Curable composition, cured product, and thermoplastic resin

Abstract

This curable composition contains (A) an alicyclic epoxy resin and (B1) an active hydrogen compound which has a pKa of 10 or less.

Description

[Technical Field]

[0001] The present invention relates to a curable composition, a cured product, and a method for producing the cured product. [Background technology]

[0002] Epoxy resins are used in a variety of electrical and electronic components. Among them, alicyclic epoxy resins have low viscosity and exhibit high transparency and weather resistance when cured, and are therefore used in optical applications such as encapsulants and surface protection films for optical semiconductor devices and organic electroluminescence devices.

[0003] On the other hand, alicyclic epoxy resins have significantly lower reactivity than general-purpose epoxy resins such as bisphenol-type epoxy resins. Therefore, the curing reaction does not proceed well with active hydrogen compounds such as amines, or the curing process takes a long time. Therefore, efforts are being made to make the curing reaction of alicyclic epoxy resins more rapid by using acid anhydride curing agents or by modifying the epoxy resin structure (first study).

[0004] For example, Patent Document 1 discloses a curable composition containing an alicyclic epoxy resin having a specific structure and an active hydrogen compound. An aliphatic amine-based curing agent is used as the active hydrogen compound. According to this document, by using an alicyclic epoxy resin having a specific structure, even an active hydrogen compound can be cured.

[0005] Patent Document 2 discloses a curable composition containing an alicyclic epoxy resin, a polyfunctional thiol, a curing agent, and a curing accelerator. An aliphatic thiol is used as the polyfunctional thiol, an acid anhydride is used as the curing agent, and a p-toluenesulfonate salt of DBU is used as the curing accelerator.

[0006] Patent Document 3 discloses a curable composition containing hexahydrophthalic acid diglycidyl ester, an alicyclic epoxy resin, a polythiol-based curing agent, and a curing accelerator.

[0007] Epoxy resins are thermosetting resins that cure by reacting with a curing agent. Most thermosetting resins are usually liquid before curing. Therefore, thermosetting resins have advantages such as high adhesion to adherends and easy improvement of adhesive strength, and because they can ensure fluidity in a liquid state, they can increase the amount of filler added compared to thermoplastic resins and enable high dispersion of the filler.

[0008] Thermoplastic resins can be recycled by remelting them. On the other hand, thermosetting resins cannot be recycled because they do not melt once they have hardened. In other words, it is difficult to peel off a cured thermosetting resin after it has been adhered to an adherend. Therefore, studies have been conducted to impart thermoplasticity to cured thermosetting resins such as epoxy resins (second study).

[0009] For example, Patent Document 4 discloses a composition containing a difunctional aromatic epoxy resin (A), a difunctional phenolic compound (B), and reinforcing fibers. Patent Document 5 discloses an adhesive containing a difunctional aromatic epoxy resin, a difunctional curing agent, and a curing catalyst. Patent Document 6 discloses an epoxy resin composition containing a difunctional aromatic epoxy resin and at least one of a difunctional amine compound, a phenolic compound, and a thiol compound. It is said that curing any of these compositions produces a thermoplastic resin in which the difunctional aromatic epoxy resin and the difunctional curing agent are linearly polymerized. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent Publication No. 2021-55001 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-53199 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-109915 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-321897 [Patent Document 5] Japanese Patent Application Publication No. 2019-194322 [Patent Document 6] Japanese Patent Application Laid-Open No. 2001-348419 Summary of the Invention [Problem to be solved by the invention]

[0011] However, in the first study (curing reactivity of alicyclic epoxy resins) described above, it was necessary to use an alicyclic epoxy resin having a specific structure in Patent Document 1. It is desirable to be able to use various alicyclic epoxy resins without being limited to such a specific structure.

[0012] In addition, the curable composition of Patent Document 2 contains a large amount of an acid anhydride curing agent, so although the curing reaction proceeds, it takes a long time to obtain a cured product. In addition, the curable composition of Patent Document 3 contains a large amount of an aromatic epoxy resin, so the curing reaction proceeds relatively easily, but if a large amount of an alicyclic epoxy resin is contained, it takes a long time to obtain a cured product.

[0013] Therefore, it is desired to make it possible to facilitate the curing reaction even when a large amount of alicyclic epoxy resin is contained, and to shorten the time required to obtain a cured product.

[0014] Regarding the second study (imparting thermoplasticity to epoxy resins), the epoxy resins contained in the compositions shown in Patent Documents 4 to 6 are aromatic epoxy resins, and when the compositions are cured, not only do the aromatic epoxy resins react with the curing agent but also the aromatic epoxy resins themselves tend to react with each other. As a result, some of the aromatic epoxy resins tend to crosslink, and the resulting cured products are unlikely to be highly linearly polymerized polymers and do not have sufficient thermoplasticity.

[0015] Furthermore, to react bifunctional compounds, the resin and curing agent must be mixed in equal amounts. Therefore, when the curing agent is solid, the resin tends to thicken easily. High-viscosity aromatic epoxy resins, in particular, exhibit a significantly higher viscosity, which can easily cause the resin to lose its liquid properties, a characteristic of thermosetting resins. Furthermore, high-viscosity aromatic epoxy resins have poor impregnation into adherends and fillers, and it is difficult to increase the filler content to suppress the increase in viscosity. Furthermore, when using aromatic epoxy resins, using primary amines as bifunctional curing agents results in three-dimensional crosslinking, making it impossible to obtain a linearly polymerized polymer.

[0016] If the cured product has sufficient thermoplasticity, it can be remelted, making it possible to recycle or self-repair. For example, if a cured product adhered to an adherend can be softened or melted by heating, it can be peeled off from the adherend, making it easy to dismantle. Furthermore, if the composition is liquid before curing, shear mixing, such as three-roll dispersion, is possible, enabling high dispersion of the filler. For example, if a filler-containing composition can be dispersed by shear mixing and then the cured product can be melted, it becomes possible to add a filler that is difficult to disperse in an extruder for thermoplastic resins in a dispersed state as a masterbatch. Therefore, it is further desired to be able to provide a cured product with thermoplastic properties while maintaining the same good workability as a thermosetting resin.

[0017] The present invention has been made in view of the above circumstances, and aims to provide a curable composition, a cured product, and a method for producing the cured product that exhibit good curing reactivity even when containing a large amount of alicyclic epoxy resin. Preferably, the present invention aims to provide a curable composition and a thermoplastic resin that can give a cured product having thermoplastic properties while also having good workability similar to that of a thermosetting resin. [Means for solving the problem]

[0018] The present invention relates to the following curable composition, cured product, method for producing the cured product, and thermoplastic resin.

[0019] [1] A curable composition comprising an alicyclic epoxy resin (A) and an active hydrogen compound (B1) having a pKa of 10 or less. [2] The curable composition according to [1], wherein the active hydrogen compound (B1) contains an aromatic thiol compound. [3] The curable composition according to [1] or [2], wherein the alicyclic epoxy resin (A) is a bifunctional alicyclic epoxy resin (A'), and the active hydrogen compound (B1) having a pKa of 10 or less is a bifunctional active hydrogen compound (B1') having a pKa of 10 or less.

[0020] [4] A curable composition comprising an alicyclic epoxy resin (A), an active hydrogen compound (B2) having a pKa of more than 10, and a cationic catalyst (C1), wherein the content ratio of the active hydrogen compound (B2) to 100 parts by mass of the alicyclic epoxy resin (A) is 40 to 200 (mass ratio). [5] The curable composition according to [4], wherein the active hydrogen compound (B2) contains an aliphatic thiol compound. [6] A curable composition comprising a difunctional alicyclic epoxy resin (A'), a difunctional active hydrogen compound (B2') having a pKa of more than 10, and a cationic catalyst (C1).

[0021] [7] A curable composition comprising an alicyclic epoxy resin (A), an active hydrogen compound (B2) having a pKa of more than 10, and a catalyst (C2) that generates cations upon reaction with the active hydrogen compound (B2) or upon irradiation with light. [8] The curable composition according to [7], wherein the active hydrogen compound (B2) contains an aliphatic thiol compound. [9] The curable composition according to [7] or [8], wherein the catalyst (C2) is a catalyst that generates cations by reacting with the active hydrogen compound (B2), and contains dicyandiamide.

[10] The curable composition according to any one of [7] to [9], wherein the alicyclic epoxy resin (A) is a difunctional alicyclic epoxy resin (A'), and the active hydrogen compound (B2) having a pKa of more than 10 is a difunctional active hydrogen compound (B2') having a pKa of more than 10.

[0022]

[11] A cured product of the curable composition according to any one of [1] to

[10] .

[0023]

[12] A method for producing a cured product, comprising: a step of reacting an active hydrogen compound (B2) with dicyandiamide under heating to obtain a composition containing guanidine; and a step of reacting the composition with an alicyclic epoxy resin (A) under heating to obtain a cured product of a curable composition containing the alicyclic epoxy resin (A).

[0024]

[13] A thermoplastic resin comprising a structural unit derived from a difunctional alicyclic epoxy resin (A') and a structural unit derived from a difunctional active hydrogen compound (B'). [Effects of the Invention]

[0025] According to the present invention, it is possible to provide a curable composition, a cured product, and a method for producing the cured product, which exhibit good curing reactivity even when containing a large amount of alicyclic epoxy resin. Preferably, it is possible to provide a curable composition and a thermoplastic resin which can give a cured product having thermoplastic properties while also having good workability similar to that of a thermosetting resin. [Brief explanation of the drawings]

[0026] [Figure 1] 1A and 1B are photographs showing the appearance of the cured product obtained from composition 2-6 before and after heating. [Figure 2] 2A and 2B are photographs showing the appearance of the cured product obtained from composition 2-7 before and after heating. [Figure 3] FIG. 3A is a diagram showing the curing reaction mechanism of Composition 2-6, and FIG. 3B is a diagram showing the TOF-MS spectrum of the cured product. [Figure 4]FIG. 4A is a photograph showing the results of SEM observation of the surface of a sample sheet of Composition 2-6, and FIGS. 4B and 4C are photographs showing the results of EDX. DETAILED DESCRIPTION OF THE INVENTION

[0027] As described above, alicyclic epoxy resins, especially bifunctional alicyclic epoxy resins having an epoxy group composed of two adjacent carbon atoms and an oxygen atom that constitute an alicyclic ring (hereinafter also referred to as "alicyclic epoxy group"), have lower curing reactivity than general-purpose epoxy resins such as bisphenol-type epoxy resins.

[0028] In order to increase the curing reactivity of such alicyclic epoxy resins with low curing reactivity, H + It is effective to activate the alicyclic epoxy resin by having the (cations) present in the system. And the present inventors 1) H as a hardener + Use an active hydrogen compound that easily releases hydrogen (i.e., an active hydrogen compound with a low pKa); 2) H as a hardener + Use an active hydrogen compound that is less likely to release hydrogen (i.e., an active hydrogen compound with a high pKa) in combination with the cationic catalyst (C1); or 3) Use, as a curing agent, an active hydrogen compound having a high pKa in combination with a catalyst (C2) that generates cations by reaction with the compound or by irradiation with light. It has been found that the use of a thiol-based compound as the active hydrogen compound facilitates activation of the alicyclic epoxy resin and enhances its curing reactivity. In particular, it has been found that the use of a thiol-based compound as the active hydrogen compound results in a cured product with a high refractive index, and that the use of an aliphatic thiol-based compound results in a cured product with a high refractive index, flexibility, and a high flexural modulus.

[0029] That is, the curable composition according to one embodiment of the present invention comprises an alicyclic epoxy resin (A) and, as a component for curing the alicyclic epoxy resin, 1) Active hydrogen compounds (B1) with a pKa of 10 or less 2) A combination of an active hydrogen compound (B2) having a pKa of more than 10 and a cationic catalyst (C1), or 3) A combination of an active hydrogen compound (B2) having a pKa of more than 10 and a catalyst (C2) that generates cations upon reaction or irradiation with light.

[0030] Furthermore, the present inventors have found that in the above curing system, the difunctional alicyclic epoxy resin (A') is likely to undergo linear polymerization with the difunctional active hydrogen compound (B').

