JP7548078B2 - Curable resin composition and cured product thereof - Google Patents

Description

The present invention relates to a curable resin composition containing an epoxy compound and a cured product thereof.

Epoxy resins have features such as high dimensional stability, insulation, water resistance, and chemical resistance, and are therefore widely used as insulating materials and sealing materials in electronic devices, as well as in paints, adhesives, composite materials, etc. They are also used as modeling materials to obtain molded bodies by optical three-dimensional modeling using 3D printers, etc.

On the other hand, epoxy resins have the disadvantage of having low toughness and being prone to brittle fracture. For this reason, technology to improve the toughness of epoxy resins has been investigated, and one method proposed is to add a modifier to epoxy resin to improve toughness.

For example, Patent Document 1 describes the addition of high molecular weight polypropylene glycol as a toughness improver (reinforcing agent) to a thermosetting epoxy resin.
Furthermore, Patent Document 2 describes a radiation-curable composition for additive modeling in which a high-molecular-weight polypropylene glycol is added as a liquid phase separation toughening agent to a rubber toughening base resin containing an epoxy compound and a polyfunctional (meth)acrylate.

International Publication No. 2011/119216 Special table 2019-513842 publication

However, although the epoxy resin composition in which high molecular weight polypropylene glycol is added to the epoxy compound shows improved toughness in the cured product, it tends to bleed out easily, especially in high temperature environments.

Therefore, there is a demand for a resin composition that not only improves toughness, but also reduces bleeding even at high temperatures and produces a cured epoxy resin with excellent heat resistance.

The present invention aims to solve these problems and provide a curable resin composition that can produce a cured product of an epoxy resin that is highly tough and has excellent heat resistance, and the cured product.

The present invention is based on the discovery that the toughness of epoxy resins can be improved and excellent heat resistance can be imparted by using a specific urethane (meth)acrylate having a polyether chain and a urethane bond.

The present invention provides the following means.
[1] A curable resin composition comprising an epoxy compound, a monofunctional urethane (meth)acrylate, an epoxy resin curing agent, and a radical polymerization initiator, wherein the monofunctional urethane (meth)acrylate is one or more monomers selected from the reaction products of the following (i) to (iii):
(i) An equimolar reaction product of a polyether monol and a compound having a (meth)acryloyloxy group,
The compound having a (meth)acryloyloxy group is a reaction product having one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule.
(ii) an equimolar reaction product of a polyether monool, a diisocyanate, and a compound having a (meth)acryloyloxy group,
The compound having a (meth)acryloyloxy group is a reaction product having one group reactive with an isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule.
(iii) an equimolar reaction product of a polyether polyol and a compound having a (meth)acryloyloxy group,
The compound having a (meth)acryloyloxy group is a reaction product having one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule.
[2] The curable resin composition according to [1], wherein the content of the monofunctional urethane (meth)acrylate is 0.1 to 25 parts by mass based on 100 parts by mass of the epoxy compound.
[3] The curable resin composition according to [1] or [2], wherein the monofunctional urethane (meth)acrylate has a number average molecular weight of 3,000 to 30,000.
[4] The curable resin composition according to any one of [1] to [3], wherein the monofunctional urethane (meth)acrylate has a glass transition temperature of −55° C. or lower.
[5] The curable resin composition according to any one of [1] to [4], wherein the epoxy resin curing agent is a photocationic polymerization initiator, and the radical polymerization initiator is a photoradical polymerization initiator.
[6] The curable resin composition according to any one of [1] to [4], wherein the epoxy resin curing agent is a thermal cationic polymerization initiator, and the radical polymerization initiator is a thermal radical polymerization initiator.
[7] The curable resin composition according to [5], which is for optical three-dimensional modeling.

[8] A cured product obtained by curing the curable resin composition according to any one of [1] to [7].
[9] An article comprising the cured product according to [8].
[10] A fiber-reinforced composite material obtained by curing a fiber substrate impregnated with the curable resin composition according to any one of [1] to [6].
[11] An article comprising the fiber-reinforced composite material according to [10].

The present invention provides a curable resin composition that can produce a cured product of an epoxy resin that is highly tough and has excellent heat resistance, and the cured product.

The definitions and meanings of the terms and expressions used in this specification are given below.
The term "(meth)acryloyloxy group" is a general term for an acryloyloxy group and a methacryloyloxy group.
"(Meth)acrylate" is a general term for acrylate and methacrylate.
Similarly, "(meth)acrylic acid" is a general term for acrylic acid and methacrylic acid.
The term "functional group number" refers to the number of (meth)acryloyloxy groups in one molecule, unless otherwise specified. The term "average functional group number" refers to the average number of (meth)acryloyloxy groups in one molecule, with the formula weight or number average molecular weight based on a chemical formula being one unit, unless otherwise specified.
The term "monofunctional urethane (meth)acrylate" refers to a urethane (meth)acrylate having an average number of functional groups in one molecule that is substantially 1. A urethane (meth)acrylate having an average number of functional groups in one molecule that is 0.7 to 1.4, preferably 0.8 to 1.3, is considered to be a urethane (meth)acrylate having substantially one (meth)acryloyloxy group in one molecule, that is, a monofunctional urethane (meth)acrylate.
By "equimolar reaction product" is meant that the molar ratio of the reacting compounds is substantially 1, and a reaction product in which the molar ratio is 0.7 to 1.4, preferably 0.8 to 1.3, is considered to be an equimolar reaction product.
Similarly, the "equal number of moles" of reactive groups (or compounds) means that the molar ratio of the reactive groups (or compounds) is substantially 1, and when the molar ratio is 0.7 to 1.4, preferably 0.8 to 1.3, the molar numbers of the reactive groups (or compounds) are considered to be equal.
The "hydroxyl value" is determined by measurement in accordance with JIS K 1557: 2007. The "hydroxyl-equivalent molecular weight" is a value calculated from the formula 56100/(hydroxyl value)×(number of active hydrogens in the initiator).
The "NCO index" in the reaction between an isocyanate group-containing compound and a hydroxyl group-containing compound is a value expressed as a percentage of the equivalent ratio of the isocyanate groups of the isocyanate group-containing compound to the hydroxyl groups of the hydroxyl group-containing compound.
Unless otherwise specified, the term "molecular weight" refers to the formula weight based on a chemical formula, or, in the case of a compound having a molecular weight distribution, the number average molecular weight. The "number average molecular weight" is a polystyrene-equivalent molecular weight determined by gel permeation chromatography (GPC) based on a calibration curve prepared using standard polystyrene samples.
The "monomer components constituting the curable resin" refer to the epoxy compound, the monofunctional urethane (meth)acrylate, and other monomers that can be optionally blended.

[Curable resin composition]
The curable resin composition of the present invention contains an epoxy compound, a monofunctional urethane (meth)acrylate, an epoxy resin curing agent, and a radical polymerization initiator, and the monofunctional urethane (meth)acrylate is selected from the following (i) to (iii) ) reaction products.
(i) An equimolar reaction product of a polyether monol and a compound having a (meth)acryloyloxy group,
The compound having a (meth)acryloyloxy group is a compound having one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule. Product.
(ii) an equimolar reaction product of a polyether monool, a diisocyanate, and a compound having a (meth)acryloyloxy group,
The compound having a (meth)acryloyloxy group is a compound having one group reactive with an isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule. The reaction product:
(iii) an equimolar reaction product of a polyether polyol and a compound having a (meth)acryloyloxy group,
The compound having a (meth)acryloyloxy group is a compound having one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule. Product.

