Curing resin composition, cured product

Abstract

This invention provides a solvent-free curable resin composition that combines excellent adhesion, cohesive failure resistance, and flexibility, making it particularly suitable for structural bonding applications in automobiles, aircraft, and other applications where high reliability is required. [Solution] A solvent-free curable resin composition comprising a main component (X) containing a liquid epoxy resin (A), a curing agent (Y) containing a polyurethane urea resin (B) having a primary or secondary amino group at its terminus, a liquid polyamine (C), and a heterocyclic aromatic compound (D), wherein the heterocyclic aromatic compound (D) has two or more adjacent nitrogen atoms in its ring structure, and the nitrogen atoms are unsubstituted, and the composition contains 10 to 80% by mass of polyurethane urea resin (B) in a total of 100% by mass of the organic component having a primary amino group and the organic component having a secondary amino group contained in the curing agent (Y).

Description

Technical Field

[0001] The present invention relates to a curable resin composition and a cured product thereof.

Background Art

[0002] In fields such as automobiles and aircraft, various structural adhesives are used to adhesively bond and fix metals such as iron, aluminum, and stainless steel, resins, glass, ceramics, etc. In recent years, in the fields of automobiles and aircraft, weight reduction has been promoted to improve fuel efficiency, and there has been an active movement to increase the use ratio of materials made of plastic or fiber reinforced plastic (hereinafter abbreviated as FRP), or to replace iron with lighter aluminum. There is a demand for highly reliable adhesives that can firmly bond these materials.

[0003] In addition, in recent years, from the viewpoints of global environmental protection, energy cost reduction, and operator safety, there is a demand for solvent-free adhesives and lower curing temperature conditions.

[0004] Since epoxy resin compositions are excellent in heat resistance, adhesive strength, mechanical strength, electrical properties, and processability, they are widely used in various fields that require reliability, such as structural adhesives, sealants, and matrix resins for vehicle bodies and automotive parts. Among them, two-component curable epoxy adhesives are excellent in curability and have a gentle increase in viscosity after mixing, so they are also excellent in workability and are widely used as structural bonding agents.

[0005] On the other hand, since the cured product of an epoxy resin is generally lacking in flexibility and brittle, for example, when bonding materials with different linear expansion coefficients such as aluminum and FRP, a high stress is applied to the adhesive layer due to the difference in expansion rates between the materials caused by temperature changes during the manufacturing process or in the use temperature environment, and there is a problem that the destruction or deterioration of the adhesive layer is promoted.

[0006] To address these challenges, methods for imparting flexibility to adhesives as a stress relaxation design have been widely investigated. For example, various combinations of polymer epoxy materials such as epoxy-terminated polybutadiene, polyurethane, and polyester, core-shell type rubber particles, and polymer amines such as amino-terminated polybutadiene and polyamidoamine have been considered. (Patent Documents 1-4)

[0007] However, using polymer epoxy or polymer amine to make the adhesive components more flexible presents challenges such as reduced workability due to increased viscosity with increasing additive amounts, and decreased adhesive strength due to imbalances in crosslinking and compatibility with other components. In particular, with aluminum substrates, which are commonly used as lightweight metals, there is a problem that the substrate interface is prone to fracture without surface treatment such as priming or polishing, resulting in a lack of reliability. Therefore, there is a need for a highly reliable adhesive that does not require surface treatment and exhibits high adhesion, cohesive fracture resistance, and flexibility.

[0008] Patent Document 1 discloses that high stress relaxation and adhesion can be obtained by using core-shell type rubber particles as a modifier for epoxy resin. However, its flexibility is still insufficient, and it breaks at the substrate interface, so there are challenges in cohesive failure and flexibility.

[0009] Patent Document 2 explores the use of polyurethane-modified epoxy resin for flexibility enhancement, but this requires a large amount of resin to achieve flexibility, and the increased viscosity leads to reduced workability. Furthermore, the large amount of resin components results in insufficient interfacial adhesion, and cohesive failure remains a challenge.

[0010] On the other hand, Patent Document 5 discloses that excellent adhesion and flexibility can be obtained by using an amino-terminated urethane urea, whose chain is extended with a diamine having an ether group, as a modifier. However, the mode of failure is interfacial failure, and there was a need for an excellent adhesive that satisfies high adhesion, cohesive failure resistance, and flexibility. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2015-182248 [Patent Document 2] Japanese Patent Publication No. 2017-002130 [Patent Document 3] Japanese Patent Publication No. 2015-063595 [Patent Document 4] Japanese Patent Publication No. 2018-002766 [Patent Document 5] Special Publication No. 2013-521361 [Overview of the project] [Problems that the invention aims to solve]

[0012] The object of the present invention is to provide a solvent-free curable resin composition that combines excellent adhesion, cohesive failure resistance, and flexibility. [Means for solving the problem]

[0013] As a result of diligent research to solve the above problems, the inventors of the present invention have found that the problems of the present invention can be solved in the following embodiment, and have completed the present invention.

[0014] It contains a main component (X) containing liquid epoxy resin (A) and a hardening agent (Y), This invention relates to a solvent-free curable resin composition characterized by satisfying all of the following conditions (i) to (iv). (i) The curing agent (Y) comprises a polyurethane urea resin (B), a liquid polyamine (C), and a heterocyclic aromatic compound (D). (ii) Polyurethane urea resin (B) has a primary amino group or a secondary amino group at its terminus. (iii) The heterocyclic aromatic compound (D) has two or more adjacent nitrogen atoms in its ring structure, and the nitrogen atoms are unsubstituted. (iv) The polyurethane-urea resin (B) is contained in a proportion of 10 to 80% by mass in the total of 100% by mass of the organic component having a primary amino group and the organic component having a secondary amino group contained in the curing agent (Y).

[0015] The present invention also relates to the curable resin composition according to claim 1, wherein the liquid polyamine (C) has a molecular weight of less than 600.

[0016] The present invention also relates to the curable resin composition according to claim 1, wherein the polyurethane-urea resin (B) has a number average molecular weight of 1,000 or more and less than 50,000.

[0017] The present invention also relates to the curable resin composition according to claim 1, wherein the heterocyclic aromatic compound (D) is contained in a proportion of 0.3 to 7.0% by mass in the total of 100% by mass of the polyurethane-urea resin (B), the liquid polyamine (C) and the heterocyclic aromatic compound (D).

