Epoxy resin curing agent, epoxy resin composition, and paint

Abstract

To provide an epoxy resin curing agent, an epoxy resin composition and a paint that cure fast, have low viscosity, and can form a paint film with high hardness.SOLUTION: An epoxy resin curing agent and an epoxy resin composition contain the following components (A) and (B): (A) a diamine represented by the general formula (1) in the figure, where m and n are each independently a number from 0 to 4, or a modified form thereof; and (B) a polyamine having a ring structure other than the component (A), or a modified form thereof. Also provided is a paint containing them.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[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 paint field such as anticorrosive paints for ships, bridges, and land and sea iron structures, lining, reinforcement, and repair materials for concrete structures, floor materials for buildings, lining of sewers, paving materials, adhesives, etc. in the civil engineering and construction fields.

[0003] Compounds obtained by modifying polyamine with an epoxy compound or the like (modified polyamine) are also known to be useful as epoxy resin curing agents. For example, in Patent Document 1, an adduct obtained by reacting a polyglycidyl ether of polyphenol, which is solid at room temperature, with an alicyclic or alicyclic aliphatic di-primary diamine in which at least one of the primary amino groups is bonded to an endo-type carbon atom in an alicyclic ring at a predetermined ratio is disclosed to be suitable as a curing agent for epoxy resins.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Although the viscosity of modified polyamine may increase and the handleability may decrease as compared with unmodified polyamine, Patent Document 1 also describes using trimethyl-hexamethylenediamine or the like in order to reduce the viscosity of the adduct. Here, among the various applications of epoxy resin compositions, it is important that epoxy resin compositions for paints have good coating properties such as appearance, water resistance, and hardness. However, the technology disclosed in Patent Document 1 had room for improvement in obtaining a high-hardness coating while suppressing the decrease in curing speed and increase in viscosity of the epoxy resin curing agent and epoxy resin composition. The object of the present invention is to provide an epoxy resin curing agent, an epoxy resin composition, and a paint that can form a coating film that hardens quickly, has low viscosity, and high hardness. [Means for solving the problem]

[0006] The present inventors have found that an epoxy resin curing agent containing an alicyclic diamine or a modified version thereof having a predetermined structure and another polyamine or a modified version thereof having a cyclic structure can solve the above problems. In other words, the present invention relates to the following. [1] An epoxy resin curing agent containing the following components (A) and (B). (A) Diamines represented by the following general formula (1) or modified thereof [ka] In equation (1), m and n are independently numbers between 0 and 4. (B) Polyamines having a cyclic structure other than component (A) or modified thereof [2] An epoxy resin composition comprising an epoxy resin and the epoxy resin curing agent described in [1] above. [3] A paint comprising the epoxy resin composition described in [2] above. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an epoxy resin curing agent, an epoxy resin composition, and a cured product thereof that can form a coating film that hardens quickly, has low viscosity, and high hardness. [Modes for carrying out the invention]

[0008] [Epoxy resin hardener] The epoxy resin curing agent of the present invention contains the following components (A) and (B). (A) Diamines represented by the following general formula (1) or modified thereof [ka] In equation (1), m and n are independently numbers between 0 and 4. (B) Polyamines having a cyclic structure other than component (A) or modified thereof By using the epoxy resin curing agent described above, it is possible to provide an epoxy resin composition that hardens quickly, has low viscosity, and can form a coating film with high hardness. Hereinafter, the epoxy resin curing agent of the present invention will also be simply referred to as "the curing agent of the present invention."

[0009] The reason why the above effects are obtained by using the curing agent of the present invention in an epoxy resin composition is not entirely clear, but it is thought to be as follows. The curing agent of the present invention can be made less viscous by containing component (A), and when used in an epoxy resin composition, it is believed that high hardness can be obtained in the cured coating film of the epoxy resin composition. However, when component (A) is used alone as an epoxy resin curing agent, the curing speed tends to be slow, and there is room for improvement in this respect. Furthermore, as disclosed in Patent Document 1, when component (A) is used in combination with a chain-like diamine such as trimethyl-hexamethylenediamine in an epoxy resin curing agent, there is a concern that the curing speed and the hardness of the coating film, which is the cured product of the epoxy resin composition, will decrease. In the present invention, by using an epoxy resin curing agent that contains both component (A) and component (B), which is a polyamine having a ring structure or a modified version thereof, it is possible to increase the curing speed while maintaining the low viscosity derived from component (A) and the high hardness of the coating film.

