Epoxy resin composition and method for producing same

Abstract

Provided is an epoxy resin composition containing: a main agent containing an epoxy resin (A), a rosin-based resin (B), and a modifier (C) for an epoxy resin; and a curing agent (D). In addition, provided is a method for producing an epoxy resin composition, the method comprising: step 1 in which the curing agent (D) is mixed with a portion of the epoxy resin (A) to prepare a resin composition; step 2 in which the epoxy resin (A), the rosin-based resin (B), and the modifier (C) for an epoxy resin are charged into a dissolving vessel and mixed under heating at 140-170°C for 1-6 hours to obtain a master batch based on the dissolution of components (B) and (C); and step 3 in which the master batch obtained in step 2 is cooled to 50-70°C and then the resin composition obtained in step 1 is added thereto and mixed at 50-70°C for 0.5-2 hours to obtain an epoxy resin composition.

Description

Epoxy resin composition and method for producing the same

[0001] The present invention relates to an epoxy resin composition and a method for producing the same.

[0002] Demand for automotive NVH materials, which are used to reduce noise (N), vibration (V), and unpleasant vibrations and impact sounds (H) that occur when passing over uneven surfaces, is increasing because they can prevent discomfort and improve ride comfort by absorbing noise and preventing it from entering the vehicle interior. However, it is known that the vibration damping properties of materials with a multilayer structure are strongly influenced not only by the properties of the materials that make up the multilayer structure, but also by the properties of the resin used as an adhesive at the interface between those materials.

[0003] In this regard, Patent Document 1 describes an epoxy resin composition comprising: component A: an epoxy resin having an oxazolidone ring structure in its molecule; component B: an epoxy resin that is liquid at 30°C; component C: a diblock copolymer having a B-M structure (wherein M is a block consisting of a methyl methacrylate homopolymer or a copolymer containing at least 50% by weight of methyl methacrylate; B is a block that is incompatible with the epoxy resin and block M and has a glass transition temperature Tg of 20°C or lower; the blocks represented by B and M are linked via a direct bond or a linking group); and component D: an amine-based curing agent that is dicyandiamide or a derivative thereof, wherein the blending ratios of the components satisfy the following conditions: A / (A+B) = 0.05 to 0.25, C / (A+B) = 0.12 to 0.19, and D / (A+B) = 1 to 10 (wherein A to D are the contents (mass) of components A to D, respectively). Furthermore, Patent Document 1 teaches that by suitably incorporating an acrylic block copolymer with high vibration-damping properties into an epoxy resin composition, the composition has high heat resistance and a high tan δ (loss factor) over a wide temperature range, and therefore has excellent vibration-damping properties and damping properties, making it suitable for use in home appliances, automobile parts, and the like.

[0004] Patent Document 2 describes a viscoelastic resin for vibration-damping materials containing three components: (A) an epoxy resin, (B) a curing agent, and (C) a thermoplastic resin, and states that a rosin-based resin or the like can be used as the thermoplastic resin. Patent Document 2 also teaches that the viscoelastic resin for vibration-damping materials, when sandwiched between two metal plates, exhibits high vibration-damping performance and excellent adhesive performance over a wide temperature range compared to conventional vibration-damping materials.

[0005] International Publication No. 2019 / 087877 JP-A-3-000759

[0006] For example, in resin compositions such as those described in Patent Documents 1 and 2, if the amount of additive components is increased to improve vibration damping properties (loss factor), the proportion of components such as epoxy resins, which have excellent adhesive strength, decreases. Therefore, it has long been known that there is a trade-off between vibration damping properties and adhesive properties, and therefore it is generally difficult to achieve both.

[0007] Therefore, an object of the present invention is to provide an epoxy resin composition that can improve both vibration damping properties and adhesive properties through a novel configuration, and a method for producing the same.

[0008] In order to achieve the above object, the present inventors focused on a rosin-based resin to enhance vibration damping properties using an epoxy resin with excellent mechanical properties as a base, and discovered that by adding this to an epoxy resin together with an epoxy resin modifier as a third component, an epoxy resin composition can be obtained which not only has improved vibration damping properties but also excellent adhesive properties, and thus completed the present invention.

[0009] The present invention has achieved the above-mentioned object as follows: (1) An epoxy resin composition comprising a base resin containing an epoxy resin (A), a rosin-based resin (B), and an epoxy resin modifier (C), and a curing agent (D). (2) The epoxy resin composition according to (1) above, in which the epoxy resin modifier (C) comprises at least one selected from core-shell rubber particles and acrylic block copolymers. (3) The epoxy resin composition according to (1) or (2) above, in which the curing agent (D) comprises an amine-based curing agent. (4) The epoxy resin composition according to (3) above, in which the curing agent (D) comprises dicyandiamide. (5) The epoxy resin composition according to any one of (1) to (4) above, in which the rosin-based resin (B) is 10 to 180 parts by mass and the epoxy resin modifier (C) is 1 to 90 parts by mass per 100 parts by mass of the epoxy resin (A). (6) The epoxy resin composition according to (5), wherein the rosin-based resin (B) is 40 to 180 parts by mass and the epoxy resin modifier (C) is 10 to 50 parts by mass relative to 100 parts by mass of the epoxy resin (A). (7) A method for producing an epoxy resin composition, comprising the following steps 1 to 3: step 1: mixing a curing agent (D) with a portion of the epoxy resin (A) to prepare a resin composition, step 2: charging the epoxy resin (A), the rosin-based resin (B), and the epoxy resin modifier (C) into a dissolution vessel and mixing them under heating at 140 to 170°C for 1 to 6 hours to obtain a masterbatch based on a solution of the (B) and (C) components, and step 3: cooling the masterbatch obtained in step 2 to 50 to 70°C, adding the resin composition obtained in step 1, and mixing at 50 to 70°C for 0.5 to 2 hours to obtain an epoxy resin composition. (8) A method for producing an epoxy resin composition according to (7) above, wherein the rosin-based resin (B) is 10 to 180 parts by mass and the epoxy resin modifier (C) is 1 to 90 parts by mass per 100 parts by mass of the epoxy resin (A). (9) A method for producing an epoxy resin composition according to (8) above, wherein the rosin-based resin (B) is 40 to 180 parts by mass and the epoxy resin modifier (C) is 10 to 50 parts by mass per 100 parts by mass of the epoxy resin (A).

