VaRTM resin composition

Abstract

This invention provides a resin composition for VaRTM that exhibits excellent storage stability, low gel time drift, and excellent moldability. [Solution] A resin composition for VaRTM containing epoxy (meth)acrylate (A) having constituent units derived from epoxy resin and constituent units derived from (meth)acrylic acid, styrene (B), a metal catalyst (C), a polymerization inhibitor (D), and mono-2-(methacryloyloxy)ethyl malate (E), wherein the content of mono-2-(methacryloyloxy)ethyl malate (E) is 0.7 to 2 parts by mass per 100 parts by mass of the total of epoxy (meth)acrylate (A) and styrene (B), the epoxy equivalent of the epoxy resin is 170 to 500 g / eq, and the viscosity at 25°C is 250 mPa·s or less.

Description

Technical Field

[0001] The present invention relates to a resin composition for VaRTM.

Background Art

[0002] An epoxy (meth) acrylate resin composition in which an epoxy (meth) acrylate obtained from an epoxy compound and (meth) acrylic acid is dissolved in a polymerizable vinyl monomer is excellent in corrosion resistance, mechanical properties, and adhesiveness, and is used for applications such as containers and building materials for the purpose of corrosion resistance. In addition, taking advantage of mechanical properties and adhesiveness, it is used in a wide range of fields such as automotive parts, paints, and electrical and electronic materials.

[0003] On the other hand, the VaRTM (Vacuum assisted Resin Transfer Molding) molding method has the following advantages, and thus is widely used as a molding method for FRP. The VaRTM molding method does not require equipment such as an autoclave, is easy to integrally mold large structures, has little volatilization of organic solvents, and can improve the working environment. In addition, the VaRTM molding method can mold high-quality FRP with a high fiber content and a low void content. Therefore, an epoxy (meth) acrylate resin composition suitable for the VaRTM molding method is desired and development is underway.

[0004] For example, Patent Document 1 discloses a resin composition for VaRTM molding aimed at obtaining a molded product excellent in moldability, heat resistance, elongation, etc., which contains an epoxy (meth) acrylate having an epoxy equivalent of 250 to 500 and styrene as raw materials in a mass ratio of 60 / 40 to 45 / 55.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] In VaRTM molding, the resin composition is drawn into the mold by vacuum suction. If the gel time is too short, the resin hardens before it can fill the entire mold, resulting in problems with moldability. On the other hand, if the gel time is too long, the hardening is insufficient. Furthermore, epoxy (meth)acrylate resin compositions containing metal catalysts, which act as curing accelerators, offer high safety when mixed with curing agents and excellent moldability, but they suffer from a problem where the gel time changes during storage, known as gel time drift. Therefore, there is a need for an epoxy (meth)acrylate resin composition that can maintain an appropriate gel time even after storage, has excellent moldability, and is suitable for VaRTM molding. Therefore, the object of the present invention is to provide a resin composition for VaRTM that has excellent storage stability, low gel time drift, and excellent moldability. [Means for solving the problem]

[0007] The present inventors have found that the above problem can be solved by adding a specific amount of an ester compound with a specific structure to a resin composition containing epoxy (meth)acrylate obtained from a specific epoxy resin. In other words, the present invention relates to the following. [1] A resin composition for VaRTM containing epoxy (meth)acrylate (A) having constituent units derived from epoxy resin and constituent units derived from (meth)acrylic acid, styrene (B), a metal catalyst (C), a polymerization inhibitor (D), and mono-2-(methacryloyloxy)ethyl malate (E), wherein the content of mono-2-(methacryloyloxy)ethyl malate (E) is 0.7 to 2 parts by mass per 100 parts by mass of the total of epoxy (meth)acrylate (A) and styrene (B), the epoxy equivalent of the epoxy resin is 170 to 500 g / eq, and the viscosity at 25°C is 250 mPa·s or less. [2] The VaRTM resin composition according to [1] above, wherein the mass ratio of epoxy (meth)acrylate (A) content to styrene (B) content [(A) / (B)] is 50 / 50 to 70 / 30. [3] The VaRTM resin composition according to [1] or [2] above, wherein the epoxy resin is at least one selected from the group consisting of bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, brominated epoxy resin, nitrogen-containing type epoxy resin, peracetic acid oxidized type epoxy resin, and glycol type epoxy resin. [4] The VaRTM resin composition according to any one of [1] to [3] above, wherein the metal catalyst (C) is at least one selected from the group consisting of organic acid salts of transition metals and complexes of transition metals. [5] A resin composition for VaRTM according to any one of [1] to [4] above, wherein the metal catalyst (C) is an organic salt of cobalt. [6] A resin composition for VaRTM according to any one of [1] to [5] above, wherein the epoxy equivalent of the epoxy resin is 180 to 400 g / eq. [7] A VaRTM resin composition according to any one of [1] to [6] above, wherein the content of mono-2-(methacryloyloxy)ethyl malate (E) is 0.8 to 1.2 parts by mass per 100 parts by mass of epoxy (meth)acrylate (A) and styrene (B) in total. [8] The VaRTM resin composition according to any one of [1] to [7] above, wherein the viscosity of the VaRTM resin composition at 25°C is 180 mPa·s or less. [9] A VaRTM molding method comprising the step of storing the VaRTM resin composition described in any one of [1] to [8] above for one week or more, and then injecting the stored VaRTM resin composition into a mold.