[0010] <Component (A): Diamine represented by general formula (1) or a modified form thereof> The epoxy resin curing agent of the present invention contains, as component (A), a diamine represented by the following general formula (1) or a modified product thereof. [Chemical formula] In formula (1), m and n are each independently a number from 0 to 4. From the viewpoints of rapid curing property, low viscosity property, and improvement of the hardness of the coating film, in formula (1), m and n are preferably from 0 to 3, more preferably from 0 to 2, and still more preferably 0 or 1. However, from the viewpoints of improvement of rapid curing property and low viscosity property, when both m and n in formula (1) are 0, it is excluded. From the viewpoints of rapid curing property, low viscosity property, and improvement of the hardness of the coating film, m in formula (1) is 0, and n is from 1 to 4, preferably from 1 to 3, more preferably 1 or 2, and still more preferably 1.

[0011] Specific examples of the diamine represented by the general formula (1) include 1,2-diaminocyclopentane, 1,2-bis(aminomethyl)cyclopentane, 1,2-bis(aminoethyl)cyclopentane, 1,2-bis(aminopropyl)cyclopentane, 1,2-bis(aminobutyl)cyclopentane, 2-aminomethylcyclopentylamine, 2-aminoethylcyclopentylamine, 2-aminopropylcyclopentylamine, 2-aminobutylcyclopentylamine, etc. Among these, one or more of them can be used. Among the above, from the viewpoints of rapid curing property, low viscosity property, and improvement of the hardness of the coating film, the diamine represented by the general formula (1) is preferably at least one selected from the group consisting of 2-aminomethylcyclopentylamine, 2-aminoethylcyclopentylamine, 2-aminopropylcyclopentylamine, and 2-aminobutylcyclopentylamine, more preferably at least one selected from the group consisting of 2-aminomethylcyclopentylamine and 2-aminoethylcyclopentylamine, and still more preferably 2-aminomethylcyclopentylamine.

[0012] Component (A) may be the diamine represented by the general formula (1) or a modified product of the diamine. Specific examples of the modified product of the diamine represented by the general formula (1) include Mannich modified products, epoxy modified products, Michael adducts, Michael addition polycondensates, styrene modified products, polyamide modified products, etc. of the diamine represented by the general formula (1). Among these, as the modified product of the diamine represented by the general formula (1), from the viewpoints of rapid curing property, low viscosity property, and improvement in the hardness of the coating film, preferably, an epoxy modified product of the diamine represented by the general formula (1) is preferred. The epoxy modified product of the diamine represented by the general formula (1) is a reaction product of the diamine represented by the general formula (1) and an epoxy compound having at least one epoxy group. In this specification, the reaction product of the diamine represented by the general formula (1) and an epoxy compound having at least one epoxy group means a product obtained by the reaction of the diamine and the epoxy compound, and means a reaction composition containing the reaction product (adduct) of the diamine and the epoxy compound. Hereinafter, the epoxy modified product of the diamine represented by the general formula (1) is also simply referred to as "the epoxy modified product".

[0013] The epoxy compound used for the epoxy modified product may be a compound having at least one epoxy group, and a compound having two or more epoxy groups is more preferred. Specific examples of the epoxy compound include epichlorohydrin, butyl diglycidyl 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 glycol uryl, polyfunctional epoxy resin having a glycidylamino group derived from metaxylylenediamine, and 1,3-bis(aminomethyl)cyclohexane. Examples include polyfunctional epoxy resins having derived glycidylamino groups, polyfunctional epoxy resins having glycidylamino groups derived from diaminodiphenylmethane, polyfunctional epoxy resins having glycidylamino groups and / or glycidyloxy groups derived from para-aminophenol, polyfunctional epoxy resins having glycidyloxy groups derived from bisphenol A, polyfunctional epoxy resins having glycidyloxy groups derived from bisphenol F, polyfunctional epoxy resins having glycidyloxy groups derived from phenol novolac, and polyfunctional epoxy resins having two or more glycidyloxy groups derived from resorcinol. These can be used individually or in combination of two or more. From the viewpoint of rapid curing, low viscosity, and improved hardness of the coating film, epoxy compounds containing an aromatic ring or alicyclic structure in the molecule are more preferred, compounds containing an aromatic ring in the molecule are even more preferred, and polyfunctional epoxy resins having a glycidyloxy group derived from bisphenol A are even more preferred.