The above-mentioned curable resin composition can provide a cured epoxy resin product that has high toughness and excellent heat resistance.

[Epoxy Compound]
The epoxy compound is a main component of the curable resin composition of the present invention, and a cured product of the epoxy resin can be obtained by using the curable resin composition. The content of the epoxy compound in the curable resin composition is preferably 50% by mass or more, more preferably 55 to 99% by mass, and even more preferably 60 to 98% by mass.

As the epoxy compound in the present invention, an epoxy compound that has cationic polymerizability and is a known raw material for epoxy resins can be used. From the viewpoint of polymerizability and physical properties of the cured product, a compound having two or more epoxy groups in one molecule is preferred.

Examples of the epoxy compound include the cationic polymerizable compounds described in paragraphs [0026] to [0033] of JP-A No. 2019-513842, such as bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, resorcinol diglycidyl ether, catechol diglycidyl ether, hydroquinone diglycidyl ether, 4-tert-butylphenyl glycidyl ether, diglycidyl phthalate, phenol novolac type epoxy resin, cresol novolac type epoxy resin, fluorene type epoxy resin, biphenyl type epoxy resin, Examples of such epoxy compounds include aromatic epoxy compounds such as naphthalene-type epoxy resins; aliphatic epoxy compounds such as 1,2-propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and trimethylolpropane triglycidyl ether; and alicyclic epoxy compounds such as 1,2-cyclohexanedicarboxylate diglycidyl, 3,4-epoxycyclohexylmethyl (3,4-epoxy)cyclohexanecarboxylate, limonene dioxide, and dicyclopentadiene dioxide. These may be used alone or in combination of two or more. Of these, bisphenol A diglycidyl ether and bisphenol F diglycidyl ether are preferred from the viewpoint of ease of handling, etc.

[Monofunctional urethane (meth)acrylate]
The curable resin composition of the present invention contains a monofunctional urethane (meth)acrylate, and can be radically polymerized by its (meth)acryloyloxy group. In addition, the monofunctional urethane (meth)acrylate has a flexible graft chain that does not contribute to crosslinking, and thus has the characteristics of a low glass transition temperature, a small temperature dependency of the storage modulus in a wide temperature range of -20 to 80°C, and a small residual strain. It is presumed that this can satisfactorily improve the toughness and heat resistance of the epoxy resin.
The (meth)acryloyloxy group of the monofunctional urethane (meth)acrylate is preferably an acryloyloxy group from the viewpoint of the curing rate of the curable resin composition.

The monofunctional urethane (meth)acrylate in the present invention is one or more monomers selected from the reaction products of (i) to (iii) above (hereinafter also referred to as "monomer 1-1", "monomer 1-2" and "monomer 1-3"). The monofunctional urethane (meth)acrylate in the curable resin composition may be used alone or in combination of two or more kinds.

<Monomer 1-1>
Monomer 1-1 is a reaction product of (i), and is an equimolar reaction product of polyether monool (i-1) and a compound (i-2) having a (meth)acryloyloxy group, and the compound (i-2) having a (meth)acryloyloxy group is a compound having one isocyanate group per molecule and one or two (meth)acryloyloxy groups per molecule.

As monomer 1-1, a compound represented by formula (1) is preferred.

In formula (1), R ¹ is a monovalent organic group having one or two (meth)acryloyloxy groups.
R ¹² is preferably an alkylene group having 2 to 8 carbon atoms, more preferably an alkylene group having 2 to 4 carbon atoms. A plurality of R ¹² present in one molecule may be the same or different. When two or more types of R ¹² are present in one molecule, the chain of -OR ¹² - may be block or random. R ¹² is preferably one or more types selected from an ethylene group, a propylene group, a 1,2-dimethylethylene group, and a 1-ethylethylene group, more preferably one or more types selected from an ethylene group and a propylene group.

It is also preferred that (OR ¹² ) is a unit based on a monomer a having one epoxy group and an ether bond other than the ether bond of the epoxy group in one molecule. The unit based on the monomer a is preferably a unit represented by formula (11). The monomer a may be used alone or in combination of two or more kinds.

In formula (11), R ¹⁰¹ is a monovalent group represented by -R ¹⁰³ -O-R ¹⁰⁴ , and R ¹⁰² is a hydrogen atom or a monovalent group represented by -R ¹⁰⁵ -O-R ^106. R ¹⁰³ and R ¹⁰⁵ are each independently a linear or branched alkylene group having 1 to 3 carbon atoms, and R ¹⁰⁴ and R ¹⁰⁶ are each independently a linear or branched alkyl group having 1 to 18 carbon atoms.
The alkylene group of R ¹⁰³ and R ¹⁰⁵ is each independently preferably a methylene group, an ethylene group, an n-propylene group or an isopropylene group, more preferably a methylene group or an ethylene group, and further preferably a methylene group.
R ¹⁰⁴ and R ¹⁰⁶ each independently have 1 to 14 carbon atoms, more preferably 1 to 12 carbon atoms, and even more preferably 2 to 10 carbon atoms.
Examples of the linear alkyl group for R ¹⁰⁴ and R ¹⁰⁶ include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-octyl group, an n-decyl group, a lauryl group, a cetyl group, and a stearyl group, and preferably each independently is a methyl group, an ethyl group, or an n-butyl group. A branched alkyl group has a structure in which a hydrogen atom in the linear alkyl group (excluding a hydrogen atom bonded to a terminal carbon) is substituted with an alkyl group. Examples of the substituting alkyl group include a methyl group and an ethyl group. A preferred branched alkyl group is a 2-ethylhexyl group.

The monomer a is preferably a monomer represented by formula (12).

R ¹⁰¹ and R ¹⁰² in formula (12) are the same as R ¹⁰¹ and R ¹⁰² in formula (11).

Examples of the monomer represented by formula (12) include methyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, lauryl glycidyl ether, and hexyl glycidyl ether. From the viewpoint of toughness of the cured product of the curable resin composition, butyl glycidyl ether or 2-ethylhexyl glycidyl ether is preferred.

In formula (1), R ¹³ is an alkyl group having 1 to 20 carbon atoms. R ¹³ is preferably an alkyl group having 1 to 8 carbon atoms, more preferably a methyl group, an ethyl group, or a butyl group, and even more preferably a butyl group.
a is an integer from 20 to 600, preferably an integer from 35 to 500, and more preferably an integer from 65 to 250.

(Polyether monol (i-1))
The polyether monool (i-1) in the monomer 1-1 is a compound obtained by ring-opening polymerization of an initiator having an active hydrogen-containing group and having one or more active hydrogens with an alkylene oxide and/or the monomer a, and having an initiator residue, a polyether chain, and a hydroxyl group corresponding to the number of active hydrogens of the initiator.

Examples of the active hydrogen-containing group of the initiator include a hydroxyl group, a carboxyl group, and an amino group having one hydrogen atom bonded to a nitrogen atom. The active hydrogen-containing group of the initiator is preferably a hydroxyl group or a carboxyl group, more preferably a hydroxyl group, and even more preferably an alcoholic hydroxyl group.

