Liquid epoxy resin mixture, one-pack curable epoxy adhesive and cured object, method for producing liquid epoxy resin mixture, bonding method, and method for producing cured object

Abstract

A liquid epoxy resin mixture which comprises an epoxy main component and an aromatic diamine, wherein the epoxy main component includes one or more triepoxy main components selected from the group consisting of the triglycidyloxybenzene represented by formula 135TGB, the triglycidyloxybenzene represented by formula 124TGB, and the triglycidyloxybenzene represented by formula 123TGB, the triepoxy main components having an epoxy equivalent of 98-100 g / eq.

Description

Liquid epoxy resin mixture, one-component curable epoxy adhesive and cured product, as well as a method for producing a liquid epoxy resin mixture, an adhesive method, and a method for producing a cured product.

[0001] The present invention relates to a liquid epoxy resin mixture, a one-component curable epoxy adhesive and a cured product, as well as a method for producing a liquid epoxy resin mixture, a bonding method, and a method for producing a cured product. This application claims priority based on Japanese Patent Application No. 2024-181786, filed in Japan on October 17, 2024, the contents of which are incorporated herein by reference.

[0002] High-temperature resistant epoxy resins possess the property of withstanding high temperatures, and this characteristic makes them suitable for applications requiring heat resistance in the electronics, aerospace, automotive, and energy industries. For example, in the manufacture of electronic equipment, they are used to protect and seal substrates and chips. This protects electronic components from high temperatures, humidity, and vibration, improving reliability. Aircraft and space equipment require high temperatures and extreme environmental conditions, so lightweight high-temperature resistant epoxy resins with high mechanical strength properties are used. In automobiles, high heat resistance is required in various parts and components such as engines, brake systems, and electronic control units, and these parts are used in the manufacture of these components. High-temperature resistant epoxy resins are used as insulating materials and sealing materials in the manufacture of electronic equipment such as electronic components, motors, transformers, and coils. Power plants and power transmission facilities require equipment and electronic devices that operate at high temperatures, and high-temperature resistant epoxy resins are used. In addition, they may be used for bonding with metals and ceramics, and in chemical reactions at high temperatures.

[0003] Patent Document 1 discloses that an epoxy resin composition containing 1,2,4-triglycidyloxybenzene and diaminodiphenylsulfone exhibits excellent storage stability and yields a cured product with high heat resistance. Here, the epoxy equivalent of 1,2,4-triglycidyloxybenzene is described as 125 g / equivalent, and the product is described as a brown liquid. Non-Patent Document 1 discloses that triglycidyloxybenzene can be obtained by the reaction of trihydroxybenzene and glycidyl chloride, and that a completely bio-based flame-retardant thermosetting resin can be obtained from a bio-based phosphorus-containing epoxy monomer. Patent Document 2 discloses an epoxy adhesive, as well as automotive components and methods for producing the same. Here, it is described that an epoxy adhesive containing a trifunctional or more liquid epoxy can be made low viscosity, and the cured product obtained by thermosetting the epoxy adhesive has a high Tg and can be used for automotive components with excellent heat resistance and peel resistance. Patent Document 3 discloses an epoxy resin, an epoxy resin composition containing the same, and a cured product using the epoxy resin composition. Here, it is stated that the triglycidyl form of 1,2,4-triglycidyloxybenzene is a crystalline compound and has poor handling properties. It is stated that by including a cyclic compound having a cyclic structure in which oxygen atoms at positions 1 and 2 derived from 1,2,4-trihydroxybenzene are included as constituent atoms, an epoxy resin is provided that is liquid and whose cured product has excellent thermal decomposition resistance. It is also explained that the epoxy equivalent of the epoxy resin is preferably 105 g / equivalent or more. Patent Document 4 discloses an epoxy resin, an epoxy resin composition, and a cured product. Here, it is stated that 1,2,3-triglycidyloxybenzene gives an epoxy resin cured product. It is stated that by including a cyclic compound as a side reaction during epoxy resin synthesis, the epoxy resin becomes liquid at room temperature (25°C) and has excellent workability. It is also stated that if the cyclic compound is not included, the epoxy resin is prone to crystallization, which is undesirable in terms of storage stability and handling properties.

[0004] Japanese Patent Publication No. 61-186377, Japanese Patent No. 6612498, International Publication No. 2019 / 013081, Japanese Patent Publication No. 2023-100439

[0005] RSC Advances, 2015, vol. 5, 87, p70856 - 70867

[0006] Many cured epoxy resins, consisting of an epoxy main component having an aromatic skeleton and a curing agent having an aromatic skeleton, exhibit high heat resistance. This is thought to be due to the effect of high crosslinking density and rigid aromatic rings. To increase crosslinking density, it is useful to introduce many reactive functional groups into smaller molecules, thereby polyfunctionalizing them. Patent documents 1 to 4 and Non-Patent Document 1 also report the use of epoxy compounds with three or more functions.

