Epoxy resin, method for producing epoxy resin, epoxy resin composition, and epoxy resin cured product

Abstract

To provide an epoxy resin and an epoxy resin composition having good melt kneadability at 100°C or lower, excellent solvent solubility, and heat resistance of 200°C or higher, and which yield a cured product having excellent thermal decomposition stability, thermal conductivity, and tracking resistance.　The epoxy resin is represented by general formula (1) and the epoxy resin composition is characterized by having as essential components the epoxy resin and a curing agent. (In the formula, G represents a glycidyl group, and n and m each independently represent a number of 1-20. )

Description

Epoxy resin, method for producing epoxy resin, epoxy resin composition, and cured epoxy resin

[0001] The present invention relates to epoxy resins, methods for producing epoxy resins, epoxy resin compositions, and epoxy resin cured products. More specifically, it relates to epoxy resins and epoxy resin compositions that are useful as insulating materials for electrical and electronic components such as semiconductor encapsulants, laminates, and heat dissipation substrates, and that exhibit excellent handling properties as a solid at room temperature, low viscosity during molding, and solvent solubility, as well as epoxy resin cured products obtained by curing them, which exhibit excellent heat resistance and thermal conductivity.

[0002] Epoxy resins have been used in a wide range of industrial applications, but the performance requirements for them have become increasingly sophisticated in recent years. In this context, power devices, which have been under development in recent years, require further improvements in power density. As a result, the surface temperature of the chip during operation exceeds 200°C, and therefore, the development of encapsulating materials that can withstand such temperatures is desired.

[0003] Patent Document 1 relates to epoxy resins and epoxy resin compositions useful for sealing electrical and electronic components, circuit board materials, etc., which have a predetermined epoxy equivalent and softening point range, good melt-kneadability below 100°C, excellent solvent solubility, and provide cured products with excellent heat resistance, thermal decomposition stability, thermal conductivity, and tracking resistance. Patent Document 1 proposes improving melt-kneadability and solvent solubility by introducing a structure with excellent solvent solubility at the end of the biphenol-biphenylaralkyl structure, but the resulting epoxy resin cured product has a lower glass transition temperature (Tg) and therefore does not have the heat resistance required for power device applications. In other words, since the chip temperature during operation exceeds 200°C in power device applications, a Tg of 200°C or higher is required for the resin material. Furthermore, it is known that reliability can be improved by reducing the coefficient of linear expansion, such as suppressing delamination. However, Patent Document 1 does not meet these Tg requirements and does not describe the coefficient of linear expansion, so there was room for further improvement in heat resistance and coefficient of linear expansion.

[0004] Further, Patent Document 2 proposes a polyfunctional epoxy resin having a polycyclic aromatic group such as a naphthalene group, and it is shown that a cured epoxy resin product having high heat resistance can be obtained by using this epoxy resin, but there is no description regarding thermal conductivity.

[0005] WO2023 / 276851 and Japanese Patent Application Laid-Open No. 4-255714

[0006] An object of the present invention is to provide an epoxy resin composition useful for sealing electrical and electronic components, circuit board materials and the like, which provides a cured product excellent in melt kneading properties and solvent solubility, and having heat resistance and thermal conductivity suitable for power device applications, and to provide a cured product thereof. Another object of the present invention is to provide an epoxy resin used in the epoxy resin composition and a method for producing the same. A further object of the present invention is to provide a polyhydric hydroxy resin suitable as an intermediate for the epoxy resin.

[0007] The inventors of the present invention have conducted intensive studies and found that an epoxy resin having a specific structure is excellent in melt kneading properties and solvent solubility and is expected to be applicable to a wide range of uses, and that a cured product thereof effectively exhibits heat resistance and thermal conductivity suitable for power device applications.

[0008] That is, the present invention is an epoxy resin represented by the following general formula (1). (In the formula, G represents a glycidyl group, and n and m each independently represent a number of 1 to 20.)

