Epoxy resin, epoxy resin composition and cured product

Abstract

To provide: a crystalline modified epoxy resin which is useful for an insulation material having excellent reliability for electric and electronic components such as semiconductor encapsulation, laminates, and heat dissipation substrates, has excellent handleability as a solid at ordinary temperature, and has excellent low viscosity when molding and solvent solubility; an epoxy resin composition using the same; and a cured material obtained from the same, having excellent high thermal conductivity.SOLUTION: Provided is an epoxy resin containing, as a basic skeleton, a biphenyl structure having two OG groups, represented by the following general formula (1), where a content of a material corresponding to n=0 is 70-95% and an epoxy equivalent is in a range of 150-160 g / eq. (In the formula, X independently represents a direct bond or -O-, is at least partly -O-; n represents a number of 0-10, and G represents a glycidyl group.)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an epoxy resin that is useful as an insulating material for highly reliable electric and electronic components such as semiconductor encapsulation, laminates, and heat dissipation substrates, and that has excellent handleability as a solid at room temperature, low viscosity during molding, and excellent solvent solubility; an epoxy resin composition using the same; and a cured product obtained from the same that has excellent high thermal conductivity. [Background technology]

[0002] Epoxy resins have been used in a wide range of industrial applications, and their performance requirements have become increasingly sophisticated in recent years. In the electrical and electronics and power electronics fields, where electronic circuits are becoming increasingly dense and high-frequency, heat generated by electronic circuits is increasing, posing a challenge to the heat dissipation capabilities of epoxy resin compositions used in insulating parts. While this heat dissipation capability was previously achieved through the thermal conductivity of the filler, further increases in integration have created a demand for improved thermal conductivity in the epoxy resin matrix itself.

[0003] Epoxy resin compositions with excellent thermal conductivity that use epoxy resins having mesogenic structures are known. For example, Patent Document 1 discloses an epoxy resin composition containing a biphenol-type epoxy resin and a polyphenol resin curing agent as essential components, which exhibits excellent stability and strength at high temperatures and can be used in a wide range of fields, including adhesion, casting, sealing, molding, and lamination. Patent Document 2 also discloses an epoxy compound having two mesogenic structures linked by a bent chain within the molecule. Furthermore, Patent Document 3 discloses a resin composition containing an epoxy compound with a mesogenic group.

[0004] However, epoxy resins with such mesogenic structures have high melting points, and when mixed, the high-melting component is difficult to dissolve, resulting in residual dissolution, which reduces curing and heat resistance. Furthermore, high temperatures are required to uniformly mix such epoxy resins with curing agents. At high temperatures, the curing reaction of the epoxy resin proceeds rapidly, shortening the gelation time, severely limiting the mixing process and making handling difficult. Adding a soluble third component to compensate for this drawback lowers the resin's melting point, making uniform mixing easier, but the resulting cured product has a reduced thermal conductivity.

[0005] As highly thermally conductive resins that can be melt-mixed, Patent Document 4 discloses an epoxy resin obtained by epoxidizing a mixture of hydroquinone and 4,4'-dihydroxybiphenyl, and Patent Document 5 discloses an epoxy resin obtained by epoxidizing a mixture of 4,4'-dihydroxydiphenylmethane and 4,4'-dihydroxybiphenyl. However, these resins have poor solvent solubility and their applications are limited. Patent Document 6 discloses an epoxy resin composition having a diphenyl ether structure, but the curing agent is limited, and general-purpose curing agents such as phenol novolac have insufficient thermal conductivity and heat resistance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 7-90052 [Patent Document 2] Japanese Patent Application Publication No. 9-118673 [Patent Document 3] Japanese Patent Application Publication No. 11-323162 [Patent Document 4] WO2009 / 110424 [Patent Document 5] Japanese Patent Application Laid-Open No. 2010-43245 [Patent Document 6] Japanese Patent Application Laid-Open No. 2012-17405 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, an object of the present invention is to provide a crystalline modified epoxy resin which overcomes the above-mentioned problems, is useful as an insulating material for electric and electronic components such as semiconductor encapsulation, laminates, and heat dissipation substrates, has excellent handleability as a solid at room temperature, has low viscosity during molding, and has excellent solvent solubility, and is useful as an insulating material for electric and electronic components such as semiconductor encapsulation, laminates, and heat dissipation substrates, and provides an epoxy resin composition using the same, and a cured product obtained from the same which has high thermal conductivity. [Means for solving the problem]

[0008] Through extensive research, the present inventors have discovered that the above-mentioned problems can be solved by reacting a mixture of compounds having a specific phenolic hydroxyl group with epichlorohydrin, and that the resulting cured product exhibits an effect on thermal conductivity.