[0018] The present invention also relates to a cured product obtained from the curable resin composition.

Advantages of the Invention

[0019] According to the present invention, it is possible to provide a solvent-free curable resin composition having excellent adhesiveness, cohesive failure properties and flexibility. The curable resin composition of the present invention can be particularly preferably used in structural bonding fields such as automobiles and aircraft that require high reliability.

Embodiments for Carrying Out the Invention

[0020] Hereinafter, the present invention will be described in detail. As long as it conforms to the gist of the present invention, other embodiments are also included in the scope of the present invention. In addition, the numerical range specified using "~" in this specification includes the numerical values described before and after "~" as the lower limit value and the upper limit value range. In addition, various components appearing in this specification may be used alone or in combination of two or more, respectively, unless otherwise noted.

[0021] In this specification, the main agent refers to the main agent in a two-component curable resin composition, and the curing agent refers to the curing agent in a two-component curable resin composition. In this specification, solvent-free means that there is no intentional addition of volatile organic solvents and the content of volatile organic solvents not involved in the curing reaction in the curable resin composition is less than 3% by mass.

[0022] The solvent-free curable resin composition of the present invention contains a main agent (X) containing a liquid epoxy resin (A) and a curing agent (Y). A solvent-free curable resin composition characterized by satisfying all of the following (i) to (iv). (i) The curing agent (Y) contains a polyurethane-urea resin (B), a liquid polyamine (C), and a heterocyclic aromatic compound (D). (ii) The polyurethane-urea resin (B) has a primary amino group or a secondary amino group at the terminal. (iii) The heterocyclic aromatic compound (D) has two or more adjacent nitrogen atoms in the ring structure, and these nitrogen atoms have no substituents. (iv) The curing agent (Y) contains 10 to 80% by mass of the polyurethane-urea resin (B) in the total 100% by mass of the organic components having a primary amino group and the organic components having a secondary amino group.

[0023] By satisfying all of the above, when the main agent (X) forms a crosslinked structure with the curing agent (Y), the heterocyclic aromatic compound (D) strongly interacts between the polyurethane-urea resin (B) and the substrate interface, and a proper phase-separated structure is formed. Therefore, excellent flexibility is exhibited while maintaining high adhesiveness and cohesive failure properties. Accordingly, the curable resin composition of the present invention is suitably used as a structural adhesive in the field of structural bonding for automobiles, aircraft, etc., where high reliability is required. Further, the curable resin composition of the present invention is a liquid solvent-free adhesive, and is also excellent from the viewpoints of safety and environmental compatibility.

[0024] [Main agent (X)] The main component (X) contains a liquid epoxy resin (A). The main component (X) may also optionally contain other epoxy compounds other than the liquid epoxy resin (A) that contribute to the crosslinking reaction with the curing agent (Y), as well as additives.

[0025] ≪Liquid epoxy resin (A)≫

[0026] The liquid epoxy resin (A) is not particularly limited as long as it is a compound that is liquid at room temperature (23°C), but it is preferable that it has two or more epoxy groups in its molecule. Furthermore, it is preferable that its epoxy equivalent is 200 g / eq or less, and more preferably 150 to 200 g / eq. The epoxy equivalent of liquid epoxy resin (C) can be determined by measurement in accordance with JIS K-7236. Note that the epoxy equivalent of liquid epoxy resin (A) in this specification refers to the epoxy equivalent of each epoxy resin used. The liquid epoxy resin (A) contributes to the development of excellent adhesion by being incorporated into the cross-linked structure during curing.

[0027] Examples of liquid epoxy resin (A) include aromatic epoxy resins, alicyclic epoxy resins, aliphatic epoxy resins, and polyether epoxy resins. Among these, aromatic epoxy resins and alicyclic epoxy resins are preferred because they exhibit excellent adhesion. Aromatic epoxy resins are more preferred because they are readily available and have good curability and adhesion.

[0028] Examples of aromatic epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, aromatic epoxy resins having an ester skeleton, aromatic glycidylamine type epoxy resins, cardanol-modified epoxy resins, p-tert-butylphenol glycidyl ether, phenyl glycidyl ether, and cresyl glycidyl ether. Among aromatic epoxy resins, bisphenol A type epoxy resins are preferred.

[0029] Examples of alicyclic epoxy resins include hydrogenated bisphenol A type epoxy resin, hydrogenated bisphenol F type epoxy resin, alicyclic glycidylamine type epoxy resin, alicyclic epoxy resin having an ester skeleton, cyclohexane type epoxy resin, cyclohexanedimethanol type epoxy resin, and limonene dioxide.

[0030] Examples of aliphatic epoxy resins include 1,6-hexanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, propylene glycol diglycidyl ether, 2-ethylhexyl monoglycidyl ether, glyceryl glycidyl ether, and trimethylolpropane triglycidyl ether.

[0031] Examples of polyether epoxy resins include polyethylene glycol diglycidyl ether and polypropylene glycol diglycidyl ether.

[0032] The ratio of the total number of moles of all epoxy groups in the curable resin composition to the total number of moles of all primary and secondary amino groups (epoxy groups / active hydrogen groups of primary and secondary amino groups) is preferably in the range of 0.5 to 2.0, and more preferably in the range of 0.6 to 1.5. When the ratio is in the range of 0.5 to 2.0, there are fewer unreacted functional groups, and by forming a good crosslink density, high flexibility and adhesion can be achieved.

[0033] <Other epoxy compounds> Other epoxy resins are epoxy resins other than liquid epoxy resin (A) and are not particularly limited as long as they are epoxy compounds that harden with a curing agent (Y). Examples include solid epoxy resins.

[0034] <Additives> Examples of known additives include silane coupling agents, leveling agents or defoaming agents, fillers, propellants, plasticizers, superplasticizers, wetting agents, flame retardants, viscosity modifiers, preservatives, stabilizers, and colorants. Such additives include, but are not limited to, the following compounds.