[0007] When using adhesives, it is common practice to apply them in liquid form and then cure them by heating or other means. Therefore, conventional methods have proposed using liquid polyfunctional epoxy or a mixture with a separate liquid epoxy compound. In liquid polyfunctional epoxy, liquefaction is often achieved by a low molecular weight polymer structure with a molecular weight distribution. Triglycidyloxybenzene, a trifunctional epoxy compound, is one of the aromatic compounds with a very small molecular weight and can provide a high crosslinking density. The glycidyloxy group can be substituted at positions 1,2,3-, 1,2,4-, and 1,3,5- as isomers. All are single compounds without a molecular weight distribution, and the pure substance is a powder at room temperature. The theoretical epoxy equivalent of these compounds is 98 g / equivalent. Higher purity allows for higher crosslinking density, but higher purity also makes them more prone to crystallization. These epoxy main compounds have been criticized for their tendency to crystallize and become powdery. On the other hand, diamine compounds are known as curing agents for epoxy resins. Among these, aromatic diamines, which are aromatic compounds, are relatively low molecular weight polyfunctional compounds. In fact, they are known to yield highly heat-resistant cured products when combined with epoxy resins.

[0008] In combinations of epoxy base and curing agent that are expected to produce cured products with such high crosslinking density and high glass transition temperatures, both agents are solid at room temperature, making them unsuitable for applications that require coating or molding at room temperature. Therefore, epoxy resins that are viscous fluids in which a liquid epoxy base is mixed with a liquid or powdered curing agent have been dispersed have been used exclusively.

[0009] In view of these circumstances, the present invention provides a liquid epoxy resin mixture that is liquid at room temperature and whose cured product has excellent heat resistance, a cured product obtained by heating and curing the liquid epoxy resin mixture, a one-component curable epoxy adhesive consisting of the liquid epoxy resin mixture, a method for producing the liquid epoxy resin mixture, a bonding method, and a method for producing the cured product.

[0010] The inventors have discovered that when triglycidyloxybenzene is used as the main component and aromatic diamines such as 4,4'-methylenedianiline (hereinafter sometimes referred to as "MDA") and bis(4-aminophenyl)sulfone (hereinafter sometimes referred to as "BAS") are used as curing agents to obtain a highly heat-resistant cured product, both the epoxy main component and the curing agent are solid at room temperature, but can be thermally melted and mixed as a molten liquid. Once mixed, the mixture remains a viscous liquid even when cooled to room temperature. Therefore, it can be applied as a liquid and then heated and cured in a mold. Furthermore, when used as a one-component curable epoxy adhesive, it can be placed between the adherends and bonded by heat curing. The cured product obtained by heating is a highly heat-resistant epoxyamine cured resin that does not exhibit a glass transition temperature up to 240°C.

[0011] The present invention has been completed based on these findings and includes the following embodiments: [1] A liquid epoxy resin mixture containing an epoxy main component and an aromatic diamine, wherein the epoxy main component comprises one or more triepoxy main components selected from the group consisting of triglycidyloxybenzene represented by the following formula 135TGB, triglycidyloxybenzene represented by the following formula 124TGB, and triglycidyloxybenzene represented by the following formula 123TGB, and the epoxy equivalent of the triepoxy main component is 98 to 100 g / equivalent.

[0012]

[0013] [2] The liquid epoxy resin mixture according to [1], wherein the cured product obtained by heat curing the liquid epoxy resin mixture does not have a glass transition temperature of 240°C or lower. [3] The liquid epoxy resin mixture according to [1] or [2], wherein the content of the triepoxy main component is 83% by mass or more with respect to 100% by mass of the epoxy main component. [4] The liquid epoxy resin mixture according to any one of [1] to [3], wherein the epoxy main component comprises a bisphenol type compound represented by the following formula EP.

[0014] (In the formula, R is a hydrogen atom or a methyl group, and n is an integer from 0 to 5.) [5] The liquid epoxy resin mixture according to [4], wherein the content of the bisphenol type compound contained in the epoxy main component is 72% by mass or less with respect to 100% by mass of the epoxy main component.

[0015] [6] A cured product obtained by heating and curing a liquid epoxy resin mixture described in any one of items [1] to [5] at a temperature of 150°C or higher.

[0016] [7] A one-component curable epoxy adhesive comprising a liquid epoxy resin mixture as described in any one of items [1] to [5].

[0017] [8] A method for producing a liquid epoxy resin mixture, comprising mixing an epoxy main component with an aromatic diamine, wherein the epoxy main component comprises one or more triepoxy main components selected from the group consisting of triglycidyloxybenzene represented by the following formula 135TGB, triglycidyloxybenzene represented by the following formula 124TGB, and triglycidyloxybenzene represented by the following formula 123TGB, and the epoxy equivalent of the triepoxy main component is 98 to 100 g / equivalent.

[0018]

[0019] [9] A method for producing a liquid epoxy resin mixture according to [8], further comprising mixing the epoxy main agent and the aromatic diamine, heating the mixture to a temperature at which the epoxy main agent and the aromatic diamine do not undergo a curing reaction, and then cooling it to room temperature.

[10] A bonding method comprising applying a liquid epoxy resin mixture obtained by the manufacturing method according to [8] or [9] to the bonding surfaces of one or both of a pair of members to be bonded, overlapping the bonding surfaces of both members, and then heating and curing the liquid epoxy resin mixture at a temperature of 150°C or higher.

[0020] A method for producing a cured product, comprising the step of heating and curing a liquid epoxy resin mixture obtained by the manufacturing method described in

[11] [8] or [9] at a temperature of 150°C or higher.

[0021] The present invention provides a liquid epoxy resin mixture that is liquid at room temperature and whose cured product has excellent heat resistance, a cured product obtained by heating and curing the liquid epoxy resin mixture, a one-component curable epoxy adhesive consisting of the liquid epoxy resin mixture, a method for producing the liquid epoxy resin mixture, a bonding method, and a method for producing the cured product.