[0010] According to the present invention, it is possible to provide an epoxy resin composition that can improve both vibration damping properties and adhesive properties, and a method for producing the same.

[0011] 1 is a schematic diagram showing a cured product of an epoxy resin composition containing an epoxy resin (A) and a rosin-based resin (B). 2 is a schematic diagram showing a cured product of an epoxy resin composition according to an embodiment of the present invention. 3 is a schematic diagram showing a peel strength measurement.

[0012] <Epoxy Resin Composition> The epoxy resin composition according to an embodiment of the present invention is characterized by comprising a main component including an epoxy resin (A), a rosin-based resin (B), and an epoxy resin modifier (C), and a curing agent (D). In this specification, the epoxy resin (A), the rosin-based resin (B), the epoxy resin modifier (C), and the curing agent (D) are also referred to as component (A), component (B), component (C), and component (D), respectively. Each of the components of the epoxy resin composition according to an embodiment of the present invention will be described in more detail below.

[0013] [Epoxy Resin (A)] The epoxy resin (A) used in the epoxy resin composition according to the embodiment of the present invention may be any epoxy resin known in the art. Therefore, the epoxy resin (A) is not particularly limited, but is preferably, for example, a bifunctional or higher epoxy resin. The epoxy resin (A) may be, for example, at least one selected from bisphenol-type epoxy resins, novolac-type epoxy resins, alicyclic epoxy resins, aliphatic epoxy resins, glycidyl ester-type epoxy resins, and glycidyl amine-type epoxy resins. The epoxy resin (A) may be used alone or in combination of two or more.

[0014] Specific examples of bisphenol-type epoxy resins include at least one selected from bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol E-type epoxy resins, bisphenol S-type epoxy resins, bisphenol Z-type epoxy resins, and isophorone bisphenol-type epoxy resins, as well as halides, alkyl-substituted products, and hydrogenated products thereof. The bisphenol-type epoxy resin may be a monomer, a high-molecular-weight product having multiple repeating units, or a glycidyl ether of an alkylene oxide adduct.

[0015] Specific examples of novolac epoxy resins include at least one selected from phenol novolac epoxy resins, cresol novolac epoxy resins, and bisphenol A novolac epoxy resins.

[0016] Specific examples of the alicyclic epoxy resin include at least one selected from 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and 1-epoxyethyl-3,4-epoxycyclohexane.

[0017] Specific examples of the aliphatic epoxy resin include at least one selected from trimethylolpropane polyglycidyl ether, pentaerythritol polyglycidyl ether, and polyoxyalkylene diglycidyl ether.

[0018] Specific examples of the glycidyl ester type epoxy resin include at least one selected from the group consisting of phthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, and dimer acid glycidyl ester.

[0019] Specific examples of the glycidylamine type epoxy resin include at least one selected from tetraglycidyldiaminodiphenylmethane, tetraglycidyldiaminodiphenylsulfone, triglycidylaminophenol, triglycidylaminocresol, and tetraglycidylxylylenediamine.

[0020] [Rosin-Based Resin (B)] The rosin-based resin (B) used in the epoxy resin composition according to the present invention is a natural resin obtained from pine trees. It refers to rosin, which is a mixture of abietic acid and its isomers, each of which has a three-ring structure, a conjugated double bond, and a carboxyl group. Examples of rosin derivatives include ester resins derived from rosin. When it is not possible to specifically and clearly identify whether the rosin-based resin (B) has the above structure, the rosin-based resin (B) can be defined as a resin that, when blended in an amount of 40 to 60 parts by mass per 100 parts by mass of the epoxy resin (A), exhibits a peak tan δ (loss factor) of 0.03 or greater at a temperature range of 0 to 30°C. Commercially available rosin-based resins (B) include Superester A-18 and A-100 and Ester Gum AT, both manufactured by Arakawa Chemical Industries, Ltd.

[0021] When the cured product of the epoxy resin composition contains a rosin-based resin (B), it exhibits a high peak value of tan δ, particularly in the relatively low temperature range of 0 to 30°C, and therefore exhibits high vibration damping properties in the relatively low temperature range of 0 to 30°C. Therefore, the content of the rosin-based resin (B) is not particularly limited as long as it is appropriately determined taking into account the above-mentioned effects of the rosin-based resin (B). For example, the content may be 10 to 300 parts by mass per 100 parts by mass of the epoxy resin (A), and preferably 10 to 250 parts by mass, 10 to 220 parts by mass, 10 to 200 parts by mass, or 10 to 180 parts by mass per 100 parts by mass of the epoxy resin (A). Adding 10 parts by mass or more of the rosin-based resin (B) per 100 parts by mass of the epoxy resin (A) reliably increases tan δ, thereby enabling further improvement in vibration damping properties. From the viewpoint of improving vibration damping properties, the higher the content of the rosin-based resin (B), the better. For example, it may be 20 parts by mass or more, 30 parts by mass or more, 40 parts by mass or more, 50 parts by mass or more, 70 parts by mass or more, or 90 parts by mass or more per 100 parts by mass of the epoxy resin (A). On the other hand, although there is no particular upper limit, if the rosin-based resin (B) is contained in an excessive amount, the effect may saturate and costs may increase. Therefore, the content of the rosin-based resin (B) is preferably 250 parts by mass or less, 220 parts by mass or less, 200 parts by mass or less, or 180 parts by mass or less per 100 parts by mass of the epoxy resin (A), and may be 160 parts by mass or less, 140 parts by mass or less, 120 parts by mass or less, or 100 parts by mass or less.

[0022] FIG. 1 is a schematic diagram showing a cured product of an epoxy resin composition containing epoxy resin (A) and rosin-based resin (B). Referring to FIG. 1 , it can be seen that cured product 1 of the epoxy resin composition has a sea-island structure in which rosin-based resin 3 is not completely miscible with epoxy resin 2, and rosin-based resin 3 is dispersed within epoxy resin 2. In such a cured product, rosin-based resin (B) exists in a phase-separated state from epoxy resin (A), and it is believed that the properties attributable to rosin-based resin (B) can be exhibited without being significantly affected by epoxy resin (A). In fact, experimental results by the present inventors have confirmed that the addition of rosin-based resin (B) to the cured product shown in FIG. 1 can achieve a high tan δ attributable to rosin-based resin (B) in the relatively low temperature range of 0 to 30°C, thereby demonstrating high vibration damping properties in this relatively low temperature range. However, on the other hand, in the cured product of an epoxy resin composition containing only an epoxy resin (A) and a rosin-based resin (B) as the main components as shown in Figure 1, the addition of the rosin-based resin (B) relatively reduces the proportion of the epoxy resin (A) which has excellent adhesive properties, and therefore the adhesiveness tends to decrease.