[0035] Examples of silane coupling agents include trialkoxysilanes having a vinyl group, such as vinyltrimethoxysilane and vinyltriethoxysilane; trialkoxysilanes having an amino group, such as 3-aminopropyltriethoxysilane and N-(2-aminoethyl)3-aminopropyltrimethoxysilane; trialkoxysilanes having a glycidyl group, such as 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane; trialkoxysilanes having an isocyanate group, such as 3-isocyanatetopropyltriethoxysilane; and trialkoxysilanes having a mercapto group, such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane. The amount of silane coupling agent is preferably 0.05 to 10 parts by mass per 100 parts by mass of the total organic components of the main component (X).

[0036] Examples of leveling agents include polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, aralkyl-modified polymethylalkylsiloxane, polyester-modified hydroxyl-containing polydimethylsiloxane, polyether ester-modified hydroxyl-containing polydimethylsiloxane, acrylic copolymers, methacrylic copolymers, polyether-modified polymethylalkylsiloxane, alkyl acrylate copolymers, alkyl methacrylate copolymers, lecithin, and the like.

[0037] Examples of known defoaming agents include silicone resins, silicone solutions, copolymers of alkyl vinyl ethers, alkyl acrylates, and alkyl methacrylates.

[0038] [Hardening agent (Y)] The curing agent (Y) contains a polyurethane urea resin (B) having a primary or secondary amino group at its terminus, a liquid polyamine (C), and a heterocyclic aromatic compound (D). The curing agent (Y) is not limited to the polyurethane urea resin (B), liquid polyamine (C), and heterocyclic aromatic compound (D), but may also include other amine compounds, curing accelerators, and additives that contribute to the crosslinking reaction with the epoxy resin (A) in the main component (X), as needed.

[0039] Polyurethane urea resin (B) Polyurethane urea resin (B) has primary or secondary amino groups at its terminals. Polyurethane urea resin (B) can be obtained, for example, by reacting a polyol, polyisocyanate, and polyamine such that amino groups remain in the polyamine. It is preferable that the terminal amino groups be primary due to their excellent cohesive failure properties.

[0040] The number-average molecular weight of the polyurethane urea resin (B) is not particularly limited, but is preferably between 1,000 and less than 50,000. A number-average molecular weight of 1,000 or more provides excellent flexibility, while a number-average molecular weight of less than 50,000 provides low viscosity, making it easy to adjust viscosity without solvents. A number-average molecular weight of 2,000 or more and less than 48,000 is more preferable. The number-average molecular weight of polyurethane urea resin (B) was determined by gel permeation chromatography as a converted value using standard polystyrene, and further details are described in the examples.

[0041] <Polyol> Polyols are compounds that have two or more hydroxyl groups in their molecule. Typical examples include polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, and vegetable oil-based polyols.

[0042] Furthermore, examples of compounds having two or more hydroxyl groups in the molecule include polyols obtained by starting with compounds having at least two active hydroxyl groups, such as low molecular weight polyols, aliphatic amine compounds, aromatic amine compounds, alkanolamines, or bisphenols, and adding alkylene oxides such as methylene oxide, ethylene oxide, propylene oxide, tetrahydrofuran, or polyoxytetramethylene oxide.

[0043] Examples of the low molecular weight polyols include bifunctional low molecular weight polyols or trifunctional or more low molecular weight polyols.

[0044] The bifunctional low molecular weight polyols are not particularly limited and include, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, hexanediol, octanediol, nonanediol, dipropylene glycol, diethylene glycol, triethylene glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-ethyl-1,3-hexanediol, and 2-methyl-1,8-octanediol. Examples include diols, polyoxyethylene glycol (additional moles of 10 or less), polyoxypropylene glycol (additional moles of 10 or less), cyclohexanediol, cyclohexanedimethanol, tricyclodecanedimethanol, cyclopentadienedimethanol, dimergol, bisphenol A, N,N-bis(2-hydroxypropyl)aniline, dimethylolacetic acid, dimethylolpropionic acid, dimethylolbutanoic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolpentanoic acid, dihydroxysuccinic acid, dihydroxypropionic acid, and dihydroxybenzoic acid.

[0045] The low molecular weight polyols with three or more functionalities are not particularly limited, and include, for example, trimethylolethane, trimethylolpropane, 1,1,1-trimethylolbutane, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,2,6-butanetriol, trimethylolbutene, trimethylolpentene, trimethylolhexene, trimethylolheptene, trimethyloloctene, trimethylolnonene, trimethyloldecene, trimethylolundecene, trimethyloldodecene, and trimethyloltridecene. , trimethylolpentadecene, trimethylolhexadecene, trimetrolheptadecene, trimethyloloctadecene, 1,1,1-trimethylol-2-methyl-hexane, 1,1,1-trimethylol-3-methyl-hexane, 1,1,1-trimethylol-2-ethyl-hexane, 1,1,1-trimethylol-3-ethyl-hexane, trimethylolhexene, 1,2,3-octantriol, 1,3,7-octantriol, 3,7-dimethyl-1,2,3-octantriol, 1,1,1-, 1, 1,1-Trimethylol decane, 1,2,10-decanetriol, 1,1,1-Trimethylol isoheptadecane, 1,1,1-Trimethylol-sec-butane, 1,1,1-Trimethylol-tert-pentane, 1,1,1-Trimethylol-tert-nonane, 1,1,1-Trimethylol-tert-tridecane, 1,1,1-Trimethylol-tert-heptadecane, 1,1,1-Trimethylol-2-methylhexane, 1,1,1-Trimethylol-3-methylhexane, 1,1,1-Trimethylol 1,1,1-Trimethylol-2-ethyl-hexane, 1,1,1-Trimethylol-3-ethyl-hexane, 1,1,1-Trimethylol isoheptadecane, 1,2,3,4-Butanetetraol, Pentaerythritol, Dipentaerythritol, Tripentaerythritol, Glycerin, Diglycerin, Triglycerin, Polyglycerin, Ditrimethylolethane, Ditrimethylolpropane, Tris(2-hydroxyethyl)isocyanurate, Benzene-1,3,5-triol, Benzene-1,2,3-triol, Stilbene-3,Examples include 4',5-triol, sucrose, inositol, sorbitan, sorbitol, mannitol, saccharose, cellulose, and xylitol.

