JP7277136B2 - Epoxy resin, epoxy resin composition, and cured product thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to epoxy resins, epoxy resin compositions, and cured epoxy resins. More specifically, the present invention relates to an epoxy resin, an epoxy resin composition, and a cured epoxy resin, which are useful as insulating materials for electric and electronic parts such as semiconductor encapsulation, laminates, and heat dissipation substrates, and have good handleability as solids at room temperature. , Epoxy resins and epoxy resin compositions with low viscosity during molding and excellent solvent solubility, and cured epoxy resins with excellent heat resistance, thermal decomposition stability, thermal conductivity, and tracking resistance obtained by curing them. about things.

Epoxy resins have been used in a wide range of industrial applications, and their required performance has become increasingly sophisticated in recent years. Under these circumstances, power devices, which have been under development in recent years, are required to have higher power densities. , the development of a sealing material that can withstand such temperatures is desired.

Under these circumstances, Patent Document 1 discloses an epoxy resin, an epoxy resin composition, and a cured product having a biphenol-biphenylaralkyl structure, which are shown to be excellent in heat resistance, moisture resistance, and thermal conductivity. there is Patent Document 2 also discloses an epoxy resin composition having a biphenol-biphenylaralkyl structure, a method for producing a cured epoxy resin product, and a semiconductor device, and it is believed that a cured product having excellent heat resistance and thermal decomposition stability can be obtained. It is shown. However, since it is a crystalline epoxy resin that exhibits a melting point of 100° C. or higher, it is difficult to handle, so melt-kneading at a high temperature is required when mixed with a curing agent or the like. At elevated temperatures, the curing reaction between the epoxy resin and the hardener accelerates rapidly, shortening the gelation time and severely limiting the mixing process. Furthermore, since it exhibits strong crystallinity, it has a problem of solubility in solvents, making it difficult to apply it to laminates.

Patent Document 3 proposes to reduce the crystallinity by removing the crystalline component of an epoxy resin having a biphenol-biphenylaralkyl structure, but the solvent solubility is insufficient and there is a problem in practicality. In addition, when another epoxy resin is mixed to improve moldability and solvent solubility, the melting point of the resin is lowered, making it easier to mix uniformly. , it becomes difficult to maintain mechanical strength and thermal conductivity. Patent Document 4 proposes a composition capable of maintaining physical properties, but melt-kneading at 100° C. or less is difficult, and solvent solubility is also insufficient for practical use in laminates.

WO2011/074517 WO2014/065152 JP 2017-95524 A JP 2015-160893 A

An object of the present invention is to provide a cured product that has good melt-kneadability at 100° C. or less, excellent solvent solubility, and excellent heat resistance, thermal decomposition stability, thermal conductivity, and tracking resistance. An object of the present invention is to provide an epoxy resin composition useful for encapsulation of electronic parts, circuit board materials and the like, and to provide a cured product thereof. Another object is to provide an epoxy resin used in this epoxy resin composition and a polyhydric hydroxy resin suitable as an intermediate for this epoxy resin.

The present inventors have made intensive studies and found that an epoxy resin having a specific structure is expected to solve the above problems, and that the cured product has heat resistance, thermal decomposition stability, thermal conductivity, and resistance. It was found that the effect was exhibited in the tracking property.

（ここで、ｎは０～２０の数を示し、Ｇはグリシジル基を示し、OG基を２つ有するビフェニル環は４，４’体及び２，２’体を含む。） That is, the present invention provides an epoxy resin represented by the following general formula (1), characterized by having an epoxy equivalent of 180 to 220 g/eq and a softening point of 40 to 100°C. be.

(Here, n represents a number from 0 to 20, G represents a glycidyl group, and biphenyl rings having two OG groups include 4,4' and 2,2' isomers.)

In the above general formula (1), the proportion of the 4,4' form in the biphenyl ring having two OG groups is 30 to 90 mol%, and the proportion of the 2,2' form is 10 to 70 mol%. It is preferable that the ratio of the 4,4'-isomer is 50 to 90 mol% and the ratio of the 2,2'-isomer is 10 to 50 mol%.