[0023] [Epoxy resin modifier (C)] In contrast to this, in the epoxy resin composition according to an embodiment of the present invention, by using the epoxy resin modifier (C) in combination with the rosin resin (B), it is possible to expand the applicable temperature range of vibration damping properties while maintaining the effects obtained by the rosin resin (B) at a high level, and further to improve adhesiveness.

[0024] FIG. 2 is a schematic diagram showing a cured product of an epoxy resin composition according to an embodiment of the present invention. Referring to FIG. 2, unlike the sea-island structure shown in FIG. 1, a cured product 10 of an epoxy resin composition according to an embodiment of the present invention shows a complex phase-separated structure in which epoxy resin 2 and rosin-based resin 3 form a complex phase-separated structure, with rosin-based resin 3 barely interconnected within epoxy resin 2. This complex phase-separated structure is believed to be formed by the addition of epoxy resin modifier (C), which is incorporated into the sea-island structure shown in FIG. 1. In relation to this, when the loss factor of a cured product of an epoxy resin composition according to an embodiment of the present invention is measured, it is observed that the tan δ peaks attributable to epoxy resin (A), rosin-based resin (B), and epoxy resin modifier (C) become difficult to clearly separate, and these peaks tend to broaden. This broadening of the tan δ peaks is believed to be due to the change from the sea-island structure shown in FIG. 1 to the complex phase-separated structure shown in FIG. 2. Furthermore, the combined use of the rosin resin (B) and the epoxy resin modifier (C) broadens the tan δ peak, making it possible to achieve a high loss factor not only in the relatively low temperature range of 0 to 30° C. but also in the relatively high temperature range of 30 to 60° C., thereby expanding the temperature range in which vibration damping properties can be applied. It has now been discovered that, although the reason for this is not entirely clear, the addition of the epoxy resin modifier (C) can improve adhesion in addition to the improvement in vibration damping properties described above, or can achieve a good balance between vibration damping and adhesion.

[0025] The epoxy resin modifier (C) used in the epoxy resin composition according to an embodiment of the present invention may be a modifier commonly used to improve the impact resistance and toughness of epoxy resins. Therefore, the epoxy resin modifier (C) is not particularly limited, but may include, for example, at least one selected from core-shell rubber particles, carboxyl-terminated butadiene nitrile rubber (CTBN), thermoplastic elastomers, and acrylic block copolymers, and is preferably at least one selected from core-shell rubber particles and acrylic block copolymers. Without intending to be bound by any particular theory, it is believed that the addition of the epoxy resin modifier (C) bridges cracks generated in the epoxy resin due to peeling, preventing the cracks from propagating, thereby improving adhesion. For example, a cured product of the epoxy resin composition according to an embodiment of the present invention can be used to construct a vibration-damping steel plate by applying it as an adhesive layer to the interface between steel plates. In this case, the adhesiveness of the epoxy resin is important, but the presence of the epoxy resin modifier (C) in the epoxy resin makes it possible to prevent the propagation of cracks due to the bridging action described above, even if cracks occur in the epoxy resin due to peeling. For this reason, the epoxy resin composition according to the embodiment of the present invention is extremely effective for use in applications such as vibration-damping steel plates.

[0026] Among the epoxy resin modifiers (C), core-shell rubber particles are particularly effective in improving adhesion and can also be highly effective in expanding the applicable temperature range of vibration damping. Furthermore, acrylic block copolymers are particularly effective in improving vibration damping and also show a high effect in improving adhesion. For this reason, the epoxy resin modifier (C) is preferably a material with both hard and soft segments, and the use of core-shell rubber particles or acrylic block copolymers is particularly preferred because it enables a very high level of both vibration damping and adhesion.

[0027] The core-shell rubber particles are not particularly limited, but may be, for example, core-shell multilayer polymer particles composed of a core made of a crosslinked rubber containing butadiene, acrylic, silicone, or the like as a main component, and a shell made of an acrylic copolymer, etc. When added to an epoxy resin composition, the core-shell rubber particles may be in the form of a powder, or in the form of a masterbatch in which the core-shell rubber particles are pre-dispersed in an epoxy resin. However, since it may be difficult to uniformly disperse the powder in the epoxy resin, it is preferable to add the particles in the form of a masterbatch. Commercially available materials containing core-shell rubber particles include, for example, Kane Ace MX-154 manufactured by Kaneka Corporation. For example, Kane Ace MX-154 contains 40% core-shell rubber particle components and 60% epoxy resin components. Therefore, when Kane Ace MX-154 core-shell type rubber particles are used in the epoxy resin composition according to an embodiment of the present invention, the content of component (C) is 40% of the content of Kane Ace MX-154, and similarly, the content of component (A) is 60% more than the content of Kane Ace MX-154. In the core-shell type rubber particles, the shell portion corresponds to the hard portion, and the core portion corresponds to the soft portion.

[0028] The acrylic block copolymer is not particularly limited, and may be, for example, an acrylic block copolymer having a soft block and a hard block produced using a living polymerization method. Examples of acrylic block copolymers include at least one selected from a triblock copolymer having an M-B-M structure and a diblock copolymer having an M-B structure, where M is a block consisting of a homopolymer of methyl methacrylate or a copolymer containing at least 50% by weight of methyl methacrylate, B is a block that is incompatible with the epoxy resin and block M, and the blocks represented by B and M are linked via a direct bond or a linking group. Furthermore, polar groups such as carboxylic acid groups and hydroxyl groups may be introduced into the polymer of M. In the acrylic block copolymer, the hard block corresponds to the hard segment, and the soft block corresponds to the soft segment.

