Latent curing agent, thermosetting epoxy resin composition, and method for producing latent curing agent

Abstract

The latent curing agent contains porous particles holding a curing catalyst, and the porous particles contain a crosslinkable vinyl polymer and an alpha-olefin copolymer.

Description

Latent curing agent, thermosetting epoxy resin composition, and method for producing latent curing agent

[0001] The present invention relates to a latent curing agent, a thermosetting epoxy resin composition, and a method for producing the latent curing agent.

[0002] Patent Document 1 discloses a latent curing agent for curing a thermosetting epoxy resin, which uses a polymer of a radically polymerizable monomer together with a polyurea-urethane resin to lower the thermal response temperature (Patent Document 1).

[0003] Patent No. 5458596

[0004] Conventional latent curing agents have excellent temperature response, but there is a concern that the polymer will deteriorate due to yellowing, resulting in a decrease in the properties of the cured product.

[0005] An object of the present invention is to provide a latent curing agent that is excellent in temperature responsiveness and yellowing resistance.

[0006] One aspect of the present invention is a latent curing agent comprising porous particles holding a curing catalyst, the porous particles comprising a crosslinkable vinyl polymer and an α-olefin copolymer.

[0007] According to the present invention, it is possible to provide a latent curing agent that is excellent in temperature responsiveness, yellowing resistance, and storage stability.

[0008] 9 is a graph showing the particle size distribution of the latent curing agent of Example 1 after crushing. It is an SEM image (3000x) of the latent curing agent of Example 1. It is an SEM image (12000x) of the latent curing agent of Example 1. It is a chart showing the results of DSC measurement of the latent curing agent of Example 1. It is a chart enlarged from a part of FIG. 4. It is a graph showing the particle size distribution of the latent curing agent of Example 2. It is an SEM image (3000x) of the latent curing agent of Example 2. It is an SEM image (12000x) of the latent curing agent of Example 2. It is a chart showing the results of DSC measurement of the latent curing agent of Example 2. It is a chart enlarged from a part of FIG. 9. It is a graph showing the results of storage liquid life at room temperature (25°C). It is an SEM image of a cross section of the latent curing agent of Example 1. It is an Al mapping image by SEM-EDX of a cross section of the latent curing agent of Example 1. It is an SEM image of a cross section of the latent curing agent of Example 2. 1 is an Al mapping image of a cross section of the latent curing agent of Example 2 by SEM.

[0009] Hereinafter, embodiments of the present invention will be described in detail.

[0010] <Latent Curing Agent> The latent curing agent of the present embodiment contains porous particles that hold a curing catalyst.

[0011] A latent curing agent is a curing agent that does not exhibit curing properties at room temperature but exhibits curing properties when heated. For example, a latent curing agent does not harden an object to be cured, such as an epoxy resin, at room temperature, but can harden the object when heated.

[0012] <<Curing Catalyst>> The curing catalyst is a catalyst that accelerates curing by the latent curing agent. Examples of the curing catalyst include an aluminum chelate-based curing agent or a water-insoluble catalyst having a solubility in water of 5 mass % or less.

[0013] <<Aluminum Chelate-Based Curing Agents>> Examples of aluminum chelate-based curing agents include complex compounds represented by the following general formula (1), in which three β-ketoenolate anions are coordinated to aluminum. Here, no alkoxy groups are directly bonded to the aluminum. This is because direct bonding would make the aluminum susceptible to hydrolysis and make it unsuitable for emulsification treatment.

[0014]

[0015] In the above general formula (1), R １ , R ２ and R ３ each independently represents an alkyl group or an alkoxy group. Examples of alkyl groups include a methyl group and an ethyl group. Examples of alkoxy groups include a methoxy group, an ethoxy group, and an oleyloxy group.

[0016] Examples of the complex compound represented by general formula (1) include aluminum tris(acetylacetonate), aluminum tris(ethylacetoacetate), aluminum monoacetylacetonate bis(ethylacetoacetate), aluminum monoacetylacetonate bis(oleylacetoacetate), etc. These may be used alone or in combination of two or more.

[0017] Aluminum chelate-based curing agents are compounds that cannot be dissolved in water because they are prone to exothermic decomposition when in contact with water.

[0018] The content of the aluminum chelate curing agent in the porous particles is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of the latent property of the latent curing agent, the content of the aluminum chelate curing agent in the latent curing agent is 0.1 mass % or more and 60 mass % or less, more preferably 0.5 mass % or more and 55 mass % or less, and even more preferably 1 mass % or more and 50 mass % or less.

[0019] <<Water-insoluble catalyst>> The water-insoluble catalyst powder is poorly soluble or insoluble in water, and has a solubility in water of 5% by mass or less. The solubility of the water-insoluble catalyst powder in water can be confirmed by measuring the weight loss specific to the water-insoluble catalyst powder in a high temperature range of 200°C or higher when 5 g of the water-insoluble catalyst powder is added to 95 g of water at 25°C, stirred with a stirrer for 24 hours, and then passed through a filter with an average pore size of 0.1 µm.

[0020] The water-insoluble catalyst powder is in the form of particles, and its volume average particle diameter is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 10 μm or less, more preferably 1 μm or more and 10 μm or less, and even more preferably 1 μm or more and 5 μm or less. The volume average particle diameter can be measured, for example, by a particle size distribution measuring device using a laser diffraction / scattering method.

[0021] The water-insoluble catalyst is preferably an amine adduct compound, such as an adduct between an imidazole compound and an epoxy compound (imidazole adduct) or an adduct between an aliphatic amine compound and an epoxy compound (aliphatic amine adduct).

[0022] Commercially available amine adduct compounds include, for example, Amicure PN-23, Amicure PN-23J, Amicure PN-H, Amicure PN-31, Amicure PN-31J, Amicure PN-40, Amicure PN-40J, Amicure PN-50, Amicure PN-F, Amicure MY-24, Amicure MY-H (all manufactured by Ajinomoto Fine-Techno Co., Inc.), and P-05 05 (manufactured by Shikoku Chemical Industry Co., Ltd.), P-200 (manufactured by Mitsubishi Chemical Corporation), ADEKA HARDNER EH-5001P, ADEKA HARDNER EH-5057PK, ADEKA HARDNER EH-5030S, ADEKA HARDNER EH-5011S (all manufactured by ADEKA Corporation), FUJICURE FXR-1036, FUJICURE FXR-1020, FUJICURE FXR-1081 (manufactured by T&K TOKA Corporation). These may be used alone or in combination of two or more.