The epoxy resin is obtained by reacting a mixture of dihydroxybiphenyl containing 4,4'-dihydroxybiphenyl and 2,2'-dihydroxybiphenyl with an aromatic cross-linking agent having a biphenyl structure to obtain a polyhydroxy resin, It can be obtained by reacting epichlorohydrin.
The mixture of dihydroxybiphenyls can comprise 50-90% by weight of 4,4'-dihydroxybiphenyl and 10-50% by weight of 2,2'-dihydroxybiphenyl, and the aromatic cross-linking agent comprises 4, 4'-bischloromethylbiphenyl.

（ここで、ｎは０～２０の数を示す。） The present invention also provides a polyhydric hydroxy resin represented by the following general formula (2), wherein the biphenyl ring having two OH groups includes 4,4' and 2,2' isomers. Epoxy resin.

(Here, n represents a number from 0 to 20.)

The present invention also provides an epoxy resin composition comprising the above epoxy resin and a curing agent as essential components, and an epoxy resin cured product obtained by curing the epoxy resin cured product. is.

Furthermore, the present invention provides a polyhydric hydroxy resin by reacting a mixture of dihydroxybiphenyl containing 4,4'-dihydroxybiphenyl and 2,2'-dihydroxybiphenyl with an aromatic cross-linking agent having a biphenyl structure, The method for producing the above epoxy resin is characterized by reacting epichlorohydrin.

The epoxy resin of the present invention has good melt-kneadability at 100° C. or less and excellent solvent solubility. Suitable for The cured product is also excellent in heat resistance, thermal decomposition stability, thermal conductivity and tracking resistance, and is suitable for sealing electric/electronic parts, circuit board materials, and the like.

GPC chart of the epoxy resin obtained in Example 1

The present invention will be described in detail below.

The epoxy resin of the present invention is represented by the above general formula (1) and has an epoxy equivalent (g/eq.) of 180-220. n is the number of repetitions (number average) and represents a number from 0 to 20, and G is a glycidyl group. Preferred are mixtures of components with different values of n. In general formula (1), the substitution positions of the two OG groups bonded to the biphenyl ring are preferably the 4,4′ and 2,2′ positions, and the 4,4′ structure (4,4′ position structure Units having a) is more preferably 30 to 90 mol% of the whole, more preferably 50 to 90 mol%. The 2,2' form is preferably 10 to 70 mol% of the whole, more preferably 10 to 50 mol%.
From another point of view, it is more preferable that the 4,4' isomer is in the range of 100/200 to 100/110 (molar ratio). More preferably, 50 to 90 mol % are 4,4'-position structures and 10 to 50 mol % are 2,2'-position structures. Isomeric structures other than 4,4' and 2,2' may be contained, but are preferably 10 mol % or less.

The softening point of the epoxy resin of the present invention is in the range of 40-100°C. If the softening point is lower than 40°C, the epoxy resin becomes liquid or semi-solid, making it difficult to handle. will decline.

The epoxy resin of the present invention can be produced by reacting the polyhydric hydroxy resin represented by the above formula (2) with epichlorohydrin. This polyvalent hydroxy resin is also the polyvalent hydroxy resin of the present invention, and includes 4,4' and 2,2' biphenyl rings having two OH groups. The meanings of the 4,4' and 2,2' isomers are the same as those described for the epoxy resin of the present invention, and the preferred abundances are also the same.

（ここで、Xは水酸基、ハロゲン原子又は炭素数１～６のアルコキシ基を示す。） This polyhydric hydroxy resin can be produced by reacting biphenols with an aromatic condensing agent having a biphenyl structure represented by the following formula (3).

(Here, X represents a hydroxyl group, a halogen atom, or an alkoxy group having 1 to 6 carbon atoms.)

Biphenols used as starting materials for synthesis include dihydroxybiphenyls such as 4,4'-dihydroxybiphenyl and 2,2'-dihydroxybiphenyl. When 4,4'-dihydroxybiphenyl is used alone, the crystallinity increases, so it is preferable to use it together with 2,2'-dihydroxybiphenyl from the viewpoint of solvent solubility. 4,4'-dihydroxybiphenyl gives the 4,4' isomer, and 2,2'-dihydroxybiphenyl gives the 2,2' isomer.

