Epoxy resin curing agent, epoxy resin composition, and coating material

Abstract

To provide an epoxy resin curing agent, an epoxy resin composition, and a coating material which are capable of forming a coating film good in curability and appearance and excellent in water resistance, impact resistance, and adhesion to a substrate.SOLUTION: There are provided: an epoxy resin curing agent containing a modified product (A) of a cyclic structure-containing diamine (a) represented by the following general formula (1); an epoxy resin composition containing the curing agent; and a coating material. In the formula, X is a divalent group containing a cyclic structure; p and q are each independently a number of 2-10; and r and s are each independently a number of 0-4.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an epoxy resin curing agent, an epoxy resin composition, and a coating material containing the same. [Background technology]

[0002] Various polyamine compounds are widely known as epoxy resin curing agents. Epoxy resin compositions using polyamine compounds as epoxy resin curing agents are used in the fields of paints such as anticorrosive paints for ships, bridges, and land and sea iron structures, linings, reinforcement and repair materials for concrete structures, flooring materials for buildings, linings for water supply and sewerage systems, paving materials, adhesives, and other civil engineering and construction applications.

[0003] Compounds (modified polyamines) obtained by modifying polyamines with epoxy compounds or the like are also known to be useful as epoxy resin curing agents. For example, Patent Documents 1 to 3 disclose epoxy resin curing agents containing modified bis(aminomethyl)cyclohexane, which is a polyamine compound. Patent Document 1 discloses that an epoxy resin curing agent composed of a polyamine compound containing at least one of bis(aminomethyl)cyclohexane, an epoxy modified product of bis(aminomethyl)cyclohexane, and a Michael addition modified product of bis(aminomethyl)cyclohexane, and an amine compound having an alkyl group having 16 to 18 carbon atoms, can eliminate the tackiness of the surface of an epoxy resin coating film and can prevent changes such as whitening that occur when water droplets are dropped onto the coating film. Patent Document 2 discloses that an epoxy resin curing agent consisting of a polyamine compound containing bis(aminomethyl)cyclohexane or a modified product thereof, an aliphatic amine compound containing a component having an alkyl group with 12 carbon atoms or having an iodine value of 50 or more, and a curing accelerator, does not cause stickiness in the cured epoxy resin coating film, prevents whitening that occurs when water droplets are dropped onto the coating film, and has excellent storage stability. Patent Document 3 discloses that an epoxy resin curing agent composition containing a polyamine compound which is a reaction product of a compound having at least one glycidyl group per molecule with a polyamine represented by a specific formula, a polyether-modified polydimethylsiloxane having a surface tension in the range of 19 to 25 dyne / cm, and an amino-modified silicone having a total amine value in the range of 150 to 650 mgKOH / g can provide good curability, good epoxy resin cured coating film performance, and good physical properties of the epoxy resin cured product. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-3282 [Patent Document 2] JP 2001-163955 A [Patent Document 3] JP 2007-186693 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the techniques disclosed in Patent Documents 1 to 3, it is desired to further improve the water resistance, impact resistance, and adhesion to substrates of the cured coating film of the obtained epoxy resin composition. An object of the present invention is to provide an epoxy resin curing agent, an epoxy resin composition, and a coating material which have good curing properties and are capable of forming a coating film which is excellent in appearance, water resistance, impact resistance, and adhesion to a substrate. [Means for solving the problem]

[0006] The present inventors have found that an epoxy resin curing agent containing a modified product of a specific ring structure-containing diamine can solve the above problems. That is, the present invention relates to the following. [1] An epoxy resin curing agent comprising a modified product (A) of a ring-containing diamine (a) represented by the following general formula (1): [ka] In the formula, X is a divalent group containing a ring structure, p and q each independently represent a number from 2 to 10, and r and s each independently represent a number from 0 to 4. [2] The epoxy resin curing agent according to [1], wherein the ring structure includes at least one selected from the group consisting of an alicyclic hydrocarbon structure and an aromatic hydrocarbon structure. [3] The epoxy resin curing agent according to [2], wherein the ring structure contains a cyclohexane ring. [4] The epoxy resin curing agent according to any one of [1] to [3], wherein the modified product (A) of the ring-structure-containing diamine (a) includes at least one selected from the group consisting of the following (I) to (IV): (I) A Mannich reaction product of the ring-containing diamine (a), a phenol compound, and an aldehyde compound. (II) A reaction product of the ring-containing diamine (a) and an unsaturated hydrocarbon compound. (III) A reaction product of the ring-containing diamine (a) and an epoxy compound having at least one epoxy group. (IV) A reaction product of the ring-containing diamine (a) and a carboxylic acid or a derivative thereof. [5] An epoxy resin composition comprising an epoxy resin and the epoxy resin curing agent according to any one of [1] to [4]. [6][5] A paint containing the epoxy resin composition. Effect of the Invention

[0007] According to the present invention, there can be provided an epoxy resin curing agent, an epoxy resin composition, and a coating material which have good curing properties and can form a coating film which is excellent in appearance, water resistance, impact resistance, and adhesion to a substrate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Epoxy resin hardener] The epoxy resin curing agent of the present invention contains a modified product (A) of a ring-structure-containing diamine (a) represented by the following general formula (1): In this specification, the term "modified product of ring-structure-containing diamine (a)" refers to a product obtained by modifying the ring-structure-containing diamine (a) with other components, and refers to a reaction composition that includes not only the reaction product of the ring-structure-containing diamine (a) with other components, but also by-products other than the reaction product, unreacted raw materials, etc. [ka] In the formula, X is a divalent group containing a ring structure, p and q each independently represent a number from 2 to 10, and r and s each independently represent a number from 0 to 4. By using the above-mentioned epoxy resin curing agent, it is possible to provide an epoxy resin composition which has good curing properties and can form a coating film which is excellent in appearance, water resistance, impact resistance, and adhesion to a substrate. Hereinafter, the epoxy resin curing agent of the present invention may be simply referred to as the "curing agent of the present invention."

[0009] The reason why the above-mentioned effects are obtained by using the curing agent of the present invention in an epoxy resin composition is not clear, but is thought to be as follows. The ring-structure-containing diamine (a) used in the present invention has primary amino groups at both ends, so that the active hydrogen equivalent (AHEW) of the resulting modified product (A) is low and has good curability. The ring-structure-containing diamine (a) has a ring structure at X in the general formula (1), and a poly(methylene)oxy group is bonded to the primary amino group, so that the molecular weight is higher and the flexibility is higher than that of a diamine having only a ring structure. Furthermore, the molecular weight is improved by using the ring-structure-containing diamine (a) as the modified product (A), so that the water resistance, adhesion, and film-forming properties are thought to be further improved. For the above reasons, the coating film obtained by the epoxy resin composition using the curing agent of the present invention is thought to be excellent in appearance, water resistance, impact resistance, and adhesion to a substrate.

