WO2025033488A1 - Method for producing cured product of resin composition - Google Patents

Abstract

Provided is a method for producing a cured product of a resin composition, the method making it possible to obtain a cured product with good physical properties from a resin composition containing an ethylenically unsaturated group-containing resin. The method for producing a cured product of a resin composition according to the present invention irradiates, with light emitted from a light-emitting diode, a resin composition containing an ethylenically unsaturated group-containing resin (A), an ethylenically unsaturated group-containing monomer (B), a photopolymerization initiator (C), and a dye (D) to cure the resin composition. The dye (D) has a maximum absorption wavelength in the 400-1100 nm wavelength range. The light emitted from the light-emitting diode includes light (1) which is in the absorption wavelength range of the photoinitiator (C) and light (2) which is in the absorption wavelength range of the dye (D).

Description

Method for producing cured product of resin composition

The present invention relates to a method for producing a cured product of a resin composition containing an ethylenically unsaturated group-containing resin.

2. Description of the Related Art In recent years, deterioration of existing pipes buried underground, such as water pipes, sewer pipes, and electric power pipes, has become a serious problem, and various methods for repairing these pipes have been proposed.
For example, Patent Document 1 discloses a method for repairing existing pipes using a photocuring method, in which an impregnated base material made of fibers or the like is impregnated with a photocurable resin composition and used as a lining material, and further describes using a polymerizable resin such as an unsaturated polyester resin or vinyl ester resin dissolved in a solvent such as styrene as the photocurable resin composition.

Compared to the heat curing method, the photocuring method described above has a faster curing rate of the resin composition and a shorter construction time, so in recent years, the construction distances covered by the photocuring method in repair work on existing pipes have been increasing. In addition, compared to the heat curing method, the photocuring method has the advantages of less curing shrinkage of the resin composition, less curing failure, less heat generation during curing, and less emission of flammable gases during curing.

In the photocuring method, for example, a gallium lamp, a metal halide lamp, or a mercury lamp is used as the light source. Patent Document 2 also proposes a method of irradiating the resin layer with light using a photocuring device that uses a light-emitting diode (LED) that mainly irradiates ultraviolet light. LEDs generate little heat, are energy-saving, have a long life, and are excellent as light sources.

JP 2020-82408 A JP 2008-142996 A

However, in the conventional method of irradiating a resin composition of a lining material with LED light, the resin composition may not cure properly, or the physical properties of the resulting cured product may be insufficient.
For this reason, in order to improve the poor curing of the resin composition and to exhibit good physical properties of the cured product, the present inventors have conducted extensive research into a method for curing a resin composition using LED light.

The present invention was made under these circumstances, and aims to provide a method for producing a cured product of a resin composition that can obtain a cured product with good physical properties from a resin composition that contains an ethylenically unsaturated group-containing resin.

The present invention is based on the discovery that by adding a dye to a resin composition and photocuring it using two or more LEDs with different wavelength ranges, a cured product with good heat resistance and bending properties can be obtained.

The present invention provides the following means.
[1] A method for producing a cured product of a resin composition, comprising: irradiating a resin composition containing an ethylenically unsaturated group-containing resin (A), an ethylenically unsaturated group-containing monomer (B), a photopolymerization initiator (C), and a dye (D) with light emitted from a light-emitting diode to cure the resin composition, wherein the dye (D) has a maximum absorption wavelength in a wavelength range of 400 to 1100 nm, and the light emitted from the light-emitting diode contains light (1) in the absorption wavelength range of the photopolymerization initiator (C) and light (2) in the absorption wavelength range of the dye (D).
[2] A method for producing a cured product of the resin composition according to [1], wherein the light irradiated to the resin composition includes light in a wavelength range of 400 to 1100 nm and has at least two peak wavelengths.
[3] A method for producing a cured product of the resin composition according to [1] or [2], wherein the absorption coefficient of the resin composition for light having a maximum absorption wavelength of the dye (D) is 0.1 to 10,000 cm ⁻¹ .
[4] A method for producing a cured product of the resin composition according to any one of [1] to [3], wherein the light emitting diode that emits light (1) has a peak wavelength in the wavelength range of 250 to 400 nm.
[5] A method for producing a cured product of the resin composition according to any one of [1] to [4], wherein the light-emitting diode that emits light (2) has a peak wavelength in a wavelength range of 400 to 1,100 nm in which the ratio of the absorbance of the dye (D) to the absorbance at the maximum absorption wavelength of the dye (D) is 0.3 or more.
[6] A method for producing a cured product of the resin composition according to any one of [1] to [5], wherein the ethylenically unsaturated group-containing resin (A) is at least one selected from the group consisting of unsaturated polyester resins, vinyl ester resins, (meth)acrylic resins, and urethane (meth)acrylate resins.

According to the present invention, there is provided a method for producing a cured product of a resin composition, which can give a cured product having good physical properties from a resin composition containing an ethylenically unsaturated group-containing resin.
The manufacturing method of the present invention can be suitably applied to, for example, the repair of existing pipes by a light-curing method using a lining material.

The definitions and meanings of the terms and expressions used in this specification are given below.
The expression "X to Y" (X and Y are numerical values) means a numerical range with X as the lower limit and Y as the upper limit. With respect to a numerical range (e.g., a range of content, etc.), the lower limit and upper limit values described in stages may be combined independently. The lower limit and upper limit values of the numerical range may be replaced with numerical values described in the examples.
The term "light emitting diode (LED)" refers to an LED package, which is a light emitting electronic component in which a light emitting element is packaged.
The maximum absorption wavelength is a wavelength at which the absorbance is maximum, and is not limited to one point in an absorption spectrum, but may be two or more points. Among the maximum absorption wavelengths, the wavelength at which the absorbance is maximum is called the maximum absorption wavelength.
The peak wavelength is the wavelength at which the emission intensity of a light-emitting diode (LED) is maximized, and is not limited to one point in the emission spectrum, but may be two or more points. The wavelength at which the emission intensity is maximum among the peak wavelengths is called the maximum emission wavelength.

(Meth)acrylic acid is a general term for acrylic acid and methacrylic acid. Similarly, (meth)acrylate is a general term for acrylate and methacrylate, and (meth)acryloyl is a general term for acryloyl and methacryloyl.
The weight average molecular weight (Mw) and number average molecular weight (Mn) are standard polystyrene equivalent molecular weights determined by gel permeation chromatography (GPC). Specifically, they are measured by the method described in the examples below. The molecular weight distribution is a calculated value of Mw/Mn.
The acid value of the unsaturated polyester resin is the amount [mg] of potassium hydroxide (KOH) required to neutralize 1 g of the unsaturated polyester resin, as measured by a method in accordance with JIS K6901: 2008. Specifically, it is measured by the method described in the examples below.
The deflection temperature under load of the cured resin composition can be measured according to a method in accordance with JIS K7191-2:2015 Appendix A, specifically, by the method described in the examples.
The flexural strength and flexural modulus of the cured resin composition can be measured by a method in accordance with JIS K7171:2016, specifically, by the method described in the examples.