[0023] <<Porous Particles>> Porous particles are particles having a large number of pores.

[0024] The average pore diameter of the porous particles is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 1 nm or more and 300 nm or less, more preferably 3 nm or more and 200 nm or less, and even more preferably 5 nm or more and 150 nm or less. The average pore diameter is calculated based on the specific surface area (A) and the total pore volume (V) measured by the BET method according to the following formula (1).

[0025] Average pore diameter = 4 × [total pore volume (V)] / [specific surface area (A)] (1)

[0026] The volume average particle diameter of the porous particles is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 15 μm or less, more preferably 1 μm or more and 10 μm or less, and even more preferably 1 μm or more and 5 μm or less. The volume average particle diameter can be measured, for example, by a particle size distribution measuring device using a laser diffraction / scattering method.

[0027] The structure of the porous particles is not particularly limited and can be appropriately selected depending on the purpose, but it is preferable that the particles have a hollow structure. The hollow structure refers to a structure having a hollow portion consisting of a space located in the center and an outer shell portion located outside the hollow portion, and having small pore spaces inside the structure. As the hollow structure, a structure in which the hollow portion is located in the center of the porous particle is preferable.

[0028] The porous particles include a crosslinkable vinyl polymer and an α-olefin copolymer.

[0029] <<<Crosslinkable Vinyl Polymer>>> A crosslinkable vinyl polymer is a polymer having a monomer unit having two or more vinyl groups.

[0030] The crosslinkable vinyl polymer is preferably a radically polymerizable compound. The radically polymerizable compound is a compound having a radically polymerizable group. The radically polymerizable group may be any functional group capable of undergoing a radical polymerization reaction, and examples thereof include groups containing a carbon-carbon unsaturated double bond. Examples of groups containing a carbon-carbon unsaturated double bond include a vinyl group and a (meth)acryloyl group.

[0031] The crosslinkable vinyl polymer, which is a radically polymerizable compound, is preferably divinylbenzene.

[0032] The content of the crosslinkable vinyl polymer in the porous particles is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of suppressing the activation temperature of the latent curing agent from increasing, the content of the crosslinkable vinyl polymer in the latent curing agent is preferably 20% by mass or more and 95% by mass or less, more preferably 25% by mass or more and 93% by mass or less, and even more preferably 30% by mass or more and 90% by mass or less.

[0033] <<<α-Olefin Copolymer>>> The α-olefin copolymer is preferably a copolymer containing structural units derived from an α-olefin and structural units derived from an olefin other than the α-olefin.

[0034] The α-olefin may generally contain one kind of α-olefin having 2 to 20 carbon atoms alone or a combination of two or more kinds. Among these, preferred α-olefins are those having 3 or more carbon atoms, more preferred are α-olefins having 3 to 8 carbon atoms, and even more preferred are α-olefins having 5 to 8 carbon atoms.

[0035] Examples of α-olefins include 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3,3-dimethyl-1-butene, 4-methyl-1-pentene, and 1-octene. These may be used alone or in combination of two or more. Among these, 1-butene, 1-pentene, 1-hexene, and 4-methyl-1-pentene are preferred from the viewpoint of ease of availability.

[0036] As the olefin other than the α-olefin, an olefin having 2 to 4 carbon atoms is preferable, and examples thereof include ethylene, propylene, and butene.

[0037] Examples of the α-olefin copolymer include ethylene-propylene copolymer (EPR), ethylene-1-butene copolymer (EBR), ethylene-1-pentene copolymer, ethylene-1-octene copolymer (EOR), propylene-1-butene copolymer (PBR), propylene-1-pentene copolymer, propylene-1-octene copolymer (POR), etc. Among these, copolymers containing structural units derived from an α-olefin having 2 to 8 carbon atoms and structural units derived from an olefin having 2 to 3 carbon atoms are preferred.

[0038] The α-olefin copolymer may form a random copolymer or a block copolymer.

[0039] The melting point of the α-olefin copolymer is preferably 100° C. or lower, more preferably 50° C. or higher and 100° C. or lower, and even more preferably 50° C. or higher and 90° C. or lower. The melting point is a value determined as the temperature Tm at the position of the maximum peak appearing in an endothermic curve by differential scanning calorimetry (DSC).

[0040] An α-olefin copolymer having a melting point of 100°C or less has a melting point lower than that in the medium-to-high temperature range (approximately 130 to 140°C), and therefore exhibits temperature responsiveness due to melting in the medium-to-high temperature range. Therefore, an α-olefin copolymer having a melting point of 100°C or less does not inhibit the temperature responsiveness of an object to be cured in the medium-to-high temperature range.

[0041] The density of the α-olefin copolymer is 800 kg / m ３ More than 950kg / m ３ Preferably, it is 830 kg / m or less. ３ More than 900kg / m ３ More preferably, it is 850 kg / m or less. ３ More than 890kg / m ３ The density is measured in accordance with Method A (water displacement method) specified in JIS K7112-1999 using a sample that has been annealed as specified in JIS K 6760-1995.

[0042] The α-olefin copolymer may be an appropriately synthesized one or a commercially available product. Examples of commercially available products include the Tafmer series (manufactured by Mitsui Chemicals, Inc.), such as Tafmer XM-7070 and Tafmer A-4085S. "Tafmer" is a registered trademark.

[0043] The content of the polyolefin resin in the latent curing agent is not particularly limited and can be appropriately selected depending on the purpose, but it is preferably 5% by mass or more and 50% by mass or less, more preferably 7% by mass or more and 45% by mass or less, and even more preferably 10% by mass or more and 40% by mass or less, relative to 100% by mass of the total of the crosslinkable vinyl polymer and the α-olefin copolymer.

[0044] The latent curing agent of this embodiment has excellent storage stability because the porous particles holding the curing catalyst contain a crosslinkable vinyl polymer and an α-olefin copolymer, and the α-olefin copolymer has excellent resistance to polar solvents. Furthermore, because the latent curing agent does not contain polyureaurethane, yellowing does not occur after high-temperature treatment. Furthermore, the cured product obtained using the latent curing agent of this embodiment has excellent heat resistance or light resistance.