[0022] The liquid epoxy resin mixture of Example 1 １These are the H-NMR measurement results. These are the DSC measurement results of the cured product obtained by heat curing the liquid epoxy resin mixture of Example 1. This is a schematic diagram showing the adhesive test piece used for shear bond strength measurement. These are the DSC measurement results of the cured product obtained by heat curing the liquid epoxy resin mixture of Example 2. These are the DSC measurement results of the cured product obtained by heat curing the liquid epoxy resin mixture of Example 3. These are the DSC measurement results of the cured product obtained by heat curing the liquid epoxy resin mixture of Comparative Example 1. These are the DSC measurement results of the cured product obtained by heat curing the liquid epoxy resin mixture of Example 4. These are the DSC measurement results of the cured product obtained by heat curing the liquid epoxy resin mixture of Example 5.

[0023] [Liquid epoxy resin mixture] The liquid epoxy resin mixture according to this embodiment contains an epoxy main component and an aromatic diamine, wherein the epoxy main component includes one or more triepoxy main components selected from the group consisting of triglycidyloxybenzene represented by the following formula 135TGB, triglycidyloxybenzene represented by the following formula 124TGB, and triglycidyloxybenzene represented by the following formula 123TGB, and the epoxy equivalent of the triepoxy main component is 98 to 100 g / equivalent.

[0024]

[0025] The epoxy main component comprises one or more triepoxy main components selected from the group consisting of compounds in which glycidyloxy groups are bonded to the 1,3,5-positions of a benzene ring (1,3,5-triglycidyloxybenzene, sometimes referred to as "135TGB"), compounds in which glycidyloxy groups are bonded to the 1,2,4-positions of a benzene ring (1,2,4-triglycidyloxybenzene, sometimes referred to as "124TGB"), and compounds in which glycidyloxy groups are bonded to the 1,2,3-positions of a benzene ring (1,2,3-triglycidyloxybenzene, sometimes referred to as "123TGB"), wherein the epoxy equivalent weight of the triepoxy main component is 98 to 100 g / equivalent. Since these triglycidyloxybenzenes have three glycidyloxy groups bonded to a relatively small aromatic ring, it is expected that a highly heat-resistant cured product can be obtained.

[0026] The epoxy equivalent of the triepoxy main component is 98 to 100 g / equivalent, and by using high-purity triglycidyloxybenzene, the cured product obtained by heat-curing the liquid epoxy resin mixture has improved crosslinking density, resulting in a higher glass transition temperature and thus achieving even higher heat resistance. It is preferable that the cured product obtained by heat-curing the liquid epoxy resin mixture does not have a glass transition temperature below 240°C.

[0027] The aforementioned triglycidyloxybenzene can be synthesized by the methods disclosed in Patent Documents 1, 3 to 4 and Non-Patent Document 1, and it is particularly preferable to synthesize it by the method disclosed in Non-Patent Document 1, which involves the reaction of trihydroxybenzene with glycidyl chloride. Triglycidyloxybenzene with an epoxy equivalent of more than 100 g / equivalent loses its crystallinity and is liquid at room temperature, while triglycidyloxybenzene with an epoxy equivalent of 98 to 100 g / equivalent retains its crystallinity and is in powder form. The epoxy equivalent of the triepoxy main component can be measured by the potentiometric titration method described in JIS K 7236.

[0028] The content of the triepoxy main component is preferably 83% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on 100% by mass of the epoxy main component. When triglycidyloxybenzene is synthesized from trihydroxybenzene, the compound expected as a by-product is diglycidyloxyphenol (molecular weight 238.24). In order to make the epoxy equivalent amount of the mixture with triglycidyloxybenzene (molecular weight 294.30) 100 g / equivalent or less, 82.72% or more of triglycidyloxybenzene is required.

[0029] The aromatic diamine has two amino groups directly bonded to the aromatic ring. Examples of the aromatic diamine include, but are not limited to, 4,4'-methylenedianiline (MDA), bis(4-aminophenyl)sulfone (BAS), bis(3-aminophenyl)sulfone, bis(4-aminophenyl) ether, bis(3-aminophenyl) ether, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 1,4-bis(3-aminophenyl)benzene, 1,3-bis(3-aminophenyl)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, and 1,3-bis(3-aminophenoxy)benzene. As the aromatic diamine, 4,4'-methylenedianiline (MDA) or bis(4-aminophenyl)sulfone (BAS) are preferred because they are inexpensive and readily available. 4,4'-methylenedianiline (MDA) and bis(4-aminophenyl)sulfone (BAS) are known as curing agents for epoxy resins and are available as reagents. These aromatic diamines are in powder form at room temperature.

[0030] These powder compounds are mixed, typically such that the equivalent weight of the epoxy group of triglycidyloxybenzene is equal to the equivalent weight of the hydrogen atoms on the amino group of the aromatic diamine. When this mixture is heated to 80°C, it melts into a homogeneous liquid. After thorough stirring, it is cooled to room temperature to obtain a viscous liquid epoxy resin mixture. At this point, there is no change in the peaks originating from the epoxy ring and the amine protons, indicating that the reaction is not progressing. It is thought that the crystallinity is lost through mixing. The liquid epoxy resin mixture according to this embodiment is liquid at room temperature. In this specification, "liquid" means having fluidity at room temperature (20-22°C), and includes being clay-like.