[0010] <Component (A): Modified product of ring-containing diamine (a) represented by general formula (1)> The epoxy resin curing agent of the present invention contains, as component (A), a modified product of a ring-structure-containing diamine (a) represented by the following general formula (1): [ka] In the formula, X is a divalent group containing a ring structure, p and q each independently represent a number from 2 to 10, and r and s each independently represent a number from 0 to 4.

[0011] (Diamine (a) having a ring structure represented by general formula (1)) Hereinafter, the ring-structure-containing diamine (a) represented by the general formula (1) will also be referred to simply as "(ring-structure-containing) diamine (a)". In the general formula (1), X is a divalent group containing a ring structure. Preferably, the ring structure contained in X is -O-(CH2) in the general formula (1). r - and - (CH2) s It is directly bonded to -O-.

[0012] From the viewpoints of improving curability, the appearance of the resulting coating film, water resistance, impact resistance, and adhesion to the substrate, the ring structure is preferably a 5-membered or 6-membered ring, and more preferably a 6-membered ring.

[0013] Examples of the ring structure include an alicyclic hydrocarbon structure, an aromatic hydrocarbon structure, a heterocyclic structure, etc. These ring structures may have a substituent, and examples of the substituent include a hydroxy group, a cyano group, or an alkyl group having 1 to 4 carbon atoms which may have a hydroxy group or a cyano group. In this specification, the term "alicyclic hydrocarbon structure" refers to a saturated or unsaturated ring structure consisting of carbon and hydrogen, which has no aromaticity. Specific examples of the alicyclic hydrocarbon structure include a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, a cyclooctane ring, a norbornane ring, a tricyclodecane ring, an adamantane ring, etc. Among the above alicyclic hydrocarbon structures, at least one selected from the group consisting of a cyclopentane ring and a cyclohexane ring is preferred, and a cyclohexane ring is more preferred.

[0014] In this specification, the term "aromatic hydrocarbon structure" refers to a ring structure having aromaticity and consisting of carbon and hydrogen. Specific examples of the aromatic hydrocarbon structure include a benzene ring, a naphthalene ring, and an anthracene ring, with a benzene ring being preferred.

[0015] As used herein, a heterocyclic structure refers to a ring structure that contains a heteroatom in the ring. Examples of the heterocyclic structure include a heterocyclic structure containing a nitrogen atom and an oxygen atom as heteroatoms in the ring structure, a heterocyclic structure containing only a nitrogen atom as a heteroatom in the ring structure, a heterocyclic structure containing only an oxygen atom as a heteroatom in the ring structure, a heterocyclic structure containing a nitrogen atom and a sulfur atom as heteroatoms in the ring structure, and a heterocyclic structure containing only a sulfur atom as a heteroatom in the ring structure.

[0016] From the viewpoints of improving curability, the appearance of the resulting coating film, water resistance, impact resistance, and adhesion to a substrate, the ring structure preferably contains at least one selected from the group consisting of an alicyclic hydrocarbon structure and an aromatic hydrocarbon structure, more preferably contains at least one selected from the group consisting of a cyclohexane ring and a benzene ring, and further preferably contains a cyclohexane ring. X may contain two or more ring structures.

[0017] In the case where either the cis or trans isomer can be used, such as a cyclohexane ring, the ring structure may be either the cis isomer, the trans isomer, or a mixture of the cis and trans isomers.

[0018] Preferred examples of X in the general formula (1) include divalent groups represented by the following general formulae (2) to (5). [ka] In the formula, R 11 ~R 16 are each independently a hydroxy group, a cyano group, or an alkyl group having 1 to 4 carbon atoms which may have a hydroxy group or a cyano group. a to c are each independently a number from 0 to 8, and d to f are each independently a number from 0 to 4. Y 1 and Y 2 each independently is a single bond, -CH2-, -CH(CH3)-, -C(CH3)2-, or -O-. R 11 ~R 16 is preferably an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and further preferably a methyl group. Each of a to c is preferably a number of 0 to 4, more preferably a number of 0 to 2, and further preferably 0. d to f are preferably 0 to 2, more preferably 0 or 1, and further preferably 0. Y 1 and Y 2 is preferably a single bond, -CH2-, -CH(CH3)-, or -C(CH3)2-.

[0019] Among the above, from the viewpoints of improving curability, the appearance of the resulting coating film, water resistance, impact resistance, and adhesion to the substrate, X in the general formula (1) is preferably a divalent group represented by the general formula (2) or (3), more preferably a divalent group represented by the general formula (2), even more preferably a 1,3-cyclohexylene group or a 1,4-cyclohexylene group, and still more preferably a 1,4-cyclohexylene group.

[0020] In the general formula (1), p and q are preferably numbers from 2 to 5, more preferably numbers from 2 to 4, from the viewpoint of improving curability, the appearance of the resulting coating film, water resistance, impact resistance, and adhesion to a substrate, and from the viewpoint of ease of production, are even more preferably numbers from 3. r and s are preferably numbers from 1 to 3, more preferably numbers from 1 to 2, and even more preferably numbers from 1. It is preferable that p and q are the same number, and it is preferable that r and s are the same number.

[0021] From the viewpoints of improving curability, the appearance of the resulting coating film, water resistance, impact resistance, and adhesion to a substrate, the ring structure-containing diamine (a) is preferably a diamine represented by the following structural formula (a1). [ka]

[0022] The method for producing the ring-structure-containing diamine (a) is not particularly limited, and a known method can be used. Alternatively, a commercially available product can be used as the ring-structure-containing diamine (a). For example, the diamine represented by the structural formula (a1) can be obtained by carrying out an addition reaction between 1,4-cyclohexanedimethanol and acrylonitrile to produce a dinitrile compound represented by the following structural formula (a1'), and then reducing the nitrile group in the dinitrile compound to convert it to an amino group. The reaction between a diol and acrylonitrile can be carried out, for example, with reference to Reference Example 1 of WO 2015 / 147321. [ka]

[0023] The addition reaction between 1,4-cyclohexanedimethanol and acrylonitrile is preferably carried out in the presence of a basic catalyst from the viewpoint of improving reactivity. The basic catalyst is preferably an inorganic base, such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, etc. These inorganic bases may be used in the form of an aqueous solution. The above-mentioned addition reaction may be carried out in a solvent or without a solvent, but it is preferable to carry out the reaction in a solvent from the viewpoint of controlling the reaction heat. Examples of the solvent include alcohol solvents such as methanol and ethanol, and ether solvents such as dibutyl ether, tetrahydrofuran, and dioxane from the viewpoint of the solubility of the substrate and the suppression of side reactions. These may be used alone or in combination of two or more.

