Photocurable resin composition and method for producing seal member

Abstract

This photocurable resin composition comprises (A) component to (D) component in which the contents of (A) component to (C) component are in specific ranges.　(A) component: A polymer that has a number average molecular weight of 1,000-100,000 and that has a polyisobutylene backbone and two or more (meth)acryloyl groups. (B) component: A monofunctional (meth)acrylate monomer that has a linear or branched hydrocarbon group having 4-18 carbon atoms and that has one (meth)acryloyl group per molecule. (C) component: A polyfunctional (meth)acrylate monomer that has 2-4 (meth)acryloyl groups and that also has a polar functional group. (D) component: A photoradical polymerization initiator.

Description

Photocurable resin composition and method for manufacturing a sealing material

[0001] The present disclosure relates to a photocurable resin composition and a method for manufacturing a sealing material.

[0002] Conventionally, a gasket, which is a fixing sealing material used to provide airtightness or liquid tightness to parts such as devices and pipes, has generally been a so-called solid gasket formed by a mold. However, in recent years, a type of gasket called a liquid gasket, which is cured after being applied to a sealing surface with a dispenser or the like, has become widespread. Liquid gaskets have the following advantages over solid gaskets: (1) Since they do not require a mold, they can flexibly respond to changes in the shape of the work to be sealed, and (2) Since they are liquid during application and penetrate even if the sealing surface is rough, the finishing cost of the sealing surface can be reduced.

[0003] Among liquid gaskets, they are mainly classified into two types: FIPG (Formed In-Place Gasket) and CIPG (Cured In-Place Gasket). The former seals by curing after applying the gasket to one sealing surface and then bonding the other sealing surface, while the latter seals by bonding the other sealing surface after curing the gasket applied to the sealing surface. Therefore, FIPG ensures sealing performance by adhesion to the sealing surface, and CIPG ensures sealing performance by adhesion to the sealing surface and the elastic force of CIPG. CIPG has the advantage of being excellent in reworkability because it is not adhered to one of the sealing surfaces compared to FIPG.

[0004] Since the liquid gasket needs to be cured in the assembly process, it has a disadvantage in that the cycle time is longer than that of the solid gasket. However, if a photocurable resin that can be cured in a short time is used for the liquid gasket, the above disadvantage can be suppressed. As an example of using a photocurable resin as a CIPG, a photocurable resin composition suitable for a sealing material (Patent Documents 1 and 2) for preventing dust and moisture from entering the inside of electronic devices such as hard disk drives and smartphones, and various sealing materials inside fuel cells (Patent Documents 3 to 5) is shown. Among them, a polyisobutylene resin having a (meth)acryloyl group has a low glass transition temperature Tg and is excellent in gas barrier properties, heat resistance and hydrolysis resistance, and has been shown to be suitable as a component contained in a photocurable resin for a sealing material (Patent Documents 1 to 4).

[0005] JP 2021-021012 A, WO 2021 / 210598, WO 2023 / 090088, JP 2024-108382 A, JP 2022-057075 A, JP 2024-089464 A

[0006] For light-curing resins to be used as CIPG (Civil Insulated Plastic Gasket), they must have excellent long-term durability, meaning that the reaction force due to compression is not lost over a long period (sealing properties are maintained). One method for evaluating long-term durability is the compression set test, and the smaller the compression set, the better the long-term durability. Compared to the conditions described in JIS K6262 (25% compression, 70°C x 22 hours), the evaluation conditions increasingly require higher compressibility (e.g., 50%), higher temperatures (e.g., 100°C), and longer durations (e.g., 1000 hours) (e.g., fuel cell sealants). Furthermore, since fuel cell sealants are used in cell stacks where hundreds of cells are stacked, variations in the thickness of the material cause variations in the compressibility. Therefore, in addition to having sufficient reaction force even at low compressibility (e.g., 20%), it is also required that they do not crack at high compressibility (e.g., 50%). Moreover, fuel cell sealants are required to have sufficient reaction force over a wide temperature range. In other words, it is necessary to maintain sealing performance not only during operation (around 100°C) but also at low temperatures (e.g., -30°C) to maintain rubber elasticity and sufficient reaction force, considering the use of fuel cells in cold regions. Therefore, a sealing material having the following four characteristics can be said to be an excellent sealing material, and in particular, all of these characteristics must be met simultaneously for use as a sealing material for various fuel cells: (i) Low compression set (excellent long-term durability) (ii) Does not crack even at high compression ratios (excellent resistance to compression cracking) (iii) High compression reaction force at low compression ratios (excellent sealing performance) (iv) Has sufficient reaction force over a wide temperature range (excellent rubber elasticity at low temperatures)

[0007] Patent Document 3 reports that when an acrylate monomer having an alicyclic hydrocarbon group is incorporated into a photocurable resin composition, a cured product with low compression set and high reaction force at low compression is obtained. Furthermore, Patent Documents 4 to 6 report that when a polyfunctional acrylate monomer is incorporated into a photocurable resin composition, a cured product with an excellent balance between compression set and resistance to compression cracking is obtained.

[0008] The formulation of acrylate monomers having alicyclic hydrocarbon groups described in Patent Document 3 results in a deterioration of the rubber elasticity of the cured product at low temperatures if the amount of monomer is increased too much, because the glass transition temperature Tg of the monomer is high. The formulation of polyfunctional acrylate monomers described in Patent Documents 4 to 6 results in a deterioration of compressive crack resistance if the amount of monomer is increased too much, as pointed out in Patent Documents 5 or 6, because the monomer forms a crosslinked structure with a short distance between crosslinking points. On the other hand, while Patent Document 4 maintains compressive crack resistance despite incorporating a large amount of polyfunctional acrylate monomer compared to Patent Documents 5 or 6, it does not describe the reaction force at low compressibility, and when the inventor actually formulated it, the liquid stability of the photocurable resin composition was low and it separated easily, so it is considered unsuitable for practical use. As described above, the prior art has a trade-off in which improving one of the properties (i) to (iv) deteriorates another.

[0009] This disclosure is made in view of the above circumstances. The problem that the embodiments of this disclosure aim to solve is to provide a photocurable resin composition in which the resulting cured product has low compression set, excellent resistance to compression cracking, high compression reaction force at low compression ratios, and excellent rubber elasticity at low temperatures. Another problem that the embodiments of this disclosure aim to solve is to provide a method for manufacturing a sealing material using the photocurable resin composition.

[0010] The following embodiments are specific means for solving the above problems: <1> A photocurable resin composition comprising the following components (A) to (D), wherein, with respect to 100 parts by mass of the total of components (A) and (B), the content of component (A) is 45 to 85 parts by mass, the content of component (B) is 15 to 55 parts by mass, and the content of component (C) is 1 to 35 parts by mass. Component (A): A polymer having a polyisobutylene skeleton and two or more (meth)acryloyl groups, with a number average molecular weight of 1,000 to 100,000. Component (B): A monofunctional (meth)acrylate monomer having linear or branched hydrocarbon groups with 4 to 18 carbon atoms and one (meth)acryloyl group in one molecule. Component (C): A polyfunctional (meth)acrylate monomer having two to four (meth)acryloyl groups and further having polar functional groups. Component (D): A photoradical polymerization initiator. <2> The photocurable resin composition according to <1>, wherein component (A) comprises a polyisobutylene resin having a number average molecular weight of 1,000 to 100,000 and (meth)acryloyl groups at both ends. <3> The photocurable resin composition according to <1> or <2>, wherein component (B) comprises a monofunctional (meth)acrylate monomer having a linear or branched hydrocarbon group having 4 to 16 carbon atoms and one (meth)acryloyl group in one molecule. <4> The photocurable resin composition according to any one of <1> to <3>, wherein component (C) comprises a polyfunctional (meth)acrylate monomer having a polar functional group containing a nitrogen atom and two to four (meth)acryloyl groups. <5> The photocurable resin composition according to any one of <1> to <4>, wherein component (C) comprises a polyfunctional (meth)acrylate monomer having an isocyanurate skeleton and two to four (meth)acryloyl groups. <6> The photocurable resin composition according to any one of <1> to <5>, further comprising inorganic particles as component (E). <7> The photocurable resin composition according to <6>, wherein the content of component (E) is 0.1 to 30 parts by mass per 100 parts by mass of the total of components (A) and (B). <8> The photocurable resin composition according to <6> or <7>, wherein the average particle size of component (E) is 0.01 μm or more and 200 μm or less.<9> The photocurable resin composition according to any one of <1> to <8>, wherein component (D) comprises the following components (D-1) and (D-2), and the content of component (D-1) is 0.01 to 0.9 parts by mass and the content of component (D-2) is 0.1 to 5 parts by mass per 100 parts by mass of the total of components (A) and (B). Component (D-1): A photoradical polymerization initiator having a molar extinction coefficient of 10 L / (mol·cm) or more at at least one wavelength (I) between 395 nm and 435 nm. Component (D-2): A photoradical polymerization initiator having a molar extinction coefficient of less than 10 L / (mol·cm) at any wavelength between 395 nm and 435 nm, and a molar extinction coefficient of 10 L / (mol·cm) or more at at least one wavelength (II) between 280 nm and 385 nm. <10> The photocurable resin composition according to <9>, wherein component (D-1) comprises at least one compound selected from the group consisting of acylphosphine oxide compounds, α-aminoalkylphenone compounds having a 4-morpholinophenyl group, oxime ester compounds having a 4-phenylthiophenyl group, and thioxanthone compounds. <11> A photocurable resin composition according to <9> or <10>, wherein component (D-2) comprises at least one compound selected from the group consisting of α-hydroxyalkylphenone compounds, α-aminoalkylphenone compounds (excluding those having a 4-morpholinophenyl group), benzyl ketal compounds, oxime ester compounds (excluding those having a 4-phenylthiophenyl group), and benzophenone compounds. <12> A photocurable resin composition according to any one of <1> to <11>, which is a photocurable resin composition for sealing materials. <13> A photocurable resin composition according to any one of <1> to <12>, which is a photocurable resin composition for sealing materials for fuel cells. <14> A method for producing a sealing material, comprising the steps of irradiating a photocurable resin composition described in any one of <9> to <11> with light (a) containing the wavelength (I), and irradiating it with light (b) containing the wavelength (II), wherein the irradiation energy of light (a) in the wavelength range of 200 nm to 385 nm is 0.2 times or less the irradiation energy of light (a) in the wavelength range of 395 nm to 435 nm.<15> The illuminance of the light (a) is 10 mW / cm. ２ ~5,000mW / cm ２ The irradiation dose was 50 mJ / cm². ２ ~5,000mJ / cm ２ The illuminance of light (b) is 10 mW / cm². ２ ~5,000mW / cm ２ The irradiation dose was 50 mJ / cm². ２ ~10,000mJ / cm ２ The method for manufacturing a sealing material as described in <14>. <16> The method for manufacturing a sealing material as described in <14> or <15>, wherein the manufactured sealing material is for use in a fuel cell.