[0009] That is, the present invention relates to an epoxy resin represented by the following general formula (1), characterized in that the total content of n=0 units is 70 to 95% and the epoxy equivalent is in the range of 150 to 160 g / eq. [ka] (In the formula, each X independently represents a direct bond or —O—, and at least some of them are —O—. n represents a number of 0 to 10, and G represents a glycidyl group.)

[0010] In the above general formula (1), the ratio (weight ratio) of the biphenyl structure where X is a direct bond to the diphenyl ether structure where X is —O— is preferably in the range of 0.1 to 10.0.

[0011] In the above general formula (1), the biphenyl structure having two OG groups preferably has a 4,4' configuration.

[0012] The present invention also relates to an epoxy resin composition comprising an epoxy resin and a curing agent, which comprises the above-mentioned epoxy resin as an essential component as part or all of the epoxy resin.

[0013] Furthermore, the present invention relates to a cured resin product obtained by curing the above resin composition. [Effects of the Invention]

[0014] The epoxy resin and epoxy resin composition of the present invention have excellent solvent solubility, moldability, and reliability, and exhibit excellent thermal conductivity in the cured product. Furthermore, by suppressing crystallinity, yields are improved, which is advantageous in terms of production. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a GPC chart of epoxy resin A (Example 1). DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described in detail below.

[0017] The epoxy resin of the present invention is represented by the above general formula (1) and has an epoxy equivalent (g / eq) of 150 to 160. n represents a number from 0 to 10, and the average value (number average) is 0.1 to 5, preferably 0.1 to 2. Preferably, the epoxy resin is a mixture of components with different n values. Examples of compounds with n=0 include compounds in which glycidyl ether groups are bonded to both ends of a biphenyl structure and compounds in which glycidyl ether groups are bonded to both ends of a diphenyl ether. For structures with excellent thermal conductivity, the glycidyl ether group bonded to the biphenyl structure preferably has a 4,4' bond. Examples of compounds with n=1 or more include mixtures containing homopolymers derived from dihydroxybiphenyl, homopolymers derived from dihydroxydiphenyl ether, and copolymers having a co-reaction structure of dihydroxybiphenyl and dihydroxydiphenyl ether.

[0018] The epoxy resin of the present invention can be produced by reacting a mixture of dihydroxybiphenyl and dihydroxydiphenyl ether with epichlorohydrin. This reaction can be carried out in the same manner as a conventional epoxidation reaction. The epoxy resin of the present invention is a mixture containing an epoxidized product of dihydroxybiphenyl and an epoxidized product of dihydroxydiphenyl ether, as well as an epoxidized product having units derived from dihydroxybiphenyl and dihydroxydiphenyl ether in one molecule. The epoxidized products obtained by reacting a dihydroxy compound with epichlorohydrin include epoxidized products with a degree of polymerization of 0 (n=0 form) as well as polymers such as n=1 (di-form) and n=2 (tri-form).

[0019] The epoxy resin of the present invention has a total content of all n=0 isomers derived from dihydroxybiphenyl and dihydroxydiphenyl ether in the range of 70 to 95 wt %. If the content exceeds this range, molding may be impossible due to the crystallinity and high melting point derived from the dihydroxybiphenyl structure. On the other hand, if the content is below this range, crystallinity may be low, which may lead to a decrease in thermal conductivity. Furthermore, the content of compounds containing a co-reactive structure (n=1 or more) is 5 wt% to 30 wt%, preferably 5 wt% to 15 wt%. Below this range, the melting point and crystallinity may not be reduced, making molding impossible. On the other hand, above this range, thermal conductivity may be reduced. Here, the co-reactive structure refers to the random reaction of dihydroxybiphenyl and dihydroxydiphenyl ether. For example, when n=1, the resulting epoxy resin has one dihydroxybiphenyl and one dihydroxydiphenyl ether structure. By including an epoxy resin with this co-reactive structure, the resulting resin has different properties than a simple mixture of epoxy resins with a single structure consisting of each monomer.