[0031] In the liquid epoxy resin mixture according to this embodiment, the epoxy main component may contain a bisphenol-type compound represented by the following formula EP.

[0032] (In the formula, R is a hydrogen atom or a methyl group, and n is an integer from 0 to 5.)

[0033] When R is a methyl group, the bisphenol-type compound represented by formula EP is known as a bisphenol A type epoxy resin, and when R is a hydrogen atom, the bisphenol-type compound represented by formula EP is known as a bisphenol F type epoxy resin.

[0034] In the liquid epoxy resin mixture according to this embodiment, the content of the bisphenol-type compound contained in the epoxy main component is preferably 72% by mass or less, more preferably 50% by mass or less, even more preferably 30% by mass or less, and may be 17% by mass or less, 15% by mass or less, 10% by mass or less, or 5% by mass or less, based on 100% by mass of the epoxy main component.

[0035] In the liquid epoxy resin mixture according to this embodiment, the content of triglycidyloxybenzene is preferably 1.6 to 2.4 moles, more preferably 1.8 to 2.2 moles, even more preferably 1.9 to 2.1 moles, and may be 2 moles, per 3 moles of the aromatic diamine.

[0036] In the liquid epoxy resin mixture according to this embodiment, the content of triglycidyloxybenzene is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and particularly preferably 40% by mass or more, based on 100% by mass of the liquid epoxy resin mixture. In the liquid epoxy resin mixture according to this embodiment, the content of aromatic diamine is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and particularly preferably 40% by mass or more, based on 100% by mass of the liquid epoxy resin mixture. The liquid epoxy resin mixture according to this embodiment may also contain fillers, rubber components, and activators that impart adhesiveness.

[0037] [Method for Producing Liquid Epoxy Resin Mixture] The method for producing a liquid epoxy resin mixture according to this embodiment includes mixing an epoxy main agent and an aromatic diamine, wherein the epoxy main agent includes one or more triepoxy main agents selected from the group consisting of triglycidyl oxybenzene represented by the above formula 135TGB, triglycidyl oxybenzene represented by the above formula 124TGB, and triglycidyl oxybenzene represented by the above formula 123TGB, and the epoxy equivalent of the triepoxy main agent is 98 to 100 g / equivalent.

[0038] The method for producing a liquid epoxy resin mixture according to this embodiment may further heat the mixture of the epoxy main agent and the aromatic diamine to a temperature at which the epoxy main agent and the aromatic diamine do not undergo a curing reaction after mixing, and if necessary, heat and mix the mixture at a temperature at which the curing reaction does not occur. The temperature at which the curing reaction does not occur is preferably 60 to 90 °C, more preferably 70 to 80 °C. After heating to the temperature at which the curing reaction does not occur, it may be cooled to room temperature.

[0039] [Cured Product] The cured product according to this embodiment is obtained by heat-curing the liquid epoxy resin mixture according to the above-described embodiment under temperature conditions of 150 °C or higher. By heating the liquid epoxy resin mixture according to the above-described embodiment under temperature conditions of 150 °C or higher, the epoxy group of triglycidyl oxybenzene reacts with the amino group of the aromatic diamine to cure.

[0040] [Method for Producing Cured Product] The method for producing a cured product according to this embodiment includes a step of heat-curing the liquid epoxy resin mixture obtained by the production method described in the above-described embodiment under temperature conditions of 150 °C or higher.

[0041] [One-Part Curing Epoxy Adhesive] The one-part curing epoxy adhesive according to this embodiment is composed of the liquid epoxy resin mixture according to the above-described embodiment. By sandwiching the liquid epoxy resin mixture according to the above-described embodiment between substrates as adherends and then heat-curing under temperature conditions of 150 °C or higher, the plates can be adhered to each other.

[0042] [Bonding Method] In the bonding method according to this embodiment, the liquid epoxy resin mixture obtained by the manufacturing method according to the above embodiment is applied to the bonding surfaces of one or both of the pair of members to be bonded, the bonding surfaces of both members are placed together, and then the liquid epoxy resin mixture is heated and cured at a temperature of 150°C or higher.

[0043] The present invention will be described in more detail below with reference to specific examples. However, the present invention is not limited in any way to the examples shown below.

[0044] 1,3-Diglycidyloxybenzene (13DGB), 1,3,5-Triglycidyloxybenzene (135TGB), and 1,2,4-Triglycidyloxybenzene (124TGB) were synthesized with reference to Non-Patent Literature 1 (RSC Advances, 2015, vol. 5, 87, pp. 70856-70867).

[0045] Specifically, under an argon atmosphere, 1,3,5-phloroglucinol dihydrate (13 g, phloroglucinol portion 0.08 mol, manufactured by Tokyo Chemical Industry Co., Ltd.), epichlorohydrin (146.7 g, 1.6 mmol, 20 equivalents relative to the starting material), and benzyltriethylammonium chloride (2.7 g, 0.01 mol, 15 mol% relative to the starting material) were added to a 1 L round-bottom flask and heated and stirred at 80°C for 5 hours. After the reaction, the mixture was allowed to cool to room temperature and then concentrated under reduced pressure. 50 mL of ethyl acetate was added to the resulting yellow oily compound, and 50 mL of 20% by mass NaOH aqueous solution was added at 0°C. After further reaction at room temperature for 1.5 hours, 20 mL of ethyl acetate and 20 mL of 20% by mass NaOH aqueous solution were added. The reaction was then completed by stirring at 40°C for 0.5 hours. After washing with saturated brine, the organic layer was separated and concentrated to obtain the yellow oily compound.