[0046] Examples of aliphatic amine compounds include ethylenediamine, triethylenetetramine, diethylenetriamine, and triaminopropane. Examples of aromatic amine compounds include toluenediamine and diphenylmethane-4,4-diamine. Examples of alkanolamines include ethanolamine and diethanolamine. Examples of bisphenols include bisphenol A, bisphenol AP, bisphenol B, bisphenol C, bisphenol E, and bisphenol F.

[0047] Examples of polyether polyols include polymers or copolymers of methylene oxide, ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, etc., such as glycols like polyethylene glycol, polypropylene glycol, and poly(ethylene / propylene) glycol. Other examples include polyether polyols obtained by condensation of hexanediol, methylhexanediol, heptanediol, octanediol, or mixtures thereof.

[0048] Examples of polyester polyols include those obtained by the condensation reaction of the aforementioned low-molecular-weight polyol with a dibasic acid component.

[0049] Examples of dibasic acid components include aliphatic or aromatic dibasic acids such as terephthalic acid, adipic acid, azelaic acid, sebatic acid, dimer acid, hydrogenated dimer acid, phthalic anhydride, isophthalic acid, trimellitic acid, glutaric acid, pimelic acid, suberic acid, and sebacic acid, as well as their anhydrides. Other examples include polyester polyols obtained by ring-opening polymerization of cyclic ester compounds such as lactones, including ε-caprolactone, poly(β-methyl-γ-valerolactone), and polyvalerolactone.

[0050] Examples of polycarbonate polyols include those obtained by the reaction of the aforementioned low-molecular-weight polyols with carbonate compounds such as dialkyl carbonates, alkylene carbonates, and diaryl carbonates. Examples of dialkyl carbonates include dimethyl carbonate and diethyl carbonate, examples of alkylene carbonates include ethylene carbonate, and examples of diaryl carbonates include diphenyl carbonate.

[0051] Examples of polyolefin polyols include hydroxyl group-containing polybutadiene, hydrogenated hydroxyl group-containing polybutadiene, hydroxyl group-containing polyisoprene, hydrogenated hydroxyl group-containing polyisoprene, hydroxyl group-containing chlorinated polypropylene, and hydroxyl group-containing chlorinated polyethylene.

[0052] Examples of plant-based polyols include castor oil, dimer acid, or polyols derived from soybean oil.

[0053] Among these, polyether polyols and polycarbonate polyols are preferred due to their superior flexibility.

[0054] The number-average molecular weight of the above polyol is preferably 300 to 5,000, and more preferably 400 to 3,500. A number-average molecular weight of 300 to 5,000 is preferable because it results in superior adhesion and flexibility of the resulting cured product. The number-average molecular weight of the polyol was determined by gel permeation chromatography, converted to a value based on standard polystyrene; details are described in the examples.

[0055] Furthermore, the polyol may be used in combination with the above-mentioned low-molecular-weight polyols, to the extent that it does not impair the effects of the present invention, for the purpose of adjusting the urethane bond concentration or introducing various functional groups.

[0056] <Polyisocyanate> Polyisocyanates can be any compound having two or more isocyanate groups in their molecule, such as aromatic, aliphatic, or alicyclic diisocyanates. Polyisocyanates having an aromatic ring or alicyclic structure are preferred. Aromatic diisocyanates and alicyclic diisocyanates are preferred because their steric hindrance allows for moderate aggregation dissociation and excellent flexibility. Furthermore, the molecular weight of the polyisocyanate is preferably less than 300. A molecular weight of less than 300 is preferable because it allows for good proximity between urethane and urea bonds, resulting in excellent aggregation dissociation and flexibility.

[0057] Examples of aromatic diisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, xylylene diisocyanate, m-tetramethylxylene diisocyanate, p-tetramethylxylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 3,3'-dichloro-4,4'-biphenylene diisocyanate, and 1,5-tetrahydronaphthalene diisocyanate.

[0058] Examples of aliphatic diisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, lysine ester triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate tetramethylene diisocyanate, pentamethylene diisocyanate, and trimethylhexamethylene diisocyanate.

[0059] Examples of alicyclic diisocyanates include isophorone diisocyanate, 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,4-bis(isocyanate methyl)cyclohexane, hydrogenated xylylene diisocyanate, dimer acid diisocyanate, norbornene diisocyanate, and the like.

[0060] <Polyamine> The polyamine is not particularly limited as long as it is a compound having two or more amino groups in its molecule, but it is preferably a diamine. Examples include aromatic diamines, aliphatic diamines, alicyclic diamines, or polyether diamines. The molecular weight of the polyamine is preferably less than 400. When the molecular weight is less than 400, the reaction site and the urea bond are in good proximity when a crosslinked structure is formed, resulting in excellent adhesion. Preferably, the molecular weight is less than 300. Furthermore, the polyamine is preferably one that has an aromatic ring or alicyclic structure in its molecule. When it has an aromatic ring or alicyclic structure, steric hindrance results in an appropriate crosslink density and excellent flexibility, so aromatic diamines and alicyclic diamines are preferred.

[0061] Examples of aromatic diamines include m-xylenediamine, p-xylenediamine, and m-phenylenediamine.

[0062] Examples of aliphatic diamines include ethylenediamine, diaminopropane, diaminobutane, diaminohexane, 2,5-dimethylhexamethylenediamine, hexamethylenediamine, trimethylhexamethylenediamine, diethylenetriamine, and iminobispropylamine.

[0063] Examples of alicyclic diamines include isophorone diamines and metacenediamines.

[0064] Polyetherdiamines are not particularly limited as long as they are compounds having two amino groups in their molecule and a repeating ether chain structure, but examples include poly(propylene glycol)diamine, poly(ethylene glycol)diamine, poly(tetramethylene ether glycol)diamine, and poly(propylene / ethylene glycol)diamine.

[0065] The method for producing polyurethane urea resin (B) is not limited, but it can preferably be produced by the following method. Step 1: A urethane reaction is carried out between a polyol and a polyisocyanate under conditions in which there is an excess of isocyanate groups relative to hydroxyl groups, thereby obtaining a urethane prepolymer having isocyanate groups at the molecular ends. Step 2: A urea reaction is carried out between a urethane prepolymer and a polyamine under conditions in which there is an excess of amino groups relative to the isocyanate groups, to obtain a polyurethane urea resin (B) having primary or secondary amino groups at the terminals.