[0020] The mixing ratio of dihydroxybiphenyl to dihydroxydiphenyl ether, in weight ratio, is in the range of dihydroxybiphenyl / dihydroxydiphenyl ether = 0.1 to 10.0, preferably 0.2 to 5.0, more preferably 0.3 to 3.0, and even more preferably 0.5 to 2.0. The structural ratio of the resulting epoxy resin will be approximately the same as the charging ratio, so the range for the epoxy resin will also be the same. If the ratio is lower than this, the high melting point of the 4,4'-dihydroxybiphenyl epoxy compound will make it difficult to handle, and if it is higher than this, the heat resistance, thermal conductivity, and other properties of the cured product will be reduced.

[0021] The epoxy resin of the present invention is obtained by reacting a mixture of dihydroxybiphenyl and dihydroxydiphenyl ether (hereinafter referred to as the phenol mixture) with epichlorohydrin. The reaction with epichlorohydrin can be carried out, for example, by dissolving the phenol mixture in an excess amount of epichlorohydrin relative to the phenolic hydroxyl groups in the mixture, followed by reaction in the presence of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide at 50 to 150°C, preferably 60 to 100°C, for 1 to 10 hours. The amount of alkali metal hydroxide used is 0.8 to 1.2 mol, preferably 0.9 to 1.1 mol, per mol of hydroxyl groups in the phenol mixture. Epichlorohydrin is used in excess relative to the hydroxyl groups in the phenol mixture, typically 1.5 to 15 mol, preferably 3 to 10 mol, per mol of hydroxyl groups in the phenol mixture. After the reaction is completed, excess epichlorohydrin is distilled off, and the residue is dissolved in a solvent such as toluene or methyl isobutyl ketone, filtered, and washed with water to remove inorganic salts, and then the solvent is distilled off to obtain the desired epoxy resin.

[0022] In producing the epoxy resin of the present invention, a small amount of a phenolic compound other than the phenolic compounds dihydroxybiphenyl and dihydroxydiphenyl ether can be mixed into the phenol mixture as long as it does not impair the effects of the present invention. In this case, however, the total amount of the other phenolic compounds should be 50 wt% or less, preferably 30 wt% or less, and more preferably 10 wt% or less of the total phenolic compounds.

[0023] The epoxy resin of the present invention is crystalline at room temperature. The manifestation of crystallinity can be confirmed by differential scanning calorimetry (DSC) as an endothermic peak associated with the melting of crystals. Since the epoxy resin of the present invention is a mixture, the endothermic peak is generally observed as multiple peaks rather than a single peak. The melting point observed by DSC is the endothermic peak derived from the epoxy resin derived from dihydroxybiphenyl and dihydroxydiphenyl ether. The lowest endothermic peak is 50°C or higher, preferably 70°C or higher, and the highest endothermic peak is 160°C or lower, preferably 140°C or lower. A melting point lower than this range can cause blocking when formed into a powder, reducing handleability as a solid at room temperature. A melting point higher than this range can result in problems such as poor melt-kneadability with curing agents and poor solvent solubility. The melt viscosity at 150°C is preferably lower; it is generally 0.1 Pa·s or lower, preferably 0.01 Pa·s or lower.

[0024] The purity of the epoxy resin of the present invention, particularly the amount of hydrolyzable chlorine, should be low in order to improve the reliability of the electronic components to which it is applied. While not particularly limited, the content is preferably 1000 ppm or less, and more preferably 500 ppm or less. The hydrolyzable chlorine content in this invention refers to a value measured by the following method: 0.5 g of a sample was dissolved in 30 ml of dioxane, 10 ml of 1N KOH was added, and the mixture was boiled under reflux for 30 minutes. After cooling to room temperature, 100 ml of 80% acetone water was added, and the mixture was subjected to potentiometric titration with a 0.002 N AgNO3 aqueous solution.