[0014] The epoxy-modified product is obtained by a ring-opening addition reaction between a diamine represented by general formula (1) and an epoxy compound using a known method. For example, the diamine represented by general formula (1) is charged into a reactor, and the epoxy compound is added thereto all at once or in stages by dropwise addition, and the mixture is heated to cause the reaction. The addition reaction is preferably carried out under an inert atmosphere such as nitrogen gas.

[0015] The amounts of the diamine represented by general formula (1) and the epoxy compound used are not particularly limited as long as the resulting epoxy-modified product contains amino groups with active hydrogen. However, from the viewpoint of the resulting epoxy-modified product exhibiting its function as an epoxy resin curing agent, it is preferable to use an excess amount of diamine relative to the epoxy equivalent of the epoxy compound in this addition reaction. Specifically, the diamine and epoxy compound are used such that the number of active hydrogens in the diamine (number of active hydrogens in the diamine / number of epoxy groups in the epoxy compound) is preferably 50 / 1 to 4 / 1, more preferably 20 / 1 to 4 / 1.

[0016] The temperature and reaction time during the addition reaction can be appropriately selected, but from the viewpoint of reaction rate, productivity, and preventing decomposition of the raw materials, the temperature during the addition reaction is preferably 50 to 150°C, more preferably 70 to 120°C. The reaction time is preferably 0.5 to 12 hours, more preferably 1 to 6 hours, after the addition of the epoxy compound is completed.

[0017] Component (A) preferably contains a modified diamine represented by the general formula (1), and more preferably contains an epoxy modified diamine represented by the general formula (1), from the viewpoint of rapid curing, low viscosity, and improved hardness of the coating film. When component (A) contains an epoxy modified diamine represented by the general formula (1), the content of the epoxy modified diamine in component (A) is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and 100% by mass or less, from the viewpoint of rapid curing, low viscosity, and improved hardness of the coating film.

[0018] <Component (B): A polyamine having a cyclic structure other than component (A), or a modified version thereof> The epoxy resin curing agent of the present invention contains, as component (B), a polyamine having a cyclic structure other than component (A) or a modified version thereof. The polyamine is a compound (unmodified form) having at least one ring structure and at least two amino groups within its molecule. From the viewpoint of ensuring low viscosity, the number of ring member carbons in the ring structure of the polyamine is preferably 5 to 20, more preferably 5 to 12, even more preferably 5 to 8, even more preferably 5 to 6, and even more preferably 6.

[0019] The ring structures of the polyamines mentioned above include alicyclic structures, aromatic rings, and heterocyclic structures. An alicyclic structure refers to a ring structure derived from an alicyclic hydrocarbon. This alicyclic structure may be saturated or unsaturated, and may be monocyclic or polycyclic. Furthermore, the alicyclic structure may have substituents. Examples of such substituents include C1-C8 alkyl groups, hydroxyl groups, and C1-C8 alkoxy groups. Examples of such alicyclic structures include, but are not limited to, cycloalkane rings, cycloalkene rings, bicycloalkane rings, bicycloalkene rings, and tricycloalkane rings. Among these, cycloalkane rings are preferred, more preferably cycloalkane rings having 5 to 8 carbon atoms, even more preferably at least one selected from the group consisting of cyclopropane rings and cyclohexane rings, and even more preferably cyclohexane rings.

[0020] The aromatic ring may be a monoring or a fused ring, and examples include, but are not limited to, a benzene ring, a naphthalene ring, anthracene ring, a phenanthrene ring, and a tetracene ring. Among these, it is preferably at least one selected from the group consisting of a benzene ring and a naphthalene ring, and more preferably a benzene ring.

[0021] As for heterocyclic structures, ring structures containing at least one nitrogen atom as an element constituting the ring structure are preferred, and examples include piperazine rings, piperidine rings, pyridine rings, pyrimidine rings, etc.

[0022] The number of amino groups in the polyamine is preferably 2 to 4, more preferably 2. The amino groups may be directly attached to the ring structure, but from the viewpoint of improving the curing speed, it is preferable to have at least one amino group that is not directly attached to the ring structure.