[0024] From the viewpoint of controlling the reaction heat and suppressing side reactions, the addition reaction of 1,4-cyclohexanedimethanol and acrylonitrile is preferably carried out under conditions of 0 to 45° C., more preferably 5 to 35° C. More specifically, there can be mentioned a method in which acrylonitrile is added dropwise to a reactor containing 1,4-cyclohexanedimethanol, a basic catalyst, and a solvent while maintaining the internal temperature at preferably 0 to 45° C., more preferably 5 to 35° C., and after completion of the dropwise addition, the reaction is allowed to proceed for 0.5 to 12 hours. From the viewpoint of obtaining the diamine represented by the structural formula (a1) in high yield, the reaction molar ratio of acrylonitrile to 1,4-cyclohexanedimethanol is preferably 2.0 to 4.5 mol, more preferably 2.0 to 3.5 mol, and even more preferably 2.0 to 2.5 mol of acrylonitrile per 1 mol of 1,4-cyclohexanedimethanol.

[0025] After obtaining the dinitrile compound represented by the structural formula (a1') by the above-mentioned addition reaction, the compound is subjected to a reduction reaction to obtain the diamine represented by the structural formula (a1). The reduction reaction is preferably carried out by hydrogenation from the viewpoint of efficiently converting the nitrile group to an amino group.

[0026] The hydrogenation reaction is preferably carried out in the presence of a hydrogenation catalyst. Examples of the hydrogenation catalyst include known hydrogenation catalysts, such as supported heterogeneous hydrogenation catalysts in which metals such as Ni, Co, Pt, Pd, Ru, etc. are supported on carbon, silica, alumina, diatomaceous earth, etc.; so-called Ziegler type hydrogenation catalysts in which transition metal salts such as organic acid salts or acetylacetone salts of Ni, Co, Fe, Cr, etc. and reducing agents such as organoaluminum, etc.; and homogeneous hydrogenation catalysts such as so-called organometallic complexes of organometallic compounds such as Ti, Ru, Rh, Zr, etc.

[0027] The temperature during the hydrogenation reaction is preferably 0 to 200° C., more preferably 10 to 150° C., and even more preferably 20 to 100° C., from the viewpoints of improving the reaction efficiency and suppressing side reactions. The pressure during the hydrogenation reaction is preferably 0.5 to 10 MPaG, more preferably 1.0 to 10 MPaG, and further preferably 3.0 to 8.0 MPaG, from the viewpoints of improving the reaction efficiency and suppressing side reactions. The reaction time is not particularly limited, but is preferably 3 minutes to 24 hours, more preferably 10 minutes to 12 hours, and further preferably 30 minutes to 8 hours.

[0028] The hydrogenation reaction may be carried out in the presence of a solvent. The solvent is not particularly limited as long as it does not inhibit the hydrogenation reaction, but from the viewpoint of the solubility of the substrate and the product, examples of the solvent include alcohol solvents such as methanol and ethanol, and ether solvents such as dibutyl ether, tetrahydrofuran, and dioxane. These may be used alone or in combination of two or more.

[0029] After the hydrogenation reaction, the catalyst is removed from the resulting reaction solution, and purification by distillation or the like is carried out as necessary, to obtain the diamine represented by the structural formula (a1). The method for producing the diamine represented by the structural formula (a1) is not limited to the above method. The above method can also be applied to a method for producing a ring-containing diamine (a) other than the diamine represented by the structural formula (a1).

[0030] Component (A) is a modified product of the ring-structure-containing diamine (a) represented by the above general formula (1). From the viewpoints of curability, appearance of the resulting coating film, water resistance, impact resistance, and improvement of adhesion to a substrate, the modified product (A) of the ring-structure-containing diamine (a) preferably contains at least one selected from the group consisting of the following (I) to (IV): (I) A Mannich reaction product of the ring-containing diamine (a), a phenol compound, and an aldehyde compound. (II) A reaction product of the ring-containing diamine (a) and an unsaturated hydrocarbon compound. (III) A reaction product of the ring-containing diamine (a) and an epoxy compound having at least one epoxy group. (IV) A reaction product of the ring-containing diamine (a) and a carboxylic acid or a derivative thereof. In this specification, the term "reaction product" refers to a product obtained by the reaction of the ring-structure-containing diamine (a) with other components, and means a reaction composition including not only a reactant (adduct) between the ring-structure-containing diamine (a) and other components, but also by-products other than the reactant, unreacted raw materials, and the like.

[0031] (I) Mannich reaction product of ring-containing diamine (a), a phenol compound, and an aldehyde compound) The modified material (I) is a Mannich reaction product of a ring-containing diamine (a), a phenol compound, and an aldehyde compound. Examples of the phenol compound used in the modified product (I) include naturally occurring phenol compounds such as phenol, alkylphenol, alkenylphenol, terpenephenol, and cardanol. From the viewpoints of curability, appearance of the resulting coating film, water resistance, impact resistance, and improved adhesion to the substrate, the number of carbon atoms in the alkyl group in the alkylphenol is preferably 1 to 24, more preferably 1 to 18, and the number of carbon atoms in the alkenyl group in the alkenylphenol is preferably 2 to 24, more preferably 2 to 18. Specific examples of the phenol compound include phenol, cresol, ethylphenol (p-ethylphenol, etc.), isopropylphenol (o-isopropylphenol, p-isopropylphenol, etc.), butylphenol (p-tert-butylphenol, p-sec-butylphenol, o-tert-butylphenol, o-sec-butylphenol, etc.), amylphenol (p-tert-amylphenol, o-tert-amylphenol, etc.), p-octylphenol, nonylphenol, p-cumylphenol, decylphenol, undecylphenol, p-dodecylphenol, tridecylphenol, tetradecylphenol, pentadecylphenol, pentadecenylphenol, pentadecadienylphenol, pentadecatrienylphenol, hexadecylphenol, heptadecylphenol, octadecylphenol, octadecenylphenol, terpene phenol, and cardanol. These may be used alone or in combination of two or more. Among the above, from the viewpoints of reactivity with the ring-structure-containing diamine (a), curability, the appearance of the resulting coating film, water resistance, impact resistance, and improved adhesion to the substrate, the phenol compound used in the modified product (I) is preferably at least one selected from the group consisting of phenol, cresol, p-tert-butylphenol, nonylphenol, and cardanol, and more preferably phenol.

[0032] The aldehyde compound used in the modified product (I) may include formaldehyde; formaldehyde-releasing compounds such as trioxane and paraformaldehyde; and other aldehydes such as benzaldehyde. Among these, at least one selected from the group consisting of formaldehyde and formaldehyde-releasing compounds is preferred. Among these, from the viewpoint of workability in the Mannich reaction, it is more preferred to use an aqueous formaldehyde solution.