[0066] The reactions in steps 1 and 2 may be carried out with or without a solvent. If a solvent is used in steps 1 and 2, a solvent-free polyurethane urea resin (B) can be obtained by removing the solvent under reduced pressure or atmospheric pressure during or after the reaction.

[0067] The urethane formation in step 1 and the urea formation reaction in step 2 are carried out using known reactions, and catalysts may be used to adjust the reactivity.

[0068] As catalysts, known metal catalysts, amine catalysts, etc., can be used. Examples of metal catalysts include dibutyltin dilaurate, tin octoate, dibutyltin di(2-ethylhexoate), lead 2-ethylhexoate, 2-ethylhexyl titanate, titanium ethyl acetate, iron 2-ethylhexoate, cobalt 2-ethylhexoate, zinc naphthenate, cobalt naphthenate, and tetra-n-butyltin. Examples of amine catalysts include tertiary amines such as tetramethylbutanediamine. The amount of catalyst used is preferably in the range of 0.01 to 0.05 parts by mass, based on the total mass of the polyol and polyisocyanate.

[0069] The content of polyurethane urea resin (B) is 10 to 80% by mass of the total 100% by mass of the organic components having primary amino groups and organic components having secondary amino groups contained in the curing agent (Y). This range is preferable because it promotes phase separation formation and exhibits excellent adhesion and flexibility. More preferably, it is 15 to 75% by mass. The organic components having primary amino groups and organic components having secondary amino groups contained in the curing agent (Y) refer to the organic components having primary amino groups, organic components having secondary amino groups, and organic components having both primary and secondary amino groups, among the polyurethane urea resin (B), liquid polyamine (C), heterocyclic aromatic compound (D), other amine compounds, curing accelerators, and additives.

[0070] Liquid polyamine (C) The liquid polyamine (C) can be any compound that is liquid at room temperature (23°C) and has two or more primary or secondary amino groups in its molecule. Examples include aromatic polyamine compounds, aliphatic polyamine compounds, alicyclic polyamine compounds, and polyether polyamine compounds. Polyether polyamine compounds or alicyclic polyamine compounds are preferred because they have excellent adhesive and flexible properties.

[0071] Examples of aromatic polyamine compounds include m-xylenediamine, 4,4'-methylenebis(N-sec-butylaniline), diethyltoluenediamine, dimethylthiotoluenediamine, aminobenzylamine, N,N'-di-sec-butyl-p-phenylenediamine, 2,4-diamino-3,5-diethyltoluene, 2,6-diamino-3,5-diethyltoluene, and dimethylthiotoluenediamine.

[0072] Examples of aliphatic polyamine compounds include ethylenediamine, diaminopropane, diaminobutane, diaminohexane, 2,5-dimethylhexamethylenediamine, hexamethylenediamine, trimethylhexamethylenediamine, diethylenetriamine, and iminobispropylamine.

[0073] Examples of alicyclic polyamine compounds include isophoronediamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, bis(aminomethyl)norbornane, 1,2-cyclohexanediamine, 4,4'-methylenebis(N-sec-butylcyclohexaneamine), 4,4'-methylenebis(2-methylcyclohexylamine), aminoethylpiperazine, 2-(aminomethyl)piperidine, 1-(2-aminoethyl)piperidine, and dimeramine.

[0074] Examples of polyether polyamine compounds include poly(propylene glycol)diamine, poly(propylene glycol)triamine, poly(ethylene glycol)diamine, poly(ethylene glycol)triamine, poly(tetramethylene ether glycol)diamine, poly(tetramethylene ether glycol)triamine, poly(propylene / ethylene glycol)diamine, and poly(propylene / ethylene glycol)triamine.

[0075] The molecular weight of the liquid polyamine (C) is preferably less than 600. A molecular weight of less than 600 allows for the formation of a good crosslinking structure, resulting in a cured product with excellent adhesion. More preferably, the molecular weight is less than 560. The molecular weight of the liquid polyamine (C) is the sum of the atomic weights contained in the molecular formula and is calculated.

[0076] The curing rate can be adjusted by using the aforementioned polyether polyamine compound or alicyclic polyamine compound in combination with an aliphatic polyamine compound. When using the polyether polyamine compound or alicyclic polyamine compound in combination with an aliphatic polyamine compound for the purpose of adjusting the curing rate, the content of the aliphatic polyamine compound is preferably in the range of 3 to 20% by mass of the total 100% by mass of the liquid polyamine (C).

[0077] Heterocyclic aromatic compounds (D) The heterocyclic aromatic compound (D) can be any aromatic compound that has two or more adjacent nitrogen atoms in its ring structure and does not have substituents on those two adjacent nitrogen atoms. Examples include hetero 5-membered ring azoles, hetero 6-membered ring compounds, and hetero fusion ring compounds.

[0078] Examples of azoles include 1,2-pyrazole, homepizol, 3-methylpyrazole, 3,5-dimethylpyrazole, 1,2,4-triazole, 1,2,3-triazole, tetrazol, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,3,4-thiadiazole, pentazole, and their derivatives.

[0079] Examples of heterosix-membered ring compounds include pyritazine, 1,2,3-triazine, 1,2,4-triazine, 1,2,3,4-tetrazine, 1,2,4,5-tetrazine, and their derivatives.

[0080] Examples of heterofusion ring compounds include 1,2,3-benzotriazole, 5-methylbenzotriazole, 7-azindazole, cinnoline, and benzo-C-cinnoline.

[0081] Among these, azoles are preferred because they exhibit excellent adhesion and cohesive disruption properties. From the viewpoint of availability and cohesive disruption properties, 1,2-pyrazole, 3,5-dimethylpyrazole, and 1,2,4-triazole are more preferred.

[0082] Preferably, the heterocyclic aromatic compound (D) is present in an amount of 0.3 to 7.0% by mass in the total 100% by mass of the polyurethane urea resin (B), liquid polyamine (C), and heterocyclic aromatic compound (D). If the amount is 0.3% by mass or more, the two adjacent nitrogen atoms at the interface between the polyurethane urea resin (B) and the substrate interact well, improving adhesion and cohesive failure. If the amount is 7.0% by mass or less, cohesive failure and flexibility are improved. More preferably, the amount is 0.5 to 5.0% by mass.

