous resin emulsion (α) α[g], the weight of the raw materials used in the copolymer (X) X[g] , The mass Y [g] of the raw material used for the polyepoxy compound (Y), calculate the carboxyl group content rate R _CX [mol/g] in the component (X) + (Y) based on the following formula.

＜2-5.pH＞ The measurement was performed using a pH meter (Glass Electrode Hydrogen Ion Concentration Indicator HM-30G manufactured by Toa DKK Co., Ltd.).

＜2-6. Viscosity＞ Use the following conditions and equipment to measure the viscosity of the water-based resin emulsion (α). Temperature: 23℃ Measuring machine: B-type viscometer Rotor: No.1 Number of rotations: 60rpm

＜2-7. Glass transition point＞ The glass transition point Tg of the copolymer (X) is a value calculated by the above-mentioned formula (1).

＜2-8. Dispersion stability＞ The state of the aqueous resin emulsion (α) immediately after the synthesis was visually observed, and the evaluation was performed according to the following criteria. ○ (Yes): No aggregation, precipitation, separation, and gelation are observed. × (Not OK): At least any of aggregation, precipitation, separation, and gelation is observed.

＜2-9. High temperature stability＞ The high temperature stability of the aqueous resin emulsion (α) was evaluated as follows. First, the water-based resin emulsion (α) and the seal were put into a 70-ml glass bottle, and it was allowed to stand at 60°C for 7 days. Then, the state of the aqueous resin emulsion (α) in the glass bottle was visually observed, and evaluated according to the following criteria. ○ (Yes): No aggregation, thickening, precipitation, separation, and gelation are not seen. × (Not OK): At least any of aggregation, thickening, precipitation, separation, and gelation is observed.

＜2-10. Evaluation results＞ As shown in Table 2, the water-based resin emulsions (α-1) to (α-6) have good high temperature stability. It can be seen from the above that the amount of (meth)acrylate (A) added is 20 to 98% by mass relative to the total amount of the monomer and polyepoxy compound (Y), which is relative to the monomer and polyepoxy compound (Y). The total amount of ), the addition amount of the ethylenically unsaturated carboxylic acid (B) is 0.1-10% by mass, and the addition of the polyepoxy compound (Y) is relative to the total amount of the monomer and the polyepoxy compound (Y) The water-based resin emulsion (α) with an amount of 1-40% by mass has excellent high-temperature stability. On the other hand, the aqueous resin emulsion (α-7)-based polymer in which the addition amount of the polyepoxy compound (Y) is excessive does not disperse but aggregates.

<3. Examples 1 to 17 and Comparative Examples 1 to 2 (production of water-based resin composition)> To 100 parts by mass of the water-based resin emulsion (α) shown in Tables 3 and 4 (with a non-volatile content of 40% by mass), 60 parts by mass of ion-exchange water and the amount shown in Tables 3 and 4 (parts by mass) were added ) The curing agent (β) and the curing accelerator (γ) shown in Table 3 and Table 4 were added and stirred for 10 minutes to prepare the aqueous resin compositions of Examples 1-17 and Comparative Examples 1-2.

In Tables 3 and 4, the "equivalent to epoxy group" in each curing agent (β) means 1 equivalent of epoxy group contained in the aqueous resin emulsion (α), and the curing agent (β) contains The equivalent value of the functional group (F) that is reactive to epoxy groups. The "equivalent to epoxy group" in each hardening accelerator (γ) means the number of moles of hardening accelerator (γ) relative to 1 equivalent of epoxy group contained in the aqueous resin emulsion (α). As the polyamine shown in Table 3 and Table 4, ADK Hardener EH-8051 (manufactured by ADEKA Co., Ltd.) was used. The amine equivalent of the polyamine used as the hardener (β) is 187 g/mol. The carboxyl equivalent of 1,2,3,4-butanetetracarboxylic acid is 58.5g/mol.

＜4. Evaluation of film (coating)＞ Using the aqueous resin compositions of Examples 1 to 17 and Comparative Examples 1 to 2, respectively, a film (coating film) was formed by the method shown below, and the following items were evaluated. The results are shown in Table 3 and Table 4.

＜4-1. Measuring method of film yield strength＞ The water-based resin composition was cast on the entire horizontally placed rectangular flat plate made of polyethylene film with a length of 90 mm and a width of 190 mm. After drying this at 23°C for 72 hours, a coating film (cured product) hardened by aging at 50°C for 24 hours was produced. The resulting coating film was peeled from the flat plate. A rectangle with a width of 10 mm and a length of 30 mm was cut out from the peeled coating film and used as a test piece.

The longitudinal direction of this test piece was regarded as the tensile direction, and the following tests were carried out. The thickness of the test piece was measured using Quick-Micro (registered trademark) MDQ-MX manufactured by MITUTOYO Co., Ltd. The measurement was performed at 3 points for each test piece, and the average value of the measurement results at the 3 points was taken as the thickness t [mm] of the test piece.