[0009] The present invention also provides a method for producing the epoxy resin represented by the general formula (1), characterized in that after reacting 4,4'-dihydroxybiphenyl represented by the formula (2) with an aromatic crosslinking agent represented by the formula (3), a difunctional phenol compound represented by the formula (4) is further reacted to obtain a polyhydric hydroxy resin represented by the general formula (5), and then the polyhydric hydroxy resin is reacted with epichlorohydrin. (Here, X represents a hydroxyl group, a halogen atom, or an alkoxy group having 1 to 6 carbon atoms.) (In the formula, n and m each independently represent a number between 1 and 20.)

[0010] Furthermore, the present invention relates to an epoxy resin composition characterized by comprising the above-mentioned epoxy resin and curing agent as essential components, and to an epoxy resin cured product characterized by curing this epoxy resin composition.

[0011] The epoxy resin of the present invention has good melt-muddiness at temperatures below 100°C and excellent solvent solubility, making it suitable for epoxy resin compositions and their cured products used in applications such as lamination, molding, casting, and bonding. Furthermore, the cured product has heat resistance above 200°C and excellent thermal decomposition stability, thermal conductivity, and tracking resistance, making it suitable for sealing electrical and electronic components, including power devices, and as a circuit board material.

[0012] This is the GPC chart of the epoxy resin obtained in Example 1.

[0013] The present invention will be described in detail below, but the scope of the present invention is not limited to the following embodiments, and various modifications and combinations are possible to the following embodiments without changing the gist of the present invention.

[0014] The epoxy resin of the present invention is represented by general formula (1). (In the formula, G represents a glycidyl group, and n and m each independently represent a number from 1 to 20.)

[0015] In addition to the epoxy resin represented by general formula (1), which is an essential component, the epoxy resin of the present invention may also contain monomer components represented by formulas (6) and (7). (In formulas (6) and (7), G represents a glycidyl group.)

[0016] In the present invention, the epoxy equivalent of the epoxy resin, which may contain the above monomer components, is preferably 170 to 250 g / eq., and more preferably 190 to 230 g / eq. The preferred softening point of the epoxy resin is in the range of 60 to 120°C. If the softening point is lower than 60°C, the epoxy resin becomes liquid or semi-solid, making it difficult to handle. If it is higher than 120°C, the melt-kneadability tends to decrease, and if it is crystalline, the solvent solubility also tends to decrease further. More preferably, it is 90°C or lower. Furthermore, the melt viscosity of the epoxy resin at 150°C is preferably 0.1 to 1.5 Pa·s, and more preferably 0.3 to 1.0 Pa·s.

[0017] The epoxy resin of the present invention can be produced by reacting a polyvalent hydroxy resin represented by formula (5) with epichlorohydrin. The polyvalent hydroxy resin represented by formula (5) may sometimes be simply referred to as the polyvalent hydroxy resin. In the formula, G represents a glycidyl group, and n and m each independently represent a number from 1 to 20.

[0018] This polyvalent hydroxy resin can be produced by reacting a 4,4'-dihydroxybiphenyl represented by formula (2) with an aromatic crosslinking agent having a biphenyl structure represented by formula (3), and then reacting it with a difunctional phenol compound represented by formula (4). (Here, X represents a hydroxyl group, a halogen atom, or an alkoxy group having 1 to 6 carbon atoms.)

[0019] This polyvalent hydroxy resin may contain monomer components represented by formulas (2) and (4) in addition to the polyvalent hydroxy resin represented by formula (5).

[0020] The molar ratio of the synthetic raw material, 4,4'-dihydroxybiphenyl represented by formula (2), and the difunctional phenol compound (naphthalenediol) represented by formula (4) during charging is preferably 0.50 to 0.95 for 4,4'-dihydroxybiphenyl, and more preferably 0.70 to 0.95. If the ratio of 4,4'-dihydroxybiphenyl is lower than this range, the high thermal conductivity may be insufficient, and if it is higher, the crystallinity tends to increase and solvent solubility may decrease. The naphthalenediols of formula (4) are specifically 1,2-dihydroxynaphthalene, 1,3-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, 1,8-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, and 2,7-dihydroxynaphthalene. In particular, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, and 2,7-dihydroxynaphthalene are preferred from the viewpoint of reactivity during the synthesis of polyvalent hydroxy resins.