[0083] <<Other Amine Compounds>> Other amine compounds refer to amine compounds other than the polyurethane urea resin (B), liquid polyamine (C), and heterocyclic aromatic compound (D) mentioned above. As other amine compounds, known amines that cure epoxy resins can be used, provided they do not impair flexibility. Examples include aromatic polyamine compounds that are solid at room temperature, aliphatic polyamine compounds, alicyclic polyamine compounds, polyether polyamine compounds, amide compounds, and monofunctional amines.

[0084] <<Curing accelerator>> Examples of curing accelerators include tertiary amines and their salts, imidazoles and their salts, urea compounds, phosphorus compounds, organophosphine compounds and their salts, metal salts such as zinc octylate and tin octylate, compounds having hydroxyl groups such as phenols and alcohols, Lewis acids, and amine complex salts.

[0085] The curing accelerator is preferably present in an amount of 0.01 to 25% by mass of the total organic components of the curing agent (X) by 100% by mass. Note that the total organic components of the curing agent (X) refer to the organic components excluding the inorganic filler.

[0086] ≪Additives≫ The additives used may be the same as those listed as additives that may be included in the main component (X).

[0087] [[Curable resin composition]] The method for producing the curable resin composition of the present invention is not particularly limited, and it can be obtained by mixing a main component (X) containing a liquid epoxy resin (A) and a curing agent (Y) containing a polyurethane urea resin (B), a liquid polyamine (C), and a heterocyclic aromatic compound (D) by a known method.

[0088] [[Cured product]] The cured product of the present invention is obtained by curing a curable resin composition under conditions of, for example, 5 to 180°C.

[0089] The cured product of the present invention can be used as a composite. A composite is obtained by combining a cured product of the curable resin composition of the present invention with any substrate, such as a laminate having a layer made of the above cured product on a substrate, or a cured product obtained by impregnating fibers or the like with a curable resin as a matrix resin and curing it.

[0090] Laminates can be formed using known lamination methods. For example, a curable resin composition can be applied to one surface of a substrate, and then another substrate can be placed on top of the layer of curable resin composition before curing. By curing at 5 to 180°C, a laminate having layers of cured material consisting of substrates and curable resin compositions can be obtained. Using the laminate at 20 to 40°C, including during mixing, is preferable because it promotes the formation of a phase separation structure and provides excellent flexibility. From the viewpoint of reducing environmental impact, curing at room temperature is more preferable.

[0091] The substrate used in the laminate is not particularly limited. Suitable substrates include, for example, metals such as stainless steel and aluminum, thermoplastic polymers such as polyethylene, polyurethane, polyacrylate and polycarbonate and their copolymers, thermosetting polymers such as vulcanized rubber, urea-formaldehyde foam, melamine resin, wood, carbon fiber reinforced plastics, glass fiber reinforced plastics and other fiber-reinforced plastics.

[0092] The curable resin composition of the present invention can be used for bonding various substrates. The substrates to be bonded may be the same or different. When used as an adhesive, the film thickness of the curable resin composition is preferably 10 μm to 10 mm.

[0093] The curable resin composition of the present invention has high adhesion, cohesive failure resistance, and flexibility, and laminates using this curable resin composition are useful as structural adhesives for automobiles, large structures, and other applications where high reliability is required.

[0094] When a curable resin composition is used as a matrix resin, it can be obtained by mixing the curable resin composition by a known method, impregnating it with fibers or the like, and then curing it under conditions of 20 to 180°C. Since a good crosslinked structure is formed, resulting in high adhesion, it is preferable to cure it under heating conditions of 60 to 150°C. From the viewpoint of reducing environmental impact, it is even more preferable to be 130°C or lower. When heat curing, it is preferable to pre-cur it at a temperature below the glass transition temperature, and then perform the main curing at a temperature above the glass transition temperature, as this further improves the formation of the crosslinked structure.

[0095] The curable resin composition of the present invention has high adhesion to substrates and excellent flexibility, and composites using this curable resin composition as a matrix resin are useful for pressure vessels and wind turbine blades. [Examples]

[0096] The present invention will be described in more detail below with reference to examples, but these examples do not limit the scope of the present invention in any way. Unless otherwise specified, "parts" in the examples refers to "parts by mass," and "%" refers to "mass percent." In the table, "-" indicates that an ingredient is not included.

[0097] <Number average molecular weight (Mn)> The number-average molecular weights of polyols and polyurethane urea resins (B) were calculated by GPC (gel permeation chromatography) as converted values ​​based on standard polystyrene. The measurements were performed using an ACQUITY UPLC (Waters), with a 3 mM triethylamine and 10 mM LiBr N,N-dimethylformamide solution as the eluent, and three TSKgelSuperHM-M (Tosoh Corporation) columns connected in series. The measurements were performed under conditions of a flow rate of 0.6 mL / min, an injection volume of 10 μL, and a column temperature of 40°C.

[0098] <Amine value> The amine value was measured in accordance with JIS K-7237.

[0099] The abbreviations for the compounds in Table 1 are shown below. <Polyol> P-400: Bifunctional polypropylene glycol, number average molecular weight 450, manufactured by ADEKA Corporation. P-2000: Bifunctional polypropylene glycol, number average molecular weight 2,000, manufactured by ADEKA Corporation. • C-1090: Bifunctional polycarbonate polyol, number average molecular weight 1,000, manufactured by Kuraray Co., Ltd. • C-2090: Bifunctional polycarbonate polyol, number average molecular weight 2,000, manufactured by Kuraray Co., Ltd. • PH-300: Bifunctional polycarbonate polyol, number average molecular weight 3,000, manufactured by UBE. <Polyisocyanate> IPDI: Isophorone diisocyanate, molecular weight 222 TODI: 3,3'-dimethyl-4,4'-biphenylenediisocyanate, molecular weight 264 • HDI: Hexamethylene diisocyanate, molecular weight 168 <Polyamine> IPDA: Isophorone diamine, molecular weight 170, amine value 659 mgKOH / g: Organic component having a primary amino group and alicyclic structure. • MXDA: m-xylenediamine, molecular weight 136, amine value 824 mgKOH / g: an organic component having a primary amino group and an aromatic ring structure. • D-230: Polyoxypropylenediamine, molecular weight 230, amine value 490 mgKOH / g, manufactured by HUNTSMAN: Organic component with primary amino groups • D-400: Polyoxypropylenediamine, molecular weight 430, amine value 261 mgKOH / g, manufactured by HUNTSMAN: Organic component with primary amino groups • N-(2-aminoethyl)piperazine: Molecular weight 129, amine value 870 mgKOH / g, manufactured by HUNTSMAN: Organic component having primary and secondary amino groups • N,N-diethyl-1,3-diaminopropane: Molecular weight 130, amine value 863 mgKOH / g, manufactured by HUNTSMAN: Organic component having primary and tertiary amino groups.

