Epoxy resin composition and cured product

Abstract

The present invention discloses a polyurethane-modified epoxy resin composition which is able to achieve a good balance between high toughness and high elasticity. This epoxy resin composition is characterized by containing, as essential components: (A) a polyurethane-modified epoxy resin that has a polycarbonate structure in each molecule, while having a urethane modification rate of from 20% by weight to 60% by weight; (B) a polyurethane-unmodified epoxy resin that is in a liquid state at 30°C; (C) a bisphenol type solid epoxy resin that has a glass transition temperature or melting point of 50°C or higher; and (D) an amine-based curing agent that is composed of dicyandiamide or a derivative thereof. This epoxy resin composition is also characterized in that from 20.0% by weight to 50.0% by weight of the component (A), from 0.1% by weight to 50.0% by weight of the component (B) and from 0.1% by weight to 50.0% by weight of the component (C) are contained relative to the total weight of the components (A) to (D).

Description

[Technical field]

[0001] The present invention relates to a polyurethane-modified epoxy resin composition obtained by blending a polyurethane-unmodified epoxy resin for adjusting the polyurethane concentration and a curing agent with a polyurethane-modified epoxy resin, and to a cured product thereof. [Background technology]

[0002] Epoxy resins have excellent processability and can produce a variety of hardened product properties, such as high heat resistance, high insulation reliability, high rigidity, high adhesion, and high corrosion resistance, and are therefore used in large quantities for a variety of applications, including electrical insulating materials (casting, impregnation, laminates, and sealing materials), matrix resins for composite materials such as CFRP, structural adhesives, and heavy-duty corrosion-resistant paints.

[0003] On the other hand, epoxy resin cured products have low breaking elongation, low fracture toughness, and low peel strength. Therefore, in applications such as matrix resins for composite materials and structural adhesives where these properties are required, the above properties have been improved by various modifications such as rubber modification and polyurethane modification.

[0004] Patent Documents 1 and 2 disclose an epoxy resin composition prepared by blending a polyurethane-modified epoxy resin synthesized by blending polypropylene diol and isophorone diisocyanate in a bisphenol A type epoxy resin containing hydroxyl groups such that the molar ratio of NCO groups in the isophorone diisocyanate to the total OH groups of the bisphenol A type epoxy resin and the polypropylene diol is NCO / OH=1.0, and blending this with a specific epoxy resin such as polyoxyalkylene diglycidyl ether, as an adhesive for use in automotive structural adhesives having high shear strength, peel strength, and torsional shear strength, as well as excellent adhesion and impact resistance.

[0005] However, there is no description of controlling the resin properties and the properties of the cured product by specifying the concentration of the epoxy resin containing a hydroxyl group, and no data is disclosed on the viscosity of the composition or the breaking elongation, fracture toughness and glass transition temperature of the cured product.

[0006] Patent Document 3 discloses that a resin composition containing a urethane-modified epoxy resin obtained by feeding a specific diol compound and diphenylmethane diisocyanate into a bisphenol A type epoxy resin and reacting them to obtain a urethane prepolymer, and then feeding 1,4-butanediol as a chain extender to convert it into a polyurethane forms a cured product with high fracture toughness that is useful for electrical and electronic applications and building material applications.

[0007] However, in the above-mentioned urethane-modified epoxy resin, there is no description of controlling the resin properties and the cured product properties by specifying the charged concentration of the epoxy resin containing hydroxyl groups. In addition, data on the viscosity of the composition and the breaking elongation of the cured product are not disclosed. Data on fracture toughness and glass transition temperature are described, and the former shows a significant improvement, but the latter is a low temperature for an epoxy resin cured product and has insufficient heat resistance.

[0008] Furthermore, the present inventors have disclosed a urethane-modified epoxy resin in Patent Document 4, but the urethane-modified epoxy resin has a problem in that a sufficient improvement in impact resistance cannot be achieved when a certain type of curing agent is used in the composition.

[0009] Patent Document 5 studies the use of polycarbonate polyol as an adhesive with improved flexibility and toughness. It describes the effects of lowering the elastic modulus, flexibly relaxing stress, and increasing toughness, but no data on toughness is shown, only strength and elongation.

[0010] Furthermore, Patent Document 6 examines the application of polycarbonate diol to urethane-modified epoxy resins, but describes the effect of lowering fracture toughness by using polycarbonate diol, and indicates that high toughness cannot be obtained with polycarbonate diol, which has a rigid structure compared to polytetramethylene glycol and polypropylene glycol. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2007-284467 A [Patent Document 2] JP 2007-284474 A [Patent Document 3] JP 2007-224144 A [Patent Document 4] JP 2016-11409 A [Patent Document 5] JP 2017-226717 A [Patent Document 6] JP 2017-82128 A Summary of the Invention

[0012] The present invention improves the fatigue resistance, peel strength, impact resistance, and compression strength of casting materials, composite materials, and structural adhesives, and also improves the heat resistance of the cured product by improving the glass transition temperature of 110°C or higher and the Izod impact strength value (JISK7110; notched) of 30 kJ / m 2 The objective of the present invention is to provide a novel polyurethane-modified epoxy resin composition and cured product that can achieve an elastic modulus of 2.5 GPa or more and a fracture toughness of 2.0 MPa·m0.5 or more.

[0013] The present invention relates to the following components (A) to (D); (A) a polyurethane-modified epoxy resin having a polycarbonate structure in its molecule and a urethane modification rate of 20 to 60% by weight; (B) a polyurethane-unmodified epoxy resin that is liquid at 30°C; (C) Bisphenol-based solid epoxy resins having a glass transition temperature or melting point of 50°C or higher, and (D) an amine-based curing agent such as dicyandiamide or a derivative thereof; The epoxy resin composition contains the above as essential components, and is characterized in that it contains 20.0 to 50.0% by weight of component (A), 0.1 to 50.0% by weight of component (B), and 0.1 to 50.0% by weight of component (C) relative to the total of components (A) to (D).

[0014] The polycarbonate structure contained in component (A) preferably contains a structural unit represented by general formula (1). [ka] (wherein, each R is independently an alkylene group having 1 to 20 carbon atoms, and n is a number from 1 to 50.) In addition, it is preferable that the resin be a polyurethane-modified epoxy resin having a weight average molecular weight (Mw) of 10,000 or more and 50,000 or less.