Preferably, 4,4'-dihydroxybiphenyl and 2,2'-dihydroxybiphenyl are used as biphenols, and 30 to 90% by weight of 4,4'-dihydroxybiphenyl and 10 to 70% by weight of 2,2'-dihydroxybiphenyl are used. A mixture of dihydroxybiphenyls containing % by weight is used. Preferably a mixture of dihydroxybiphenyls containing 50-90% by weight of 4,4'-dihydroxybiphenyl and 10-50% by weight of 2,2'-dihydroxybiphenyl is used. The mixture of dihydroxybiphenyls can contain dihydroxybiphenyls other than those mentioned above, but preferably 10 to 50% by weight or less.
As the proportion of 4,4'-dihydroxybiphenyl increases, the softening point of the epoxy resin increases, but the solubility decreases.

In the above formula (3), X represents a hydroxyl group, a halogen atom or an alkoxy group having 1 to 6 carbon atoms. Specific examples of aromatic condensing agents include 4,4'-bishydroxymethylbiphenyl, 4,4'-bischloromethylbiphenyl, 4,4'-bisbromomethylbiphenyl, 4,4'-bismethoxymethyl biphenyl, 4,4'-bisethoxymethylbiphenyl. From the viewpoint of reactivity, 4,4'-bishydroxymethylbiphenyl or 4,4'-bischloromethylbiphenyl is preferred, and from the viewpoint of reducing ionic impurities, 4,4'-bishydroxymethylbiphenyl, or 4,4'-bismethoxymethylbiphenyl is preferred.

The molar ratio in reacting the biphenols and the aromatic condensing agent is generally in the range of 0.1 to 0.5 mol of the aromatic condensing agent per 1 mol of the biphenols, and more preferably. is in the range of 0.2-0.4 mol. If it is less than 0.1 mol, the resulting polyhydric hydroxy resin will have a high ratio of n=0 isomers, and there is a concern that the solubility may decrease, such as exhibiting crystallinity. On the other hand, when the amount is more than 0.5 mol, the softening point and melt viscosity are increased due to the increase in molecular weight, which impairs handling workability and moldability.

The reaction between the biphenols and the aromatic condensing agent can be carried out without a catalyst or in the presence of an acid catalyst such as an inorganic acid or an organic acid. When using 4,4'-bischloromethylbiphenyl, the reaction can be carried out without a catalyst, but in general, the chloromethyl group reacts with the hydroxyl group to suppress side reactions such as formation of an ether bond. Secondly, it is preferable to carry out in the presence of an acidic catalyst. The acidic catalyst can be appropriately selected from well-known inorganic acids and organic acids. Acids, organic acids such as trifluoromethosulfonic acid, Lewis acids such as zinc chloride, aluminum chloride, iron chloride and boron trifluoride, solid acids, and the like.

The reaction is usually carried out at 100-250° C. for 1-20 hours. The temperature is preferably 100 to 180°C, more preferably 140 to 180°C. If the reaction temperature is low, the reactivity will be poor and time will be required, and if the reaction temperature is high, the resin may decompose.

Examples of solvents used in the reaction include alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol, methyl cellosolve, ethyl cellosolve, diethylene glycol dimethyl ether, and triglyme, and aromatic compounds such as benzene, toluene, chlorobenzene, and dichlorobenzene. Among these, ethyl cellosolve, diethylene glycol dimethyl ether, triglyme and the like are particularly preferred. After completion of the reaction, the polyhydric hydroxy resin obtained may be used as a raw material for the epoxidation reaction with the solvent remaining, although the solvent may be removed by a method such as distillation under reduced pressure, washing with water, or reprecipitation in a poor solvent. may be used.

The polyhydric hydroxy resin thus obtained can be used not only as a raw material for epoxy resins, but also as an epoxy resin curing agent. Further, by combining with a curing agent such as hexamine, it can be applied as a phenolic resin molding material.

A method for producing the epoxy resin of the present invention by reacting the polyhydric hydroxy resin represented by the above formula (2) with epichlorohydrin will be described. This reaction can be carried out in a manner similar to well-known epoxidation reactions.