A method for producing a cured product of a resin composition according to an embodiment of the present invention (hereinafter also referred to as the present embodiment) includes irradiating a resin composition containing an ethylenically unsaturated group-containing resin (A), an ethylenically unsaturated group-containing monomer (B), a photopolymerization initiator (C), and a dye (D) with light emitted from an LED to cure the resin composition, wherein the dye (D) has a maximum absorption wavelength in a wavelength range of 400 to 1100 nm, and the light emitted from the LED contains light (1) in the absorption wavelength range of the photopolymerization initiator (C) and light (2) in the absorption wavelength range of the dye (D).
In this way, by adding a dye to a resin composition and photocuring it by irradiating it with light of a predetermined wavelength using an LED, a cured product with good heat resistance and bending properties can be produced.

[Resin composition]
The resin composition of the present embodiment contains an ethylenically unsaturated group-containing resin (A), an ethylenically unsaturated group-containing monomer (B), a photopolymerization initiator (C), and a dye (D).
From the viewpoint of good physical properties of a cured product, the resin composition preferably has a total content of the ethylenically unsaturated group-containing resin (A) and the ethylenically unsaturated group-containing monomer (B) of 90 mass % or more and less than 100 mass %, more preferably 92.0 to 99.9 mass %, and even more preferably 95.0 to 99.9 mass %, in the resin composition.

[Ethylenically unsaturated group-containing resin (A)]
The ethylenically unsaturated group-containing resin (A) is a resin having polymerizability due to an ethylenically unsaturated group. The ethylenically unsaturated group-containing resin (A) is not particularly limited, but may be, for example, an unsaturated polyester resin, a vinyl ester resin, a (meth)acrylic resin, or a urethane (meth)acrylate resin. The ethylenically unsaturated group-containing resin (A) may be used alone or in combination of two or more. Among these, unsaturated polyester resins and vinyl ester resins are preferred, and unsaturated polyester resins are more preferred, since they are more likely to provide good cured product properties.

From the viewpoint of good physical properties of the cured product, the content of the ethylenically unsaturated group-containing resin (A) in the resin composition is preferably 30.0% by mass or more, more preferably 40.0% by mass or more, and even more preferably 50.0% by mass or more, relative to 100% by mass of the total of the ethylenically unsaturated group-containing resin (A) and the ethylenically unsaturated group-containing monomer (B), and is preferably 80% by mass or less, more preferably 70.0% by mass or less, and even more preferably 60.0% by mass or less.

(Unsaturated polyester resin)
The unsaturated polyester resin is preferably a reaction product of a diol and a dibasic acid. The unsaturated polyester resin can be produced by applying a known synthesis method using a condensation reaction, using a diol and a dibasic acid as reaction raw materials. The unsaturated polyester resin may be used alone or in combination of two or more kinds.

<Diol>
The diol, which is a reaction raw material of the unsaturated polyester resin, is a compound having two hydroxyl groups in one molecule, and from the viewpoint of good physical properties of the cured product of the resin composition, for example, alkanediol, glycol ether, etc. are preferably used. The diol may be used alone or in combination of two or more kinds.
Examples of alkanediols include ethylene glycol, propylene glycol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 2-ethyl-1,5-pentanediol, 2,4-ethyl-1,5-pentanediol, 2,6-hexane ... Examples of the cyclohexanediol include ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol, 1,2-octanediol, 1,2-nonanediol, 1,4-cyclohexanediol, 1,8-octanediol, 1,9-nonanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2-di(4-hydroxycyclohexyl)propane, and hydrogenated products of bisphenol A, bisphenol F, and bisphenol S.
Examples of glycol ethers include diethylene glycol, dipropylene glycol, polyethylene glycol, and polypropylene glycol.
Among these, from the viewpoints of availability, ease of handling of the resin composition, production costs, and the like, 2-methyl-1,3-propanediol, ethylene glycol, propylene glycol, neopentyl glycol, diethylene glycol, dipropylene glycol, and hydrogenated bisphenol A are preferred, 2-methyl-1,3-propanediol, propylene glycol, neopentyl glycol, and hydrogenated bisphenol A are more preferred, and propylene glycol and neopentyl glycol are even more preferred.

<Dibasic Acid>
The dibasic acid as the reaction raw material for the unsaturated polyester resin preferably includes an ethylenically unsaturated group-containing dibasic acid and an ethylenically unsaturated group-free dibasic acid. The dibasic acid also includes an acid anhydride.

Unsaturated polyester resins are obtained by forming ester bonds through the reaction of 1 mole of hydroxyl groups of a diol with 1 mole of carboxyl groups of a dibasic acid, so the total amount of dibasic acid used in producing the unsaturated polyester resin is preferably 80 to 120 mole parts, more preferably 90 to 110 mole parts, and even more preferably 95 to 105 mole parts, per 100 mole parts of the diol, and may even be 100 mole parts.

Of the dibasic acids, the ethylenically unsaturated group-containing dibasic acid is preferably 30 to 80 parts by mole, more preferably 40 to 70 parts by mole, and even more preferably 45 to 65 parts by mole, per 100 parts by mole of the diol, from the viewpoint of good physical properties of the cured product of the resin composition.
From the same viewpoint, the amount of the dibasic acid not containing an ethylenically unsaturated group is preferably 20 to 70 parts by mole, more preferably 30 to 60 parts by mole, and further preferably 35 to 55 parts by mole, per 100 parts by mole of the diol.

The ethylenically unsaturated group-containing dibasic acid is a compound having two carboxy groups (including acid anhydrides) and at least one ethylenically unsaturated group in one molecule. The ethylenically unsaturated group-containing dibasic acid may be used alone or in combination of two or more kinds.
Examples of ethylenically unsaturated group-containing dibasic acids include maleic anhydride, fumaric acid, itaconic acid, citraconic acid, chloromaleic acid, etc. Among these, from the viewpoints of availability, ease of handling of the resin composition, production costs, etc., maleic anhydride and fumaric acid are preferred, and maleic anhydride is preferably used.

The content of the ethylenically unsaturated group-containing dibasic acid in the dibasic acid is, from the viewpoint of good physical properties of the cured product of the resin composition, preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, even more preferably 45 mol% or more, and is preferably 80 mol% or less, more preferably 75 mol% or less, even more preferably 70 mol% or less, even more preferably 65 mol% or less, based on 100 mol% of the dibasic acid.

The dibasic acid having no ethylenically unsaturated group is a compound having two carboxy groups (including acid anhydrides) in one molecule and having no ethylenically unsaturated group. The dibasic acid having no ethylenically unsaturated group may be used alone or in combination of two or more kinds.
Examples of dibasic acids not containing an ethylenically unsaturated group include phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, tetrahydrophthalic acid, endomethylenetetrahydrophthalic acid, hexahydrophthalic acid (1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid), naphthalenedicarboxylic acid, trimellitic acid, pyromellitic acid, chlorendic acid (HETT acid), tetrabromophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, succinic anhydride, chlorendic anhydride, trimellitic anhydride, pyromellitic anhydride, 4-methylphthalic acid, 5-methylisophthalic acid, 5-methylterephthalic acid, etc. Among these, isophthalic acid and terephthalic acid are preferred from the viewpoints of availability, ease of handling of the resin composition, and production costs.

The content of the dibasic acid not containing an ethylenically unsaturated group in the dibasic acid is, from the viewpoint of good physical properties of the cured product of the resin composition, preferably 20 mol% or more, more preferably 25 mol% or more, even more preferably 30 mol% or more, even more preferably 35 mol% or more, and is preferably 80 mol% or less, more preferably 70 mol% or less, even more preferably 60 mol% or less, even more preferably 55 mol% or less, based on 100 mol% of the dibasic acid.

