Sealing material production method, and sealing material

Abstract

A sealing material production method according to the present disclosure comprises a step for irradiating a photocurable resin composition with light (a) including at least one wavelength (I) of 395-435 nm, and irradiating the same with light (b) including at least one wavelength (II) of 200-385 nm. In the light (a), the irradiation energy in the wavelength range of 200-385 nm is 0.2 times or less of the irradiation energy in the wavelength range of 395-435 nm. The photocurable resin composition contains, at a specific ratio, a specific component (A), a specific component (B), a specific component (C), and a specific component (D).

Description

Method for manufacturing sealing material and sealing material

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

[0002] Conventionally, fixed sealing materials (hereinafter also referred to as "gaskets") have been used to provide airtightness and liquid-tightness to components such as equipment and piping. Solid gaskets have generally been used as gaskets. Solid gaskets are formed using a mold. In recent years, liquid gaskets have become popular. Liquid gaskets are obtained by applying a liquid curable resin composition to the sealing surface using a dispenser or the like and then curing it. Liquid gaskets have the following advantages (i) and (ii) over solid gaskets: (i) Because no mold is required for production, the shape of the liquid gasket can be made to match the shape of the workpiece to be sealed; and (ii) Because the liquid curable resin composition can penetrate even rough sealing surfaces, the finishing costs of the sealing surface can be reduced.

[0003] Liquid gaskets are mainly classified into formed-in-place gaskets (FIPGs) and cured-in-place gaskets (CIPGs). In FIPGs, a liquid curable resin composition is applied to a first sealing surface to form a coating of the curable resin composition. The coating is then brought into contact with a second sealing surface, and the coating is cured to seal the first and second sealing surfaces. In CIPGs, a liquid curable resin composition is applied to the first sealing surface, cured to form a cured product of the curable resin (hereinafter simply referred to as the "cured product"). The second sealing surface is then brought into contact with the cured product and pressure is applied to seal the first and second sealing surfaces. Therefore, in FIPGs, sealing is ensured by adhesion between the first and second sealing surfaces and the cured product. In CIPGs, sealing is ensured by adhesion between the first sealing surface and the cured product and the elasticity of the cured product. In CIPG, the second sealing surface and the cured product are not bonded to each other, and therefore CIPG has the advantage over FIPG in that it is easier to rework.

[0004] Liquid gaskets require the curing of a curable resin composition during the assembly process. This can result in a longer cycle time for liquid gaskets than for solid gaskets. However, if a photocurable resin composition that can be cured in a short time is used as the raw material for the liquid gasket, the cycle time can be shortened.

[0005] Patent Document 1 discloses a photocurable resin composition that can be suitably used as a sealing material for preventing dust and moisture from entering the interior of electronic devices (for example, hard disk drives or smartphones). Patent Document 2 discloses a photocurable resin composition that can be suitably used as various sealing materials for the interior of fuel cells.

[0006] In order to use a cured product as a CIPG, it is necessary for the cured product to maintain its sealing properties for a long period of time (i.e., the cured product must have excellent resistance to sag and not lose its elasticity for a long period of time). A compression set test is known as a method for evaluating sag resistance. The smaller the compression set, the better the sag resistance.

[0007] Known techniques for reducing the compression set of a cured product include blending an acrylic monomer having a propylene glycol skeleton into a photocurable resin composition (Patent Document 3), blending a polyfunctional photocurable monomer into a photocurable resin composition (Patent Document 4), blending a high-molecular-weight styrene-based elastomer into a photocurable resin composition (Patent Document 5), and blending two types of photoradical polymerization initiators into a photocurable resin composition (Patent Document 6).

[0008] Compression set tests are often performed in accordance with JIS K6262 under measurement conditions (compression rate: 25%, temperature: 70°C, holding time: 22 hours) in which a cured product compressed to a compression rate of 25% is left at 70°C for 22 hours. However, as described in Patent Document 7, fuel cell sealing materials are sometimes used at compression rates of up to 60%.

[0009] Patent Document 1: JP 2021-021012 A Patent Document 2: JP 2022-057075 A Patent Document 3: JP 2017-122139 A Patent Document 4: JP 2022-024078 A Patent Document 5: WO 2020 / 137658 Patent Document 6: WO 2016 / 194870 Patent Document 7: JP 2005-285537 A

[0010] To use a cured photocurable resin as a sealant for fuel cells (particularly for CIPG), it is necessary to have low compression set under evaluation conditions stricter than those specified in JIS K6262. For example, low compression set is required even at a compression rate of approximately 50%. The operating temperature of a polymer electrolyte fuel cell is as high as nearly 100°C. Additionally, a long life is also required for the cured photocurable resin. Therefore, durability evaluation requires low compression set even after compression at temperatures significantly higher than 100°C for a period significantly longer than 22 hours. However, as shown below, conventional cured photocurable resins have shown insufficient performance in terms of low compression set and other aspects under such strict evaluation conditions.

[0011] Patent Document 3 describes that the incorporation of an acrylic monomer having a propylene glycol skeleton reduces the compression set at 100°C for 72 hours under 25% compression. However, since the propylene glycol skeleton has poor heat resistance, the compression set increases in tests at higher temperatures and for longer periods.

[0012] Patent Document 4 describes that the incorporation of a polyfunctional photocurable monomer reduces compression set at 25% compression for 100 hours at 120°C and 100 hours at 150°C. However, as pointed out in Patent Document 4, the polyfunctional photocurable monomer impairs the extensibility and flexibility of the cured product, so that the sealant may be damaged at a high compression rate such as 50%, or if the part to be sealed has low rigidity, the elastic force of the sealant may deform the part during compression.

[0013] Patent Document 5 describes that the incorporation of a high-molecular-weight styrene elastomer having a weight-average molecular weight of 200,000 or more reduces the compression set at 70°C for 22 hours under 25% compression. However, at high temperatures above the glass transition temperature of polystyrene (100°C), the styrene elastomer flows, resulting in a large compression set.

[0014] Patent Document 6 describes that blending two types of initiators reduces compression set under 25% compression at 70°C for 22 hours. However, when the present inventors prepared a cured product according to Patent Document 6 and performed a compression set test at 140°C for 72 hours under 50% compression, the compression set was large.

[0015] Therefore, there is a demand for a method for producing a sealing material that can produce a sealing material that exhibits small compression set in a compression set test at a high compression ratio (compression ratio: 50%), at a high temperature (temperature: 140°C), and for a long period of time (holding time: 72 hours) by curing in a short time (total light irradiation time: 10 seconds or less).

[0016] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a method for producing a sealing material that can produce a sealing material that exhibits small compression set in a high-temperature, long-term compression set test by curing in a short time, and the sealing material.

[0017] Specific means for solving the above problems include the following aspects.

[0018] <1> A method for producing a sealing material, comprising the steps of irradiating a photocurable resin composition with light (a) having at least one wavelength (I) of 395 nm to 435 nm, and then irradiating with light (b) having at least one wavelength (II) of 200 nm to 385 nm, wherein the irradiation energy of the light (a) in the wavelength range of 200 nm to 385 nm is 0.2 times or less than the irradiation energy of the wavelength range of 395 nm to 435 nm, and the photocurable resin composition contains the following components (A) to (D): component (A) is contained in an amount of 10 parts by mass to 70 parts by mass, component (B) is contained in an amount of 30 parts by mass to 90 parts by mass, component (C) is contained in an amount of 0.01 parts by mass to 0.9 parts by mass, and component (D) is contained in an amount of 0.1 parts by mass to 5 parts by mass, relative to a total of 100 parts by mass of the component (A) and the component (B). Component (A): a polymer having a number average molecular weight of 1,000 or more and having two or more (meth)acryloyl groups; Component (B): a monofunctional (meth)acrylate having a homopolymer glass transition temperature (Tg) of 20°C or less, an alkyl group having 5 to 30 carbon atoms, and one (meth)acryloyl group per molecule; Component (C): a photoradical polymerization initiator having a molar absorption coefficient of 10 L / (mol cm) or more at wavelength (I); and Component (D): a photoradical polymerization initiator having a molar absorption coefficient of less than 10 L / (mol cm) at any wavelength from 395 nm to 435 nm and a molar absorption coefficient of 10 L / (mol cm) or more at wavelength (II). <2> The illuminance of the light (a) is 100 mW / cm ２ ~5000mW / cm ２ , irradiation dose 100 mJ / cm ２ ~5000mJ / cm ２ and the illuminance of the light (b) is 100 mW / cm ２ ~5000mW / cm ２ , irradiation dose 200 mJ / cm ２ ~10000mJ / cm ２<3> The method for producing a sealing material according to <1>, wherein the polymer is a urethane (meth)acrylate (A-1), or a (meth)acrylate (A-2) having a skeleton containing polyisobutylene and having no urethane bond. <4> The method for producing a sealing material according to <3>, wherein the polymer is the urethane (meth)acrylate (A-1), and the urethane (meth)acrylate (A-1) has a skeleton consisting of at least one of hydrogenated polybutadiene and hydrogenated polyisoprene. <5> The method for producing a sealing material according to <3>, wherein the polymer is the (meth)acrylate (A-2). <6> The method for producing a sealing material according to any one of <1> to <5>, wherein the component (C) contains at least one selected from the group consisting of an acylphosphine oxide-based compound, an α-aminoalkylphenone-based compound, an oxime ester-based compound, and a thioxanthone-based compound. <7> The method for producing a sealing material according to any one of <1> to <6>, wherein the component (D) includes at least one selected from the group consisting of an α-hydroxyalkylphenone compound, a benzil ketal compound, and a benzophenone compound. <8> The method for producing a sealing material according to any one of <1> to <7>, wherein the sealing material is used for a fuel cell. <9> A sealing material comprising a structural unit derived from the following component (A) and a structural unit derived from the following component (B), and having a compression set (in accordance with JIS K6262:2013, but with a compression rate of 50%, a temperature of 140°C, and a holding time of 72 hours) of 35% or less: Component (A): a polymer having a number average molecular weight of 1,000 or more and having two or more (meth)acryloyl groups; and Component (B): a monofunctional (meth)acrylate having a homopolymer glass transition temperature (Tg) of 20°C or less, having an alkyl group with 5 to 30 carbon atoms, and having one (meth)acryloyl group per molecule. <10> The sealing material according to <9>, wherein the polymer is a urethane (meth)acrylate (A-1), or a (meth)acrylate (A-2) having a skeleton containing polyisobutylene and having no urethane bond.