[0031] That is, in a curing system using an acid anhydride, the epoxy group of the alicyclic epoxy resin reacts with the acid anhydride and then opens the ring to form an oxygen anion (-O - ), it reacts with other alicyclic epoxy resins (not just acid anhydrides) and is prone to three-dimensional crosslinking (see below). [ka] [ka]

[0032] In contrast, in the curing systems 1) to 3) above, the epoxy groups of the alicyclic epoxy resin react with the active hydrogen compound to form cations (H + ) to form -OH, so it does not react with other alicyclic epoxy resins, but only with active hydrogen compounds (see below). In other words, the reaction proceeds without passing through oxygen anions, making it difficult for alicyclic epoxy resins to react with each other. Therefore, it can bond linearly in the order of alicyclic epoxy resin - active hydrogen compound - alicyclic epoxy resin... without three-dimensional crosslinking. This allows for the production of a cured product with thermoplastic properties. [ka] [ka]

[0033] As a result, the curable composition can provide a cured product with thermoplasticity while maintaining the same excellent workability as a thermosetting resin. Furthermore, such a cured product with thermoplasticity exhibits self-repairing properties, such that, even if cracks occur, the product softens or melts upon heating, eliminating the cracks. Therefore, for example, a cured product adhered to an adherend can be peeled off from the adherend by softening or melting it upon heating, allowing it to be recycled.

[0034] The constitution of the curable composition will be described in detail below.

[0035] 1.Curable composition A curable composition according to one embodiment of the present invention comprises an alicyclic epoxy resin (A), an active hydrogen compound (B), and an optional curing catalyst (C).

[0036] 1-1.Alicyclic epoxy resin (A) The alicyclic epoxy resin (A) is a compound having two or more epoxy groups in one molecule, preferably a compound having an epoxy group consisting of two or more adjacent carbon atoms and oxygen atoms that constitute an alicyclic ring (hereinafter also referred to as "alicyclic epoxy group"). Since the epoxy group consisting of carbon atoms and oxygen atoms that constitute an alicyclic ring has low curing reactivity, it is particularly effective to cure it with the active hydrogen compound (B) / curing catalyst (C) described above in 1) to 3).

[0037] The number of epoxy groups contained in one molecule of the alicyclic epoxy resin (A) is not particularly limited, but is preferably 2 or more, and more preferably 2 to 4. That is, the alicyclic epoxy resin (A) may be a difunctional alicyclic epoxy resin (A') having two epoxy groups in one molecule, or a trifunctional or higher functional alicyclic epoxy resin having three or more epoxy groups in one molecule.

[0038] The alicyclic epoxy group in the compound having an alicyclic epoxy group includes a cyclohexene oxide group, a cyclopentene oxide group, etc. Examples of the compound having an alicyclic epoxy group include a compound represented by the following formula (i): [ka]

[0039] In the above formula (i), X represents a single bond or a linking group. Examples of the linking group include a divalent hydrocarbon group, an alkenylene group in which some or all of the carbon-carbon double bonds have been epoxidized (hereinafter also referred to as an "epoxidized alkenylene group"), a carbonyl group, an ether bond, an ester bond, a siloxane bond, a carbonate group, an amide group, and a group in which multiple of these are linked together. The cyclohexene oxide group in formula (i) may have a substituent (e.g., an alkyl group) bonded to it.

[0040] Examples of the divalent hydrocarbon group include a linear or branched alkylene group having 1 to 18 carbon atoms and a divalent alicyclic hydrocarbon group. Examples of the linear or branched alkylene group having 1 to 18 carbon atoms include a methylene group, a methylmethylene group, a dimethylmethylene group, an ethylene group, a propylene group, and a trimethylene group. Examples of the divalent alicyclic hydrocarbon group include cycloalkylene groups (including cycloalkylidene groups) such as a 1,2-cyclopentylene group, a 1,3-cyclopentylene group, a cyclopentylidene group, a 1,2-cyclohexylene group, a 1,3-cyclohexylene group, a 1,4-cyclohexylene group, and a cyclohexylidene group.

[0041] Examples of the alkenylene group in the epoxidized alkenylene group include linear or branched alkenylene groups having 2 to 8 carbon atoms, such as a vinylene group, propenylene group, 1-butenylene group, 2-butenylene group, butadienylene group, pentenylene group, hexenylene group, heptenylene group, and octenylene group. The epoxidized alkenylene group is preferably an alkenylene group in which all of the carbon-carbon double bonds have been epoxidized, and more preferably an alkenylene group in which all of the carbon-carbon double bonds have been epoxidized and have 2 to 4 carbon atoms.

[0042] Examples of the compound represented by formula (i) include (3,4,3',4'-diepoxy)bicyclohexyl, bis(3,4-epoxycyclohexylmethyl)ether, 1,2-epoxy-1,2-bis(3,4-epoxycyclohexyl-1-yl)ethane, 2,2-bis(3,4-epoxycyclohexyl-1-yl)propane, 1,2-bis(3,4-epoxycyclohexyl-1-yl)ethane, and compounds represented by the following formulas (i-1) to (i-9). In the following formulas (i-5) and (i-7), l and m each represent an integer of 1 to 30. In the following formula (i-5), R' is an alkylene group having 1 to 8 carbon atoms, and among these, a linear or branched alkylene group having 1 to 3 carbon atoms, such as a methylene group, an ethylene group, a propylene group, or an isopropylene group, is preferred.

[0043] [ka]

[0044] Examples of the compound having an alicyclic epoxy group include the following compounds in addition to the compound represented by the above formula (i). [ka]

[0045] Examples of compounds having an alicyclic epoxy group include, in addition to the compound represented by formula (i), compounds having three or more alicyclic epoxy groups in the molecule represented by the following formulas (ii-1) to (ii-3), and compounds having one alicyclic epoxy group in the molecule represented by the following formulas (iii-1) to (iii-3). In the following formulas (ii-1) and (ii-2), n1 to n6 each represent an integer of 1 to 30.

[0046] [ka]

[0047] [ka]

[0048] The epoxy equivalent of the alicyclic epoxy resin (A) is not particularly limited, but for example, to improve the refractive index, it is preferable that the epoxy equivalent be appropriately low in order to increase the content of sulfur-containing active hydrogen compounds such as thiol compounds. Similarly, to improve the flexural modulus, it is preferable that the epoxy equivalent be appropriately low in order to increase the content of polyfunctional active hydrogen compounds. From these perspectives, the epoxy equivalent of the alicyclic epoxy resin (A) is preferably 70 to 200 g / eq, more preferably 80 to 140 g / eq. The epoxy equivalent can be measured in accordance with JIS K 7236.

[0049] The content of the alicyclic epoxy resin (A) varies depending on the intended use, the presence or absence of a filler, and the like, but may be, for example, 1 to 70 parts by mass per 100 parts by mass of the non-volatile components of the curable composition. When the content of the alicyclic epoxy resin (A) is within the above range, a curable composition with a lower viscosity is easily obtained, and a cured product with higher transparency and weather resistance is easily obtained. Note that the non-volatile components refer to components that do not volatilize at room temperature, specifically components other than the solvent.

[0050] 1-2. Active hydrogen compound (B) / curing catalyst (C) The active hydrogen compound (B) is a compound containing a functional group having active hydrogen. Examples of the functional group having active hydrogen include a phenolic hydroxyl group, a thiol group, and an amino group. The number of functional groups having active hydrogen contained in one molecule of the active hydrogen compound (B) may be two or more. In other words, the active hydrogen compound (B) may be a bifunctional active hydrogen compound (B') having two functional groups having active hydrogen in one molecule, or a trifunctional or higher active hydrogen compound having three or more functional groups having active hydrogen in one molecule.

[0051] As described above, the curable composition contains, as components for curing the alicyclic epoxy resin (A), 1) an active hydrogen compound (B1) having a pKa of 10 or less, 2) an active hydrogen compound (B2) having a pKa of more than 10 and a cationic catalyst (C1), or 3) an active hydrogen compound (B2) having a pKa of more than 10 and a catalyst (C2) that generates cations upon reaction or light irradiation.

[0052] Regarding 1) (Active hydrogen compound (B1)) The pKa of the active hydrogen compound (B1) in 1) above is 10 or less, preferably 6 to 10. An active hydrogen compound having such a low pKa is H + Since it easily releases hydrogen, it easily activates the alicyclic epoxy resin. Therefore, it is possible to cure the alicyclic epoxy resin even without the presence of a catalyst. The active hydrogen compound (B1) may be a bifunctional active hydrogen compound (B1') or a trifunctional or higher functional active hydrogen compound.

[0053] In this specification, pKa is the acid dissociation equilibrium constant, pKa = -logKa, Ka = [HO + ][B - ] / [BH](BH: organic acid, B - (pKa: conjugate base of organic acid). When two or more acidic groups are contained in one molecule of the curing agent, pKa means the first dissociation constant pKa1.

[0054] The acid dissociation constant (pKa) of active hydrogen compounds varies depending on the structure of the active hydrogen compound. That is, the pKa of compounds in which the functional group containing active hydrogen is directly bonded to an aromatic group (aromatic ring) is lower than the pKa of compounds in which the functional group is directly bonded to an aliphatic group. The pKa of compounds decreases in the order of thiols, alcohols, and amines.

[0055] The acid dissociation constant (pKa) also varies depending on the type of solvent surrounding the active hydrogen compound. In this specification, to distinguish between active hydrogen compounds (B1) and (B2), the pKa in water is used as an indicator. The pKa can be calculated from the concentration of the substance and the hydrogen ion concentration by measuring the hydrogen ion concentration in water using, for example, a pH meter. Alternatively, if the pKa value is publicly known in literature (e.g., pKa Data Compiled by R. Williams, https: / / organicchemistrydata.org / hansreich / resources / pka / pka_data / pka-compilation-williams.pdf), that value can be used. If the pKa value is not publicly known in literature, the active hydrogen compound can be described using a rational formula, and the pKa value of a compound that is two or more carbon atoms away from the carbon atom bonded to the active hydrogen-containing functional group (a compound that corresponds to a site with two or more carbon atoms starting from the carbon atom bonded to the active hydrogen-containing functional group) can be used.

[0056] In the case of water-insoluble active hydrogen compounds, the pKa can be estimated from the structure around the functional group that becomes the active hydrogen. For example, the pKa of 4,4'-thiobisbenzenethiol can be taken as the pKa value of thiophenol.

[0057] Examples of the active hydrogen compound (B1) having a pKa of 10 or less include thiol compounds having a pKa of 10 or less and bisphenol compounds having a pKa of 10 or less. These curing agents can be compounds in which an active hydrogen functional group such as a thiol or alcohol is directly bonded to a conjugated structure such as a benzene ring. A curing agent in which an active hydrogen functional group is bonded to a conjugated structure like this is likely to release hydrogen ions because the conjugated base state is stabilized.

[0058] Bisphenol compounds with a pKa of 10 or less are compounds that have two phenolic hydroxyl groups in one molecule, and examples include bisphenols such as 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 1,1-bis(4-hydroxyphenyl)ethane (bisphenol AD), bis(hydroxyphenyl)methane (bisphenol F), bisphenolfluorene, and biscresolfluorene.

[0059] The thiol compound having a pKa of 10 or less may be any compound having two or more thiol groups in one molecule and having a pKa that satisfies the above range, and is preferably a thiol compound containing an aromatic ring (aromatic thiol compound). The number of aromatic rings contained in one molecule of the aromatic thiol compound may be at least one, preferably one to three, and more preferably one to two.