From the viewpoint of ease of handling and good curing properties of the resin composition, the acid value of the unsaturated polyester resin is preferably 3.0 to 25.0 KOHmg/g, more preferably 5.0 to 20.0 KOHmg/g, and even more preferably 8.0 to 15.0 KOHmg/g.

The weight average molecular weight (Mw) of the unsaturated polyester resin is preferably 5,000 to 20,000, more preferably 7,000 to 17,000, and even more preferably 9,000 to 15,000, from the viewpoints of ease of handling of the resin composition and good physical properties of the cured product.
From the same viewpoint, the number average molecular weight (Mn) of the unsaturated polyester resin is preferably 1,000 to 7,000, more preferably 2,000 to 6,000, and further preferably 3,000 to 5,000.
From the same viewpoint, the molecular weight distribution (Mw/Mn) of the unsaturated polyester resin is preferably from 1.00 to 15.00, more preferably from 1.50 to 10.00, and further preferably from 2.00 to 5.00.

(Vinyl ester resin)
The vinyl ester resin is preferably a reaction product of an epoxy compound and an unsaturated monobasic acid. The vinyl ester resin may be a reaction product of a reaction raw material including an epoxy compound and an unsaturated monobasic acid, and further, if necessary, a bisphenol compound, an unsaturated polybasic acid, etc. The vinyl ester resin using an epoxy compound and an unsaturated monobasic acid as reaction raw materials can be produced by applying a known synthesis method using an addition reaction. The obtained vinyl ester resin is diluted with an ethylenically unsaturated group-containing monomer (B) if necessary. The vinyl ester resin may be used alone or in combination of two or more kinds.

<Epoxy Compound>
The epoxy compound, which is a reaction raw material for the vinyl ester resin, is a compound having at least two, preferably two, epoxy groups in one molecule. The epoxy compound may be used alone or in combination of two or more kinds.
Examples of epoxy compounds include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol AF type epoxy resins, tert-butylcatechol type epoxy resins, naphthalene type epoxy resins, naphthol type epoxy resins, anthracene type epoxy resins, glycidyl ester type epoxy resins, biphenyl type epoxy resins, linear aliphatic epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, heterocyclic epoxy resins, spiro ring-containing epoxy resins, cyclohexane dimethanol type epoxy resins, naphthylene ether type epoxy resins, etc. Among these, from the viewpoints of availability, ease of handling of the resin composition, and production costs, etc., bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, and bisphenol AF type epoxy resins are preferred, and bisphenol A type epoxy resins are preferably used.

From the viewpoint of ease of synthesis of the vinyl ester resin and good curing properties of the resin composition, the epoxy compound preferably has an epoxy equivalent of 170 to 1000, more preferably 170 to 500, and even more preferably 170 to 300.

<Unsaturated monobasic acid>
The unsaturated monobasic acid is preferably a monocarboxylic acid having an ethylenically unsaturated group. The unsaturated monobasic acid may be used alone or in combination of two or more kinds.
Examples of the unsaturated monobasic acid include (meth)acrylic acid, crotonic acid, cinnamic acid, etc. Among these, from the viewpoint of ease of synthesis of the vinyl ester resin and good curing property of the resin composition, (meth)acrylic acid and crotonic acid are preferred, (meth)acrylic acid is more preferred, and from the viewpoint of chemical resistance, methacrylic acid is even more preferred.

When the vinyl ester resin is a reaction product of an epoxy compound and an unsaturated monobasic acid, it is obtained by reacting 1 mole of an epoxy group of the epoxy compound with 1 mole of a carboxy group of the unsaturated monobasic acid to form an ester bond.
The amount of the unsaturated monobasic acid to be blended when producing the vinyl ester resin is preferably 30 molar parts or more, more preferably 40 molar parts or more, and even more preferably 50 molar parts or more of the carboxyl group of the unsaturated monobasic acid relative to 100 molar parts of the epoxy group of the epoxy compound from the viewpoint of good curing properties of the resin composition, and is preferably 120 molar parts or less, more preferably 110 molar parts or less, and even more preferably 105 molar parts or less from the viewpoint of making the viscosity of the resin composition easy to handle, and may be 100 molar parts relative to 100 molar parts of the epoxy group of the epoxy compound.

<Bisphenol compounds>
The vinyl ester resin preferably contains a bisphenol compound as a reaction raw material. The bisphenol compound may be used alone or in combination of two or more kinds.
Examples of bisphenol compounds include bisphenol A, bisphenol AP, bisphenol AF, bisphenol B, bisphenol BP, bisphenol C, bisphenol E, bisphenol F, bisphenol G, bisphenol M, bisphenol S, bisphenol P, bisphenol PH, bisphenol TMC, and bisphenol Z. Among these, bisphenol A, bisphenol E, bisphenol F, and bisphenol S are preferred from the viewpoints of availability, production cost, and viscosity of the resin composition that is easy to handle, and bisphenol A, bisphenol E, and bisphenol F are more preferred, and bisphenol A is even more preferred from the viewpoints of corrosion resistance, versatility, and price.

When a bisphenol compound is included as a reaction raw material for the vinyl ester resin, the total amount of the unsaturated monobasic acid and the bisphenol compound to be used when producing the vinyl ester resin is preferably 80 to 120 molar parts, more preferably 90 to 110 molar parts, and even more preferably 95 to 105 molar parts, per 100 molar parts of the epoxy groups of the epoxy compound, and may be 100 molar parts.

When a bisphenol compound is included as a reaction raw material for the vinyl ester resin, the amount of the bisphenol compound to be blended when producing the vinyl ester resin is preferably 10 to 70 molar parts, more preferably 20 to 60 molar parts, and even more preferably 25 to 50 molar parts per 100 molar parts of the epoxy groups of the epoxy compound, from the viewpoint of good physical properties of the cured product of the resin composition.

The vinyl ester resin may contain an unsaturated polybasic acid as a reactant.
The unsaturated polybasic acid is a compound having at least two carboxy groups (including acid anhydrides) and at least one unsaturated group in one molecule. The unsaturated polybasic acid may be used alone or in combination of two or more kinds.
Examples of unsaturated polybasic acids include maleic anhydride, fumaric acid, itaconic acid, citraconic acid, chloromaleic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, etc. Among these, from the viewpoints of availability, ease of handling of the resin composition, production costs, etc., maleic anhydride, fumaric acid, succinic acid, glutaric acid, and adipic acid are preferred, succinic acid, fumaric acid, and maleic anhydride are more preferred, and fumaric acid is even more preferred.

When an unsaturated polybasic acid is included as a reaction raw material for the vinyl ester resin, the amount of unsaturated polybasic acid to be used in producing the vinyl ester resin is preferably 0.5 to 15 molar parts, more preferably 1 to 10 molar parts, and even more preferably 3 to 8 molar parts per 100 molar parts of the epoxy groups of the epoxy compound, from the viewpoint of good physical properties of the cured product of the resin composition.

From the viewpoint of ease of handling and good curing properties of the resin composition, the acid value of the vinyl ester resin is preferably 3.0 to 50.0 KOHmg/g, more preferably 5.0 to 40.0 KOHmg/g, and even more preferably 10.0 to 35.0 KOHmg/g.