[10] A molded article obtained by VaRTM molding of any one of the VaRTM resin compositions described in [1] to [8] above. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a resin composition for VaRTM that has excellent storage stability, low gel time drift, and excellent moldability. [Modes for carrying out the invention]

[0009] The resin composition for VaRTM of the present invention contains epoxy (meth)acrylate (A), styrene (B), a metal catalyst (C), a polymerization inhibitor (D), and mono-2-(methacryloyloxy)ethyl malate (E), having constituent units derived from epoxy resin and constituent units derived from (meth)acrylic acid, wherein the content of mono-2-(methacryloyloxy)ethyl malate (E) is 0.7 to 2 parts by mass per 100 parts by mass of the total of epoxy (meth)acrylate (A) and styrene (B), the epoxy equivalent of the epoxy resin is 170 to 500 g / eq, and the viscosity at 25°C is 250 mPa·s or less. The resin composition for VaRTM of the present invention, having the above-described structure, exhibits excellent storage stability, low gel time drift, and excellent moldability. The reason for these excellent effects is not entirely clear, but it is thought to be as follows. The VaRTM resin composition of the present invention contains epoxy (meth)acrylate, styrene, and a metal catalyst, resulting in excellent VaRTM moldability and enabling the production of molded articles suitable for the above-mentioned applications. However, when epoxy (meth)acrylate and a metal catalyst are present together, instability occurs, leading to the consumption of polymerization inhibitors during storage and potentially causing gel time drift. Mono-2-(methacryloyloxy)ethyl malate can form a salt with the metal catalyst or coordinate to it, resulting in a more stable metal catalyst compound. This suppresses the direct reaction between the metal catalyst and epoxy (meth)acrylate, thus exhibiting excellent storage stability.

[0010] [Epoxy (meth)acrylate (A)] The VaRTM resin composition of the present invention contains epoxy (meth)acrylate (A) having constituent units derived from epoxy resin and constituent units derived from (meth)acrylic acid. The epoxy equivalent of the epoxy resin is 170 to 500 g / eq. In the present invention, "(meth)acrylate" means at least one selected from the group consisting of "acrylate" and "methacrylate," and "(meth)acrylic acid" means at least one selected from the group consisting of "acrylic acid" and "methacrylic acid."

[0011] The epoxy (meth)acrylate (A) has constituent units derived from epoxy resin. The epoxy resin may be any epoxy compound having at least two epoxy groups in one molecule, and is not particularly limited, but is preferably at least one selected from the group consisting of bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, brominated epoxy resin, nitrogen-containing epoxy resin, peracetic acid oxidized epoxy resin, and glycol type epoxy resin, more preferably at least one selected from the group consisting of bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, and brominated epoxy resin, even more preferably at least one selected from the group consisting of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and novolac type epoxy resin, and even more preferably bisphenol A type epoxy resin.

[0012] More specifically, examples include glycidyl ethers synthesized by the reaction of epichlorohydrin or methylepichlorohydrin with bisphenol A, bisphenol F, or brominated bisphenol A; polyglycidyl ethers obtained by the reaction of polynuclear phenol resins, such as phenol novolacs and brominated novolacs, with epichlorohydrin or methylepichlorohydrin; and glycidyl ethers obtained by the reaction of ethylene oxide or propylene oxide-added glycols of bisphenol A or bisphenol F, or hydrogenated bisphenol A, with epichlorohydrin or methylepichlorohydrin. The epoxy resin may be used alone or in combination of two or more types.

[0013] The epoxy equivalent of the epoxy resin is 170 to 500 g / eq, preferably 180 to 400 g / eq, more preferably 180 to 350 g / eq, even more preferably 180 to 330 g / eq, even more preferably 200 to 330 g / eq, and even more preferably 250 to 320 g / eq. By having the epoxy equivalent of the epoxy resin within the above range, the composition can be made low viscosity, moldability can be improved, and the mechanical properties of the resulting molded article can also be improved.