[0023] Specific examples of the aforementioned polyamines include aromatic ring-containing aliphatic polyamines such as orthoxylylenediamine, metaxylylenediamine (MXDA), and paraxylylenediamine (PXDA); isophoronediamine (IPDA), mensendiamine, norbornanediamine, tricyclodecanediamine, adamantanediamine, diaminocyclohexane, 1,2-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-3,6-diethylcyclohexane, diaminodiethylmethylcyclohexane, and 3,3'-dimethyl-4,4 Examples include polyamines having an alicyclic structure such as '-diaminodicyclohexylmethane (bis(4-amino-3-methylcyclohexyl)methane), 3,3',5,5'-tetramethyl-4,4'-diaminodicyclohexylmethane, and 4,4'-diaminodicyclohexylmethane; aromatic polyamines such as phenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, diethyltoluenediamine, and 2,2'-diethyl-4,4'-methylenedianiline; and polyamines having a heterocyclic structure such as N-aminoethylpiperazine and N,N'-bis(aminoethyl)piperazine. One of these can be used alone or in combination of two or more.

[0024] Examples of modified polyamines include Mannich modified polyamines, epoxy modified polyamines, Michael adducts, Michael adduct-polycondensate products, styrene modified polyamines, and polyamide modified polyamines, with epoxy modified polyamines being preferred. The epoxy-modified polyamine is a reaction product of the polyamine and an epoxy compound having at least one epoxy group. The epoxy compound, the method for producing the epoxy-modified product, and their preferred ranges are the same as those described in the description of the epoxy-modified diamine for component (A).

[0025] Furthermore, in the curing agent of the present invention, if component (A) is an epoxy modified product of a diamine represented by the general formula (1) and component (B) is an epoxy modified product of a polyamine having a ring structure, a mixture of component (A) and component (B) can also be produced by reacting a mixture of the diamine represented by the general formula (1) and the polyamine having a ring structure with the epoxy compound.

[0026] Among the above, from the viewpoint of rapid curing, low viscosity, and improved hardness of the coating film, component (B) is preferably a polyamine having an alicyclic structure or a modified thereof, such as isophorone diamine, mensendiamine, norbornanediamine, tricyclodecanediamine, adamantanediamine, diaminocyclohexane, 1,2-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-3,6-diethylcyclohexane, diaminodiethylmethylcyclohexane, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane (bis(4-amino-3-methylcyclohexyl)methane), 3,3',5,5' -Tetramethyl-4,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexylmethane, or modified versions thereof are more preferred, at least one selected from the group consisting of isophoronediamine, 1,3-bis(aminomethyl)cyclohexane, or modified versions thereof is even more preferred, isophoronediamine, 1,3-bis(aminomethyl)cyclohexane, or epoxy modified versions thereof are even more preferred, and it is even more preferable to include at least one selected from the group consisting of epoxy modified isophoronediamine and epoxy modified 1,3-bis(aminomethyl)cyclohexane, and from the viewpoint of rapid curing and low viscosity, it is even more preferable to include epoxy modified 1,3-bis(aminomethyl)cyclohexane. If component (B) contains at least one selected from the group consisting of epoxy modified isophoronediamine and epoxy modified 1,3-bis(aminomethyl)cyclohexane, the content of the epoxy modified in component (B) is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and 100% by mass or less, from the viewpoint of rapid curing, low viscosity, and improvement of coating film hardness.

[0027] The molar ratio of component (A) to component (B) in the epoxy resin curing agent of the present invention is preferably 1 / 99 to 99 / 1, more preferably 10 / 90 to 90 / 10, even more preferably 20 / 80 to 80 / 20, even more preferably 30 / 70 to 70 / 30, and even more preferably 40 / 60 to 60 / 40, from the viewpoint of balancing rapid curing, low viscosity, and hardness of the coating film.

[0028] The curing agent of the present invention may be an epoxy resin curing agent comprising component (A) and component (B), or it may contain other curing agent components. Examples of other curing agent components include polyamine-based curing agents other than components (A) and (B), phenol-based curing agents, acid anhydride-based curing agents, etc. However, the total content of component (A) and component (B) in the curing agent of the present invention is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more, and 100% by mass or less, based on the total curing agent components in the curing agent. The total amount of curing agent components in the curing agent refers to the total amount of components contained in the curing agent that have two or more active hydrogen atoms capable of reacting with the epoxy groups in the epoxy resin.

[0029] The active hydrogen equivalent of the curing agent of the present invention is preferably 25 or more from the viewpoint of improving the hardness of the coating film, and preferably 150 or less, more preferably 130 or less, from the viewpoint of improving low viscosity and rapid curing. Active hydrogen equivalent (hereinafter also referred to as "AHEW") is the mass per mole of active hydrogen in the epoxy resin curing agent.