[0019] According to one embodiment of the present disclosure, there is provided a method for producing a sealing material, which can produce a sealing material with small compression set in a high compression ratio, high temperature, and long-term compression set test with short curing time, and a sealing material.

[0020] In the present disclosure, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits. In the present disclosure, when multiple substances corresponding to each component are present in the composition, the amount of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified. In the numerical ranges described in stages in the present disclosure, the upper or lower limit described in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. In the numerical ranges described in the present disclosure, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. In the present disclosure, combinations of preferred embodiments are more preferred embodiments. In the description of groups (atomic groups) in the present disclosure, a description that does not specify whether they are substituted or unsubstituted includes both unsubstituted and substituted groups. In the present disclosure, "(meth)acrylate" means at least one of acrylate and methacrylate. In the present disclosure, "urethane (meth)acrylate" means a (meth)acrylate polymer having a urethane skeleton.

[0021] (1) Method for Producing a Sealing Material The method for producing a sealing material of the present disclosure includes a step (hereinafter also referred to as the "irradiation step") of irradiating a photocurable resin composition with light (a) containing at least one wavelength (I) in the range of 395 nm to 435 nm, and then irradiating with light (b) containing at least one wavelength (II) in the range of 200 nm to 385 nm. The irradiation energy of the light (a) in the wavelength range of 200 nm to 385 nm is 0.2 times or less than the irradiation energy in the wavelength range of 395 nm to 435 nm. The photocurable resin composition contains the following components (A) to (D) (i.e., component (A), component (B), component (C), and component (D)). The content of the component (A) is 10 parts by mass to 70 parts by mass, the content of the component (B) is 30 parts by mass to 90 parts by mass, the content of the component (C) is 0.01 parts by mass to 0.9 parts by mass, and the content of the component (D) is 0.1 parts by mass to 5 parts by mass, relative to 100 parts by mass of the total of the component (A) and the component (B). Component (A): a polymer having two or more (meth)acryloyl groups and a number average molecular weight (hereinafter also referred to as "Mn") of 1,000 or more; Component (B): a monofunctional (meth)acrylate having a homopolymer glass transition temperature (Tg) of 20°C or less, an alkyl group having 5 to 30 carbon atoms, and one (meth)acryloyl group per molecule; Component (C): a photoradical polymerization initiator having a molar absorption coefficient of 10 L / (mol cm) or more at wavelength (I); and Component (D): a photoradical polymerization initiator having a molar absorption coefficient of less than 10 L / (mol cm) at any wavelength from 395 nm to 435 nm and a molar absorption coefficient of 10 L / (mol cm) or more at wavelength (II).

[0022] The phrase "the irradiation energy of the light (a) in the wavelength range of 200 nm to 385 nm is 0.2 times or less than the irradiation energy in the wavelength range of 395 nm to 435 nm" indicates that the light (a) may include light in the wavelength range of 200 nm to 385 nm, as long as the effects of the present disclosure are not impaired. Light in the wavelength range of 200 nm to 385 nm that may be included in the light (a) does not sufficiently promote curing of the photocurable resin composition. The ratio of the irradiation energy in the wavelength range of 200 nm to 385 nm in the light (a) to the irradiation energy in the wavelength range of 395 nm to 435 nm can be calculated, for example, by measuring the emission spectrum of the light (a) using a spectroradiometer. "Number average molecular weight" refers to the value obtained by converting the molecular weight measured by gel permeation chromatography (hereinafter also referred to as "GPC") into polystyrene equivalents. Gel permeation chromatography (GPC) measurements can be performed under the measurement conditions described below to obtain the number average molecular weight (Mn) and weight average molecular weight (Mw) in polystyrene equivalents. <Measurement conditions> Apparatus: HLC-8320 manufactured by Tosoh Corporation Column: TSKgel-SuperMultipore HZ-M (4.6 mm ID x 15 cm) x 3 (for small molecules, exclusion limit molecular weight 2 million) manufactured by Tosoh Corporation Column temperature: 40°C Eluent: tetrahydrofuran (0.35 ml / min) Detector: RI Sample concentration: 0.1%

[0023] "Molar absorption coefficient" refers to the value of ε shown in the following formula (A). "ε" is determined by the Lambert-Beer equation for an acetonitrile solution containing a photoradical polymerization initiator. In formula (A), "I" represents the intensity of transmitted light. "Io" represents the intensity of transmitted light through pure acetonitrile. "c" represents the molar concentration (M). "d" represents the thickness (cm) of the solution layer. "log(Io / I)" represents the absorbance. Formula (A): ε = log(Io / I) / (c × d) The molar absorption coefficient of a photoradical polymerization initiator can be measured, for example, according to the following method. Using acetonitrile as the solvent, the photoradical polymerization agent is dissolved to a concentration of 1 g / L, and the absorbance is measured at room temperature using a quartz cell with a UV-visible spectrophotometer, and calculated using the Lambert-Beer law. For wavelengths where the absorbance exceeds 2.0, the photoradical polymerization initiator is dissolved at a concentration where the absorbance falls within the range of 0.1 to 2.0, and the absorbance is measured at room temperature using a quartz cell with an ultraviolet-visible spectrophotometer, and the absorbance is calculated using the Beer-Lambert law.

[0024] Hereinafter, "irradiating with light (a) containing at least one wavelength (I) in the range of 395 nm to 435 nm" will also be referred to as "light irradiation (a)." Hereinafter, "irradiating with light (b) containing at least one wavelength (II) in the range of 200 nm to 385 nm" will also be referred to as "light irradiation (b)."

[0025] The method for producing a sealing material according to the present disclosure has the above-described configuration, and therefore can produce a sealing material that exhibits small compression set in a compression set test at a high compression ratio (compression ratio: 50%), a high temperature (temperature: 140°C), and a long time (holding time: 72 hours) by curing in a short time (total light irradiation time: 10 seconds or less). Therefore, a sealing material with excellent reliability and durability can be produced with good productivity.

[0026] This effect is presumably due to, but not limited to, the following reasons: When the photocurable resin composition contains component (A), a crosslinked structure is formed by the irradiation step. This improves the settling resistance of the sealing material. As a result, the compression set of the sealing material at high temperatures is reduced. When the content of component (A) is less than 10 parts by mass, the effect of adding component (A) is insufficient. When the content of component (A) is more than 70 parts by mass, the compression resistance of the sealing material deteriorates, causing cracks in the sealing material when compressed. When the photocurable resin composition contains component (B), the glass transition temperature of the sealing material is lowered, and the sealing material has rubber elasticity at low temperatures (e.g., 0°C). When the monofunctional (meth)acrylate of component (B) has an alkyl group having 5 or more carbon atoms, it is miscible with component (A) and the hydrolysis resistance of the sealing material is improved. When the content of component (C) is 0.01 parts by mass or more, curing of the photocurable resin composition proceeds by light irradiation (a). The curing of the photocurable resin composition by light irradiation (a) does not progress sufficiently, and the reaction rate of the photocurable resin composition does not fully increase. Therefore, the subsequent light irradiation (b) sufficiently progresses the curing of the photocurable resin composition (for this reason, the photocurable resin composition contains component (D)). When the content of component (C) is 0.9 parts by mass or less, the compression set of the sealing material is reduced. When the content of component (D) is 0.1 parts by mass or more, the curing of the photocurable resin composition by light irradiation (b) progresses. As a result, the curing of the photocurable resin composition progresses sufficiently after light irradiation (a). When the content of component (D) is less than 0.1 parts by mass, the curing of the photocurable resin composition does not progress sufficiently. When the content of component (D) is 5 parts by mass or less, the compression set of the sealing material is reduced. In the present disclosure, the photocurable resin composition is partially cured by light irradiation (a), and then fully cured by light irradiation (b). By doing so, even if the contents of components (C) and (D) are small, the photocurable resin composition can be cured in a short time by performing the irradiation step. As a result, the compression set of the sealing material is small.When only one of light irradiation (a) and light irradiation (b) is performed in the irradiation step, it is difficult to achieve both rapid curing of the curable resin composition and reduced compression set of the sealing material. Specifically, when the content of the photoradical polymerization initiator (i.e., components (C) and (D)) is high, the curing of the curable resin composition can be sufficiently promoted in a short time using high-intensity light, but the compression set of the resulting sealing material is large. When the content of the photoradical polymerization initiator (i.e., components (C) and (D)) is low and high-intensity light is used, the photoradical polymerization initiator is consumed completely before the curing of the curable resin composition has sufficiently progressed. Therefore, the curing of the curable resin composition cannot be sufficiently promoted in a short time. When the content of the photoradical polymerization initiator (i.e., components (C) and (D)) is low and low-intensity light is used, the compression set of the sealing material is small, but it takes a long time to cure the curable resin composition. For these reasons, it is presumed that the method for producing a sealing material according to the present disclosure can produce a sealing material with small compression set in a high compression ratio, high temperature, and long-term compression set test with short curing time.