The weight average molecular weight (Mw) of the vinyl ester resin is preferably 300 to 20,000, more preferably 500 to 10,000, and even more preferably 700 to 5,000, from the viewpoints of ease of handling of the resin composition and good physical properties of the cured product.
From the same viewpoint, the number average molecular weight (Mn) of the vinyl ester resin is preferably 200 to 15,000, more preferably 400 to 5,000, and further preferably 600 to 3,000.
From the same viewpoint, the molecular weight distribution (Mw/Mn) of the vinyl ester resin is preferably 1.00 to 5.00, more preferably 1.00 to 3.00, and further preferably 1.10 to 2.50.

((Meth)acrylic resin)
The (meth)acrylic resin is preferably a copolymer of an alkyl (meth)acrylate and a hydroxyl group-containing (meth)acrylate. A known synthesis method using addition polymerization can be applied to produce the (meth)acrylic resin by copolymerizing an alkyl (meth)acrylate and a hydroxyl group-containing (meth)acrylate. The copolymer may be a random copolymer or a block copolymer. The (meth)acrylic resin may be used alone or in combination of two or more kinds.

<(Meth)acrylic acid alkyl ester>
The (meth)acrylic acid alkyl ester, which is a constituent unit of the (meth)acrylic resin, has an alkyl group in the alkyl ester moiety having preferably 1 to 20 carbon atoms, more preferably 1 to 12, even more preferably 1 to 8, and still more preferably 4 to 8. The (meth)acrylic acid alkyl ester may be used alone or in combination of two or more kinds.
Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-propyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate.

<Hydroxyl Group-Containing (Meth)Acrylate>
The hydroxyl group-containing (meth)acrylate, which is a structural unit of the (meth)acrylic resin, is a compound having a hydroxyl group and an acryloyl group. The hydroxyl group-containing (meth)acrylate may be used alone or in combination of two or more kinds.
Examples of hydroxyl group-containing (meth)acrylates include 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, caprolactone-modified 2-hydroxyethyl (meth)acrylate, diethylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, 1-(2-hydroxyethyl) 2-(2-methacryloyloxyethyl) phthalate, N-methylol (meth)acrylate, 1-(2-hydroxyethyl) 2-(2-methacryloyloxyethyl) phthalate, and N-methylol (meth)acrylate. Examples of the hydroxyl group-containing (meth)acrylate include primary hydroxyl group-containing (meth)acrylates such as methacrylamide, secondary hydroxyl group-containing (meth)acrylates such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate, and tertiary hydroxyl group-containing (meth)acrylates such as 2,2-dimethyl-2-hydroxyethyl (meth)acrylate. Among these, primary hydroxyl group-containing (meth)acrylates are preferred, and 2-hydroxyethyl (meth)acrylate is preferably used, from the viewpoints of availability, ease of handling of the resin composition, and production costs.

When producing a (meth)acrylic resin copolymer, the blending ratio of the (meth)acrylic acid alkyl ester and the hydroxyl group-containing (meth)acrylate is preferably 60.0 to 99.9 molar parts, more preferably 80.0 to 99.8 molar parts, and even more preferably 90.0 to 99.7 molar parts of the (meth)acrylic acid alkyl ester per 100 molar parts in total of the (meth)acrylic acid alkyl ester and the hydroxyl group-containing (meth)acrylate, from the viewpoint of good physical properties of the cured resin composition.

(Urethane (meth)acrylate resin)
The urethane (meth)acrylate resin is preferably a polyurethane having a (meth)acryloyloxy group. The urethane (meth)acrylate resin can be produced by a known synthesis method. For example, an ethylenically unsaturated group-containing oligomer can be obtained by reacting a polyisocyanate with a polyhydroxy compound or a polyhydric alcohol, and then reacting the unreacted isocyanato group with a hydroxyl group-containing (meth)acrylic compound and, if necessary, a hydroxyl group-containing allyl ether compound. The urethane (meth)acrylate resin may be used alone or in combination of two or more kinds.

[Ethylenically unsaturated group-containing monomer (B)]
The ethylenically unsaturated group-containing monomer (B) is a monomer having polymerizability due to an ethylenically unsaturated group. Examples of the ethylenically unsaturated group include a vinyl group (including an allyl group) and a (meth)acryloyl group. The ethylenically unsaturated group-containing monomer (B) may be used alone or in combination of two or more kinds.

Examples of monomers having a vinyl group include styrene derivatives such as styrene, p-chlorostyrene, vinyltoluene, α-methylstyrene, dichlorostyrene, divinylbenzene, tert-butylstyrene, vinylbenzyl butyl ether, vinylbenzyl hexyl ether, and divinylbenzyl ether; vinyl acetate, diallyl fumarate, diallyl phthalate, and triallyl isocyanurate.

Examples of monomers having a (meth)acryloyl group include (meth)acrylic acid, monofunctional (meth)acrylates, polyfunctional (meth)acrylates, acryloylmorpholine, 2-hydroxyethyl (meth)acrylamide, 2-hydroxyethyl-N-methyl (meth)acrylamide, and 3-hydroxypropyl (meth)acrylamide.

Examples of monofunctional (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, stearyl (meth)acrylate, tridecyl (meth)acrylate, phenoxyethyl (meth)acrylate, ethylene glycol monomethyl ether (meth)acrylate, ethylene glycol monoethyl ether (meth)acrylate, ethylene glycol monobutyl ether (meth)acrylate, and ethylene glycol monohexyl ether (meth)acrylate. acrylate, ethylene glycol mono 2-ethylhexyl ether (meth)acrylate, diethylene glycol monomethyl ether (meth)acrylate, diethylene glycol monoethyl ether (meth)acrylate, diethylene glycol monobutyl ether (meth)acrylate, diethylene glycol monohexyl ether (meth)acrylate, diethylene glycol mono 2-ethylhexyl ether (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, caprolactone-modified 2-hydroxyethyl (meth)acrylate, allyl (meth)acrylate, etc.

Examples of polyfunctional (meth)acrylates include alkanediol di(meth)acrylates such as ethylene glycol di(meth)acrylate, 1,2-propylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate; diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate. Examples of the polyoxyalkylene glycol di(meth)acrylates include polyoxyalkylene glycol di(meth)acrylates such as trimethylolpropane di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, pentaerythritol diacrylate monostearate, 1,3-bis((meth)acryloyloxy)-2-hydroxypropane, ethoxylated bisphenol A di(meth)acrylate, and tris-(2-(meth)acryloxyethyl)isocyanurate.

Among these, from the viewpoints of availability, favorable physical properties of the cured product of the resin composition, and production costs, etc., preferred ethylenically unsaturated group-containing monomers (B) are styrene, methyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tetraethylene glycol di(meth)acrylate, with styrene and phenoxyethyl (meth)acrylate being preferably used.

From the viewpoint of good physical properties of the cured product, the content of the ethylenically unsaturated group-containing monomer (B) in the resin composition is preferably 20.0 to 70.0 mass%, more preferably 30.0 to 60.0 mass%, and even more preferably 40.0 to 50.0 mass%, relative to 100 mass% in total of the ethylenically unsaturated group-containing resin (A) and the ethylenically unsaturated group-containing monomer (B).