[0030] The epoxy resin curing agent of the present invention has low viscosity. For example, the viscosity of a 60% by mass benzyl alcohol solution of the epoxy resin curing agent at 25°C is preferably 1,800 mPa·s or less, more preferably 1,500 mPa·s or less, and even more preferably 1,200 mPa·s or less. The lower limit of the viscosity is not particularly limited, but is usually 50 mPa·s or more. The viscosity of a 60% by mass benzyl alcohol solution of epoxy resin curing agent at 25°C can be measured using an E-type viscometer, specifically by the method described in the examples.

[0031] [Epoxy resin composition] The epoxy resin composition of the present invention contains an epoxy resin and the epoxy resin curing agent. Because the epoxy resin composition of the present invention contains the epoxy resin curing agent, it can cure quickly, have low viscosity, and form a coating film with high hardness.

[0032] <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, or heterocyclic compounds. From the viewpoint of obtaining a coating film with high hardness, it is preferable that the epoxy resin contains an aromatic ring or an alicyclic structure within its molecule. Specific examples of the epoxy resin include at least one resin selected from the following: epoxy resins having glycidylamino groups derived from metaxylylenediamine, epoxy resins having glycidylamino groups derived from paraxylylenediamine, epoxy resins having glycidylamino groups derived from 1,3-bis(aminomethyl)cyclohexane, epoxy resins having glycidylamino groups derived from 1,4-bis(aminomethyl)cyclohexane, epoxy resins having glycidylamino groups derived from diaminodiphenylmethane, epoxy resins having glycidylamino groups and / or glycidyloxy groups derived from para-aminophenol, epoxy resins having glycidyloxy groups derived from bisphenol A, epoxy resins having glycidyloxy groups derived from bisphenol F, epoxy resins having glycidyloxy groups derived from phenol novolac, and epoxy resins having glycidyloxy groups derived from resorcinol. Two or more of the above epoxy resins can also be used in mixture form.

[0033] Among the above, from the viewpoint of obtaining a highly hard coating film, it is preferable that the epoxy resin mainly consists of at least one selected from the group consisting of an epoxy resin having a glycidylamino group derived from metaxylylenediamine, an epoxy resin having a glycidylamino group derived from paraxylylenediamine, an epoxy resin having a glycidyloxy group derived from bisphenol A, and an epoxy resin having a glycidyloxy group derived from bisphenol F. From the viewpoint of obtaining a highly hard coating film, availability, and economic efficiency, it is more preferable that the epoxy resin mainly consists of an epoxy resin having a glycidyloxy group derived from bisphenol A. The term "main component" as used herein means that the product may contain other components without departing from the spirit of the present invention, preferably 50 to 100% by mass of the total, more preferably 70 to 100% by mass, and even more preferably 90 to 100% by mass.

[0034] The epoxy resin content in the epoxy resin composition of the present invention is preferably 30 to 90% by mass, more preferably 40 to 80% by mass, and even more preferably 50 to 75% by mass, from the viewpoint of rapid curing, low viscosity, and improved hardness of the coating film.

[0035] The amount of 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. Furthermore, the content of the epoxy resin curing agent in the epoxy resin composition of the present invention is preferably 10 to 70% by mass, more preferably 15 to 50% by mass, and even more preferably 15 to 35% by mass, from the viewpoint of rapid curing, low viscosity, and improvement of the hardness of the coating film.

[0036] The epoxy resin composition of the present invention may further contain known curing accelerators, non-reactive diluents such as benzyl alcohol, etc., to the extent that they do not impair the effects of the present invention.

[0037] Furthermore, the epoxy resin composition of the present invention may also contain other components depending on the application, such as fillers, plasticizers and other modifying components, thixotropes and other flow-adjusting components, pigments, leveling agents, tackifiers, and elastomer fine particles. However, from the viewpoint of effectively obtaining the effects of the present invention, the total content of epoxy resin and epoxy resin curing agent in the epoxy resin composition is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and 100% by mass or less.

[0038] There are no particular restrictions on the method for preparing the epoxy resin composition of the present invention. It can be manufactured by mixing an epoxy resin, an epoxy resin curing agent, and other components as needed using known methods and apparatus. There are no particular restrictions on the mixing order of the components contained in the epoxy resin composition. The epoxy resin curing agent may be prepared and then mixed with the epoxy resin, or the epoxy resin may be prepared by simultaneously mixing components (A), (B), and other components that constitute the epoxy resin curing agent with the epoxy resin.