[0046] The sample was purified by column chromatography using a column packed with 100 g of silica gel and a toluene:ethyl acetate solution in a 2:1 (volume ratio) ratio as the developing solvent, yielding 16.3 g of white solid 135TGB (70% yield). The water content of the 135TGB was 0.3% by mass.

[0047] 124TGB was synthesized from 1,2,4-phloroglucinol dihydrate (manufactured by Tokyo Chemical Industry Co., Ltd.) using the same method as for 135TGB, and purified by column chromatography. The water content of 124TGB was 0.3% by mass, which was about the same as that of 135TGB.

[0048] The epoxy equivalents of the synthesized 135 TGB and 124 TGB were measured by potentiometric titration in accordance with JIS K 7236. The specific procedure is as follows: A potentiometric titrator AT-710 (manufactured by Kyoto Electronics Manufacturing Co., Ltd.) was used as the measuring apparatus, a composite glass electrode (manufactured by Kyoto Electronics Manufacturing Co., Ltd.) was used as the electrode, and chloroform (special grade reagent), acetic acid (special grade reagent), tetraethylammonium bromide / acetic acid = 25 g / 100 mL, and 0.1 mol / L chloric acid acetic acid solution were used as the solvents. The sample and 30 mL of chloroform were added to a 100 mL Erlenmeyer flask and stirred at room temperature. After stirring, 20 mL of acetic acid and 10 mL of reaction solution were added. Titration was performed using a potentiometric titrator, and the obtained inflection point was taken as the endpoint. A blank test was also performed in the same manner, and the epoxy equivalent was calculated from the following formula.

[0049] Epoxy equivalent (g / eq) = (1000 × s) / {[V] １ -V ０ ] × N × f × t ０} t ０ =1-(t-ts) / 1000

[0050] s; Mass of the sample (g) V １ ; Volume of titrant (mL) in this test V ０ ; Volume of titrant in blank test (mL) N; Concentration of titrant (mol / L) f; Factor of titrant [1.003] t; Temperature of titrant during test and blank test [21.2°C] ts; Temperature of titrant at standardization [20.8°C]

[0051] As a result, the epoxy equivalent of 135 TGB was 99 g / equivalent. The epoxy equivalent of 124 TGB was also 99 g / equivalent. Since the calculated molecular weight is 294, the theoretical epoxy equivalent is 98 g / equivalent, indicating high purity. This is thought to be due to the fact that, unlike Non-Patent Document 1, the purity was increased by purification using column chromatography in the final step. Bis(4-aminophenyl) sulfone (BAS) and 4,4'-methylenedianiline (MDA) were purchased from Fujifilm Wako Pure Chemical Industries, Ltd., and their purity was 98% or higher.

[0052] [Example 1] 0.5 g of 1,3,5-triglycidyloxybenzene (135TGB) powder and 0.25 g of 4,4'-methylenedianiline (MDA) powder were placed in a glass petri dish and melted on an 80°C hot plate. The mixture was stirred with a spatula for 1 minute to obtain a homogeneous liquid. Degassing was performed using a centrifuge. The mixture did not solidify even when returned to room temperature, and a colorless, transparent liquid epoxy resin mixture (Example 1) was obtained. Here, it is possible that the epoxy group of 1,3,5-triglycidyloxybenzene and the amine of 4,4'-methylenedianiline (MDA) partially reacted to form a different compound, resulting in a loss of crystallinity. １ Upon examining the 1H-NMR spectrum, as shown in Figure 1, there was no change in the peaks originating from the epoxy ring and amine protons, and no reaction progress was observed even after heating up to 80°C. This suggests that the crystallinity was lost due to the mixing of 135TGB and MDA.

[0053]

[0054] The mixed liquid of 135TGB and MDA (the liquid epoxy resin mixture of Example 1) was heated and cured in a 180°C oven for 30 minutes to obtain the cured product of Example 1. Using a differential scanning calorimeter (DSC) "DSC6200" from Seiko Instruments Inc., the curing process was performed twice, with heating and cooling at a rate of 10°C / min in the range of 40 to 280°C, to investigate the thermal transition of the cured product of Example 1. Figure 2 shows the DSC measurement results for the cured product of Example 1 during the second thermal cycle. No thermal transition was observed during either heating or cooling within this measurement temperature range.