[0027] In addition to the irradiation step, the method for producing a sealing material according to the present disclosure may further include a step of preparing a photocurable resin composition (hereinafter also referred to as a "preparation step") and a step of molding the photocurable resin composition into the shape of a sealing material (hereinafter also referred to as a "molding step"). The preparation step, molding step, and irradiation step are performed in this order. Below, a description will be given of a case where the method for producing a sealing material according to the present disclosure includes the preparation step, molding step, and irradiation step.

[0028] (1.1) Preparation Step In the preparation step, a photocurable resin composition is prepared.

[0029] The method for preparing the photocurable resin composition is not particularly limited and may be any known method. The photocurable resin composition may be kneaded using a kneader. Examples of kneaders include a kneader, a Banbury mixer, a roll mill, and a single-screw extruder.

[0030] (1.1.1) Photocurable Resin Composition The photocurable resin composition contains components (A) to (D) in specific proportions.

[0031] (1.1.1.1) Component (A) The photocurable resin composition contains component (A). Component (A) is a polymer having an Mn of 1000 or more and having two or more (meth)acryloyl groups. Component (A) preferably has two (meth)acryloyl groups.

[0032] The Mn of component (A) is 1,000 or more, preferably 1,000 to 100,000, more preferably 3,000 to 80,000, and even more preferably 5,000 to 60,000. When the Mn of component (A) is 1,000 or more, the resulting sealing material has excellent adhesive strength. When the Mn of component (A) is 100,000 or less, the solubility of component (A) in the photocurable resin composition is even better.

[0033] The content of component (A) is 10 parts by mass to 70 parts by mass, relative to 100 parts by mass of the total of components (A) and (B). Depending on the structure of component (A), for example, when component (A) contains a bifunctional urethane (meth)acrylate having a polyether skeleton, the content of component (A) may be 10 parts by mass to 40 parts by mass, or 10 parts by mass to 30 parts by mass. Depending on the structure of component (A), for example, when component (A) contains a urethane (meth)acrylate having a polydiene skeleton, the content of component (A) may be 30 parts by mass to 70 parts by mass, or 40 parts by mass to 70 parts by mass.

[0034] The polymer is not particularly limited, but is particularly preferably a (meth)acrylate polymer having a (meth)acryloyl group in a part of the polymer backbone (particularly at the end of the polymer backbone). The backbone of the (meth)acrylate polymer is not particularly limited, and examples thereof include a urethane backbone (i.e., urethane (meth)acrylate), a hydrocarbon backbone without a double bond (e.g., polyisobutylene, hydrogenated polybutadiene, hydrogenated polyisoprene, etc.), a polyacrylic acid backbone, a polyether backbone, a hydrocarbon backbone with a double bond, a polyester backbone, and a polycarbonate backbone.

[0035] Among these, the polymer is preferably a urethane (meth)acrylate (A-1) (hereinafter also referred to as "component (A-1)") or a (meth)acrylate (A-2) (hereinafter also referred to as "component (A-2)") that has a skeleton containing polyisobutylene and does not have a urethane bond. This makes it possible for the method for producing a sealing material of the present disclosure to produce a sealing material with small compression set.

[0036] Hereinafter, a urethane (meth)acrylate having two (meth)acryloyl groups will also be referred to as a "bifunctional urethane (meth)acrylate."

[0037] (1.1.1.1.1) Component (A-1) As described above, the component (A-1) is a urethane (meth)acrylate (A-1) having an Mn of 1,000 or more and having two or more (meth)acryloyl groups.

[0038] The component (A-1) may have a skeleton such as a hydrocarbon skeleton without a double bond (for example, hydrogenated polybutadiene or hydrogenated polyisoprene), a polyether skeleton, a hydrocarbon skeleton with a double bond, a polyester skeleton, or a polycarbonate skeleton.

[0039] In particular, the component (A-1) preferably contains a hydrocarbon skeleton having no double bonds or a polyether skeleton. By including a hydrocarbon skeleton having no double bonds or a polyether skeleton in the component (A-1), the resulting sealing material has the physical properties required for a sealing material for fuel cells (i.e., heat resistance, hydrolysis resistance, and rubber elasticity at low temperatures).

[0040] The component (A-1) is preferably a urethane acrylate, from the viewpoint of achieving an excellent photocuring rate for the photocurable resin composition.

[0041] The component (A-1) may be a commercially available product. Examples of bifunctional urethane (meth)acrylates having a polyether skeleton include the Art Resin series (UN-6200, UN-6207, UN-6306, UN-6304, UN-6305, UN-6060S, etc.) manufactured by Negami Chemical Industrial Co., Ltd. The component (A-1) may contain only one type, or two or more types. For example, when the component (A-1) contains two or more types of bifunctional urethane (meth)acrylates having a polyether skeleton (for example, two types, UN-6304 and UN-6305), a cured product with excellent rubber elasticity at low temperatures can be obtained.

[0042] It is preferable that the polymer is the urethane (meth)acrylate (A-1), and that the urethane (meth)acrylate (A-1) contains a skeleton consisting of at least one of hydrogenated polybutadiene and hydrogenated polyisoprene (hereinafter also referred to as a "polydiene skeleton"), which allows for the production of a cured product with even more excellent heat resistance and hydrolysis resistance.

[0043] The following describes the case where component (A-1) contains a polydiene skeleton.

[0044] Examples of the component (A-1) include the following component (A-1-1) and the following component (A-1-2): Component (A-1-1): a urethane reaction product of a polydiene alcohol, a polyisocyanate, and a (meth)acrylate having a hydroxyl group; Component (A-1-2): an addition reaction product of a polydiene alcohol with a compound having an isocyanate group and a (meth)acryloyl group.

[0045] The following describes preferred raw material compounds for the component (A-1-1), namely, polydiene diol, polyisocyanate, and compound containing a hydroxyl group and a (meth)acryloyl group.

[0046] Examples of polydiene diols include polybutadiene diol, polyisoprene diol, and butadiene-styrene copolymer diols. Examples of hydrogenated polydiene diols include hydrogenated polybutadiene diol, hydrogenated polyisoprene diol, and hydrogenated products of butadiene-styrene copolymer diols. Of these, those in which the double bonds are hydrogenated are preferred because they provide good compression set at high temperatures. Of these, hydrogenated polybutadiene diol or hydrogenated polyisoprene diol is preferred. Hydrogenated polybutadiene diol and hydrogenated polyisoprene diol may be used in combination. The Mn of the polydiene diol is preferably 500 to 5,000, more preferably 1,000 to 4,000.

[0047] As the polyisocyanate, a compound having two isocyanate groups per molecule (hereinafter also referred to as "diisocyanate") is preferred. Using a compound having three or more isocyanate groups per molecule may result in gelation during synthesis, or even if synthesis is possible without gelation, cracking may occur under high compression. Examples of diisocyanates include aliphatic diisocyanates (e.g., hexamethylene diisocyanate), alicyclic diisocyanates (e.g., isophorone diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate), and aromatic diisocyanates (e.g., tolylene diisocyanate, diphenylmethane diisocyanate, tolidine diisocyanate, naphthalene diisocyanate, xylylene diisocyanate).

[0048] Examples of compounds containing a hydroxyl group and a (meth)acryloyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, caprolactone-modified 2-hydroxyethyl (meth)acrylate, and glycidol di(meth)acrylate. Among these compounds, preferred compounds containing a hydroxyl group and a (meth)acryloyl group are hydroxyalkyl (meth)acrylates (e.g., 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate).