[0033] The method for producing the modified product (I) is not particularly limited, and a known method can be used. For example, an aldehyde compound or a solution thereof is added dropwise to a mixture of a ring-structure-containing diamine (a) and a phenolic compound at preferably 80° C. or less, more preferably 60° C. or less, and after the addition is completed, the temperature is raised to preferably 80 to 180° C., more preferably 90 to 150° C., and the reaction is carried out for preferably 0.5 to 12 hours while removing the distillate from the reaction system. The reaction molar ratio of the ring-structure-containing diamine (a), the phenol compound, and the aldehyde compound in the Mannich reaction is not particularly limited as long as the resulting modified product (I) contains an amino group having active hydrogen. From the viewpoints of reactivity with the ring-structure-containing diamine (a), curability, the appearance, water resistance, impact resistance, and improved adhesion to substrates of the resulting coating film, the reaction molar ratio is preferably within the following range. The aldehyde compound is used in an amount of preferably 0.3 to 2 mol, more preferably 0.5 to 1.5 mol, per mol of the ring-containing diamine (a), and the phenol compound is used in an amount of preferably 0.3 to 2 mol, more preferably 0.5 to 1.5 mol, per mol of the ring-containing diamine (a).

[0034] ((II) Reaction product of ring-containing diamine (a) and unsaturated hydrocarbon compound) The modified product (II) is a reaction product of the ring-containing diamine (a) and an unsaturated hydrocarbon compound. The unsaturated hydrocarbon compound used in the modified product (II) is preferably an unsaturated hydrocarbon compound having 2 to 10 carbon atoms from the viewpoints of reactivity with the ring-containing diamine (a), curability, and the appearance, water resistance, impact resistance, and adhesion to a substrate of the resulting coating film. Examples of the unsaturated hydrocarbon compound include unsaturated aliphatic hydrocarbon compounds having 2 to 10 carbon atoms, and aromatic hydrocarbon compounds having 2 to 10 carbon atoms and an ethylenically unsaturated bond, such as at least one selected from the group consisting of ethylene, propylene, butene, pentene, hexene, heptene, octene, nonene, decene, isobutylene, 2-pentene, 3-methyl-1-butene, 2-methyl-2-butene, 2,3-dimethyl-2-butene, cyclohexene, cyclohexadiene, styrene, and divinylbenzene. Among the above, from the viewpoints of reactivity with the ring-structure-containing diamine (a), curability, the appearance of the resulting coating film, water resistance, impact resistance, and improved adhesion to the substrate, the unsaturated hydrocarbon compound is preferably an aromatic hydrocarbon compound having an ethylenically unsaturated bond such as styrene or divinylbenzene, and more preferably styrene.

[0035] The method for producing the modified product (II) is not particularly limited, and a known method can be used. For example, the modified product (II) can be obtained by subjecting a ring-structure-containing diamine (a) and an unsaturated hydrocarbon compound to an addition reaction under a basic catalyst such as lithium amide, usually at 25 to 150°C, preferably 60 to 150°C. More specifically, the unsaturated hydrocarbon compound or its solution is added to a mixture of the ring-structure-containing diamine (a) and a basic catalyst by dropwise addition, preferably at 80°C or less, more preferably at 60°C or less, and after the addition is completed, the temperature is raised to preferably 60 to 150°C, more preferably 90 to 150°C, and the reaction is carried out for 0.5 to 12 hours. The reaction molar ratio of the ring-structure-containing diamine (a) to the unsaturated hydrocarbon compound in the addition reaction is not particularly limited as long as the resulting modified product (II) contains an amino group having active hydrogen, but is preferably in the range of 0.1 to 5.0 mol, more preferably 0.4 to 3.0 mol, even more preferably 0.5 to 1.5 mol, and still more preferably 0.8 to 1.2 mol, per 1 mol of the ring-structure-containing diamine (a).

[0036] ((III) Reaction product of ring-containing diamine (a) and epoxy compound having at least one epoxy group) The modified product (III) is a reaction product of a ring-containing diamine (a) and an epoxy compound having at least one epoxy group. The epoxy compound used in the modified product (III) may be a compound having at least one epoxy group, and more preferably a compound having two or more epoxy groups.

[0037] Examples of the epoxy compound used in the modified product (III) include epichlorohydrin, butyl glycidyl ether, neopentyl glycol diglycidyl ether, 1,3-propanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, biphenol diglycidyl ether, dihydroxynaphthalene diglycidyl ether, dihydroxyanthracene diglycidyl ether, triglycidyl isocyanurate, tetraglycidyl glycoluril, and polyfunctional epoxy resins having a glycidylamino group derived from metaxylylenediamine, and polyfunctional epoxy resins having a glycidylamino group derived from 1,3-bis(aminomethyl)cyclohexane. Examples of the epoxy resin include a polyfunctional epoxy resin having a glycidylamino group derived from diaminodiphenylmethane, a polyfunctional epoxy resin having a glycidylamino group and a glycidyloxy group derived from paraaminophenol, a polyfunctional epoxy resin having a glycidyloxy group derived from bisphenol A, a polyfunctional epoxy resin having a glycidyloxy group derived from bisphenol F, a polyfunctional epoxy resin having a glycidyloxy group derived from phenol novolac, and a polyfunctional epoxy resin having a glycidyloxy group derived from resorcinol. One or more of these may be used.

[0038] Among the above, from the viewpoints of economy, curability, the appearance of the resulting coating film, water resistance, impact resistance, and improved adhesion to the substrate, the epoxy compound is preferably an epoxy compound containing an aromatic ring or an alicyclic structure in the molecule, more preferably an epoxy compound containing an aromatic ring in the molecule, and even more preferably a polyfunctional epoxy resin having a glycidyloxy group derived from bisphenol A.

[0039] The method for producing the modified product (III) is not particularly limited, and a known method can be used. For example, it can be obtained by subjecting a ring-structure-containing diamine (a) and an epoxy compound to an addition reaction under heating conditions. More specifically, the ring-structure-containing diamine (a) or its solution is stirred while an epoxy compound or its solution is added dropwise, etc., at preferably 80°C or less, more preferably 60°C or less, and after the addition is completed, the temperature is raised to preferably 60 to 150°C, more preferably 70 to 120°C, and the reaction is carried out for 0.5 to 12 hours. The ratio of the ring-structure-containing diamine (a) and the epoxy compound used in the addition reaction is not particularly limited as long as the resulting modified product (III) contains an amino group having active hydrogen, but it is preferable to use an excess amount of the ring-structure-containing diamine (a) relative to the epoxy equivalent of the epoxy compound. Specifically, the ring-structure-containing diamine (a) and the epoxy compound are reacted at a ratio of the number of active hydrogen atoms in the ring-structure-containing diamine (a) / the number of epoxy groups in the epoxy compound, which is preferably 4 / 1 to 50 / 1, more preferably 8 / 1 to 20 / 1.