[0014] The ratio of constituent units derived from epoxy resin to the total amount of epoxy (meth)acrylate (A) is preferably 40 to 90% by mass, more preferably 50 to 90% by mass, even more preferably 50 to 80% by mass, and even more preferably 60 to 80% by mass.

[0015] The epoxy (meth)acrylate (A) has constituent units derived from (meth)acrylic acid. (Meth)acrylic acid is at least one selected from the group consisting of acrylic acid and methacrylic acid, and is preferably methacrylic acid.

[0016] In addition to the structural unit derived from (meth)acrylic acid, the epoxy (meth)acrylate (A) may contain a structural unit derived from a compound having a carbon-carbon unsaturated bond other than (meth)acrylic acid. Examples of the compound having a carbon-carbon unsaturated bond include crotonic acid, cinnamic acid, sorbic acid, and the like. The content of the structural unit derived from (meth)acrylic acid relative to the total content of the structural unit derived from (meth)acrylic acid and the structural unit derived from a compound having a carbon-carbon unsaturated bond other than (meth)acrylic acid is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 99% by mass or more. And it is preferably 100% by mass or less, and even more preferably 100% by mass.

[0017] The total ratio of the structural unit derived from (meth)acrylic acid and the structural unit derived from a compound having a carbon-carbon unsaturated bond other than (meth)acrylic acid to the total amount of the epoxy (meth)acrylate (A) is preferably 10 to 60% by mass, more preferably 10 to 50% by mass, still more preferably 20 to 50% by mass, and even more preferably 20 to 40% by mass.

[0018] The ratio of the structural unit derived from (meth)acrylic acid to the total amount of the epoxy (meth)acrylate (A) is preferably 10 to 60% by mass, more preferably 10 to 50% by mass, still more preferably 20 to 50% by mass, and even more preferably 20 to 40% by mass.

[0019] The mass ratio of the structural unit derived from the epoxy resin to the structural unit derived from (meth)acrylic acid [epoxy resin / (meth)acrylic acid] is preferably 40 / 60 to 90 / 10, more preferably 50 / 50 to 90 / 10, still more preferably 50 / 50 to 80 / 20, and even more preferably 60 / 40 to 80 / 20.

[0020] The method for producing epoxy (meth)acrylate (A) is not limited as long as it is a method that can produce epoxy (meth)acrylate (A) having constituent units derived from epoxy resin with an epoxy equivalent of 170 to 500 g / eq and constituent units derived from (meth)acrylic acid, but the method described below is preferred.

[0021] The mass ratio [epoxy resin / (meth)acrylic acid] of the amount of epoxy resin used to the amount of (meth)acrylic acid used is preferably 40 / 60 to 90 / 10, more preferably 50 / 50 to 90 / 10, even more preferably 50 / 50 to 80 / 20, and even more preferably 60 / 40 to 80 / 20.

[0022] It is preferable to add an esterification catalyst before the reaction between the epoxy resin and (meth)acrylic acid begins. The esterification catalyst is preferably at least one selected from the group consisting of compounds containing tertiary nitrogen atoms, phosphorus compounds, amine salts, and antimony compounds, with compounds containing tertiary nitrogen atoms being more preferable. Compounds containing a tertiary nitrogen atom include triethylamine, pyridine derivatives, and imidazole derivatives, with imidazole derivatives being preferred. Examples of phosphorus compounds include trimethylphosphine and triphenylphosphine. Examples of amine salts include tetramethylammonium chloride and benzyltriethylamine chloride. Examples of antimony compounds include triphenylantimony and trimethylantimony. The amount of esterification catalyst used is preferably 0.005 to 0.7% by mass, more preferably 0.01 to 0.6% by mass, even more preferably 0.05 to 0.5% by mass, and even more preferably 0.08 to 0.5% by mass, relative to the total amount of epoxy resin and (meth)acrylic acid.

[0023] The reaction temperature is preferably 100 to 160°C, more preferably 110 to 150°C, and even more preferably 120 to 140°C. By the above method, epoxy (meth)acrylate (A) with excellent manufacturing stability and minimal discoloration can be obtained.

[0024] [Styrene(B)] The resin composition for VaRTM of the present invention contains styrene(B). The styrene(B) content in the VaRTM resin composition of the present invention is preferably 30 to 50% by mass, more preferably 30 to 45% by mass, even more preferably 30 to 43% by mass, even more preferably 30 to 42% by mass, and even more preferably 35 to 42% by mass, based on the total amount of the VaRTM resin composition. By having a styrene(B) content within the above range, the composition can be made low viscosity, moldability can be improved, and the mechanical properties of the resulting molded article can also be improved.