[0100] (Manufacturing Example 1) In a dropping vessel equipped with a nitrogen gas inlet tube, stirrer, thermometer, and refluxer, 69.7 parts of C-2090 as a polyol, 18.4 parts of TODI as a polyisocyanate, and 0.01% of dibutyltin dilaurate relative to the total mass of the polyol and polyisocyanate were charged and uniformly stirred. The mixture was then stirred under a nitrogen atmosphere at 100°C for 2 hours to synthesize an isocyanate-terminated prepolymer. After that, 50 parts of ethyl acetate were added to obtain an isocyanate-terminated prepolymer solution. Subsequently, in another container equipped with a nitrogen gas inlet tube, stirrer, thermometer, and refluxer, 11.9 parts of IPDA and 50 parts of ethyl acetate were charged. Under a nitrogen atmosphere at 40°C, the isocyanate-terminated prepolymer solution was added dropwise over 30 minutes while uniformly stirring, and the mixture was stirred for 1 hour to obtain a polyurethane urea resin solution having primary amino groups at the ends. The solvent in the obtained polyurethane urea resin solution was removed under reduced pressure to obtain polyurethane urea resin (B-1). The reaction endpoint was confirmed by FT-IR analysis by the disappearance of an absorption (around 2270 cm-1) originating from the isocyanate group. The resulting polyurethane urea resin (B-1) had a number-average molecular weight of 4000 and an amine value of 28.3 mgKOH / g.

[0101] (Manufacturing Examples 2-3 and 5-8, Comparative Manufacturing Example 1) Except for the compounds and formulations shown in Table 1, the same procedure as in Production Example 1 was performed to obtain the polyurethane urea resins (B-2 to B-3, B-5 ​​to B-8, P-1) for Production Examples 2-3 and 5-8, and Comparative Production Example 1. The number-average molecular weights and amine values ​​of the obtained polyurethane urea resins (B-2 to B-3, B-5 ​​to B-8, P-1) are shown in Table 1.

[0102] (Manufacturing example 4) In a dropping vessel equipped with a nitrogen gas inlet tube, stirrer, thermometer, and refluxer, 8.3 parts of P-400 as a polyol, 8.2 parts of IPDI as a polyisocyanate, and 0.01% of dibutyltin dilaurate as a catalyst relative to the total mass of the polyol and polyisocyanate were charged and uniformly stirred. The mixture was then stirred under a nitrogen atmosphere at 100°C for 2 hours to synthesize an isocyanate-terminated prepolymer. After that, 50 parts of ethyl acetate were added to obtain an isocyanate-terminated prepolymer solution. Subsequently, in another container equipped with a nitrogen gas inlet tube, stirrer, thermometer, and refluxer, 83.5 parts of D-230 and 50 parts of ethyl acetate were charged. Under a nitrogen atmosphere at 40°C, the isocyanate-terminated prepolymer solution was added dropwise over 30 minutes while uniformly stirring, and the mixture was stirred for 1 hour to obtain a mixed solution of polyurethane urea resin (A-4) having primary amino groups at the ends and liquid polyamine (D-230). The solvent in the resulting mixed solution was removed under reduced pressure to obtain a mixture of polyurethane urea resin (B-4) and liquid polyamine (D-230) in a mass ratio of 70:30. The endpoint of the reaction was confirmed by the disappearance of absorption (around 2270 cm-1) derived from the isocyanate group by FT-IR. The number-average molecular weight of the obtained polyurethane urea resin (B-4) was 1200, and the amine value of the mixed solution was 358 mgKOH / g.

[0103] (Comparative manufacturing example 2) In a reaction vessel equipped with a nitrogen gas inlet tube, a stirrer, a thermometer, and a moisture trap, 865 g of dimer hydrogenated acid, 600 g of soybean oil fatty acid, 945 g of tetraethylenepentamine, and 0.3 g of iron powder were added and reacted under a nitrogen atmosphere at 200°C for 1 hour to obtain polyamidoamine (P-2). The amine value of the obtained polyamidoamine (P-2) was 390 mgKOH / g.

[0104] [Table 1]

[0105] The abbreviations for the compounds in Tables 2-4 are shown below. <Liquid epoxy resin (A)> jER828: Bisphenol A type epoxy resin, epoxy equivalent 190 g / eq, manufactured by Mitsubishi Chemical Corporation. jER806: Bisphenol F type epoxy resin, epoxy equivalent 170 g / eq, manufactured by Mitsubishi Chemical Corporation. Tetrad-X: N,N,N',N'-tetraglycidyl-m-xylenediamine, epoxy equivalent 98 g / eq, manufactured by Mitsubishi Gas Chemical Company. EX-252: Hydrogenated bisphenol A epoxy resin, epoxy equivalent 213 g / eq, manufactured by Nagase ChemteX Corporation. <Liquid polyamine (C)> • D-230: Polyoxypropylenediamine, molecular weight 230, amine value 490 mgKOH / g, manufactured by HUNTSMAN: Organic component with primary amino groups • D-400: Polyoxypropylenediamine, molecular weight 430, amine value 261 mgKOH / g, manufactured by HUNTSMAN: Organic component with primary amino groups T-3000: Polyoxypropylenediamine, molecular weight 3000, amine value 445 mgKOH / g, manufactured by Huntsman. • PRIAMINE 1075: Dimer amine, molecular weight 550, amine value 205 mgKOH / g, manufactured by Cargill: Organic component containing a primary amino group • TETA: Triethylenetetramine, molecular weight 146: an organic component having primary and secondary amino groups. <Amine compounds> P-1: Polyurethane urea resin with tertiary amino groups at the ends, manufactured in Comparative Production Example 1: Organic component having tertiary amino groups • P-2: Polyamide amine resin produced in comparative manufacturing example 2: Organic components having primary and secondary amino groups Octylamine: An organic component having a primary amino group. <Curing accelerator> • Bis(dimethylaminomethyl)phenol: an organic component having a tertiary amino group.