[0015] The above component (A) is preferably a polyurethane-modified epoxy resin represented by the following formula (2), which is obtained by modifying a bisphenol-based epoxy resin (a) having an epoxy equivalent of 150 to 200 g / eq and a hydroxyl group equivalent of 2000 to 3000 g / eq with a medium- to high-molecular-weight polyol compound (b), a polycarbonate diol compound (b-2), a polyisocyanate compound (c), and a low-molecular-weight polyol compound (d) having a number-average molecular weight of less than 200 as a chain extender. Preferably, the epoxy resin (a) is used in an amount of 50 to 80% by weight based on the total amount of the components (a), (b), (b-2), (c) and (d), and the polycarbonate diol (b-2) is used in an amount of 20 to 55% by weight based on the total amount of the components (b) and (b-2), and the epoxy resin (a) is reacted with the components (b), (b-2) and (c) to produce a urethane prepolymer (P), and then a low molecular weight polyol compound (d) is added so that the molar ratio of the NCO group of the urethane prepolymer (P) to the OH group of the low molecular weight polyol compound (d) is in the range of 0.9:1 to 1:0.9 to carry out a polyurethane-forming reaction to obtain a polyurethane-modified epoxy resin. As a method for producing the above-mentioned polyimide, it is preferable to react the above-mentioned components (a), (b), (b-2) and (c) and then react the component (d). [ka] (wherein, each R1 is independently H or an alkyl group, and a is a number from 0 to 10.)

[0016] The present invention also relates to a cured epoxy resin product obtained by curing the above-mentioned epoxy resin composition. This epoxy resin cured product has a glass transition temperature of 110°C or higher and an Izod impact strength of 30kJ / m 2 or more, elastic modulus 2.5GPa or more, fracture toughness 2.0MPa m 0.5 More than this is desirable.

[0017] The epoxy resin composition of the present invention can improve the strength, fracture toughness, and impact strength of the cured product, and can also inhibit a decrease in the glass transition temperature, making the resin composition and cured product thereof suitable for use as adhesives, coating materials, electric and electronic materials, matrix resins for composite materials, etc. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The epoxy resin composition of the present invention contains, as essential components, (A) a polyurethane-modified epoxy resin having a polycarbonate structure in the molecule and a urethane modification rate of 20 to 60% by weight, (B) a polyurethane-unmodified epoxy resin that is liquid at 30°C, (C) a solid epoxy resin having a bisphenol structure and a glass transition temperature or melting point of 50°C or higher, and (D) an amine-based curing agent that is dicyandiamide or a derivative thereof. Each of these components is also called a polyurethane-modified epoxy resin, a liquid epoxy resin, a solid epoxy resin, an amine-based curing agent, or a component (A), a component (B), a component (C), or a component (D). Each component will be described below.

[0019] In the epoxy resin composition of the present invention, component (A) is a polyurethane-modified epoxy resin having a polycarbonate structure in the molecule, and the weight concentration of the polyurethane constituent component is preferably 20.0 to 60.0% by weight.

[0020] The polyurethane-modified epoxy resin can be produced by reacting an epoxy resin (a) with a medium- to high-molecular-weight polyol compound (b), a polycarbonate diol compound (b-2), a polyisocyanate compound (c), and a low-molecular-weight polyol compound (d). Here, the epoxy resin (a), the medium- to high-molecular-weight polyol compound (b), the polycarbonate diol compound (b-2), the polyisocyanate compound (c), and the low-molecular-weight polyol compound (d) are also referred to as components (a), (b), (b-2), (c), and (d), respectively. The polyurethane components are the components other than the epoxy resin (a) as a raw material, i.e., the polyol compound (b), the polycarbonate diol compound (b-2), the polyisocyanate compound (c) and the low-molecular-weight polyol compound (d), and the urethane modification rate refers to the ratio of the total weight of these polyurethane components to the total weight of the polyurethane-modified epoxy resin.

[0021] Components (b), (b-2), and (d) are all polyol-based compounds, but are different in that component (b) has a number average molecular weight of 200 or more, while component (d) has a number average molecular weight of less than 200. In addition, even if a compound that corresponds to component (b-2) may also correspond to component (b) or (d), it is treated as a compound of component (b-2) and not as a compound of component (b) or (d).

[0022] The polycarbonate diol compound (b-2) may be a medium to high molecular weight polyol compound, but the effects of the present invention can be exhibited by containing this structure in particular. As the polycarbonate diol compound (b-2), compounds having aromatic, aliphatic, alicyclic, etc. structures can be used as long as they are diols having a carbonate bond in the molecule, and for example, those obtained by esterification reaction of carbonic acid derivatives with aliphatic polyols can be used. Specifically, reaction products of diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene glycol (PTMG) with dimethyl carbonate, diphenyl carbonate, phosgene, etc. can be mentioned. These may be used alone or in combination of two or more. Commercially available products include UH-100, UH-200, and UH-300 manufactured by Ube Industries, Ltd., and T5650J, T5651, T5652, G3452, T4691, T4692, G4672, and T4671 manufactured by Asahi Kasei Corporation.

[0023] The polycarbonate diol compound (b-2) is preferably an aliphatic polycarbonate diol compound represented by the following formula (3). [ka] (wherein, each R is independently an alkylene group having 1 to 20 carbon atoms, and n is a number from 1 to 50.) By using such a compound, the structure of the above formula (1) can be introduced into the polyurethane-modified epoxy resin. The physical properties of the polyurethane-modified epoxy resin or composition change depending on the molecular weight, crystallinity, polarity, structure, etc. of this compound. In consideration of flexibility and compatibility with other resins, it is particularly preferable that the polycarbonate diol compound (b-2) has a number average molecular weight of about 800 to 3000.

[0024] The medium- to high-molecular-weight polyol compound (b) has a number average molecular weight of 200 or more, excluding the polycarbonate diol compound (b-2). The OH group may be a secondary hydroxyl group, but if it is a primary hydroxyl group, the reactivity is excellent.

[0025] Preferably, it is a compound represented by any one of the following formulas (4) to (11), and one or more kinds can be used in combination. [ka] (wherein R2 is H or a methyl group, b1, b2, and b3 are independently numbers from 1 to 50, and c is a number of 0 or 1.) [ka] (wherein R2 is H or a methyl group, and d1, d2, e1, and e2 are independently numbers from 1 to 20.)