The film yield strength test was performed by the method shown below using Autograph AG-X (manufactured by Shimadzu Corporation). Set the distance between the chucks to 10 mm, and grasp both sides of the test piece in the longitudinal direction with the chucks. In an environment with a temperature of 23°C and a relative humidity (RH) of 50%, the test piece is stretched at a speed of 100 mm/min.

Regarding the distance between the chucks as L [mm] and the change in the length of the test piece (the difference between the distance between the chucks during the test and the distance between the chucks before the test) as ΔL [mm], the strain S It is calculated with 100×ΔL/L[%]. In addition, the load applied to the test piece (measured load) is regarded as F[N], and the maximum value of the load until the test piece breaks is regarded as F _max [N], and the following conditions will be met from the beginning of the test The point is regarded as the yield point Y(S _y , F _y ).

(Conditions for yield point) Strain S is 2% or more (S _y 2%). The change in the load F accompanied by the increase in the strain S changes from an increase to a decrease. Until F=F _y -0.01F _max , dF/dS<0 continues. In S≦S _y +0.05%, _{the point where F>F y} does not exist.

(式中的W為試驗片之寬度[mm]，t為試驗片之厚度[mm])。 _{The film yield strength of the stress σ y} applied to the test piece at the yield point Y is calculated by the formula shown below.

(W in the formula is the width of the test piece [mm], and t is the thickness of the test piece [mm]).

＜4-2. Water swelling resistance rate＞ In the same manner as the above-mentioned measurement of the yield point, a coating film was formed on a flat plate made of a polyethylene film. The resulting coating film was peeled from the flat plate. A square with a length of 10 mm and a width of 10 mm was cut out from the peeled coating film.

After weighing the cut out coating film, it was immersed in ion exchange water at 23°C for 24 hours. Take out the immersed coating film from the ion-exchanged water, immediately weigh the coating film, and use this as the quality of the coating film before drying. Then, the coating film was dried at 105°C for 3 hours, and the coating film was weighed again, and this was regarded as the quality of the coating film after drying. From the quality of the coating film before drying and the quality of the coating film after drying, the value obtained by the following formula (4) was regarded as the water swelling resistance rate.

Water swelling resistance rate (%)={(the quality of the coating film before drying-the quality of the coating film after drying)/the quality of the coating film after drying}×100… (4)

<4-3. Rust resistance> Using a brush, the water-based resin composition was applied to the cold-rolled steel sheet (hereinafter referred to as "base material") so that the ^{weight per unit area was 50 g/m 2.} The coated substrate was dried in a constant temperature bath at 60°C for 10 minutes to form a coating film on the surface of the substrate.

A rectangular area with a length of 30 mm and a width of 45 mm on the coating film formed on the surface of the substrate was regarded as the test area. To form the diagonal line of the rectangle of the test area, form a cut mark formed by two intersecting straight lines (ie X-shaped) on the coating film, and use it as a test body. The cut marks are formed by using a cutter to reach the substrate from the coating film. For the test body with cut marks, a neutral salt spray test (item 4.2.1) was performed in accordance with JIS Z-2371 (2000).

In the test body after the neutral salt spray test, the occupied area [area%] of the bulge of the coating film in the test area, the size of the bulge [mm], and the size of the flow rust from the cut mark [mm] are measured. The size of the bulge is the longest size in the area occupied by an independent bulge. In addition, the size of the flow rust is the maximum value of the width of the rust centered on the cross-cut part.

＜4-4. Adhesion of coating film to metal materials＞ In the same manner as in the evaluation of the rust resistance described above, a coating film was formed on the surface of the cold-rolled steel sheet. According to JIS K-5400 (1990) "8.5.2 Checkerboard Tape Method", the steel plate with the coating film is used as a test piece, and the coating film is penetrated by using a cutter to introduce 1mm checkerboard cut marks ( 100 grids), laminated with cellophane tape (Cellotape, registered trademark). After 1 hour, the scotch tape (registered trademark) was peeled off, the number of squares remaining without peeling the coating film from the steel plate was counted, and the adhesion of the coating film to the metal material was evaluated.

<4-5. Evaluation results> As shown in Tables 3 and 4, those containing aqueous resin emulsions (α-1) to (α-6), polyamines, or 1,2,3,4-butanetetracarboxylic acid Hardening agent (β), 1,4-diazabicyclo[2.2.2] octane (DABCO) or imidazole hardening accelerator (γ) The hardened product of the water-based resin composition of Examples 1-17, which is a film The yield strength is 10 [N/mm ² ] or more, and the yield strength of the film is high. In addition, the cured products of the water-based resin compositions of Examples 1 to 17 have low water swelling resistance, good water resistance, and good adhesion to metal materials. In addition, the water-based resin compositions of Examples 1 to 4, 6 to 9, and 11 to 17 had less swelling of the cured product system and good rust resistance.

In contrast, the cured products of the aqueous resin composition of Comparative Example 1 and Comparative Example 2 that did not contain the curing accelerator (γ) were compared with the cured products of the aqueous resin composition of Examples 1-17. The yield strength of the film was Poor. [Industrial Utilization Possibility]

According to the present invention, it is possible to provide an aqueous resin composition which can obtain a cured product with high yield strength of the film, high water resistance and high adhesion to metal materials.