[0025] The epoxy resin composition of the present invention, which is comprised of an epoxy resin and a curing agent, is characterized by containing the above-mentioned modified epoxy resin as an essential component as part or all of the epoxy resin, and advantageously, the modified epoxy resin accounts for 70 wt% or more, and more preferably 90 wt% or more, of the total epoxy resin. If the proportion of the modified epoxy resin used is less than this, the effect of improving the thermal conductivity of the cured product is small.

[0026] In addition to the epoxy resins used as essential components of the present invention, the epoxy resin composition of the present invention may contain other ordinary epoxy resins having two or more epoxy groups in the molecule. Examples of such raw materials include bisphenol A, bisphenol F, 3,3',5,5'-tetramethyl-4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl ketone, fluorene bisphenol, 4,4'-biphenol, 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl, zorcinol, catechol, hydroquinone, 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-dihydroxynaphthalene, and the above dihydroxynaphthalenes. Dihydric phenols such as allylated or polyallylated products of hydroxynaphthalene, 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, and 1,1,2,2-tetrakis(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, dicyclopentadiene-based resins, and the like; or halogenated bisphenols such as tetrabromobisphenol A; and the like are used, and glycidyl ethers derived from these raw material phenols are also used.These epoxy resins can be used alone or in combination of two or more.

[0027] The curing agent used in the epoxy resin composition of the present invention can be any of those generally known as curing agents for epoxy resins, including dicyandiamide, acid anhydrides, polyhydric phenols, aromatic and aliphatic amines, etc. Among these, polyhydric phenols are preferably used as curing agents in fields requiring high electrical insulation, such as semiconductor encapsulants. Specific examples of curing agents are shown below.

[0028] Examples of polyhydric phenols include dihydric phenols such as bisphenol A, bisphenol F, bisphenol S, fluorene bisphenol, 4,4'-biphenol, 2,2'-biphenol, hydroquinone, resorcinol, and naphthalenediol; and trihydric or higher phenols such as tris-(4-hydroxyphenyl)methane, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, phenol novolac, o-cresol novolac, naphthol novolac, and polyvinylphenol. Further examples include polyhydric phenolic compounds synthesized from dihydric phenols such as phenols, naphthols, bisphenol A, bisphenol F, bisphenol S, fluorene bisphenol, 4,4'-biphenol, 2,2'-biphenol, hydroquinone, resorcinol, and naphthalenediol, and condensing agents such as formaldehyde, acetaldehyde, benzaldehyde, p-hydroxybenzaldehyde, and p-xylylene glycol.

[0029] Examples of acid anhydride curing agents include phthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylhimic anhydride, dodecynylsuccinic anhydride, nadic anhydride, and trimellitic anhydride.

[0030] Examples of amine curing agents include aromatic amines such as 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylsulfone, m-phenylenediamine, and p-xylylenediamine; and aliphatic amines such as ethylenediamine, hexamethylenediamine, diethylenetriamine, and triethylenetetramine.

[0031] The above-mentioned epoxy resin composition can contain one or more of these curing agents in combination.

[0032] The compounding ratio of epoxy resin to curing agent is preferably in the range of 0.8 to 1.5 in terms of equivalent ratio of epoxy groups to functional groups in the curing agent. Outside this range, unreacted epoxy groups or functional groups in the curing agent remain even after curing, which is undesirable because it reduces the reliability of the sealing function.

[0033] The resin composition of the present invention may contain oligomers or polymeric compounds such as polyesters, polyamides, polyimides, polyethers, polyurethanes, petroleum resins, indene resins, indene-coumarone resins, and phenoxy resins as other modifiers, etc. The amount added is usually in the range of 1 to 30 parts by weight per 100 parts by weight of the total resin components.

[0034] The resin composition of the present invention can be blended with additives such as inorganic fillers, pigments, flame retardants, thixotropic agents, coupling agents, flow improvers, etc. Examples of inorganic fillers include thermally conductive fillers such as silica powders such as spherical or crushed fused silica and crystalline silica, alumina powders, glass powders, mica, talc, calcium carbonate, alumina, and hydrated alumina. When used in a semiconductor encapsulant, the blending amount is preferably 70% by weight or more, and more preferably 80% by weight or more.