[0026] [ka] (Here, h1 and h2 are independently numbers from 1 to 20, and i is a number from 1 to 50.) [ka] (Here, j1, j2, and j3 are independently numbers from 1 to 20, and k1 and k2 are independently numbers from 1 to 50.) [ka] (Here, l1, l2, l3, l4, and l5 are independently numbers from 1 to 20, and m1 and m2 are independently numbers from 1 to 50.) [ka] (Here, o1, o2, o3, and o4 are independently numbers from 1 to 20.)

[0027] [ka] (Here, q1, q2, q3, and q4 are independently numbers from 1 to 20.) [ka] (Here, r, s, and t are independently numbers from 1 to 20, and n is a number from 1 to 50.)

[0028] The medium- to high-molecular-weight polyol compound (b) preferably has a number-average molecular weight of 200 or more, a molecular structure of any one of the above formulas (4) to (12), and excellent compatibility with the epoxy resin (a). For example, polyethylene glycols and polypropylene glycols obtained by ring-opening polyaddition of ethylene oxide or propylene oxide to a polyhydric alcohol such as ethylene glycol or glycerin can be exemplified, but polypropylene glycol represented by formula (13) in which c in formula (4) is 0 and R2 is a methyl group is preferred from the viewpoints of availability and a good balance between price and properties. In addition, the number of OH groups in the polyol compound (b) may be 2 or more, but is preferably 2. [ka] (Here, b1 and b2 are independently numbers from 1 to 50.)

[0029] As the polypropylene glycol, a polypropylene glycol having a number average molecular weight of 1500 to 5000, preferably 2000 to 3000, is preferred from the viewpoints of not thickening or semi-solidifying the polyurethane-modified epoxy resin composition and ensuring good tackiness, conformability to the bonding surface, castability, and good impregnation of carbon fiber or glass fiber of the composition.

[0030] The epoxy resin (a) is preferably liquid at room temperature, and from this viewpoint, the epoxy equivalent is preferably 200 g / eq or less. Preferably, the epoxy resin has an epoxy equivalent of 150 to 200 g / eq and a hydroxyl equivalent of 2000 to 3000 g / eq. More preferably, the epoxy resin is a secondary hydroxyl group-containing bisphenol-based epoxy resin represented by the above formula (2), having an epoxy equivalent of 150 to 200 g / eq and a hydroxyl equivalent of 2000 to 2600 g / eq. In the formula, R1 is independently H or an alkyl group, and a is a number of 0 to 10. In the case of an alkyl group, the carbon number is preferably in the range of 1 to 3, and more preferably 1.

[0031] Particularly preferred epoxy resins (a) are bisphenol A type epoxy resins represented by formula (14) or bisphenol F type epoxy resins represented by formula (15). In the formula, a1 and a2 are numbers from 0 to 10, and when there is a molecular weight distribution, it is preferable that the average value (number average value) satisfies the above range. The a1 and a2 are determined so as to satisfy the above epoxy equivalent and hydroxyl equivalent. [ka]

[0032] The polyisocyanate compound (c) is preferably one represented by formula (16), in which R4 is a divalent group selected from formulas (16a) to (16f). Among these, those having excellent compatibility with the epoxy resin (a) are preferred. Specific examples include toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), hydrogenated xylylene diisocyanate (HXDI), isophorone diisocyanate (IPDI), naphthalene diisocyanate, etc., and MDI represented by formula (17) is preferred from the viewpoints of low molecular weight, no thickening, low cost, safety, etc. The number of NCO groups in the polyisocyanate compound (c) may be 2 or more, and is preferably 2. [ka] (wherein R4 is a divalent group selected from formulas 16a to 16f). [ka] [ka]

[0033] The low molecular weight polyol compound (d) is a polyol compound having a number average molecular weight of less than 200. It is used as a chain extender. It is preferably a diol compound having two primary hydroxyl groups represented by formula (18). [ka] (Here, R5 is an alkylene group represented by formula 18a, and g is a number from 1 to 10.)

[0034] Specific examples of the low molecular weight polyol compound (d) include polyhydric alcohols such as 1,4-butanediol, 1,6-pentanediol, etc. Among these, 1,4-butanediol is more preferred in terms of availability and a good balance between price and properties.

[0035] Next, polyurethane-modified epoxy resins using each of the components (a), (b), (b-2), (c) and (d) will be explained together with the reaction mechanism. Each component can be used alone or in combination of two or more.

[0036] The OH groups in the epoxy resin (a) are mainly secondary OH groups contained in epoxy resins with a degree of polymerization of 1 (n in formula (2) is a component of 1, so it is called n=1 form). When it contains an epoxy resin with a degree of polymerization of 2 or more (called n>1 form), it also contains secondary OH groups, and the same applies here. Hereinafter, n=1 form and n>1 form will be collectively referred to as n=1 or more form. On the other hand, when the OH groups of the polyol compound (b) and the polycarbonate diol compound (b-2) are primary OH groups, when the epoxy resin (a), the polyol compound (b), the polycarbonate diol compound (b-2) and the polyisocyanate compound (c) are charged and reacted, the primary OH groups of these compounds react preferentially with the NCO group of the polyisocyanate compound (c).

[0037] Typically, the primary OH groups in the polyol compound (b) and polycarbonate diol compound (b-2) react with the NCO groups in the polyisocyanate compound (c) first to produce the NCO-terminated urethane prepolymer (P1).Then, the secondary OH groups of n=1 or more in the epoxy resin (a) react with some of the terminal NCO groups of the urethane prepolymer (P1) to form urethane bonds, and it is believed that the urethane prepolymer (P2) has n=1 or more units in the epoxy resin (a) added to both ends or one end of the urethane prepolymer.

[0038] In other words, the urethane prepolymer (P) is thought to be a mixture of NCO-terminated urethane prepolymer (P1) and urethane prepolymer (P2) in which an n=1 or greater unit in the epoxy resin (a) has been added to both ends or one end of P1; however, because the molar ratio of NCO groups is large and a large excess of epoxy resin is also used, it is thought that mainly urethane prepolymer (P2) in which epoxy resin has been added to both ends is produced.