[0021] In the aromatic crosslinking agent represented by formula (3) above, X represents a hydroxyl group, a halogen atom, or an alkoxy group having 1 to 6 carbon atoms. Specifically, examples of aromatic crosslinking agents include 4,4'-bishydroxymethylbiphenyl, 4,4'-bischloromethylbiphenyl, 4,4'-bisbromomethylbiphenyl, 4,4'-bismethoxymethylbiphenyl, and 4,4'-bisethoxymethylbiphenyl. From the viewpoint of reactivity, 4,4'-bishydroxymethylbiphenyl or 4,4'-bischloromethylbiphenyl are preferred, and from the viewpoint of reducing ionic impurities, 4,4'-bishydroxymethylbiphenyl or 4,4'-bismethoxymethylbiphenyl are preferred.

[0022] When reacting phenols, including 4,4'-dihydroxybiphenyl represented by formula (2) and the difunctional phenol compound (naphthalenediol) represented by formula (4) above, with an aromatic crosslinking agent, the molar ratio is generally preferably in the range of 0.2 to 0.7 moles of aromatic crosslinking agent per mole of phenol, and more preferably in the range of 0.4 to 0.7 moles. If the ratio is less than 0.2 moles, the proportion of the n=0 form of the resulting polyvalent hydroxy resin tends to be high, raising concerns about decreased solubility, such as exhibiting crystallinity. On the other hand, if the ratio is more than 0.7 moles, the amount of high molecular weight components tends to be high, which may make stable production difficult.

[0023] The reaction between the above phenols and aromatic crosslinking agents can be carried out without a catalyst or in the presence of an acid catalyst such as an inorganic acid or organic acid. When using 4,4'-bischloromethylbiphenyl, the reaction can be carried out without a catalyst, but generally, it is preferable to carry out the reaction in the presence of an acid catalyst to suppress side reactions such as the formation of ether bonds by the reaction of chloromethyl groups and hydroxyl groups. As this acid catalyst, it can be appropriately selected from well-known inorganic acids and organic acids, for example, mineral acids such as hydrochloric acid, sulfuric acid, and phosphoric acid; organic acids such as formic acid, oxalic acid, trifluoroacetic acid, p-toluenesulfonic acid, metasulfonic acid, and trifluoromethasulfonic acid; Lewis acids such as zinc chloride, aluminum chloride, iron chloride, and boron trifluoride; or solid acids.

[0024] Typically, this reaction is carried out at 100 to 250°C for 1 to 20 hours. Preferably, it is carried out at 100 to 180°C, and more preferably at 140 to 180°C. If the reaction temperature is too low, the reactivity is poor and it takes too long, and if the reaction temperature is too high, there is a risk of resin decomposition.

[0025] As solvents used in the reaction, alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol, methyl cellosolve, ethyl cellosolve, diethylene glycol dimethyl ether, and triglime, or aromatic compounds such as benzene, toluene, chlorobenzene, and dichlorobenzene are often used, with ethyl cellosolve, diethylene glycol dimethyl ether, and triglime being particularly preferred. After the reaction is complete, the obtained polyvalent hydroxy resin may have the solvent removed by methods such as vacuum distillation, washing with water, or reprecipitation in a poor solvent, but it may also be used as a raw material for the epoxidation reaction with the solvent still present.

[0026] The polyvalent hydroxy resin obtained in this way can be used not only as a raw material for epoxy resins, but also as an epoxy resin curing agent. Furthermore, by combining it with curing agents such as hexamine, it can also be applied as a phenolic resin molding material.