[0011] This disclosure provides a photocurable resin composition in which the resulting cured product exhibits low compression set, excellent resistance to compression cracking, high compressive reaction force at low compression ratios, and excellent rubber elasticity at low temperatures. Furthermore, this disclosure provides a method for manufacturing a sealing material using the photocurable resin composition.

[0012] In this disclosure, numerical ranges expressed using "~" mean a range that includes the numbers before and after "~" as the lower and upper limits. In this disclosure, the amount of each component in a composition means the total amount of multiple substances present in the composition, unless otherwise specified, if there are multiple substances corresponding to each component in the composition. In numerical ranges described in steps in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in steps. In numerical ranges described in this disclosure, the upper or lower limit of that numerical range may be replaced with the values ​​shown in the examples. In this disclosure, a preferred combination of embodiments means a more preferred embodiment. In the notation of groups (atomic groups) in this disclosure, notation that does not specify substitution and unsubstituted includes both those with and without substituents. In this disclosure, "(meth)acrylate" means at least one of acrylate and methacrylate. In this disclosure, "urethane (meth)acrylate" means a (meth)acrylate polymer having a urethane backbone.

[0013] "Number-average molecular weight" and "weight-average molecular weight" refer to the values ​​obtained by converting the molecular weight measured by gel permeation chromatography (hereinafter also referred to as "GPC") to polystyrene equivalent. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) in polystyrene equivalent can be obtained by performing gel permeation chromatography (GPC) measurements under the measurement conditions described below. <Measurement Conditions> Apparatus: HLC-8320 manufactured by Tosoh Corporation Column: TSKgel-SuperMultipore HZ-M (4.6 mm ID × 15 cm) × 3 tubes manufactured by Tosoh Corporation (for low molecular weight, exclusion limit molecular weight 2,000,000) Column temperature: 40°C Eluent: Tetrahydrofuran (0.35 ml / min) Detector: Differential refractometer (RI) Sample concentration: 0.1%

[0014] The "molar extinction coefficient" refers to the value of ε shown in the following equation (A). ε is determined by the Lambert-Beer law for an acetonitrile solution containing a photoradical polymerization initiator. In equation (A), I is the intensity of transmitted light, Io is the intensity of transmitted light of pure acetonitrile solvent, c is the molar concentration (M), d is the thickness of the solution layer (cm), and log(Io / I) represents the absorbance. Equation (A): ε = log(Io / I) / (c × d) The molar extinction coefficient of a photoradical polymerization initiator can be measured, for example, by the following method: Using acetonitrile as the solvent, dissolve the photoradical polymerization agent to a concentration of 1 g / L, measure the absorbance using a quartz cell with a UV-Vis spectrophotometer under room temperature conditions, and calculate the molar extinction coefficient using the Lambert-Beer law. For wavelengths where the absorbance exceeds 2.0, the photoradical polymerization initiator is dissolved at a concentration that results in an absorbance in the range of 0.1 to 2.0. The absorbance is measured at room temperature using a quartz cell with a UV-Vis spectrophotometer, and the result is calculated using the Lambert-Beer law.

[0015] Hereinafter, "irradiating with light (a) containing at least one wavelength (I) between 395 nm and 435 nm" will also be referred to as "light irradiation (a)". Hereinafter, "irradiating with light (b) containing at least one wavelength (II) between 200 nm and 385 nm" will also be referred to as "light irradiation (b)".

[0016] (Photocurable resin composition) The photocurable resin composition according to this disclosure comprises the following components (A) to (D), wherein, with respect to 100 parts by mass of the total of components (A) and (B), the content of component (A) is 45 to 85 parts by mass, the content of component (B) is 15 to 55 parts by mass, and the content of component (C) is 1 to 35 parts by mass. (A) Component: A polymer having a polyisobutylene skeleton and two or more (meth)acryloyl groups, with a number-average molecular weight of 1,000 to 100,000. (B) Component: A monofunctional (meth)acrylate monomer having linear or branched hydrocarbon groups with 4 to 18 carbon atoms and one (meth)acryloyl group per molecule. (C) Component: A polyfunctional (meth)acrylate monomer having two to four (meth)acryloyl groups and further having polar functional groups. (D) Component: Photoradical polymerization initiator.

[0017] Conventional photocurable resin compositions, as mentioned above, have problems in that the resulting cured product is inferior in at least one of the following: compression set, resistance to compression cracking, compression reaction force at low compression ratios, and rubber elasticity at low temperatures. The inventors have found that by including components (A) to (D) in a photocurable resin composition, and by setting the content of components (A) to (C) within the aforementioned specific range, the resulting cured product exhibits low compression set, excellent resistance to compression cracking, high compression reaction force at low compression ratios, and excellent rubber elasticity at low temperatures. The estimated mechanism is shown below.

[0018] The inclusion of component (A) forms a cross-linked structure, reducing the compression set and improving the reaction force at low compression. Too little of component (A) results in insufficient compounding effect, while too much worsens the resistance to compression cracking, leading to cracking at high compression. Furthermore, if the molecular weight of component (A) exceeds 100,000, the cross-linked structure decreases, resulting in insufficient reaction force at low compression. In addition, component (A) has excellent heat resistance and hydrolysis resistance, and its low glass transition temperature allows the cured product to exhibit rubber elasticity even at low temperatures and have sufficient reaction force. The inclusion of component (B) allows the glass transition temperature of the cured product to be lowered without impairing the glass transition temperature of component (A), so the cured product can exhibit rubber elasticity even at low temperatures and have sufficient reaction force. Furthermore, having an alkyl group with 4 or more carbon atoms allows for miscibility with component (A), and the resulting cured product has excellent hydrolysis resistance. The inclusion of component (C) improves the reaction force at low compression. On the other hand, compression set, resistance to compression cracking, and rubber elasticity at low temperatures are not impaired. The reason why the compression crack resistance is not impaired is not entirely clear, but it is thought that this is because component (C) has polar functional groups, which slightly impairs its miscibility with component (A), causing the cured product to form a phase-separated structure. Too little (C) results in insufficient compounding effect, while too much (D) prevents miscibility with component (A) and causes separation. Component (D) is necessary for curing the photocurable resin composition by light irradiation.

[0019] The photocurable resin composition relating to this disclosure will be described in detail below. Furthermore, the photocurable resin composition relating to this disclosure can be suitably used as a photocurable resin composition for sealing materials, and more suitably used as a photocurable resin composition for sealing materials in fuel cells.

[0020] <Component (A): A polymer having a number average molecular weight of 1,000 to 100,000 and comprising a polyisobutylene skeleton and two or more (meth)acryloyl groups> The photocurable resin composition according to this disclosure comprises component (A), wherein the content of component (A) is 45 to 85 parts by mass per 100 parts by mass of the total of components (A) and (B).