[0060] Examples of aromatic thiol compounds include: 1,2-Dimercaptobenzene, 1,3-Dimercaptobenzene, 1,4-Dimercaptobenzene, 1,2-Bis(mercaptomethyl)benzene, 1,3-Bis(mercaptomethyl)benzene, 1,4-Bis(mercaptomethyl)benzene, 1,3-Bis(mercaptoethyl)benzene, 1,4-Bis(mercaptoethyl)benzene, 1,2-Bis(mercaptomethoxy)benzene, 1,3-Bis(mercaptomethoxy)benzene, 1,4-Bis(mercaptomethoxy)benzene, 1,2-Bis(mercaptoethoxy)benzene, 1,3-Bis(mercaptoethoxy)benzene, 1,4-Bis(mercaptoethoxy)benzene, 2,2'-Dimercaptobiphenyl, 4 bifunctional aromatic thiol compounds such as 4'-dimercaptobiphenyl, 4,4'-dimercaptobibenzyl, 2,5-toluenedithiol, 3,4-toluenedithiol, 1,4-naphthalenedithiol, 1,5-naphthalenedithiol, 2,6-naphthalenedithiol, 2,7-naphthalenedithiol, 2,4-dimethylbenzene-1,3-dithiol, 4,5-dimethylbenzene-1,3-dithiol, 9,10-anthracenedimethanethiol, 1,3-di(p-methoxyphenyl)propane-2,2-dithiol, 1,3-diphenylpropane-2,2-dithiol, phenylmethane-1,1-dithiol, and 2,4-di(p-mercaptophenyl)pentane; 1,2,3-trimercaptobenzene, 1,2,4-trimercaptobenzene, 1,3,5-trimercaptobenzene, 1,2,3-tris(mercaptomethyl)benzene, 1,2,4-tris(mercaptomethyl)benzene, 1,3,5-tris(mercaptomethyl)benzene, 1,2,3-tris(mercaptoethyl)benzene, 1,2,4-tris(mercaptoethyl)benzene, 1,3,5-tris(mercaptoethyl)benzene, 1,2,3-tris(mercaptomethoxy)benzene, 1,2,4-tris(mercaptomethoxy)benzene, 1,3,5-tris(mercaptomethoxy)benzene, 1,2,3-tris(mercaptoethoxy)benzene, 1,2,4-tris(mercaptoethoxy)benzene, 1,3,5-tris(mercaptoethoxy)benzene, 1,2,3,4-tetramercaptobenzene, 1,2,3,5-tetramercaptobenzene, 1,2,4,5-tetramercaptobenzene, 1,2,3,4-tetrakis(mercaptomethyl)benzene, 1,2,3,5-tetrakis(mercaptomethyl)benzene, 1,2,4,5-tetrakis(mercaptomethyl)benzene, 1,2,3,4-tetrakis(mercaptoethyl)benzene, 1,2,3,5-tetrakis(mercaptoethyl)benzene, 1,2,4,5- Aromatic thiol compounds with three or more functional groups, such as tetrakis(mercaptoethyl)benzene, 1,2,3,4-tetrakis(mercaptoethyl)benzene, 1,2,3,5-tetrakis(mercaptomethoxy)benzene, 1,2,4,5-tetrakis(mercaptomethoxy)benzene, 1,2,3,4-tetrakis(mercaptoethoxy)benzene, 1,2,3,5-tetrakis(mercaptoethoxy)benzene, and 1,2,4,5-tetrakis(mercaptoethoxy)benzene etc.

[0061] The aromatic thiol compound may further contain a sulfur atom in addition to the thiol group. Examples of such aromatic thiol compounds include: Bifunctional aromatic thiol compounds such as 1,2-bis(mercaptomethylthio)benzene, 1,3-bis(mercaptomethylthio)benzene, 1,4-bis(mercaptomethylthio)benzene, 1,2-bis(mercaptoethylthio)benzene, 1,3-bis(mercaptoethylthio)benzene, 1,4-bis(mercaptoethylthio)benzene, and 4,4'-thiobisbenzenethiol; 1,2,3-tris(mercaptomethylthio)benzene, 1,2,4-tris(mercaptomethylthio)benzene, 1,3,5-tris(mercaptomethylthio)benzene, 1,2,3-tris(mercaptoethylthio)benzene, 1,2,4-tris(mercaptoethylthio)benzene, 1,3,5-tris(mercaptoethylthio)benzene, 1,2,3,4-tetrakis(mercaptomethylthio)benzene, 1,2,3,5- Aromatic thiol compounds with three or more functional groups, such as tetrakis(mercaptomethylthio)benzene, 1,2,4,5-tetrakis(mercaptomethylthio)benzene, 1,2,3,4-tetrakis(mercaptoethylthio)benzene, 1,2,3,5-tetrakis(mercaptoethylthio)benzene, 1,2,4,5-tetrakis(mercaptoethylthio)benzene, and 1,3,5-triazine-2,4,6-trithiol (thiocyanuric acid) These may be used alone or in combination of two or more.

[0062] The thiol equivalent of the thiol compound having a pKa of 10 or less is not particularly limited, but is, for example, 300 g / eq or less, and preferably 150 g / eq or less. When the thiol equivalent is in this range, the curing reactivity of the curable composition and the refractive index of the cured product are more likely to be increased.

[0063] As described above, the number of thiol groups (number of functional groups) contained in one molecule of a thiol compound having a pKa of 10 or less is 2 (bifunctional) or 3 or more (trifunctional or more), and is preferably 2 to 10, more preferably 2 to 4, and more preferably 3. When the number of thiol groups is within this range, the curing reactivity of the curable composition and the refractive index of the cured product are more likely to be increased.

[0064] The weight-average molecular weight of the thiol compound having a pKa of 10 or less is not particularly limited, but is preferably 100 to 10,000, and more preferably 100 to 1,000. The weight-average molecular weight can be measured by GPC in terms of polystyrene.

[0065] Among these, the active hydrogen compound (B1) having a pKa of 10 or less preferably contains a thiol compound having a pKa of 10 or less, and more preferably contains a thiol compound having a pKa of 7 or less.

[0066] The content of the active hydrogen compound (B1) having a pKa of 10 or less is preferably 15 to 400 parts by mass per 100 parts by mass of the total amount of epoxy group-containing resins (preferably the total amount of alicyclic epoxy resins (A)). When the content of the active hydrogen compound (B1) is 15 parts by mass or more, the alicyclic epoxy resin is more easily activated, and sufficient curing reactivity is more likely to be obtained. When the content of the active hydrogen compound (B1) is 400 parts by mass or less, an increase in viscosity of the cured composition is more easily suppressed, and therefore handleability is less likely to be impaired. From the same viewpoint, the content of the active hydrogen compound (B1) is more preferably 30 to 200 parts by mass per 100 parts by mass of the total amount of epoxy group-containing resins (preferably the total amount of alicyclic epoxy resins (A)).

[0067] Regarding 2) In the case of 2) above, the components that cure the alicyclic epoxy resin include an active hydrogen compound (B2) having a pKa of more than 10 and a cationic catalyst (C1).

[0068] (Active hydrogen compound (B2)) The pKa of the active hydrogen compound (B2) in 2) above is greater than 10, preferably 10 to 14. An active hydrogen compound having such a high pKa is H + It is difficult to release H by itself, so it is difficult to activate alicyclic epoxy resins. + The alicyclic epoxy resin can be cured by further combining it with a cationic catalyst (C1) capable of generating the following. The active hydrogen compound (B2) may be a bifunctional active hydrogen compound (B2') or a trifunctional or higher active hydrogen compound.

[0069] The active hydrogen compound (B2) having a pKa of more than 10 preferably includes an amine compound having a pKa of more than 10 or a thiol compound having a pKa of more than 10.

[0070] The amine compound having a pKa of more than 10 may be any compound having two or more amino groups in one molecule and having a pKa that satisfies the above range, preferably 11 or more, more preferably 15 or more, and preferably includes an amine compound containing an aromatic ring (aromatic amine compound). Examples of aromatic amine compounds include 4,4'-diaminodiphenyl sulfide (ASD, manufactured by Seika Corporation) and 4,4'-diaminodiphenyl sulfone (Seikacure S, manufactured by Seika Corporation). In the present invention, primary amines can also be used. This is thought to be due to the fact that the pKa changes when the primary amine becomes a secondary amine after reaction, and that the steric hindrance of the epoxy group in alicyclic epoxy resins is greater than that in aromatic epoxy resins.

[0071] The thiol compound having a pKa of more than 10 may be any compound having two or more thiol groups in one molecule and having a pKa that satisfies the above range, and is preferably a thiol compound not containing an aromatic ring (aliphatic thiol compound). The aliphatic thiol compound may be an aliphatic thiol compound having an ester bond in the molecule, or may be an aliphatic thiol compound not having an ester bond in the molecule.

[0072] Examples of aliphatic thiol compounds having an ester bond in the molecule include: bifunctional aliphatic thiol compounds such as 1,4-bis(3-mercaptobutyryloxy)butane (KarenzMT (registered trademark) BD1, manufactured by Showa Denko K.K.); Trimethylolpropane tris(3-mercaptopropionate) (manufactured by SC Organic Chemical Co., Ltd., TMMP), tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate (manufactured by SC Organic Chemical Co., Ltd., TEMPIC), pentaerythritol tetrakis(3-mercaptopropionate) (manufactured by SC Organic Chemical Co., Ltd., PEMP), tetraethylene glycol bis(3-mercaptopropionate) (manufactured by SC Organic Chemical Co., Ltd., EGMP-4), dipentaerythritol Examples of such aliphatic thiol compounds include tri- or higher functional compounds such as pentaerythritol tetrakis(3-mercaptopropionate) (DPMP, manufactured by SC Organic Chemical Industry Co., Ltd.), pentaerythritol tetrakis(3-mercaptobutyrate) (KarenzMT (registered trademark) PE1, manufactured by Showa Denko K.K.), and 1,3,5-tris(3-mercaptobutyryloxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (KarenzMT (registered trademark) NR1, manufactured by Showa Denko K.K.).

[0073] Examples of aliphatic thiol compounds that do not have an ester bond in the molecule include compounds represented by the following formula (1) or (2). [ka]

[0074] In formula (1), R 1 and R 2 are each independently selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 12 carbon atoms. 3 , R 4 , R 5 and R 6 are each independently selected from the group consisting of a mercaptomethyl group, a mercaptoethyl group, and a mercaptopropyl group.

[0075] Examples of the compound represented by formula (1) include 1,3,4,6-tetrakis(2-mercaptoethyl)glycoluril (manufactured by Shikoku Chemical Industry Co., Ltd., TS-G), 1,3,4,6-tetrakis(3-mercaptopropyl)glycoluril (manufactured by Shikoku Chemical Industry Co., Ltd., C3 TS-G), 1,3,4,6-tetrakis(mercaptomethyl)glycoluril, 1,3,4,6-tetrakis(mercaptomethyl)-3a-methylglycoluril, 1,3,4,6-tetrakis(2-mercaptoethyl)-3a-methylglycoluril, 1,3,4,6-tetrakis(3-mercaptopropyl)-3a-methylglycoluril, 1,3,4,6-tetrakis(mercaptomethyl)-3a,6a-dimethylglycoluril, 1,3,4,6-tetrakis(2-mercaptoethyl)-3a,6a-dimethylglycoluril, 1,3,4,6-tetrakis(3-mercaptopropyl)-3a,6a-dimethylglycoluril, etc. Of these, 1,3,4,6-tetrakis(2-mercaptoethyl)glycoluril and 1,3,4,6-tetrakis(3-mercaptopropyl)glycoluril are particularly preferred.

[0076] [ka]

[0077] In formula (2), A is a residue of a polyhydric alcohol having n+m hydroxyl groups. R 7 are independently alkylene groups having 1 to 10 carbon atoms. R 8 are independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. m is an integer equal to or greater than 0. n is an integer of 3 or greater.

[0078] Examples of the compound represented by formula (2) include pentaerythritol trippropanethiol (Multhiol Y-3, manufactured by SC Organic Chemicals Co., Ltd.), pentaerythritol tetrapropanethiol, etc. Of these, pentaerythritol trippropanethiol is particularly preferred.