[0027] The method for producing the epoxy resin of the present invention by the reaction of a polyvalent hydroxy resin represented by the above general formula (5) with epichlorohydrin will be described. This reaction can be carried out in the same manner as well as well known epoxidation reactions.

[0028] For example, the polyvalent hydroxy resin is dissolved in excess epichlorohydrin, and then reacted at 50 to 150°C, preferably 60 to 120°C, for 1 to 10 hours in the presence of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide. The amount of epichlorohydrin used in this case is 2 to 10 moles, preferably 4 to 8 moles, per mole of hydroxyl groups in the polyvalent hydroxy resin. The amount of alkali metal hydroxide used is 0.8 to 2 moles, preferably 0.9 to 1.2 moles, per mole of hydroxyl groups in the polyvalent hydroxy resin. After the reaction is complete, the excess epichlorohydrin is removed by distillation, the residue is dissolved in a solvent such as toluene or methyl isobutyl ketone, filtered, washed with water to remove inorganic salts, and then the solvent is removed by distillation to obtain the target epoxy resin represented by the general formula (1). A catalyst such as a quaternary ammonium salt may be used when carrying out the epoxidation reaction.

[0029] The purity of the epoxy resin of the present invention, particularly the amount of hydrolyzable chlorine, should be low from the viewpoint of improving the reliability of the electronic components to which it is applied. Although not particularly limited, it is preferably 1000 ppm or less, and more preferably 500 ppm or less. In this invention, hydrolyzable chlorine refers to the value measured by the following method: 1.0 g of the sample is dissolved in 30 ml of dioxane, 10 ml of 0.1 N KOH is added, boiled under reflux for 30 minutes, cooled to room temperature, 100 ml of 80% acetone water is added, and the value is obtained by potentiometric titration with a 0.002 N AgNO3 aqueous solution.

[0030] The epoxy resin composition of the present invention comprises an epoxy resin and a curing agent, and includes the epoxy resin of the above general formula (1) as the epoxy resin component.

[0031] In addition to the epoxy resin of general formula (1) used as an essential component, the epoxy resin composition of the present invention may also contain other ordinary epoxy resins having two or more epoxy groups in their molecules. Examples include bisphenol A, bisphenol F, 3,3',5,5'-tetramethyl-4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl ketone, fluorenebisphenol, 4,4'-biphenol, 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl, 2,2'-biphenol, resorcinol, catechol, and t-butylcatechol. t-butylhydroquinone, 1,2-dihydroxynaphthalene, 1,3-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, 1,8-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,4-dihydroxynaphthalene, 2,5-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 2,8-dihydroxy Synaphthalene, allyl or polyallylated dihydroxynaphthalene, divalent phenols such as allylated bisphenol A, allylated bisphenol F, and allylated phenol novolac, or phenol novolac, bisphenol A novolac, o-cresol novolac, m-cresol novolac, p-cresol novolac, xylenol novolac, poly-p-hydroxystyrene, tris-(4-hydroxyphenyl)methane, 1,1,2,2-tetrahydroxy Examples include trivalent or higher phenols such as s(4-hydroxyphenyl)ethane, fluoroglycinol, pyrogallol, t-butylpyrogallol, allylated pyrogallol, polyallylated pyrogallol, 1,2,4-benzenetriol, 2,3,4-trihydroxybenzophenone, phenol aralkyl resins, naphthol aralkyl resins, and dicyclopentadiene resins, or glycidyl ethers derived from halogenated bisphenols such as tetrabromobisphenol A. These epoxy resins can be used individually or in mixtures of two or more types.

[0032] The epoxy resin composition of the present invention preferably contains 50 wt% or more of the epoxy resin of the above general formula (1) as the epoxy resin component. More preferably, it contains 70 wt% or more of the total epoxy resin, and more preferably 80 wt% or more. If the proportion used is less than this, the moldability of the epoxy resin composition may deteriorate, and the effect of improving heat resistance, thermal conductivity, etc., when cured may be small.