[0021] The polyisobutylene skeleton refers to the structure shown below, where n is 2 or greater. Furthermore, component (A) may have only one of the following structures, or two or more.

[0022]

[0023] (A) As the monomer constituting component, isobutylene is mainly used, but other monomers may be copolymerized as long as they do not impair the effects of the present disclosure. Examples of other monomers include olefins having 4 to 12 carbon atoms, vinyl ethers, aromatic vinyl compounds, vinylsilanes, and allylsilanes. Specifically, isoprene, amylene, 1,3-butadiene, 1-butene, 2-butene, 2-methyl-1-butene, 3-methyl-1-butene, pentene, 4-methyl-1-pentene, hexene, vinylcyclohexene, α-pinene, β-pinene, limonene, styrene, indene, α-methylstyrene, methoxystyrene, methylstyrene (which may be o-, m-, or p-), trimethylstyrene, chlorostyrene, dichlorostyrene, methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether, vinyltrichlorosilane, vinylmethyl Examples include dichlorosilane, vinyldimethylchlorosilane, vinyldimethylmethoxysilane, vinyltrimethylsilane, divinyldichlorosilane, divinyldimethoxysilane, divinyldimethylsilane, 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, trivinylmethylsilane, tetravinylsilane, allyltrichlorosilane, allylmethyldichlorosilane, allyldimethylchlorosilane, allyldimethylmethoxysilane, allyltrimethylsilane, diallyldichlorosilane, diallyldimethoxysilane, diallyldimethylsilane, and the like.

[0024] Among these, isoprene, amylene, 1,3-butadiene, 1-butene, α-pinene, β-pinene, limonene, styrene, indene, α-methylstyrene, methylstyrene (including o-, m-, and p-forms), methyl vinyl ether, ethyl vinyl ether, and isobutyl vinyl ether are preferred from the viewpoint of copolymerizability.

[0025] If other monomers copolymerizable with isobutylene are used, they may be included in component (A) in an amount of preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 10% by mass or less, from the viewpoint of maintaining the effects of this disclosure.

[0026] The number-average molecular weight of component (A) is 1,000 to 100,000, and is preferably 2,000 to 100,000, more preferably 3,000 to 80,000, and even more preferably 5,000 to 50,000, from the viewpoint of compression set, resistance to compression cracking, compression reaction force at low compression ratios, and rubber elasticity at low temperatures.

[0027] (A) The molecular weight distribution of component (A) is not particularly limited, but from the viewpoint of compression set and ease of handling, it is preferably in the range of 1.0 to 1.8, more preferably in the range of 1.0 to 1.5, and even more preferably in the range of 1.0 to 1.3, expressed as (weight average molecular weight Mw) / (number average molecular weight Mn).

[0028] The number of (meth)acryloyl groups in component (A) is two or more, and from the viewpoint of compression set, resistance to compression cracking, compression reaction force at low compression ratio, and rubber elasticity at low temperatures, it is preferable to have two to ten groups, more preferably two to five groups, and particularly preferable to have two groups. Furthermore, from the viewpoint of reactivity during photocuring, the (meth)acryloyl groups are preferably acryloyl groups.

[0029] There are no particular restrictions on the way in which the (meth)acryloyl group in component (A) is bonded to the main chain of the polymer, but examples include ester bonds, ether bonds, amide bonds, urethane bonds, thioether bonds, carbonate bonds, urea bonds, and bonds consisting of divalent or greater hydrocarbon groups that do not have heteroatoms. Among these, ester bonds, ether bonds, amide bonds, or urethane bonds are preferred from the viewpoint of ease of synthesis and availability.

[0030] In the (A) component, there is no particular limitation on the bonding position of the (meth)acryloyl group, and it may be bonded at any position in the main chain. However, from the viewpoints of compression set, compression crack resistance, compression reaction force at a low compression rate, and rubber elasticity at low temperature, it is preferably bonded to at least one or more of the ends of the main chain, and more preferably bonded to both ends of the main chain.

[0031] In the structure of the (meth)acryloyl group in the (A) component, there is no particular limitation, but from the viewpoints of availability of raw materials and ease of production, it is preferably a structure represented by the following formula (A).

[0032]

[0033] In formula (A), R １Ａ represents a hydrogen atom or a methyl group, R ２Ａ represents an alkylene group having 2 to 6 carbon atoms, and R ３Ａ each independently represents a monovalent hydrocarbon group or an alkoxy group having 1 to 20 carbon atoms, nA represents an integer of 0 to 4, and * represents the bonding position with another structure.

[0034] Specific examples of R ２Ａ in formula (A) include, for example, -CH ２ CH ２ -, -CH ２ CH ２ CH ２ -, -CH ２ CH ２ CH ２ CH ２ -, -CH ２ CH ２ CH ２ CH ２ CH ２ -, -CH ２ CH ２ CH ２ CH ２ CH ２ CH ２ - and the like. Among these, -CH ２ CH ２ -, -CH ２ CH ２ CH ２ -, -CH ２ CH ２ CH ２CH ２ - is preferred from the viewpoint of raw material availability and reactivity.

[0035] R in equation (A) ３Ａ Specific examples of monovalent hydrocarbon groups and alkoxy groups having 1 to 20 carbon atoms in this context include methyl group, ethyl group, propyl group, isopropyl group, butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, 2-ethylhexyl group, nonyl group, decanyl group, methoxy group, ethoxy group, propoxy group, isopropoxy group, and butoxy group.

[0036] Among these, in terms of reactivity, nA is 0, or nA is 1 or 2 and R ３Ａ It is preferable that the group is a methyl group, and from the viewpoint of raw material availability, it is more preferable that nA is 0.

[0037] (A) There are no particular restrictions on the method for producing component (A), but the production methods described in International Publication No. 2013 / 047314, Japanese Patent Publication No. 2013-216782, International Publication No. 2017 / 099043, etc. may be referenced. Specifically, in the presence of a monofunctional and / or polyfunctional polymerization initiator, TiCl ４ One possible method involves producing a polyisobutylene polymer skeleton by living cationic polymerization of isobutylene using a Lewis acid catalyst and an electron donor component such as a nitrogen-containing compound, and then functionalizing the polymer's ends with a phenoxyalkyl (meth)acrylate compound or the like. These reactions are carried out at low temperatures, such as -70°C. These methods are preferred because the raw materials are readily available and highly productive, and they are suitable for industrial use.

[0038] Furthermore, component (A) may be a commercially available product. An example of a commercially available product is "KANEKA EPION EP400V" manufactured by Kaneka Corporation, but it is not limited to this product.

[0039] Component (A) may be used alone or in any combination of two or more types. The content of component (A) is preferably 45 to 80 parts by mass, and more preferably 50 to 70 parts by mass, based on 100 parts by mass of the total of components (A) and (B), from the viewpoint of compression set, resistance to compression cracking, compression reaction force at low compression ratio, and rubber elasticity at low temperatures. Furthermore, the content of component (A) is preferably 35% to 80% by mass, and more preferably 40% to 75% by mass, based on the total mass of the photocurable resin composition.

[0040] <Component (B): A monofunctional (meth)acrylate monomer having a linear or branched hydrocarbon group with 4 to 18 carbon atoms and one (meth)acryloyl group in one molecule> The photocurable resin composition according to this disclosure contains component (B), and the content of component (B) is 15 to 55 parts by mass per 100 parts by mass of the total of components (A) and (B).

[0041] Component (B) is preferably an acrylate monomer from the viewpoint of reactivity during photocuring. Furthermore, component (B) is preferably an alkyl (meth)acrylate monomer from the viewpoint of compression set at high temperatures and hydrolysis resistance. In addition, the molecular weight of component (B) is preferably less than 1,000.

[0042] The number of carbon atoms (also called "carbon number") in the linear hydrocarbon group in component (B) is 4 to 18, preferably 4 to 16, more preferably 4 to 10, and particularly preferably 6 to 9, from the viewpoint of compressive reaction force at low temperatures. The number of carbon atoms (also called "carbon number") in the branched hydrocarbon group in component (B) is 4 to 18, preferably 5 to 18, more preferably 5 to 16, and particularly preferably 6 to 16, from the viewpoint of compressive reaction force at low temperatures. Furthermore, the hydrocarbon group in component (B) is preferably an alkyl group from the viewpoint of compression set at high temperatures.

[0043] Examples of linear or branched alkyl groups having 4 to 18 carbon atoms include butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, isopentyl group, tert-pentyl group, neopentyl group, hexyl group, isohexyl group, heptyl group, octyl group, isooctyl group, 2-ethylhexyl group, nonyl group, isononyl group, decyl group, isodecyl group, undecyl group, dodecyl group (lauryl group), 2-hexyldecyl group, stearyl group, and isostearyl group.