[0079] In addition, as an aliphatic thiol compound having no ester bond in the molecule, a polythiol compound having three or more functional groups and having two or more sulfide bonds in the molecule can also be used. Examples of such thiol compounds include 1,2,3-tris(mercaptomethylthio)propane, 1,2,3-tris(2-mercaptoethylthio)propane, 1,2,3-tris(3-mercaptopropylthio)propane, 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane, 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,8 ... Mercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, tetrakis(mercaptomethylthiomethyl)methane, tetrakis(2-mercaptoethylthiomethyl)methane, tetrakis(3-mercaptopropylthiomethyl)methane, 1,1,3,3-tetrakis(mercaptomethylthio)propane, 1,1,2,2-tetrakis(mercaptomethylthio)ethane, 1,1,5,5-tetrakis(mercaptomethylthio)-3-thiapentane, 1,1,6,6-tetrakis(mercaptomethylthio) 1,1,9,9-tetrakis(mercaptomethylthio)-5-(3,3-bis(mercaptomethylthio)-1-thiapropyl)-3,7-dithiahexane, 2,2-bis(mercaptomethylthio)ethanethiol, 3-mercaptomethylthio-1,7-dimercapto-2,6-dithiaheptane, 3,6-bis(mercaptomethylthio)-1,9-dimercapto-2,5,8-trithianonane, 3-mercaptomethylthio-1,6-dimercapto-2,5-dithiahexane, 1,1,9,9-tetrakis(mercaptomethylthio)-5-(3,3-bis(mercaptomethylthio)-1-thiapropyl)3,7-dithianonane, Tris(2,2-bis(mercaptomethylthio)ethyl)methane, tris(4,4-bis(mercaptomethylthio)-2-thiabutyl)methane, tetrakis(2,2-bis(mercaptomethylthio)ethyl)methane, tetrakis(4,4-bis(mercaptomethylthio)-2-thiabutyl)methane, 3,5,9,11-tetrakis(mercaptomethylthio)-1,13-dimercapto-2,6,8,12-tetrathiatridecane, 3,5,9,11,15,17-hexakis(mercaptomethylthio)-1,19-Dimercapto-2,6,8,12,14,18-hexathianonadecane, 9-(2,2-bis(mercaptomethylthio)ethyl)-3,5,13,15-tetrakis(mercaptomethylthio)-1,17-dimercapto-2,6,8,10,12,16-hexathiaheptadecane, 3,4,8,9-tetrakis(mercaptomethylthio)-1,11-dimercapto-2,5,7,10-tetrathiaundecane, 3,4,8,9,13,14-hexakis(mercaptomethylthio)-1,16-di Mercapto-2,5,7,10,12,15-hexathiahexadecane, 8-[bis(mercaptomethylthio)methyl]-3,4,12,13-tetrakis(mercaptomethylthio)-1,15-dimercapto-2,5,7,9,11,14-hexathiapentadecane, 4,6-bis[3,5-bis(mercaptomethylthio)-7-mercapto-2,6-dithiaheptylthio]-1,3-dithiane, 4-[3,5-bis(mercaptomethylthio)-7-mercapto-2,6-dithiaheptylthio]-6 -mercaptomethylthio-1,3-dithiane, 1,1-bis[4-(6-mercaptomethylthio)-1,3-dithianylthio]-1,3-bis(mercaptomethylthio)propane, 1-[4-(6-mercaptomethylthio)-1,3-dithianylthio]-3-[2,2-bis(mercaptomethylthio)ethyl]-7,9-bis(mercaptomethylthio)-2,4,6,10-tetrathiaundecane, 3-[2-(1,3-dithietanyl)]methyl-7,9-bis(mercaptomethylthio)-1,11- Polythiol compounds not having a cyclic structure, such as dimercapto-2,4,6,10-tetrathiaundecane, 9-[2-(1,3-dithietanyl)]methyl-3,5,13,15-tetrakis(mercaptomethylthio)-1,17-dimercapto-2,6,8,10,12,16-hexathiaheptadecane, and 3-[2-(1,3-dithietanyl)]methyl-7,9,13,15-tetrakis(mercaptomethylthio)-1,17-dimercapto-2,4,6,10,12,16-hexathiaheptadecane; 4,6-bis[4-(6-mercaptomethylthio)-1,3-dithianylthio]-6-[4-(6-mercaptomethylthio)-1,3-dithianylthio]-1,3-dithiane, 4-[3,4,8,9-tetrakis(mercaptomethylthio)-11-mercapto-2,5,7,10-tetrathiaundecyl]-5-mercaptomethylthio-1,3-dithiolane, 4,5-bis[3,4-bis(mercaptomethylthio)-6-mercapto-2,5- dithiahexylthio]-1,3-dithiolane, 4-[3,4-bis(mercaptomethylthio)-6-mercapto-2,5-dithiahexylthio]-5-mercaptomethylthio-1,3-dithiolane, 4-[3-bis(mercaptomethylthio)methyl-5,6-bis(mercaptomethylthio)-8-mercapto-2,4,7-trithiaoctyl]-5-mercaptomethylthio-1,3-dithiolane, 2-{bis[3,4-bis(mercaptomethylthio) (e)-6-mercapto-2,5-dithiahexylthio]methyl}-1,3-dithietane, 2-[3,4-bis(mercaptomethylthio)-6-mercapto-2,5-dithiahexylthio]mercaptomethylthiomethyl-1,3-dithietane, 2-[3,4,8,9-tetrakis(mercaptomethylthio)-11-mercapto-2,5,7,10-tetrathiaundecylthio]mercaptomethylthiomethyl-1,3-dithietane, 2-[3-bis Examples of polythiol compounds having a cyclic structure include (mercaptomethylthio)methyl-5,6-bis(mercaptomethylthio)-8-mercapto-2,4,7-trithiaoctyl]mercaptomethylthiomethyl-1,3-dithietane and 4-{1-[2-(1,3-dithietanyl)]-3-mercapto-2-thiapropylthio}-5-[1,2-bis(mercaptomethylthio)-4-mercapto-3-thiabutylthio]-1,3-dithiolane.

[0080] The thiol equivalent of a thiol compound having a pKa of more than 10 is not particularly limited, but is, for example, 90 to 160 g / eq, and preferably 90 to 140 g / eq. When the thiol equivalent is within this range, the curing reactivity of the curable composition is good. This makes it easier to further increase the curing reactivity of the curable composition, and also makes it easier to further increase the refractive index and flexural modulus of the cured product.

[0081] As described above, the number of thiol groups (number of functional groups) contained in one molecule of a thiol compound having a pKa of more than 10 is 2 (bifunctional) or 3 (trifunctional) or more, preferably 2 to 4, more preferably 3 to 4, and even more preferably 4. When the number of thiol groups is equal to or greater than the lower limit, the curing reactivity of the curable composition is more likely to be increased, and the refractive index and flexural modulus of the cured product are also more likely to be increased. Furthermore, when the number of thiol groups is 4 or less, the number of thiol groups remaining unreacted can be further reduced, thereby preventing a decrease in physical properties.

[0082] The weight-average molecular weight of the thiol compound having a pKa of more than 10 is not particularly limited, but is preferably 100 to 10,000, and more preferably 100 to 1,000. The weight-average molecular weight can be measured by the same method as above.

[0083] The content of the active hydrogen compound (B2) having a pKa of more than 10 is 40 to 200 parts by mass per 100 parts by mass of the total amount of epoxy group-containing resins (preferably the total amount of alicyclic epoxy resins). When the content of the curing agent (B2) is 40 parts by mass or more, the alicyclic epoxy resin is more easily activated, and the curing reactivity is more easily increased. When the content of the active hydrogen compound (B2) is 200 parts by mass or less, an increase in viscosity of the cured composition can be further suppressed, and therefore handling properties are less likely to be impaired. From the same viewpoint, the content of the curing agent (B2) is more preferably 50 to 150 parts by mass per 100 parts by mass of the total amount of epoxy group-containing resins (preferably the total amount of alicyclic epoxy resins).

[0084] (Cation catalyst (C1)) The cationic catalyst (C1) is H +This compound promotes the release of cations, facilitating the reaction between epoxy resin and active hydrogen compounds without promoting self-polymerization of the epoxy resin itself. The fact that it does not promote self-polymerization can be confirmed by the fact that a mixture of epoxy resin and catalyst alone does not generate heat (cure) when heated. In the self-polymerization reaction, two epoxy groups react with one epoxy group. In other words, an alicyclic epoxy resin with two epoxy groups reacts with four epoxy groups per molecule, which increases the degree of crosslinking and tends to reduce toughness. In contrast, cationic catalyst (C1) promotes the activation of epoxy groups and active hydrogen compounds without causing such self-polymerization. Direct addition of cationic catalyst (C1), which generates cations, allows the reaction to proceed rapidly. Therefore, it can also be used as a catalyst for two-component curable compositions in cold regions where heating is not possible or when it is desirable to reduce the heating / light irradiation energy required to generate cations such as catalyst (C2).

[0085] Activation of an epoxy group refers to the interaction with the oxygen of the epoxy group, facilitating nucleophilic attack on the carbon of the epoxy group. Compounds that can interact with the oxygen of an epoxy group include positively charged compounds. The reaction mechanism involves the oxygen atom of the epoxy group interacting with a positively charged catalyst, causing the carbon atom of the epoxy group to acquire a slight positive charge, facilitating nucleophilic attack by the activated hydrogen compound. Activation of an active hydrogen compound refers to the abstraction of hydrogen from the active hydrogen compound. Therefore, the cationic catalyst (C1) is a base used during the curing of the epoxy resin, and is preferably a compound that maintains a positively charged state after hydrogen abstraction and has a three-dimensional structure that can interact with the oxygen of the epoxy group.

[0086] Such a cationic catalyst (C1) is preferably an amine, such as an ammonium salt, an amine having an amidine structure, or an amine having a guanidine structure. Examples of ammonium salts include triethylmethylammonium 2-ethylhexane salt (product name: U-CAT 18X, manufactured by San-Apro Co., Ltd.). Examples of amines having an amidine structure include diazabicycloundecene (DBU) and diazabicyclononene (DBN), and examples of salts of these amines include 2-ethylhexanoate of DBU (product name: SA1, manufactured by San-Apro Co., Ltd.). Examples of amines having a guanidine structure (including biguanides) include tetramethylguanidine, and examples of salts include 1,2-Dicyclohexyl-4,4,5,5-tetramethylbiguanidium n-butyltriphenylborate (product name: WPGK-300 (Fujifilm Wako)). Among these, amines having an amidine structure or a salt thereof, and amines having a guanidine structure or a salt thereof are preferred, and amines having a guanidine structure or a salt thereof are more preferred.

[0087] The content of the cationic catalyst (C1) is preferably 1 to 10 parts by mass per 100 parts by mass of the total amount of epoxy group-containing resins (preferably the total amount of alicyclic epoxy resins). When the content of the cationic catalyst (C1) is 1 part by mass or more, the alicyclic epoxy resin is more easily activated, making it easier to achieve sufficient curing reactivity. When the content of the cationic catalyst (C1) is 10 parts by mass or less, the time during which the product can be used without curing after adding the catalyst (referred to as pot life) can be extended. Furthermore, deterioration of physical properties such as glass transition temperature and elastic modulus due to excess catalyst remaining in the cured product can be further suppressed. From the same perspective, the content of the cationic catalyst (C1) is more preferably 1 to 5 parts by mass per 100 parts by mass of the total amount of epoxy group-containing resins (preferably the total amount of alicyclic epoxy resins).

[0088] Regarding 3) In the case of 3) above, the components that cure the alicyclic epoxy resin include an active hydrogen compound (B2) having a pKa of more than 10 and a catalyst (C2) that generates cations upon reaction or light irradiation. As mentioned above, active hydrogen compounds with high pKa are H + It is difficult to release H by itself, so it is difficult to activate alicyclic epoxy resins.+ By further combining the catalyst (C2) capable of generating the above, the curing reactivity of the alicyclic epoxy resin can be enhanced. Furthermore, since the timing of the curing can be adjusted by the timing of the reaction and light irradiation, it is easy to achieve compatibility with storage stability. Furthermore, curable compositions containing catalyst (C2) retain fluidity even when stored at 40°C for 24 hours, for example, and have excellent storage stability. Therefore, catalyst (C2) is particularly suitable as a catalyst for one-component curable compositions.

[0089] (Active hydrogen compounds (B2) with pKa exceeding 10) The active hydrogen compound (B2) having a pKa of more than 10 can be the same as those described above, and is selected depending on the type of catalyst (C2). For example, when the catalyst (C2) is dicyandiamide, the active hydrogen compound (B2) is preferably an active hydrogen compound that reacts with dicyandiamide to produce guanidine (a reaction accelerator).

[0090] When the active hydrogen compound (B2) is a thiol-based compound, dicyandiamide reacts with the compound by heating as follows to produce guanidine. [ka]

[0091] The resulting guanidine further reacts with thiol compounds to form guanidinium ions, which promote ring-opening of cycloaliphatic epoxy resins (see below). [ka]

[0092] The compound that reacts with dicyandiamide to produce guanidine is preferably an aliphatic thiol compound, more preferably an aliphatic thiol compound with four or more functionalities, and even more preferably 1,3,4,6-tetrakis(2-mercaptoethyl)glycoluril and 1,3,4,6-tetrakis(3-mercaptopropyl)glycoluril.

[0093] The content of the active hydrogen compound (B2) having a pKa of more than 10 can be the same as in the above-mentioned 2).

[0094] (Catalyst (C2) that generates cations upon reaction or light irradiation) The catalyst (C2) that generates cations upon reaction or light irradiation is a catalyst that generates cations upon reaction with the active hydrogen compound (B2) or light irradiation.

[0095] The catalyst that generates cations through the reaction has the same function as the cationic catalyst (C1), except that it activates the active hydrogen compound (B2) and then becomes positively charged, thereby contributing to the activation of the epoxy group. Examples of such catalysts include dicyandiamide. This is desirable because it allows for the control of the initiation of curing by controlling the reaction with the active hydrogen compound (B2).

[0096] Examples of catalysts that generate cations upon irradiation with light include photobase generators, such as carboxylates, salts containing borate anions, and quaternary ammonium salts.

[0097] When a carboxylate or a salt containing a borate anion is used, a strong base such as an amidine, guanidine, or phosphazene base can be generated from a weak base such as an aliphatic amine compound, which facilitates a chain reaction with the alicyclic epoxy resin and increases the curing reactivity. When a quaternary ammonium salt is used, it is preferable that the salt contains imidazole or amidine as a base-reactive substance, from the viewpoint of increasing the curing reactivity.