[0049] Preferred methods for producing component (A-1-1) include, for example, Production Method 1 or Production Method 2. Production Method 1 is a method in which a polydiene diol is reacted with a diisocyanate to produce a urethane prepolymer having an isocyanate group, and the prepolymer is then reacted with a compound containing a hydroxyl group and a (meth)acryloyl group. Production Method 2 is a method in which a polydiene diol, a diisocyanate, and a compound containing a hydroxyl group and a (meth)acryloyl group are reacted. In the present disclosure, the polydiene urethane (meth)acrylate obtained by Production Method 1 is preferred. This makes it easy to control the molecular weight. The polydiene urethane (meth)acrylate obtained by Production Method 1 has excellent solubility in other components. The resulting composition has excellent adhesive strength.

[0050] In the production of the preferred component (A-1-1), the molar ratio of the polydiene diol to the diisocyanate (polydiene diol:diisocyanate) is preferably 1:2.2 to 1:1.05, more preferably 1:2 to 1:1.1, and even more preferably 1:1.8 to 1:1.1. When the component (A-1) is reacted at this ratio, the resulting component (A-1) has excellent solubility with other (meth)acrylates, and the resulting sealing material has excellent adhesive strength.

[0051] (1.1.1.1.2) Component (A-2) As described above, component (A-2) is a copolymer having an Mn of 1000 or more, two or more (meth)acryloyl groups, and a copolymer of polyisobutylene (-[CH２ C(CH ３ ) ２

[0033] The (meth)acrylate (A-2) has a skeleton containing a methyl group-containing methyl group-containing methyl group unit (M-1)-unit and does not have a urethane bond. The skeleton of the component (A-2) may be made of polyisobutylene.

[0052] The polymer is preferably the (meth)acrylate (A-2), whereby the method for producing a sealing material according to the present disclosure can produce a sealing material with a smaller compression set than when the polymer is component (A-1).

[0053] The component (A-2) may be a commercially available product, such as "KANEKA EPION EP400V" manufactured by Kaneka Corporation.

[0054] (1.1.1.2) Component (B) The photocurable resin composition contains component (B), which is a monofunctional (meth)acrylate having a homopolymer glass transition temperature (Tg) of 20°C or lower, an alkyl group having 5 to 30 carbon atoms, and one (meth)acryloyl group per molecule.

[0055] The glass transition temperature (Tg) of the homopolymer of component (B) is 20°C or lower, and may be 0°C or lower. The glass transition temperature (Tg) of the homopolymer of component (B) can be determined from the intersection of the baseline of a heat flux curve obtained using a differential scanning calorimeter and the tangent at the inflection point. The measurement may be performed using the following measuring equipment and conditions. The heat flux curve is obtained by heating approximately 5 mg of a sample to 70°C at 20°C / min, holding it for 5 minutes, cooling it to -150°C at -20°C / min, holding it for 5 minutes, and then heating it again to 70°C at 20°C / min. <Measuring equipment and measuring conditions> Measuring equipment: DSC 214 Polymer manufactured by NETZSCH Measurement atmosphere: Nitrogen atmosphere

[0056] Examples of the component (B) include alkyl (meth)acrylates represented by the following general formula (1) and (meth)acrylates of ethylene oxide adducts of alkyl alcohols represented by the following general formula (2): The component (B) may be used alone or in any combination of two or more.

[0057]

[0058]

[0059] In the general formula (1) and the general formula (2), R １ represents a hydrogen atom or a methyl group. ２ represents an alkyl group having 5 to 30 carbon atoms. In the general formula (2), n is an integer of 1 to 4.

[0060] Examples of the alkyl group having 5 to 30 carbon atoms include a pentyl group, an isopentyl group, a tert-pentyl group, a neopentyl group, a hexyl group, a 2-ethylhexyl group, an isohexyl group, a heptyl group, an octyl group, an isooctyl group, a nonyl group, an isononyl group, a decyl group, an isodecyl group, an undecyl group, a dodecyl group (a lauryl group), and an isostearyl group.

[0061] From the viewpoint of excellent photocuring speed, the monofunctional (meth)acrylate is a monofunctional acrylate (i.e., R １ is a hydrogen atom).

[0062] The content of component (B) is 30 to 90 parts by mass, relative to 100 parts by mass of the total of components (A) and (B). When component (B) is a (meth)acrylate of an ethylene oxide adduct of an alkyl alcohol represented by general formula (2), the content of component (B) may be 70 to 90 parts by mass, or may be 75 to 85 parts by mass. When component (B) is an alkyl (meth)acrylate represented by general formula (1), the content of component (B) may be 30 to 70 parts by mass, or may be 40 to 60 parts by mass.

[0063] (1.1.1.3) Component (C) The photocurable resin composition contains component (C), which is a photoradical polymerization initiator having a molar absorption coefficient of 10 L / (mol cm) or more at at least one wavelength (I) in the range of 395 nm to 435 nm.

[0064] Examples of the component (C) include acylphosphine oxide compounds, α-aminoalkylphenone compounds that satisfy the conditions for the component (C), oxime ester compounds that satisfy the conditions for the component (C), and thioxanthone compounds. The component (C) may be used alone or in any combination of two or more.

[0065] "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.

[0066] Examples of acylphosphine oxide compounds include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (DARCUR TPO) and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Omnirad 380 (819)). Examples of α-aminoalkylphenone compounds that satisfy the conditions of component (C) include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one (Omnirad 369) and 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one (IRGACURE 379 or 379EG). Examples of oxime ester compounds that satisfy the requirements for component (C) include 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoyloxime) (IRGACURE OXE01), etc. 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.

[0067] In particular, the component (C) preferably contains at least one selected from the group consisting of an acylphosphine oxide compound, an α-aminoalkylphenone compound that satisfies the requirements for the component (C), an oxime ester compound that satisfies the requirements for the component (C), and a thioxanthone compound. This allows the curing of the photocurable resin composition to proceed efficiently in the irradiation step (a) by light irradiation. The component (C) may be at least one selected from the group consisting of an acylphosphine oxide compound, an α-aminoalkylphenone compound that satisfies the requirements for the component (C), an oxime ester compound that satisfies the requirements for the component (C), and a thioxanthone compound. From the viewpoint of further reducing the compression set of the resulting sealing material, the component (C) more preferably contains an acylphosphine oxide compound, and even more preferably is an acylphosphine oxide compound.

[0068] The content of component (C) is 0.01 to 0.9 parts by mass relative to 100 parts by mass of the total of components (A) and (B). From the viewpoint of further reducing compression set, the content of component (C) is preferably 0.05 to 0.9 parts by mass, more preferably 0.05 to 0.5 parts by mass, even more preferably 0.05 to 0.4 parts by mass, and particularly preferably 0.1 to 0.4 parts by mass.

[0069] (1.1.1.4) Component (D) The photocurable resin composition contains component (D), which is a photoradical polymerization initiator having a molar absorption coefficient of less than 10 L / (mol cm) at any wavelength from 395 nm to 435 nm and a molar absorption coefficient of 10 L / (mol cm) or more at at least one wavelength (II) from 200 nm to 385 nm.

[0070] Examples of the component (D) include an α-hydroxyalkylphenone compound, an α-aminoalkylphenone compound that satisfies the requirements for the component (D), an oxime ester compound, a benzyl ketal compound, or a benzophenone compound that satisfies the requirements for the component (D), etc. The component (D) may be used alone or in any combination of two or more types.

[0071] "α-Hydroxyalkylphenone compounds" refer to compounds having an α-hydroxyalkylphenone structure. "Benzil ketal compounds" refer to compounds having a benzil ketal structure. "Benzophenone compounds" refer to compounds having a benzophenone structure.

[0072] Examples of α-hydroxyalkylphenone compounds include 2-hydroxy-1-[4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl]-2-methylpropan-1-one (Omnirad 127D), 1-hydroxycyclohexylphenyl ketone (Omnirad 184), 2-hydroxy-2-methyl-1-phenylpropan-1-one (Omnirad 1173), 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one (Omnirad 2959), and oligo[2-hydroxy-2-methyl-1-[4-1-(methylvinyl)phenyl]propanone (ESACURE ONE). Examples of α-aminoalkylphenone compounds that satisfy the requirements for component (D) include 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one (IRGACURE 907). Examples of benzyl ketal compounds include 2,2-dimethoxy-1,2-diphenylethan-1-one (Omnirad 651). Examples of oxime ester compounds that satisfy the requirements for component (D) include ethanone, 1-[9-(ethyl)-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime) (IRGACURE OXE02). 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.

[0073] The component (D) preferably contains at least one selected from the group consisting of an α-hydroxyalkylphenone compound, a benzyl ketal compound, and a benzophenone compound. This allows the curing of the photocurable resin composition to proceed efficiently and sufficiently in the irradiation step (b) by light irradiation. The component (D) may be at least one selected from the group consisting of an α-hydroxyalkylphenone compound, a benzyl ketal compound, and a benzophenone compound.