[0029] Specific examples of acrylic block copolymers include at least one selected from polymethyl methacrylate / polybutyl acrylate / polymethyl methacrylate triblock copolymers, polystyrene / polybutadiene / polymethyl methacrylate triblock copolymers, and polymethyl methacrylate / polybutyl acrylate diblock copolymers. By combining an acrylic block copolymer in which a polymer incompatible with epoxy resins is selected as the soft block (block B) and a polymer compatible with epoxy resins is selected as the hard block (block M) with an epoxy resin (A), the acrylic block copolymer can be suitably microdispersed in the epoxy resin (A). Microdispersing an acrylic block copolymer having such a structure in the epoxy resin (A) can improve tan δ while suppressing deterioration in the mechanical properties of the cured product of the epoxy resin composition. In particular, introducing polar groups such as carboxylic acid groups or hydroxyl groups into polymethyl methacrylate is more preferable because it improves adhesion. Examples of commercially available acrylic block copolymers include Nanostrength D51N and M52N manufactured by ARKEMA.

[0030] The content of the epoxy resin modifier (C) is not particularly limited and may be appropriately determined taking into consideration the above-mentioned effects of the epoxy resin modifier (C). For example, it may be 1 to 200 parts by mass, preferably 1 to 150 parts by mass, 1 to 120 parts by mass, 10 to 100 parts by mass, or 1 to 90 parts by mass per 100 parts by mass of the epoxy resin (A). By adding 1 part by mass or more of the epoxy resin modifier (C) per 100 parts by mass of the epoxy resin (A), it is possible to fully exhibit the effect of expanding the applicable temperature range of vibration damping due to the formation of a complex phase separation structure as shown in FIG. 2, and the above-mentioned effect of improving adhesion. From the viewpoint of making these effects more pronounced, the higher the content of the epoxy resin modifier (C), the more preferable it may be, for example, 3 parts by mass or more, 5 parts by mass or more, 7 parts by mass or more, 9 parts by mass or more, 10 parts by mass or more, or 20 parts by mass or more per 100 parts by mass of the epoxy resin (A). On the other hand, although there is no particular upper limit, excessive inclusion of the epoxy resin modifier (C) may saturate the effect and lead to increased costs. Therefore, the content of the epoxy resin modifier (C) is preferably 150 parts by mass or less, 120 parts by mass or less, 100 parts by mass or less, or 90 parts by mass or less per 100 parts by mass of the epoxy resin (A), and may be 70 parts by mass or less, 50 parts by mass or less, 30 parts by mass or less, 25 parts by mass or less, 20 parts by mass or less, 18 parts by mass or less, 16 parts by mass or less, 14 parts by mass or less, or 12 parts by mass or less. Kane Ace MX, such as the above-mentioned Kane Ace MX-154, is a liquid masterbatch in which core-shell rubber particles are dispersed in a high concentration of single particles in a curable epoxy resin, etc., and the content of the epoxy resin modifier (C) referred to in this specification is calculated based on the content excluding the epoxy resin. Meanwhile, the epoxy resin content is added to the parts by mass of the epoxy resin (A). Furthermore, although not particularly limited, the content of the epoxy resin modifier (C) is preferably equal to or less than the content of the rosin-based resin (B), and more preferably less than the content of the rosin-based resin (B).

[0031] In particular, when the epoxy resin modifier (C) is a core-shell type rubber particle, the rosin resin (B) is preferably 90 to 250 parts by mass per 100 parts by mass of the epoxy resin (A), and the epoxy resin modifier (C), i.e., the core-shell type rubber particle, is preferably 20 to 50 parts by mass. In this case, the rosin resin (B) may be 120 parts by mass or more and / or 200 parts by mass or less per 100 parts by mass of the epoxy resin (A). Similarly, the epoxy resin modifier (C) may be 40 parts by mass or less per 100 parts by mass of the epoxy resin (A).

[0032] On the other hand, when the epoxy resin modifier (C) is an acrylic block copolymer, the rosin resin (B) is preferably 40 to 180 parts by mass relative to 100 parts by mass of the epoxy resin (A), and the epoxy resin modifier (C), i.e., the acrylic block copolymer, is preferably 10 to 120 parts by mass, more preferably 10 to 100 parts by mass.

[0033] Although not particularly limited, as described above, the content of the epoxy resin modifier (C) is preferably equal to or less than the content of the rosin-based resin (B), and more preferably less than the content of the rosin-based resin (B). In this regard, in a specific embodiment of the present invention, the contents of the epoxy resin (A), the rosin-based resin (B), and the epoxy resin modifier (C) may satisfy a relationship in which the parameter K, represented by the following formula, is 0 to 0.74. This makes it possible to further improve the loss factor in both the relatively low temperature range of 0 to 30°C and the relatively high temperature range of 30 to 60°C. K = [B] / ([A] + [B] + [C]) - [C] / ([A] + [B] + [C]), where [A] is the content of epoxy resin (A) in parts by mass, which is 100; [B] is the content ratio of rosin-based resin (B) in parts by mass per 100 parts by mass of epoxy resin (A); and [C] is the content ratio of epoxy resin modifier (C) in parts by mass per 100 parts by mass of epoxy resin (A). K may be 0.10 or more, 0.20 or more, or 0.30 or more. Similarly, K may be 0.70 or less, 0.60 or less, or 0.50 or less.

[0034] [Curing Agent (D)] In the epoxy resin composition according to an embodiment of the present invention, by adding a curing agent (D) to the base resin containing the epoxy resin (A), rosin-based resin (B), and epoxy resin modifier (C) described above, a complex phase-separated structure as shown in FIG. 2 can be formed in the cured product obtained after the reaction of the base resin with the curing agent (D). As described above in connection with FIG. 1 and the related drawings, such a complex phase-separated structure cannot be formed by simply adding a rosin-based resin (B) to the epoxy resin (A). It can only be formed by using the rosin-based resin (B) and the epoxy resin modifier (C) in combination with the epoxy resin (A). That is, in the epoxy resin composition according to an embodiment of the present invention, a base resin containing a specific combination of the epoxy resin (A), rosin-based resin (B), and epoxy resin modifier (C) is important, thereby achieving the object of the present invention to provide an epoxy resin composition that can improve both vibration damping and adhesion. Therefore, the curing agent (D) used in the epoxy resin composition is not particularly limited and may be any curing agent known to those skilled in the art. The curing agent (D) may be solid or liquid at room temperature. For example, the curing agent (D) may contain or be at least one selected from amines, polyhydric phenols, and acid anhydrides, and preferably contains or is an amine, i.e., an amine-based curing agent.