[0098] Among these, from the viewpoint of easily generating a strong base and easily increasing curing reactivity, (8E)-8-ethylidene-4-methoxy-5,6,7,8 tetrahydronaphthalene-1-carboxylic acid 1,8-diazabicyclo[5,4,0]undec-7-ene, 1,2-diisopropyl-3-[bis(dimethylamino)methylene]guanidium 2-(3-benzoylphenyl)propionate, 1,2-dicyclohexyl-4,4,5,5-tetramethyldiguadium n-butyltriphenylborate, and (2-(9-oxoxanthen-2-yl)propionic acid 1,5,7-triazabicyclo[4,4,0]dec-5-ene)) are preferred.

[0099] The content of catalyst (C2) is preferably 0.5 to 10 parts by mass per 100 parts by mass of the total amount of epoxy group-containing resins (preferably the total amount of alicyclic epoxy resins). When the content of catalyst (C2) is 0.5 parts by mass or more, the alicyclic epoxy resins are more easily activated, making it easier to achieve sufficient curing reactivity. When the content of catalyst (C2) is 10 parts by mass or less, deterioration of physical properties such as glass transition temperature and elastic modulus due to excess catalyst remaining in the cured product can be further suppressed. From the same perspective, the content of catalyst (C2) is more preferably 1 to 5 parts by mass per 100 parts by mass of the total amount of epoxy group-containing resins (preferably the total amount of alicyclic epoxy resins).

[0100] In the case of the catalyst (C2) that generates cations through a reaction, the content of the catalyst (C2) is preferably 0.5 to 10 parts by mass, and more preferably 1 to 5 parts by mass, per 100 parts by mass of the active hydrogen compound (B2). When the content of the catalyst (C2) is within the above range, a sufficient amount of guanidine is easily generated through the reaction with the active hydrogen compound (B2), and the curing reactivity is easily increased.

[0101] 1-3.Other ingredients The curable composition may further contain other components depending on the intended use. Examples of the other components include other epoxy resins, sensitizers, antioxidants, surfactants, coupling agents, stabilizers, fillers, solvents, etc.

[0102] Examples of the other epoxy resin include an aliphatic epoxy resin, an aromatic epoxy resin, etc. When the curable composition further contains the other epoxy resin, the content of the other epoxy resin is preferably less than the content of the alicyclic epoxy resin, for example, from the viewpoint of suppressing a decrease in storage stability and flexural modulus.

[0103] Furthermore, when using a catalyst (C2) that generates cations upon irradiation with light, a sensitizer may be used in combination. The sensitizer has the function of improving the sensitivity of the curing reaction. The sensitizer may be any compound that can transfer stimulus energy such as heat or light to other substances, and sensitizers containing a naphthalene structure, an anthracene structure, or a thioxanthone structure may be used. The mass ratio of the sensitizer to the catalyst (C2) (sensitizer / catalyst (C2)) may be, for example, 0.1 to 0.5, from the viewpoint of increasing the activity of the catalyst (C2).

[0104] When a thiol compound is used as the active hydrogen compound (B), the pot life can be extended by using a stabilizer as a curing accelerator. Examples of the stabilizer include borates such as triethyl borate, triisopropyl borate, trimethyl borate, tri-n-propyl borate, and tri-n-butyl borate.

[0105] Furthermore, when the curable composition is used in coatings, etc., the alicyclic epoxy resin (A) has a low viscosity, so it is expected that it can be used without adding a solvent, but if an even lower viscosity is required, a solvent may be further contained. The content of the solvent is preferably 0 to 100%, more preferably 0 to 50%, and even more preferably 0 to 20%, based on the non-volatile components of the curable composition.

[0106] Furthermore, from the viewpoint of further shortening the curing time of the curable composition, it is preferable that the content of the acid anhydride curing agent is small. Specifically, the content of the acid anhydride curing agent may be 40 parts by mass or less, preferably 20 parts by mass or less, and more preferably 10 parts by mass or less, per 100 parts by mass of the curable composition.

[0107] In the above embodiment, the curable composition contains the alicyclic epoxy resin (A), the active hydrogen compound (B), and an optional curing catalyst (C), but the present invention is not limited thereto and may be a two-component curable composition that combines a first liquid and a second liquid that are mixed at the time of use.

[0108] For example, when a cationic catalyst (C1) is used, a two-component curable composition may be prepared by combining a first component containing an alicyclic epoxy resin (A) and the cationic catalyst (C1) with a second component containing an active hydrogen compound (B2). The alicyclic epoxy resin (A) may be contained in at least one of the first and second components. From the viewpoint of ease of mixing, it is preferable that the viscosities of the first and second components of the two-component curable composition are similar. In other words, the alicyclic epoxy resin (A) may be contained in both the first and second components to adjust the viscosities of the first and second components. Furthermore, when a catalyst (C2) is used, a two-component curable composition may be prepared by combining a first component containing an alicyclic epoxy resin (A) with a second component containing an active hydrogen compound (B2) and the catalyst (C2). From the viewpoint of ease of mixing, it is preferable that the viscosities of the first and second components of the two-component curable composition are similar. When the alicyclic epoxy resin (A) is added to both the first and second components to adjust the viscosities of the first and second components, a two-component curable composition may be prepared by combining a first component containing an alicyclic epoxy resin (A) and the catalyst (C2) with a second component containing the alicyclic epoxy resin (A) and the active hydrogen compound (B2).

[0109] In the curable composition according to the above embodiment, the (A) component and the (B) component may be combined with components having any number of functional groups. However, from the viewpoint of having good curing reactivity and further imparting a thermoplastic resin to the cured product, it is preferable to combine a bifunctional (A) component with a bifunctional (B) component.

[0110] That is, the curable composition can contain a difunctional alicyclic epoxy resin (A'), a difunctional active hydrogen compound (B'), and an optional curing catalyst (C). The curable composition can also contain, as a component for curing the difunctional alicyclic epoxy resin (A'), 1) Contains a bifunctional active hydrogen compound (B1') having a pKa of 10 or less, 2) containing a bifunctional active hydrogen compound (B2') having a pKa of more than 10 and a cationic catalyst (C1), or 3) It may contain a bifunctional active hydrogen compound (B2') having a pKa of more than 10 and a catalyst (C2) that generates cations upon reaction or irradiation with light.

[0111] The difunctional alicyclic epoxy resin (A') is the above-mentioned difunctional alicyclic epoxy resin (A'). Examples of the difunctional alicyclic epoxy resin (A') include the compound represented by the above-mentioned formula (i).

[0112] The bifunctional active hydrogen compound (B1') is the bifunctional active hydrogen compound (B1') described above. Examples of the bifunctional active hydrogen compound (B1') include the bifunctional bisphenol compounds having a pKa of 10 or less and bifunctional thiol compounds having a pKa of 10 or less.

[0113] The thiol equivalent of the bifunctional thiol compound having a pKa of 10 or less is not particularly limited, but is, for example, 2000 g / eq or less, and preferably 60 to 250 g / eq. When the thiol equivalent is in this range, the curing reactivity of the curable composition and the refractive index of the cured product are more likely to be increased.

[0114] The bifunctional active hydrogen compound (B2') is the bifunctional active hydrogen compound (B2') described above. Examples of the bifunctional active hydrogen compound (B2') include the bifunctional amine compounds having a pKa of more than 10 and the bifunctional thiol compounds having a pKa of more than 10 described above.

[0115] The thiol equivalent of the bifunctional thiol compound having a pKa of more than 10 is not particularly limited, but is, for example, 90 to 180 g / eq, and preferably 110 to 160 g / eq. When the thiol equivalent is in this range, the curable composition has good curing reactivity.

[0116] The cationic catalyst (C1) and the catalyst (C2) that generates cations by reaction or light irradiation are the same as the above-described cationic catalyst (C1) and catalyst (C2) that generates cations by reaction or light irradiation.

[0117] Specific examples and contents of the bifunctional alicyclic epoxy resin (A'), bifunctional active hydrogen compound (B1'), bifunctional active hydrogen compound (B2'), cationic catalyst (C1), and catalyst (C2) that generates cations upon reaction or light irradiation can be the same as those in the above-described embodiment. The mass ratio of the bifunctional alicyclic epoxy resin (A') to the bifunctional active hydrogen compound (B1') or the bifunctional active hydrogen compound (B2') can be the same as the mass ratio of the alicyclic epoxy resin (A) to the active hydrogen compound (B1) or the active hydrogen compound (B2).

[0118] 2.Cured product A cured product according to one embodiment of the present invention is a cured product of the above-mentioned curable composition.

[0119] (refractive index) Although cured products of alicyclic epoxy resins have good transparency, they tend to have a lower refractive index than cured products of aromatic epoxy resins because they do not contain aromatic rings. In contrast, when the active hydrogen compound (B) of the curable composition contains a thiol-based compound, the cured product contains sulfur element and therefore has a high refractive index. Cured products with a high refractive index are suitable for optical applications, for example.

[0120] The refractive index of a cured product composed only of resin at a wavelength of 589 nm (approximate D-line wavelength) is preferably 1.52 or more, more preferably 1.52 to 1.70, and even more preferably 1.56 to 1.66. Furthermore, inorganic particles may be added to increase the refractive index. The refractive index can be measured using an Abbe refractometer at a wavelength of 589 nm.

[0121] The refractive index of the cured product can be adjusted by the type and content of the thiol compound contained in the curable composition, the number of functional groups (the number of thiol groups), etc. For example, aromatic thiol compounds are more likely to increase the refractive index of the cured product than aliphatic thiol compounds. Furthermore, when the content of the thiol compound in the curable composition is high and the number of functional groups is large, the refractive index of the cured product tends to be high.

[0122] (bending properties) Cured products of curable compositions containing conventional acid anhydride curing agents or cationic curing agents tend to be brittle due to their high crosslink density. In contrast, when the curable composition contains a thiol compound, particularly an aliphatic thiol compound, as the active hydrogen compound (B) as the curing agent (see 2) and 3) above), flexibility can be imparted to the cured product, making it easier to increase toughness. That is, cured products of curable compositions containing thiol compounds exhibit a high flexural modulus equivalent to that of cured products using acid anhydride curing agents while maintaining good flexibility. The reason for this is unclear, but is presumed to be as follows.

[0123] The first reason is that thiol compounds do not react with alicyclic epoxy resins because their reaction mechanism does not involve oxygen anions, making it easier for the flexible structure derived from thiol compounds to be incorporated relatively uniformly into the molecular structure. The second reason is that the curing reactivity of alicyclic epoxy resins with thiol compounds is high, resulting in the generation of many hydroxyl groups through ring opening. As a result, the hydrogen bonds between the generated hydroxyl groups result in a high elastic modulus against initial stress. However, when stress greater than the hydrogen bonds is applied, the hydrogen bonds are broken, resulting in a low elastic modulus, which is thought to result in a high strain rate and yield point.

[0124] Specifically, the cured product of the curable composition may have a yield point in the stress-strain curve of a bending test in accordance with JIS K 7171. The flexural modulus of the cured product containing no filler measured by the bending test may be 2900 to 4000 N / mm 2 Preferably, the strength is 3100 to 3600 N / mm 2More preferably, it is 3200 to 3500 N / mm 2 It is more preferable that the bending strength of the cured product measured by the bending test is 100 to 180 N / mm 2 It is preferable that the strength is 110 to 180 N / mm 2 More preferably, it is 130 to 170 N / mm 2 The strain rate of the cured product measured by the above bending test is preferably 4 to 10%, more preferably 5 to 10%, and even more preferably 8 to 10%.

[0125] The bending test of the cured product can be carried out in accordance with JIS K 7171. Specifically, a 3mm thick cured product was cut into a size of 80mm x 10mm to serve as a test specimen. Using this test specimen, a three-point bending test was performed in accordance with JIS K 7171, with a support distance of 50mm and a test speed of 1.5mm / min, to measure the flexural modulus, flexural strength, and flexural strain (hereafter referred to as the strain rate). The yield point is the first point during the test at which an increase in strain occurs without an accompanying increase in stress.

[0126] The flexural modulus, strain rate, and flexural strength of the cured product can be adjusted by the type and number of functional groups of the thiol compound. For example, if the thiol compound has a ring structure or a large number of functional groups, the flexural modulus, etc. of the cured product tends to be high.