[0035] Examples of pigments include organic or inorganic extender pigments, scaly pigments, etc. Examples of thixotropic agents include silicone-based, castor oil-based, aliphatic amide wax, oxidized polyethylene wax, and organic bentonite-based agents.

[0036] Furthermore, a curing accelerator can be used in the epoxy resin composition of the present invention as needed. Examples include amines, imidazoles, organic phosphines, Lewis acids, etc. Specific examples include amines such as 1,8-diazabicyclo(5,4,0)undecene-7, triethylenediamine, benzyldimethylamine, triethanolamine, dimethylaminoethanol, and tris(dimethylaminomethyl)phenol; imidazoles such as 2-methylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, and 2-heptadecylimidazole; and tributylphosphines. Examples include organic phosphines such as sphingosine, methyldiphenylphosphine, triphenylphosphine, diphenylphosphine, and phenylphosphine; or tetra-substituted phosphonium tetra-substituted borates such as tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium ethyltriphenylborate, and tetrabutylphosphonium tetrabutylborate; and Lewis acids such as tetraphenylboron salts such as 2-ethyl-4-methylimidazole tetraphenylborate and N-methylmorpholine tetraphenylborate. The amount added is usually in the range of 0.01 to 5 parts by weight per 100 parts by weight of the total resin components.

[0037] Furthermore, if necessary, the resin composition of the present invention may contain a release agent such as carnauba wax or OP wax, a coupling agent such as γ-glycidoxypropyltrimethoxysilane, a colorant such as carbon black, a flame retardant such as antimony trioxide, a stress reducer such as silicone oil, a lubricant such as calcium stearate, or the like.

[0038] The resin composition of the present invention can be dissolved in an organic solvent to form a varnish, which can then be impregnated into a fibrous material such as glass cloth, aramid nonwoven fabric, or polyester nonwoven fabric made of liquid crystal polymer or the like, followed by removing the solvent to form a prepreg. In some cases, the resin composition can also be applied to a sheet-like material such as copper foil, stainless steel foil, polyimide film, or polyester film to form a laminate.

[0039] The resin composition of the present invention can be heat-cured to form the cured resin product of the present invention. This cured product can be obtained by molding the epoxy resin composition by a method such as casting, compression molding, or transfer molding. The temperature at which this is done is usually in the range of 120 to 220°C. [Example]

[0040] The present invention will be specifically explained below with reference to Synthesis Examples, Examples, and Comparative Examples. However, the present invention is not limited to these. Unless otherwise specified, "parts" means parts by weight, and "%" means % by weight. Measurement methods were as follows.

[0041] 1) Epoxy equivalent Using a potentiometric titrator, methyl ethyl ketone was used as the solvent, and tetraethylammonium bromide acetate solution was added, followed by measurement using a 0.1 mol / L perchloric acid-acetic acid solution in the potentiometric titrator.

[0042] 2) Melting point The DSC peak temperature was determined using a differential scanning calorimeter (EXSTAR6000 DSC / 6200 manufactured by SII NanoTechnology Inc.) at a heating rate of 5°C / min. This DSC peak temperature was taken as the melting point of the resin.

[0043] 3) Melt viscosity Measurement was carried out at 150°C using a Brookfield CAP2000H rotational viscometer.

[0044] 4) Softening point Measurement was performed by the ring and ball method according to JIS-K-2207.

[0045] 5) GPC measurement The main body (Tosoh Corporation, HLC-8320GPC) was equipped with columns (Tosoh Corporation, three TSKgel SuperMultiporeHZ-NG columns and one TSKgel SuperHZ1000 column) 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 refractive index detector was used. 0.1 g of sample was dissolved in 10 mL of THF and filtered through a microfilter, and 50 μL of this was used as the measurement sample.

[0046] 6) Glass transition temperature (Tg) Tg was determined using a thermomechanical measurement device (EXSTAR6000TMA / 6100 manufactured by SII NanoTechnology Inc.) at a heating rate of 10°C / min.