[0035] Specific examples of amine-based curing agents include at least one selected from dicyandiamide, diaminodiphenylsulfone, diaminodiphenylmethane, metaphenylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, m-xylenediamine, trimethylhexamethylenediamine, 2-methylpentamethylenediamine, diethylaminopropylamine, isophoronediamine, 1,3-bisaminomethylcyclohexane, bis(4-aminocyclohexyl)methane, norbornenediamine, 1,2-diaminocyclohexane, Laromine C-260, polyoxypropylenediamine D-230, polyoxypropylenetriamine T-403, polycyclohexylpolyamine mixtures, and N-aminoethylpiperazine. Among these, dicyandiamide is preferred because it prevents the performance of the epoxy resin composition from changing due to moisture in the air, enables the quality of the epoxy resin composition to be stably maintained for a long period of time, and allows curing to be completed at a relatively low temperature. Here, the relatively low temperature means a temperature of about 100 to 130°C.

[0036] Specific examples of polyhydric phenols include dihydric phenols such as bisphenol A, bisphenol F (isomer mixture), 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxybenzophenone, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl sulfone, fluorene bisphenol, 4,4'-dihydroxybiphenyl, 2,2'-dihydroxybiphenyl, hydroquinone, resorcinol, 1,5-naphthalenediol, 1,6-naphthalenediol, 2,6-naphthalenediol, and 2,7-naphthalenediol; and trihydric or higher phenols such as tris(hydroxyphenyl)methane mixtures, tris-(4-hydroxyphenyl)methane, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, phenol novolak, o-cresol novolak, naphthol novolak, and polyvinylphenol.

[0037] Specific examples of acid anhydrides include phthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylhimic anhydride, nadic anhydride, and trimellitic anhydride.

[0038] The content of the curing agent (D) varies depending on the type and can be appropriately selected depending on the type of curing agent used. For example, when the curing agent (D) is an amine-based curing agent, particularly dicyandiamide, the content is typically 1 to 25 parts by mass per 100 parts by mass of the epoxy resin (A). For example, the content of the curing agent (D) may be 2 parts by mass or more, 3 parts by mass or more, or 5 parts by mass or more per 100 parts by mass of the epoxy resin (A). Similarly, the content of the curing agent (D) may be 20 parts by mass or less, 15 parts by mass or less, or 10 parts by mass or less per 100 parts by mass of the epoxy resin (A). Preferably, the amount of the amine-based curing agent, particularly dicyandiamide, is such that the number of moles of active hydrogen is 0.5 to 1.0 times the total number of moles of epoxy groups in the epoxy resin (A) contained in the epoxy resin composition. By setting the number of moles of active hydrogen to 0.5 times or more, a cured product with good heat resistance and good mechanical properties (i.e., high strength) can be obtained. Furthermore, by setting the ratio to 1.0 or less, a cured product with good mechanical properties can be obtained. The total number of moles of epoxy groups in the epoxy resin (A) contained in the epoxy resin composition can be calculated from the amount of the epoxy resin charged.

[0039] [Curing Accelerator (E)] The epoxy resin composition according to an embodiment of the present invention may optionally contain a curing accelerator (E). Examples of the curing accelerator (E) include at least one selected from urea compounds, tertiary amines and their salts, imidazole and its salts, Lewis acids, and Bronsted acids and their salts. Among these, urea compounds are preferred for their balance of storage stability and curing acceleration ability. Examples of urea compounds include at least one selected from N,N-dimethyl-N'-(3,4-dichlorophenyl)urea, toluenebis(dimethylurea), 4,4'-methylenebis(phenyldimethylurea), and 3-phenyl-1,1-dimethylurea. Commercially available urea compounds include DCMU99 (manufactured by Hodogaya Chemical Co., Ltd.), Omicure 24, Omicure 52, and Omicure 94 (all manufactured by Emerald Performance, LLC).

[0040] The content of the curing accelerator (E) is not particularly limited, but is preferably 1 to 7 parts by mass, and more preferably 3 to 5 parts by mass, per 100 parts by mass of the epoxy resin (A). By using the curing accelerator (E) within this range, the reaction can be sufficiently accelerated, and the elastic modulus and heat resistance of the cured product can be further improved.

[0041] [Additive (F)] The epoxy resin composition according to the embodiment of the present invention may optionally contain an additive (F) including at least one selected from a thermoplastic resin, a thermoplastic elastomer, an elastomer, an antifoaming agent, a leveling agent, and the like.

[0042] Additives (F), such as thermoplastic resins, thermoplastic elastomers, or elastomers, can be used to modify the viscoelasticity of the epoxy resin composition according to the present invention, optimizing the viscosity, storage modulus, and thixotropy, as well as improving the fracture toughness of the cured product of the epoxy resin composition. Thermoplastic resins, thermoplastic elastomers, and elastomers can be used alone or in combination of two or more. These additives can be blended in an amount of 1 to 15 parts by mass, preferably 1 to 10 parts by mass, per 100 parts by mass of the total epoxy resin composition. The thermoplastic resins and the like can be dissolved in the epoxy resin or can be contained in the epoxy resin composition in the form of fine particles, long fibers, short fibers, woven fabrics, nonwoven fabrics, mesh, pulp, or the like.

[0043] The thermoplastic resin preferably has at least one bond selected from the group consisting of a carbon-carbon bond, an amide bond, an imide bond, an ester bond, an ether bond, a carbonate bond, a urethane bond, a urea bond, a thioether bond, a sulfone bond, an imidazole bond, and a carbonyl bond in its main chain. More specifically, examples of the thermoplastic resin include engineering plastics such as polyacrylate, polyamide, polyaramid, polyester, polycarbonate, polyphenylene sulfide, polybenzimidazole, polyimide, polyetherimide, polysulfone, and polyethersulfone. Among these, polyimide, polyetherimide, polysulfone, and polyethersulfone are particularly preferred due to their excellent heat resistance. Furthermore, it is preferable for these thermoplastic resins to have a functional group reactive with epoxy resins, from the viewpoint of improving the fracture toughness and maintaining environmental resistance of the cured product of the epoxy resin composition according to the present invention. Preferred functional groups reactive with epoxy resins include a carboxyl group, an amino group, and a hydroxyl group.