[0033] As curing agents used in the epoxy resin composition of the present invention, all commonly known curing agents for epoxy resins can be used, including dicyandiamide, acid anhydrides, polyhydric phenols, aromatic amines, and aliphatic amines. Among these, polyhydric phenols are preferred as curing agents in fields requiring high electrical insulation properties, such as semiconductor encapsulants. Specific examples of curing agents are shown below.

[0034] Examples of polyhydric phenols include dihydric phenols such as bisphenol A, bisphenol F, bisphenol S, fluorenebisphenol, 4,4'-biphenol, 2,2'-biphenol, hydroquinone, resorcinol, and naphthalenediol, as well as trihydric or higher phenols represented by tris-(4-hydroxyphenyl)methane, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, phenol novolac, o-cresol novolac, naphthol novolac, and polyvinylphenol. Furthermore, there are polyhydric phenolic compounds synthesized from dihydric phenols such as phenols, naphthols, bisphenol A, bisphenol F, bisphenol S, fluorenebisphenol, 4,4'-biphenol, 2,2'-biphenol, hydroquinone, resorcinol, and naphthalenediol, and condensing agents such as formaldehyde, acetaldehyde, benzaldehyde, p-hydroxybenzaldehyde, and p-xylylene glycol.

[0035] Examples of the acid anhydride curing agent include phthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyl hymic anhydride, dodecenyl succinic anhydride, nadic anhydride, and trimellitic anhydride.

[0036] Examples of the amine curing agent include aromatic amines such as 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl sulfone, m-phenylenediamine, and p-xylylenediamine, and aliphatic amines such as ethylenediamine, hexamethylenediamine, diethylenetriamine, and triethylenetetramine.

[0037] One or two or more of these curing agents may be mixed and used in the epoxy resin composition described above.

[0038] The compounding ratio of the epoxy resin to the curing agent is preferably such that the equivalent ratio of epoxy groups to functional groups in the curing agent is in the range of 0.8 to 1.5. Outside this range, unreacted epoxy groups or functional groups in the curing agent remain after curing, which reduces the reliability of the sealing function, and is therefore not preferred.

[0039] In the epoxy resin composition of the present invention, oligomers or polymer compounds such as polyester, polyamide, polyimide, polyether, polyurethane, petroleum resin, indene resin, indene-coumarone resin, and phenoxy resin may be appropriately compounded as other modifiers and the like. The addition amount is usually in the range of 1 to 30 parts by weight per 100 parts by weight of the total resin components.

[0040] Additives such as inorganic fillers, pigments, flame retardants, thixotropic agents, coupling agents, and fluidity improvers can be compounded in the epoxy resin composition of the present invention. Examples of the inorganic filler include spherical or crushed silica powders such as fused silica and crystalline silica, alumina powder, glass powder, and also mica, talc, calcium carbonate, alumina, hydrated alumina, and the like.

[0041] Examples of pigments include organic or inorganic extender pigments, scaly pigments, and the like. Examples of thixotropic agents include silicone-based, castor oil-based, aliphatic amide waxes, oxidized polyethylene waxes, organic bentonite-based, and the like.

[0042] A curing accelerator may be used in the epoxy resin composition of the present invention as necessary. Examples include amines, imidazoles, organic phosphines, Lewis acids, and the like. Specifically, tertiary amines such as 1,8-diazabicyclo(5,4,0)undecene-7, triethylenediamine, benzyldimethylamine, triethanolamine, dimethylaminoethanol, tris(dimethylaminomethyl)phenol; imidazoles such as 2-methylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 2-heptadecylimidazole; organic phosphines such as tributylphosphine, methyldiphenylphosphine, triphenylphosphine, diphenylphosphine, phenylphosphine; tetra-substituted phosphonium tetra-substituted borates such as tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium ethyltriphenylborate, tetrabutylphosphonium tetrabutylborate; and tetraphenylboron salts such as 2-ethyl-4-methylimidazole tetraphenylborate, N-methylmorpholine tetraphenylborate. The addition amount is usually in the range of 0.01 to 5 parts by weight per 100 parts by weight of the total resin components.