[0047] 7) 5% weight loss temperature (Td5), residual coal rate Using a thermogravimetric / differential thermal analyzer (SII NanoTechnology EXSTAR6000TG / DTA6200), the 5% weight loss temperature (Td5) was measured under a nitrogen atmosphere at a heating rate of 10°C / min. The weight loss at 700°C was also measured and calculated as the residual carbon percentage.

[0048] 8) Thermal conductivity Measurements were made using a NETZSCH LFA447 thermal conductivity meter by the transient hot wire method.

[0049] Example 1 50.0 g of 4,4'-dihydroxybiphenyl and 27.2 g of 4,4'-dihydroxydiphenyl ether were dissolved in 373 g of epichlorohydrin and 56.0 g of diethylene glycol dimethyl ether, and 73.9 g of 48% aqueous sodium hydroxide solution was added dropwise over 3 hours at 60°C under reduced pressure (approximately 130 Torr). During this time, the water produced was removed from the system by azeotropy with epichlorohydrin, and the distilled epichlorohydrin was returned to the system. After the addition was completed, the reaction was continued for another hour to dehydrate the mixture. After that, the epichlorohydrin was distilled off, and 460 g of toluene was added. The mixture was then washed with water to remove salt. The water was then removed by separation, and the toluene was distilled off under reduced pressure, yielding 83.3 g of a white crystalline epoxy resin (epoxy resin A). The epoxy equivalent was 156, the hydrolyzable chlorine content was 45 ppm, the melting points were 75°C and 137°C, and the viscosity at 150°C was 5 mPa·s. GPC analysis determined that the n=0 (monomer) content of the epoxy resin obtained from 4,4'-dihydroxybiphenyl was 70.6%. The n=0 (monomer) content of the epoxy resin obtained from 4,4'-dihydroxydiphenyl ether was 21.0%. The content of n=1 or more was 8.3%.

[0050] Example 2 50.0 g of 4,4'-dihydroxybiphenyl and 54.3 g of 4,4'-dihydroxydiphenyl ether were dissolved in 500 g of epichlorohydrin and 75 g of diethylene glycol dimethyl ether, and 98.6 g of 48% aqueous sodium hydroxide was added dropwise over 3 hours at 60°C under reduced pressure (approximately 130 Torr). During this time, the water produced was removed from the system by azeotropy with epichlorohydrin, and the distilled epichlorohydrin was returned to the system. After the addition was completed, the reaction was continued for another hour to dehydrate the mixture. After that, the epichlorohydrin was distilled off, and 620 g of toluene was added. The salt was removed by water washing. After the water was removed by separation, the toluene was distilled off under reduced pressure, yielding 124 g of white crystalline epoxy resin (Epoxy Resin B). The epoxy equivalent was 158, the hydrolyzable chlorine content was 40 ppm, the melting points were 74°C and 123°C, and the viscosity at 150°C was 5 mPa·s. GPC analysis revealed that the proportion of n=0 (monomer) in the epoxy resin obtained from 4,4'-dihydroxybiphenyl was 53.8%, and the proportion of n=0 (monomer) in the epoxy resin obtained from 4,4'-dihydroxydiphenyl ether was 36.2%, while the proportion of n=1 or more was 10.0%.

[0051] Comparative Example 1 100.0 g of 4,4'-dihydroxydiphenyl ether was dissolved in 460 g of epichlorohydrin and 70 g of diethylene glycol dimethyl ether, and 90.8 g of 48% aqueous sodium hydroxide solution was added dropwise over 3 hours at 60°C under reduced pressure (approximately 130 Torr). During this time, the water produced was removed from the system by azeotropy with epichlorohydrin, and the distilled epichlorohydrin was returned to the system. After the addition was completed, the reaction was continued for another hour to dehydrate the mixture. The epichlorohydrin was then distilled off, and 580 g of toluene was added. The salt was then removed by washing with water. The water was then removed by separation, and the toluene was distilled off under reduced pressure to yield 126 g of white crystalline epoxy resin (Epoxy Resin C). The epoxy equivalent was 163, the hydrolyzable chlorine content was 150 ppm, the melting point was 83°C, and the viscosity at 150°C was 10 mPa·s. GPC analysis revealed that the proportion of n=0 (monomer) in the epoxy resin obtained from 4,4'-dihydroxydiphenyl ether was 91.2%, and the proportion of n=1 or more was 8.8%.