[0044] Examples of component (B) include alkyl (meth)acrylate represented by the following formula (B-1), and (meth)acrylate of an ethylene oxide adduct of an alkyl alcohol represented by the following formula (B-2).

[0045]

[0046] In equations (B-1) and (B-2), R １Ｂ R represents a hydrogen atom or a methyl group. ２Ｂ nB represents a linear or branched alkyl group having 4 to 18 carbon atoms, and nB represents an integer from 1 to 4.

[0047] Component (B) may be used alone or in any combination of two or more types. The content of component (B) is preferably 20 to 55 parts by mass, and more preferably 30 to 50 parts by mass, per 100 parts by mass of the total of components (A) and (B), from the viewpoint of compression set, resistance to compression cracking, compression reaction force at low compression ratio, and rubber elasticity at low temperatures.

[0048] <Component (C): A polyfunctional (meth)acrylate monomer having two to four (meth)acryloyl groups and further having polar functional groups> The photocurable resin composition according to this disclosure contains component (C), and the content of component (C) is 1 to 35 parts by mass with respect to 100 parts by mass of the total of components (A) and (B).

[0049] Component (C) has a polar functional group along with a (meth)acryloyl group. The polar functional group may be a structural part having a bond between carbon and a nonmetallic element other than carbon and hydrogen, and examples of nonmetallic elements include N, P, O, S, F, and Cl. Here, the polar functional group is different from the (meth)acryloyl group that component (C) has, and polar functional groups containing a (meth)acryloyl group (specifically, (meth)acryloyloxy group, etc.), which are combinations of a (meth)acryloyl group and its linking group, are not included in the aforementioned polar functional group. Examples of polar functional groups in component (C) include isocyanurate skeleton, urethane bond, urea bond, amide group, imide group, amino group, carbonate bond, ester bond (except for the (meth)acryloyl group), carbonyl group, hydroxyl group, ether bond, etc. In particular, the polar functional group is preferably a polar functional group containing a nitrogen atom, more preferably a polar functional group having a structure in which a carbonyl group is bonded to a nitrogen atom, and even more preferably an isocyanurate skeleton, from the viewpoint of compression set, resistance to compression cracking, compression reaction force at low compressibility, and rubber elasticity at low temperatures. The number of polar functional groups in component (C) is not particularly limited, but may be, for example, 1 to 10, and more specifically, 1 to 5.

[0050] Component (C) is preferably an acrylate monomer from the viewpoint of reactivity during photocuring. Furthermore, the molecular weight of component (C) is preferably less than 2,000, more preferably less than 1,500, even more preferably less than 1,000, and may be less than 500. Component (C) is preferably a polyfunctional (meth)acrylate monomer having three or four (meth)acryloyl groups from the viewpoint of compression set, resistance to compression cracking, compression reaction force at low compressibility, and rubber elasticity at low temperatures. Furthermore, from the viewpoint of compression set, resistance to compression cracking, compression reaction force at low compressibility, and rubber elasticity at low temperatures, component (C) is particularly preferably having an isocyanurate skeleton and a urethane bond as polar functional groups.

[0051] Component (C) may be used alone or in any combination of two or more types. The content of component (C) is preferably 5 to 30 parts by mass, and more preferably 5 to 20 parts by mass, per 100 parts by mass of the total of components (A) and (B), from the viewpoint of compression set, resistance to compression cracking, compression reaction force at low compression ratio, and rubber elasticity at low temperatures.

[0052] <Component (D): Photo-radical polymerization initiator> The photocurable resin composition according to this disclosure contains component (D). Component (D) is a compound that generates radicals upon irradiation with light and initiates the polymerization of components (A), (B), and (C), which are compounds having radical polymerizable groups.

[0053] (D)Specific examples of components include benzyl, benzoin, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]-1-propanone], 2-hydroxy-1-[4-[4-(2-H Aromatic ketone compounds such as droxy-2-methylpropionyl)benzyl]phenyl]-2-methylpropan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-ylphenyl)-butan-1-one, ADEKA optomer N-1414 [manufactured by ADEKA Corporation], phenylglyoxylic acid methyl ester, ethylanthraquinone, and phenanthrenequinone; Benzophenone compounds such as benzophenone, 2-methylbenzophenone, 3-methylbenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 4-[[(4-methylphenyl)thio]phenyl]phenylmethanone, methyl-2-benzoylbenzoate, 1-[4-(4-benzoylphenylsulfanyl)phenyl]-2-methyl-2-(4-methylphenylsulfonyl)propan-1-one, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, and 4-methoxy-4'-dimethylaminobenzophenone; Acylphosphine oxide compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, ethyl-(2,4,6-trimethylbenzoyl)phenylphosphineate, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide;Thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 1-chloro-4-propylthioxanthone, 3-[3,4-dimethyl-9-oxo-9H-thioxanthone-2-yl]oxy]-2-hydroxypropyl-N,N,N-trimethylammonium chloride and fluorothioxanthone; acridone compounds such as acridone and 10-butyl-2-chloroacridone; oxime ester compounds such as 1-[4-(phenylthio)phenyl]-1,2-octanedione 2-(O-benzoyl oxime) and 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]ethanone 1-(O-acetyl oxime); Examples include 2,4,5-triarylimidazole dimers such as 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2-(o-chlorophenyl)-4,5-di(m-methoxyphenyl)imidazole dimer, 2-(o-fluorophenyl)-4,5-phenylimidazole dimer, 2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer, 2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer, 2,4-di(p-methoxyphenyl)-5-phenylimidazole dimer, and 2-(2,4-dimethoxyphenyl)-4,5-diphenylimidazole dimer; and acridine derivatives such as 9-phenylacridine and 1,7-bis(9,9'-acridinyl)heptane.

[0054] Furthermore, from the viewpoint of compression set, compression reaction force at low compressibility, and reactivity during photocuring, component (D) preferably includes the following components (D-1) and (D-2). Component (D-1): A photoradical polymerization initiator having a molar extinction coefficient of 10 L / (mol·cm) or more at at least one wavelength (I) between 395 nm and 435 nm. Component (D-2): A photoradical polymerization initiator having a molar extinction coefficient of less than 10 L / (mol·cm) at any wavelength between 395 nm and 435 nm, and a molar extinction coefficient of 10 L / (mol·cm) or more at at least one wavelength (II) between 280 nm and 385 nm.

[0055] Component (D) preferably contains component (D-1) from the viewpoint of compression set and compression reaction force at low compressibility. Examples of component (D-1) include acylphosphine oxide compounds, α-aminoalkylphenone compounds that satisfy the conditions for component (D-1), oxime ester compounds that satisfy the conditions for component (D-1), thioxanthone compounds, and the like.

[0056] "Acylphosphine oxide compounds" refer to compounds having an acylphosphine oxide structure. "α-aminoalkylphenone compounds" refer to compounds having an α-aminoalkylphenone structure. "Oxime ester compounds" refer to compounds having an oxime ester structure. "Thioxanthone compounds" refer to compounds having a thioxanthone structure.

[0057] Examples of acylphosphine oxide compounds include 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (Omnirad TPO, manufactured by IGM Resins) and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 380 (819), manufactured by IGM Resins). Examples of α-aminoalkylphenone compounds that satisfy the conditions of component (D-1) include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one (Omnirad 369, manufactured by IGM Resins) and 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-ylphenyl)-butan-1-one (IRGACURE 379 and 379EG, manufactured by BASF). Examples of oxime ester compounds that satisfy the conditions of component (D-1) include 1-[4-(phenylthio)phenyl]-1,2-octanedione 2-(O-benzoyl oxime) (IRGACURE OXE01, manufactured by BASF). Examples of thioxanthone compounds include thioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 1-chloro-4-propylthioxanthone, 3-[3,4-dimethyl-9-oxo-9H-thioxanthone-2-yl]oxy]-2-hydroxypropyl-N,N,N-trimethylammonium chloride, and fluorothioxanthone.

[0058] In particular, from the viewpoint of reactivity during photocuring, component (D-1) preferably contains at least one compound selected from the group consisting of acylphosphine oxide compounds, α-aminoalkylphenone compounds having a 4-morpholinophenyl group, oxime ester compounds having a 4-phenylthiophenyl group, and thioxanthone compounds. This allows for efficient partial curing of the photocurable resin composition in the irradiation step by light irradiation (a) described later. Component (D-1) may also be at least one compound selected from the group consisting of acylphosphine oxide compounds, α-aminoalkylphenone compounds satisfying the conditions of component (D-1), oxime ester compounds satisfying the conditions of component (D-1), and thioxanthone compounds. From the viewpoint of further lowering the compression set of the resulting photocurable resin composition, component (D-1) is more preferably an acylphosphine oxide compound, and even more preferably an acylphosphine oxide compound.