[0043] Further, if necessary, release agents such as carnauba wax and OP wax, coupling agents such as γ-glycidoxypropyltrimethoxysilane, colorants such as carbon black, flame retardants such as antimony trioxide, low stress agents such as silicone oil, and lubricants such as calcium stearate can be used in the epoxy resin composition of the present invention.

[0044] The epoxy resin composition of the present invention can be prepared as a varnish by dissolving an organic solvent, then impregnated into fibrous materials such as glass cloth, aramid nonwoven fabric, or polyester nonwoven fabric such as liquid crystal polymer, and then the solvent is removed to form a prepreg. Alternatively, it can be applied to sheet materials such as copper foil, stainless steel foil, polyimide film, or polyester film to form a laminate.

[0045] The epoxy resin composition of the present invention can be heated and cured to produce a cured resin product of the present invention. This cured product can be obtained by molding the epoxy resin composition using methods such as casting, compression molding, or transfer molding. The temperature during this process is typically in the range of 120 to 220°C.

[0046] The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to these. Unless otherwise specified, "parts" refers to parts by weight, and "%" refers to percentage by weight. The measurements were taken using the following methods.

[0047] 1) An epoxy equivalent potentiometric titrator was used, with chloroform as the solvent, and tetraethylammonium brominated acetate solution was added. The titration was then performed using a potentiometric titrator with a 0.1 mol / L perchloric acid-acetic acid solution.

[0048] 2) Melt viscosity was measured at 150°C using a Brookfield CAP2000H rotational viscometer.

[0049] 3) Softening point: Measured using the ring-and-ball method in accordance with JIS K-2207.

[0050] 4) A GPC measurement unit (Tosoh Corporation, HLC-8220GPC) was used, with columns (Tosoh Corporation, TSKgel SuperMultiporeHZ-N: 3 tubes, TSKgel SuperHZ-1000: 1 tube) connected in series, and the column temperature was set to 40°C. Tetrahydrofuran (THF) was used as the eluent at a flow rate of 1 mL / min, and a differential refractive index detector was used. For the measurement sample, 0.1 g of the sample was dissolved in 10 mL of THF, filtered through a microfilter, and 50 μL of the result was used. Data processing was performed using Tosoh Corporation's GPC-8020 Model II version 6.00.

[0051] 5) The glass transition temperature (Tg) and coefficient of linear expansion were determined using a thermomechanical measuring device (EXSTAR6000TMA / 6100, manufactured by SII Nanotechnology Co., Ltd.) under a heating rate of 10°C / min. The coefficient of linear expansion in the range of 60°C–80°C was also determined.

[0052] 6) Thermal conductivity: Thermal conductivity was measured using the transient hot-wire method with a NETZSCH LFA447 thermal conductivity meter.

[0053] 7) Melt-mixability The melt-mixability of the epoxy resins and curing agents listed in Table 1 at 100°C was confirmed and evaluated according to the following criteria: ○: Mixable, △: Difficult to mix, ×: Unmelted components present.

[0054] 8) Two g of resin and two g of methyl ethyl ketone were weighed into a solvent-soluble sample bottle, heated to dissolve, and then the temperature was gradually lowered in a constant temperature bath. The temperature in the bath where the resin precipitated was measured. The higher the precipitation temperature (°C), the lower the solvent solubility.