[0044] As additive (F), a defoaming agent or leveling agent can be added to improve surface smoothness. These additives can be blended in an amount of 0.01 to 3 parts by mass, preferably 0.01 to 1 part by mass, per 100 parts by mass of the total epoxy resin composition. By controlling the blending amount within this range, the effect of smoothing the surface can be fully exerted. Furthermore, pigments and other additives can also be blended as necessary.

[0045] In the epoxy resin composition according to the embodiment of the present invention, the blending amounts of components (A) to (D) are preferably 50% by mass or more, and more preferably 80% by mass or more, of the total epoxy resin composition so that the composition remains liquid as a whole. Note that the solvent is not treated as an additive.

[0046] <Method for Producing Epoxy Resin Composition> There are no particular limitations on the method for producing the epoxy resin composition according to the present invention. Therefore, the epoxy resin composition may be produced by any appropriate method known to those skilled in the art. For example, all components constituting the epoxy resin composition may be mixed simultaneously. This method is effective when the epoxy resin (A), rosin-based resin (B), epoxy resin modifier (C), and curing agent (D) used are all liquid. On the other hand, when the epoxy resin modifier (C) and / or curing agent (D) are in powder form, for example, the epoxy resin modifier (C) and / or curing agent (D) may be premixed with a portion of the epoxy resin (A) contained in the composition. More specifically, these components may be uniformly dispersed in a portion of the epoxy resin (A) to prepare a masterbatch, which may then be used to prepare the epoxy resin composition. Mixing machines such as a three-roll mill, planetary mixer, kneader, universal mixer, homogenizer, and homogenizer dispenser can be used for the mixing operation. For example, the epoxy resin composition can be produced by a production method including the following steps 1 to 3. Step 1: mixing a curing agent (D) with a portion of the epoxy resin (A) to prepare a resin composition; Step 2: charging the epoxy resin (A), a rosin-based resin (B), and an epoxy resin modifier (C) into a dissolution vessel and mixing them under heat at 140 to 170°C for 1 to 6 hours to obtain a masterbatch based on the dissolution of the (B) and (C) components; and Step 3: cooling the masterbatch obtained in Step 2 to 50 to 70°C, adding the resin composition obtained in Step 1, and mixing them at 50 to 70°C for 0.5 to 2 hours to obtain an epoxy resin composition.

[0047] The components may be appropriately blended in the proportions as described in relation to the epoxy resin composition. For example, the components may be appropriately blended in steps 1 and 2 above so that the final epoxy resin composition contains 10 to 300 parts by mass, preferably 10 to 180 parts by mass or 40 to 180 parts by mass, of the rosin resin (B) and 1 to 200 parts by mass, preferably 1 to 90 parts by mass or 10 to 50 parts by mass of the epoxy resin modifier (C) per 100 parts by mass of the epoxy resin (A). Similarly, the curing agent (D) may be appropriately blended in such a manner that, for example, 1 to 25 parts by mass per 100 parts by mass of the epoxy resin (A).

[0048] When adding a curing accelerator (E), an additive (F), or the like to the epoxy resin composition according to the embodiment of the present invention, these components may be added in either of the above steps 1 and 2. In this case, the curing accelerator (E) may be blended in an amount of, for example, 1 to 7 parts by mass per 100 parts by mass of the epoxy resin (A), and the additive (F) may be blended in an amount of, for example, 1 to 15 parts by mass per 100 parts by mass of the entire epoxy resin composition.

[0049] A film of the epoxy resin composition according to an embodiment of the present invention can be obtained by dissolving the composition in release paper or the like and applying the solution. The film is useful as a surface protection film or adhesive film when attached to a substrate. A preferred method of use involves applying the epoxy resin composition according to an embodiment of the present invention to the surface of a substrate such as release paper. The resulting coating layer may be attached to another substrate in an uncured state and cured, or the coating layer itself may be cured and used as a film.

[0050] The components of the epoxy resin composition of this embodiment are identified and their amounts determined by diluting the epoxy resin composition appropriately with a solvent, separating the components by taking advantage of their different solubilities, and then analyzing the separated components using various analytical methods. More specifically, the epoxy resin (A) is generally analyzed by pyrolysis gas chromatography / mass spectrometry (pyrolysis GC / MS), but can also be analyzed more simply by confirming the presence of OH groups using infrared spectroscopy (IR). The rosin-based resin (B) is analyzed by field desorption mass spectrometry (FD / MS). The epoxy resin modifier (C) is analyzed by nuclear magnetic resonance spectroscopy (NMR). Other components, such as the curing agent (D), curing accelerator (E), and additive (F), can be analyzed by any appropriate analytical method known to those skilled in the art. The results obtained by the above analytical methods can be suitably used to confirm the composition of a composition with a known blend ratio or to identify the composition of a composition with an unknown blend ratio when determining the parameters applied in this embodiment.

[0051] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0052] In the following examples, epoxy resin compositions were produced by combining various components, and the loss factor (vibration damping property) and peel strength (adhesion property) of the obtained epoxy resin compositions were examined.

[0053] The raw materials used in this example are as follows. [Raw Materials] [Epoxy Resin (A)] Bisphenol A type bifunctional epoxy resin (trade name: YD-128, manufactured by Nippon Steel Chemical & Material Co., Ltd., viscosity (25°C) 13,000 mPa·s, liquid at room temperature) Bisphenol A type bifunctional epoxy resin (trade name: YD-127, manufactured by Nippon Steel Chemical & Material Co., Ltd., viscosity (25°C) 9,000 mPa·s, liquid at room temperature) [Rosin Resin (B)] Rosin ester (trade name: Super Ester A-18, manufactured by Arakawa Chemical Industries, Ltd.) Rosin ester (trade name: Super Ester A-100, manufactured by Arakawa Chemical Industries, Ltd.) Rosin ester (trade name: Ester Gum AT, manufactured by Arakawa Chemical Industries, Ltd.) [Epoxy Resin Modifier (C)] Core-shell type rubber (trade name: Kane Ace MX-154, manufactured by Kaneka Corporation) Acrylic block copolymer (diblock copolymer of poly(methyl methacrylate) / poly(butyl acrylate)) (trade name: Nanostrength D51N, manufactured by Arkema) Acrylic block copolymer (triblock copolymer of poly(methyl methacrylate) / poly(butyl acrylate) / poly(methyl methacrylate), further copolymerized with dimethylacrylamide) (trade name: Nanostrength M52N, manufactured by Arkema) [Curing agent (D)] Dicyandiamide (trade name: DICY15, manufactured by Mitsubishi Chemical Corporation) [Curing accelerator (E)] 3-(3,4-dichlorophenyl)-1,1-dimethylurea (trade name: DCMU99, manufactured by Hodogaya Chemical Co., Ltd.)