[0045] In the latent curing agent of this embodiment, the porous particles have a hollow structure, and thus the curing catalyst, such as an aluminum chelate-based curing agent, can be unevenly distributed in the outer shell portion located outside the hollow structure. This facilitates heat transfer to the curing catalyst held in the porous particles, improving the temperature responsiveness of the latent curing agent.

[0046] In the latent curing agent of this embodiment, the melting point of the α-olefin copolymer is 100° C. or less, and since the α-olefin copolymer has a low melting point, the latent curing agent can exhibit temperature responsiveness due to melting in the medium to high temperature range.

[0047] The latent curing agent of this embodiment is used when the density of the α-olefin copolymer is 800 kg / m ３ More than 950kg / m ３ When the α-olefin copolymer has a thickness of 1000 nm or less, the α-olefin copolymer has high transparency and impact resistance, and therefore discoloration and reduction in strength of the latent curing agent containing porous particles can be prevented.

[0048] In the latent curing agent of the present embodiment, the content of the α-olefin copolymer is 5% by mass or more and 50% by mass or less, relative to 100% by mass of the total of the crosslinkable vinyl polymer and the α-olefin copolymer, so that curing at low temperatures becomes possible and the one-component storage stability in the epoxy is improved.

[0049] In the latent curing agent of the present embodiment, the crosslinkable vinyl polymer is a radically polymerizable compound, so that the latency of the latent curing agent can be increased. Furthermore, the radically polymerizable compound is divinylbenzene, so that the latency of the latent curing agent can be reliably increased.

[0050] The latent curing agent of the present embodiment has a curing catalyst that is an aluminum chelate curing agent or a water-insoluble catalyst having a solubility in water of 5% by mass or less, and therefore can improve the one-component storage stability while lowering the thermal response temperature.

[0051] In the latent curing agent of this embodiment, since the water-insoluble catalyst is an amine adduct compound, it is possible to reliably lower the thermal response temperature while improving the one-component storage stability. Furthermore, since the amine adduct compound is an imidazole adduct or an aliphatic amine adduct, it is possible to more reliably lower the thermal response temperature while improving the one-component storage stability.

[0052] <Method for Producing Latent Curing Agent> In the method for producing a latent curing agent, the latent curing agent obtained contains porous particles holding the curing catalyst described above.

[0053] The method for producing the latent curing agent includes a step of preparing a solution by dissolving a curing catalyst, a crosslinkable vinyl monomer, a polymerization initiator, and an α-olefin copolymer in a non-polar solvent (hereinafter referred to as a dissolving step).

[0054] The curing catalyst is the same as the curing catalyst held in the porous particles in the above-mentioned latent curing agent.

[0055] The amount of the curing catalyst to be added is not particularly limited as long as it can polymerize the crosslinkable vinyl monomer, and can be appropriately selected depending on the purpose. For example, the amount of the curing catalyst to be added in 100% by mass of the oil phase is 0.1% by mass or more and 60% by mass or less, preferably 0.5% by mass or more and 55% by mass or less, and more preferably 1% by mass or more and 50% by mass or less.

[0056] The crosslinkable vinyl monomer is a monomer having two or more vinyl groups, and is equivalent to the monomer unit constituting the crosslinkable vinyl polymer in the above-mentioned latent curing agent.

[0057] The amount of the crosslinkable vinyl monomer to be added is not particularly limited as long as the crosslinkable vinyl monomer can be polymerized, and can be appropriately selected depending on the purpose. For example, the amount of the crosslinkable vinyl monomer to be added relative to 100% by mass of the oil phase is 20% by mass or more and 60% by mass or less, preferably 25% by mass or more and 55% by mass or less, and more preferably 30% by mass or more and 50% by mass or less.

[0058] <<Polymerization initiator>> The polymerization initiator is not particularly limited and can be appropriately selected depending on the type of crosslinkable vinyl monomer, and examples thereof include thermal polymerization initiators, photopolymerization initiators, etc. These may be used alone or in combination of two or more.

[0059] -Thermal Polymerization Initiator- Examples of the thermal polymerization initiator include azo-based initiators, peroxide initiators, persulfate initiators, redox (oxidation-reduction) initiators, etc. These may be used alone or in combination of two or more.

[0060] As the azo initiator, commercially available products can be used, and examples of such commercially available products include VA-044, VA-46B, V-50, VA-057, VA-061, VA-067, VA-086, 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) (VAZO 33), 2,2′-azobis(2-amidinopropane) dihydrochloride (VAZO 50), 2,2′-azobis(2,4-dimethylvaleronitrile) (VAZO 52), 2,2′-azobis(isobutyronitrile) (VAZO 64), 2,2′-azobis-2-methylbutyronitrile (VAZO 67), and 1,1-azobis(1-cyclohexanecarbonitrile) (VAZO 88) (all manufactured by DuPont). Examples of suitable azobis(methylisobutyrate) include 2,2'-azobis(2-cyclopropylpropionitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., where "VAZO" is a trademark), 2,2'-azobis(2-cyclopropylpropionitrile), and 2,2'-azobis(methylisobutyrate) (V-601) (all manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0061] Examples of peroxide initiators include benzoyl peroxide, acetyl peroxide, lauroyl peroxide, decanoyl peroxide, dicetyl peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate (Perkadox 16S) (manufactured by Akzo Nobel, where "Perkadox" is a trademark), di(2-ethylhexyl)peroxydicarbonate, t-butyl peroxypivalate (Lupersol 11) (manufactured by Elf Atochem, where "Lupersol" is a trademark), t-butylperoxy-2-ethylhexanoate (Trigonox 21-C50) (manufactured by Akzo Nobel, where "Trigonox" is a trademark), and dicumyl peroxide.

[0062] Examples of persulfate initiators include potassium persulfate, sodium persulfate, and ammonium persulfate.

[0063] Redox (oxidation-reduction) initiators include, for example, combinations of persulfate initiators with reducing agents such as sodium metabisulfite and sodium bisulfite, systems based on organic peroxides and tertiary amines, e.g., systems based on benzoyl peroxide and dimethylaniline, systems based on organic hydroperoxides and transition metals, and systems based on cumene hydroperoxide and cobalt naphthate.