For example, after dissolving the polyhydric hydroxy resin in excess epichlorohydrin, in the presence of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide at 50 to 150 ° C., preferably 60 to 120 ° C. A method of reacting for 10 hours can be mentioned. The amount of epichlorohydrin used in this case is in the range of 0.8 to 2 mol, preferably 0.9 to 1.2 mol, per 1 mol of hydroxyl groups in the polyhydroxy resin. After completion of the reaction, excess epichlorohydrin is distilled off, 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 a compound of the general formula ( The desired epoxy resin represented by 1) can be obtained. A catalyst such as a quaternary ammonium salt may be used in the epoxidation reaction.

The purity of the epoxy resin of the present invention, particularly the amount of hydrolyzable chlorine, should be less from the viewpoint of improving the reliability of electronic components to which it is applied. Although not particularly limited, it is preferably 1000 ppm or less, more preferably 500 ppm or less. In addition, the hydrolyzable chlorine referred to in the present invention refers to the value measured by the following method. That is, after dissolving 0.5 g of a sample in 30 ml of dioxane, adding 10 ml of 1N-KOH and boiling under reflux for 30 minutes, cooling to room temperature, further adding 100 ml of 80% acetone water, and applying a potential difference with an aqueous 0.002N-AgNO ₃ solution. It is a value obtained by titration.

The epoxy resin composition of the present invention contains an epoxy resin and a curing agent, and contains the epoxy resin of general formula (1) as an epoxy resin component.

In the epoxy resin composition of the present invention, other ordinary epoxy resins having two or more epoxy groups in the molecule may be used in combination with the epoxy resin of general formula (1) used as an essential component. Examples 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, 2,2'-biphenol, resorcin, catechol , t-butyl catechol, t-butyl hydroquinone, 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 Naphthalene, allylated or polyallylated dihydroxynaphthalene, allylated bisphenol A, allylated bisphenol F, dihydric phenols such as allylated phenol novolak, or phenol novolak, bisphenol A novolak, o-cresol novolak, m- cresol novolak, p-cresol novolak, xylenol novolak, poly-p-hydroxystyrene, tris-(4-hydroxyphenyl)methane, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, fluoroglycinol, pyrogallol , t-butyl pyrogallol, allylated pyrogallol, polyallylated pyrogallol, 1,2,4-benzenetriol, 2,3,4-trihydroxybenzophenone, phenol aralkyl resin, naphthol aralkyl resin, dicyclopentadiene-based resin, etc. There are glycidyl etherified products derived from the above phenols or halogenated bisphenols such as tetrabromobisphenol A. These epoxy resins can be used singly or in combination of two or more.

The epoxy resin composition of the present invention desirably contains 50% by weight or more of the epoxy resin component of the epoxy resin represented by the general formula (1) as the epoxy resin. More preferably, it is 70% by weight or more, more preferably 80% by weight or more of the total epoxy resin. If the proportion is less than this range, the moldability of the epoxy resin composition is deteriorated, and the effect of improving the heat resistance and thermal conductivity of the cured product is small.

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

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, naphthalene diol, or , tris-(4-hydroxyphenyl)methane, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, phenol novolak, o-cresol novolak, naphthol novolak, polyvinylphenol, etc. There are phenols. Furthermore, dihydric phenols such as phenols, naphthols, bisphenol A, bisphenol F, bisphenol S, fluorene bisphenol, 4,4'-biphenol, 2,2'-biphenol, hydroquinone, resorcinol, and naphthalenediol, There are polyhydric phenolic compounds synthesized with condensing agents such as formaldehyde, acetaldehyde, benzaldehyde, p-hydroxybenzaldehyde and p-xylylene glycol.

Examples of acid anhydride curing agents include phthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyl himic anhydride, dodecynylsuccinic anhydride, nadic anhydride, and trimellitic anhydride.

Amine curing agents include aromatic amines such as 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylsulfone, m-phenylenediamine and p-xylylenediamine; There are aliphatic amines such as ethylenediamine, hexamethylenediamine, diethylenetriamine and triethylenetetramine.

One or a mixture of two or more of these curing agents can be used in the epoxy resin composition.

The mixing ratio of the epoxy resin and the curing agent is preferably in the range of 0.8 to 1.5 in terms of the equivalent ratio of the epoxy groups to the functional groups in the curing agent. Outside this range, unreacted epoxy groups or functional groups in the curing agent remain even after curing, and the reliability of the sealing function is lowered, which is not preferable.