Examples of initiators having one active hydrogen include monohydric alcohols, monohydric phenols, monovalent carboxylic acids, and amine compounds having one hydrogen atom bonded to a nitrogen atom. The initiator is preferably a monohydric aliphatic alcohol or a monohydric aliphatic carboxylic acid, and more preferably a monohydric aliphatic alcohol. A polyoxyalkylene monool having a lower molecular weight than the target polyether monool may also be used as the initiator.

The number of carbon atoms of the monohydric aliphatic alcohol as the initiator is preferably 1 to 20, more preferably 2 to 8. Specific examples of the monohydric aliphatic alcohol as the initiator include ethanol, propanol, 2-propanol, and n-butanol.
The number of carbon atoms of the monovalent aliphatic carboxylic acid used as the initiator is preferably 2 to 20, more preferably 2 to 8, including the carbon atoms of the carboxy group.

When the alkylene oxide and the monomer a undergo ring-opening polymerization, the ratio of the mass of the monomer a to the total mass of the two is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 10 to 80% by mass, from the viewpoint of the toughness of the cured product of the curable resin composition.

The number of carbon atoms in the alkylene oxide is preferably 2 to 8, and more preferably 2 to 4. Specific examples of the alkylene oxide include propylene oxide, ethylene oxide, 1,2-butylene oxide, and 2,3-butylene oxide.

The oxyalkylene group in the polyether monool (i-1) preferably consists of only an oxypropylene group or a combination of an oxypropylene group and a group other than the oxypropylene group. The oxyalkylene group other than the oxypropylene group is preferably an oxyethylene group.
The ratio of oxypropylene groups to all oxyalkylene groups in the polyether monool (i-1) is preferably 50 to 100% by mass, more preferably 60 to 100% by mass. When the initiator is a polyoxyalkylene monool having a lower molecular weight than the target polyether monool, the oxyalkylene groups in the initiator are regarded as oxyalkylene groups in the obtained polyether monool.

In the polyether monool (i-1), a polyoxyalkylene monool having a low hydroxyl value, i.e., a high molecular weight, can be produced by ring-opening polymerization of an alkylene oxide having 3 or more carbon atoms, preferably propylene oxide, as an initiator in the presence of a composite metal cyanide complex catalyst.
The polyoxyalkylene monool having a low hydroxyl value includes polyoxyalkylene monools having a hydroxyl value of 40 mgKOH/g or less.
A polyoxyalkylene monool having a low hydroxyl value and an oxyethylene group can be produced by using a polyoxyalkylene monool having a high hydroxyl value and an oxyethylene group, for example, a hydroxyl value of 50 mgKOH/g or more, as an initiator and ring-opening polymerizing an alkylene oxide having 3 or more carbon atoms, preferably propylene oxide, in the presence of a composite metal cyanide complex catalyst.
In the polyether monol, the polyoxyalkylene monol having a high hydroxyl value and the polyoxyalkylene monol having a high hydroxyl value as the initiator can also be produced by using an alkali catalyst such as potassium hydroxide.

In the production of polyoxyalkylene monool, the initiator and alkylene oxide to be added to the reaction system are usually ones with low moisture content, with moisture removed by degassing under reduced pressure or the like. Usually, the lower the moisture content of the initiator in the production of polyoxyalkylene monool, the better, preferably 500 ppm by mass or less, more preferably 300 ppm by mass or less. If the moisture content is within the above range, the amount of polyoxyalkylene diol produced from water is suppressed, and as a result, the amount of by-products caused by polyoxyalkylene diol is suppressed, and it is easy to adjust the upper limit of the average number of hydroxyl groups in the obtained polyoxyalkylene monool to 1.2 or less.

The lower the water content of polyether monol (i-1) used as the raw material for monomer 1-1, the better. It is preferably 300 mass ppm or less, more preferably 250 mass ppm or less, and even more preferably 50 to 200 mass ppm relative to polyether monol (i-1). When the water content is within the above range, the generation of by-products of water and isocyanate group-containing compounds is low, and the stability of monomer 1-1, which is the reaction product, is improved. Furthermore, it is easy to suppress changes in the appearance of the curable resin composition over time, and it is easy to obtain a cured product of the curable resin composition with high toughness.

The average number of hydroxyl groups in one molecule of the polyether monol (i-1) is preferably 0.80 to 1.20, more preferably 0.90 to 1.10.
The hydroxyl value of the polyether monool (i-1) is preferably from 1.6 to 18.1 mgKOH/g, more preferably from 2.8 to 14.0 mgKOH/g, and further preferably from 3.1 to 11.2 mgKOH/g.

The polyether monool (i-1) in monomer 1-1 may be a mixture of two or more polyether monools. In this case, each polyether monool is preferably a polyoxyalkylene monool that falls within the above category.

An example of polyether monool (i-1) is one represented by formula (1a).

In formula (1a), R ¹² , R ¹³ and a have the same symbols as those in formula (1).

(Compound (i-2) Having a (Meth)acryloyloxy Group)
The compound (i-2) having a (meth)acryloyloxy group is a compound having one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule. The compound (i-2) having a (meth)acryloyloxy group is preferably a (meth)acrylate having an isocyanate group bonded to an aliphatic hydrocarbon group or an alicyclic hydrocarbon group, more preferably an isocyanate alkyl (meth)acrylate.
The number of carbon atoms in the alkylene group excluding the isocyanate group of the isocyanatoalkyl group is preferably 8 or less, and more preferably 4 or less.

An example of the compound (i-2) having a (meth)acryloyloxy group is a compound represented by formula (1b).

In formula (1b), R ¹¹ is a hydrogen atom or a methyl group, and is preferably a hydrogen atom.
s is an integer of 1 to 4, preferably 1 or 2.

Specific examples of the compound (i-2) having a (meth)acryloyloxy group include 2-isocyanate ethyl (meth)acrylate, isocyanate methyl methacrylate, etc. Commercially available products include, for example, Karenz AOI (registered trademark; hereafter abbreviated) and Karenz MOI (registered trademark) (both manufactured by Showa Denko K.K.).

An example of the compound (i-2) having a (meth)acryloyloxy group is a compound represented by formula (1c).

In formula (1c), R ¹¹ is a hydrogen atom or a methyl group, and is preferably a hydrogen atom.
R ¹⁴ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and is preferably a methyl group.
t is an integer of 1 to 8, preferably an integer of 1 to 4, and more preferably an integer of 1 to 2.
u is an integer of 0 to 4, preferably an integer of 0 to 2.

Specific examples of the compound (i-2) having a (meth)acryloyloxy group include 2,2-(bisacryloyloxymethyl)propyl isocyanate and 1,1-(bisacryloyloxymethyl)ethyl isocyanate (product name "Kalends BEI (registered trademark)", manufactured by Showa Denko KK), and preferably 1,1-(bisacryloyloxymethyl)ethyl isocyanate.

For example, when polyether monool (i-1) is polyoxypropylene monool, monomer 1-1 is preferably one or more selected from the compounds represented by formula (1-1-1), formula (1-1-2) and formula (1-1-3).

In formula (1-1-1), formula (1-1-2), and formula (1-1-3), m, n1, and n2 each independently represent an integer of preferably 20 to 600, more preferably an integer of 35 to 500, and even more preferably an integer of 65 to 250.
Bu is a butyl group.

<Monomer 1-2>
Monomer 1-2 is a reaction product of (ii), which is an equimolar reaction product of polyether monool (ii-1), diisocyanate (ii-2) and a compound (ii-3) having a (meth)acryloyloxy group, and the compound (ii-3) having a (meth)acryloyloxy group is a compound having one group reactive with an isocyanate group per molecule and having one or two (meth)acryloyloxy groups per molecule.