[0064] Photopolymerization Initiator Examples of photopolymerization initiators include acetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophenone, benzophenone, 2-chlorobenzophenone, p,p'-dichlorobenzophenone, p,p-bisdiethylaminobenzophenone, Michler's ketone, benzil, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-propyl ether, benzoin isobutyl ether, benzoin-n-butyl ether, benzyl methyl ketal, thioxanthone, 2-chlorothioxanthone, 2-hydroxy-2-methyl-1-phenyl-1-one, 1-(4-isopropylphenyl)2-hydroxy-2-methylpropan-1-one, methylbenzoyl formate, 1-hydroxycyclohexyl phenyl ketone, azobisisobutyronitrile, benzoyl peroxide, di-tert-butyl peroxide, etc. These may be used alone or in combination of two or more.

[0065] Among these, as the polymerization initiator, a radical polymerization initiator is preferred from the viewpoint of being able to react with various materials and to polymerize freely, a polymerization initiator containing a peroxide as a main component is more preferred, and a polymerization initiator containing a peroxydicarbonate as a main component is particularly preferred from the viewpoint of being active at low temperatures.

[0066] The amount of polymerization initiator added in a latent curing agent containing a curing catalyst is not particularly limited as long as it can polymerize the crosslinkable vinyl monomer, and can be appropriately selected depending on the purpose. For example, the amount of polymerization initiator added is 0.1% by mass or more and 15% by mass or less, preferably 0.5% by mass or more and 13% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, relative to the blending amount of the crosslinkable vinyl monomer.

[0067] The α-olefin copolymer is equivalent to the α-olefin copolymer in the above-mentioned latent curing agent.

[0068] The amount of the α-olefin copolymer added is not particularly limited as long as it can exhibit thermal responsiveness, and can be appropriately selected depending on the purpose. For example, the amount of the α-olefin added is 1% by mass or more and 60% by mass or less, preferably 3% by mass or more and 55% by mass or less, and more preferably 5% by mass or more and 50% by mass or less, relative to 100% by mass of the total of the crosslinkable vinyl polymer and the α-olefin copolymer.

[0069] <<Nonpolar Solvent>> The nonpolar solvent is not particularly limited and can be appropriately selected depending on the purpose. Examples of nonpolar solvents include n-hexane, n-heptane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, and mineral oil. These may be used alone or in combination of two or more. Among these, cyclohexane is preferred from the viewpoint of compatibility with divinylbenzene and the α-olefin copolymer.

[0070] <<Other Components>> The other components are not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include dispersants and surfactants.

[0071] In the dissolved matter obtained in the dissolving step, the curing catalyst, the crosslinkable vinyl monomer, the polymerization initiator, and the α-olefin copolymer can be dissolved substantially uniformly in the non-polar solvent.

[0072] The method for producing a latent curing agent includes a step of preparing an emulsion by emulsifying the dissolved material obtained in the dissolving step in water (hereinafter referred to as an emulsification step). In the emulsification step, the mode of emulsification is not particularly limited and can be appropriately selected depending on the purpose, but suspension emulsification is preferred. Through this emulsification, the dissolved material becomes a finely divided emulsion.

[0073] The method for producing the latent curing agent includes a step of heating the emulsion obtained in the emulsification step to obtain granules (hereinafter referred to as a polymerization step).

[0074] The heating temperature in the polymerization step is not particularly limited and can be appropriately selected depending on the purpose. Taking into consideration the activation temperature or radical generation temperature of the initiator and the formation of porous materials, the heating temperature is preferably a temperature corresponding to the boiling point of the solvent used. For example, when the solvent used is cyclohexane, the heating temperature is preferably set to 70°C to 90°C.

[0075] The heating time in the polymerization step is not particularly limited and can be appropriately selected depending on the purpose. Taking into consideration the time required for polymer production, the heating time is about 1 to 9 hours.

[0076] In the polymerization step, the emulsion is heated to polymerize the monomer portion in the emulsion, thereby obtaining granules. The obtained granules are a latent curing agent.

[0077] The method for producing a latent curing agent according to this embodiment further includes a step of crushing the granules obtained in the polymerization step (hereinafter referred to as the crushing step). Crushing refers to applying a separating force to secondary particles to turn them into primary particles. The granules obtained in the polymerization step are in the form of clumps, and by crushing these clumps of curing agent into primary particles, a particulate latent curing agent can be obtained.

[0078] The method for producing a latent curing agent of the present embodiment includes a dissolving step, an emulsifying step, and a polymerization step, and thereby makes it possible to obtain a latent curing agent that is excellent in temperature responsiveness, yellowing resistance, and storage stability.

[0079] In the method for producing a latent curing agent of the present embodiment, the dissolved material obtained in the dissolving step is emulsified in the emulsifying step, whereby the curing catalyst can be dispersed in the emulsion, and therefore the curing catalyst can be dispersed and present in the granular material that constitutes the latent curing agent after the polymerization step.

[0080] In the method for producing a latent curing agent of this embodiment, an epoxy resin can be blended with the latent curing agent, making it possible to prepare a one-component liquid adhesive for curing at medium to high temperatures.

[0081] In the method for producing a latent curing agent of this embodiment, the agent can be prepared by a process similar to that of ordinary suspension polymerization, and therefore recovery by filtering or centrifugation is possible. Therefore, the method for producing a latent curing agent of this embodiment is simple and has excellent recoverability of catalyst particles.

[0082] In the method for producing the latent curing agent of this embodiment, by further including a crushing step, the clumped curing agent can be crushed into primary particles, and the latent curing agent can be made into a particulate form.

[0083] <Thermosetting Epoxy Resin Composition> The thermosetting epoxy resin composition of the present embodiment contains the above-described latent curing agent, an epoxy resin, and a silane-based compound.

[0084] The content of the latent curing agent in the thermosetting epoxy resin composition is not particularly limited and can be appropriately selected depending on the purpose. Considering that the latent curing agent is a catalyst-type curing agent, the content of the latent curing agent in the curing components including the epoxy resin, silane compound, and latent curing agent is preferably 0.1% by mass or more and 30% by mass or less, more preferably 0.5% by mass or more and 25% by mass or less, and even more preferably 1% by mass or more and 20% by mass or less.

[0085] <<Epoxy Resin>> Epoxy resin is a curable resin having an epoxy group.