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-cumarone resin, phenoxy resin, etc. may be used as other modifiers. It may be blended as appropriate. The amount added is usually in the range of 1 to 30 parts by weight with respect to 100 parts by weight of the total resin components.

Additives such as inorganic fillers, pigments, flame retardants, thixotropic agents, coupling agents, fluidity improvers and the like can be added to the epoxy resin composition of the present invention. Examples of inorganic fillers include spherical or crushed fused silica, silica powder such as crystalline silica, alumina powder, glass powder, mica, talc, calcium carbonate, alumina, and hydrated alumina. When used as a sealing material, the blending amount is preferably 70% by weight or more, more preferably 80% by weight or more.

Pigments include organic or inorganic extender pigments, scaly pigments, and the like. Examples of the thixotropic agent include silicon-based, castor oil-based, aliphatic amide wax, oxidized polyethylene wax, and organic bentonite-based agents.

Furthermore, a curing accelerator can be used in the epoxy resin composition of the present invention, if necessary. Examples include amines, imidazoles, organic phosphines, Lewis acids, etc. Specific examples include 1,8-diazabicyclo(5,4,0)undecene-7, triethylenediamine, benzyldimethylamine, tri Tertiary amines such as ethanolamine, dimethylaminoethanol, tris(dimethylaminomethyl)phenol, 2-methylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 2- imidazoles such as heptadecylimidazole; organic phosphines such as tributylphosphine, methyldiphenylphosphine, triphenylphosphine, diphenylphosphine, and phenylphosphine; tetraphenylphosphonium/tetraphenylborate; tetraphenylphosphonium/ethyltriphenylborate; Tetra-substituted phosphonium/tetra-substituted borate such as butylphosphonium/tetrabutylborate, 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.

Furthermore, if necessary, the epoxy resin composition of the present invention may contain a releasing agent such as carnauba wax or OP wax, a coupling agent such as γ-glycidoxypropyltrimethoxysilane, a coloring agent such as carbon black, Flame retardants such as antimony oxide, stress reducing agents such as silicone oil, and lubricants such as calcium stearate can be used.

The epoxy resin composition of the present invention is made into a varnish state by dissolving an organic solvent, impregnated with a fibrous material such as a glass cloth, an aramid nonwoven fabric, a polyester nonwoven fabric such as a liquid crystal polymer, and the like, and then the solvent is removed to obtain a prepreg. can be In some cases, a laminate can be obtained by coating a sheet-like material such as a copper foil, a stainless steel foil, a polyimide film, a polyester film, or the like.

The resin cured product of the present invention can be obtained by heat-curing the epoxy resin composition 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 this time is usually in the range of 120 to 220°C.

The present invention will be specifically described below with reference to Synthesis Examples, Examples and Comparative Examples. However, the present invention is not limited to these. Unless otherwise specified, "parts" represent parts by weight and "%" represents weight percent. Moreover, the measurement method was each measured by the following methods.

1) Measurement of Epoxy Equivalent Using a potentiometric titrator, using methyl ethyl ketone as a solvent, adding a tetraethylammonium bromide acetic acid solution, and measuring using a 0.1 mol/L perchloric acid-acetic acid solution with a potentiometric titrator.

2) Melting point A DSC peak temperature was obtained with a differential scanning calorimeter (EXSTAR6000 DSC/6200, manufactured by SII Nanotechnology Co., Ltd.) under the condition of a heating rate of 5°C/min. That is, this DSC peak temperature was taken as the melting point of the resin.

3) Melt viscosity Measured at 150°C using a CAP2000H rotational viscometer manufactured by BROOKFIELD.

4) Softening point Measured by the ring and ball method according to JIS-K-2207.

5) GPC Measurement A column (TSKgelG4000HXL, TSKgelG3000HXL, TSKgelG2000HXL, manufactured by Tosoh Corporation) in series with a main body (HLC-8220GPC manufactured by Tosoh Corporation) was used, and the column temperature was set to 40°C. Tetrahydrofuran (THF) was used as an eluent at a flow rate of 1 mL/min, and a differential refractive index detector was used as a detector. As a measurement sample, 0.1 g of the sample was dissolved in 10 mL of THF and filtered through a microfilter, and 50 μL of the solution was used. For data processing, GPC-8020 model II version 6.00 manufactured by Tosoh Corporation was used.