[0059] Component (D-1) may be used alone or in any combination of two or more types. From the viewpoint of compression set, compression reaction force at low compressibility, rubber elasticity at low temperatures, and reactivity during photocuring, the content of component (D-1) is preferably 0.01 to 0.9 parts by mass, more preferably 0.02 to 0.7 parts by mass, even more preferably 0.05 to 0.5 parts by mass, and particularly preferably 0.05 to 0.2 parts by mass, per 100 parts by mass of the total of components (A) and (B).

[0060] From the viewpoint of reactivity during photocuring, component (D) preferably contains component (D-2). Examples of component (D-2) include α-hydroxyalkylphenone compounds, α-aminoalkylphenone compounds that satisfy the conditions for component (D-2), oxime ester compounds that satisfy the conditions for component (D-2), benzyl ketal compounds, benzophenone compounds, and the like.

[0061] "α-hydroxyalkylphenone compounds" refer to compounds having an α-hydroxyalkylphenone structure. "Benzyl ketal compounds" refer to compounds having a benzyl ketal structure. "Benzophenone compounds" refer to compounds having a benzophenone structure.

[0062] Examples of α-hydroxyalkylphenone compounds include 2-hydroxy-1-[4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl]-2-methylpropan-1-one (Omnirad 127D, IGM Resins), 1-hydroxycyclohexylphenyl ketone (Omnirad 184, IGM Resins), 2-hydroxy-2-methyl-1-phenylpropan-1-one (Omnirad 1173, IGM Resins), 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one (Omnirad 2959, IGM Resins), and oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]-1-propanone] (ESACURE Examples include ONE (manufactured by IGM Resins). Examples of α-aminoalkylphenone compounds that satisfy the conditions of component (D-2) include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (IRGACURE 907, manufactured by BASF). Examples of benzyl ketal compounds include 2,2-dimethoxy-1,2-diphenylethane-1-one (Omnirad 651, manufactured by IGM Resins). Examples of oxime ester compounds that satisfy the conditions of component (D-2) include 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]ethanone 1-(O-acetyloxime) (IRGACURE OXE02, manufactured by BASF). Examples of benzophenone compounds include benzophenone, 2-methylbenzophenone, 3-methylbenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 4-(4-methylphenylthio)benzophenone, 1-[4-(4-benzoylphenylsulfanyl)phenyl]-2-methyl-2-(4-methylphenylsulfonyl)propan-1-one, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, and 4-methoxy-4'-dimethylaminobenzophenone.

[0063] The (D-2) component is preferably at least one selected from the group consisting of α-hydroxyalkylphenone compounds, α-aminoalkylphenone compounds (excluding those having a 4-morpholinophenyl group), benzyl ketal compounds, oxime ester compounds (excluding those having a 4-phenylthiophenyl group), and benzophenone compounds. This allows the photocurable resin composition to be sufficiently cured efficiently in the irradiation step by light irradiation (b) described later. The (D-2) component may also be at least one selected from the group consisting of α-hydroxyalkylphenone compounds, benzyl ketal compounds, and benzophenone compounds.

[0064] Component (D-2) may be used alone or in any combination of two or more types. From the viewpoint of compression set and reactivity during photocuring, the content of component (D-2) is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 4 parts by mass, and even more preferably 0.5 to 2 parts by mass, per 100 parts by mass of the total of components (A) and (B).

[0065] The content of component (D) is preferably 0.1 to 6 parts by mass, more preferably 0.2 to 5 parts by mass, and even more preferably 0.5 to 4 parts by mass, based on 100 parts by mass of the total of components (A) and (B), from the viewpoint of compression set, compression reaction force at low compressibility, rubber elasticity at low temperatures, and reactivity during photocuring.

[0066] <Component (E): Inorganic particles> The photocurable resin composition according to this disclosure preferably contains inorganic particles as component (E).

[0067] Examples of inorganic particles include silica, alumina, titania, zirconia, germania, cerium oxide, zinc oxide, boron nitride, silicon carbide, zeolite, talc, mica, hydrotalcite, smectite, bentonite, sepiolite, kaolinite, calcium carbonate, and hydroxyapatite. Metal particles can also be used as inorganic particles. Among these, silica, alumina, or titania are preferred from the viewpoint of compression set, resistance to compression cracking, compression reaction force at low compression ratios, and rubber elasticity at low temperatures, with silica being more preferred. There are no particular restrictions on the shape of the inorganic particles, and examples include spherical, plate-shaped, needle-shaped, fibrous, and irregularly shaped. Among these, spherical is preferred from the viewpoint of ease of handling of the resulting photocurable resin composition.

[0068] The average particle diameter of inorganic particles is preferably 0.01 μm to 200 μm, more preferably 0.01 μm to 100 μm, even more preferably 0.01 μm to 10 μm, and particularly preferably 0.01 μm to 2 μm, from the viewpoint of compression set, resistance to compression cracking, compression reaction force at low compressibility, and rubber elasticity at low temperatures. In this disclosure, the average particle diameter of inorganic particles refers to the volume-average particle diameter measured by laser diffraction particle size distribution analysis.

[0069] The inorganic particles are preferably inorganic particles whose surfaces are modified with organic groups, and from the viewpoint of dispersibility in components (A) and (B), the organic groups are more preferably hydrophobic groups such as alkyl groups and polydimethylsiloxane groups, or groups having radical polymerizability. There are no particular limitations on the surface treatment method for the inorganic particles, but examples include contacting the inorganic particles with a surface treatment agent such as a silane coupling agent, titanate coupling agent, aluminum coupling agent, fatty acid (e.g., stearic acid or oleic acid), or surfactant, or contacting the inorganic particles with an organosilicon compound such as dimethyldichlorosilane, hexamethyldisilazane, or silicone oil, and reacting the hydroxyl groups remaining on the surface of the inorganic particles with the organosilicon compound.

[0070] Component (E) may be used alone or in any combination of two or more types. From the viewpoint of compression set, resistance to compression cracking, compression reaction force at low compression ratio, and rubber elasticity at low temperatures, the content of component (E) is preferably 0.1 to 30 parts by mass, more preferably 1 to 25 parts by mass, and particularly preferably 3 to 20 parts by mass, per 100 parts by mass of the total of components (A) and (B).

[0071] <Other photoradical polymerizable polymers other than component (A)> The photocurable resin composition according to this disclosure may contain other photoradical polymerizable polymers other than component (A) as optional components, as long as they do not impair the effects of this disclosure.

[0072] Other photo-radical polymerizable polymers besides component (A) include (meth)acrylate polymers having (meth)acryloyl groups in part of the polymer skeleton (particularly at the ends of the polymer skeleton). The skeleton of the (meth)acrylate polymer is not particularly limited and includes urethane skeletons (i.e., urethane (meth)acrylate), hydrocarbon skeletons without double bonds (e.g., hydrogenated polybutadiene, hydrogenated polyisoprene, etc.), polyacrylic acid ester skeletons, polyether skeletons, hydrocarbon skeletons with double bonds, polyester skeletons, polycarbonate skeletons, etc. The number of radical polymerizable functional groups in one molecule of other photo-radical polymerizable polymers besides component (A) is not particularly limited, but is preferably 1 to 5, more preferably 1 to 3, and even more preferably 1 or 2.

[0073] In particular, among the photoradical polymerizable polymers other than component (A), urethane (meth)acrylate is preferred from the viewpoint of ease of availability and ease of manufacture. Urethane (meth)acrylate may have a skeleton such as a hydrocarbon skeleton without double bonds (e.g., hydrogenated polybutadiene, hydrogenated polyisoprene, etc.), a polyether skeleton, a hydrocarbon skeleton with double bonds, a polyester skeleton, or a polycarbonate skeleton.

[0074] In particular, urethane (meth)acrylate is preferably composed of a hydrocarbon skeleton without double bonds or a polyether skeleton, from the viewpoint of compression set at high temperatures, compression reaction force at low temperatures, and hydrolysis resistance, and is more preferably composed of at least one of hydrogenated polybutadiene and hydrogenated polyisoprene as the hydrocarbon skeleton without double bonds.

[0075] Other photoradical polymers excluding component (A) may be commercially available products. Examples of difunctional urethane (meth)acrylates having a polyether backbone include the Art Resin series from Negami Kogyo Co., Ltd. (UN-6200, UN-6207, UN-6306, UN-6304, UN-6305, UN-6060S, etc.). Examples of difunctional urethane (meth)acrylates having a hydrogenated polybutadiene backbone include TEAI-1000 from Nippon Soda Co., Ltd. Other photoradical polymers excluding component (A) may consist of only one type or two or more types.

[0076] Other photoradical polymerizable polymers other than component (A) may be used alone or in any combination of two or more. The content of other photoradical polymerizable polymers other than component (A) is preferably 0 to 50 parts by mass, more preferably 0 to 25 parts by mass, even more preferably 0 to 10 parts by mass, and particularly preferably 0 parts by mass, based on 100 parts by mass of the total of components (A) and (B). In other words, it is particularly preferable that the photocurable resin composition according to this disclosure does not contain other photoradical polymerizable polymers other than component (A).