[0086] The epoxy resin is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include alicyclic epoxy resins, glycidyl ether type epoxy resins, glycidyl ester type epoxy resins, and solvent-containing epoxy resins obtained by dissolving these in a solvent.

[0087] The alicyclic epoxy resin is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include vinylcyclopentadiene dioxide; vinylcyclohexene mono- or dioxide; dicyclopentadiene oxide; epoxy-[epoxy-oxaspiro C8-15 alkyl]-cycloC5-12 alkane such as 3,4-epoxy-1-[8,9-epoxy-2,4-dioxaspiro[5.5]undecane-3-yl]-cyclohexane; epoxy C5-12 cycloalkyl C1-3 alkyl-epoxy C5-12 cycloalkane carboxylate such as 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarborate and 4,5-epoxycyclooctylmethyl-4',5'-epoxycyclooctanecarboxylate; and bis(C1-3 alkyl-epoxy C5-12 cycloalkyl C1-3 alkyl)dicarboxylate such as bis(2-methyl-3,4-epoxycyclohexylmethyl)adipate. These may be used alone or in combination of two or more.

[0088] As the alicyclic epoxy resin, 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate (manufactured by Daicel Corporation, Celloxide #2021P, epoxy equivalent: 128 to 140) is preferably used because it is readily available as a commercial product.

[0089] In the above examples, the descriptions C8-15, C5-12, and C1-3 mean that the number of carbon atoms is 8 to 15, the number of carbon atoms is 5 to 12, and the number of carbon atoms is 1 to 3, respectively, and indicate that there is a range of compound structures.

[0090] The structural formula of an example of an alicyclic epoxy resin is shown below.

[0091]

[0092] The glycidyl ether type epoxy resin or glycidyl ester type epoxy resin may be, for example, liquid or solid, and preferably has an epoxy equivalent of typically about 100 to 4,000 and two or more epoxy groups per molecule. Examples include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, and phthalate ester type epoxy resin. These may be used alone or in combination of two or more. Among these, bisphenol A type epoxy resin is preferred from the viewpoint of resin properties. These epoxy resins also include monomers and oligomers.

[0093] The content of the epoxy resin is not particularly limited and can be appropriately selected depending on the purpose. When the epoxy resin is used in combination with a catalytic latent curing agent, the content of the catalytic latent curing agent in the curing components including the epoxy resin, the silane compound, and the latent curing agent is preferably 0.1 mass % or more and 30 mass % or less, more preferably 0.5 mass % or more and 25 mass % or less, and even more preferably 1 mass % or more and 20 mass % or less.

[0094] <<Silane Compound>> Examples of the silane compound include aryl silanol compounds, etc. The aryl silanol compound is represented by, for example, the following general formula (A).

[0095] In general formula (A), m is 2 or 3, preferably 3, and the sum of m and n is 4. Ar is an aryl group which may have a substituent.

[0096] The arylsilanol compound represented by formula (A) is a monool or diol.

[0097] Examples of aryl groups include phenyl groups; naphthyl groups such as 1-naphthyl and 2-naphthyl; anthracenyl groups such as 1-anthracenyl, 2-anthracenyl, 9-anthracenyl, and benz[a]-9-anthracenyl; phenaryl groups such as 3-phenaryl and 9-phenaryl; pyrenyl groups such as 1-pyrenyl; azulenyl groups; fluorenyl groups; biphenyl groups such as 2-biphenyl, 3-biphenyl, and 4-biphenyl; thienyl groups; furyl groups; pyrrolyl groups; imidazolyl groups; and pyridyl groups. These groups may be used alone or in combination of two or more. Among these, phenyl groups are preferred from the viewpoints of availability and cost. The m Ar groups may be the same or different, but are preferably the same from the viewpoint of availability.

[0098] These aryl groups may have, for example, 1 to 3 substituents, such as electron-withdrawing groups and electron-donating groups.

[0099] Examples of electron-withdrawing groups include halogen groups such as chloro and bromo groups, trifluoromethyl groups, nitro groups, sulfo groups, carboxyl groups, alkoxycarbonyl groups such as methoxycarbonyl and ethoxycarbonyl groups, and formyl groups. Examples of electron-donating groups include alkyl groups such as methyl, ethyl, and propyl groups, alkoxy groups such as methoxy and ethoxy groups, hydroxy groups, amino groups, and monoalkylamino groups such as monomethylamino groups, and dialkylamino groups such as dimethylamino groups.

[0100] Specific examples of the phenyl group having a substituent include a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenyl group, a 2,6-dimethylphenyl group, a 3,5-dimethylphenyl group, a 2,4-dimethylphenyl group, a 2,3-dimethylphenyl group, a 2,5-dimethylphenyl group, a 3,4-dimethylphenyl group, a 2,4,6-trimethylphenyl group, a 2-ethylphenyl group, and a 4-ethylphenyl group.

[0101] The acidity of the hydroxyl group of the silanol group can be increased by using an electron-withdrawing group as a substituent, while the acidity of the hydroxyl group of the silanol group can be decreased by using an electron-donating group as a substituent. Therefore, the curing activity can be controlled by the substituent.

[0102] Here, the m Ars may have different substituents, but it is preferable that the m Ars have the same substituents in terms of availability. Alternatively, only some Ars may have substituents, and the other Ars may have no substituents.

[0103] Of these, triphenylsilanol and diphenylsilanediol are preferred, with triphenylsilanol being particularly preferred.

[0104] The content of the silane compound is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of dissolving the silane compound in the epoxy resin, the content of the silane compound in the curing component containing the epoxy resin and the silane compound is preferably 0.1 mass % or more and 40 mass % or less, more preferably 0.5 mass % or more and 35 mass % or less, and even more preferably 1 mass % or more and 30 mass % or less.

[0105] <<Other Components>> The other components are not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include an oxetane compound, a filler, a pigment, and an antistatic agent.

[0106] <<<Oxetane Compound>>> In the curable composition, by using an oxetane compound in combination with an epoxy resin, the exothermic peak can be made sharper.

[0107] Examples of oxetane compounds include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis{[(3-ethyl-3-oxetanyl)methoxy]methyl}benzene, 4,4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl, 1,4-benzenedicarboxylic acid bis[(3-ethyl-3-oxetanyl)]methyl ester, 3-ethyl-3-(phenoxymethyl)oxetane, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, di[1-ethyl(3-oxetanyl)]methyl ether, 3-ethyl-3-{[3-(triethoxysilyl)propoxy]methyl}oxetane, oxetanyl silsesquioxane, and phenol novolac oxetane. These compounds may be used alone or in combination of two or more.