[0040] (IV) Reaction product of ring-containing diamine (a) with carboxylic acid or its derivative) The modified product (IV) is a reaction product of a ring-containing diamine (a) and a carboxylic acid or a derivative thereof. Examples of the carboxylic acid or derivative thereof used in the modified product (IV) include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, α-ethylacrylic acid, α-propylacrylic acid, α-isopropylacrylic acid, α-n-butylacrylic acid, α-t-butylacrylic acid, α-pentylacrylic acid, α-phenylacrylic acid, α-benzylacrylic acid, crotonic acid, 2-pentenoic acid, 2-hexenoic acid, 4-methyl-2-pentenoic acid, 2-heptenoic acid, 4-methyl-2-hexenoic acid, 5-methyl-2-hexenoic acid, 4,4-dimethyl-2-pentenoic acid, 4-phenyl-2-butenoic acid, cinnamic acid, o-methylcinnamic acid, m-methylcinnamic acid, p-methylcinnamic acid, and 2-octenoic acid, as well as their esters, amides, acid anhydrides, and acid chlorides. Among the above, the carboxylic acid or derivative thereof is preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, and derivatives thereof, more preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, and alkyl esters thereof, even more preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, and alkyl esters thereof, still more preferably an alkyl ester of acrylic acid, and even more preferably methyl acrylate.

[0041] The method for producing the modified product (IV) is not particularly limited, and a known method can be used. For example, it can be obtained by reacting a ring-structure-containing diamine (a) with a carboxylic acid or its derivative under heating conditions. More specifically, a method can be mentioned in which a carboxylic acid or its derivative is added dropwise, etc., at preferably 80°C or less, more preferably 60°C or less, to a ring-structure-containing diamine (a) or its solution while stirring, and after the addition is completed, the temperature is preferably raised to 60-150°C, and the reaction is carried out for 0.5-12 hours. The reaction molar ratio of the ring-structure-containing diamine (a) to the carboxylic acid or a derivative thereof in the addition reaction is not particularly limited as long as the resulting modified product (IV) contains an amino group having active hydrogen, but is preferably in the range of 0.3 to 1.0 mol, more preferably 0.6 to 1.0 mol, per 1 mol of the ring-structure-containing diamine (a).

[0042] The modified products (I) to (IV) may be produced in a solvent or without a solvent. The reaction with the ring-containing diamine (a) is preferably carried out in an inert atmosphere such as nitrogen gas.

[0043] As the component (A), one or more modified products of the ring-structure-containing diamine (a) can be used in combination. Among the above, from the viewpoints of curability, appearance of the resulting coating film, water resistance, impact resistance, and improved adhesion to substrates, component (A) preferably includes (III) a reaction product of the ring-structure-containing diamine (a) and an epoxy compound having at least one epoxy group. The epoxy compound is preferably a compound having two or more epoxy groups, more preferably an epoxy compound having an aromatic ring or alicyclic structure in the molecule and having two or more epoxy groups, even more preferably an epoxy compound having an aromatic ring in the molecule and having two or more epoxy groups, and even more preferably a polyfunctional epoxy resin having a glycidyloxy group derived from bisphenol A. The content of the reaction product of (III) the ring-structure-containing diamine (a) and an epoxy compound having at least one epoxy group in component (A) is, from the viewpoints of curability, the appearance of the resulting coating film, water resistance, impact resistance, and improvement in adhesion to a substrate, preferably 50 mass % or more, more preferably 60 mass % or more, even more preferably 70 mass % or more, still more preferably 80 mass % or more, still more preferably 90 mass % or more, and still more preferably 95 mass % or more, but 100 mass % or less.

[0044] From the viewpoint of improving the appearance, water resistance, impact resistance, and adhesion to the substrate of the resulting coating film, the active hydrogen equivalent of component (A) is preferably 70 or more, more preferably 80 or more, and even more preferably 90 or more, and from the viewpoint of improving curability, it is preferably 300 or less, more preferably 250 or less, and even more preferably 200 or less. The active hydrogen equivalent of component (A) (hereinafter also referred to as "AHEW") is the mass of component (A) per mole of active hydrogen.

[0045] The AHEW of component (A) can be calculated from the amine value measured by, for example, the dropping method. In addition, when component (A) is composed of a single compound and its structure is known, it can also be calculated from a theoretical value.

[0046] The curing agent of the present invention may be an epoxy resin curing agent consisting of only component (A), or may contain other curing agent components. In this specification, the curing agent component means a component contained in the epoxy resin curing agent and having two or more active hydrogens capable of reacting with the epoxy group in the epoxy resin. Examples of the other curing agent components include amine-based curing agents other than component (A), phenol-based curing agents, and acid anhydride-based curing agents, and from the viewpoint of fast curing properties, amine-based curing agents are preferred. The amine-based curing agent may be a polyamine compound or a modified product thereof other than the component (A). The polyamine compound is not particularly limited as long as it has at least two amino groups in the molecule. Examples of the polyamine compound or a modified product thereof include linear aliphatic polyamine compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexamethylenediamine, 2-methylpentamethylenediamine, and trimethylhexamethylenediamine; 1,2-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, menthenediamine, isophoronediamine, norbornanediamine, tricyclodecanediamine, adamantanediamine, diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-3,6-diethylcyclohexane, diaminodiethylmethylcyclohexane, and 3,3'-dimethyl-4,4'-diaminodicyclohexyl. Examples of the polyamine compounds include polyamine compounds having an alicyclic structure such as methane and 4,4'-diaminodicyclohexylmethane; polyamine compounds having an aromatic ring such as orthoxylylenediamine, metaxylylenediamine, and paraxylylenediamine, phenylenediamine, diaminodiphenylmethane, and diaminodiphenylsulfone; polyamine compounds having a heterocyclic structure such as N-aminomethylpiperazine and N-aminoethylpiperazine; polyetherpolyamine compounds; reaction products obtained by reacting the above polyamine compounds with an epoxy compound having at least one epoxy group, an unsaturated hydrocarbon compound, a carboxylic acid or a derivative thereof, etc.; Mannich reaction products obtained by reacting the above polyamine compounds with a phenol compound and an aldehyde compound; ketimines (ketimines) obtained by reacting the above polyamine compounds with a ketone compound; and the like. These compounds may be used alone or in combination of two or more.