[0074] The content of component (D) is 0.1 to 5 parts by mass relative to 100 parts by mass of the total of components (A) and (B). From the viewpoint of further reducing compression set, the content of component (D) is preferably 0.2 to 4 parts by mass, more preferably 0.5 to 2 parts by mass.

[0075] (1.1.1.5) Other Components The photocurable resin composition may contain other components as long as the effects of the present disclosure are not impaired. Examples of other components include a thermal polymerization initiator, an ultraviolet absorber, a light stabilizer, an antioxidant, a polymerization inhibitor, a silane coupling agent, a non-reactive polymer, a filler, metal fine particles, metal oxide fine particles, an ion trapping agent, an antifoaming agent, a leveling agent, a dye or a pigment, etc.

[0076] (1.2) Molding Step In the molding step, the photocurable resin composition is molded into the shape of the sealing material.

[0077] The method for molding the photocurable resin composition is appropriately selected depending on the shape of the sealing material, and any known method may be used.

[0078] When the sealing material is in the form of a bead, the photocurable resin composition can be molded, for example, using a coating device having a needle-shaped coating unit, which ejects the photocurable resin composition from the needle-shaped coating unit to mold the photocurable resin composition into a bead shape.

[0079] When the shape of the sealing material is not bead-shaped, examples of the molding method of the photocurable resin composition include a method of injecting the composition into a molding die. The cavity of the molding die (i.e., the molding space) corresponds to the shape of the sealing material. The configuration of the molding die is not particularly limited, and any known configuration may be used. The material of the molding die is not particularly limited as long as it can cure the photocurable resin composition in the irradiation step, and examples include glass, resin, and metal. The molding die may also be equipped with a heating means, a cooling means, a decompression means, a pressurization means, etc. The method of injecting the photocurable resin composition into the molding die is not particularly limited, and any known method may be used.

[0080] (1.3) Irradiation Step In the irradiation step, the photocurable resin composition is irradiated with light (a) containing at least one wavelength (I) of 395 nm to 435 nm, and then with light (b) containing at least one wavelength (II) of 200 nm to 385 nm, thereby curing the photocurable resin composition and obtaining a sealing material.

[0081] (1.3.1) Light Irradiation (a) The wavelength of light (a) is appropriately selected depending on the type of component (C) and the type of component (D), etc., as long as it includes at least one wavelength (I) between 395 nm and 435 nm. Wavelength (I) may include at least one wavelength between 395 nm and 420 nm, or at least one wavelength between 400 nm and 410 nm, or may include 405 nm. Light (a) having a maximum peak of irradiance in the wavelength range of 395 to 435 nm within the wavelength range of 200 to 450 nm can be preferably used. The wavelength range with the maximum peak of irradiance is preferably 395 to 420 nm, more preferably 400 to 410 nm. The irradiance of light (a) is appropriately selected depending on the type of component (C) and the type of component (D), etc. The irradiance of light (a) is 100 mW / cm ２ ~5000mW / cm ２ or 200 mW / cm ２ ~2000mW / cm ２ or 500 mW / cm ２ ~1500mW / cm ２The irradiation dose of the light (a) is appropriately selected depending on the type of the component (C) and the type of the component (D), etc. The irradiation dose of the light (a) is 100 mJ / cm ２ ~5000mJ / cm ２ or 200 mJ / cm ２ ~4000mJ / cm ２ or 1000 mJ / cm ２ ~4000mJ / cm ２ may be.

[0082] In the light irradiation (a), the wavelength was 405 nm and the illuminance was 500 mW / cm ２ ~1500mW / cm ２ , the irradiation dose is 1000 mJ / cm ２ ~4000mJ / cm ２ This allows partial curing of the photocurable resin composition to proceed efficiently in a short period of time.

[0083] The light source for the light irradiation (a) is preferably an LED (light emitting diode), but multi-wavelength light sources such as low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, and metal halide lamps equipped with wavelength cut filters can also be used.

[0084] The light irradiation (a) may be carried out while heating the photocurable resin composition. After the light irradiation (a) is carried out, the photocurable resin composition may be heated as necessary.

[0085] (1.3.2) Light Irradiation (b) The wavelength of light (b) is appropriately selected depending on the type of component (C) and the type of component (D), etc., as long as it includes at least one wavelength (II) between 200 nm and 385 nm. Wavelength (II) may include at least one wavelength between 300 nm and 385 nm, at least one wavelength between 350 nm and 380 nm, or 365 nm. Light (b) having a maximum peak of irradiance in the wavelength range of 200 to 385 nm within the wavelength range of 200 to 450 nm can be preferably used. The wavelength range with the maximum peak of irradiance is preferably 300 to 385 nm, more preferably 350 to 385 nm. The irradiance of light (b) is appropriately selected depending on the type of component (C) and the type of component (D), etc. The irradiance of light (b) is 100 mW / cm ２ ~5000mW / cm ２ or 200 mW / cm ２ ~3000mW / cm ２ or 500 mW / cm ２ ~2000mW / cm ２ The irradiation dose of the light (b) is appropriately selected depending on the type of the component (C) and the type of the component (D), etc. The irradiation dose of the light (b) is 200 mJ / cm ２ ~10000mJ / cm ２ or 500 mJ / cm ２ ~10000mJ / cm ２ or 2000 mJ / cm ２ ~7000mJ / cm ２ may be.

[0086] In the case of light irradiation (b), the wavelength was 365 nm and the illuminance was 500 mW / cm ２ ~2000mW / cm ２ , the irradiation dose is 2000 mJ / cm ２ ~7000mJ / cm ２ This allows the curing of the photocurable resin composition to proceed efficiently and sufficiently in a short time.

[0087] The light source for light irradiation (b) is not particularly limited, and examples thereof include an LED, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, and a UV (ultraviolet) electrodeless lamp.

[0088] The light irradiation (b) may be carried out continuously after the light irradiation (a). The light irradiation (b) may be carried out while heating the photocurable resin composition. After the light irradiation (b), the photocurable resin composition may be heated as needed.

[0089] (1.3.3) Preferred modes of light irradiation (a) and light irradiation (b) The illuminance of the light (a) is 100 mW / cm ２ ~5000mW / cm ２ , irradiation dose 100 mJ / cm ２ ~5000mJ / cm ２ and the illuminance of the light (b) is 100 mW / cm ２ ~5000mW / cm ２ , irradiation dose 200 mJ / cm ２ ~10000mJ / cm ２ This makes it possible to achieve both low compression set and short-time curing.

[0090] (1.4) Sealing Material The sealing material (hereinafter also simply referred to as "sealing material") manufactured by the sealing material manufacturing method of the present disclosure is suitably used for purposes such as waterproofing, water control, vibration isolation, vibration damping, stress relaxation, gap filling, rattle prevention, slippage prevention, or impact noise reduction.

[0091] The shape of the sealing material is appropriately selected depending on the application of the sealing material, and examples thereof include a ring, packing, gasket, diaphragm, oil seal, bearing seal, lip seal, plunger seal, door seal, lip, face seal, gas delivery plate seal, wafer support seal, and barrel seal.

[0092] The sealing material exhibits small compression set in a high-compression, high-temperature, long-term compression set test. In other words, the sealing material exhibits excellent sealing properties over a long period of time from low to high temperatures. Therefore, the sealing material is preferably used in fuel cells. Examples of fuel cells include solid polymer fuel cells.

[0093] Hereinafter, the sealing material for fuel cells will also be referred to as "sealing material for fuel cells."

[0094] Examples of the shape of the fuel cell sealing material include an O-ring shape, a V-ring shape, a rod shape, a sheet shape, and a block shape.

[0095] In fuel cells, it is important to seal the components of a single cell or to seal between the components of a single cell. A fuel cell sealing material can provide good sealing between the components and between the components. Examples of the components of a single cell include an electrolyte membrane, electrodes, separators, and a frame.

[0096] (2) Sealing Material The sealing material of the present disclosure contains a structural unit derived from the following component (A) and a structural unit derived from the following component (B). The compression set (based on JIS K6262:2013, except that the compression ratio is changed to 50%, the temperature to 140°C, and the holding time to 72 hours) is 35% or less. Component (A): A polymer having two or more (meth)acryloyl groups and a number average molecular weight of 1,000 or more. Component (B): A monofunctional (meth)acrylate having an alkyl group with 5 to 30 carbon atoms and one (meth)acryloyl group per molecule, the glass transition temperature (Tg) of which as a homopolymer is 20°C or less.

[0097] The sealing material of the present disclosure has the above-described configuration, and therefore exhibits small compression set in a compression set test conducted at a high compression ratio, at a high temperature, and for a long period of time.

[0098] (2.1) Structural units derived from component (A) Examples of component (A) include those exemplified as component (A) in the method for producing a sealing material of the present disclosure. Among these, the polymer is preferably a urethane (meth)acrylate (A-1) or a (meth)acrylate (A-2) that includes a skeleton made of polyisobutylene and does not have a urethane bond. This reduces the compression set of the sealing material.