[0108] The content of the oxetane compound in the curing composition is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 10 parts by mass or more and 100 parts by mass or less, and more preferably 20 parts by mass or more and 70 parts by mass or less, relative to 100 parts by mass of the epoxy resin.

[0109] The thermosetting epoxy resin composition of the present embodiment is a compound of a latent curing agent and an epoxy resin, and therefore can be a one-component liquid adhesive for curing at medium to high temperatures.

[0110] The thermosetting epoxy resin composition of the present embodiment contains a latent curing agent, an epoxy resin, and a silane-based compound, thereby accelerating the curing of the epoxy resin. Furthermore, the silane-based compound is triphenylsilanol, which reliably accelerates the curing of the epoxy resin.

[0111] The present embodiment will be further described below using experimental examples. Various tests and evaluations were performed according to the following methods. In the following, "parts" and "%" are by weight or mass unless otherwise specified.

[0112] <Production of Latent Curing Agent and Thermosetting Epoxy Resin Composition> [Example 1] 800 parts of distilled water, 0.05 parts of a surfactant (Newrex R, manufactured by NOF Corporation; "Newrex" is a registered trademark), and 4 parts of polyvinyl alcohol (Kuraray Poval 5-88, manufactured by Kuraray Co., Ltd.; "Kuraray Poval" is a registered trademark) as a dispersant were placed in a 3-liter polymerization vessel equipped with a thermometer and mixed to prepare an aqueous phase.

[0113] To this aqueous phase, 40 parts of divinylbenzene (mixture of isomers) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a crosslinkable vinyl monomer, 10 parts of a propylene-α-olefin copolymer (manufactured by Mitsui Chemicals, Inc., Tafmer XM-7070, melting point 75°C, Tafmer is a registered trademark) as an α-olefin copolymer, 30 parts of an aluminum chelate curing agent (manufactured by Kawaken Fine Chemicals Co., Ltd., Aluminum Chelate D) as a curing catalyst, and 0.04 parts of an aliphatic diacyl peroxide (manufactured by NOF Corporation, Perloyl L, "Perloyl" is a registered trademark) as an initiator were added to form an oil phase dissolved in 30 parts of cyclohexane as a non-polar solvent, and the mixture was emulsified and mixed using a homogenizer (manufactured by IKA Japan, T-50) at 10,000 rpm for 5 minutes, followed by radical polymerization at 80°C for 6 hours. After the reaction was completed, the polymerization reaction liquid was allowed to cool to room temperature, and the polymer particles were separated by filtration and air-dried to obtain a lump of latent curing agent.

[0114] The lump latent curing agent was crushed using a jet mill (A-O jet mill, manufactured by Seishin Enterprise Co., Ltd.) to obtain particulate latent curing agent.

[0115] Four parts of the crushed latent curing agent, 80 parts of bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, EP828), and 8 parts of triphenylsilanol were mixed almost uniformly to obtain a thermosetting epoxy resin composition.

[0116] Example 2 In the oil phase, 10 parts of an ethylene-α-olefin copolymer (manufactured by Mitsui Chemicals, Inc., Tafmer A-4085S, melting point 66°C, "Tafmer" is a registered trademark) was mixed in place of the propylene-α-olefin copolymer as the α-olefin copolymer. Except for this, a latent curing agent and a thermosetting epoxy resin composition were produced in the same manner as in Example 1.

[0117] [Example 3] In the oil phase, the blending amount of divinylbenzene (isomer mixture) as the crosslinkable vinyl monomer was 30 parts, and the blending amount of propylene-α-olefin copolymer (Tafmer XM-7070) as the α-olefin copolymer was 20 parts. Except for this, a latent curing agent and a thermosetting epoxy resin composition were produced in the same manner as in Example 1.

[0118] Example 4 In the oil phase, the blending amount of divinylbenzene (isomer mixture) as the crosslinkable vinyl monomer was 45 parts, and the blending amount of propylene-α-olefin copolymer (Tafmer XM-7070) as the α-olefin copolymer was 5 parts. Except for this, a latent curing agent and a thermosetting epoxy resin composition were produced in the same manner as in Example 1.

[0119] Comparative Example 1 For the oil phase, 100 parts of a 24% isopropanol solution of aluminum monoacetylacetonate bis(ethylacetoacetate) (Kawaken Fine Chemicals Co., Ltd., Aluminum Chelate D), 70 parts of a polyfunctional isocyanate compound, a methylenediphenyl-4,4'-diisocyanate (3 moles) / trimethylolpropane (1 mole) adduct (Mitsui Chemicals, Inc., D-109), 30 parts of divinylbenzene (Merck & Co., Inc.) as a radical polymerizable compound, and 1% by mass (0.3 parts) of a radical polymerization initiator, PERLOYL L (NOF Corporation, "PERLOYL" is a registered trademark), were dissolved in 100 parts of ethyl acetate. Except for these, a latent curing agent and a thermosetting epoxy resin composition were produced in the same manner as in Example 1.

[0120] Comparative Example 2 In the oil phase, the blending amount of divinylbenzene (isomer mixture) as the crosslinkable vinyl monomer was 20 parts, and the blending amount of propylene-α-olefin copolymer (Tafmer XM-7070) as the α-olefin copolymer was 30 parts. Except for this, a latent curing agent and a thermosetting epoxy resin composition were produced in the same manner as in Example 1.

[0121] Comparative Example 3 In the oil phase, the blending amount of divinylbenzene (isomer mixture) as the crosslinkable vinyl monomer was 49 parts, and the blending amount of propylene-α-olefin copolymer (Tafmer XM-7070) as the α-olefin copolymer was 1 part. Except for this, a latent curing agent and a thermosetting epoxy resin composition were produced in the same manner as in Example 1.