[0106] <Preparation of curable resin composition> [Example 1] The curable resin composition of Example 1 was prepared by stirring and degassing 10 parts of jER828 as liquid epoxy resin (A), 6.4 parts of polyurethane urea resin (B-1) obtained in Production Example 1, 2.7 parts of D-400 and 0.5 parts of TETA as liquid polyamine (C), 0.3 parts of 3,5-dimethylpyrazole as heterocyclic aromatic compound (D), and 1.1 parts of bis(dimethylaminomethyl)phenol as a curing accelerator at room temperature.

[0107] [Examples 2-13, 15-26 and Comparative Examples 1-8] Except for the changes in the compound composition shown in Tables 2-4, the same procedure as in Example 1 was followed to prepare the curable resin compositions for Examples 2-13, 15-26, and Comparative Examples 1-8.

[0108] [Example 14] The curable resin composition of Example 14 was prepared by stirring and degassing 10 parts of jER828 as liquid epoxy resin (C), 6.1 parts of a mixture of polyurethane urea resin (B-4) obtained in Production Example 4 and liquid polyamine (D-230) (4.3 parts of polyurethane urea resin (B-4), 1.8 parts of D-230), 0.4 parts of TETA, 0.2 parts of 3,5-dimethylpyrazole as heterocyclic aromatic compound (D), and 0.7 parts of bis(dimethylaminomethyl)phenol as a curing accelerator at room temperature.

[0109] [Table 2]

[0110] [Table 3]

[0111] [Table 4]

[0112] <Evaluation of curable resin compositions> The curable resin compositions prepared in the examples and comparative examples were subjected to the following tests. The results are shown in Tables 2 to 4.

[0113] [Adhesion and cohesive failure] Each curable resin composition was applied to an aluminum substrate (100 mm long, 25 mm wide, 2 mm thick) to a length of 10 mm, width of 25 mm, and thickness of 0.2 mm. This was then bonded to another aluminum substrate, and the mixture was cured at 25°C for 7 days while maintaining a thickness of 0.2 mm. Test specimens for measuring adhesion and cohesive failure were obtained. The obtained test specimens were subjected to shear adhesion testing using a tensile testing machine at a temperature of 25°C and relative humidity of 50%, with a tensile speed of 50 mm / min. Adhesion was determined according to the following evaluation criteria. Furthermore, the test specimens were visually inspected after the shear adhesion measurement, and cohesive failure was determined according to the following evaluation criteria. (Adhesion evaluation criteria) ◎: Shear adhesion strength of 17 MPa or higher (good) ○: Shear adhesive strength of 10 MPa or more and less than 17 MPa (usable) ×: Shear adhesive strength is less than 10 MPa (not usable) (Criteria for evaluating cohesive failure) ◎: More than 90% of the total surface area of ​​the test specimen shows cohesive failure (good). ○: Cohesive failure occurs in 50% or more but less than 90% of the total surface area of ​​the test specimen (usable). ×: Less than 50% of the total surface area of ​​the test specimen shows cohesive failure (unusable).

[0114] [Flexibility] Each resin composition adhesive was filled into a 1 mm thick sheet mold, the surface was smoothed, and it was cured at 25°C for 7 days. Then, dumbbell-shaped test specimens for flexibility evaluation were punched out using a No. 3 dumbbell mold. The resulting test specimens were measured for elongation at break using a tensile testing machine at a tensile speed of 10 mm / min under conditions of 25°C and 50% relative humidity. (Evaluation Criteria) ◎: Elongation at break is 120% or higher (good) ○: Breaking elongation is 70% or more and less than 120% (usable) ×: Breaking elongation is less than 70% (unusable)

[0115] <Overall Rating> The curable resin compositions prepared in the examples and comparative examples were comprehensively evaluated according to the following criteria. The evaluation results are shown in Tables 2 to 4.

[0116] (Overall evaluation criteria) ◎: The evaluation result is ◎ in all evaluation items. (Excellent) There is no ○:× judgment, but there is a ○ judgment. (Usable) ×: A "×" rating is given in any of the evaluation items. (Not usable)

[0117] The curable resin composition of the present invention yielded excellent results in terms of adhesion, cohesive failure, and flexibility. On the other hand, the curable resin composition of the comparative example was inferior to the example in some or all of the following aspects: adhesion, cohesive failure, and flexibility.

Claims

1. It contains a main component (X) containing liquid epoxy resin (A) and a hardening agent (Y), A solvent-free curable resin composition characterized by satisfying all of the following conditions (i) to (iv). (i) The curing agent (Y) comprises a polyurethane urea resin (B), a liquid polyamine (C), and a heterocyclic aromatic compound (D). (ii) Polyurethane urea resin (B) has a primary amino group or a secondary amino group at its terminal. (iii) The heterocyclic aromatic compound (D) has two or more adjacent nitrogen atoms in its ring structure, and the nitrogen atoms are unsubstituted. (iv) The curing agent (Y) contains 10 to 80% by mass of polyurethane urea resin (B) in a total of 100% by mass of the organic component having a primary amino group and the organic component having a secondary amino group.

2. The curable resin composition according to claim 1, wherein the molecular weight of the liquid polyamine (C) is less than 600.

3. The curable resin composition according to claim 1, wherein the number average molecular weight of the polyurethane urea resin (B) is 1,000 or more and less than 50,000.

4. The curable resin composition according to claim 1, wherein the total of 100% by mass of the polyurethane urea resin (B), liquid polyamine (C), and heterocyclic aromatic compound (D) contains 0.3 to 7.0% by mass of the heterocyclic aromatic compound (D).

5. A cured product comprising the curable resin composition according to any one of claims 1 to 4.

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