[0055] (Dynamic Viscoelasticity Measurement) Furthermore, when the dynamic viscoelasticity of the cured product of Example 1 was measured under the following conditions using a rheometer MCR302 of Anton Paar Japan Co., Ltd., the storage elastic modulus (G') was 270 MPa at 180°C and the tangent of the sine (tanδ) was 0.1. From these values, it can be seen that the cured product of Example 1 has not softened and is in a solid state. Thereafter, since no transition is observed up to at least 280°C, which is the observation range, it can be said that the cured product of Example 1 is a material that does not soften up to at least 280°C. Sample shape: Thickness 1 mm, diameter 8 mm Temperature range: 25 to 180°C Temperature increase rate: 8°C / min, held at 180°C for 40 minutes Frequency: 1 s －１ Strain: 1%

[0056] (Thermomechanical Measurement) For the cured product of Example 1, thermomechanical measurement was carried out using "TMA-60" manufactured by Shimadzu Corporation under the following conditions in the atmosphere. No softening point or glass transition point was observed in the temperature range from over 300°C to 320°C. Sample shape: Height 12 mm, width 4.0 mm, depth 3.4 mm Temperature range: 25 to 320°C Temperature increase rate: 2°C / min Constant load mode: Compression 1 g

[0057] (Thermogravimetric Analysis Test) For the cured product of Example 1, thermogravimetric analysis was carried out using "DTG60" manufactured by Shimadzu Corporation in the atmospheric atmosphere at a temperature increase rate of 10°C / min in the range from 25°C to 400°C. The weight loss rate at 320°C was 3.4%.

[0058] (Shear bond strength measurement) The leading edge of two aluminum alloy plates (A6061-T6, 70 mm x 15 mm x 1.5 mm) was blast-treated at 15 mm x 15 mm. Teflon® tape was applied to 5 mm x 15 mm on each side of the blasted area of ​​one of the blast-treated aluminum alloy plates to form a 5 mm wide x 15 mm groove in the center. A mixed liquid of 135 TGB and MDA (liquid epoxy resin mixture of Example 1) was applied to the surface of the 5 mm wide x 15 mm long portion at the tip of the groove. The two aluminum alloy plates were then bonded together and fixed, and heated and cured at 180°C for 30 minutes to bond them, creating an adhesive test specimen (Figure 3). The thickness of the adhesive layer was adjusted to 0.3 mm. The sample was mounted on a tensile testing machine (RTF1350, load cell 50kN) manufactured by A&D Co., Ltd., equipped with a constant temperature chamber. Tensile tests were performed at a speed of 1 mm / min at room temperature of 20-22°C, and the maximum shear stress until fracture was defined as the shear bond strength. As a result, the shear bond strength was 17 MPa.

[0059] (Measurement of shear bond strength after heating at 120°C for 72 hours) Bonded test specimens prepared in the same manner as in the previous example were heated at 120°C for 3 days (72 hours), and then subjected to a tensile test under the same conditions. The shear bond strength was 16 MPa, indicating that the bond strength was maintained.

[0060] (Measurement of shear bond strength after heating at 200°C for 24 hours) When bond test specimens prepared in the same manner as in the previous example were heated at 200°C for one day (24 hours) and then subjected to a tensile test under the same conditions, the shear bond strength was 19 MPa, indicating that high shear bond strength was still maintained. This increase in shear bond strength is thought to be due to post-curing being advanced by heating to a temperature higher than the curing temperature.

[0061] (Measurement of shear bond strength after heating at 200°C for 72 hours) When bond test specimens prepared in the same manner as in the previous example were heated at 200°C for 3 days (72 hours) and then subjected to a tensile test under the same conditions, the shear bond strength was 15 MPa. Although the value had decreased slightly, it still maintained a high shear strength.

[0062] [Example 2] Powder of 135 TGB and powder of bis(4-aminophenyl) sulfone (BAS) were measured out in a mass ratio of 1.6:1 and heated and mixed on an 80°C hot plate, resulting in a creamy paste. After cooling to room temperature, a clay-like liquid epoxy resin mixture (Example 2) was obtained. １ ¹H-NMR measurements showed that no reaction progressed when heated up to 80°C.

[0063]

[0064] A clay-like liquid epoxy resin mixture (liquid epoxy resin mixture of Example 2) was degassed using a small benchtop centrifuge (10,000 rpm, 2 min), and then heated and cured in a 180°C oven for 30 minutes to obtain the cured product of Example 2. Using a differential scanning calorimeter (DSC), the curing process was performed twice, with heating and cooling in the range of 40 to 280°C at a rate of 10°C / min, to investigate the thermal transition of the cured product. Figure 4 shows the DSC measurement results for the cured product of Example 2 during the second thermal cycle. No thermal transition was observed during either heating or cooling within this measurement temperature range.

[0065] (Dynamic Viscoelasticity Measurement) Furthermore, using the MCR302 rheometer from Anton Paar Japan Co., Ltd., the dynamic viscoelasticity of the cured product of Example 2 was measured under the same conditions as in Example 1, in a temperature range of 25 to 180°C. The storage modulus (G') was 300 MPa at 180°C, and the sinusoidal tangent (tanδ) was 0.1. From these values, it became clear that the cured product of Example 2 did not soften in the temperature range up to 180°C and remained in a solid state. Subsequently, no transition was observed up to at least 280°C, which is within the observation range. Therefore, it can be said that the cured product of Example 2 is a material that does not soften up to at least 280°C.

[0066] (Shear bond strength measurement) For the clay-like mixture of 135TGB and BAS, bond test specimens were prepared in the same manner as in Example 1, and the shear bond strength was measured at a speed of 1 mm / min at room temperature of 20-22°C. The shear bond strength was 18 MPa.

[0067] (Measurement of shear bond strength after heating at 200°C for 24 hours) When bond test specimens prepared in the same manner as above were heated at 200°C for one day (24 hours) and then subjected to a tensile test under the same conditions, the shear bond strength was 16 MPa, indicating that it still maintained high shear strength.