[0122] Comparative Example 4 800 parts of distilled water, 0.05 parts of a surfactant (NEUREX RT, manufactured by NOF Corporation; "NEUREX" is a registered trademark), and 4 parts of polyvinyl alcohol (Kuraray Poval 5-88, manufactured by Kuraray Co., Ltd.) as a dispersant were placed in a 3-liter interfacial polymerization vessel equipped with a thermometer and mixed approximately uniformly. To this mixture, an oil phase solution prepared by dissolving 11 parts of a 24% isopropanol solution of aluminum monoacetylacetonate bis(ethylacetoacetate) (Kawaken Fine Chemicals Co., Ltd., Aluminum Chelate D) and 11 parts of a methylenediphenyl-4,4'-diisocyanate (3 moles) trimethylolpropane (1 mole) adduct (Mitsui Chemicals, Inc., D-109) in 30 parts of ethyl acetate was added, and the mixture was emulsified and mixed at 10,000 rpm for 10 minutes using a homogenizer (IKA Japan, T-50), followed by interfacial polymerization overnight at 60°C.

[0123] After the reaction was completed, the polymerization reaction solution was allowed to cool to room temperature, and the interfacially polymerized particles were filtered off and air-dried to obtain 20 parts of a latent curing agent in the form of spheres with a particle size of about 10 μm.

[0124] [Particle size distribution] The particle size distribution of the latent curing agent after disintegration was measured using a laser diffraction / scattering particle size distribution analyzer (MT3300EX II, manufactured by Microtrac-Bell Co., Ltd.). The particle size distribution of the latent curing agent of Example 1 is shown in Figure 1, and the particle size distribution of the latent curing agent of Example 2 is shown in Figure 6.

[0125] 1, the average particle size of the latent curing agent in Example 1 was 4.5 μm and the maximum particle size was 15.6 μm. Also, as shown in FIG. 6, the average particle size of the latent curing agent in Example 2 was 4.9 μm and the maximum particle size was 15.6 μm. The average particle sizes and maximum particle sizes of Examples 1 and 2 are shown in Table 1.

[0126]

[0127] [SEM Images] SEM images of the crushed latent curing agent were taken using a scanning electron microscope (SEM) (JSM-6510A, manufactured by JEOL Ltd.). SEM images (3000x and 12000x) of the latent curing agent of Example 1 are shown in Figures 2 and 3, and SEM images (3000x and 12000x) of the latent curing agent of Example 2 are shown in Figures 7 and 8.

[0128] 2, 3, 7 and 8, it was found that the latent curing agents of Examples 1 and 2 were all particulate in shape.

[0129] [Differential Scanning Calorimetry] Differential scanning calorimetry (DSC) of the latent curing agent after disintegration was performed using a differential scanning calorimeter (DSC6200, manufactured by Hitachi High-Tech Science Corporation). DSC was performed by blending bisphenol A epoxy resin (EP828, manufactured by Mitsubishi Chemical Corporation), triphenylsilanol (manufactured by Tokyo Chemical Industry Co., Ltd.) and latent curing agent in a weight ratio of 80:8:4, at a temperature rise rate of 10°C / min and measuring a weight of 5 mg. The DSC results of the latent curing agent of Example 1 are shown in Figures 4 and 5, and the DSC results of the latent curing agent of Example 2 are shown in Figures 9 and 10. The exothermic onset temperature, exothermic peak temperature, and total heat release value in the DSC of the latent curing agents of Examples 1 and 2 are also shown in Table 2.

[0130]

[0131] From Figures 4, 5, and Table 2, it can be seen that the latent curing agent of Example 1 has a melting point near 140°C due to the α-olefin copolymer, indicating that the temperature response begins at the melting point of the α-olefin copolymer. Since the propylene-α-olefin copolymer (Tafmer XM-7070) in the latent curing agent of Example 1 has a melting point of 75°C alone, it is possible that the unsaturated bonds in the α-olefin copolymer bonded to the vinyl polymer when it was blended with a vinyl monomer and a peroxide initiator during suspension polymerization and thermally polymerized. Furthermore, since the exothermic peak temperature was near 190°C, it can be seen that the latent curing agent of Example 1 is suitable as a medium- to high-temperature curing epoxy curing catalyst.

[0132] 9, 10, and Table 2, the presence of a melting point attributable to the α-olefin copolymer near 130°C for the latent curing agent of Example 2 is confirmed, indicating that the temperature response begins at the melting point of the α-olefin copolymer. Furthermore, since the melting point of the ethylene-α-olefin copolymer (Tafmer A-4085S) alone in the latent curing agent of Example 2 is 66°C, it is possible that the unsaturated bonds in the α-olefin copolymer bonded to the vinyl polymer when it was blended with a vinyl monomer and a peroxide initiator during suspension polymerization and thermally polymerized. Furthermore, since the exothermic peak temperature was near 182°C, it is clear that the latent curing agent of Example 2 is suitable as a medium- to high-temperature curing epoxy curing catalyst.

[0133] The latent curing agent was placed in an aluminum container and heated on a hot plate (Shamal Hot Plate HHP-412, manufactured by AS ONE Corporation) at 180°C for 12 hours, and discoloration was confirmed. The results are shown in Table 3.

[0134]

[0135] As can be seen from Table 3, after heat treatment at 180°C for 12 hours, yellowing was confirmed in the polyurea urethane type microcapsules of Comparative Examples 1 and 4. On the other hand, no yellowing was observed in the latent curing agents of Examples 1 and 2, which were produced using a crosslinkable vinyl monomer and an α-olefin copolymer.

[0136] [Storage Stability (Room Temperature Storage Life)] Using a tuning fork vibro viscometer (SV-100 manufactured by A&D Co., Ltd.), the storage stability of a mixture of bisphenol A epoxy resin (EP828 manufactured by Mitsubishi Chemical Corporation), triphenylsilanol (manufactured by Tokyo Chemical Industry Co., Ltd.) and a latent curing agent in a weight ratio of 80:8:4 was confirmed when stored at 25° C. The results are shown in FIG. 11 and Table 4.

[0137]

[0138] 11 and Table 4, the latent curing agents of Examples 1 and 2, which were produced using a crosslinkable vinyl monomer and an α-olefin copolymer, exhibited good one-component storage stability in epoxy resin when stored at room temperature. The viscosity multiplication factor after 90 days of storage in epoxy resin at room temperature was about 1.3 times for Example 1 and about 1.1 times for Example 2, demonstrating good room temperature storage stability.