[0047] However, from the viewpoints of curability, the appearance of the resulting coating film, water resistance, impact resistance, and improved adhesion to the substrate, the content of component (A) in the curing agent of the present invention is preferably 50 mass% or more, more preferably 60 mass% or more, even more preferably 70 mass% or more, still more preferably 80 mass% or more, still more preferably 90 mass% or more, and still more preferably 95 mass% or more, and 100 mass% or less, based on the total curing agent components in the curing agent. The total amount of hardener components in the hardener means the total amount of components having two or more active hydrogens capable of reacting with the epoxy groups in the epoxy resin, which are contained in the hardener.

[0048] The active hydrogen equivalent weight (AHEW) of all curing agent components in an epoxy resin curing agent is preferably 70 or more, more preferably 80 or more, and even more preferably 90 or more from the viewpoint of improving the appearance, water resistance, impact resistance, and adhesion to a substrate of the resulting coating film, and is preferably 300 or less, more preferably 250 or less, and even more preferably 200 or less from the viewpoint of improving curing properties. The AHEW of all curing agent components in an epoxy resin curing agent is the mass per mole of active hydrogen of all curing agent components in an epoxy resin curing agent.

[0049] [Epoxy resin composition] The epoxy resin composition of the present invention contains an epoxy resin and the epoxy resin curing agent. Since the epoxy resin composition of the present invention contains the epoxy resin curing agent, the epoxy resin composition of the present invention has good curing properties and can form a coating film that is excellent in appearance, water resistance, impact resistance, and adhesion to a substrate.

[0050] <Epoxy resin> The epoxy resin, which is the main component of the epoxy resin composition, may be any of saturated or unsaturated aliphatic compounds, alicyclic compounds, aromatic compounds, and heterocyclic compounds. From the viewpoints of curability, appearance of the resulting coating film, water resistance, impact resistance, and improved adhesion to substrates, it is preferable that the epoxy resin contains an aromatic ring or an alicyclic structure in the molecule. Specific examples of the epoxy resin include at least one resin selected from the group consisting of epoxy resins having a glycidylamino group derived from metaxylylenediamine, epoxy resins having a glycidylamino group derived from paraxylylenediamine, epoxy resins having a glycidylamino group derived from 1,3-bis(aminomethyl)cyclohexane, epoxy resins having a glycidylamino group derived from 1,4-bis(aminomethyl)cyclohexane, epoxy resins having a glycidylamino group derived from diaminodiphenylmethane, epoxy resins having a glycidylamino group and / or a glycidyloxy group derived from paraaminophenol, epoxy resins having a glycidyloxy group derived from bisphenol A, epoxy resins having a glycidyloxy group derived from bisphenol F, epoxy resins having a glycidyloxy group derived from phenol novolac, and epoxy resins having a glycidyloxy group derived from resorcinol. The above epoxy resins can also be used in combination of two or more kinds.

[0051] Among the above, from the viewpoints of curability, appearance of the resulting coating film, water resistance, impact resistance, and improved adhesion to substrates, the epoxy resin is preferably one having as a main component at least one selected from the group consisting of epoxy resins having a glycidylamino group derived from meta-xylylenediamine, epoxy resins having a glycidylamino group derived from para-xylylenediamine, epoxy resins having a glycidyloxy group derived from bisphenol A, and epoxy resins having a glycidyloxy group derived from bisphenol F, and from the viewpoints of obtaining a coating film with high hardness, availability, and economy, one having as a main component an epoxy resin having a glycidyloxy group derived from bisphenol A is more preferred. The term "main component" used here means that other components may be contained within a range that does not deviate from the spirit of the present invention, and preferably means 50 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 90 to 100% by mass of the total.

[0052] The content ratio of the epoxy resin to the epoxy resin curing agent in the epoxy resin composition of the present invention is such that the ratio of the number of active hydrogens in the epoxy resin curing agent to the number of epoxy groups in the epoxy resin (number of active hydrogens in the epoxy resin curing agent / number of epoxy groups in the epoxy resin) is preferably 1 / 0.5 to 1 / 2, more preferably 1 / 0.75 to 1 / 1.5, and even more preferably 1 / 0.8 to 1 / 1.2.

[0053] The content of the epoxy resin as the main component in the epoxy resin composition of the present invention is preferably 30 to 90 mass %, more preferably 40 to 80 mass %, and even more preferably 40 to 75 mass %, from the viewpoints of curability, the appearance of the resulting coating film, water resistance, impact resistance, and improvement in adhesion to a substrate. The content of the epoxy resin curing agent in the epoxy resin composition of the present invention is preferably 10 to 70 mass %, more preferably 15 to 50 mass %, and even more preferably 15 to 40 mass %, from the viewpoints of curability, appearance of the resulting coating film, water resistance, impact resistance, and improvement in adhesion to a substrate.

[0054] The epoxy resin curing agent or epoxy resin composition of the present invention may further contain a known curing accelerator, a non-reactive diluent, etc., within the range not impairing the effects of the present invention. Examples of the curing accelerator include phenol compounds, organic acids, organic acid salts, tertiary amines, quaternary ammonium salts, imidazoles, organic phosphorus compounds, quaternary phosphonium salts, diazabicycloalkenes, organic metal salt compounds, boron compounds, and metal halides. Examples of the non-reactive diluent include benzyl alcohol, furfuryl alcohol, tetrafurfuryl alcohol, aromatic hydrocarbon formaldehyde resins, and the like. One or more of these can be used.

[0055] The epoxy resin composition of the present invention may further contain other components, such as modifying components such as fillers and plasticizers, flow adjusting components such as thixotropic agents, pigments, leveling agents, tackifiers, and elastomer fine particles, depending on the application. However, from the viewpoint of effectively obtaining the effects of the present invention, the total content of the epoxy resin and the epoxy resin curing agent in the epoxy resin composition is preferably 50 mass % or more, more preferably 70 mass % or more, and even more preferably 80 mass % or more, and 100 mass % or less.

[0056] The epoxy resin composition of the present invention may contain a solvent (water and a volatile solvent) other than the non-reactive diluent, but the content thereof in the epoxy resin composition is preferably 5% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less.

[0057] <Method of producing epoxy resin composition> There is no particular restriction on the method for producing the epoxy resin composition, and the epoxy resin, the epoxy resin curing agent, and other components as necessary can be mixed and produced using a known method and device. There is also no particular restriction on the order of mixing the components contained in the epoxy resin composition, and after preparing the epoxy resin curing agent, this may be mixed with the epoxy resin, or the component (A) constituting the epoxy resin curing agent and other components may be mixed with the epoxy resin simultaneously.