[0052] Comparative Example 2 100.0 g of 4,4'-dihydroxybiphenyl was dissolved in 700 g of epichlorohydrin and 105 g of diethylene glycol dimethyl ether. Then, 98.6 g of 48% aqueous sodium hydroxide solution was added dropwise over 3 hours at 60°C under reduced pressure (approximately 130 Torr). During this time, the water produced was removed from the system by azeotropy with epichlorohydrin, and the distilled epichlorohydrin was returned to the system. After the addition was completed, the reaction was continued for another hour to dehydrate the mixture, then cooled to room temperature and filtered to recover the precipitate. The precipitate was then washed with water to remove salts and further dried to yield 112 g of a crystalline powder epoxy resin (epoxy resin D). The epoxy equivalent was 163, the hydrolyzable chlorine content was 345 ppm, and the melting point was 172°C. GPC analysis of the resulting resin revealed that 93.7% of the components were n=0 and 5.9% were n=1 or greater.

[0053] Checking solvent solubility Solvent solubility was determined by adding epoxy resins A and B obtained in Examples 1 and 2 and epoxy resins C and D obtained in Comparative Examples 1 and 2 to 5 g of solvent (methyl ethyl ketone, toluene, cyclohexanone) so that the solid content concentration was 10 wt %, thoroughly stirring at room temperature, and then visually checking for insoluble matter. The presence of insoluble matter was marked with ×, and the absence of insoluble matter was marked with ◯. Furthermore, when insoluble matter was confirmed to have dissolved upon heating to 60°C, the result was marked with △. The results are shown in Table 1.

[0054] [Table 1]

[0055] Examples 3 and 4 and Comparative Examples 3 to 5 The epoxy resin components used were epoxy resins A and B obtained in Examples 1 and 2, epoxy resins C and D obtained in Comparative Examples 1 and 2, and a biphenyl-based epoxy resin (epoxy resin E: YX-4000H manufactured by Japan Epoxy Resins; epoxy equivalent: 195). Phenol novolac resin (PN; hydroxyl equivalent: 105 g / eq., softening point: 67°C) was used as the curing agent. Triphenylphosphine was used as the curing accelerator, and epoxy resin compositions were obtained according to the formulation shown in Table 2. The values ​​in the table indicate parts by weight of the formulation. These epoxy resin compositions were molded at 175°C and post-cured at 175°C for 5 hours to obtain cured specimens, which were then used to measure various physical properties.

[0056] [Table 2]

[0057] As is clear from these results, the epoxy resins obtained in the examples have low melt viscosity, good solvent solubility, and excellent thermal conductivity when cured.Furthermore, they have high Tg and good thermal stability.

Claims

1. An epoxy resin having a basic skeleton of a biphenyl structure having two OG groups represented by the following general formula (1), characterized in that the ratio (former / latter: weight ratio) of biphenyl structures in which X is a direct bond to diphenyl ether structures in which X is -O- is in the range of 0.2 to 5.0, the total content of n=0 units is 70 to 95 wt%, and the epoxy equivalent is in the range of 150 to 160 g / eq. 【Chemistry 1】 (In the formula, each X independently represents a direct bond or —O—, some of which are —O— and the remainder are direct bonds. n represents a number from 0 to 10, and G represents a glycidyl group.)

2. 2. The epoxy resin according to claim 1, wherein, in the general formula (1), the ratio (former / latter: weight ratio) of the biphenyl structure in which X is a direct bond to the diphenyl ether structure in which X is —O— is in the range of 0.5 to 2.

0.

3. 2. The epoxy resin according to claim 1, wherein the biphenyl structure having two OG groups is a 4,4' configuration.

4. An epoxy resin composition comprising the epoxy resin according to any one of claims 1 to 3 and a curing agent as essential components.

5. A cured resin product obtained by curing the resin composition according to claim 4.

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