[0127] The cured product of the curable composition containing the active hydrogen compound (B2) of 3) above and dicyandiamide as the catalyst (C2) contains guanidine as the main product and thiocyanic acid as the by-product of the reaction with the active hydrogen compound (B2).

[0128] The content of guanidine in the cured product is, for example, 0.005 to 1 mass %, and preferably 0.01 to 0.2 mass %.

[0129] The guanidine content can be measured by ion chromatography. Specifically, it can be measured by the following procedure. 1) First, pre-crush the hardened material with a hammer until it is small enough to fit into the crusher (if it cannot be crushed, crush it while frozen). Set the M22 blade in an IKA universal crusher M20, add the pre-crushed material while it is water-cooled, and crush for 1 minute. Sieve the crushed hardened material through a 60 mesh sieve, and repeat this process until approximately 2 g of fine powder is obtained. 2) Next, add five times the amount of water to the obtained fine powder, heat in a PCT pressure vessel at 120°C for 20 hours, allow to cool to room temperature, and filter using filter paper (5C). The obtained extract is weighed into a test tube, adjusted to the specified volume with water, dissolved or extracted with ultrasound for 10 minutes, and filtered using a membrane filter. 3) The resulting solution is subjected to ion chromatography under the following conditions: (Measurement conditions) Equipment: TOSOH IC-2010 Column: Shodex IC YS-50 (125 x 4.6 mm ID) Short column: Shodex IC YS-G (10 x 4.6 mm ID) Suppressor: Non-suppressor Eluent: 4mM CH3SO3H Eluent flow rate: 1.0mL / min Column temperature: 40℃ Injection volume: 30μl Detector: Electrical conductivity (CD)

[0130] Furthermore, when the curable composition contains a bifunctional alicyclic epoxy resin (A') and a bifunctional active hydrogen compound (B'), the resulting cured product has a structure in which the bifunctional alicyclic epoxy resin (A') and the bifunctional active hydrogen compound (B') are linearly polymerized, and therefore has sufficient thermoplasticity. That is, the cured product is a thermoplastic resin containing structural units derived from the bifunctional alicyclic epoxy resin (A') and structural units derived from the bifunctional active hydrogen compound (B').

[0131] The mass ratio of the structural units derived from the bifunctional alicyclic epoxy resin (A') to the structural units derived from the bifunctional active hydrogen compound (B') (bifunctional active hydrogen compound (B1') or bifunctional active hydrogen compound (B2')) in the thermoplastic resin is the same as the mass ratio of the bifunctional alicyclic epoxy resin (A') to the bifunctional active hydrogen compound (B') (bifunctional active hydrogen compound (B1') or bifunctional active hydrogen compound (B2')) in the curable composition.

[0132] The total content of the structural units derived from the bifunctional alicyclic epoxy resin (A') and the structural units derived from the bifunctional active hydrogen compound (B') can be 4% by mass or more, preferably 60% by mass or more, based on the non-volatile content of all structural units constituting the thermoplastic resin. When this total content is within the above range, higher thermoplasticity is likely to be obtained. Furthermore, when the active hydrogen compound (B') is a thiol-based compound, the refractive index of the thermoplastic resin is likely to be further increased.

[0133] The thermoplastic resin has a self-repairing property. That is, the thermoplastic resin has sufficient thermoplasticity and its molecules easily move when heated because the bifunctional alicyclic epoxy resin (A') and the bifunctional active hydrogen compound (B') are polymerized in a highly linear manner, thereby exhibiting physical self-repairing properties. Furthermore, this thermoplastic resin easily forms intermolecular hydrogen bonds because the epoxy groups of the alicyclic epoxy resin (A') have many hydroxyl groups generated by reaction with the bifunctional active hydrogen compound (B'). Furthermore, when the active hydrogen compound (B') contains an aromatic ring, it easily forms intermolecular π-π bonds. These reversible bonds allow the resin to exhibit chemical self-healing properties. It is believed that these actions give the thermoplastic resin a self-repairing property.

[0134] 3. Manufacturing method of the cured product The cured product can be produced by heating and curing the curable composition.

[0135] The heating temperature varies depending on the type of active hydrogen compound (B), but when a thiol compound is used, for example, it can be 0 to 250° C., preferably 60 to 120° C., and more preferably 100 to 120° C. The heating time can be 0.02 to 3 hours, and preferably 0.1 to 1 hour.

[0136] When the curable composition contains the catalyst (C2) that generates cations by the reaction of 3) above, the alicyclic epoxy resin (A), the active hydrogen compound (B2), and the catalyst (C2) may be mixed simultaneously and then heated to cure; alternatively, the active hydrogen compound (B2) and the catalyst (C2) may be reacted first, and then the alicyclic epoxy resin (A) may be mixed therewith and heated to cure.

[0137] For example, the cured product can be obtained through a step of reacting the active hydrogen compound (B2) with dicyandiamide under heating to obtain a composition containing guanidine, and a step of reacting the composition with the alicyclic epoxy resin (A) by heating to obtain a cured product. In this way, by pre-reacting the active hydrogen compound (B2) with dicyandiamide before mixing with the alicyclic epoxy resin (A), the curing reaction can be initiated in a shorter time, making the curing reaction occur more easily.

[0138] The heating temperature when reacting the active hydrogen compound (B2) with dicyandiamide may be within a range in which the active hydrogen compound (B2) and dicyandiamide react, and may be, for example, 60 to 120°C, more preferably 100 to 120°C. The reaction time may be such that at least a certain amount of guanidinium ions are produced, and may be, for example, 0.1 to 1 hour, depending on the temperature. After heating to a temperature at which the dicyandiamide and thiol can react, the mixture may be cooled and cured at a low temperature below room temperature, or the heated temperature may be maintained or raised to the aforementioned heating temperature range and cured in a short time.

[0139] When the curable composition contains the catalyst (C2) that generates cations upon irradiation with light (3), the light irradiation conditions may be within a range that allows a base to be generated from the photobase generator. For example, the wavelength of the irradiated light is preferably 200 to 500 nm. The irradiation dose is preferably 10 to 10,000 mJ / cm. 2 After cations are generated by light irradiation, the composition may be cured at a low temperature below room temperature, or may be heated to the above-mentioned heating temperature range and cured in a short time.

[0140] 4. Uses of the cured product The cured product is obtained from a curable composition containing an alicyclic epoxy resin (A), and therefore exhibits excellent transparency and weather resistance. In particular, the use of a thiol-based compound as the active hydrogen compound (B) not only enables curing by light irradiation or low-temperature heating, but also produces a cured product with a high refractive index and moderate flexibility and flexural modulus. Therefore, it is suitable for optical applications such as encapsulants and adhesives for optical semiconductor devices and organic electroluminescent devices, surface protective films, and transparent display substrates; structural adhesives that can withstand damage such as collisions in manufacturing environments where it is difficult to heat the entire adherend, such as the automotive industry; protective films for touch panel sensors; and coatings that protect the surfaces of electronic devices and automobiles. In particular, the cured product has a high modulus of elasticity, which allows it to maintain its adhesive position with the adherend under weak external forces, while its yield point allows it to bend under strong external forces without cracking. Therefore, it is suitable for structural adhesives in the automotive industry. [Example]

[0141] The present invention will be further described below with reference to examples and comparative examples, but the technical scope of the present invention is not limited thereto.

[0142] 1. Material Preparation 1-1.Epoxy resin <Alicyclic epoxy resin (A)> A-1: Celloxide 2021P (manufactured by Daicel Corporation, bifunctional, epoxy equivalent 130g / eq) [Chemical] A-2: Celoxide 8010 (manufactured by Daicel Corporation, bifunctional, epoxy equivalent 100 g / eq) [Chemical] A-3: Celoxide 2081 (manufactured by Daicel Corporation, bifunctional, epoxy equivalent 200 g / eq) A-4: THI-DE (manufactured byENEOS Corporation, bifunctional, epoxy equivalent 80 g / eq) [Chemical] A-5: X-40-2669 (manufactured by Shin-Etsu Chemical Co., Ltd., bifunctional, epoxy equivalent 200 g / eq) [Chemical]

[0143] A-6: KR-470 (manufactured by Shin-Etsu Chemical Co., Ltd., tetrafunctional, epoxy equivalent 200 g / eq) [Chemical]

[0144] <Aromatic epoxy resin> 835LV (manufactured by DIC Corporation, bisphenol A / F type epoxy resin, epoxy equivalent 165 g / eq) JER604 (manufactured by Mitsubishi Chemical Corporation, tetrafunctional, epoxy equivalent 120 g / eq) JER630 (manufactured by Mitsubishi Chemical Corporation, trifunctional, epoxy equivalent 98 g / eq) 850S (manufactured by DIC Corporation, bifunctional, epoxy equivalent 189 g / eq)

[0145] 1-2. Curing agent <Active hydrogen compound (B1) with pKa of 10 or less> B1-1: 1,3,5-triazine-2,4,6-trithiol (thiocyanuric acid) (manufactured by Tokyo Chemical Industry Co., Ltd., aromatic thiol (trifunctional), thiol equivalent 59.1 g / eq, pKa 4 - 6.5) B1-2: 4,4'-Thiobisbenzenethiol (manufactured by Fujifilm Wako Pure Chemical Corporation, aromatic thiol (bifunctional), thiol equivalent 126.2 g / eq, C6H5SH: pKa 6.52 - 8.2) B1-3: Bisphenol A (manufactured by Mitsui Chemicals, phenol (bifunctional), hydroxyl equivalent 114 g / eq, literature value: pKa 9.6)

[0146] <Active hydrogen compound with pKa exceeding 10 (B2)> B2-1: TS-G (manufactured by Shikoku Kasei Co., Ltd., aliphatic thiol (tetrafunctional), thiol equivalent 96 g / eq, CH3CH2SH: pKa 10.5)

Chemical formula

Chemical formula

Chemical formula

Chemical formula

[0147] B2-5: ASD (manufactured by Seika Corporation, aromatic amine (bifunctional), amine equivalent 54.075 g / eq, C6H5NH2: pKa 28)

Chemical formula

[0148] <Aliphatic amine-based compound> Isophoronediamine (Fujifilm Wako Co., Ltd., aliphatic amine (bifunctional), amine equivalent 42.575 g / eq, reference Et2NH: pKa 36)

[0149] <Acid anhydride> Rikacid MH-700 (manufactured by Shin-Nippon Rika Co., Ltd., equivalent weight 163.5g / eq)

[0150] The pKa was determined by the following method.

[0151] (pKa) For compounds whose pKa values ​​are publicly known in the literature (https: / / organicchemistrydata.org / hansreich / resources / pka / pka_data / pka-compilation-williams.pdf), the pKa value listed in the literature was used. For compounds whose pKa values ​​are not publicly known in the literature, the active hydrogen compound was described using a rational formula, and the pKa value of the compound that is two or more carbon atoms away from the functional group containing the active hydrogen was used. The pKa value of B1-3 was taken from the Hazardous Substances Data Bank (HSDB): 513- PubChem (nih.gov).

[0152] 1-3.Curing catalyst <Cation Catalyst (C1)> C1-1: SA1 (San-Apro Co., Ltd., phenol salt of DBU, hot base catalyst) C1-2: SA102 (San-Apro Co., Ltd., 2-ethylhexane salt of DBU, hot base catalyst) C1-3: Tetramethylguanidine (Tokyo Chemical Industry Co., Ltd., base catalyst) C1-4: DBU (Tokyo Chemical Industry Co., Ltd., diazabicycloundecene, base catalyst) C1-5: TPP-MK (manufactured by Hokko Chemical Industry Co., Ltd., tetraphenylphosphonium tetra-p-tolylborate, phosphorus-based curing accelerator) C1-6: 2E4MZ (Shikoku Chemicals, 2-ethyl-4-methylimidazole, general-purpose cationic catalyst)

[0153] <Catalyst (C2) that generates cations upon reaction or light irradiation> C2-1: DDA5 (dicyandiamide, latent catalyst) C2-2: WPBG-266 (Fujifilm Wako Co., Ltd., 1,2-diisopropyl-3-[bis(dimethylamino)methylene]guanidinium 2-(3-benzoylphenyl)propionate, photobase catalyst) C2-3: WPBG-300 (Fujifilm Wako Co., Ltd., 1,2-dicyclohexyl-4,4,5,5-tetramethyldiguaiazium n-butyltriphenylborate, photobase catalyst) C2-4: 2-(9-oxoxanthen-2-yl)propionic acid 1,5,7-triazabicyclo[4.4.0]dec-5-ene (photobase catalyst)

[0154] 1-4.Sensitizers Kayacure DETX-S (Nippon Kayaku Co., Ltd., 2,4-diethylthioxanthone)

[0155] 2. Examination of curing reactivity <Preparation of Compositions 1 to 47> Each material was uniformly stirred and mixed in the mixing ratios shown in Tables 1 to 3 using a Mixing Mixer (ARE-310) in stirring mode at 2000 rpm for 30 seconds, with the epoxy resin mass being 3 g, to prepare Compositions 1 to 47.