6) Glass transition point (Tg)
Tg was determined with a thermomechanical measurement device (EXSTAR6000TMA/6100 manufactured by SII Nanotechnology Co., Ltd.) under the condition of a temperature increase rate of 10° C./min.

7) 5% weight loss temperature (Td5), residual carbon ratio Using a thermogravimetry/differential thermal analyzer (EXSTAR6000TG/DTA6200, manufactured by SII Nanotechnology), under a nitrogen atmosphere, at a heating rate of 10°C/min. , the 5% weight loss temperature (Td5) was measured. Also, the weight loss at 700° C. was measured and calculated as the residual charcoal rate.

8) Thermal conductivity Thermal conductivity was measured by the unsteady hot wire method using a NETZSCH LFA447 thermal conductivity meter.

Example 1
38.9 g of 4,4'-dihydroxybiphenyl, 38.9 g of 2,2'-dihydroxybiphenyl, 119.6 g of diethylene glycol dimethyl ether, and 41.9 g of 4,4'-bischloromethylbiphenyl were charged into a 1000 ml four-necked flask, Under a nitrogen stream, the temperature was raised to 170° C. while stirring, and the mixture was reacted for 2 hours to produce a polyhydric hydroxy resin. After completion of the reaction, 45.6 g of diethylene glycol dimethyl ether was recovered, 455.1 g of epichlorohydrin was added, and 70.5 g of a 48% sodium hydroxide aqueous solution was added dropwise at 62° C. under reduced pressure (about 130 Torr) over 4 hours. During this time, the generated water was removed from the system by azeotroping with epichlorohydrin, and the distilled epichlorohydrin was returned to the system. After the dropwise addition was completed, the reaction was further continued for 1 hour. Thereafter, epichlorohydrin was distilled off, methyl isobutyl ketone was added, and after removing salts by washing with water, filtration and washing were carried out, and then methyl isobutyl ketone was distilled off under reduced pressure to obtain 129 g of an epoxy resin (epoxy resin). A). This epoxy resin A had an epoxy equivalent of 200, a softening point of 51° C., a melt viscosity of 0.19 Pa·s, and a hydrolyzable chlorine content of 65 ppm. A GPC chart of the obtained resin is shown in FIG.

Example 2
The reaction was carried out in the same manner as in Example 1 except that the amount of 4,4'-dihydroxybiphenyl used was 54.4 g and the amount of 2,2'-dihydroxybiphenyl used was 23.3 g to obtain 128 g of an epoxy resin. (epoxy resin B). This epoxy resin B had an epoxy equivalent of 200, a softening point of 84° C., a melt viscosity of 0.19 Pa·s, and a hydrolyzable chlorine content of 78 ppm.

Reference example 1
77.5 g of 4,4′-dihydroxybiphenyl, 180.8 g of diethylene glycol dimethyl ether, and 52.3 g of 4,4′-bischloromethylbiphenyl were charged, heated to 170° C. with stirring under a nitrogen stream, and reacted for 2 hours. rice field. 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% aqueous sodium hydroxide solution was added dropwise at 62° C. under reduced pressure (about 130 Torr) over 4 hours. 129 g of epoxy resin was obtained in the same manner (epoxy resin C). This epoxy resin C had an epoxy equivalent of 196, a melting point of 126° C., a melt viscosity of 0.68 Pa·s, and hydrolyzable chlorine of 390 ppm.

（ここで、ｍは０～２０の数を示し、Ｇはグリシジル基を表す。） Reference example 2
30 g of the epoxy resin C obtained in Reference Example 1 was placed in a 200 ml four-necked flask, and a phenol novolak type epoxy resin D represented by the following formula (4) (epoxy equivalent: 175, m = 1 by GPC measurement. 9.0%, m = 2 components; 37.7%, m = 3 components; 17.1%, m = 4 components; 8.2%, and the total content of m = 5 or more components is 27.9 %.) was added and melt-kneaded at 150° C. for 30 minutes to obtain an epoxy resin E. This epoxy resin E had an epoxy equivalent of 187, a softening point of 92° C., a melt viscosity of 0.13 Pa·s, and a hydrolyzable chlorine content of 280 ppm.