[0025] The mass ratio of epoxy (meth)acrylate (A) content to styrene (B) content [(A) / (B)] is preferably 50 / 50 to 70 / 30, more preferably 55 / 45 to 70 / 30, even more preferably 57 / 43 to 70 / 30, even more preferably 58 / 42 to 70 / 30, and even more preferably 58 / 42 to 65 / 35. By having the mass ratio of epoxy (meth)acrylate (A) content to styrene (B) content within the above range, the composition can be made low viscosity, moldability can be improved, and the mechanical properties of the resulting molded article can also be improved.

[0026] [Metal catalyst (C)] The resin composition for VaRTM of the present invention contains a metal catalyst (C). The metal catalyst (C) is preferably at least one selected from the group consisting of organic acid salts of transition metals and complexes of transition metals, and more preferably an organic acid salt of a transition metal. Preferably, the organic acid salt of a transition metal is an organic acid salt of cobalt. In other words, the metal catalyst (C) is more preferably an organic salt of cobalt, even more preferably at least one selected from the group consisting of cobalt 2-ethylhexanoate, cobalt octoate, and cobalt naphthenate, and even more preferably cobalt 2-ethylhexanoate.

[0027] The content of the metal catalyst (C) in the VaRTM resin composition of the present invention is preferably 0.001 to 0.2% by mass, more preferably 0.005 to 0.15% by mass, even more preferably 0.007 to 0.1% by mass, even more preferably 0.008 to 0.08% by mass, and even more preferably 0.01 to 0.05% by mass, based on the total amount of the VaRTM resin composition. By having the metal catalyst (C) content within the above range, moldability can be improved. Furthermore, even when the VaRTM resin composition of the present invention contains the above amount of metal catalyst (C), it exhibits excellent storage stability, reduces gel time drift, and maintains excellent moldability after long-term storage.

[0028] [Polymerization inhibitor (D)] The resin composition for VaRTM of the present invention contains a polymerization inhibitor (D). The polymerization inhibitor (D) is preferably phenols, organic copper salts, inorganic copper salts, amidines, hydrazine salts, quaternary ammonium salts, amines, nitro compounds, oximes, sulfur, amine hydrochlorides, etc., and is preferably phenols.

[0029] The phenol is preferably at least one selected from the group consisting of methyl hydroquinone, hydroquinone, tert-butyl hydroquinone, and monomethyl ether hydroquinone, and more preferably hydroquinone. By using the above polymerization inhibitor (D), the composition can be made low viscosity, moldability can be improved, storage stability can be further improved, gel time drift can be reduced, and moldability after long-term storage can be improved.

[0030] The content of polymerization inhibitor (D) in the resin composition for VaRTM of the present invention is preferably 0.0001 to 0.20% by mass, more preferably 0.001 to 0.10% by mass, even more preferably 0.005 to 0.070% by mass, even more preferably 0.010 to 0.050% by mass, and even more preferably 0.020 to 0.040% by mass, based on the total amount of the resin composition for VaRTM. Furthermore, the content of the polymerization inhibitor (D) in the resin composition for VaRTM of the present invention is preferably 0.0001 to 0.20 parts by mass, more preferably 0.001 to 0.10 parts by mass, even more preferably 0.005 to 0.070 parts by mass, even more preferably 0.010 to 0.050 parts by mass, and even more preferably 0.020 to 0.040 parts by mass, based on 100 parts by mass of the total of epoxy (meth)acrylate (A) and styrene (B). By having the polymerization inhibitor (D) content within the above range, the composition can be made low viscosity, moldable, and further improved storage stability, gel time drift can be reduced, and moldability after long-term storage can be excellent.

[0031] [Mono-2-(methacryloyloxy)ethylmalate (E)] The resin composition for VaRTM of the present invention contains mono-2-(methacryloyloxy)ethyl malate (E). The content of mono-2-(methacryloyloxy)ethyl malate (E) is 0.7 to 2 parts by mass per 100 parts by mass of epoxy (meth)acrylate (A) and styrene (B) combined.

[0032] The aforementioned mono-2-(methacryloyloxy)ethyl maleate (E) can be obtained by the reaction of 2-hydroxyethyl methacrylate with maleic anhydride. The reaction temperature is preferably 30 to 150°C, more preferably 50 to 120°C, and more preferably 80 to 120°C.

[0033] The content of mono-2-(methacryloyloxy)ethyl malate (E) is 0.7 to 2 parts by mass, preferably 0.7 to 1.5 parts by mass, more preferably 0.8 to 1.3 parts by mass, even more preferably 0.8 to 1.2 parts by mass, and even more preferably 0.9 to 1.2 parts by mass, based on 100 parts by mass of epoxy (meth)acrylate (A) and styrene (B) combined. Having the mono-2-(methacryloyloxy)ethyl malate (E) content within this range provides good storage stability for the resin composition and reduces gel time drift.