[0156] <Evaluation> The curing reactivity of the resulting composition was evaluated by the following method.

[0157] (Exothermic peak temperature measured by DSC) 3.0 mg of the resulting composition was placed in an aluminum sample pan and subjected to differential scanning calorimetry (DSC) measurement. Specifically, a Shimadzu DSC-60 was used to measure the exothermic peak temperature (thermosetting temperature) observed when the temperature was raised from room temperature (25°C) at a rate of 20°C / min. And it was evaluated according to the following criteria. ◎: The exothermic peak temperature in DSC measurement is lower than 199°C (the exothermic peak temperature of acid anhydride) ○: The exothermic peak temperature in DSC measurement is 199°C or higher and less than 250°C △: An exothermic peak is observed in the DSC measurement, but the exothermic peak temperature is 250°C or higher ×: No exothermic peak is observed in the DSC measurement If the rating was ◯ or higher, the reactivity was judged to be good.

[0158] The evaluation results of compositions 1 to 13 are shown in Table 1, the evaluation results of compositions 14 to 29 in Table 2, and the evaluation results of compositions 30 to 47 in Table 3. Regarding the curing type (form), the curing form using an active hydrogen compound (B1) was classified as "1," the curing form using an active hydrogen compound (B2) and a cationic catalyst (C1) was classified as "2," and the curing form using an active hydrogen compound (B2) and a catalyst (C2) that generates cations by reaction or the like was classified as "3."

[0159] [Table 1]

[0160] [Table 2]

[0161] [Table 3]

[0162] As shown in Tables 1 to 3, compositions 37 to 41 and 44 (Examples) containing an active hydrogen compound (B1) with a pKa of 10 or less, compositions 23, 25 to 29, 33, 34, 36 and 45 (Examples) containing an active hydrogen compound (B2) with a pKa greater than 10 in combination with a cationic catalyst (C1), compositions 14 to 20 and 24 (Examples) containing an active hydrogen compound (B2) and dicyandiamide, and compositions 30 to 32 and 35 (Examples) containing an active hydrogen compound (B2) and a photobase catalyst all exhibited curing reactivity comparable to or better than that of a composition containing an acid anhydride curing agent (Comparative Example), despite the use of an alicyclic epoxy resin. In particular, compositions other than compositions 24 and 45 exhibited lower exothermic peak temperatures than the exothermic peak temperature of the acid anhydride, indicating good curing reactivity.

[0163] Among these, aliphatic thiols and aliphatic amines (active hydrogen compounds (B2)) have a high pKa and low curing reactivity when used alone, whereas aromatic thiols (active hydrogen compounds (B1)) have a low pKa and exhibit good curing reactivity even when used alone (comparison of compositions 37 to 41 with compositions 2 and 4).

[0164] Furthermore, it is clear that although aliphatic thiols (active hydrogen compounds (B2)) have a high pKa and exhibit low curing reactivity when used alone, they exhibit good curing reactivity when used in combination with the cationic catalyst (C1) (comparison of compositions 25 to 29 with composition 4).

[0165] Furthermore, it can be seen that although aliphatic thiol (active hydrogen compound (B2)) has a high pKa and low curing reactivity when used alone, it exhibits good curing reactivity when used in combination with dicyandiamide (catalyst (C2)) (comparison of composition 15 and composition 4). Furthermore, it was found that the combined use of a photobase catalyst (catalyst (C2)) showed good curing reactivity (comparison of composition 4 with compositions 30-32 and 35). In particular, it was shown that the exothermic peak temperature after light irradiation was lower than the exothermic peak temperature before light irradiation. These results indicate that the curing properties are further enhanced by light irradiation (see compositions 30-32 and 35).

[0166] 3. Quantitation of guanidine content 3-1. Preparation of the composition <Preparation of Compositions R0 to R5> The materials were mixed uniformly in the blending ratios shown in Table 4 using a vacuum mixer, Awatori Rentaro ARV-310P, at 2000 rpm for 100 seconds, and then degassed to prepare compositions.

[0167] <Preparation of measurement sample> Compositions 14, 15, R0, R1 and R4 prepared above were heated and cured under the conditions shown in Table 4 to prepare cured product samples. The other compositions were used as samples as they were.

[0168] Evaluation (Crushing) For the cured sample, an M22 blade was attached to the universal crusher M20, and the water-cooled hardened material crushed with a hammer was added and crushed for 1 minute. The crushed material was then placed on a 60-mesh stainless steel screen and sieved. The 60-mesh pass material was collected and placed back into the M20, and this process was repeated until 2 g of the pass material was obtained.

[0169] (extraction) 10 g of water, five times the amount of the fine powder, was added, and the mixture was heated in a pressure vessel at 120°C for 20 hours, allowed to cool to room temperature, and then filtered using filter paper (5C).

[0170] (Ion chromatograph measurement) The obtained extract or sample was weighed into a test tube, and the volume was adjusted with water. The solution was then dissolved or extracted with ultrasound for 10 minutes and filtered through a membrane filter. The resulting solution was subjected to ion chromatography measurement. The measurement conditions were as follows: (Measurement Conditions) Equipment: TOSOH IC-2010 Column: Shodex IC YS-50 (125 x 4.6 mm ID) Short column: Shodex IC YS-G (10 x 4.6 mm ID) Suppressor: Non-suppressor Eluent: 4mM CH3SO3H Eluent flow rate: 1.0mL / min Column temperature: 40℃ Injection volume: 30μl Detector: Electrical conductivity (CD)

[0171] The measurement results are shown in Table 4.

[0172] [Table 4]

[0173] As shown in Table 4, no guanidine was detected in compositions R1 to R3, and only trace amounts of guanidine were detected in the cured product of composition R0 and composition R5. In contrast, the cured products of Compositions 14, 15, and R4 contained guanidine in amounts greater than the predetermined amount, indicating that the aliphatic thiol compound (B2-1) reacted with dicyandiamide (C2-1) to produce guanidine.

[0174] 4. Consideration of refractive index 4-1. Preparation of cured product <Preparation of Cured Product 1> The materials were mixed uniformly in the blending ratios shown in Table 5 using a vacuum mixer, Awatori Rentaro ARV-310P, at 2000 rpm for 100 seconds, followed by degassing to prepare compositions. The resulting composition was poured into a mold and cured by heating at 90°C for 3 hours and then at 120°C for 4 hours to obtain a cured product 1 having a thickness of 3 mm.

[0175] <Preparation of Cured Products 2 and 3> The materials were mixed uniformly in the blending ratios shown in Table 5 using a vacuum mixer, Awatori Rentaro ARV-310P, at 2000 rpm for 100 seconds, followed by degassing to prepare compositions. The resulting composition was poured into a mold and cured by heating at 120°C for 1 hour, to obtain cured products 2 and 3 with a thickness of 3 mm.

[0176] <Preparation of Cured Product 4> The composition 23 prepared above was poured into a mold and heated at 60° C. for 1 hour to be cured, thereby obtaining a cured product 4.

[0177] <Preparation of Cured Product 5> The composition 24 prepared above was poured into a mold and cured by heating at 130° C. for 1 hour, to obtain a cured product 5 having a thickness of 3 mm.

[0178] <Preparation of Cured Products 6 and 7> The materials were mixed uniformly in the blending ratios shown in Table 5 using a vacuum mixer, Awatori Rentaro ARV-310P, at 2000 rpm for 100 seconds, followed by degassing to prepare compositions. The resulting composition was poured into a mold and cured by heating at 100°C for 1 hour, to obtain cured products 6 and 7 with a thickness of 3 mm.

[0179] Evaluation The refractive indexes of the cured products 1 to 7 prepared above were evaluated by the following method.

[0180] (refractive index) The refractive index of the cured product was measured using an Abbe Refractometer DR-A1-Plus at a wavelength of 589 nm. Monobromonaphthalene was used as the intermediate liquid.

[0181] The measurement results are shown in Table 5.

[0182] [Table 5]

[0183] As shown in Table 5, cured products 6 and 7 (Examples) of compositions containing an active hydrogen compound (B1) with a pKa of 10 or less, cured product 4 (Example) of a composition using an active hydrogen compound (B2) with a pKa of more than 10 in combination with a cationic catalyst, and cured products 2, 3 and 5 (Examples) of compositions containing an active hydrogen compound and dicyandiamide all have higher refractive indices than cured product 1 (Comparative Example) of a composition containing an acid anhydride curing agent.

[0184] 5. Examination of bending properties 5-1. Preparation of cured product <Preparation of Cured Products 1 to 5> The above-prepared cured products 1 to 5 were prepared.

[0185] <Preparation of Cured Products 8 to 10> The materials were mixed uniformly in the blending ratios shown in Table 6 using a vacuum mixer, Awatori Rentaro ARV-310P, at 2000 rpm for 100 seconds, followed by degassing to prepare compositions. The resulting composition was poured into a mold and heated at 100°C for 0.5 hour, and then further heated at 120°C for 0.5 hour to cure, yielding cured products 8 to 10 with a thickness of 3 mm.

[0186] 5-2.Evaluation The flexural properties of the cured products 1 to 5 and 8 to 10 prepared above were evaluated by the following method.

[0187] (Flexural modulus and flexural strength) The resulting cured product was cut into a size of 80 mm x 10 mm to prepare a test piece, which was used to determine the flexural modulus, flexural strength, and strain rate according to the method of JIS K 7171.

[0188] (strain rate and yield point) The presence or absence of a yield point of the test piece was determined from the presence or absence of a point in the stress-strain curve where the stress does not increase but the strain increases.

[0189] The measurement results are shown in Table 6.

[0190] [Table 6]

[0191] As shown in Table 6, cured product 4 (Example) of a composition using a combination of an active hydrogen compound with a pKa of more than 10 and a cationic catalyst, and cured products 2, 3 and 5 (Examples) of compositions containing an active hydrogen compound and dicyandiamide all have higher flexural strength, flexural modulus, strain rate and yield point than cured product 1 (Comparative Example) of a composition containing an acid anhydride curing agent. Furthermore, it can be seen that cured products 2 to 5 (Examples) have higher flexural modulus and strain rate than cured products 9 and 10 (Comparative Examples) which used aromatic epoxy resins.

[0192] 6. Thermoplasticity 6-1. Preparation of Compositions 2-1 to 2-11 The components shown in Table 7 were blended in the blending ratios shown in the same table, and mixed under the following mixing conditions 1 or 2. (Mixing condition 1) The mixture was stirred and mixed uniformly at 2000 rpm for 100 seconds using a vacuum mixer, Awatori Rentaro (ARV-310P), and degassed to prepare a composition. (Mixing condition 2) The mixture was stirred and mixed uniformly for 30 seconds using a vacuum mixer, Awatori Rentaro (ARE-310), at a stirring mode of 2000 rpm to prepare a composition. Compositions 2-2, 2-3, 2-5, 2-6, 2-8 and 2-9 correspond to the above-mentioned compositions 34, 35, 38, 39, 44 and 47, respectively.

[0193] Evaluation The resulting compositions were evaluated as follows.

[0194] 6-2-1. Viscosity of the composition The viscosity (25°C, 5 rpm, 30 seconds) of each composition prepared under mixing condition 1 was measured using a cone-plate viscometer (TVE-35H, cone rotor: 3° x R9.7, manufactured by Toki Sangyo Co., Ltd.).

[0195] 6-2-2. Evaluation of the cured product The thermoplasticity and self-repair properties (appearance, bending test) of the cured products of each composition prepared under mixing condition 2 were evaluated by the following methods. The cured products of compositions 2-6 were further analyzed by TOF-MS.

[0196] (1)Thermoplastic The resulting composition was poured into a mold containing two slide glasses (Matsunami Glass Industrial Co., Ltd., Matsunami Slide Glass Model S7214) sandwiched between 1 mm thick silicone rubber, and heated and cured under the curing conditions shown in the table to obtain a 1 mm thick cured product. Regarding curing condition 2 for Composition 2-3, the composition was poured into a mold and irradiated with a high-pressure mercury lamp UV irradiator (Eye Graphics Co., Ltd., (registered trademark) ECS-4011GX) at an irradiation dose of 9000 mJ, followed by heating at 120°C for 1 hour to obtain a 1 mm thick cured product.