[0039] As the charging ratio of the epoxy resin (a) is increased, both ends or one end is blocked with n=1 or more in the epoxy resin (a), the terminal NCO groups are consumed, the amount of the urethane prepolymer (P2) that does not react with the low molecular weight polyol compound (d) serving as a chain extender increases, the ratio of the original urethane prepolymer (P1) having an NCO group at the end decreases, and the amount of polyurethane produced by the reaction between the terminal NCO groups of P1 and the OH groups of the low molecular weight polyol compound (d) serving as a chain extender decreases, and it is believed that the molecular weight distribution of the polyurethane-modified epoxy resin also shifts to the lower molecular weight side.

[0040] Conversely, if the ratio of epoxy resin (a) is decreased, the amount of urethane prepolymer (P2) in which both ends or one end is blocked with n=1 or more in epoxy resin (a) decreases, and the ratio of the original urethane prepolymer (P1) whose end remains an NCO group increases. Therefore, the amount of polyurethane produced by the reaction between the terminal NCO group of P1 and the OH group of the low molecular weight polyol compound (d), which is a chain extender, increases, and it is thought that the molecular weight distribution of the polyurethane-modified epoxy resin also shifts to the high molecular weight side.

[0041] Epoxy resin (a) is often a mixture of a monomer with a repeat number n of 0 and a polymer with a repeat number n of 1 or more, but in the case of the polymer, it has a secondary OH group generated by ring-opening of the epoxy group. This OH group is reactive with the NCO group of the polyisocyanate compound (c) or the terminal NCO group of the urethane prepolymer (P), so the n=1 or more in the epoxy resin (a) reacts with it. Incidentally, the n=0 form, which does not have an OH group, does not participate in this reaction.

[0042] When the polyol compound (b), the polycarbonate diol compound (b-2), and the polyisocyanate compound (c) are all bifunctional, the number of moles of OH groups and NCO groups corresponds to the ratio of the number of moles of the polyol compound (b) and the polycarbonate diol compound (b-2) to the number of moles of the polyisocyanate compound (c). The molar ratio of NCO group / OH group is preferably 1.5 to 6. When the components (b), (b-2) and (c) are bifunctional, the molar ratio of these components or (c) / [(b)+(b-2)] is preferably 1.5 to 6. By increasing the molar ratio, i.e., by using an excess of polyisocyanate compound (c), a larger amount of urethane prepolymer having isocyanate groups at both ends can be obtained. The lower the molar ratio is, the closer to 1.0, the more the molecular weight of the urethane prepolymer produced increases, resulting in an excessively high viscosity. In addition, a urethane polymer having an isocyanate at one end or a urethane polymer having an OH group at the end is more likely to be produced. On the other hand, if the molar ratio is too high, the molecular weight of the urethane prepolymer produced becomes too small, and the compatibility with the matrix resin increases, resulting in an unclear phase separation structure, which is undesirable because it may not be possible to fully exhibit the modifying effect. By making the molar ratio of NCO groups more excessive as described above, a urethane prepolymer with more modified ends is produced, which in turn produces a urethane prepolymer (P2) with both ends further modified by epoxy resins with n=1 or more. Therefore, when the epoxy resin hardens, these urethane prepolymers (P2) are more easily and reliably introduced into the crosslinked parts, which is thought to lead to improved toughness even with a small amount.

[0043] After obtaining a urethane prepolymer (P) in the epoxy resin (a), a low molecular weight polyol compound (d) is added so that the molar ratio (P):(d) of the NCO groups in the urethane prepolymer (P) to the OH groups in the low molecular weight polyol compound (d) falls within the range of 0.9:1 to 1:0.9, and a polyurethane-forming reaction is carried out to obtain the polyurethane-modified epoxy resin used in the present invention.

[0044] The low molecular weight polyol compound (d) is preferably used in an amount such that the NCO group at the end of the urethane prepolymer (P) and the OH group of the low molecular weight polyol compound (d) are approximately equimolar. That is, since the polyol compound (b), the polycarbonate diol compound (b-2) and the low molecular weight polyol compound (d) have OH groups, and the polyisocyanate compound (c) has NCO groups, it is preferable that the number of moles of OH groups (B) of (b) + (b-2) + (d) is approximately the same as the number of moles of NCO groups (C) of (c). The ratio is preferably in the range of 0.9:1 to 1:0.9. The molecular weight of the polyurethane produced increases as the ratio of the number of moles of OH groups to the number of moles of NCO groups approaches 1.

[0045] In the method for producing the polyurethane-modified epoxy resin used in the present invention, for example, epoxy resin (a) is used in an amount of 50 to 80% by weight based on the total amount of polyol compound (b), polycarbonate diol compound (b-2), polyisocyanate compound (c) and low molecular weight polyol compound (d), and polycarbonate diol (b-2) is used in an amount of 20 to 55% by weight based on the total amount of components (b) and (b-2), and reacted in the presence of epoxy resin (a) (reaction 1). In this reaction 1, the reaction of the polyol compound (b) and the polycarbonate diol compound (b-2) with the polyisocyanate compound (c) occurs preferentially to produce a urethane prepolymer (P1), and then a part of the urethane prepolymer (P1) reacts with the epoxy resin (a) to produce mainly a urethane prepolymer (P2) having both ends epoxidized, with a small amount of the urethane prepolymer (P2) having one end epoxidized being produced and a mixture of the urethane prepolymer (P1) having both ends remaining NCO.

[0046] In the reaction of the above urethane prepolymer (P1) with the epoxy resin (a), it is necessary to react the low-reactive secondary OH groups in the epoxy resin (a) where n=1 or more with the NCO groups to generate urethane bonds, so the reaction temperature is preferably in the range of 80 to 150°C and the reaction time is preferably in the range of 1 to 5 hours.

[0047] Then, a low molecular weight polyol compound (d) is added so that the molar ratio (P):(d) of the NCO group in the urethane prepolymer (P) to the OH group in the low molecular weight polyol compound (d) is in the range of 0.9:1 to 1:0.9, and a polyurethane reaction is carried out (reaction 2). Note that the epoxy group of the epoxy resin (n=0) and the OH group of the polyol compound (d) do not react because they are alcoholic OH groups.

[0048] The reaction temperature of Reaction 2 is preferably in the range of 80 to 150°C, and the reaction time is preferably in the range of 1 to 5 hours. However, since Reaction 2 is a reaction between the NCO group and the OH group in the low-molecular-weight polyol compound (d), milder conditions than Reaction 1 may be used.

[0049] In the above reactions (Reactions 1 and 2), a catalyst can be used as necessary. The catalyst is used for the purpose of sufficiently completing the formation of the urethane bond, and examples of the catalyst include amine compounds such as ethylenediamine, tin compounds, and zinc compounds.