[0034] [Properties of resin compositions for VaRTM] The viscosity of the VaRTM resin composition at 25°C is 250 mPa·s or less, preferably 200 mPa·s or less, more preferably 180 mPa·s or less, even more preferably 170 mPa·s or less, and even more preferably 160 mPa·s or less. There is no lower limit to the viscosity of the VaRTM resin composition at 25°C, but it is preferably 50 mPa·s or more. When the viscosity of the VaRTM resin composition at 25°C is within the above range, it becomes suitable for VaRTM molding and exhibits excellent moldability. The viscosity of the VaRTM resin composition at 25°C can be determined by the method described in the examples below.

[0035] Furthermore, depending on the application, the VaRTM resin composition of the present invention may contain any additives such as solvents, catalysts, and fillers, to the extent that they do not impair the effects of the present invention.

[0036] [VaRTM molding method and molded product] The VaRTM resin composition containing epoxy (meth)acrylate (A), etc., is suitable for VaRTM molding and can be molded under any molding conditions when used in a VaRTM molding method, but it is preferable to mold it by the following molding method. The present invention relates to a VaRTM molding method that includes the step of injecting the VaRTM resin composition into a mold. The mold is preferably made of a highly flexible material that can be deformed by reducing the internal pressure and also by injecting a resin composition into it. Examples of such materials include thermoplastic resins (plastics), thermoplastic resin elastomers, and silicone elastomers, with silicone elastomers being preferred. Furthermore, the shape is preferably film-like. Molds made of silicone elastomer can be reused and do not need to be discarded after use, allowing for the mass production of molded bodies of the same shape without generating waste.

[0037] The VaRTM molding method of the present invention is typically carried out by the following steps. First, a release agent or the like is applied to a lower mold made of metal, glass, or the like, as needed. Next, glass fibers or carbon fibers are placed on the lower mold, and the upper mold is placed over it, ensuring that the lower mold and the upper mold are in close contact. As mentioned above, the upper mold used here is preferably made of silicone elastomer. Next, the VaRTM resin composition is injected into the upper mold while reducing the pressure inside the mold. It is preferable to incorporate a curing agent into the VaRTM resin composition before injecting it into the mold, and it is even more preferable to further incorporate a curing accelerator, a curing assist, and a photoradical initiator. After injection, the mold is left at room temperature (approximately 0-40°C) and then demolded to obtain the molded body. As described above, the mold made of silicone elastomer can be reused. The time for leaving the material at room temperature can be adjusted as appropriate depending on the amount and type of curing agent, but it is usually 1 to 50 hours, preferably 5 to 30 hours. The molded articles obtained in this way have excellent mechanical strength. Therefore, they can be used in a variety of applications, including those requiring high mechanical strength.

[0038] The VaRTM molding method of the present invention may further include a step of storing the VaRTM resin composition for one week or more, and then injecting the VaRTM resin composition into a mold. As described above, the resin composition for VaRTM has excellent storage stability, low gel time drift, and excellent moldability due to having the above-mentioned structure, making it suitable for applications requiring long-term storage. More specifically, because it maintains excellent moldability even after being stored for more than a week, it can be suitably used in applications requiring storage for more than a week.

[0039] The storage period is preferably one week or more, more preferably two weeks or more, even more preferably three weeks or more, and even more preferably four weeks or more. There is no upper limit to the storage period, but it is preferably eight weeks or less, more preferably seven weeks or less, even more preferably six weeks or less, and even more preferably five weeks or less. The storage period of the VaRTM resin composition being within the above range clarifies the storage stability of the VaRTM resin composition.

[0040] The VaRTM molding method includes the step of storing the VaRTM resin composition for the aforementioned period, and then injecting the VaRTM resin composition into a mold.

[0041] The VaRTM molding method of the present invention is typically carried out by the following steps. First, a release agent or the like is applied to a lower mold made of metal, glass, or the like, as needed. Next, glass fibers or carbon fibers are placed on the lower mold, and the upper mold is placed over it, ensuring that the lower mold and the upper mold are in close contact. As mentioned above, the upper mold used here is preferably made of silicone elastomer. Next, the VaRTM resin composition is injected into the upper mold while reducing the pressure inside the mold. It is preferable to incorporate a curing agent into the VaRTM resin composition before injecting it into the mold, and it is even more preferable to further incorporate a curing accelerator, a curing assist, and a photoradical initiator. After injection, the mold is left at room temperature (approximately 0-40°C) and then demolded to obtain the molded body. As described above, the mold made of silicone elastomer can be reused. The time for leaving the material at room temperature can be adjusted as appropriate depending on the amount and type of curing agent, but it is usually 1 to 50 hours, preferably 5 to 30 hours. The molded articles obtained in this way have excellent mechanical strength. Therefore, they can be used in a variety of applications, including those requiring high mechanical strength.