[0039] [paint] The present invention provides a paint containing the epoxy resin composition. By containing the epoxy resin composition, the paint of the present invention can form a coating film that hardens quickly, has low viscosity, and high hardness. Examples of such paints include marine paints, heavy-duty anticorrosion paints, tank paints, pipe interior paints, exterior paints, and floor coatings.

[0040] The epoxy resin composition content in the paint of the present invention is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more, and 100% by mass or less, from the viewpoint of rapid curing, low viscosity, and improvement of the hardness of the coating film. [Examples]

[0041] 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. The epoxy resin curing agent, epoxy resin composition, and cured product (coating film) thereof were evaluated according to the following methods.

[0042] <Dry to the touch> A zinc phosphate treated steel sheet (manufactured by Paltec Co., Ltd.; SPCC-SD PB-N144 0.8×70×150 mm) was used as the substrate. Under conditions of 23°C and 50% RH, the epoxy resin composition for each example was applied to the substrate using an applicator to form a coating film (coating film thickness immediately after application: 200 μm). This coating film was stored under conditions of 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. Example: Excellent (Even when pressing the thumb with a force of approximately 50N, the coating does not become sticky, and no fingerprints are left behind.) G: Good (When pressing the thumb with a force of approximately 50N, the coating does not feel sticky, but fingerprints remain after touching it.) F: Acceptable (The coating becomes sticky when a thumb is pressed against it with a force of approximately 50N) P: Defective (The coating becomes sticky when a thumb is pressed against it with a force of approximately 5N)

[0043] <Pencil hardness> An epoxy resin composition was applied to a substrate (zinc phosphate treated steel sheet) in the same manner as described above to form a coating film (thickness immediately after application: 200 μm). This coating film was stored at 23°C and 50% RH, and its pencil hardness was measured after 1, 2, and 7 days in accordance with JIS K5600-5-4:1999. The results are shown in Table 1.

[0044] <Waterproof Spot Test> An epoxy resin composition was applied to a substrate (zinc phosphate treated iron plate) in the same manner as described above to form a coating film (thickness immediately after application: 200 μm). This coating film was stored at 23°C and 50% RH, and after 1, 2, and 7 days, 2-3 drops of pure water were dropped onto the surface of the coating film using a dropper, and the area was capped with a 50 mL screw-top bottle. 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: There is a slight change, but it is good F: There is a change

[0045] <RCI curing time> On a glass plate (manufactured by Taiyuu Kikai Co., Ltd., 25×348×2.0 mm), under the conditions of 23°C and 50% R.H., the epoxy resin composition of each example was applied using an applicator with a thickness of 76 μm to form a coating film. The glass plate with the coating film formed was set in a paint drying time measuring instrument (manufactured by Taiyuu Kikai Co., Ltd.), and the streaks when the needle of the measuring instrument scratched the surface of the coating film were observed, and the arrival times at each drying stage (tacky dry, semi-dry, fully dry) were measured according to the following criteria. The results are shown in Table 1. A shorter time indicates a faster curing rate. Tacky dry: The time when needle marks start to remain on the glass plate Semi-dry (dust free): The time when the needle marks emerge from the coating film onto the surface of the coating film Fully dry (dry through): The time when no needle marks remain on the coating film

[0046] <Appearance of the coating film> The epoxy resin composition was applied onto a substrate (zinc phosphate-treated steel plate) in the same manner as described above to form a coating film (thickness immediately after application: 200 μm). The appearance of the obtained coating film after 1 day was visually observed, and the transparency, smoothness, and gloss were evaluated according to the following criteria. (Transparency) Ex: Excellent (no turbidity) G: Good (slightly turbid, but no problem in use) F: Passable (slightly cloudy) P: Poor (cloudy) (Smoothness) Ex: Excellent (no unevenness) G: Good (slightly uneven, but no problem in use) F: Passable (some unevenness) P: Poor (peeling or unevenness over the entire surface) (Gloss) Ex: Excellent (with gloss) G: Good (slightly inferior gloss, but no problem in use) F: Acceptable (low gloss) P: Defective (no gloss)

[0047] <Viscosity of the hardening agent solution> The viscosity of each epoxy resin curing agent solution at 25°C was measured using an E-type viscometer, "TVE-22H type viscometer, cone plate type" (manufactured by Toki Sangyo Co., Ltd.).