[0099] The content of the structural units derived from component (A) is not particularly limited, but is preferably 10 parts by mass to 70 parts by mass, relative to a total of 100 parts by mass of the structural units derived from component (A) and the structural units derived from component (B). Examples of the content of the structural units derived from component (A) include the same ranges as those exemplified for the content of component (A) in the method for producing a sealing material.

[0100] (2.2) Structural units derived from component (B) Examples of component (B) include those similar to those exemplified as component (B) in the method for producing a sealing material of the present disclosure. The content of the structural units derived from component (B) is not particularly limited, and is preferably 30 parts by mass to 90 parts by mass, relative to 100 parts by mass of the total of the structural units derived from component (A) and the structural units derived from component (B). Examples of the content of the structural units derived from component (B) include the same range as the range exemplified as the content of component (B) in the method for producing a sealing material.

[0101] (2.3) Compression Set The compression set of the sealing material of the present disclosure is 35% or less, preferably 30% or less, and the closer to 0%, the better. The method for measuring the compression set is the same as that described in the Examples. Examples of a method for adjusting the compression set to 35% or less include the above-mentioned method for producing the sealing material of the present disclosure.

[0102] The method for producing the sealing material of the present disclosure is not particularly limited, and the sealing material is suitably produced by the method for producing the sealing material of the present disclosure.

[0103] The uses of the sealing material of the present disclosure include the same uses as those exemplified above as the uses of the sealing material produced by the method for producing a sealing material of the present disclosure.

[0104] Hereinafter, the present disclosure will be described more specifically with reference to examples, but the present disclosure is not limited to the following examples as long as it does not deviate from the gist of the disclosure.

[0105] [1] Preparation The following materials were prepared as raw materials for the sealing material.

[0106] [1.1] Component (A) The following PUA-1, PUA-2, UN-6304, and UN-6305 were prepared as the component (A-1). The following EP400V was prepared as the component (A-2).

[0107] [1.1.1] Component (A-1) "UN-6304": bifunctional urethane acrylate having a polyether skeleton ("Art Resin UN-6304" manufactured by Negami Chemical Industrial Co., Ltd., Mw: 13,000, Tg: -74°C, viscosity: 200,000 mPa·s at 25°C) "UN-6305": bifunctional urethane acrylate having a polyether skeleton ("Art Resin UN-6305" manufactured by Negami Chemical Industrial Co., Ltd., Mw: 27,000, Tg: -74°C, viscosity: 1,600,000 mPa·s at 25°C) "PUA-1": urethane acrylate having a hydrogenated polybutadiene skeleton (urethane acrylate component contained in the product of Synthesis Example 1 below) "PUA-2" : Urethane acrylate having a hydrogenated polyisoprene skeleton (urethane acrylate component contained in the product of Synthesis Example 2 below)

[0108] [1.1.2] Component (A-2) "EP400V": acryloyl-terminated polyisobutylene ("KANEKA EPION EP400V" manufactured by Kaneka Corporation, Mn = 15,000, Mw = 17,000, viscosity 3,500,000 mPa·s at 23°C)

[0109] [1.2] Component (B) As component (B), the following M-120, LA, and NOAA were prepared.

[0110] "M-120": acrylate of 2-ethylhexyl alcohol ethylene oxide 2 mole adduct (Aronix "M-120" manufactured by Toagosei Co., Ltd.), Tg: -65°C. "LA": ​​lauryl acrylate ("LA" manufactured by Osaka Organic Chemical Industry Ltd.), Tg: -23°C. "NOAA": n-octyl acrylate ("NOAA" manufactured by Osaka Organic Chemical Industry Ltd.), Tg: -65°C.

[0111] [1.3] Component (C) As component (C), the following TPO, O-380, and O-369 were prepared.

[0112] "O-380": bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide ("Omnirad 380" manufactured by IGM Resins), ε (405 nm): 515 L / (mol cm) "O-369": 2-benzyl-2-dimethylamino-4'-morpholinobutyrophenone ("Omnirad 369" manufactured by IGM Resins), ε (405 nm): 57 L / (mol cm) "TPO": 2,4,6-trimethylbenzoyl-diphenylphosphine oxide ("Omnirad TPO" manufactured by IGM Resins), ε (405 nm): 202 L / (mol cm)

[0113] [1.4] Component (D) As component (D), the following O-127D, O-184, O-651, and E-ONE were prepared.

[0114] "O-127D": 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one ("Omnirad 127D" manufactured by IGM Resins), the molar extinction coefficient ε is less than 10 L / (mol cm) at 395 to 435 nm (for example, ε(405 nm): 0 L / (mol cm)), ε(365 nm): 33 L / (mol cm) "O-184": 1-hydroxy-cyclohexyl-phenyl-ketone ("Omnirad 184" manufactured by IGM Resins), the molar extinction coefficient ε is less than 10 L / (mol cm) at 395 to 435 nm (for example, ε(405 nm): 0 L / (mol cm)), ε(365 nm): 18 L / (mol cm) "O-651": 2,2-dimethoxy-1,2-diphenylethan-1-one ("Omnirad 651" manufactured by IGM Resins), the molar absorption coefficient ε is less than 10 L / (mol cm) at 395 to 435 nm (for example, ε(405 nm): 0 L / (mol cm)), ε(365 nm): 121 L / (mol cm) "E-ONE": oligo[2-hydroxy-2-methyl-1-[4-1-(methylvinyl)phenyl]propanone ("ESACURE ONE" manufactured by IGM Resins), the molar absorption coefficient ε is less than 10 L / (mol cm) at 395 to 435 nm (for example, ε(405 nm): 0 L / (mol cm)), ε(365 nm): 33 L / (mol cm))

[0115] [1.5] Synthesis Example 1 PUA-1 (urethane acrylate having a hydrogenated polybutadiene skeleton) as component (A-1) was synthesized as follows.

[0116] A 3 L four-neck separable flask was charged with 900 g (0.48 mol as hydroxyl groups) of GI-3000 (hydroxyl value 30.0 mg KOH / g, Mn approximately 4,000) manufactured by Nippon Soda Co., Ltd. as a hydrogenated polybutadiene having hydroxyl groups, 0.71 g of 2,6-di-t-butyl-p-cresol, and 406 g of lauryl acrylate (hereinafter referred to as "LA"), and the contents were stirred and mixed with a stirrer. A thermometer, a gas inlet tube, and a reflux condenser were attached to the flask, and the mixture was stirred while a mixed gas of oxygen and nitrogen (5% oxygen) was circulated above the liquid. 71.2 g of isophorone diisocyanate (0.64 mol as isocyanate groups) was added and mixed. 22 g of LA in which 0.014 g of ferric acetylacetonate had been dissolved was added to the solution and mixed, after which the temperature was raised. After stirring and mixing for 1 hour at 80°C, 23.1 g of 4-hydroxybutyl acrylate (0.16 moles of hydroxyl groups) was added and the reaction was continued for 3 hours. The disappearance of the isocyanate groups was confirmed by IR spectroscopy, and the synthesis was terminated. The resulting product was a mixture containing 70% urethane acrylate having a hydrogenated polybutadiene skeleton (i.e., "PUA-1") and 30% LA as a diluent monomer. GPC analysis of the resulting product confirmed that the peak of the PUA-1 component was distinct from the monomer components. The polystyrene-equivalent molecular weight of the PUA-1 component was 16,000 in Mn and 36,000 in Mw.

[0117] [1.6] Synthesis Example 2 PUA-2 (urethane acrylate having a hydrogenated polyisoprene skeleton) as component (A-1) was synthesized as follows.

[0118] A 500 mL four-neck separable flask was charged with 180 g (0.17 mol of hydroxyl groups) of Epole (hydroxyl value 51.6 mg KOH / g, Mn approximately 2,500) manufactured by Idemitsu Kosan Co., Ltd., as a hydrogenated polyisoprene having hydroxyl groups, 0.1 g of 2,6-di-t-butyl-p-cresol, and 88 g of n-octyl acrylate (hereinafter referred to as "NOAA"), and the contents were stirred and mixed using a stirrer. A thermometer, gas inlet tube, and reflux condenser were attached to the flask, and the contents were stirred while a mixed gas of oxygen and nitrogen (5% oxygen) was passed through the liquid above. 3 g (0.02 mol of isocyanate groups) of 2-acryloyloxyethyl isocyanate ("Karenz AOI" manufactured by Showa Denko K.K.) was added and mixed. To this solution, 5 g of NOAA in which 0.003 g of ferric acetylacetonate had been dissolved was added and mixed, and the temperature was then raised. After stirring and mixing at 60°C for 30 minutes, the mixture was cooled to 40°C. 24 g of isophorone diisocyanate (0.22 mol as isocyanate groups) was added to the solution and mixed, and the temperature was then raised. After stirring and mixing at 80°C for 2 hours, 10 g of 4-hydroxybutyl acrylate (0.07 mol as hydroxyl groups) was added and the reaction was allowed to proceed for 7 hours. The disappearance of the isocyanate groups was confirmed by IR spectroscopy, and the synthesis was terminated. The resulting product was a mixture containing 70% urethane acrylate having a hydrogenated polyisoprene skeleton (i.e., "PUA-2") and 30% NOAA as a diluent monomer. GPC analysis of the resulting product confirmed the peak of the PUA-2 component, distinguishable from the monomer components. The polystyrene-equivalent molecular weight of the PUA-2 component was Mn 11,000 and Mw 44,000.