[0042] The VaRTM molding method of the present invention may further include a step of storing the VaRTM resin composition for one week or more, and then injecting the VaRTM resin composition into a mold. As described above, the resin composition for VaRTM has excellent storage stability, low gel time drift, and excellent moldability due to having the above-mentioned structure, making it suitable for applications requiring long-term storage. More specifically, because it maintains excellent moldability even after being stored for more than a week, it can be suitably used in applications requiring storage for more than a week. [Examples]

[0043] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. The physical properties measured and evaluated in these examples were performed by the following methods.

[0044] [Physical properties and evaluation of resin compositions] <Viscosity> Each resin composition was measured out in 180g portions into 225mL cylindrical glass bottles, immersed in a water bath heated to 25°C for at least 30 minutes, and after confirming that the temperature of the resin composition reached 25°C using a thermometer, its viscosity was measured using a single-cylinder rotational viscometer. The measurement method conformed to JIS K6901:2008 "Viscosity".

[0045] <Moldability and storage stability> (1) Moldability evaluation (VaRTM molding) On the mold surface (600mm x 1000mm), glass fiber reinforced material (roving cloth, 570g / m²) 2A 500mm x 500mm, 6-ply mold ("WR570C-100", manufactured by Nitto Boseki Co., Ltd.), resin supply line, and vacuum line were placed on top of it. These were then covered in order with peel ply (release cloth, "Bleeder Lease B", manufactured by Airtech), flow media (resin diffusion net, "Greenflow 75", manufactured by Airtech), and bagging film (plastic film, "Ipplon KM1300", manufactured by Airtech). The edges of the bagging film and the space between the mold surface and the resin supply line and vacuum line were sealed with sealant tape ("AT-200Y", manufactured by Airtech). Next, the pressure inside the space between the mold surface and the bagging film was reduced to 10kPa or less. On the other hand, 100 parts by mass of the VaRTM resin composition prepared in each example and comparative example, and 1.0 part by mass of a curing agent (methyl ethyl ketone peroxide, "Permec N", manufactured by NOF Corporation) were placed in a container, stirred until homogeneous, and then vacuum degassed to obtain a composition containing the curing agent. A composition containing a curing agent was injected from the resin supply line to impregnate the glass fiber reinforcement. When the composition reached the vacuum line, the resin supply line and the vacuum line were shut off. The injection of the composition took approximately 20 minutes. After shutting off each line, the mixture was cured at room temperature (approximately 25°C) for 16 hours to obtain a molded body.

[0046] The appearance of the molded articles obtained by the above VaRTM molding process was evaluated visually according to the following criteria. ○: No areas of the glass fiber reinforced material that are not impregnated with the composition are observed (ratio of unimpregnated area in the glass fiber reinforced material: less than approximately 1%). △: A small portion of the glass fiber reinforced material is not impregnated with the composition (ratio of unimpregnated area in the glass fiber reinforced material: approximately 1% or more but less than approximately 5%). ×: There are areas in the glass fiber reinforced material that are not impregnated with the composition (ratio of unimpregnated area in the glass fiber reinforced material: approximately 5% or more)

[0047] (2) Storage stability evaluation (moldability of the resin composition after 30 days of storage) The resin compositions prepared in each example and comparative example were stored in a 40°C incubator for 30 days, and then VaRTM molding was performed using the same method as described in "(1) Moldability Evaluation" above. The appearance of the obtained molded articles was evaluated visually according to the following criteria. ○: No areas of the glass fiber reinforced material that are not impregnated with the composition are observed (ratio of unimpregnated area in the glass fiber reinforced material: less than approximately 1%). △: A small portion of the glass fiber reinforced material is not impregnated with the composition (ratio of unimpregnated area in the glass fiber reinforced material: approximately 1% or more but less than approximately 5%). ×: There are areas in the glass fiber reinforced material that are not impregnated with the composition (ratio of unimpregnated area in the glass fiber reinforced material: approximately 5% or more)

[0048] [Evaluation of hardened material] To evaluate the mechanical properties of molded articles obtained by VaRTM molding, cured products (cast plates) were manufactured using a resin composition, and the mechanical properties of these cured products were measured.