As monomer 1-2, a compound represented by formula (2) is preferred.

In formula (2), ^R2 is a monovalent organic group having one or two (meth)acryloyloxy groups.
R ²² is preferably an alkylene group having 2 to 8 carbon atoms, more preferably an alkylene group having 2 to 4 carbon atoms. A plurality of R ²² present in one molecule may be the same or different. When two or more types of R ²² are present in one molecule, the chain of -OR ²² - may be block or random. R ²² is preferably selected from an ethylene group, a propylene group, a 1,2-dimethylethylene group, and a 1-ethylethylene group, more preferably one or more types selected from an ethylene group and a propylene group.
Similarly to (OR ¹² ) in formula (1), (OR ²² ) is also preferably a unit based on a monomer a having one epoxy group and an ether bond other than the ether bond of the epoxy group in one molecule. The preferred embodiment of the monomer a is the same as that of the monomer 1-1.
R ²³ is an alkyl group having 1 to 20 carbon atoms, preferably an alkyl group having 2 to 8 carbon atoms, and more preferably a butyl group.
^R24 is a divalent group obtained by removing two isocyanate groups from a diisocyanate. Examples of diisocyanates will be described later.
b is an integer of 20 to 600, preferably an integer of 35 to 500, and more preferably an integer of 65 to 250.

(Polyether monol (ii-1))
The polyether monol (ii-1) is the same as the polyether monol (i-1) in the monomer 1-1, and the preferred embodiments are also the same.

An example of the polyether monool (ii-1) is one represented by formula (2a).

In formula (2a), R ²² , R ²³ and b have the same meanings as the same symbols in formula (2).

(Diisocyanate (ii-2))
The diisocyanate (ii-2) is a compound having two isocyanate groups in one molecule.
Examples of the diisocyanate (ii-2) include non-yellowing aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and various modified products of these diisocyanates (modified products having two isocyanate groups). The diisocyanates may be used alone or in combination of two or more.
From the viewpoint of toughness of the cured product of the curable resin composition, the diisocyanate (ii-2) is preferably at least one selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates.

Specific examples of non-yellowing aromatic diisocyanates include xylylene diisocyanate and tetramethylxylylene diisocyanate.
Specific examples of the aliphatic diisocyanate include 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate.
Alicyclic diisocyanates include isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 2,5-norbornane diisocyanate, and 2,6-norbornane diisocyanate.

An example of diisocyanate (ii-2) is a compound represented by formula (2b).

In formula (2b), R ²⁴ has the same meaning as the same symbol in formula (2).
As the diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate are preferred from the viewpoint of toughness of the cured product of the curable resin composition.

(Compound (ii-3) Having a (Meth)acryloyloxy Group)
The compound (ii-3) having a (meth)acryloyloxy group is a compound having one group reactive with an isocyanate group in one molecule and having one or two (meth)acryloyloxy groups in one molecule.
Examples of the group that reacts with an isocyanate group include a hydroxyl group and an amino group having a nitrogen atom bonded to a hydrogen atom. The number of hydroxyl groups and the number of hydrogen atoms bonded to the nitrogen atom in the group that reacts with an isocyanate group are preferably each 1. Furthermore, the group that reacts with an isocyanate group is preferably a hydroxyl group bonded to an aliphatic hydrocarbon group or an alicyclic hydrocarbon group.

As the compound (ii-3) having a (meth)acryloyloxy group, hydroxyalkyl (meth)acrylates and hydroxycycloalkyl (meth)acrylatenates are preferred, and hydroxyalkyl (meth)acrylates in which the hydroxyalkyl group has 8 or less carbon atoms are particularly preferred.

An example of the compound (ii-3) having a (meth)acryloyloxy group is a compound represented by formula (2c).

In formula (2c), R ²¹ is a hydrogen atom or a methyl group, and is preferably a hydrogen atom.
p is an integer of 1 to 4, and preferably an integer of 1 or 2.

Specific examples of the compound (ii-3) having a (meth)acryloyloxy group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate. Commercially available products include Light Ester HO-250(N), Light Ester HOP(N), Light Ester HOA(N), Light Ester HOP-A(N), and Light Ester HOB(N) (all manufactured by Kyoeisha Chemical Co., Ltd.), and 4-HBA (manufactured by Osaka Organic Chemical Industry Ltd.).

An example of the compound (ii-3) having a (meth)acryloyloxy group is a compound represented by formula (2d).

In formula (2d), R ²¹ is a hydrogen atom or a methyl group, and is preferably a hydrogen atom.
R ²⁵ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and is preferably a methyl group.
q is an integer of 1 to 8, preferably an integer of 1 to 4, and more preferably an integer of 1 to 2.
r is an integer of 0 to 4, preferably an integer of 0 to 2.

Specific examples of the compound (ii-3) having a (meth)acryloyloxy group include 2,2-(bisacryloyloxymethyl)propan-1-ol and 1,1-(bisacryloyloxymethyl)ethane-1-ol, with 1,1-(bisacryloyloxymethyl)ethane-1-ol being preferred.

<Monomer 1-3>
Monomer 1-3 is a reaction product of (iii), and is an equimolar reaction product of polyether polyol (iii-1) and a compound (iii-2) having a (meth)acryloyloxy group, and the compound (iii-2) having a (meth)acryloyloxy group is a compound having one isocyanate group per molecule and one or two (meth)acryloyloxy groups per molecule.

As the monomer 1-3, a compound represented by the formula (III) is preferable.
R ³ -NH-C(=O)-Z ¹ ...(III)
In formula (III), ^R3 is a monovalent organic group having one or two (meth)acryloyloxy groups.
^Z1 is a residue of a polyether polyol obtained by removing one hydrogen atom from one of the hydroxyl groups in the polyether polyol.

More preferably, monomer 1-3 is a compound represented by formula (3).

In formula (3), ^R3 is the same as ^R3 in formula (III).
R ³² is preferably an alkylene group having 2 to 8 carbon atoms, more preferably an alkylene group having 2 to 4 carbon atoms. A plurality of R ³² present in one molecule may be the same as or different from each other. When two or more types of R ³² are present in one molecule, the chain of -OR ³² - may be block or random. R ³² is preferably one or more types selected from an ethylene group, a propylene group, a 1,2-dimethylethylene group, and a 1-ethylethylene group, more preferably one or more types selected from an ethylene group and a propylene group.
Similarly to (OR ¹² ) in formula (1), (OR ³² ) is also preferably a unit based on a monomer a having one epoxy group and an ether bond other than the ether bond of the epoxy group in one molecule. The preferred embodiment of the monomer a is the same as that of the monomer 1-1.
c is an integer of 20 to 600, preferably an integer of 35 to 500, and more preferably an integer of 65 to 250.

(Polyether polyol (iii-1))
The polyether polyol (iii-1) is a compound obtained by ring-opening polymerization of an alkylene oxide and/or the monomer a with an initiator having an active hydrogen-containing group and having two or more active hydrogens, and having an initiator residue, a polyether chain, and hydroxyl groups corresponding to the number of active hydrogens of the initiator.