[0054] [Preparation of Epoxy Resin Compositions] First, a portion of component (A) was set aside from the epoxy resin compositions of each Example and Comparative Example shown in Tables 1 to 3, and components (D) and (E) were uniformly dispersed in the set aside portion of component (A) using a three-roll mill to prepare resin composition 1. Next, all components from each Example and Comparative Example, except for the amount used to prepare resin composition 1, were weighed into a glass flask and heated and mixed at 150°C for 3 hours to obtain a uniform masterbatch. Next, the obtained masterbatch was cooled to below 60°C, and then resin composition 1 was weighed and added. The mixture was heated and mixed at 60 to 70°C for 1 hour to obtain a uniform dispersion, yielding an epoxy resin composition. The compositions of the obtained epoxy resin compositions are shown in Tables 1 to 3, where the amount of component (A) is defined as 100 parts by mass and the contents of the other components are respectively indicated. Furthermore, Kane Ace MX-154 contains 40% of a core-shell type rubber particle component and 60% of an epoxy resin component, and therefore, in epoxy resin compositions containing Kane Ace MX-154, the content of component (C) for Kane Ace MX-154 in Tables 1 to 3 represents a value of 40% of the amount of Kane Ace MX-154 itself added, and similarly, the content of component (A) represents a value obtained by adding a value of 60% to the amount of Kane Ace MX-154 itself added.

[0055] [Preparation of Sandwich Steel Plates] First, the epoxy resin compositions obtained in each Example and Comparative Example were applied to a 0.4 mm thick steel plate using an applicator to a uniform thickness of 400 μm. Then, another steel plate (0.4 mm thick) was attached to the applied plate using a Teflon spacer. The resulting sandwich steel plate was then pressed and held at 150°C for 2 hours in a hot press to obtain a sandwich steel plate with the cured epoxy resin composition embedded at the interface. The resulting sandwich steel plate was then cut to a size of 40 mm long x 10 mm wide to obtain a test piece for measuring loss factor (tan δ). Further, a sandwich steel plate was prepared in the same manner, measuring 70 mm long x 15 mm wide, with the non-bonded portion measuring 30 mm in the longitudinal direction. The non-bonded portion of the steel plate was then expanded into a T-shape as shown in Figure 3 to obtain a T-peel test piece for measuring peel strength.

[0056] [Measurement of Loss Factor (tan δ)] The loss factor (tan δ) of each Example and Comparative Example was measured by performing dynamic mechanical analysis (DMA) on the test pieces for loss factor (tan δ) measurement obtained above. A Hitachi High-Tech Science Corporation DMA7100 was used as the measurement device. Measurements were performed in a flexural mode with a two-cycle heating cycle: heating from -100°C to 200°C at 2°C / min, cooling from 200°C to -100°C, and then heating again from -100°C to 200°C at 2°C / min. The measurement frequency was set to 10 Hz. The loss factor (tan δ) data reported (peak values ​​from 0 to 30°C and 30 to 60°C) are data from the second heating cycle. DMA is a method for measuring the mechanical properties of a sample by applying time-varying strain or stress (vibration) to the sample and measuring the resulting stress or strain. DMA can be used to measure the temperature and frequency dependence of the viscoelastic properties of a sample, such as storage modulus, loss modulus, and loss factor. Of these, the loss factor is generally used as an index of vibration damping.

[0057] [Measurement of Peel Strength (T-Peel Test)] Using an Autograph AGS-H manufactured by Shimadzu Corporation, set to a gauge length of 30 mm, a tensile test was performed on the T-peel test piece obtained above using a 500 N load cell at a head speed of 100 mm / min, thereby measuring the peel strength of the resin at the steel plate / steel plate interface.

[0058] [Evaluation of Peel Strength] The peel strength was evaluated as pass (○) when the peel strength improved compared to an example in which the ratio of component (B) was the same but component (C) was not added, and as fail (×) when the peel strength decreased. For examples in which component (B) was added but component (C) was not added, or examples in which component (B) was not added but component (C) was added, the peel strength was evaluated as pass (○) when the peel strength improved compared to an example in which neither component (B) nor (C) was added, and as fail (×) when the peel strength decreased. Specific comparison targets for peel strength are shown in Tables 1 to 3.

[0059] Epoxy resin compositions that had peak tan δ values ​​of 0.0300 or greater at both 0 to 30°C and 30 to 60°C and that were evaluated as pass (◯) in peel strength were evaluated as being capable of improving both vibration damping properties and adhesive properties. The results are shown in Tables 1 to 3.

[0060]

[0061]

[0062]

[0063] Referring to Tables 1 to 3, in Comparative Example 1, which contained only the (A) component of the (A) to (C) components, and Comparative Examples 2 to 7, which contained only the (A) and (B) components, as the amount of the (B) component added was increased to 50 to 90 parts by mass per 100 parts by mass of the (A) component, a high peak value of tan δ was observed in the relatively low temperature range of 0 to 30°C, and therefore high vibration damping properties were exhibited, but a corresponding tendency for adhesiveness to decrease was observed. This decrease in adhesiveness is thought to be due to the relative decrease in the proportion of the (A) component, which has excellent adhesiveness, as the amount of the (B) component added increased. Furthermore, in Comparative Examples 1 to 7, the peak value of tan δ was low in the relatively high temperature range of 30 to 60°C, and therefore sufficient vibration damping properties could not be obtained in this relatively high temperature range.