[0049] (1) Manufacturing of hardened products (casting plates) One part by mass of a curing agent (methyl ethyl ketone peroxide, "Permec N", manufactured by NOF Corporation) was added to the resin compositions prepared in each example and comparative example. The composition containing the curing agent was poured into a 3 mm thick tempered glass cell with a release cellophane attached, cured at room temperature (approximately 25°C) for 16 hours, and then post-cured at 120°C for 2 hours to produce a cured product (cast plate). The obtained cured products (cast plates) were evaluated as follows.

[0050] <Tensile strength and tensile elongation> The resulting cured material (cast plate) was processed according to JIS K7164:2005, Type 1B, Type B, and a tensile test was performed at a test speed of 1 mm / min in a room at 23°C to determine the tensile strength and tensile elongation. The tensile elongation was calculated using an extensometer in accordance with JIS K7161-1:2014 and JIS K7161-2:2014. The higher the tensile strength value, the better the mechanical properties. Similarly, the higher the tensile elongation value, the better the mechanical properties.

[0051] <Temperature of deflection under load> The above-mentioned cast plate was processed in accordance with JIS K7191-1:2015, and the temperature of deflection under load was measured. A higher value for the temperature of deflection under load indicates superior mechanical properties.

[0052] [Manufacturing of epoxy (meth)acrylate] Manufacturing Example 1 In a four-necked flask equipped with a thermometer, stirrer, reflux condenser, and gas inlet tube, 667 g of epoxy resin (epoxy equivalent 188, bisphenol A type, Epiclon 850, manufactured by Dainippon Ink and Chemicals, Inc.), 110 g of bisphenol A, and 0.39 g of triphenylphosphine were charged. The mixture was reacted at 150°C for 1 hour with stirring while blowing in nitrogen to obtain a bisphenol A type epoxy resin with an epoxy equivalent of 300 g / eq. Next, 223 g of methacrylic acid (manufactured by Mitsubishi Gas Chemical Corporation) and 0.2 g of methylhydroquinone as a polymerization inhibitor were added, and the mixture was stirred at 90°C until homogeneous while blowing in dry air to obtain a mixture. The mixture was cooled to 60°C, 2.0 g of 2-methylimidazole was added, and the mixture was heated to 130°C and reacted for 3 hours to obtain bisphenol A type epoxy methacrylate (A1).

[0053] Manufacturing Example 2 In a four-necked flask equipped with a thermometer, stirrer, reflux condenser, and gas inlet tube, 662 g of epoxy resin (epoxy equivalent 188, bisphenol A type, Epiclon 850, manufactured by Dainippon Ink and Chemicals, Inc.), 140 g of bisphenol A, and 0.40 g of triphenylphosphine were charged. The mixture was reacted at 150°C for 1 hour with stirring while blowing in nitrogen to obtain a bisphenol A type epoxy resin with an epoxy equivalent of 350 g / eq. Next, 197 g of methacrylic acid (manufactured by Mitsubishi Gas Chemical Corporation) and 0.2 g of methylhydroquinone as a polymerization inhibitor were added, and the mixture was stirred at 90°C until homogeneous while blowing in dry air to obtain a mixture. The mixture was cooled to 60°C, 2.0 g of 2-methylimidazole was added, and the mixture was heated to 130°C and reacted for 3 hours to obtain bisphenol A type epoxy methacrylate (A2).

[0054] Manufacturing Example 3 In a four-necked flask equipped with a thermometer, stirrer, reflux condenser, and gas inlet tube, 650 g of epoxy resin (epoxy equivalent 188, bisphenol A type, Epiclon 850, manufactured by Dainippon Ink and Chemicals, Inc.), 215 g of bisphenol A, and 0.43 g of triphenylphosphine were charged. The mixture was reacted at 150°C for 1 hour with stirring while blowing in nitrogen to obtain a bisphenol A type epoxy resin with an epoxy equivalent of 550 g / eq. Next, 135 g of methacrylic acid (manufactured by Mitsubishi Gas Chemical Corporation) and 0.2 g of methylhydroquinone as a polymerization inhibitor were added, and the mixture was stirred at 90°C until homogeneous while blowing in dry air to obtain a mixture. The mixture was cooled to 60°C, 2.0 g of 2-methylimidazole was added, and the mixture was heated to 130°C and reacted for 3 hours to obtain bisphenol A type epoxy methacrylate (A3).

[0055] [Production of mono-2-(methacryloyloxy)ethyl malate] Manufacturing Example 4 130 g of 2-hydroxyethyl methacrylate and 98 g of maleic anhydride were placed in a reaction vessel and reacted at 100°C for 2 hours to obtain mono-2-(methacryloyloxy)ethyl maleate as a viscous liquid.