[0068] (Measurement of shear bond strength after heating at 200°C for 72 hours) When bond test specimens prepared in the same manner as above were heated at 200°C for 3 days (72 hours) and then subjected to a tensile test under the same conditions, the shear bond strength was 14 MPa, indicating that it still maintained high shear strength.

[0069] (Measurement of shear bond strength after heating at 200°C for 168 hours) When bond test specimens prepared in the same manner as above were heated at 200°C for 7 days (168 hours) and then subjected to a tensile test under the same conditions, the shear bond strength was 13 MPa, indicating that it still maintained high shear strength.

[0070] [Example 3] 0.1 g of 1,2,4-triglycidyloxybenzene (124TGB) powder and 0.05 g of 4,4'-methylenedianiline (MDA) powder were placed in a glass petri dish and melted on a hot plate at 80°C. The mixture was stirred with a spatula for 1 minute to obtain a homogeneous liquid. Degassing was performed using a centrifuge. The mixture did not solidify even when returned to room temperature, and a colorless, transparent liquid epoxy resin mixture (Example 3) was obtained.

[0071]

[0072] The mixed liquid of 124TGB and MDA (the liquid epoxy resin mixture of Example 3) was heated and cured in a 180°C oven for 30 minutes to obtain the cured product of Example 3. Using a differential scanning calorimeter (DSC), the thermal transition of the cured product was investigated by performing two heating and cooling cycles in the range of 100 to 240°C at a rate of 10°C / min. Figure 5 shows the DSC measurement results for the cured product of Example 3 during the second thermal cycle. No thermal transition was observed during either heating or cooling within this measurement temperature range. Therefore, it can be said that the cured product of Example 3 is a material that does not soften up to at least 240°C.

[0073] (Shear bond strength measurement) For the mixed liquid of 124TGB and MDA (liquid epoxy resin mixture of Example 3), adhesive test pieces were prepared in the same manner as in Example 1, and a tensile test was performed under the same conditions as in Example 1. The shear bond strength was 18 MPa.

[0074] [Comparative Example 1] 0.33 g of liquid 1,3-diglycidyloxybenzene (13DGB) and 0.15 g of powder 4,4'-methylenedianiline (MDA) were placed in a glass petri dish and melted on an 80°C hot plate. The mixture was stirred with a spatula for 1 minute to obtain a homogeneous mixed liquid (liquid epoxy resin mixture of Comparative Example 1). Degassing was performed using a centrifuge. The mixture did not solidify even when returned to room temperature, and a colorless, transparent liquid was obtained.

[0075]

[0076] The mixed liquid of 13DGB and MDA (the liquid epoxy resin mixture of Comparative Example 1) was heated and cured in a 180°C oven for 30 minutes to obtain the cured product of Comparative Example 1. Using a differential scanning calorimeter (DSC), the thermal transition of the cured product was investigated by heating and cooling twice in the range of 100 to 240°C at a rate of 10°C / min. Figure 6 shows the DSC measurement results for the cured product of Comparative Example 1 during the second thermal cycle. Glass transition was observed at around 150°C during heating and at 140°C during cooling. It is thought that the cured product of Comparative Example 1, by using a bifunctional epoxy compound instead of a trifunctional epoxy compound, had a lower crosslinking density, resulting in a lower glass transition temperature (Tg) than the cured products of Examples 1 to 3.

[0077] [Example 4] 0.33 g of 1,3,5-triglycidyloxybenzene (135TGB) powder, 0.63 g of liquid bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, "JER828"), and 0.33 g of 4,4'-methylenedianiline (MDA) powder were placed in a glass petri dish and melted on an 80°C hot plate. The mixture was stirred with a spatula for 1 minute to obtain a homogeneous liquid. Degassing was performed using a centrifuge. The mixture did not solidify even when returned to room temperature, and a colorless, transparent liquid epoxy resin mixture (Example 4) was obtained. The molar ratio of 135TGB, JER828, and MDA was 2:3:3, and the ratio of the number of epoxy moles of 135TGB, the number of epoxy moles of JER828, and the number of active amine hydrogen moles of MDA was 1:1:2.

[0078] The liquid epoxy resin mixture of Example 4 was heat-cured at 180°C for 30 minutes to obtain the cured product of Example 4. As with Example 1, DSC measurements were performed in the range of 40 to 280°C to investigate the thermal transition of the cured product. Figure 7 shows the DSC measurement results for the cured product of Example 4 during the second thermal cycle. No thermal transition was observed during either heating or cooling within this measurement temperature range.

[0079] (Dynamic Viscoelasticity Measurement) Furthermore, as with Example 1, the dynamic viscoelasticity of the cured product of Example 4 was measured, and the storage modulus (G') was 370 MPa at 180°C, and the sinusoidal tangent (tanδ) was 0.05. From these values, it became clear that the cured product of Example 4 did not soften in the temperature range up to 180°C and remained in a solid state.

[0080] (Thermomechanical Measurement) Thermomechanical measurements were performed on the cured product of Example 4 under the same conditions as in Example 1. No softening point or glass transition point was observed even in the temperature range from over 300°C to 320°C.

[0081] (Shear bond strength measurement) For the liquid epoxy resin mixture of Example 4, bond test pieces were prepared in the same manner as in Example 1, and the shear bond strength was measured at a rate of 1 mm / min at room temperature of 20-22°C. The shear bond strength was 20 MPa.