[0119] [2] Examples 1 to 15 and Comparative Examples 1 to 16 [2.1] Preparation Step Components (A) to (D) were blended in the proportions shown in Tables 1 to 4 and stirred and mixed in a conventional manner to obtain photocurable resin compositions. When preparing the photocurable resin compositions, the mixtures were heated to approximately 80°C as necessary. The number of parts of component (B) includes the component (B) contained in the products of Synthesis Examples 1 and 2, and indicates the total number of parts of component (B) contained in the products of Synthesis Examples 1 and 2 and the component (B) added later.

[0120] [2.2] Molding process, irradiation process, and evaluation of reaction rate and rapid curing property [2.2.1] Molding process A 1 mm thick silicone mold placed on a PET (polyethylene terephthalate) film was prepared. The photocurable resin composition prepared in [2.1] was poured into the silicone mold and laminated with a PET film.

[0121] [2.2.2] Irradiation Step The photocurable resin composition poured into the silicone mold was irradiated with light having a wavelength of 405 nm (hereinafter also referred to as "irradiation light (405 nm)") (corresponding to light (a)), and then with light having a wavelength of 365 nm (hereinafter also referred to as "irradiation light (365 nm)") (corresponding to light (b)). This resulted in a cured product of the photocurable resin composition (hereinafter also referred to as "first sealant"). A 405 nm LED (surface-type LED irradiator manufactured by CCS Corporation) was used as the light source for the irradiation light (405 nm). A 365 nm LED (surface-type LED irradiator manufactured by ARK TECH Corporation) was used as the light source for the irradiation light (365 nm). A C12684 illuminance meter manufactured by Hamamatsu Photonics K.K. was used to measure the illuminance.

[0122] The irradiation light (405 nm) did not include light in the wavelength range of 200 nm to 385 nm. In other words, the irradiation energy of the light (a) in the wavelength range of 200 nm to 385 nm was 0.2 times or less (i.e., 0 times) the irradiation energy in the wavelength range of 395 nm to 435 nm.

[0123] [2.2.3] Evaluation of reaction rate The IR spectrum of the first sealing material and the IR spectrum of the uncured photocurable resin composition were measured using a Perkin Elmer FT-IR spectrometer "Spectrum Two." The heights of the peaks derived from C=O bonds and C=C bonds were calculated from the IR spectrum, and the reaction rate was calculated using the following formula (B).

[0124] Formula (B): Reaction rate (%) = {1 - ((peak height attributable to C=C bonds after curing) / (peak height attributable to C=O bonds after curing)) / ((peak height attributable to C=C bonds before curing))} × 100

[0125] The peak attributable to the C═O bond is at 1730 cm －１ The peak at 1410 cm was used as a peak derived from a C═C bond. －１ or 810 cm －１ The peaks around

[0126] Using the calculated reaction rate results, the reaction rate of the photocurable resin composition was evaluated based on the following reaction rate evaluation criteria. The evaluation results are shown in Tables 1 to 4. An acceptable evaluation result for the reaction rate of the photocurable resin composition is "A1."

[0127] [2.2.3.1] Evaluation criteria for reaction rate "A1": Reaction rate is 95% or more "B1": Reaction rate is less than 95% A "reaction rate of less than 95%" indicates that the curing of the photocurable resin composition had not progressed sufficiently, and a first sealing material could not be obtained.

[0128] [2.2.4] Evaluation of rapid curing properties For Examples and Comparative Examples in which the reaction rate of the photocurable resin composition was 95% or higher (Examples and Comparative Examples in which the evaluation result was "A1"), the irradiation time with the 405 nm LED and the irradiation time with the 365 nm LED were added together to calculate the total irradiation time.

[0129] The rapid-curing property of the photocurable resin composition was evaluated based on the total irradiation time and the following evaluation criteria for the total irradiation time. The evaluation results are shown in Tables 1 to 4. An acceptable evaluation result for the rapid-curing property of the photocurable resin composition is "A2."

[0130] [2.2.4.1] Evaluation criteria for fast curing "A2": Total irradiation time is 10 seconds or less "B2": Total irradiation time is more than 10 seconds

[0131] [2.3] Molding process, irradiation process, and compression set measurement For the examples and comparative examples in which the reaction rate of the photocurable resin composition was 95% or more (examples and comparative examples in which the evaluation result was "A1"), compression set measurement was carried out by the following method.

[0132] [2.3.1] Molding and Irradiation Steps Except for changing the size of the silicone frame mold, the irradiation step was carried out in the same manner as in [2.2.2] above to obtain a cured product of the photocurable resin composition (hereinafter also referred to as the "second sealant"). The size of the second sealant was 7 mm long x 2 mm wide x 1 mm thick.

[0133] [2.3.2] Compression set test (50% compression, 140°C, 72 hours) A compression set test was performed using a jig conforming to JIS K6262:2013. The second sealant was compressed at a compression rate of 50% using the jig to obtain a second sealant with the jig. The second sealant with the jig was placed in a thermostatic chamber (temperature: 140°C) and left for 72 hours. Thereafter, the second sealant with the jig was removed from the thermostatic chamber, the compression was released, and the second sealant was removed from the jig. Next, the second sealant was left at room temperature (25°C) for 30 minutes. Finally, the thickness of the second sealant was measured, and the compression set (hereinafter also referred to as "compression set (50% compression, 140°C, 72 hours)") was calculated.

[0134] The compression set of the sealing material was evaluated based on the compression set (50% compression, 140°C, 72 hours) and the following evaluation criteria for compression set. The evaluation results are shown in Tables 1 to 4. The acceptable range for the compression set of the sealing material is "A3+" or "A3".

[0135] [2.3.2.1] Evaluation criteria for compression set "A3+": Compression set is 35% or less "A3": Compression set is more than 35% but less than 45% "B3": Compression set is more than 45%

[0136] [2.3.3] Compression set test (50% compression, 120°C, 1000 hours) The compression set of the second sealing material (hereinafter also referred to as "compression set (50% compression, 120°C, 1000 hours)") was calculated in the same manner as in [2.3.2] above, except that the second sealing material with the jig was placed in a thermostatic chamber (temperature: 120°C) and left for 1000 hours. The compression set (50% compression, 120°C, 1000 hours)) is shown in Tables 1 to 4.

[0137] [2.4] Overall Evaluation Using the evaluation results of the fast curing property and the evaluation results of the compression set, the manufacturing methods of the sealing material were comprehensively evaluated according to the following evaluation criteria.

[0138] [2.4.1] Evaluation criteria for manufacturing method of sealing material "A4+": Compression set evaluation result is "A3+", and fast curing property is judged as "A2" "A4": Compression set evaluation is "A3", and fast curing property is judged as "A2" "B4": Compression set evaluation is "A3+" or "A3", and fast curing property is judged as "B2" "B4-": Compression set evaluation is "B3" or compression set not evaluated

[0139]

[0140]

[0141]

[0142]

[0143] [3] Results [3.1] Comparative Examples 1 to 16 In Comparative Examples 1 and 8, light irradiation (a) was not performed. In Comparative Examples 2, 5, 9, 10, 14, and 15, the (D) component was not included, and light irradiation (b) was not performed. In Comparative Examples 3, 4, 6, 13, and 16, the (C) component was not included, and light irradiation (a) was not performed. In Comparative Example 7, the content of the (C) component was not within the range of 0.01 parts by mass to 0.9 parts by mass. In Comparative Examples 11 and 12, the content of the (D) component was not within the range of 0.1 parts by mass to 5 parts by mass. Therefore, the overall evaluation of Comparative Examples 1 to 16 was "B4" or "B4-". These results revealed that the manufacturing methods of the sealing materials of Comparative Examples 1 to 16 are not capable of manufacturing sealing materials with small compression set in high-compression ratio, high-temperature, and long-term compression set tests by short-time curing.

[0144] [3.2] Examples 1 to 15 The methods for producing sealing materials in Examples 1 to 15 included an irradiation step in which light irradiation (a) and light irradiation (b) were performed. The photocurable resin compositions contained components (A) to (D) in specific proportions. Therefore, the overall evaluation of Examples 1 to 15 was "A4+" or "A4." These results demonstrated that the methods for producing sealing materials in Examples 1 to 15 were capable of producing sealing materials with small compression set in high-compression ratio, high-temperature, and long-term compression set tests with short curing times.