[0048] Example 1 (Preparation and evaluation of epoxy resin curing agent solution and epoxy resin composition) (Preparation of epoxy resin curing agent solution A) Using 2-aminomethylcyclopentylamine (hereinafter referred to as AMCPA) and 1,3-bis(aminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd., 1,3-BAC) as raw material diamines, and a polyfunctional epoxy resin having a glycidyloxy group derived from bisphenol A (manufactured by Mitsubishi Chemical Corporation, "jER828", epoxy equivalent: 186 g / equivalent) as the epoxy compound, an epoxy-modified epoxy resin curing agent of AMCPA and 1,3-BAC (molar ratio 50 / 50) was obtained in the following manner. In a 1-liter separable flask equipped with a stirrer, thermometer, nitrogen inlet tube, dropping funnel, and condenser, 228 g of 2-aminomethylcyclopentylamine and 284 g of 1,3-bis(aminomethyl)cyclohexane were charged, and the mixture was heated to 80°C under a nitrogen stream while stirring. While maintaining the temperature at 80°C, 372 g of epoxy compound (Mitsubishi Chemical Corporation's "jER828") was added dropwise over 2 hours. After the addition was complete, the temperature was raised to 100°C and the reaction was carried out for 2 hours to obtain epoxy-modified products of AMCPA and 1,3-BAC (molar ratio 50 / 50). The ratio of active hydrogens in the starting diamine to epoxy groups in the epoxy compound was 8 / 1.

[0049] The obtained epoxy-modified product was diluted by adding benzyl alcohol, a non-reactive diluent, in an amount equal to 40% by mass of the total volume, to obtain epoxy resin curing agent solution A with a concentration of 60% by mass of the epoxy-modified product. The active hydrogen equivalent (AHEW) of epoxy resin curing agent solution A (total amount including benzyl alcohol) was 105.

[0050] (Preparation of epoxy resin composition) As the main component of the epoxy resin composition, a polyfunctional liquid epoxy resin having glycidyloxy groups derived from bisphenol A (Mitsubishi Chemical Corporation's "jER828", epoxy equivalent 186 g / equivalent) was used. The epoxy resin and the epoxy resin curing agent solution A were blended and mixed so 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) was 1 / 1, and an epoxy resin composition was prepared. The obtained epoxy resin composition was used for various evaluations using the method described above. The results are shown in Table 1.

[0051] Example 2 (Preparation of epoxy resin curing agent solution B) In Example 1, an epoxy-modified epoxy resin curing agent, consisting of AMCPA and IPDA (molar ratio 50 / 50), was obtained using the same method as in Example 1, except that the amount of AMCPA used was changed to 228 g, and isophorone diamine (IPDA) was used instead of 1,3-BAC at a rate of 340 g. Benzyl alcohol, a non-reactive diluent, was added to this solution to a concentration of 40% by mass of the total volume to obtain epoxy-modified epoxy resin curing agent solution B with a concentration of 60% by mass. The active hydrogen equivalent of epoxy-modified epoxy resin curing agent solution B (total amount including benzyl alcohol) was 112.

[0052] (Preparation of epoxy resin composition) An epoxy resin composition was prepared in the same manner as in Example 1, except that epoxy resin curing agent solution B was used instead of epoxy resin curing agent solution A, and various evaluations were performed using the method described above. The results are shown in Table 1.

[0053] Comparative Example 1 (Preparation of comparative epoxy resin curing agent solution a) An epoxy-modified 1,3-BAC product, which is an epoxy resin curing agent, was obtained in the same manner as in Example 1, except that 568 g of 1,3-BAC was used instead of 228 g of AMCPA and 284 g of 1,3-BAC. A non-reactive diluent, benzyl alcohol, was added to this solution to a concentration of 40% by mass of the total volume to obtain a comparative epoxy resin curing agent solution a with a concentration of 60% by mass of the epoxy-modified product. The active hydrogen equivalent of the comparative epoxy resin curing agent solution a (total amount including benzyl alcohol) was 112.

[0054] (Preparation of epoxy resin composition) An epoxy resin composition was prepared in the same manner as in Example 1, except that comparative epoxy resin curing agent solution a was used instead of epoxy resin curing agent solution A. Various evaluations were then performed using the method described above. The results are shown in Table 1.

[0055] Comparative Example 2 (Preparation of comparative epoxy resin curing agent solution b) In Comparative Example 1, an epoxy-modified product of IPDA, which is an epoxy resin curing agent, was obtained in the same manner as in Comparative Example 1, except that 680 g of IPDA was used instead of 568 g of 1,3-BAC. Benzyl alcohol, a non-reactive diluent, was added to this solution to a concentration of 40% by mass of the total volume to obtain comparative epoxy resin curing agent solution b, in which the epoxy-modified product was 60% by mass. The active hydrogen equivalent of comparative epoxy resin curing agent solution b (total amount including benzyl alcohol) was 125.