[0082] (Measurement of shear bond strength after heating at 200°C for 24 hours) When bond test specimens prepared in the same manner as above were heated at 200°C for one day (24 hours) and then subjected to a tensile test under the same conditions, the shear bond strength was 24 MPa, indicating that it still maintained high shear strength.

[0083] (Measurement of shear bond strength after heating at 200°C for 72 hours) When bond test specimens prepared in the same manner as above were heated at 200°C for 3 days (72 hours) and then subjected to a tensile test under the same conditions, the shear bond strength was 21 MPa, indicating that it still maintained high shear strength.

[0084] (Measurement of shear bond strength after heating at 200°C for 168 hours) When bond test specimens prepared in the same manner as above were heated at 200°C for 7 days (168 hours) and then subjected to a tensile test under the same conditions, the shear bond strength was 19 MPa, indicating that it still maintained high shear strength.

[0085] [Example 5] 0.33 g of 1,3,5-triglycidyloxybenzene (135TGB) powder, 1.26 g of liquid bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, "JER828"), and 0.50 g of 4,4'-methylenedianiline (MDA) powder were placed in a glass petri dish and melted on an 80°C hot plate. The mixture was stirred with a spatula for 1 minute to obtain a homogeneous liquid. Degassing was performed using a centrifuge. The mixture did not solidify even when returned to room temperature, and a colorless, transparent liquid epoxy resin mixture (Example 5) was obtained. The molar ratio of 135TGB, JER828, and MDA was 4:12:9, and the ratio of the number of epoxy moles of 135TGB, the number of epoxy moles of JER828, and the number of active amine hydrogen moles of MDA was 1:2:3. The liquid epoxy resin mixture of Example 5 was heat-cured at 180°C for 30 minutes to obtain the cured product of Example 5. As with Example 1, the temperature was increased and decreased twice in the range of 40 to 280°C at a rate of 10°C / min, and the thermal transition of the cured product of Example 5 was investigated. Figure 8 shows the DSC measurement results for the cured product of Example 5 after the second thermal cycle. Glass transition was observed around 170°C during the heating measurement, and glass transition was observed at 200°C during the cooling measurement.

[0086] The liquid epoxy resin mixture of the present invention consists of a mixture of powdered epoxy compound and powdered aromatic diamine at room temperature, and the mixture is liquid at room temperature. Therefore, it is suitable for applications such as coating and molding at room temperature. The liquid epoxy resin mixture of the present invention can be used as a one-component curable epoxy adhesive. Furthermore, the cured product obtained by heat curing the liquid epoxy resin mixture of the present invention shows no glass transition temperature from at least the low temperature side up to 240°C and has excellent heat resistance, so deformation and softening at high temperatures are suppressed and it is useful in applications where high heat resistance is required.

[0087] 1…Adhesion test piece

Claims

1. A liquid epoxy resin mixture containing an epoxy main component and an aromatic diamine, wherein the epoxy main component comprises one or more triepoxy main components selected from the group consisting of triglycidyloxybenzene represented by the following formula 135TGB, triglycidyloxybenzene represented by the following formula 124TGB, and triglycidyloxybenzene represented by the following formula 123TGB, and the epoxy equivalent of the triepoxy main component is 98 to 100 g / equivalent.

2. The liquid epoxy resin mixture according to claim 1, wherein the cured product obtained by heat curing the liquid epoxy resin mixture does not have a glass transition temperature of 240°C or lower.

3. The liquid epoxy resin mixture according to claim 1, wherein the content of the triepoxy main component is 83% by mass or more based on 100% by mass of the epoxy main component.

4. The liquid epoxy resin mixture according to claim 1, wherein the epoxy main component comprises a bisphenol-type compound represented by the following formula EP. (In the formula, R is a hydrogen atom or a methyl group, and n is an integer from 0 to 5.) 5. The liquid epoxy resin mixture according to claim 4, wherein the content of the bisphenol-type compound contained in the epoxy main component is 72% by mass or less based on 100% by mass of the epoxy main component.

6. A cured product obtained by heating and curing a liquid epoxy resin mixture according to any one of claims 1 to 5 at a temperature of 150°C or higher.

7. A one-component curable epoxy adhesive comprising a liquid epoxy resin mixture according to any one of claims 1 to 5.

8. A method for producing a liquid epoxy resin mixture, comprising mixing an epoxy main component with an aromatic diamine, wherein the epoxy main component comprises one or more triepoxy main components selected from the group consisting of triglycidyloxybenzene represented by the following formula 135TGB, triglycidyloxybenzene represented by the following formula 124TGB, and triglycidyloxybenzene represented by the following formula 123TGB, and the epoxy equivalent of the triepoxy main component is 98 to 100 g / equivalent.

9. A method for producing a liquid epoxy resin mixture according to claim 8, comprising mixing the epoxy main component and the aromatic diamine, then heating the mixture to a temperature at which the epoxy main component and the aromatic diamine do not undergo a curing reaction, and then cooling it to room temperature.

10. A bonding method comprising applying a liquid epoxy resin mixture obtained by the manufacturing method described in claim 8 or 9 to the bonding surfaces of one or both of a pair of members to be bonded, overlapping the bonding surfaces of both members, and then heating and curing the liquid epoxy resin mixture at a temperature of 150°C or higher.

11. A method for producing a cured product, comprising the step of heating and curing a liquid epoxy resin mixture obtained by the manufacturing method described in claim 8 or 9 at a temperature of 150°C or higher.

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