[Photopolymerization initiator (C)]
The photopolymerization initiator (C) initiates a polymerization reaction of the resin composition. By irradiating the resin composition containing the photopolymerization initiator (C) with light in the absorption wavelength range of the photopolymerization initiator (C), the ethylenically unsaturated group-containing resin (A) and the ethylenically unsaturated group-containing monomer (B) are copolymerized, and a cured product of the resin composition is obtained.
As the photopolymerization initiator (C), a polymerization initiator that generates radicals by irradiation with light is preferred, and from the viewpoint of reactivity, an intramolecular cleavage type photopolymerization initiator that does not require a hydrogen donor is more preferred. The photopolymerization initiator (C) may be used alone or in combination of two or more kinds.

Examples of the photopolymerization initiator (C) include benzoin and its alkyl ethers, such as benzoin, benzoin methyl ether, and benzoin ethyl ether; acetophenones, such as acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, and 4-(1-tert-butyldioxy-1-methylethyl)acetophenone; α-hydroxyalkylphenones, such as 1-hydroxycyclohexyl phenyl ketone and 2-hydroxy-2-methyl-1-phenyl-propan-1-one; anthraquinones, such as 2-methylanthraquinone, 2-amyl anthraquinone, 2-tert-butyl anthraquinone, and 1-chloro anthraquinone; 2,4-dimethylthioxanthone, 2,4-diisopropylthioxanthone, and 2-chlorothio Thioxanthones such as xanthone; ketals such as acetophenone dimethyl ketal and benzil dimethyl ketal; benzophenones such as benzophenone, 4-(1-tert-butyldioxy-1-methylethyl)benzophenone and 3,3',4,4'-tetrakis(tert-butyldioxycarbonyl)benzophenone; morpholines such as 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one; acylphosphine oxides such as phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide; and xanthones.

Among these, the photopolymerization initiator (C) is preferably one that absorbs the light irradiated by a general ultraviolet light LED (UV-LED) and generates radicals, and 2,2-dimethoxy-2-phenylacetophenone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and 1-hydroxycyclohexyl phenyl ketone are preferred, and in a preferred embodiment of the present invention, two types of initiators, 2,2-dimethoxy-2-phenylacetophenone and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, are used in combination.

The total content of the photopolymerization initiator (C) in the resin composition is preferably 0.001 to 15.0 parts by mass, more preferably 0.01 to 5.0 parts by mass, and even more preferably 0.10 to 1.0 parts by mass, per 100 parts by mass of the total of the ethylenically unsaturated group-containing resin (A) and the ethylenically unsaturated group-containing monomer (B), from the viewpoint of appropriately promoting the curing of the resin composition.

[Dye (D)]
Dye (D) is a compound having a maximum absorption wavelength in the wavelength region of 450 to 1100 nm. It is presumed that by irradiating light in the absorption wavelength region of dye (D) having such light absorption characteristics, dye (D) absorbs the light, the light energy is converted into heat energy, and the temperature during curing increases, improving the curability and resulting in a cured product with good physical properties.

From the viewpoint of enabling the resin composition to obtain good curing properties by efficient use of irradiated light, it is preferable that the maximum absorption wavelength of the dye (D) is in the wavelength range of 400 to 1100 nm. In other words, it is preferable that the dye (D) has a maximum absorption wavelength in the wavelength range of 400 to 1100 nm.

The wavelength range of the maximum absorption wavelength of the dye (D) is more preferably 460 nm or more, even more preferably 480 nm or more, even more preferably 500 nm or more, and more preferably 1000 nm or less, even more preferably 900 nm or less, even more preferably 850 nm or less.

From the same viewpoint, the absorption coefficient of the resin composition for light having the maximum absorption wavelength of the dye (D) is preferably 0.1 to 10,000 cm ^-1 , more preferably 0.5 to 1,000 cm ^-1 , and further preferably 1.0 to 500 cm ^-1 .

The colorant (D) may be a synthetic colorant or a natural colorant as long as it has the above-mentioned light absorption characteristics. The colorant (D) may be a dye or a pigment, and is preferably one that can be mixed in the resin composition without being unevenly distributed.
Examples of the dye (D) include dyes and pigments of green, red, blue, yellow, etc. The dye (D) may be used alone or in combination of two or more. Specific examples include anthraquinone-based, phthalocyanine-based, triphenylmethane-based, benzimidazolone-based, quinacridone-based, azochelate-based, azo-based, isoindoline-based, isoindolinone-based, pyranthrone-based, indanthrone-based, anthrapyrimidine-based, dibromoanthran-based, flavanthrone-based, perylene-based, perinone-based, quinophthalone-based, thioindigo-based, dioxazine-based, xanthene-based, and other dyes.
Specific examples of the dye (D), from the viewpoint of good curing properties of the resin composition, include dyes such as "Red A-2G", "Red B", "Blue A-2R", "Blue N", and "Green A-G" (all manufactured by Nippon Kayaku Co., Ltd.) and "Karenz IRT" (manufactured by Resonac Co., Ltd.), and pigments such as "Chromofine Red 6152EC" and "Cyanine Blue A-5109" (all manufactured by Dainichiseika Chemicals Co., Ltd.). Among these, "Kayaset Blue N" and "Karenz IRT" are preferred, and "Karenz IRT" is more preferred, because they have a large absorption coefficient at the maximum absorption wavelength.

The content of the dye (D) in the resin composition is preferably 0.001 to 1.0 part by mass, more preferably 0.01 to 0.5 part by mass, and even more preferably 0.02 to 0.2 part by mass, relative to 100 parts by mass in total of the ethylenically unsaturated group-containing resin (A) and the ethylenically unsaturated group-containing monomer (B), from the viewpoint of good curability of the resin composition and good physical properties of the cured product.
From the same viewpoint, the content of the dye (D) in the resin composition is preferably 0.001 to 1.0 mass %, more preferably 0.01 to 0.5 mass %, and even more preferably 0.02 to 0.2 mass % in the resin composition.

[Other ingredients]
The resin composition may contain other components in addition to the ethylenically unsaturated group-containing resin (A), the ethylenically unsaturated group-containing monomer (B), the photopolymerization initiator (C) and the dye (D). The other components may be added within a range that does not impair the effects of the present invention.
Examples of other components include additives such as other resins, polymerization inhibitors, catalysts, thixotropic agents, curing accelerators, catalysts, thickening aids, curing retarders, surfactants, interface modifiers, wetting and dispersing agents, defoamers, leveling agents, coupling agents, light stabilizers, waxes, flame retardants, plasticizers, fillers, internal release agents, low-shrinkage agents, toners, viscosity reducers, separation inhibitors, and compatibilizers.

The polymerization inhibitor can be used to suppress the progress of the polymerization reaction of the resin composition. In the present embodiment, the resin composition preferably contains a polymerization inhibitor.
As the polymerization inhibitor, a known one can be used, and examples thereof include hydroquinone, methylhydroquinone, trimethylhydroquinone, phenothiazine, catechol, 4-tert-butylcatechol, copper naphthenate, etc. The polymerization inhibitor may be used alone or in combination of two or more kinds.

The resin composition can be produced by mixing an ethylenically unsaturated group-containing resin (A), an ethylenically unsaturated group-containing monomer (B), a photopolymerization initiator (C), and a dye (D). The other components described above may be added and mixed as necessary.

The order of mixing is not particularly limited. For example, the ethylenically unsaturated group-containing resin (A) is mixed and dissolved in the ethylenically unsaturated group-containing monomer (B), and the photopolymerization initiator (C), the compound (D), and optionally other components are added and mixed to obtain a resin composition.
The mixing method is not particularly limited, and can be performed using, for example, a disperser, a planetary mixer, a kneader, etc. The kneading temperature is preferably 10 to 40°C, more preferably 15 to 30°C, and from the viewpoint of ease of mixing, etc., further preferably 20 to 30°C.