Claims (14)

An aqueous resin composition comprising an aqueous resin emulsion (α), a hardening agent (β) and a hardening accelerator (γ), The aforementioned aqueous resin emulsion (α) contains: Copolymer (X), A polyepoxy compound (Y) that does not have ethylenically unsaturated bonds and has two or more epoxy groups in one molecule, and Aqueous medium (Z); The content rate of the polyepoxy compound (Y) is 1-40% by mass relative to the total amount of the copolymer (X) and the polyepoxy compound (Y), The aforementioned copolymer (X) contains: A structural unit derived from (meth)acrylate (A), and A structural unit derived from ethylenically unsaturated carboxylic acid (B); The content of the structural unit derived from the (meth)acrylate (A) is 20 to 98% by mass relative to the total amount of the copolymer (X) and the polyepoxy compound (Y), The content of the structural unit derived from the ethylenically unsaturated carboxylic acid (B) is 0.1-10% by mass relative to the total amount of the copolymer (X) and the polyepoxy compound (Y), The aforementioned structural unit derived from (meth)acrylate (A) includes a structural unit derived from hydrophilic (meth)acrylate (A1) with a carbon number of 2 or less in the alcohol-derived part, The content of the structural unit derived from the hydrophilic (meth)acrylate (A1) is 15 to 98% by mass relative to the total amount of the copolymer (X) and the polyepoxy compound (Y), One or both of the aforementioned copolymer (X) and the aforementioned polyepoxy compound (Y) contain a carboxyl group, The aforementioned curing agent (β) contains a compound having a functional group (F) reactive with epoxy groups, The content of the functional group (F) contained in the curing agent (β) is 0.010 equivalent or more and 3.0 equivalent or less with respect to 1 equivalent of epoxy group contained in the aqueous resin emulsion (α), The aforementioned hardening accelerator (γ) contains tertiary amines that do not have functional groups reactive with epoxy groups, The content of the hardening accelerator (γ) is 0.0070 mol or more and 1.5 mol or less with respect to 1 equivalent of epoxy groups contained in the aqueous resin emulsion (α). The aqueous resin composition of claim 1, wherein the (meth)acrylate (A) includes an alkyl (meth)acrylate. The aqueous resin composition of claim 1 or 2, wherein the aforementioned ethylenically unsaturated carboxylic acid (B) comprises α, β-unsaturated monocarboxylic acid, α, β-unsaturated dicarboxylic acid, and a vinyl group containing a carboxyl group. At least one of the group of compounds. The aqueous resin composition according to any one of claims 1 to 3, wherein the aforementioned polyepoxy compound (Y) is composed of a bisphenol type epoxy compound, a hydrogenated bisphenol type epoxy compound, a diglycidyl ether, and three At least one selected from the group consisting of glycidyl ether, tetraglycidyl ether, diglycidyl ester, triglycidyl ester, and tetraglycidyl ester. The aqueous resin composition according to any one of claims 1 to 4, wherein the copolymer (X) includes the structural unit derived from the (meth)acrylate (A) and the ethylenically unsaturated carboxylic acid ( B) The structural unit. The aqueous resin composition according to any one of claims 1 to 4, wherein the copolymer (X) contains a structural unit derived from an ethylenically unsaturated aromatic compound (C) having a benzene ring and an ethylenically unsaturated bond. The aqueous resin composition of claim 6, wherein the aforementioned ethylenically unsaturated aromatic compound (C) is an aromatic vinyl compound. The aqueous resin composition according to any one of claims 1 to 7, wherein the hardener (β) contains at least one selected from the group consisting of unsubstituted or having only one substituent, amine group, carboxyl group, and mercapto group Either. The aqueous resin composition according to any one of claims 1 to 8, wherein the hardening accelerator (γ) is selected from the group consisting of tertiary aliphatic amines, tertiary alicyclic amines, and tertiary heteroaromatic amines At least 1 compound in the group. The aqueous resin composition according to any one of claims 1 to 9, wherein the aqueous resin emulsion (α) is in the aqueous medium (Z), and becomes a monomer of the structural unit of the copolymer (X). Emulsion polymerized into an emulsion in the presence of polyepoxy compound (Y). The aqueous resin composition according to any one of claims 1 to 10, wherein the carboxyl group content in the total amount of the copolymer (X) and the polyepoxy compound (Y) is 0.10×10 ^-4 mol/g above. The aqueous resin composition according to any one of claims 1 to 11, wherein the epoxy group content in the total amount of the copolymer (X) and the polyepoxy compound (Y) is 0.50×10 ^-4 mol /g above. A coating film comprising a cured product of the aqueous resin composition according to any one of claims 1 to 12. A method for forming a film, which includes: The coating step of applying the water-based resin composition according to any one of claims 1 to 12 to the surface to be coated, and A hardening step of hardening the aforementioned coated aqueous resin composition.