[0056] [Manufacturing of resin compositions for VaRTM] Example 1 600 g of epoxy (meth)acrylate (A1), 400 g of styrene, 10 g of the aforementioned mono-2-(methacryloyloxy)ethyl malate, 1.5 g of 2-ethylhexanoate cobalt(II) (12% Nikka Octic Cobalt, 12% as Co, manufactured by Nippon Chemical Industrial Co., Ltd.) (0.18 g in terms of Co), and 0.3 g of hydroquinone were added to obtain a resin composition for VaRTM. The evaluation results of the obtained VaRTM resin composition are shown in Table 1.

[0057] The amount of hydroquinone was determined so that the gelation time, as determined by the following method, would be 90 minutes. A composition was prepared by removing hydroquinone from the aforementioned VaRTM resin composition and temperature-controlled to 25°C. Hydroquinone was added to 100 parts by mass of the composition in the following amounts: 0 parts by mass (not added), 0.02 parts by mass, and 0.04 parts by mass, to obtain three VaRTM resin compositions with different amounts of hydroquinone. One part by mass of a curing agent (methyl ethyl ketone peroxide, "Permec N", manufactured by NOF Corporation) was added to the resin composition to obtain a composition containing the curing agent. The gelation time of the composition containing the curing agent was determined in accordance with JIS K6901:2008 "Room temperature curing characteristics (exothermic method)", and the amount of hydroquinone that resulted in a gelation time of 90 minutes was determined from the approximation curve created from the results.

[0058] Comparative Examples 1 and 2 A resin composition for VaRTM was obtained in the same manner as in Example 1, except that the type of epoxy (meth)acrylate and the amount of each component were changed as shown in Table 1. The evaluation results of the obtained VaRTM resin composition are shown in Table 1.

[0059] [Table 1]

[0060] Table 1 shows that the resin compositions of the examples exhibit good moldability. Furthermore, the good moldability after 30 days of storage indicates excellent storage stability. Moreover, the cured products obtained from the resin compositions of the examples all showed high tensile strength, tensile elongation, and load deflection temperature. This indicates that the molded articles also have excellent mechanical properties. Therefore, the resin compositions of the present invention are suitable for use in VaRTM molding due to their excellent moldability. Furthermore, the resin compositions of the present invention are particularly suitable for applications requiring long-term storage because of their excellent storage stability and low gel time drift.

Claims

1. It contains epoxy (meth)acrylate (A), styrene (B), a metal catalyst (C), a polymerization inhibitor (D), and mono-2-(methacryloyloxy)ethyl malate (E), which have constituent units derived from epoxy resin and constituent units derived from (meth)acrylic acid. The content of mono-2-(methacryloyloxy)ethyl maleate (E) is 0.7 to 2 parts by mass per 100 parts by mass of epoxy (meth)acrylate (A) and styrene (B). The epoxy equivalent of the epoxy resin is 170 to 500 g / eq. A resin composition for VaRTM having a viscosity of 250 mPa·s or less at 25°C.

2. The VaRTM resin composition according to claim 1, wherein the mass ratio of epoxy (meth)acrylate (A) content to styrene (B) content [(A) / (B)] is 50 / 50 to 70 / 30.

3. The VaRTM resin composition according to claim 1 or 2, wherein the epoxy resin is at least one selected from the group consisting of bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, brominated epoxy resin, nitrogen-containing type epoxy resin, peracetic acid oxidized type epoxy resin, and glycol type epoxy resin.

4. The VaRTM resin composition according to claim 1 or 2, wherein the metal catalyst (C) is at least one selected from the group consisting of organic acid salts of transition metals and complexes of transition metals.

5. The VaRTM resin composition according to claim 1 or 2, wherein the metal catalyst (C) is an organic salt of cobalt.

6. The VaRTM resin composition according to claim 1 or 2, wherein the epoxy equivalent of the epoxy resin is 180 to 400 g / eq.

7. The VaRTM resin composition according to claim 1 or 2, wherein the content of mono-2-(methacryloyloxy)ethyl maleate (E) is 0.8 to 1.2 parts by mass per 100 parts by mass of epoxy (meth)acrylate (A) and styrene (B) in total.

8. The VaRTM resin composition according to claim 1 or 2, wherein the viscosity of the VaRTM resin composition at 25°C is 180 mPa·s or less.

9. A VaRTM molding method comprising the steps of storing the VaRTM resin composition according to claim 1 or 2 for one week or more, and then injecting the stored VaRTM resin composition into a mold.

10. A molded article obtained by VaRTM molding the VaRTM resin composition according to claim 1 or 2.

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