In addition, even when the resin composition of the present embodiment is used to form a composite material with a fiber substrate, a cured product having good physical properties can be obtained.
The types of fibers of the fiber substrate include, from the viewpoint of mechanical strength, so-called reinforced fibers such as organic fibers such as amide, alanide, vinylon, polyester, and phenol, carbon fibers, glass fibers, metal fibers, and ceramic fibers, as well as composite fibers thereof. The fiber substrate may be one type alone or two or more types in combination. Among these, aramid fibers, carbon fibers, and glass fibers are preferred, and glass fibers are more preferred from the viewpoints of strength, availability, and price, and glass fibers and polyester fibers having light transmittance are even more preferred.

Examples of the form of the fiber substrate include sheets, chopped strands, chopped, and milled fibers. Examples of sheets include those formed by aligning multiple reinforcing fibers in one direction, bidirectional fabrics such as plain weave and twill weave, multiaxial fabrics, non-crimp fabrics, nonwoven fabrics, mats, knits, braids, and paper made from reinforcing fibers. The form of the fiber substrate may be one type alone or two or more types in combination, and may be a single layer or multiple layers laminated.

[Light Emitting Diode (LED)]
In the method for producing a cured product of the resin composition of the present embodiment, the resin composition is cured by irradiating it with light emitted from an LED. The light emitted from the LED includes light (1) in the absorption wavelength range of the photopolymerization initiator (C) and light (2) in the absorption wavelength range of the dye (D).
In this manner, by irradiating the resin composition with light from an LED that corresponds to the absorption wavelengths of the photopolymerization initiator (C) and the dye (D) in the resin composition, a cured product having good physical properties can be obtained.
Therefore, it is preferable that the light irradiated to the resin composition includes light in the wavelength range of 400 to 1100 nm and has at least two peak wavelengths. The wavelength range included in the light irradiated to the resin composition preferably includes the maximum absorption wavelength of the dye (D), and is more preferably 460 nm or more, even more preferably 480 nm or more, still more preferably 500 nm or more, and more preferably 1000 nm or less, even more preferably 900 nm or less, and still more preferably 850 nm or less.

From the viewpoint of promoting the polymerization reaction of the resin composition by the photopolymerization initiator (C), the LED that emits the light (1) preferably has a peak wavelength in the wavelength range of 250 to 400 nm, and the wavelength range can be appropriately set in accordance with the maximum absorption wavelength of the photopolymerization initiator (C). In a preferred embodiment of the present invention, the maximum absorption wavelength of the phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide used as the photopolymerization initiator (C) is 366 nm, and an LED having a peak wavelength of 385 nm is used.
The LED that emits the light (1) may be composed of one light-emitting element or may have multiple light-emitting elements, and may be mounted on an LED illuminator.
The light (1) may include a part or the entire absorption wavelength range of the photopolymerization initiator (C).

The LED that emits light (2) preferably has a peak wavelength in a wavelength range including the maximum absorption wavelength of dye (D), from the viewpoints of improving the curability of the resin composition and achieving good physical properties of the cured product due to a rise in temperature during curing caused by conversion of light energy into thermal energy due to light absorption by dye (D).
From a similar viewpoint, it is preferable that the LED that emits the light (2) has a peak wavelength in a wavelength region in which the ratio of the absorbance of the dye (D) to the absorbance of the maximum absorption wavelength of the dye (D) in the wavelength region of 400 to 1100 nm (hereinafter also referred to as relative absorbance) is 0.3 or more.
The LED that emits the light (2) may be composed of one light-emitting element or may have multiple light-emitting elements, and may be mounted on an LED illuminator.
The light (2) may include a part or the entire absorption wavelength range of the dye (D).
The LED may be such that a light-emitting element that emits light (1) and a light-emitting element that emits light (2) are packaged in a single LED, or may be packaged in different LEDs.

According to the manufacturing method of this embodiment, even if the total integrated light amount of the light (1) and the light (2) irradiated from the LED to the resin composition is approximately the same as the integrated light amount when only the light (1) is irradiated, the cured product properties of the resin composition can be improved.
When there are a plurality of LEDs emitting light (1) and light (2), these LEDs may be mounted on the same LED illuminator and may be configured to emit light simultaneously or switchably. Also, the LED emitting light (1) and the LED emitting light (2) may be mounted on different LED illuminators.

The irradiance of each of the light (1) and the light (2) is not particularly limited, and is appropriately set depending on the shape and thickness of the resin composition, the equipment environment of the apparatus for producing the cured product, and the like.
The irradiance of the light (1) is preferably 1.0 mW/ ^cm2 or more, more preferably 5.0 mW/cm2 ^{or more, and even more preferably 20.0 mW/cm2 or more, from the viewpoint of improving the curability of the resin composition and obtaining good physical properties of the cured product, and is preferably 1000 mW/cm2 or less, more preferably 500 mW/cm2 or less , and} even more preferably 100 mW/cm2 or ^less , from the viewpoint of the heat resistance and energy efficiency of the LED irradiator.
The irradiance of the light (2) is preferably 1.0 mW/ ^cm2 or more, more preferably 5.0 mW/cm2 or ^more , and even more preferably 20.0 mW/cm2 or ^more , from the viewpoint of increasing the temperature during photocuring and obtaining good physical properties of the cured product, and is preferably 1000 mW/cm2 or ^less , more preferably 500 mW/cm2 ^or less, and even more preferably 100 mW/cm2 or ^less , from the viewpoint of the heat resistance and energy efficiency of the LED irradiator.

The irradiation time of the light (1) and the light (2) applied to the resin composition is appropriately set taking into consideration the accumulated light amount and the irradiance. For example, it is preferably about 1 second to 60 minutes, more preferably 10 to 50 minutes, and even more preferably 20 to 40 minutes.

The cumulative amount of light irradiated by the light (1) to the resin composition is, from the viewpoint of sufficient curing of the resin composition, preferably 0.01 J/ ^cm2 or more, more preferably 0.1 J/ ^cm2 or more, even more preferably 1.0 J/ ^cm2 or more, and is preferably 2000 J/cm2 or ^less , more preferably 1000 J/cm2 or ^less , even more preferably 500 J/cm2 ^or less.
From the same viewpoint, the integrated light amount of the light (2) irradiated to the resin composition is preferably 0.01 J/ ^cm2 or more, more preferably 0.1 J/cm2 or ^more , even more preferably 1.0 J/ ^cm2 or more, and is preferably 2000 J/cm2 or ^less , more preferably 1000 J/cm2 or ^less , even more preferably 500 J/cm2 or ^less .
From the same viewpoint, the total integrated light amount of the light irradiated to the resin composition by the light (1) and the light (2) is preferably 0.02 J/ ^cm2 or more, more preferably 0.2 J/ ^cm2 or more, even more preferably 2.0 J/ ^cm2 or more, and is preferably 4000 J/cm2 or ^less , more preferably 2000 J/cm2 or ^less , even more preferably 1000 J/cm2 or ^less .