[0139] [α-Olefin Copolymer Content] The relationship between the α-olefin copolymer content and emulsification possibility was confirmed. The results are shown in Table 5. The emulsification conditions were as follows: the emulsion was performed at 10,000 rpm for 5 minutes using a homogenizer (T-50, manufactured by IKA Japan Co., Ltd.), and the state of the emulsion was confirmed.

[0140]

[0141] As can be seen from Table 5, phase separation occurred before emulsification in Comparative Example 2. On the other hand, emulsification was possible in Examples 1 to 4. This indicates that emulsification is possible when the content of the α-olefin copolymer is in the range of 5% by mass or more and 50% by mass or less, relative to 100% by mass of the total of the crosslinkable vinyl polymer and the α-olefin copolymer.

[0142] [SEM-EDS] Scanning electron microscope (SEM)-energy dispersive X-ray spectroscopy (EDS) was used to perform Al element mapping of the latent curing agents of Examples 1 and 2. The results of Example 1 are shown in Figures 12 and 13, and the results of Example 2 are shown in Figures 14 and 15.

[0143] 12 and 14 show that the inside of the latent curing agents of Examples 1 and 2 has a hollow structure. Also, from Fig. 13 and 15, it is seen that in the latent curing agents of Examples 1 and 2, Al derived from the aluminum chelate curing agent is scattered inside the resin of the outer shell portion located outside the hollow portion.

[0144] Preferred embodiments of the present invention will be described below.

[0145] (Appendix 1) A latent curing agent comprising porous particles holding a curing catalyst, the porous particles comprising: a crosslinkable vinyl polymer; and an α-olefin copolymer.

[0146] (Appendix 2) The latent curing agent according to Appendix 1, wherein the porous particles have a hollow structure.

[0147] (Appendix 3) The latent curing agent according to Appendix 1, wherein the α-olefin copolymer has a melting point of 100°C or less.

[0148] (Note 4) The density of the α-olefin copolymer is 800 kg / m ３ More than 950kg / m ３ 2. The latent curing agent of claim 1, wherein:

[0149] (Appendix 5) The latent curing agent according to Appendix 1, wherein the content of the α-olefin copolymer is 5% by mass or more and 50% by mass or less, relative to 100% by mass of the total of the crosslinkable vinyl polymer and the α-olefin copolymer.

[0150] (Appendix 6) The latent curing agent according to claim 1, wherein the crosslinkable vinyl polymer is a radically polymerizable compound.

[0151] (Appendix 7) The latent curing agent according to Appendix 6, wherein the radical polymerizable compound is divinylbenzene.

[0152] (Appendix 8) The latent curing agent according to Appendix 1, wherein the curing catalyst is an aluminum chelate-based curing agent or a water-insoluble catalyst having a solubility in water of 5% by mass or less.

[0153] (Appendix 9) The latent curing agent according to Appendix 8, wherein the water-insoluble catalyst is an amine adduct compound.

[0154] (Appendix 10) The latent curing agent according to Appendix 9, wherein the amine adduct compound is an imidazole adduct or an aliphatic amine adduct.

[0155] (Appendix 11) A latent curing agent comprising porous particles holding a curing catalyst, wherein the porous particles have a hollow structure.

[0156] (Appendix 12) A thermosetting epoxy resin composition comprising the latent curing agent according to any one of Appendices 1 to 11, an epoxy resin, and a silane-based compound.

[0157] (Appendix 13) The thermosetting epoxy resin composition according to Appendix 12, wherein the silane compound is triphenylsilanol.

[0158] (Appendix 14) A method for producing a latent curing agent containing porous particles holding a curing catalyst, the method comprising the steps of: preparing a solution by dissolving the curing catalyst, a crosslinkable vinyl monomer, a polymerization initiator, and an α-olefin copolymer in a non-polar solvent; emulsifying the solution in water to prepare an emulsion; and heating the emulsion to obtain a granule.

[0159] (Appendix 15) A method for producing the latent curing agent according to Appendix 14, comprising a step of crushing the granules.

[0160] Although the embodiments of the present invention have been described above, the present invention is not limited to the specific embodiments, and various modifications and changes are possible within the scope of the invention described in the claims.

[0161] This application claims priority based on Japanese Patent Application No. 2024-015486, filed February 5, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. A latent curing agent comprising porous particles carrying a curing catalyst, the porous particles comprising: a crosslinkable vinyl polymer; and an α-olefin copolymer.

2. The latent curing agent according to claim 1, wherein the porous particles have a hollow structure.

3. The latent curing agent according to claim 1, wherein the melting point of the α-olefin copolymer is 100°C or less.

4. The density of the α-olefin copolymer is 800 kg / m ３ More than 950kg / m ３ 2. The latent curing agent of claim 1, wherein:

5. The latent curing agent according to claim 1, wherein the content of the α-olefin copolymer is 5% by mass or more and 50% by mass or less, relative to 100% by mass of the total of the crosslinkable vinyl polymer and the α-olefin copolymer.

6. The latent curing agent according to claim 1, wherein the crosslinkable vinyl polymer is a radically polymerizable compound.

7. The latent curing agent according to claim 6, wherein the radical polymerizable compound is divinylbenzene.

8. The latent curing agent according to claim 1, wherein the curing catalyst is an aluminum chelate-based curing agent or a water-insoluble catalyst having a solubility in water of 5% by mass or less.

9. The latent curing agent of claim 8, wherein the water-insoluble catalyst is an amine adduct compound.

10. The latent curing agent according to claim 9, wherein the amine adduct compound is an imidazole adduct or an aliphatic amine adduct.

11. A latent curing agent comprising porous particles holding a curing catalyst, wherein the porous particles have a hollow structure.

12. A thermosetting epoxy resin composition comprising the latent curing agent according to any one of claims 1 to 11, an epoxy resin, and a silane-based compound.

13. The thermosetting epoxy resin composition according to claim 12, wherein the silane compound is triphenylsilanol.

14. A method for producing a latent curing agent containing porous particles holding a curing catalyst, the method comprising the steps of: preparing a solution by dissolving the curing catalyst, a crosslinkable vinyl monomer, a polymerization initiator, and an α-olefin copolymer in a non-polar solvent; emulsifying the solution in water to prepare an emulsion; and heating the emulsion to obtain granules.

15. A method for producing the latent hardener according to claim 14, comprising the step of crushing the granules.

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