[0077] <Other photoradical polymerizable monomers excluding components (B) and (C)> The photocurable resin composition according to this disclosure may contain, as an optional component, other photoradical polymerizable monomers excluding components (B) and (C), insofar as they do not impair the effects of this disclosure.

[0078] Other photo-radical polymerizable monomers excluding components (B) and (C) include monofunctional (meth)acrylate monomers having only linear or branched hydrocarbon groups with 1 to 3 carbon atoms as hydrocarbon groups, monofunctional (meth)acrylate monomers having only linear or branched hydrocarbon groups with 19 or more carbon atoms as hydrocarbon groups, monofunctional (meth)acrylate monomers having alicyclic hydrocarbon groups, monofunctional (meth)acrylate monomers having aromatic rings, monofunctional (meth)acrylate monomers having ethylene glycol chains, monofunctional (meth)acrylate monomers having propylene glycol chains, monofunctional (meth)acrylate monomers having heterocyclic rings, polyfunctional (meth)acrylate monomers, (meth)acrylic acid, (meth)acrylamide monomers, olefin monomers, styrene monomers, and the like. The number of radical polymerizable functional groups in one molecule of other photo-radical polymerizable monomers excluding components (B) and (C) is not particularly limited, but is preferably 1 to 4, more preferably 1 to 2, and even more preferably 1.

[0079] Other photoradical polymerizable monomers, excluding components (B) and (C), may be used individually or in any combination of two or more. From the viewpoint of compression set, resistance to compression cracking, compression reaction force at low compression ratios, and rubber elasticity at low temperatures, the content of other photoradical polymerizable monomers, excluding components (A) and (B), is preferably 0 to 25 parts by mass, more preferably 0 to 10 parts by mass, even more preferably 0 to 5 parts by mass, and particularly preferably 0 parts by mass, per 100 parts by mass of the total of components (A) and (B). In other words, it is particularly preferable that the photocurable resin composition according to this disclosure does not contain other photoradical polymerizable monomers, excluding components (B) and (C).

[0080] <Components that do not exhibit photoradical polymerizability> The photocurable resin composition according to this disclosure may contain components that do not exhibit photoradical polymerizability, as long as they do not impair the effects of this disclosure. Examples of components that do not exhibit photoradical polymerizability include thermal polymerization initiators, ultraviolet absorbers, light stabilizers, antioxidants, polymerization inhibitors, silane coupling agents, nonreactive polymers, ion trapping agents, defoaming agents, leveling agents, dyes and pigments, etc.

[0081] (Sealing Material) The sealing material according to this disclosure is a sealing material obtained by curing a photocurable resin composition according to this disclosure. The shape of the sealing material is appropriately selected according to the application of the sealing material, and examples include rings, packings, gaskets, diaphragms, oil seals, bearing seals, lip seals, plunger seals, door seals, lips, face seals, gas delivery plate seals, wafer support seals, and barrel seals.

[0082] The sealing material exhibits low compression set, excellent crack resistance at high compression ratios, excellent compressive reaction force at low compression ratios, sufficient compressive reaction force at low temperatures, and excellent water resistance. Therefore, the sealing material is preferably used for fuel cell applications. Examples of fuel cells include polymer electrolyte membrane fuel cells.

[0083] Hereafter, sealing materials for fuel cell applications will also be referred to as "fuel cell sealing materials."

[0084] Examples of shapes for sealing materials used in fuel cells include O-rings, V-rings, rods, sheets, and blocks.

[0085] In fuel cells, it is important to seal the components of a single cell, or to seal the spaces between the components of a single cell. Fuel cell sealing materials can effectively seal these components and the spaces between them. Examples of single cell components include an electrolyte membrane, electrodes, separators, and a frame.

[0086] (Method for Manufacturing a Sealing Material) The method for manufacturing a sealing material according to the present disclosure is not particularly limited, but it includes, in this order, a step of irradiating a photocurable resin composition according to the present disclosure with light (a) containing the wavelength (I), and a step of irradiating it with light (b) containing the wavelength (II) (hereinafter also referred to as the "irradiation step"), wherein the irradiation energy of light (a) in the wavelength range of 200 nm to 385 nm is 0.2 times or less the irradiation energy of light (a) in the wavelength range of 395 nm to 435 nm. Furthermore, the photocurable resin composition according to the present disclosure used in the method for manufacturing the sealing material according to the present disclosure comprises, in part (D), the following components (D-1) and (D-2): (D-1) component: a photoradical polymerization initiator having a molar extinction coefficient of 10 L / (mol・cm) or more at at least one wavelength (I) between 395 nm and 435 nm; (D-2) component: a photoradical polymerization initiator having a molar extinction coefficient of less than 10 L / (mol・cm) at any wavelength between 395 nm and 435 nm, and a molar extinction coefficient of 10 L / (mol・cm) or more at at least one wavelength (II) between 280 nm and 385 nm. Preferably, the content of component (D-1) is 0.01 to 0.9 parts by mass and the content of component (D-2) is 0.1 to 5 parts by mass per 100 parts by mass of the total of components (A) and (B).

[0087] The method for manufacturing a sealing material according to this disclosure may further include, in addition to the irradiation step, a step of preparing a photocurable resin composition (hereinafter also referred to as the "preparation step") and a step of molding the photocurable resin composition into the shape of a sealing material (hereinafter also referred to as the "molding step"). The preparation step, the molding step, and the irradiation step are carried out in this order. The following describes the case in which the method for manufacturing a sealing material according to this disclosure includes a preparation step, a molding step, and an irradiation step.

[0088] <Preparation Process> In the preparation process, the photocurable resin composition is prepared.

[0089] The method for preparing the photocurable resin composition is not particularly limited and any known method is acceptable. The photocurable resin composition may be kneaded using a kneader. Examples of kneaders include kneaders, Banbury mixers, roll mills, and single-screw extruders.

[0090] <Molding Process> In the molding process, the light-curing resin composition is molded into the shape of a sealing material.

[0091] The molding method for the light-curing resin composition can be appropriately selected according to the shape of the sealing material, and any known method is acceptable.

[0092] When the shape of the sealing material is bead-shaped, one possible method for molding the photocurable resin composition is to use a coating apparatus having a needle-shaped coating section. The coating apparatus extrudes the photocurable resin composition from the needle-shaped coating section to form the photocurable resin composition into a bead shape.

[0093] If the shape of the sealing material is not bead-shaped, a method for molding the photocurable resin composition may be, for example, injection into a mold. The voids (i.e., molding space) of the mold correspond to the shape of the sealing material. The configuration of the mold is not particularly limited and any known configuration is acceptable. The material of the mold is not particularly limited as long as it can cure the photocurable resin composition in the irradiation process, and examples include glass, resin, and metal. The mold may also be equipped with heating means, cooling means, depressurization means, pressurization means, etc. The method of injecting the photocurable resin composition into the mold is not particularly limited and any known method is acceptable.

[0094] <Irradiation Process> In the irradiation process, the photocurable resin composition is irradiated with light (a) containing at least one wavelength (I) between 395 nm and 435 nm, and then with light (b) containing at least one wavelength (II) between 200 nm and 385 nm. As a result, the photocurable resin composition is cured to obtain a sealing material.

[0095] -Light Irradiation (a)- The wavelength of light (a) is appropriately selected according to the type of component (D-1), etc., as long as it includes at least one wavelength (I) between 395 nm and 435 nm. Wavelength (I) may include at least one between 395 nm and 420 nm, at least one between 400 nm and 410 nm, or 405 nm. The illuminance of light (a) is appropriately selected according to the type of component (D-1), etc. The illuminance of light (a) is 100 mW / cm². ２ ~5,000mW / cm ２However, 200 mW / cm ２ ~2,000mW / cm ２ Also, 500 mW / cm ２ ~1,500mW / cm ２ This is also acceptable. The irradiation dose of light (a) is appropriately selected according to the type of component (D-1), etc. The irradiation dose of light (a) is 100 mJ / cm². ２ ~5,000mJ / cm ２ Alternatively, 200 mJ / cm ２ ~4,000mJ / cm ２ Alternatively, 1,000 mJ / cm² may be used. ２ ~4,000mJ / cm ２ That's fine.

[0096] In light irradiation (a), the wavelength was 405 nm and the illuminance was 500 mW / cm². ２ ~1,500mW / cm ２ The irradiation dose was 1,000 mJ / cm². ２ ~4,000mJ / cm ２ This is preferable. This allows for efficient partial curing of the photocurable resin composition in a short amount of time.