[0197] The resulting cured product was placed in an oven heated to 120°C while held upright by clips, and heated at 120°C for 1 hour. The state of the upright cured product was then visually observed to evaluate its thermoplasticity. Evaluation was based on the following criteria. 4: The cured product is collapsed, indicating thermoplasticity 3: The cured product can be removed from the mold while maintaining the shape of the mold, but if left standing for a certain period of time before heating at 120°C for one hour, the cured product will collapse (this indicates thermoplasticity, although it is not fully cured). 2: The mixture has thickened but cannot be removed from the mold (it has not hardened). 1: Maintains upright position and does not exhibit thermoplasticity

[0198] (2) Self-repairing property - appearance The cured products obtained in the same manner as in (1) above were placed between glass slides and placed in a freezer at a temperature lower than the curing temperature, i.e., -30°C, to induce cracks. If no cracks were observed, the glass slides were bent to the extent that they would not break, to induce cracks. The cured products with cracks at room temperature were then heated at 120°C for 5 minutes, after which the state of cracks was visually observed. Evaluation was then performed based on the following criteria. 3: The cracks have disappeared 2: No cracks even when bent 1: Remained hard and cracks did not disappear

[0199] (3) Self-healing property - bending test (Preparation of evaluation samples) A blend of 100 parts by mass of Celloxide 2021P (Daicel), 80 parts by mass of TS-G (Shikoku Kasei), and 1 part by mass of DDA5 was mixed and degassed using a vacuum mixer, Awatori Rentaro (ARV-310P), at a mixing mode of 2000 rpm for 180 seconds to prepare Composition A. The resulting Composition A was poured into a mold and heated at 120°C for 1 hour to obtain two 1 mm-thick cured products. Separately, composition B was prepared by kneading and degassing the blending ratio of composition 2-6 or 8 using a vacuum mixer, Awatori Rentaro (ARV-310P), at a mixing mode of 2000 rpm for 100 seconds. The composition B prepared above was then poured between the two cured products prepared above and heated under the conditions listed in Table 7. This resulted in a cured product with a three-layer structure (cured product A (for exterior walls) / cured product B (to be evaluated) / cured product A (for exterior walls)) with a total thickness of 3 mm.

[0200] (bending test) A bending test of the resulting cured product was carried out in accordance with JIS K 6911. Specifically, a 3 mm thick cured product was cut into a size of 80 x 10 mm to prepare a test specimen. Using this test specimen, the flexural modulus was measured in a three-point bending test according to JIS K 6911, with a support distance of 50 mm and a test speed of 1.5 mm / min. The flexural modulus was calculated using the following formula: Elastic modulus (N / mm 2 ) = Inclination × Distance between supports / Cross-sectional area of ​​test piece The slope was calculated by the least squares method using all data between two points of test force 10N and 20N, with the vertical axis representing the test force and the horizontal axis representing the displacement. After cutting the cured product to the size required for the bending test, cellophane tape was applied only to the four thicker sides of the test piece to prevent the inner layer structure from slipping off due to impact during the test. The tests were carried out in the following order of 1 to 9. After heating, the samples were cooled at room temperature for 1 hour before testing. 1. Initial heating: Place in an oven heated to 120°C for 10 minutes (to repair cracks that occurred when cutting to the size of the test specimen) 2. Initial measurement: bending test 3. Measurement at break: bending test 4. 120℃ Repair: Place in an oven heated to 120℃ for 10 minutes 5.120℃-Elasticity measurement: Bending test 6. 100℃ Repair: Place in an oven heated to 100℃ for 10 minutes 7. 100℃ measurement: bending test 8. 140℃ Repair: Place in an oven heated to 140℃ for 10 minutes 9. 140℃ measurement: bending test The repair rate (%) at each temperature was evaluated based on the following formula. Repair rate (%) = (measurement value at each temperature - measurement value at break) / (initial measurement value - measurement value at break) x 100 The measured value means the flexural modulus measured in a bending test. When the repair rate is positive, it indicates that self-repairing properties have been exhibited, and the temperature at which the repair rate becomes positive is defined as the temperature at which self-repairing is possible. When the repair rate is negative, it is defined as 0%, indicating that self-repairing properties have not been exhibited.

[0201] (4)TOF-MS analysis The structure of the cured product of Composition 2-6 was analyzed by TOF-MS. Specifically, 10 mg of the cured product was weighed, 5 mL of chloroform was added, and ultrasonic treatment was performed for 10 minutes. 1 μL of the sample solution was applied to an FD emitter, and measurement was performed using a JEOL JMS-T100GCV under the following conditions. Sample: Chloroform dilution Ionization mode: FD+ Analytical m / z range: 29.00 to 3000.00

[0202] The evaluation results of Compositions 2-1 to 2-11 are shown in Table 7. Of these, the appearance of the cured product obtained from Composition 2-6 before heating is shown in Figure 1A, and the appearance after heating is shown in Figure 1B; the appearance of the cured product obtained from Composition 2-7 before heating is shown in Figure 2A, and the appearance after heating is shown in Figure 2B. The reaction mechanism of Composition 2-6 is shown in Figure 3A, and the TOF-MS spectrum of the cured product is shown in Figure 3B. The evaluation results of (3) Self-repairing property - bending test for Compositions 2-6 and 2-8 are shown in Table 8. In Table 7, the curing type (form) is as follows: a curing form using an active hydrogen compound (B1) is designated as "1," a curing form using an active hydrogen compound (B2) and a cationic catalyst (C1) is designated as "2," and a curing form using an active hydrogen compound (B2) and a catalyst (C2) that generates cations by reaction or the like is designated as "3."

[0203] [Table 7]

[0204] [Table 8]

[0205] As shown in Table 7, the cured products of Compositions 2-9 and 2-11 did not soften even after heating at 120°C for 1 hour, indicating that they did not exhibit thermoplasticity. Furthermore, after heating at 120°C for 5 minutes, the cured products did not soften but remained hard, and the cracks did not disappear. This indicates that they do not have self-healing properties.

[0206] In contrast, the cured products of Compositions 2-1 to 2-8 softened when heated at 120°C for 1 hour, demonstrating thermoplasticity. Furthermore, after heating at 120°C for 5 minutes, the cured products were soft and the cracks had disappeared, demonstrating self-repairing properties (see Table 7). Furthermore, the repair rate of Compositions 2-6 and 2-8 improved, particularly at 120°C and 140°C, demonstrating good self-repairing properties (see Table 8).

[0207] Furthermore, as mentioned above, in a curing system using an acid anhydride, the epoxy groups of the alicyclic epoxy resin react with an active hydrogen compound and then open the ring to form oxygen anions (-O-). This allows them to react not only with active hydrogen compounds but also with other alicyclic epoxy resins, resulting in three-dimensional crosslinking. In contrast, in the present invention, the epoxy groups of the alicyclic epoxy resin react with an active hydrogen compound and then become -OH groups in the presence of cations (H+ in this case). This means that they do not react with other alicyclic epoxy resins but only with active hydrogen compounds. Therefore, the difference between the structure of a conventional reaction and the structure of the present invention is whether the oxygen derived from the epoxy group is -O- or -OH, resulting in a difference in the weight of one H. Therefore, when reacting with -O-, the weight of one H is subtracted from the molecular weight of the epoxy resin + active hydrogen compound, but when reacting with -OH, the molecular weight of the epoxy resin + active hydrogen compound remains unchanged, resulting in a higher molecular weight. The molecular weight of the epoxy resin and active hydrogen compound in the formulation of Composition 2-6 is 444.1, as shown in Figure 3A. In the TOF-MS spectrum of Example 6 shown in Figure 3B, the main peaks are 444.1143, 888.2360, and 1332.3430, confirming the molecular weight in units of 444.1, which is the molecular weight containing an -OH group. Furthermore, the peaks attributable to the alicyclic epoxy resin (A) A-2 (molecular weight 194.1) and the peaks attributable to the active hydrogen compound (B1) B1-1 (molecular weight 249.9) appear alternately (see Figure 3). In other words, the repeating structure (molecular weight 444.1) in which the alicyclic epoxy resin (A) - thiol compound (B1) -... was detected. These findings confirm that the expected reaction occurred, i.e., the alicyclic epoxy resin and thiol compound polymerized linearly.

[0208] 7. Examination of kneadability (1) Preparation of sample sheet 14.25 g of PP (MA3) (Novatec PP manufactured by Polypro Corporation, general injection molding grade, polypropylene resin) and 0.75 g of the cured product of Composition 2-6 (thermoplastic resin) were melt-mixed at 180°C for 10 minutes using a kneading device, Labo Plastomill (Roller Mixer R30) (manufactured by Toyo Seiki Co., Ltd.), and then press-molded at 180°C to obtain a sample sheet with a thickness of 0.31 mm.

[0209] (2) Evaluation method A portion of the obtained sample sheet was cut into a strip using a razor blade. After making a crack in the center, the strip was fractured in liquid nitrogen. This was placed on a sample stage covered with carbon tape, with the observation surface facing up, and metallized with Os. The surface of the metal-deposited sample sheet was then subjected to SEM observation and EDS analysis, followed by image analysis. Image analysis was performed on three fields of view using 3k S-mapping images of the sample. The area, major axis, and average distance between neighboring particles in Table 9 show the maximum (Max), minimum (Min), median (Med), standard deviation (SD), and average (Ave) values ​​measured for 123 spherical particles.

[0210] The results of SEM observation of the surface of the sample sheet of Composition 2-6 are shown in Figure 4A, and the results of EDX analysis are shown in Figures 4B and 4C. The image analysis results are also shown in Table 9. Figure 4B is a mapping image in which the area where carbon element (C) is detected (continuous phase) is displayed in gray, and Figure 4C is a mapping image in which the area where sulfur element (S) is detected (dispersed phase) is displayed in gray.

[0211] [Table 9]

[0212] As shown in the EDS analysis results (Figures 4B and 4C), spherical particles (dispersed phase) containing elemental sulfur (S) derived from the cured product (thermoplastic resin) of the composition were well dispersed in the continuous phase of the matrix resin, PP. The size of the spherical particles was approximately several hundred nanometers to 2 μm. Furthermore, as shown in Table 9, the area, major axis and average distance between adjacent particles of the thermoplastic resin were all small, indicating that the particles were well dispersed. These findings indicate that the thermoplastic resin obtained by curing the above-mentioned curable composition containing the bifunctional epoxy resin (A') and the bifunctional active hydrogen compound (B') is well dispersed in the matrix resin and is suitable as a masterbatch.

[0213] This application claims priority based on Japanese Patent Application No. 2022-138414, filed August 31, 2022, and Japanese Patent Application No. 2022-138424, filed August 31, 2022. The contents of the specifications and drawings of these applications are incorporated herein by reference in their entirety. [Industrial Applicability]

[0214] According to the present invention, it is possible to provide a curable composition that exhibits good curing reactivity even when it contains a large amount of an alicyclic epoxy resin.

Claims

1. A composition comprising a difunctional alicyclic epoxy resin (A') and a difunctional active hydrogen compound (B1') having a pKa of 10 or less, the content of the bifunctional active hydrogen compound (B1') having a pKa of 10 or less is 15 to 400 parts by mass per 100 parts by mass of the total amount of the bifunctional alicyclic epoxy resin (A'); Curable composition.

2. The bifunctional active hydrogen compound (B1') having a pKa of 10 or less is a bifunctional bisphenol compound having a pKa of 10 or less or a bifunctional thiol compound having a pKa of 10 or less. The curable composition of claim 1.

3. The bifunctional thiol compound having a pKa of 10 or less is a bifunctional aromatic thiol compound. The curable composition of claim 2.

4. The content of the bifunctional alicyclic epoxy resin (A') is 44.4 parts by mass or more and 70 parts by mass or less per 100 parts by mass of the non-volatile components of the curable composition. The curable composition of claim 1.

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

6. A refractive index of 1.52 or more and 1.70 or less. A cured product of the curable composition according to claim 5.

7. A thermoplastic resin comprising a cured product of the curable composition according to claim 1, the epoxy resin (B1′) contains a structural unit derived from the difunctional alicyclic epoxy resin (A′) and a structural unit derived from the difunctional active hydrogen compound (B1′) having a pKa of 10 or less, Thermoplastic resin.

8. The total content of the structural units derived from the bifunctional alicyclic epoxy resin (A') and the structural units derived from the bifunctional active hydrogen compound (B1') having a pKa of 10 or less contained in the thermoplastic resin is 4 mass% or more based on the non-volatile content of all structural units constituting the thermoplastic resin. The thermoplastic resin according to claim 7.

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