[0058] [paint] The present invention provides a coating material containing the epoxy resin composition. The coating material of the present invention contains the epoxy resin composition, and thus can form a coating film having good curability, and excellent appearance, water resistance, impact resistance, and adhesion to a substrate. Examples of the coating material include marine coating materials, heavy-duty anticorrosive coating materials, coating materials for tanks, coating materials for pipe interiors, coating materials for exteriors, and coating materials for flooring.

[0059] The content of the epoxy resin composition in the coating material of the present invention is, from the viewpoints of curability, the appearance of the resulting coating film, water resistance, impact resistance, and improvement in adhesion to the substrate, preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and even more preferably 95% by mass or more, but 100% by mass or less. EXAMPLES

[0060] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In each example, various measurements and evaluations were carried out as follows.

[0061] ( 1 H-NMR analysis) The structure of the ring-containing diamine obtained in Production Example 1 was identified as follows: 1 The measurement conditions were as follows: Nuclear magnetic resonance spectrometer: AVANCEIII-500 manufactured by Bruker Biospin Corporation Probe: 5mmφ double resonance multinuclear probe (BBFO Plus Smart probe) Deuterated solvent; deuterated chloroform Measuring nucleus; 1 H Measurement temperature; room temperature

[0062] (Dry to the touch) A zinc phosphate-treated steel plate (SPCC-SD PB-N144, 0.8 mm x 70 mm x 150 mm, manufactured by Paltec Co., Ltd.) was used as the substrate. The epoxy resin composition of each example was applied to the substrate using an applicator at 23°C and 50% RH to form a coating film (coating thickness immediately after application: 200 μm). This coating film was stored at 23°C and 50% RH, and evaluated by touch after 1, 2, and 7 days according to the following criteria. The results are shown in Table 1. Ex: Excellent (Even when pressed with a force of about 50N using a thumb, the coating does not become sticky and no fingerprints remain) G: Good (the coating is not sticky when the thumb is pressed against it with a force of about 50N, but fingerprints remain after touching it) F: Fair (the coating is sticky when you press your thumb against it with a force of about 50N) P: Poor (the coating is sticky when pressed with a thumb with a force of about 5N)

[0063] (Water resistance spot test) In the same manner as above, the epoxy resin composition was applied onto a substrate (zinc phosphate-treated iron plate) to form a coating (thickness immediately after application: 200 μm). This coating was stored under conditions of 23°C and 50% RH, and after 1 and 7 days, 2 to 3 drops of pure water were dropped onto the coating surface with a dropper, and the area was covered with a 50 mL screw cap. After 24 hours, the water was wiped off, and the appearance was visually observed and evaluated according to the following criteria. The results are shown in Table 1. Ex: No change G: Slight changes, but good F: Changed

[0064] (RCI curing time) The epoxy resin composition of each example was applied to a glass plate (25mm x 348mm x 2.0mm, manufactured by Taiyu Kizai Co., Ltd.) using a 76μm applicator at 23℃ and 50% RH to form a coating. The glass plate on which the coating was formed was set in a paint drying time measuring device (manufactured by Taiyu Kizai Co., Ltd.), and the time it took to reach each drying stage (touch dry, semi-dry, completely dry) was measured according to the following criteria by observing the marks left when the needle of the measuring device scratched the coating surface. The results are shown in Table 1. A shorter time indicates a faster curing speed. Set to Touch: The time when the needle begins to leave a mark on the glass plate. Semi-dry (Dust Free): The time it takes for the needle marks to appear on the surface of the coating. Dry through: The time when no trace of the needle remains on the coating

[0065] (Appearance of the coating) In the same manner as above, the epoxy resin composition was applied onto a substrate (zinc phosphate-treated steel sheet) to form a coating film (thickness immediately after application: 200 μm). The appearance of the resulting coating film was visually observed after one day, and the transparency, smoothness, and gloss were evaluated according to the following criteria. <Transparency> Ex: Excellent (no turbidity) G: Good (slightly cloudy, but no problem in use) F: Fair (slightly cloudy) P: Poor (cloudy) <Smoothness> Ex: Excellent (no unevenness) G: Good (slightly uneven, but no problem in use) F: Acceptable (some unevenness) P: Poor (cracking or unevenness on the entire surface) <Glossiness> Ex: Excellent (glossy) G: Good (slightly less glossy, but no problems in use) F: Fair (low gloss) P: Poor (no gloss)

[0066] (Eriksen test) In the same manner as above, the epoxy resin composition was applied to a substrate (zinc phosphate-treated steel plate) using an applicator to form a coating (coating thickness immediately after application: 200 μm). This coating was stored under conditions of 23°C and 50% RH, and after 7 days, the coating was subjected to an Erichsen test under conditions of 23°C and 50% RH in accordance with JIS K 5600-5-2:1999 (cupping resistance) using an Erichsen film strength tester ("HD-4510" manufactured by Ueshima Seisakusho Co., Ltd.) to measure the minimum indentation depth until the coating was defective. The results are shown in Table 1. A larger value indicates that the coating has a higher ability to follow deformation and has better adhesion to the substrate.

[0067] (DuPont impact test) The epoxy resin composition was applied to a substrate (zinc phosphate-treated steel plate) in the same manner as above to form a coating film (thickness immediately after application: 200 μm). This coating film was stored under conditions of 23° C. and 50% RH, and after 7 days, a DuPont impact test (weight drop resistance test) was performed on the coating film in accordance with JIS K 5600-5-3:1999. A DuPont drop impact tester (manufactured by Mize Testing Instruments Co., Ltd.) was used to drop a 500g weight onto the coating surface (front) and back from heights of 50cm, 30cm, 20cm, and 10cm, respectively, and the heights at which the coating could withstand the impact are shown in Table 1. A higher value indicates a higher impact resistance for the coating. If the coating could not withstand an impact from a height of 10cm, it was recorded as "10F."

[0068] (Cross-cut peel test) Cross-cutting was performed according to a method in accordance with JIS K 5600-5-6:1999, and the adhesion of the coating film to the substrate was evaluated. The epoxy resin composition was applied to a substrate (zinc phosphate-treated steel plate) in the same manner as above to form a coating film (thickness immediately after application: 200 μm). This coating film was stored under conditions of 23° C. and 50% RH, and after 7 days, six cuts were made on the coating film surface using a cutter knife, reaching the substrate. At this time, the interval between the cuts was 1 mm. Furthermore, six cuts were made from above the cuts in a direction perpendicular to the cuts, reaching the substrate in the same manner as above, to form 25 1 mm square grids. Cellophane tape was firmly pressed onto the grid portions, and the end of the tape was peeled off at an angle of 45° in one go, and the number of grids remaining on the substrate was visually confirmed. Table 1 shows the test results based on the six-level classification of 0 to 5 specified in JIS K 5600-5-6:1999. A classification of "0" is the best and "5" is the worst. The number of grids remaining on the substrate, X, is shown as "X / 25" in Table 1. The larger the value of X, the more resistant the coating is to peeling and the better the adhesion to the substrate.