[0050] In reaction 2, the small amount of urethane prepolymer (P1) having NCO at both or just one end reacts with the low molecular weight polyol compound (d) to extend the chain length and form polyurethane, while the urethane prepolymer (P2) having both ends an adduct of n=1 or more in the epoxy resin (a) remains unreacted. That is, the polyurethane-modified epoxy resin used in the present invention is a mixture of a resin component in which an n=1 or more moiety in the epoxy resin (a) is added mainly to both ends of the urethane prepolymer (P), a resin component in which an n=1 or more moiety in the epoxy resin (a) is added as a small or trace component to one end of the urethane prepolymer (P) and the other end is an NCO group, a resin component in which both ends of the urethane prepolymer (P) are NCO groups, and an n=0 moiety in the epoxy resin (a), and it is preferable that the epoxy equivalent is in the range of 180 to 1000 g / eq and the viscosity at 120°C is in the range of 0.1 to 20 Pa s.

[0051] The reaction formula for obtaining the polyurethane-modified epoxy resin (A) used in the composition of the present invention is shown below.

[0052] The following formula 19 is a schematic diagram of the urethane prepolymer process as the above-mentioned reaction 1. When a bisphenol-based epoxy resin (a) mainly composed of n=0 and n=1 units, a medium- to high-molecular-weight polyol compound (b) and a polyisocyanate compound (c) are reacted with each other, a urethane prepolymer (P) is produced. This urethane prepolymer (P) is produced in three forms: urethane prepolymer (U) with NCO groups at both ends, urethane prepolymer (T) with an epoxy resin having an NCO group at one end and a secondary hydroxyl group at the other end (n=1), and urethane prepolymer (S) with an epoxy resin having an n=1 secondary hydroxyl group at both ends. However, because polyisocyanate compound (c) and bisphenol-based epoxy resin (a) are used in large excess, the main product is urethane prepolymer (S) with an epoxy resin having an n=1 secondary hydroxyl group at both ends (n=1), and it is considered that the production of urethane prepolymer (T) with an epoxy resin having an NCO group at one end and a secondary hydroxyl group at the other end (n=1) and urethane prepolymer (U) with NCO groups at both ends is extremely small. Among the epoxy resins (a), the n=0 epoxy resins that do not have secondary hydroxyl groups are not involved in the reaction.

[0053] [ka]

[0054] The following formula 20 is a schematic explanation of the urethane polymer process (polyurethane process) as the above reaction 2. When a low molecular weight polyol (d) is added to a mixture of the urethane prepolymer (U) having NCO groups at both ends generated in the above reaction 1, the urethane prepolymer (T) having an NCO group at one end and an n=1 epoxy resin added to the other end, the urethane prepolymer (S) having an n=1 epoxy resin added to both ends, and the n=0 epoxy resin that did not participate in the reaction because it does not have a secondary hydroxyl group, and reacted, (V) and (W) are generated by reaction with the small amount of (T) generated and a very small amount of (U) component, but only in small amounts, and (S) remains uninvolved in the reaction and becomes (A), and it is considered that, overall, a low molecular weight polyurethane (A) having an epoxy resin added to the end is mainly generated. In this way, almost all polyurethane becomes a mixture of urethane prepolymer (S) with n=1 epoxy resin attached to both ends, low molecular weight urethane polymer (A) with n=1 epoxy resin attached to both ends, and n=0 epoxy resin, and it is believed that almost all urethane is modified with epoxy resin.

[0055] [ka]

[0056] The epoxy resin composition of the present invention can be obtained by blending the above-mentioned polyurethane-modified epoxy resin (A) with a polyurethane-unmodified liquid epoxy resin (B) as an adjuster for the polyurethane concentration, a bisphenol-type solid epoxy resin (C) having a glass transition temperature or melting point of 50°C or higher as a compatibility and viscosity adjuster and an agent for improving tackiness in a resin sheet or prepreg state, and an amine-based curing agent (D). If necessary, the resin composition of the present invention can be blended with other epoxy resins (component E) for fine adjustment of viscosity and Tg, a curing accelerator (F), and even inorganic fillers such as calcium carbonate, talc, and titanium dioxide as extenders and reinforcing materials.

[0057] The liquid epoxy resin (B) is not particularly limited as long as it is an epoxy resin that is not polyurethane-modified and is liquid at 30°C. However, bisphenol A type epoxy resin or bisphenol F type epoxy resin is preferred from the viewpoints of availability and a good balance between price and properties.

[0058] The polyurethane concentration in the epoxy resin composition can be increased or decreased by increasing or decreasing the amount of the liquid epoxy resin (B). The polyurethane concentration is calculated by the following formula: Polyurethane concentration = {(b) + (b-2) + (c) + (d)} x 100 / {(a) + (b) + (b-2) + (c) + (d) + (B) + (C) + (D)} Here, (a)-(d), (B), (C), and (D) are the weights of the corresponding essential components. When other components, such as other epoxy resins (E) and curing accelerators (F), are added to the essential components, the amounts of these other components are added to the denominator.

[0059] As the polyurethane concentration in the cured product increases, the properties of the cured product, such as bending strain, impact strength, and glass transition temperature, change. In general, as the polyurethane concentration increases, the bending strain and impact strength of the cured product tend to increase.

[0060] When a liquid bisphenol A type epoxy resin is used as the liquid epoxy resin (B), it is preferable that the polyurethane modification rate (=polyurethane concentration) in the cured product is in the range of 7 to 15 wt%, so that the Izod impact value (unnotched) of the cured product is 30 kJ / m 2 As a result, it is possible to achieve a glass transition temperature of 110°C or higher, and excellent impact properties can be achieved.

[0061] The epoxy resin composition of the present invention contains a bisphenol-type solid epoxy resin (C) having a glass transition temperature or melting point of 50° C. or higher. As such a solid epoxy resin (C), any resin having a glass transition temperature or melting point of 50° C. or higher can be used, and for example, a high molecular weight type of bisphenol type epoxy resin is useful, and other examples include solid bisphenol F type epoxy resin, biphenyl type epoxy resin, dicyclopentadiene type epoxy resin, and further epoxy resins modified from these, or phenoxy resin. When used to adjust the viscosity or increase the Tg of the resin composition, it is preferable to use 0.1 to 50% by weight based on the total composition weight.