[0097] The light source for light irradiation (a) is preferably an LED (light-emitting diode), but a multi-wavelength light source such as a low-pressure mercury lamp, medium-pressure mercury lamp, high-pressure mercury lamp, ultra-high-pressure mercury lamp, or metal halide lamp equipped with a wavelength cut filter can also be used.

[0098] Light irradiation (a) may be performed while heating the photocurable resin composition. After performing light irradiation (a), the photocurable resin composition may be heated as needed.

[0099] - Light Irradiation (b) - The wavelength of light (b) is appropriately selected according to the type of component (D-1) and the type of component (D-2), etc., as long as it includes at least one wavelength (II) between 200 nm and 385 nm. Wavelength (II) may include at least one between 300 nm and 385 nm, at least one between 350 nm and 380 nm, or 365 nm. The illuminance of light (b) is appropriately selected according to the type of component (D-1) and the type of component (D-2), etc. The illuminance of light (b) is 100 mW / cm². ２ ~5,000mW / cm ２ However, 200 mW / cm ２ ~3,000mW / cm ２ Also, 500 mW / cm ２ ~2,000mW / cm ２ This may also be the case. The irradiation dose of light (b) is appropriately selected according to the type of component (D-1) and the type of component (D-2), etc. The irradiation dose of light (b) is 200 mJ / cm². ２ ~10,000mJ / cm ２ Also, 500 mJ / cm ２ ~10,000mJ / cm ２ Alternatively, 2,000 mJ / cm² may be used. ２ ~7,000mJ / cm ２ That's fine.

[0100] In light irradiation (b), the wavelength was 365 nm and the illuminance was 500 mW / cm². ２ ~2,000mW / cm ２ The irradiation dose was 2,000 mJ / cm². ２ ~7,000mJ / cm ２ This is preferable. This allows the photocurable resin composition to cure sufficiently quickly and efficiently.

[0101] The light source for light irradiation (b) is not particularly limited and includes LEDs, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, UV (ultraviolet) electrodeless lamps, etc.

[0102] Light irradiation (b) may be performed continuously after light irradiation (a). Light irradiation (b) may be performed while heating the photocurable resin composition. After light irradiation (b), the photocurable resin composition may be heated as needed.

[0103] In particular, the illuminance of the aforementioned light (a) is 100 mW / cm². ２ ~5,000mW / cm ２ The irradiation dose was 100 mJ / cm². ２ ~5,000mJ / cm ２ The illuminance of light (b) is 100 mW / cm². ２ ~5,000mW / cm ２ The irradiation dose was 200 mJ / cm². ２ ~10,000mJ / cm ２ It is preferable that the range is as described above. Within this range, the sealing material can be obtained with short curing time without impairing the effects of this disclosure.

[0104] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to the following examples unless it exceeds the spirit of the disclosure.

[0105] 1. Preparation of Photocurable Resin Compositions The following abbreviations are used for the materials shown in the Examples and Comparative Examples.

[0106] (A) Component EP400V: Acryloyl-terminated polyisobutylene (KANEKA EPION EP400V manufactured by Kaneka Corporation, Mn = 15,000, Mw = 17,000, viscosity 3,500,000 mPa·s @ 23℃)

[0107] (B) Components: NOAA: n-octyl acrylate (NOAA manufactured by Osaka Organic Chemical Industry Co., Ltd.) IDAA: isodecyl acrylate (IDAA manufactured by Osaka Organic Chemical Industry Co., Ltd.) MT-1522: 2-hexyldecyl acrylate (Aronics MT-1522 manufactured by Toagosei Co., Ltd.)

[0108] (C) Component M-313: A mixture of diacrylate (having a hydroxyl group and an isocyanurate skeleton) and triacrylate (having an isocyanurate skeleton) of tris(2-hydroxyethyl) isocyanurate (Aronix M-313, manufactured by Toagosei Co., Ltd.) ・MFA-1: A bifunctional acrylate having a urethane skeleton. Product of Synthesis Example 1. ・MFA-2: A trifunctional acrylate having an isocyanurate skeleton and a urethane skeleton. Product of Synthesis Example 2. ・MFA-3: A mixture of a tetrafunctional acrylate having an isocyanurate skeleton and a urethane skeleton and triacrylate (having an isocyanurate skeleton) of tris(2-hydroxyethyl) isocyanurate. Product of Synthesis Example 3. ・MFA-4: A mixture of diacrylate (having a hydroxyl group and an ether skeleton) and triacrylate (having a hydroxyl group and an ether skeleton) of diglycerin.

[0109] (C) Component comparison component ((C') component) ・1,9-NDDA: 1,9-nonanediol diacrylate (has no polar functional groups other than acryloyl groups) (Light Acrylate 1.9ND-A manufactured by Kyoeisha Chemical Co., Ltd.) ・M-309: Trimethylolpropane triacrylate (has no polar functional groups other than acryloyl groups) (Aronics M-309 manufactured by Toagosei Co., Ltd.) ・M-403: Mixture of dipentaerythritol pentaacrylate (has hydroxyl groups and an ether skeleton) and hexaacrylate (has an ether skeleton) (Aronics M-403 manufactured by Toagosei Co., Ltd.)

[0110] (D-1) Component O-380: Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 380, manufactured by IGM Resin)

[0111] (D-2) Components: O-1173: 2-hydroxy-2-methyl-1-phenylpropan-1-one (Omnirad 1173, manufactured by IGM Resins) and O-651: 2,2-dimethoxy-1,2-diphenylethane-1-one (Omnirad 651, manufactured by IGM Resins)

[0112] (E) Component NHM-3N: Surface hydrophobic treated silica (SILFIL NHM-3N manufactured by Tokuyama Corporation, average particle size 0.15 μm)

[0113] <Synthesis Example 1: Bifunctional Acrylate with Urethane Skeleton (MFA-1)> 222 g of isophorone diisocyanate (2.00 mol as isocyanate groups), 0.010 g of acetylacetone ferric and 0.26 g of 2,6-di-t-butyl-p-cresol were placed in a 1 L four-necked separable flask. A thermometer, gas inlet tube, reflux condenser, and stirrer were attached to the flask, and the mixture of oxygen and nitrogen (5% oxygen) was circulated over the liquid while stirring at 65°C until dissolved. 292 g of 4-hydroxybutyl acrylate (2.02 mol as hydroxyl groups) was added to this solution and mixed, after which the temperature was increased. The reaction was carried out at 80°C for 5 hours, and the disappearance of the isocyanate groups was confirmed by IR spectroscopy, thus completing the synthesis.

[0114] <Synthesis Example 2: Trifunctional Acrylate (MFA-2) Having Isocyanurate and Urethane Skeletons> 366 g of Asahi Kasei Corporation's Duranate TPA-100 (isocyanate group content 23.0 wt%) (2.00 mol as isocyanate groups), 0.013 g of ferric acetylacetone, and 0.33 g of 2,6-di-t-butyl-p-cresol were charged into a 1 L four-necked separable flask. A thermometer, gas inlet tube, reflux condenser, and stirrer were attached to the flask, and the mixture of oxygen and nitrogen (5% oxygen) was circulated over the liquid while stirring at 65°C until dissolved. 292 g of 4-hydroxybutyl acrylate (2.02 mol as hydroxyl groups) was added to this solution and mixed, after which the temperature was increased. The reaction was carried out at 80°C for 3 hours, and the disappearance of the isocyanate groups was confirmed by IR spectroscopy, thus completing the synthesis.

[0115] <Synthesis Example 3: Mixture of a tetrafunctional acrylate having an isocyanurate skeleton and a urethane skeleton and a triacrylate of tris(2-hydroxyethyl) isocyanurate (MFA-3)> 651 g of M-313 (hydroxyl value 46.0 mg KOH / g) manufactured by Toagosei Co., Ltd. (0.53 mol as hydroxyl groups), 0.007 g of ferric acetylacetone, and 0.35 g of 2,6-di-t-butyl-p-cresol were placed in a 1 L four-necked separable flask. A thermometer, gas inlet tube, reflux condenser, and stirrer were attached to the flask, and the mixture of oxygen and nitrogen gas (5% oxygen) was circulated over the liquid while stirring at 60°C until dissolved. 49.0 g of isophorone diisocyanate (0.44 mol as isocyanate groups) was added to this solution and mixed, after which heating was started. The reaction was carried out at 80°C for 3 hours, and the disappearance of the isocyanate group was confirmed by IR spectroscopy, thus ending the synthesis.

[0116] (Examples 1-14 and Comparative Examples 1-8) 6-1. Preparation of Photocurable Resin Composition First, each component except for component (E) was blended in the proportions shown in Table 1 and stirred and mixed according to a conventional method. At that time, it was heated to about 80°C as needed. Subsequently, component (E) was added to the above blend in the proportion shown in Table 1 and mixed for 10 minutes using a planetary stirring and defoaming apparatus to obtain a photocurable resin composition. When component (E) was not included, mixing using a planetary stirring and defoaming apparatus was not performed.