[0056] (Preparation of epoxy resin composition) In Comparative Example 1, the epoxy resin composition was prepared in the same manner as in Comparative Example 1, except that comparative epoxy resin curing agent solution b was used instead of comparative epoxy resin curing agent solution a. Various evaluations were then performed using the method described above. The results are shown in Table 1.

[0057] Comparative Example 3 (Preparation of comparative epoxy resin curing agent solution c) In Comparative Example 1, an epoxy-modified epoxy resin curing agent, consisting of 1,3-BAC and IPDA (molar ratio 50 / 50), was obtained using the same method as in Comparative Example 1, except that 284 g of 1,3-BAC and 340 g of IPDA were used instead of 568 g of 1,3-BAC. Benzyl alcohol, a non-reactive diluent, was added to this solution to a concentration of 40% by mass of the total volume to obtain comparative epoxy resin curing agent solution c with a concentration of 60% by mass of the epoxy-modified epoxy resin curing agent. The active hydrogen equivalent of comparative epoxy resin curing agent solution c (total amount including benzyl alcohol) was 119.

[0058] (Preparation of epoxy resin composition) In Comparative Example 1, the epoxy resin composition was prepared in the same manner as in Comparative Example 1, except that comparative epoxy resin curing agent solution c was used instead of comparative epoxy resin curing agent solution a. Various evaluations were then performed using the method described above. The results are shown in Table 1.

[0059] Comparative Example 4 (Preparation of comparative epoxy resin curing agent solution d) An epoxy-modified epoxy resin curing agent, AMCPA, and trimethylhexamethylenediamine (molar ratio 50 / 50) was obtained in the same manner as in Example 1, except that 316 g of trimethylhexamethylenediamine was used instead of 1,3-BAC. Benzyl alcohol, a non-reactive diluent, was added to this solution to a concentration of 40% by mass of the total volume to obtain a comparative epoxy resin curing agent solution d with a concentration of 60% by mass of the epoxy-modified epoxy resin curing agent. The active hydrogen equivalent of the comparative epoxy resin curing agent solution d (total amount including benzyl alcohol) was 109.

[0060] (Preparation of epoxy resin composition) An epoxy resin composition was prepared in the same manner as in Example 1, except that comparative epoxy resin curing agent solution d was used instead of epoxy resin curing agent solution A, and various evaluations were performed using the method described above. The results are shown in Table 1.

[0061] [Table 1]

[0062] Table 1 shows that the epoxy resin curing agent of the present invention has fast curing properties and low viscosity. Furthermore, the coating film formed by the epoxy resin composition containing this curing agent has a short curing time (dry through) and reaches a pencil hardness of 2H after 7 days, indicating high hardness. In contrast, the epoxy resin curing agent and epoxy resin composition of this comparative example were inferior in curing speed, viscosity, or coating film hardness. [Industrial applicability]

[0063] According to the present invention, it is possible to provide an epoxy resin curing agent, an epoxy resin composition, and a cured product thereof that can form a coating film that hardens quickly, has low viscosity, and high hardness.

Claims

1. The following components (A) and (B): (A) Diamines represented by the following general formula (1) or modified thereof 【Chemistry 1】 In equation (1), m and n are each independently numbers between 0 and 4. (B) Polyamines having a ring structure other than component (A) or modified thereof An epoxy resin curing agent containing, The molar ratio of component (A) to component (B) in the epoxy resin curing agent is 30 / 70 to 70 / 30. An epoxy resin curing agent wherein the modified substance is a Mannich modified product, an epoxy modified product, a Michael adduct, a Michael adduct / polycondensate, a styrene modified product, or a polyamide modified product.

2. The epoxy resin curing agent according to claim 1, wherein the component (B) is a polyamine having an alicyclic structure or a modified version thereof.

3. The epoxy resin curing agent according to claim 2, wherein component (B) is at least one selected from the group consisting of isophoronediamine, 1,3-bis(aminomethyl)cyclohexane, or modified versions thereof.

4. The epoxy resin curing agent according to claim 1, wherein the diamine represented by the general formula (1) is 2-aminomethylcyclopentylamine.

5. An epoxy resin composition comprising an epoxy resin and an epoxy resin curing agent according to any one of claims 1 to 4.

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

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