[0062] The epoxy resin composition of the present invention preferably contains 20.0 to 50.0% by weight of component (A), 10 to 40% by weight of component (B), and 0.1 to 50.0% by weight of component (C) relative to the total of components (A) to (D). If the amount of component (A) is less than 20.0% by weight, the sea-island structure is not clearly formed and sufficient impact strength cannot be obtained, and if it exceeds 50.0% by weight, the phase separation state becomes a structure in which the sea-island structure interpenetrates each other, and sufficient impact strength may also not be obtained. Component (C) is designed to appropriately adjust the viscosity to suppress the resin flow during molding while maintaining the resin impregnation and fluidity. If it exceeds 50.0% by weight, the viscosity becomes too high and handling may become difficult. The epoxy resin composition of the present invention preferably has an initial viscosity of 100 to 2000 Pa·s, and more preferably has an initial viscosity of 1100 to 1500 Pa·s.

[0063] As the curing agent (D), dicyandiamide (DICY) or its derivatives are used because they can be made into a one-component solution with excellent storage stability and are easily available.

[0064] When the curing agent (D) is DICY, the ratio of the number of moles of epoxy groups in the total epoxy resin including the polyurethane-modified epoxy resin and the polyurethane-unmodified epoxy resin (B) to the number of moles of active hydrogen groups in DICY is preferably set in the range of 1:0.3 to 1:1.2, and more preferably 1:0.9 to 1:1.1, from the viewpoint of the properties of the cured product.

[0065] In the epoxy resin composition of the present invention, a multifunctional epoxy resin having three or more functionalities can be used as another epoxy resin (E) for fine adjustment of viscosity or increasing Tg. When a multifunctional epoxy resin is used, the crosslink density increases, the phase separation state changes, or fracture toughness is lost, so it is preferable to use 0.1 to 10% by weight based on the total composition weight. Examples of multifunctional epoxy resins having three or more functionalities include phenol novolac type epoxy resins, cresol novolac type epoxy resins, glycidylamine type epoxy resins such as tetraglycidyldiaminodiphenylmethane, glycidylphenylether type epoxy resins such as tetrakis(glycidyloxyphenyl)ethane and tris(glycidyloxyphenyl)methane, and glycidylamine type and glycidylphenylether type epoxy resins such as triglycidylaminophenol. Furthermore, epoxy resins obtained by modifying these epoxy resins, and brominated epoxy resins obtained by brominating these epoxy resins, etc. can be used.

[0066] The epoxy resin composition of the present invention may further contain a curing accelerator (F). As the curing accelerator (F), a crystalline imidazole compound such as 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid addition salt (2MA-OK) or a urea compound such as 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) may be used. The amount of the curing accelerator (F) is preferably in the range of 0.1 to 5 wt% based on the total amount of the epoxy resin including the polyurethane-modified epoxy resin and the polyurethane-unmodified liquid epoxy resin (B) and the curing agent (D).

[0067] The epoxy resin composition of the present invention does not impair processability such as tackiness, conformability to an adhesion surface, castability into a mold, and impregnation into carbon fiber, glass fiber, and fabrics thereof.

[0068] A cured product of the epoxy resin composition of the present invention can be obtained by casting the epoxy resin composition into a mold, or applying it as an adhesive to an adherend and laminating it, or applying it as a paint to an object to be coated, or impregnating carbon fiber, glass fiber, or woven fabrics thereof with the composition, and then heating it to a temperature of 80°C to 200°C and maintaining it for several hours.

[0069] The cured product of the epoxy resin composition of the present invention has an Izod impact value (unnotched) of 30 kJ / m 2 or higher, and furthermore, the glass transition temperature can be 110°C or higher, the elastic modulus can be 2.5 GPa or higher, and the fracture toughness can be 2.0 MPa·m0.5 or higher. EXAMPLES

[0070] The present invention will now be described in detail with reference to examples. The present invention is not limited to these examples, and various modifications and alterations are possible without departing from the gist of the present invention. The properties shown in the examples were evaluated according to the following methods.

[0071] (1) Determination of the presence or absence of residual NCO groups by IR: 0.05 g of the obtained polyurethane-modified epoxy resin was dissolved in 10 ml of tetrahydrofuran, and then the solution was applied to a KBr plate using a Micro Spatula flat plate and dried at room temperature for 15 minutes to evaporate the tetrahydrofuran to prepare a sample for IR measurement. This was set in a PerkinElmer FT-IR Spectrum-One device and the characteristic absorption band of the NCO group, 2270 cm -1 When the stretching vibration absorption spectrum of the compound disappeared, it was determined that no remaining NCO groups existed. (2) Epoxy equivalent: Quantified according to JIS K 7236. (3) Hydroxyl equivalent: 25 ml of dimethylformamide is placed in a 200 ml glass-stoppered Erlenmeyer flask, and a sample containing 11 mg / equivalent or less of hydroxyl is added and dissolved. 20 ml of 1 mol / L-phenylisocyanate toluene solution and 1 ml of dibutyltin maleate catalyst solution are added with a pipette, shaken well to mix, and then sealed and allowed to react for 30 to 60 minutes. After the reaction is complete, 20 ml of 2 mol / L-dibutylamine toluene solution is added, shaken well to mix, and left for 15 minutes to react with the excess phenylisocyanate. Next, 30 ml of methyl cellosolve and 0.5 ml of bromocresol green indicator are added, and the excess amine is titrated with a standardized methyl cellosolve perchlorate solution. The indicator changes from blue to green and then to yellow, so the first point at which it turns yellow is taken as the end point, and the hydroxyl equivalent is calculated using the following formulas I and II. Hydroxyl group equivalent (g / eq)=(1000×W) / C(SB)...(i) C: Concentration of methyl perchlorate cellosolve solution (mol / L) W: sample weight (g) S: Titration volume of methyl perchlorate cellosolve solution (ml) B: Amount (ml) of methyl perchlorate cellosolve solution required for blank test during titration C=(1000×w) / {121×(sb)}···(ii) w: Amount of tris-(hydroxymethyl)-aminomethane weighed for standardization (g) s: Amount (ml) of methyl perchlorate cellosolve solution required for titration of tris-(hydroxymethyl)-aminomethane b: Titration volume (ml) of methyl perchlorate cellosolve solution required for blank test during standardization