(Here, m represents a number from 0 to 20, and G represents a glycidyl group.)

Solvent solubility Solvent solubility was determined by adding 5 g of a solvent (methyl ethyl ketone, toluene, cyclohexanone) to epoxy resin A obtained in Example 1, epoxy resin B obtained in Example 2, epoxy resin C obtained in Reference Example 1 or The epoxy resin E obtained in Reference Example 2 was added so that the solid content concentration (g of epoxy resin/100 g of solvent) was 30% by weight, 50% by weight, or 70% by weight. Insoluble matter was visually confirmed. The case where insoluble matter was present was evaluated as x, and the case where there was no insoluble matter was evaluated as ◯. In addition, Δ indicates that the insoluble matter was confirmed to dissolve when the insoluble matter was confirmed to be heated to 60°C. Melting points (mp) or softening points (sp) were also measured. Table 1 shows the results.

Examples 3-5 and Comparative Examples 1-4
As an epoxy resin component, epoxy resin A obtained in Example 1, epoxy resin B obtained in Example 2, epoxy resin C obtained in Reference Example 1, epoxy resin D used in Reference Example 2, or epoxy resin F below was used. Curing agents A to B were used as the curing agent, and triphenylphosphine was used as the curing accelerator to obtain an epoxy resin composition with the formulation shown in Table 2. Numerical values in the table indicate parts by weight in the formulation.
This epoxy resin composition was molded at 175° C. and post-cured at 175° C. for 5 hours to obtain a cured product test piece, which was subjected to various physical property measurements.

The epoxy resins, curing agents, and curing accelerators used are shown below.
Epoxy resin F: o-cresol novolac type epoxy resin (Nippon Steel Chemical & Material YDCN-700-3, epoxy equivalent 200)
Curing agent A: Triphenolmethane type polyhydric hydroxy resin (TPM-100 manufactured by Gun Ei Chemical Industry Co., Ltd., OH equivalent 97.5, softening point 105 ° C.)
Curing agent B: phenolic novolac resin (hydroxyl equivalent 105, softening point 67°C)
Curing accelerator; triphenylphosphine

As is clear from these results, the epoxy resins obtained in Examples have excellent solvent solubility, and the cured products thereof have good thermal stability. can be expected. Furthermore, it is suitable for power devices and in-vehicle applications due to its good thermal conductivity.

Claims (7)

An epoxy resin represented by the following general formula (1), characterized by having an epoxy equivalent of 180 to 220 g/eq and a softening point of 40 to 100°C.

(Here, n represents a number from 0 to 20, G represents a glycidyl group, biphenyl rings having two OG groups include 4,4' and 2,2', and 4,4' is 50 to 70 mol%, and the 2,2' isomer is 30 to 50 mol%.) A mixture of dihydroxybiphenyl containing 4,4′-dihydroxybiphenyl and 2,2′-dihydroxybiphenyl is reacted with an aromatic cross-linking agent having a biphenyl structure to obtain a polyvalent hydroxy resin, which is then reacted with epichlorohydrin. The epoxy resin of claim 1 obtained. 3. The epoxy resin of claim 2, wherein the aromatic cross-linking agent is 4,4'-bischloromethylbiphenyl. A mixture of 4,4'-dihydroxybiphenyl and dihydroxybiphenyl containing 2,2'-dihydroxybiphenyl is reacted with an aromatic cross-linking agent having a biphenyl structure to obtain a polyvalent hydroxy resin, and then reacted with epichlorohydrin. The method for producing an epoxy resin according to claim 1, characterized by: A polyhydric hydroxy resin represented by the following general formula (2), wherein the biphenyl ring having two OH groups includes 4,4' and 2,2' isomers, and the proportion occupied by the 4,4' isomers is 50 to 70 mol%, and the proportion of the 2,2' form is 30 to 50 mol% .

(Here, n represents a number from 0 to 20.) An epoxy resin composition comprising the epoxy resin according to any one of claims 1 to 3 and a curing agent as essential components. A cured epoxy resin product obtained by curing the epoxy resin composition according to claim 6 .

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