[0145] [3.3] Comparison of Example 1 with Comparative Examples 1 to 6 In Comparative Example 1, the photocurable resin composition was the same as in Example 1, but light irradiation (a) was not performed. The compression set of Comparative Example 1 was insufficient. In Comparative Examples 2 to 4, the photocurable resin composition contained one of the components (C) and (D), and the content of one of the components (C) and (D) was the same as in Example 1 (0.5 parts by mass). In Comparative Examples 2 and 3, the illuminance was the same as in Example 1 (750 mW / cm ２ ), but the reaction rate was not sufficient. In Comparative Example 4, the illuminance was low (50 mW / cm ２ ), the reactivity was sufficiently increased, and the compression set was comparable to that of Example 1, but the rapid curing property was insufficient. In Comparative Examples 5 and 6, the photocurable resin composition contained either the component (C) or the component (D), and the content of the component (C) or the component (D) was the same as the total content of the component (C) and the content of the component (D) in Example 1 (1 part by mass). In Comparative Examples 5 and 6, the illuminance was the same as that of Example 1 (750 mW / cm ２ ) and the reaction rate was sufficient, but the compression set was insufficient.

[0146] [3.4] Comparison of Examples 1 to 4 with Comparative Example 7 In Examples 2 and 3, the content of component (C) was lower than in Example 1, and the compression set was lower than in Example 1. In Example 4, the content of component (C) was lower than in Examples 2 and 3, and the compression set was higher than in Example 1. In Comparative Example 7, the content of component (C) was high, and the compression set was insufficient. A comparison of Example 1 and Example 3 shows that when the compression set (compression rate: 50%, temperature: 140°C, holding time: 72 hours) was good, the compression set (compression rate: 50%, temperature: 120°C, holding time: 1,000 hours) was also good.

[0147] [3.5] Comparison of Example 3 with Comparative Examples 8 to 10 In Comparative Example 8, the photocurable resin composition was the same as in Example 3, but light irradiation (a) was not performed. In Comparative Example 8, the compression set was worse than in Example 3, and the rapid curing property was insufficient. In Comparative Examples 9 and 10, the photocurable resin composition did not contain component (D), and the content of component (C) was the same as that in Example 3 (0.1 parts by mass), which was relatively low. In Comparative Example 9, the illuminance was the same as that in Example 3 (750 mW / cm ２ ), but the reaction rate was insufficient. In Comparative Example 10, the illuminance was low (30 mW / cm ２ ), the reaction rate and compression set were comparable to those of Example 3, but the rapid curing property was insufficient.

[0148] [3.6] Comparison of Example 3 with Examples 5 and 6 As component (C), "TPO" (Example 5), which is an acylphosphine oxide compound like "Omnirad 380," and "Omnirad 369" (Example 6), an α-aminoalkylphenone compound, were investigated. In Examples 5 and 6, both had sufficient compression set. Examples 3 and 5 (acylphosphine oxide compounds) had better compression set.

[0149] [3.7] Comparison of Example 3 with Examples 7 to 10 and Comparative Examples 11 and 12. Cases where the content of component (D) was greater than 0.5 parts by mass were examined. When the content of component (D) was 2 parts by mass or greater, the compression set increased as the content of component (D) increased (Examples 8, 9, and 10, Comparative Examples 11 and 12). When the content of component (D) was 0.2 parts by mass, the compression set was higher than that of Example 3 (Example 7).

[0150] [3.8] Comparison of Example 3 with Examples 11 and 12 As component (D), "Omnirad 184" (Example 11), an α-hydroxyalkylphenone compound like "Omnirad 127D," and "Omnirad 651" (Example 12), a benzyl ketal compound, were investigated. The compression set evaluation was satisfactory.

[0151] [3.9] Comparison of Example 13, Example 14, and Comparative Examples 13-15. A urethane acrylate with a hydrogenated polybutadiene skeleton was used as the component (A), and lauryl acrylate, an alkyl acrylate, was used as the component (B). As with the previous polyether-skeleton urethane acrylates, the compression set was good when the components (C) and (D) were contained in specific proportions and an irradiation process including light irradiation (a) and light irradiation (b) was performed (Example 13). However, when either the component (C) or the component (D) was contained and an irradiation process including light irradiation (a) or light irradiation (b) was performed, the reaction rate was insufficient, or the reaction rate was sufficient but the compression set was insufficient (Comparative Examples 13-15). When a urethane acrylate with a hydrogenated isoprene skeleton was used as the component (A), the compression set was sufficient (Example 14).

[0152] [3.10] Comparison between Example 15 and Comparative Example 16 Polyisobutylene diacrylate was used as component (A) and n-octyl acrylate, an alkyl acrylate, was used as component (B). As in the case of using urethane acrylates up to now, the compression set was good when the components (C) and (D) were contained in a specific ratio and an irradiation step including light irradiation (a) and light irradiation (b) was carried out (Example 15). On the other hand, when only the component (D) was contained and an irradiation step including only light irradiation (b) was carried out, the reaction rate was sufficient but the compression set was insufficient (Comparative Example 16).

[0153] The disclosures of Japanese Patent Application No. 2023-097316, filed on June 13, 2023, and Japanese Patent Application No. 2023-207953, filed on December 8, 2023, are incorporated herein by reference in their 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 was specifically and individually indicated to be incorporated by reference.

Claims

1. A method for producing a sealing material, comprising the steps of irradiating a photocurable resin composition with light (a) having at least one wavelength (I) of 395 nm to 435 nm, and then irradiating with light (b) having at least one wavelength (II) of 200 nm to 385 nm, wherein the irradiation energy of the light (a) in the wavelength range of 200 nm to 385 nm is 0.2 times or less than the irradiation energy of the wavelength range of 395 nm to 435 nm, and the photocurable resin composition contains the following components (A) to (D), wherein, relative to a total of 100 parts by mass of the components (A) and (B), the content of the component (A) is 10 parts by mass to 70 parts by mass, the content of the component (B) is 30 parts by mass to 90 parts by mass, the content of the component (C) is 0.01 parts by mass to 0.9 parts by mass, and the content of the component (D) is 0.1 parts by mass to 5 parts by mass. Component (A): a polymer having a number average molecular weight of 1000 or more and having two or more (meth)acryloyl groups. Component (B): a monofunctional (meth)acrylate having a homopolymer glass transition temperature (Tg) of 20° C. or less, an alkyl group having 5 to 30 carbon atoms, and one (meth)acryloyl group per molecule. Component (C): a photoradical polymerization initiator having a molar absorption coefficient of 10 L / (mol cm) or more at the wavelength (I). Component (D): a photoradical polymerization initiator having a molar absorption coefficient of less than 10 L / (mol cm) at any wavelength from 395 nm to 435 nm, and a molar absorption coefficient of 10 L / (mol cm) or more at the wavelength (II).

2. The illuminance of the light (a) is 100 mW / cm ２ ~5000mW / cm ２ , irradiation dose 100 mJ / cm ２ ~5000mJ / cm ２ and the illuminance of the light (b) is 100 mW / cm ２ ~5000mW / cm ２ , irradiation dose 200 mJ / cm ２ ~10000mJ / cm ２ The method for producing a sealing material according to claim 1 , 3. The method for producing a sealing material according to claim 1 or 2, wherein the polymer is a urethane (meth)acrylate (A-1), or a (meth)acrylate (A-2) having a skeleton containing polyisobutylene and having no urethane bond.

4. The method for producing a sealing material according to claim 3, wherein the polymer is the urethane (meth)acrylate (A-1), and the urethane (meth)acrylate (A-1) contains a skeleton consisting of at least one of hydrogenated polybutadiene and hydrogenated polyisoprene.

5. The method for producing a sealing material according to claim 3, wherein the polymer is the (meth)acrylate (A-2).

6. The method for producing a sealing material according to claim 1 or 2, wherein the component (C) includes at least one selected from the group consisting of acylphosphine oxide compounds, α-aminoalkylphenone compounds, oxime ester compounds, and thioxanthone compounds.

7. The method for producing a sealing material according to claim 6, wherein the component (D) includes at least one selected from the group consisting of an α-hydroxyalkylphenone compound, a benzil ketal compound, and a benzophenone compound.

8. The method for producing a sealing material according to claim 7, wherein the sealing material is used for a fuel cell.

9. A sealing material containing a structural unit derived from the following component (A) and a structural unit derived from the following component (B), and having a compression set (based on JIS K6262:2013, except that the compression ratio is changed to 50%, the temperature to 140°C, and the holding time to 72 hours) of 35% or less. Component (A): A polymer having a number average molecular weight of 1000 or more and having two or more (meth)acryloyl groups. Component (B): A monofunctional (meth)acrylate having a homopolymer glass transition temperature (Tg) of 20°C or less, an alkyl group having 5 to 30 carbon atoms, and having one (meth)acryloyl group per molecule.

10. The sealing material according to claim 9, wherein the polymer is a urethane (meth)acrylate (A-1), or a (meth)acrylate (A-2) having a skeleton containing polyisobutylene and having no urethane bond.