[0072] (4) Viscosity: The viscosity of the resin composition before curing at 40° C. was measured using an E-type viscometer. (5) Glass transition temperature (Tg): The glass transition temperature (Tg) was determined from the peak temperature of the tan δ curve of a cured test piece using a dynamic viscoelasticity measuring device at a heating rate of 2° C. / min. (6) Bending test: Test pieces were prepared by casting the cured materials into the shape specified in JIS K 6911 using a mold. A bending test was carried out using a universal testing machine at a room temperature of 23°C and a crosshead speed of 1 mm / min to measure the bending strength, bending strain, and bending modulus. (7) Izod impact strength: Measured without a notch at room temperature of 23°C according to the Izod test method of JIS K7110. (8) Tack: The resin composition before curing was melted at 60-80°C and coated with a bar coater at 100 g / m 2 The coating was applied to a substrate such as release paper at a thickness of 10 μm, and a 40 μm-thick polyethylene film was attached as a cover material, and the coating was judged based on whether it could be peeled off without leaving any resin residue at 25° C. Those that could be peeled off without any problems were marked with an O, and those where resin residue was visible on the peeled surface were marked with an X. (9) Fracture toughness: Test pieces were prepared by casting the cured material into the shape specified in JIS K 6911, and tested using a universal testing machine at room temperature of 23°C and a crosshead speed of 0.5 mm / min. Before testing, notches were made in the test pieces by placing a razor blade on the test piece and impacting the razor blade with a hammer.

[0073] The raw materials used are as follows. The unit of equivalent is (g / eq). Epoxy resin (a): Epotohto YDF-170 made by Nippon Steel Chemical & Material Co., Ltd., bisphenol F type epoxy resin, epoxy equivalent = 170, hydroxyl equivalent = 2489 Polyol (b): ADEKA ADEKA Polyether P-2000, polypropylene glycol, number average molecular weight 2000, hydroxyl equivalent 1020 Polycarbonate diol compound (b-2): Asahi Kasei Duranol T5652, polycarbonate diol, number average molecular weight 2000, hydroxyl equivalent 991 Polyisocyanate (c): Cosmonate PH, 4,4'-diphenylmethane diisocyanate, manufactured by Mitsui Chemicals Low molecular weight polyol (d): 1,4-butanediol (reagent) Liquid epoxy resin (B): Epotohto YD-128, made by Nippon Steel Chemical & Material Co., Ltd., bisphenol A type epoxy resin, epoxy equivalent = 187 Solid epoxy resin (C): (C-1) Bisphenol A type bifunctional solid epoxy resin (YD-014, Nippon Steel Chemical & Material Co., Ltd., solid at room temperature) (C-2) Bisphenol A type bifunctional solid epoxy resin (YD-019, Nippon Steel Chemical & Material Co., Ltd., solid at room temperature) Other epoxy resins (E): Phenol novolac type bifunctional epoxy resin (KDPN-1020, Nippon Steel Chemical & Material Co., Ltd., liquid at room temperature) Hardener (D): EVONIK DICYANEX 1400F, dicyandiamide Curing accelerator (F): Curesol 2MA-OK (manufactured by Shikoku Chemical Industry Co., Ltd.)

[0074] Synthesis Example 1 The epoxy resin (a) used was "Epotohto YDF-170", the polyol (b) was "Adeka Polyether P-2000", the polycarbonate diol (b-2) was "Duranol T5652", the polyisocyanate (c) was "Cosmonate PH", and the low molecular weight polyol (d) was 1,4-butanediol. The amounts of these used are shown in Table 1. Epotohto YDF-170, Adeka Polyether P-2000, and Duranol T5652 were charged into a 1000ml four-necked separable flask equipped with a nitrogen inlet tube, stirrer, and temperature controller, and mixed with stirring at room temperature for 15 minutes. Next, Cosmonate PH was added and reacted at 120°C for 2 hours (Reaction 1: Urethane prepolymer process, this reaction product is called the primary reactant). After that, 1,4-butanediol was added and reacted at 120°C for 2 hours (reaction 2: polyurethane step), to obtain a polyurethane-modified bisphenol F type epoxy resin (resin 1). Here, the epoxy resin (a) was charged so that it was 72% by weight relative to 100% by weight of the product of reaction 2. The molar ratio of OH groups to NCO groups (b)+(b-2):(c) was 1:2.4. The ratio of NCO groups in the first reaction product to OH groups in (d) was 1. The completion of the reaction was confirmed by IR measurement, where the absorption spectrum of the NCO groups had disappeared.

[0075] Synthesis Examples 2-10 Except for using the raw material compositions shown in Tables 1 and 2, the reaction was carried out in the same manner as in Synthesis Example 1 to obtain polyurethane-modified bisphenol F epoxy resins (resins 2 to 10; the resin numbers correspond to the Synthesis Example numbers). The molar ratio of NCO groups in the first reaction product to OH groups in (d) was always 1. Completion of the reaction was confirmed by IR measurement, whereby the absorption spectrum of the NCO groups disappeared.

[0076] In Tables 1 and 2, the blend amount is g, and the values ​​in parentheses indicate weight percent. (a) Concentration (wt%) indicates the concentration of epoxy resin (a) in each resin, and (b) OH group:(c) NCO group (molar ratio) indicates the molar ratio of OH group in (b) to NCO group in (c).

[0077] [Table 1]

[0078] [Table 2]

[0079] Next, examples of epoxy resin compositions and cured epoxy resin products using the polyurethane-modified epoxy resins (resins 1 to 10) obtained in the above-mentioned Synthesis Examples 1 to 10 will be shown. The results are also summarized in Tables 3 and 4.