[0069] Production Example 1 (Production of ring-containing diamine: aminopropyl-modified cyclohexanedimethanol (CHDM-AP)) CHDM-AP represented by the following structural formula was produced by the following method. 25.5g (0.178mol) of 1,4-cyclohexanedimethanol, 1.4g (0.013mol) of 50% by mass aqueous potassium hydroxide solution, and 25mL of tetrahydrofuran were mixed in a 200mL flask, and 21.25g (0.40mol) of acrylonitrile was added dropwise over about 1 hour while maintaining the internal temperature at 25-31°C. After the dropwise addition, the mixture was stirred at room temperature for 3 hours. After the reaction was completed, the solvent was removed using an evaporator, and 40.8g of acrylonitrile-modified cyclohexanedimethanol was obtained. Next, 15.36 g of acrylonitrile-modified cyclohexanedimethanol, 7.68 g of Raney cobalt catalyst ("RANEY 2724" manufactured by W.R. Grace Japan Co., Ltd.) and 150 mL of tetrahydrofuran were mixed in a 200 mL autoclave, and hydrogen was introduced at a pressure of 7.5 MPa while maintaining the temperature at 80°C to carry out a hydrogenation reaction for 1 hour. The obtained composition was purified by distillation, and finally 5.06 g of aminopropyl-modified cyclohexanedimethanol was obtained with a purity of 94.5%. [ka] 1 H-NMR chemical shift: δ 4.80 ppm (s, 4H, -CH H 2), 3.21-3.47ppm(m, 12H, -C H 2-OC H 2-, -C H 2NH2), 2.79ppm(t, 4H, -C H 2CH2NH2), 0.93-1.81ppm(m, 10H, -C6 H 10 -)

[0070] Example 1 (Production and Evaluation of Epoxy Resin Curing Agent Solution and Epoxy Resin Composition) (1) Manufacturing of epoxy resin hardener solution 129 g of CHDM-AP obtained in Production Example 1 was charged into a 1-liter separable flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, a dropping funnel, and a cooling tube, and the temperature was raised to 80° C. while stirring under a nitrogen stream. While maintaining the temperature at 80° C., 37.2 g (an amount such that the number of active hydrogens in CHDM-AP / the number of epoxy groups in the epoxy compound=10 / 1) of a multifunctional epoxy resin having a glycidyloxy group derived from bisphenol A ("jER828" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 186 g / equivalent) was dropped over 2 hours as an epoxy compound. After the dropwise addition was completed, the temperature was raised to 100° C. and the reaction was carried out for 2 hours to obtain a reaction product (epoxy modified product) of CHDM-AP and jER828, which corresponds to component (A). Benzyl alcohol, a non-reactive diluent, was added in an amount of 40% by mass of the total amount to dilute the mixture, and an epoxy resin curing agent solution with a concentration of the epoxy modified product of 60% by mass was obtained. The active hydrogen equivalent weight (AHEW) of the epoxy resin hardener solution (total amount including benzyl alcohol) was 160.

[0071] (2) Preparation of epoxy resin composition A polyfunctional epoxy resin having a glycidyloxy group derived from bisphenol A ("jER828" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent weight 186 g / equivalent) was used as the epoxy resin, which is the main component of the epoxy resin composition. The epoxy resin and the epoxy resin curing agent solution were mixed together in such a way that the ratio of the number of active hydrogens in the epoxy resin curing agent to the number of epoxy groups in the main epoxy resin (number of active hydrogens in epoxy resin curing agent / number of epoxy groups in main epoxy resin) was 1 / 1 to prepare an epoxy resin composition. The obtained epoxy resin composition was subjected to various evaluations by the above-mentioned methods, and the results are shown in Table 1.

[0072] Comparative Example 1 (1) Preparation of epoxy resin hardener solution In Example 1, 71 g of 1,3-bis(aminomethyl)cyclohexane (1,3-BAC, manufactured by Mitsubishi Gas Chemical Co., Ltd.), which is a ring structure-containing diamine not corresponding to component (a), was used instead of 129 g of CHDM-AP. The same operation as in Example 1 was performed except for the above to obtain a reaction product (epoxy modified product) of 1,3-BAC and jER828. Benzyl alcohol, which is a non-reactive diluent, was added in an amount of 40 mass% of the total amount to dilute the product, and an epoxy resin curing agent solution with a concentration of the epoxy modified product of 60 mass% was obtained. The active hydrogen equivalent (AHEW) of the epoxy resin curing agent solution (total amount including benzyl alcohol) was 100.

[0073] (2) Preparation of epoxy resin composition Using the epoxy resin curing agent solution obtained in (1) above, an epoxy resin composition was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0074] [Table 1]

[0075] From Table 1, it can be seen that the epoxy resin composition containing the epoxy resin curing agent of the present invention has good curability and the appearance of the coating film obtained, and further, can form a coating film which is superior in water resistance, impact resistance, and adhesion to a substrate to the epoxy resin composition of Comparative Example 1. [Industrial Applicability]

[0076] According to the present invention, there can be provided an epoxy resin curing agent, an epoxy resin composition, and a coating material which are capable of forming a coating film having good curability and appearance, and excellent water resistance, impact resistance, and adhesion to a substrate.

Claims

1. An epoxy resin curing agent containing a modified product (A) of a ring-structure-containing diamine (a) represented by the following general formula (1). 【Chemistry 1】 In the formula, X is a divalent group containing a ring structure. p and q are independently numbers from 2 to 10, and r and s are independently numbers from 0 to 4.

2. The epoxy resin curing agent according to claim 1, wherein the ring structure comprises at least one selected from the group consisting of alicyclic hydrocarbon structures and aromatic hydrocarbon structures.

3. The epoxy resin curing agent according to claim 2, wherein the ring structure includes a cyclohexane ring.

4. The epoxy resin curing agent according to any one of claims 1 to 3, wherein the modified product (A) of the ring structure-containing diamine (a) includes at least one selected from the group consisting of (I) to (IV) below. (I) Mannich reaction products of the ring-structure-containing diamine (a), phenol compound, and aldehyde compound. (II) Reaction product of the ring structure-containing diamine (a) and an unsaturated hydrocarbon compound (III) Reaction product of the ring-structure-containing diamine (a) and an epoxy compound having at least one epoxy group (IV) Reaction product of the ring-structure-containing diamine (a) with a carboxylic acid or its derivative

5. An epoxy resin composition comprising an epoxy resin and an epoxy resin curing agent according to any one of claims 1 to 3.

6. A paint comprising the epoxy resin composition of claim 5.

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