The alkylene oxide is preferably an alkylene oxide having a carbon number of 2 to 4. Specific examples of the alkylene oxide having a carbon number of 2 to 4 include propylene oxide, ethylene oxide, 1,2-butylene oxide, and 2,3-butylene oxide.
Moreover, the monomer a is preferably a monomer represented by the above formula (12). Examples of the monomer represented by formula (12) include methyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, lauryl glycidyl ether, and hexyl glycidyl ether. From the viewpoint of toughness of the cured product of the curable resin composition, butyl glycidyl ether or 2-ethylhexyl glycidyl ether is preferable.

When the alkylene oxide and the monomer a undergo ring-opening polymerization, the ratio of the mass of the monomer a to the total mass of the two is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 10 to 80% by mass, from the viewpoint of the toughness of the cured product of the curable resin composition.

The active hydrogen-containing group of the initiator includes a hydroxyl group, a carboxyl group, and an amino group having a hydrogen atom bonded to a nitrogen atom. The active hydrogen-containing group of the initiator is preferably a hydroxyl group, more preferably an alcoholic hydroxyl group.

Examples of initiators having two or more active hydrogen atoms include water, polyhydric alcohols, polyhydric phenols, polycarboxylic acids, and amine compounds having two or more hydrogen atoms bonded to nitrogen atoms. The initiator is preferably water or a dihydric aliphatic alcohol, more preferably a dihydric aliphatic alcohol. A polyoxyalkylene polyol having a lower molecular weight than the target polyether polyol may also be used as the initiator.

The carbon number of the dihydric aliphatic alcohol used as the initiator is preferably 2 to 8. Specific examples of the dihydric aliphatic alcohol used as the initiator include ethylene glycol, propylene glycol, polypropylene glycol such as dipropylene glycol, and 1,4-butanediol.

The oxyalkylene groups in the polyether polyol (iii-1) are preferably composed of only oxypropylene groups, or a combination of oxypropylene groups and other groups. The oxyalkylene groups other than oxypropylene groups are preferably one or more selected from oxyethylene groups and oxytetramethylene groups. The ratio of oxypropylene groups to all oxyalkylene groups in the polyether polyol is preferably 50 to 100 mass%, more preferably 80 to 100 mass%.
When the initiator is a polyoxyalkylene polyol having a lower molecular weight than the target polyether polyol, the oxyalkylene group in the initiator is regarded as the oxyalkylene group in the obtained polyether polyol.

Among the polyether polyols (iii-1), a polyoxyalkylene polyol having a low hydroxyl value, i.e., a high molecular weight, can be produced by ring-opening polymerization of an alkylene oxide having 3 or more carbon atoms, preferably propylene oxide, as an initiator in the presence of a composite metal cyanide complex catalyst.
Examples of polyoxyalkylene polyols having a low hydroxyl value include polyoxyalkylene polyols having a hydroxyl value of 40 mgKOH/g or less.
Of the polyether polyols (iii-1), a polyoxyalkylene polyol having a low hydroxyl value and an oxyethylene group can be produced by ring-opening polymerization of an alkylene oxide having 3 or more carbon atoms, preferably propylene oxide, using a polyoxyalkylene polyol having a high hydroxyl value and an oxyethylene group, for example a hydroxyl value of 50 mgKOH/g or more, as an initiator in the presence of a composite metal cyanide complex catalyst.
Among the polyether polyols (iii-1), the polyoxyalkylene polyol having a high hydroxyl value and the polyoxyalkylene polyol having a high hydroxyl value serving as the initiator can also be produced using an alkali catalyst such as potassium hydroxide.

The average number of hydroxyl groups in one molecule of the polyether polyol (iii-1) is preferably 1.60 to 2.00, more preferably 1.70 to 2.00, and even more preferably 1.80 to 1.96. A polyether polyol having an average number of hydroxyl groups in one molecule of 1.60 to 2.00 is sometimes called a polyether diol.
The hydroxyl value of the polyether polyol (iii-1) is preferably from 1.6 to 18.1 mgKOH/g, more preferably from 2.8 to 14 mgKOH/g.

Polyether polyol (iii-1) may be a mixture of two or more polyether polyols. In this case, each polyether polyol is preferably a polyether polyol that falls within the above category.

An example of polyether polyol (iii-1) is one represented by formula (3a).

In formula (3a), R ³² and c have the same meanings as the same symbols in formula (3).

(Compound (iii-2) Having a (Meth)acryloyloxy Group)
The compound (iii-2) having a (meth)acryloyloxy group is a compound having one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule. The compound (iii-2) having a (meth)acryloyloxy group is the same as the compound (i-2) having a (meth)acryloyloxy group in the monomer 1-1, and the preferred embodiments are also the same.

From the viewpoint of obtaining a cured epoxy resin product having high toughness and excellent heat resistance, the content of the monofunctional urethane (meth)acrylate in the curable resin composition is preferably 0.1 to 25 parts by mass, more preferably 0.5 to 20 parts by mass, and even more preferably 1 to 15 parts by mass, per 100 parts by mass of the epoxy compound.

From the viewpoint of toughness and excellent heat resistance of the cured product of the curable resin composition (epoxy resin), the molecular weight of the monofunctional urethane (meth)acrylate is preferably 3,000 to 30,000, more preferably 4,000 to 25,000, and even more preferably 5,000 to 20,000. When two or more types of monomers (monofunctional urethane (meth)acrylates) are used in combination, it is preferable that the molecular weight of each is within the above range.

From the viewpoint of obtaining a cured epoxy resin having high toughness and excellent heat resistance, the monofunctional urethane (meth)acrylate preferably has a glass transition temperature of −55° C. or lower, more preferably −85 to −58° C., and even more preferably −80 to −60° C.
The glass transition temperature of the monofunctional urethane (meth)acrylate in the present invention is a value determined by dynamic viscoelasticity measurement of a homopolymer of the monofunctional urethane (meth)acrylate. Specifically, it is determined by the method described in the examples.

[Epoxy resin hardener]
As the epoxy resin curing agent, a known one can be used, and examples thereof include amines, imidazoles, acid anhydrides, cationic polymerization initiators, etc., depending on the type of epoxy compound and the use of the cured product of the curable resin composition, etc. Among these, cationic polymerization initiators are preferably used from the viewpoint of good curability, etc.

As the cationic polymerization initiator, a photo-induced cationic polymerization initiator or a thermal cationic polymerization initiator is preferably used. When the epoxy resin curing agent is a photo-induced cationic polymerization initiator, the radical polymerization initiator described below is preferably a photo-induced radical polymerization initiator, and when the epoxy resin curing agent is a thermal cationic polymerization initiator, the radical polymerization initiator is preferably a thermal radical polymerization initiator. In other words, it is preferable that both the cationic polymerization initiator and the radical polymerization initiator are photo-induced polymerization initiators or thermal polymerization initiators. The cationic polymerization initiator and the radical polymerization initiator share a common absorbed energy source for initiating polymerization, so that a cured product of the curable resin composition can be efficiently obtained.

When a photopolymerization initiator is used, the curable resin composition can be cured quickly without heating to a high temperature, and the curable resin composition does not suffer thermal damage to the periphery thereof. As the photopolymerization initiator, one that can be used by irradiation with ultraviolet light having a wavelength of 380 nm or less is preferable from the viewpoint of controlling the polymerization reaction.
On the other hand, when a thermal polymerization initiator is used, the curable resin composition can be cured by heating, etc., even in a location where it is difficult to irradiate with ultraviolet light, visible light, etc. As the thermal polymerization initiator, one that can be used by heating within a range of 50 to 120° C. is preferable from the viewpoint of controlling the polymerization reaction.