[0064] On the other hand, in Examples 1 to 4, in which the (C) component was added in the same amount (90 parts by mass) of the (B) component as in Comparative Examples 6 and 7, which showed high vibration damping properties at low temperatures, a high tan δ peak value was also observed at a relatively high temperature range of 30 to 60°C, thereby expanding the applicable temperature range of vibration damping properties. Furthermore, in Comparative Examples 8 and 17, in which only the (C) component was added, a high tan δ peak value was not observed at a temperature range of 30 to 60°C. Therefore, it is believed that the improvement in vibration damping properties at high temperatures is not simply due to the addition of the (C) component, but rather to the combination of the (B) and (C) components. More specifically, it is believed that the combination of the (B) and (C) components broadened the tan δ peak due to the change to a complex phase-separated structure as shown in Figure 2, thereby enabling a high loss factor to be achieved not only in the temperature range of 0 to 30°C, but also in the temperature range of 30 to 60°C. Furthermore, in Examples 1 to 4, core-shell rubber particles were used as component (C). Compared to the peel strength of 7.1 N in Comparative Example 6, which was used to compare adhesiveness, the peel strength improved significantly as the amount of component (C) added increased, and Example 4, which contained 23.4 parts by mass of component (C), achieved a peel strength of 37.8 N, which is more than five times that of Comparative Example 6.

[0065] Comparative Examples 9 to 11 and Examples 5, 6, 16, and 17 demonstrate the effect of adding an acrylic block copolymer as component (C). Specifically, in the case of the acrylic block copolymer, as in the case of the core-shell rubber particles, only Examples 5, 6, 16, and 17, in which components (B) and (C) were used in combination, exhibited high vibration damping properties not only in the low temperature range but also in the high temperature range, thereby expanding the temperature range in which vibration damping can be applied. In particular, when an acrylic block copolymer was added as component (C), a very high loss factor was obtained in both the low temperature and high temperature ranges. Furthermore, in Examples 16 and 17, the amount of acrylic block copolymer added as component (C) was significantly increased compared to Examples 5 and 6. Even in these cases, the high loss factor was maintained sufficiently in both the low temperature and high temperature ranges, and the adhesiveness was also improved. On the other hand, in Comparative Examples 12 to 14, in which the amount of acrylic block copolymer added as component (C) was increased compared to Comparative Examples 10 and 11 without adding component (B), the loss factor in the high temperature range was improved in Comparative Examples 12 and 14, but because component (B) was not added, a sufficient loss factor in the low temperature range could not be obtained in any of Comparative Examples 12 to 14. These results show that, although the addition of an acrylic block copolymer as component (C) can significantly improve vibration damping properties, such an effect cannot be obtained by component (C) alone, but must be obtained by using component (B) in combination with component (C).

[0066] Next, Examples 7 to 10 demonstrate the effect of adding both core-shell rubber particles and an acrylic block copolymer as component (C). Specifically, in Examples 7 to 10, the amount of acrylic block copolymer added was kept constant while the amount of core-shell rubber particles added was increased. In these cases, a high loss factor was obtained in both the low-temperature and high-temperature ranges, but the significant improvement in vibration damping properties shown in Examples 5, 6, 16, and 17 was not observed. However, by adding the core-shell rubber particles, a tendency for adhesion to increase significantly with increasing addition amount was observed.

[0067] Similarly, in Comparative Examples 15 and 16 and Example 11, in which the type of component (B) was changed, only in Example 11, in which the component (B) and the component (C) were used in combination, was it possible to achieve a high loss factor in both low and high temperature ranges while improving the adhesiveness, and therefore to expand the applicable temperature range of vibration damping properties.

[0068] Examples 12 to 15, 18, and 19 demonstrate the effect of adding more than 100 parts by mass of component (B). Adding a large amount of component (B) significantly improved vibration damping, especially at low temperatures. Furthermore, when a large amount of component (B) was added, peeling occurred unless component (C) was added, making it impossible to properly prepare T-peel test specimens for comparison. However, while a tendency for adhesiveness to decrease with increasing amounts of component (B) was observed in Examples 12 to 15, 18, and 19, even in Example 19, where 200 parts by mass of component (B) were added, high adhesiveness could be maintained by using component (C) in combination.

[0069] 1, 10 Cured product of epoxy resin composition 2 Epoxy resin 3 Rosin resin

Claims

1. An epoxy resin composition comprising a main component including an epoxy resin (A), a rosin-based resin (B), and an epoxy resin modifier (C), and a curing agent (D).

2. 2. The epoxy resin composition according to claim 1, wherein the epoxy resin modifier (C) comprises at least one selected from core-shell type rubber particles and acrylic block copolymers.

3. 3. The epoxy resin composition according to claim 1, wherein the curing agent (D) comprises an amine-based curing agent.

4. 4. The epoxy resin composition of claim 3, wherein the curing agent (D) comprises dicyandiamide.

5. 3. The epoxy resin composition according to claim 1, wherein the rosin-based resin (B) is 10 to 180 parts by mass and the epoxy resin modifier (C) is 1 to 90 parts by mass, relative to 100 parts by mass of the epoxy resin (A).

6. 6. The epoxy resin composition according to claim 5, wherein the rosin-based resin (B) is 40 to 180 parts by mass and the epoxy resin modifier (C) is 10 to 50 parts by mass relative to 100 parts by mass of the epoxy resin (A).

7. A method for producing an epoxy resin composition, comprising the following steps 1 to 3: Step 1: preparing a resin composition by mixing a curing agent (D) with a portion of the epoxy resin (A); Step 2: A step of charging the epoxy resin (A), the rosin-based resin (B), and the epoxy resin modifier (C) into a dissolution vessel, and mixing them under heating at 140 to 170°C for 1 to 6 hours to obtain a masterbatch based on the dissolved components (B) and (C); and Step 3: A step of cooling the masterbatch obtained in step 2 to 50 to 70°C, then adding the resin composition obtained in step 1, and mixing at 50 to 70°C for 0.5 to 2 hours to obtain an epoxy resin composition.

8. 8. The method for producing an epoxy resin composition according to claim 7, wherein the rosin-based resin (B) is 10 to 180 parts by mass and the epoxy resin modifier (C) is 1 to 90 parts by mass relative to 100 parts by mass of the epoxy resin (A).

9. 9. The method for producing an epoxy resin composition according to claim 8, wherein the rosin-based resin (B) is 40 to 180 parts by mass and the epoxy resin modifier (C) is 10 to 50 parts by mass, relative to 100 parts by mass of the epoxy resin (A).