[0055] Example 1 In a 1000 ml four-necked flask, 60.0 g (0.32 mol) of 4,4'-dihydroxybiphenyl, 132.7 g of diethylene glycol dimethyl ether, and 56.7 g (0.23 mol) of 4,4'-bischloromethylbiphenyl were charged. The mixture was heated to 160°C under a nitrogen stream with stirring and reacted for 7 hours. Then, 12.9 g (0.08 mol) of 1,6-dihydroxynaphthalene was added and reacted to produce a polyvalent hydroxy resin. After the reaction was complete, 51.7 g of diethylene glycol dimethyl ether was recovered, and 540 g of epichlorohydrin was added. 69.4 g of 48% sodium hydroxide aqueous solution was added dropwise over 4 hours at 62°C under reduced pressure (approximately 130 Torr). During this time, the water produced was removed from the system by azeotrope with the epichlorohydrin, and the distilled epichlorohydrin was returned to the system. After the dropwise addition was complete, the reaction was continued for another hour. Subsequently, epichlorohydrin was removed by distillation, and methyl isobutyl ketone was added and dissolved. After removing the salt by washing with water, the mixture was filtered, and methyl isobutyl ketone was removed by vacuum distillation to obtain 95 g of epoxy resin (epoxy resin A). The epoxy equivalent of epoxy resin A was 201 g / eq., the softening point was 84°C, the melt viscosity was 0.85 Pa·s, and the hydrolyzable chlorine content was 68 ppm. The GPC chart of the obtained resin is shown in Figure 1. The number-average molecular weight (Mn) measured by GPC was 720, and the monomer component ratio was 22%. Furthermore, the melt-moldability and solvent solubility of the obtained resin were evaluated, and the results are shown in Table 1.

[0056] Example 2 The reaction was carried out in the same manner as in Example 1, except that 12.9 g (0.08 mol) of 2,7-dihydroxynaphthalene was used instead of 12.9 g (0.08 mol) of 1,6-dihydroxynaphthalene, and 79 g of epoxy resin was obtained (Epoxy Resin B). The epoxy equivalent of Epoxy Resin B was 197 g / eq., the softening point was 79°C, the melt viscosity was 0.82 Pa·s, the hydrolyzable chlorine content was 71 ppm, the Mn measured by GPC was 690, and the monomer component ratio was 23%. The melt-moldability and solvent solubility of the obtained resin were also evaluated, and the results are shown in Table 1.

[0057] Example 3 The reaction was carried out in the same manner as in Example 1, except that 12.9 g (0.08 mol) of 1,5-dihydroxynaphthalene was used instead of 12.9 g (0.08 mol) of 1,6-dihydroxynaphthalene, and 93 g of epoxy resin was obtained (Epoxy Resin C). The epoxy equivalent of this epoxy resin C was 199 g / eq., the softening point was 71°C, the melt viscosity was 0.70 Pa·s, the hydrolyzable chlorine content was 44 ppm, the Mn measured by GPC was 650, and the proportion of monomer components was 24%. The melt-moldability and solvent solubility of the obtained resin were also evaluated, and the results are shown in Table 1.

[0058] Comparative Example 1: In a 1000 ml four-necked flask, 65.6 g (0.35 mol) of 4,4'-dihydroxybiphenyl, 114.8 g of diethylene glycol dimethyl ether, and 49.2 g (0.20 mol) of 4,4'-bischloromethylbiphenyl were charged. The mixture was heated to 160°C under a nitrogen atmosphere with stirring and reacted for 3 hours. Further reaction was carried out with 7.8 g (0.04 mol) of dihydroxydiphenylmethane (4,4'-dihydroxydiphenylmethane: 36.2%, 2,4'-dihydroxydiphenylmethane: 46.6%, 2,2'-dihydroxydiphenylmethane: 17.2%) to produce a polyvalent hydroxy resin. After the reaction was complete, 49.5 g of diethylene glycol dimethyl ether was recovered, 435 g of epichlorohydrin was added, and 72.7 g of a 48% sodium hydroxide aqueous solution was added dropwise over 4 hours at 62°C under reduced pressure (approximately 130 Torr). The procedure was the same as in Example 1, except that 120 g of epoxy resin was obtained (epoxy resin D). The epoxy equivalent of epoxy resin D was 210 g / eq., the softening point was 90°C, the melt viscosity was 0.53 Pa·s, and the hydrolyzable chlorine content was 77 ppm. The melt-moldability and solvent solubility of the obtained resin were also evaluated, and the results are shown in Table 1.