[0080] Example 1 The polyurethane-modified epoxy resin (A), the polyurethane-modified bisphenol F type epoxy resin (resin 1) obtained in Synthesis Example 1, the polyurethane-unmodified liquid epoxy resin (B), Epotohto YD-128, the bisphenol type solid epoxy resin (C), YD-014 (C-1) or YD-019 (C-2), the other epoxy resin (E), KDPN-1020, the hardener (D), dicyandiamide, and the hardening accelerator (F), 2MA-OK, were charged in a 300 ml dedicated disposable cup in the proportions shown in Table 3, and the mixture was stirred and mixed while vacuum degassing for 20 minutes using a vacuum planetary mixer for rotation and revolution laboratory to obtain a liquid resin composition. Here, the molar ratio of epoxy group to dicyandiamide was 1:0.5, and 140 g of a polyurethane-modified bisphenol F type epoxy resin composition was prepared with a polyurethane concentration of 11.1 wt% in the cured product. Next, this liquid resin composition was poured into a mold having a groove shape of the dimensions of the test piece for the Izod impact test of JISK7110. The dimensions of the test piece for the bending test and the fracture toughness test piece were 100mmL×10mmW×4mmt, and the dimensions of the test piece for the DMA test were 100mmL×10mmW×1mmt. The liquid resin composition was poured into a mold or a silicon frame, and cut to a size suitable for the measurement. The pourability at this time was at a level that allowed for sufficient pouring with a margin. Next, the mold in which the resin was poured was placed in a hot air oven, and heat cured at 130°C for 50 minutes and then at 150°C for 50 minutes to prepare a test piece of the epoxy resin cured product. The test results using this test piece are shown in Table 3.

[0081] Examples 2 to 7, Comparative Examples 1 to 5 Polyurethane-modified bisphenol F-type epoxy resin compositions with different polyurethane concentrations in the cured products were prepared in the same manner as in Example 1, except that the polyurethane-modified epoxy resin (A), unmodified liquid epoxy resin (B), unmodified solid epoxy resin (C-1) and (C-2), other epoxy resins (E), curing agent (D) and curing accelerator (F) were mixed in the compositions shown in Tables 3 and 4. Next, the liquid resin composition was poured into a mold and thermally cured to prepare a test piece for evaluating characteristics, in the same manner as in Example 1. The physical properties and test results of the obtained composition are shown in Tables 3 and 4.

[0082] In Tables 3 and 4, the blending amount is in grams. In the overall evaluation, ◯ indicates good, and × indicates poor.

[0083] [Table 3]

[0084] [Table 4]

[0085] The compositions containing the urethane-modified epoxy resin of Examples 1 to 7, compared with Comparative Examples 1 to 5, exhibited high heat resistance, high elasticity, high fracture toughness, and high impact strength all at the same time.

Claims

1. The following components (A) to (D): (A) a polyurethane-modified epoxy resin having a polycarbonate structure in its molecule and a urethane modification rate of 20 to 60% by weight; (B) a polyurethane-unmodified epoxy resin that is liquid at 30°C; (C) a bisphenol-type solid epoxy resin having a glass transition temperature or melting point of 50° C. or higher, and (D) an amine-based curing agent which is dicyandiamide; An epoxy resin composition comprising, as an essential component, An epoxy resin composition comprising 20.0 to 50.0% by weight of component (A), 0.1 to 50.0% by weight of component (B), and 0.1 to 50.0% by weight of component (C) relative to the total of components (A) to (D).

2. 2. The epoxy resin composition according to claim 1, wherein the polycarbonate structure of the component (A) contains a structural unit represented by general formula (1). 【Chemistry 1】 Here, each R is independently an alkylene group having 1 to 20 carbon atoms, and n is a number from 1 to 50.

3. 3. The epoxy resin composition according to claim 1, wherein the component (A) is a polyurethane-modified epoxy resin having a weight average molecular weight (Mw) of 10,000 or more and 50,000 or less.

4. Component (A) is represented by the following formula (2), and is obtained by modifying a bisphenol-based epoxy resin (a) having an epoxy equivalent of 150 to 200 g / eq and a hydroxyl group equivalent of 2000 to 3000 g / eq with a medium- to high-molecular-weight polyol compound (b) having a number average molecular weight of 200 or more, a polycarbonate diol compound (b-2), a polyisocyanate compound (c), and a low-molecular-weight polyol compound (d) having a number average molecular weight of less than 200 as a chain extender: The epoxy resin composition according to any one of claims 1 to 3, which is a polyurethane-modified epoxy resin to which the epoxy resin (a) is added, is obtained by reacting the epoxy resin (a) with the components (b), (b-2), and (c) to produce a urethane prepolymer (P), using 50 to 80% by weight of the epoxy resin (a) based on the total amount of the components (a), (b), (b-2), (c), and (d), and using 20 to 55% by weight of the polycarbonate diol (b-2) based on the total amount of the components (b) and (b-2), and then adding a low-molecular-weight polyol compound (d) so that the molar ratio of the NCO group of the urethane prepolymer (P) to the OH group of the low-molecular-weight polyol compound (d) is in the range of 0.9:1 to 1:0.9, to carry out a polyurethane reaction. 【Chemistry 2】 Here, R １ are each independently H or an alkyl group, and a is a number from 0 to 10.

5. A bisphenol-based epoxy resin (a) represented by the following formula (2) and having an epoxy equivalent of 150 to 200 g / eq and a hydroxyl group equivalent of 2000 to 3000 g / eq, In preparing a polyurethane-modified epoxy resin by modifying the epoxy resin with a medium- to high-molecular-weight polyol compound (b) having a number average molecular weight of 200 or more, a polycarbonate diol compound (b-2), a polyisocyanate compound (c), and a low-molecular-weight polyol compound (d) having a number average molecular weight of less than 200 as a chain extender, 5. A method for producing an epoxy resin composition according to any one of claims 1 to 4, comprising the steps of: reacting epoxy resin (a) with components (b), (b-2) and (c) in an amount of 50 to 80% by weight of epoxy resin (a) based on the total amount of components (a), (b), (b-2), (c) and (d), and using polycarbonate diol (b-2) in an amount of 20 to 55% by weight based on the total amount of components (b) and (b-2) to produce a urethane prepolymer (P), and then adding low-molecular-weight polyol compound (d) so that the molar ratio of NCO groups of the urethane prepolymer (P) to OH groups of the low-molecular-weight polyol compound (d) is in the range of 0.9:1 to 1:0.9 to carry out a polyurethane reaction, thereby producing a polyurethane-modified epoxy resin having a urethane modification rate of 20 to 60% by weight by addition of epoxy resin (a), and using this polyurethane-modified epoxy resin as component (A). 【Chemistry 3】 Here, R １ are each independently H or an alkyl group, and a is a number from 0 to 10.

6. 5. An epoxy resin cured product obtained by curing the epoxy resin composition according to claim 1.

7. Glass transition temperature is 110°C or higher, and Izod impact strength value (without notch) according to JIS K7110 is 30 kJ / m ２ or more, elastic modulus 2.5 GPa or more, fracture toughness 2.0 MPa m ０．５ The epoxy resin cured product according to claim 6.

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