The method of irradiating the resin composition with light (1) and light (2) by LED is not particularly limited. Irradiation with light (1) and light (2) may be performed simultaneously, sequentially, or continuously. Irradiation with light (1) and light (2) may be performed multiple times. From the viewpoint of efficiently producing a cured product by shortening the curing time, it is preferable to perform irradiation with light (2) before irradiation with light (1), or to perform irradiation with light (1) and irradiation with light (2) simultaneously, and it is more preferable to perform irradiation with light (1) and irradiation with light (2) simultaneously.

It is preferable that the entire resin composition is irradiated with light as uniformly as possible. From the viewpoint of efficiently producing a cured product by shortening the curing time, it is preferable to irradiate with light from a plurality of LEDs at the same time.
The resin composition may be irradiated with light from an LED directly, or may be irradiated through a glass surface by casting the resin composition into a light-transmitting mold such as glass.

[Physical properties of the cured product]
The cured product of the resin composition has excellent heat resistance, and the deflection temperature under load is preferably 80.0° C. or higher, more preferably 82.0° C. or higher, and even more preferably 85.0° C. or higher.

The cured product of the resin composition has excellent mechanical strength, and the flexural strength is preferably 100 MPa or more, more preferably 105 MPa or more, and even more preferably 108 MPa or more.
The flexural modulus is preferably 2800 MPa or more, more preferably 2900 MPa or more, and further preferably 3000 MPa or more.

The present invention will be specifically explained below based on examples, but the present invention is not limited to the following examples.

[Synthesis of ethylenically unsaturated group-containing resin (A)]
As the ethylenically unsaturated group-containing resin (A), unsaturated polyester resins (a1) and (a2), and vinyl ester resins (b1) and (b2) were synthesized.
The physical properties of the ethylenically unsaturated group-containing resin (A) were measured by the following methods. The results are shown in Table 1.

[Acid value]
In accordance with JIS K6901:2008 "Partial acid value (indicator titration method)," the acid value was determined by measuring the mass of potassium hydroxide required to neutralize the acid components in the measurement sample using a mixed indicator of bromothymol blue and phenol red using an "Autoburette UCB-2000" (manufactured by Hiranuma Sangyo Co., Ltd.).
For the vinyl ester resins (b1) and (b2), the mixtures with the reactive diluent (ethylenically unsaturated group-containing monomer (B)) obtained in each synthesis example were used as measurement samples.

[Weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw/Mn)]
The weight average molecular weight Mw and number average molecular weight Mn of the unsaturated polyester resin were measured by gel permeation chromatography (GPC) under the following measurement conditions, and were calculated as standard polystyrene equivalent molecular weights. The molecular weight distribution Mw/Mn was calculated from the values of the number average molecular weight Mn and the weight average molecular weight Mw.

<Measurement conditions>
・Apparatus: High-performance liquid chromatograph "Prominence" (manufactured by Shimadzu Corporation)
・Column: "Shodex LF-804" (manufactured by Resonac Co., Ltd.)
Detector: Differential refractometer "Shodex RI-71S" (manufactured by Resonac Co., Ltd.)
Column temperature: 40°C
Sample: 0.2 mass% solution of unsaturated polyester resin in tetrahydrofuran Developing solvent: tetrahydrofuran Flow rate: 1.0 mL/min

Synthesis Example 1
A 3 L four-neck separable flask equipped with a thermometer, a stirrer, a gas inlet tube, and a reflux condenser was charged with 224.6 g of propylene glycol (27.5 parts by mole per 100 parts by mole of diols in total) and 810.5 g of neopentyl glycol (2,2-dimethyl-1,3-propanediol) (72.5 parts by mole per 100 parts by mole of diols in total), 472.6 g of isophthalic acid (26.5 parts by mole per 100 parts by mole of diols), 356.6 g of terephthalic acid (20.0 parts by mole per 100 parts by mole of diols), and 563.1 g of maleic anhydride (53.5 parts by mole per 100 parts by mole of diols) and subjected to a condensation reaction at 215° C. for 10 hours under a nitrogen gas atmosphere to obtain an unsaturated polyester resin (a1).

Synthesis Example 2
An unsaturated polyester resin (a2) was obtained in the same manner as in Synthesis Example 1, except that the raw material composition shown in Table 1 was used.

[Synthesis Example 3]
In a 5L four-necked separable flask equipped with a thermometer, a stirrer, a gas inlet tube and a reflux condenser, 1512 g of "Epomic R140P" (bisphenol A type epoxy resin; manufactured by Mitsui Chemicals, Inc., epoxy equivalent 188) as an epoxy compound and 429 g of bisphenol A (47 moles per 100 moles of epoxy groups of the epoxy compound) were added and stirred and mixed, and heated to 80°C. Next, 3.9 g of triethylamine (manufactured by Daicel Corporation) was added as a catalyst, and the mixture was heated to 145°C and reacted for 1 hour under a nitrogen gas atmosphere. The epoxy equivalent of the epoxy compound is a value measured in accordance with JIS K7236:2001.
After cooling the reaction product to 110°C, 429g (10% by mass based on the total amount of the blended components) of styrene, which is an ethylenically unsaturated group-containing monomer (B), was added as a reactive diluent. Furthermore, 0.04g of copper naphthenate (0.0019 parts by mass relative to 100 parts by mass of the epoxy compound, bisphenol compound, and unsaturated monobasic acid) and 1.3g of trimethylhydroquinone (0.056 parts by mass relative to 100 parts by mass of the epoxy compound, bisphenol compound, and unsaturated monobasic acid) were added as polymerization inhibitors, and 6.9g of 2,4,6-tris(dimethylaminomethyl)phenol ("Seikuol TDMP", manufactured by Seiko Chemical Industry Co., Ltd., purity over 95% by mass) (0.3 parts by mass relative to 100 parts by mass of the epoxy compound, bisphenol compound, and unsaturated monobasic acid) were added as an esterification catalyst, and the mixture was heated to 110°C.
Then, 365 g of methacrylic acid (53 mol per 100 mol of the total amount of epoxy groups in the epoxy compound) was dropped as an unsaturated monobasic acid over a period of 30 minutes, and the mixture was heated to 130° C. and reacted for 2 hours to produce a vinyl ester resin (b1).
The reaction product was cooled to 90°C, and 0.13 g (0.003 mass% based on the total amount of the blended components) of hydroquinone as a polymerization inhibitor was added, and 1,546 g (36 mass% based on the total amount of the blended components) of styrene, which is the ethylenically unsaturated group-containing monomer (B), was added as a reactive diluent to obtain a mixture of vinyl ester resin (b1) and styrene (mass ratio 54.0/46.0).

Synthesis Example 4
In a 5 L four-neck separable flask equipped with a thermometer, a stirrer, a gas inlet tube, and a reflux condenser, 1,950 g of Epomic R140P as an epoxy compound was heated to 80° C., and 407 g (10 mass % based on the total amount of the blended components) of phenoxyethyl methacrylate, which is the ethylenically unsaturated group-containing monomer (B), as a reactive diluent, 0.04 g of 5% copper naphthenate (0.0014 parts by mass relative to 100 parts by mass of the epoxy compound and the unsaturated monobasic acid), 0.9 g of methylhydroquinone (0.03 parts by mass relative to 100 parts by mass of the epoxy compound and the unsaturated monobasic acid), and 1.6 g of trimethylhydroquinone (0.057 parts by mass relative to 100 parts by mass of the epoxy compound and the unsaturated monobasic acid) as polymerization inhibitors, and 2,4,6-tris(dimethylaminomethyl)phenol ("Seikuol") as an esterification catalyst were added. 8.5 g of "dimethylaminopropyltrimethylsilyl (TDMP)" (0.3 part by mass per 100 parts by mass of the total of the epoxy compound and the unsaturated monobasic acid) was added and heated to 100° C., and 891 g of methacrylic acid (100 mol per 100 mol of the total of the epoxy groups of the epoxy compound) was added dropwise as the unsaturated monobasic acid over a period of 30 minutes, followed by a reaction for 2 hours to obtain a vinyl ester resin (b2).
The reaction product was cooled to 90°C, and 815 g (20 mass% based on the total amount of the blended components) of phenoxyethyl methacrylate, which is the ethylenically unsaturated group-containing monomer (B), was added as a reactive diluent to obtain a mixture of vinyl ester resin (b2) and phenoxyethyl methacrylate (mass ratio 70.0/30.0).