<Photocationic Polymerization Initiator>
The cationic photopolymerization initiator has a structure in which a cationic moiety that absorbs light and an anionic moiety that serves as a source of acid generation are paired, and is also called a photoacid generator.
Examples of the photocationic polymerization initiator include diazonium salt compounds, iodonium salt compounds, sulfonium salt compounds, phosphonium salt compounds, selenium salt compounds, oxonium salt compounds, ammonium salt compounds, bromine salt compounds, etc. These may be used alone or in combination of two or more.

Of these, from the viewpoint of good curing properties, sulfonium salt compounds are preferably used. Examples of sulfonium salt compounds include arylsulfonium salts such as (4-hydroxyphenyl)methylbenzylsulfonium salt, triphenylsulfonium salt, diphenyl[4-(phenylthio)phenyl]sulfonium salt, 4-(4-biphenylylthio)phenyl-4-biphenylylphenylsulfonium salt, and tri-p-tolylsulfonium salt, with triarylsulfonium salt being preferred.

Examples of the anion moiety of the photocationic polymerization initiator include [(Y) _s1B (Phf) _4-s1 ] ^- (wherein Y is a phenyl group or a biphenylyl group; Phf is a phenyl group in which one or more hydrogen atoms are substituted with one or more selected from a perfluoroalkyl group, a perfluoroalkoxy group, and a halogen atom; s1 is an integer from 0 to 3), _BF4- ^, [(Rf) _{s2PF6 -s2} ] ^- (Rf is an alkyl group in which 80% or more of the hydrogen atoms are substituted with fluorine atoms; s2 is an integer from 0 to 5), _AsF6- ^, _SbF6- ^, _SbF5OH- ^, and the like.

Specific examples of the photocationic polymerization initiator include (4-hydroxyphenyl)methylbenzylsulfonium tetrakis(pentafluorophenyl)borate, 4-(4-biphenylylthio)phenyl-4-biphenylylphenylsulfonium tetrakis(pentafluorophenyl)borate, 4-(phenylthio)phenyldiphenylsulfonium phenyltris(pentafluorophenyl)borate, [4-(4-biphenylylthio)phenyl]-4-biphenylylphenylsulfonium phenyltris(pentafluorophenyl)borate, diphenyl[4-(phenylthio)phenylsulfonium] hexafluoroantimonate, diphenyl[4-(phenylthio)phenyl]sulfonium tris(pentafluoroethyl)trifluorophosphate, diphenyl[4-(phenylthio)phenyl]sulfonium tetrakis(pentafluorophenyl)borate, and diphenyl[4-(phenylthio)phenyl]sulfonium. hexafluorophosphate, 4-(4-biphenylylthio)phenyl-4-biphenylylphenylsulfonium tris(pentafluoroethyl)trifluorophosphate, bis[4-(diphenylsulfonio)phenyl]sulfide phenyltris(pentafluorophenyl)borate, [4-(2-thioxanthonylthio)phenyl]phenyl-2-thioxanthonylsulfonium phenyltris(pentafluorophenyl)borate, and the like.
In addition, for example, commercially available products such as those under the trade names "CPI (registered trademark; hereinafter, abbreviated)-101A", "CPI-100P", "CPI-110P", and "CPI-200K" (all manufactured by San-Apro Co., Ltd.), "CYRACURE UVI-6990", "CYRACURE UVI-6992" (all manufactured by Dow Chemical Co., Ltd.), "UVACURE1590" (manufactured by Daicel-Allnex Co., Ltd.), "CD-1010", "CD-1011", and "CD-1012" (all manufactured by Arkema), "Irgacure (registered trademark; hereinafter, abbreviated) 264" (manufactured by BASF Corporation), "CIT-1682" (manufactured by Nippon Soda Co., Ltd.), and "PHOTOINITIATOR 2074" (manufactured by Rhodia Japan Co., Ltd.) are preferably used.

<Thermal cationic polymerization initiator>
The thermal cationic polymerization initiator is a compound that generates an acid when heated to initiate a polymerization reaction of an epoxy compound, and has a configuration in which a cationic portion that absorbs heat is paired with an anionic portion that serves as the source of acid generation.

Examples of thermal cationic polymerization initiators include iodonium salt compounds and sulfonium salt compounds. These may be used alone or in combination of two or more.

Examples of the cationic moiety of the thermal cationic polymerization initiator include 4-hydroxyphenyl-methyl-benzylsulfonium ion, 4-hydroxyphenyl-methyl-(2-methylbenzyl)sulfonium ion, 4-hydroxyphenyl-methyl-1-naphthylmethylsulfonium ion, and p-methoxycarbonyloxyphenyl-benzyl-methylsulfonium ion.
Specific examples of the anion moiety of the thermal cationic polymerization initiator include the same as the examples of the anion moiety of the photocationic polymerization initiator described above.

Specific examples of thermal cationic polymerization initiators include 4-hydroxyphenyl-methyl-benzylsulfonium phenyltris(pentafluorophenyl)borate, 4-hydroxyphenyl-methyl-(2-methylbenzyl)sulfonium phenyltris(pentafluorophenyl)borate, 4-hydroxyphenyl-methyl-1-naphthylmethylsulfonium phenyltris(pentafluorophenyl)borate, and p-methoxycarbonyloxyphenyl-benzyl-methylsulfonium phenyltris(pentafluorophenyl)borate.

From the viewpoint of an appropriate curing speed, the content of the epoxy resin curing agent in the curable resin composition is preferably 0.001 to 20 parts by mass, more preferably 0.01 to 10 parts by mass, and even more preferably 0.1 to 7 parts by mass, per 100 parts by mass of the total of the monomer components constituting the curable resin.

[Radical Polymerization Initiator]
The radical polymerization initiator initiates addition polymerization of the monofunctional urethane (meth)acrylate. As the radical polymerization initiator, a known one can be used, and a photoradical polymerization initiator or a thermal radical polymerization initiator is preferably used.

<Photoradical polymerization initiator>
Examples of the photoradical polymerization initiator include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methylpropiophenone, diethoxyacetophenone, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropanone, 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropanone, 4-(2-hydroxyethoxy)-phenyl(2-hydroxy-2-propyl)ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin-n -butyl ether, benzoin phenyl ether, benzyl dimethyl ketal, benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone-4-methoxybenzophenone, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, methylphenyl glyoxylate, benzyl, camphorquinone, and the like.
In addition, for example, commercially available products such as those having the trade names "Irgacure 184", "Irgacure 127", "Irgacure 149", "Irgacure 261", "Irgacure 369", "Irgacure 500", "Irgacure 651", "Irgacure 754", "Irgacure 784", "Irgacure 819", "Irgacure 907", "Irgacure 1116", "Irgacure 1173", "Irgacure 1664", "Irgacure 1700", "Irgacure 1800", "Irgacure 1850", "Irgacure 2959", "Irgacure 4043", "Darocure (registered trademark; hereinafter, abbreviated) 1173", and "Darocure MBF" (all manufactured by BASF Corporation) are preferably used.