[0059] Comparative Example 2: 77.5 g (0.42 mol) of 4,4'-dihydroxybiphenyl, 180.8 g of diethylene glycol dimethyl ether, and 52.3 g (0.21 mol) of 4,4'-bischloromethylbiphenyl were charged and reacted under a nitrogen atmosphere with stirring, heating to 170°C for 2 hours. After the reaction, 123 g of diethylene glycol dimethyl ether was recovered, 385.4 g of epichlorohydrin was added, and 69.4 g of a 48% sodium hydroxide aqueous solution was added dropwise over 4 hours at 62°C under reduced pressure (approximately 130 Torr), except that the reaction was carried out in the same manner as in Example 1 to obtain 129 g of epoxy resin (epoxy resin E). The epoxy equivalent of epoxy resin E was 196 g / eq., the melting point was 126°C, the melt viscosity was 0.68 Pa·s, and the hydrolyzable chlorine content was 390 ppm. The melt-moldability and solvent solubility of the obtained resin were also evaluated, and the results are shown in Table 1.

[0060] Examples 4-6 and Comparative Examples 3-6: Epoxy resins A-C obtained in Examples 1-3, epoxy resins D-E obtained in Comparative Examples 1-2, and epoxy resins F and G shown below were used as epoxy resin components. A phenol novolac resin was used as a curing agent and triphenylphosphine as a curing accelerator, and each epoxy resin composition was obtained with the formulations shown in Table 1. The values ​​in the table represent parts by weight in the formulation. The melt-moldability and solvent solubility of epoxy resins F and G were evaluated, and the results are shown in Table 1. Each of these epoxy resin compositions was molded at 175°C, post-cured at 180°C for 3 hours, and cured specimens were obtained, which were then subjected to various physical property measurements.

[0061] The epoxy resins, hardeners, and curing accelerators used are as follows: Epoxy resin F: Dinaphthol aralkyl type epoxy resin (manufactured by Nippon Steel Chemical & Material Co., Ltd., product name: Epotote ESN-375, epoxy equivalent: 166 g / eq.) Epoxy resin G: Cresol novolac type epoxy resin (manufactured by Nippon Steel Chemical & Material Co., Ltd., product name: Epotote YDCN-700-7, epoxy equivalent: 200 g / eq.) Hardener: Phenol novolac resin (hydroxyl group equivalent: 105 g / eq., softening point: 67°C) Curing accelerator: Triphenylphosphine

[0062]

[0063] As is clear from these results, the epoxy resin cured products obtained in the examples have good thermal conductivity and high heat resistance above 200°C, making them suitable for power devices and automotive applications. Furthermore, their excellent solvent solubility suggests they can be used in a wide range of applications.

Claims

1. An epoxy resin represented by the following general formula (1). (In the formula, G represents a glycidyl group, and n and m each independently represent a number from 1 to 20.) 2. A method for producing the epoxy resin described in claim 1, characterized by reacting a 4,4'-dihydroxybiphenyl represented by formula (2) with an aromatic crosslinking agent represented by formula (3), then further reacting it with a difunctional phenol compound represented by formula (4) to obtain a polyvalent hydroxy resin represented by general formula (5), and then reacting this polyvalent hydroxy resin with epichlorohydrin. (Here, X represents a hydroxyl group, a halogen atom, or an alkoxy group having 1 to 6 carbon atoms.) (In the formula, n and m each independently represent a number between 1 and 20.) 3. An epoxy resin composition characterized by comprising the epoxy resin and curing agent described in claim 1 as essential components.

4. An epoxy resin cured product characterized by being obtained by curing the epoxy resin composition described in claim 3.

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