[Production of resin composition]
Each ethylenically unsaturated group-containing resin (A) obtained in the above synthesis examples was used to produce a resin composition. Details of the dye (D) used in the production of the resin composition are shown in Table 2.
In accordance with JIS K 0115:2020, an absorption spectrum was measured for a styrene solution containing the dye (D) at a concentration of 0.001% by mass using an ultraviolet-visible spectrophotometer ("UV-1900i", manufactured by Shimadzu Corporation; quartz cell for spectrophotometer "T-1-UV-10", manufactured by Tosoh Quartz Corporation).
The relative absorbance in Table 2 is the ratio of absorbance to the absorbance at the maximum absorption wavelength in the wavelength range of 400 to 1100 nm.

[Production Example 1]
To 100 parts by mass of a mixture (adjusted to a mass ratio of 54.9/45.1) obtained by dissolving the unsaturated polyester resin (a1) in styrene, which is the ethylenically unsaturated group-containing monomer (B), 0.11 parts by mass of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO) and 0.11 parts by mass of 2,2-dimethoxy-2-phenylacetophenone (DMPA) were added as photopolymerization initiators (C), and the mixture was stirred and mixed at 2000 to 3000 rpm for 10 minutes using a high-speed disperser ("Homo Disper 2.5 Type", manufactured by Primix Corporation).
Furthermore, 0.03 parts by mass of "Karenz IRT" was added and mixed with stirring for 1 minute to produce resin composition 1.

[Production Examples 2 to 18]
Resin compositions 2 to 18 were produced in the same manner as in Example 1, except that the raw materials were mixed in the compositions shown in Tables 3 and 4.

[Production of Cured Product]
Using each of the resin compositions produced in the above Production Examples, a cured product of the resin composition was produced in the following manner.

[Examples 1 to 14 and Comparative Examples 1 to 8]
A mold was prepared by sandwiching a U-shaped NBR rubber spacer (10 mm wide, 4 mm thick) between two glass plates (300 mm long x 300 mm wide x 5 mm thick) along three sides of the plate surfaces and fixing them with clips.
A resin composition was poured into the gap between the two glass plates of the prepared mold (inside the mold), and the mold was irradiated with LED light from outside the glass plate surfaces.
The LED (LED (1)) emitting light (1) and the LED (LED (2)) emitting light (2) had the maximum emission wavelengths shown in Tables 3 and 4, respectively. LED (1) and LED (2) were irradiated from opposite sides of the glass plate of the mold, and when both were irradiated, they were irradiated simultaneously.
After irradiation for 30 minutes, the plate was left to stand at room temperature (23° C.) for 12 hours for curing, and then removed from the mold to obtain a cured product.

The irradiance was adjusted by placing a separately prepared glass plate at the position where the mold was to be placed, and adjusting the position and output of the LED irradiator based on the irradiance value measured by directing the LED light transmitted through the glass plate at the receiver of a spectroradiometer (USR-45VA, manufactured by Ushio Inc.).

[Measurement and Evaluation of Cured Product]
The following items were measured and evaluated for each of the produced cured products (measurement environment: temperature 23° C., humidity 50% RH). The evaluation results are shown in Tables 3 and 4.

[Deflection temperature under load]
Measurements were performed under the following conditions in accordance with JIS K 7191-2:2015 Appendix A.
<Measurement conditions>
・Equipment: Heat deflection temperature (HTD) tester "S-3M" (manufactured by Toyo Seiki Co., Ltd.)
・Test piece dimensions: Width 10 mm x Length 100 mm x Thickness 4 mm
Load: bending stress 1.80 MPa
- Specified deflection: 0.34 mm
Heating rate: 120°C/hr
The average value of the measurements for the three test pieces was taken as the deflection temperature under load of the cured product.
When the deflection temperature under load is 80.0° C. or higher, the cured product can be said to have good heat resistance.

[Flexural strength and flexural modulus]
Measurements were performed under the following conditions in accordance with JIS K 7171:2016.
<Measurement conditions>
・Apparatus: "Autograph AGS-10kNX" (manufactured by Shimadzu Corporation)
- Analysis software: "TRAPEZIUM LITE X" (Shimadzu Corporation)
・Test piece dimensions: Width 10 mm x Length 80 mm x Thickness 4 mm
Test speed: 1.7 mm/min
The average values measured for the five test pieces were taken as the bending strength and bending modulus of each cured product.
If the bending strength is 100 MPa or more and the bending modulus is 2,800 MPa or more, the cured product can be said to have good bending properties.

According to the method for producing a cured product of the resin composition of this embodiment, it has been confirmed that a cured product having good heat resistance and bending properties can be obtained by irradiating a resin composition containing an ethylenically unsaturated group-containing resin (A), an ethylenically unsaturated group-containing monomer (B), and a photopolymerization initiator (C) with LED light.

Claims (6)

a resin composition including an ethylenically unsaturated group-containing resin (A), an ethylenically unsaturated group-containing monomer (B), a photopolymerization initiator (C), and a dye (D) is irradiated with light emitted from a light-emitting diode to cure the resin composition;
Dye (D) has a maximum absorption wavelength in the wavelength range of 400 to 1100 nm,
the light emitted from the light-emitting diode includes light (1) in the absorption wavelength range of the photopolymerization initiator (C) and light (2) in the absorption wavelength range of the dye (D);
A method for producing a cured product of a resin composition. The method for producing a cured product of the resin composition according to claim 1, wherein the light irradiated to the resin composition includes light in the wavelength range of 400 to 1100 nm and has at least two peak wavelengths. The method for producing a cured product of a resin composition according to claim 1 or 2, wherein the absorption coefficient of the resin composition for light having a maximum absorption wavelength of the dye (D) is 0.1 to 10,000 cm ⁻¹ . The method for producing a cured product of the resin composition according to claim 1 or 2, wherein the light emitting diode that emits light (1) has a peak wavelength in the wavelength range of 250 to 400 nm. The method for producing a cured product of the resin composition according to claim 1 or 2, wherein the light emitting diode that emits light (2) has a peak wavelength in a wavelength range of 400 to 1100 nm where the ratio of the absorbance of the dye (D) to the absorbance at the maximum absorption wavelength of the dye (D) is 0.3 or more. The method for producing a cured product of the resin composition according to claim 1 or 2, wherein the ethylenically unsaturated group-containing resin (A) is at least one selected from the group consisting of unsaturated polyester resins, vinyl ester resins, (meth)acrylic resins, and urethane (meth)acrylate resins.