<Thermal Radical Polymerization Initiator>
Examples of the thermal radical polymerization initiator include azo compounds; and organic peroxides such as hydroperoxides, dialkyl peroxides, peroxy esters, diacyl peroxides, peroxydicarbonates, peroxyketals, and ketone peroxides. Specific examples of the thermal radical polymerization initiator include azobisisobutyronitrile, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-di(2-ethylhexanoyl)peroxyhexane, t-butylperoxybenzoate, t-butyl peroxide, cumene hydroperoxide, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-dibutylperoxyhexane, 2,4-dichlorobenzoyl peroxide, 1,4-di(2-t-butylperoxyisopropyl)benzene, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, methyl ethyl ketone peroxide, and 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate.

From the viewpoint of an appropriate polymerization rate, the content of the radical polymerization initiator in the curable resin composition is preferably 0.001 to 20 parts by mass, more preferably 0.01 to 18 parts by mass, and even more preferably 0.1 to 15 parts by mass, per 100 parts by mass of the monofunctional urethane (meth)acrylate. Also, the content is preferably 0.001 to 2 parts by mass, more preferably 0.005 to 1 part by mass, and even more preferably 0.01 to 1 part by mass, per 100 parts by mass of the total of the monomer components constituting the curable resin.

[Other ingredients]
The curable resin composition may contain other components in addition to the epoxy compound, the monofunctional urethane (meth)acrylate, the epoxy resin curing agent and the radical polymerization initiator from the viewpoint of good handling and improvement of the toughness and heat resistance of the cured product. Examples of the other components include other monomer components other than the epoxy compound and the monofunctional urethane (meth)acrylate, colorants such as pigments and dyes, silane coupling agents, tackifier resins, antioxidants, light stabilizers, metal deactivators, rust inhibitors, antiaging agents, moisture absorbents, hydrolysis inhibitors, antistatic agents, defoamers, fillers, etc. These other components in the curable resin composition may be blended in a content within a range that does not impair the effects of the present invention.
The curable resin composition may contain a solvent, but from the viewpoints of drying property and suppression of deterioration of surrounding members during curing, it is preferable that the composition does not contain a solvent, particularly when the composition is used for three-dimensional modeling, etc. The content of the solvent is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 1 part by mass or less, per 100 parts by mass of the curable resin composition.

<Other monomer components>
The other monomer components are compounds which copolymerize with the epoxy compound and the monofunctional urethane (meth)acrylate, and may be used alone or in combination of two or more kinds.
As the other monomer component, for example, any of the monomer components exemplified in paragraphs [0036] to [0043] of JP-A No. 2019-513842 can be used, and examples thereof include (meth)acrylates such as polyfunctional urethane (meth)acrylates having two or more (meth)acryloyloxy groups, alkyl (meth)acrylates, hydroxyl group-containing (meth)acrylates, and amino group-containing (meth)acrylates.

[Method for producing curable resin composition]
The curable resin composition of the present invention can be produced by uniformly mixing the epoxy compound, the monofunctional urethane (meth)acrylate, the epoxy resin curing agent, the radical polymerization initiator, and other components as necessary, using a known mixing device such as a self-revolving stirring and defoaming device, a homogenizer, a planetary mixer, a three-roll mill, a bead mill, etc. The components in the curable resin composition may be mixed simultaneously or by successive addition.

When the epoxy resin curing agent is a photocationic polymerization initiator and the radical polymerization initiator is a photoradical polymerization initiator, the curable resin composition can be suitably used for optical three-dimensional modeling.

[Cured product of curable resin composition]
The cured product of the present invention can be obtained by subjecting the above-mentioned curable resin composition of the present invention to light irradiation or heat treatment, which quickly cures the composition.

When the curable resin composition is irradiated with light to cure, the light source can be appropriately set according to the light absorption ability of the photopolymerization initiator, and for example, ultraviolet light emitting diodes (LEDs), low pressure mercury lamps, high pressure mercury lamps, mercury xenon lamps, metal halide lamps, tungsten lamps, arc lamps, excimer lamps, excimer lasers, semiconductor lasers, YAG lasers, laser systems combining lasers with nonlinear optical crystals, high frequency induced ultraviolet generators, etc. can be used as light sources. The integrated light amount is, for example, about 0.01 to 5 J/ ^cm2 .
After the light irradiation, a heat treatment may be further performed. By performing a heat treatment, the curing can be improved. Usually, the heating temperature is about 40 to 200°C, and the heating time is about 1 minute to 15 hours. Also, the curing property can be improved by leaving the composition at room temperature (about 15 to 25°C) for about 1 to 48 hours.

When the curable resin composition is cured by heat treatment, the heating temperature is usually about 40 to 250°C, and the heating time is about 5 minutes to 24 hours. Preferably, the heating time is shortened when the heating temperature is high, and the heating time is lengthened when the heating temperature is low.

[Application]
The curable resin composition can be used for known applications of epoxy resins, such as insulating materials and sealing materials in electronic devices, adhesives, pressure sensitive adhesives, paints, etc. It can also be suitably used as a molding material for obtaining a molded body by optical three-dimensional modeling using a 3D printer or the like.
Examples of the uses of the cured product of the curable resin composition and the cured product include various substrates such as metals, resin films, glass, paper, and wood having a cured coating film of the coating material; surface protective films, hard coats, antifouling films, and antireflection films for semiconductor elements, organic electroluminescence elements, and organic thin-film solar cell elements; various optical members such as lenses, prisms, filters, optical waveguides, light guide plates, light diffusion plates, and diffraction elements; interlayer insulators; protective insulating films for printed alignment substrates; casting materials, etc. Also included are fiber-reinforced composite materials obtained by curing fiber substrates (e.g., glass fibers, carbon fibers, aramid fibers, boron fibers, etc.) impregnated with the curable resin composition, and articles including the fiber-reinforced composite materials.
In such articles and applications, the excellent properties of the cured product of the curable resin composition of the present invention, namely, high toughness and excellent heat resistance, can be satisfactorily exhibited.

The present invention will be described in detail below based on examples, but the present invention is not limited to the following examples.

[Production of curable resin composition]
Curable resin compositions were prepared according to the following synthesis examples and examples.

Synthesis Example 1 Synthesis of Monofunctional Urethane Acrylate 0.5 g of zinc hexacyanocobaltate-tert-butyl alcohol complex and 112 g of n-butanol as an initiator were placed in a pressure-resistant reactor equipped with a stirrer and a nitrogen inlet tube, and 4887 g of propylene oxide (hereinafter abbreviated as "PO") was added at a constant rate under a nitrogen atmosphere at 130°C to obtain intermediate A. 1148 g of intermediate A and 0.2 g of DMC-TBA were placed in a pressure-resistant vessel, and 1997 g of PO and 856 g of ethylene oxide (hereinafter abbreviated as "EO") were added at a constant rate over 5.5 hours under a nitrogen atmosphere at 130°C.
It was confirmed that the internal pressure of the pressure-resistant reactor had stopped decreasing, and polyether monol (hydroxyl value: 5.23 mg KOH/g, hydroxyl value-based molecular weight: 10,730, average number of hydroxyl groups: 1.08, EO constitutional units: 21% by mass) was obtained.
Into a reaction vessel equipped with a stirrer and a nitrogen inlet tube, 296.1 g of the polyether monol, 3.90 g (NCO index 100) of 2-acryloyloxyethyl isocyanate ("Karenz AOI", manufactured by Showa Denko K.K.), and 0.024 g of a 25% by mass toluene solution of bismuth 2-ethylhexanoate were placed and stirred at 70° C. for 3 hours to obtain a monofunctional urethane acrylate (number average molecular weight 16,230, glass transition temperature -74° C.).