[0117] 6-2. Preparation of Samples for Evaluation of Photocurable Resin Compositions The photocurable resin composition prepared in 6-1 was poured into a 1 mm thick silicone mold (size: 7 mm x 2 mm) placed on a PET film, laminated with PET film, and photocured. In Examples 12 and 14, the samples were irradiated using a 405 nm LED (surface-type LED irradiator manufactured by CCS Corporation) under the conditions shown in Table 1, and then irradiated using a 365 nm LED (surface-type LED irradiator manufactured by CCS Corporation) under the conditions shown in the table. For the other examples and comparative examples, the samples were irradiated using a 365 nm LED (surface-type LED irradiator manufactured by CCS Corporation) under the conditions shown in Table 1. A Hamamatsu Photonics C12684 illuminometer was used for illuminance measurement.

[0118] 6-3. Evaluation of Liquid Stability of Photocurable Resin Composition The photocurable resin composition prepared in 6-1 was left at 25°C for 24 hours in a light-shielded state. After that, the appearance of the photocurable resin composition was observed and the liquid stability was judged as follows: A: No separation observed F: Separation observed

[0119] 6-4. Evaluation of High-Temperature Compression Cracking Resistance of Photocurable Resin Compositions The evaluation samples obtained in 6-2 were compressed using a jig to a compressibility of 50% or 55%, and then placed in a constant-temperature bath at 105°C for 24 hours. After that, the jig was removed from the constant-temperature bath, cooled to 25°C, and the compression was released, and the sample was removed from the jig. The appearance of the sample was observed, and the high-temperature compression cracking resistance was judged as follows. If the sample broke at a compressibility of 50%, the evaluation in 6-5 was not performed. A: No breakage at a compressibility of 55% B: No breakage at a compressibility of 50%, but breakage at a compressibility of 55% C: Breakage at a compressibility of 50%

[0120] 6-5. Evaluation of High-Temperature Compression Set of Photocurable Resin Compositions The evaluation samples obtained in 6-2 were subjected to compression set tests using fixtures and conditions in accordance with JIS K6262:2013. Using the fixture, the samples were compressed so that the compressibility of the cured material was 50%, and then placed in a constant-temperature bath at 140°C for 72 hours. After that, the fixture was removed from the constant-temperature bath, cooled to 25°C, the compression was released, and the sample was removed from the fixture and left at 25°C for 30 minutes. Finally, the thickness of each sample was measured and the compression set was calculated, and the high-temperature compression set was judged as follows: A: Compression set less than 10% B: Compression set 10% or more and less than 20% C: Compression set 20% or more

[0121] 6-6. A rheometer Discovery HR-20 manufactured by TA Instruments was used to evaluate the reaction force of the photocurable resin composition at low compression and low temperatures. First, the evaluation sample obtained in 6-2 was compressed to a compressibility of 20% at a speed of 1 μm / s at 25°C and held for 30 minutes. Next, while maintaining the compressibility of 20%, the temperature was raised to 105°C and held for 30 minutes. Next, while maintaining the compressibility of 20%, the temperature was lowered to -35°C and held for 30 minutes. The surface pressure after holding for 30 minutes at each temperature of -35°C, 25°C, and 105°C was calculated and the following judgments were made. (i) Reaction force at low compression A: Surface pressure at 25°C and 105°C is greater than 0.20 MPa B: Surface pressure at 25°C or 105°C is greater than 0.20 MPa in only one of the two C: Surface pressure at 25°C and 105°C is 0.20 MPa or less (ii) Reaction force at low temperature A: Surface pressure at -35°C is greater than 0.05 MPa B: Surface pressure at -35°C is greater than 0 MPa and 0.05 MPa or less C: Surface pressure at -35°C is 0 MPa or less

[0122] The evaluation results are summarized in Table 1.

[0123]

[0124] As shown in Table 1, the photocurable resin compositions of Examples 1 to 14 exhibited excellent liquid stability, and the resulting cured products had low compression set, excellent resistance to compression cracking, high compressive reaction force at low compression ratios, and excellent rubber elasticity at low temperatures. On the other hand, the photocurable resin compositions of Comparative Examples 1 to 8 had poor liquid stability, or the resulting cured products were inferior in either compression set, resistance to compression cracking, or compressive reaction force at low compression ratios.

[0125] The disclosure of Japanese Patent Application No. 2024-211794, filed on 4 December 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

Claims

1. A photocurable resin composition comprising the following components (A) to (D), wherein, per 100 parts by mass of the total of components (A) and (B), the content of component (A) is 45 to 85 parts by mass, the content of component (B) is 15 to 55 parts by mass, and the content of component (C) is 1 to 35 parts by mass. (A) component: A polymer having a polyisobutylene skeleton and two or more (meth)acryloyl groups, with a number average molecular weight of 1,000 to 100,000. (B) component: A monofunctional (meth)acrylate monomer having linear or branched hydrocarbon groups with 4 to 18 carbon atoms and one (meth)acryloyl group per molecule. (C) component: A polyfunctional (meth)acrylate monomer having two to four (meth)acryloyl groups and further having polar functional groups. (D) component: A photoradical polymerization initiator.

2. The photocurable resin composition according to claim 1, wherein component (A) comprises a polyisobutylene resin having a number average molecular weight of 1,000 to 100,000 and having (meth)acryloyl groups at both ends.

3. The photocurable resin composition according to claim 1, wherein component (B) comprises a monofunctional (meth)acrylate monomer having a linear or branched hydrocarbon group having 4 to 16 carbon atoms and one (meth)acryloyl group in one molecule.

4. The photocurable resin composition according to claim 1, wherein component (C) comprises a polyfunctional (meth)acrylate monomer having a polar functional group containing a nitrogen atom and having two to four (meth)acryloyl groups.

5. The photocurable resin composition according to claim 1, wherein component (C) comprises a polyfunctional (meth)acrylate monomer having an isocyanurate skeleton and having two to four (meth)acryloyl groups.

6. The photocurable resin composition according to claim 1, further comprising inorganic particles as component (E).

7. The photocurable resin composition according to claim 6, wherein the content of component (E) is 0.1 to 30 parts by mass with respect to 100 parts by mass of the total of components (A) and (B).

8. The photocurable resin composition according to claim 6, wherein the average particle size of component (E) is 0.01 μm or more and 200 μm or less.

9. The photocurable resin composition according to claim 1, wherein component (D) comprises the following components (D-1) and (D-2), and the content of component (D-1) is 0.01 to 0.9 parts by mass and the content of component (D-2) is 0.1 to 5 parts by mass per 100 parts by mass of the total of components (A) and (B). Component (D-1): A photoradical polymerization initiator having a molar extinction coefficient of 10 L / (mol・cm) or more at at least one wavelength (I) between 395 nm and 435 nm. Component (D-2): A photoradical polymerization initiator having a molar extinction coefficient of less than 10 L / (mol・cm) at any wavelength between 395 nm and 435 nm, and a molar extinction coefficient of 10 L / (mol・cm) or more at at least one wavelength (II) between 280 nm and 385 nm.

10. The photocurable resin composition according to claim 9, wherein component (D-1) comprises at least one compound selected from the group consisting of acylphosphine oxide compounds, α-aminoalkylphenone compounds having a 4-morpholinophenyl group, oxime ester compounds having a 4-phenylthiophenyl group, and thioxanthone compounds.

11. The photocurable resin composition according to claim 9, wherein component (D-2) comprises at least one compound selected from the group consisting of α-hydroxyalkylphenone compounds, α-aminoalkylphenone compounds (excluding those having a 4-morpholinophenyl group), benzyl ketal compounds, oxime ester compounds (excluding those having a 4-phenylthiophenyl group), and benzophenone compounds.

12. The photocurable resin composition according to claim 1, which is a photocurable resin composition for sealing materials.

13. The photocurable resin composition according to claim 1, which is a photocurable resin composition for use as a sealing material for fuel cells.

14. A method for producing a sealing material, comprising the steps of irradiating a photocurable resin composition according to any one of claims 9 to 11 with light (a) containing the wavelength (I), and irradiating it with light (b) containing the wavelength (II), wherein the irradiation energy of light (a) in the wavelength range of 200 nm to 385 nm is 0.2 times or less the irradiation energy of light (a) in the wavelength range of 395 nm to 435 nm.

15. The illuminance of the light (a) is 10 mW / cm². ２ ~5,000mW / cm ２ The irradiation dose was 50 mJ / cm². ２ ~5,000mJ / cm ２ The illuminance of light (b) is 10 mW / cm². ２ ~5,000mW / cm ２ The irradiation dose was 50 mJ / cm². ２ ~10,000mJ / cm ２ The method for manufacturing a sealing material according to claim 14.

16. The method for manufacturing a seal material according to claim 14, wherein the manufactured seal material is for use in a fuel cell.

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