The number average molecular weight of the obtained monofunctional urethane acrylate was measured by gel permeation chromatography (GPC) under the following measurement conditions.
<Measurement conditions>
Equipment used: "HLC-8120GPC", manufactured by Tosoh Corporation Columns used: The following two types of columns were connected in series in this order: "TSKgel (registered trademark) G7000H _XL ", manufactured by Tosoh Corporation, 1 column "TSKgel (registered trademark) GMH _XL ", manufactured by Tosoh Corporation, 2 columns Column temperature: 40°C
Detector: Refractive index (RI) detector Eluent: Tetrahydrofuran Flow rate: 0.8 mL/min Sample concentration: 0.5% by mass
Sample injection volume: 100 μL
・Standard sample: polystyrene

The glass transition temperature of the monofunctional urethane acrylate was determined by dynamic viscoelasticity measurement as follows.
0.3 parts by mass of a photoradical polymerization initiator ("Irgacure 819", manufactured by BASF) was added to 100 parts by mass of a monofunctional urethane acrylate, and mixed with a planetary stirrer. The resulting mixture was irradiated under a nitrogen gas atmosphere with a conveyor-type UV irradiator (manufactured by Oak Manufacturing Co., Ltd.; mercury xenon lamp, illuminance 100 mW/ ^cm2 , accumulated light amount 3 J/ ^cm2 ) to obtain a cured sample of the monofunctional urethane acrylate (homopolymer; length 15 mm, width 5 mm, thickness 2 mm).
The loss modulus of the cured sample was measured using a dynamic viscoelasticity measuring device ("EXSTAR TMA/SS6100", manufactured by Seiko Instruments Inc.; tensile mode, temperature range: -80 to 130°C, heating rate: 3°C/min, measurement frequency: 1 Hz), and the temperature at the peak was taken as the glass transition temperature.

[Examples 1 to 5] Preparation of curable resin compositions Curable resin compositions were prepared by blending the components according to the blending compositions shown in Table 1. Examples 1 and 2 are working examples, and Examples 3 to 5 are comparative examples.
Details of each component are as follows:
Epoxy compound: bisphenol A diglycidyl ether Monofunctional urethane acrylate: produced in Synthesis Example 1 Polyether polyol: polypropylene glycol; "Preminol (registered trademark) S4011", manufactured by AGC Inc.; molecular weight calculated based on hydroxyl value: 10,190
Epoxy resin curing agent: triarylsulfonium salt of special phosphorus anion having perfluoroalkyl group; "CPI-200K" manufactured by San-Apro Co., Ltd.; photocationic polymerization initiator (photoacid generator), 50 mass% propylene carbonate solution Radical polymerization initiator: 2-hydroxy-2-methylpropiophenone; "Irgacure 1173" manufactured by BASF; photoradical polymerization initiator

[evaluation]
Test specimens were prepared using each of the curable resin compositions produced in Examples 1 to 5, and were evaluated by the following tests. The evaluation results are shown in Table 1.
[Preparation of test specimen]
The curable resin composition was poured into a mold with a polyethylene film attached, and the polyethylene film side of the glass plate with the polyethylene film attached was placed on top of the curable resin composition. Under a nitrogen gas atmosphere, ultraviolet light was irradiated from the glass plate side using a conveyor-type UV irradiator (manufactured by Oak Manufacturing Co., Ltd.; mercury xenon lamp, illuminance 100 mW/cm ² , cumulative light amount 3 J/cm ² ). After leaving it for 12 hours, the polyethylene films on both sides were peeled off to obtain a test specimen of the cured product of the curable resin composition with a length of 90 mm, a width of 5 mm, and a thickness of 200 μm.

[Tensile test]
A tensile test was performed on the test specimen using a tensile tester (Tensilon universal testing machine "RTG-1310", manufactured by A&D Co., Ltd.; tensile speed 300 mm/min, chuck distance 20 mm) to measure the tensile strength (TS) and breaking elongation. The higher the tensile strength and breaking elongation, the higher the toughness.

[Heat resistance test]
The test specimen was left to stand in a thermo-hygrostat (80°C, 1% RH) for 48 hours, and then the presence or absence of bleeding out on the surface of the test specimen was confirmed by visual observation. If no bleeding out occurred, it can be said that the heat resistance is excellent.

From the evaluation results shown in Table 1, it was found that the curable resin compositions containing a monofunctional urethane acrylate (Examples 1 and 2) had higher tensile strength and breaking elongation of the cured product than the uncontaining composition (Example 3), did not show any bleeding even at a high temperature of 80°C, and had improved toughness and excellent heat resistance. On the other hand, the curable resin compositions containing a polyether polyol (Examples 4 and 5) had lower tensile strength and breaking elongation of the cured product than the uncontaining composition (Example 3), showed bleeding at a high temperature of 80°C, and had poor heat resistance.

Claims (11)

The composition includes an epoxy compound, a monofunctional urethane (meth)acrylate, an epoxy resin curing agent, and a radical polymerization initiator,
The curable resin composition, wherein the monofunctional urethane (meth)acrylate is one or more monomers selected from the reaction products of the following (i) to (iii):
(i) An equimolar reaction product of a polyether monol and a compound having a (meth)acryloyloxy group,
The compound having a (meth)acryloyloxy group is a compound having one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule,
The polyether monol is a reaction product having a hydroxyl value of 1.6 to 18.1 mgKOH/g .
(ii) an equimolar reaction product of a polyether monool, a diisocyanate, and a compound having a (meth)acryloyloxy group,
The compound having a (meth)acryloyloxy group is a compound having one group reactive with an isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule,
The polyether monol is a reaction product having a hydroxyl value of 1.6 to 18.1 mgKOH/g .
(iii) an equimolar reaction product of a polyether polyol and a compound having a (meth)acryloyloxy group,
The compound having a (meth)acryloyloxy group is a compound having one isocyanate group in one molecule and one or two (meth)acryloyloxy groups in one molecule,
The polyether polyol is a reaction product having a hydroxyl value of 1.6 to 18.1 mgKOH/g . The curable resin composition according to claim 1, wherein the content of the monofunctional urethane (meth)acrylate is 0.1 to 25 parts by mass per 100 parts by mass of the epoxy compound. The curable resin composition according to claim 1 or 2, wherein the monofunctional urethane (meth)acrylate has a number average molecular weight of 3,000 to 30,000. The curable resin composition according to any one of claims 1 to 3, wherein the monofunctional urethane (meth)acrylate has a glass transition temperature of -55°C or lower. The curable resin composition according to any one of claims 1 to 4, wherein the epoxy resin curing agent is a photocationic polymerization initiator, and the radical polymerization initiator is a photoradical polymerization initiator. The curable resin composition according to any one of claims 1 to 4, wherein the epoxy resin curing agent is a thermal cationic polymerization initiator, and the radical polymerization initiator is a thermal radical polymerization initiator. The curable resin composition according to claim 5, which is for optical three-dimensional modeling. A cured product obtained by curing the curable resin composition according to any one of claims 1 to 7. An article comprising the cured product according to claim 8. A fiber-reinforced composite material obtained by curing a fiber substrate impregnated with the curable resin composition according to any one of claims 1 to 6. An article comprising the fiber-reinforced composite material according to claim 10.